US3411025A - Method and apparatus for producing charged aerosols - Google Patents

Description

5mm mm QLU'LL A. M. MARKS METHOD AND APPARATUS FOR PRODUCING CHARGED AEROSOLS 4 Sheets-Sheet 1 Filed March 11., 1965 IN VEN TOR.

w Z, .lllAl w A. M. MARKS Nov. 12, 1968 METHOD AND APPARATUS FOR PRODUCING CHARGEDAEROSOLS 4 Sheets-Sheet 2 Filed March 11, 1965 INVENTOR.

(s/vaav/zv/ 57/0172 3 v/iawd 5 M; m Mr W W h Nov. 12, 1968 MARKS 3,411,025

METHOD AND APPARATUS FOR PRODUCING CHARGED AEROSOLS Filed March 11, 1965 4 Sheets-Sheet 5 FIG. 7

m -2 m f /0 INVENTOR. fizm/ 4/, Ma s A. M. MARKS Nov. 12, 1968 METHOD AND APPARATUS FOR PRODUCING CHARGED AEROSOLS Filed March 11, 1965 4 Sheets-Sheet 4 R m m4 m m w w United States Patent 3,411,025 METHOD AND APPARATUS FOR PRODUCING CHARGED AEROSOLS Alvin M. Marks, 15316 10th Ave., Whitestone, N.Y. 11357 Filed Mar. 11, 1965, Ser. No. 438,930 12 Claims. (Cl. 31011) ABSTRACT OF THE DISCLOSURE A device to convert the heat kinetic power of a moving gas to electric power in which a moving gas under pressure containing a condensable vapor cools as it flows through ions in an electric field, the vapor condenses on the ions to form minute charged droplets and thereafter further condenses upon the droplets to form larger charged droplets which are passed through a conversion space having a repelling electric field. A collector electrode at the exit of the conversion space discharges the charged droplets, an electrical load is connected between the collector electrode and the ionizer. Various means for charging, forming, controlling and introducing the droplets are also disclosed.

This invention relates to a device for transducing the thermal and/or kinetic power of a moving charged aerosol gas to electric power and vice versa, with good aerodynamic and electrical efficiency.

In the conversion process, the charged particle is moving in a carrier gas against an electric field, which induces a slip velocity opposite to the velocity of the carrier gas. When the particle radius is small in relation to the electric charge per particle, a great number of charged particles may be present in a unit volume of gas and the charge density is large, but the slip velocity may then be a large fraction of the gas velocity. Excessive frictional power loss, and little or no power conversion may result. When the particle radius is large in relation to its electric charge, the slip velocity is small but there may be too few charged particles per unit volume and the charge density may be too small, and hence only a little power may be converted.

It has been shown that to efiiciently and abundantly transduce power through the medium of a charged aerosol with negligible slip power loss, the charged particle must have an optimum radius in relation to its charge, and the number of charged particles per unit volume must be such as to provide the required charge density. The mathematical-physics of these relationships, set forth in U.S. Patent No. 2,638,555, has been substantially confirmed experimentally.

Definitions The following terms employed herein are defined as follows:

The charge density of a charged aerosol is defined as the electric charge per unit volume of the charged aerosol.

The term chafo is an acronym for charged aerosol and formation.

Standard conditions for the gas are defined as 10 newtons/m. at 300 K.; or, approximately one atmosphere at 27 C.

Certain physical variables such as gas temperature and pressure are expressed relative to ambient conditions, using known physical laws.

supersaturated vapor, as used herein, is a vapor in that condition in which it is capable of condensing upon an electrically neutral aerosol droplet.

A superheated vapor is one in which an electrically neutral droplet will evaporate. However, a supersaturated ice vapor tends to preferentially condense on ions or charged particles. A charged liquid particle may be stable in superheated vapor, where a neutral liquid particle will evaporate, provided the superheat is not too great.

The particle mobility is related to particle radius, particle charge, gas density and other physical parameters. Optimum values of these physical parameters for a charged aerosol gas to operate as an efficient power transducer are hereinafter derived.

Maximum electric field intensity necessary to operate the charged aerosol generator under the conditions of maximum power conversion occurs at just under the breakdown electric field for the charged aerosol gas under the conditions of operation.

The breakdown electric field in air under standard conditions is approximately 3 X 10 volts/m. The breakdown electric field strength of a gas is increased in approximately direct proportion to the gas density. The converted electric power increases as the square of the electric field intensity, and hence as the square of the gas density.

Mobility is defined as the velocity given to a charged particle or ion in a gas by a unit electric field intensity. It is expressed in the MKS system as the units m. /voltsee. In air under standard conditions, negative ions or positive ions have a mobility of approximately 10 m. /volt-sec.

Under ambient conditions the application of the breakdown electric field intensity results in an ion velocity of about 300 m./ sec. through the air. For power transducing devices, 300 m./sec. is a subsonic velocity within a suitable operating velocity range.

The optimum mobility of a charged aerosol particle is defined as that which results in a charged aerosol particle having an arbitrary negligibly small slip velocity, taken herein as 1% of the carrier gas velocity, under the near breakdown electric field intensity.

If an ion be placed under standard conditions in a gas stream moving at 300 m./sec. with an opposing electric field of maximum intensity, the forward motion of the gas is then equal to the slip velocity of the ion and the net velocity of the ion is zero; the kinetic power of the gas is lost in internal frictional heat; and no net power conversion results. Hence positive or negative free ions cannot be used for efficiently transducing heat-kinetic power to electric power.

Nor can unattached or free electrons be used as a power transducer between a moving gas and the electrical circuit, since their mobility is even greater than the mobility of a free ion.

For efficient power conversion the charged aerosol particles must have an optimum mobility which corresponds to an optimum ratio of radius to electric charge. To use a still smaller mobility would not result in a useful improvement; the larger radius particle might result in fewer particles per unit volume and result in a smaller charge density. The optimum mobility of a charged aerosol particle depends on the choice of gas velocity. This velocity is usually chosen subsonic, not exceeding about 0.5 Mach to keep the gas friction power losses small. The gas velocity cannot be much less than 0.5 Mach to maintain a substantial electric current transport via the charged aerosol gas. As an example, under standard con ditions and with subsonic gas velocity, the optimum mobility for the charged aerosol particle is 10- m. /voltsee.

A mathematical-physics analysis will later set forth these relationships in detail, enabling the specification of optimum radius in relation to the electric charge under the various conditions of operation.

3 Objects One of the objects of this invention is to provide an eflicient charged aerosol power converter, which avoids one or more of the disadvantages and limitations of the methods and apparatus of the prior art.

An object of this invention is to provide an improved power transducer utilizing a charged aerosol of optimum characteristics suitable for employment as a generator, pump or thrustor.

Another object of this invention is to provide an improved jet pump by the use of charged aerosols of optimum characteristics.

An object of this invention is to provide new and improved methods and devices for producing charged aerosols having an optimum mobility.

An object of this invention is to efiiciently produce a charged aerosol comprising charged liquid particles having an optimum ratio of radius to electric charge.

A further object of this invention is to minimize the frictional power loss due to the slip of the charged paritcles relative to the gas in a charged aerosol power transducer, by providing charged aerosol particles of optimum mobility.

Another object of this invention is to provide improved methods of forming and charging aerosols.

Another object of this invention is to modify the electrojet process so as to produce charged aerosol particles of optimum mobility.

Another object of this invention is an improved condensation process producing charged aerosol particles of optimum mobility.

Another object of the invention is to provide :a method and apparatus in which condensation of vapor onto an ion continues, fonming a singly charged droplet of increasing radius, until the mobility is decreased to a suitable optimum value.

Another object of the invention is to provide a method and apparatus in which multiply charged liquid particles acquire additional liquid from surrounding vapor to increase the particle radius and decrease the mobility to an optimum value.

A further object of this invention is to equalize the charging current produced by each unit area of a charging array.

This invention also concerns a new method and apparatus of introducing thermal jet power into a gas for increasing its kinetic power through the use of a charged aerosol jet.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings, in which similar reference characters indicate corresponding parts, in which:

FIGURE 1 is a cross-sectional view taken along the axis of flow of one form of a charged aerosol converter according to the present invention, showing an assembly of elements forming an airfoil array.

FIGURE 2 shows a cross-sectional view, taken on line 2-2 of FIGURE 1 normal to the axis of flow.

FIGURE 3 is a cross-sectional detail view similar to FIGURE 1 of another form of the charged aerosol converter, utilizing an improved condensation type charged aerosol formation and charging process.

FIGURE 4 is a longitudinal cross-sectional detail view of still another form of the charged aerosol converter, utilizing an improved combination of an electrojet type and condensation type charged aerosol forming and charging process.

FIGURE 5 is an enlarged fragmentary, somewhat isometric view of a charged aerosol formation and charging device, according to the present invention.

FIGURE 6 graphically represents the particle radius versus mobility for singly charged particles, and for multiply charged particles.

FIGURE 7 shows a graph of a mathematical function useful in calculating the optimum radius of a charged aerosol particle.

FIGURE 8 shows a graph of the optimum radius for singly charged particles versus relative gas density. The solid curves were calculated for different given values of relative breakdown electric intensity for the gas. The dashed curves correspond to different electric power densities.

Referring to the drawings and particularly to FIGURE 1, there is shown a conduit 10 containing the charged aerosol converter assembly. This assembly comprises: The chafo section 31, for forming and charging the charged aerosol; the converter section 32 where the heatkinetic power is transduced to electric power, or vice versa; and the collector section 33 where the charged aerosol is discharged and connected to the external load current.

The charged aerosol A number of different processes may be employed to form and clharge the aerosol. In the process hereinafter termed the electrojet process, a fluid jet is emitted from an orifice into a gas stream in the presence of a strong electric field. The fluid is subject to electric forces, and to mechanical forces generated by the slip of the particle relative to the gas stream. The mechanical forces and the electrical forces tend to disrupt the fluid drop; the surface tension forces tend to keep the fluid drop together. The breakup into smaller charged droplets continues until an equilibrium condition between these contending forces is established. A charged aerosol is formed which comprises particles of the order of one micron in radius, with many charges on each particle.

The electrojet process is an efficient method for producing charged aerosol particles. However, if the ratio of the electric charge to the radius of the charged aerosol particles is large, then the mobility of such particles may be too large for them to act as an eflicient power transducer.

In a process hereinafter referred to as the condensation process, a gas containing a condensable vapor is directed through a nozzle and continuously expanded to decrease the temperature of the vapor in the presence of ions, whereupon the vapor condenses to form charged aerosol droplets suspended in the flowing gas stream. Effective condensation of the vapor onto a singly charged particle causes the charged liquid droplet to increase in radius. In this manner a charged aerosol may be formed having optimum mobility and capable of acting as an eflicient power transducer.

However, charged aerosol particles produced by the condensation process may produce singly charged particles thaving radii so small that their slip and frictional power loss is excessive. Moreover, to obtain effective vapor condensation onto the charged particles, a large temperature drop was heretofore required which was obtained by a gas-vapor flow through a nozzle having a large expansion ratio. Gases flowing in nozzles having large expansion ratios are usually accompanied by excessive frictional power losses.

These difliculties with the condensation process are overcome by the present invention.

Accordingly to one form of this invention a suitable subsonic gas velocity is maintained with small proportionate flows of jets of condensable vapors. A large drop in temperature is obtained by conversion of the superheat of the jet into jet kinetic power imparted to the carrier gas.

According to another form of this invention, the condensable vapor is initially slightly superheated, and cools by mixing with the cooler carrier gas. In both cases the vapor condenses onto charged particles such as ions and liquid droplets.

The electric charge on the particle is predetermined by the process of formation. The condensation process,

produces singly charged particles. The electrojet process, except with ultra thin jets, produces multiply charged particles. Utilizing either method, the radius of the charged particle may be too small in relation to its charge, the mobility too large, and the slip velocity greater than 1% of the gas velocity; and hence eflicient operating conditions may not be attained.

The problem solved herein is that of producing charged particles of such small mobility that they are capable of performing as an efiicient thermal-kinetic-electric power transducer.

According to one form of this invention this result is achieved by the condensation of vapor onto the previously formed and charged particles, whether singly or multiply charged, causing the radius of the particles to increase and their mobility to decrease until it becomes optimum.

According to another form of the invention, there may be used an electrojet process employing ultrathin jets of liquid. These ultrathin liquid jets are mechanically disrupted by the gas into particles having an optimum radius for a few electric charges. The charge on each particle is controlled by the voltage applied to the jet. A charged aerosol results which is capable of efficient power transduction.

The converter section The converter section 32 includes an airfoil array 16. Each airfoil in the array has a streamlined cross section so that the airfoil array is in effect an array of slit-nozzles 41. The charged aerosol-gas flows through these slit-nozzles and electrothermodynamic power conversion occurs. Each airfoil 16 has a conducting strip 17 on its upper and lower surface.

The conducting strips 17 apply an electric field to the chafo ionizer electrode 30 which is carried by the conduit upstream of the airfoils 16. The function of the chafo ionizer electrode 30 is to supply ions used as nuclei to form and charge the aerosol. The ionizer electrode 30 may be an array of points, wires or thin tubes. The conversion region of the nozzle 41 lies between the planes 51 and 52, which are separated by a distance L. The collector electrode section 33 performs the function of discharging the charged aerosol at the end plane 52 of the conversion region of the nozzle 41.

One form of collector electrode 33, shown in FIGURE 3 is a plurality of thin tungsten wire points 34, which function in a manner hereinafter described.

The chafo, converter and collector sections are mounted within the duct 10, which is shown in FIGURE 2 as rectangular in section. The duct 10 may be suitably split with a flange joint generally indicated at 37 to enable the ready assembly of the transducer components within the duct.

The chafo section, the converter section, and the collector section are spaced and insulated from each other by the insulating spacers 35 and 36 respectively.

The chafo electrode 29 may be entirely fabricated of metal and connected directly to and supported within the metal duct 10 which may be at ground potential.

The converter section 32 comprises an array of airfoil elements 16 constructed of insulating material, for example, fused quartz. Each airfoil element 16 has conducting charging strips 17, 17' therein just downstream of the thickest portion of the airfoil. If the voltage applied between the charging strips and the chafo electrode 29 were increased sufiiciently; or if the electrode spacings were not everywhere equal, within the usual dimensional tolerances, then current density imbalance may occur. To avoid this it is sometimes preferred to utilize the balast resistor network hereinafter described. The conducting strips 17, 17 are connected by balast resistors 18, 18 (see FIGURE 3) to a common lead 19 within the airfoil element. A function of this structure is to equalize the current per unit cross section of the array. When the charging voltage is applied between the charging strips 17, 17' and the chafo electrode 29, little or no current will reach the charging strips. However, if more than a little (say 1%) of the current density of the power converter is diverted at any place to one of the charging strips 17, 17, then a voltage drop occurs in its balast resistor which limits such current. This tends to equalize the current density taken from each area of the array.

When the charging electrode 17 is at a suitable potential relative to the chafo electrode 29, the aerosol formation and charging processes herein described occur in the chafo region 40. For example, the electrode 17 may be at +3 kv. relative to the chafo electrode 29, which may be at zero or ground potential.

The mobility of the charged particles 44 in the conversion region of the nozzles 41 must have approximately the optimum value. During the formation of the charged aerosol particles 44, there exists only free electrons, negative ions, or charged particles of relatively large mobility. In the chafo region 40, the ions or just-formed small charged aerosol particles have a mobility from 10 to 10 times greater than the larger charged aerosol particles in the conversion section of the nozzle 41.

The collector section The charged aerosol particles are discharged at the exit plane 52 of the conversion (nozzzle space 41. Since they now carry no charge, they areTfo longer affected by the electric field. In some cases these uncharged particles are unstable and evaporate to form a vapor in the carrier gas. The current flow in the discharge region is conducted by positive ions emitted from the point electrodes 33 which discharge the charged aerosol particles at the exit plane 52. These positive ions traverse the region at the exit plane 52. These positive ions traverse the region 46 rapidly because of their relatively large mobility. The charged particle 47 at the exit plane 52 of the conversion space 41 is shown as it is being discharged by a positive ion 48 from the point electrode 34 (see FIGURE 3).

In the conversion space 41, the large space charge density causes a substantial increase of electric potential in the downstream direction. On the other hand, in the charging region 40 and in the discharging region 46, there is little electric potential buildup due to space charge density. Charge density in coulombs/m. is equal to current density in amps/m. divided by velocity in m./ sec. Except for slight leakage currents, the current is the same across each of the regions 40', 41 and 46. However, the mobilities and velocities of the ions in the regions 40 and 46 are large, compared to the conversion region 41 where the charged aerosol particles in the carrier gas have a relatively small velocity. It follows that the charge densities are small in the charging region 40 and discharging region 46; and that the charge density is large in the conversion region 41. Hence there are small potential gradients in the regions 40 and 46, but there is a large potential gradient between entrance plane 51 and the exit plane 52 of the conversion region 41.

Ions are emitted from the point electrode 34 to discharge the charged aerosol at the exit plane 52. The space charge of the negatively charged aerosol in the conversion space 41 results in a large negative potential, at the exit plane 52. For example, referring to FIGURE 3, =--53 kv. The current I produces a potential difference =I R across the load resistor 50, which has a resistance R, and a potential difference between the collector point and the potential due to the charged aerosol at the plane 52. The potential difference is of the order of 3 kv., causing an ion current emission from point 34 sufficient to continuously discharge the charged aerosol moving across the exit plane 52. Most of the generated potential difference appears across the load since In this example =-50 kv.

The charged aerosol particle By supersaturated vapor, there is herein meant a vapor in that condition in which it is capable of condensing upon an electrically neutral aerosol droplet. A superheated vapor is one in which an electrically neutral droplet will evaporate.

Under superheated conditions electrically neutral liquid droplets evaporate. However, charged aerosol particles form by condensation from a vapor onto a charged ion or droplet even under superheated vapor conditions. Hence the electrically charged aerosol particles are more stable than electrically neutral particles. Consequently charged aerosol particles may form and grow in the chafo region and exist in the conversion space, all in slightly superheated vapor; then evaporate to again form vapor dispersed in the gas stream, after being discharged in the collector region.

Alternatively, it may be preferred to operate the chafo region and the conversion region in the supercooled vapor state to increase the electric breakdown strength of the charged aerosol gas. Superheated vapor may then be subsequently introduced into the stream after passing the collector region to evaporate the neutralized liquid droplets.

The potential at the charging electrode 17 is maintained by a potential source 51 which is connected between the grounded chafo electrode 30 and the electrode 17. The current required to maintain the charging voltage at the charging electrode is negligible compared to the current emitted by the chafo electrode 30 and collected by the collector electrode 34. This is because the electrons or negative ions emitted from the chafo electrode, for the most part, never reach the charging electrode 17 Instead, these ions or electrons are captured by the condensing vapor and form charged aerosol droplets of very small mobility and which are, therefore, carried by the gas stream into the conversion region 41. In the conversion region, the charged aerosol particles react with their own space charge field, and the field provided by the charging electrodes, and power is extracted from the charged aerosol-gas by a decrease in velocity or temperature or both. Thereafter the charged aerosol particles are discharged at the end plane 52 of the conversion space 41, for example, as shown at 47, by positive ions of large mobility such as 48 emitted from the point source 34.

The corona electrode The chafo corona electrode 29 may be a hollow needle, not shown, or one or more thin tubes 30 having a series of minute holes 22 therein. The very small holes required may be drilled by an electron beam technique. Within the tube 30 there is maintained a superheated vapor 23. The superheat is at a suitable temperature above that of the gas stream 15. The tube 30 provides a jet of vapor indicated by the arrow 48 whose kinetic power is added to the gas stream 15. In certain devices, according to this invention, the kinetic power of the jet equals the friction power loss plus the converted electric power. Ions from the corona field form about the tube 30'. These ions form nuclei on which to condense vapor in the jet 48 forming the required charged aerosol droplets 44.

The gas stream 15 is preferably operated at subsonic velocity. A large expansion of the carrier gas stream 15 is not required to produce the condensation. Instead, vapor condensation onto charged ions or droplets is produced by a temperature drop caused by the conversion of the thermal power of the superheated vapor 23 into the kinetic power of the jet streams 48, which provides additional kinetic power to the gas stream 15. Only a small proportion of the gas mass, of the order of 10 parts, is required to provide sufiicient liquid for the charged aerosol droplets. Hence a large temperature drop may occur in the vapor jets 48, which constitutes only a small proportion of the flow, with little change in the temperature and pressure of the main flow and little effect on the overall thermodynamic efliciency.

The charged aerosol jet pump The charged aerosol jet constitutes a novel jet pump which efliciently transfers its kinetic power to the gas stream without the inefiiciencies normally due to turbulence. No ordinary jet pump does this. In the ordinary jet pump, the mixing of a jet with a slower gas stream is accompanied by boundary turbulence, and the transfer of kinetic power from the jet to the gas is accompanied by excessive frictional power loss.

However, with the present invention, the supersaturated vapor in the jet condenses upon ions forming charged particles of small mobility, intermixing with, and entrapping the gas. The kinetic power of the charged aerosol jet is efficiently transferred to the gas stream without the usual turbulence. Therefore, the charged aerosol jet pump has a greater efficiency than obtainable with an ordinary jet pump. In this invention, the charged aerosol jet pump may be used to advantage to provide additional power to the gas stream.

The jet aerosol transducer The operation of the device shown in FIGURE 3 is as follows: The superheated vapor is introduced at a temperature and pressure such that, on passing through the holes, high velocity jets of electrically supersaturated vapor are formed whose temperature and pressure is about the same as the temperautre of the flowing gas 15. Very small liquid drops 21 are first formed around the ions produced by the corona field about the pipe electrode 30. These charged drops initially have a radius smaller than that required for their operation as an efficient power transducer. However, as the vapor jets mix with the charged droplets, additional vapor is condensed thereon in the liquid state, thereby increasing the radius of these charged drops. FIGURES 3 and 4 show charged drops 21 having a small radius when first formed close to the openings 22. Exposed to the supersaturated vapor 23 from the jet 48 the charged droplets increase in radius until just prior to entering the conversion space. With the increase in radius, and with no additional charges added, the larger droplets 44 perform as efiicient power transducers in the conversion space 41 and are discharged at the eXit plane 52 by the electrode 34. External means (not shown) are provided for causing a flow of gas 15 through the conduit 10. The gas 15 preferably has a low molecular weight and a high electrical breakdown.

The velocities of the gas 15 in the duct 10 is preferably subsonic. Suitable velocities range between 300 to 500 m./sec. This corresponds to 0.3 to 0.6 Mach for a low molecular gas such as hydrogen or helium. As an example of a low molecular weight gas composition having large electric breakdown characteristic we may employ the following range of compositions:

TABLE I.COMPOSITION OGIlIHE CHARGED AEROSOL- Gas Symbol Parts by Molecular Weight Weight Hydrogen O-50 2 Helium He 0-50 4 Condensable Vapor and Aerosol Droplets 10- -20 Electron or Ion Scavenger-gas or Vapor 1-20 Total The scavenger gas should be non-reactive with the condensable vapor employed or may be identical therewith. For example, the scavenger gas may also be a condensable vapor such as water or alcohol. As another example, diphenyl chloride having appreciable vapor pressure at the operating temperature may be employed to form a charged aerosol droplet, and the vapor will also act as a scavenger gas. Water vapor is similarly useful. In other cases the scavenger gas is different from the condensable vapor, for example water vapor and chlorine gas.

The charged aerosol droplets produced by the electro' jet process may have too large a mobility because for a given charge the radius of the charged particles was too small.

This invention provides a soltuion to this problem by providing a supersaturated vapor in the vicinity of a charged aerosol particle which may be initially formed by the electrojet. The supersaturated vapor condenses onto the charged aerosol particle and increases its radius until a charged particle having the optimum mobility is attained.

In the condensation process, as previously practiced, the gas entering the converter contained unsaturated superheated vapor or a carrier gas with vapor. Upon expansion of the gas in the nozzle, the vapor was strongly cooled and became supersaturated and condensed upon ions present to form charged aerosol droplets.

With steam normally considered to be in the condition of superheat, condensation will nevertheless occur upon charged ions or charged aerosol droplets. For example, in superheated steam at about atmospheres pressure, the condensation upon ions or charged droplets is more rapid as the degree of superheat is decreased from say +60 C. towards saturation or 0 C. superheat. The greater the superheat the smaller are the charged particles produced, and the mobility of these particles may be too great for useful power conversion. Therefore, it will be generally preferred to Work under conditions of slight superheat, saturation or supersaturation such that effective condensation occurs to produce charged particles of the required small mobility.

The improved condensation techniques described herein differ from the condensation technique above described in that the required supersaturated vapor is provided by the vapor jet issuing from orifices in the immediate vicinity of the ions produced by the corona, while the main gas stream may contain the vapor under slightly undersaturated conditions. The gas which is moving at subsonic velocity undergoes only change in velocity and/ or temperature in the airfoil section 16 corresponding to the power converted. No temperature drop is employed without a corresponding extraction of electric power.

Electrojet ccmdensationv power converter FIGURE 4 shows a detail view of a power converter according to this invention, for a combined electrojetcondensation process. In this figure the tube 11 is preferably made of 'micro tubing, of the order of 0.1 mm. ID. and 0.2 mm. O.D., having orifices 12 of the oder of 0.02. mm. in the tube wall in a line parallel to the tube axis. The tube 11 is connected to a source of liquid (not shown) under pressure, which is emitted in jets of liquid through the holes 12. These liquid jets form a spray of charged liquid particles 13 under the influence of the electric field and the gas flow.

A second tube 14, mounted upstream from the tube 11, carries a superheated vapor. The vapor is expelled through a plurality of holes 22 in tube 14. The diameters of the tube 14 and the holes 22 which emit the vapor may be larger than the corresponding diameters of tube 11 and holes 12. The vapor jets 21 issuing from openings 22 in the tube 14 have a velocity somewhat greater than the velocity of the gas stream 15.

Electrodes 17, 17' positioned downstream from tubes 11 are mounted on the airfoils 16, 16'. The charged aerosol particles are entrained in the gas flow between the airfoils 16, 16. One or more collector electrodes 33 are mounted downstream from the exit plane 52 and connected to a load 20.

The operation of the device as shown in FIGURE 4 is as follows: Tube 14 which contains a superheated vapor, emits a jet 21 of supersaturated vapor into the gas stream 15 at a velocity somewhat greater than the gas velocity. The superheated vapor jet 21 from tube 14 decreases in temperature and in enthalpy which is efficiently converted into kinetic power, and transfered to the total gas-vaporaerosol flow in the duct 10. The jet 21 is in a supersaturated state, and deposits liquid on charged ions or droplets in the chafo region 40, further downstream.

Utilizing the electrojet process, tube 11 discharges a liquid jet of small diameter which breaks up immediately into small charged aerosol particles 13. With the electrojet process, as the electric field intensity is increased, the charge increases and the radius of the charged particles decreases. When these charged particles are first formed, their radius is too small in relation to their charge. However, according to this invention, the supersaturated vapor jet 21 deposits additional liquid on each charged particle, increasing the radius. The final radius of the charged particles at the entrance plane 51 of the conversion space 41 may be controlled by a number and diameter of orifices 16 per unit length of the tube 14, and the temperature and pressure of the superheated vapor 23 in the tube 14, as well as the temperature, pressure and velocity of the flowing gas 15, as Well as other factors known to control the charged aerosol produced by the electrojet process at 13. A suitable choice of these control factors enables an optimum ratio of radius to electric charge to be attained.

The charging electrodes Referring to the charging electrode 17, 17' shown in FIGURE 3, it is neccesary to maintain a uniform ion emission from the corona field created about electrode 30. Variations in the distance of electrode 30 from the electrode 17 induce a greater current discharge from portions of the electrode 30 closest to the electrode 17. To produce a balanced or uniform emission from the entire length of the corona electrode 30, it is preferred to utilize a plurality of spaced resistive strips 18, 18 attached to central electrode 19 within the insulating airfoil section 16.

As an example, the corona electrode emits 30 microamperes/ mm. of length, the leakage current to electrode 17 is 0.1 microampere/mm., the resistors 18, 18 have a resistance of 10 ohms/mm. length of the airfoil section, and the potential difference between the charging electrode 17 and the electrode 30 is 2 kv.; then, the potential difference across the resistors 18, 18' is 1 kv., and the total potential difference from the electrode 30 to the common lead 19 is 3 'kv. Any increase in current through resistors 18, 18 over any portion of the length of the airfoil, produces a greater potential difference locally across one of the resistors. This tends to reduce the potential difference between the charging electrodes 17, 17' and the electrode 30, and thus decreases local current emission. Thus, while the resistors 18, 18 have negligible power dissipation, they self-regulate and make uniform the emission of ion current per unit length from the corona about the electrode 30.

The resistors 18, 18 may comprise a continuous strip placed between the outer conducting strips 17 and the lead conductor 19. The resistors 18 may have a resistance per unit length. This simplifies the construction. Alternative to a fixed resistance we may employ a non-linear ballast resistor.

The resistance of the ballast resistor 18 is a function of the current. A voltage drop is thereby produced which is a non-linear function of the current. Ballast resistors are known in the art in which the resistance drop is for example in proportion to the fifth power of the current. This tends to produce a more sharply limited maximum current through the resistor and produces better regulation.

At the discharge end of the conversion space, the discharge current emitted from the collector points 34 is also self-regulating. If the charged aerosol which passes the exit plane were not neutralized by the local positive ion point source, then the charge density would increase with a buildup of space potential at the exit plane, and cause "an increase in the potential difference between the exit plane and the collector points, and an increase in the ion emission from the nearest collector point. This eifect tends to insure the uniform and complete discharge of the charged aerosol passing across the exit plane by the collector points.

FIGURE shows another form of aerosol formation and charging device which, for example, may be employed in lieu of the tube type 30 charging electrode 17, 17' in FIGURE 3 or in lieu of the tube 12 and charging electrodes 17, 17 in FIGURE 4.

In FIGURE 5 an insulating cylindrical tube 60 or airfoil (not shown) has an axis XX', along which is placed a thin wire, such as a tungsten wire 61. The wire may be coaxially supported within the tube 60 by, for example, spiders 62. Along the outer surface of the tube 60 and along the line parallel to the axis X-XX' there are a series of minute holes 63, 63a, etc. On the outer surface of the tube 60 there is a conducting strip 64 which serves the function of a charging electrode. The interior of the tube 60 contains a superheated vapor 65. Upon issuing from the holes 63 the vapor is supercooled. The vapor 65 along with charged ions issues from the intern-a1 corona produced by the wire 61, through the holes 63, 63a, etc. forming a wedge shaped beam 66 of charged liquid particles 67.

The operation of the device will be understood from previous descriptions in connection with the operation of the corresponding structures shown in FIGURES 3 and 4. The advantage of the device shown in FIGURE 5 is that the charging electrode and the wire 61 which provides ions by corona discharge, are all contained within a single simple structure and the ions are thus intermingled within the shortest distance and most concentrated manner possible within the emerging superheated jets.

The holes 63, 63a can vary in diameter from 1-100 A. microns and may be spaced from each other in any suitable manner, to provide the required mass flow of charged liquid particles relative to the mass flow of the carrier gas 15. The charged aerosol particles 67, 68 quickly disperse by mutual repulsion and intermix intimately with the carrier gas 15. The conducting charging strips 64 may be a metal strip deposited in the form of a plating upon the outer surface of the insulating tube 60. The connection to the conducting strip 64 is to the potential source 51 (see FIGURES 3 and 4) and the wire 61 is grounded.

An advantage of this device shown in FIGURE 5 is that the airfoils 16 downstream of the chafo device no longer require conducting strips and may be constructed entirely of insulating material. This greatly simplifies the construction and is a particular advantage when the entire assembly must be miniaturized.

In FIGURE 6 the curve A is for the electrojet process only; not the combined electrojet-condensation technique described herein in connection with FIGURE 4. The curves A and B are calculated for ambient conditions.

In FIGURE 6 curve A shows mobility versus particle radius calculated for the electrojet process. Curve A was calculated for larger diameter liquid jets by equating the surface tension forces tending to hold the drop together to the electric forces tending to tear the drop apart. This limiting condition is called the Raleigh limit. The corresponding mobility was calculated from the Stokes Cunningham or Millikan equation. These calculations show 12 a minimum mobility of about 10 m. /volt-sec. This mobility is too large for efficient power transduction.

However, using the electrojet process, with ultrathin jets of liquid issuing from very small holes, large particles with a single charge having an optimum mobility can be produced. Since tubes with such small holes are difficult to make, it is preferred to employ another process according to this invention, in which the condensation process is combined with the electrojet process to produce particles of optimum mobility. The elfect is to displace the curve A to the left so that the mobility is now less than 10* m. volt-sec.

Curve B in FIGURE 6 refers to singly charged particles commonly produced using the condensation method. Under certain conditions of operation, as previously practiced, for example with single charges in superheated steam, the radius of the charged particle which is formed may be smaller than that shown on the graph and the mobility is decreased to less than 10- m. /volt-sec.

With the novel condensation process of this invention, the radius of the charged particle is increased and the mobility is decreased to less than 10 m. /vo1t-sec.

In this example, utilizing the improved condensation process and the device of FIGURE 3, with water vapor and air; with a current density of 10 amps/m a velocity of 300 m./sec.; a gas density of about 9 times ambient, or 11.6 kg./m. the charge density in the conversion space is 0.033 coulombs/m. the length L of the conversion space is about 7.4 mm. and the converted power density is 1 megawatt/m2.

This data is summarized in the following table:

TABLE II.-0PERATING CHARACTERISTICS OF A CHARGED AEROSOL GENERATOR WITH A WATER-AIR AEROSOL Variable Symbol Value Units Potential 5 100,000 Volts. Power Density Converted p 10 Watts/m. Charge Density p 3.3X10' Coulombs/ni. Velocity of Gas-Aerosol. U 300 mJsec. Density of Gas-Aerosol 5 11.6 Kglm. Length of Conversion Space... L 7. 4X10- M. Particle Radius r 2X10 M.

Charges per Particle N 1 Charge per Particle Ne 1.6)(10- Coulomhs.

The values in Table II are illustrative only and not limiting.

The principles may be applied to design charged aerosol generators having multiple stages in which power is extracted successively from a gas stream. Using the example of Table II, and with 50 such multiple stages per meter length of the converter, the power conversion concentration is 50 megawatts/m Similar results may be obtained with the combined electrojet-condensation process shown in FIGURE 4. However, in this case the number of charges and the radius of the particle are each greater, but their ratio is the same as in the previous case.

In the electrojet methods, as heretobefore practiced, liquid jets having a diameter of the order of microns, were utilized, and it was primarily the electrical forces which caused the disruption of the jet into charged particles having radii of the order of 1 micron, averaging about 12,600 charges per particle.

The particle radius and charge is determined by the well known Raleigh limit, which requires an electric potential difference between the jet orifice and the charging electrode of the order of 2,000 volts.

Curve A in FIGURE 6 shows that the mobility of the charged particles produced solely by electrical disruption, greatly exceeds the optimum due to the presence of too many charges upon the particle.

In another process according to this invention, ultrathin liquid jets of the order of 1 micron in diameter are employed. These ultrathin jets require little or no electric force to break up into particles of the order of 0.5 micron in radius. The ultrathin jets are disrupted by the M=Mach number.

mechanical forces between the jet and the flowing gas stream, and the surface tension of the jet itself.

Under these circumstances, a small potential difference of the order of one hundred volts applied between the ultra thin jet orifice and the charging electrode, will introduce a controlled small number of charges; thus forming charged aerosol particles of optimum mobility.

The advantage of this technique is that no vapor need be employed. The particles are instantaneously charged and formed and have the optimum mobility without the requirement for further accretion of condensed vapor.

The ultrathin electrojet method may be used with other power conversion devices such as that shown in FIGURE 3. In the case of FIGURE 3 a liquid is substituted for the superheated vapor within the tube 30.

Any of the devices disclosed herein may be used for producing charged aerosol particles for other applications. In certain cases the collector electrodes may be omitted. For example, positive and negative aerosol forming devices may be arranged to mutually discharge each other. In other uses, the ground may be used as the collector electrode and the other electrode potentials arranged accordingly. Positive charged aerosols may be used instead of negative charged aerosols without departing from the scope of the invention.

Table of symbols a =1.74 A b- :552

b=Relative breakdown electric intensity for any gas relative to hydrogen under standard conditions.

b =Breakdown electric intensity for hydrogen under standard conditions.

b =Breakdown electric intensity for air under standard conditions=3.08 X 10 volts/m.

b =Relative breakdown electric intensity for any gas relative to air under standard conditions.

c =Sonic velocity for hydrogen at standard conditions (meters/sec).

D=Molecular diameter (meter).

D =Molecular diameter of hydrogen (meters).

E =Electric breakdown field intensity (volts/meter).

e=Electronic charge=1.60 10 coulombs.

e =Permittivity of empty space=8.85 10 f=(D/D =molecular cross section relative to hydrogen.

'y=Surface tension of liquid drop newtons/ 1T1.

K=Relative electric breakdown field intensity for any moving aerosol. This value is normalized with respect to breakdown field intensity for the gas component of the aerosol taken at static standard conditions.

k=v/E; mobility (meters /v0lt-sec.).

Standard conditions T0=300 K. P0=105 newtons/mf Mathematical-physics analysis A mathematical-physics analysis follows, in which radius r of the charged droplet for efiicient power transduction between the moving gas and the electric field is determined as a function of various operating parameters.

The mobility k of a charged particle moved with a velocity v through a gas by an electric field of intensity E is, by definition:

k=v/E (1) The Stokes-Cunningham equation is:

k=(Ne/1rp.r) (1+0.87)\/r) (2) k: u/E (3 The gas velocity u may be expressed in terms of M the Mach No. of the gas; the sonic velocity 0 of hydrogen gas H at standard conditions, the absolute temperature T and m the atomic or molecular weight of the gas:

The mobility k may be expressed in terms of the operating conditions, by substituting (4) and (5) into (3):

According to the kinetic theory of gases the viscosity ,u may be expressed in terms of ,u the viscosity of H under standard conditions:

While Sutherlands formula is more accurate, formula (7) is sufiiciently accurate and is preferred because the derivations hereinafter are simpler.

According to the kinetic theory of gases, the mean free path may be expressed in terms of X 0 1 f a.) 1 f a) In (2) let:

r =r (9) Then (2) may be readily solved for r r (0.87Nex/61r k) (10) Multiplying by r, and using substitutions (l0) and S, Equation 2 may bewritten:

A plot of 0 versus S is shown graphically in FIGURE 6.

To evaluate r in terms of standard conditions for hydrogen gas H substitute for k, ,u and A from (6), (7) .and (8) respectively into (10) and simplify:

r ={[0.87)\ b /61rp. c ][lJNK/ MT (14) Let X: [liNK/ MT where X is an operating parameter. Also let:

r =[0.87eb /61r,u c (16) Making substitutions (l5 and (16) into (14) r =r X 7) Evaluate S in terms of standard conditions for hydrogen 15 gas H using (8) and (17) for A and r respectively, and then simplify using a Equation 12 may be written in terms of (13), (16), (17) and (18):

Applying conditions (30) to general equation (19):

r=r X=r (bNK/ MT,,) for X51 (31) Hence, for small values of 5 r is approximately inde- 5 pendent of molecular diameter and gas density.

Case II 50:2/5 ii1=2/S Applying conditions (32) in general Equation 19:

r: (2r /1.74)\ X 6 1420 xfX 5,,(m) (33) Restrictions A TABLE III.PHYSICAL CONSTANTS OF HYDROGEN GAS UNDER VARIOUS CONDITIONS Parameter Symbol Value Units Temp., K.

Viscosity a 8. 7 10- Newton-see/mfi. 288.0 Mean Free Path 1. 18X10 288.0 Sonic Velocity e 12 Breakdown Electric Intensity Relative to Air.. 0,

This data has been converted to standard conditions in Table IV.

The values of a A c and b are computed using:

a varies as x/T from (7) (20) varies as 1/a,, or as T /p from (8) (21) c varies as x/T (22) The breakdown electric intensity for hydrogen gas under standard conditions is:

b =b b where b =0.65 (23) Restriction (34) follows from the definition of optimum mobility. Restriction (35) is a reasonable choice that facilitates calculation:

TABLE IV.PHYSICAL CONSTAN'IS FOR HYDROGEN GAS FOR STANDARD CONDITIONS Parameter Symbol Value Units Viscosity m 8. 89 10- Newton-secJmfi. Mean Free Path. M 1. 24X10- Meters. Sonic Ve1ocity c 1.33X10 Meters/sec. Breakdown Electric Field Intensity b1 2. O0X10 Volts/m.

The value of r is computed using the data of Table From (37) the values of X may be computed for cor- IV in (16).

r =3.91 10- meters (24) Having A from Table IV, and r from (24), the value of a is:

Evaluating S in (18) from (25):

Evaluating r by putting the value of M from Table IV into (19):

r: (2.16x 10 t/5, (meters) 27) The radius of the singly charged particle may be expressed in terms of angstroms:

responding values of bK:

Case I with restrictions A From (31) and (37):

r=10r (bK)" N (39) r =39.1(bK) N" (Angstroms) (40) Case II with restrictions A From (33) and (37):

r =14.2fn(bK6 (Angstroms) (41) For hydrogen gas, with singly charged particles:

r =14.2bK8 (42) Case II, Formulae 41 and 42, are useful approximations only for 6 100. Values of S usually fall between the extremes of Cases I and II. In most cases it is, therefore, best to use Equation 19.

Case I, Formula 31, may be used for values of relative density less than 5; and Case II, Formula 33, may be used for values of relative density of or more.

17 The following Table V which shows (r/N) versus 5,, was computed from the general Formula 28 for hydrogen as a carrier gas for the various given values of the operating parameter X.

TABLE Tr-RELATIVE DENSITY VERSUS THE RADIUS OF A SINGLY CHARGED PARTICLE X MI 0.. s r1.

5.52 10.0 43 10.00 5.52 47 27.00 2.0 05 55.2 1.0 05 100. 00 0. 552 140 1, 000. 00 0. 5552 1, 420 4 1.00 27.0 80 2.00 10 0.110 00 10.00 2. 70 0. 518 112 20.00 1.38 1.42 153 27. 00 1. 00 2. 414 189 35. o 0. 789 3. 05 225 55. 20 0. 5 s. 47 022 100. 00 0. 270 20. 7 550 1, 000. 00 0. 0270 2, 020 5, 000 50 0 1 18.4 120 1.24 10 0.110 100 10. 0 1. s4 0. 013 107 12.4 1. 2.414 283 36.8 0.5 8.47 408 55. 2 0. 33s 15. 5 725 100 0. 184 50. 7 1. 200 500 0. 030a 6,380

In FIGURE 8 there is shown radius r of a singly charged particle versus relative density 6 computed for values of X=10, 2 0 and 30 corresponding to values for bK=l, 4 and 9 respectively.

The dashed line p on FIGURE 8 is for a power density of 10 watts/m. utilizing a hydrogen water aerosol. For Composition N o. l, a hydrogen water aerosol; b, the molecular weight relative to air is 0.07, the electrical breakdown field intensity relative to hydrogen is 1.0, and K, the electrical breakdown strength of the charged aerosol relative to the carrier gas is taken as 1.0. For composition No. 2 which is composition No. 1 inhibited with a scavenger gas corresponding values are 0.07, 2.0 and 1.0. For Composition No. 3 which is the same as Composition N0 2 but supercooled, the corresponding values are 0.07, 2.0 and 3.0.

TABLE VI.OPERAIING PARAMETERS FOR CHARGED AEROSOLS OF VARIOUS COMPOSITIONS The data is plotted and points from this data are plotted and numbered according to the composition number and VARIOUS CARRIER GASES-VISCOSITIES OF GASES ARE NORMALIZED TO 300 K.

Carrier Gas Viscosity newton, 4 /1 1 1 sec./m.

1 237x10- 2. 24 0. 635 0 84X10 1. 00 1.00 2. 60x10 3. 00 1. 6

Case 1 above shows the particle radius is independent of cross section for small values of relative density 6 However, Case II shows that for larger values of relative density 6,, the relative molecular cross section is an important factor in computing the radius of the charged particle.

For example, for steam in which 6,, exceeds 100, the radius r in FIGURE 7 must be multiplied by 1.6. However, the Table VII shows that helium has a cross section of 0.635 compared to hydrogen. Therefore, radius r for helium for values of relative density exceeding is only 62.5% of that shown in FIGURE 7. I-Ielium is, therefore, the preferred carrier gas where for eificient operation, charged particles of the smallest radius are required. Hydrogen, however, may be preferred when other factors are considered.

The following table summarizes the limits on the operating parameters:

To compute charge per particle, and charge to mass ratio for a water drop produced by electrical disruption, the Raleigh limit for the maximum charge for a stable sphere of radius r is used:

'y, the surface tension of water is 0.073 newtons/m.

Hence for a Water the charge to mass ratio is:

q =4.8 F coulombs/kg. (44) The number of electrons per drop is given by:

In Equations 44 and 45'r is expressed in microns.

The number of charges on a multiply charged particle having a radius of 1,0. -for the charged particle to have the optimum mobility may be computed from FIGURE 7:

r/N=350 A. per electron charge or 28 electron charges per drop of 1 4 radius.

According to Equation 45, upon disrupting a sphere to a radius of 1,0 or 10 A., approximately l.26 10 charges remain on the particle. In such case r/N=0.81 A. per electric charge, which is too small. FIGURE 7 shows that to achieve optimum mobility it is required that: rNs350.

However, the electrojet process, modified to use ultrathin jets which are charged to a controlled low voltage,

provides the 28 charges on a 1n radius droplet required to achieve optimum mobility.

The above analysis has been presented for the optimum mobility conditions defined by the slip factor oc=0.01; or for a charged particle having a slip velocity of 1% of the velocity of the carrier gas with an electric field intensity near breakdown.

An important feature of this invention is the establishment of a useful operating range by control of the parameter X. For X =10, or a particle radius of about 350 A. is required for a power density of 10 watts/m1 However, charged particles having much smaller radii may be used if the parameter X is decreased to 5, 3 or 2.

To decrease the parameter X, there may be employed a slip factor increased to 10%; smaller values of breakdown electric field intensity to bK=1, and larger values of MT to 2.5 may be employed.

FIGURE 8 shows curves marked X =5, 3 or 2 in which the charged particle radii is much decreased.

The following is an example of operating parameters for which X =2:

Hydrogen gas as a carrier f=1 Slip factor 10% oc=0.10 Mach No. M=0.5

Certain liquids such as water, alcohol, etc. are known to be molecular electric dipoles; that is, have an electric dipole moment. The ion first attaches to one of these molecular dipoles, and then other molecular dipoles quickly attach. When the charged liquid droplets are brought into an electrical field, the molecular dipoles are oriented; the charged liquid drop increases in free energy, decreases in entropy, and decreases in temperature. The orientation of the molecular dipoles in a charged water drop decreases its absolute temperature about 36%; whereupon the oriented dipole molecules lose their ability to re-evaporate. Vapor molecules striking the charged aerosol droplets are captured, become oriented in the electrical field. The charged aerosol droplets thus continue to grow.

The electric field intensity increases from the charging space to the conversion space. As the charged aerosol liquid droplet traverses the conversion space in a generator, the repelling electric field intensity decreases. The radius of the charged droplet stops growing and reaches equilibrium at optimum mobility. The particles have an optimum mobility during their traverse of the conversion space. Beyond this point the electric field intensity decreases further until it is zero at the collector plane, the molecular dipoles in the liquid drop disorient, the temperature of the charged drop increases, and the drop becomes smaller in radius as it evaporates. Hence ions from the collector preferably discharge the charged aerosol particles just before they start to evaporate. Upon discharge, the molecular dipoles are disoriented, the neutral droplets suddenly increase in temperature and rapid evaporation of the droplet occurs. The droplet liquid returns to the vapor phase within the carrier stream.

The condition of the carrier gas and contained vapor is now the same at the exit as at the entrance to the electrical converter device. Hence electrical converter devices may be placed one after the other in the gas stream and by staging, additional power may then be extracted from the carrier gas.

In the case of a pump, the power from the electrical circuit is transduced, producing an increase in pressure and temperature of the moving gas. In a pump, an accelerating electric field is applied to the charged droplet in an electrical converter section similar to that previously described. In this case the electric field intensity increases from a minimum at the entrance to the conversion space, to a maximum at the collector electrodes, and the charged aerosol particles continue to grow until discharged at the collector plane, after which they may evaporate as described above. Staging may also be used to increase the buildup of pressure and temperature differentials.

Summarizing, an optimum range of particle radius has been set forth. The corresponding parameters have been established. Various methods of accomplishing suitable ranges of electric charge and particle radius have been set forth. These comprise the several modifications of the condensation method, electrojet method and a combined condensation electrojet technique.

The parameters of operation may be chosen in accordance with the operational requirements; the methods of charging and forming the aerosol may be chosen from amongst the various methods disclosed herein; and the device may be constructed according to any of the various devices illustrated and described herein, all without departing from the scope of this invention.

Having thus fully described the invention, what is claimed as new to be secured by Letters Patent of the United States is:

1. A device to convert the heat kinetic power of a moving gas to electric power output comprising a conduit, a moving gas under presure in said conduit, means comprising a tube having a plurality of nozzle-like holes therein within the conduit to emit supercooled vapor jets into the gas at a temperature pressure and velocity somewhat greater than that of the gas, ionizer means within the conduit to form ions in an electric field in the region of the supercooled vapor, whereby the vapor will condense upon said ions to form minute charged droplets, and whereby the vapor will further condense upon the said minute charged droplets to form a charged aerosol having larger droplets, a conversion space having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, a collector electrode at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrode and the ionizer.

2. A device to convert the heat kinetic power of a moving gas to electric power comprising a conduit, a moving gas in said conduit said gas containing a condensable vapor having a low mean molecular weight, high electrical breakdown, a velocity of the order of 300 to 1000 m./sec., and a pressure exceeding one atmosphere, means within the conduit comprising a tube having a plurality of nozzle-like holes therein to emit jets of supercooled vapor into the gas at a temperature pressure and velocity somewhat greater than that of the gas, ionizer means within the conduit to form ions in an electric field in the region of the supercooled vapor, whereby minute charged droplets will condense upon said ions, and whereby the vapor will further condense upon the charged droplets to form a charged aerosol having larger droplets, a conversion space having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, a collector electrode at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrode and the ionizer.

3. A device to convert the heat kinetic power of a moving gas to electric power comprising a conduit, a moving gas under pressure in said conduit, a condensable vapor in the gas, means comprising a first tube within the conduit connected to a source of conductive liquid under pressure and having a plurality of spaced openings therein to eject liquid jets, means to apply an electric field to said jets, whereby said jets form minute charged droplets, a second tube carried within the conduit upstream of the first tube, said second tube being connected to a source of superheated vapor under pressure and having a plurality of spaced openings therein whereby supercooled vapor issues from the said second tube at a velocity approximating the velocity of the gas, whereby the supercooled vapor will condense upon the minute charged droplets to form a charged aerosol having larger droplets, a conversion space having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, a collector electrode at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrode and the liquid source.

4. A device according to claim 3 in which th tube openings are of the order of 1 to microns in diameter.

5. A device to convert the heat kinetic power of the moving gas'to electric power comprising a conduit, a moving gas under pressure in said conduit, a condensable vapor in the gas, means comprising first tube electrodes within the conduit having a plurality of spaced openings to emit a supercooled vapor jet into the gas stream at a temperature, pressure and velocity somewhat greater than that of the gas, means within the conduit comprising a plurality of spaced insulating airfoil members having conductive strips thereon and disposed downstream of the tube electrode, a source of electrical potential connected between said strips and said tube electrodes to form ions in an electric field in the region of the vapor, whereby the vapor will condense upon ions to form minute charged droplets, second tubes within the conduit upstream of the first tubes, said second tubes being connected to a source of superheated vapor and having a plurality of spaced openings therein whereby supercooled vapor issues from the said second tubes at a velocity approximating the velocity of the gas, whereby the supercooled vapor will condense upon the said minute charged droplets to form a charged areosol having larger droplets, a conversion space between said airfoil members having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, a collector electrode at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrode and the first tube electrodes.

6. A device to convert the heat kinetic power of a moving gas to electric power comprising a conduit, :1 moving gas under pressure in said conduit, a vapor in the gas, pipe electrodes within the conduit having a plurality of spaced openings to emit a supercooled vapor into the gas stream at a temperature, pressure and velocity somewhat greater than that of the gas, a plurality of spaced insulating airfoil members within the conduit and disposed downstream of the pipe electrodes, conductive strips on said airfoil members, a central electrode within the airfoil members, a resistive strip between each of the conductive strips and the central electrode, and a source of electrical potential connected between said strips and said pipe electrodes, whereby ions are formed in an electric field in the region of the vapor which condenses upon said ions to form minute charged droplets, second tubes within the conduit upstream of the first tube, said second tubes having a plurality of spaced openings and connected to a source of superheated vapor, whereby supercooled vapor issues from the said second tubes at approximately the velocity of the gas and condenses upon the said minute charged droplets to form larger charged droplets, a conversion space between said airfoil members having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, collector electrodes at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrodes and the pipe electrodes.

7. A device according to claim 6 in which the resistance comprises non-linear ballast resistors.

8. A device to convert the heat kinetic power of a moving gas to electric power comprising a conduit, a moving source of gas under pressure in said conduit, a vapor in the gas, means comprising dielectric tube disposed normal to the longitudinal axis of the conduit, said tub connected to a source of superheated vapor, said tube having a plurality of spaced openings to emit supercooled vapor jets, an axial conducting wire electrode within the tubes, a charging strip on the outer surface of the tube adjacent the openings therein, a source of electrical potential difference connected between the axial wire electrode and the strip whereby ions are produced within the vapor jets from the openings, said vapor condensing upon the ions to form minute charged droplets, a second tube upstream of the first tube, said second tube being connected to a source of superheated vapor and having a plurality of spaced openings therein whereby supercooled vapor is issued from the said second tube at approximately the velocity of the gas and condenses upon the minute charged droplets to form a charged aerosol having larger droplets, a conversion space having a repelling electric field to convert the heat kinetic power of the charged aerosol gas to electric power, a collector electrode at the exit of the conversion space to discharge the charged droplets, and an electrical load to receive the output electric power connected between the collector electrode and the wire electrode.

9. The method of converting the heat-kinetic power of a moving gas into electrical power comprising the steps of passing a non-conducting gas at subsonic velocity through a conduit, introducing a supercooled vapor into the gas, maintaining a conducting liquid under pressure in a tube placed within the conduit, forming a small diameter charged jet from said liquid in an electric field within said moving gas, whereby said jet breaks up into minute charged droplets and whereby the vapor condenses upon the minute charged droplets to form a charged aerosol gas having charged droplets of larger radius, and of approximately optimum mobility, directing said charged aerosol gas of optimum mobility against a repelling electric field and thereafter neutralizing the charge on the aerosol by collector means downstream from the repelling electric field, and supplying the output electric power to an electrical load connected between the collector means and the conducting liquid.

10. A device for producing and charging an aerosol comprising a dielectric tube, a source of superheated vapor at a temperature and pressure substantially above that of the gas on the exterior of the tube, a plurality of openings along the tube to emit supercooled jets, an axial conducting wire electrode within the tube, a charging strip on the outer surface thereof adjacent the openings therein, a source of electrical potential difference connected between the axial wire and the strips, whereby ions are produced within the vapor jets from the openings said vapor condensing upon the ions to form minute charged droplets in the gas constituting a charged aerosol gas.

11. A device for producing and charging a charged aerosol gas comprising a dielectric tube, a source of superheated vapor at a temperature and pressure substantially above that of the gas on the exterior of the tube, a plurality of openings along the tube to emit supercooled jets, an axial conducting wire electrode within the tube, a charging strip on the outer surface thereof adjacent the openings therein, a source of electric potential difference connected between the axial wire and the strips, whereby ions are produced within the vapor jets from the openings, said vapor condensing upon the ions to form minute charged droplets in the gas, a second tube upstream of the jets of said first tube, said second tube being connected to a source of superheated vapor having a temperature and pressure substantially greater than that of the gas, and having a plurality of spaced openings thereon whereby supercooled vapor issues from the said second tube and condenses upon the minute charged droplets to form a charged aerosol having larger droplets, constituting a charged aerosol gas.

12. The method of converting the heat kinetic power of a moving gas into electrical power comprising the steps of passing a non-conducting gas through a conduit, introducing a supercooled vapor produced from jets issuing at a somewhat greater pressure temperature and velocity than the gas from the orifices in an upstream pipe, said upstream pipe being supplied with superheated vapor under substantially greater temperature and pressure than that of the moving gas into said gas, introducing ions into the supercooled vapor from a corona within the supercooled vapor to form minute charged droplets, increasing the radius of the minute charged droplets by condensationof the vapor thereon to form larger charged droplets of approximately optimum mobility, passing said larger charged droplets through a repelling electric field, discharging the larger charged droplets by collector means, and supplying electrical power to a load connected between the collector means and the ionizer means.

References Cited UNITED STATES PATENTS 3,225,225 12/1965 Wattendorf et a1 3106 MILTON O. HIRSHFIELD, Primary Examiner.

DAVID SLINEY, Assistant Examiner.

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