Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
  • F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
  • F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
  • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
  • F01N3/027—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using electric or magnetic heating means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
  • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
  • F01N3/106—Auxiliary oxidation catalysts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N9/00—Electrical control of exhaust gas treating apparatus
  • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N9/00—Electrical control of exhaust gas treating apparatus
  • F01N9/007—Storing data relevant to operation of exhaust systems for later retrieval and analysis, e.g. to research exhaust system malfunctions
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2610/00—Adding substances to exhaust gases
  • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
  • F01N2900/04—Methods of control or diagnosing
  • F01N2900/0408—Methods of control or diagnosing using a feed-back loop
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/05—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of air, e.g. by mixing exhaust with air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
  • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
  • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
  • F01N3/2033—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using a fuel burner or introducing fuel into exhaust duct
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/40—Engine management systems

Definitions

• the invention relates to an exhaust filter regeneration regime, method and apparatus for example for use in a diesel engine exhaust stream.
• Such equipment is used in the removal of carbon monoxide, hydrocarbons and NOX pollutants and particulates made in exhaust systems.
• soot removal is usually achieved most effectively through the use of a filter.
• Regenerated traps such as CRTs (Continuously Regenerated Traps)
• CRTs Continuous Regenerated Traps
• DPF diesel particulate filter
• Regeneration is achieved when the exhaust temperature reaches above around 600°C at which point the component of the exhaust gas stream reacts with the soot creating an exothermic reaction, which increases the trap temperature as soot is oxidised and burnt away.
• the regeneration occurs at a lower temperature in the presence of a catalyst.
• the temperature of the exhaust gas and filter are critical to the regeneration process, which lead to various problems with the technology. For example, for certain engine duty cycles it is not possible to achieve an exhaust gas temperature which enables unassisted regeneration. It is known to reduce the regeneration temperature by introducing a catalyst component upstream of the filter, which reacts with the upstream exhaust gas to create an N0 2 enriched atmosphere. This stimulates the regeneration burning process enabling regeneration temperatures to be reduced to around 380°C. There are, however, cases where the engine duty cycle is such that exhaust stream temperature never exceeds the 380°C regeneration target temperature and, therefore, other approaches are required to assist with the regeneration.
• the invention allows implementation of the control strategy that is adaptable to multiple usages and duty cycles.
• Fig. 1 is a schematic block diagram showing an engine implementing an exhaust filter regeneration regime in accordance with the present invention
• Fig. 2 is a flow diagram demonstrating the steps implemented in the regeneration regime control strategy
• Fig. 3 is a flow diagram demonstrating the steps implemented
• Fig. 4 is a schematic block diagram showing a further improved approach to enhancing the regeneration regime
• Figs.5 a and 5b are views of the injector head of the present invention, and;
• Fig.6 is a schematic view of the electric catalytic heating element.
• Fig. 1 shows in block diagram the principal components of an engine incorporating the system according to the invention.
• air is fed from inlet manifold 10 to an engine 12 from which the exhaust is fed to an exhaust manifold 14.
• the exhaust stream then passes through exhaust conduit 16a to a catalytic reducer 18 for reducing CO and HC.
• the reduced exhaust stream then passes via exhaust conduit 16b to a diesel particulate filter (DPF) 20 where particulate matter such as soot is removed from the exhaust stream and the exhaust stream passes through exhaust conduit 16c.
• DPF diesel particulate filter
• a fuel injector 22 is mounted in the exhaust conduit 16a close to exhaust manifold 14.
• the fuel injector 22 may be mounted directly in the exhaust manifold 14, to benefit from highest exhaust stream temperature.
• the fuel metered by the fuel injector 22 into the exhaust stream is oxidised by the catalytic converter 18 thus providing heat.
• the heat assists in raising the temperature of the DPF 20 to an appropriate level to allow combustion in conjunction with the oxygen present and beyond.
• significant temperature increases up to the required level of approximately 550°C , but more preferably temperatures of 650 to 700 °C are available by this approach. Temperatures above this range can have the effect of damaging the catalytic converter.
• the system further includes a regeneration controller which can be separate from or part of an engine control unit ((ECU) 24 which controls the fuel injector 22 and also receives signals from sensors 26, 28, 30, 32, 34, 36, 38 and 40 as described in more detail below.
• ECU engine control unit
• the ECU 24 implements a fuel injection strategy by fuel injector 22 to obtain the desired level of regeneration of DPF 20.
• the sensed signals are used to determine when to switch fuel injection on and off and hence commence and terminate regeneration.
• Fuel injection start is triggered when the DPF is detected to exceed a predetermined particulate load and the relevant temperature conditions are detected for commencement of the catalytic reaction with the injected fuel in the catalytic converter 18.
• fuel injection is terminated when the particulate load is detected to drop below a predetermined threshold or when the temperature conditions are detected as being insufficient to support regeneration.
• the particulate load is determined as a function of the pressure drop across the DPF 20 and mass flow through the engine and the temperature detected at the catalytic converter 18.
• the ECU 24 also controls the fuel injection regime via fuel injector 22 to ensure that an appropriate regeneration level is attained.
• fuel injection is controlled as a function of the temperature of the catalytic converter 18 to avoid slippage of unburned fuel past the catalytic converter resulting in unwanted emissions in the form of white smoke, resulting from excessive injected fuel.
• a method of regeneration is provided which is controlled entirely by on-board components requiring no operator involvement and which can be achieved for any operating vehicle's duty cycle.
• it is achieved by artificially increasing the system operating temperature to above 550°C to ensure that soot is burnt off by virtue of the high pressure fuel injection regime providing an increased exhaust gas temperature downstream of the catalytic converter 18.
• fuel may be injected at high pressure (100 bar) or low pressure (2 bar) dependent on the operating conditions of the engine.
• the catalytic converter 18 comprises a high platinum load metal catalyst of a cordierite metal or silicon carbide material with mineral wash coat which is found to reduce CO and HC by up to 95%.
• the DPF 20 is a silicon carbide filter found to reduce mass particulate by 95% and nearly eliminate visible black smoke.
• the sensors comprise an inlet manifold absolute pressure (IM PA ) sensor 26 and an inlet manifold absolute temperature (IM TA ) sensor 28 provided on the inlet manifold 10.
• An engine speed (ES) sensor 30 is provided on the engine 12, or at the inlet manifold to measure cylinder inlet manifold pressure variation, which fluctuate each time the cylinder ports open hence representing engine speed.
• a temperature sensor 31 is provided for sensing the temperature of exhaust gas (TI) exiting the engine exhaust manifold 14 before the fuel injector 22, with a further temperature sensor 32 T CI on the entry face of the catalytic converter.
• a sensor 34 senses the temperature of gas at the exit face of the catalytic converter 18 (Tco)-
• Sensor 36 senses the pressure at the inlet to the DPF 20 allowing the pressure drop (P DPF with respect to atmospheric (i.e. pressure of the DPF outlet), across the DPF to be measured.
• Sensor 40 senses the temperature T D0 of gas exiting the DPF 20.
• the sensors comprise elongate probes extending into the body of the component whose temperature is sensed. The sensors extend radially into the component such that the axial position of the sensor can be determined exactly. This is of importance, for example, when it is necessary to obtain the temperature at each axial end of a component.
• the ECU monitors whether the particulate load on the DPF 20, Fioad > exceeds a predetermined threshold.
• the value of F ⁇ oad can be derived from: 1.
• F load c (P DPF * IM TA )/(ES * I MPA )
• c is a constant that can be calibrated during development of the system or derived from a lookup table.
• Equation 1 represents the relationship between pressure drop across the filter P DPFs mass flow and the particulate load.
• P DPF increases as the filter becomes loaded with carbon until it is necessary to perform a regeneration of the filter to remove the carbon.
• P DPF is also proportional to the mass flow of gas through the filter it is necessary to normalise P DPF against exhaust mass flow.
• the exhaust mass flow is determined by the quantity of air taken in on each engine stroke which in turn determined by the temperature of the air at the inlet manifold (IM TA ) and its absolute pressure (IM PA ) and the engine speed (ES).
• the amount of air taken in will fall proportionally with increasing IM TA and increase proportionally with increasing IM PA and ES. This is reflected in Equation 1 above.
• the threshold value which F ⁇ oa must exceed to trigger regeneration may represent full particulate loading of the filter or partial particulate loading of the filter and may either be stored as a constant in the control software or calibrated during development or installation. It will be appreciated that alternative manners in which F L0AD can be monitored are possible. For example the peak values P DP F can be monitored to identify the significant trends.
• the peak values are generally increasing then this can be identified as a result of the particulate load threshold having been reached.
• Appropriate behaviour can be calibrated allowing such recognition.
• the short term fluctuation in PD PF resulting from opening and closing of the exhaust valves in the engine cylinders can be disregarded, as only the maximum values are derived.
• a curve of maximum values can be constructed by interpolating between successive maximum values. As a result the particulate load can be determined without reference to the engine speed.
• the ECU 24 further determines whether the catalytic converter 18 is at a suitable temperature for the combustion of fuel injected into the exhaust stream to take place. In particular, as the catalytic converter will only stimulate oxidation of the fuel at a high temperature above approximately 230°C the system checks that both the input and output temperatures T C o, T ⁇ exceed the threshold temperature. If the particulate load and catalytic converter temperature both exceed the respective thresholds then block 204, the ECU commences the fuel injector regime. The system then monitors for a trigger event which will terminate the regeneration process. In block 206 the system monitors whether F ⁇ oad , as given by Equation 1 above, falls below a lower threshold representing an appropriate reduction in the particulate load.
• fuel injection is terminated.
• the system further monitors in block 210 for a reduction in temperature of the catalytic converter 18 such that combustion of the injected fuel will no longer take place as a result of which fuel injection will not be triggered.
• the system can monitor to establish whether Tco and Tci fall below a lower temperature threshold which in this case may be the same the 230°C threshold value for triggering fuel injection in block 202. If so then once again in block 212 then fuel injection is aborted. As a result of abortion of fuel injection the required temperature rise cannot be achieved.
• Drops in temperature of the catalytic converter can take place for various reasons, for example because of the duty cycle of a vehicle.
• One specific example would be the decrease in exhaust temperature if the engine load of a vehicle decreased.
• the temperature T C o can further be monitored to identify when the catalytic converter temperature exceeds a damage threshold.
• regeneration can be terminated if T C o deviates from a Tco setpoint which the system is attempting to achieve by fuel injection (as discussed in more detail below), for example by more than 30°C for more than 10 seconds.
• the system further monitors to establish whether a time-out condition has taken place. Accordingly a timer is instigated upon commencement of the regeneration process at block 204 and if this exceeds a threshold value, for example 5 minutes, then in block 216 fuel injection is once again terminated.
• a threshold value for example 5 minutes
• the system further monitors in block 220 to establish whether the temperature T D0 of the DPF 20 exceeds a self-sustaining threshold.
• a rapid increase in the temperature of the DPF is seen such that a high T D0 indicates that regeneration has been initiated and fuel injection can be terminated.
• no further fuel injection is required although it may be desired to introduce a level of fuel injection necessary to sustain regeneration for example at a lower level than that required to initiate regeneration, but sufficient to maintain the exhaust stream temperature at the desired level.
• the system further monitors in block 222 to establish whether the temperature T D0 of the DPF 20 exceeds a safe working threshold, for example 1000°C.
• a safe working threshold for example 1000°C.
• the fuel injection regime in block 204 is preferably controlled so as to achieve optimum efficiency and emissions reduction.
• the fuel passes straight through the catalytic converter 18 without oxidation resulting in white smoke and also having a quenching effect on the catalytic converter, reducing its temperature.
• a small amount of fuel should be added at the initiation temperature of 230°C but as the temperature increases a high rate of fuel injection can be tolerated.
• An appropriate control strategy can be further seen with reference to table 1 and Fig. 3.
• the T C o set point is set as the measured value (reaching 230°C). From a look-up table corresponding to Table I, the corresponding ramp rate can derived for that T C o set point as 1°C per second. As a result the fuel injection is controlled to provide an increase in T C o at that rate. This can be done, for example by varying the amount or frequency of fuel injection. Where the injector is switched on for a short period every 20ms, the period for which the injector remains on can be varied to meet the required amount of fuel into the exhaust.
• This period can be determined from a further look up table, for example calibrated upon development of the system or can be determined using a feed- back approach such as a PID (proportional/integral/derivative) control algorithm as a result of which the metering of fuel injection will be rapidly tailored to converge the temperature rate with the desired value.
• the amount of fuel injection may be reduced for situations where the engine speed and load are high, thereby preventing unwanted pass through of fuel.
• table 1 may vary in an additional dimension with engine speed and/or load.
• the system continues to measure Tco and in block 302 monitors to establish whether the measured T C o has met the next set point (in the first instance 270°C from Table I).
• the T C o setpoint is set to the next set point value (i.e. 270°C) and the set point ramp is determined accordingly.
• the set point ramp is increased to 2 degrees per second and the fuel injection regime metered accordingly to achieve this.
• the system also checks at block 302 to ensure that the period during which fuel injection has been metered according to the ramp rate does not exceed a time-out period which can be individually determined for each set point value, as set out in Table 1 and is set at the expected time taken to reach the next setpoint or slightly longer. If so regeneration is aborted as the desired temperature rate increase cannot be sustained to initiate regeneration.
• T C o reaches its upper temperature level e.g. 550°C at which point regeneration should be triggered. It will be seen that the set point ramps downwards again as T C o approaches the upper limit to ensure that overshoot is avoided and reduce the risk of production of white smoke from unburned fuel.
• T C o reaches 550°C
• fuel injection can be aborted, so as not to exceed the setpoint value. This may be appropriate in situations where regeneration is occurring as a self sustaining exothermic reaction. However, situations may arise where regeneration is not self sustaining and as such it will be necessary to inject fuel to sustain the 550°C set point i.e. at a 0°C/s ramp rate.
• the rate of fuel injection is dictated by both the engine speed and load and the temperature T C o. It will be seen that the time out period for the higher temperature values is significantly reduced again to avoid over- injection of fuel and providing a maximum time for the fuel injection regime of the sum of the maximum permitted times for each individual step increase.
• An alternative fuel injection rate strategy can be implemented, based on a known maximum injection rate.
• the fuel injection rate is set so as not to produce fuel slippage or exceed a maximum temperature.
• the maximum rate of fuel injection is given by the following equation:
• FR is the final fuel injection rate in ml/sec, at a specific engine operating conditions.
• FRES is the fuel injection rate with respect to measured engine speed.
• FRT1 is the fuel injection rate with respect to engine exhaust manifold temperature.
• FRT C ⁇ is the fuel injection rate with respect to T ⁇ .
• FRT C o is the fuel injection rate with respect to Tco.
• the final amount of fuel injected is therefore dependent on the operating temperature at the engine exhaust manifold, the temperature across the catalytic converter and the engine speed.
• the final fuel injection rate is trimmed back progressively when the maximum operating temperature of the catalytic converter is approached. As a result a desired and controlled rate of temperature rise is obtained even during rapidly changing engine conditions when an engine is in use.
• the fuel rate with respect to each of these parameters is determined from a look up table which is entered in ECU 24 to suit the type of vehicle and application of the vehicle.
• Examples of the look up tables are as follows, where each parameter of the table is derived dependant on type and application of vehicle, engine size or any other appropriate parameter.
• the maximum fuel rate is designed to be highest when the engine has been working hard and the engine core temperature is high but then the engine goes to a period of idle.
• the maximum fuel injection figure peaks when both the front and rear of the catalytic converter are at optimum temperature, T ⁇ and T C o respectively, and the amount of fuel injected is reduced if the catalytic converter temperature is too high, to prevent damage to the catalytic converter.
• fuel injection is only enabled when the filter back pressure F ⁇ oad is above a threshold, as discussed above.
• This F load parameter may be entered into equation 2 as a binary 1 or 0 product term, thereby providing a further fail safe mechanism.
• a compressor (not shown) is used to deliver air, at a typical pressure of 2 bar, to an inlet 70 of an injector head 22, shown in side cross- section in figure 5a and in end view in Fig. 5b.
• the injector head is mounted radially in the exhaust gas stream in conduit 16a between sensor 32 and the entry face of the catalytic converter and directs fuel in an axial direction aligned and common with the flow direction of exhaust gas in the conduit.
• the fuel is metered, for example, via a peristaltic pump (not shown) of the type supplied by Rietschle Thomas UK Ltd, or any appropriate pump which allows on demand constant ml/minute metering to a fuel exit point 52 adjacent an air exit aperture 54.
• the peristaltic pump is driven by a stepper motor with high step resolution so that the fuel rate can be finely controlled.
• compressed air enters the injector head 22 via air inlet 70 and fuel enters the injector head via fuel inlet 72.
• the air and fuel pass to respective exits 54, 52 via discrete passages 74, 76.
• the air and fuel mix at the junction of the exit points.
• air flow is maintained for a short period, for example, five seconds, to ensure that all remaining fuel is dissipated.
• the corresponding low-pressure operation ensures that fuel entrained in the compressed air and mixed in the conduit is not, for example, injected at high speeds through the converter such that it hits the high temperature TPF which of course would present a significant hazard. Furthermore the fuel can be injected directly from existing fuel lines or the existing fuel tank and an additional holding tank is not required.
• operation of the system can be further improved by maintaining a history of vehicle operation and regeneration regime.
• This can be used, for example, to improve the control strategy in various ways. For example it may be observed that regeneration is more efficient at higher or lower catalytic converter temperatures such that the relevant trigger points can be adjusted accordingly. Alternatively it may be observed that a higher or lower DPF pressure drop corresponds to completion or initiation of regeneration such that the fuel injection regime can be amended accordingly.
• the specific fuel injection rate strategies discussed above with reference to table 1 and table 2 can be adjusted for example by adjusting the setpoint step values, the desired rates of combustion or fuel injection amounts.
• the system can identify relationships between fuel injection level, catalytic converter temperature, and temperature rise such that the desired ramp rate can be achieved more quickly.
• additional information can be derived from a stored history of performance. For example when a vehicle frequently adopts one or more specific duty cycles then the system may recognise from vehicle operational perimeters that one of those duty cycles is being entered and adjust the control strategy accordingly. For example when a certain duty cycle involves significant increases in exhaust temperature then a less intensive fuel injection regime may be instigated.
• the ramp rate varies inversely with the difference between the temperature set point and a temperature mid point immediate the upper and lower set point limits. Accordingly a more complex ramp rate regime can be obtained by, for example, selecting a "mid point" which may not be centred exactly between the upper and lower temperature set point limits and introducing appropriate constants. This can be adjusted from cycle to cycle based on recorded regeneration regime history data. Alternatively, more a complex look up table can be provided which once again can be dynamically adjusted.
• the fuel line 400 running to the fuel injector 22 includes a chamber portion 402 wrapped around or passing through a region containing heated water recirculated from the radiator or engine compartment .
• fuel to the fuel injector 22 is pre-heated using waste heat as a result of which high temperatures are more easily attained.
• FIG. 6 A further improvement is shown in figure 6 whereby an electrical heater 60 is located immediately before the front face 18 of the catalytic converter 18.
• the main method of heat transfer from the heater 60 to the catalytic converter 18 is via radiation. This is more efficient than using the exhaust gas to transfer heat via convection, as a large amount of power is required to get significant temperature rise of the exhaust gas.
• a further enhancement of this is to catalyse the surface of the heater 60.
• a heater of relatively low power 500W can achieve a significant temperature rise above the temperature of the exhaust. It is therefore possible to get the catalytic material on the surface of the heater to a temperature where it is active even when the engine is idling. This heat is then contributed to the front of the catalytic converter 18 which then achieves the main temperature rise.
• An additional temperature sensor 64 is located adjacent the heater and is used to allow control of the electrical power to the heater and/or the amount of fuel, in accordance with equation 2, injected, thereby preventing damage to the catalytic coating through over heating.
• any appropriate pressure, temperature and engine speed sensors can be adopted and any appropriate fuel injector retrofitted to the exhaust manifold.
• the system can be controlled by a designated or existing engine control unit under software or hardware implementation of the control approach and algorithms as discussed above.
• the control algorithm is implemented via a microcontroller and digital logic with appropriate analogue inputs to an A to D converter. In the case the performance history of the vehicle is maintained this can be stored at memory at ECU or elsewhere in any appropriate form.
• an effective and flexible exhaust filter regeneration regime control can be implemented irrespective of the vehicle type or duty cycle introduced allowing rapid and efficient regeneration whilst reducing emissions to the a minimum. Furthermore, regeneration is performed on demand, when required, rather than during a predetermined window.
• the invention can be applied to any appropriate engine or fuel type and that fuel injection can take place in any appropriate part of the exhaust stream.
• the approaches as described above can be described to any appropriate temperature dependent exhaust treatment regime or other temperature raising mechanisms which rely on fuel injection.
• the fuel injection can be metered by adjusting fuel alignment, fuel injection rate or fuel injection pulse duration, fuel injection pressure variation or fuel type variation.
• control can be implemented using appropriate sensed parameters of operation of the engine and the exhaust stream components and using any appropriate sensors and injectors.

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• 2005
  • 2005-03-16 JP JP2007503406A patent/JP2007529678A/ja not_active Abandoned
  • 2005-03-16 WO PCT/GB2005/000998 patent/WO2005090759A1/en active Application Filing
  • 2005-03-16 EP EP05718046A patent/EP1730390A1/en not_active Withdrawn
  • 2005-03-16 US US10/591,338 patent/US20080000219A1/en not_active Abandoned

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