DE102008036278A1 - Control operation of diesel engine after-treatment with recovery of waste heat - Google Patents

Abstract

A diesel engine exhaust aftertreatment system will be described. The plant may include: a heat transfer device having a first side and a second side; a heating element downstream of the first side of the heat transfer device; a filter downstream of the heating element and an outlet path downstream of the filter leading to the second side of the heat transfer device, the outlet path being isolated from an outer surface of the filter to inhibit heat transfer from the heated exhaust exiting the filter to the outer surface of the filter.

Description

Background and brief

The Efficiency of a diesel particulate filter (DPF) in an exhaust aftertreatment system for one lean-burn internal combustion engine can through regular regeneration of the particulate filter can be improved. The regeneration includes typically raising the temperature of the particulate filter, thereby Adsorbed particles are burned. While a regeneration exothermic is and enough Generate energy to be self-sustaining after initiation, lean-burn internal combustion engines typically have one Exhaust gas temperature lower than needed to trigger regeneration is. Therefore, many particulate filter devices include heat sources, For example, catalysts or heating elements to the regeneration process initiate. The particulate filter, on the other hand, can with too high temperatures damaged become. For example, you can in the particulate filter integrated catalyst particles sinter (what the activity the catalyst decreases), the structural integrity of the filter element may be damaged be etc.

The The present inventors have recognized that these heat limitations a compromise between efficiency and reliability force a particulate filter. Particulate filter devices who try by reusing waste heat from the regeneration process to save energy directly to heat the particulate filter possibly self-sustained reactions, especially without a separate one cooling mechanism to control excessive temperatures. Alternatively you can Particulate filter devices that do not waste heat from the regeneration reaction Recycle, also lower the fuel economy, what to increased Operating costs leads. In addition, an additional Heat shield and / or cooling used when the temperature of the particulate filter drain is too high to be safe to downstream devices to stream, which increases manufacturing and / or maintenance costs.

The above problems can at least partially in one example by a diesel engine exhaust aftertreatment system be addressed. The plant can use a heat transfer device a first and a second side, a heating element downstream of first side of the heat transfer device, a filter downstream of the heating element and an outlet path downstream of the filter leading to the second side of the heat transfer device leads, include, wherein the outlet path is isolated from an outer surface of the filter, to a heat transfer from the heated one Exhaust gas exiting the filter to inhibit the outer surface of the filter.

On this way can be a desirable one Operating efficiency of the heating element can be achieved while, too a thermal degradation is addressed. For example, the Aftertreatment plant a recycling of waste heat from the Allow regeneration, without the particulate filter directly the heat load the heated one Expose exhaust gases that escape from the particulate filter, causing the Potential of self-sustaining regeneration that leads to over-temperature conditions leads, which may degrade the particulate filter or other components becomes. Furthermore, the temperature of the emerging from the particulate filter Gases are lowered toward Sollendrohrbedingungen because heat on transmit the exhaust gas entering the system from the engine becomes. Furthermore, heat energy of at least the heating element can be supplied to the regeneration process Enable, the engine can under conditions of low temperature combustion (LTC, short of English Low Temperature Combustion) are operated. Low-temperature combustion processes can less Generate particles, using the smaller particulate filter device allow smaller particulate filters the risk of over-temperature can reduce and less fuel for heating during the initial one Activation etc. may require.

Brief description of the drawings

1 illustrates a diesel engine aftertreatment system with waste heat recovery;

2A . 2 B . 3A and 3B show summary flowcharts and block diagrams for operating the diesel engine aftertreatment unit with waste heat recovery;

Detailed description

With reference to 1 can be an engine 10 an intake manifold 100 include that with a bank of combustion cylinders 102 can be fluid-connected. The combustion cylinder 102 can with an exhaust manifold 104 keep in touch. A heat transfer device 106 can with the exhaust manifold 104 be connected. The heat transfer device 106 can be at least two pages 106A and 106B which allow the transfer of heat between gases on each side without mixing with the gases. The heat transfer device 106 can be of different kinds. For example, the heat transfer device 106 a shell-and-tube heat exchanger, a plate heat exchanger, etc., and while this is in 1 is not shown, the Wärmeübertragungsvorrichtun 106 Include baffles on one or more sides to facilitate efficient heat transfer.

A first page 106A the heat transfer device 106 can with a downstream of the first page 106A the heat transfer device 106 arranged heating element 108 be connected. The heating element 108 may supply heat from an external fuel-maintained flame from the combustion of the fuel injected into the exhaust stream from an electrically operated heating element, etc. The heating element 108 can continue with the downstream of the heating element 108 arranged particulate filter 110 be connected. The particle filter 110 may be of a different nature (eg zeolite) and may be a filter element 112 in the form of a monolith or a shaking layer or a combination thereof. The particle filter 110 may be inert or may include catalytically active material. The particle filter 110 can with a second page 106B the heat transfer device 106 connected downstream of the particulate filter 110 is arranged. An outlet channel 114 can the particle filter 110 with the second page 106B the heat transfer device 106 connect. The outlet channel 114 can from the outside surface of the particulate filter 110 be insulated to allow heat transfer from the particle filter 110 to inhibit exiting heated exhaust gas.

The second page 106B the heat transfer device 106 can with an additional emission control device 112 downstream of the second side 106B of the heat transfer device 106 be connected. For example, the emission control device 112 a NOx filter, NOx catalyst, urea-SCR catalyst, or various others, or combinations thereof. The emission control device 112 can continue with a tailpipe 114 downstream of the emission control device 112 be connected.

While this is in 1 not shown, the system may include an exhaust gas recirculation (EGR) circuit connected to the exhaust manifold 104 and the intake manifold 100 can be fluid-connected. The EGR cycle may include a heat transfer device, such as an EGR cooler. The EGR cycle may also include a catalyst, for example, an oxidation catalyst or various other EGR catalyst species or combinations thereof. The plant may also include a high pressure diesel fuel injection system for supplying injected fuel to combustion cylinders 102 include. For example, the diesel fuel injection system may be a common rail system that is adapted to adjusting injection timing based on the operation of the engine 10 allows.

A heating element control system may be the controller 12 include that in 1 is shown as a microcomputer comprising a microprocessor, input / output ports, an executable program electronic storage medium and read-only memory calibration memory, a random access memory, a battery powered memory, and a data bus. The tax system 12 can different signals from temperature and pressure sensors 160 and receive signals from an engine control system, such as air / fuel ratio, engine speed, crank angle, fuel injection timing, oxygen concentration, etc. The controller 12 may also have stored control algorithms for operating the heating element 108 in response to signals or combinations of signals received from different sensors and from an engine control system, by operating various actuators 170 contain.

An engine control system may be an in 1 as a microcomputer shown control unit 14 comprising: a microprocessor, input / output ports, an executable program electronic storage medium and read-only memory calibration memory, a random access memory, a battery powered memory, and a data bus. The control unit 14 can in addition to the already explained various signals from with the engine 10 connected sensors 140 including measurement of the inducted mass air flow from an air flow meter (MAF); Engine coolant temperature (ECT); Engine speed, throttle position (TP) from a throttle position sensor; and manifold vacuum MAP from a manifold pressure sensor. The control unit 14 may also include stored control algorithms for operating various devices in response to signals or combinations of signals from different ones with the engine 10 connected sensors are included. Finally, the controller can 14 different signals to actuators 150 in the engine 10 send.

As further described herein, the heater control system may control heater operation based on various operating conditions. 2A FIG. 11 is a high level flowchart for a method of operating a heater control system in response to system parameters. FIG. First, the heating element control system reads 202 Outlet system parameters, such as temperature and pressure, and engine operating conditions, such as engine speed, fuel injection timing, fuel / air ratio, etc. Then, the heater determines ment tax system 204 whether the conditions for a particulate filter regeneration are suitable. For example, clogging of the particulate filter may be reflected in the pressure drop across the particulate filter. Thus, if the pressure drop exceeds a predetermined threshold, regeneration may be appropriate. The pressure drop threshold may be selected based on a setpoint magnitude of the backpressure experienced by the engine, setpoint values of the filter load, and the like. Alternatively, the engine controller may set a flag that overrides or triggers particulate filter regeneration in response to a condition or conditions, as described below. If the heater control system determines that starting the regeneration process is not appropriate, the routine will go to end. If starting the regeneration process is appropriate, the routine will increase 206 before and enters the in 2 B shown heater control routine.

Referring now to 2 B determines the routine at 210 the pressure drop across the particulate filter. Next, the routine determines at 212 whether the pressure drop is greater than a predetermined value. This value may represent a threshold for an allowable degree of contamination of the filter and may include factors that account for a measurement error, etc. The value at 212 may differ from the value at step 204 from 2A differ; For example, a pressure drop that occurs at step 204 from 2A can trigger a regeneration cycle, the at step 212 from 2 B exceed the selected value. The at 212 The selected value may correspond to a range of filter conditions that are not so polluted at 204 from 2A a regeneration is triggered.

When the pressure drop at 212 exceeds the threshold, the routine continues to increase 214 The routine measures the temperature of the exhaust gas flow downstream of the heating element and upstream of the particulate filter. Next, the routine determines at 216 whether the temperature exceeds a threshold temperature. For example, the threshold temperature may be the ignition temperature of the regeneration reaction, the temperature required to maintain a particular regeneration reaction rate, etc. If the temperature is below the threshold temperature, the routine will increase 218 in front. For example, at the beginning of the regeneration cycle, where the exhaust gas does not have sufficient heat energy to activate regeneration combustion reactions, the temperature may be below the threshold temperature. at 218 The routine operates the heating element in accordance with a heater operation algorithm, an example of which 3A and 3B is described. From 218 then the routine returns 210 back.

If the temperature exceeds the threshold temperature, the routine will increase 220 in front of where the heating element is switched off before going to step 210 returns. For example, the temperature may exceed the threshold temperature once the regeneration process has ignited and heated exhaust gases from the particulate filter may transfer heat from a second side 106B the heat transfer device 106 to a first page 106A the heat transfer device 106 begin to transfer.

When the pressure drop at 212 does not exceed the threshold, the routine advances 222 in front. A pressure drop that does not exceed the threshold may indicate that the regeneration process is completed, although other approaches may be used to indicate the completion of the regeneration process. For example, the temperature change across the filter may fall below a temperature difference threshold, indicating that the reaction rate has dropped to a value indicative of minimum combustion activity. Alternatively, other approaches that directly measure the temperature or other properties of the filter, such as electrical conductivity, weight, etc., may be used 222 the routine deactivates the heating element and advances to the end of the routine.

3A shows a view of the aftertreatment system containing the heating element 308 and the filter 310 includes, and shows the position of multiple sensors. The sensors can be temperature sensors downstream of the heating element 308 but upstream of the filter 310 include, for example, T1, temperature sensors included in the filter 310 are arranged, for example, T2, or sensors, downstream of the filter 310 are arranged, for example, T3. Pressure sensors like P1, the upstream of the filter 310 is located, and P2, the downstream of the filter 310 may also be included. 3B shows a high-level algorithm for a heater control for use with the in 2 B described Heizelementsteuerroutine. The heater control algorithm reads engine and exhaust operating parameters into the regeneration process model 320 , Examples of engine operating parameters include engine speed, fuel / air ratio, fuel injection timing, etc. Examples of exhaust parameters include oxygen concentration, aftertreatment plant temperatures, pressures, etc.

The regeneration process model 320 calculates a target temperature Tdes upstream of the filter 310 and downstream of the heating element 308 and directs the target Tdes to the comparator 322 , For example, the regeneration process model 320 a desired regeneration reaction rate from the heater controller 12 or from the Mo gating 14 read. Furthermore, the regeneration process model 320 read an aftertreatment system pressure P1, an exhaust oxygen concentration, and a stored reaction rate coefficient to calculate Tdes. The regeneration process model 320 can by an auto-adaptive method over the lifetime of the filter 310 updated to compensate for changes in the activity of the regeneration process. If the filter 310 For example, if a catalyst is included, an auto-adaptive approach may help to compensate for changes in catalyst activity to provide more efficient regeneration conditions throughout the life of the filter 210 provided.

At the comparator 322 Tdes is compared with a measured temperature, for example T1, T2 or T3. For example, at the beginning of the initiation of the regeneration process, there may be some undesirable delay in detecting a change in temperature downstream of the filter 312 pass through the thermal mass of the filter 312 can be caused. At the front edge of the filter 312 For example, during the time delay, an undesirable hot spot may develop which may degrade the filter or result in an over-temperature condition during self-sustained responses. Thus, using T1 at the comparator 322 provide an advantageous control of the heating element. However, if the regeneration process achieves stable operation, it may be desirable to have T2 or T3 on the comparator 211 as a reference, which may allow for better control of the entire plant. The comparator 322 generates an error signal Terr that enters the heater control unit 324 is read. The heater control unit 324 can be parameter for controlling the heating element 308 include. Furthermore, the heating element control unit 324 be designed for proportional-integral-derivative (PID) control, wherein the parameters can be varied over different temperature ranges to provide a stable control over some temperature ranges and a refined control over other temperature ranges. Furthermore, the parameters may be pre-configured or by the heater control device 12 be voted on by yourself. As an example of the functionality of the heating element 324 For example, when Terr indicates that the measurement temperature (represented by T1, T2 or T3) is less than Tdes, the heater controller may be used 324 operate the heating element to bring the measuring temperature into a desired range of Tdes. Alternatively, if Terr indicates that the sensing temperature (represented by T1, T2, or T3) is greater than Tdes, the heater may pass through the heater controller 324 shut down or shut down.

Both the in 3B shown heating element control algorithm as well as in 2A and 2 B The heater control system shown may also respond to other conditions, such as those illustrated below. The driver demand and / or engine load may affect the frequency and occurrence of filter regeneration. For example, it may be desirable for the particulate filter to regenerate after a threshold time interval has elapsed since the last regeneration cycle, or it may be desirable to retard regeneration while the engine is under a heavy load. This allows the engine control unit 14 Set a flag that triggers or delays a regeneration process. The heating element control device 12 may in turn be on at least one of the engine control unit 14 received engine condition respond.

The conditions in the combustion cylinders 102 may also affect the operation of the heater control system. For example, by the engine control device 14 low temperature combustion conditions, for example, where the engine is operated under very lean conditions, produce a lower engine exhaust temperature and may provide more power from the heater 108 require as conditions where the combustion cylinders 102 more fuel is supplied, which may produce a higher engine exhaust temperature. As another example, the regeneration process model 320 other engine conditions from the engine control unit 14 For example, speed, fuel injection, air-fuel ratio, which may provide alternative estimates of engine exhaust oxygen concentration, unburned fuel concentration, concentration of various exhaust gases, such as NOx and Cox, etc., all of which may affect the regeneration reaction rate.

The Operating conditions relating to can be used and / or adapted to the above figures can, for Example fuel / air ratio, Engine speed, fuel injection quantity and / or timing, Exhaust and / or inlet oxygen concentration, exhaust gas recirculation amounts, Driver request and / or others include.

Herein, various exemplary processes are described to illustrate system coordination; however, due to system structure, there may also be various alternative processes. For example, as an additional example, exhaust gas entering the exhaust aftertreatment system under a first exhaust condition may be heated by a heating element prior to entering the filter. Such a condition can occur when, for example, the particulate filter regeneration process is triggered in response to a signal from a motor controller indicating that the pressure across the filter has reached a threshold. As the temperature of the particulate filter increases, the rate of the exothermic regeneration reaction may increase, raising the temperature of the exhaust gas exiting the filter. Heat energy from the exhaust gas can then be transferred to the exhaust gas entering the aftertreatment system in the heat transfer device. When the temperature of the exhaust gas reaches a threshold, the heater controller may shut off the heater, saving fuel. Once the regeneration process is completed, which is detected by a pressure difference measurement, the heating element can remain switched off. In addition, the heater controller and the engine controller may be responsive to change the operation of the heater in response to changing engine loads, driver demands, etc. that may alter the oxygen concentration in the exhaust stream and thus affect the regeneration process or the frequency of the reaction in a manner requires more or less feed from the heating element.

It It should be understood that the configurations and routines disclosed herein are exemplary in nature and that these specific designs not restrictive may be understood as many amendments possible are. The subject matter of the present disclosure includes all novel ones and not obvious combinations and subcombinations of different systems and outlet configurations, algorithms as well other features, functions, and / or properties disclosed herein become. The following claims show particular certain combinations and sub-combinations, which are considered novel and not obvious. These claims can to "an" element or "a first" element or a Correspondence of the same. These claims are to be understood as being they comprise integrating one or more such elements, neither claiming nor excluding two or more of these elements. Other combinations and sub-combinations of the disclosed features, functions, elements and / or properties by modification the present claims or by submitting new claims in this or a related application. Such claims whether they are facing each other the scope of protection of the original claims wider, narrower, same or different, also as considered in the subject matter of the present disclosure.

Claims (18)

Diesel engine exhaust aftertreatment system, which includes: a heat transfer device with a first page and a second page; a heating element downstream the first side of the heat transfer device; one Filter downstream the heating element; and an exhaust path downstream of the Filter leading to the second side of the heat transfer device, wherein the outlet path from an outer surface of the Filters is isolated to heat transfer from the exiting from the filter heat exhaust gas on the outer surface of the Inhibit filters. The plant of claim 1, further comprising a heater control device for controlling the operation of the heating element in response to a temperature and / or a pressure of the exhaust gas, wherein the heating element control device continues to respond to a motor control device. Plant according to claim 2, wherein the heating element control device continues to respond to an engine condition obtained by the engine controller, wherein the engine condition is engine speed, air / fuel ratio, fuel injection timing, and / or Engine load includes. The plant of claim 1, further comprising a downstream one third side of the heat transfer device built catalyst includes. Plant according to claim 1, characterized in that the heat transfer device a Tube bundle heat exchanger includes. Plant according to claim 1, characterized in that substantially all of it into the first side of the heat transfer device penetrating exhaust gas after passing through at least the heating element, passed the filter and the outlet path to the second side of the heat transfer device becomes. Plant according to claim 6, characterized in that the heating element is a fuel-operated heating element. Plant according to claim 1, characterized in that the heating element directly upstream of the Particle filter is arranged and wherein the heat transfer device directly downstream of the particulate filter is arranged. Method for operating a diesel engine exhaust aftertreatment system with a heat transfer device, a particulate filter and egg a heating element, comprising: during a first exhaust condition: passing a first volume of exhaust gas through a first passage of the heat transfer device, operating the heating element to raise the temperature of the first volume of exhaust gas exiting the heat transfer device, directing the first volume of the one out of the heating element exiting exhaust gas through the particulate filter, directing the first volume of exhaust gas exiting the particulate filter through an exhaust passage to a second passage of the heat transfer device, the exhaust passage being isolated from an outer surface of the filter to transfer heat from the heated exhaust exiting the filter to the exhaust passage External surface of the filter to inhibit, and heating a second volume of exhaust gas, which is passed from the engine to the first passage of the heat transfer device, with that of the first volume of the exhaust gas in the second passage of Wärmeübert propagating energy transmitted energy; and during a second exhaust condition: passing a third volume of exhaust gas through the first passage of the heat transfer device, passing the third volume of the exhaust gas through the heating element without operating the heating element, passing the third volume of exhaust gas exiting the heating element through a particulate filter, directing the third one Volume of exhaust gas exiting from the particulate filter through the exhaust passage to the second passage of the heat transfer device and cooling a fourth volume of the exhaust gas from the engine to the first passage of the heat transfer device by means of the energy transmitted to the third volume of the exhaust gas in the second passage of the heat transfer device. The method of claim 9, further comprising Controlling the operation of the heating element in response to at least a temperature of the exhaust aftertreatment system comprises. The method of claim 10, further comprising Passing the exhaust gas from the second passage to a catalyst wherein the operation of the heating element in response to a Temperature of the catalyst is adjusted. Method according to claim 11, characterized in that that the heating element continues to respond in response to at least one Pressure and an oxygen concentration of the exhaust gas is adjusted. Diesel engine exhaust aftertreatment system comprising: a Heat transfer device with a first passage and a second passage, wherein the first passage between a first page and a second page the device is located, the second side is opposite the first side, the second passage between a third page and a fourth Side of the device is the fourth side opposite the third side lies; a first exhaust path, the exhaust gas from directing the engine to the first side; a second outlet path, the exhaust gas passes from the second side to the third side, wherein the second path is a heating element and a downstream of the heating element built-in particle filter comprises; a third outlet path, the exhaust gas from the fourth side passes, the third path a catalytic emission control device comprises; and one control unit for operating the heating element during a first mode, where heat from the exhaust gas in the second passage to the exhaust gas in the first one Passage passage and to deactivate the heating element during a second mode, being heat from the exhaust gas in the first passage to the exhaust gas in the second Passage passage is, the control unit the system in response to temperature of the catalytic emission control device switch between the first mode and the second mode. Plant according to claim 13, characterized that the controller Continue the plant in response to the temperature during the Regeneration of the particulate filter between the first and second Change mode. Plant according to claim 13, characterized that the controller the operation of the heating element in response to engine operating conditions adapts. Plant according to claim 13, characterized that the heat transfer device a Tube bundle heat exchanger includes. Plant according to claim 16, characterized that substantially all of the exiting from the second side of the heat transfer device Exhaust gas after passing through at least the heating element and the particulate filter to the third side of the heat transfer device is directed. Plant according to claim 17, characterized in that that the heating element is arranged directly upstream of the particulate filter is and wherein the heat transfer device directly downstream of the particulate filter is arranged.