Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
  • F02D41/0047—Controlling exhaust gas recirculation [EGR]
  • F02D41/0065—Specific aspects of external EGR control
• • 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
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
  • F02M26/02—EGR systems specially adapted for supercharged engines
  • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
  • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
  • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
  • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
  • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
  • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
  • F02M26/33—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage controlling the temperature of the recirculated gases
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
  • F02M26/45—Sensors specially adapted for EGR systems
  • F02M26/46—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition
  • F02M26/47—Sensors specially adapted for EGR systems for determining the characteristics of gases, e.g. composition the characteristics being temperatures, pressures or flow rates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
  • F02D41/0047—Controlling exhaust gas recirculation [EGR]
  • F02D41/0065—Specific aspects of external EGR control
  • F02D2041/0067—Determining the EGR temperature
  • F02D2041/007—Determining the EGR temperature by estimation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
  • F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
  • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
  • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
  • F02M26/23—Layout, e.g. schematics
  • F02M26/25—Layout, e.g. schematics with coolers having bypasses
• • 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 estimate of the temperature of the exhaust gas of a combustion engine at the output of an EGR circuit fitted to the engine.
• thermocouple measurement The measurement of the exhaust gas temperature at the outlet of the EGR circuit can be made from a thermocouple measurement. This solution is precise but expensive (including thermocouple cost, cost of the acquisition chain). It also requires to provide, in the engine compartment, the volume necessary for its integration.
• the average deviations were then reduced to about fifty degrees Celsius.
• a main objective of the invention is to improve the accuracy of the temperature estimation at the output of the EGR circuit.
• Another object of the invention is to reduce the complexity of calculations of this temperature, while keeping a possible margin of error acceptable.
• the invention proposes, according to a first aspect, a method for estimating the exhaust gas temperature Ts of an engine at the output of an EGR circuit fitted to the engine, based on a model taking into account the loss of thermal energy of the exhaust gases at the EGR cooler of the EGR circuit, characterized in that the model also takes into account the heat exchange between the exhaust gases and the walls of the exhaust gas. a conduit leading the exhaust gases to the EGR cooler.
• said model takes into account the following heat exchanges: the internal heat exchanges between the gases and the wall of said duct; external exchanges between the wall of said tube and the external environment of the engine compartment, such as convective exchanges linked to an air flow and radiative exchanges of components external to the duct; cooling the gases through the EGR cooler; said model is based on simplified equations of conservation of thermal energy of the gases taking into account the different heat exchanges throughout the EGR circuit allowing: (a) an evaluation of the thermal exchanges between the exhaust gases and the walls of a duct bringing the exhaust gases to the EGR cooler of the EGR circuit; (b) an evaluation of the thermal exchanges of the exhaust gases with the inlet of the EGR cooler, taking into account the evaluation of step (a); (c) an evaluation of the thermal exchanges of the exhaust gases in the EGR cooler;
• said equations are a system of three equations with three unknowns T p , T 2 and T 3 , knowing that T p is the estimated temperature of the walls of said duct and that T 2 is the estimated temperature of the exhaust gas at the inlet of the cooler , the three equations corresponding respectively to the three evaluations (a), (b) and (c);
• the temperature T 3 is mainly estimated from the knowledge of the temperature of the exhaust gas entering the EGR circuit, the temperature of the engine cooling water at the engine outlet, the specific heat of the EGR gas at constant pressure, the mass flow rate of the EGR gases, the specific heat of said duct, and the geometric and mass characteristics of the duct;
• the model is a system of first-order, linear and independent differential equations; these latter equations are found by making the following approximations: the convective external exchanges linked to a flow of air around the duct are of the same order of magnitude as the radiative exchanges by components external to the duct; the convection temperature is approximately equal to the temperature of the water
• Figure 1 shows schematically the various elements of a compartment of a combustion engine equipped with an EGR circuit.
• FIG. 2 schematically represents a longitudinal sectional view of an EGR cooler and a portion of its inlet and outlet ducts.
• FIG. 3 represents a block diagram of a thermal assembly equivalent to the EGR cooler assembly according to FIG. 2, illustrating a first embodiment of the invention.
• FIG. 4 represents a diagram showing a block diagram of a thermal assembly equivalent to the EGR cooler assembly according to FIG. 2, illustrating a second embodiment of the invention.
• FIG. 5 represents a diagram illustrating large steps of an estimation method according to the invention.
• FIG. 6 is a graph showing the evolution of the temperature at the outlet of the EGR circuit as a function of the EGR cycles, and whether the temperatures are measured or estimated.
• the invention which will be described later presents the following two embodiments, making it possible to obtain an estimate of the exhaust gas temperature at the outlet of the EGR cooler: - development of equations close to physical phenomena, reducing them to their most strictly necessary to be able to be integrated into a motor software; a significant improvement in the accuracy of the exhaust gas temperature estimator in the EGR circuit is obtained since the model used is closer to reality. - Drastic simplification of the equations mentioned in the first embodiment. The goal is to minimize calculation time and software size.
• the two proposed embodiments are easily applicable to all internal combustion engines equipped with EGR circuits (diesel engine, gasoline, etc.).
• This engine compartment comprises an internal combustion engine 10 supplied with air by an intake duct 11 and releasing its exhaust gas through a discharge duct 12.
• This engine compartment is further provided with a turbocharger 50 comprising a compressor 51 located on the intake duct 11 to compress the fluid-fuel from the track 53.
• cooling means 40 and a flap 30 are provided between the compressor 51 and the engine 10.
• the air that reaches the engine 10 is cold.
• the turbine 52 of the turbocharger 50 is located at the end of the exhaust duct 12 and is coupled to the compressor 51.
• the exhaust gases are from the engine compartment and then exhausted via the track 54.
• this assembly comprises an EGR circuit 20 whose input 28 is connected to the exhaust duct 12 and whose outlet 29 is connected to the intake circuit 11.
• This EGR circuit 20 comprises an EGR cooler 22 connected upstream by an inlet duct 25 and downstream by an outlet duct 27, for cooling the exhaust gases for reinjecting them into the engine 10.
• FIG. 2 schematically represents a longitudinal sectional view of an EGR cooler 22 connected in upstream by the gas inlet duct 25 and downstream by the gas outlet duct 27.
• T 2 is the temperature of the exhaust gas at the inlet of the cooler 21;
• T 3 is the temperature of the exhaust gas at the outlet of the cooler 21;
• T p is the temperature of the wall 26 of the inlet duct 25. It will also be noted that the mass flow rate of the exhaust gases in the circuit
• the applicant has made exhaust gas temperature readings along the EGR circuit 20 showing that about 35% of the gas energy at the inlet 28 of the circuit 20 can be lost in the inlet conduit 25 and that about 65 % is lost in the cooler 22.
• the temperature of the inlet gases 28 of the circuit 20 can not be confused with the temperature of the gases entering the cooler 22.
• ⁇ is the thermal conductivity of the EGR gas, which is a constant for the exhaust gas under consideration; Pr is a constant ⁇ 0.7; there o.Vr - D is charac t st ⁇ que . . . . r- JJ • j. - 1
• Characteristic diameter In the case of an EGR duct, it can be taken as equal to the internal diameter of the duct (D egr ); * h ext :
• the convective exchanges related to the flow of air around the circuit 20 are described macroscopically by a convective exchange coefficient h ext .
• This coefficient is considered constant and is adjusted in order to recalibrate the model with respect to tests carried out.
• the average temperature of the air passing through the engine compartment (T convectlve ) generally follows an evolution close to that of the cooling water temperature at the output of the engine 10. In fact, the water temperature at the outlet of the engine compartment is a good indicator of the temperature in the engine compartment. This simplifies by writing:
• the form factor (f v ) which is defined as "the way the inlet duct 25 sees the rest of the underhood" is imposed here at 1.
• the inlet duct 25 upstream of the cooler 22 generally has emissivities ( ⁇ ) of the order of 0.8.
• M e is the mass of gas enclosed in the inlet duct 25. It is so small compared to the other terms of the equations that it can be considered as zero.
• - Cpegr is the specific heat of EGR gases at constant pressure. This value depends on the nature of the gases. It is typically close to 1150 J / kg.K.
• - Cp stainless steel is the specific heat of the EGR gases in walls 26 of the inlet duct 25, value depending on the nature of the material (eg stainless steel here).
• - Q eg r is the EGR flow through the inlet duct 25. It is not measured, but it is estimated by calculating a difference between a measurement of Qf ra is (flow measured at the output of the compressor 51) and a measure of Q word (flow entering the engine).
• Other existing techniques known to those skilled in the art, may alternatively be used to estimate Q egr . These chosen techniques are typically specific to each engine ECU used or to each planned software.
• An estimate of the temperature at the outlet of the cooler 22 is then obtained by taking into account the heat dissipation at the inlet duct 25, thus making the estimate accurate because true to reality.
• the EGR circuit 20 is considered to be a combination of two heat exchangers 100 and 200 in series.
• the first exchanger 100 consists of the inlet duct 25 upstream of the cooler 22. In this exchanger 100, circulate the EGR gas cooled by the ambient environment 150 prevailing in the engine compartment (T rad ⁇ at ⁇ ve and T convect ⁇ ve explained above). The temperature of the gases at the outlet of this first exchanger 100 is the temperature T 2 .
• the second heat exchanger 200 consists of the EGR cooler 22. In this exchanger 200 circulates the EGR gas (at the temperature T 2 ) which are cooled by the water of the cooling circuit 250 engine (T water ). The temperature of the gases at the outlet of this second exchanger 200 is the temperature T3. 1.
• This efficiency summarizes the thermal performance of the inlet duct 25, that is to say the way the EGR gases are cooled in contact with the wall 26 of the duct 25 which itself is cooled by the environment of the undercap.
• the concept of efficiency is generally used in steady state. However, the mass of the inlet duct 25 being large (several hundred grams), the temperature (T p ) of the wall 26 of the duct 25 is not reached for several minutes and therefore, the notion of efficiency n ' is more exploitable simply, that is to say, without involving differential equations easily integrable in a calculator.
• the energy conservation equation (1) can be complicated to solve, in particular because of the T 4 term linked to the radiative exchanges under the hood.
• the convective exchanges linked to the flow of air around the inlet duct 25 are of the same order of magnitude as the set of radiative exchanges between the inlet duct 25 and the various components of the sub duct 25.
• -capot cylinder head, exhaust manifold, turbocharger, apron, ski, ..
• the water water temperature T in engine output is usually a good indicator of the thermal environment in the engine compartment, which further simplifies to:.. DT p ⁇ M mox .C Pmox ⁇ h ⁇ nt .S (T 2 -T p ) + 2.h ext . (T water -T p ) (5)
• the time scale that governs the wall temperature of the inlet duct 25 upstream of the cooler is of the order of one hundred seconds.
• the time scale that governs the temperature of the EGR gas at the cooling inlet 22 is of the order of one second. T2 changes over time are therefore almost instantaneous compared with changes in T p over time.
• Equation (2) related to the conservation of energy, can then be simplified by:
• Tp 00 T avt . (l-Sl) + Sl. teau
• the time scale that governs the temperature of the EGR gas at the cooler inlet is of the order of one second. At this scale, the wall temperature of the EGR duct upstream of the cooler changes little.
• S 1 is directly linked to ⁇ 2 by the relation: ⁇ 2 - h ⁇ s
• T 2 the time constant T 2 will only show small variations, and will therefore be considered constant, but other possibilities for describing this time constant may be be expected, such as a description based on a more complex model or mathematical rule managed by a program.
• an average EGR flow can be used to determine a single time constant, but other possibilities for describing this time constant can be provided, such as description based on a more complex model or mathematical rule managed by a program.
• T ⁇ T avf ( ⁇ - ⁇ i) + ⁇ V T water
• Ki, K2, ⁇ p and T2 are known (see calculation methods above), knowing the orders of magnitude assigned to M mox , Q egr , h ext and h nostint and based on measurements and / or estimates. .
• Equation (3) is retained here.
• the time constant (13) is then introduced into the EGR temperature estimator to take into account the thermal inertia of the cooler 22.
• This constant can be measured on engine benches or be estimated from data received from a manufacturer. cooler.
• This constant can be adjusted in order to readjust the model compared to tests previously carried out on an engine compartment.
• the estimated temperature T 3 is then deduced at the outlet of the cooler 22.
• different curves of the temperature of the gases T 3 at the outlet of the cooler 22 allow comparisons between:
• the curve 4 gives the result of an estimate of T3 in the case where the heat dissipation is not taken into account by the inlet duct 25.
• the average deviations between the estimation of the temperature of the EGR gas at the cooling outlet 22 according to the invention and the measurements are from 8 to 12 ° C.
• this new estimator makes it possible to correctly follow the evolutions of the gas temperatures all along the EGR circuit.
• the estimation according to the invention has the advantage of being very simple and therefore easy to integrate into a computer.
• the proposal to simplify the description of heat exchange in the EGR circuit 20 is therefore entirely satisfactory.
• one or the other of the simplified formulations is extremely simple to solve for a computer.
• the estimation of the exhaust gas temperature at the outlet of the EGR circuit 20 is thus done in three successive steps:
• the wall temperature 26 of the inlet duct 25 upstream of the cooler 22 is estimated (T p );
• the temperature of the EGR gas at the inlet of the cooler 22 is estimated (T 2 ): Finally, the temperature of the EGR gas at the outlet of the cooler 22 is estimated (Zj).
• the invention also relates to a vehicle equipped with an electronic temperature estimator comprising calculating means or computer and storage means or data storage predetermined and / or measured, in order to implement the method of estimating temperature according to the invention. It will be possible in particular to provide an algorithm defining the temperature estimate at the output of the EGR circuit 20, the execution of which requires little computing means and few resources, given the simplicity of the process that it implements. It is therefore an ideal system to be integrated in a computer on board.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Analytical Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Exhaust-Gas Circulating Devices (AREA)

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• 2006
  • 2006-11-17 FR FR0610065A patent/FR2908825B1/fr active Active
• 2007
  • 2007-10-31 WO PCT/FR2007/052286 patent/WO2008059153A2/fr active Application Filing
  • 2007-10-31 JP JP2009536768A patent/JP5079815B2/ja not_active Expired - Fee Related
  • 2007-10-31 EP EP07866527A patent/EP2100019A2/de not_active Withdrawn
  • 2007-10-31 US US12/514,821 patent/US8037737B2/en not_active Expired - Fee Related

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