阅读说明：本技术 一种发动机排气温度计算方法 (Engine exhaust temperature calculation method ) 是由 齐儒赞 张慧峰 苗志慧 高天宇 陈昊 刘笑飞 杜大瑞 于 2021-08-27 设计创作，主要内容包括：本发明属于发动机技术领域,公开了一种发动机排气温度计算方法。该发动机排气温度计算方法包括以下步骤：根据发动机排气管入口气体温度、发动机排气管管壁温度,获取发动机排气管出口气体温度；根据发动机排气管出口气体温度、催化器内化学反应产生的热量、催化器内载体传递至外部环境的温度,获取催化器内载体的热量；根据催化器内载体的热量、涡轮机进气管管壁温度,获取涡轮机进气管进气温度、涡轮机进气温度和涡轮机排气管温度；根据涡轮机排气管温度,获得发动机排气管后排气门温度。该发动机排气温度计算方法能够准确计算出发动机排气温度,从而达到延长发动机寿命的目的。(The invention belongs to the technical field of engines and discloses a method for calculating exhaust temperature of an engine. The engine exhaust temperature calculation method includes the steps of: acquiring the temperature of the gas at the outlet of the engine exhaust pipe according to the temperature of the gas at the inlet of the engine exhaust pipe and the temperature of the pipe wall of the engine exhaust pipe; acquiring heat of a carrier in the catalyst according to the temperature of gas at the outlet of an exhaust pipe of the engine, the heat generated by chemical reaction in the catalyst and the temperature of the carrier in the catalyst transferred to the external environment; acquiring the inlet air temperature of a turbine inlet pipe, the inlet air temperature of a turbine and the temperature of a turbine exhaust pipe according to the heat of a carrier in a catalytic converter and the wall temperature of the turbine inlet pipe; and obtaining the temperature of the rear exhaust valve of the exhaust pipe of the engine according to the temperature of the exhaust pipe of the turbine. The engine exhaust temperature calculation method can accurately calculate the engine exhaust temperature, so that the purpose of prolonging the service life of the engine is achieved.)

1. An engine exhaust temperature calculation method for calculating an engine exhaust temperature in an engine exhaust system including an engine exhaust pipe (1), a catalyst (2), a turbine (3), and an engine exhaust pipe rear exhaust valve (4) which are communicated in this order, characterized by comprising the steps of:

acquiring the temperature of the gas at the outlet of the engine exhaust pipe according to the temperature of the gas at the inlet of the engine exhaust pipe and the temperature of the pipe wall of the engine exhaust pipe;

acquiring heat of a carrier in the catalyst according to the temperature of gas at the outlet of an exhaust pipe of the engine, the heat generated by chemical reaction in the catalyst and the temperature of the carrier in the catalyst transferred to the external environment;

acquiring the inlet air temperature of a turbine inlet pipe, the inlet air temperature of a turbine and the temperature of a turbine exhaust pipe according to the heat of a carrier in a catalytic converter and the wall temperature of the turbine inlet pipe;

and obtaining the temperature of the rear exhaust valve of the exhaust pipe of the engine according to the temperature of the exhaust pipe of the turbine.

2. The engine exhaust gas temperature calculation method according to claim 1, characterized in that the engine exhaust pipe (1) outlet gas temperature satisfies the formula:

wherein, T_{Gas temperature at the outlet of the exhaust pipe}Is the temperature of the exhaust gas at the outlet of the engine exhaust pipe, T_{Inlet gas temperature of exhaust pipe}Is the engine exhaust pipe inlet gas temperature, T_{Wall temperature of exhaust pipe}The temperature of the pipe wall of the exhaust pipe of the engine, alpha is the heat transfer coefficient of the gas, A is the cross section area of the exhaust pipe (1) of the engine, and cp is the energy joule required by increasing 1 opening degree per kilogram of gas.

3. The engine exhaust temperature calculation method according to claim 2, characterized in that the engine exhaust pipe (1) pipe wall temperature T_{Exhaust of gasesWall temperature of pipe}The calculation formula of (2) is as follows:

wherein, V_{Vehicle speed}The current speed of the whole vehicle.

4. The engine exhaust temperature calculation method according to claim 3, characterized in that the amount of heat of the carrier in the catalyst satisfies the formula:

Q_c＝Q_qc+Q_f-Q_chwherein Q is_cIs the heat of the carrier in the catalyst, Q_qcHeat transferred to the carrier for the temperature of the gas at the outlet of the engine exhaust pipe, Q_fHeat generated for chemical reactions in the catalyst, Q_chIs the temperature that the carrier in the catalyst delivers to the external environment.

5. The engine exhaust temperature calculation method according to claim 1, wherein the turbine intake temperature satisfies the formula:

wherein, T_{Turbine inlet air temperature}Is the turbine inlet air temperature, T_{Inlet temperature of turbine inlet duct}Is the turbine inlet pipe temperature, T_{Turbine inlet duct wall temperature}Is the turbine inlet duct wall temperature.

6. The engine exhaust temperature calculation method according to claim 5, characterized in that the turbine exhaust pipe (33) temperature satisfies the formula:

7. the engine exhaust temperature calculation method according to any one of claims 1 to 6, characterized in that, in the steady-state mode, the engine post-exhaust valve temperature in the steady-state mode is obtained based on the engine speed, the relative charge amount, the exhaust gas mass and flow rate coefficient, the air-fuel ratio, and the ignition efficiency.

8. The engine exhaust temperature calculation method according to any one of claims 1 to 6, characterized in that, in the fuel cut-off mode, the engine exhaust valve rear temperature in the fuel cut-off mode is obtained based on the engine speed, the exhaust gas mass and flow coefficient, and the engine water temperature.

9. The engine exhaust gas temperature calculation method according to any one of claims 1 to 6, characterized in that the engine exhaust valve rear temperature in the scavenging mode is obtained based on the exhaust gas mass and flow rate, the scavenging coefficient, and the intake valve rear fresh air temperature in the scavenging mode.

10. The engine exhaust temperature calculation method according to any one of claims 1 to 6, characterized in that in the dynamic mode, the engine exhaust valve after-temperature in the steady-state mode is obtained based on the exhaust gas temperature at the steady-state operation, the exhaust gas mass and flow coefficient, and the ambient temperature.

Technical Field

The invention relates to the technical field of engines, in particular to a method for calculating exhaust temperature of an engine.

Background

The engine exhaust temperature is called engine exhaust temperature for short, and refers to the temperature in an engine exhaust manifold, and the engine exhaust temperature is one of important parameters representing the combustion state of an engine and is an important factor influencing the reliability and consistency of the engine. The existing automobile, especially the automobile equipped with a supercharged engine, can severely raise the exhaust temperature of the engine when the automobile runs at high speed for a long time under severe working conditions. As the exhaust temperature of the engine rises, the performance of the engine is reduced, the oil consumption is increased, the emission exceeds the standard, and the loss of internal parts of the engine is accelerated. Therefore, corresponding measures are needed to control the exhaust temperature of the engine, and the situation that the exhaust temperature of the engine is too high is avoided.

In the prior art, a temperature sensor is arranged in an exhaust manifold of an engine, but when a supercharged engine is in a full-load working state, the temperature of exhaust gas discharged by the supercharged engine can reach 1000 ℃, the exhaust gas of a turbine is discharged from an exhaust hole at the speed of 50-230 m/s, and the exhaust frequency is as high as 200HZ, so that any sensor cannot work sufficiently under such a severe environment, the exhaust temperature of the engine cannot be monitored in real time, and is fed back to an ECU (electronic control Unit) to control the engine, so that the exhaust pipeline and a supercharger are irreversibly influenced by the overhigh exhaust temperature, and the service life of the engine is influenced.

Disclosure of Invention

The invention aims to provide an engine exhaust temperature calculation method, which can calculate the engine exhaust temperature and prolong the service life of an engine.

In order to achieve the purpose, the invention adopts the following technical scheme:

an engine exhaust temperature calculation method is used for calculating the engine exhaust temperature in an engine exhaust system, wherein the engine exhaust system comprises an engine exhaust pipe, a catalyst, a turbine and an engine exhaust pipe rear exhaust valve which are sequentially communicated, and the engine exhaust temperature calculation method comprises the following steps:

acquiring the temperature of the gas at the outlet of the engine exhaust pipe according to the temperature of the gas at the inlet of the engine exhaust pipe and the temperature of the pipe wall of the engine exhaust pipe;

acquiring heat of a carrier in the catalyst according to the temperature of gas at the outlet of an exhaust pipe of the engine, the heat generated by chemical reaction in the catalyst and the temperature of the carrier in the catalyst transferred to the external environment;

acquiring the inlet air temperature of a turbine inlet pipe, the inlet air temperature of a turbine and the temperature of a turbine exhaust pipe according to the heat of a carrier in a catalytic converter and the wall temperature of the turbine inlet pipe;

and obtaining the temperature of the rear exhaust valve of the exhaust pipe of the engine according to the temperature of the exhaust pipe of the turbine.

Preferably, the engine exhaust pipe outlet gas temperature satisfies the formula:

wherein, T_{Gas temperature at the outlet of the exhaust pipe}Is the temperature of the exhaust gas at the outlet of the engine exhaust pipe, T_{Inlet gas temperature of exhaust pipe}Is the engine exhaust pipe inlet gas temperature, T_{Wall temperature of exhaust pipe}For engine exhaust pipe wall temperature, α is the gas heat transfer coefficient, A is the cross-sectional area of the engine exhaust pipe, and cp is the energy joules required to raise 1 degree of opening per kilogram of gas.

Preferably, the temperature T of the pipe wall of the exhaust pipe of the engine_{Wall temperature of exhaust pipe}The calculation formula of (2) is as follows:

wherein, V_{Vehicle speed}The current speed of the whole vehicle.

Preferably, the heat of the carrier in the catalyst satisfies the formula:

Q_c＝Q_qc+Q_f-Q_chwherein Q is_cIs the heat of the carrier in the catalyst, Q_qcHeat transferred to the carrier for the temperature of the gas at the outlet of the engine exhaust pipe, Q_fHeat generated for chemical reactions in the catalyst, Q_chIs the temperature that the carrier in the catalyst delivers to the external environment.

Preferably, the turbine inlet temperature satisfies the formula:

wherein the content of the first and second substances,

T_{turbine inlet air temperature}Is the turbine inlet air temperature, T_{Inlet temperature of turbine inlet duct}Is the turbine inlet pipe temperature, T_{Turbine inlet duct wall temperature}Is the turbine inlet duct wall temperature.

Preferably, the turbine exhaust temperature satisfies the formula:

preferably, in the steady-state mode, the engine exhaust valve rear temperature in the steady-state mode is obtained according to the engine speed, the relative air charge amount, the exhaust gas mass and flow coefficient, the air-fuel ratio and the ignition efficiency.

Preferably, in the fuel cut-off mode, the engine exhaust valve rear temperature in the fuel cut-off mode is obtained from the engine speed, the exhaust gas mass and flow coefficient, and the engine water temperature.

Preferably, in the scavenging mode, the engine exhaust valve rear temperature in the scavenging mode is obtained based on the exhaust gas mass and flow rate, the scavenging coefficient, and the intake valve rear fresh air temperature.

Preferably, in the dynamic mode, the temperature after the exhaust valve of the engine in the steady-state mode is obtained according to the exhaust gas temperature, the exhaust gas mass and flow coefficient and the ambient temperature in the steady-state operation.

The invention has the beneficial effects that:

according to the engine exhaust temperature calculation method provided by the invention, the engine exhaust pipe, the catalyst, the turbine and the rear exhaust valve of the engine exhaust pipe are sequentially communicated, and the numerical values of the outlet gas temperature of the engine exhaust pipe of the pipe component, the temperature and the heat of a carrier in the catalyst, the temperature of each component in the turbine and the temperature of the rear exhaust valve of the engine exhaust pipe are obtained according to the exhaust temperature calculation model and a thermal equilibrium method. The flow of the tail gas of the engine in the exhaust system of the engine is regarded as one-dimensional steady-state flow, and mathematical models of different structural temperatures of the exhaust system are deduced according to the energy conservation and the one-dimensional steady-state pipe convection heat transfer model.

Compared with the prior art, in a complex engine exhaust system, the engine exhaust temperature calculation method is based on the first law of thermodynamics, and the change of the temperature of each structure in the exhaust process of the engine can be deduced through the establishment of a mathematical model by only obtaining the exhaust temperature of an inlet, the temperature of a pipe wall and the exhaust mass flow. Compared with a sensor temperature measurement method, the problem of sensor loss caused by severe working conditions is solved, and the exhaust temperature of the engine can be accurately calculated, so that the exhaust temperature of the engine is controlled, the loss of internal parts of the engine due to overhigh temperature is avoided, and the purpose of prolonging the service life of the engine is achieved.

Drawings

FIG. 1 is a schematic diagram of the engine exhaust system required in the engine exhaust temperature calculation method of the present invention;

FIG. 2 is a model of calculating an engine exhaust pipe outlet gas temperature in the engine exhaust temperature calculation method of the present invention;

FIG. 3 is a model for calculating the temperature of the exhaust pipe wall of the engine in the engine exhaust temperature calculation method according to the present invention;

FIG. 4 is a model of the calculation of the catalyst bed temperature in the engine exhaust temperature calculation method of the present invention;

FIG. 5 is a schematic view of the structure of a turbine required in the engine exhaust temperature calculation method of the present invention;

FIG. 6 is a model of a turbine intake pipe temperature calculated in the engine exhaust temperature calculation method of the present invention;

FIG. 7 is a model of the calculation of turbine outlet duct temperature in the engine exhaust temperature calculation method of the present invention;

FIG. 8 is a model for calculating the temperature of the exhaust valve of the engine in the steady state mode according to the engine exhaust temperature calculation method of the present invention;

FIG. 9 is a model for calculating the temperature of the exhaust valve of the engine in the fuel cut mode in the engine exhaust temperature calculation method of the present invention;

FIG. 10 is a model of calculating the temperature of the exhaust valve rear of the engine in the scavenging mode in the engine exhaust temperature calculation method of the invention;

FIG. 11 is a model for calculating the temperature of the exhaust valve of the engine in the dynamic mode in the engine exhaust temperature calculation method of the present invention;

FIG. 12 is a flow chart of an engine exhaust temperature calculation method of the present invention.

In the figure:

1. an engine exhaust pipe; 2. a catalyst; 3. a turbine; 4. an engine exhaust pipe rear exhaust valve;

31. a turbine inlet duct; 32. a turbine body; 33. a turbine exhaust duct.

Detailed Description

In order to make the technical problems solved, technical solutions adopted and technical effects achieved by the present invention clearer, the technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

As shown in fig. 1, the engine exhaust system includes an engine exhaust pipe 1, a catalyst 2, a turbine 3, and an engine exhaust pipe rear exhaust valve 4, and the engine exhaust system includes four parts, which are sequentially communicated with each other to form a series structure.

The first part is a pipe part consisting of an engine exhaust pipe 1, the second part is a catalyst 2, and the catalyst 2 is an exhaust gas purification device and can convert harmful gases such as CO, HC and NOx discharged by automobile exhaust into harmless carbon dioxide, water and nitrogen through oxidation and reduction. The third part is a turbine 3, the turbine 3 is divided into three parts, namely a turbine inlet pipe 31, a turbine body 32 and a turbine outlet pipe 33, wherein the inlet temperature of the turbine inlet pipe 31 is the temperature of the exhaust gas after passing through the catalyst 2, namely the default catalyst 2 temperature is the same as the exhaust gas temperature after reaching the steady state, and the exhaust gas flowing from the turbine inlet pipe 31 enters the turbine outlet pipe 33 through the turbine body 32. The fourth part is an engine exhaust pipe rear exhaust valve 4, and the engine exhaust pipe rear exhaust valve 4 is the final engine exhaust temperature.

The embodiment provides an engine exhaust temperature calculation method for calculating an engine exhaust temperature in an engine exhaust system, the engine exhaust temperature calculation method comprising the steps of:

acquiring the temperature of the gas at the outlet of the engine exhaust pipe according to the temperature of the gas at the inlet of the engine exhaust pipe and the temperature of the pipe wall of the engine exhaust pipe;

acquiring heat of a carrier in the catalyst according to the temperature of gas at the outlet of an exhaust pipe of the engine, the heat generated by chemical reaction in the catalyst and the temperature of the carrier in the catalyst transferred to the external environment;

acquiring the inlet air temperature of a turbine inlet pipe, the inlet air temperature of a turbine and the temperature of a turbine exhaust pipe according to the heat of a carrier in a catalytic converter and the wall temperature of the turbine inlet pipe;

and obtaining the temperature of the rear exhaust valve of the exhaust pipe of the engine according to the temperature of the exhaust pipe of the turbine.

According to the engine exhaust temperature calculation method provided by the invention, the engine exhaust pipe 1, the catalyst 2, the turbine 3 and the engine exhaust pipe rear exhaust valve 4 are sequentially communicated, and the values of the engine exhaust pipe outlet gas temperature, the temperature and the heat of a carrier in the catalyst, the temperature of each component in the turbine 3 and the temperature of the engine exhaust pipe rear exhaust valve of pipe components are obtained according to an exhaust temperature calculation model and a thermal equilibrium method. The flow of the tail gas of the engine in the exhaust system of the engine is regarded as one-dimensional steady-state flow, and mathematical models of different structural temperatures of the exhaust system are deduced according to the energy conservation and the one-dimensional steady-state pipe convection heat transfer model.

Compared with the prior art, in a complex engine exhaust system, the engine exhaust temperature calculation method is based on the first law of thermodynamics, and the change of the temperature of each structure in the exhaust process of the engine can be deduced through the establishment of a mathematical model by only obtaining the exhaust temperature of an inlet, the temperature of a pipe wall and the exhaust mass flow. Compared with a sensor temperature measurement method, the problem of sensor loss caused by severe working conditions is solved, and the exhaust temperature of the engine can be accurately calculated, so that the exhaust temperature of the engine is controlled, the loss of internal parts of the engine due to overhigh temperature is avoided, and the purpose of prolonging the service life of the engine is achieved.

The first to fourth portions will be described one by one.

1. The first part is to calculate the exhaust temperature of the exhaust pipe 1 of the pipe type part engine

Our known quantities when this part of the calculation include: exhaust gas temperature at the inlet of the exhaust pipe, exhaust gas mass flow, and a characteristic curve determined by the exhaust gas mass flow

According to the first law of thermodynamics: energy is available in a variety of different forms, and can be converted from one form to another and transferred from one object to another, while the amount of energy remains constant during conversion and transfer. Therefore, the difference between the heat of the inlet and the heat of the outlet of the exhaust pipe is the heat transferred to the wall of the exhaust pipe during the process of the exhaust gas passing through the pipe.

Thus, the following equation 1 can be obtained:

Qj-Qc＝Qg…………………………………………………………………1；

wherein Qj is the heat of the inlet of the exhaust pipe of the engine; qc is the heat at the outlet of the exhaust pipe of the engine; qg is the amount of heat transferred by the engine exhaust to the exhaust pipe walls.

On both sides of equation 1, the derivative of time is taken at the same time, and the obtained result is the relationship between the heat flows of the three, and equation 2 is obtained:

and because there is the following relationship between heat and temperature, as in equations 3 and 4:

Q＝cmΔT………………………………………………………………………3；

wherein c is the specific heat capacity of the waste gas, and m is the mass of the waste gas.

The heat flow through the exhaust gas is proportional to the temperature difference between the two sides and related to the thermal conductivity of the material, resulting in equation 4:

wherein alpha is the heat transfer coefficient of waste gas, namely the heat transferred by 1 square meter in 1S when the air temperature difference at two sides of the enclosure structure is 1 DEG, and the unit is W/m²℃；

And substituting the formula 1 to obtain a relational expression between the exhaust temperature at the outlet of the exhaust pipe and the exhaust temperature at the inlet, the temperature of exhaust gas transferred to the pipe wall of the exhaust pipe and the exhaust mass flow, wherein the heat transfer coefficient alpha is a function of the mass flow because the area A of the exhaust pipe can be approximately regarded as a constant, and the temperature of the gas at the outlet of the exhaust pipe of the engine can be calculated by modeling according to the formula shown in FIG. 2 according to the conditions.

Therefore, the engine exhaust pipe outlet gas temperature satisfies the formula:

wherein, T_{Gas temperature at the outlet of the exhaust pipe}Is the temperature of the exhaust gas at the outlet of the engine exhaust pipe, T_{Inlet gas temperature of exhaust pipe}Is the engine exhaust pipe inlet gas temperature, T_{Wall temperature of exhaust pipe}For engine exhaust pipe wall temperature, α is the gas heat transfer coefficient, a is the cross-sectional area of the engine exhaust pipe 1, and cp is the energy joule required to raise 1 opening per kilogram of gas.

In the above formula T_{Wall temperature of exhaust pipe}The temperature of the pipe wall of the exhaust pipe of the engine needs to be calculated as unknown quantity.

Specifically, the heat flow calculation method of the pipe wall temperature is obtained according to the first law of thermodynamics in the same way, as shown in formula 5:

wherein the content of the first and second substances,the heat flow of the pipe wall of the exhaust pipe of the engine is the heat flow of the pipe wall;the heat flow transferred to the wall of the exhaust pipe for exhaust;the heat flux transferred to the environment for the exhaust pipe wall.

Substituting into the correlation formula to obtain: the temperature of the wall of the exhaust pipe of the engine, the exhaust temperature of the inlet, the temperature of the exhaust gas transmitted to the wall of the exhaust pipe, the exhaust mass flow and the vehicle speed.

The temperature of the engine exhaust pipe wall can be calculated from this formula by modeling as shown in fig. 3 after the following definitions.

(1) And m × cp is equal to A, the mass and specific heat capacity of the pipe wall are approximately constant, and the product of the mass and the specific heat capacity is defined as a calibration parameter AC:

(2) a vehicle speed-dependent characteristic curve relating to the mass flow of the exhaust gas is defined.

Therefore, the temperature T of the exhaust pipe wall of the engine_{Wall temperature of exhaust pipe}The calculation formula of (2) is as follows:

wherein, V_{Vehicle speed}The current speed of the whole vehicle.

The calculation of the temperature of the pipe wall transmitted to the environment involves a characteristic curve relating to the speed of the vehicle, i.e. characteristic curve f (V)_{Vehicle speed})×(T_{Wall temperature of exhaust pipe}-T_{Temperature of external environment of exhaust pipe})。

The exhaust gas temperature of the pipe components can be obtained by knowing the exhaust pipe inlet gas temperature, the temperature of the pipe wall of the exhaust pipe and the characteristic curve related to the exhaust mass flow.

2. The second part being the calculation of the temperature of the catalyst 2

Since the catalyst 2 has a good heat transfer capacity, it is generally considered that the temperature of the carrier of the catalyst 2 is the same as the exhaust gas temperature in the carrier. Depending on the heat balance of the carriers in the catalyst 2, the heat of the carriers in the catalyst 2 satisfies the following formula:

Q_c＝Q_qc+Q_f-Q_ch…………………………………………………………6；

wherein Q is_cIs the heat of the carrier in the catalyst, Q_qcHeat transferred to the carrier for the temperature of the gas at the outlet of the engine exhaust pipe, Q_fHeat generated for chemical reactions in the catalyst, Q_chIs the temperature that the carrier in the catalyst delivers to the external environment.

On both sides of equation 6, the derivative with respect to time is taken at the same time, and the obtained result is the relationship between the heat flows.

After the formula is developed, a relational expression between the temperature of the carrier in the catalyst and the heat generated by chemical reaction in the catalyst, the temperature of the exhaust gas transferred to the carrier and the mass flow of the exhaust gas is obtained. Knowing the heat generated by chemical reaction in the catalyst, the initial temperature of the catalyst 2 and the temperature transferred to the environment by the catalyst 2 in the running process, calculating to obtain the carrier temperature of the catalyst, and obtaining the default catalyst temperature which is the same as the exhaust gas temperature after the catalyst reaches the steady state. Therefore, the catalyst bed temperature at the outlet can be calculated by modeling as shown in fig. 4 according to the following formula, and therefore, the bed temperature model of the catalyst 2 in fig. 4 is a calculation method of the catalyst 2 temperature in the dynamic process.

(1) The gas pipe area a can be considered approximately constant and the heat transfer coefficient a is a function of the mass flow.

(2) The mass and specific heat capacity of the carrier are approximately constant, and the product of the mass and specific heat capacity is defined as a calibration parameter AC.

(3) A vehicle speed-dependent characteristic curve relating to the mass flow of the exhaust gas is defined.

Meanwhile, different mathematical models are established under different working conditions of the engine to calculate the temperature change caused by the exothermic reaction, and the normal working condition and the scavenging working condition are considered at the moment. The influence of the internal reaction heat release and coefficient of the catalytic converter 2 needs to be considered under normal working conditions, and the influence of the mass flow of the exhaust gas and the fresh air on the reaction needs to be considered under scavenging working conditions.

3. The third part is calculating the temperature of the turbine part

As shown in fig. 5, the turbine 3 is divided into three parts, namely a turbine inlet pipe 31, a turbine body 32 and a turbine outlet pipe 33, wherein the inlet temperature of the turbine inlet pipe 31 is the temperature of the exhaust gas after passing through the catalyst 2, that is, the temperature of the catalyst 2 is equal to the temperature of the exhaust gas after reaching the steady state, and the exhaust gas flowing from the turbine inlet pipe 31 passes through the turbine body 32 and enters the turbine outlet pipe 33.

During the modeling process, the exhaust gas is considered to undergo adiabatic expansion in the turbine 3, wherein adiabatic expansion specifically means that there is no heat exchange with the outside, but the gas does work to the outside and the gas expands. During this process the gas volume increases and the pressure, and thus the temperature, decreases. And assuming that all parts within the turbine 3, including the rotor, are at the same temperature, the surface areas of the turbine inlet 31 and turbine outlet 33 are each half the surface area of the entire turbine body 32. From the heat balance, there is the following equation:

wherein the heat Q is derived from the time to obtain the heat flow. Wherein the content of the first and second substances,is the heat flow of the turbine inlet pipe 31 in front of the turbine body 32,is the heat flow of the turbine exhaust pipe 33 behind the turbine body 32, alpha is the heat transfer coefficient, the heat transfer coefficient refers to the temperature difference of air at two sides of the enclosure structure of 1 degree, the heat transferred in 1S through 1 square meter is in the unit of W/m²DEG C; a represents an area. T is_inTemperature, T, before the gas enters the turbine body 32_outTemperature, T, of the gas after it enters the turbine body 32_wallIs the temperature of the tube wall.

The turbine body 32 work causes a change in exhaust temperature, according to the principle of conservation of energy, as shown in equation 8 below:

P＝α·A·(T_in-T_out)………………………………………………………………8；

for adiabatic expansion, the inlet and outlet temperatures and pressures have the following relationship equation 9:

wherein n is a polytropic exponent and T is an absolute temperature. In the case of the turbine 3, the pressure before the turbine body 32 and the pressure after the turbine body 32 are easily obtained, and therefore, a mathematical calculation model of the temperature at various places of the turbine 3 can be obtained using the above formula.

Establishing the temperature T of the turbine inlet 31 as shown in FIG. 6_InOf the mathematical model, turbine inlet temperature T_InNamely:

wherein the content of the first and second substances,

T_{turbine inlet air temperature}Is the turbine inlet air temperature, T_{Inlet temperature of turbine inlet duct}For the turbine inlet 31 temperature, T_{Turbine inlet duct wall temperature}Is the turbine inlet duct wall temperature.

Establishing a turbine exhaust pipe temperature T as shown in FIG. 7_OutOf the mathematical model, turbine exhaust pipe temperature T_OutNamely:

4. the fourth part is to calculate the temperature of the exhaust pipe rear exhaust valve 4 of the engine

The establishment of the mathematical model of the exhaust temperature behind the exhaust valve is based on different working conditions of the engine, and the actual running state is taken as a standard, and the mathematical model is divided into four working conditions of steady-state exhaust temperature, exhaust temperature during fuel cut, exhaust temperature during scavenging and dynamic temperature calculation. Under different working conditions, conditions influencing the temperature of the exhaust pipe rear exhaust valve of the engine are different.

(1) Engine exhaust valve post-temperature in steady state mode

In general, the exhaust gas temperature rises with an increase in the rotation speed and the load, and the air-fuel ratio and the ignition angle also have an influence thereon. The air-fuel ratio is larger than 1, the temperature can rise, and the air-fuel ratio is smaller than 1, the temperature can fall; increasing the firing angle, the temperature will decrease, whereas the temperature will increase. At this time, in the steady-state mode, the engine exhaust valve rear temperature in the steady-state mode is obtained according to the engine speed, the relative air charge amount, the exhaust gas mass and flow coefficient, the air-fuel ratio and the ignition efficiency. The mathematical model shown in fig. 8 is established to calculate the exhaust valve rear temperature of the engine in the steady-state mode by considering the influence of the ignition angle and the air-fuel ratio on the exhaust temperature through the engine speed and the relative air charge.

Further, the ambient temperature, the engine water temperature, rapid heating of the catalyst 2, warming-up of the catalyst 2, and the like all have an influence on the exhaust gas temperature. Under normal and stable conditions, the steady-state exhaust temperature is equal to the corrected temperature of the ambient temperature minus the corrected temperature of the exhaust temperature under certain rotation speed and relative air charging quantity, and the corrected temperature of the steady-state exhaust temperature due to heating of the catalytic converter 2, air-fuel ratio, ignition angle efficiency T and the like.

(2) Engine exhaust valve rear temperature in fuel cut-off mode

After fuel cut, the exhaust temperature will approach a fixed temperature determined by the speed and temperature of the water from the manifold temperature at that time, and this process is modeled in a model by a low pass filter. At this time, a mathematical model as shown in fig. 9 is established, and in the fuel cut-off mode, the temperature behind the exhaust valve of the engine in the fuel cut-off mode is obtained according to the engine speed, the exhaust gas mass and flow coefficient, the engine water temperature and the fuel cut-off flag.

(3) Exhaust gas temperature at scavenging

During scavenging, the corresponding temperatures of the excess air and the fresh air in the cylinder need to be taken into account. A simple exhaust gas, fresh air mixing process can be used to describe the temperature change. At this time, a mathematical model as shown in fig. 10 is established, and in the scavenging mode, the engine exhaust valve rear temperature is obtained from the exhaust gas mass and flow rate, the scavenging coefficient, and the intake valve rear fresh air temperature.

(4) Exhaust temperature in dynamic mode

For the temperature after the exhaust valve, the mass and specific heat capacity of the exhaust valve affect the dynamics of the exhaust temperature, and if the mass and specific heat capacity of the exhaust valve are large, the step delay of the temperature is large. In addition, the mass of the exhaust gas and the specific heat capacity of the exhaust gas also have an effect. In the dynamic mode, at this time, a mathematical model as shown in fig. 11 is established, and the temperature after the exhaust valve of the engine in the steady-state mode is obtained from the exhaust gas temperature, the exhaust gas mass and flow rate coefficient, and the ambient temperature in the steady-state operation.

And respectively establishing a mathematical model according to the different working conditions, and calculating the temperature behind the exhaust valve of the engine.

As shown in fig. 12, the engine exhaust temperature calculation method according to the present embodiment includes the steps of:

s1, acquiring the temperature of the gas at the outlet of the engine exhaust pipe according to the temperature of the gas at the inlet of the engine exhaust pipe and the temperature of the pipe wall of the engine exhaust pipe;

s2, acquiring heat of a carrier in the catalyst according to the temperature of gas at the outlet of an engine exhaust pipe, the heat generated by chemical reaction in the catalyst and the temperature transferred to the external environment by the carrier in the catalyst;

s3, acquiring the inlet air temperature of the inlet pipe of the turbine, the inlet air temperature of the turbine and the outlet pipe temperature of the turbine according to the heat of the carrier in the catalyst and the pipe wall temperature of the inlet pipe of the turbine;

and S4, obtaining the temperature of the rear exhaust valve of the exhaust pipe of the engine according to the temperature of the exhaust pipe of the turbine.

The method for calculating the exhaust temperature of the engine provided by the embodiment is a method for estimating the numerical value of the exhaust temperature by establishing an exhaust temperature mathematical model, and is a method for obtaining the exhaust temperature of the engine under different working conditions by establishing the mathematical model of the temperature of the pipe component, the temperature of the carrier of the catalyst 2, the temperature of the turbine 3 and the like.

In the description herein, it is to be understood that the terms "upper", "lower", "right", and the like are based on the orientations and positional relationships shown in the drawings and are used for convenience in description and simplicity in operation, but do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be constructed in a particular operation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used merely for descriptive purposes and are not intended to have any special meaning.

In the description herein, references to the description of "an embodiment," "an example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example.

In addition, the foregoing is only the preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.