阅读说明：本技术 一种用于天然气发动机的egr流量计量系统及方法 (EGR flow metering system and method for natural gas engine ) 是由 王朋飞 张超 韩立 朱征宇 贾宏国 于 2021-08-30 设计创作，主要内容包括：本发明公开了一种用于天然气发动机的EGR流量计量系统及方法。EGR流量计量系统包括天然气发动机、增压器、混合器、第一文丘里管、第二文丘里管、EGR阀及天然气气轨,第一文丘里管的喉口直径大于第二文丘里管的喉口直径；混合器的出气口连接天然气发动机的进气口,用于混合空气、EGR废气及天然气；混合器的其中一个进气口连接增压器的增压器压气机,混合器的另一个进气口连接天然气气轨,发动机的EGR废气出口依次连接第一文丘里管、第二文丘里管及EGR阀后连接至混合器的第三个进气口；天然气发动机的排气口连接增压器的增压器涡轮机。本发明能满足天然气发动机对不同负荷工况的EGR流量精度要求。(The invention discloses an EGR flow metering system and method for a natural gas engine. The EGR flow metering system comprises a natural gas engine, a supercharger, a mixer, a first Venturi tube, a second Venturi tube, an EGR valve and a natural gas air rail, wherein the diameter of a throat of the first Venturi tube is larger than that of the throat of the second Venturi tube; the air outlet of the mixer is connected with the air inlet of the natural gas engine and used for mixing air, EGR waste gas and natural gas; one air inlet of the mixer is connected with a supercharger compressor of the supercharger, the other air inlet of the mixer is connected with a natural gas rail, and an EGR waste gas outlet of the engine is connected with a first Venturi tube, a second Venturi tube and an EGR valve in sequence and then is connected with a third air inlet of the mixer; the exhaust port of the natural gas engine is connected with a supercharger turbine of the supercharger. The invention can meet the EGR flow accuracy requirement of the natural gas engine on different load working conditions.)

1. The EGR flow metering system for the natural gas engine is characterized by comprising the natural gas engine (11), a supercharger (22), a mixer (17), a first Venturi tube (14), a second Venturi tube (15), an EGR valve (16) and a natural gas air rail (19), wherein the throat diameter of the first Venturi tube (14) is larger than that of the second Venturi tube (15); the air outlet of the mixer (17) is connected with the air inlet of the natural gas engine (11) and is used for mixing air, EGR waste gas and natural gas; one of the air inlets of the mixer (17) is connected with a booster (22) compressor of the booster (22), the other air inlet of the mixer (17) is connected with the natural gas rail (19), and an EGR waste gas outlet of the engine is connected with the first Venturi tube (14), the second Venturi tube (15) and the EGR valve (16) in sequence and then is connected with a third air inlet of the mixer (17); the exhaust port of the natural gas engine (11) is connected with a supercharger (22) turbine of the supercharger (22).

2. The EGR flow metering system for a natural gas engine according to claim 1, further comprising an EGR cooler (12) and a check valve (13) provided between the natural gas engine (11) and the first venturi tube (14), and an intake charge air cooler (21) and an electronic throttle valve (20) provided between the supercharger (22) and the mixer (17).

3. The EGR flow rate metering system for a natural gas engine according to claim 2, further comprising an intake air temperature pressure sensor (18) and an oxygen sensor (23), the intake air temperature pressure sensor (18) being provided at an intake port of the natural gas engine (11), the oxygen sensor (23) being provided at a turbocharger (22) turbine exhaust port of the turbocharger (22).

4. The EGR flow metering system for a natural gas engine according to claim 3, characterized in that a first inlet pressure sensor (141) is provided on the first venturi tube (14), the first inlet pressure sensor (141) being configured to measure a pressure of exhaust gas at an inlet of the first venturi tube (14);

an inlet temperature sensor (142) is arranged on the first Venturi tube (14), and the inlet temperature sensor (142) is used for measuring the temperature of the waste gas at the inlet of the first Venturi tube (14);

a first differential pressure sensor (143) is arranged on the first Venturi tube (14), and the first differential pressure sensor (143) is used for measuring the pressure difference between the inlet of the first Venturi tube (14) and the throat of the first Venturi tube (14);

a second inlet pressure sensor (151) is arranged on the second Venturi tube (15), and the second inlet pressure sensor (151) is used for measuring the waste gas pressure at the inlet of the second Venturi tube (15);

and a second differential pressure sensor (152) is arranged on the second Venturi tube (15), and the second differential pressure sensor (152) is used for measuring the pressure difference between the inlet of the second Venturi tube (15) and the throat of the second Venturi tube (15).

5. The EGR flow metering system for a natural gas engine according to claim 4, characterized by further comprising an ECU control unit (24), the first inlet pressure sensor (141), the inlet temperature sensor (142), the first differential pressure sensor (143), the second inlet pressure sensor (151), the intake air temperature pressure sensor (18), the oxygen sensor (23), the EGR valve (16), the electronic throttle valve (20), the supercharger (22), and the natural gas rail (19) all being connected with the ECU control unit (24).

6. An EGR flow measurement method based on the EGR flow measurement system for a natural gas engine according to any one of claims 1 to 5, characterized by comprising the steps of:

A. when the change rate of the instantaneous pressure of the intake air mixture at the air inlet of the natural gas engine is less than or equal to 20%, the natural gas engine is in a steady state working condition, and the EGR flow measuring method comprises the following steps:

a1, when the natural gas engine is in a steady-state working area with the required EGR flow higher than 100kg/h, namely the required EGR flow range is 100kg/h-250kg/h, judging that the EGR correction flow of the first Venturi tube is effective, and selecting the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine intake system;

a2, when the natural gas engine is in a steady-state working area with the required EGR flow lower than 100kg/h, namely the required EGR flow range is 0-100kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in the control calculation of the natural gas engine intake system;

B. when the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engine is more than 20%, the natural gas engine is in a transient working condition, and the EGR flow measuring method comprises the following steps:

b1, when the required EGR flow of the natural gas engine is in a transient working area higher than 120kg/h, judging that the EGR correction flow of the first Venturi tube is effective, and taking the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine system;

b2, when the required EGR flow of the natural gas engine is in a transient working area lower than 80kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in the control calculation of the natural gas engine system;

and B3, when the required EGR flow of the natural gas engine is 80-120kg/h, performing interpolation calculation on the EGR correction flow of the first Venturi tube and the EGR correction flow of the second Venturi tube, and then participating in control calculation of the natural gas engine system.

7. The EGR flow metering method of claim 6, wherein the flow metering formula of the venturi is as follows:

wherein P is the venturi inlet pressure, T_EGRIs the venturi inlet temperature; r is an ideal gas constant with the value of 287.0J/(kg.k), and delta P is the pressure difference between the inlet and the throat of the Venturi tube; ar is the effective area of the Venturi tube.

8. The EGR flow measurement method according to claim 6, wherein the EGR flow finally participating in the flow calculation of the intake system of the natural gas engine is the original calculated flow M output by the venturi tube_EGgrRawMultiplying the correction coefficient Fac, and in the whole engine working area, fitting the EGR rate measured by the exhaust equipment on the natural gas engine rack in the control unit and then back-calculating the standard EGR flow and the original calculated flow M of the Venturi tube_EGgrRawForming a function, obtaining Fac of each working area according to the current operating condition of the natural gas engine, and multiplying the correction coefficient Fac by the original calculated flow M of the Venturi tube_EGgrRawAnd finally obtaining the EGR corrected flow participating in the flow calculation of the natural gas engine air inlet system.

9. A vehicle, characterized in that the vehicle comprises:

one or more processors;

a memory for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement the EGR flow metering method of any of claims 6-8.

10. A computer readable storage medium, having stored thereon a computer program, characterized in that the program, when being executed by a processor, realizes the EGR flow metering method according to any one of claims 6-8.

Technical Field

The invention relates to the technical field of EGR flow measurement of natural gas engines, in particular to an EGR flow measurement system and method for a natural gas engine.

Background

With the implementation of the national six-stage emission regulation, the national control on various emission pollutants is more and more strict, so that the current technical route of the natural Gas engine at the national six-stage is equivalent combustion plus EGR (Exhaust Gas recirculation), that is, the Exhaust Gas after combustion of the natural Gas engine is sent into the natural Gas engine for utilization, thereby effectively reducing NO_XAnd the like. How to accurately control the EGR flow rate becomes a major factor in the six gas turbine control system in China. In the prior art, a single venturi tube is generally adopted for measuring the EGR flow of exhaust gas, the single venturi tube is completely fixed due to the structural size, but a part of working area of a natural gas engine is sensitive, and the EGR flow measuring precision of the part of working area can meet the requirement; however, some working areas of the natural gas engine are wide, and the phenomenon that the EGR flow metering precision does not meet the requirement necessarily exists in the working areas. In addition, the single venturi tube also aggravates the inaccuracy of the EGR flow measurement due to the influence of the accuracy error of the machining size inside the venturi tube, and causes the deviation of the control accuracy control of the whole engine air inlet system. When the differential pressure sensor and the pressure sensor on the venturi tube measure pressure signals and differential pressure signals in different ranges, the problem that the deviation of output signals and actual signals is large also exists, and further the deviation exists in the EGR flow accuracy measured by the venturi tube. In the natural gas engine in the sixth stage of China, due to the deviation of EGR flow measurement caused by the comprehensive factors, the emission pollutants are increased, the gas consumption of the engine is different, and the service life of the engine and the service life of an aftertreatment device are further influenced.

Accordingly, the prior art is yet to be improved and developed.

Disclosure of Invention

In order to solve the technical problems, the invention provides an EGR flow metering system and method for a natural gas engine, which can meet the EGR flow accuracy requirements of the natural gas engine on different load working conditions.

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

an EGR flow metering system for a natural gas engine comprises the natural gas engine, a supercharger, a mixer, a first Venturi tube, a second Venturi tube, an EGR valve and a natural gas air rail, wherein the diameter of a throat of the first Venturi tube is larger than that of the throat of the second Venturi tube; the air outlet of the mixer is connected with the air inlet of the natural gas engine and used for mixing air, EGR waste gas and natural gas; one air inlet of the mixer is connected with a supercharger compressor of the supercharger, the other air inlet of the mixer is connected with the natural gas rail, and an EGR waste gas outlet of the engine is connected with the first Venturi tube, the second Venturi tube and the EGR valve in sequence and then is connected with a third air inlet of the mixer; and the exhaust port of the natural gas engine is connected with a supercharger turbine of the supercharger.

As an alternative to the above EGR flow rate measuring system for a natural gas engine, the EGR flow rate measuring system further includes an EGR cooler and a check valve provided between the natural gas engine and the first venturi tube, and an intake intercooler and an electronic throttle valve provided between the supercharger and the mixer.

As an alternative to the above EGR flow rate measuring system for a natural gas engine, the EGR flow rate measuring system further includes an intake air temperature pressure sensor and an oxygen sensor, the intake air temperature pressure sensor is provided at an intake port of the natural gas engine, and the oxygen sensor is provided at an exhaust port of a turbocharger turbine of the supercharger.

As an alternative to the above EGR flow metering system for a natural gas engine, the first venturi is provided with a first inlet pressure sensor for measuring the pressure of the exhaust gas at the inlet of the first venturi;

an inlet temperature sensor is arranged on the first Venturi tube and used for measuring the temperature of the waste gas at the inlet of the first Venturi tube;

the first Venturi tube is provided with a first differential pressure sensor which is used for measuring the pressure difference between the inlet of the first Venturi tube and the throat of the first Venturi tube;

a second inlet pressure sensor is arranged on the second Venturi tube and used for measuring the waste gas pressure at the inlet of the second Venturi tube;

and a second differential pressure sensor is arranged on the second Venturi tube and used for measuring the pressure difference between the inlet of the second Venturi tube and the throat of the second Venturi tube.

As an alternative to the above EGR flow rate measurement system for a natural gas engine, the EGR flow rate measurement system further includes an ECU control unit, and the first inlet pressure sensor, the inlet temperature sensor, the first differential pressure sensor, the second inlet pressure sensor, the intake air temperature pressure sensor, the oxygen sensor, the EGR valve, the electronic throttle valve, the supercharger, and the natural gas rail are all connected to the ECU control unit.

An EGR flow metering method based on the EGR flow metering system for the natural gas engine comprises the following steps:

A. when the change rate of the instantaneous pressure of the intake air mixture at the air inlet of the natural gas engine is less than or equal to 20%, the natural gas engine is in a steady state working condition, and the EGR flow measuring method comprises the following steps:

a1, when the natural gas engine is in a steady-state working area with the required EGR flow higher than 100kg/h, namely the required EGR flow range is 100kg/h-250kg/h, judging that the EGR correction flow of the first Venturi tube is effective, and selecting the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine intake system;

a2, when the natural gas engine is in a steady-state working area with the required EGR flow lower than 100kg/h, namely the required EGR flow range is 0-100kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in the control calculation of the natural gas engine intake system;

B. when the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engine is more than 20%, the natural gas engine is in a transient working condition, and the EGR flow measuring method comprises the following steps:

b1, when the required EGR flow of the natural gas engine is in a transient working area higher than 120kg/h, judging that the EGR correction flow of the first Venturi tube is effective, and taking the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine system;

b2, when the required EGR flow of the natural gas engine is in a transient working area lower than 80kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in the control calculation of the natural gas engine system;

and B3, when the required EGR flow of the natural gas engine is 80-120kg/h, performing interpolation calculation on the EGR correction flow of the first Venturi tube and the EGR correction flow of the second Venturi tube, and then participating in control calculation of the natural gas engine system.

As an alternative to the EGR flow metering method for natural gas engines described above, the flow metering formula for the venturi is as follows:

wherein P is the venturi inlet pressure, T_EGRIs the venturi inlet temperature; r is an ideal gas constant with the value of 287.0J/(kg.k), and delta P is the pressure difference between the inlet and the throat of the Venturi tube; ar is the effective area of the Venturi tube.

As an alternative of the EGR flow measuring method for the natural gas engine, the EGR flow which finally participates in the flow calculation of the air inlet system of the natural gas engine is the original calculated flow M output by the venturi tube_EGgrRawMultiplying by a correction factor Fac, and calculating the standard EGR flow in the control unit by fitting the EGR rate measured by the exhaust equipment on the natural gas engine stand in the whole engine working areaVolume and venturi tube original calculated flow M_EGgrRawForming a function, obtaining Fac of each working area according to the current operating condition of the natural gas engine, and multiplying the correction coefficient Fac by the original calculated flow M of the Venturi tube_EGgrRawAnd finally obtaining the EGR corrected flow participating in the flow calculation of the natural gas engine air inlet system.

A vehicle, the vehicle comprising:

one or more processors;

a memory for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement any of the above described methods of EGR flow metering for natural gas engines.

A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements any of the above described EGR flow metering methods for a natural gas engine.

The invention has the advantages that: the EGR flow rate of the first Venturi tube or the second Venturi tube with higher output precision can be flexibly selected to output EGR flow rate of the first Venturi tube or the second Venturi tube to participate in engine EGR flow control when the natural gas engine operates at different loads, so that the precision of the EGR flow rate entering the natural gas engine is effectively improved, the EGR rate entering a cylinder is accurately controlled, and the mixed gas component burnt in the cylinder of the engine is accurately controlled, thereby accurately controlling the combustion condition in the cylinder of the engine, effectively improving the thermal efficiency of the engine and effectively reducing NO_XThe emission of pollutants and the prolonging of the service life of the natural gas engine and the postprocessor.

Drawings

FIG. 1 is a schematic diagram of an EGR flow metering system for a natural gas engine according to the present invention;

FIG. 2 is a schematic diagram of the venturi of the present invention;

fig. 3 is a flow chart of an EGR flow measurement method of a natural gas engine in the present invention.

Reference numerals:

11. a natural gas engine; 111. an engine intake; 112. an engine exhaust pipe; 12. an EGR cooler; 13. a one-way valve; 14. a first venturi tube; 141. a first inlet pressure sensor; 142. an inlet temperature sensor; 143. a first differential pressure sensor; 15. a second venturi tube; 151. a second inlet pressure sensor; 152. a second differential pressure sensor; 16. an EGR valve; 17. a mixer; 18. an intake air temperature pressure sensor; 19. a natural gas rail; 20. an electronic throttle valve; 21. an air intake intercooler; 22. a supercharger; 221. a supercharger compressor; 222. a supercharger turbine; 23. an oxygen sensor; 24. an ECU control unit.

Detailed Description

The following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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.

Example one

It should be noted that, for convenience of description, only a part of structures related to the present invention, not all of the structures, are shown in the drawings.

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 by those skilled in the art according to specific situations.

Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

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

The invention provides an EGR flow metering system for a natural gas engine. As shown in fig. 1, the EGR flow metering system includes a natural gas engine 11, a supercharger 22, a mixer 17, a first venturi tube 14, a second venturi tube 15, an EGR valve 16 and a natural gas rail 19. referring to fig. 1 and 2, the throat diameter of the first venturi tube 14 is larger than that of the second venturi tube 15, so the first venturi tube 14 may also be referred to as a large venturi tube, and the second venturi tube 15 may also be referred to as a small venturi tube. The first venturi tube 14 is connected to the second venturi tube 15 by a short length of tubing.

The outlet of the mixer 17 is connected to the inlet of the natural gas engine 11, and the mixer 17 is used for mixing air, EGR exhaust gas, and natural gas, and then sending the mixed gas into the engine inlet 111. The mixer 17 comprises three air inlets, respectively a fresh air inlet, an EGR exhaust gas inlet and a natural gas inlet. The fresh air inlet is connected to the supercharger compressor 221 of the supercharger 22. As shown in fig. 1, supercharger 22 includes a supercharger compressor 221 and a supercharger compressor 222. The booster compressor 221 is used for supplying fresh air into the natural gas engine 11, and the booster compressor 222 is used for discharging exhaust gas of the natural gas engine 11. The natural gas inlet of the mixer 17 is connected with a natural gas rail 19, and the natural gas rail 19 can control the air input of the natural gas. An EGR exhaust gas outlet of the engine (referring to fig. 1, the EGR exhaust gas outlet is a six-cylinder outlet of an exhaust pipe 112 of the engine) is connected to an EGR exhaust gas inlet of a mixer 17 after being connected to a first venturi tube 14, a second venturi tube 15 and an EGR valve 16 in sequence. An exhaust port of the natural gas engine 11 is connected with a supercharger compressor 222 of the supercharger 22.

The EGR valve 16 is an intelligent EGR valve 16, and the EGR valve 16 is directly arranged on the mixer 17, so that the length of a pipeline from the EGR valve 16 to the mixer 17 can be shortened, the speed of controlling EGR waste gas to enter a cylinder can be effectively improved, and the response speed of the whole engine air inlet system is improved. The EGR valve 16 is installed downstream of the second venturi tube 15, and the influence of the exhaust pulsation on the control of the opening degree of the EGR valve 16 can be effectively prevented, indirectly improving the accuracy of controlling the flow rate of EGR exhaust gas entering the mixer 17.

As shown in fig. 1, the EGR flow rate measurement system further includes an EGR cooler 12 and a check valve 13 provided between the natural gas engine 11 and the first venturi tube 14. The EGR cooler 12 is connected with six cylinder outlets of the engine exhaust pipe 112 at the upstream and is connected with the one-way valve 13 at the downstream, and is used for cooling the exhaust gas taken out from the natural gas engine exhaust pipe 112 and preventing the service life of a sensor on a Venturi tube from being reduced due to overhigh temperature of the exhaust gas. In addition, utilize EGR cooler 12 cooling EGR waste gas, reduce EGR waste gas temperature, can prevent effectively that EGR waste gas from heating the gas mixture, causing the engine cylinder to have higher detonation risk. The check valve 13 is installed behind the EGR cooler 12 and before the venturi tube, and can be used to control the air flow direction of EGR exhaust gas, prevent the exhaust gas reflux coming out from the EGR cooler 12, thereby ensuring that sufficient EGR exhaust gas enters the venturi tube, and ensuring that the engine has a large EGR rate. In addition, the check valve 13 can eliminate part of exhaust pulsation, and can effectively eliminate the measurement error of the sensor caused by the exhaust pulsation after the exhaust pulsation is eliminated, so that the accuracy of the measurement signal of the sensor is ensured.

The check valve 13 is connected with a first venturi tube 14, and the first venturi tube 14 is connected with a second venturi tube 15 through a short section of pipeline, which is the core device of the EGR flow metering system of the present invention. In one embodiment, the throat diameter of the first venturi tube 14 is about 18mm, the throat diameter of the second venturi tube 15 is about 13mm, and the throat diameter ratio of the first venturi tube 14 to the second venturi tube 15 is about 1.38. Of course, the throat diameter ratio of the first venturi tube 14 to the second venturi tube 15 is not limited thereto, and other selection may be made according to the operating characteristics of the engine.

As shown in fig. 2, the first venturi tube 14 is provided with a first inlet pressure sensor 141 for measuring the EGR gas pressure at the inlet of the first venturi tube 14, the first venturi tube 14 is further provided with an inlet temperature sensor 142 for measuring the EGR gas temperature at the inlet of the first venturi tube 14, the first venturi tube 14 is provided with a first differential pressure sensor 143, and the first differential pressure sensor 143 is used for measuring the pressure difference between the inlet of the first venturi tube 14 and the throat of the first venturi tube 14. The second venturi tube 15 is provided with a second inlet pressure sensor 151, the second inlet pressure sensor 151 is used for measuring the pressure of the waste gas at the inlet of the second venturi tube 15, the second venturi tube 15 is provided with a second differential pressure sensor 152, and the second differential pressure sensor 152 is used for measuring the pressure difference between the inlet of the second venturi tube 15 and the throat of the second venturi tube 15.

As shown in fig. 1, the EGR flow rate measurement system further includes an intake charge air cooler 21 and an electronic throttle valve 20 provided between the supercharger 22 and the mixer 17. The intake intercooler 21 is connected upstream to the supercharger compressor 221 and downstream to the electronic throttle 20. The air intake intercooler 21 is located behind the supercharger compressor 221, and can effectively cool fresh air at the outlet of the compressor and reduce the temperature of intake air, so that the temperature of mixed air is reduced, and the detonation risk is reduced.

With continued reference to fig. 1, the EGR flow rate measurement system further includes an intake temperature and pressure sensor 18 and an oxygen sensor 23, the intake temperature and pressure sensor 18 is disposed at an intake of the natural gas engine 11, and the oxygen sensor 23 is disposed at an exhaust of the supercharger compressor 222. The intake temperature and pressure sensor 18 is installed after the mixer 17 and before the intake passage 111 of the engine, the load of the engine is the load state of the engine which is distinguished by combining the intake temperature and pressure sensor 18 and the rotating speed signals of all the engines, and the pressure signal output by the intake temperature and pressure sensor 18 is also used for calculating the pressure change rate of the engine and distinguishing the transient state working condition and the steady state working condition of the engine.

As shown in fig. 1, the EGR flow rate measurement system further includes an ECU (Electronic Control Unit) Control Unit 24 for controlling the operation of the entire EGR flow rate measurement system. All sensors and actuators in the EGR flow metering system are connected to the ECU control unit 24. Specifically, the sensors include a first inlet pressure sensor 141, an inlet temperature sensor 142, a first differential pressure sensor 143, a second inlet pressure sensor 151, the intake air temperature pressure sensor 18, and the oxygen sensor 23, which are all connected to the ECU control unit 24, and the ECU control unit 24 receives signals transmitted by the sensors. The actuators include an EGR valve 16, an electronic throttle 20, a supercharger 22, and a natural gas rail 19, all connected to an ECU control unit 24, and the ECU control unit 24 receives signals from the actuators and adjusts the operation of the actuators.

In the invention, the flow metering formula of the Venturi tube is as follows:

the unit of flow measurement is kg/h in the formula. In the above formula, P is the venturi inlet pressure in hpa; t is_EGRIs the venturi inlet temperature in units; r is an ideal gas constant with the value of 287.0J/(kg.k); delta P is the pressure difference between the inlet and the throat of the Venturi tube, and the unit hpa; ar is effective area of Venturi tube in cm²。

In the present invention, the pressure change rate is calculated as follows:

the pressure rate of change is given in hpa/ms. In the above formula, P_iIs at the t_ims mixture intake pressure, P_i-1Is at the t_{i- 1}ms mixture intake pressure.

Example two

Based on the EGR flow metering system for the natural gas engine, the invention further provides an EGR flow metering method for the natural gas engine. Referring to fig. 3, the EGR flow metering method includes the steps of:

s100, the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engineWhen the pressure change rate of the intake air mixture at the air inlet of the natural gas engine is less than or equal to 20 percent (namely when the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engine is less than or equal to a pressure change rate threshold value), the natural gas engine is in a steady-state working condition, and the EGR flow metering method comprises the following steps:

s110, when the natural gas engine is in a steady-state working area where the required EGR flow is higher than 100kg/h (namely when the natural gas engine is in a steady-state working area where the required EGR flow is higher than an EGR flow threshold), namely when the required EGR flow range is 100kg/h-250kg/h, judging that the EGR correction flow of a first Venturi tube is effective, and selecting the EGR correction flow of the first Venturi tube to participate in control calculation of an air intake system of the natural gas engine;

specifically, 100kg/h is the EGR flow threshold of the natural gas engine, the EGR metering flow interval of the natural gas engine is 0-250kg/h, and the pressure change rate threshold is 20%. However, the setting of the threshold is not limited to this, and the EGR flow threshold and the pressure change rate threshold may be preset again according to the performance index requirements of different natural gas engines.

S120, when the natural gas engine is in a steady-state working area with the required EGR flow lower than 100kg/h, namely the required EGR flow range is 0-100kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in control calculation of an air intake system of the natural gas engine;

s200, the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engineWhen the EGR flow is larger than 20%, the natural gas engine is in a transient working condition, and the EGR flow measuring method comprises the following steps:

s210, when the required EGR flow of the natural gas engine is in a transient working area higher than 120kg/h (100kg/h 120%), judging that the EGR correction flow of the first Venturi tube is effective, and taking the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine system;

s220, when the required EGR flow of the natural gas engine is in a transient working area lower than 80kg/h (100kg/h 80%), judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in control calculation of the natural gas engine system;

and S230, when the required EGR flow of the natural gas engine is 80-120kg/h (100kg/h +/-20%), performing interpolation calculation on the EGR correction flow of the first Venturi tube and the EGR correction flow of the second Venturi tube, and then participating in control calculation of the natural gas engine system.

By the EGR flow measuring method, the EGR correction flow of different venturi tubes is adopted to participate in the control calculation of the natural gas engine system under different working conditions of the natural gas engine, and the EGR flow precision requirements of the natural gas engine on different load working conditions can be met.

Similarly to the embodiment, in the EGR flow metering method of the present invention, the flow metering formula of the venturi tube is as follows:

wherein P is the venturi inlet pressure, T_EGRIs the venturi inlet temperature; r is an ideal gas constant with the value of 287.0J/(kg.k), and delta P is the pressure difference between the inlet and the throat of the Venturi tube; ar is the effective area of the Venturi tube.

In the EGR flow measurement method, the EGR correction flow of the venturi tube is mentioned because not the actual measured flow value of the venturi tube but the corrected correction flow value is finally involved in the calculation. The EGR flow which finally participates in the flow calculation of the natural gas engine air inlet system is the original calculated flow M output by the venturi tube_EGgrRawMultiplying the correction coefficient Fac, and in the whole engine working area, fitting the EGR rate measured by the exhaust equipment on the natural gas engine rack in the control unit and then back-calculating the standard EGR flow and the original calculated flow M of the Venturi tube_EGgrRawForming a function to obtain each working area according to the current operating condition of the natural gas engineFac, multiplying the correction coefficient Fac by the original calculated flow M of the Venturi tube_EGgrRawAnd finally obtaining the EGR corrected flow participating in the flow calculation of the natural gas engine air inlet system.

Similarly to the embodiment, in the EGR flow measurement method of the present invention, the pressure change rate is calculated as follows:

the pressure rate of change is given in hpa/ms. In the above formula, P_iIs at the t_ims mixture intake pressure, P_i-1Is at the t_{i- 1}ms mixture intake pressure.

EXAMPLE III

The third embodiment of the present invention further provides a vehicle, and the components of the vehicle may include but are not limited to: the vehicle body, one or more processors, memory, and a bus connecting the various system components (including the memory and the processors).

The memory, as a computer readable storage medium, may be used to store software programs, computer executable programs, and modules, such as program instructions corresponding to the EGR flow metering method for a natural gas engine in an embodiment of the invention. The processor implements the EGR flow metering method for a natural gas engine described above by executing software programs, instructions, and modules stored in the memory to perform various functional applications and data processing of the vehicle.

The memory can mainly comprise a program storage area and a data storage area, wherein the program storage area can store an operating system and an application program required by at least one function; the storage data area may store data created according to the use of the terminal, and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory may further include memory remotely located from the processor, and these remote memories may be connected to the vehicle over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

Example four

A fourth embodiment of the present invention further provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements an EGR flow metering method for a natural gas engine, the EGR flow metering method for a natural gas engine comprising the steps of:

s100, the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engineWhen the mass ratio is less than or equal to 20%, the natural gas engine is in a steady state working condition, and the EGR flow measuring method comprises the following steps:

s110, when the natural gas engine is in a steady-state working area with the required EGR flow higher than 100kg/h, namely the required EGR flow range is 100kg/h-250kg/h, judging that the EGR correction flow of the first Venturi tube is effective, and selecting the EGR correction flow of the first Venturi tube to participate in control calculation of an air intake system of the natural gas engine;

s120, when the natural gas engine is in a steady-state working area with the required EGR flow lower than 100kg/h, namely the required EGR flow range is 0-100kg/h, judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in control calculation of an air intake system of the natural gas engine;

s200, the instantaneous pressure change rate of the intake air mixture at the air inlet of the natural gas engineWhen the EGR flow is larger than 20%, the natural gas engine is in a transient working condition, and the EGR flow measuring method comprises the following steps:

s210, when the required EGR flow of the natural gas engine is in a transient working area higher than 120kg/h (100kg/h 120%), judging that the EGR correction flow of the first Venturi tube is effective, and taking the EGR correction flow of the first Venturi tube to participate in the control calculation of the natural gas engine system;

s220, when the required EGR flow of the natural gas engine is in a transient working area lower than 80kg/h (100kg/h 80%), judging that the EGR correction flow of the second Venturi tube is effective, and selecting the EGR correction flow of the second Venturi tube to participate in control calculation of the natural gas engine system;

and S230, when the required EGR flow of the natural gas engine is 80-120kg/h (100kg/h +/-20%), performing interpolation calculation on the EGR correction flow of the first Venturi tube and the EGR correction flow of the second Venturi tube, and then participating in control calculation of the natural gas engine system.

Of course, embodiments of the present invention provide a computer-readable storage medium whose computer-executable instructions are not limited to the method operations described above, but may also perform related operations in an EGR flow metering method for a natural gas engine provided by any of the embodiments of the present invention.

From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.

In the above embodiment, each included unit and module is only divided according to functional logic, but is not limited to the above division as long as the corresponding function can be realized; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Numerous obvious variations, adaptations and substitutions will occur to those skilled in the art without departing from the scope of the invention. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.