Air flow calculation method and device, gas engine and vehicle

Abstract

The invention discloses an air flow calculation method and device, a gas engine and a vehicle, the method and device are applied to the gas engine, and the gas engine at least comprises a throttle valve and a Venturi tube; the output end of the throttle valve is connected with the input end of the Venturi tube; the air flow calculation method comprises the steps that the upstream pressure and the downstream pressure of a throttle valve are obtained; determining the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure; determining a working mode of the gas engine according to the pressure ratio; and determining the air flow of the gas engine according to the air inlet flow of the throttle valve, the air inlet flow of the Venturi tube, the working mode and the filter coefficient. According to the air flow calculation method provided by the invention, the problem of contradiction between noise suppression and response speed of air flow estimation under the high-flow working condition can be solved, and the gas control precision and the system stability are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas engines, and in particular to a method and device for calculating air flow, a gas engine, and a vehicle. Background Art

[0002] In gas engines, the throttle and intake venturi calculate the fresh air volume, and the final air volume value is obtained by using the simultaneous equations of the two. However, the current approach has the following problems:

[0003] Reduced signal sensitivity: When the pressure ratio is close to 1, the equation is sensitive to input errors (such as pressure sensor noise and opening signal jitter), causing the calculated air volume to fluctuate violently;

[0004] Poor control stability: Fluctuations are transmitted to the gas quantity and air-fuel ratio control modules, causing gas injection oscillations. Summary of the Invention

[0005] The present invention provides a method and device for calculating air flow, a gas engine, and a vehicle. The operating mode of the gas engine is determined by the pressure ratio of the throttle valve, thereby dynamically adjusting the filter parameters and adaptively adjusting the air flow calculation method according to different operating modes. This fundamentally solves the contradiction between noise suppression and response speed in air flow estimation under high-flow conditions, and significantly improves the gas control accuracy and system stability.

[0006] According to a first aspect of the present invention, a method for calculating air flow is provided, which is applied to a gas engine, wherein the gas engine comprises at least a throttle valve and a venturi tube; the output end of the throttle valve is connected to the input end of the venturi tube; the method for calculating air flow comprises:

[0007] obtaining an upstream pressure and a downstream pressure of the throttle valve;

[0008] determining a pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure;

[0009] determining an operating mode of the gas engine according to the pressure ratio;

[0010] The air flow rate of the gas engine is determined according to the intake flow rate of the throttle valve, the intake flow rate of the venturi tube, the working mode and a filter coefficient.

[0011] Optionally, determining the operating mode of the gas engine according to the pressure ratio includes:

[0012] When the pressure ratio is greater than or equal to a first threshold, the operating mode of the gas engine is transient;

[0013] When the pressure ratio is less than the first threshold, the operating mode of the gas engine is steady state.

[0014] Optionally, after determining the operating mode of the gas engine according to the pressure ratio, it includes:

[0015] When the operating mode of the gas engine is transient, the air flow rate of the gas engine is determined by formulas (1), (2) and (3);

[0016]

[0017] where y is the air flow rate, α is the filtering coefficient, x is the air flow rate after weight ratio calculation, n is the time, T is the sampling frequency, f c is the cut-off frequency, τ is the calibrated value of the electronic control unit in the gas engine, and e is the natural constant;

[0018] When the operating mode of the gas engine is steady state, the air flow rate of the gas engine is determined by formula (4);

[0019]

[0020] where b0, b1, a1 and a2 are all calibrated values of the electronic control unit in the gas engine.

[0021] Optionally, the intake air flow rate of the throttle valve is determined by formulas (5), (6), (7) and (8):

[0022]

[0023] where m is the intake air flow rate of the throttle valve, A is the flow area, P us is the upstream pressure of the throttle valve, P ds is the downstream pressure of the throttle valve, R is the ideal gas constant, T us is the upstream temperature of the throttle valve, and k is the adiabatic index.

[0024] Optionally, the intake air flow rate of the Venturi tube is determined by formula (9):

[0025]

[0026] where q m is the intake air flow rate of the Venturi tube, C is the discharge coefficient, β is the ratio of the throat diameter to the inlet diameter of the Venturi tube, ε is the expansion coefficient, d is the throat diameter of the Venturi tube, Δp is the static pressure difference between the inlet and the throat of the Venturi tube, p is the pressure at the inlet of the Venturi tube, R is the ideal gas constant, and T is the inlet temperature of the Venturi tube.

[0027] Optionally, after determining the operating mode of the gas engine according to the pressure ratio, it includes:

[0028] Determine the weight ratio of the gas engine based on the pressure ratio, the intake air flow of the throttle valve, and the intake air flow of the Venturi tube.

[0029] Optionally, the pressure ratio is the downstream pressure of the throttle valve divided by the upstream pressure of the throttle valve.

[0030] According to a second aspect of the present invention, there is provided a device for calculating air flow, which is applied to a gas engine. The gas engine at least includes: a throttle valve and a Venturi tube; the output end of the throttle valve is connected to the input end of the Venturi tube; the air flow calculation device includes;

[0031] A pressure acquisition module for acquiring the upstream pressure and the downstream pressure of the throttle valve;

[0032] A pressure ratio calculation module for determining the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure;

[0033] An operating mode determination module for determining the operating mode of the gas engine according to the pressure ratio;

[0034] An air flow calculation module for determining the air flow of the gas engine according to the intake air flow of the throttle valve, the intake air flow of the Venturi tube, the operating mode, and the filtering coefficient.

[0035] According to a third aspect of the present invention, there is provided a gas engine, including: an engine body, an intake pipeline, an exhaust pipeline, an air filter, a supercharger, an intercooler, a throttle valve, a Venturi tube, an exhaust gas recirculation valve, an exhaust gas recirculation cooler, and the air flow calculation device described in the second aspect of the present invention;

[0036] Both the intake pipeline and the exhaust pipeline are connected to the engine body. The air filter, the supercharging end of the supercharger, the intercooler, the throttle valve, and the Venturi tube are sequentially arranged in the intake pipeline. The turbine end of the supercharger is arranged in the exhaust pipeline. The exhaust gas recirculation valve and the exhaust gas recirculation cooler are arranged between the exhaust pipeline and the intake pipeline.

[0037] According to a fourth aspect of the present invention, there is provided a vehicle, including the gas engine described in the third aspect of the present invention.

[0038] The present invention discloses a method and device for calculating air flow rate, a gas engine and a vehicle, which are applied to a gas engine. The gas engine at least includes a throttle valve and a Venturi tube; the output end of the throttle valve is connected to the input end of the Venturi tube; the method for calculating air flow rate includes: obtaining the upstream pressure and downstream pressure of the throttle valve; determining the pressure ratio of the throttle valve according to the upstream pressure and downstream pressure; determining the working mode of the gas engine according to the pressure ratio; and determining the air flow rate of the gas engine according to the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the working mode and the filtering coefficient. The method for calculating air flow rate provided by the present invention determines the working mode of the gas engine through the pressure ratio of the throttle valve, thereby dynamically adjusting the filtering parameters, and adaptively adjusting the method for calculating air flow rate according to different working modes, fundamentally solving the problem of the contradiction between noise suppression and response speed in air flow rate estimation under high flow rate conditions, and significantly improving the gas control accuracy and system stability.

[0039] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 is a schematic structural diagram of the gas engine provided by the embodiment of the present invention;

[0042] Figure 2 is a flowchart of a method for calculating air flow rate provided by the embodiment of the present invention;

[0043] Figure 3 is a flowchart of another method for calculating air flow rate provided by the embodiment of the present invention;

[0044] Figure 4 is a flowchart of another method for calculating air flow rate provided by the embodiment of the present invention;

[0045] Figure 5 is a result waveform diagram of the method for calculating air flow rate provided by the embodiment of the present invention;

[0046] Figure 6 is a schematic structural diagram of the device for calculating air flow rate provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0049] It should be understood that various forms of processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0050] Figure 1 is a schematic structural diagram of a gas engine provided by an embodiment of the present invention, Figure 2 is a flowchart of a method for calculating an air flow rate provided by an embodiment of the present invention, referring to Figure 1 and Figure 2 ,

[0051] A method for calculating an air flow rate provided by an embodiment of the present invention is applied to a gas engine. The gas engine at least includes: a throttle valve 5 and a Venturi tube 6; the output end of the throttle valve 5 is connected to the input end of the Venturi tube 6.

[0052] Among them, a gas engine is an internal combustion engine powered by a gas fuel (such as natural gas, biogas, liquefied petroleum gas, etc.). It generates power by burning the gas and is widely used in fields such as power generation, transportation, and industrial power. The working principle of a gas engine is similar to that of a gasoline / diesel engine, and both belong to internal combustion engines. The difference is that the fuel used in a gas engine is gas.

[0053] Throttle valve: The throttle valve 5 is an important component of a gas engine. By adjusting the valve opening of the throttle valve, the air flow into the gas engine is controlled, thereby adjusting the load and power output of the engine.

[0054] Venturi tube: The Venturi tube 6 is also an important component of a gas engine. It uses cross-sectional contraction to accelerate the air flow and generates a low-pressure area at the throat according to Bernoulli's principle.

[0055] As Figure 1 shown, the output end of the throttle valve 5 in the gas engine is connected to the input end of the Venturi tube 6 so that air can smoothly enter the engine body 1.

[0056] Reference Figure 2 , the calculation method for air flow provided by the embodiment of the present invention includes:

[0057] S101. Obtain the upstream pressure and downstream pressure of the throttle valve.

[0058] Among them, the upstream pressure: refers to the gas pressure at the inlet of the throttle valve 5, that is, the intake end pressure of the throttle valve 5.

[0059] The downstream pressure: refers to the gas pressure at the outlet of the throttle valve 5, that is, the exhaust end pressure of the throttle valve 5.

[0060] Specifically, an upstream pressure sensor is installed on the left side of the throttle valve 5 (i.e., the intake end, Figure 1 not shown in Figure 1 ); a downstream pressure sensor is installed on the right side (i.e., the exhaust end,

[0061] not shown in

[0062] The upstream pressure and downstream pressure of the throttle valve 5 are obtained through the upstream pressure sensor and the downstream pressure sensor.

[0063] Optionally, the pressure ratio is the downstream pressure of the throttle valve 5 divided by the upstream pressure of the throttle valve 5.

[0064] Specifically, according to the upstream pressure and downstream pressure of the throttle valve 5 obtained in the above step S101, taking the downstream pressure as the numerator and the upstream pressure as the denominator, the pressure ratio of the throttle valve 5 can be calculated.

[0065] S103. Determine the working mode of the gas engine according to the pressure ratio.

[0066] Specifically, according to the pressure ratio of the throttle valve calculated in the above step S102, the working mode of the gas engine is determined. The working mode of the gas engine is determined according to the magnitude relationship between the pressure ratio and the set threshold value. Among them, the working mode can be transient or steady state.

[0067] S104. Determine the air flow rate of the gas engine based on the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the operating mode, and the filtering coefficient.

[0068] Among them, the filtering coefficient can be determined by looking up a table according to the load change rate of the engine (i.e., the change speed of the engine output power or torque) and the pressure ratio obtained in step S102 (i.e., the ratio of the downstream pressure to the upstream pressure of the throttle valve 5).

[0069] Exemplarily, when the load change rate of the engine > 50% / s and the pressure ratio is 0.2 - 0.5, the filtering coefficient can be 0.1; when the load change rate of the engine > 50% / s and the pressure ratio is 0.5 - 0.8, the filtering coefficient can be 0.2; when the load change rate of the engine < 10% / s and the pressure ratio is 0.2 - 0.5, the filtering coefficient can be 0.8; when the load change rate of the engine < 10% / s and the pressure ratio is 0.5 - 0.8, the filtering coefficient can be 0.5. Specifically, based on the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the operating mode of the engine, and the filtering coefficient, determine the air flow rate of the gas engine. The specific calculation method will be elaborated in detail below and will not be repeated here.

[0070] The air flow rate calculation method provided by the embodiments of the present invention determines the operating mode of the gas engine through the pressure ratio of the throttle valve, thereby dynamically adjusting the filtering parameters, and adaptively adjusting the air flow rate calculation method according to different operating modes, fundamentally solving the problem of the contradiction between noise suppression and response speed in air flow rate estimation under high flow rate conditions, and significantly improving the gas control accuracy and system stability.

[0071] Based on the above embodiments of the invention, the embodiments of the present invention further refine the determination of the operating mode of the gas engine according to the pressure ratio. Figure 3 It is a flowchart of another air flow rate calculation method provided by the embodiments of the present invention. The calculation method provided by the embodiments of the present invention includes:

[0072] S201. Obtain the upstream pressure and downstream pressure of the throttle valve.

[0073] S202. Determine the pressure ratio of the throttle valve according to the upstream pressure and downstream pressure.

[0074] S203. Compare the pressure ratio of the throttle valve with a first threshold; when the pressure ratio of the throttle valve is greater than or equal to the first threshold, then execute step S2031; when the pressure ratio of the throttle valve is less than the first threshold, then execute step S2032.

[0075] S2031. When the pressure ratio is greater than or equal to the first threshold, the operating mode of the gas engine is transient.

[0076] Among them, the transient operating mode of the gas engine is a state in which the gas engine experiences rapid changes in load or speed within a short period of time. For example, sudden acceleration or emergency braking of a vehicle, etc.

[0077] Specifically, according to the gas engine compression ratio determined in the above step S202, the compression ratio is compared with the first threshold. When the compression ratio is greater than or equal to the first threshold, it is determined that the operating mode of the gas engine is transient.

[0078] S2032: When the compression ratio is less than the first threshold, the operating mode of the gas engine is steady state.

[0079] Among them, the steady-state operating mode of the gas engine is a state in which the engine operates for a long time at a constant load and speed. For example, long-term constant-speed cruising of a vehicle.

[0080] Specifically, according to the gas engine compression ratio determined in the above step S202, the compression ratio is compared with the first threshold. When the compression ratio is less than the first threshold, it is determined that the operating mode of the gas engine is steady state.

[0081] S204: Determine the air flow rate of the gas engine according to the intake air flow rate of the throttle valve, the intake air flow rate of the venturi tube, the operating mode, and the filtering coefficient.

[0082] Based on the above embodiments, the embodiments of the present invention are further refined after determining the operating mode of the gas engine according to the compression ratio. The calculation method of the air flow rate provided by the embodiments of the present invention includes:

[0083] When the operating mode of the gas engine is transient, the air flow rate of the gas engine is determined by formulas (1), (2), and (3);

[0084]

[0085] Among them, y is the air flow rate, α is the filtering coefficient, x is the air flow rate after weighted ratio calculation, n is the time, T is the sampling frequency, f c is the cut-off frequency, τ is the calibrated value of the electronic control unit in the gas engine, and e is the natural constant;

[0086] Specifically, when it is determined that the operating mode of the gas engine is transient, first-order low-pass filtering is adopted, and the cut-off frequency f c is 5 - 10 Hz to ensure the response speed in the case of sudden load changes;

[0087] When the operating mode of the gas engine is steady state, the air flow rate of the gas engine is determined by formula (4);

[0088]

[0089] Among them, b0, b1, a1, and a2 are all calibration quantities of the electronic control unit in the gas engine.

[0090] The calibration quantity of the Electronic Control Unit (ECU) refers to the adjustable parameters predefined and stored in the ECU, which are used to optimize the control logic of the engine, transmission, emission system, etc., and can be preset through experiments.

[0091] Specifically, when it is determined that the working mode of the gas engine is steady state, high-order low-pass filtering (such as second-order) is adopted, and the cut-off frequency f c is 1 - 2 Hz.

[0092] Optionally, the intake air flow rate of the throttle valve is determined by formulas (five), (six), (seven), and (eight):

[0093]

[0094] Among them, m is the intake air flow rate of the throttle valve, A is the flow-through area, P us is the upstream pressure of the throttle valve, P ds is the downstream pressure of the throttle valve, R is the ideal gas constant, T us is the upstream temperature of the throttle valve, and k is the adiabatic index.

[0095] Specifically, the flow-through area A refers to the minimum effective cross-sectional area through which air flows at a certain opening degree of the throttle valve. The flow-through area A can be obtained by looking up a table according to the opening degree of the throttle valve; the upstream pressure P us of the throttle valve can be obtained by an upstream pressure sensor; the downstream pressure P ds of the throttle valve can be obtained by a downstream pressure sensor; the adiabatic index k generally takes 1.4.

[0096] Optionally, the intake air flow rate of the Venturi tube is determined by formula (nine):

[0097]

[0098] Among them, q m is the intake air flow rate of the Venturi tube, C is the discharge coefficient, β is the ratio of the throat diameter to the inlet diameter of the Venturi tube, ε is the expansion coefficient, d is the throat diameter of the Venturi tube, Δp is the static pressure difference between the inlet and the throat of the Venturi tube, p is the pressure at the inlet of the Venturi tube, R is the ideal gas constant, and T is the inlet temperature of the Venturi tube.

[0099] Based on the above-mentioned invention embodiments, the embodiments of the present invention further refine after determining the working mode of the gas engine according to the pressure ratio. Figure 4It is a flowchart of another method for calculating air flow provided by an embodiment of the present invention. Refer to Figure 4 , the air flow calculation method provided by the embodiment of the present invention includes:

[0100] S301. Obtain the upstream pressure and downstream pressure of the throttle valve.

[0101] S302. Determine the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure.

[0102] S303. Determine the working mode of the gas engine according to the pressure ratio.

[0103] S304. Determine the weight ratio of the gas engine based on the pressure ratio, the intake air flow of the throttle valve, and the intake air flow of the Venturi tube.

[0104] Specifically, the weight ratio is calibrated based on the accuracy characteristics of different calculation methods. Different calculation methods refer to the calculation formula of the throttle valve and the calculation formula of the Venturi tube. The weight coefficient is calibrated so that the finally calculated air flow is consistent with the air flow measured on the test bench; the test bench is used to test the power performance, economy, and emissions of the internal combustion engine, etc., such as: the universal characteristic curve (MAP diagram); cold start performance; turbocharger matching, etc.

[0105] The weight ratio corresponding to the air flow equation of the throttle valve and the air flow equation of the Venturi tube under different pressure ratios of the throttle valve can be determined through Table 1:

[0106]

[0107] Among them, Y is the pressure ratio of the throttle valve; J is the weight ratio of the throttle valve equation, and W is the weight ratio of the Venturi tube.

[0108] Exemplarily, if the result of the ratio of the downstream pressure to the upstream pressure (pressure ratio) of the throttle valve is 0.6, then the weight ratio corresponding to the throttle valve equation is 0.7, and the weight ratio of the Venturi tube is 0.3, that is, the finally determined weight ratio of the gas engine is the weight ratio of the throttle valve equation × 0.7 + the weight ratio of the Venturi tube equation × 0.3.

[0109] S305. Determine the air flow of the gas engine according to the intake air flow of the throttle valve, the intake air flow of the Venturi tube, the working mode, and the filtering coefficient.

[0110] Figure 5 It is a result waveform diagram of the air flow calculation method provided by the embodiment of the present invention. Refer to Figure 5 , Figure 5The blue line U in [figure] shows the fluctuation of the air flow rate before using the air flow rate calculation method provided by the embodiment of the present invention; the orange line V shows the fluctuation of the air flow rate after using the air flow rate calculation method provided by the embodiment of the present invention. Herein, the abscissa represents time, and the ordinate represents the air flow rate, with the unit being kg / h (kilograms per hour). It can be clearly seen from Figure 5 that through the air flow rate calculation method provided by the embodiment of the present invention, the fluctuation range of the air flow rate can be made smaller.

[0111] According to the same inventive concept, Figure 6 is a schematic structural diagram of the air flow rate calculation device provided by the embodiment of the present invention. Referring to Figure 6 , the embodiment of the present invention further provides an air flow rate calculation device, which is applied to a gas engine system. The gas engine system at least includes: a throttle valve and a Venturi tube; the output end of the throttle valve is connected to the input end of the Venturi tube; the air flow rate calculation device includes;

[0112] A pressure acquisition module 100, configured to acquire the upstream pressure and the downstream pressure of the throttle valve;

[0113] A pressure ratio calculation module 200, configured to determine the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure;

[0114] A working mode determination module 300, configured to determine the working mode of the gas engine according to the pressure ratio;

[0115] An air flow rate calculation module 400, configured to determine the air flow rate of the gas engine according to the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the working mode, and the filtering coefficient.

[0116] The air flow rate calculation device provided by the embodiment of the present invention can achieve the same technical effects as the air flow rate calculation method in any of the above-mentioned embodiments of the present invention, and will not be elaborated herein.

[0117] According to the same inventive concept, referring to Figure 1 , the embodiment of the present invention further provides a gas engine, including: an engine body 1, an intake pipeline A, an exhaust pipeline B, an air filter 2, a supercharger 3, an intercooler 4, a throttle valve 5, a Venturi tube 6, an exhaust gas recirculation valve 7, an exhaust gas recirculation cooler 8, and the air flow rate calculation device in the above-mentioned embodiment of the present invention ( Figure 1 not shown in [figure]);

[0118] Both the intake pipeline A and the exhaust pipeline B are connected to the engine body 1. The air filter 2, the supercharging end 31 of the supercharger, the intercooler 4, the throttle valve 5, and the Venturi tube 6 are sequentially arranged on the intake pipeline A. The turbine end 32 of the supercharger is arranged on the exhaust pipeline B. The exhaust gas recirculation valve 7 and the exhaust gas recirculation cooler 8 are arranged between the exhaust pipeline A and the intake pipeline B.

[0119] Among them, the air filter 2 is a core component of the gas engine, mainly used to filter dust, particulate matter and other impurities in the air, ensuring that clean air enters the supercharger 3. The input end of the air filter 2 is connected to the air in the external environment, and the output end of the air filter 2 is connected to the supercharging end 31 of the supercharger 3. The supercharging end 31 of the supercharger is responsible for compressing the air and then transmitting it to the intercooler 4. The output end of the supercharging end 31 of the supercharger is connected to the intercooler 4. The main function of the intercooler 4 is to cool the air compressed by the supercharger 3, thereby improving the efficiency and performance of the engine. The exhaust gas recirculation valve 7 can reduce the combustion temperature and inhibit the generation of exhaust gas. The exhaust gas recirculation cooler 8 can reduce the temperature of the exhaust gas discharged from the engine, preventing high temperature from directly entering the intake system and causing knocking or a decrease in combustion efficiency.

[0120] The gas engine provided by the embodiment of the present invention can achieve the same technical effects as the air flow calculation device in the above-mentioned embodiment of the invention, which will not be elaborated here.

[0121] According to the same inventive concept, the embodiment of the present invention also provides a vehicle, including the gas engine in the above-mentioned embodiment of the invention.

[0122] The vehicle provided by the embodiment of the present invention can achieve the same technical effects as the gas engine in the above-mentioned embodiment of the invention, which will not be elaborated here.

[0123] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for calculating air flow rate, characterized in that, Applied to a gas engine, the gas engine at least includes: a throttle valve and a Venturi tube; an output end of the throttle valve is connected to an input end of the Venturi tube; the method for calculating the air flow rate includes: Obtain the upstream pressure and the downstream pressure of the throttle valve; Determine the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure; Determine the working mode of the gas engine according to the pressure ratio; Determine the air flow rate of the gas engine according to the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the working mode and the filtering coefficient.

2. The calculation method of air flow rate according to claim 1, characterized in that The determining the working mode of the gas engine according to the pressure ratio includes: When the pressure ratio is greater than or equal to a first threshold, the working mode of the gas engine is transient; When the pressure ratio is less than the first threshold, the working mode of the gas engine is steady state.

3. The calculation method of air flow rate according to claim 2, wherein, After determining the working mode of the gas engine according to the pressure ratio, it includes: When the working mode of the gas engine is transient, determine the air flow rate of the gas engine through formulas (one), (two) and (three); Wherein, y is the air flow rate, α is the filtering coefficient, x is the air flow rate after weighted ratio calculation, n is the time, T is the sampling frequency, f c is the cut-off frequency, τ is the calibrated value of the electronic control unit in the gas engine, and e is the natural constant; When the working mode of the gas engine is steady state, determine the air flow rate of the gas engine through formula (four); Among them, b0, b1, a1, and a2 are all calibration quantities of the electronic control unit in the gas engine.

4. The calculation method of air flow rate according to claim 1, characterized in that, The intake air flow rate of the throttle valve is determined through formulas (five), (six), (seven) and (eight): Wherein, m is the intake air flow rate of the throttle valve, A is the flow area, P us is the upstream pressure of the throttle valve, P ds is the downstream pressure of the throttle valve, R is the ideal gas constant, T us is the upstream temperature of the throttle valve, and k is the adiabatic index.

5. The calculation method of air flow rate according to claim 4, characterized in that, The intake air flow rate of the Venturi tube is determined through formula (nine): where q m is the intake air flow rate of the Venturi tube, C is the discharge coefficient, β is the ratio of the throat diameter to the inlet diameter of the Venturi tube, ε is the expansion coefficient, d is the throat diameter of the Venturi tube, Δp is the static pressure difference between the tube inlet and the throat of the Venturi tube, p is the pressure at the inlet of the Venturi tube, R is the ideal gas constant, and T is the inlet temperature of the Venturi tube.

6. The calculation method of air flow rate according to claim 5, characterized in that, After determining the working mode of the gas engine according to the pressure ratio, it includes: Determine the weight ratio of the gas engine based on the pressure ratio, the intake air flow rate of the throttle valve and the intake air flow rate of the Venturi tube.

7. The calculation method of air flow rate according to claim 6, wherein The pressure ratio is the downstream pressure of the throttle valve divided by the upstream pressure of the throttle valve.

8. A device for calculating air flow rate, characterized in that, Applied to a gas engine, the gas engine at least includes: a throttle valve and a Venturi tube; an output end of the throttle valve is connected to an input end of the Venturi tube; the device for calculating the air flow rate includes: A pressure acquisition module for acquiring the upstream pressure and the downstream pressure of the throttle valve; A pressure ratio calculation module for determining the pressure ratio of the throttle valve according to the upstream pressure and the downstream pressure; A working mode determination module for determining the working mode of the gas engine according to the pressure ratio; An air flow rate calculation module for determining the air flow rate of the gas engine according to the intake air flow rate of the throttle valve, the intake air flow rate of the Venturi tube, the working mode and the filtering coefficient.

9. A gas engine, characterized in that, Includes: An engine body, an intake pipeline, an exhaust pipeline, an air filter, a supercharger, an intercooler, a throttle valve, a Venturi tube, an exhaust gas recirculation valve, an exhaust gas recirculation cooler and the device for calculating the air flow rate according to claim 8; Both the intake pipeline and the exhaust pipeline are connected to the engine body, and the air filter, the supercharging end of the supercharger, the intercooler, the throttle valve and the Venturi tube are sequentially arranged on the intake pipeline, and the turbine end of the supercharger is arranged on the exhaust pipeline, and the exhaust gas recirculation valve and the exhaust gas recirculation cooler are arranged between the exhaust pipeline and the intake pipeline.

10. A vehicle, characterized in that, Includes the gas engine according to claim 9.

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