Compression ignition type methanol engine cylinder pressure rapid calculation method and system based on manifestation spraying characteristics

Abstract

The invention belongs to the field of engine working performance analysis, and particularly relates to a cylinder pressure rapid calculation method and system for a compression ignition type methanol engine based on the actual spraying characteristic. The method comprises the steps that 1, initial conditions of cylinder pressure calculation are determined according to model parameters of the compression ignition type methanol engine, discretization processing is conducted on the working process of the whole engine from compression starting to combustion ending, and the discretization processing is divided into equal-interval calculation step lengths; 2, after oil injection is started, the penetration distance, the air entrainment rate, the turbulence energy and the evaporation rate of methanol mist spray in each step length are calculated through a manifestation discretization model; 3, based on the parameters in the step 2, the ignition delay period and the combustion rate of evaporated methanol are calculated; and 4, according to the combustion rate calculated in the step 3, the overall heat release rate in the cylinder can be calculated, and rapid calculation of the cylinder pressure is achieved. According to the method, modeling is carried out on the basis of the in-cylinder manifestation characteristic of the methanol spray, and the in-cylinder pressure is quickly and accurately predicted, so that the performance prediction and control optimization capability of the compression ignition type methanol engine is enhanced.

Description

Technical Field

[0001] The invention belongs to the field of engine performance analysis, and in particular relates to a method and a system for quickly calculating cylinder pressure of a compression ignition methanol engine based on phenomenological spray characteristics. Background Art

[0002] The methanol engine is a highly efficient, low-pollution clean energy power system, and is one of the important ways to reduce greenhouse gas emissions and cope with the energy crisis. During the operation of the methanol engine, the cylinder pressure is a key operating parameter that determines the combustion performance and overall efficiency. Therefore, accurate and rapid prediction and calculation of cylinder pressure is crucial for the optimization and control of the combustion process of the compression ignition methanol engine.

[0003] The methods for predicting the cylinder pressure of a compression ignition engine are experimental measurement, numerical simulation (CFD) and semi-empirical formula. In terms of experimental measurement, two cylinder pressure measurement experimental devices for diesel engines are proposed in the prior art. The experimental measurement method uses a high-precision pressure sensor to directly measure the actual pressure data in the engine cylinder, but the test equipment is expensive and the cost is high. In terms of numerical simulation methods, the existing technology has a large amount of calculation and serious simulation time consumption, which makes it difficult to meet the needs of rapid prediction and control. The semi-empirical formula method is based on a large amount of experimental data and establishes an empirical relationship between cylinder pressure and combustion parameters through fitting or interpolation methods. The prior art has a high calculation speed, but relies on specific working condition experimental data. When the working condition deviates from the experimental conditions, the prediction accuracy decreases. Therefore, a cylinder pressure calculation method that can ensure both calculation efficiency and sufficient accuracy is needed, so as to be better used for the optimization design and control of the working performance of compression ignition methanol engines. Summary of the invention

[0004] The present invention provides a method for quickly calculating cylinder pressure based on phenomenological spray characteristics for a compression ignition methanol engine. Based on the phenomenological characteristic modeling of methanol spray in the cylinder, the cylinder pressure is quickly and accurately predicted, thereby enhancing the performance prediction and control optimization capabilities of the compression ignition methanol engine.

[0005] The invention provides a cylinder pressure rapid calculation system based on phenomenological spray characteristics for a compression ignition methanol engine, which is used to implement a cylinder pressure rapid calculation method based on phenomenological spray characteristics for a compression ignition methanol engine.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for quickly calculating cylinder pressure of a compression ignition methanol engine based on phenomenological spray characteristics, the method comprising the following steps:

[0008] Step 1: Determine the initial conditions for cylinder pressure calculation based on the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equally spaced calculation steps;

[0009] Step 2: After the injection starts, the phenomenological discretization model is used to calculate the penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate of the methanol spray in each step length;

[0010] Step 3: Based on the parameters in step 2, calculate the ignition delay period and the combustion rate of evaporated methanol;

[0011] Step 4: Based on the combustion rate calculated in step 3, the overall heat release rate in the cylinder can be calculated, enabling rapid calculation of the cylinder pressure.

[0012] Furthermore, the step 1 is specifically to use the energy conservation equation to calculate the cylinder temperature change in each discretization step from compression to before the start of injection:

[0013]

[0014] In the formula is the heat transfer in the cylinder within one step, is the volume work done by the working fluid, m is the mass of the working fluid, c v is the specific heat capacity of the working fluid; according to the above formula, based on the initial temperature T 1 Solve for the temperature T at the end of the first step 2 , T 2 As the initial temperature of the next step, the temperature of each step from compression to the start of injection is calculated iteratively; after the temperature of each step is known, the ideal gas state equation pV=mRT is used to calculate the pressure p of the corresponding step.

[0015] 3. The calculation method according to claim 1, wherein the step 2 is specifically that the mass conservation and energy conservation equations of each control body are:

[0016]

[0017] In the formula, To control the fuel mass flow rate into the body, To control the fuel mass flow out of the body, In order to control the axial momentum flow into the body, To control the axial momentum flow out of the body.

[0018] Furthermore, the initial state of the first control body is determined to calculate the parameters of the subsequent control bodies. The first control body does not exchange mass with the previous control body, so it can be considered that it is full of fuel. At the same time, its average speed is the speed at which the fuel leaves the nozzle, which is calculated by the following formula:

[0019]

[0020] In the formula, is the fuel mass flow rate, μ is the nozzle flow coefficient, d n is the nozzle diameter.

[0021] Furthermore, the step 2 specifically calculates the change of the in-cylinder turbulent kinetic energy k caused by the development of the methanol spray:

[0022]

[0023] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, which is calculated using the following formula:

[0024] ε=(2k / 3) 1.5 / L j

[0025] Where, L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0026] L j =(ρ f / ρ a ) 0.5 d N

[0027] In the formula, ρ f is the fuel density.

[0028] Furthermore, the step 3 uses the following formula to calculate the ignition delay period τ i :

[0029]

[0030] In the formula, S p is the average piston speed, R is the gas constant, E A is the apparent activation energy of the fuel;

[0031] When the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay period formula, the fuel evaporated in step 4 begins to burn;

[0032] The calculation process of the combustion rate of evaporated methanol using the laminar-turbulent characteristic time model is as follows:

[0033]

[0034] In the formula, x represents the mass fraction of fuel, τ c is the characteristic time of combustion; characteristic time τ c From the laminar characteristic time τ l and turbulence characteristic time τ t And the delay coefficient f is composed of:

[0035] τ c =τ l +fτ t

[0036] Where, laminar characteristic time τ l The calculation is done using the following formula:

[0037] τ l =A -1 [Fuel] 0.75 [O 2 ] -1.5 exp(E / RT)

[0038] Where A is the proportional constant in the Arrhenius formula; [Fuel] is the concentration fraction of the fuel in the mixture participating in the combustion; [O 2 ] is the concentration fraction of oxygen in the mixed gas;

[0039] Turbulence characteristic time τ t The calculated turbulent kinetic energy k and turbulent energy dissipation rate ε are:

[0040] τ t =C 2 k / ε

[0041] Where C 2 is the calibration parameter;

[0042] The calculation formula of the delay coefficient f is:

[0043]

[0044] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0045]

[0046] In the formula, is the mole fraction of carbon dioxide in the combustion products, is the mole fraction of water in the combustion products, Y CO is the mole fraction of carbon monoxide in the combustion products, is the mole fraction of hydrogen in the combustion products, is the mole fraction of nitrogen.

[0047] Furthermore, the step 4 is specifically to calculate the overall heat release rate dQ in the cylinder according to the calculated combustion rate. comb / dt:

[0048]

[0049] Where LHV is the lower heating value of methanol, N noz is the number of nozzles on the injector; after calculating the heat release rate, substitute this value into the energy conservation equation in the cylinder after combustion:

[0050]

[0051] The instantaneous temperature of each calculation step in the cylinder is obtained, and then the ideal gas state equation pV=mRT is used to obtain the pressure p of each corresponding step, thereby realizing the complete cylinder pressure calculation before and after combustion of the compression ignition methanol engine.

[0052] A cylinder pressure rapid calculation system for a compression ignition methanol engine based on phenomenological spray characteristics, the system using the above-mentioned cylinder pressure rapid calculation method for a compression ignition methanol engine based on phenomenological spray characteristics, the system comprising:

[0053] Calculation step equal interval division module: Determine the initial conditions for cylinder pressure calculation according to the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equal interval calculation steps;

[0054] Parameter calculation module: After the injection starts, the phenomenological discretization model is used to calculate the penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate of the methanol spray in each step length;

[0055] Combustion rate calculation module: based on the parameters obtained by the parameter calculation module, calculate the ignition delay period and the combustion rate of evaporated methanol;

[0056] Heat release rate calculation module: Based on the combustion rate calculated by the combustion rate calculation module, the overall heat release rate in the cylinder can be calculated to achieve rapid calculation of cylinder pressure.

[0057] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for rapid cylinder pressure measurement based on phenomenological spray characteristics for a compression ignition methanol engine as described above is implemented.

[0058] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the above-mentioned method for rapid cylinder pressure measurement based on phenomenological spray characteristics for a compression ignition methanol engine.

[0059] The beneficial effects of the present invention are:

[0060] The present invention is based on a phenomenological modeling method, combines the spray penetration, evaporation, entrainment and other links in the methanol combustion process, and adopts a simplified mathematical model to describe these processes, thereby achieving rapid and accurate prediction of cylinder pressure.

[0061] The calculation method described in the present invention effectively reduces the complexity of the calculation while retaining the physical meaning of methanol engine combustion.

[0062] Compared with the numerical simulation method and the semi-empirical formula method, the present invention has higher calculation efficiency while ensuring prediction accuracy.

[0063] Compared with the experimental measurement method, the present invention adopts a mathematical modeling method to realize cylinder pressure prediction, which has lower cost.

[0064] The present invention is applicable to various types of compression ignition methanol engines and is not limited to specific types or operating conditions, and has wide application value and engineering practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a flow chart of the method of the present invention.

[0066] Figure 2 It is a schematic diagram of the phenomenological discretization of methanol spray according to the present invention.

[0067] Figure 3 It is the calculation verification result of the spray penetration distance of a certain type of compression ignition methanol engine according to the present invention.

[0068] Figure 4 The invention compares the cylinder pressure calculation result and the experimental result of a certain type of compression ignition methanol engine. DETAILED DESCRIPTION

[0069] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0070] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0071] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0072] The following is attached to this application specification Figure 1-4 , the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0073] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0074] Implementation Method 1

[0075] This embodiment provides a method for quickly calculating cylinder pressure of a compression ignition methanol engine based on phenomenological spray characteristics, the calculation method comprising the following steps:

[0076] Step 1: Determine the initial conditions for cylinder pressure calculation based on the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equally spaced calculation steps;

[0077] Step 2: After the injection starts, the phenomenological discretization model is used to calculate the parameters of the methanol spray such as penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate in each step length;

[0078] Specifically, after the fuel injection starts, the methanol spray is axially moved as follows: Figure 2 The phenomenological discretization shown is divided into multiple control bodies, and the mass conservation and momentum conservation equations are applied to each control body to calculate the flow rate and momentum parameters of each control body, and then all the control body state parameters are added to obtain the parameters such as the penetration distance and entrainment rate of each instantaneous methanol spray;

[0079] Calculate the change of turbulent kinetic energy in the cylinder caused by the development of methanol spray;

[0080] Calculate the evaporation rate of methanol spray in each step length;

[0081] Step 3: Based on the parameters in step 2, calculate the ignition delay period and the combustion rate of evaporated methanol;

[0082] Step 4: Based on the combustion rate calculated in step 3, the overall heat release rate in the cylinder can be calculated, enabling rapid calculation of the cylinder pressure.

[0083] Furthermore, the step 1 is specifically to use the energy conservation equation to calculate the cylinder temperature change in each discretization step from compression to before the start of injection:

[0084]

[0085] In the formula is the heat transfer in the cylinder within one step, is the volume work done by the working fluid, m is the mass of the working fluid, c v is the specific heat capacity of the working fluid; according to the above formula, based on the initial temperature T 1 Solve for the temperature T at the end of the first step 2 , T 2 As the initial temperature of the next step, the temperature of each step from compression to the start of injection is calculated iteratively; after the temperature of each step is known, the pressure p of each corresponding step can be calculated using the ideal gas state equation pV=mRT.

[0086] Furthermore, the step 2 is specifically that the mass conservation and energy conservation equations of each control body are:

[0087]

[0088] In the formula, To control the fuel mass flow rate into the body, To control the fuel mass flow out of the body, In order to control the axial momentum flow into the body, To control the axial momentum flow out of the body.

[0089] Furthermore, in order to determine the mass and momentum parameters of each control body in the phenomenological spray, it is necessary to determine the initial state of the first control body to realize the calculation of the parameters of the subsequent control bodies; the first control body has no mass exchange with the previous control body, and it can be considered that its interior is full of fuel, and its average speed can be considered as the speed of the fuel leaving the nozzle, which is calculated by the following formula:

[0090]

[0091] In the formula, is the fuel mass flow rate, μ is the nozzle flow coefficient, d n is the nozzle diameter.

[0092] Furthermore, the step 2 specifically calculates the change of the in-cylinder turbulent kinetic energy k caused by the development of the methanol spray:

[0093]

[0094] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, which is calculated using the following formula:

[0095] ε=(2k / 3) 1.5 / L j

[0096] Where, L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0097] L j =(ρ f / ρ a ) 0.5 d N

[0098] In the formula, ρ f is the fuel density.

[0099] Furthermore, the step 3 uses the following formula to calculate the ignition delay period τ i :

[0100]

[0101] Where S p is the average piston speed, R is the gas constant, E A is the apparent activation energy of the fuel.

[0102] When the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay period formula, the fuel evaporated in step 4 begins to burn;

[0103] The calculation process of the combustion rate of evaporated methanol using the laminar-turbulent characteristic time model is as follows:

[0104]

[0105] In the formula, x represents the mass fraction of fuel, τ c is the characteristic time of combustion; characteristic time τ c From the laminar characteristic time τ l and turbulence characteristic time τ t And the delay coefficient f is composed of:

[0106] τ c =τ l +fτ t

[0107] Where, laminar characteristic time τl The calculation is done using the following formula:

[0108] τ l =A -1 [Fuel] 0.75 [O 2 ] -1.5 exp(E / RT)

[0109] Where A is the proportional constant in the Arrhenius formula; [Fuel] is the concentration fraction of the fuel in the mixture participating in the combustion; [O 2 ] is the concentration fraction of oxygen in the mixed gas;

[0110] Turbulence characteristic time τ t The calculated turbulent kinetic energy k and turbulent energy dissipation rate ε are:

[0111] τ t =C 2 k / ε

[0112] Where C 2 is the calibration parameter;

[0113] The calculation formula of the delay coefficient f is:

[0114]

[0115] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0116]

[0117] In the formula, is the mole fraction of carbon dioxide in the combustion products, is the mole fraction of water in the combustion products, Y CO is the mole fraction of carbon monoxide in the combustion products, is the mole fraction of hydrogen in the combustion products, is the mole fraction of nitrogen.

[0118] Furthermore, the step 4 is specifically to calculate the overall heat release rate dQ in the cylinder according to the combustion rate calculated in step 3. comb / dt:

[0119]

[0120] Where LHV is the lower heating value of methanol, N noz is the number of nozzles on the injector; after calculating the heat release rate, substitute this value into the energy conservation equation in the cylinder after combustion:

[0121]

[0122] According to the above formula, the instantaneous temperature of each calculation step in the cylinder can be obtained, and then the ideal gas state equation pV=mRT can be used to obtain the pressure p of each corresponding step, thereby realizing the complete cylinder pressure calculation before and after combustion of the compression ignition methanol engine.

[0123] Implementation Method 2

[0124] This embodiment provides a cylinder pressure rapid calculation system for a compression ignition methanol engine based on phenomenological spray characteristics. The system uses the cylinder pressure rapid calculation method for a compression ignition methanol engine based on phenomenological spray characteristics as described in Embodiment 1. The system includes:

[0125] Calculation step equal interval division module: Determine the initial conditions for cylinder pressure calculation according to the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equal interval calculation steps;

[0126] Parameter calculation module: After the injection starts, the phenomenological discretization model is used to calculate the parameters such as the penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate of the methanol spray in each step length;

[0127] Specifically, after the fuel injection starts, the methanol spray is axially moved as follows: Figure 2 The phenomenological discretization shown is divided into multiple control bodies, and the mass conservation and momentum conservation equations are applied to each control body to calculate the flow rate and momentum parameters of each control body, and then all the control body state parameters are added to obtain the parameters such as the penetration distance and entrainment rate of each instantaneous methanol spray;

[0128] Calculate the change of turbulent kinetic energy in the cylinder caused by the development of methanol spray;

[0129] Calculate the evaporation rate of methanol spray in each step length;

[0130] Combustion rate calculation module: based on the parameters obtained by the parameter calculation module, calculate the ignition delay period and the combustion rate of evaporated methanol;

[0131] Heat release rate calculation module: Based on the combustion rate calculated by the combustion rate calculation module, the overall heat release rate in the cylinder can be calculated to achieve rapid calculation of cylinder pressure.

[0132] Furthermore, the working principle of the calculation step equal interval division module is specifically to use the energy conservation equation to calculate the cylinder temperature change within each discretization step from compression to before the start of injection.

[0133]

[0134] In the formula is the heat transfer in the cylinder within one step, is the volume work done by the working fluid, m is the mass of the working fluid, c v is the specific heat capacity of the working fluid; according to the above formula, based on the initial temperature T 1 Solve for the temperature T at the end of the first step 2 , T 2 As the initial temperature of the next step, the temperature of each step from compression to the start of injection is calculated iteratively; after the temperature of each step is known, the pressure p of each corresponding step can be calculated using the ideal gas state equation pV=mRT.

[0135] Furthermore, the step 2 is specifically that the mass conservation and energy conservation equations of each control body are:

[0136]

[0137]

[0138] In the formula, To control the fuel mass flow rate into the body, To control the fuel mass flow out of the body, In order to control the axial momentum flow into the body, To control the axial momentum flow out of the body.

[0139] Furthermore, in order to determine the mass and momentum parameters of each control body in the phenomenological spray, it is necessary to determine the initial state of the first control body to realize the calculation of the parameters of the subsequent control bodies; the first control body has no mass exchange with the previous control body, and it can be considered that its interior is full of fuel, and its average speed can be considered as the speed of the fuel leaving the nozzle, which is calculated by the following formula:

[0140]

[0141] In the formula, is the fuel mass flow rate, μ is the nozzle flow coefficient, d n is the nozzle diameter.

[0142] Furthermore, the working principle of the parameter calculation module is specifically to calculate the change of the turbulent kinetic energy k in the cylinder caused by the development of methanol spray:

[0143]

[0144] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, which is calculated using the following formula:

[0145] ε=(2k / 3) 1.5 / L j

[0146] Where, L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0147] L j =(ρ f / ρ a ) 0.5 d N

[0148] In the formula, ρ f is the fuel density.

[0149] Furthermore, the combustion rate calculation module works by using the following formula to calculate the ignition delay period τ i :

[0150]

[0151] Where S p is the average piston speed, R is the gas constant, E A is the apparent activation energy of the fuel.

[0152] When the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay period formula, the fuel evaporated in step 4 begins to burn;

[0153] The calculation process of the combustion rate of evaporated methanol using the laminar-turbulent characteristic time model is as follows:

[0154]

[0155] In the formula, x represents the mass fraction of fuel, τ c is the characteristic time of combustion; characteristic time τ c From the laminar characteristic time τ l and turbulence characteristic time τ t And the delay coefficient f is composed of:

[0156] τ c =τ l +fτ t

[0157] Where, laminar characteristic time τ l The calculation is done using the following formula:

[0158] τ l =A -1 [Fuel] 0.75 [O 2 ] -1.5 exp(E / RT)

[0159] Where A is the proportional constant in the Arrhenius formula; [Fuel] is the concentration fraction of the fuel in the mixture participating in the combustion; [O2 ] is the concentration fraction of oxygen in the mixed gas;

[0160] Turbulence characteristic time τ t The calculated turbulent kinetic energy k and turbulent energy dissipation rate ε are:

[0161] τ t =C 2 k / ε

[0162] Where C 2 is the calibration parameter;

[0163] The calculation formula of the delay coefficient f is:

[0164]

[0165] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0166]

[0167] In the formula, is the mole fraction of carbon dioxide in the combustion products, is the mole fraction of water in the combustion products, Y CO is the mole fraction of carbon monoxide in the combustion products, is the mole fraction of hydrogen in the combustion products, is the mole fraction of nitrogen.

[0168] Furthermore, the working principle of the heat release rate calculation module is specifically as follows: according to the calculated combustion rate, the overall heat release rate dQ in the cylinder can be calculated. comb / dt:

[0169]

[0170] Where LHV is the lower heating value of methanol, N noz is the number of nozzles on the injector; after calculating the heat release rate, substitute this value into the energy conservation equation in the cylinder after combustion:

[0171]

[0172] According to the above formula, the instantaneous temperature of each calculation step in the cylinder can be obtained, and then the ideal gas state equation pV=mRT can be used to obtain the pressure p of each corresponding step, thereby realizing the complete cylinder pressure calculation before and after combustion of the compression ignition methanol engine.

[0173] Implementation Method 3

[0174] An embodiment of the present invention provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the memory is used to store software programs and modules, and the processor executes various functional applications and data processing by running the software programs and modules stored in the memory. The memory and the processor are connected via a bus. Specifically, the processor implements any step in the first embodiment above by running the computer program stored in the memory.

[0175] It should be understood that in the embodiments of the present invention, the processor referred to may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0176] The memory may include a read-only memory, a flash memory, and a random access memory, and provides instructions and data to the processor. A part or all of the memory may also include a nonvolatile random access memory.

[0177] As can be seen from the above, the electronic device provided in the embodiment of the present invention can realize the cylinder pressure fast calculation method as described in the first embodiment by running a computer program. The calculation method effectively reduces the complexity of the calculation while retaining the physical meaning of methanol engine combustion. Therefore, compared with the numerical simulation method and the semi-empirical formula method, the present invention has higher calculation efficiency while ensuring the accuracy of prediction. At the same time, compared with the experimental measurement method, the present invention adopts a mathematical modeling method to realize cylinder pressure prediction, which is relatively low in cost.

[0178] It should be understood that if the above-mentioned integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the present invention implements all or part of the processes in the above-mentioned implementation method, and can also be completed by instructing the relevant hardware through a computer program. The above-mentioned computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method implementations when executed by the processor. Among them, the above-mentioned computer program includes computer program code, and the above-mentioned computer program code can be in source code form, object code form, executable file or some intermediate form. The above-mentioned computer-readable medium may include: any entity or device capable of carrying the above-mentioned computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the above-mentioned computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0179] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

[0180] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the above-mentioned device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the implementation method can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method implementation method, which will not be repeated here.

[0181] It should be noted that the methods and detailed examples provided in the above embodiments can be combined with the devices and equipment provided in the embodiments, and references can be made to each other, and no further details will be given.

[0182] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0183] In the embodiments provided by the present invention, it should be understood that the disclosed device / terminal equipment and method can be implemented in other ways. For example, the device / equipment implementation described above is only illustrative, for example, the division of the above modules or units is only a logical function division, and in actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0184] The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above-mentioned embodiments, or replace some of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for quickly calculating cylinder pressure of a compression ignition methanol engine based on phenomenological spray characteristics, characterized in that: The calculation method comprises the following steps: Step 1: Determine the initial conditions for cylinder pressure calculation based on the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equally spaced calculation steps; Step 2: After the injection starts, the phenomenological discretization model is used to calculate the penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate of the methanol spray in each step length; Step 3: Based on the parameters in step 2, calculate the ignition delay period and the combustion rate of evaporated methanol; Step 4: Based on the combustion rate calculated in step 3, the overall heat release rate in the cylinder can be calculated, enabling rapid calculation of the cylinder pressure.

2. The calculation method according to claim 1, characterized in that: Specifically, step 1 uses the energy conservation equation to calculate the change in cylinder temperature within each discretized step from compression to before the start of injection. In the formula, is the heat transfer in the cylinder within one step, is the volume work done by the working fluid, m is the mass of the working fluid, c v is the specific heat capacity of the working fluid; according to the above formula, the temperature T2 at the end of the first step is solved according to the temperature T1 of the initial condition, and T2 is used as the initial temperature of the next step for iterative calculation to obtain the temperature of each step from compression to the start of injection; after the temperature of each step is known, the ideal gas state equation pV=mRT is used to calculate the pressure p of each corresponding step.

3. The calculation method according to claim 1, characterized in that: Specifically, the mass conservation and energy conservation equations of each control body are: In the formula, To control the fuel mass flow rate into the body, To control the fuel mass flow out of the body, In order to control the axial momentum flow into the body, To control the axial momentum flow out of the body.

4. The calculation method according to claim 3, characterized in that: Determine the initial state of the first control body to calculate the parameters of the subsequent control bodies; the first control body has no mass exchange with the previous control body, and its interior is full of fuel. At the same time, its average speed is the speed at which the fuel leaves the nozzle, which is calculated by the following formula: In the formula, is the fuel mass flow rate, μ is the nozzle flow coefficient, d n is the nozzle diameter.

5. The calculation method according to claim 4, characterized in that: The step 2 specifically calculates the change of the in-cylinder turbulent kinetic energy k caused by the development of methanol spray: Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, which is calculated using the following formula: ε=(2k / 3) 1.5 / L j Where, L j is the turbulent energy scale in the cylinder, calculated using the following formula: L j =(ρ f / r a ) 0.5 d N In the formula, ρ f is the fuel density.

6. The calculation method according to claim 5, characterized in that: The step 3 uses the following formula to calculate the ignition delay period τ i : In the formula, S p is the average piston speed, R is the gas constant, E A is the apparent activation energy of the fuel; When the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay period formula, the fuel evaporated in step 4 begins to burn; The calculation process of the combustion rate of evaporated methanol using the laminar-turbulent characteristic time model is as follows: In the formula, x represents the mass fraction of fuel, τ c is the characteristic time of combustion; characteristic time τ c From the laminar characteristic time τ l and turbulence characteristic time τ t and the delay factor f composition: t c =t l +ft t Where, laminar characteristic time τ l The calculation is done using the following formula: τ l =A -1 [Fuel] 0.75 [O2] -1.5 exp(E / RT) In the formula, A is the proportional constant in the Arrhenius formula; [Fuel] is the concentration fraction of fuel in the mixture participating in combustion; [O2] is the concentration fraction of oxygen in the mixture; Turbulence characteristic time τ t The calculated turbulent kinetic energy k and turbulent energy dissipation rate ε are: t t =C2k / ε In the formula, C2 is the calibration parameter; The calculation formula of the delay coefficient f is: Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as: In the formula, is the mole fraction of carbon dioxide in the combustion products, is the mole fraction of water in the combustion products, Y CO is the mole fraction of carbon monoxide in the combustion products, is the mole fraction of hydrogen in the combustion products, is the mole fraction of nitrogen.

7. The calculation method according to claim 2, characterized in that: Specifically, step 4 is to calculate the overall heat release rate dQ in the cylinder according to the calculated combustion rate: comb / dt: Where LHV is the lower heating value of methanol, N noz is the number of nozzles on the injector; after calculating the heat release rate, substitute this value into the energy conservation equation in the cylinder after combustion: The instantaneous temperature of each calculation step in the cylinder is obtained, and then the ideal gas state equation pV=mRT is used to obtain the pressure p of each corresponding step, thereby realizing the complete cylinder pressure calculation before and after combustion of the compression ignition methanol engine.

8. A cylinder pressure rapid calculation system for a compression ignition methanol engine based on phenomenological spray characteristics, characterized in that: The system uses the method for rapid calculation of cylinder pressure based on phenomenological spray characteristics for a compression ignition methanol engine as described in any one of claims 1 to 7, and the system comprises: Calculation step equal interval division module: Determine the initial conditions for cylinder pressure calculation according to the compression ignition methanol engine model parameters, discretize the entire engine working process from the beginning of compression to the end of combustion, and divide it into equal interval calculation steps; Parameter calculation module: After the injection starts, the phenomenological discretization model is used to calculate the penetration distance, air entrainment rate, turbulent kinetic energy and evaporation rate of the methanol spray in each step length; Combustion rate calculation module: based on the parameters obtained by the parameter calculation module, calculate the ignition delay period and the combustion rate of evaporated methanol; Heat release rate calculation module: Based on the combustion rate calculated by the combustion rate calculation module, the overall heat release rate in the cylinder can be calculated to achieve rapid calculation of cylinder pressure.

9. A computer device, characterized in that: The method comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images