Marine engine performance prediction method and system based on average value and manifestation model

Abstract

The invention belongs to the technical field of marine engine performance simulation and control, and particularly relates to a marine engine performance prediction method and system based on an average value and a manifestation model. The method comprises the steps of 1, inputting initial conditions and boundary conditions of a marine engine; 2, based on the initial conditions and the boundary conditions in the step 1, average value modeling is conducted on a supercharger assembly, an air inlet pipe and an air outlet pipe of the marine engine air path part; 3, on the basis of the initial conditions and the boundary conditions in the step 1, carrying out visualized modeling on the fuel injection and combustion process of the cylinder part of the marine engine; 4, calculating the energy conservation of the in-cylinder state of the marine engine; and step 5, outputting a performance prediction result based on a calculation result in the step 4. The method is used for solving the problem that in the prior art, balance cannot be obtained between simulation precision and calculation speed.

Description

Technical Field

[0001] The invention belongs to the technical field of marine engine performance simulation and control, and in particular relates to a marine engine performance prediction method based on an average value and a phenomenological model and a system thereof. Background Art

[0002] Marine engines are the core power source of ships, and their operating performance has a direct impact on the ship's navigation efficiency, fuel consumption, and emission performance. During ocean voyages, marine engines usually need to work for long periods of time, with frequent load changes and complex operating conditions. Therefore, being able to accurately predict the performance of marine engines is the key to ensuring their efficient operation and reducing operating costs.

[0003] Traditional marine engine performance prediction methods are mainly divided into two categories: zero-dimensional models and full-physics simulation models. Zero-dimensional models are often used in real-time control and rapid evaluation scenarios due to their simple calculations, but they simplify key links such as air paths, combustion processes, and injection characteristics, resulting in large limitations in the accuracy of simulation results, especially under complex working conditions. It cannot accurately reflect the true performance of the engine. Patent CN116186988A proposes a zero-dimensional model for simulating cylinder blowby failures, in which double Wiebe functions are used to simulate combustion heat release. This method has a high calculation speed, but relies on specific working condition experimental data. When the working conditions deviate from the experimental conditions, the prediction accuracy decreases.

[0004] Fully physical simulation models (such as computational fluid dynamics models) can simulate the physical processes inside the engine in detail, including airflow dynamics, combustion characteristics, and heat conduction, and therefore have significant advantages in prediction accuracy. However, such models are extremely computationally intensive and often take a long time to complete a simulation, making them difficult to apply to real-time control systems that require fast feedback, especially in hardware-in-the-loop simulations (HIL) or embedded systems that require frequent updates of simulation results. Excessive computational complexity can significantly reduce the response speed of the control system.

[0005] Therefore, how to strike a balance between simulation accuracy and calculation speed becomes a key challenge in marine engine performance prediction. Summary of the invention

[0006] The present invention provides a method and system for predicting performance of a marine engine based on an average value and a phenomenological model, so as to solve the problem in the prior art that a balance cannot be achieved between simulation accuracy and calculation speed.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for predicting performance of a marine engine based on average value and phenomenological model, the method comprising the following steps:

[0009] Step 1: Input the initial conditions and boundary conditions of the marine engine;

[0010] Step 2: Based on the initial conditions and boundary conditions of step 1, average value modeling is performed for the supercharger components and the intake and exhaust pipes of the gas path of the marine engine;

[0011] Step 3: Based on the initial conditions and boundary conditions of step 1, phenomenological modeling is performed for the fuel injection and combustion process of the cylinder of the marine engine;

[0012] Step 4: Calculate the energy conservation of the state in the cylinder of the marine engine;

[0013] Step 5: Based on the calculation results of step 4, output the performance prediction results.

[0014] Furthermore, the step 1 specifically includes inputting geometric parameters, operating parameters and external environmental conditions of the marine engine, including compression ratio, stroke, speed, injection timing and injection rate.

[0015] Furthermore, the step 2 is specifically to calculate the mass flow of the compressor and the turbine in the marine engine supercharger assembly based on the average value model according to the input initial conditions and boundary conditions; this step quickly calculates the pressure and temperature distribution of each node of the supercharger and the intake and exhaust pipes in the gas path and the gas mass flow by making simplified assumptions on the gas flow in the average value model.

[0016] Furthermore, for the supercharger components, the temperature of the air after passing through the compressor components is T d The calculation is done using the following formula:

[0017]

[0018] Where T u is the compressor inlet temperature; r c is the compressor pressure ratio; k a is the specific heat ratio of air; η c is the compressor efficiency;

[0019] Air flow through the compressor Calculated by the following formula:

[0020]

[0021] Where W c is the compressor power; c p,a is the specific heat of air at constant pressure;

[0022] Compressor power W c By the law of conservation of momentum of the supercharger shaft, it is calculated as:

[0023]

[0024] Where W T is the turbine power; τ tc is the supercharger moment of inertia;

[0025] Turbine power W T The formula for the adiabatic expansion process through the turbine is expressed as:

[0026]

[0027] Where c p,e is the constant pressure specific heat capacity of exhaust gas; T e is the exhaust gas temperature; is the exhaust gas flow rate; η T is the turbine efficiency; r T is the turbine expansion ratio; k e is the specific heat ratio of exhaust gas.

[0028] Furthermore, for the gas path of the marine engine intake and exhaust pipes, the principles of conservation of mass and conservation of energy are applied to the intake container and the exhaust container respectively to solve their respective state parameters;

[0029] The temperature and pressure in the state parameters of the inlet and exhaust containers are calculated using the following expressions:

[0030]

[0031]

[0032] In the formula and Represents mass flow rate and enthalpy flow rate; the subscripts in and out represent flow into and out of the container; represents heat transfer loss; u represents the internal energy of the gas in the container;

[0033] Based on the above relationship, the temperature of the inlet and exhaust pipes can be calculated, and then combined with the ideal gas state equation pV=mRT to calculate the corresponding pressure.

[0034] Furthermore, the step 3 is specifically, in the calculation of the fuel injection and combustion process in the cylinder of the marine engine, based on the principle of phenomenological model, considering the penetration, entrainment, turbulent energy change and premixed-diffusion combustion process of the spray, and realizing the prediction of the combustion rate and heat release rate through a simplified physical and chemical model;

[0035] The penetration distance and entrainment rate of each instantaneous spray are calculated using the following formula:

[0036]

[0037]

[0038] Where Δp inj is the difference between the injection pressure and the cylinder pressure, ρ g is the working fluid density in the cylinder, t is the time from the start of injection to the calculation step, d noz is the nozzle diameter, T is the instantaneous temperature in the cylinder, m f is the injection mass flow rate.

[0039] Furthermore, after the start of the in-cylinder fuel injection, the change of the in-cylinder turbulent kinetic energy k caused by the development of the spray is described by the following formula:

[0040]

[0041] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, and the ε is calculated using the following formula:

[0042] ε=(2k / 3) 1.5 / L j

[0043] Where L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0044] L j =(ρ f / ρ a ) 0.5 d N

[0045] Where ρ f is the fuel density; the ignition delay period τ is calculated using the following formula i :

[0046]

[0047] Where A is the empirical constant; R is the gas constant; E is the apparent activation energy of the fuel; n is the cylinder pressure index; the fuel starts to burn only when the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay formula;

[0048] In order to calculate the combustion rate of fuel, the following characteristic time model is used:

[0049]

[0050] Where x represents the mass fraction of fuel, τ c is the characteristic time of combustion;

[0051] 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:

[0052] τ c =τ l +fτ t

[0053] Where laminar characteristic time τ l The calculation is done using the following formula:

[0054] τ l =A -1 [Fuel] 0.75 [O2] -1.5 exp(E / RT)

[0055] Where 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;

[0056] Turbulence characteristic time τ t Calculated based on the turbulent kinetic energy k and the turbulent energy dissipation rate ε:

[0057] τ t =C2k / ε

[0058] Where C2 is the calibration parameter;

[0059] The calculation formula of the delay coefficient f is:

[0060]

[0061] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0062]

[0063] Finally, based on the calculated combustion rate, the overall heat release rate dQ in the cylinder can be calculated comb / dt:

[0064]

[0065] Where LHV is the lower heating value of the fuel, N noz It is the number of spray holes on the injector.

[0066] Furthermore, the step 4 is specifically that after the combustion process is completed, the model uses the energy conservation equation to calculate the cylinder state parameters at each moment. By combining the energy conservation equation with the simplified gas state equation, the model can quickly calculate the temperature and pressure changes at different crankshaft angles;

[0067] The energy conservation equation in the cylinder after combustion starts is:

[0068]

[0069] 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; when the instantaneous temperature T in the cylinder is known, the ideal gas state equation pV=mRT can be used to calculate the instantaneous pressure p in the cylinder, thus completing the calculation of the state parameters in the cylinder.

[0070] A marine engine performance prediction system based on average value and phenomenological model, the prediction system uses the marine engine performance prediction method based on average value and phenomenological model as described above, the prediction system comprises:

[0071] Average value modeling module: input the initial conditions and boundary conditions of the marine engine; perform average value modeling on the turbocharger components and the intake and exhaust pipes of the marine engine gas path;

[0072] Phenomenological modeling module: Based on initial conditions and boundary conditions, phenomenological modeling is performed on the fuel injection and combustion process of the cylinder of a marine engine;

[0073] Calculation module: calculates the energy conservation of the state in the cylinder of a marine engine;

[0074] Output module: outputs performance prediction results based on the calculation results.

[0075] A computer-readable storage medium stores a computer program, and the computer program implements the above method when executed by a processor.

[0076] The beneficial effects of the present invention are:

[0077] The present invention can not only retain the accuracy of key physical processes, but also greatly reduce the computational complexity by simplifying non-key processes, thereby achieving fast and efficient performance prediction.

[0078] The present invention simplifies key physical processes and establishes reasonable mathematical modeling. The average value model is adopted in the gas path of the marine engine and the phenomenological model is adopted in the combustion process of the cylinder part. This optimizes the simulation accuracy and calculation speed. The present invention is particularly suitable for real-time applications and performance evaluation scenarios that require fast feedback.

[0079] The present invention simplifies non-critical physical processes, reduces the amount of calculation, and achieves efficient real-time simulation.

[0080] Although the model of the present invention simplifies some processes, it can still accurately simulate the key performance parameters of the marine engine and meet the requirements of high-precision simulation.

[0081] The present invention can be flexibly applied to different types of marine engines such as medium-speed engines and low-speed engines, has strong adaptability, and is also suitable for performance evaluation under various working conditions.

[0082] The present invention achieves a balance between calculation speed and simulation accuracy and is suitable for performance optimization and real-time control applications of marine diesel engines.

[0083] After the model simulation is completed, the output results of the model will be compared with the actual experimental data to verify its accuracy and reliability. By adjusting and optimizing the model parameters, the accuracy of the simulation results can be further improved to ensure that the model is suitable for different types of marine engines. The optimized model can also be applied to the hardware-in-the-loop simulation system to achieve accurate prediction of the real-time performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 It is a flow chart of the method of the present invention.

[0085] Figure 2 It is the performance prediction result of a certain type of marine medium-speed engine according to the present invention.

[0086] Figure 3 It is the performance prediction result of a certain type of marine low-speed engine according to the present invention. DETAILED DESCRIPTION

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The following is attached to this application specification Figure 1-3, 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.

[0091] 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.

[0092] Implementation Method 1

[0093] This embodiment provides a method for predicting the performance of a marine engine based on an average value and a phenomenological model, the prediction method comprising the following steps:

[0094] Step 1: Input the initial conditions and boundary conditions of the marine engine;

[0095] Step 2: Based on the initial conditions and boundary conditions of step 1, average value modeling is performed for the supercharger components and the intake and exhaust pipes of the gas path of the marine engine;

[0096] Step 3: Based on the initial conditions and boundary conditions of step 1, phenomenological modeling is performed for the fuel injection and combustion process of the cylinder of the marine engine;

[0097] Step 4: Calculate the energy conservation of the state in the cylinder of the marine engine;

[0098] Step 5: Based on the calculation results of step 4, output the performance prediction results.

[0099] Furthermore, the step 1 specifically includes inputting the geometric parameters, operating parameters and external environmental conditions of the marine engine, including compression ratio, stroke, speed, injection timing, injection rate, etc. The initial conditions can be obtained from the actual engine operation data or the data provided by the engine manufacturer. The determination of boundary conditions plays a vital role in the accuracy of the model.

[0100] Furthermore, the step 2 is specifically as follows: according to the input initial conditions and boundary conditions, the present invention will calculate the mass flow of the compressor and turbine in the marine engine supercharger assembly based on the average value model, and describe the process of air flowing into and out of the cylinder in the engine intake and exhaust pipes; this step quickly calculates the pressure and temperature distribution of each node of the supercharger and the intake and exhaust pipes in the gas path and the gas mass flow rate by making simplified assumptions on the gas flow in the average value model.

[0101] Furthermore, for the supercharger components, the temperature of the air after passing through the compressor components is T d The calculation is done using the following formula:

[0102]

[0103] Where T u is the compressor inlet temperature; r c is the compressor pressure ratio; k a is the specific heat ratio of air; η c is the compressor efficiency;

[0104] Air flow through the compressor Calculated by the following formula:

[0105]

[0106] Where W c is the compressor power; c p,a is the specific heat of air at constant pressure;

[0107] Compressor power W c By the law of conservation of momentum of the supercharger shaft, it is calculated as:

[0108]

[0109] Where W T is the turbine power; τ tc is the supercharger moment of inertia;

[0110] Turbine power W T The formula for the adiabatic expansion process through the turbine is expressed as:

[0111]

[0112] Where c p,e is the constant pressure specific heat capacity of exhaust gas; T e is the exhaust gas temperature; is the exhaust gas flow rate; η T is the turbine efficiency; r T is the turbine expansion ratio; k e is the specific heat ratio of the exhaust gas; thus, the gas path average value modeling of the marine engine supercharger assembly is completed.

[0113] Furthermore, for the gas path of the marine engine intake and exhaust pipes, the present invention adopts the principle of an open thermal system to simplify the intake pipe and the exhaust pipe into two containers for storing ideal gas; the principles of conservation of mass and conservation of energy are applied to the intake container and the exhaust container respectively to solve the state parameters such as pressure and temperature of each container;

[0114] The temperature and pressure in the state parameters of the inlet and exhaust containers are calculated using the following expressions:

[0115]

[0116]

[0117] In the formula and Represents mass flow rate and enthalpy flow rate; the subscripts in and out represent flow into and out of the container; represents heat transfer loss; u represents the internal energy of the gas in the container;

[0118] Based on the above relationship, the temperature of the inlet and exhaust pipes can be calculated, and then combined with the ideal gas state equation pV=mRT to calculate the corresponding pressure.

[0119] Furthermore, the step 3 is specifically that, in the calculation of the fuel injection and combustion process in the cylinder of the marine engine, the present invention is based on the principle of phenomenological model, taking into account the penetration, entrainment, turbulent energy change and premixed-diffusion combustion process of the spray, and realizing the prediction of the combustion rate and heat release rate through a simplified physical and chemical model;

[0120] The penetration distance and entrainment rate of each instantaneous spray are calculated using the following formula:

[0121]

[0122]

[0123] Where Δp inj is the difference between the injection pressure and the cylinder pressure, ρ g is the working fluid density in the cylinder, t is the time from the start of injection to the calculation step, d noz is the nozzle diameter, T is the instantaneous temperature in the cylinder, m f is the injection mass flow rate.

[0124] Furthermore, after the start of the in-cylinder fuel injection, the change of the in-cylinder turbulent kinetic energy k caused by the development of the spray is described by the following formula:

[0125]

[0126] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, and the ε is calculated using the following formula:

[0127] ε=(2k / 3) 1.5 / L j

[0128] Where L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0129] Lj =(ρ f / ρ a ) 0.5 d N

[0130] Where ρ f is the fuel density; the ignition delay period τ is calculated using the following formula i :

[0131]

[0132] Where A is the empirical constant; R is the gas constant; E is the apparent activation energy of the fuel; n is the cylinder pressure index; the fuel starts to burn only when the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay formula;

[0133] In order to calculate the combustion rate of fuel, the following characteristic time model is used:

[0134]

[0135] Where x represents the mass fraction of fuel, τ c is the characteristic time of combustion;

[0136] 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:

[0137] τ c =τ l +fτ t

[0138] Where laminar characteristic time τ l The calculation is done using the following formula:

[0139] τ l =A -1 [Fuel] 0.75 [O2] -1.5 exp(E / RT)

[0140] Where 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;

[0141] Turbulence characteristic time τ t Calculated based on the turbulent kinetic energy k and the turbulent energy dissipation rate ε:

[0142] τ t =C2k / ε

[0143] Where C2 is the calibration parameter;

[0144] The calculation formula of the delay coefficient f is:

[0145]

[0146] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0147]

[0148] Finally, based on the calculated combustion rate, the overall heat release rate dQ in the cylinder can be calculated comb / dt:

[0149]

[0150] Where LHV is the lower heating value of the fuel, N noz It is the number of spray holes on the injector.

[0151] Furthermore, the step 4 is specifically that after the combustion process is completed, the model uses the energy conservation equation to calculate the cylinder state parameters at each moment. By combining the energy conservation equation with the simplified gas state equation, the model can quickly calculate the temperature and pressure changes at different crankshaft angles;

[0152] The energy conservation equation in the cylinder after combustion starts is:

[0153]

[0154] 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; when the instantaneous temperature T in the cylinder is known, the ideal gas state equation pV=mRT can be used to calculate the instantaneous pressure p in the cylinder, thus completing the calculation of the state parameters in the cylinder.

[0155] Specifically, step 5 is to output key performance parameters of the marine engine after modeling and calculation in the above steps, including power, torque, cylinder pressure, heat release rate, etc. The results can be used for performance prediction, fuel economy evaluation and emission analysis.

[0156] Implementation Method 2

[0157] This embodiment provides a marine engine performance prediction system based on average value and phenomenological model, the prediction system uses the marine engine performance prediction method based on average value and phenomenological model as described in embodiment 1, and the prediction system includes:

[0158] Average value modeling module: input the initial conditions and boundary conditions of the marine engine; perform average value modeling on the turbocharger components and the intake and exhaust pipes of the marine engine gas path;

[0159] Phenomenological modeling module: Based on initial conditions and boundary conditions, phenomenological modeling is performed on the fuel injection and combustion process of the cylinder of a marine engine;

[0160] Calculation module: calculates the energy conservation of the state in the cylinder of a marine engine;

[0161] Output module: outputs performance prediction results based on the calculation results.

[0162] The average value modeling module first inputs the geometric parameters, operating parameters and external environmental conditions of the marine engine, specifically including compression ratio, stroke, speed, injection timing and injection rate.

[0163] The average value modeling module will then calculate the mass flow of the compressor and turbine in the marine engine supercharger assembly based on the average value model according to the input initial conditions and boundary conditions; this step quickly calculates the pressure and temperature distribution of each node of the supercharger and the intake and exhaust pipes in the gas path and the gas mass flow by making simplified assumptions about the gas flow in the average value model.

[0164] For the turbocharger components, the temperature of the air after passing through the compressor components is T d The calculation is done using the following formula:

[0165]

[0166] Where T u is the compressor inlet temperature; r c is the compressor pressure ratio; k a is the specific heat ratio of air; η c is the compressor efficiency;

[0167] Air flow through the compressor Calculated by the following formula:

[0168]

[0169] Where W c is the compressor power; c p,a is the specific heat of air at constant pressure;

[0170] Compressor power W c By the law of conservation of momentum of the supercharger shaft, it is calculated as:

[0171]

[0172] Where W T is the turbine power; τ tc is the supercharger moment of inertia;

[0173] Turbine power W TThe formula for the adiabatic expansion process through the turbine is expressed as:

[0174]

[0175] Where c p,e is the constant pressure specific heat capacity of exhaust gas; T e is the exhaust gas temperature; is the exhaust gas flow rate; η T is the turbine efficiency; r T is the turbine expansion ratio; k e is the specific heat ratio of exhaust gas.

[0176] For the gas path of the marine engine intake and exhaust pipes, the principles of conservation of mass and conservation of energy are applied to the intake and exhaust containers respectively to solve their respective state parameters;

[0177] The temperature and pressure in the state parameters of the inlet and exhaust containers are calculated using the following expressions:

[0178]

[0179]

[0180] In the formula and Represents mass flow rate and enthalpy flow rate; the subscripts in and out represent flow into and out of the container; represents heat transfer loss; u represents the internal energy of the gas in the container;

[0181] Based on the above relationship, the temperature of the inlet and exhaust pipes can be calculated, and then combined with the ideal gas state equation pV=mRT to calculate the corresponding pressure.

[0182] The phenomenological modeling module is based on the principle of phenomenological model in the calculation of fuel injection and combustion process in the cylinder of the marine engine, taking into account the penetration, entrainment, turbulent energy change and premixed-diffusion combustion process of the spray, and predicting the combustion rate and heat release rate through a simplified physical and chemical model;

[0183] The penetration distance and entrainment rate of each instantaneous spray are calculated using the following formula:

[0184]

[0185]

[0186] Where Δp inj is the difference between the injection pressure and the cylinder pressure, ρ g is the working fluid density in the cylinder, t is the time from the start of injection to the calculation step, d noz is the nozzle diameter, T is the instantaneous temperature in the cylinder, m f is the injection mass flow rate.

[0187] After the injection starts, the change of the turbulent kinetic energy k in the cylinder caused by the development of the spray is described by the following formula:

[0188]

[0189] Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, and the ε is calculated using the following formula:

[0190] ε=(2k / 3) 1.5 / L j

[0191] Where L j is the turbulent energy scale in the cylinder, calculated using the following formula:

[0192] L j =(ρ f / ρ a ) 0.5 d N

[0193] Where ρ f is the fuel density; the ignition delay period τ is calculated using the following formula i :

[0194]

[0195] Where A is the empirical constant; R is the gas constant; E is the apparent activation energy of the fuel; n is the cylinder pressure index; the fuel starts to burn only when the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay formula;

[0196] In order to calculate the combustion rate of fuel, the following characteristic time model is used:

[0197]

[0198] Where x represents the mass fraction of fuel, τ c is the characteristic time of combustion;

[0199] 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:

[0200] τ c =τ l +fτ t

[0201] Where laminar characteristic time τ l The calculation is done using the following formula:

[0202] τl =A -1 [Fuel] 0.75 [O2] -1.5 exp(E / RT)

[0203] Where 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;

[0204] Turbulence characteristic time τ t Calculated based on the turbulent kinetic energy k and the turbulent energy dissipation rate ε:

[0205] τ t =C2k / ε

[0206] Where C2 is the calibration parameter;

[0207] The calculation formula of the delay coefficient f is:

[0208]

[0209] Where r is the ratio of the mass of all combustion products to the mass of all reactants, expressed as:

[0210]

[0211] Finally, based on the calculated combustion rate, the overall heat release rate dQ in the cylinder can be calculated comb / dt:

[0212]

[0213] Where LHV is the lower heating value of the fuel, N noz It is the number of spray holes on the injector.

[0214] After the combustion process is completed, the calculation module uses the energy conservation equation to calculate the cylinder state parameters at each moment. By combining the energy conservation equation with the simplified gas state equation, the model can quickly calculate the temperature and pressure changes at different crankshaft angles.

[0215] The energy conservation equation in the cylinder after combustion starts is:

[0216]

[0217] 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; when the instantaneous temperature T in the cylinder is known, the ideal gas state equation pV=mRT can be used to calculate the instantaneous pressure p in the cylinder, thus completing the calculation of the state parameters in the cylinder.

[0218] After the modeling and calculation in the above steps, the output module outputs key performance parameters of the marine engine, including power, torque, cylinder pressure, heat release rate, etc.; the results can be used for performance prediction, fuel economy evaluation and emission analysis.

[0219] Implementation Method 3

[0220] 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.

[0221] 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.

[0222] 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.

[0223] It can be seen from the above that the electronic device provided in the embodiment of the present invention can implement the marine engine performance prediction method as described in embodiment 1 by running a computer program. By simplifying the key physical processes and reasonable mathematical modeling, an average value model is adopted in the gas path part of the marine engine, and a phenomenological model is adopted in the combustion working process of the cylinder part, so as to optimize the simulation accuracy and calculation speed. It is particularly suitable for real-time applications and performance evaluation scenarios that require fast feedback.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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 predicting marine engine performance based on average value and phenomenological model, characterized in that: The prediction method comprises the following steps: Step 1: Input the initial conditions and boundary conditions of the marine engine; Step 2: Based on the initial conditions and boundary conditions of step 1, average value modeling is performed for the supercharger components and the intake and exhaust pipes of the gas path of the marine engine; Step 3: Based on the initial conditions and boundary conditions of step 1, phenomenological modeling is performed for the fuel injection and combustion process of the cylinder of the marine engine; Step 4: Calculate the energy conservation of the state in the cylinder of the marine engine; Step 5: Based on the calculation results of step 4, output the performance prediction results.

2. The marine engine performance prediction method according to claim 1, characterized in that: The step 1 specifically includes inputting the geometric parameters, operating parameters and external environmental conditions of the marine engine, including compression ratio, stroke, speed, injection timing and injection rate.

3. The marine engine performance prediction method according to claim 1, characterized in that: Specifically, step 2 is to calculate the mass flow of the compressor and turbine in the marine engine supercharger assembly based on the average value model according to the input initial conditions and boundary conditions; this step quickly calculates the pressure and temperature distribution of each node of the supercharger and the intake and exhaust pipes in the gas path and the gas mass flow by making simplified assumptions about the gas flow in the average value model.

4. The marine engine performance prediction method according to claim 3, characterized in that: For the turbocharger components, the temperature of the air after passing through the compressor components is T d The calculation is done using the following formula: Where T u is the compressor inlet temperature; r c is the compressor pressure ratio; k a is the specific heat ratio of air; η c is the compressor efficiency; Air flow through the compressor Calculated by the following formula: Where W c is the compressor power; c p,a is the specific heat of air at constant pressure; Compressor power W c By the law of conservation of momentum of the supercharger shaft, it is calculated as: Where W T is the turbine power; τ tc is the supercharger moment of inertia; Turbine power W T The formula for the adiabatic expansion process through the turbine is expressed as: Where c p,e is the constant pressure specific heat capacity of exhaust gas; T e is the exhaust gas temperature; is the exhaust gas flow rate; η T is the turbine efficiency; r T is the turbine expansion ratio; k e is the specific heat ratio of exhaust gas.

5. The marine engine performance prediction method according to claim 4, characterized in that: For the gas path of the marine engine intake and exhaust pipes, the principles of conservation of mass and conservation of energy are applied to the intake and exhaust containers respectively to solve their respective state parameters; The temperature and pressure in the state parameters of the inlet and exhaust containers are calculated using the following expressions: In the formula and Represents mass flow rate and enthalpy flow rate; the subscripts in and out represent flow into and out of the container; represents heat transfer loss; u represents the internal energy of the gas in the container; Based on the above relationship, the temperature of the inlet and exhaust pipes can be calculated, and then combined with the ideal gas state equation pV=mRT to calculate the corresponding pressure.

6. The marine engine performance prediction method according to claim 1, characterized in that: Specifically, step 3 includes, in the calculation of fuel injection and combustion process in the cylinder of the marine engine, based on the principle of phenomenological model, considering the penetration, entrainment, turbulent energy change and premixed-diffusion combustion process of the spray, and realizing the prediction of the combustion rate and heat release rate through a simplified physical and chemical model; The penetration distance and entrainment rate of each instantaneous spray are calculated using the following formula: Where Δp inj is the difference between the injection pressure and the cylinder pressure, ρ g is the working fluid density in the cylinder, t is the time from the start of injection to the calculation step, d noz is the nozzle diameter, T is the instantaneous temperature in the cylinder, m f is the injection mass flow rate.

7. The marine engine performance prediction method according to claim 6, characterized in that: After the injection starts, the change of the turbulent kinetic energy k in the cylinder caused by the development of the spray is described by the following formula: Where M represents the total mass of the spray area; u j is the nozzle exit velocity; ε is the turbulent energy dissipation rate, and the ε 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 Where ρ f is the fuel density; the ignition delay period τ is calculated using the following formula i : Where A is the empirical constant; R is the gas constant; E is the apparent activation energy of the fuel; n is the cylinder pressure index; the fuel starts to burn only when the crankshaft angle in the cylinder exceeds the value calculated by the ignition delay formula; In order to calculate the combustion rate of fuel, the following characteristic time model is used: Where 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) Where 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 Calculated according to the turbulent kinetic energy k and the turbulent energy dissipation rate ε: t t =C2k / ε Where 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: Finally, based on the calculated combustion rate, the overall heat release rate dQ in the cylinder can be calculated comb / dt: Where LHV is the lower heating value of the fuel, N noz It is the number of spray holes on the injector.

8. The marine engine performance prediction method according to claim 1, characterized in that: Specifically, step 4 is that after the combustion process is completed, the model uses the energy conservation equation to calculate the cylinder state parameters at each moment. By combining the energy conservation equation with the simplified gas state equation, the model can quickly calculate the temperature and pressure changes at different crankshaft angles; The energy conservation equation in the cylinder after combustion starts is: 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; when the instantaneous temperature T in the cylinder is known, the ideal gas state equation pV=mRT can be used to calculate the instantaneous pressure p in the cylinder, thus completing the calculation of the state parameters in the cylinder.

9. A marine engine performance prediction system based on average value and phenomenological model, characterized in that: The prediction system uses the marine engine performance prediction method based on average value and phenomenological model as claimed in any one of claims 1 to 8, and the prediction system comprises: Average value modeling module: input the initial conditions and boundary conditions of the marine engine; perform average value modeling on the turbocharger components and the intake and exhaust pipes of the marine engine gas path; Phenomenological modeling module: Based on initial conditions and boundary conditions, phenomenological modeling is performed on the fuel injection and combustion process of the cylinder of a marine engine; Calculation module: calculates the energy conservation of the state in the cylinder of a marine engine; Output module: outputs performance prediction results based on the calculation results.

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.

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