Quantitative estimation method for power enhancement potential of air cooler

Abstract

The invention discloses an air cooling machine power enhancement potential quantitative estimation method, and belongs to the technical field of engine power estimation. The air cooling machine power strengthening potential quantitative estimation method comprises the steps that air cooling machine performance parameters, a heat engine state reverse dragging cylinder pressure curve and a heat release rate curve are obtained; a one-dimensional simulation model of the air cooler is established, and thermodynamic cycle gas state parameters of the air cooler are obtained; establishing a three-dimensional combustion simulation model, and calculating the thermodynamic state of gas in a combustion chamber in a compression stage after an intake valve is closed; establishing a three-dimensional structure simulation model of the air cooling machine cylinder part; the three-dimensional combustion simulation model is adopted for oil gas chamber optimization, heat-mechanical load verification is carried out on all parts, and the optimized heat release rate is obtained; and inputting the optimized heat release rate into a one-dimensional simulation model, and quantitatively calculating the power strengthening potential of the air cooling machine. According to the quantitative estimation method for the power strengthening potential of the air cooling machine, the power strengthening potential of the air cooling machine is quantitatively estimated through the digital simulation technology, and the strengthening design efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of engine power estimation, and particularly to a method for quantitatively estimating the power enhancement potential of an air-cooled engine. Background Art

[0002] Diesel engines can be divided into air-cooled engines and water-cooled engines according to different cooling methods. Air-cooled engines are widely used in water-scarce and high-temperature environments. Limited by the cooling capacity of the air-cooling form, the heat dissipation capacity of air-cooled engines is relatively low. Therefore, the power design upper limit of most existing models is lower than that of water-cooled engines, and relatively few studies have been conducted on the power enhancement of air-cooled engines. With the increasing demand for productivity, it is necessary to further enhance the power of air-cooled engines. Along with the optimization of the cooling structure design and the development of research on superalloy materials, air-cooled engines can withstand higher mechanical loads and thermal loads, gradually meeting the conditions for further enhancing the power of air-cooled engines.

[0003] Before carrying out the actual power enhancement, it is necessary to explore the power enhancement potential, which can help determine whether the enhanced model has the potential to be applied to the corresponding scenario, provide data support for the enhancement process, and guide the enhancement of air-cooled engines from a theoretical level. The current process of exploring the power enhancement potential of air-cooled engines relies on orthogonal experiments and uses an exhaustive method for experimental exploration. Related work mainly depends on actual machine experiments, which takes a long time.

[0004] Water-cooled engines have a coolant circulation, and it is easy to measure and calculate their cooling capacity. During the enhancement process, it is only necessary to ensure that the coolant temperature does not exceed a certain threshold. However, the heat that the cooling system of an air-cooled engine can carry is not easy to measure. During the process of increasing the power of an air-cooled engine in an engineering experiment, there is an operation of directly increasing the fuel injection volume for power upper limit testing. Since it is not easy to measure the cooling demand, it is impossible to ensure whether the cooling system can meet the cooling demand after the increase, and it is easy to damage the experimental air-cooled engine due to excessive thermal-mechanical loads on the components. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for quantitatively estimating the power enhancement potential of an air-cooled engine, which uses digital simulation technology to quantitatively estimate the power enhancement potential of an air-cooled engine and improve the enhancement design efficiency. By embedding the calculation and verification of thermal-mechanical loads in the power enhancement estimation, it is verified that the enhancement process is within the allowable range of the cooling capacity during the design of the enhancement process, avoiding the situation where the estimated enhancement potential conditions do not match the actual situation, reducing the risk of damaging the air-cooled engine during the verification link of the enhancement design process, reducing economic losses, and avoiding potential safety hazards.

[0006] To achieve the above object, the present invention provides a method for quantitatively estimating the power enhancement potential of an air-cooled engine. Before estimating the enhancement potential, it is first necessary to determine the air-cooled engine to be enhanced, which allows power improvement and whose application scenario has a need for power enhancement. Allowing power improvement means that the thermal-mechanical load of the target air-cooled engine under rated conditions does not reach the allowable upper limit, or the in-cylinder heat flow distribution can be optimized to increase power without increasing the thermal-mechanical load; or material and structure optimizations have been carried out to increase the upper limit of the thermal-mechanical load that restricts its power improvement.

[0007] The method for quantitatively estimating the power enhancement potential of an air-cooled engine includes the following steps: S1. Obtain the performance parameters of the air-cooled engine and the reverse-dragging cylinder pressure curve of the air-cooled engine's thermal machine state through the air-cooled engine bench test; through thermodynamic analysis, calculate and obtain the preliminary heat release rate under the condition that the boundary parameters take empirical values.

[0008] The performance parameters of the air-cooled engine include the intake air flow rate under stable conditions and the air-cooled engine cylinder pressure curve.

[0009] The basic test equipment is a dynamometer, which adopts a speed control mode to make the air-cooled engine operate under a constant speed condition. The corresponding acquisition equipment includes a cylinder pressure sensor, a combustion analyzer, and the corresponding combustion analysis software, and a flow meter is used to measure the intake air flow rate during the test. The cylinder pressure sensor is used to collect the air-cooled engine cylinder pressure curve. The data acquisition condition is to collect after the air-cooled engine has been stable at the target condition for 3 minutes, collect multiple engine cycles, and conduct thermodynamic analysis on each transient cycle. The combustion analysis software can read the cylinder pressure, temperature, and heat release rate. However, the results obtained based on relatively simple empirical formulas are not accurate enough and are only for reference. Combustion simulation calculation requires calculating the heat release rate curve based on the multi-cycle cylinder pressure and taking the arithmetic mean as the heat release rate of this condition. The combustion start point of the combustion analyzer is a reliable parameter. Specifically, the combustion start point refers to the crankshaft angle corresponding to when the cumulative heat release is greater than 2% of the total fuel heat, and the general accuracy value is 0.1 degree of crankshaft angle.

[0010] In the process of calculating the heat release rate, according to the first law of thermodynamics, the fuel heat release rate in the cylinder is equal to the sum of the change rate of the internal energy of the working medium in the cylinder, the heat transfer rate between the working medium in the cylinder and the wall surface, and the change rate of the work done by the working medium. Specifically: The heat release rate calculation formula is: ; Among them, ; Among them, ; Among them, .

[0011] Among them, represents differentiation, represents the combustion heat release, represents the crankshaft angle,U represents the internal energy, L represents the heat transfer amount, represents the work done; represents the fuel heat release rate, represents the change rate of the internal energy of the working fluid in the cylinder, represents the heat transfer rate between the working fluid in the cylinder and the wall surface, represents the change rate of the work done by the working fluid; P is the measured cylinder pressure, V represents the real-time cylinder volume, F represents the heat dissipation area, K represents the polytropic index, represents the rotational speed; represents the part number, namely the cylinder head, cylinder liner, piston; represents the heat transfer coefficient, represents the gas temperature in the cylinder, represents the part wall temperature.

[0012] In the above formula, the process of calculating the heat release rate involves obtaining the values of the wall temperature and the gas temperature. The gas temperature can be read through a combustion analyzer. Since the wall temperature of an air-cooled engine is generally higher than that of a water-cooled engine, this will result in a softer combustion process. Therefore, accurately determining the wall temperature can effectively improve the accuracy of combustion simulation. Due to the difficulty of measurement, the wall temperature is iteratively solved by digital simulation after the model is established.

[0013] S2. Establish a one-dimensional simulation model of the air-cooled engine based on the design parameters of the air-cooled engine and the performance parameters in S1 to obtain the gas state parameters of the thermodynamic cycle of the air-cooled engine.

[0014] Using GT-POWER software, perform one-dimensional modular modeling on the air-cooled engine. For the gas distribution system pipeline, it is preferred to use GEM3D software to one-dimensionalize the three-dimensional scanned pipeline model.

[0015] The model parameters should be consistent with the target air-cooled engine. For an air-cooled engine with a turbocharger, the turbocharger system MAP must be accurately input. The core calibration target of the one-dimensional simulation model is to accurately calculate the gas distribution system data of the air-cooled engine and calculate the indicated power, so that the heat release rate is consistent with the direct output result profile of the combustion analyzer, and ensure the consistency between the simulated value and the measured value of the intake air flow. Generally, the requirement is that the difference is less than 5%. At this time, the wall temperature uses empirical values. For example, the wall temperatures of the piston and cylinder head are set to 600K, and the wall temperature of the cylinder liner is set to 500K.

[0016] S3. Establish a three-dimensional combustion simulation model based on the test results, calculate the thermodynamic state parameters of the gas in the combustion chamber during the compression stage after the intake valve closes, and iterate with the one-dimensional simulation model to optimize the wall temperature.

[0017] Using the Converge software, a three-dimensional combustion simulation model of the engine was established to conduct three-dimensional simulation of the compression stroke. The RNG k-ε model was selected as the turbulence model.

[0018] The initial gas state was provided by the results of the one-dimensional simulation model. The compression stroke was calibrated using the reverse-dragging cylinder pressure curve in the hot engine state of the air-cooled engine to determine the temperature of the engine inner wall surface. The hot engine state refers to the situation where, after the air-cooled engine runs stably at this speed for three minutes, the fuel supply system stops supplying fuel, and the air-cooled engine is reverse-dragged by the dynamometer to maintain the speed.

[0019] The wall surface temperature was calculated using the compression curve. In the three-dimensional calculation, it was ensured that the pressure error within the range of 10° crankshaft angle before and after the combustion start point was less than 2% compared with the measured value. Specific analysis: During the compression process, the heat transfer rate of the working medium in the cylinder to the wall surface is negative, that is, the wall surface heats the gas. For the gas in the cylinder, it satisfies: ; The heat transfer rate between the working medium in the cylinder and the wall surface is equal to the sum of the change rate of the internal energy of the working medium in the cylinder and the change rate of the work done by the piston on the working medium. When the wall surface temperature is set relatively high, the change in internal energy is greater than the actual change. The pressure and temperature of the gas in the cylinder increase, the work done by the piston on the working medium increases, and the pressure and temperature in the cylinder at the combustion start point are higher than those in the actual working condition, which will affect the accuracy of the combustion simulation calculation results. Adjust the wall surface temperature to make the calculated pressure at the combustion start point of the three-dimensional combustion simulation model equal to the measured pressure. Correspondingly, the wall surface temperature was corrected in the one-dimensional simulation model, which would change the intake state. This process requires multiple iterations; ensure that the pressure error within the range of 10° crankshaft angle before and after the combustion start point is less than 2% compared with the test value.

[0020] S4. Establish a three-dimensional structural simulation model of the air-cooled engine cylinder components to calculate the thermal-mechanical loads of each component.

[0021] In the finite element analysis software, the calculated temperature, heat transfer rate, and the measured cylinder pressure were used as the inner wall surface temperature boundary conditions to calculate the thermal-mechanical loads of each component, and compared with its material properties to determine whether its thermal-mechanical loads meet the requirements. Among them, the outer boundaries are all air, and the outer wall surface temperature can be measured using a thermocouple.

[0022] S5. Within the allowable stress range of each component, use the three-dimensional combustion simulation model to optimize the oil and gas chamber and verify the thermal-mechanical loads of each component to obtain the optimized heat release rate.

[0023] After the wall temperature calculation is completed, the heat release rate is accurately calculated based on the measured cylinder pressure curve. A three-dimensional combustion simulation model is used to simulate the combustion process, and the heat release rate calculated using the measured cylinder pressure is used for calibration. The combustion simulation must be calibrated for the spray model, and parameters such as spray penetration distance and cone angle need to be accurate. Generally, the engineering requirements of this industry require the calculation error to be less than 10%, and under strict conditions, the error is required to be less than 5%.

[0024] The optimization content includes but is not limited to injection pressure, injection hole direction, injection hole diameter, and piston configuration. Among them, the turbulence model selects the model, the KH-RT model is adopted in the spray breakup model, and the SAGE model is selected for the combustion model. The optimization process needs to be adapted to the three-dimensional structure simulation model of the air-cooled engine cylinder parts for stress verification, and the circulating fuel injection volume is increased within the allowable range for power enhancement.

[0025] After the calibration of the three-dimensional combustion simulation model is completed, the matching simulation calculation of the oil and gas chamber is carried out for power enhancement and other power enhancements. For air-cooled engines with a turbocharging system, increasing the thermal efficiency and making more fuel burn near the top dead center will reduce the exhaust gas temperature, and after-injection needs to be supplemented to supply the turbine to maintain its original working state. It is sufficient to make the in-cylinder pressure at the exhaust valve opening moment in the three-dimensional combustion simulation the same as the original state through after-injection. After iterative optimization, three-dimensional thermal-mechanical load verification is carried out to avoid exceeding the material allowable value.

[0026] After the thermal efficiency is optimized, the maximum value of the calculated results of the component thermal-mechanical load is lower than the material allowable upper limit, and the circulating fuel injection volume can be increased, thereby directly increasing the power and ensuring the energy supply of the turbocharging system. This can eliminate after-injection and reduce the requirements for the fuel supply system. At this time, a margin for the thermal-mechanical load is left according to the application scenario after the enhanced air-cooled engine, such as being lower than 90% of the maximum allowable value.

[0027] In the process of calculating the power potential, the turbocharging system, intercooling system, fuel supply system, and cylinder oil and gas chamber matching are all one-dimensional simulation calculation independent modules, and only the boundary condition information transmission is completed in the model. Therefore, after each module is enhanced, the parameters of the corresponding simulation model module are modified, and this method can still be used to achieve the purpose of quantitatively estimating the power improvement potential.

[0028] S6. Input the optimized heat release rate into the one-dimensional simulation model to quantitatively calculate the power enhancement potential of the air-cooled engine, which is the estimated value of the power enhancement potential.

[0029] The advantages and positive effects of the method for quantitatively estimating the power enhancement potential of the air-cooled engine described in the present invention are: 1. It can quantitatively predict the power enhancement potential and determine whether the proposed enhanced air-cooled engine can meet the original enhancement target.

[0030] 2. The power quantitative estimation process is embedded in the three-dimensional structure simulation verification, which ensures that the air-cooled engine will not be damaged due to insufficient cooling capacity of its cooling system after strengthening, and only the material property parameters in the model need to be changed when applying new materials.

[0031] 3. The data required for the power potential quantitative estimation calculation are design parameters and measured values of conventional bench tests, with low requirements for the test system and low data acquisition costs.

[0032] 4. By replacing the orthogonal test with simulation calculation, the time and economic costs of the power strengthening whole-machine test verification of the air-cooled engine can be reduced, and the potential safety hazards in the whole-machine test process can be reduced.

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0034] Figure 1 is the flowchart of the embodiment of the present invention; Figure 2 is the data transmission direction of the main boundary conditions of the embodiment of the present invention; Figure 3 is the one-dimensional simulation model of the air-cooled engine of the embodiment of the present invention; Figure 4 is the three-dimensional combustion simulation model of the air-cooled engine of the embodiment of the present invention; Figure 5 is the temperature simulation result in the three-dimensional structure simulation model of the air-cooled engine of the embodiment of the present invention. Detailed Embodiments

[0035] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Embodiment This embodiment takes the power strengthening potential quantitative estimation of a 12-cylinder air-cooled engine as an example. This model is equipped with a turbocharging system, with a designed compression ratio of 17, the original designed single-cylinder cyclic fuel injection amount under rated conditions of 119 mg, and a power of 441 kW.

[0037] As Figure 1 、 Figure 2 shown. The method for quantitatively estimating the power strengthening potential of an air-cooled engine includes the following steps: S1. Use the engine bench to conduct an external characteristic bench test to obtain the performance parameters of the air-cooled engine. Use a Siemens AC dynamometer and adopt a speed control mode to make the air-cooled engine operate under a constant speed condition.

[0038] Use a cylinder pressure sensor to collect the cylinder pressure curve of the air-cooled engine. After installing the angle marker, use an AVL combustion analyzer to collect data. One data point is recorded for every 0.1° crankshaft rotation angle, that is, a total of 7,200 data points are collected within 720° crankshaft rotation angle of a single engine cycle. Use the post-processing software AVL indicom to process the data.

[0039] After the target working condition is stable for 3 minutes, collect the cylinder pressure data of 50 engine cycles, conduct thermodynamic analysis on each engine cycle one by one, initially calculate the heat release rate curve and take the arithmetic mean as the heat release rate of this working condition.

[0040] S2, as Figure 3 shown. Use the one-dimensional whole-engine simulation software GT-POWER to establish a one-dimensional simulation model of the air-cooled engine. The model includes a complete engine block, combustion chamber, valve train system, fuel supply system, and turbocharging system.

[0041] Design parameters such as the model cylinder diameter, stroke, compression ratio, and firing order are input into the engine block model. The engine block model also sets a friction model, and the parameters of this model are derived from the calculation results of the cylinder pressure curve and the measured values of the dynamometer, and the model calibration is completed.

[0042] The model combustion chamber includes a combustion model and a heat transfer model. Among them, the in-cylinder combustion model adopts the three-Webb function model to make the model fitting curve consistent with the calculated heat release rate curve. The injector model on the combustion chamber sets the injection timing, cyclic fuel injection quantity, and injection pressure.

[0043] The pipeline parameters of the model valve train system are modeled based on the actual machine scan and converted into a one-dimensional model using GEM 3D. The main parameters include length and pipe diameter.

[0044] The MAP of the turbocharging system equipped with the model is provided by the manufacturer, and the other system modeling data are obtained according to the model design parameters.

[0045] After the calibration of the one-dimensional simulation model is completed, calculate and collect the result data of the valve train and in the cylinder of the air-cooled engine, and take the thermodynamic state parameter value of the working medium in the cylinder after the intake valve closes.

[0046] S3, as Figure 4 shown. Use the three-dimensional combustion simulation software converge to establish a three-dimensional combustion simulation model of a single-cylinder combustion chamber, calculate the thermodynamic state in the combustion chamber during the compression stroke, and the initial gas state is provided by the one-dimensional simulation results. Among them, the turbulent model selects the RNGk-ε model.

[0047] Calibration is carried out using the motoring cylinder pressure curve of the engine in the warm state, and the inner wall temperature of the air-cooled engine is determined after iteration. The combustion start point of this air-cooled engine is 11 degrees of crankshaft rotation before top dead center. Iterative calculation is performed to make the pressure error within 10 degrees of crankshaft rotation before and after this point less than 2%. The iteration process uses a step size of 5K. Finally, the bottom surface temperature of the cylinder head is set to 585K, the piston temperature is set to 635K, and the cylinder liner temperature is set to 515K.

[0048] S4. As Figure 5 shown. A three-dimensional structural simulation model of the air-cooled engine cylinder components (cylinder head, cylinder liner, piston) is established. In the ANSYS finite element structural analysis software, the calculated temperature and the measured cylinder pressure are used as the inner boundary conditions to calculate the thermal-mechanical loads of each component and compare them with their material properties to determine the allowable power increase. In the calculation settings, tetrahedral meshes are used for mesh generation, the calculation type is transient calculation, and the boundary condition is the third type of boundary condition, that is, the wall temperature and heat transfer rate are set.

[0049] S5. The converge software is used to simulate and calculate the combustion process. The KH-RT model is selected for the spray breakup model, and the SAGE model is selected for the combustion model. Calibration is carried out using the heat release rate calculated from the measured cylinder pressure. After spray calibration, the error of the three-dimensional simulation calculation results is less than 5%, meeting the accuracy requirements of the project.

[0050] After the calibration of the three-dimensional combustion simulation model is completed, a comparison is made with the heat release rate of a water-cooled engine with a similar displacement. Its combustion duration is longer, and the thermal efficiency can be improved. A double swirl piston is selected for the matching of the oil and gas chamber, and parameters such as the injector hole diameter, number, and direction are adjusted to perform predictive calculations for power increase. After iterative optimization, three-dimensional thermal-mechanical stress verification is carried out to determine that it does not exceed the allowable value of the material. Considering the high reliability requirements, the iteration stops when it is lower than 85% of the maximum allowable value of the material, and it is considered that the optimization is completed.

[0051] S6. The three-dimensional simulation calculation results are substituted into the one-dimensional simulation model. When it is obtained that the optimization method is to change the piston shape, change the number of injector holes to 6, match the injection angle, and increase the cyclic fuel injection amount from 119 mg to 126 mg, the power value of the air-cooled engine after the optimization and strengthening is 472.2 kW, which is the estimated value of its power strengthening potential.

[0052] Therefore, by using the method for quantitatively estimating the power strengthening potential of the air-cooled engine described in the present invention, digital simulation technology is used to quantitatively estimate the power strengthening potential of the air-cooled engine, improving the strengthening design efficiency. The calculation and verification of thermal-mechanical loads are embedded in the power strengthening estimation. In the design strengthening process, it is verified that the strengthening process is within the allowable range of the cooling capacity, avoiding the situation where the estimated strengthening potential conditions do not match the actual situation, reducing the risk of damaging the air-cooled engine in the verification link of the strengthening design process, reducing economic losses, and avoiding potential safety hazards.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for quantitatively estimating the power enhancement potential of an air-cooled machine, characterized in that It includes the following steps: S1. Obtain the performance parameters of the air-cooled engine and the reverse-dragging cylinder pressure curve of the air-cooled engine in the hot engine state through the air-cooled engine bench test; through thermodynamic analysis, calculate the preliminary heat release rate under the condition that the boundary parameters take empirical values; S2. Establish a one-dimensional simulation model of the air-cooled engine based on the design parameters of the air-cooled engine and the performance parameters in S1, and obtain the thermodynamic state parameters of the gas in the thermodynamic cycle of the air-cooled engine; S3. Establish a three-dimensional combustion simulation model according to the test results, calculate the thermodynamic state parameters of the gas in the combustion chamber during the compression stage after the intake valve closes, and iterate with the one-dimensional simulation model to optimize the wall temperature; S4. Establish a three-dimensional structural simulation model of the cylinder parts of the air-cooled engine and calculate the thermal-mechanical loads of each part; S5. Within the allowable stress range of each part, use the three-dimensional combustion simulation model to optimize the oil and gas chamber and verify the thermal-mechanical loads of each part to obtain the optimized heat release rate; S6. Input the optimized heat release rate into the one-dimensional simulation model to quantitatively calculate the power enhancement potential of the air-cooled engine.

2. The quantitative estimation method for the power enhancement potential of an air-cooled machine according to claim 1, characterized in that In S1, the performance parameters of the air-cooled engine include the intake air flow rate under stable conditions and the cylinder pressure curve of the air-cooled engine.

3. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 2, characterized in that, In S1, the formula for calculating the heat release rate is: ； Among them, ; Among them, ; Among them, ; Among them, represents differentiation, represents the heat release of combustion, represents the crankshaft angle, U represents internal energy, L represents the heat transfer amount, represents the work done; represents the fuel heat release rate, represents the change rate of the internal energy of the working fluid in the cylinder, represents the heat transfer rate between the working fluid in the cylinder and the wall surface, represents the change rate of the work done by the working fluid; P is the measured cylinder pressure, V represents the real-time cylinder volume, F represents the heat dissipation area, K represents the polytropic index, represents the rotational speed, represents the part number, represents the heat transfer coefficient, represents the gas temperature in the cylinder, represents the part wall temperature.

4. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 3, characterized in that, In S2, use the simulation software GT-POWER to establish a one-dimensional simulation model of the air-cooled engine. The one-dimensional simulation model of the air-cooled engine includes the engine body, combustion chamber, exhaust pipe, intake pipe and turbocharging system.

5. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 4, characterized in that, In S3, use the reverse-dragging cylinder pressure curve in the hot engine state for compression stroke calibration and calculate the wall temperature of the air-cooled engine.

6. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 5, characterized in that, In S3, use the three-dimensional combustion simulation software converge to establish a three-dimensional combustion simulation model of a single-cylinder combustion chamber. The initial gas state adopts the simulation results of the one-dimensional simulation model, and the turbulence model selects the RNGk-ε model.

7. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 6, characterized in that, The calculation of the wall temperature of the air-cooled engine is specifically as follows: during the compression process, the heat transfer rate of the working medium in the cylinder to the wall is negative, the wall heats the gas, and the gas in the cylinder satisfies ； The heat transfer rate between the working medium in the cylinder and the wall is equal to the sum of the change rate of the internal energy of the working medium in the cylinder and the change rate of the work done by the piston on the working medium; adjust the wall temperature to make the calculated pressure at the combustion start point of the three-dimensional combustion simulation model equal to the measured pressure, and correct the wall temperature in the one-dimensional simulation model.

8. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 7, characterized in that, In the one-dimensional simulation model, correct the wall temperature so that the error between the cylinder pressure and the test value within 10° crankshaft angle before and after the combustion start point is less than 2%.

9. A method for quantitatively estimating the power enhancement potential of an air-cooled machine according to claim 8, characterized in that, In S4, when calculating the thermal-mechanical loads of each part, use the calculated wall temperature, heat transfer rate and measured cylinder pressure as the inner wall boundary conditions.

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