The aerodynamics and heat transfer performance in the rear-mounted automobile cabin have an important influence on the engine's safety and the operational stability of the automobile. The article uses STAR-CCM and GT-COOL software to establish the 3D wind tunnel model and engine cooling system model of the internal combustion engine. At the same time, we established a 3D artificial coupling model through parameter transfer. The research results show that the heat transfer coefficient decreases with the increase of the comprehensive drag coefficient of the nacelle. This shows that the cabin flow field has an important influence on the heat transfer coefficient. The mainstream temperature rise of the engine room increases with the increase of the engine load. It is proved that vehicle speed affects the amount of heat dissipation of the engine room internal combustion engine under certain load conditions. The article provides a more effective and fast calculation method for the research on the heat dissipation of the internal combustion engine and the optimization of the cooling system equipment.

The heat dissipation of the whole internal combustion engine and the heat dissipation of various internal combustion engines are affected by many complicated factors. Factors include combustion in the cylinder, the flow of air, coolant, lubricating oil, fuel, internal combustion engine structure, working conditions, external cooling system, environment, and so on. The academic circle has a set of mature theories and methods in internal combustion engine heat dissipation research. The primary method is to rely on the combination of experiment and simulation analysis to provide a design basis and optimization method for the engine compartment heat dissipation in the automotive development process. This paper conducts an experimental study on the performance of the internal combustion engine radiator, and the process will be explained in detail later [

Current internal combustion engine problems include calculation of internal combustion engine performance, including fluid flow and combustion, heat transfer and temperature field of components, lubrication and cooling systems, etc. Mature software is available now. We can directly use these local problem models and the coupling relationship between the boundary conditions of each model to establish a unified coupling model. This can significantly reduce the demand for thermal boundary conditions and improve the accuracy of calculation estimates. In addition, to further improve the availability of calculation results, we still need test data of similar reference prototypes. Based on the test data of the existing high-supercharged 4-cylinder internal combustion engine, this paper adjusts the coupling model to calculate the boundary conditions to estimate the heat dissipation of the internal combustion engine.

The heat flow of the whole machine and its distribution are calculated by loop iteration. Many boundary conditions of each local model are interrelated. For example, the time and space average temperature of the surface of the combustion chamber parts required for the performance calculation of the internal combustion engine can be obtained by the integral calculation of the spatial temperature distribution of the parts obtained by the finite element calculation of the temperature field of the parts. The transient temperature and heat transfer coefficient in the cylinder obtained by the performance calculation can be processed by time average and spatial distribution to obtain the boundary temperature and heat transfer conditions required for the finite element calculation of the part.

The empirical parameter method takes the rated power of the engine as the design working condition. The calculation of the target heat dissipation of the internal combustion engine is shown in

^{2}; ^{2}/kW;

The thesis assumes that

The formula

The average temperature

The time average temperature and time average heat transfer coefficient

For the calculation requirements of the temperature field of the parts:

Among them,

The meanings of the superscripts appearing here in the text are as follows: s stands for spatial average; t stands for time average; subscripts: z stands for in-cylinder; w stands for part wall; p stands for piston; h stands for cylinder head; v stands for valve; c stands for cylinder liner; r stands for piston ring; g stands for valve sealing surface; o stands for lubricating oil [

Let's take the exhaust valve as an example for analysis. The thermal coupling relationship between the valve and the cylinder head is mainly on the valve seat surface [

For the sealing surface of the cylinder head valve seat ring:

The temperature

We use the finite difference method to solve the Reynolds lubrication equation to calculate the thickness of the lubricating oil film between the piston ring and the cylinder liner.

The coupling relationship between the bottom of the ring groove and the piston ring can adopt the first type boundary condition of complete contact. The heat transfer coefficient

The mathematical model of internal combustion engine heat dissipation is based on the

In the formula:

In the original scheme, the low-speed climbing engine has a low equilibrium water temperature, and the internal combustion engine has a large heat dissipation margin. Initially, the optimized size of the internal combustion engine heat dissipation core was set at 703 mm × 440 mm × 16 mm. We reduced the core thickness of internal combustion engine heat dissipation by 11 mm. The size comparison of the two schemes is shown in

Geometric parameters | Original plan | Optimization |
---|---|---|

Flat tube height | 1.5 | 1.5 |

Flat tube material thickness | 0.22 | 0.22 |

Fin wave height | 5 | 5 |

Fin pitch | 2.4 | 2.4 |

Fin material thickness | 0.07 | 0.07 |

Fin efficiency | 0.85 | 0.85 |

Working condition point number | Wind speed (m/s) | Water flow rate (L/min) | Heat dissipation (kW) |
---|---|---|---|

1 | 2 | 40 | 24.3 |

2 | 2 | 60 | 26.8 |

3 | 2 | 80 | 27.2 |

4 | 2 | 100 | 28.1 |

5 | 4 | 40 | 36.3 |

6 | 4 | 60 | 41.2 |

7 | 4 | 80 | 43.8 |

8 | 4 | 100 | 45.5 |

9 | 6 | 40 | 41.8 |

10 | 6 | 60 | 49.6 |

11 | 6 | 80 | 53.9 |

12 | 6 | 100 | 56.8 |

13 | 8 | 40 | 45.2 |

14 | 8 | 60 | 55.2 |

15 | 8 | 80 | 61.2 |

16 | 8 | 100 | 65.4 |

In the formula:

The parameters of low-speed climbing conditions and high-speed climbing conditions are shown in

Parameter name | Low-speed climbing | High-speed climbing |
---|---|---|

Environment temperature (°C) | 40 | 45 |

Vehicle speed (km/h) | 40 | 120 |

Road slope (%) | 10 | 3 |

Engine speed (r/min) | 1629 | 2564 |

Transmission gear | 3 | 7 |

The simulation result of the equilibrium water temperature of the engine water outlet is shown in

We load the new sample into a car for a ring mold test [

The balance water temperature of the low-speed climbing of the new internal combustion engine heat dissipation scheme designed in the thesis has increased by 16.3°C, while meeting the design limit of 115°C. The heat dissipation quality of the internal combustion engine is reduced by 1.2 kg. This achieves the goal of reducing the heat dissipation of the internal combustion engine and the optimal cooling system performance.

The article calculates the performance and boundary conditions of the newly designed diesel engine to extrapolate and predict the heat dissipation of the whole engine and the distribution of heat dissipation of various parts. The heat dissipation of the whole machine is calculated from

Project name | Heat dissipation |
Project name | Heat dissipation |
---|---|---|---|

Total heat transfer of piston | 29.7 | Total heat dissipation of exhaust valve | 2.9 |

The amount of heat dissipated from the piston to the oil | 23.7 | Heat dissipation from the valve seat to the cylinder head | 2.5 |

Total heat dissipation of cylinder liner | 53.9 | Total heat dissipation through cooling water | 108.8 |

Heat dissipation from the piston to the cylinder liner | 6.0 | Total heat dissipation through oil | 38.1 |

Total heat dissipation of cylinder head | 57.9 | Total heat dissipation through the air | 62.9 |

Cylinder head exhaust duct heat dissipation | 37.1 | Total heat dissipation of engine | 209.8 |

Project name | Heat dissipation |
Project name | Heat dissipation |
---|---|---|---|

Total heat transfer of piston | 35.2 | Total heat dissipation of exhaust valve | 3.5 |

The amount of heat dissipated from the piston to the oil | 28.3 | Heat dissipation from the valve seat to the cylinder head | 3.0 |

Total heat dissipation of cylinder liner | 60.2 | Total heat dissipation through cooling water | 125.6 |

Heat dissipation from the piston to the cylinder liner | 6.9 | Total heat dissipation through oil | 44.9 |

Total heat dissipation of cylinder head | 68.7 | Total heat dissipation through the air | 82.2 |

Cylinder head exhaust duct heat dissipation | 44.0 | Total heat dissipation of engine | 252.7 |

It can be seen from

This article |
Literature [ |
Heat dissipation efficiency change(%) | |
---|---|---|---|

Intercooler heat dissipation | 50568.4219 | 48220.8906 | −4.64 |

Heat dissipation capacity of the radiator | 167450.9032 | 214101.5938 | 21.79 |

Condenser heat dissipation | 17562.9809 | 13528.5928 | −29.82 |

Engine heat dissipation | 7209.0746 | 7833.1178 | 7.97 |

Total heat dissipation | 242790.7836 | 283684.195 | 14.42 |

Maximum temperature of temperature field (°C) | 74.98 | 83.78 | 11.74 |

In the process of predicting the heat dissipation of the whole machine, the coupling boundary conditions between the models and parts can be determined more accurately through the coupling relationship between the models and calculation iterations. This shows that the analysis model and analysis method are correct. The cooling constant of the radiator at the rated power point is lower than the design index. This shows that the selection of the parameters of the fan and the radiator matching the engine is not feasible. The maximum temperature of the engine compartment temperature field at the rated power point and the maximum torque point did not reach the maximum allowable operating temperature of the engine compartment 90°C. The maximum temperature of the air in the engine compartment is controlled within the design index value. This shows that the temperature field characteristics in the engine compartment meet the design requirements.