Research on vehicle thermal management technology
Compared with traditional diesel engines, gas engines have the dual advantages of energy saving and environmental protection. Due to the characteristics of natural gas, the thermal load of gas engines is higher. Especially in the National VI stage, the technical route of natural gas engines generally adopts the EGR route to reduce NOx emissions. The heat load is further increased, so an efficient fan technology is needed to solve the problem of vehicle thermal balance.
When the gas engine is running, parts in contact with high-temperature gas are subject to thermal radiation. If not properly cooled, the internal combustion engine will overheat, the air intake will decrease, abnormal combustion (deflagration, pre-ignition, etc.), engine oil deterioration and burning will occur. Increased friction and wear of parts will cause an overall deterioration in the power, economy, and reliability of the internal combustion engine. However, if the cooling is too strong, the gasoline engine mixture will be poorly formed, the oil will be diluted by combustion, the internal combustion engine will work roughly, and the heat dissipation loss and friction loss will increase. , parts wear increases. Therefore, the main task of the cooling system is to ensure that the internal combustion engine operates at the most appropriate temperature.
Engine operating conditions and cooling system requirements
The thermal balance of the vehicle thermal management system includes the balance of three aspects:
1) The water pump head is equal to the sum of the water resistance of each part of the pipeline;
2) The fan static pressure is equal to the sum of the wind resistance of each heat exchanger;
3) The heat emitted by the engine is equal to the heat absorbed by the air.
A good cooling system should meet the following requirements:
1) The heat dissipation capacity can meet the needs of the internal combustion engine when operating under various working conditions. When the working conditions and environmental conditions change, it can still ensure that the internal combustion engine works reliably and maintains the optimal cooling water temperature;
2) The pressure on the system should be eliminated within a short period of time;
3) The volume of the expansion space accounts for 4-6% of the total volume;
4) It has a high water adding rate. The initial filling volume can reach more than 90% of the system volume;
5) When the engine is running at high speed and the system pressure cap is opened, the water pump inlet should be at positive pressure;
6) It has a certain ability to work without water shortage, and the amount of water shortage is greater than the volume of coolant that was not filled for the first time;
7) Set up a water temperature alarm device;
8) Seal well and prevent air or water leakage;
9) The cooling system consumes little power. After starting, it can reach normal operating temperature in a short time.
10) Reliable in use, long life and low manufacturing cost.
