柴油机冷却系统设计

柴油机冷却系统设计

摘要

柴油机运转时气缸内的燃烧温度达到1800℃到2000℃，瞬时温度高达3000℃，与高温燃气相互接触的零件（如缸盖，活塞，气缸，气阀，喷油器等）受到强烈的加热，如不加以适当的冷却，发动机会过热，充气系数下降，燃烧不正常，发生早燃和爆燃现象，与高温接触零件过热，导致材料机械性能降低，和产生严重的热应力，导致变形和裂纹，另外温度过高会使得机油变质，烧损和结焦失去润滑性能，破坏润滑油膜，零件的摩擦和磨损加剧，从而导致发动机的动力性，可靠性，经济性，耐久性，全面恶化。

如果系统的冷却能力过强，机油被燃油稀释（即因缸壁过冷，可燃混合气体在缸壁冷凝并聚集，冲刷缸筒上的润滑油膜，未蒸发的燃油经缸壁流到油底壳，稀释机油），同时恶化混合气体形成及燃烧，增加机油粘度和摩擦效率，造成零件间的磨损加剧，摩擦损失增加，柴油机工作粗暴，另外通过冷却系统带走的热量是燃油燃烧的热量，一般约占燃烧热量的20%-30%，这是一种损失，如果冷却过强，散热损失增加，会降低发动机的经济性。

因此发动机过冷或者过热（即发动机冷却能力过强或者过弱）都会对发动机的动力性，经济性，工作可靠性带来不利的影响。因此设计良好的冷却系统，能够保证发动机始终处于最适宜的温度下工作，已获得较高的发动机经济性能，动力性能，工作可靠性指标等。冷却系统的功用就是使发动机在各种工况下都保持在适当的温度范围内，冷却系统既要防止发动机过热，又要防止冬季发动机过冷，在冷态下的发动机启动之后，冷却系统还要保证发动机迅速升温，尽快达到正常的工作温度。

关键词：散热器；风扇；冷却水泵；硅油风扇离合器；节温器

Abstract

Cylinder diesel engine running inside the combustion temperature reaches 1800 ℃to 2000℃,the instantaneous temperature up to 3000 ℃,and the high temperature gas components in contact with each other (such as cylinder head, piston, cylinder, valve, injector, etc.) by the strong heating,If not properly cooled,the engine will overheat,inflatable coefficient decreased,abnormal combustion,burning and exploding phenomenon occurred early,with the high temperature contact parts overheat,resulting in lower mechanical properties of materials, and severe heat stress,leading to deformation and crack In addition,the oil temperature is too high will cause deterioration,loss of coke burning and lubricating properties,destruction of oil film,part of the friction and wear increased,resulting in engine power,reliability,economy, durability,overall deterioration.

If the system's cooling capacity is too strong,oil is the fuel dilution (ie, cooling due to cylinder wall,combustible gas mixture in the cylinder wall,condensation and aggregation of erosion on the cylinder lubricating oil film,not by evaporation of the fuel flow to the sump cylinder wall,diluted oil), while deterioration of gas mixture formation and combustion,increasing efficiency of oil viscosity and friction,causing increased wear between parts,friction losses increase in gross engine work, while the heat through the cooling system is the fuel burn away the heat, generally about burning calories -30% to 20%,which is a loss,if the cooling is too strong, increase the heat loss will reduce the engine's economy.

So the engine cold or hot (ie, engine cooling is too strong or too weak) will be the engine of power,economy, adversely affect the reliability of work. Therefore,well-designed cooling system ensures the engine always work under the most suitable temperature,the engine has been high economic performance, dynamic performance,operational reliability indicators.Function of the cooling system is to make the engine in various operating conditions are maintained at the appropriate temperature range,cooling systems,it is necessary to prevent