现代机械多是以热机为动力,常见的热机有蒸汽机、内燃机、喷气发动机等,热机通常是以气体膨胀对外做功的形式将内能转化为机械能.内能的主要来源有燃料燃烧、原子核裂变、太阳能和地热能等.下面我们以典型的内燃机——汽油机和柴油机为例来全面认识一下热机.一、四冲程内燃机的工作原理及特征1.四冲程汽油机如图1,四冲程汽油机主要部件有汽缸、活塞、曲轴、连杆、进气门、排气门、火花塞等.燃料在气缸 Most modern machines are driven by heat engines, and the common heat engines include steam engines, internal combustion engines and jet engines, etc. The heat engines usually convert the internal energy into mechanical energy in the form of external gas expansion. The main sources of internal energy include fuel combustion, nuclear fission, Solar and geothermal energy etc .. Here we take a typical internal combustion engine - gasoline engine and diesel engine as an example to fully understand the heat engine.A four-stroke internal combustion engine working principle and characteristics 1. Four-stroke gasoline engine Figure 1, four-stroke gasoline engine main components are Cylinder, piston, crankshaft, connecting rod, intake valve, exhaust valve, spark plug, etc. Fuel in the cylinder