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汽油机采用顶置气门可提高升功率,降低燃油消耗率。众所周知,这主要是由于顶置气门汽油机的进气道短,气流较平直,转弯少,因而充量系数较高,燃烧室结构紧凑、合理,可使用较大的压缩比,因而热效率提高所致。近年来,汽车、摩托车用汽油机均采用顶置气门。但各国的通用小型汽油机除个别机型外又都保留侧置气门。因为侧置气门汽油机零件少、重量轻、成本住、虽然侧置气门汽油机的燃油消耗率高一些,但因小汽油机马力小,汽油总消耗量少,故人们对其经济性未予重视。世界性的能源短缺又促使人们重视这一问题。
Gasoline engine with overhead valve can increase the power, reduce fuel consumption. As we all know, this is mainly due to the overhead valve gasoline engine intake port is short, the air flow is relatively straight, less turning, so the charge coefficient is higher, the combustion chamber compact, reasonable, can use a larger compression ratio, so the thermal efficiency To In recent years, cars, motorcycles gasoline engines are used overhead valve. However, common small gasoline engines in all countries except for some models have retained the side valve. Because the side valve gasoline engine parts less, light weight, cost of living, while the side valve gasoline fuel consumption rate higher, but small gasoline engine horsepower, total gasoline consumption less, so people have not paid attention to its economy. In turn, the world’s energy shortage has drawn attention to this issue.