测定柴油机或汽油机机械效率(η_m)是一件非常麻烦的事情,而且亦不易测准。尤其单缸发动机,除用电力测功器反拖来测定机械效率外别无其它好法。在我们以往的工作中曾使用过一种简便的方法来估算发动机的机械效率。并将其估算值多次与用电力测功器反拖时测得的数值作了比较。比较结果,估算值一般比实测值约低3%。为此我们认为这种简便估算法可以在生产上使用,只是将估计值加上3%就非常接近实测值了。现将此法介绍如下,供使用者参考。首先将要测定机械效率的发动机,无负荷地逐渐加速至额定转速。待机油和冷却水的温度均达到额定工况的允许值时记录此时消耗m_x~((*))克油的时间t_x。此部份油对外不做功,完全 Determining the mechanical efficiency (η_m) of a diesel or gasoline engine is a very troublesome task and it is not easy to calibrate it. In particular, single-cylinder engines, in addition to using power dynamometer anti-drag to determine the mechanical efficiency, there is no other good method. In our previous work we used an easy way to estimate the mechanical efficiency of the engine. And compares the estimated value with the measured value of the electric dynamometer backflushing many times. Compared with the result, the estimated value is generally about 3% lower than the measured value. For this reason we think this simple method of estimation can be used in production, just add 3% of the estimated value is very close to the measured value. This method is introduced below, for the user reference. First of all, the engine whose mechanical efficiency is to be measured is gradually accelerated to the rated speed without any load. When the temperature of the standby oil and the cooling water reach the allowable value of the rated working condition, record the time t_x of the oil consumed m_x ~ ((*)) at this moment. This part of the oil does not do work on the outside, completely