. Automotive industries . ngine speedand load. Tests made thus far at the Bureau of Stand-ards indicate that the efficiency for a given load is inde-pendent of the speed over the range of speeds covered inthis discussion. One further assumption, the relationof friction horsepower at part load to that at full loadmust precede the calculation of fuel consumption perbrake horsepower-hour. An approximate relation, de-rived from tests on an automobile engine has been usedfor this purpose. In calculating the fuel consumption in pounds perbrake horsepower-hour, the first step is the determina-tion of
. Automotive industries . ngine speedand load. Tests made thus far at the Bureau of Stand-ards indicate that the efficiency for a given load is inde-pendent of the speed over the range of speeds covered inthis discussion. One further assumption, the relationof friction horsepower at part load to that at full loadmust precede the calculation of fuel consumption perbrake horsepower-hour. An approximate relation, de-rived from tests on an automobile engine has been usedfor this purpose. In calculating the fuel consumption in pounds perbrake horsepower-hour, the first step is the determina-tion of the brake horsepower developed at the speedselected. The brake horsepower developed at full loadat that speed is also determined, and hence permits thepercentage of full load at which the engine is operatingto be deduced. Knowing this, the friction horsepowercan be obtained by the relationship between the frictionhorsepower at full and part load, given in Fig. 5. Threesteps remain: (a) the addition of the friction horse-. Full Load,percent Fig. 5—The relation betvfriction horsepowe power to the brake horsepower to obtain the indicatedhorsepower; (b) the division of the brake horsepowerby the indicated horsepower to obtain the mechanicalefficiency; (c) the multiplication of the fuel-consump-tion expressed in pounds per indicated horsepower-hour() by the mechanical efficiency, to obtain values offuel consumption in pounds per brake calculated by this method are given in Fig. 5. Percentage values, given in Fig. 5, show the largerengine to have a 15 per cent lower fuel consumption thanthe smaller engine. This figure is unfair to the smallengine, as the increased weight of the large enginemeans that the ability of the car is reduced. Publisheddata show that usually in a series of engines built byany one company, the weight per brake horsepower is lessthe greater the horsepower. Let this effect be neglectedto take care of any weight increase in the tran
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectaeronautics, bookyear
