Title: Relationship of brake power to various energy efficiencies and other engine parameters: the efficiency rule

Authors: R.D. Matthews

Addresses: Department of Mechanical Engineering, University of Texas, Austin, Texas, USA

Abstract: A precise mathematical relationship between the brake power of a piston engine and the various energy efficiencies and other engine parameters of interest is developed. This equation, called the Efficiency Rule for convenience, is: Pb = η_ti • η_c • η_v • η_M • LHV FA • p • D • N/X. Similar equations are also developed for indicated power, indicated and brake mean effective pressure, and indicated and brake specific fuel consumption. These equations are significant for several reasons. Most importantly, they are physically meaningful, can be used to explain observed engine characteristics, and can illuminate methods for improving engine performance. Examples of the usefulness of these equations are presented and discussed. It is expected that these equations will prove to be valuable educational and research tools.

Keywords: brake power; indicated power; specific fuel consumption; mean effective pressure; indicated thermal efficiency; volumetric efficiency; mechanical efficiency; combustion efficiency; piston engines; internal combustion engines; engine thermodynamics; energy efficiency.

DOI: 10.1504/IJVD.1983.061302

International Journal of Vehicle Design, 1983 Vol.4 No.5, pp.491 - 500

Published online: 25 May 2014 *

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