Calculations and Measurements of the Temperature Field in a Motored Engine and Their Implications for Knock 890844

This paper is concerned with prediction and comparison with measurement of the temperature field in a motored four stroke reciprocating engine, the Ricardo E6, in which an artifical hot spot has been created through electrical heating of the exhaust valve. The purpose is to ascertain the extent to which hot spots affect the temperature field and the implications of this for knock. The calculations are perfomed using the EPISO finite volume solution procedure with a compressible flow version of the k-ϵ model. In the energy variance equation, which is added to the usual k -ϵ equation set, turbulent flux and volume expansion terms and the dissipation rate are obtained from simple algebraic relationships.
The experiments use Freon as a working fluid, in order to obtain Reynolds number similarity with air motion, but at much lower engine speed. A thin film resistance thermometer is used for temperature measurement. The probe is rapidly traversed across the cylinder using a high speed hydraulic system. There is a moderate agreement between experimental and computational mean temperature and temperature variance results. The hot spot has a significant effect on both the mean and variance. Experimental temperature length scale results are in good agreement with velocity length scale measurements of other authors for the same engine.


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