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Thermal boundary layer modelling in 'motored' spark ignition engines

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conference contribution
posted on 2009-12-23, 12:32 authored by R.J. Jenkin, E.H. James, Weeratunge MalalasekeraWeeratunge Malalasekera
A newly developed piece-wise method for calculating the effects of near-wall turbulence on the transport of enthalpy and hence the thermal boundary layer temperature profile in "motored" spark-ignition engines has been compared with methods that have previously been employed in the development of expressions for the gas-wall interface heat flux. Near-wall temperature profiles resulting from the inclusion of the respective expressions in a "quasi-dimensional" thermodynamic engine simulation have been compared and in one case show considerable differences throughout the compression and expansion strokes of the "motored" engine cycle. However, the corresponding heat fluxes calculated from the simulated temperature profiles all show good agreement with measured results. It is postulated that gas-wall interface heat flux is largely controlled by the boundary layer behavior close to the combustion chamber surfaces and the temperature profile in the outer regions of the boundary layer has considerably less influence. Comparisons have also been made between measured TDC near-wall temperature data (expressed in dimensionless form) and the wall function approach when modified for use in the cylinders of reciprocating engines. The high swirl case shows good agreement with the wall functions, but the low swirl case does not. This is attributed to the changing nature of the hydrodynamic boundary layer in the two instances with the low swirl case being more consistent with laminar behavior. Engine simulations incorporating the new method for the evaluation of near-wall turbulence effects have been used to demonstrate the thermal boundary layer behavior throughout the compression and expansion strokes of a "motored" cycle. Piston-induced work effects are observed to have a significant influence.



  • Mechanical, Electrical and Manufacturing Engineering


JENKIN, R.J., JAMES, E.H. and MALALASEKERA, W., 1996. Thermal boundary layer modelling in 'motored' spark ignition engines. SAE Conference, International Fall Fuels and Lubricants Meeting and Exposition, San Antonio, Texas, 14-17 October 1996, paper 961965, pp. 219-236


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SAE Paper 961965 © 1996 SAE International. This paper is posted on this site with permission from SAE International. As a user of this site, you are permitted to view this paper on-line, and print one copy of this paper at no cost for your use only. This paper may not be copied, distributed or forwarded to others for further use without permission from SAE.This conference paper is also available from http://www.sae.org/technical/papers/961965




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