Title: Simulation studies of the effects of low-heat-rejection on turbocompound diesel engine performance

Authors: D.N. Assanis, J.B. Heywood

Addresses: Assistant Professor, Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana IL 61801, USA. ' Director, Sloan Automotive Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 01139, USA

Abstract: A computer simulation of a turbocharged turbo compound diesel engine has been developed to study the effects of low-heat-rejection on system performance. It is shown that high combustion chamber wall surface temperatures cause a significant drop in volumetric efficiency. As a result, even a fully-insulated engine achieves a modest thermal efficiency improvement (less than 5 per cent) over a base line cooled engine. The efficiency benefit can be somewhat increased if a comprehensive optimisation of key system variables such as injection timing, compound turbine gear ratio, strategy of insulation, and turbomachinery performance is carried out for a given low-heat-rejection configuration. Substantial thermal efficiency gains (up to 15 percent) can be achieved if the system approaches a truly adiabatic condition. This requires that the wall surface temperatures follow the variation in gas temperatures. For practical ceramic materials, cyclic surface temperature variations up to 250 K are expected. However, the resulting improvement in thermal efficiency is associated with a marked increase in component thermal loading.

Keywords: low heat rejection; ceramics; diesel engines; turbocharging exhaust heat; exhaust heat utilisation; fuel economy; simulation; vehicle design.

DOI: 10.1504/IJVD.1987.061197

International Journal of Vehicle Design, 1987 Vol.8 No.3, pp.282 - 299

Published online: 25 May 2014 *

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