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Investigation of Compressor Correction Quantities for Automotive Applications

Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two stage charging increases these variations. The variations are the motivation for analyzing the correction quantities and their validity. A novel surge avoidance strategy is found in the correction equations, where the result is that a reduction in inlet pressure can increase the surge margin of eight studied maps. The method for investigating the applicability of the strategy is general. An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. A set of experimental measurements from an engine test cell and from a gas stand shows a small, but clearly measurable trend, with decreasing compressor pressure ratio for decreasing compressor inlet pressure. A method is developed, enabling measurements to be analyzed with modified corrections. An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. The resulting decrease in high altitude engine performance, due to compressor limitations, are quantified and shows a reduction in altitude of 200-600 m, for when engine torque has to be reduced due to limited compressor operation.

Oskar Leufven and Lars Eriksson

International Journal of Engine Research, 2012

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Last updated: 2021-11-10