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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