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The representation of GT component maps using Mach numbers

Published online by Cambridge University Press:  03 February 2016

V. E. Kyritsis ,
P. Pilidis  and
K. Ramsden
V. E. Kyritsis
Affiliation:
Department of Power and Propulsion, Cranfield University, Bedford, UK
P. Pilidis
Affiliation:
Department of Power and Propulsion, Cranfield University, Bedford, UK
K. Ramsden
Affiliation:
Department of Power and Propulsion, Cranfield University, Bedford, UK
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Abstract

Component maps are produced under certain environmental conditions using air as the working fluid during static ground operation. Any changes of the component characteristics when operating under different temperature conditions and/or with different working fluid are partially taken into account, because of the existence of the gas constant and the ratio of the specific heats in the non-dimensional mass flow and rotational speed. This provides a second order correction for the component characteristics, which may be adequate for the initial modeling of engines. However, for rigorous performance calculations correction factors are applied to the non-dimensional mass flow, rotational speed and pressure ratio distributions of a map, when deviations from the reference conditions under which it was extracted, are experienced. In the current study, a different approach is considered in order to eliminate the inaccuracies caused by the varying temperature and chemical composition. It makes direct use of inlet and circumferential Mach numbers based upon stagnation temperature in conjunction with dimensionless enthalpy variation. A sensitivity analysis against gas property variations is conducted to quantify the benefits gained in precision. Generally, the well-known relationships correlating the Mach number with total and static properties are based on the assumption of perfect gas and constant gas properties. Introducing dependency on temperature and/or chemical composition for the caloric properties of the semi-perfect gas, proper mean values are defined and some theoretical corrections are provided for the well-known equations. The mass flow compatibility equation is then based on the ‘corrected’ expression correlating dimensionless mass flow and Mach number and takes full account of gas property variations.

Type
Research Article
Information
The Aeronautical Journal , Volume 111 , Issue 1121 , July 2007 , pp. 453 - 460
Copyright
Copyright © Royal Aeronautical Society 2007 

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