GT2003-38234 MODEL BASED GAS TURBINE PARAMETER CORRECTIONS

Abstract

ABSTRACT Ambient conditions have a significant impact on the temperatures and pressures in the flow path and on the fuel flow of any gas turbine. Making observed data comparable requires a correction of the raw data to sea level Standard Day conditions. The most widely applied gas turbine parameter correction method is based on keeping some dimensionless Mach number similarity parameters invariant. These similarity parameters are composed of the quantity to be corrected multiplied by temperature to the power 'a' and pressure to the power 'b' with exponent 'a' being theoretically either 0, +0.5 or -0.5 and 'b' either 0 or 1.0. To improve the accuracy of this approach it is common practice to empirically adapt the temperature and pressure exponents 'a' and 'b' in such a way that the correction process leads to a better correlation of the data. INTRODUCTION The purpose of correcting measured data from a gas turbine test is to make the results comparable with those from other engines or with acceptance test criteria, for example. The basic question to be answered is: What would be the engine performance if the test would have been at Standard Day conditions? This question applies not only to measurements taken on a normal test bed where the local altitude and the weather conditions dictate the conditions of the incoming air but also to experiments in an altitude test facility (ATF) if due to facility limitations the conditions at the engine face are not as desired, for example. Data correction algorithms are applied also when monitoring engine deterioration: it is essential to compare data which has been corrected to the same ambient conditions. Finding empirical exponents requires either many consistently measured data that cover a wide range of ambient temperatures and pressures or a computer model of the engine. A high fidelity model is especially well suited for creating optimally matched exponents and for exploring the phenomena that make these exponents deviate from their theoretical value. This paper discusses the questions that arise when creating empirical exponents with a thermodynamic model of the gas turbine