A Sub-idle Compressor Characteristic Generation Method With Enhanced Physical Background

Abstract

Sub-idle is a very challenging operating region as the performance of a gas turbine engine changes significantly compared with design condition.<i. In addition, the regulations for new and existing engines are becoming stricter and the prediction of engine relight capability is essential. In order to predict the performance of an engine, detailed component maps are required. The data obtained from rig tests are insufficient at tow speeds, creating the need for generation of maps within the sub-idle regime. The first step toward this direction is the use of an extrapolation process. This is a purely mathematical process and the results are not usually of sufficient accuracy. In addition, this method does not provide any insight on the physical phenomena governing the operation of the compressor at low speeds. The accuracy of the resulting compressor map can be increased with a better low speed region definition; this can be achieved via the thorough study of a locked rotor compressor, enabling the derivation of the zero rotational .speed line and allowing an interpolation process for the generation of the low speed part of the characteristic. In this work, an enhanced sub-idle compres.sor map generation technique is proposed. The suggested methodology enables the generation of characteristics at far off-design conditions with enhanced physical background. Alternative parameters for map representation are also introduced. Provided that the all the blade rows of the compressor are of known geometry, a numerical analysis is used for the calculation of the characteristic of the half stage and a .stage .stacking method is employed to create the entire compressor characteristic. This way, the sub-idle region of the map can be calculated through interpolation, which provides a more accurate and predictive technique. Application of the method for compressor map generation showed that the proposed interpolation approach is robust and capable of enhancing any performance simulation tool used for the prediction of transient altitude relight or ground-starting maneuvers.

Theoretical Analysis of the Aerodynamics of Low-Speed Fans in Free and Load-Controlled Windmilling Operation

“…This might be a problem for the downstream elements (such as the stator, if any is present). Massive separation inside the stator has been reported in many studies ( [12,14,16], cite7-2 and Ref. [7]).…”

“…The use of an IGV enhances the energy recovery, but at the detriment of the fan operating mode performance. If possible, the inversion of the flow direction is an efficient solution [11,16] since the velocity triangle is much more adapted to turbine operation: the diffuser acts like a turbine nozzle. But this pragmatic solution may not be applied due to integration constraints.…”

“…Between these two limits, a load-controlled windmilling operation can be imposed. If the resistive torque of the shaft is correctly set, some energy recovery is possible [16].…”

Actualización de los mapas de operación del compresor Axial y la generación de las matrices de diagnóstico de la turbina de gas PGT25, para evaluar su desempeño a condiciones reales de operación

“…18 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 (Balsa & Mellor, 1975), (Budinger & Kaufman, 1955), (Carchedi & Wood, 1975) y (Milner & Wenzel, 1975) para la LM2500 en el incremento de presión por etapa, que está relacionado con coeficientes adimensionales del compresor, la curva se determina los procedimientos de estimación de las características de cada etapa descritas por (Muir et al, 1989). (Zachos et al, 2011) propusieron la generación de mapas de operación en la región de ralentí, que es una región de operación a bajas velocidades de giro, las condiciones de ralentí presentan cambios significativos en comparación con la condición de diseño y por ende al desempeño de una turbina de gas. Los valores obtenidos de ensayos en un banco de pruebas son insuficientes a bajas velocidades, creando la necesidad de la generación de mapas de operación dentro del régimen de ralentí.…”

“…Los valores obtenidos de ensayos en un banco de pruebas son insuficientes a bajas velocidades, creando la necesidad de la generación de mapas de operación dentro del régimen de ralentí. (Zachos et al, 2011) (Staroselsky & Ladin, 1979), la inestabilidad genera vibraciones en el compresor este puede sufrir daños internos o incluso la destruirse. El surge se puede alcanzar al tener una disminución en el flujo másico y como consecuencia el flujo se invierta dentro del compresor, lo que puede conducir a la destrucción total del compresor.…”