Abstract

Conventional gas turbines are a very mature technology and performance improvements are becoming increasingly difficult and costly to achieve. Pressure Gain Combustion has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycles. Up to date, the majority of studies in the field has concentrated on the connection of the turbine to various types of pressure gain combustion systems. The current work focusses on the connection of an array of pulsed detonation tubes at the outlet of an axial compressor. An ideal 0-D plenum is assumed between the compressor outlet and the pulsed detonation tubes’ inlet. The tubes are simulated as time-dependent mass sinks in this plenum. A solution of the time-dependent mass conservation equations delivers the pressure variation in this ideal plenum for various combinations of its size, the tube number, the tube frequency, their firing pattern and their closing time. This pressure variation is subsequently used as a boundary condition in a numeric model of a compressor that can resolve very fast changes of its operational condition. The model is based on the solution of the time-dependent 1-D Euler equations with source terms for the blade forces and the work exchange with the fluid along the compressor stages. These source terms are computed from the operational map of the compressor. The influence of the aforementioned five parameters (number of tubes, frequency, closing time, firing pattern and plenum size) on the compressor operational stability and the flow in its stages is studied in detail. The aim is to benchmark the design of a plenum that results in the lowest possible compressor outlet pressure fluctuation without becoming too large. At the same time, the pressure fluctuations and their propagation along the compressor stages are analyzed.

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