AN ALGORITHM FOR THE DESIGN OF AN AXIAL FLOW COMPRESSOR OF A POWER GENERATION GAS TURBINE

Abstract

This paper focuses on the development of an algorithm for designing an axial flow compressor for a power generation gas turbine and attempts to bring to the public domain some parameters regarded as propriety data by plant manufacturers. The theory used in this work is based on simple thermodynamics and aerodynamics principles in a mean stream line analysis that assumes that the flow conditions prevailing at the mean radius fully represent the flow at all other radii. Gas Turbine Unit II (GT-II) in Omotosho Power Plant Phase I located in Ondo state was used to validate this work. The specifications used include mass flow rate, rotational speed, number of stages, pressure ratio, ambient air temperature and pressure etc. A computer program was written based on the formulated algorithm and the code was implemented in Microsoft Excel. The axial velocity was obtained using an iterative process that converged to a value of 163.74m/s for the design condition. The blade camber angles for each stage of the compressor were also determined using iterative processes. The results showed a compressor overall stagnation temperature rise of 354.5 ⁰C and work input of 51.5MW at an ambient air temperature of 15 ⁰C. The stagnation temperature rise and compressor work input were computed to be 369 ⁰C and 53.6MW respectively at an ambient air temperature of 27 ⁰C and which agrees reasonably well with the measured values of 375 ⁰C and 54.6MW in GT-II. The total to total efficiency was 0.86 for both ambient air temperature values.

http://dx.doi.org/10.4314/njt.v34i2.16