PERFORMANCE DEGRADATION ANALYSIS OF COMBINED CYCLE POWER PLANT UNDER HIGH AMBIENT TEMPERATURE

Abstract

The mechanism of performance degradation of a natural gas combined cycle power plant under high ambient temperature is studied by analysing the perfor-mance characteristics and thermal properties of the working fluids. Real operat-ing data under typical seasonal conditions are collected and studied. The results reveal that the power output of the natural gas combined cycle system decreases by 22.6%, and the energy efficiency decreases from 57.28-56.3% when the ambi-ent temperature increases from 5-35 °C. Gas turbine total power output and steam turbine power output decrease by 17.0% and 16.2%, respectively, as ambi-ent temperature increases from 5-35 °C. The enthalpy difference of the flue gas between the turbine inlet and outlet change slightly with varying ambient temper-ature. The fuel and air input decrease by 16.0% and 16.2%, respectively, as am-bient temperature increases from 5-35 °C. By analysing the calculated results, the decrement in air and fuel input d is considered as the immediate cause of sys-tem power output reduction. The proportion of power consumed by air compres-sor reaches 50.4% at 35 °C. This is considered to be caused by air compressor idle.