| Under the backdrop of China’s commitment to carbon peaking and carbon neutrality,renewable energy generation is poised to be the primary component of the country’s installed power generation in the future.However,the randomness and volatility of renewable energy still pose challenges to the peak shaving capacity of the power grid.With their fast startup and strong peak shaving capacity,gas turbine combined cycle is expected to play a pivotal role in the future power grid structure.This paper uses the standard gas turbine model to study the partial load operation characteristics of the PG9351FA from the perspective of temperature control strategies.On this basis,the off-design operation regular pattern of the S109FA combined cycle reference unit without performance heaters and the retrofitted unit with performance heaters are studied.The research findings are as follows:As the temperature level of the gas turbine increases,the load range for exhaust gas temperature control with the participation of the adjustable guide vanes is expanded.The opening rate of the adjustable guide vane in the pressure ratio bias correction section is faster than that in the constant exhaust temperature section,and the range of the constant T3 reference regulated load is restricted.Under partial load conditions,the pressure ratio and turbine inlet temperature will simultaneously affect the efficiency of the gas turbine.Therefore,it is necessary to consider the impact of both on temperature control strategies optimization.Under partial load conditions,the operating parameters of the gas turbine in the combined cycle unit are not significantly different from those of the simple cycle unit under the combined cycle IGV temperature control strategy.The exhaust gas temperature at the tail of the HRSG,the main/reheat steam flow rate,and the medium/low-pressure steam temperature increase with the enhancement of the combined cycle load.The main/reheat steam temperature is affected by the turbine exhaust temperature,flow rate,and the desuperheater.The medium/low-pressure steam flow rate is affected by the turbine exhaust temperature and flow rate.Under base load conditions,the gas turbine pressure ratio and turbine exhaust flow rate decrease as the ambient temperature rises,while the turbine inlet temperature remains relatively constant.The turbine exhaust temperature increases with the rise of ambient temperature;The medium/low-pressure steam flow decreases as the turbine exhaust flow decreases;The main/reheat steam temperature is affected by the turbine exhaust temperature and the desuperheater;The exhaust gas temperature at the tail of the HRSG,the main/reheat steam flow rate,and the medium/low-pressure steam temperature are affected by the turbine exhaust temperature and flow rate.Across the entire operating range,the trend of desuperheater’s temperature drop and heat transfer rate slow down as the steam heat capacity increases,but increase sharply with the rise of the turbine exhaust temperature.The heat flow and heat exchange required for the performance heater increase with the fuel flow rate elevation.Performance heaters have little impact on gas turbine parameters and main steam parameters.Configuring performance heaters will reduce the production of medium/low-pressure steam in the HRSG,increase the medium/low-pressure steam temperature,lower the tail gas temperature of the HRSG,and sacrifice some bottom cycle efficiency to improve gas turbine efficiency. |
