I want to calculate the consumption power of an air compressor in a gas turbine power plant. The gas turbine brand is Siemens (STG5-2000E), but I can't calculate the inlet air mass flow rate in order to multiply it with the real change of the enthalpy. Is there any curve of the inlet guide vane (IGV) angle and the air flow rate and how can the consumption power been calculated?
The most accurate way to determine the air flow through a gas turbine is by energy balance. ASME PTC 22 has a procedure to do this. Basically, the energy in equals the energy out. Assuming that you are not doing anything fancy, like evap cooling, wet compression, steam injection etc. If you set the reference enthalpy at the air inlet temperature the inlet energy is equal to the sensible + chemical energy in the fuel. The outlet energy is the electrical energy + the sensible energy in the exhaust + the heat and mechanical losses of the machine. Do this calculation on the original design information on the machine to get an approximation of the heat and machine losses where you know the design airflow. Use these losses to calculate the exhaust loss. Knowing the exhaust energy and the exhaust temperature and reference air temperature you can calculate the exhaust flow. Subtracting the fuel flow from the exhaust flow will give you the air flow.