Mathematical modeling and simulation of a cogeneration plant

This work aims to develop mathematical models to simulate a single shaft gas turbine based cogeneration
plant with variable geometry compressor. At off-design the variable vanes are re-staggered to
improve the cogeneration performance. Two modes of operation are identified with the first mode being
for part load of less than 50% running to meet the part load demand. This is achieved by controlling the
fuel flow and air bleeding at the downstream of the compressor to avoid surge formation. The second
mode of operation is for part load greater than 50%. It is running to meet both the part load demand and
the exhaust gas temperature set value by simultaneously regulating the fuel flow and the variable vanes
opening. To accommodate change of compressor parameters during variable vanes re-stagger correction
coefficients are introduced. A behavior of a 4.2 MW power generating cogeneration plant is simulated.
The effect of variation of power and ambient temperature on cogeneration parameters like fuel
consumption, temperature, pressure, variable vanes opening, efficiency and steam generated is studied.
Comparison between the field data and the simulation results is in good agreement. To support the
calculations required for off-design analysis, a computer program is developed in MatLAB environment.