combined cycle regenerative gas turbine decreases about 19%. It is because of reduces the exhaust gases
temperature. Therefore, the total power output for the most combined cycle configuration increases with
increase of the ambient temperature, it is because of the increases in the steam turbine cycle more than the
gas turbine power output, also the total power output increase with increases the ambient temperature.
Fig. 3(b) shows the effect of ambient temperature on overall thermal efficiency of the combined cycle
for different configuration of gas turbine. The overall thermal efficiency decreases with increases the
ambient temperature. It is because of the decrease the thermal efficiency for gas turbine compared with
thermal efficiency of the steam turbine cycle. The overall thermal efficiency also decreases due to
increases the losses of the exhaust gases. It can be seen that the overall thermal efficiency of the combined
cycle obtained maximum value with regenerative gas turbine configuration about 62.8% at ambient
temperature 273K and the minimum value of the overall thermal efficiency was about 53% for intercooler
gas turbine configuration at ambient temperature 333K. As the ambient temperature increases, the
compressors specific work increases, thus reducing overall thermal efficiency for the combined cycle with
all gas turbine configurations. The compressor of a gas turbine is designed to operate with a constant
volume of air. While the ambient temperature increases, its specific mass is reduced. In order to ensure the
same air volumetric flow, the mass flow is reduced, as a result causing the power output of the gas turbine
and the amount of heat generated in the HRSG to fall. Also the temperature at the inlet of the combustion
chamber increases, this lead to reduced the burning fuel and decreases the turbine inlet temperature, then
decreases the gas turbine efficiency and decreases the overall thermal efficiency of combined cycle.
The simulation varies the gas turbine compression ratio from 3 to 30. This simulation is intended to
show the effect compression ratio has on the performance of the combined cycle for different gas turbine
configuration. Fig. 4(a) shows the variation of compression ratio on total power output of combined cycle
for different gas turbine configuration. The compression ratio is affected by many factors such as work of
compressor and power output of a gas turbine. The work of compressor is a function of inlet air
temperature at the compressor air intake. The power output of a gas turbine is a function of turbine inlet
temperature. As the compression ratio increases, the air exiting the compressors is hotter, therefore less
fuel is required (lowering the air fuel ratio) to reach the desired turbine inlet temperature, for a fixed gas
flow to the gas turbine. The work required in the compressor and the power output of the gas turbine,
steadily increases with compression ratio, then cause decreases in the exhaust gases temperature. This
lower gas temperature causes less steam to be produced in the HRSG, therefore lowering the outputs of
the steam cycle. It is noticed that the total power output increases with compression ratio. However the
variation of total power output is minor at lower compression ratio while it is significant at higher
compression ratio for all gas turbine configurations. The higher total power output obtained with simple
gas turbine configuration and lower value obtained with regenerative gas turbine configuration. It is
because The power output of the gas turbine increases with compression ratio up to a certain value and
then decreases for regenerative and intercooler gas turbine configuration. The combined cycle power
output also has a similar trend to the gas turbine but the maximum value is reached at pressure ratio
between 15 and 25. While the power output of combined cycle for simple and two shafts configuration
increases constantly with increases the compression ratio.
combined cycle regenerative gas turbine decreases about 19%. It is because of reduces the exhaust gases
temperature. Therefore, the total power output for the most combined cycle configuration increases with
increase of the ambient temperature, it is because of the increases in the steam turbine cycle more than the
gas turbine power output, also the total power output increase with increases the ambient temperature.
Fig. 3(b) shows the effect of ambient temperature on overall thermal efficiency of the combined cycle
for different configuration of gas turbine. The overall thermal efficiency decreases with increases the
ambient temperature. It is because of the decrease the thermal efficiency for gas turbine compared with
thermal efficiency of the steam turbine cycle. The overall thermal efficiency also decreases due to
increases the losses of the exhaust gases. It can be seen that the overall thermal efficiency of the combined
cycle obtained maximum value with regenerative gas turbine configuration about 62.8% at ambient
temperature 273K and the minimum value of the overall thermal efficiency was about 53% for intercooler
gas turbine configuration at ambient temperature 333K. As the ambient temperature increases, the
compressors specific work increases, thus reducing overall thermal efficiency for the combined cycle with
all gas turbine configurations. The compressor of a gas turbine is designed to operate with a constant
volume of air. While the ambient temperature increases, its specific mass is reduced. In order to ensure the
same air volumetric flow, the mass flow is reduced, as a result causing the power output of the gas turbine
and the amount of heat generated in the HRSG to fall. Also the temperature at the inlet of the combustion
chamber increases, this lead to reduced the burning fuel and decreases the turbine inlet temperature, then
decreases the gas turbine efficiency and decreases the overall thermal efficiency of combined cycle.
The simulation varies the gas turbine compression ratio from 3 to 30. This simulation is intended to
show the effect compression ratio has on the performance of the combined cycle for different gas turbine
configuration. Fig. 4(a) shows the variation of compression ratio on total power output of combined cycle
for different gas turbine configuration. The compression ratio is affected by many factors such as work of
compressor and power output of a gas turbine. The work of compressor is a function of inlet air
temperature at the compressor air intake. The power output of a gas turbine is a function of turbine inlet
temperature. As the compression ratio increases, the air exiting the compressors is hotter, therefore less
fuel is required (lowering the air fuel ratio) to reach the desired turbine inlet temperature, for a fixed gas
flow to the gas turbine. The work required in the compressor and the power output of the gas turbine,
steadily increases with compression ratio, then cause decreases in the exhaust gases temperature. This
lower gas temperature causes less steam to be produced in the HRSG, therefore lowering the outputs of
the steam cycle. It is noticed that the total power output increases with compression ratio. However the
variation of total power output is minor at lower compression ratio while it is significant at higher
compression ratio for all gas turbine configurations. The higher total power output obtained with simple
gas turbine configuration and lower value obtained with regenerative gas turbine configuration. It is
because The power output of the gas turbine increases with compression ratio up to a certain value and
then decreases for regenerative and intercooler gas turbine configuration. The combined cycle power
output also has a similar trend to the gas turbine but the maximum value is reached at pressure ratio
between 15 and 25. While the power output of combined cycle for simple and two shafts configuration
increases constantly with increases the compression ratio.
การแปล กรุณารอสักครู่..