Page 57 - Handbook of Electrical Engineering

36 HANDBOOK OF ELECTRICAL ENGINEERING

Figure 2.11 Heat rate and efficiency versus power rating.
◦
The reduction in output power is typically 0.5 to 0.8%/ C.
The fuel consumption can be calculated approximately from,

Power output × Heat rate 3
Fuel consumption = m /h (or kg/h)
Fuel LHV
For situations where there is a mixture of gases it is advisable to consult the manufacturer
of the gas turbine, since he will have a data bank containing all kinds of fuel compositions and
heating values.
The heat rate and overall thermal efficiencies for typical modern gas turbines in the range
of ISO power ratings 1 MW to 200 MW are shown in Figure 2.11. The data were derived from
Reference 6.

2.3 POWER OUTPUT FROM A GAS TURBINE
In sub-section 2.2 the performance of a gas turbine was determined as the energy obtainable at the
output shaft coupling. The energy equations are based on a unit of mass flow, 1.0 kg/s, of the fluid
passing through the gas turbine i.e. from the air intake to the exhaust aperture.
The mass flow through the turbine is about 1% higher than that through the compressor because
of the presence of the burnt fuel. Hence the mass flow rate (m) to produce the output power is,
Output power to the generator
m = kg/s
Output energy per unit mass

W out kW kg
= = kg/s
U out kj