Page 56 - Handbook of Electrical Engineering

GAS TURBINE DRIVEN GENERATORS 35

2.2.5 Heat Rate and Fuel Consumption

The heat rate is the ratio of heat given up by the fuel, in terms of its lower calorific or heating value
(LHV), to the power available at the gas turbine coupling to its generator. It has the SI units of
kJ/kWh. The lower heating value of typical fuels is given in Table 2.3.

The heat rate for a particular gas turbine will be given by its manufacturer at ISO conditions,
and at various ambient temperatures. The typical variation of heat rate and power output, in relation to
their ISO values, are shown in Figure 2.10. For a definition of ISO conditions see sub-section 2.3.2.

Table 2.3. Lower heating values of fuels
3
Fuel Lower heating value (LHV) Btu/ft for gases
3
MJ/m for gases Btu/lb for liquids
MJ/kg for liquids
GASES
Natural gas 35.40 to 39.12 950 to 1050
Methane 33.94 911
Ethane 60.77 1,631
Propane 87.67 2,353
Butane 115.54 3,101
Hydrogen 10.17 273
Hydrogen sulphide 23.14 621
LIQUIDS
Diesel oil 45.36 19,500
Kerosene 41.87 18,000
Distillate 44.89 19,300
Crude oil 44.66 19,200

Figure 2.10 Power output and heat rate versus ambient air temperature.