A simple-cycle gas turbine used for power generation has a thermal efficiency of about 34 percent. Since 1 kwh is theoretically equivalent to 3,415 Btu, the simple-cycle gas turbine has a fuel connsumption of: 3,415 / 0.34 = about 10,000 Btu/kwh. Given the heating value (i.e, heat of combustion) of a fuel, we can easily calculate the simple-cycle gas turbine fuel usage. For example, natural gas has a net heating value of about 21,500 Btu/pound. Thus, the natural gas consumption in a simple-cycle gas turbine would be: 10,000 / 21,500 = 0.47 pounds/kwh = 0.21 kg/kwh. As another example, a typical diesel oil has a net heating value of 130,000 Btu/gallon. Thus, the diesel oil consumption in a simple-cycle gas turbine would be: 10,000 / 130,000 = 0.077 gallon/kwh. (The gallon used just above is the U.S. gallon rather than the Imperial gallon) A combined-cycle gas turbine will have a higher thermal efficiency and, hence, lower fuel consumptions.
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with decrease in fuel consumption the amount of steam produced is also reduced.Hence when lower quantity of steam passes through the turbine the torque generated is less and since generator and turbine are coupled on a single shaft the generator torque also decrease which reduces load.
A pen and paper. Miles driven divided by gallons of fuel used gives you mpg.
Turbine cycle heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the turbine divided by the electrical energy output. The energy input is the difference between the energy in the steam supplied to, and leaving from the turbine. The total energy supplied is the sum of the steam mass flow rates to the turbine multiplied by their respective enthalpies. The energy leaving is the sum of mass flow rates exiting the turbine multiplied by their respective enthalpies. Take the difference in the total energy supplied and leaving, divide by the electrical output and this gives you heat rate, typically expressed in Btu/kWh or kJ/kWh. This is easy for a single source of steam passing through the turbine to a condenser, but gets a bit more tricky for reheat turbines with multiple extractions as all the streams in and out have to be accounted for.
Bleed air in gas turbine engines is compressed air taken from within the engine, after the compressor stage(s) and before the fuel is injected in the burner
Gear ratios will let the engine run at the speed and load at which it is most efficient, which is good for low fuel consumption and an exhaust that is as clean as possible.