The Basic cycle Analysis of simple gas turbine cycle.

 

The Basic cycle Analysis of simple gas turbine cycle.

 

 

 

THE BASIC CYCLE

 

Simple cycle gas plants are a type of natural gas power plant that produces electricity by forcing hot gas through a turbine. They differ from combined cycle gas plants in that they are solely used to supply the electrical grid's peak power needs since their waste heat is not transferred to another external heat engine. These turbines have a high specific power, which indicates that the amount of power they produce is comparatively large for their size.

 

Different power plants, such as coal or nuclear, provide baseload power to the grid, which meets the minimum electricity requirements. Peaking power plants, such as simple cycle gas plants, can fulfil the fluctuating electricity demands. As a result, simple cycle plants have excellent operational flexibility and may be swiftly started up to suit these needs. However, because they use less of the energy in the fuel they are using, this is less efficient than combined cycle plants. These plants have an efficiency of about 35%.

 

They compensate for any inefficiency with expense. According to the EIA, mixed cycle plants cost between US$500 and 550/kW, and simple cycle plants cost about US$389/kW.

 

Simple cycle power plants are not used for long periods of time throughout the year due to their low efficiency and ability to only provide peaking power. This gives them a very low capacity factor, which means that they are, on average, not running very close to their maximum output. At most, these plants are typically only running for a few hours per day.

 

Analysis of a Simple Gas Turbine Cycle

 

The actual performance of a gas turbine plant differs considerably from the Brayton cycle because of the deviations from the ideal cycle. These deviations include friction, shock, and heat transfer and aerodynamic losses in the compressor and turbine, losses in combustion chamber, piping, mechanical losses, etc. With large number of variables affecting the performance of the gas turbine plant, it will be really different! Unless it is possible to estimate its performance, Certain assumptions are made. To simplify the analysis, consider the following:

 

Assumptions are made:

 

l. There is no pressure loss in the combustion chamber, and in piping, etc. 

2. There is no increase in the rate of mass flow due to the addition of the fuel. 

3. The specific heat remains constant at all temperatures and same for compressor as well as turbine flow.

4. Radiation and mechanical losses are neglected.