Open cycle gas turbine:
Open cycle gas turbine Basic gas turbine It consists of a compressor, a combustion chamber and a gas turbine . The compressor and the gas turbine are mounted on the same shaft The compressor unit is either centrifugal or axial flow type.
Various process involved:
Various process involved 1-2 Isentropic(reversible adiabatic) compression. 2-3 constant pressure heat supply in the combustion chamber. 3-4 Isentropic(reversible adiabatic)expansion of combustion gases. Combustion products are exhausted into atmosphere.
Closed cycle gas turbine:
Closed cycle gas turbine It consists of a compressor,air heater, turbine & a cooler. Fuel is burnt externally & heat is supplied to working substance in heater. It is an external combustion turbine.
Advantages of closed cycle gas turbine:
Advantages of closed cycle gas turbine External combustion plants so wide variety of fuel can be burned in closed cycle gas turbine whereas only air can be used as working fluid in open cycle gas turbine. Products of combustion do not come directly in contact with turbine blades in closed cycle gas turbine. Minimum operating pressure can be set above atmospheric pressure. Heat transfer coefficients (h=q/( A.t ))are higher at high pressures so reduces the size of heat exchangers.
Disadvantages of closed cycle gas turbine:
Disadvantages of closed cycle gas turbine External furnace for combustion process. More complicated and costly. System must be strong enough to resist high pressures. Coolant is used for pre-cooling whereas no coolant is required in open cycle gas turbine. Atmosphere act as sink.