Design problems from Applied Thermal Science
(University of Arkansas at Little Rock)

Air-standard gas turbine

Air-standard gas turbine with counterflow heat exchanger

Air-standard gas turbine engine with a two-stage compressor with intercooling, a two-stage turbine with reheating, and a regenerative heat exchanger

Refrigerator


Design #1: air-standard gas turbine

An air-standard gas turbine operates with a pressure ratio of 15-to-1, and the inlet conditions are 14.7 psia and 60 F. The engine is required to deliver 1000hp. The maximum allowable temperature in the engine is 2500R due to structural considerations with regard to the turbine blades.

Determine the state temperatures and pressures in between each component, the required air mass flow rate, the rates of heat addition and rejection, the compressor power, and the thermal efficiency of the cycle. Perform a sensitivity analyses to determine how the compressor pressure ratios affects cycle efficiency and net power output. Also determine which working fluid would permit the highest thermal efficiency: air, helium, or carbon dioxide.


Design #2: air-standard gas turbine with counterflow heat exchanger

Add a counterflow heat exchanger to the above cycle to allow regeneration of exhaust heat, i.e., to allow preheating of the air entering the combustion chamber.

Perform a sensitivity analysis to determine the effect of compressor pressure ratio on the cycle efficiency and on net power output.


Design #3: air-standard gas turbine engine with a two-stage compressor with intercooling, a two-stage turbine with reheating, and a regenerative heat exchanger

An air-standard gas turbine engine has a two-stage compressor with intercooling, a two-stage turbine with reheating, and a regenerative heat exchanger. The compressor inlet conditions are 14.7 psia and 60 F, and the turbine inlet temperature is 2000 F. The pressure ratio for each compressor and turbine stage is 4:1. The air mass flow rate is 250 lbm/s.

Draw a pressure v. specific volume diagram of this cycle, using CyclePad to help calculate all of the states. Determine the net power output and the thermal efficiency of this cycle. Perform sensitivity analyses to determine the effects of compressor pressure ratios on the cycle efficiency and net power production


Design #4: Refrigerator

Open the Solved Refrigerator from the CyclePad library.

Determine the phase (liquid, gas, or liquid-gas mixture) of the refrigerant at each state. Determine the change in enthalpy of the refrigerant as it flows through the throttle valve. What is the temperature of the refrigerated space corresponding to this cycle? What is the temperature of the space to which heat is being rejected?



(these problems are from Prof. Jovanovic's course, Applied Thermal Science, at the University of Arkansas, Little Rock)