Other Gas Power System Applications A turboprop engine

Chapter 9, Problem 92P

(choose chapter or problem)

A turboprop engine consists of a diffuser, compressor, combustor, turbine, and nozzle. The turbine drives a propeller as well as the compressor. Air enters the diffuser at \(12 \mathrm{\ lbf} /\text { in. }^{2}, \ 460^{\circ} \mathrm{R}\), with a volumetric flow rate of \(30,000 \mathrm{\ ft}^{3} / \mathrm{min}\) and a velocity of 520 ft/s. In the diffuser, the air decelerates isentropically to negligible velocity. The compressor pressure ratio is 9, and the turbine inlet temperature is \(2100^{\circ} \mathrm{R}\). The turbine exit pressure is \(25 \text { lbf/in. }{ }^{2}\), and the air expands to \(12 \text { lbf/in. }{ }^{2}\) through a nozzle. The compressor and turbine each has an isentropic efficiency of 87%, and the nozzle has an isentropic efficiency of 95%. Using an air-standard analysis, determine

(a) the power delivered to the propeller, in hp.

(b) the velocity at the nozzle exit, in ft/s.

Neglect kinetic energy except at the diffuser inlet and the nozzle exit.