Thermal Effeciency

[My names Turkish]

All,
Exam question I had in AGK last time was: What is the Thermal Effeciency of A Jet Engine and Piston Engine, the figues given were 60%, 70% and 80% I think. Can anyone suggest the correct combination?

[Keith.Williams.]

The "conventional wisdom" answer is about 30 to 34% for piston engines and about 20% for gas turbines. It is of course possible to achieve better and worse figures in real life, but these are the types of figures that JAR exams would be looking for.

You quoted only three figures. Could it be that the fourth option was somewhere in the 20 to 30% range?

[My names Turkish]

Keith, Thanks for the reply, it may well have been, I did the exam a while back and I dont remember the exact answer. Hopefuly that now I do it will pop up in the exam tomorrow.