Thermodynamics help - gas turbine analysis

The dopers out there who are good with the various elements of thermodynamics and mech eng will know by now that I’m an BEng/MEng Aeronautical Engineering student.

Right now, I’m studying for my thermodynamic and fluid mechanics exam in a week. I seem to have lost some of my notes, which isnt cool.

I’m going through jet engine analysis at the moment, and need to know how to create block diagrams and thermodynamic cycles to start the analysis.

I’ve searched really, really hard on the internet to find block diagrams and p/t diagrams of the following:

  • Turbojet
  • Turbofan
  • Turboprop
  • Turboshaft

I think those last two are pretty much the same, but I’ll put both on there just in case!

If anyone knows where I can find this information on the internet, or has it in digital format they could send me, it’d be much appreciated.

Thank you in advance,

Harry

Found something on the Carnot Cycle. That help any?

http://www.grc.nasa.gov/WWW/K-12/airplane/carnot.html

More stuff.

http://www.aerospaceweb.org/question/propulsion/q0033.shtml

You have a compressor, combustion chamber, turbine, then a heat exchanger as your for blocks. For an ideal cycle the pressure is constant for the combustion chamber and heat exchanger, and your entropy is constant across the turbine and compressor. That should be enough to do the analysis.

All gas turbines use the Brayton cycle. Search that and you’ll find all the material you need.

I forgot to add, thats your basic cycle. You might simply exhaust to atmosphere, and have no heat exachange, or go through a nozzle etc. To be honest though, if you are a week away from finals and can’t construct block diagrams and p/t diagrams on your own, you are in a heap of trouble and should seek help from your professor/T.A. asap.

Thank you all for your help, guys.

I’m not a week away from finals, it’s cool. This is a small part of Fluid Mechanics and Thermodynamics 1, and I’m pretty good at the rest of it. Thanks for your concern though!

I’m all learned up on the Carnot and Otto cycle (on the syllabus), but we’ve not been introduced to the Brayton cycle, or at least not by name. Now I know what to search for, I can revise it!

Thank you all again.

Have you checked in your thermo book? Most of these things you’re looking for are explained pretty well in a basic intro to thermodynamics book. I just looked in the index of the one I use and sure enough I find headings for turbojet, turbofan and turboprop engines.

Textbooks; not just for doorstops anymore. :cool:

As the others have said, any basic thermodynamics book will have good p-T or T-s diagrams for basic engine types. For anything more complicated than a turbofan, turbojet, or turboprop (afterburners, combined cycle engines, etc) you should go to your school’s tech library and find a gas turbine book.

I might recommend Jack Mattingly’s Elements of Gas Turbine Propulsion. It has a pretty good treatment of engine thermodynamics, and is a common text for propulsion courses in many universities.