Turbine

[raghavendrasistla]

i am building a jet from scrap and i would like to know a couple of things. First of all what should be the angle of the turbine blades to make the engine most efficient secondly what should i do about the carbon deposite in the combustion chamber and what metal should i use to make the turbine and the axial compressor.

 

[insideman]

You must learn a great deal before determining what angle a turbine blade should be set at.

What size turbine? What rpm? to fly at what airspeeds?

 

[WKTaylor]

raghavendrasistla... Your simple questions are NOT simple!!

Check the following websites for engineering/design info:

http://www.aiaa.org

[bookstore] for texts/references on turbine engine design [sizing, structure, configuration etc].

http://www.sae.org

[bookstore] for texts/references on turbine engine design [sizing, testing, materials, stds, etc].

http://www.asm-intl.org

[bookstore] for texts/references on turbine engine materials [high temp metals, coatings, NDI, etc].

Check the following websites for existing class-room-sized microturbine engines [teaching/learning aides]:

http://www.turbinetechnologies.com/

http://www.agilis.com/

Regards, Wil Taylor

 

The angle of your blades is determined by the characteristics of your nozzle guide vanes (NGV's). Most turbine blades are 'target' type and not true aerodynamic foils. The NGV's moderate the exhast gasses by increasing the gas speed, lowering the pressure, and angling the flow to impinge on the concave face of the blade. The 'throat area' of these NGV's is the main control of engine speed and flow character, it must be finely calculated. A few hours on a Cray II supercomputer should suffice.
You can chemically clean the combustion chamber of carbon, ensure that all cooling air orifices are clean or you will warp or heat erode the vessel.
Turbine discs are usually made of high temperature inconel or steel to tolerences of 0.0005" or less. Unless you have the capability to manufacuter a 'blisk' (Disc and blades as one unit) you will have to find a way to secure your blades that is fool-proof. Most turbines use the 'fir-tree' design which requires exquisite machining and skill. (At speed a turbine blade in a larger engine will have the same apparent weight as a pick-up truck due to centrifugal force.)
Axial compressors are usually made of low corrosion steel in multiple stacked discs on a single shaft, centrafugal comressors are usually single stage affairs but can be double sided.
I am very sorry to say, but if you are asking these sort of questions your desired goal is far beyond your cababilities. I have not even spoken of fuel control, bearing support members, oil systems, buffer and cooling air, as well as a litany of other critical details. I have worked in aviation for 22 years and overhaul of jet engines for 15 of that, I would not attempt to build an engine of my own.
Consider re-building a scrap engine (Something common so spares will be easy to find.) that has had it's 'C of A' revoked. Stand well back when you start it, and do not EVER consider using it to fly anything.

Regards, Ken.

 

[Kenneth]

OK, the legal disclaimer first: "You'll put your eye out."

Now some links:

http://www.google.com/search?hl=en&q=homebuilt+"jet+engine"+plans&btnG=Google+Search

http://www.aardvark.co.nz/pjet/links.htm

Have fun!