Compressor and Turbine design/matching

[ddthj]

Hello all,

After a long hiatus I'm back with new questions. I'm looking to design my own compressor and turbine. I have found a lot of mixed material online about designing one or the other, but not much about matching them. I took a look through the diy-turbines thread (and I'll be taking a lot more looks through it as I progress), but it assumes you're using a turbo. 

Long term goal is to build a turboshaft, aiming for 100-150shp. Also curious if I can get away with a single shaft (no free turbine), but that's a decision for later.

For now I'm just looking for what numbers I need to have line up between the compressor's design and the turbine's design. Links to reading material would be appreciated.

Thanks for your help!

[turboron]

ddthj, there are several ways to approach sizing and matching the diy gas turbine components. A good place to start is to use the continuity equation. The equation states that the product of the density times the area times the velocity is equal to a constant. In other words, rho1xA1xV1 = rho2xA2xV2 = Constant. To start the sizing assume that the mass flow (air flow) is proportional to your compressor's inducer area. We usually assume 10 pounds per minute per square inch of inducer area. The mass flow is constant though out the engine. Once you know the mass flow you can use the perfect gas law to calculate the pressures and temperatures though out the engine. The perfect gas law is that the pressure times the specific volume is equal the gas constant times the temperature. The specific volume is the inverse of the density. Once you know the pressures and temperatures at each station you can use the continuity equation to size the areas needed for each component. You must be careful with the units used in each equation. Look all these terms and equations up online to get a better understanding.

Thanks, Ron

[racket]

www.ebay.com/itm/Gas-Turbine-Engines-for-Model-Aircraft-ExLib-by-Schreckling-Kurt/372934588776?epid=1600227717&hash=item56d4a23968:g:4iIAAOSwCbJeMjDQ

goes into some detail of getting a balance between comp and turb