# Homework Help: Thermodynamics Question (Centrifugal Compressor)

1. Apr 14, 2009

### Noisia

Hi there guys,

Sorryto make my first post on here a request, but i am a little puzzled at the moment by this latest question I have been set! My lecture notes do not seem to cover this in any detail at all, and resources on the internet are either avoiding me or i am just plain blind!

1. Inlet blade angle : -55 degrees, Outlet blade angle : 0 degrees, mass flow rate of air : 4.32 kg/s, rotor inlet radius : 45mm, rotor radius at tip : 0.14m, outlet dimensions are r2 : 0.2m and h2 : 22mm, rotor has 21 blades, rotation speed is 15000rpm. Air enters compressor at temperature of 300K and pressure of 1.0atm.

Starting with a guessed value for c1, and using an iterative process, find Ma1 and the inlet velocity triangle satisfying the prescribed mass flow rate

2. As for equations I am not even sure what i should be using. These are what i have so far:

c = u + v

M1 = V1 / ([gamma]*R*T)^1/2

Then using v = V(flow rate) / A

I think that there is a fundamental error in my working so far, whether the equations are totally in the wrong direction i dont know! If you guys could just set me in the right direction it would be much appreciated as this has been doing my head in for a while now!

Regards