3D POTENTIAL FLOW ANALYSIS

3D potential flow analysis [12] is performed to analyze gas field velocities in the channels to determine aerodynamic forces on compressor blades. It is assumed that the flow is potential in a fixed coordinate system. Viscosity absence, external forces potentiality, and channel inlet gas vorticity absence are sufficient conditions to determine flow potentiality.

A flow potential is defined via FEA. The pressure field can be defined from the Cauchy-Lagrange integral. Gas compressibility is taken into account iteratively by the way of flow potential determination with nonuniform density. The iterative process is convergent for subsonic flows.

Fig. 16 shows the relative velocities field of the centrifugal compressor channel, calculated according to the gas potential flow model. The model allows one to determine flow degree of irregularity in the channel.

In Fig. 17 static pressure field calculated according to the same model is shown. This field is used to estimate bladed disk strength.

CENTRIFUGAL COMPRESSOR DESIGN EXAMPLES

Parameters for CC with vane diffuser design are:

P₁* = 60 KPa,
T₁ * = 300 K,
n = 25000…35000 rpm
G = 1.5 kg/s
P₃/P₁ = 3.5
D₁ = 90…110 mm
c_1z/u = 1...1.5
D₂/D₁ = 2.0...3.0
α₃ = 80^o...100^o
D4/D3=1.3

Optimal stage compressor flowpath with vaned diffuser draft is shown on the Fig.18a, velocity triangles are on the Fig.18b.

The following parameters are received in an optimal point:

n = 29000 rpm,
c_1z/u = 1.01,
H_t = 0.86,
B2 = 95.8.
Eff=91.2%

<< Back    1    2   3    4    5    6   7    8    9   10    11    Next >>