Combustion and Cooling Performance in an Aero-Engine Annular Combustor

Abstract

Fluid-solid coupling simulation in an aero-engine annular combustor with full film cooling is conducted to investigate the integrated contribution of combustion and cooling to the thermal load in a completely structure annular tube. The predicted profile of the exit temperature is in a quite good agreement with the rig-test data, indicating that the CFD analysis can explore the major performance of the fluid flow and combustion in the gas turbine combustor. A counter-rotating vortex pair (CRVP) ensures the ignition and flame stability formed in the head zone of the combustor, and the strong injections from the first row of the in-line dilution holes retard flame diffusion downstream. The rotation leads to a non-symmetry of exit temperature distribution. The tubes are cooled by the full film from discrete tiny holes with the average diameter 1.5 mm. The flow structures in the downstream zones of several typical cooling holes are analyzed to study the contribution of dilution jets to film formation and cooling performance. Generally, the air film is very uniform and can protect tubes nearly whole surface very well. However, any strong injections from dilution holes may penetrate and damage the film, and high temperature areas might be induced near the dilution holes.

Keywords: Aero-engine; Combustor; Flow field; Film cooling; CFD simulation

Nomenclature

Cp,s

specific heat capacity [J kg−1 K −1]

d

particle diameter [m]

Click to view the MathML source

fineness particle diameter [m]

D

diameter of hole [m]

h

specific enthalpy [J kg−1]

ht

specific total enthalpy [J kg−1]

k

turbulence kinetic energy [m2 s−2]

m

product component number [-]

n

size dispersion exponent [-]

P

static pressure [Pa]

R

reaction rate [mol l−1 s−1]

SE

energy source [-]

S

row center line space [m]

SM

momentum source [-]

T

temperature [K]

t

time [s]

U

velocity vector [m s−1]

v

stoichiometric coefficient [-]

W

molar mass [kg]

Greek symbols

θ

non-dimensional temperature [-]

ρ

density [kg m−3]

λ

thermal conductivity [W m−1 K−1]

μ

molecular viscosity [m2 s−1]

δ

three dimensional identity matrix [-]

ω

specific dissipation rate [s−1]

Subscripts

E

energy

f

fluid or flow direction

i

component

j

progress of elementary reaction

jet

fuel

l

laterally

M

momentum

p

normal pressure

s

solid

t

total

Article Outline

Nomenclature

1. Introduction

2. Model description

2.1. Geometry and grid

2.2. Boundary conditions and flux distribution

2.3. Combustion model

2.4. Radiation model

2.5. Governing equations and CFD solver

3. Result and discussion

3.1. Fuel droplet spray and atomization

3.2. Combustion characters in the tube

3.3. Film cooling on annular tubes

3.3.1. Film performance on different strips

3.3.2. Temperature distribution on tubes along axis

4. Conclusion

References

1. Introduction

A combustion chamber is the most heavily thermal load part in an aero engine, in which both ignition and combustion keep going on, and normally whose service life is very short. Since very limit data can be obtained from expensive engine tests due