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Show 4> l it, h Yf* k e Sf r+ 0 Me Me/<^h Me/cr/u Me Me/^t Me/CTS^ k-e model constants •S^, 0 dp / 9u, 9uj N 2 / 9ufc \ 0 w/« = -p2ULSf Pk -pe (CuPk -C2cPt){ k ' © • • i X f t ) * -^ Pfc = /9u, 9u,\ 2 / 9u^ \ dut dxj Cle-=1.44, C 2 t = 1.92, CM=0.09, <rk=l, rre=1.3, erB=0.7, CTfa=0.7, <rSf=l • Table 1 Definitions of exchange coefficient T * and source term S NUMERICAL SOLUTION Numerical simulations are carried out by solving the basic set of governing equations for two-dimensional steady turbulent premixed propane-air reactive flow : continuity, momentum, enthalpy, fuel mass fraction, turbulent kinetic energy, turbulent energy dissipation and flame surface density (Table 1). The equations are discretized on a staggered, nonuniform cartesian grid using a finite-volume procedure (Patankar [15]) with a hybrid differencing scheme for the convective terms. The mean flow equations are solved by using the S I M P L E C procedure (Van Doormaal and Raithby [20]) for handling the pressure-velocity coupling. The set of algebraic equations which gives rise to a tri-diagonal system of equations is solved by the line-by-line TriDiagonal Matrix Algorithm ( T D M A ). RESULTS AND DISCUSSION In all the cases presented in this section, the inlet stream is a mixture of air and propane and has a pressure of 1 atm and a temperature of 300 K. The ignition of flame is done by imposing a non-zero value for the flame surface density Sf. Note that several numerical tests have been realised on the initial value of Sf and have shown the independence of the converged solution from the initial value of Sf. Combustion is supposed adiabatic, i.e., heat losses due to radiation and heat transfer to the walls are neglected. Following Montazel [14] and Maistret [9], this assumption is reasonable because the combustion chamber walls remain so hot after flame extinction that fresh premixed gas ignites spontaneously whitout need of spark ignition. w 4 |
