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MAE 5310: COMBUSTION FUNDAMENTALS

MAE 5310: COMBUSTION FUNDAMENTALS. Coupled Thermodynamic and Chemical Systems: Plug Flow Reactor November 5, 2012 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk. PLUG FLOW REACTOR OVERVIEW. Assumptions Steady-state, steady flow

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MAE 5310: COMBUSTION FUNDAMENTALS

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  1. MAE 5310: COMBUSTION FUNDAMENTALS Coupled Thermodynamic and Chemical Systems: Plug Flow Reactor November 5, 2012 Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk

  2. PLUG FLOW REACTOR OVERVIEW • Assumptions • Steady-state, steady flow • No mixing in the axial direction. This implies that molecular and/or turbulent mass diffusion is negligible in the flow direction • Uniform properties in the direction perpendicular to the flow (flow is one dimensional). This implies that at any cross-section, a single velocity, temperature, composition, etc., completely characterize the flow • Ideal frictionless flow. This assumption allows the use Euler equation to relate pressure and velocity • Ideal gas behavior. State relations to relate T, P, r, Yi, and h • Goal: Develop a system of 1st order ODEs whose solution describes the reactor flow properties, including composition, as a function of distance, x T=T(x) [Xi]=[Xi](x) P=P(x) V=u(x) Dx

  3. GOVERNING EQUATIONS Mass conservation x-momentum conservation Energy conservation P is the local perimeter of the reactor Species conservation

  4. USEFUL FORMS Results from expanding conservation of mass Results from expanding the energy equation Differentiation of functional relationship for ideal-gas calorific equation of state, h=h(T,Yi) Differentiation of ideal-gas equation of state Differentiation of definition of mixture molecular weight expressed in terms of species mass fractions

  5. POTENTIAL SOLUTION SET • In these equations the heat transfer rate has been set to zero for simplicity • Mathematical description of the plug-flow reactor is similar to constant pressure and constant volume reactor models developed previously • All 3 result in a coupled set of ODEs • Plug Flow Reactor are expressed as functions of spatial coordinate, x, rather than time, t

  6. APPLICATION TO COMBUSTION SYSTEM MODELING Turbine Air Primary Zone f~0.3 f ~ 1.0 T~2500 K Compressor Conceptual model of a gas-turbine combustor using 2 WSRs and 1 PFR

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