ME 475/675 Introduction to Combustion

1. ME 475/675 Introduction to Combustion Lecture 25

2. Announcements • Please see me after class to confirm you attendance at the distinguished lecture • Midterm 2 • November 5, 2014 (two weeks) • HW 9 (Example 6.2 and its numerical solution) • Due Friday, Oct. 24, 2014

3. Steady-State Well-Stirred Reactor • Mass Conservation for M species • One inlet and one outlet: Accumulation = generation + net inflow • Where • Since well-mixed properties leaving are same as this insideCV • Steady State • Find molar concentrations [i] from mass fractions Yi

4. Energy Conservation (to find T) • Steady State: • Residence Time • ; • All these conditions (equations) are algebraic (not differential)

5. Example 6.2 • Develop a simplified model of a well-stirred reactor using the same simplified chemistry and thermodynamics used in Example 6.1 (equal and constant cp’s and MW’s, and one-step global kinetics). Use the model to determine the blowout characteristics of a spherical (80-mm-diameter) reactor with premixed reactants (C2H6-air) entering at 298 K. Plot the equivalence ratio at blowout as a function of mass flowrate for . Assume the reactor is adiabatic. • MWF=MWOx= MWP= 29; cp,F= cp,Ox= cp,Pr= 1200 J/kgK • The enthalpy of formation of the air and products are zero, and that of the fuel is • 4*107 J/kg • The stoichiometric air-fuel ratio is 16.0 and restrict combustion to stoichiometric or lean conditions, . • Constant pressure, constant volume, or well stirred reactor?

6. Last Lecture • Species Production • Inlet Conditions • ;

7. Species Conservation • Fuel • 1 • Oxidizer • 2 • Product • 3

8. Energy Conservation (to find T)

9. MathCAD Solution .