燃烧学导论概念与应用第八章习题.pdf

《燃烧学导论：概念与应用》第八章习题参考答案* 本章习题：1， 3 ， 4 ，5，6，7，8 8.1 Given: the outward propagation of a spherical laminar flame into an infinite medium of unburned gas Find: an expression for the radial velocity of the flame front, v Assumptions: spherical symmetry Approach: use conservation of mass and definition of flame speed • min ρ S A where A 4πr 2 Flame front u L f f f 4 3 m ρ πr b b 3 f Conservation of mass: dm • b min dt dr ρ 4πr2 f ρ S 4πr2 b f dt u L f dr ρ S thus, f v u L dt f ρb Comments: since ρ ρ ,the flame front moves into the unburned gas at a speed greater than u b the flame speed. This is due to the outward expansion of the burned gases. And there is also a flame sheet assumption. 8.2 GIVEN: the thermodynamics employed in chapter 8 SHOW: that Δh (ν +1)c (T −T ) for an adiabatic flame C P b u ASSUMPTIONS: cP of species are constant and equal APPROACH: apply conservation of energy across flame and h ho +c (T −T )