Abstract
Ignition delay of stagnation-point oxidizing flows over a wall with the injection of fuel is analyzed numerically. The validity of various criteria of ignition delay, i.e., the adiabaticity criterion and the thermal runaway criteria (∂ 2 T max / ∂t 2 = 0 and ∂ 2 ω max /∂t 2 = 0), is investigated for the problems of cold flow/jot wall and hot flow/cold wall. For cold flow/ hot wall systems, the ignition delay decreases with the mass flux of fuel (m w ) if m w is below a critical value (m wc ). The ignition delay is kinetically controlled for m w < m w,c . For m w > m w, c, the ignition delay increases with m w and is diffusionally controlled by the deficient oxidizer. The adiabaticity criterion is suggested from the viewpoints of practice and simplicity. For hot flow/cold wall systems, the ignition delay decreases with m w and is diffusionally controlled by the deficient fuel. The criterion of ∂ 2 ω max /∂t 2 = 0 is suggested both qualitatively and quantitatively. In addition, the effects of flow strain rate, Lewis numbers and Prandtl number on ignition delay are investigated. © 2002 Elsevier Science Ltd. All rights reserved.