Inverse Livengood-Wu integration method for analyzing ignition delay times in reactors with varying conditions

摘要

Ignition delay time at different temperature and pressure conditions is a useful global metric of fuel performance screening and kinetic modeling. Measurements of ignition delay are facile; however interpretation can be complicated for systems with changing temperature and pressure. This is especially true for techniques like ignition delays measured in the miniature shock tube, which have complex temperature and pressure state histories (after an initial constant period) induced by the pressure waves. An inverse-Livengood Wu integral technique is demonstrated to de-convolve the constant condition ignition delay times from measured ignition delay times using information on the state history of the reactor, with both local optimization via relaxed newton iteration and global optimization via the genetic algorithm. In this brief paper, the approximative inverse problem, using known chemical mechanism and detailed modeling to estimate the temperature and pressure state history is demonstrated. Using the method, measurements of ignition delay times in systems like the miniature shock tube compare very favorably to those performed using more conventional techniques, such as regular shock tubes. Additionally, the results of indirect comparison using inverse L-W method using the HRRST data and the direct comparison consistently show there is disagreement between the published ignition data for acetone, demonstrating the feasibility and usefulness of the proposed method. The full method can be performed if simultaneous independent temperature measurement is available.