Abstract
A high-accuracy knocking prediction model with low computational loads is necessary to develop thermal-efficiency improvement technologies for SI engines efficiently using computational techniques. Livengood-Wu integral has been applied widely as the simplest model for predicting knocking. In the previous reports, ignition delay time equations for a premium-gasoline surrogate fuel were developed to reproduce the temperature-, pressure-, equivalence ratio-, and EGR-dependences of ignition delay time produced using a detailed reaction mechanism. “Reverse Livengood-Wu integral” using an error correction equation was proposed to cancel the advances of timing predicted using Livengood-Wu integral with the ignition delay time equations, from ignition timing produced using the detailed reaction mechanism. The reverse Livengood-Wu integral requires iterative calculation to seek the correct ignition timing. In the present report, it has been found that ignition delay times using the equations are shorter than those using the detailed reaction mechanism with the high initial pressures over 6 MPa. Therefore, the ignition delay time equations have been revised for the expansion of those application conditions to 12 MPa. Also, a new equation has been developed to correct the prediction errors without iterative calculation. It has been investigated whether autoignition prediction using these equations can be effective or not in predicting experimental knocking occurrence timings in an SI engine. The difference of several % in estimating unburned-zone temperature causes the difference of several crank angle degrees in predicting autoignition timing.
