Prediction of Pre-Ignition Borderline on Supercharged SI Engine by Livengood-Wu Integral

<div class="section abstract"><div class="htmlview paragraph">The LSPI (Low Speed Pre-Ignition) is one of the consecutive abnormal combustion cycles of supercharged SI engine with direct injection fuel supply system [<span class="xref">1</span>]. The LSPI occurs when the engine is running at low speed and high load condition. It is important for the SI engine to control essentially with alternative fuel, e-fuel and hydrogen in the future.</div><div class="htmlview paragraph">It is considered that the LSPI would be caused by the autoignition of the deposit, the lubricating oil from ring crevice, the lubricating oil from piston crown and so on [<span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>, <span class="xref">5</span>]. Among of these causes, this research focuses on the scattering lubricating oil from piston crown. The previous our research has reported on the two points. One is about the frequency and quantity of the lubricating oil scattering from piston crown [<span class="xref">6</span>]. Another is about the frequency of abnormal combustion by the engine test [<span class="xref">7</span>]. As the result, it has been cleared that the frequency of abnormal combustion is 1/10 of scattering frequency of the lubricating oil from piston crown. Moreover, it has been evaluated in-cylinder condition by the Livengood-Wu integral when the autoignition occurred.</div><div class="htmlview paragraph">The LSPI would occur suddenly, continue several cycles and return to the normal combustion cycle again. However, it is difficult to find the borderline that the LSPI would occur or not for each engine and operating condition. This research will try to define the borderline of the occurring LSPI or not.</div><div class="htmlview paragraph">The experimental data show the autoignition timing has three patterns. The autoignition timing advances from ATDC to BTDC when the consecutive abnormal combustion cycles proceed, it delays from BTDC to ATDC and all abnormal combustion cycles appear at ATDC. It is proposed that the borderline of LSPI is defined by the analysis of those autoignition with the Livengood-Wu integral.</div></div>