Knock recognition based on vibration signal and Wiebe function in a heavy-duty spark ignited engine fueled with Methane

Abstract

Increasing demands on higher performance and lower fuel consumption and emissions have lead the path for internal combustion engine development; this race is nowadays directly related of CO2 emissions reduction. In spark-ignited (SI) engines, knock is one of the major barriers to achieve high thermal efficiency at high loads. The knocking risk is even higher in heavy-duty (HD) engines due to the size of the cylinders and to the low rotation speed. This paper proposes a knock detection strategy based on the combination of knock sensors and combustion modeling applied to a HD natural gas (NG) engine. The aim is to have a reliable, economic and computationally efficient algorithm to be implemented directly on the engine ECU.The method proposed has been applied to an extensive set of experimental data acquired on a SI NG heavy-duty engine. The results of the proposed knock estimation method are benchmarks with those based on in-cylinder pressure analysis using piezoelectric transducers. The extension of the method based on in-cylinder pressure to a high displacement heavy-duty NG engine not only represents an innovation, but improves the knock recognition based on in-cylinder pressure compared with conventional methods as MAPO or IMAP. Besides, the development of an alternative method based on knock sensor signal, allows to obtain a higher or equal sensitivity compared to the traditional MAPO method based on in-cylinder pressure, with the advantage of only using knock sensors.