New Index for Diagnosis of Abnormal Combustion Using a Crankshaft Position Sensor in a Diesel Engine 2019-01-0720

Most research of internal combustion engine focuses on improving the fuel economy and reducing exhaust emissions to satisfy regulations and marketability. Engine combustion is a key factor in determining engine performance. Generally, engine operating parameters are optimized for the best performance and less exhaust emissions. However, abnormal combustion results in engine conditions that are far from an optimized operation. Abnormal combustion, including a misfire, can happen for a variety of reasons, such as superannuated vehicles, extreme changes in the driving environment, etc. Abnormal combustion causes serious deterioration of not only noise, vibration and harshness (NVH), but also the fuel economy and exhaust emission. NVH stands for unwanted noise, vibration and harshness from the vehicle. The misfiring especially deteriorates vehicle comfortability. Abnormal combustion at one cylinder breaks the exciting force balance between cylinders and causes unexpected vibration. Controlling and diagnosing the engine combustion quality are essential technologies for maintaining the optimal performance. There have been many methods and studies for evaluating the combustion quality or stability using the crankshaft position sensor. In this paper, a newly developed index related to the combustion characteristics is used to evaluate the combustion quality. Abnormal combustion is defined in this paper as partial burning and misfiring, in which the conditions are generated by retarding the injection timing individually at only one cylinder. Additionally, an order analysis of vibration at the engine was conducted to evaluate a correlation between the vibration deterioration and a new index. A new index that facilitates real-time calculations can contribute to the diagnosis of abnormal combustion and the assessment of the combustion quality, though it is needed to calibrate the base level of a new index at whole operating points for each engine and operative conditions. Furthermore, it can contribute towards estimating the vibration deterioration with a crankshaft position sensor in future studies.