In-cycle diesel low temperature combustion control based on SOC detection

Challenges remain in diesel low temperature combustion implementation due to combustion inconsistency or instability. One possible solution is the introduction of closed-loop combustion control systems. In this paper, an in-cycle control method is proposed, which tries to bring the tricky combustion under control by reducing fluctuations of combustion center. Firstly, an SOC (Start of Combustion) online detection method based on the reconstruction of the drag pressure trace and detection of the real-time in cylinder pressure differences with the ideal drag pressure trace is presented. The drag pressure trace estimation measure proposed features a step-by-step update of estimation reference and equivalent adiabatic coefficient. Due to this step-by-step method, the pressure difference threshold for SOC detection is reduced to 0.2 MPa, with both good real-time performance and reliability. Secondly, the SOC detection method is applied in an in-cycle combustion control case under double-injection circumstance. Experiments are performed to find the relationship between SOC, combustion center and exhaust recirculation rate. An algorithm which adaptively adjusts the second injection timing according to the SOC of the pilot injection is designed according to the relationship obtained through experiments. Test results indicate that the fluctuations of the combustion center is successfully reduced.