A method to precisely control the diesel substitution rate of diesel-natural gas dual fuel engine

Highlights: • A closed-loop control algorithm is proposed to control the diesel substitution rate. • The estimated diesel substitution rate is employed as the control feedback. • A support vector regression based model is used to estimate this substitution rate. • The estimation model produces a desirable estimation. • The results confirm the precise control performance of this control algorithm. - Abstract: Precise control of the diesel substitution rate (DSR) plays a vital role in ensuring the safety and low emissions of diesel-natural gas dual fuel engines. However, an open-loop control strategy is generally employed to control the DSR, which poses a significant challenge to the precise control of the DSR. Therefore, an effective and reliable method to precisely control the DSR is urgently needed for the diesel-natural gas dual fuel engine. In this study, a support vector regression (SVR)-based model is developed to estimate the DSR, and then, a closed-loop control algorithm with the feedback of the estimated DSR is proposed to control the DSR in real time. Five easily available engine variables are employed as the inputs of the estimation model: (1) injection quantity per cycle of diesel (IQPCd); (2) injection quantity per cycle of natural gas (IQPCg); (3) engine speed; (4) inlet air flow; and (5) excess air coefficient. Cross validation is introduced to determine the kernel function and some SVR parameters. Experiments reveal that the proposed estimation model produces a desirable estimation, with a root mean square error (RMSE) of 0.46% and a maximum absolute error (MAE) of 1.89%. Furthermore, in the actual operation, the actual DSR is effectively controlled in the vicinity of the given DSR via the proposed DSR closed-loop control algorithm, with a deviation of less than 1.32%.