Study on Naphtha Combustion in HCCI Engines

Article Study on Naphtha Combustion in HCCI Engines An Lu 1, Junior James Achumu 2 and Junfeng Yang 2,* 1 School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 2 School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK * Correspondence: [email protected] Received: 15 July 2024; Revised: 18 October 2024; Accepted: 22 October 2024; Published: 28 October 2024 Abstract: The chemical kinetics model studies have been conducted in this paper to assess ignition characteristics of coal-based naphtha (with carbon range C3–C10, RON of 54) for use in advanced engines. Reactivity of coal-based naphtha (CBN) was compared with two surrogate models: PRF54 (46 mole% n-heptane/54 mole% iso-octane) model and 3-component (42.561 mole% NC7H16, 43.683 mole% IC8H18 and 13.756 mole% IC6H14) model. Both two models reasonably predicted the ignition delay times (IDTs) of CBN at 10, 15 bar and 640–900 K. In addition, the experimental and simulation study of coal-based naphtha HCCI combustion was carried out. CHEMKIN-PRO software was used to simulate the effects of intake temperature (Tin) and equivalent ratio (Φ) on the combustion process of naphtha HCCI engine. The results show that the combustion of coal-based naphtha HCCI is sensitive to the Tin. With the increase of Tin, the combustion phase of HCCI is obviously advanced, the concentration of OH and HO2 increases in the middle and low temperature reaction process, and the corresponding curve moves forward as a whole. The change of Φ has little effect on the concentration of OH and HO2 before ignition, and the change of ignition time with the mixture concentration is not obvious. It should be pointed out that when the Tin is high or mixture is rich, the coal-based naphtha HCCI engine is prone to knock, and the peak phase will appear before top dead center (TDC). This phenomenon is especially obvious when the Tin is very high. It can be seen that the coal-based naphtha is suitable for low-temperature lean combustion.