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In this study, a three-dimensional multi-phase model is developed to numerically investigate the effect of gas diffusion layer spatial variation properties on water management and performance of proton exchange membrane fuel cells. The research mainly focuses on the influence of non-uniform porosity distribution in through-plane direction under different operating pressure and anode inlet humidity. Besides, the non-uniform distribution of wettability is also discussed. The results demonstrate that the spatial variation porosity and wettability distribution could affect the saturation profile of liquid water inside the cathode gas diffusion layer and catalyst layer. In addition, higher operating pressure leads to better performance and lower membrane water content, especially for the fuel cells with spatially variable porosity and wettability distribution. Under the operating condition without cathode inlet humidification, higher anode inlet humidity causes higher membrane water content. Finally, the wettability distribution in gas diffusion layer also influences the fuel cells water management and performance, but the influence mechanism of spatially variable wettability is more indirect than porosity.

This paper investigates the effect of naphtha (RON = 65.6) and commercial gasoline (RON = 94.0) on Multiple Premixed Compression Ignition (MPCI) mode. The experiment is conducted on a single cylinder research diesel engine with compression ratio of 16.7. The engine is operated at an engine speed of 1600 rpm for the IMEP from 0.4 to 1.4 MPa. Commercial diesel (CN = 56.5) is also tested in Conventional Diesel Combustion (CDC) mode as a baseline. At each operating point, the injection strategy and intake conditions are adjusted to meet with the criteria (NOx

Straight-run naphtha is tested in the newly raised combustion concept, called multiple premixed compression ignition (MPCI) mode, on a single cylinder diesel engine under different speeds. The partially premixed compression ignition (PPCI) mode is also investigated for comparison. The MPCI mode proposed by the authors was realized by multiple premixed combustion processes in a sequence of “spray–combustion–spray–combustion” around the compression top dead center (TDC). The spray and combustion events are preferred to be separated completely, with a dominant feature of “Combust After Injection End, Inject After Combustion End” to ensure the multiple-stage premixed compression ignition. The PPCI mode is well known as the “spray–spray–combustion” sequence with the start of combustion (SOC) separated from the end of injection (EOI). The straight-run naphtha has a research octane number (RON) of 58.8, and the compression ratio and displacement of the test engine is 16.7 and 0.5L. Double injection strategy is employed to generate the PPCI and MPCI modes. Maximum pressure rise rate and NOx emission of the MPCI mode is lower than that of PPCI mode, and it is easier to produce MPCI mode at lower engine speed. Diesel is also tested under double injection strategy just as the PPCI mode, but the fuel efficiency and emission performance is worse than that of straight-run naphtha.

Spark induced compression ignition (SICI) is a relatively new combustion control technology and a promising combustion mode in gasoline engines with high efficiency. SICI can be divided into two categories, SACI and SI–CI. This paper investigated the SICI combustion process using combustion visualization and engine experiment respectively. Ignition process of SICI was captured by high speed photography in an optical engine with different compression ratios. The results show that SICI is a combustion mode combined with partly flame propagation and main auto-ignition. The spark ignites the local mixture near spark electrodes and the flame propagation occurs before the homogeneous mixture is auto-ignited. The heat release from central burned zone due to the flame propagation increases the in-cylinder pressure and temperature, resulting in the unburned mixture auto-ignition. The SICI combustion process can be divided into three stages of the spark induced stage, the flame propagation stage and the compression ignition stage. The SICI combustion mode is different from the spark ignition (SI) knocking in terms of the combustion and emission characteristics. Furthermore, three typical combustion modes including HCCI, SICI, SI, were compared on a gasoline direct injection engine with higher compression ratio and switchable cam-profiles. The results show that SICI has an obvious combustion characteristic with two-stage heat release and lower pressure rise rate. The SICI combustion mode can be controlled by spark timings and EGR rates and utilized as an effective method for high load extension on the gasoline HCCI engine. The maximum IMEP of 0.82 MPa can be achieved with relatively low NOx emission and high thermal efficiency. The SICI combustion mode can be applied in medium–high load region for high efficiency gasoline engines.