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The anti-knock quality of fuels are of vital importance for improving spark ignition (SI) engine efficiency. 2-pheylethanol (2-PE) is one of potential high-octane booster, which can be derived from lignin as a biomass component. To ascertain the possibility of 2-PE as a bio-additive in SI engines, combustion characteristics and emission performance of 2-PE addition were investigated in a downsized gasoline engine. Blending 2-PE in gasoline resulted to a decrease in cylinder pressure and heat release rate. As increase of 2-PE addition, ignition delay and combustion duration of 2-PE-gasoline become postponed, combustion phasing is retarded， and COVIMEP increased significantly. The reason is thought to be correlated with its relatively lower gas-phase reactivity and higher heat of vaporization. At elevated intake pressure, the number of knock cycles and MAPO significantly increased of SI engine，addition of 2-PE exhibits good knocking resistance because of its high octane number and physicochemical properties. For regulated gas emissions, 2-PE addition produces more unburned hydrocarbon, carbon oxide and less nitrogen oxides. The blending of 2-PE in gasoline tends to increase particle matter emissions and enlarge the particle size.

Gasoline compression ignition (GCI) is one of the most promising combustion concepts to maintain low pollutant emissions and high efficiency. However, knock phenomenon is an obstacle to GCI combustion. In this paper, experimental investigation is conducted to study GCI knocking characteristics. Firstly, analysis of engine performance and knocking trends was conducted, which shows an increasing trend of both brake mean effective pressure (BMEP) and knock intensity as injection timing advances. Secondly, comparison of knocking characteristics between the modes of spark-ignition (SI) and GCI was performed. The results of statistical and heat release analysis show that the combustion process of the two combustion modes are quite different. Knock in SI engine is a random phenomenon caused by auto-ignition of end gas. On the contrast, knock in GCI engine is ascribed to local rapid burning rate, which doesn't happens randomly. Finally, double-injection strategy is applied to obtain different mixture in premixed degree. With more fuel pilot injecting into cylinder, higher BMEP and knock intensity can be observed. The results shall give insights into the possibilities of getting better engine performance while controlling cycle-to-cycle variations and knock intensity in acceptable regions.

Knock is one of the main obstacles for optimizing combustion process of SI engines fueled with alternative biomass fuel n-butanol. In this paper, knock characteristic of SI engine fueled with n-butanol and RON 92 gasoline is studied on a single cylinder SI engine. The onset timing, intensity and frequency of knock for these two fuels at different EGR rate are compared. Additionally, the effects of different compression ratios and intake pressures on knock intensity of SI engine are also studied and results are presented. The study results show that EGR can decrease knock intensity and delay knock onset timing due to its cooling and dilution effects. It is observed under a low EGR rate of 3%, knock intensity of n-butanol is significantly reduced whereas combustion pressure has negligible change. The probability distribution of n-butanol knock intensity is more concentrated compared with that of gasoline under a given EGR rate, which indicated n-butanol had smaller combustion variations. The application of EGR on high intake pressure and high compression ratio n-butanol engine can effectively suppression knock combustion.

It is necessary to investigate the designs of model to maximize the performance of proton exchange membrane fuel cell (PEMFC). In this study, a novel design and modeling method are proposed based on different flow fields. The proposed model considers the voltage losses caused by the current leakage, gas crossover, and by-product pollution. A regression analysis is conducted to study the influence of the working conditions on the accuracy. Final results showed that the coefficient of determination increased both from 0.977 to 0.952 to 0.998 at 50 °C and 70 °C, respectively. The prediction accuracy for the open-circuit voltage and low-current density is significantly improved. In addition, the prediction accuracy of different impedance materials decreases with increasing temperature and pressure.