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Combustion instability often occurs inside the combustion chamber of aero engine. Fuel atomization and evaporation, one of the controlling processes of combustion rate, is an important mechanism of the combustion instability. To tackle combustion instability, it challenges a deep understanding of the underlying mechanism of fuel atomization and evaporation. In this paper, acoustic field was established to simulate the pressure oscillation. Transient spray images of ethanol and kerosene were recorded using high-speed camera. The obtained images were processed by MATLAB to extract and analyze the related data. Spatial fuel atomization characteristics was analytically examined by multi-threshold image method to analyze the effect of the high frequency acoustic field on the fuel break-up and disintegration. The results show that the half spray cone angle on the side with speaker is suppressed by the presence of the imposed acoustic field compared with the case without speaker.

In the present study a novel surrogate model for biodiesel including methyl decanoate (MD) and methyl crotonate (MC) was proposed and validated. In the binary mixture of surrogate fuel, MD was chosen to represent saturated methyl esters, which exhibited great low-temperature reactivity with typical negative temperature-coefficient (NTC) behavior and MC represented unsaturated components in real biodiesel, which was mainly responsible for soot formation and evolution. The proportion of MD and MC was determined by matching the characteristics such as derived cetane number (DCN), molecular weight (MW), atom number, H/C ratio and unsaturated degree. All of the criterions were calculated by the least square principles and the calculated surrogate of biodiesel was comprised of 92% MD and 8% MC in mole fraction. Furthermore, detailed kinetic model of the surrogate fuel was constructed and developed with modifications, which was composed of 2918 species and 9164 reactions.

Euro VI emission standards have set a very strict limitation on particulate matter emissions of Gasoline Direct Injection (GDI) engine. It is difficult for GDI engine to meet the Euro VI PN regulation (6×1011#/km) without a series of complicated after-treatment devices such as Gasoline Particulate Filter (GPF). Previous research shows that GDI vehicles under cold start condition account for more than 50% of both particle number and mass emissions during the entire NEDC driving cycle. Dual Injection Gasoline engine is based on the GDI engine by adding a set of port fuel injection system. The good mixing characteristics of the port fuel injection system can help to reduce the particulate matter emissions of the GDI engine during the cold start condition.

The aim of this study is to evaluate the land requirement, energy consumption and GHG (greenhouse gases) emissions of microalgal biodiesel (M-BD) and Jatropha curcas seeds (J-BD) based biodiesel from the perspective of life cycle assessment (LCA). Mass and energy balance was used through the whole LCA calculation for each process. Two types of biodiesel (100% biodiesel: BD100, and 20% blends of biodiesel: BD20) were assumed to be combusted in the suitable diesel engine. Displacement method was adopted to measure the co-products credits. The results showed that the land requirement of producing 1 kg biodiesel from microalgae was about 1/31 of that from Jatropha curcas seeds. The well to pump (WTP) stage for microalgal biodiesel had higher fossil energy requirement but lower petroleum energy consumption and GHG emissions compared to Jatropha curcas and conventional diesel (CD). The WTP energy efficiency for J-BD100 and M-BD 100 were 26% and 17.4%, respectively.

Gasoline direct injection (GDI) has been a mainstream technology due to its higher thermal efficiency and better power output. However, with increasingly stringent emission regulations introduced (EURO VI PN limits: 6 x l011#/km), high particulate matter (PM) emission of GDI engine has been a serious problem that limits its further development. Previous studies have found that cold-start and warm-up operation conditions play the dominant role in engine-out particulate emissions. In this paper, emission characteristics during the cold-start were first studied by controlling the coolant temperature. A Cambustion DMS500 fast particle spectrometer was employed to analyze the PM emissions. In order to reduce the engine-out emissions of cold-start, a dual injection system which combines port-fuel-injection (PFI) and direct-injection (DI) was applied in a four-cylinder gasoline engine.

Ammonia has attracted the attention of a growing number of researchers in recent years. However, some properties of ammonia (e.g., low laminar burning velocity, high ignition energy, etc.) inhibit its direct application in engines. Several routes have been proposed to overcome these problems, such as oxygen enrichment, partial fuel cracking strategy and co-combustion with more reactive fuels. Improving the reactivity of ammonia from the oxidizer side is also practical. Ozone is a highly reactive oxidizer which can be easily and rapidly generated through electrical plasma and is an effective promoter applicable for a variety of fuels. The dissociation reaction of ozone increases the concentration of reactive radicals and promotes chain-propagating reactions. Thus, obtaining accurate rate constants of reactions related to ozone is necessary, especially at elevated to high pressure range which is closer to engine-relevant conditions.

To achieve higher efficiencies and lower emissions, dual-fuel strategies have arisen as advanced engine technologies. In order to fully utilize engine fuels, understanding the combustion chemistry is urgently required. However, due to computation limitations, detailed kinetic models cannot be used in numerical engine simulations. As an alternative, approaches for developing reduced reaction mechanisms have been proposed. Nevertheless, existing simplified methods neglecting the real engine combustion processes, which is the ultimate goal of reduced mechanism. In this study, we propose a novel simplified approach based on fuel reactivity. The high-reactivity fuel undergoes pyrolysis first, followed by the pyrolysis and oxidation of the low-reactivity fuel. Therefore, the simplified mechanism consists of highly lumped reactions of high-reactivity fuel, radical reactions of low-reactivity fuel and C0-C2 core mechanisms.