In order to improve the accuracy of numerical simulation, a new heat transfer model is developed by using a modular approach in the Anstalt für Verbrennungskraftmaschinen (AVL)-Boost software. The improved heat transfer model mainly considers the effects of the swirl and boiling heat transfer inside the engine. In addition, a chemical kinetics mechanism including 475 reactions and 134 species is employed to predict the combustion of diesel engines fueled with biodiesel. The result shows that the boiling heat transfer will occur, especially in the high-temperature area. Analysis shows that the improved model is reliable and its precision is increased. Finally, the perturbation method is employed to investigate the relatively important inputs as the complex nonlinear function with a lot of output data and input data produced by the improved model. The relative effects of different parameters such as EGR, injection mass, injection timing, compression ratio, inlet air pressure, fuel injection pressure, exhaust pressure and inlet air temperature on performance and emission characteristics are compared. The eight parameters are investigated on four outputs of brake power, Brake Specific Fuel Consumption (BSFC), NO_x and HC. The injected fuel mass plays an important role in emissions and performance. The EGR, compression ratio and inlet air pressure have a great effect on the HC and NO_x emission.

To improve the combustion and emission characteristics of diesel engines, methanol-diesel fuels with different mixing ratios (DM0, DM10, DM20, DM30, and DM40) were used to investigate the effects of methanol addition on the combustion and emission of a four-stroke diesel engine in terms of cylinder pressure, brake power, brake-specific fuel consumption, and nitrogen oxides, soot, and carbon monoxide emissions. Firstly, an improved entire diesel engine model was developed using AVL-BOOST software and validated by the experimental results. The results showed that the increase of methanol content in the fuel mixture had a negative impact on the performance characteristic of the diesel engine, but significantly improved the emission characteristic of the diesel engine. With the methanol ratio in the mixed fuel increased to 10%, 20%, 30%, and 40%, the cylinder pressure of the engine increased by 0.89%, 1.48%, 2.29%, and 3.17%, respectively. However, the power decreased by 3.76%, 6.74%, 11.35%, and 15.45%, the torque decreased by 3.76%, 6.74%, 11.35%, and 15.45%, respectively, and the brake specific fuel consumption increased by 3.77%, 6.92%, 12.33%, and 17.61%, respectively. In addition, with the methanol ratio in the mixed fuel increased to 10%, 20%, 30%, and 40%, the carbon monoxide emission decreased by 21.32%, 39.04%, 49.81%, and 56.59% and the soot emission decreased by 0.25%, 8.69%, 16.81%, and 25.28%, respectively. Therefore, the addition of methanol to the fuel can improve the combustion and emission characteristics of the engine.

In this work, an effective numerical simulation method was developed and used to analyze the effects of natural gas mixing ratio and pilot-main injection, main-post injection, and pilot-main-post injection strategies on the combustion and emission characteristics of diesel engine fueled with dual fuel. Firstly, the one-dimensional calculation model and three-dimensional CFD model of the engine were established by AVL-BOOST and AVL-Fire, respectively. In addition, the simplified chemical kinetics mechanism was adopted, which could accurately calculate the combustion and emission characteristics of the engine. The results show that the cylinder pressure and heat release rate decrease with the increase of the natural gas mixing ratio and the NO_x emission is reduced. When the NG mixing ratio is 50%, the NO_x and CO emission are reduced by 47% and 45%, respectively. When the SODI3 is 24 °CA ATDC, the NO_x emission is reduced by 29.6%. In addition, with suitable pilot-main injection and pilot-main-post injection strategies, the combustion in the cylinder can be improved and the trade-off relationship between NO_x and soot can be relaxed. Thus, the proper main-post injection strategy can improve the combustion and emission characteristics, especially the reduction in the NO_x and CO emissions.

With the improvement and development of micro-mechanical manufacturing technology, people can produce an increasing variety of micro-electromechanical systems in recent years, such as micro-satellite thrusters, micro-sensors, micro-aircrafts, micro-medical devices, micro-pumps, and micro-motors. At present, these micro-mechatronic systems are driven by traditional energy power systems, but these traditional energy power systems have such disadvantages as short endurance time, large size, and low energy density. Therefore, efforts were made to study micro-energy dynamical systems with small size, light gravity, high density and energy, and long duration so as to provide continuous and reliable power for these systems. In general, the micro-thermal photoelectric system not only has a simple structure, but also no moving parts. The micro-thermal photoelectric system is a micro-energy power system with good application prospects at present. However, as one of the most important structural components of micro-thermal photoelectric systems, the microburner, is the key to realize the conversion of fuel chemical energy to electric energy in micro-thermal photoelectric system. The studies of how to improve the flame stability and combustion efficiency are very necessary and interesting. Thus, some methods to improve the performance of micro-burners were introduced and summarized systematically, hoping to bring some convenience to researchers in the field.

In this paper, the aerodynamic characteristics of two vehicles and three vehicles in the platoon under different vehicle spacings have been explored in detail. Firstly, the realizable k- model was used to verify the numerical method based on a single 35° Ahmed body. Then, the aerodynamic characteristics such as drag characteristics, surface pressure, wake structure, and turbulent kinetic energy distribution were analyzed for the platoon of two and three 35° Ahmed bodies. Although the RANS (Reynolds-averaged Navier–Stokes) model had got good results for simulating a single 35° Ahmed body, when simulating two 35° Ahmed bodies in the platoon, it was found that there is still a big error compared with the experimental data. In the three 35° Ahmed body, the drag coefficient of the leading body is almost unchanged compared with that of the leading body in the two-vehicle platoon, while the drag coefficients of the middle body and the trailing body are both reduced compared with those of the single body. For x/L = 0.25, the middle body is about 56% of the single-body value, and the trailing car is about 88% of the single-body value. It can be seen that the drag reduction effect of three 35° Ahmed bodies is larger than that of two 35° Ahmed bodies. It is shown that the aerodynamic characteristics are very sensitive to the selected platoon vehicle model. Because model with different geometric shapes will produce different wake structures, different aerodynamic phenomena will occur when they are arranged in the platoon.