Commercial diesel consists of hundreds of hydrocarbons such as alkanes, cycloalkanes, and aromatics. The components of the fuel’s composition are what determine its physical and ignition properties, and their variations affect engine performance. In this study, n-heptane, n-dodecane, tetralin, and decalin were chosen as typical additives to blend with commercial diesel according to the China VI standard (Heavy Duty Diesel Vehicle Pollutant Emission Limits and Measurement Methods) in 20% and 50% volume fractions, respectively. The physical properties of the fuel blends, such as viscosity, density, cetane number (CN), and distillation range, were measured first. Then, the commercial diesel’s lower heat value was measured, and blended fuels were calculated accordingly. The CN of the blended fuel is tested by an Ignition Quality Tester (IQT), which is known as the derived cetane number (DCN). The results show that adding n-dodecane increases the value of DCN, while tetralin reduces the DCN, and n-heptane and decalin have negative effects. This study uses a type of WP12 diesel engine made by Weichai that meets China’s emission regulation 6. During the tests, the fuel injection strategy was kept as a pure diesel operation without any modifications. Compared with pure diesel operation, the bench test results show the following characteristics: the maximum torque output increased with increased decalin, followed by tetralin and n-dodecane, while n-heptane has a side effect compared to pure diesel operation. The addition of n-dodecane and n-heptane can reduce fuel consumption, while tetralin will increase it, and decalin has no obvious effect on fuel consumption. It was found that n-heptane increases HC and NOx emissions significantly. Furthermore, n-dodecane slightly increases CO, HC and NOx emissions. Decalin increases CO and HC emissions when mixed in a large proportion. In addition, tetralin causes a substantial increase in HC, CO and NOx emissions at medium and high loads.

When a bubble rises freely in still water, it often moves along a zigzag or spiral trajectory. In order to explore the mechanism of this movement, an experiment was conducted to record the changes in the movement trajectory and bubble shape. The results show that this movement can be explained by the swing of trailing vortices and the change in vorticity. There is asymmetric shedding of the trailing vortices. The change in bubble velocity caused by the shedding of the bubble trailing vortices will lead to an asymmetric change in the vorticity of the trailing vortices. Two factors lead to an asymmetric change in the drag force of the trailing vortices on both sides of the bubble, resulting in the zigzag trajectory. Only when the aspect ratio λ reaches 2.0 will the bubble move along the zigzag. The trailing vortices moving in two orthogonal directions will lead to a spiral trajectory. The movement of the trailing vortices not only changes the trajectory of the bubble but also changes its shape. The effect of the trailing vortices on the bubble can be equivalent to a low-pressure area around a bubble. When a bubble moves along a zigzag trajectory, the low-pressure area at the trailing of a bubble swings back and forth in a plane, and the bubble is flatter. When moving along a spiral trajectory, the low-pressure area rotates around the trailing of the bubble and becomes more spherical. Compared with a zigzag trajectory, a bubble has a higher velocity and lower frequency when moving along a spiral trajectory.

With its high cetane number and oxygen content, polyoxymethylene dimethyl ether (PODE) can promote engine combustion and reduce particulate emissions, which has become a key research object of diesel surrogate fuel. This study further explores the effects of blending PODE on emission characteristics of a China VI diesel engine. Diesel/PODE blends with the PODE volume blending ratios of 10%, 20% and 30% have been experimentally investigated in a China VI heavy-duty diesel engine at 1900 rpm and four different loads. Furthermore, the effects of EGR rates (Exhaust Gas Recirculation) rates (0–20%) on combustion and emission characteristics have been also discussed at 1700 r/min engine speed and 50% engine load condition. An exhaust gas analyzer and a particle counter were used to collect NOx, CO and THC emissions and particulate number (PN) emissions. The results show that the CO and THC emissions can be significantly reduced with the increase in the mixing ratio of PODE. Additionally, the particle number concentration can be also reduced, especially at low and high loads. The NOx emissions can be improved by increasing EGR rates. Interestingly, there is a trade-off relationship between PN and NOx emissions. In general, blending PODE can effectively reduce NOx and PN emissions simultaneously.

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Xiongan New Area is another important new area after Shenzhen Special Economic Zone and Shanghai Pudong New Area. According to the development strategy of high-point positioning of the new area, providing safe, reliable, clean and economic modern energy system for Xiongan New Area is one of the important tasks in the construction of the new area. In the process of establishing and optimizing the energy system, reliable data of energy consumption and load characteristics should be obtained first. This paper analyses the types of buildings in the new area and the local climate and meteorological changes, and takes into account the energy consumption of various internal and external factors. Based on this, the different climate conditions of different buildings in a year are discussed. The load characteristics of thermal and cold power are analyzed. Finally, a prediction method of thermal and cold load data considering climate and meteorological information, typical structural parameters of buildings, internal and external disturbances is established.