The increasing temperature of lithium‐ion batteries during charging and discharging affects its operational performance. The current studies mainly adopt simplified model, less considering the effect of the battery internal electrochemical reaction on the air cooling performance, and the air cooling structure needs to be further optimized. In order to solve the problems above, the coupled electrochemical‐thermal air cooling model was established, and the air cooling structure was optimized in terms of the relative position and height of the battery pack inlet and outlet, the distribution, and spacing of cells. The results show the better air cooling performance is achieved when the inlet and outlet are aligned on the same side. When the lateral inlet and outlet aligned on the same side, the lower outlet height is more important for improving the heat dissipation performance of the battery pack, but the worse temperature uniformity emerges. According to the cooling performance of different positions in the battery pack, a method for nonequidistant symmetrical distribution of cells is able to improve the temperature uniformity. The optimal combination of the air cooling structure with various factors is obtained.

For internal combustion engines with multi-cylinders, the differences of fuel injection, air distribution, and even exhaust gas recirculation between cylinders may result in cylinder-to-cylinder imbalance, and then the exhaust emission and engine performance will be poor. The individual cylinder air–fuel ratio control is one of the important techniques used to improve fuel economy and reduce exhaust emission. For the large-bore gas fuel engine with gas fuel injection devices, their mass flow rates would be affected more seriously by the valve lifts than the injector of gasoline engine. In this study, we propose an individual cylinder air–fuel ratio estimation algorithm, based on Kalman filtering, for a gas fuel engine with asymmetrical exhaust runners. The coefficient matrix update step is added to the iterative process of common Kalman observer. The individual cylinder air–fuel ratios are estimated with one single universal exhaust gas oxygen sensor located on each side exhaust manifold. Furthermore, the estimation and feedback control performances with the proposed estimation algorithm are validated with a one-dimensional engine simulation tool. The results indicate that the modified Kalman observer can estimate the individual cylinder air–fuel ratio of gas fuel engine with asymmetrical exhaust runner precisely, with the maximum error smaller than 1% under steady-state conditions, and compensate the gas fuel injection devices for their mass flow rate differences.

In recent decades, research on alternative fuel engines is becoming more and more popular. Compressed natural gas (CNG) has the advantages of abundant reserves and a lower cost. It can reduce vehicle emissions relatively quickly and has little impact on the entire transportation infrastructure. As the fourth generation of a gas fuel supply method, gas fuel direct injection (DI) technology can effectively avoid volumetric efficiency reduction and power reduction problems of the port fuel injection (PFI) method. However, the former’s mixing path and duration are shortened greatly, which often leads to poor mixing uniformity. In order to improve the in-cylinder mixing uniformity, the in-cylinder mixing process of the CNG-fueled engine is taken as the research object in this study. The computational fluid dynamics (CFDs) models of the mixing process for the PFI and DI modes are established, and their mixing uniformities are compared. Besides, based on the authors’ previous research, the influence mechanism of the piston crown shape and fuel injection angle on the mixing process of the CNG DI engine is explored. The results show that the probability distribution frequency (PDF) of the best mixture concentration region (BMCR) is as high as 72% for the PFI mode, which is much higher than for the DI mode. The shorter jet impingement distance of the flat top piston leads to higher turbulent kinetic energy (TKE) intensity, and the in-cylinder mixing uniformity will be improved. When gas fuel is injected into an area with a higher in-cylinder TKE, the average in-cylinder TKE will be higher, and the in-cylinder mixture will be more homogeneous.

As an important load-bearing part of the automobile chassis, the subframe is connected to the body and suspension system, and it is of great significance to perform the research on subframe lightweighting to improve the ride comfort and handling stability of the automobile. In order to comprehensively reflect the influence of operating conditions on the subframe, and at the same time consider the performance requirements such as strength and modal, the lightweight design of the subframe was performed with the combination of multi-condition topology optimization and multi-objective optimization methods. A rigid-flexible coupled multibody dynamic model of the front suspension was constructed to extract the loads at each articulation point of the subframe under multiple working conditions. Furthermore, the subframe was optimized for multi-condition topology in combination with the compromise programing method. Subsequently, the subframe was reconstructed based on the topology optimization results and a radial basis function (RBF) neural network approximation model was constructed using the optimal Latin hypercube tests. Then, the NSGA-II algorithm was adopted for multi-objective optimization of the reconstructed subframe. The optimized front subframe satisfies the performance requirements with the first-order frequency increased by 4 Hz, a weight reduction of 2.5 kg, the lightweight rate reaches 9.1%.

To explore the potential for further enhancing the gas mixing uniformity of natural gas (NG) engines, this paper identifies turbulent kinetic energy (TKE), which has an essential impact on gas mixing, as the entry point of the research. After establishing a computational fluid dynamics (CFD) model for NG engines’ direct injection and mixing processes, the inlet pressure is selected as the experimental variable to investigate the influence of TKE on gas mixing uniformity. In particular, by proposing the theoretical concept of the core mixing stage, the numerical variation rule between the best mixture concentration region (BMCR) percentage and the mean turbulent kinetic energy (MTKE) of the core mixing stage is analyzed under certain injection timing conditions. The results indicate that, with identical intake pressures, an advanced gas injection timing elevates the total turbulence kinetic energy (TTKE) during the core mixing stage, thereby amplifying the uniformity of the gas mixture at the ignition. In specific scenarios, as the intake pressure increases, the decreasing trend in the BMCR proportion closely resembles the diminishing trend in the MTKE during the core mixing stage. Scrutinizing the variation trend in either parameter allows for an approximate prediction of the variation trend in the other parameter. When the intake pressure is gradually raised from the naturally aspirated state, the adequacy of the gas jet development is progressively reduced by the increasing back pressure in the cylinder.