To improve the thermal management performance and solve the refrigerant carbon emissions issue of electric vehicle, this article proposed a transcritical CO₂ heat pump air conditioning system suitable for electric vehicle with natural CO₂ as refrigerant, and performance analysis was conducted. The results show that: this system can still ensure a heating capacity of 5 kW and 36 ℃ at the outlet in an environment of -20 ℃. As the compressor speed increases, the heating capacity increases, but Coefficient Of Performance (COP) decreases. The appropriate increment in the air volume of the internal gas cooler can effectively increase the heating capacity and COP, but excessive air volume will lead to low outlet air temperature, which is not conducive to heating. At ambient temperature of 40 ℃ and compressor speed of 7 000 r/min, the cooling capacity is 4.2 kW and the COP is 1.1. As the air volume of the internal evaporator increases, the cooling capacity and COP increase, indicating that the appropriate increment in air volume can effectively improve cooling performance.

In order to obtain a suitable shape curve of the CO₂ adjustable ejector regulating probe for automobile air conditioning, this paper proposed three kinds of probe schemes including linear, concave and convex probe based on the Homogeneous Equilibrium Model (HEM), and the analyzed changes of the ejector flow rate and elicitation ratio in the process of probe movement with the aid of the Computational Fluid Dynamics (CFD) tool, and compared the differences in the performance of the adjustable ejector with the three kinds of probe schemes. The results show that: When the probe radius at the throat is small, with the increase of the probe radius at the throat, the entrainment ratios of the ejector of each scheme increase slowly due to the decrease of the primary flow rate, and when the probe radius at the throat exceeds the high efficiency adjustment radius, the entrainment ratios of the ejector of each scheme decrease dramatically until they can’t be induced; compared to the other 2 probe schemes, the concave probe scheme has a larger entrainment ratio within the high efficiency working area, and it has a stronger overall performance.

In order to replace Positive Temperature Coefficient (PTC) electric heater in vehicle thermal management, this paper studied the heating characteristics of the triangular cycle through experimental and theoretical methods and proposed corresponding control strategy. First of all, in terms of component selection, the paper proposed that the triangular cycle had higher performance requirements for the condenser and electric expansion valve. Secondly, the bench test obtained a heating capacity of approximately 6 kW. Thirdly, the impact of different electronic expansion valve openings, air conditioner unit inlet air temperature and inlet air volume on performance was studied through the checked model, and it was found that the larger opening help the compressor to exert greater capacity and obtain greater heating capacity. Under high inlet air temperature and high outlet pressure condition, the triangular cycle has greater heating capacity. Finally, the paper proposed a triangular cycle control map covering 2 000 ~ 6 500 r/min compressor speed and -20~-10 ℃ inlet air temperature.

In order to realize active equalization of 48 V mild hybrid battery pack, and improve energy utilization rate, firstly the group design and consistency check of 48 V mild hybrid system battery of a vehicle were conducted, then the topological structure of the active equalization circuit was determined, and then the equalization opening threshold and equalization control strategy of active equalization circuit were designed based on the information of the battery terminal voltage collected by the BMS. The results of simulation analysis indicate that the State Of Charge (SOC) bias errors of the battery module after active equalization does not exceed 0.005.

To address the issue of the unsuitability of the original suspension parameters after upgrading a central motor electric vehicle to a In Wheel motor car, A half-car passive suspension model is established in MATLAB/Simulink to analyze the problem. The spring stiffness and damping coefficients of the front and rear suspensions are taken as independent variables, while the root mean square values of the vehicle’s center of gravity acceleration, pitch angle acceleration, suspension deflection, and tire load are considered as optimization objectives. The grey wolf optimization algorithm is employed to search for the optimal stiffness and damping parameters. The simulation results show that after optimization, the handling stability of the suspension remains within a reasonable range, while the comfort level is improved by 12.73%.

To improve the low efficiency of the current diagnosis method using subjective evaluation method, this paper proposed a method for identifying vehicle abnormal noise based on Convolutional Neural Network (CNN). A four post vibration test stand was used to collect raw abnormal noise signals with high signal-to-noise ratio in a semi anechoic chamber environment as the research object to extract the Mel-spectrogram of the signal as input to the neural network, then, a convolutional neural network was constructed to perform deep level feature extraction, compression, and classification recognition on the data. It was found that the average recognition rate can reach 90.5%. Finally, the transfer learning method was used to optimize the model. The test results indicate that VGG and ResNet models can improve recognition accuracy, and the ResNet network has better recognition performance in the test set.

A testing device for air pressure resistance of door seal has been designed to simulate the changes of air pressure in door cavity of a car under side crash condition and test the ultimate air pressure resistance of door seal. Based on this, this article studied the influence of different temperatures, material hardness, and part structure on air pressure resistance of the door seal in combination with a high and low temperature environment box. Through multiple experimental comparisons, it has been proven that the ultimate air pressure resistance of door seal is negatively correlated with temperature. Increasing the back plate ribs and appropriately increasing the material hardness can significantly improve air pressure resistance.