Abstract:To improve the energy efficiency of electric commercial vehicles and fully utilize their energy-saving potential, this study utilizes multi-gear automated mechanical transmission (AMT) electric heavy trucks as the research object and proposes a shifting strategy based on the optimal system efficiency. First, based on the electric drive system configuration, the loss mechanism and dynamic efficiency characteristics of each component are analyzed, and the shifting strategy based on the optimal system efficiency is formulated through the electric drive system efficiency surface. Second, a bond graph model of the electric drive system is established, and the simulation analysis of the shift strategy is carried out by using the reconstructed suburban working conditions. Finally, the effectiveness and superiority of the proposed strategy are verified through the real vehicle experiments. The research results indicate that the proposed strategy achieves real-time control of the optimal output efficiency of the electric drive system, and reduces the overall vehicle energy consumption by 3.86% compared with the traditional economic gearshift strategy.

Abstract:The current gearbox simulation load spectrum is difficult to fully reflect the load state of the gearbox gear, because driver’s intention is not fully considered. In order to improve the accuracy of gearbox reliability analysis, a mining vehicle equipped with a 12 speed gearbox was taken as the research object. Based on the shifting rules of power and economy, a multi-gear gearbox simulation load spectrum acquisition method considering gear combination strategy was proposed by fully considering the allowable gears of different vehicle speeds. Based on the driver conditions of mining vehicle, the proposed method was used to obtain multi-gear gearbox simulation load spectrum, and compared with the simulation load spectrum obtained based on power and economic shifting schedule. The result show that compared with the traditional method of obtaining load spectrum based on shifting schedule, the proposed method obtains different critical gears. The critical gear obtained by traditional method is 6th gear, with a working time accounting for 53.25%, and the proportion (53.14%) is the highest in the load range of 2 000 N?m~2 400 N?m. The proposed method obtains the critical gear is 7th gear, with a working time accounting for 54.49%, and the proportion is the highest (52.78%) in the load range of 2 400 N?m~2 800 N?m. From the perspective of load accumulation, it can be observed that the obtained 7th gear load accumulation of the proposed method increases 2.33% compared with the obtained 6th gear load accumulation of the traditional method. The research result prove the effectiveness of the proposed method and lay the foundation for the reliability design of multi-gear gearbox.

Abstract:Engineering vehicles operate under high torque, high load, and complex environmental conditions, facing numerous technical challenges. Particularly during the starting phase, the significant slippage of clutch discs significantly impacts the precision of clutch torque control. Therefore, to achieve adaptive start-up control for AMT engineering vehicles, an adaptive control method combining linear quadratic regulator (LQR) and deep neural network was proposed for the AMT start-up process. At the upper level of the control strategy, a constant engine speed strategy was formulated based on different starting intentions, and the LQR was used to obtain the reference speed corresponding to the reference torque of the clutch under different environments. With considering the complexity of the operating environment, a certain range of perturbations was introduced into the vehicle dynamics model to generate a series of reference rotational speed trajectories as the training data set for the deep neural network, and a robust data model offline was obtained. At the lower level of the control strategy, a clutch friction factor adaptive controller was designed to estimate the clutch friction factor in real time. Finally, the effectiveness of the adaptive start control method for engineering vehicles equipped with AMT was verified by simulation tests. The results show that the proposed method has good starting performance under the condition of unknown friction coefficients and can adapt to different starting intentions and driving environments. Compared with the PID controller which does not depend on the mechanism model, it has higher adaptive ability and robustness.

Abstract:Vehicle handling stability is an important part of the vehicle performance. In the vehicle suspension and subframe system, subframe is often studied as a rigid connection, however, the front subframe undergoes elastic deformation in actual driving process. Therefore, this paper flexibly treats the front subframe of a certain vehicle and establishes a rigid-flexible coupled vehicle model to study the handling stability of the whole vehicle. The lateral dynamics of the whole vehicle is analyzed, the three-degree-of-freedom vehicle kinematics equations are derived, and the vehicle kinematics simulation is conducted for comparative analysis to study the influence of the front subframe flexibility on the KC characteristics of the suspension system and the transient handling stability of the whole vehicle. The NSGA-II algorithm is applied to optimize the bushing stiffness at the front subframe joint, which improves the transient handling stability of the whole vehicle. The optimization results show that at 0.5 Hz, the yaw rate gain relative to the steering wheel angle is reduced by 8%, the body roll angle relative to the lateral acceleration gain is reduced by 1.1%, and the lateral acceleration delay time relative to the steering wheel angle is reduced by 10.5%.

Abstract:Hybrid electric vehicles often experiences key-on/off conditions. Increasing vibration isolation performance of the powertrain mounting system (PMS) under key-on/off conditions is one of the important measures to enhance NVH (noise, vibration and harshness) performance of the vehicle. A model with 13 DOFs for PMS was established, and acceleration of the mounts at active side was estimated under the key-on/off condition. Also, vibration acceleration of the mounts at positive side, passive side and the seat rail were measured. The comparison between calculations and experiments validated the proposed model. Deterministic and uncertain optimization methods for reducing the vibration dose value of longitudinal acceleration of the powertrain were proposed, and the mount parameters were the design variable. Key on/off experiments were carried out to validate the proposed methods. The experimental results show that the two optimization methods can effectively enhance the vibration performance of the PMS, and the uncertain optimization method can make the PMS more robust and effectively deal with the influence of parameter uncertainty.

Abstract:Considering the characteristics of deep ocean currents, this study numerically investigates the effects of reduced velocity (U*) and rotational speed (α) on the vortex-induced vibration(VIV) response and heat transfer performance of a circular cylinder subjected to oscillatory inflow. The results reveal multiple extrema in the peak amplitude ratios in both the streamwise (A*_peaks，x) and transverse (A*_peaks，y) directions. As α increases, the maximum A*_peaks，x increases, while the corresponding U* decreases. Significant variations are observed in cylinder displacement and lift/drag coefficients with changes in α and U*. The time-averaged displacement in the x-direction increases with U*, whereas the average displacement in the y-direction and the lift coefficient both increase with α. The motion trajectory of the cylinder lacks a distinct pattern within the range of 0≤α≤1.0, but becomes circular at α =1.5. With increasing U*, the average Nusselt number increases, and the distribution of local Nusselt numbers gradually forms a circular pattern. As α increases, the vortex shedding transitions from a 2S pattern to a single-row configuration, with the wake stretching into a U-shaped structure. Temperature field analysis reveals weaker heat exchange at the front stagnation point, while heat transfer and local thermal efficiency at the rear stagnation point are significantly enhanced.

Abstract:The analysis of gas-liquid two-phase characteristics in heating rod bundle channels is critical for ensuring the safe operation of nuclear reactors. While experimental methods are commonly used to investigate two-phase flow in rod bundle channels, wire mesh sensors are typically applied under room temperature conditions and have seen limited use in electrically heated rod bundle experiments. This study employs the electrostatic field method in finite element simulation software to analyze the influence of electric field in electrically heated rod bundle channels on wire mesh sensor measurements. The simulation results are verified by experiments. Both the simulation and experimental results show that,within a charged rod bundle channel, an increase in the excitation voltage applied to the transmitting electrode enhances the sensor’s sensitivity to gas-liquid two-phase flow, thereby improving its detection capability. Imaging experiments conducted under a 20 V excitation voltage confirm the feasibility and effectiveness of wire mesh sensor measurements under such conditions.

Abstract:To improve the ignition and combustion performance of NH₃ in engines, blending it with the high-reactivity-fuel dimethyl ether (DME) is an effective strategy. This study conducts simulations of NH₃/DME/air premixed laminar flames to investigate the effects of DME addition on key combustion characteristics, including laminar flame speed, reaction pathways, and NO formation. The results show that both the adiabatic flame temperature and the laminar flame speed increase significantly with higher DME blending ratios. A strong correlation is observed between laminar flame speed and the concentration of reactive free radicals, suggesting that the increased radical concentration due to DME is the main contributor to the enhanced flame speed. Furthermore, the normalized NO concentration in the flame rises significantly with increasing DME content, reaching approximately 50% when the DME blending ratio reaches 80%. Reaction pathway analysis indicates that DME addition inhibits the conversion of nitrogen species to N₂, thereby leading to increased NO emissions. Sensitivity analysis shows that DME significantly alters the dominant elementary reactions. As the DME ratio increases, the sensitivity of nitrogen-group reactions considerably declines, while hydrogen- and carbon-group reactions increasingly govern the combustion process of the blended fuel.

Abstract:To investigate the dynamic characteristics of an ultra-supercritical circulating fluidized bed (CFB) boiler during main fuel trip (MFT) and boiler trip (BT) events, a mathematical model of a 660MW ultra-supercritical CFB boiler was established using the Apros simulation platform. The model dynamically simulates MFT and BT scenarios under coal conbustion conditions at 100% BMCR (boiler maximum continuous rating), 75% THA (turbine heat acceptance) and 50% THA operating loads. Numerical results show that under 50% THA operating conditions, the steam-water separator rapidly transitions from dry to wet operation following MFT and BT activation and gradually returns to dry operation after system reset. These frequent dry-wet transitions increase thermal stress on the steam-water separator, potentially reducing its service life and compromising equipment safety. Therefore, triggering MFT and BT under low-load conditions should be avoided to ensure system reliability.

Abstract:This study designs and simulates a high-efficiency compound waste heat boiler capable of operating independently. The boiler is designed to function within a gas-steam combined cycle and can also operate independently without a gas turbine. A three-dimensional numerical model of the boiler is established using computational fluid dynamics(CFD) software to simulate its performance under three steady-state operating modes. In addition, the overall characteristics of the dynamic switching process between different modes are analyzed. The simulation results show that all three modes can meet heat load demands by adjusting the supplementary gas combustion during steady-state operation. During dynamic switching, the control method proposed in this study ensures stable operation of the waste heat boiler throughout the entire transition process. Seamless switching between the three operating modes is successfully achieved.