Yufeng Gan

The three-chamber air spring is the crucial component of the variable stiffness air suspension, capable of achieving multi-level stiffness adjustment within a wide stiffness ratio range. The thesis examined the thermal hysteresis effect of the air in the chambers and established a multi-level stiffness mechanical characteristic model of the three-chamber air spring, which includes the Bouc-Wen model and the standard fractional derivative model. The stiffness ratio range of the air spring under four-level stiffness switching control is analyzed, and the optimal stiffness of the spring under different road grade conditions is obtained through optimization. A variable stiffness switching control strategy for the three-chamber air spring that dynamically adjusts with road grade is proposed. The results show that, compared with the single-chamber air suspension, the vehicle body acceleration of the three-chamber air spring under switching control is reduced by 17.85% to the greatest extent, verifying the effectiveness of the variable stiffness switching control strategy.

The wheels of lunar rovers are prone to bouncing during travel in the low gravity and rugged terrain conditions of the lunar surface, and poor matching of wheel alignment parameters can easily lead to tire wear in such conditions. Focusing on the double-wishbone suspension of lunar rovers, this study presents a wheel alignment parameter optimization method for tire wear reduction. First, a tire brush model is established, and it is determined that the toe angle and camber angle are the main factors affecting the tire wear work. And as the camber angle and toe angle increase, the tire wear work becomes greater. Then, a multi-body dynamic model of the double-wishbone independent suspension in a low-gravity environment is established. Taking the minimum tire wear as the optimization objective, the optimal solution set of alignment parameters such as the tire camber angle and toe angle obtained and the optimal hardpoint coordinate positions are determined. The variation range of the toe angle is optimized from [−0.55°, 1.58°] to [−0.37°, 1.32°]. After optimization, the variation in the toe angle is reduced by 20.4%, the change rate of the camber angle becomes smoother, and the comprehensive wear work of the tire is reduced by 17.47%. The research results provide theoretical guidance for the optimization of wheel alignment parameters of the double-wishbone suspension of the lunar rover.

Horizontal-axis wind turbines are widely used for wind energy harvesting, but they often encounter flow separation near the blade root, leading to power loss and structural fatigue. A varying-parameter flow deflector (FD) is proposed as a passive flow control method. The FD adopts varying parameters along the blade spanwise direction to match the varying local angle of attack. Numerical simulation using the transition SST k-ω turbulence model combined with the response-surface methodology are used to investigate the effect of the varying-parameter FD on the flow structure and aerodynamic performance of the NREL Phase VI wind turbine. The results indicate that optimal performance can be achieved when the normal position of the FD increases from the blade root to the tip, and the install angle of the FD should be greater than 62° at blade section of r/R = 63.1%. Furthermore, response-surface methodology was employed to optimize the deflector parameters, with analysis of variance revealing the relative significance of geometric factors (l₁ > l₂ > θ₁ > θ₂). Compared with the original blade, the shaft torque of the controlled blade with the optimal FD is improved by 24.7% at 10 m/s.

The external combustion hot blast stove is widely used in the steelmaking industry due to the advantage of providing a large amount of high-temperature and stable hot blast for blast furnaces. To research the thermal efficiency and stability of external combustion hot blast stoves, the non-equilibrium porous medium model coupled with transient thermal analysis is used to discuss the characteristics of two types of external combustion hot blast stoves during the cyclic operation process. In this paper, a comparison of the numerical data and in situ data during one cycle to ensure the accuracy of the calculation, which of the results showed that the temperature maximum relative error value is within 3%. The numerical results displayed that the velocity and temperature distribution of fluid are mainly affected by pressure, flow rate, cycle time, and geometric structure, where the hot blast temperature is affected by the cycle time but the distribution of velocity and relative pressure are affected by the height of hot blast branch. It can be concluded that the flow field and the structure of type A hot blast stove are more stable than that of type B by comparing the results of two types of hot blast stoves.

The hot blast stove is an important facility in the steel industry, which of the expansion gaps design has a significant buffering effect on the thermal stress with a high-temperature operating process. In this paper, a 3D numerical model of a hot blast stove was established to calculate the thermal stress distribution and analyze the remaining thickness of expansion gaps with different parts during the operating process. Young’s Modulus of the refractory linings was obtained by comparing with the experiment data and numerical data under the different temperatures and considering the influence of mortar. The result shows that Young’s Modulus of the refractory brick increased as the temperature, and the comparison of the experiment and simulation data of Young’s Modulus under three different temperatures displayed good agreement between the two sets of data. The first/third principle stress for the refractory linings can be reduced effectively by designing the expansion gap rationally, and the equivalent stresses of the shell are mainly concentrated at the joint and the neck. In addition, the expansion gaps are decreased under the thermal expansion and moved along a radial direction for the combustion/checker dome and the combustion/checker chamber.