Aiming at the problem that the damping characteristic of the shock absorber changes due to different oil temperature, based on the actual structure of the vehicle hydraulic shock absorber, according to the hydrodynamics and oil dynamic model, a damping characteristic model of hydraulic shock absorber with shim stacks considering the influence of temperature was established, and its effectiveness was verified by the shock absorber vibration test bench. On this basis, the variation law of damping characteristic parameters of shock absorbers at different temperatures was studied. The results show that as the oil temperature decreases, the damping coefficient of the hydraulic shock absorber increases, the initial and secondary valve opening speeds of the shock absorber are smaller, the envelope of the dynamometer diagram increases, and vice versa. The damping characteristic of recovery stroke is more sensitive to temperature than that of compression stroke.

In order to reduce the thermal load on the piston of an aviation piston engine, the temperature field calculation model of the piston was established, and the model was calibrated with the piston surface temperature measured by the hardness plug method, and the influence of the piston temperature field under rated operating conditions, the height of the piston firepower shore and the height of the first ring groove on the piston temperature field was analyzed. The results show that the piston temperature decreases in a gradient in the direction from the top of the piston to the bottom of the piston, with the highest temperature of 317.63 ? in the center of the piston top, and the thermal stress is mainly concentrated on the upper surface of the inner cavity and the ring groove area. The piston thermal load increases with the increase of the firepower shore height and decreases with the increase of the first ring groove height. Compared with the original piston model, the top temperature of the piston and the temperature of the first ring groove are reduced by more than 6 ? after structure optimization, and the piston thermal load is significantly improved.

In order to study the influence of combustion chamber structure on the combustion and emission characteristics of diesel engines, CONVERGE software was used to design four different types of combustion chambers with different indentation diameters and depths under the condition of ensuring the same compression ratio, and simulations were carried out for four different combustion chamber structures. The calculation results show that as the diameter of the indentation increases and the depth decreases, the fuel and air mixture in the cylinder becomes more adequate, the mean temperature in the cylinder increases and the pressure in the cylinder does not differ much. Due to the increase in combustion temperature in the cylinder, the amount of NOx generated increases. As the diameter of the indentation increases and the depth decreases, the fuel and air mixture is sufficient and the combustion temperature rises quickly, so the amount of Soot generated in the first stage decreases, but the temperature in the cylinder decreases in the later stage, which is not conducive to the oxidation of Soot generated in the first stage, resulting in a higher quality of Soot.