The squeeze film damper (SFD) is difficult to meet the vibration control requirements of the rotor at both the critical speed and other rotor speeds at the same time due to the fixed structural parameters. The control method of piezoelectric ceramic actuator (PZT) actively changing the SFD oil film gap is proposed to suppress the critical amplitude of the rotor system. The dynamic model of the rotor system with PZT is established. The mechanical controllable characteristics of SFD are revealed, and the vibration damping performance of the controllable SFD (CSFD) is studied at critical speed. Both experiment and theory show that the proposed method can effectively suppress the critical amplitude of the rotor system with different imbalance.

Variable-displacement piston pumps, in comparison with quantitative pumps, offer high volumetric efficiency, energy savings, and variable displacement advantages. The outlet flow pulsation of these pumps is influenced by several factors, including swash plate inclination angle vibration, cavitation bubbles, flow distribution structure, and valve control structure. This complexity poses challenges in accurately predicting the flow pulsation at the outlet of variable-displacement piston pumps. In response to this challenge, a novel outlet flow pulsation model for variable-displacement piston pumps is proposed, taking into account the coupling effects of cavitation bubbles and swash plate inclination angle vibration, building upon an existing model. Initially, the effects of cavitation bubbles and swash plate inclination vibrations on flow pulsation were analyzed. Subsequently, a comprehensive flow pulsation model for variable-displacement piston pumps was developed, considering the coupling effects of cavitation bubbles and swash plate inclination angle vibrations. This model was compared with three other existing flow pulsation models. The accuracy of the results was validated using a constructed test bench, with an accuracy improvement of approximately 12% compared to traditional theoretical models. Finally, an optimization model for outlet flow pulsation was proposed. The structural parameters of the valve plate, aimed at minimizing flow pulsation, were determined using the multi-agent particle swarm optimization algorithm. These findings underscore the importance of considering the coupled effects of cavitation bubble and swash plate inclination angle vibration in the design optimization process for reducing low-flow pulsation. This study provides a theoretical foundation for the design of variable-displacement piston pumps with minimized vibration and noise levels.

Blade loss leads to excessive unbalanced vibrations of the rotor system in the gas generator of an aero-turboshaft engine. A squeeze film damper (SFD) cannot meet vibration control requirements owing to its fixed structural parameters. In this study, the outer ring of the SFD oil film is designed as three movable bearing pads. Piezoelectric actuators (PZTs) are used to adjust the oil film force by changing the radial displacement of the bearing pads, and sudden unbalanced vibration control of the rotor system is realised based on a switching control strategy. The oil film force formula of the split-pad squeeze film damper (SSFD) is derived, and a mathematical model of the SSFD-rotor system controlled by PZTs is established using finite element and lumped mass methods. The effects of the bearing pad clearance and stiffness of the PZTs on the rotor vibration characteristics are discussed, and the vibration control effect of the SSFD on the sudden unbalanced response of the rotor system is studied theoretically and experimentally. The results show that rotor vibration can be reduced by reducing the bearing pad clearance and increasing the stiffness of the PZTs. The SSFD can effectively suppress the sudden unbalanced response of the rotor system. The experimental value of the peak transient amplitude of the rotor decrease by 32%, and the rotor orbit in the stable state decreases with increasing PZT voltage.

In harsh environments, turbochargers require continuous adjustment of the rotating speed, which can lead to differences in erosive wear on the blades compared to erosive wear under constant speed conditions. In this study, the erosion model expression for an aluminum alloy plate with a fitted Ks value of 20 mu m under the erosion of 160 mu m SiO2 particles is obtained through erosive wear experiments. Taking a turbocharger compressor as the research object, the influence of four commonly used working speeds on blade wear is analyzed. The results show that when the speed increases from 70,000 rpm to 130,000 rpm, the maximum wear rate concentration values for the main and splitter blades increase by approximately 590% and 310%, respectively.

针对现有弹状流理论模型忽略气泡破碎与融合效应而无法准确预测水动力学特性难题,建立基于破碎与融合效应的弹状流理论模型.分析泰勒气泡湍动能和表面张力能,推导泰勒气泡破碎的理论公式.基于气相质量守恒,提出气泡融合理论模型,结合破碎公式、融合模型以及经典的弹状流理论,形成了考虑气泡破碎与融合效应的弹状流理论模型.搭建弹状流实验装置,基于高速摄影法测量泰勒气泡速度,对比研究新建理论模型、传统模型与实验数据的吻合度.结果表明:新建模型与实验数据一致性好,误差范围为12％,较经典理论模型提高了7％.证明考虑气泡融合与破碎效应的新建模型较现有理论模型更合理.

An aluminum alloy erosion wear test rig was built in this study. The wear rates of the target materials at different surface roughness were measured. An improved Finnie model was developed to predict the wear rate for aluminum alloy plates at different surface roughness. The optimized model was used to analyze the effects of different surface roughness on the erosion wear of the main and splitter blades of the compressor. The study shows that as the surface roughness increases from 1 mu m to 60 mu m, the size of wear concentration areas of the pressure surfaces of the main and splitter blades spread from the blade height of 80% to 30% and 50%, respectively.

The radiated noise of an axial piston pump has been reduced previously by modifying shell structure. However, the effects of these methods of reducing vibration and noise are not clear. In this study, a noise reduction method that uses a phononic crystal structure on the vibration noise transmission path of a piston pump was developed. First, It was determined that the radiated noise frequency of the piston pump was the maximum peak frequency of the excavator field sound pressure level. A phononic crystal cell structure was designed based on the main noise peak frequency range of the axial piston pump. Comparing the vibration characteristics of the piston pump with and without the phononic crystal revealed that the vibration frequency of the piston pump can be significantly attenuated in the range of 409-1181.7 Hz. Finally, The average total sound pressure level of the external-field radiated noise of the axial piston pump was calculated based on the laid and non-laid phononic crystal structures. The results show that the average total sound pressure level amplitude decreases by 8.3 dB(A) in the frequency range of 0-1500 Hz. This study provides theoretical guidance for the design of an axial piston pump with low vibration and noise. (c) 2022 Elsevier Ltd. All rights reserved.

An axial piston pump can produce a serious cavitation phenomenon in the high- and low-pressure ‎transition process. Cavitation bubbles expand, compress, rebound and collapse when they enter the high-‎pressure oil drainage area. This affects the outlet flow ripple as well as the pressure pulsation of the ‎piston pump. However, the effect of the cavitation bubbles is ignored in the current outlet flow ripple ‎model of axial piston pumps. It affects the optimization design of the axial piston pump distribution area ‎structure parameters with the objective of reducing the pressure and flow rate. Therefore, a method of ‎optimizing the fluid dynamic characteristics and the flow distribution area structure parameters of an axial ‎piston pump considering the cavitation bubble evolution is proposed. A single-cavity dynamic model was ‎established to study the bubble evolution as the piston chamber pressure changes. According to the ‎cavitation cloud (group cavitation) characteristics of the axial piston pump, theoretical models of the ‎outlet flow ripple and the pressure pulsation of a piston pump were established considering the cavitation ‎bubble characteristics. The influence of cavitation characteristics on the outlet flow ripples and pressure ‎pulsation of the axial piston pump was analyzed and compared with that without cavitation. Comparison ‎with the experimental results, verified that the outlet flow ripple model becomes more accurate when ‎cavitation bubble characteristics are considered. Based on the multi-agent particle swarm optimization ‎‎(MAPSO) algorithm, an optimization model of the piston pump outlet flow ripple was established ‎considering the cavitation bubble characteristics. The optimized design parameters for the flow ‎distribution area of the axial piston pump were evaluated. The proposed method can provide theoretical ‎guidance for the design of a low flow ripple axial piston pump.‎

Axial piston pump is complex fluid machinery with mechanical fluid coupling, and it has the characteristics of multiple noise sources. In order to solve the high noise problem of axial piston pump, this paper proposes a noise reduction method by identifying the main noise sources of axial piston pump and laying new damping materials to reduce noise. It breaks through the existing method of optimizing the parameters of piston pump shell and valve plate structure. A multi-parameter trajectory sensitivity identification and noise reduction method for vibration transmission path of axial piston pump is proposed in this paper. First, the lumped parameter method is used to establish the mathematical model of vibration transmission path of axial piston pump. The sensitivity of structural vibration response to transmission path multi-parameters are analyzed based on trajectory sensitivity method. The most sensitive parameters in the main noise transmission path are determined. Then, the experimental study of radiated noise transmission path of axial piston pump is carried out. A new type of viscous damping material is proposed to reduce the noise on the transmission path of the main noise source. The experimental results show that the noise of piston pump is reduced by 2.32 dB. The research results provide a new method and way for the design and manufacture of low noise piston pump.