Featured Application: The proposed integral squeeze film bearing damper can effectively decrease the vibration of an unbalanced single-side cantilevered rotor system such as a flue gas turbine and pump. Abstract: In this paper, vibration control of an unbalanced single-side cantilevered rotor system using a novel integral squeeze film bearing damper in terms of stability, energy distribution, and vibration control is analyzed. A finite element model of such a system with an integral squeeze film bearing damper (ISFBD) is developed. The stability, energy distribution, and vibration control of the unbalanced single-side cantilevered rotor system are calculated and analyzed based on the finite element model. The stiffness of the integral squeeze film bearing damper is designed using theoretical calculation and finite element model (FEM) simulation. The influence of installation position and quantity of integral squeeze film bearing dampers on the vibration control of the unbalanced cantilevered rotor system is discussed. An experimental platform is developed to validate the vibration control effect. The results show that the installation position and quantity of the integral squeeze film bearing dampers have different effects on the stability, energy distribution, and vibration control of the unbalanced cantilevered rotor system. When ISFBDs are installed at both bearing housings, the vibration control is best, and the vibration components of the time and frequency domains have good vibration control effects in four working conditions. External excitations are mainly caused by the impact load and pulsation excitation of the fluid. When the excitation frequencies are close to the natural frequencies of the system, the resonance occurs in the system, causing unpredictable losses.With the rapid development of the single-side cantilevered rotor system, the vibration problems have become increasingly prominent. These problems pose a huge threat to safety production and economic benefits. In actual civil and military equipment, rotor systems often vibrate due to unbalance, resulting in impeller fracture, seal failure, bearing damage, valve failure, pipeline leakage, and loose foundation [6]. These faults cause equipment damage or even major safety accidents, along with unpredictable personal injury to users. So, it is necessary to control the vibration of the unbalanced single-side cantilevered rotor.The vibration mechanism of the unbalanced single-side cantilevered rotor system has already been researched by many scholars. According to the obtained theory, the vibration control of the system is divided into four types: structural modification, vibration absorption, vibration isolation, and vibration damping. At the same time, the vibration control method is divided into two types: active and passive control. Active control refers to the use of the sensor to collect signals and feedback for the controller to drive the damper to reduce vibration. Passive control refers to vibration control that can be performed without add...
A unit cell approach is employed to predict the effective moisture diffusion property in fiber-reinforced biopolymer. The permeable fibers distributed in the matrix are taken as inclusion phases in the system. Based on a unit cell model, the calculation method for moisture diffusion coefficients is developed in this paper. Moisture diffusion property and effective diffusion coefficients are numerically investigated under different temperature and volume fractions of fibers. The calculated results agree well with Gueribiz's solutions. Therefore, it is reliable in predicting moisture diffusion property of composite using the unit cell model. The present result shows that the effective diffusion coefficient of a composite depends on both temperature and volume fraction of fibers. The effective diffusion coefficient of regular hexagon pattern composite is larger than that of square pattern at the same temperature and volume fraction.
This paper proposes a method for optimizing unbalanced force and unbalanced moment of the multistage disk based on sequence quadratic program algorithm to solve the vibration problem of gas turbine tie rod rotor. This method guides the assembly phase of the multistage disks. The influence of unbalanced force and unbalanced moment on the vibration of the tie rod rotor are analyzed based on the characteristics of rotor structure and assembly process. A dynamic model of the unbalanced force and unbalanced moment of the tie rod rotor is established. The sequence quadratic program algorithm is used to optimize multi-dimension of unbalanced force and moment, so the global optimal solution can be obtained. In order to verify the effectiveness of the optimization method proposed in this paper, vibration control experiments are carried out for traditional tie rod rotor and gas turbine tie rod rotor structure. The results show that both unbalanced force optimization and unbalanced moment optimization can control the tie rod rotor vibration effectively, and unbalanced moment optimization is better. Unbalanced moment optimization is used to perform constant speed and speed-up experiment on the gas turbine tie rod rotor structure. At 1200r/min, the maximum vibration reduction of the system is 76.68%. And the vibration has a decrease of 43.3% at the first-order critical speed. The proposed method in this paper can be used not only for the guidance of tie rod rotor assembly of gas turbine, but also for the vibration control during operation.
The pressure-induced-flow (PIF) processing can effectively prepare high-performance polymer materials. This paper studies the influence of pressure-induced-flow processing on the morphology, thermodynamic and mechanical properties of polypropylene (PP)/polyamide 6 (PA6) blends, PP/polyolefin elastomer (POE) blends and PP/thermoplastic urethane (TPU) blends. The results show that pressure-induced-flow processing can significantly improve the thermodynamic and mechanical properties of the blends by regulating internal structure. Research shows that the pressure-induced-flow processing can increase the strength and the toughness of the blends, particularly in PP/TPU blends.
The flow characteristics in the rim clearances of turbines are sensitive to the turbine rim structures. From this standpoint, rotor–stator cavity models with dislocated clearances are proposed in this study to reveal the effect of dislocated turbine rim lips on hot gas ingestion and the clearance flow characteristics. The results show that the rim clearance flow is unstable, and Kelvin–Helmholtz vortices are induced by the relatively large difference in circumferential velocity of the flow fields inside and outside the rim seal. Moreover, the dislocated turbine rim lips decrease the effectiveness of the rim seal. Ultimately, the responses of the flow characteristics to the dislocated rims are determined to be primarily reflected in the effect of the forward or backward step flow on the Kelvin–Helmholtz vortices in turbine rims.
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