Dynamic Characteristics of Fluid Force Induced by Swirling Leakage Flow Between Rotational and Stationary Disks

2012 ◽  
Author(s):  
Takayuki Sugiyama ◽  
Shigehiko Kaneko
Keyword(s):  
Dynamic Characteristics ◽  
Tangential Velocity ◽  
Oscillatory System ◽  
Axial Rotation ◽  
Design Stage ◽  
Leakage Flow ◽  
Force Coefficient ◽  
Fluid Force ◽  
Excited Vibration ◽  
Divergent Channel

Axial self-excited vibration may be induced in a balance piston by fluid with a tangential velocity component that flows into the piston orifices. To avoid such vibration, knowledge of the dynamic characteristics of axial self-excited vibration induced by swirling leakage flow is required at the design stage. In this research, the effect of axial rotation and swirl strength on the added fluid force coefficients is clarified by modeling the piston orifice as the combination of rotational and stationary disks, and deriving the unsteady fluid force generated by swirling leakage flow between the disks. As a result, reduction of the relative velocity in the circumferential direction is shown to destabilize the oscillatory system. In particular, the effect of swirl strength on the fluid force coefficient is found to be larger in the case of the divergent channel than in the case of the parallel flow path.

Fluid Force Moment on a Centrifugal Impeller Shroud in Precessing Motion

1997 ◽  
Vol 119 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Yoshinobu Tsujimoto ◽  
Yoshiki Yoshida ◽  
Hideo Ohashi ◽  
Norihiro Teramoto ◽  
Shin Ishizaki
Keyword(s):  
Flow Model ◽  
Tangential Velocity ◽  
Inviscid Flow ◽  
Bulk Flow ◽  
Centrifugal Impeller ◽  
Shear Stresses ◽  
Leakage Flow ◽  
Fluid Force ◽  
Clearance Flow ◽  
Force Moment

Experimental results of fluid moment on a centrifugal impeller shroud in precessing motion are discussed based on the bulk flow model to elucidate the fundamental flow mechanism. It is shown that the backshroud/casing clearance flow and the destabilizing fluid force moment can be simulated by the bulk flow model fairly well if the measured behavior of the resistance is correctly incorporated in the model. From the calculations with and without steady and unsteady wall shear stresses, the unsteady component of the clearance flow is shown to be basically a two-dimensional inviscid flow induced by the change in the flow thickness. The effects of the leakage flow rate and the resistance at the leakage flow entry are discussed, paying attention to the steady tangential velocity of the leakage flow.

J101041 Dynamic Characteristics of Fluid Force Induced by Swirling Leakage Flow between Rotational and Stationary Disks

2012 ◽  
Vol 2012 (0) ◽  
pp. _J101041-1-_J101041-5
Author(s):  
Takayuki SUGIYAMA ◽  
Shigehiko KANEKO
Keyword(s):  
Dynamic Characteristics ◽  
Leakage Flow ◽  
Fluid Force

Steam flow excited vibration and dynamic characteristics of seal in different rotor whirling motion

2021 ◽  
Vol 160 ◽  
pp. 107029
Author(s):  
Heyong Si ◽  
Lihua Cao ◽  
Pan Li ◽  
Dongchao Chen
Keyword(s):  
Dynamic Characteristics ◽  
Steam Flow ◽  
Whirling Motion ◽  
Excited Vibration

Fluid Force Moment on the Backshroud of a Francis Turbine Runner in Precession Motion

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Bingwei Song ◽  
Hironori Horiguchi ◽  
Yumeto Nishiyama ◽  
Shinichiro Hata ◽  
Zhenyue Ma ◽  
...  
Keyword(s):  
Flow Model ◽  
Swirl Flow ◽  
Francis Turbine ◽  
Leakage Flow ◽  
Fluid Force ◽  
Disk Rotation ◽  
Leakage Flow Rate ◽  
Turbine Runner ◽  
Force Moment ◽  
Axial Clearance

The fundamental characteristics of rotordynamic fluid force moment on the backshroud of a Francis turbine runner in precession motion were studied using model tests and computations based on a bulk flow model. The runner is modeled by a disk positioned close to a casing with a small axial clearance. An inward leakage flow is produced by an external pump in the model test. The effects of the leakage flow rate, the preswirl velocity at the inlet of the clearance, and the axial clearance on the fluid force moment were examined. It was found that the fluid force moment encourages the precession motion at small forward precession angular velocity ratios and the region encouraging the precession motion is affected by the preswirl velocity. Through the comparisons of the fluid force moment with and without the rotation of the disk, it was found that the normal moment without the disk rotation did not have the effect to encourage the precession motion. Thus, the swirl flow due to disk rotation was found to be responsible for the encouragement of the precession motion.

Nonlinear Analysis of Rotordynamic Fluid Forces in the Annular Plain Seal by Using Extended Bulk-Flow Analysis: Influence of Static Eccentricity and Whirling Amplitude

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Koya Yamada ◽  
Atsushi Ikemoto ◽  
Tsuyoshi Inoue ◽  
Masaharu Uchiumi
Keyword(s):  
Perturbation Analysis ◽  
Flow Analysis ◽  
Flow Theory ◽  
Bulk Flow ◽  
Design Stage ◽  
Fluid Force ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Static Eccentricity ◽  
Harmonic Components

Rotor-dynamic fluid force (RD fluid force) of turbomachinery is one of the causes of the shaft vibration problem. Bulk flow theory is the method for analyzing this RD fluid force, and it has been widely used in the design stage of machine. The conventional bulk flow theory has been carried out under the assumption of concentric circular shaft's orbit with a small amplitude. However, actual rotating machinery's operating condition often does not hold this assumption, for example, existence of static load on the machinery causes static eccentricity. In particular, when such a static eccentricity is significant, the nonlinearity of RD fluid force may increase and become non-negligible. Therefore, conventional bulk flow theory is not applicable for the analysis of the RD fluid force in such a situation. In this paper, the RD fluid force of the annular plain seal in the case of circular whirling orbit with static eccentricity is investigated. The case with both the significant static eccentricity and the moderate whirling amplitude is considered, and the perturbation analysis of the bulk-flow theory is extended to investigate the RD fluid force in such cases. In this analysis, the assumption of the perturbation solution is extended to both static terms and whirling terms up to the third order. Then, the additional terms are caused by the coupling of these terms through nonlinearity, and these three kinds of terms are considered in the extended perturbation analysis of the bulk flow theory. As a result, a set of nonlinear analytical equations of the extended perturbation analysis of the bulk flow theory, for the case with both the significant static eccentricity and the moderate whirling amplitude, is deduced. The RD fluid force for such cases is analyzed, and the occurrence of constant component, backward synchronous component, and super-harmonic components in the RD fluid force is observed in addition to the forward synchronous component. The representation of RD fluid force coefficients (RD coefficients) are modified for the case with significant static eccentricity, and the variation of RD fluid force coefficients for the magnitude of static eccentricity is analyzed. These analytical results of RD fluid force and its RD coefficients are compared with the numerical results using finite difference analysis and experimental results. As a result, the validity of the extended perturbation analysis of the bulk-flow theory for the case with both the significant static eccentricity and the moderate whirling amplitude is confirmed.

Effect of the Leakage Flows and the Upstream Platform Geometry on the Endwall Flows of a Turbine Cascade

2006 ◽  
Author(s):  
E. de la Rosa Blanco ◽  
H. P. Hodson ◽  
R. Vazquez
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Separation Bubble ◽  
Tangential Velocity ◽  
Low Pressure ◽  
Leakage Flow ◽  
Backward Facing Step ◽  
Surface Separation ◽  
Pressure Surface

This work describes the effect that the injection of leakage flow from a cavity into the mainstream has on the endwall flows and their interaction with a large pressure surface separation bubble in a low-pressure turbine. The effect of a step in hub diameter ahead of the blade row is also simulated. The blade profile under consideration is a typical design of modern low-pressure turbines. The tests are conducted in a low speed linear cascade. These are complemented by numerical simulations. Two different step geometries are investigated, i.e., a backward-facing step and a forward-facing step. The leakage tangential velocity and the leakage mass flow rate are also modified. It was found that the injection of leakage mass flow gives rise to a strengthening of the endwall flows independently of the leakage mass flow rate and the leakage tangential velocity. The experimental results have shown that below a critical value of the leakage tangential velocity, the net mixed-out endwall losses are not significantly altered by a change in the leakage tangential velocity. For these cases, the effect of the leakage mass flow is confined to the wall, as the inlet endwall boundary layer is pushed further away from the wall by the leakage flow. However, for values of the leakage tangential velocity around 100% of the wheelspeed, there is a large increase in losses due to a stronger interaction between the endwall flows and the leakage mass flow. This gives rise to a change in the endwall flows structure. In all cases, the presence of a forward-facing step produces a strengthening of the endwall flows and an increase of the net mixed-out endwall losses when compared with a backward-facing step. This is because of a strong interaction with the pressure surface separation bubble.

Control of Shroud Leakage Loss by Reducing Circumferential Mixing

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Budimir Rosic ◽  
John D. Denton
Keyword(s):  
Significant Proportion ◽  
Tangential Velocity ◽  
Secondary Flows ◽  
Main Stream ◽  
Leakage Flow ◽  
Flow Angle ◽  
Blade Row ◽  
Stator Blade ◽  
The Difference ◽  
Mixing Losses

Shroud leakage flow undergoes little change in the tangential velocity as it passes over the shroud. Mixing due to the difference in tangential velocity between the main stream flow and the leakage flow creates a significant proportion of the total loss associated with shroud leakage flow. The unturned leakage flow also causes negative incidence and intensifies the secondary flows in the downstream blade row. This paper describes the experimental results of a concept to turn the rotor shroud leakage flow in the direction of the main blade passage flow in order to reduce the aerodynamic mixing losses. A three-stage air model turbine with low aspect ratio blading was used in this study. A series of different stationary turning vane geometries placed into the rotor shroud exit cavity downstream of each rotor blade row was tested. A significant improvement in flow angle and loss in the downstream stator blade rows was measured together with an increase in turbine brake efficiency of 0.4 %.

Self-excited Vibration Characteristics and Exciting Fluid Force of Multiple Plates Supported by Air Pressure

2020 ◽  
Vol 2020 (0) ◽  
pp. 610
Author(s):  
Shunsuke YAMAZAKI ◽  
Masakazu TAKEDA ◽  
Keiichi HIROAKI ◽  
Masahiro WATANABE
Keyword(s):  
Vibration Characteristics ◽  
Air Pressure ◽  
Fluid Force ◽  
Excited Vibration

Study on Characteristics and Operating Parameters of Axial Rotating Hydrocyclone

2009 ◽  
Author(s):  
Yan Xu ◽  
Zunce Wang ◽  
Fengxia Lv ◽  
Sen Li
Keyword(s):  
Pressure Drop ◽  
Laboratory Experiments ◽  
Separation Efficiency ◽  
Rotation Speed ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Axial Rotation ◽  
Rotating Wall ◽  
Simulation Results

The axial rotation of the hydrocyclone affects its internal flow characteristics and separating effect directly, as some local applications require the static hydrocyclone rotates about its own axis. Based on CFD, velocity distribution in the axial rotating hydrocyclone is studied. It is shown that as the rotation speed increasing, the tangential velocity improves and its gradient reduces in free vortex region observably, while the radial velocity has an incremental trend in the section of the small cone. The laboratory experiments are carried out for the static hydrocyclone of disposal capacity of 4 m3/h at 100r/min ∼ 300r/min. The relationships among rotation speed, flowrate, pressure drop and separated efficiency are achieved, which agree well with the numerical simulation results. The results indicate that the disposal capacity of hydrocyclone subjected to the rotation wall can be more flexible than that with no-rotating wall, the scope of best disposal capacity gradually enlarges with the increase of rotation speed of wall. Appropriate rise of the rotation speed is favor of the separation efficiency at the steady flowrate, however the increase of the flowrate and rotation speed induces the growth of the hydrocyclone’s pressure drop correspondingly to some extent.

A Study on Leakage Flow Induced Vibration From Engineering Viewpoint

2015 ◽  
Author(s):  
Fumio Inada
Keyword(s):  
Damping Ratio ◽  
Axial Flow ◽  
Engineering System ◽  
Dimensional System ◽  
Leakage Flow ◽  
Fluid Inertia ◽  
Flow Induced Vibration ◽  
One Dimensional ◽  
Annular Gap ◽  
Excited Vibration

Leakage-flow-induced vibration for a relatively short gap is studied analytically to provide useful information to design structures that include a leakage flow. The relationship between the analysis of a one-dimensional system and that of an annular gap is explained first. Then, the mechanism of flutter-type instability is reproduced from previous study after correcting an error. Finally, the self-excited vibration potential of an engineering system is shown from sample calculations. It is shown that an axial flow becomes dominant in the short-gap approximation, and in this case, the analysis of a one-dimensional flow can be expanded to that of an annular flow. The result that negative damping can occur in the case of a divergent passage owing to the delay induced by fluid inertia was obtained from a previous study. It was suggested analytically that the damping ratio could become negative and its absolute value could become more than 10% in a system that is frequently encountered in a plant, if the natural frequency decreases. The value could be sufficient to generate self-excited vibration.

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