Numerical Analysis for the Stability of Cylinder Gas Film Seal

2013 ◽  
Vol 655-657 ◽  
pp. 526-530
Author(s):  
Gang Ma ◽  
Jun He ◽  
Xin Min Shen
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Reynolds Equation ◽  
Working Condition ◽  
Critical Mass ◽  
System Stability ◽  
Dynamics Analysis ◽  
Rotor Speed ◽  
Analysis Model ◽  
The Stability

Non-contacting gas film seal applies to the high speed working condition and a numerical method was presented for analyzing the effect of speed on the stability of cylinder gas film seal. The dynamics analysis model was established, solving the time-dependent Reynolds equation coupling with the dynamic equations. Through numerical simulation, the critical speed of cylinder gas film seal system and the diagram of critical mass versus rotor speed were obtained. The influence of the speed on dynamic stability was studied. The results show that the system stability becomes worse as rotor speed increases.

Study on Gyroscopic Effect of Magnetic Flywheel Rotor

2011 ◽  
Vol 130-134 ◽  
pp. 970-975
Author(s):  
Xiang Long Wen ◽  
Cao Cao
Keyword(s):  
Feedback Control ◽  
High Speed ◽  
System Stability ◽  
Rotor Speed ◽  
Gyroscopic Effect ◽  
Pd Control ◽  
The Stability ◽  
Gyroscopic Effects ◽  
Zero Points ◽  
Flywheel Rotor

In the high-speed, gyroscopic effects of the flywheel rotor greatly influence the rotor stability. The pole-zero points move to right of s-plane and the damping terms of the pole points become smaller. The stability of the system will get worse with the increasing of rotor speed when the traditional decentralized PD controller is used only. In the paper, a cross-feedback control with decentralized PD control is used for compensating gyroscopic effect. The simulation results show that the system stability is better using the cross-feedback control with decentralized PD control than using the traditional decentralized PD control.

Dynamic stability of micropolar lubricated hydrodynamic offset-halves journal bearings

2020 ◽  
pp. 135065012093685
Author(s):  
Sanyam Sharma ◽  
Chimata M Krishna
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Critical Mass ◽  
Journal Bearings ◽  
Aspect Ratios ◽  
Input Parameters ◽  
Output Characteristics ◽  
The Stability ◽  
Offset Factor

The plain circular journal bearings are not found to be stable by researchers when used in high speed rotating machineries. Hence, extensive research in the study of stability characteristics of non-circular bearings or lobed bearings assumed importance, of late. Present article deals with the stability analysis of non-circular offset bearing by taking selected set of input and output parameters. Modified Reynolds equation for micropolar lubricated rigid journal bearing system is solved using finite element method. Two kinds of input parameters namely, offset factors (0.2, 0.4) and aspect ratios (1.6, 2.0) have been selected for the study. The important output characteristics such as load, critical mass, whirl frequency ratio, and threshold speed are computed and plotted for various set of values of input parameters. The results obtained indicate that micropolar lubricated circular offset bearing is highly stable for higher offset factor and higher aspect ratio.

Stability and Control of Tooling System for High-Speed Machining

2014 ◽  
Vol 684 ◽  
pp. 375-380
Author(s):  
Deng Sheng Zheng ◽  
Jian Chen ◽  
D.F. Tao ◽  
L. Lv ◽  
Gui Cheng Wang
Keyword(s):  
Natural Frequency ◽  
High Speed ◽  
System Stability ◽  
Finite Model ◽  
High Speed Machining ◽  
Cnc Machine ◽  
And Performance ◽  
The Stability ◽  
Tooling System ◽  
And Control

Tooling system for high-speed machining is one of the key components of high-end CNC machine , its stability and reliability directly affects the quality and performance of the machine. Based on the finite element method, developing a 3D finite model of high-speed machining tool system, studying on the stability of the high Speed machining tool from the natural frequency by the method of modal analysis. Analysis the amount of the overhang and clamping of the tooling , different shank taper interference fit and under different speed conditions, which affects the natural frequency of high-speed machining tool system. Proposed to the approach of improving system stability, which also provides a theoretical basis for the development of new high-speed machining tool system.

Study on Kinematics Sensitivities of Folder Mechanism with Clearance

2011 ◽  
Vol 121-126 ◽  
pp. 4764-4769
Author(s):  
Ying Cai Yuan ◽  
Yan Li ◽  
Yi Ming Wang ◽  
Qiang Guo
Keyword(s):  
Sensitivity Analysis ◽  
High Velocity ◽  
High Speed ◽  
Development Trend ◽  
Matrix Analysis ◽  
Analysis Model ◽  
Design Variables ◽  
The Matrix ◽  
The Stability ◽  
Definition Of

High velocity and stability are the development trend and inevitable requirement, but the clearance would make the stability of mechanical system deceased, especially in high speed. To the folder mechanism with clearances in high velocity, combined with the definition of sensitivity and the kinematics analysis, the kinematics sensitivity analysis model is derived by the matrix analysis method. Through the sensitivity analysis model, it can be easy to get the relationship of the design variables and the mechanism’s robustness, which provides the base to design the folder mechanism in high velocity.

Stability Analysis of High-Speed Railway Vehicle Based on Multibody Dynamics Analysis

2013 ◽  
Vol 392 ◽  
pp. 156-160
Author(s):  
Ju Seok Kang
Keyword(s):  
Stability Analysis ◽  
Multibody Dynamics ◽  
High Speed ◽  
Equations Of Motion ◽  
Contact Forces ◽  
Design Parameters ◽  
Railway Vehicle ◽  
Dynamics Analysis ◽  
Contact Points ◽  
The Stability

Multibody dynamics analysis is advantageous in that it uses real dimensions and design parameters. In this study, the stability analysis of a railway vehicle based on multibody dynamics analysis is presented. The equations for the contact points and contact forces between the wheel and the rail are derived using a wheelset model. The dynamics equations of the wheelset are combined with the dynamics equations of the other parts of the railway vehicle, which are obtained by general multibody dynamics analysis. The equations of motion of the railway vehicle are linearized by using the perturbation method. The eigenvalues of these linear dynamics equations are calculated and the critical speed is found.

Dynamics Analysis and Vibration Isolation Design of Shared Foundation on Marine Turbo Generator Set

2013 ◽  
Vol 572 ◽  
pp. 193-196
Author(s):  
Chong Liu ◽  
Chang Hua Qiu ◽  
Lei Gao
Keyword(s):  
High Speed ◽  
Vibration Isolation ◽  
Stable Operation ◽  
Dynamical Response ◽  
Dynamics Analysis ◽  
Analysis Model ◽  
Lumped Mass ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Turbo Generator

Considering the ship's limited space, high speed and miniaturization have been design directions in marine turbo generator set. The shared foundation with steel plate welding is designed to support the marine turbo generator set. Stiffness and dynamic characteristic of the shared foundation will directly affect the stable operation of the turbo generator set. The paper established the dynamics analysis model for the shared frame of marine turbo generator set according to the 'Lumped Mass Method'. Taking account of the frequency-domain analysis operability, the operational modal analysis and dynamical response on foundation were carried out by Virtual Lab. Based on these results; the intensity and location of exciting force were ascertained. And then, we designed the shared foundation vibration isolation system, and analyzed the characteristics of the vibration isolation mounting. The result shows that the vibration isolation system can minimize output force transmissibility and reduce the effect of the marine turbo generator set vibration.

Dynamics Analysis of the Triangular Rotary Engine Structures

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Chiu-Fan Hsieh
Keyword(s):  
Mathematical Models ◽  
Dynamic Properties ◽  
Volume Ratio ◽  
Thermal Conditions ◽  
System Stability ◽  
Dynamics Analysis ◽  
Analysis Model ◽  
Rotary Engine ◽  
Fluid Analysis ◽  
Rotary Engines

A triangular rotary engine includes several main components such as an eccentric shaft, a sun gear, a triangular rotor, a chamber, and apex seals. This study constructs the mathematical models for the chamber and triangular rotor profiles in a rotary engine, as well as for the kinematics and contact force of its apex seals by using the epitrochoid and envelope principles. The chamber profile is represented by design parameter, trochoid ratio, whose limitations are investigated together with the volume ratio. To simplify the calculation, the dynamics analysis model ignores the effects of combustion and thermal conditions in rotary engines. Gas force effect is taken into account by first constructing a fluid analysis model that measures the gas fluid moment on the triangular rotor. Then, based on the mathematical models of chamber and rotor, a systematic dynamics analysis model for a rotary engine is built. It allows analyzing the kinematics and the stress variations in all components of the engine. The dynamics model considers both output shaft torsion and fluid moment. The dynamics analysis then uses three cases of trochoid ratio to illustrate the effects of chamber profile design on the system dynamics properties of rotary engines. The results not only show the dynamic properties and differences in various mechanism designs but also indicate the stability and stress level in the components. In conclusion, the higher trochoid ratio with a larger variation in the chamber profile curvature reduces system stability and increases vibrations, stress fluctuations, and large stress peaks risk.

Robust Control of Permanent Magnet Synchronous Motor: Synergetic Approach

2020 ◽  
Vol 21 (8) ◽  
pp. 480-488
Author(s):  
A. A. Kuz’menko
Keyword(s):  
Robust Control ◽  
Sliding Mode Control ◽  
Permanent Magnet ◽  
Sliding Mode ◽  
System Stability ◽  
Stability Conditions ◽  
Rotor Speed ◽  
Control Laws ◽  
Mode Control ◽  
The Stability

Permanent magnet synchronous motors (PMSM) are widely used in practice due to its high-energy efficiency, compactness, reliability and high regulation performance. When controlling a PMSM rotor speed, the main control principle is the principle of cascade control with PI-regulators, which includes an external control loop for speed and two internal loops for stator currents along the (d, q)-axes. There are attempts to eliminate the disadvantages of this principle using for the control laws synthesis of modern methods of nonlinear control such methods as linearization feedback, backstepping, predictive control, sliding mode control, methods of robust and adaptive control, fuzzy and neural network control, a combination of these methods etc. However, in most cases, the use of these methods are intended to by means of an appropriate method to synthesize a static or dynamic set points for the standard PI-controllers of rotor speed and currents. In this paper we propose to consider two approaches of synergetic control theory (SCT) to construct a robust control law of PMSM: a sliding mode control laws design by the SCT method with subsequent invariant manifolds aggregation and the principle of integral adaptation (PIA). These approaches implement vector control and are not guided by the standard structure of the principle of cascade regulation of PMSM. The proposed approaches simplify the stability analysis of the closed-loop system: stability conditions consist of stability conditions of functional equations of SCT and the stability conditions for finish decomposed system, which the dimension is substantially less than the dimension of the original system. From the results of the comparisons of synthesized the PMSM robust control laws, we can say that more preferable laws synthesized in accordance with the PIA. The theoretical positions of this paper are illustrated by the results of modeling, which are showing the fulfillment of the control tasks: the achievement of targets, robustness to the change of the PMSM load moment.

Stability of High Speed Rotors With Internal Friction

1974 ◽  
Vol 96 (3) ◽  
pp. 960-968 ◽  
Author(s):  
J. M. Vance ◽  
J. Lee
Keyword(s):  
Internal Friction ◽  
Differential Equations ◽  
Numerical Solution ◽  
High Speed ◽  
Critical Speed ◽  
Rotating Machinery ◽  
Rigid Foundation ◽  
Flexible Rotor ◽  
Mathematical Methods ◽  
The Stability

The problem of nonsynchronous whirl induced by internal friction is shown to be important when rotating machinery is designed for operation at supercritical speeds. Mathematical methods are used to determine the stability speed threshold of nonsyncronous whirl instability for an unbalanced flexible rotor on a rigid foundation. This threshold of instability is shown to be the same as the threshold for balanced rotors established by previous investigations. The location of the external damping (foundation or rotor) is shown to be important in determining stability when the foundation is made very rigid. The effect of shaft stiffness orthotropy on nonsynchronous whirl induced by internal friction is also investigated. Results from the stability analyses are verified by numerical solution of the differential equations. It is concluded that rotors can be safely operated up to speeds about eighty percent above the significant critical speed if the external damping is larger than the internal friction, and that shaft stiffness orthotropy has an insignificant effect on friction-induced whirl.

Rotordynamics analysis of a single helical gear transmission system for high speed applications

2020 ◽  
Vol 14 (3) ◽  
pp. 7040-7048
Author(s):  
Najeeb Ullah ◽  
C. Xi ◽  
T. Cong ◽  
H. Yucheng
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Transmission Error ◽  
Gear Transmission ◽  
Dynamic Mesh ◽  
Coupled Systems ◽  
Acceleration Response ◽  
Vibration Acceleration ◽  
Gear Transmission System ◽  
The Stability

Since the non-linear dynamic response under various high-speed conditions can directly affect the life of gear transmission systems. In addition, the transmission error and dynamic mesh force play a key role in noise and harshness analysis of gear bearing coupled systems. So, in this piece of work, a 12 degree of freedom dynamic model is developed to probe the vibration response by using finite element method and taking into account the bearing and flexible shafts in the first part. Subsequently, some meshing gear characteristics such as dynamic and vibration acceleration response under different rotational speeds (1000-9000 rev/minute) were analyzed whereas critical speed appeared at 6500 rev/minute. Then, the stability analysis is performed to investigate the dynamics behind the critical speed by using MASTA. It was observed that natural frequency of 0.45 kHz for a fourth harmonic order is analogous to critical speed which further causes sudden elevation in both dynamic mesh force and transmission error.

Sign in / Sign up

Export Citation Format

Share Document