Nonlinear Transient Response of Tilting 4 Pad Bearings: Turbocharger Systems

2013 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen ◽  
R. Gordon Kirk ◽  
Yongxin Feng
Keyword(s):  
High Speed ◽  
High Performance ◽  
Dynamical Behavior ◽  
Transient Vibration ◽  
Nonlinear Dynamical ◽  
Rotor Systems ◽  
Tilting Pad ◽  
Speed Range ◽  
Nonlinear Transient ◽  
Tilting Pad Bearings

High speed and high performance engines are often equipped with turbochargers to increase power density over the operating speed range. Tilting pad bearings are now much more applied in many types of rotor systems. This paper presents nonlinear dynamical behavior of a typical turbocharger supported by two tilting 4 pad bearings. The bearing oil-film force was calculated by a database method and the influence of both pad offset and preload were studied. The nonlinear transient vibration is represented by bifurcation diagrams. The results directly show that pad offset and preload greatly influence the nonlinear vibrations of the turbocharger-tilting pad bearings system. In some certain speed range, the motions of the bearing pads are different from that of the bearing journal centerline.

Nonlinear Flutter Response of Tilting 4 Pad Bearings-Rotor System

2011 ◽  
Author(s):  
Jiayang Ying ◽  
Yinghou Jiao ◽  
Zhaobo Chen ◽  
R. Gordon Kirk
Keyword(s):  
Transient Vibration ◽  
Oil Film ◽  
Rotor Systems ◽  
Tilting Pad ◽  
Jeffcott Rotor ◽  
Rotor Bearing ◽  
Nonlinear Transient ◽  
Rotor Center ◽  
Design Speed ◽  
Tilting Pad Journal Bearing

Nonlinear analysis is increasingly applied in the dynamics analysis of rotor bearing systems. The use of tilting-pad bearings is now a standard feature of many types of rotor systems. The concern for oil film excitation of the rotor lowest natural frequency is eliminated by the use of the tilting pad journal bearings. For new higher speed or larger low speed applications, the possibility of the pad flutter instability still remains and most commonly used design tools do not consider the pad inertia as a standard feature. In this paper, taking the Jeffcott rotor supported by two 4 pad bearings as an example, the influence of pad inertia and journal diameter were studied. The influence of shaft diameter and pad inertia was determined by the transient response of a simple rotor-bearing system operating over a wide design speed range. The tilting pad journal bearing oil-film force was calculated by a database method. The resulting nonlinear transient vibration is discussed using bifurcation diagrams, orbits, frequency spectrum plots, phase trajectories, and Poincare maps. The results directly show that journal diameter and pad inertia greatly influence the nonlinear vibrations of the journal and rotor center.

scholarly journals Propeller control strategy for coaxial compound helicopters

2018 ◽  
Vol 233 (10) ◽  
pp. 3775-3789 ◽  
Author(s):  
Ye Yuan ◽  
Douglas Thomson ◽  
Renliang Chen
Keyword(s):  
Control Strategy ◽  
High Speed ◽  
High Performance ◽  
Control Strategies ◽  
Flight Dynamics ◽  
Axial Thrust ◽  
Handling Qualities ◽  
Speed Range ◽  
Compound Helicopter ◽  
Flight Dynamics Model

The coaxial compound configuration has been proposed as a concept for future high-performance rotorcraft. The co-axial rotor system does not require an anti-torque device, and a propeller provides axial thrust. A well-designed control strategy for the propeller is necessary to improve the performance and the flight dynamics characteristics. A flight dynamics model of coaxial compound helicopter is developed to analyze these influences. The performance and the flight dynamics characteristics in different propeller strategies were first investigated. The results show that there is an improvement in the performance in high-speed flight when the propeller provides more propulsive forces. It also illustrates that a reasonable allocation of the rotor and the propeller in providing thrust can further reduce the power consumption in the mid speed range. In other words, the propeller control strategy can be an effective method to improve the cruise-efficiency. The flight dynamics analysis in this paper includes trim and handling qualities. The trim results prove that the propeller strategy can affect the collective pitch, longitudinal cyclic pitch, and the pitch attitude. If the control strategy is designed only to decrease the required power, it will result in a discontinuity in the trim characteristics. Handling qualities are investigated based on the ADS-33E-PRF requirement. The result demonstrates that the bandwidth and phase delay results and eigenvalue results in various speed at different propeller strategies are all satisfied. However, some propeller control strategies lead to severe inter-axis coupling in high-speed flight. Based on these results, this paper proposes the propeller control strategy for the coaxial compound helicopter. This strategy ensures good trim characteristics and handling qualities, which satisfy the related requirements, and improves the flight range or the performance in high-speed flight.

Nonlinear Modeling of Tilting-Pad Bearings With Application to a Flexible Rotor Analysis

2013 ◽  
Author(s):  
Jianming Cao ◽  
Tim Dimond ◽  
Paul Allaire
Keyword(s):  
High Speed ◽  
Dynamic Stiffness ◽  
Nonlinear Modeling ◽  
Transient Behavior ◽  
Pressure Profile ◽  
Flexible Rotor ◽  
Time Step ◽  
Assembly Method ◽  
Tilting Pad ◽  
Tilting Pad Bearings

Tilting-pad bearings are widely used in high-speed rotating machines to improve the system’s stability. Linearized static or dynamic stiffness and damping coefficients are often applied to rotordynamic analyses. This method has limits due to the nonlinear effects of tilting-pad bearing under severe unbalance conditions or large shaft vibration. This work presents a new modeling and assembly method of a linear flexible rotor with nonlinear tilting-pad bearings. The pressure profile on each pad is calculated using an approximate finite element method by solving Reynolds equation derived from a nonlinear tilting-pad bearing model. Nonlinear bearing forces are calculated based upon the shaft instantaneous position and velocity with an update at each time step. Effects of the bearing pad&pivot are evaluated first by applying a rigid rotor on tilting-pad bearings first. The nonlinear transient behavior of a flexible eight-stage compressor supported on two tilting-pad bearings is investigated. The nonlinear numerical transient response of the system under severe unbalance conditions, including coupled motions of bearing pads, bearing pivots and the shaft, and nonlinear bearing forces, is solved using a 4th order Runge-Kutta integration after assembling the system together. Under severe unbalance conditions. Sub and super harmonic response is shown to exist from both rotor and bearing components.

Tilting Pad Bearing Pivot Friction and Design Effects on Thermal Bow-Induced Rotor Vibration

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Dongil Shin ◽  
Alan B. Palazzolo
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Design Parameters ◽  
Flexible Beam ◽  
Thermally Induced ◽  
Tilting Pad ◽  
Speed Range ◽  
Transient Simulations ◽  
Nonlinear Transient ◽  
Tilting Pad Journal Bearing

Abstract The Morton effect (ME) is a thermally induced vibration problem observed in a rotor supported by hydrodynamic bearings. The journal’s synchronous orbiting induces nonuniform viscous heating on its circumference, and the ensuing thermal bow often causes unacceptable vibration levels in the rotor. This paper investigates the influence of the tilting pad journal bearing (TPJB)’s pivot design on the severity and instability speed range of ME vibration. Simulations are conducted with two different types of pivots: cylindrical (CYL) and spherical (SPH), which produce different pad degrees-of-freedom and nonlinear pivot stiffness due to their geometries. The friction between pad and pivot, which only exists with the spherical pivot, is modeled, and its impact on the ME is evaluated. The example rotor model, as obtained from the literature, is single overhung, with experimentally measured excessive vibration and large journal temperature differentials, near 8000 rpm. The bearing and journal are modeled with three-dimensional (3D) finite elements, and the shaft with flexible beam elements for ME simulation. Nonlinear transient simulations are carried out for a wide operating speed range with varying pivot design parameters. Simulation results indicate that the predicted ME instability is sensitive to the pivot shape, pivot flexibility, and pad-pivot friction.

Flexure Pivot Tilting Pad Hybrid Gas Bearings: Operation With Worn Clearances and Two Load-Pad Configurations

2007 ◽  
Author(s):  
Luis San Andre´s ◽  
Keun Ryu
Keyword(s):  
High Speed ◽  
High Performance ◽  
Test System ◽  
Viscous Drag ◽  
Widespread Application ◽  
Critical Speeds ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Modal Damping ◽  
Tilting Pad

Gas film bearings enable the successful deployment of high-speed micro-turbomachinery. Foil bearings are in use; however, cost and lack of calibrated predictive tools prevent their widespread application. Other types of bearing configurations, simpler to manufacture and fully engineered, are favored by commercial turbomachinery manufacturers. Externally pressurized tilting pad bearings offer a sound solution for stable rotor support. This paper reports measurements of the rotordynamic response of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on flexure pivot tilting pad hybrid gas bearings. The tests are performed for various imbalances, increasing supply pressures, and under load-on-pad (LOP) and load-between-pad (LBP) configurations. Presently, the initial condition of the test bearings shows sustained wear and dissimilar pad clearances after extensive testing reported earlier, see Ref. [1]. In the current measurements, there are no noticeable differences in rotor responses for both LOP and LBP configurations due to the light-weight rotor, i.e. small static load acting on each bearing. External pressurization into the bearings increases their direct stiffnesses and reduces their damping, while raising the system critical speeds with a notable reduction in modal damping ratios. The rotor supported on the worn bearings shows a ∼10% drop in first critical speeds and roughly similar modal damping than when tested with pristine bearings. Pressurization into the bearings leads to large times for rotor deceleration, thus demonstrating the little viscous drag typical of gas bearings. Rotor deceleration tests with manually controlled supply pressures eliminate the passage through critical speeds, thus paving a path for rotordynamic performance without large amplitude motions over extended regions of shaft speed. The rotordynamic analysis shows critical speeds and peak amplitudes of motion agreeing very well with the measurements. The synchronous rotor responses for increasing imbalances demonstrate the test system linearity. Superior stability and predictable performance of pressurized flexure pivot gas bearings can further their implementation in high performance oil-free microturbomachinery. More importantly, the measurements show the reliable performance of the worn bearings even when operating with enlarged and uneven clearances.

Bump-Type Foil Bearings and Flexure Pivot Tilting Pad Bearings for Oil-Free Automotive Turbochargers: Highlights in Rotordynamic Performance

2015 ◽  
Author(s):  
Keun Ryu ◽  
Zachary Ashton
Keyword(s):  
High Performance ◽  
Load Capacity ◽  
Mechanical Efficiency ◽  
Outer Diameter ◽  
Gas Bearings ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Thermal Growth ◽  
Tilting Pad ◽  
Tilting Pad Bearings

Oil-free turbochargers require gas bearings in compact units of enhanced rotordynamic stability, mechanical efficiency, and improved reliability with reduced maintenance costs compared with oil-lubricated bearings. Implementation of gas bearings into automotive turbochargers requires careful thermal management with accurate measurements verifying model predictions. Foil bearings are customarily used in oil-free microturbomachinery because of their distinct advantages including tolerance to shaft misalignment and centrifugal/thermal growth, and large damping and load capacity compared with rigid surface gas bearings. Flexure pivot tilting pad bearings are widely used in high performance turbomachinery since they offer little or no cross-coupled stiffnesses with enhanced rotordynamic stability. The paper details the rotordynamic performance and temperature characteristics of two prototype oil-free turbochargers; one supported on foil journal and thrust bearings and the other one is supported on flexure pivot tilting pad journal bearings and foil thrust bearings of identical sizes (OD and ID) with the same aerodynamic components. The tests of the oil-free turbochargers, each consisting of a hollow rotor (∼0.4 kg and ∼23 mm in outer diameter at the bearing locations), are performed for various imbalances in NVH (i.e, cold air driven rotordynamics rig) and gas stand test facilities up to 130 krpm. No forced cooling air flow streams are supplied to the test bearings and rotor. The measurements demonstrate the stable performance of the rotor-gas bearing systems in an ambient NVH test cell with cold forced air into the turbine inlet. Posttest inspection of the test flexure pivot tilting pad bearings after the hot gas stand tests evidences seizure of the hottest bearing, thereby revealing a notable reduction in bearing clearance as the rotor temperature increases. The compliant flexure pivot tilting pad bearings offer a sound solution for stable rotor support only at an ambient temperature condition while demonstrating less tolerance for shaft growth, centrifugal and thermal, beyond its clearance. The current measurements give confidence in the present gas foil bearing technology for ready application into automotive turbochargers for passenger car and commercial vehicle applications with increased reliability.

On the Effect of Pad Clearance and Preload Manufacturing Tolerances on Tilting Pad Bearings Rotordynamic Coefficients

2013 ◽  
Author(s):  
Jose L. Gomez ◽  
Saira Pineda ◽  
Sergio E. Diaz
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Numerical Code ◽  
Perturbation Approach ◽  
The Finite Element Method ◽  
Rotordynamic Coefficients ◽  
Dynamic Coefficients ◽  
Tilting Pad ◽  
Manufacturing Tolerances ◽  
Tilting Pad Bearings

Tilting pad bearings (TPB) are commonly used in high-speed and high-power turbomachines, due to its contributions in avoiding rotor instabilities. Studies related to the estimation of dynamic coefficients have been carried out considering a uniform value of the geometric parameters (clearance, pre-load) for all bearing pads. These assumptions give a reasonable agreement on the direct coefficients prediction while, recently, some discrepancies have been found on the cross-coupled coefficients. In this work, a numerical study is devised to analyze the influence of the pre-load and clearance variations from pad to pad, due to manufacturing tolerances, on the dynamic coefficients prediction. The numerical code for the estimation of the dynamic coefficients uses the finite element method to integrate the Reynolds’s equation through a perturbation approach. Variations on the pre-load and clearance for each bearing’s pad were performed, producing plots quantifying the sensitivity of the tilting pad bearing cross coupled coefficients to manufacturing tolerances.

A Comprehensive Analysis and Solution for Traction Motor Speed Measurement in High Speed Train

2012 ◽  
Vol 253-255 ◽  
pp. 2052-2057
Author(s):  
Jin Qi Ren ◽  
Yao Hua Li ◽  
Qiong Xuan Ge ◽  
Xun Ma ◽  
Lu Zhao
Keyword(s):  
High Speed ◽  
High Performance ◽  
High Speed Train ◽  
Motor Speed ◽  
Clock Period ◽  
Traction Motor ◽  
Speed Measurement ◽  
Speed Range ◽  
Update Rate ◽  
Hardware In Loop

In high speed train, to obtain precise speed is important to high performance control, though the transducers used in the train are usually low resolution. The speed measurement was analyzed both on precision and update rate according to the control requirement. A comprehensive measure and calculation solution for traction motor speed measurement is presented. Measure clock period is adjusted according to motor’s different speed range and can obtain good measurement precision both in low and high speed range. The speed update rate can also be guaranteed. The proposed method is implemented and validated by hardware in loop simulation system.

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