Sealing Technology: Rub Test Rig for Abrasive/Abradable Systems

2007 ◽  
Author(s):  
Ulrich Rathmann ◽  
Sven Olmes ◽  
Alex Simeon
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Rig ◽  
Visual Appearance ◽  
Major Interest ◽  
Rubbing Behavior ◽  
Blade Tip ◽  
Detailed Assessment ◽  
The University

Performance and efficiency optimization is one of the major tasks in the turbo machinery industry. Therefore efforts for scientific and technical improvements focus on optimization and reduction of losses. Secondary losses are of major interest because of their parasitic character related to stage efficiency and power output. One of these losses is over tip leakage of blades. Common practice is a minimization of this clearance with abrasive/abradable combinations. With this technique the blade tip (abrasive material) can rub into its counterpart (heat-shield, abradable material on casings or liners) and therefore minimize the operating tip-clearance. This technology is well established in compressor and turbine engineering since many years [1]. Field experience shows that abrasive/abradable systems do not always work as intended. In some cases rubbing conditions are reversed so that the intended abradable cuts into the abrasive. Any benefit on operating tip-clearance will then be minor at best or even negative. Rubbing behavior is difficult to predict, especially for new materials or geometries where no experience is available. In close cooperation with the University of Applied Sciences Rapperswil (Switzerland), ALSTOM has developed a test rig that allows simulating engine-operating conditions and therefore evaluate abrasive/abradable combinations before actual implementation into an engine. The rig is designed to reproduce circumferential velocities and incursion rates that are typical for gas turbine engines in the compressor as well as in the turbine. Forces and temperatures are measured as quantitative data, visual appearance and metallographic condition of test specimens are recorded as qualitative data that allow a more detailed assessment of material combinations and operating conditions. This paper describes the design of a high-speed wear rig facility to test single blade and fully shrouded rub configurations. In addition the validation of the test rig against real engine experience and knowledge is shown.

Subsynchronous Vibration Patterns Under Reduced Oil Supply Flow Rates

2017 ◽  
Author(s):  
B. R. Nichols ◽  
R. L. Fittro ◽  
C. P. Goyne
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
System Stability ◽  
Supporting Evidence ◽  
Test Rig ◽  
Flow Rates ◽  
Oil Supply ◽  
Bending Mode ◽  
Wide Range

Many high-speed, rotating machines across a wide range of industrial applications depend on fluid film bearings to provide both static support of the rotor and to introduce stabilizing damping forces into the system through a developed hydrodynamic film wedge. Reduced oil supply flow rate to the bearings can cause cavitation, or a lack of a fully developed film layer, at the leading edge of the bearing pads. Reducing oil flow has the well-documented effects of higher bearing operating temperatures and decreased power losses due to shear forces. While machine efficiency may be improved with reduced lubricant flow, little experimental data on its effects on system stability and performance can be found in the literature. This study looks at overall system performance of a test rig operating under reduced oil supply flow rates by observing steady-state bearing performance indicators and baseline vibrational response of the shaft. The test rig used in this study was designed to be dynamically similar to a high-speed industrial compressor. It consists of a 1.55 m long, flexible rotor supported by two tilting pad bearings with a nominal diameter of 70 mm and a span of 1.2 m. The first bending mode is located at approximately 5,000 rpm. The tiling-pad bearings consist of five pads in a vintage, flooded bearing housing with a length to diameter ratio of 0.75, preload of 0.3, and a load-between-pad configuration. Tests were conducted over a number of operating speeds, ranging from 8,000 to 12,000 rpm, and bearing loads, while systematically reducing the oil supply flow rates provided to the bearings under each condition. For nearly all operating conditions, a low amplitude, broadband subsynchronous vibration pattern was observed in the frequency domain from approximately 0–75 Hz. When the test rig was operated at running speeds above its first bending mode, a distinctive subsynchronous peak emerged from the broadband pattern at approximately half of the running speed and at the first bending mode of the shaft. This vibration signature is often considered a classic sign of rotordynamic instability attributed to oil whip and shaft whirl phenomena. For low and moderate load conditions, the amplitude of this 0.5x subsynchronous peak increased with decreasing oil supply flow rate at all operating speeds. Under the high load condition, the subsynchronous peak was largely attenuated. A discussion on the possible sources of this subsynchronous vibration including self-excited instability and pad flutter forced vibration is provided with supporting evidence from thermoelastohydrodynamic (TEHD) bearing modeling results. Implications of reduced oil supply flow rate on system stability and operational limits are also discussed.

Investigation of the Blade Tip Clearance Effects on Performance and Stability of a Mixed-Flow Pump: High Speed Camera Recordings of the Flow Structures, Local Measurements and Numerical Simulation

2015 ◽  
Author(s):  
Alberto Serena ◽  
Lars E. Bakken
Keyword(s):  
High Speed ◽  
Detailed Comparison ◽  
Performance Comparison ◽  
Tip Clearance ◽  
Tip Vortex ◽  
High Speed Camera ◽  
Tip Leakage Flow ◽  
Quality Video ◽  
Local Measurements ◽  
Blade Tip

The tip leakage flow affects turbomachines performance generating losses and reducing the effective blading; in addition, unsteady phenomena arise, negatively influencing the machine stability. In this paper, an overview of the existing models is presented. Local measurements of the pressure pulsations, visual flow observations and high quality video recordings from a high speed camera are performed in a novel pump laboratory, which provides the desired visualization of the rotating channels, and allows to study the fluctuating and intermittent nature of this phenomenon, and detect any asymmetry among the channels. A detailed comparison of the vortex tip structure for various tip clearances and with a whole set of numerical simulations finally completes the analysis. The three main focus areas are: tip vortex location, structure and evolution, performance comparison between shrouded and open impeller, at different tip clearance sizes, and study of the rotating instabilities.

scholarly journals Research on Blade-Casing Rub-Impact Mechanism by Experiment and Simulation in Aeroengines

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jie Hong ◽  
Tianrang Li ◽  
Zhichao Liang ◽  
Dayi Zhang ◽  
Yanhong Ma
Keyword(s):  
High Speed ◽  
High Performance ◽  
Element Model ◽  
Physical Parameters ◽  
Test Rig ◽  
Calculation Results ◽  
Rotor Support ◽  
Blade Tip ◽  
Set Up ◽  
The Impact

Aeroengines pursue high performance, and compressing blade-casing clearance has become one of the main ways to improve turbomachinery efficiency. Rub-impact faults occur frequently with clearance decreasing. A high-speed rotor-support-casing test rig was set up, and the mechanism tests of light and heavy rub-impact were carried out. A finite element model of the test rig was established, and the calculation results were in good agreement with the experimental results under both kinds of rub-impact conditions. Based on the actual blade-casing structure model, the effects of the major physical parameters including imbalance and material characteristics were investigated. During the rub-impact, the highest stress occurs at the blade tip first and then it is transmitted to the blade root. Deformation on the impact blade tip generates easily with decreased yield strength, and stress concentration at the blade tip occurs obviously with weaker stiffness. The agreement of the computation results with the experimental data indicates the method could be used to estimate rub-impact characteristics and is effective in design and analyses process.

Radiative Heat Transfer Analysis of Railroad Bearings for Wayside Hot-Box Detector Optimization

2017 ◽  
Author(s):  
Arthur Mealer ◽  
Constantine Tarawneh ◽  
Stephen Crown
Keyword(s):  
Temperature Data ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Infrared Sensor ◽  
Test Rig ◽  
Detection Systems ◽  
Railway Safety ◽  
Railroad Bearings ◽  
Railroad Bearing ◽  
The University

The railroad industry utilizes wayside detection systems to monitor the temperature of freight railcar bearings in service. The wayside hot-box detector (HBD) is a device that sits on the side of the tracks and uses a non-contact infrared sensor to determine the temperature of the train bearings as they roll over the detector. Various factors can affect the temperature measurements of these wayside detection systems. The class of the railroad bearing and its position on the axle relative to the position of the wayside detector can affect the temperature measurement. That is, the location on the bearing cup where the wayside infrared sensor reads the temperature varies depending on the bearing class (e.g., class K, F, G, E). Furthermore, environmental factors can also affect these temperature readings. The abovementioned factors can lead to measured temperatures that are significantly different than the actual operating temperatures of the bearings. In some cases, temperature readings collected by wayside detection systems did not indicate potential problems with some bearings, which led to costly derailments. Attempts by certain railroads to optimize the use of the temperature data acquired by these wayside detection systems has led to removal of bearings that were not problematic (about 40% of bearings removed were non-verified), resulting in costly delays and inefficiencies. To this end, the study presented here aims to investigate the efficacy of the wayside detection systems in measuring the railroad bearing operating temperature in order to optimize the use of these detection systems. A specialized single bearing dynamic test rig with a configuration that closely simulates the operating conditions of railroad bearings in service was designed and built by the University Transportation Center for Railway Safety (UTCRS) research team at the University of Texas Rio Grande Valley (UTRGV) for the purpose of this study. The test rig is equipped with a system that closely mimics the wayside detection system functionality and compares the infrared sensor temperature reading to contact thermocouple and bayonet temperature sensors fixed to the outside surface of the bearing cup. This direct comparison of the temperature data will provide a better understanding of the correlation between these temperatures under various loading levels, operating speeds, and bearing conditions (i.e. healthy versus defective), which will allow for an optimization of the wayside detectors. The impact on railway safety will be realized through optimized usage of current wayside detection systems and fewer nonverified bearings removed from service, which translates into fewer costly train stoppages and delays.

Numerical Study of the Flow Past a Turbine Blade Tip: Effect of Relative Motion Between Blade and Shroud

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Sumanta Acharya ◽  
Louis Moreaux
Keyword(s):  
Turbine Blade ◽  
Relative Motion ◽  
High Speed ◽  
Numerical Study ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Static Case ◽  
Blade Tip ◽  
Geometric Effects ◽  
Blade Tips

Turbine blade tips are often the most susceptible to material failure due to the high-speed leakage flow and associated large thermal loadings. In this paper, the effect of the blade rotation and relative motion between the blade tip and shroud is studied numerically. Three different simulations have been undertaken: (1) a static case where the blade and the shroud are stationary (used as the reference case) (2) a linearly moving blade (or shroud) and (3) a rotating blade. Comparisons between cases 1 and 2 identify the effects of relative motion, while comparison between cases 2 and 3 delineate the effects of rotational Coriolis and centrifugal forces. Geometric effects were also studied through different combinations of tip gaps and squealer depths with the relative motion and rotational effects included. The calculations were done using a commercial flow solver, Fluent, using a block body-fitted mesh, Reynolds-averaged transport equations and a turbulence model. Results confirm the significant effects of the relative motion between the blade tip and shroud, and indicate that the assumption of pressure-driven leakage flows for blade tips is inappropriate. While rotational forces also play a role, the magnitude of their effects are relatively small compared to the relative motion effects. Geometric effects are also important with the lower tip clearance reducing leakage flow and allowing the tip coolant to migrate towards the SS with relative motion.

Blade Tip Clearance Flow and Compressor NSV: The Jet Core Feedback Theory as the Coupling Mechanism

2007 ◽  
Author(s):  
Jean Thomassin ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
High Speed ◽  
Feedback Mechanism ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Coupling Mechanism ◽  
Blade Vibration ◽  
Potential Core ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip

This paper investigates the role of tip clearance flow in the occurrence of non-synchronous vibrations (NSV) observed in the first axial rotor of a high-speed high-pressure compressor (HPC) in an aero-engine. NSV is an aero-elastic phenomenon where the rotor blades vibrate at non-integral multiples of the shaft rotational frequencies in operating regimes where classical flutter is not known to occur. A physical mechanism to explain the NSV phenomenon is proposed based on the blade tip trailing edge impinging jet like flow, and a novel theory based on the acoustic feedback in the jet potential core. The theory suggests that the critical jet velocity, which brings a jet impinging on a rigid structure to resonance, is reduced to the velocities observed in the blade tip secondary flow when the jet impinges on a flexible structure. The feedback mechanism is then an acoustic wave traveling backward in the jet potential core, and this is experimentally demonstrated. A model is proposed to predict the critical tip speed at which NSV can occur. The model also addresses several unexplained phenomena, or missing links, which are essential to connect tip clearance flow unsteadiness to NSV. These are the pressure level, the pitch-based reduced frequency, and the observed step changes in blade vibration and mode shape. The model is verified using two different rotors that exhibited NSV.

Recasting the Fay-Riddell formulae for computing the stagnation point heat flux

2000 ◽  
Vol 214 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Zuppardi ◽  
A Esposito
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Speed ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Total Enthalpy ◽  
High Enthalpy ◽  
Computing Procedure ◽  
The University ◽  
Made In

The Fay-Riddell formulae, used to compute the heat flux at the stagnation point of spherical bodies in very high speed, laminar flow and dissociating air, have been revived and recast. As these formulae were obtained by fitting a number of results of the original Fay-Riddell computing procedure, which suffered from inaccuracies concerning operative parameters, it is to be expected that these inaccuracies also influence the correctness of the formulae. A sensitivity analysis has been made in order to identify the most critical parameter. Recast formulae have been calibrated using the results of the improved version of the Fay-Riddell computing procedure and then validated both by numerical results of a Navier-Stokes code and by experimental data. For this purpose two sets of heat flux measurements have been made in HEBDAF (high enthalpy blown-down arc facility) at the University of Naples, matching the operating conditions of the formula for a frozen boundary layer and non-catalytic wall. Recast formulae are valid in the range of free-stream total enthalpy between 3 and 37 MJ/kg.

Investigation on the Turbine Blade Tip Clearance Monitoring Based on Eddy Current Pulse-Trigger Method

2016 ◽  
Author(s):  
Weimin Wang ◽  
Huajin Shao ◽  
Lifang Chen ◽  
Huibin Song
Keyword(s):  
Turbine Blade ◽  
Eddy Current ◽  
Tip Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Rotating Speed ◽  
Laboratory Setup ◽  
Blade Tip ◽  
Scale Test ◽  
Blade Tip Clearance

The efficiency and reliability of turbomachinery will be improved by blade tip clearance (BTC) and blade tip timing (BTT) monitoring. Several types of sensors such as eddy-current, capacitance and optical probes are used to realize this objective. Eddy current sensor (ECS) is an ideal choice with its advantage of durablity and that it is unaffected by gas stream properties such as contamination, water vapor, and moisture. However, the bandwidth of ECS is usually less than 100 kHz, which will limit the resolution of the monitoring result. In this paper, a pulse-trigger technology based BTC method was presented. This method optimizes the static radial and circumferential calibration technology to obtain the sensitivity of the ECS in the different relative locations against the tip of blade. The information from the clearance sensor will be fused with that from the once per revolution (OPR) or key phase sensor. The method is more generally applicable in the condition where the ECS is insufficient sampling caused by the limit of narrow bandwidth, especially under the high blade tip velocity condition. A small scale and larger scale BTC measurement rig are established to validate the feasibility of this method. The small one is easy to calibrate with high accuracy and can be used to illustrate the performance of the method, while the larger scale test rig is close to real industry turbine blade. In this apparatus, the axial displacement and radial displacement of rotor vibration as well as the clearance can be monitored together so that further investigation can be conducted. Experimental research was carried out on both test rig at different rotating speed. The results show that the method presented in this paper can improve the accuracy of tip clearance monitored by ECS very well. Furthermore, this work is a proof-of-concept demonstration using a laboratory setup providing the basis for BTC active control and blade health monitoring (BHM) based on ECS.

Numerical Study of Influence of Rotor Tip Gap Increase due to Age Deterioration in 3-Stage Gas Turbine

2020 ◽  
Author(s):  
Koichi Yonezawa ◽  
Junichi Sakamoto ◽  
Kazuyasu Sugiyama ◽  
Shuichi Ohmori ◽  
Shuichi Umezawa
Keyword(s):  
Gas Turbine ◽  
Rotor Blade ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Age Related ◽  
Balance Analysis ◽  
Blade Tip

Abstract Influences of age-related deterioration on the increase in rotor tip gap width are discussed numerically. In the gas turbine examined in the present study, there are two kinds of geometries around the rotor blade tip. In the first stage, there is clearance between the blade tip and the casing without any seal structures. On the other hand, there is a shroud and seal fin on the rotor blade tip. The blade geometries were measured using a 3-D scanner in a working power plant, and the tip clearances were varied by changing the casing contour. Steady-state CFD simulations were carried out. Tip gap widths were varied by shifting the casing wall. For simplicity, the blade geometries were not changed. The influence of tip clearance was examined by changing the geometries in each stage separately. Boundary conditions were determined using the previously developed hybrid method of heat balance analysis and CFD simulation, which can simulate the operating conditions of a working gas turbine. The results showed that the turbine performance degradation could spread to the following stage. Observation of entropy fields revealed that the increase in the tip leakage flow affected the flow in the following nozzle, and the loss increased.

scholarly journals New Sensors and Techniques for the Structural Health Monitoring of Propulsion Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Mark Woike ◽  
Ali Abdul-Aziz ◽  
Nikunj Oza ◽  
Bryan Matthews
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Crack Detection ◽  
Rotating Disk ◽  
Tip Clearance ◽  
Turbine Engines ◽  
Structural Health ◽  
Major Interest ◽  
Blade Tip ◽  
Blade Tip Clearance

The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA), through the Aviation Safety Program (AVSP), has taken a lead role in the development of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. This paper presents a summary of key results and findings obtained from three different structural health monitoring approaches that have been investigated. This includes evaluating the performance of a novel microwave blade tip clearance sensor; a vibration based crack detection technique using an externally mounted capacitive blade tip clearance sensor; and lastly the results of using data driven anomaly detection algorithms for detecting cracks in a rotating disk.

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