Full-scale Test Rig Research Articles

Rolling contact fatigue prediction for rails and comparisons with test rig results

Tests in a full-scale roller rig, a full-scale linear test rig, and a twin-disc machine are numerically evaluated and compared in terms of rolling contact fatigue loading. From previously evaluated contact patch sizes, a Wöhler curve relationship is established and matched towards experimentally established fatigue lives. In addition, non-linear finite-element simulations are carried out. Key data needed for the numerical evaluations, as well as difficulties in translating experimental data to numerical models are highlighted. A key parameter here is the interfacial wheel—rail friction. Additional simulations were carried out to establish the latter. However, the conformal contact in the linear test rig makes such simulations very uncertain.

Forced Response of Mistuned Bladed Disks in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results

An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

Buoyancy Driven Natural Ventilation through Horizontal Openings

An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening and the diameter of the opening, respectively. The basic nature of airflow through single-sided openings, including airflow rate, air velocity, temperature difference between the rooms and the dimensions of the horizontal openings, were measured. A bi-directional airflow rate was measured using the constant injection tracer gas technique. Smoke visualizations showed that the airflow patterns are highly transient and unstable, and that the airflow rate oscillates with time. Correlations between the Froude (Archimedes) number Fr (Ar) and the L/D ratio are presented. In some cases the measured airflow rates fit quite well with the Epstein’s formula but in other cases the measured data show clear deviations from the Epstein’s formula. Thus, revised formulas for natural ventilation are proposed.

Experimental investigation and modelling of the interaction between an AVR and ballast load frequency controller in a stand-alone micro-hydroelectric system

Extensive field experience in micro-hydroelectric systems in remote rural communities demonstrates that the use of a typical automatic voltage regulator (AVR), as supplied with a brushless self-exciting synchronous alternator, can be the cause of unsatisfactory system performance. This paper presents results from experiments undertaken on a full-scale micro-hydroelectric test rig as well as system modelling with PSCAD. The source of the instability is considered to stem from the similar time constants of the ballast load frequency controller and the AVR as two competing feedback control systems. System modelling is used to verify steady state operating points, and confirms that the under-frequency roll-off characteristic of the AVR also contributes to unsatisfactory performance.

Design procedure for cooling ducts to minimise efficiency loss due to temperature rise in PV arrays

The principal variable to be fixed in the design of a PV cooling duct is its depth, and hence the hydraulic diameter of its cross-section D. Analysis of the flow and heat transfer in the duct under still-air (buoyant flow) conditions, when the temperature rise is greatest, is validated by measurements on a full-scale test rig. It is shown that there is an optimum value of this design variable, such that for an array of length L the minimum temperature occurs when the ratio L/ D is about 20. The optimum value is not affected much by other quantities, including the slope of the array. In practical situations, the flow is obstructed by devices across the duct inlet and outlet to exclude insects, birds and rain, and by structural support members crossing the duct interior. It is shown that the latter are no cause for concern, since the effect of the reduction in the flow-rate due to their presence is more than offset by an increase in heat transfer through additional turbulent mixing. It is also shown that array temperatures are strongly reduced by wind effects, which increase both the heat lost from the front surface of the array and by enhancement of the flow in the duct. Though the trends are clear, limitations are encountered in the present state of knowledge in both areas.

An Experimental Study of Static and Dynamic Characteristics of a 580mm(22.8in.) Diameter Direct Lubrication Tilting Pad Journal Bearing

Abstract Direct lubrication tilting pad journal bearings (DLTPJ bearings) have rarely been applied to large-scale rotating machinery, such as turbines or generators, whose journal diameters are more than 500mm. In this paper, static and dynamic characteristics of a 580mm(22.8in.) diameter DLTPJ bearing were studied experimentally using a full-scale bearing test rig. In the static test, distribution of metal temperature, oil film pressure, and bearing loss were measured in changing oil flow rate, with mean bearing pressure ranging up to 2.9MPa. The maximum metal temperature of the DLTPJ bearing was compared to that of a conventional flood lubrication bearing, and it was confirmed that the direct lubrication could increase load capacity. In the dynamic test, spring and damping coefficients of oil film were obtained by exciting the bearing casing that was floated by air bellows. These data will be used for analysis and design of steam turbine rotors and their bearing systems. Also, vibration of pads was investigated because metal failure on upper pads due to vibration has been found in some actual machines. In order to generate oil film pressure on the surface of upper pads, a Rayleigh-step was machined there, and it was confirmed that vibration was reduced by the Rayleigh-step.

A full-scale test rig for railway rolling noise: simulation and measurement of dynamic wheelset–track interaction

A new outdoor rolling-noise test rig on a 25 m stretch of full-scale track will enable the study of vibrations of wheel and rail and of the pertinent noise emission under controlled conditions. The arrangement can be seen as a physical realization of the Track–Wheel Interaction Noise Software (TWINS) computer software. The track and wheel, which are not in mechanical contact, are excited in vertical and lateral directions using electrodynamic actuators. The track can be statically pre-loaded by up to 30 tonnes. The use of the rig is presently under development. The aim is that the radiated noise from separate railway components could be found as the wheel and the track can be excited both together and separately. Amplitude and phase of the applied forces are predetermined by use of an algorithm taking into account the real wheel–rail interaction properties. In that way different wheel–rail contact conditions can be simulated. Eight partners have co-operated in the development and operation of the CHARMEC/Lucchini Railway Noise Test Rig in Surahammar, Sweden. In ongoing experiments, the dynamics of both the wheel and rail have been examined in the frequency domain. For the track, comparisons have been made between data obtained from the rig and those from field measurements on a standard Swedish line. Both dynamic response and spatial decay rates have been studied. The performance of the rig has also been compared to results from TWINS and to results from the literature. Good agreement was obtained in the frequency range from 100 to 5000 Hz. Some results from preliminary measurements of noise emission will be given.

Integrated Experimental and Numerical Approach for Fuel-Air Mixing Prediction in a Heavy-Duty Gas Turbine LP Burner

An integrated experimental-numerical procedure has been developed for fuel-air mixing prediction in a heavy-duty gas turbine burner. Optical measurements of the degree of mixing have been performed in a full-scale test rig operating with cold flow. Experimental data have been utilized to validate a CFD RANS numerical model. In fact, it is recognized that the turbulence behavior of jets in swirling air-flow stream is not accurately described by standard k-ε turbulence models; therefore advanced turbulence models have been assessed by means of experimental data. The degree of mixing between simulated fuel and air streams has been evaluated at the burner exit section by means of a planar Mie scattering technique. The experimental apparatus consists of a pulsed Nd:YAG laser and a high resolution CCD video camera connected to a frame grabber. The acquired instantaneous images have been processed through specific procedures that also take into account the laser beam spatial nonuniformity. A second-order discretization scheme with a RSM turbulence model gives the best accordance with the experimental data. Such CFD model will be part of a more general method addressed to numerical prediction of turbulent combustion flames in LP technology.

Reliable Rotor Dynamic Design of High-Pressure Compressors Based on Test Rig Data1

The overall design of high-pressure centrifugal compressors is largely influenced by rotordynamic aspects. Rotor instability may restrict operating speed and/or maximum discharge pressure if the destabilizing effects have not been considered accurately during the design phase. A test rig for high pressures has been designed and operated successfully in order to achieve dynamic labyrinth seal coefficients through simulation of original conditions in every aspect. Details are given of the full-scale test rig, which uses active magnetic bearings as a key feature, as well as results from the comprehensive test program. Later on, these results are employed for the design of a compressor for very high pressures, demonstrating the complexity of this design task. Validation of the labyrinth test data and the rotor dynamic analysis is provided by the results from a PTC 10 class I test on a reinjection compressor. During shop testing, this machine has been run with and without swirl brakes and the test results agree very well with the predictions.

Fatigue Prediction of Thin Hard Coatings on the Steel Races of Hybrid Bearings Used in High Speed Machine Tool Spindles

The rotational speed requirements of high speed spindles led to the development of angular contact hybrid bearings with ceramic balls and PVD coated steel races. The present paper describes the determination and verification of critical coating fatigue stresses as well as their application in coating fatigue calculations of hybrid bearing steel races. The fatigue limits of low temperature deposited PVD coatings were determined by the application of the impact test and its FEM simulation and validated through their successful application to the prediction of coating life in rolling contact fatigue tests of coated specimens. Furthermore, a computer program that performs the quasi-static simulation of bearing operation yields the necessary kinematic and dynamic parameters for a FEM simulation of the stress field occurring in coated rings. For the investigated bearings, an adequate fatigue performance of their coated races was computationally exhibited. The PVD coated hybrid bearings illustrated the predicted behavior in long duration tests, conducted in full scale test rigs.

Starting and Steady-State Friction Torque of Grease-Lubricated Rolling Element Bearings at Low Temperatures—Part II: Correlation with Less-Complex Test Methods

Today, torque measurements are conducted in full-scale test rigs, either standardized or specially designed. This is a time-consuming approach, especially at low temperatures, and it is therefore of high priority to find some less complex test method(s) correlating with bearing friction at different temperatures. The paper deals with five possible candidate test methods to predict low temperature starting and running friction: apparent viscosity, base oil viscosity, sliding friction, base oil traction properties and yield stress. The pros and cons of these methods are discussed and empirical expressions are presented for the methods where good correlation was found. It is stated that base oil viscosity at the temperature of interest is the best method to predict bearing friction torque at low temperature starting. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kisslmmee, Florida, October 8–11, 1995

Flex Cycle Combustor Development and Demonstration

An innovative, “flex-cycle” combustion system has been developed for the Garrett Model 400-1 Integrated Power Unit (IPU), a 425 shp (317 kW) gas turbine engine designed for use on future fighter aircraft. Demonstration of this system required real-time transient operation of the combustor in a full-scale test rig. The transient testing was unique, having been performed with an electronic control, which modulated all combustor operating parameters according to programmed engine component maps, drag curves, fuel schedules, and selected ambient test conditions. The axially injected annular combustor is capable of engine starts in two seconds, as well as producing 200 shp (149 kW) for emergency use at all altitudes up to 50,000 ft (15,240 m). The combustion system is capable of switching operation from the emergency power stored energy (SE) mode to the normal-air breathing (NAB) auxiliary power mode without loss of engine power. The flex-cycle combustor supplies emergency power in the SE mode with a temperature rise of 2200°F (1222°C) and in the NAB mode with a temperature rise of 1600°F (889°C). Specific features that make these requirements possible include air-assisted simplex airblast fuel atomizers with integral check valves, and effusion-cooled combustor liner walls. This paper describes the flex-cycle combustion system design, test methods used, and significant test results. Steady-state performance, in both the SE and NAB operating modes, and real-time transient test results are discussed. The transient testing included rapid starts as well as transitions from the SE to NAB operating regimes.

SEMI-ACTIVE SUSPENSIONS - A COMPARISON BETWEEN THEORY AND EXPERIMENTS

SUMMARY A full-scale half car suspension test rig is used to evaluate the performance of switchable dampers in semi-active control. A theoretical model is developed for the test rig and its parameters are identified. Two types of switchable shocks are used. A low bandwidth tri-state damper originally designed for manual setting changes is shown to be too slow for real-time ride quality improvement Semi-active control is successfully demonstrated with a high bandwidth multi-state damper. Conventional ON-OFF, optimal ON-OFF, optimal multi-state control and a robust form of multi-state control are implemented and compared. Semi-active control is shown to give a performance as good as the best of all available passive states at every frequency. Trends in the experimental results are accurately predicted by the theoretical model

Advanced turbofan engine combustion system design and test verification

A combustion system design for an advanced turbofan gas turbine engine is discussed. The design process includes the modeling of both the combustor internal and external flowfields. The external flow analysis was conducted to determine the cold side heat-transfer rates and to establish the external pressure field around the outside of the combustor. Following the external flow analysis, the combustor internal flowfield was analyzed to optimize the combustor performance. Various airflow splits and fuel injection locations were evaluated to arrive at the final design. A full-scale annular high-pressure test rig was designed, fabricated, and instrumented to record all the pertinent combustor performance data. The combustor was test evaluated to determine all of the performance parameters, i.e., combustion efficiency, pattern factor, ignition characteristics, lean blowout fuel/air ratios, and liner wall temperatures.

Full-scale testing of a high speed linear synchronous motor and calculation of end-effects

A description is given of apparatus constructed to perform full-scale tests on linear synchronous motor (LSM) designs suitable for 100-passenger vehicles, traveling at speeds up to 400 km/hr. Test results are presented that illustrate the terminal characteristics of the machine, which are shown to be predictable using a simple mathematical model. In all forms of linear machine the air-gap flux takes time to develop at the entry end of the stator and a further time to decay at the exit end. This effect, which is due to induced secondary currents, is known as the longitudinal end effect. A simple method is described for predicting the effect, and the results are confirmed by measurements on a full-scale test rig.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Blowdown tests to verify calculation methods for loss-of-coolant accidents

The HDR Facility represents a full scale test rig for the simulation of nuclear power plant accidents. The experimental and analytical investigations are basically aimed at the identification of the main phenomena and influences occurring during severe accidents and at the verification of calculation models and codes to describe those accidental effects. During Phase I of the program (1975–1983) blowdown investigations covering design basis accidents aspects formed the focal point of the research activities. The investigated components were full scale isolation valves, pressure vessel internals (especially core barrel) and the containment vessel and internal structures.

Measurement of smoke in large scale fire tests

Large scale fire tests involving actual products and prototypes are of major importance in that they enable the interactions of various materials, prototypes and design features to be evaluated. The fire regime can be selected to reproduce the anticipated end-use hazard. This paper discusses the various approaches used to measure smoke in large scale fire tests, and their requirement and their limitations, as well as correlations between full scale test rigs.

Precast concrete tunnel linings — A review of current test procedures : Lance, G A Construction Industry Research and Information Association technical note 104, May 1981, 60P

This note describes 28 tests on complete rings, individual segments and joints of precast concrete for tunnel linings. Strength tests have been reported on behaviour in compression, bending, combined bending and compression, and resistance to ram loading and pullout. It is concluded that there is not at present an economic case for constructing a full scale test rig. (TRRL)

Testing joints in driving rain

Tests on model joints, and even on full-scale test rigs, can only give partial answers to the problems of joint weathertightness. The Soviet Central Research and Design Institute for Dwellings now regularly supplements this orthodox research testing with readings taken in actual premises during driving rain. The equipment and methods used are described in this article, originally prepared for a meeting of CIB working group W61 on joints in exterior walls.

Wear properties of dry bearing liners at ambient and elevated temperatures

Dry bearings have been used increasingly over the last few years to replace conventional grease-lubricated metallic bearings in aerospace applications, particularly where maintenance is difficult or in hostile environments where fluid lubrication is impossible. The friction and wear properties of a wide range of experimental and commercial dry bearing liners have been examined in conditions of reciprocating line contact on a modified pin-on-ring apparatus at temperatures up to 150 °C. The development of the apparatus is briefly described. Accelerated wear data are provided in a few hours as opposed to the several months required for full-scale bearing test rigs. The specific wear rates differed appreciably under ambient conditions, varying by approximately two orders of magnitude. The application of additional heat generally increased the wear rate although some materials had an optimum performance at temperatures above ambient. In general liners containing synthetic reinforcing fibres, e. g. polyamide or polyester, appear to exhibit superior wear properties to those containing glass fibres. Comparisons are drawn between the data obtained from these accelerated tests and the results of those obtained on journal bearings.