Paper 5: Research at C.E.R.L. on Turbine Blade Erosion

1967 ◽  
Vol 182 (8) ◽  
pp. 61-68
Author(s):  
M. J. Moore ◽  
R. W. Langford ◽  
J. C. Tipping
Keyword(s):  
Water Drop ◽  
Operating Conditions ◽  
Front Face ◽  
Blade Row ◽  
Water Drops ◽  
Actual Damage ◽  
Drop Impacts ◽  
The Impact ◽  
Good Agreement ◽  
Made In

Water drops shedding from a cascade of turbine fixed blades have been observed under simulated operating conditions in the C.E.R.L. steam tunnel. The sizes and velocities of the water drops are correlated with conditions downstream in the wake of the blades. The results are shown to be in good agreement with observations made in turbines, and are used to predict the extent and pattern of erosion on a following moving blade row. Upon comparison of the predicted pattern with the actual damage to a moving blade it is found that the impacting drops create pits in the metal surface which are smaller in diameter than the water drops. The physical process occurring when a drop impacts on a surface containing a small pit is illustrated by simple laboratory tests. The impact pressure generated in the water drop causes the front face of the drop to accelerate and strike the base of the pit at up to three times the impact velocity of the drop. This fundamental process accounts for the characteristic pitting of eroded surfaces, and also for the changes in erosion rate observed during continuous water drop bombardment of specimens in material test rigs.

An experimental investigation of fluid flow resulting from the impact of a water drop with an unyielding dry surface

1981 ◽  
Vol 373 (1755) ◽  
pp. 419-441 ◽  
Keyword(s):  
Water Drop ◽  
Roughness Parameter ◽  
Fluid Velocities ◽  
Spatial Dimensions ◽  
Water Drops ◽  
The Moment ◽  
High Degree ◽  
First Contact ◽  
The Impact

The flow of fluid associated with the impact of water drops of radius R at a speed V onto unyielding dry metal surfaces of known roughness R a is described. Spatial dimensions of the deforming drop are normalized by transformations of the kind x ' — x/R , and time scales are normalized according to t ' = tV/R , to permit comparison of events where or differ. It is shown that the primary influence of the surface roughness parameter R a is the determination of the condition for the ejection of secondary droplets by the excitation of an instability in the developing watersheet; provided R a ≪ R , it is possible to evaluate the condition to a high degree of accuracy, and for R a = 0.84 μm it is found to be α4/3 RV 1.69 > 7.4, where α is the eccentricity of the drop at the moment of impact. Deceleration of the drop apex does not commence until > 0.6, contrary to the prediction of Engel (1955) but in good agreement with that of Savic & Boult (1957). Close examination of the very early stages of impact suggests strongly that the so-called watersheet originates at a moment t ' — 0.01 after first contact, regardless of the absolute values of R, V or R a ; the initial normalized watersheet velocity is of order 5. Where there is ejected material, its normalized velocity at the moment of ejection is of the order of 20 % greater than that of the watersheet substrate. Simple calculations also suggest that initial fluid velocities greater than 10 are required immediately before the initiation of the watersheet ( t '< 0.01). Impacts at speeds considerably greater than the appropriate terminal fall speed in air show no deviations in character from those investigated at much lower speeds. A simple subsidiary experiment also suggests that greater impact velocities are required to produce splashing on inclined targets.

scholarly journals Effects of Stator Indexing on Performance in a Low Speed Multistage Axial Compressor

1997 ◽  
Author(s):  
Wendy S. Barankiewicz ◽  
Michael D. Hathaway
Keyword(s):  
Peak Pressure ◽  
Axial Compressor ◽  
Loss Coefficient ◽  
Operating Conditions ◽  
Nasa Lewis Research ◽  
Performance Measurements ◽  
Peak Efficiency ◽  
Blade Row ◽  
The Impact ◽  
Multistage Axial Compressor

The results of an experimental investigation to determine the impact of stator row indexing or clocking on multistage axial compressor performance are presented. Testing was conducted in the NASA Lewis Research Center’s Four-Stage Axial Compressor Facility. The impact of stator row indexing on both the overall and stator 3 blade element performance is presented for both the peak efficiency and peak pressure operating conditions. The change in overall performance due to stator indexing is 0.2% for both operating conditions. Indexing resulted in a 5% change in stator 3 mass averaged loss coefficient at the peak efficiency condition and a 10% change at the peak pressure condition. Since the mass-averaged stator 3 loss coefficient is on the order of 7%, the changes in loss coefficient due to indexing are on the order of 0.35–0.7%. These changes are considered to be small and are of the same order of magnitude as the passage-to-passage differences in loss coefficient due to manufacturing and assembly tolerances in the test compressor. The effects of stator-stator wake interactions are also shown and indicate that for rows with unequal blade counts it may be necessary to survey across more than one blade row pitch for accurate blade row performance measurements.

Unshrouded Rotor Tip Clearance Effects in Expander Cycle Turbines

2002 ◽  
Author(s):  
Lennard Helmers ◽  
Jens Klingmann
Keyword(s):  
Laser Doppler Anemometry ◽  
Tangential Velocity ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Position ◽  
Design Parameters ◽  
Channel Measurements ◽  
Velocity Mapping ◽  
Blade Row ◽  
The Impact

Steady flow in axial one-stage turbines is assessed numerically and experimentally. The simulations are performed on coarse meshes using a standard numerical approach (3D, steady state, kε-turbulence model, wall function at solid boundaries). In order to allow for conclusions drawn from these rapid numerical studies, the approach was compared with an explicit LDA (Laser Doppler anemometry) mapping of the velocity field downstream the rotor on a representative turbine stage. A two-component LDA system allowed for measurements of axial and tangential velocity components at varying depth (radius) in the flow channel, Measurements thus correspond to a full plane at constant axial position in the rotating frame of reference of the rotor. Comparison between LDA velocity mapping and CFD results shows good agreement. A series of subsequent simulations is thus used to judge the impact of varied blade/stage design parameters. Two turbine layouts are defined for identical operating conditions and shaft power. The flow in the unshrouded rotor blade row is analyzed for the influence of varying tip clearance size and the dependency on stage velocity triangles. – Known correlations for tip clearance losses (typically used in mean line predictions) are used, though the blade row geometry considered is beyond the limits the correlations are intended for. The absolute loss level found in CFD simulations differs significantly from what is expected when using loss correlations. Still the variation with tip gap size is predicted well by some of the investigated models. As dependency of tip clearance losses on stage velocity triangles is considered, none of the tested correlations gives results consistent with the numerical simulations. The use of standard correlations ‘beyond the limits’ is thus considered to introduce high uncertainty. Due to the good consistency between LDA and numerical results, the conclusions are considered to be valid for stage designs similar to the ones analyzed.

scholarly journals Energy Analysis in Ice Hockey Arenas and Analytical Formula for the Temperature Profile in the Ice Pad with Transient Boundary Conditions

2019 ◽  
Author(s):  
Andrea Ferrantelli ◽  
Klaus Viljanen ◽  
Jarek Kurnitski
Keyword(s):  
Boundary Conditions ◽  
Temperature Profile ◽  
Indoor Air ◽  
Analytical Formula ◽  
Operating Conditions ◽  
Ice Hockey ◽  
Practical Applications ◽  
State Regime ◽  
The Impact ◽  
Good Agreement

The energy efficiency of ice hockey arenas is a central concern for the administrations, as these buildings are well known to consume a large amount of energy. Since they are composite, complex systems, solutions to such a problem can be approached from many different areas, from managerial to technological to more strictly physical. In this paper we consider heat transfer processes in an ice hockey hall, during operating conditions, with a bottom-up approach based upon on-site measurements. Detailed heat flux, relative humidity and temperature data for the ice pad and the indoor air are used for a heat balance calculation in the steady-state regime, which quantifies the impact of each single heat source. We then solve the heat conduction equation for the ice pad in transient regime, and obtain a generic analytical formula for the temperature profile that can be used in practical applications. We then apply this formula to the resurfacing process for validation, and find good agreement with an analogous numerical solution. Since it is given with implicit initial condition and boundary conditions, it can be used not only in ice hockey halls, but in a large variety of engineering applications.

scholarly journals Analytical model for assessing the bus efficiency preservation factor

2020 ◽  
Vol 17 (4) ◽  
pp. 197-202
Author(s):  
K. K. Taysaev ◽  
◽  
A. V. Terent'ev ◽  
Keyword(s):  
Service Life ◽  
Technical Problem ◽  
Environmental Safety ◽  
Operating Conditions ◽  
Regulatory Requirements ◽  
Operation System ◽  
Transport Safety ◽  
Technical Operation ◽  
The Impact ◽  
Made In

When evaluating the conditions under which decisions have to be made in the bus technical operation system, it is necessary to consider factors that were unknown at the time of the bus design preparation or uncertain factors of the external environment, which arise during operation of buses at different stages of its service life. These include the tightening of regulatory requirements for comfort, structure and environment safety. At present, as a result of the increased impact of the external social environment on the assessment of the bus operation quality and the need to implement the achievements of the scientific and technical process on timely basis in ensuring the passenger transport safety, the importance of these factors has significantly increased and is becoming apparent during one service life of buses. A comprehensive indicator for assessing the impact of environmental activity on the bus life is the efficiency preservation factor (EPF). Therefore, the development of methods and mathematical models that reliably determine and predict the value of the EPF of buses for different operating conditions is a pressing scientific and technical problem, and its solution is demanded by practice. The article presents a model for assessing the EPF of buses, which allows solving problems according to several relevant efficiency criteria, namely, reliability, structural and environmental safety, operating costs.

Time Evolutions of Water Drops Impacting on a Rotating Disk

2011 ◽  
Vol 354-355 ◽  
pp. 609-614
Author(s):  
Jing Yin Li ◽  
Xiao Fang Yuan ◽  
Qiang Han
Keyword(s):  
High Speed ◽  
Water Drop ◽  
Experimental Studies ◽  
Rotating Disk ◽  
Deposition Process ◽  
Video Camera ◽  
Rossby Number ◽  
High Speed Video Camera ◽  
Water Drops ◽  
The Impact

Experimental studies of a water drop impinging on a rotating disk using a high-speed video camera have been performed. The photos of the impact were analyzed in detail. Three kinds of the deposition patterns were observed with the variation in Rossby number. It is found that Rossby number plays an important role in the deposition process of the drop impacting on the rotating disk, leading to some new stages not observed for drop impact on a stationary plate.

A theoretical study on drop impact sound and rain noise

1991 ◽  
Vol 227 ◽  
pp. 345-355 ◽  
Author(s):  
Y. P. Guo ◽  
J. E. Ffowcs Williams
Keyword(s):  
Wave Packet ◽  
Water Surface ◽  
Theoretical Study ◽  
Water Drop ◽  
Pressure Fluctuations ◽  
Acoustic Energy ◽  
Sound Waves ◽  
Momentum Exchange ◽  
Drop Impacts ◽  
The Impact

This paper examines the sound waves generated when a spherical water drop impacts upon an initially quiescent water surface. The pressure fluctuations and the acoustic energy radiated by the initial impact are calculated analytically. It is shown that the rapid momentum exchange between the fluid in the falling drop and that in the main water body causes the radiation of compressive waves. These waves are radiated in the form of a wave packet with a densely packed edge which is heard in the far field as a noisy shock-like pulse followed by a quickly decreasing tail. The wave packet carries with it sound energy proportional to the kinetic energy of the falling drop and to the cube of the impact Mach number. Applications of these analytic results to the study of noise from natural rain are discussed, and an illustrative example is given where the noise level due to rain showers is linearly related to the rainfall rate, which is shown to be consistent with observations.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Truck Tire Operating Temperatures on Flat and Curved Test Surfaces

2005 ◽  
Vol 33 (3) ◽  
pp. 156-178 ◽  
Author(s):  
T. J. LaClair ◽  
C. Zarak
Keyword(s):  
Flat Surface ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Load Pressure ◽  
Truck Tire ◽  
Endurance Testing ◽  
Operating Temperatures ◽  
The Impact ◽  
Tread Rubber ◽  
Cylindrical Test

Abstract Operating temperature is critical to the endurance life of a tire. Fundamental differences between operations of a tire on a flat surface, as experienced in normal highway use, and on a cylindrical test drum may result in a substantially higher tire temperature in the latter case. Nonetheless, cylindrical road wheels are widely used in the industry for tire endurance testing. This paper discusses the important effects of surface curvature on truck tire endurance testing and highlights the impact that curvature has on tire operating temperature. Temperature measurements made during testing on flat and curved surfaces under a range of load, pressure and speed conditions are presented. New tires and re-treaded tires of the same casing construction were evaluated to determine the effect that the tread rubber and pattern have on operating temperatures on the flat and curved test surfaces. The results of this study are used to suggest conditions on a road wheel that provide highway-equivalent operating conditions for truck tire endurance testing.

A NEW WELDING MATERIAL FOR REGENERATION IN THE WELDING TECHNOLOGY BASED ON NICKEL. ANALYSIS OF THE COMPOSITION AND PROPERTIES OF DEFORMABLE HEAT-RESISTANT HIGH-CHROMIUM NICKEL-BASED ALLOYS FOR WELDED PARTS. ANALYSIS OF EXISTING FUELLING STATIONS TYPES AND VEHICLES USING HYDROGEN, HYDROGEN PRODUCTION AND STORING METHODS

2019 ◽  
pp. 43-48
Author(s):  
Ben Nengjun ◽  
Zhou Pengfei ◽  
Oleksandr Labartkava ◽  
Mykhailo Samokhin
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Nickel Alloys ◽  
Total Content ◽  
Operating Conditions ◽  
High Temperature Strength ◽  
High Chromium ◽  
Salt Corrosion ◽  
Tcp Phases ◽  
The Impact

This work involves an analysis of high-chromium high-temperature deformable wieldable nickel alloys for use in GTE repair assemblies. It is shown that the alloys EP868 (VZh98) and Haynes 230 can be used in welded assemblies with an operating temperature of 800-1100 °C. The alloys Nimonic 81, Nimonic 91, IN 935, IN 939, and Nicrotan 2100 GT also have a high potential for use in welded assemblies. They are characterized by a combination of good weldability, high-temperature strength, and resistance to scaling. There have been conducted studies on high-temperature salt corrosion of model nickel alloys. They allowed establishing the patterns of the impact of base metal alloying with chromium, aluminum, titanium, cobalt, tungsten, molybdenum, niobium, tantalum and rare earth metals on the critical temperature of the start of salt corrosion Tcor and the alloy mass loss. It has been established that alloys with a moderate concentration (13-16%) of chromium can possess satisfactory hightemperature corrosion resistance (HTC resistance) under the operating conditions of ship GTE. The HTC resistance of CrAl-Ti alloys improves upon reaching the ratio Ti/Al ˃ 1. Meanwhile, the ratio Ti/Al ˂ 1 promotes the formation of corrosion products with low protective properties. The positive effect of tantalum on the HTC resistance of alloys is manifested at higher test temperatures than that of titanium, and the total content of molybdenum and tungsten in alloys is limited by the condition 8Mo2 – 2W2 = 89. The presence of refractory elements stabilizes the strengthening phase and prevents formation of the ɳ-phase. However, their excess promotes formation of the embrittling topologically close packed (TCP) phases and boundary carbides of an unfavorable morphology. Based on the studies of the HTC resistance, there has been identified a class of model high-temperature corrosionresistant nickel alloys with a moderate or high chromium content (30%), Ti/Al ˃ 1, and a balanced content of refractory and rare-earth elements.

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