Effects of location, shape and width of a suction slot on the water removal performance of a hollow stator blade

2017 ◽  
Vol 232 (5) ◽  
pp. 461-472 ◽  
Author(s):  
Liang Li ◽  
Xiaoming Wu ◽  
Jiandao Yang ◽  
Zhenping Feng
Keyword(s):  
Mach Number ◽  
Pressure Difference ◽  
Water Film ◽  
Experimental Tests ◽  
Water Removal ◽  
Moderate Increase ◽  
Suction Pressure ◽  
Suction Surface ◽  
Stator Blade ◽  
Suction Slot

Experimental tests were implemented on a wet steam test rig to investigate the effects of location, shape and width of a suction slot on the water removal performance of a hollow stator blade. A straight cascade with varying outlet Mach numbers and suction pressure differences was used for the tests. The inlet flow conditions were consistent with the real running condition before the last stage stator of a 1000-MW nuclear steam turbine. Results show that the flow Mach number and suction pressure difference affect the amount of water removed. A moderate increase in the suction pressure difference triggers water film vaporisation, which decreases water removal performance. The amount of water removed continuously increases, as the slot location moves from 0.24 to 0.42 times the axial chord in the suction surface. Compared with the straight slot, the step-shaped slot cannot improve the water removal performance. On the contrary, the result is poor when the Mach number is above 0.7 because additional sharp corner leads to more serious water vaporisation. A suction slot with an arc-shaped inlet significantly improves the water removal performance by eliminating water film vaporisation under the test conditions. A 0.35-mm-width suction slot is apt to allow water film across, and a 2-mm-width suction slot cannot form an effective suction pressure difference along the slot height, both leading to poor water removal performance. Meanwhile, 0.7- and 1-mm-width suction slots promote good water removal performance, but the latter is less affected by water vaporisation.

Experimental Study on Effects of Slot Hot Blowing on Secondary Water Droplet Size and Water Film Thickness

2008 ◽  
Author(s):  
Chunguo Li ◽  
Xinjun Wang ◽  
Daijing Cheng ◽  
Bi Sun
Keyword(s):  
Droplet Size ◽  
Water Droplet ◽  
Pressure Difference ◽  
Water Film ◽  
Droplet Size Distribution ◽  
Experimental Tests ◽  
Suction Side ◽  
Maximum Diameter ◽  
Water Droplets ◽  
Water Separation

The effects of the slot hot blowing of the hollow stator blades on the size of secondary water droplets and the thickness of the water film were experimentally investigated in this paper. The experiment was carried out on the turbine blade cascades in a wet air tunnel with an inlet air wetness fraction of 7.9%, an outlet air velocity of 170m/s, a slot width of 1.0mm and a slot angle of 45° to blade surface. The Malvern Droplet and Particle Size Analyser was utilized to measure the secondary water droplet size and distribution downstream of the hollow stator blades in the experimental tests. The experimental results show that the maximum diameter and Sauter mean diameter of the secondary water droplets were reduced greatly and the water droplet size distribution became narrower. The larger blowing pressure difference resulted in the smaller secondary water droplets and the narrower water droplet size distributions. In addition, the efficiency of water separation from the hollow stator blade surfaces was higher for slot on the suction side than that of the pressure side case. Another simplified experimental test was also carried out on the flat plate to investigate the effect of slot hot blowing on the thickness of the water film downstream of the slot. The conductivity probes were used to measure the thickness of the water film downstream and upstream of the blowing slot. The results show that the slot hot blowing reduced the thickness of the water film downstream of the slot, which was affected by the blowing pressure difference and temperature difference between the hot blowing air and the main airflow. In conclusion, the slot hot blowing of the hollow stator blades has reduced the size of the secondary water droplets and secondarily has evaporated a little water film on the blade surfaces. Both effects are beneficial to reduce the erosion damage to the rotor blades.

Experimental Study on Effects of Slot Hot Blowing on Secondary Water Droplet Size and Water Film Thickness

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Chunguo Li ◽  
Xinjun Wang ◽  
Daijing Cheng ◽  
Bi Sun
Keyword(s):  
Droplet Size ◽  
Water Droplet ◽  
Pressure Difference ◽  
Water Film ◽  
Droplet Size Distribution ◽  
Experimental Tests ◽  
Suction Side ◽  
Maximum Diameter ◽  
Water Droplets ◽  
Water Separation

The effects of the slot hot blowing of the hollow stator blades on the size of secondary water droplets and the thickness of the water film were experimentally investigated in this paper. The experiment was carried out on the turbine blade cascades in a wet air tunnel with an inlet air wetness fraction of 7.9%, an outlet air velocity of 170 m/s, a slot width of 1.0 mm, and a slot angle of 45 deg to blade surface. The Malvern droplet and particle size analyzer was utilized to measure the secondary water droplet size and distribution downstream of the hollow stator blades in the experimental tests. The experimental results show that the maximum diameter and Sauter mean diameter of the secondary water droplets were reduced greatly, and the water droplet size distribution became narrower. The larger blowing pressure difference resulted in the smaller secondary water droplets and the narrower water droplet size distributions. In addition, the efficiency of water separation from the hollow stator blade surfaces was higher for slot on the suction side than that of the pressure side case. Another simplified experimental test was also carried out on the flat plate to investigate the effect of slot hot blowing on the thickness of the water film downstream of the slot. The conductivity probes were used to measure the thickness of the water film downstream and upstream of the blowing slot. The results show that the slot hot blowing reduced the thickness of the water film downstream of the slot, which was affected by the blowing pressure difference and temperature difference between the hot blowing air and the main airflow. In conclusion, the slot hot blowing of the hollow stator blades has reduced the size of the secondary water droplets and secondarily has evaporated a little water film on the blade surfaces. Both effects are beneficial to reduce the erosion damage to the rotor blades.

Unsteady Numerical Simulation of Shock Systems in Vaneless Counter-Rotating Turbine

2005 ◽  
Author(s):  
Huishe Wang ◽  
Qingjun Zhao ◽  
Xiaolu Zhao ◽  
Jianzhong Xu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Nozzle Design ◽  
Suction Surface ◽  
Rotor Wake ◽  
Wake Interaction ◽  
Unsteady Numerical Simulation ◽  
Almost All

A detailed unsteady numerical simulation has been carried out to investigate the shock systems in the high pressure (HP) turbine rotor and unsteady shock-wake interaction between coupled blade rows in a 1+1/2 counter-rotating turbine (VCRT). For the VCRT HP rotor, due to the convergent-divergent nozzle design, along almost all the span, fishtail shock systems appear after the trailing edge, where the pitch averaged relative Mach number is exceeding the value of 1.4 and up to 1.5 approximately (except the both endwalls). A group of pressure waves create from the suction surface after about 60% axial chord in the VCRT HP rotor, and those waves interact with the inner-extending shock (IES). IES first impinges on the next HP rotor suction surface and its echo wave is strong enough and cannot be neglected, then the echo wave interacts with the HP rotor wake. Strongly influenced by the HP rotor wake and LP rotor, the HP rotor outer-extending shock (OES) varies periodically when moving from one LP rotor leading edge to the next. In VCRT, the relative Mach numbers in front of IES and OES are not equal, and in front of IES, the maximum relative Mach number is more than 2.0, but in front of OES, the maximum relative Mach number is less than 1.9. Moreover, behind IES and OES, the flow is supersonic. Though the shocks are intensified in VCRT, the loss resulted in by the shocks is acceptable, and the HP rotor using convergent-divergent nozzle design can obtain major benefits.

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

EXTRACTION OF MINUTE GAS BUBBLES FROM LIQUIDS FLOWING IN A SIMULATED CARDIOPULMONARY BYPASS SYSTEM BY A VENTURI-ASPIRATOR UNIT

2002 ◽  
Vol 02 (03n04) ◽  
pp. 297-312
Author(s):  
WEN-JEI YANG ◽  
AMR EID ◽  
R. ECHIGO
Keyword(s):  
Cardiopulmonary Bypass ◽  
Flow Rate ◽  
Whole Blood ◽  
Pressure Difference ◽  
Gas Bubbles ◽  
Blood Oxygenation ◽  
Straight Tube ◽  
Suction Pressure ◽  
Total Flow ◽  
Total Flow Rate

An experimental study is performed to extract minute gas bubbles from liquids flowing in a simulated cardiopulmonary bypass system using a Venturi-aspirator unit. In other words, oxygen bubbles in oxygenated blood are simulated by air bubbles in water with AP30 (about same viscosity as whole blood). This study is intended to determine the feasibility of using a Venturi aspirator unit to extract minute gas bubbles from a simulated cardiopulmonary bypass system. Testing of the Venturi-type bubble extraction is carried out using three different test sections. Two Venturis are used, and a straight tube configuration is used as a control. The two Venturis are similar, with the exception that one has a longer inlet cone which causes the entering liquid to accelerate at a slower rate. Results are obtained for effectiveness of the aspirator unit as functions of total flow rate, extraction suction, suction pressure difference, and hydraulic head. It is concluded from the study that:(i) The effectiveness of the Venturis is typically between 90 and 100 percent. It increases with an increase in suction or suction pressure difference but decreases with an increase in total flow rate.(ii) The Venturi is most suitable for extraction of minute gas bubbles, especially for use with AP30 (whole blood), which yields substantially higher effectiveness than water.(iii) It is anticipated that a Venturi-aspirator unit can be superior to other bubble separation device as the cardiopulmonary bypass system for applications in extra corporeal blood oxygenation.

scholarly journals Control of the Unsteady Flow in a Stator Blade Row Interacting With Upstream Moving Wakes

1993 ◽  
Author(s):  
T. Valkov ◽  
C. S. Tan
Keyword(s):  
Unsteady Flow ◽  
Pressure Fluctuations ◽  
Spectral Element ◽  
Navier Stokes ◽  
Suction Surface ◽  
Model Calculations ◽  
Blade Loading ◽  
Pressure Surface ◽  
Blade Row ◽  
Stator Blade

A computational approach, based on a spectral-element Navier-Stokes solver, has been applied to the study of the unsteady flow arising from wake-stator interaction. Direct, as well as turbulence-model calculations, provide insight into the mechanics of the unsteady flow and demonstrate the potential for controlling its effects. The results show that the interaction between the wakes and the stator blades produces a characteristic pattern of vortical disturbances, which have been correlated to the pressure fluctuations. Within the stator passage, the wakes migrate towards the pressure surface where they evolve into counter-rotating vortices. These vortices are the dominant source of disturbances over the pressure surface of the stator blade. Over the suction surface of the stator blade, the disturbances are due to the distortion and detachment of boundary layer fluid. They can be reduced by tailoring the blade loading or by applying non-uniform suction.

scholarly journals Suppression of the Kapitza instability in confined falling liquid films

2018 ◽  
Vol 860 ◽  
pp. 608-639 ◽  
Author(s):  
Gianluca Lavalle ◽  
Yiqin Li ◽  
Sophie Mergui ◽  
Nicolas Grenier ◽  
Georg F. Dietze
Keyword(s):  
Linear Stability ◽  
Pressure Difference ◽  
Film Surface ◽  
Water Film ◽  
Narrow Channel ◽  
Liquid Films ◽  
Interfacial Instability ◽  
Critical Conditions ◽  
Driving Mechanism ◽  
Strong Confinement

We revisit the linear stability of a falling liquid film flowing through an inclined narrow channel in interaction with a gas phase. We focus on a particular region of parameter space, small inclination and very strong confinement, where we have found the gas to strongly stabilize the film, up to the point of fully suppressing the long-wave interfacial instability attributed to Kapitza (Zh. Eksp. Teor. Fiz., vol. 18 (1), 1948, pp. 3–28). The stabilization occurs both when the gas is merely subject to an aerostatic pressure difference, i.e. when the pressure difference balances the weight of the gas column, and when it flows counter-currently. In the latter case, the degree of stabilization increases with the gas velocity. Our investigation is based on a numerical solution of the Orr–Sommerfeld temporal linear stability problem as well as stability experiments that clearly confirm the observed effect. We quantify the degree of stabilization by comparing the linear stability threshold with its passive-gas limit, and perform a parametric study, varying the relative confinement, the Reynolds number, the inclination angle and the Kapitza number. For example, we find a 30 % reduction of the cutoff wavenumber of the instability for a water film in contact with air, flowing through a channel inclined at $3^{\circ }$ and of height 2.8 times the film thickness. We also identify the critical conditions for the full suppression of the instability in terms of the governing parameters. The stabilization is caused by the strong confinement of the gas, which produces perturbations of the adverse interfacial tangential shear stress that are shifted by half a wavelength with respect to the wavy film surface. This tends to reduce flow-rate variations within the film, thus attenuating the inertia-based driving mechanism of the Kapitza instability.

Transonic Relief in Fans and Compressors

2020 ◽  
Author(s):  
Demetrios Lefas ◽  
Robert J. Miller
Keyword(s):  
Mach Number ◽  
Physical Mechanism ◽  
Strong Shock ◽  
Area Ratio ◽  
Surface Boundary ◽  
Suction Surface ◽  
Surface Boundary Layer ◽  
Will Self ◽  
Optimal Area ◽  
Transonic Fan

Abstract Every supersonic fan or compressor blade row has a streamtube, the ‘sonic streamtube’, which operates with a blade relative inlet Mach number of one. A key parameter in the design of the ‘sonic streamtube’ is the area ratio between the blade throat area and upstream passage area, Athroat/Ainlet. In this paper, it is shown that one unique value exists for this area ratio. If the area ratio differs, even slightly, from this unique value then the blade either chokes or has its suction surface boundary layer separated due to a strong shock. It is therefore surprising that in practice designers have relatively little problem designing blade sections with an inlet relative Mach number close to unity. This paper shows that this occurs due to a physical mechanism known as ‘transonic relief’. If a designer makes a mistake, and designs a blade with a ‘sonic streamtube’ which has the wrong area ratio, then ‘transonic relief’, will self-adjust the spanwise streamtube height automatically moving it towards the unique optimal area ratio, correcting for the designer’s error. Furthermore, as the blade incidence changes, the spanwise streamtube height self-adjusts, moving the area ratio towards its unique optimal value. Without ‘transonic relief’, supersonic and transonic fan and compressor design would be impossible. The paper develops a simple model which allows ‘transonic relief’ to be decoupled from other mechanisms, and to be systematically studied. The physical mechanism on which it is based is thus determined and its implications for blade design and manufacturing discussed.

Studies on Characteristic Frequency and Length Scale of Shock Induced Motion in Transonic Diffuser Using a High Order LES Approach

2015 ◽  
Author(s):  
Debasish Biswas ◽  
Tomohiko Jimbo
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Unsteady Flow ◽  
Separation Bubble ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Propulsion Systems ◽  
Shock Oscillation ◽  
Shock Location ◽  
Suction Slot

Unsteady transonic flows in diffuser have become increasingly important, because of its application in new propulsion systems. In the development of supersonic inlet, air breathing propulsion systems of aircraft and missiles, detail investigations of these types of flow behavior are very much essential. In these propulsion systems, naturally present self-sustaining oscillations, believed to be equivalent to dynamically distorted flow fields in operational inlets, were found under all operating conditions. The investigations are also relevant to pressure oscillations known to occur in ramjet inlets in response to combustor instabilities. The unsteady aspects of these flows are important because the appearance of undesirable fluctuations generally impose limitation on the inlet performance. Test results of ramjet propulsion systems have shown undesirable high amplitude pressure fluctuations caused by the combustion instability. The pressure fluctuations originated from the combustor extend forward into the inlet and interact with the diffuser flow-field. Depending on different parameters such as the diffuser geometry, the inlet/exit pressure ratio, the flow Mach number, different complicated phenomena may occur. The most important characteristics are the occurrence of shock induced separation, the length of separation region downstream of the shock location, and the oscillation of shock location as well as the oscillation of the whole downstream flow. Sajben experimentally investigated in detail the time mean and unsteady flow characteristics of supercritical transonic diffuser as a function of flow Mach number upstream the shock location and diffuser length. The flows exhibited features similar to those in supersonic inlets of air-breathing propulsion systems of aircraft. A High-order LES turbulence model developed by the author is assessed with experimental data of Sajben on the self-excited shock oscillation phenomena. The whole diffuser model configuration including the suction slot located at certain axial location around the bottom and side walls to remove boundary layer, are included in the present computation model. The time-mean and unsteady flow characteristics in this transonic diffuser as a function of flow Mach number and diffuser length are investigated in detail. The results of study showed that in the case of shock-induced separation flow, the length and thickness of the reverse flow region of the separation-bubble change, as the shock passed through its cycle. The instabilities in the separated layer, the shock /boundary layer interaction, the dynamics of entrainment in the separation bubble, and the interaction of the travelling pressure wave with the pressure fluctuation region caused by the step-like structure of the suction slot play very important role in the shock-oscillation frequency.

Experimental and Numerical Studies on a Curved Back Transonic Airfoil

2017 ◽  
Author(s):  
Prathapanayaka Rajeevalochanam ◽  
R. Senthil Kumaran ◽  
S. N. Agnimitra Sunkara ◽  
Nilotpole Kalita ◽  
P. P. Sharath
Keyword(s):  
Mach Number ◽  
Aerodynamic Characteristics ◽  
Turbine Stage ◽  
Numerical Studies ◽  
Drastic Increase ◽  
Stator Blade ◽  
Domain Iii ◽  
Annular Cascade ◽  
Transonic Airfoil ◽  
Airfoil Cascade

The curvature of a turbine blade airfoil downstream of the throat location significantly affects its aerodynamic performance, specifically at Mach number close to unity. In the present work, a low aspect ratio (0.64), highly curved back airfoil corresponding to stator blade ‘mean’ section of a high-pressure (HP) turbine stage is studied. The details of the blade parameters, experimental test setup, CFD solver and numerical setup are explained in the paper. Its aerodynamic characteristics are obtained numerically using a commercial CFD solver and are compared to those from experimental cascade test results. For numerical assessment, CFD simulations are carried out on three configurations viz. (i) Full turbine stage (stator and rotor) domain (ii) Isolated turbine stator row domain (iii) Stator mean section airfoil cascade domain. The loss predictions obtained through CFD are also compared against the loss estimates calculated using two loss models. The experimental cascade pressure loss across the blade row at design point Mach number 0.996 increases to 250% of that at lower Mach numbers. This drastic increase is not desirable. But the airfoil performs appreciably well in a ‘stage’ setup i.e. with downstream rotor. Therefore, the present study brings out the behaviour of the stator airfoil performance in a linear cascade, annular cascade and stage environments.

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