Increasing Inducer Stability and Suction Performance With a Stability Control Device

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Leading Edge ◽  
High Energy ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Blade Tip ◽  
Rotordynamic Forces ◽  
Suction Performance

An inducer is used as the first stage of high suction performance pump. It pressurizes the fluid to delay the onset of cavitation, which can adversely affect performance in a centrifugal pump. In this paper, the performance of a water pump inducer has been explored with and without the implementation of a stability control device (SCD). This device is an inlet cover bleed system that removes high-energy fluid near the blade leading edge and reinjects it back upstream. The research was conducted by running multiphase, time-accurate computational fluid dynamic (CFD) simulations at the design flow coefficient and at low, off-design flow coefficients. The suction performance and stability for the same inducer with and without the implementation of the SCD has been explored. An improvement in stability and suction performance was observed when the SCD was implemented. Without the SCD, the inducer developed backflow at the blade tip, which led to rotating cavitation and larger rotordynamic forces. With the SCD, no significant cavitation instabilities developed, and the rotordynamic forces remained small. The lack of cavitation instabilities also allowed the inducer to operate at lower inlet pressures, increasing the suction performance of the inducer.

Influence of a Stability Control Device on the Performance of a Cavitating Water Pump Inducer

2014 ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Stable Operation ◽  
Dynamic Simulations ◽  
The Stability ◽  
Rotordynamic Forces

An inducer performance has been explored with and without the implementation of a stability control device. Multiphase, time-accurate computational fluid dynamic simulations have been conducted at the design flow coefficient and at two low off-design flow coefficients. At the design flow coefficient, the inducer performance was similar with and without the stability control device. At low flow coefficients, the inducer without the stability control device exhibited significant cavitation instabilities, which led to high rotordynamic forces on the inducer blades. When the stability control device was incorporated into the inducer design, nearly all of the cavitation instabilities were suppressed at low flow coefficients and the rotordynamic forces were reduced by more than an order of magnitude. Stable operation at flow coefficients far below the design value leads to a significant increase in the suction performance of the inducer, allowing pumps to operate at lower inlet pressures.

Suppression of Cavitation in Inducers by J-Grooves

2006 ◽  
Vol 129 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Young-Do Choi ◽  
Junichi Kurokawa ◽  
Hiroshi Imamura
Keyword(s):  
High Speed ◽  
Leading Edge ◽  
Design Flow ◽  
Low Flow ◽  
Axial Pressure ◽  
Flow Rates ◽  
New Device ◽  
Axial Pressure Gradient ◽  
Blade Tip ◽  
Suction Performance

Cavitation is a serious problem in the development of high-speed turbopumps, and an inducer is often used to avoid cavitation in the main impeller. Thus, the inducer often operates under the worst conditions of cavitation. If it could be possible to control and suppress cavitation in the inducer by some new device, it would also be possible to suppress cavitation occurring in all types of pumps. The purpose of our present study is to develop a new, effective method of controlling and suppressing cavitation in an inducer using shallow grooves, called “J-Grooves.” J-Grooves are installed on the casing wall near the blade tip to use the high axial pressure gradient that exists between the region just downstream of the inducer leading edge and the region immediately upstream of the inducer. The results show that the proper combination of backward-swept inducer with J-Grooves improves the suction performance of the turbopump remarkably, at both partial flow rates and the design flow rate. The rotating backflow cavitation occurring at low flow rates and the cavitation surge which occurs near the best efficiency point can be almost fully suppressed by installing J-Grooves.

Steady and Transient Computations of Interaction Effects in a Centrifugal Compressor With Different Types of Diffusers

2010 ◽  
Author(s):  
S. Anish ◽  
N. Sitaram
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Leading Edge ◽  
Design Flow ◽  
Flow Coefficient ◽  
Pressure Recovery ◽  
Maximum Efficiency ◽  
Vaned Diffuser ◽  
Lower Flow ◽  
Transient Simulations

A computational study has been conducted to analyze the performance of a centrifugal compressor under various levels of impeller-diffuser interactions. The study has been conducted using a low solidity vaned diffuser (LSVD), a conventional vaned diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using Reynolds-Averaged Navier-Stokes simulations. A commercial software ANSYS CFX is used for this purpose. The intensity of interaction is varied by keeping the diffuser vane leading edge at three different radial locations. Frozen rotor and transient simulations are carried out at four different flow coefficients. At design flow coefficient maximum efficiency occurs when the leading edge is at R3 (ratio of radius of the diffuser leading edge to the impeller tip radius) = 1.10. At lower flow coefficient higher stage efficiency occurs when the diffuser vanes are kept at R3 = 1.15 and at higher flow coefficient R3 = 1.05 gives better efficiency. It is observed that at lower flow coefficients positive incidence causes separation of flow at the suction side of the diffuser vane. When the flow rate is above design point there is a negative incidence at the leading edge of the diffuser vane which causes separation of flow from the pressure side of the diffuser vane. Compressor stage performance as well as performance of individual components is calculated at different time steps. Large variations in the stage performances at off-design flow coefficients are observed. The static pressure recovery coefficient (Cp) value is found to be varying with the relative position of impeller and diffuser. It is observed that maximum Cp value occurred at time step where Ψloss value is lowest. From the transient simulations it has been found that the strength and location of impeller exit wake affect the diffuser vane loading which in turn influences the diffuser static pressure recovery.

Wake–Boundary Layer Interactions in an Axial Flow Turbine Rotor at Off-Design Conditions

1989 ◽  
Vol 111 (2) ◽  
pp. 181-192 ◽  
Author(s):  
H. P. Hodson ◽  
J. S. Addison
Keyword(s):  
Rotor Blade ◽  
Axial Flow ◽  
Leading Edge ◽  
Surface Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Experimental Investigations ◽  
Pressure Side ◽  
Suction Surface ◽  
Edge Separation

A series of experimental investigations has been undertaken in a single-stage low-speed turbine. The measurements involved rotor blade surface flow visualization, surface-mounted hot-film anemometry, and exit pitot traverses. The effects of varying the flow coefficient and Reynolds number upon the performance of the rotor blade at midspan are described. At the design flow coefficient (φ = 0.495), the rotor pressure surface flow may be regarded as laminar, while on the suction surface, laminar flow gives way to unsteady stator wake-induced transition and then to turbulent flow. Over the range of Reynolds numbers investigated (1.8×105–3.3×105), the rotor midspan performance is dominated by the suction surface transition process; suction surface separation is prevented and the rotor midspan loss coefficient remains approximately constant throughout the range. At positive incidence, suction surface leading edge separation and transition are caused by a velocity overspeed. Reattachment occurs as the flow begins to accelerate toward the throat. The loss associated with the separation becomes significant with increasing incidence. At negative incidence, a velocity overspeed causes leading edge separation of the pressure side boundary layers. Reattachment generally occurs without full transition. The suction surface flow is virtually unaffected. Therefore, the rotor midspan profile loss remains unchanged from the zero incidence value until pressure side stall occurs.

Influence of Surface Roughness on Three-Dimensional Separation in Axial Compressors

2004 ◽  
Vol 126 (4) ◽  
pp. 455-463 ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Tom P. Hynes ◽  
Nicholas A. Cumpsty
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Major Effect ◽  
Surface Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Suction Surface

Surface roughness on a stator blade was found to have a major effect on the three-dimensional (3D) separation at the hub of a single-stage low-speed axial compressor. The change in the separation with roughness worsened performance of the stage. A preliminary study was carried out to ascertain which part of the stator suction surface and at what operating condition the flow is most sensitive to roughness. The results show that stage performance is extremely sensitive to surface roughness around the leading edge and peak-suction regions, particularly for flow rates corresponding to design and lower values. Surface flow visualization and exit loss measurements show that the size of the separation, in terms of spanwise and chordwise extent, is increased with roughness present. Roughness produced the large 3D separation at design flow coefficient that is found for smooth blades nearer to stall. A simple model to simulate the effect of roughness was developed and, when included in a 3D Navier–Stokes calculation method, was shown to give good qualitative agreement with measurements.

A Shape Memory Alloy-Based Morphing Axial Fan Blade: Functional Characterization and Fluid Dynamic Performance

2016 ◽  
Author(s):  
Alessio Suman ◽  
Annalisa Fortini ◽  
Nicola Aldi ◽  
Mattia Merlin ◽  
Michele Pinelli
Keyword(s):  
Control System ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Fluid Dynamic ◽  
High Energy ◽  
Time Range ◽  
Axial Fan ◽  
Polymeric Compound ◽  
Intended Application ◽  
Blade Tip

In a traditional automotive cooling system, energy optimization could be achieved by controlling the engine temperature by means of several sensors placed inside the cooling circuit. Nevertheless, in some cases the increasing use of a great number of sensor devices makes the control system too bulky, expensive and not sufficiently robust for the intended application. This paper presents the development of a heavy-duty automotive cooling axial fan with morphing blades activated by Shape Memory Alloy (SMA) strips that work as actuator elements in the polymeric blade structure. The application of smart materials to compact, high-energy density devices as well as the development of modeling and control systems has been of great interest during the last decade. SMAs are frequently combined within monolithic or composite host materials to produce adaptive structures whose properties could be tuned in response to external stimuli. The blade was designed to achieve the activation of the strips (purposely thermo-mechanically treated) by means of an air stream flow. With the aim of studying the morphing capability of the adaptive structure together with the recovery behavior of the NiTi strips, four different polymeric compounds have been compared in a specifically-designed wind tunnel. Digital image analysis techniques have been performed to quantitatively analyze the blade deflections and to evaluate the most suitable polymeric matrix for the intended application. As the airstream flow increases in temperature, the strips recover the memorized bent shape, leading to a camber variation. To study the possibility of employing SMA strips as actuator elements, a comparison with common viscous clutch behavior is proposed. The time range actuator response indicates that the SMA strips provide a lower frequency control that fits well with the engine coolant thermal requirement. The experimental results demonstrate the capability of SMA materials to accommodate the lower power actuators in the automotive field. Finally, the blade tip airfoils, reconstructed using a CAD procedure, were used to study the fluid dynamic behavior of the blade tip airfoil. A CFD numerical simulation was carried out in order to highlight the differences in the airfoil performance due to the different shapes of the blade. The analyses showed that the activated blade tip airfoil led to an increase in the lift coefficient according to the stiffness provided by the polymeric compound. This innovative passive control system results from the selection of (i) the memorized shape of the SMA strips and (ii) the polymeric compound used for the blade structure.

Influence of Surface Roughness on Three-Dimensional Separation in Axial Compressors

2004 ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Tom P. Hynes ◽  
Nicholas A. Cumpsty
Keyword(s):  
Surface Roughness ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Leading Edge ◽  
Major Effect ◽  
Surface Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Suction Surface

Surface roughness on a stator blade was found to have a major effect on the three-dimensional (3D) separation at the hub of a single-stage low-speed axial compressor. The change in the separation with roughness worsened performance of the stage. A preliminary study was carried out to ascertain which part of the stator suction surface and at what operating condition the flow is most sensitive to roughness. The results show that stage performance is extremely sensitive to surface roughness around the leading edge and peak-suction regions, particularly for flow rates corresponding to design and lower values. Surface flow visualization and exit loss measurements show that the size of the separation, in terms of spanwise and chordwise extent, is increased with roughness present. Roughness produced the large 3D separation at design flow coefficient that is found for smooth blades nearer to stall. A simple model to simulate the effect of roughness was developed and, when included in a 3D Navier-Stokes calculation method, was shown to give good qualitative agreement with measurements.

Over Rotor Casing Surface Streak Measurements in a High Speed Axial Compressor

2007 ◽  
Author(s):  
Matthew A. Bennington ◽  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Charles P. Gendrich
Keyword(s):  
Shear Stress ◽  
High Speed ◽  
Reverse Flow ◽  
Leading Edge ◽  
Ccd Camera ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Substantial Impact ◽  
Axial Shear ◽  
Blade Tip

Time averaged wall shear stress patterns were recorded during quasi-steady throttling to stall in a high speed compressor. The technique utilized a CCD camera to capture digital images of oil streaks on a transparent casing section located over the rotor. The most notable feature of the surface streaking was a bifurcation line of zero time average axial shear stress. The location of this feature was found to represent the location where the approach fluid and the reverse flow from the tip gap meet and separate from the casing surface. The location of this line with respect to the rotor leading edge was denoted as xzs. The values of xzs were found to be positive (downstream of the leading edge) at high flow coefficients, and moved upstream as the compressor mass flow was reduced. Compressor stall was observed to occur when xzs was negative, with magnitude of order 6% of the axial blade tip chord. In other words, the zero axial shear line crossed the leading edge plane at a flow coefficient slightly higher than the stall point. The present paper describes the location of xzs as a function of both the flow coefficient and the local blade tip clearance. Both of these independent variables were found to have a substantial impact on the endwall flow near the leading edge, with little variation downstream. A simplified model was used to better understand the flow mechanisms associated with changes in xzs. An interpretation of these results will be given in terms of experimental and computational efforts related to blade tip flows that are described in the recent literature.

Fan Performance Scaling With Inlet Distortions

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
J. J. Defoe ◽  
M. Etemadi ◽  
D. K. Hall
Keyword(s):  
Design Flow ◽  
Flow Coefficient ◽  
Axial Fan ◽  
Fan Performance ◽  
Physical Mechanisms ◽  
Viscous Losses ◽  
Performance Scaling ◽  
Large Distortion ◽  
Stator Blade ◽  
Primary Focus

Applications such as boundary-layer-ingesting (BLI) fans and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. The objectives are to (1) identify the physical mechanisms which govern the fan response to inflow distortions and (2) determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The model does not include viscous losses so that changes in diffusion factor are the primary focus. Distortions in stagnation pressure and temperature as well as swirl are considered. The key findings are that unless sharp pitchwise gradients in the diffusion response, strong radial flows, or very large distortion magnitudes are present, the response of the blade rows for strong distortions can be predicted by scaling up the response to a weaker distortion. In addition, the response to distortions which are composed of nonuniformities in several inlet quantities can be predicted by summing up the responses to the constituent distortions.

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