Academic literature on the topic 'Cobra pressure probe'
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Journal articles on the topic "Cobra pressure probe"
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Miller, E. C., M. R. L’Ecuyer, and E. F. Benisek. "Flow Field Surveys at the Rotor Inlet of a Radial Inflow Turbine." Journal of Engineering for Gas Turbines and Power 110, no. 3 (July 1, 1988): 552–61. http://dx.doi.org/10.1115/1.3240170.
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Experiments were performed using a five-port cobra probe to survey the flow field at the rotor inlet of a 110-mm-dia turbocharger radial inflow turbine wheel. The turbine housing was modified to accommodate a probe insert to position the probe tip 4.1 mm above the rotor tip while preserving the internal contour of the production turbine housing. The cobra probe was traversed axially and circumferentially to determine the rotor inlet flow properties while the turbine was operated at design flow conditions with a reduced turbine inlet temperature. Measurements were made with the probe tip in the near-nulled position to determine the local values of total pressure, static pressure, velocity, and flow angle as functions of Z and θ. Results are presented showing the distribution of the housing total pressure loss coefficient, the rotor inlet mass flux, and the rotor inlet tangential velocity. In addition, values for rotor inlet mass average properties are given.
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Coldrick, Simon, Paul Ivey, and Roger Wells. "Considerations for Using 3-D Pneumatic Probes in High-Speed Axial Compressors." Journal of Turbomachinery 125, no. 1 (January 1, 2003): 149–54. http://dx.doi.org/10.1115/1.1515334.
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This paper describes preparatory work towards three-dimensional flowfield measurements downstream of the rotor in an industrial, multistage, axial compressor, using a pneumatic pressure probe. The probe is of the steady-state four-hole cobra probe type. The design manufacture and calibration of the probe is described. CFD calculations have been undertaken in order to assess the feasibility of using such a probe in the high-speed compressor environment where space is limited. This includes effects of mounting the probe in close proximity to the downstream stator blades and whether it is necessary to adjust the calibration data to compensate for these effects.
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Sitaram, N., and J. M. Issac. "An experimental investigation of a centrifugal compressor with hub vane diffusers." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 211, no. 5 (August 1, 1997): 411–27. http://dx.doi.org/10.1243/0957650971537312.
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The present investigation reports results of experimental studies on a centrifugal compressor equipped with hub vane diffusers. The diffuser vane height ( h/b) is varied as follows: 0 (vaneless), 0.2, 0.3, 0.4 and 1 (vane). The experiments were carried out on a low specific speed centrifugal compressor with a radial tipped impeller with an inducer at the inlet. The measurements consist of determining performance characteristics, measuring static pressures on the hub and shroud and flow traverses with a precalibrated cobra probe at the diffuser exit over one passage at five flow coefficients, viz. φ = 0.23 (near surge), 0.34 (near peak pressure rise), 0.45, 0.60 and 0.75 (near maximum flow). The peak energy coefficient is maximum for the hub vane diffuser with an h/b ratio of 0.2. The hub vane diffusers have a wider operating range than the vane diffuser. At high flow coefficients, the static pressure rise is substantially low at the throat region of the vane diffuser as the incidence on to the vane leading edge is very high. The mass averaged static pressure coefficient is high in the low-volume range for the hub vane diffuser of h/b = 0.3, but in the high-volume range it is high for the vaneless diffuser.
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Zaidi, Sohail H., and Robin L. Elder. "Flow Studies using Laser Anemometry Technique in a Small Power Unit Radial Inflow Turbine." International Journal of Rotating Machinery 3, no. 2 (1997): 107–15. http://dx.doi.org/10.1155/s1023621x97000110.
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T-100 is a multipurpose small power unit developed by Sundstrand Power Systems (USA). An extensive research programme was launched for the detailed tests of the rig components including inlet protection system, Compressor stage, Combustor and the Turbine stage. Turbomachinery Group at Cranfield was involved in the study of the Turbine unit used in this programme. From the design point of view, detailed aerodynamics in these small units are of great interest especially where high velocities and narrow passages are involved. Experimental study was carried out to investigate the flow in the region between the nozzle guide vanes and the turbine rotor entry. The main concern was to find out how the nozzle guide vane flow was modified by the rotor and how the rotor flow was affected by the nozzle guide vanes. Laser measurements were taken at these positions for various flow conditions. An other area which needs considerable attention is downstream of the turbine rotor where the turning of flow and mixing process make the situation very complicated. Laser studies were undertaken in that region and to gain more confidence on laser results, a Cobra pressure probe was traversed at these stations. This paper describes various steps undertaken to obtain laser results within the machine. At the end typical laser results have been presented and discussed.
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Brown, Christopher, Timothy Crouch, David Burton, and Mark C. Thompson. "Understanding the Aerodynamic Benefits of Drafting in the Wake of Cyclists." Proceedings 49, no. 1 (June 15, 2020): 32. http://dx.doi.org/10.3390/proceedings2020049032.
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A new approach is presented to characterize the aerodynamic benefit from riding in the wake of another cyclist at different downstream locations. The method presented uses the dynamic pressure deficit in the wake of a cycling mannequin to estimate percentage drag savings. In the experiments, the time-averaged velocity behind a cycling mannequin was recorded in 1 × 0.95 m cross-planes by two four-hole pressure (Cobra) probes for four static leg positions (0°, 90°, 180°, and 270°). It was found that the wake of the cycling mannequin propagated to one side or the other as it developed downstream, depending on the strength of the two large-scale counter-rotating streamwise vortical structures shed off the hips of the mannequin. In the near wake, the complex wake dynamics resulted in an inaccurate prediction of the relative drag reduction based upon a dynamic pressure deficit. However, as the wake developed and stabilised further downstream, the dynamic pressure deficit was found to provide a reasonable estimate of the aerodynamic drag reduction of riding in the wake of the lead rider.
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Argüelles Díaz, Katia María, Jesús Manuel Fernández Oro, and Eduardo Blanco Marigorta. "Extended Angular Range of a Three-Hole Cobra Pressure Probe for Incompressible Flow." Journal of Fluids Engineering 130, no. 10 (September 4, 2008). http://dx.doi.org/10.1115/1.2969457.
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This paper analyzes the operative characteristics of a three-hole cobra type probe especially designed to attain an angular range higher than 180deg for planar turbulent flows. A new calibration and data reduction method are also introduced, discriminating three different zones inside the angular range of the calibration. This methodology improves the probe performance, extending its operative angular range from the typical ±30degto±105deg. In addition, the transmission of the uncertainty—from the pressure measurements to the flow variables—is estimated, showing reasonably low levels for the whole angular range. Furthermore, the sensibility of the probe calibration to the Reynolds number and the pitch angle is considered, and the influence of the turbulence level is outlined. Regarding these factors, the probe precision in the extended angular range is found to be similar to that of the traditional range. Finally, the probe is tested in a flow field with large variations of the incidence angle, and the results obtained with the new method are compared to those given by the traditional calibration.
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Yu, Kehui, Xuhui He, Chenzhi Cai, Lei Yan, and Yunfeng Zou. "Aerodynamic characteristics of trains on a viaduct with non-uniform cross-section under crosswinds by wind tunnel tests." Advances in Structural Engineering, January 6, 2021, 136943322098609. http://dx.doi.org/10.1177/1369433220986099.
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This paper focuses on the aerodynamic characteristics of trains on a non-uniform double-track railway bridge under crosswinds through a scaled 1:40 sectional model wind tunnel test. Pressure measurements of five cross-sections of two types of trains, one with round roof and one with blunt roof, at the upstream and downstream tracks of the bridge were conducted under crosswinds with wind attack angles between −12° and 12°. The mean wind speed and turbulence intensity profiles around the windward surface of the train in the downwind and upward directions were also measured using cobra probe to obtain the boundary layer above the bridge surface. The results show that the shapes of train and bridge, as well as the wind attack angle, affect the aerodynamic characteristic of the train on the non-uniform bridge girder. The mean and fluctuating pressure coefficients are similar for all five cross-sections of the trains while the train is at the upstream track. However, when the train is at the downstream track, the extreme mean and fluctuating pressure coefficients around the windward and top surfaces of each cross-section on the train are different. At the downstream track, the mean wind speed profile and the turbulence intensity profile around the top of the train vary dramatically due to the separation flow caused by the leading edge of the bridge girder.
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Schölch, M., and S. Wilke. "Verfahren zur Bestimmung von Strömungsrichtung, statischem Druck und Gesamtdruck mit einer Kobrasonde / Method for determining static and dynamic pressure and the direction of velocity vector with a cobra probe." tm - Technisches Messen 58, JG (January 1991). http://dx.doi.org/10.1524/teme.1991.58.jg.287.
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Shahabuddin, M. "Single-Phase Flow Analysis: An Attempt to Mitigate Particle Deposition on the Glass Window of a Fluidized Bed Solar Receiver." Journal of Solar Energy Engineering 138, no. 4 (April 19, 2016). http://dx.doi.org/10.1115/1.4033068.
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The problem of particle deposition on the glass window of a solar receiver has restricted its continuous operation by reducing solar radiation transmission. A rigorous attempt has been made in this analysis by exploring the understanding of particle deposition mechanisms and their mitigating strategies. A simplified form of a fluidized bed solar receiver (FBSR) having the same flow phenomena of FBSR is chosen for the numerical analysis. In the numerical analysis, the turbulent flow in the receiver is investigated by renormalized group (RNG) theory based k–ε models. The validation of the numerical model is carried out by measuring the turbulent flow properties using a turbulent flow instrumentation (TFI) Cobra probe. The results of this analysis revealed that mass flow into the secondary concentrator of the receiver was reduced significantly when the ratio between the outlets and inlet areas was 0.5, and the ratio between the aperture and receiver diameter was 0.41. When using window shielding jets, only 5% of the inlet mass as a window jet was sufficient to prevent any particle deposition on the glass window, however, the number of jets was found to be an important factor. At a constant mass flow rate, increasing the number of window shielding jets reduced the suction pressure from the core to the aperture, which helped to restrict the inlet flow in the secondary concentrator.
Dissertations / Theses on the topic "Cobra pressure probe"
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Ng, Eton Yat-Tuen, and eton_ng@hotmail com. "Vehicle engine cooling systems: assessment and improvement of wind-tunnel based evaluation methods." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2002. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080422.100014.
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The high complexity of vehicle front-end design, arising from considerations of aerodynamics, safety and styling, causes the airflow velocity profile at the radiator face to be highly distorted, leading to potentially reduced airflow volume for heat dissipation. A flow visualisation study showed that the bumper bar significantly influenced the cooling airflow, leading to three-dimensional vortices in its wake and generating an area of relatively low velocity across at least one third of the radiator core. Since repeatability and accuracy of on-road testing are prejudiced by weather conditions, wind-tunnel testing is often preferred to solve cooling airflow problems. However, there are constraints that limit the accuracy of reproducing on-road cooling performance from wind-tunnel simulations. These constraints included inability to simulate atmospheric conditions, limited tunnel test section sizes (blockage effects) and lack of ground effect simulations. The work presented in this thesis involved use of on-road and wind-tunnel tests to investigate the effects of most common constraints present in wind tunnels on accuracy of the simulations of engine cooling performance and radiator airflow profiles. To aid this investigation, an experimental technique for quantifying radiator airflow velocity distribution and an analytical model for predicting the heat dissipation rate of a radiator were developed. A four-hole dynamic pressure probe (TFI Cobra probe) was also used to document flow fields in proximity to a section of radiator core in a wind tunnel in order to investigate the effect of airflow maldistribution on radiator heat-transfer performance. In order to cope with the inability to simulate ambient temperature, the technique of Specific Dissipation (SD) was used, which had previously been shown to overcome this problem.
Conference papers on the topic "Cobra pressure probe"
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Mallipudi, Susheela, M. Selig, and K. Long. "Use of a Four Hole Cobra Pressure Probe to Determine the Unsteady Wake Characteristics of Rotating Objects." In 24th AIAA Aerodynamic Measurement Technology and Ground Testing Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2004. http://dx.doi.org/10.2514/6.2004-2299.
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Jaatinen, Ahti, Teemu Turunen-Saaresti, Aki Grönman, Pekka Röyttä, and Jari Backman. "Experimental Study of the Effect of the Tip Clearance to the Diffuser Flow Field and Stage Performance of a Centrifugal Compressor." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68445.
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The effect of tip clearance to the centrifugal compressor diffuser flow fields and stage overall performance are studied experimentally. The relative tip clearance (tip clearance divided by the impeller exit blade height) is increased by shimming the shroud side casing of a high-speed variable speed driven industrial centrifugal compressor. Four different relative tip clearances are studied: 0.027, 0.053, 0.082, and 0.106. The stage efficiency and pressure ratios are measured, as well as the diffuser flow fields. The diffuser flow fields are measured both at the diffuser inlet and outlet. The total pressure and flow angle are measured with a cobra probe, and the total pressure and temperature with three Kiel probes. Static pressures are measured adjacent to the probe measurements. As expected, increasing the tip clearance leads to lower stage efficiency and pressure ratios. The decrement in the efficiency due to the increasing of the tip clearance is higher with higher mass flows, and at lower rotational speeds. Increasing tip clearance increases the size of the secondary flow region present at the impeller outlet near the shroud.
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Coldrick, Simon, Paul Ivey, and Roger Wells. "Considerations for Using 3D Pneumatic Probes in High Speed Axial Compressors." In ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30045.
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This paper describes preparatory work towards three dimensional flowfield measurements downstream of the rotor in an industrial, multistage, axial compressor, using a pneumatic pressure probe. The probe is of the steady state four hole cobra probe type. The design manufacture and calibration of the probe is described. CFD calculations have been undertaken in order to assess the feasability of using such a probe in the high speed compressor environment where space is limited. This includes effects of mounting the probe in close proximity to the downstream stator blades and whether it is necessary to adjust the calibration data to compensate for these effects.
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Lippett, D., G. Woollatt, P. C. Ivey, P. Timmis, and B. A. Charnley. "The Design, Development and Evaluation of 3D Aerofoils for High Speed Axial Compressors: Part 1 — Test Facility, Instrumentation and Probe Traverse Mechanism." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68792.
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This paper, in two parts, reports measurements from, and simulation of, Cranfield University’s 3-stage high-speed axial compressor. Using this newly built rig, supported by European Commission, a consortium of gas-turbine companies have tested a set of conventionally stacked 2D rotor and stator blades. The results from this experiment were used to evaluate and assess the performance of several commercially available CFD codes leading to the collaborative design of an advanced three-dimensional blade set seeking, if possible, a 2% efficiency gain. The limited axial spacing between the measurement planes and the blade rows required the design of a unique seven probe assembly and traverse mechanism able to yaw and pitch the probes and to control the insertion depths. This mechanism was designed to accommodate different probes, such as cobra, fast response (pneumatic) and temperature measuring probes, and deliver area traverses between rotor and stators throughout the compressor. For probe calibration a high speed wind tunnel section was designed to accommodate this mechanism enabling calibrations for Mach numbers up to 0.78, as well as for a wide range of pitch and yaw angles values. This mechanism combined with a post processing programme incorporating a mapping technique for the relative offset of the measurement points on the probe secured very detailed results throughout the compressor. Measurements show the complex three dimensional flow structure and secondary flows associated with tip-leakage, endwall boundary layers, wake transportation and blade row interactions. The importance of a rigorous mapping procedure was particularly useful where the wake thickness was small and pressure gradients high in comparison to the probe size.
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Kang, Jeong-Seek. "Experimental Investigation of Nozzle Vane Clocking in a 2-Stage Low Pressure Turbine." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25604.
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This study presents an experimental investigation on the effects of nozzle clocking in a 2-stage low pressure turbine. The objective was to incorporate the clocking test results into a new turboshaft engine. The test turbine was manufactured with the same aero geometries between the transition duct of the turbine inlet and the exit expansion duct as that of the development engine and it was tested under the same engine representative conditions. Two miniature Cobra probes were used to measure the turbine inlet and exit flow, both circumferentially for 30° and radially over the range of 2% ∼ 98% span. Furthermore, six arc-type rakes with 54 Kiel heads were used to measure the total temperature and total pressure at the exit of the second stage. The measurements were performed for four different nozzle clocking positions. The overall efficiency was evaluated in three different ways, including mechanical and thermodynamic methods. All three methods produced identical clocking positions, in order from the best position to the worst. The overall change in the mechanical and thermodynamic efficiency as measured by probe traverse, as well as the thermodynamic efficiency measured by the rakes, were 0.69%, 0.77%, and 0.42%, respectively. The distribution of efficiency across the span showed that clocking affects the efficiency differently in radial positions and a phase shift of the best clocking position to the next adjacent clocking position was observed. The efficiency change due to clocking was found to be related to the deviations in both the time-averaged velocity and in the total pressure at the exit of the second rotor. This deviation is a result of the relative location of the wake package originating from the first nozzle with respect to the leading edge of the second nozzle.
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Zachos, Pavlos K., Vassilios Pachidis, Bernard Charnley, and Pericles Pilidis. "Flowfield Investigation of a Compressor Cascade at High Incidence—Part 1: Pneumatic Probe Measurements." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59906.
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The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade performance remains unexplored at very far off-design conditions, such as windmilling, characterised by operation under extremely low mass flows and rotational speeds which, in turn, imply highly negative incidence angle values. In this paper, the flow field generated by a 3-dimensional linear compressor cascade at a highly negative incidence angle and zero rotational speed is experimentally investigated using a pneumatic miniature cobra probe. The main objective of the study is to derive the total pressure loss through the blades at such a highly negative incidence angle. An overview of the blade geometry as well as of the experimental facility is given whereas the measurement strategy and the data acquisition technique are also presented. An uncertainty study taking into account the most significant factors affecting the quality of the results has been carried out. As shown by the measurements taken at specific positions downstream of the blades, the flowfield is dominated by highly separated flows on the pressure surface, which contribute to the increased values of the total pressure loss coefficient which seems to be weakly dependent on the inlet Mach number. The quantitative measure of the pressure losses at the extremely negative incidence angle examined can be considered to be a validation platform for correspondent numerical studies of similar flow conditions. Additionally, the experimental results obtained can be used to extend the applicability of the current pressure loss models, increasing the predictive capability of the through flow numerical approaches towards far off-design areas of component or whole engine operation.
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Kassens, I., and M. Rautenberg. "Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-086.
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In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller. The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured. Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.
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Chima, R. V., E. R. McFarland, J. R. Wood, and J. Lepicovsky. "On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0573.
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The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, side-wall interference was minimized and excellent periodicity was obtained.
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Turunen-Saaresti, Teemu, Aki-Pekka Gro¨nman, and Ahti Jaatinen. "Experimental Study of Pinch in Vaneless Diffuser of Centrifugal Compressor." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-60162.
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A centrifugal compressor is often equipped with a vaneless diffuser because the operation range of a vaneless diffuser is wider than the operation range of vaned diffuser, and the geometry of the vaneless diffuser is simple and inexpensive. The flow field after the centrifugal compressor rotor is highly complicated and the velocity is high. A moderate amount of this velocity should be recovered to the static pressure. It is important to study the flow field in the vaneless diffuser in order to achieve guidelines for design and an optimal performance. In this article, the experimental study of the pinch in the vaneless diffuser is conducted. Five different diffuser heights were used, b/b2 = 1, b/b2 = 0.903, b/b2 = 0.854, b/b2 = 0.806 and b/b2 = 0.903 (shroud). In three of the cases, the pinch was made to both walls of the diffuser, hub and shroud, and in one case, the pinch was made to the shroud wall. The total and the static pressure, the total temperature and the flow angle were measured at the diffuser inlet and outlet by using a cobra-probe, kiel-probes and flush-mounted pressure taps. In addition, the static pressure in the diffuser was measured at three different radius ratios. The overall performance, the mass flow, the pressure ratio and the isentropic efficiency of the compressor stage were also monitored. Detailed flow field measurements were carried out at the design rotational speed and at the three different mass flows (close to the surge, design and close to the choke). The isentropic efficiency and the pressure ratio of the compressor stage was increased with the pinched diffuser. The efficiency of the rotor and the diffuser was increased, whereas the efficiency of the volute/exit cone was decreased. The pinch made to the shroud wall was the most effective. The pinch made the flow angle more radial and increased the velocity at the shroud where the secondary flow (passage wake) from the rotor is present.
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Di Liberti, Jean-Luc. "Effect of the Exit System on the Performance of a Low Specific Speed Industrial Centrifugal Compressor Stage." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38570.
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A low specific speed stage was tested with two different size volutes and a return vane system. The stage was instrumented with pressure probes at various locations, including the inlet and discharge flanges, diffuser inlet, diffuser exit, and return vane inlet. Cobra probes were positioned at the diffuser inlet and the return vane inlet for the return vane configuration to measure the flow angles. High frequency transducers were installed in the diffuser. This paper presents the test results showing the effect of two different volute sizes and of the return vane system on surge margin, rotating stall onset, and overall rotor and stage performance. Rotating stall criteria are reviewed, since this stage was previously tested with a different diffuser pinch. The performance is compared with some CFD analysis.