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Artykuły w czasopismach na temat "Cobra probe"
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De Guzman, M. M., C. A. J. Fletcher i J. D. Hooper. "Computational Investigation of Cobra probe operation". International Journal of Numerical Methods for Heat & Fluid Flow 4, nr 5 (maj 1994): 425–45. http://dx.doi.org/10.1108/eum0000000004047.
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De Guzman, M. M., C. A. J. Fletcher i M. Behnia. "Gas particle flows about a Cobra probe with purging". Computers & Fluids 24, nr 2 (luty 1995): 121–34. http://dx.doi.org/10.1016/0045-7930(94)00026-u.
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Miller, E. C., M. R. L’Ecuyer i E. F. Benisek. "Flow Field Surveys at the Rotor Inlet of a Radial Inflow Turbine". Journal of Engineering for Gas Turbines and Power 110, nr 3 (1.07.1988): 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 i Roger Wells. "Considerations for Using 3-D Pneumatic Probes in High-Speed Axial Compressors". Journal of Turbomachinery 125, nr 1 (1.01.2003): 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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Harada, H. "Performance Characteristics of Shrouded and Unshrouded Impellers of a Centrifugal Compressor". Journal of Engineering for Gas Turbines and Power 107, nr 2 (1.04.1985): 528–33. http://dx.doi.org/10.1115/1.3239765.
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The overall performance of shrouded and unshrouded identical impellers of a centrifugal compressor were tested and compared. A closed loop test stand with Freon gas as the working fluid was employed for the experiments. The inlet and outlet velocity distributions of both impellers were measured using a three-hole cobra probe and a hot-film probe to determine the velocity distribution and unsteady flows due to wakes and inlet stall.
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An, Jian-xiong. "Trigeminal Neuralgia Induced by Cobra Venom in the Rat Leads to Deficits in Abilities of Spatial Learning and Memory". Pain Physician 2;18, nr 2;3 (14.03.2015): E207—E216. http://dx.doi.org/10.36076/ppj/2015.18.e207.
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Background: Patients with chronic pain usually suffer from cognitive impairment, with memory deterioration being the most common deficit that affects daily functioning and quality of life. The causes for this impairment are not clear despite intensive clinical studies. Few studies have evaluated impaired learning using animal models of persistent pain. Objective: In this study, a new trigeminal neuralgia model induced by cobra venom was adopted to explore effects of chronic pain on spatial learning and memory in rats. Study Design: Controlled animal study. Setting: Department of Anesthesiology, Pain Medicine & Critical Care Medicine, Aviation General Hospital of China Medical University. Methods: Thirty adult male Sprague-Dawley rats were randomly divided into 2 groups (n = 15): NS control group and cobra venom group, 0.9% sterile saline or cobra venom solution was injected into the sheath of the infraorbital nerve (ION), respectively. The development of trigeminal neuralgia was accessed by changes in free behavioral activity 3 days before the surgery and 3, 7, 12, 20, and 30 days after the surgery to identify whether the model was successful or not. Morris water maze test determined the abilities of spatial learning and memory at the time points before the surgery, and 2 weeks and 5 weeks after the surgery. We also observed the ultrastructure of the ION and medulla oblongata of rats following 8 weeks of chronic trigeminal neuropathic pain. Results: Rats with the cobra venom injection displayed significantly more face grooming and fewer exploratory activities compared to the NS control group or baseline (P < 0.01). Both groups improved their latency to reach the platform with the largest difference on the first day (P < 0.01), but without memory deficits in a probe trial for the second water maze protocol. For the third water maze testing, the rats in the cobra venom group experienced decreased abilities of spatial learning and memory, a longer latency with spatial memory deficits during the probe trial (P < 0.05). At the ultrastructural level, we found changes in the medulla oblongata after cobra venom injection resulting in severe demyelination and loss of axons that might be implicated in the causes of cognitive deficits. Limitations: Limitations include partial vision loss in the eye on the lesion side of the rats that might be missed and the absence of evaluating the ultrastructural changes in other parts of the brain. Conclusions: The results of this study suggest that trigeminal neuralgia induced by cobra venom in adult rats can impair spatial learning and memory function over time and results in demonstrable changes in the ultrastructure of the medulla oblongata. This new animal model may be useful for future studies on the effect of chronic pain on learning and cognition. Key words: Cognitive deficits, memory deterioration, cobra venom, trigeminal neuralgia, electron microscopy
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An, Jianxiong. "Trigeminal Neuralgia Induced by Cobra Venom Leads to Cognitive Deficits Associated with Downregulation of CREB/BDNF Pathway". Pain Physician 2, nr 20;2 (14.02.2017): 53–67. http://dx.doi.org/10.36076/ppj/2017/67.
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Background: Chronic pain often results in cognitive impairment. Our previous study showed that trigeminal neuralgia induced by cobra venom leads to spatial learning and memory deficits, although the underlying mechanism remains unclear. However, recent evidence indicates that the c-AMP-responsive element binding protein (CREB)/brain derived neurotrophic factor (BDNF) pathway plays a critical role in various etiologies of cognitive deficits. Objectives: Our aim was to explore the CREB/BDNF pathway to determine the molecular mechanisms involved in the pathogenesis of cognitive impairment caused by cobra venominduced trigeminal neuralgia. Study Design: A randomized, controlled animal study. Setting: Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University. Methods: Fifty male Sprague–Dawley rats were randomly divided into 3 groups: cobra venom group, sham group, and control group. Cobra venom or saline was injected into the sheath of the infraorbital nerve (ION), respectively. Video recordings and mechanical thresholds were used to analyze changes in behavioral activity 3 days before surgery and 4, 7, 14, 21, 28, and 56 days after surgery. Morris water maze tests were conducted at 4- and 8-week time points after surgery to evaluate spatial learning and memory. We also investigated expression changes of phosphorylated CREB (p-CREB) and BDNF in the hippocampus and prefrontal cortex (PFC) using western blotting and immunohistochemistry. Results: Cobra venom-treated rats exhibited significant changes in face grooming, as well as exploratory and resting behaviors, compared with the control group and sham group (both P < 0.001). Rats in the cobra venom group exhibited slightly impaired acquisition (P < 0.05) without memory deficits (P > 0.05) in the first water maze protocol. In the second water maze test, rats in the cobra venom group exhibited spatial learning and memory deficits, with fewer platform site crossings during the probe trial (P < 0.05). Moreover, results showed decreased p-CREB and BDNF expressions in the hippocampus and PFC in the cobra venom group, with significant differences at 9 weeks post-surgery (P < 0.05). Limitations: No signaling inhibitor or genetic manipulation was administered to further confirm upstream factors of the CREB/BDNF pathway in cognitive deficits caused by chronic trigeminal neuralgia. Conclusions: The findings suggest that cognitive impairment caused by cobra venom-induced trigeminal neuralgia is associated with downregulation of the CREB/BDNF pathway in the hippocampus and PFC. Key words: Cognitive impairment, the CREB/BDNF pathway, cobra venom, trigeminal neuralgia, hippocampus, prefrontal cortex, free behavior, Morris water maze
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Chen, J., B. S. Haynes i D. F. Fletcher. "Cobra probe measurements of mean velocities, Reynolds stresses and higher-order velocity correlations in pipe flow". Experimental Thermal and Fluid Science 21, nr 4 (maj 2000): 206–17. http://dx.doi.org/10.1016/s0894-1777(00)00004-2.
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Aripov, T. F., U. M. Beknazarov i V. G. Omel'yanenko. "An investigation of the interaction of cobra venom cytotoxins with liposomes by the fluorescent-probe method". Chemistry of Natural Compounds 22, nr 6 (listopad 1986): 703–6. http://dx.doi.org/10.1007/bf00598357.
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Li, Chun Guang, Yang Liu i John C. K. Cheung. "Wind Tunnel Test of Honeycomb in Improving Flow Quality". Advanced Materials Research 774-776 (wrzesień 2013): 275–78. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.275.
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The function of honeycomb with different length and width in improving flow quality were studied in the course of building a new small section open loop wind tunnel. Instantaneous velocities of turbulent flow in the tunnel were measured by cobra probe. The focus of this study was put on the effect of the honeycomb in attenuating the total turbulence intensity including the free-turbulence carried by the incoming flow and the turbulence generated by the square cells themselves. The change tendency of the mean wind velocity and the total turbulence characteristics in the decay area have been studied by varying the length to cell size ratio L/D, and ratio of distance between the square cells and the measuring position to cell size X/D.
Rozprawy doktorskie na temat "Cobra probe"
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Stephens, Arthur William, i arthur stephens esb ie. "Aerodynamic Cooling of Automotive Disc Brakes". RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070108.121737.
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Sufficient heat dissipation is crucial to the effective operation of friction based braking systems. Such cooling is generally provided by ensuring a sufficient supply of cooling air to the heated components, hence the aerodynamics in the region of the brake components is extremely important. The objective of the research was to develop an understanding of how aerodynamics could be used to improve the cooling of automotive disc brakes. Two separate sets of wind tunnel experiments were developed. Tests were performed on a vented disc (rotor) to measure the internal flow through the vents on a rotating vented disc under various conditions, including an isolated disc in still air, the disc in still air with the wheel on, the disc in moving air with the wheel on, and an on-road simulation using a ¼ car. On vehicle tests were also performed in a wind tunnel using a purpose built brake test rig. These tests measured the thermal performance of different brake discs under various operating parameters; including constant load braking, and cooling from high temperature under various speeds, wheels and disc types. It was found that airflow through vented rotors was significantly reduced during simulated on-road driving, compared to when measured in isolation, but not particularly affected by the vehicles speed. In the situations tested, vented discs offered a 40+% improvement in cooling over an equivalent sized solid rotors. However the research indicates that the greatest benefit of vented rotors over solid will be in vehicles where air entering the wheel cavity is limited, such as low drag vehicles. It was also found that the most significant improvements in brake thermal performance could be achieved by maximising the airflow into the region of the brake components; including increasing the open area of the wheel, and increasing the vehicle velocity. Other improvements can be achieved by using a wheel material with good conductive capability, and increasing the mass of the disc. Evidence of vortex shedding was also discovered in the airflow at the exit of an internal vented rotor, any reduction in this flow disturbance should lead to increased airflow with associated improvements in thermal performance.
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Brundin, Desirée. "An Experimental Study of the High-Lift System and Wing-Body Junction Wake Flow Interference of the NASA Common Research Model". Thesis, KTH, Optimeringslära och systemteori, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209242.
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This thesis investigates the turbulent flow in the wake of the wing-body junction of the NASA Common Research Model to further reveal its complex vortical structure and to contribute to the reference database used for Computational Fluid Dynamics validation activities. Compressible flows near two wall-boundary layers occurs not only at the wing-body junction but at every control surface of an airplane, therefore increased knowledge about this complex flow structure could potentially improve the estimates of drag performance and control surface efficiency, primarily for minimizing the environmental impact of commercial flight. The airplane model is modified by adding an inboard flap to investigate the influence from the deflection on the vorticity and velocity field. Future flap designs and settings are discussed from a performance improvement point of view, with the investigated flow influence in mind. The experimental measurements for this thesis were collected using a Cobra Probe, a dynamic multi-hole pressure probe, for Reynolds numbers close to one million based on the wing root chord. A pre-programmed three-dimensional grid was used to cover the most interesting parts of the junction flow. The facility used for the tests is a 120 cm by 80 cm indraft, subsonic wind tunnel at NASA Ames Research Center’s Fluid Mechanics Lab, which provides an on-set flow speed of around Mach 0.15, corresponding to approximately 48 m/s.Den här avhandlingen undersöker det turbulenta flödet runt övergången mellan flygplanskropp och vinge på en NASA Common Research Model för att vidare utforska den komplexa, tredimensionella strukturen av flödet och bidra till NASA’s officiella databas för jämförelser med simulerade flöden. Kompressibla flöden nära tvåväggsgränsskikt uppkommer inte bara vid övergången mellan flygplanskropp och vinge utan även vid varje kontrollyta på ett flygplan. Ökad kunskap om flödets beteende vid sådana områden kan därför bidra till en bättre uppskattning av prestanda och effektivitet av kontrollytorna och flygplanet i sin helhet, vilket kan bidra till minskad miljöpåverkan från kommersiell flygtrafik. Flygplansmodellen är modifierad genom montering av en vingklaff på den inre delen av vingen, detta för att undersöka hur olika vinklar på klaffarnas nedböjning påverkar flödets struktur och hastighetsfält. Framtida klaffdesigner och inställningar för ökad prestanda diskuteras även utifrån denna påverkan. Mätningarna i vindtunneln gjordes med en Cobra Probe, ett dynamisk tryckmätningsinstrument, speciellt designad för turbulenta och instabila flöden. Reynoldsnumren som generades av den subsoniska, indrags-vindtunneln var ungefär en miljon baserad på vingrotens längd, vilket motsvarar knappt en tiondel av normala flygförhållanden för samma flygplansmodell.
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Ng, Eton Yat-Tuen, i 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.
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Lyu, Pu-Hsien, i 呂普賢. "Cobra venom toxins binding to their potential target as probed by SPR". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/yea893.
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El, Masri Ghaleb. "Single Molecule Imaging of Membrane Proteins: A study of the CorA Transporter by Scanning Probe Microscopy". Thesis, 2009. http://hdl.handle.net/1807/18287.
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Elucidating the structure-function relationships of membrane proteins is critical for the design of therapeutic agents to treat disease and for understanding numerous cellular processes such as signal transduction and molecular or ion transport. Recent advances in the application of correlated single molecule imaging techniques have provided new insights into protein-protein and protein-membrane interactions. To demonstrate the potential of these approaches, we have used in situ atomic force microscopy and single molecule fluorescence microscopy to characterize the interactions between membrane receptors and their soluble ligands, examine the monomer-dimer equilibrium in a family of adhesion receptors, and elucidate protein-mediated membrane restructuring of a supported lipid bilayer. Building on these studies, we examined the CorA ion transporter protein. We demonstrated single molecule resolution of reconstituted CorA molecules in supported lipid bilayers using a correlated AFM-TIRF microscopy platform. This approach provided new insights into a purported mechanism of CorA activation that involved ion binding.
Książki na temat "Cobra probe"
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ill, Basu Suddhasattwa, red. Cobra in my kitchen: Stories, poems & prose pieces. New Delhi: Rupa & Co., 2005.
Znajdź pełny tekst źródłaStreszczenia konferencji na temat "Cobra probe"
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Huang, Jung-Tang, Hou-Jun Hsu, Pen-Shan Chao, Kuo-Yu Lee, Chan-Shoue Wu, Sheng-Hsiung Shih, Ming-Zhe Lin, Feng-Yue Lee i Zheng-Chang Lan. "Fabrication of a MEMS-Based Cobra Probe". W 2007 IEEE Conference on Electron Devices and Solid-State Circuits. IEEE, 2007. http://dx.doi.org/10.1109/edssc.2007.4450249.
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Coldrick, Simon, Paul Ivey i Roger Wells. "Considerations for Using 3D Pneumatic Probes in High Speed Axial Compressors". W 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 i 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". W 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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Jaatinen, Ahti, Teemu Turunen-Saaresti, Aki Grönman, Pekka Röyttä i Jari Backman. "Experimental Study of the Effect of the Tip Clearance to the Diffuser Flow Field and Stage Performance of a Centrifugal Compressor". W 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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Mallipudi, Susheela, M. Selig i K. Long. "Use of a Four Hole Cobra Pressure Probe to Determine the Unsteady Wake Characteristics of Rotating Objects". W 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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Zachos, Pavlos K., Vassilios Pachidis, Bernard Charnley i Pericles Pilidis. "Flowfield Investigation of a Compressor Cascade at High Incidence—Part 1: Pneumatic Probe Measurements". W 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., i M. Rautenberg. "Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor". W 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 i J. Lepicovsky. "On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study". W 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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Wilkes, Jason, Natalie Smith, Balaji Venkataraman, Marco Vagani i Sara Goucher. "Experimentally Measured Effectiveness of Different Shroud Swirl Brake Profiles in a Centrifugal Compressor". W ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91676.
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Abstract As centrifugal compressors are pushed to operate at higher pressures and higher power levels, destabilizing gas forces often increase the challenge of designing a stable rotordynamic system. While technical innovations like damper seals, swirl brakes, and damper bearings that help stabilize compressors are numerous, predicting the impact that these improvements will have on a specific system is somewhat of an art form. To this end, researchers are constantly improving the depth of knowledge on these features so that the impact of these improvements is well defined. In the current work, the authors experimentally measured the impact of different swirl brake/vane concepts on the flow characteristics of a centrifugal compressor shroud cavity. The eye seal configuration studied here is a tooth on rotor labyrinth eye seal. The different shroud swirl vane geometries considered consist of various castellated features, each having the intent to reduce swirl velocity in the shroud cavity prior to entering the seal. The purpose of the testing was to determine whether a significant reduction in swirl velocity entering or exiting the seal could be measured with the different anti-swirl vane profiles over a conventional shroud cavity that was tested with the same setup. The metrics that determine the effectiveness of the swirl brake were based on upstream and downstream measurements of swirl velocity using pitot-probes at different depths in the shroud cavity, and measurements of seal exit angle and velocity using a traversing cobra-probe. The test data presented herein show definitively that the different swirl brake designs, including a slotted seal, a long vane, and a short vane, have a major impact on swirl velocities relative to the conventional shroud design. The most effective at reducing swirl entering/leaving the seal is the slotted seal, while the concepts employing shroud vanes were more effective at reducing swirl in the shroud cavity.
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Kang, Jeong-Seek. "Experimental Investigation of Nozzle Vane Clocking in a 2-Stage Low Pressure Turbine". W 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.