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Ahti Jaatinen - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of the Effect of the Tip Clearance To the Diffuser Flow Field and Stage Performance of a Centrifugal Compressor
Proceedings of the Asme Turbo Expo 2012 Vol 8 Pts a-C, 2012Co-Authors: Ahti Jaatinen, Aki-pekka Grönman, Teemu Turunen-saaresti, Pekka Röyttä, Jari L. H. BackmanAbstract:The effect of tip Clearance to the centrifugal compressor diffuser flow\nfields and stage overall performance are studied experimentally. The\nrelative tip Clearance (tip Clearance divided by the impeller exit blade\nheight) is increased by shimming the shroud side casing of a high-speed\nvariable speed driven industrial centrifugal compressor Four different\nrelative tip Clearances are studied: 0.027, 0.053, 0.082, and 0.106. The\nstage efficiency and pressure ratios are measured, as well as the\ndiffuser flow fields. The diffuser flow fields are measured both at the\ndiffuser inlet and outlet. The total pressure and flow angle are\nmeasured with a cobra probe, and the total pressure and temperature with\nthree Kiel probes. Static pressures are measured adjacent to the probe\nmeasurements. As expected, increasing the tip Clearance leads to lower\nstage efficiency and pressure ratios. The decrement in the efficiency\ndue to the increasing of the tip Clearance is higher with higher mass\nflows, and at lower rotational speeds. Increasing tip Clearance\nincrecises the size of the secondary flow region present at the impeller\noutlet near the shroud.
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Influence of the Different Design Parameters to the Centrifugal Compressor Tip Clearance Loss
Journal of Turbomachinery, 2012Co-Authors: Teemu Turunen-saaresti, Ahti JaatinenAbstract:In this paper the effect of the tip Clearance was studied with six\ndifferent centrifugal compressors and data available in literature. The\nchanges in the overall performance of the compressor stage were\nexamined. The aim was to study the influence of the different design\nparameters to the tip Clearance loss. It was evident by the previous\nstudies that the sensitivity of the centrifugal compressor to the tip\nClearance loss varies with different designs. However, for the designer\nit is important to know the effect of the tip Clearance loss in order to\ninitially evaluate the quality of different designs. Analysis of the\ndata demonstrated that no clear correlation between the sensitivity of\nthe tip Clearance loss and the specific speed, the diffusion ratio, the\nblade number and the ratio of blade heights exists.
Teemu Turunen-saaresti - One of the best experts on this subject based on the ideXlab platform.
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Numerical investigation of centrifugal compressor tip Clearance
Proceedings of the ASME Turbo Expo, 2015Co-Authors: Ahti Jaatinen-värri, Aki-pekka Grönman, Jari L. H. Backman, Teemu Turunen-saaresti, Jonna TiainenAbstract:Copyright © 2015 by ASME. In this paper, the effect of the axial tip Clearance on the performance and flow fields of a centrifugal compressor is studied numerically. The compressor is equipped with a pinched vaneless diffuser. Six different axial Clearances were modelled and the relative axial tip Clearance was varied from 0.027 to 0.154. The tip Clearance was changed by transferring the shroud in the axial direction. The modelled results are compared to measured results obtained in previous projects. The results indicate that the effect of tip Clearance to the impeller performance is linear, even though the Clearance is increased to such amounts which are seldom used in traditional compressors. The Clearance has significant effect on the flow fields. Even though the mass flow averaged tangential velocity remained constant with the increasing Clearance, the velocity fields show increase in tangential velocity in the passage wake between the suction side of the splitter blade and pressure side of the full blade and decreased in the other blade passage with increasing Clearance. Radial velocity contours showed that the backflow region near the shroud increased in size when the Clearance is increased. The growth was stronger on the suction side of the splitter blade. Even though there is quite a difference in the stage efficiency between the highest and lowest Clearance, the difference in velocity triangles at the impeller exit is small. This should be taken into a consideration when compressors with high relative axial tip Clearances are designed.
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Experimental Study of the Effect of the Tip Clearance To the Diffuser Flow Field and Stage Performance of a Centrifugal Compressor
Proceedings of the Asme Turbo Expo 2012 Vol 8 Pts a-C, 2012Co-Authors: Ahti Jaatinen, Aki-pekka Grönman, Teemu Turunen-saaresti, Pekka Röyttä, Jari L. H. BackmanAbstract:The effect of tip Clearance to the centrifugal compressor diffuser flow\nfields and stage overall performance are studied experimentally. The\nrelative tip Clearance (tip Clearance divided by the impeller exit blade\nheight) is increased by shimming the shroud side casing of a high-speed\nvariable speed driven industrial centrifugal compressor Four different\nrelative tip Clearances are studied: 0.027, 0.053, 0.082, and 0.106. The\nstage efficiency and pressure ratios are measured, as well as the\ndiffuser flow fields. The diffuser flow fields are measured both at the\ndiffuser inlet and outlet. The total pressure and flow angle are\nmeasured with a cobra probe, and the total pressure and temperature with\nthree Kiel probes. Static pressures are measured adjacent to the probe\nmeasurements. As expected, increasing the tip Clearance leads to lower\nstage efficiency and pressure ratios. The decrement in the efficiency\ndue to the increasing of the tip Clearance is higher with higher mass\nflows, and at lower rotational speeds. Increasing tip Clearance\nincrecises the size of the secondary flow region present at the impeller\noutlet near the shroud.
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Influence of the Different Design Parameters to the Centrifugal Compressor Tip Clearance Loss
Journal of Turbomachinery, 2012Co-Authors: Teemu Turunen-saaresti, Ahti JaatinenAbstract:In this paper the effect of the tip Clearance was studied with six\ndifferent centrifugal compressors and data available in literature. The\nchanges in the overall performance of the compressor stage were\nexamined. The aim was to study the influence of the different design\nparameters to the tip Clearance loss. It was evident by the previous\nstudies that the sensitivity of the centrifugal compressor to the tip\nClearance loss varies with different designs. However, for the designer\nit is important to know the effect of the tip Clearance loss in order to\ninitially evaluate the quality of different designs. Analysis of the\ndata demonstrated that no clear correlation between the sensitivity of\nthe tip Clearance loss and the specific speed, the diffusion ratio, the\nblade number and the ratio of blade heights exists.
Hao Duan - One of the best experts on this subject based on the ideXlab platform.
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unsteady leakage flow through axial Clearance of an orc scroll expander
Energy Procedia, 2017Co-Authors: Panpan Song, Wei Lin Zhuge, Yangjun Zhang, Lei Zhang, Hao DuanAbstract:Abstract As the scroll-type expander (STE) becomes an attractive expansion device for small-scale organic Rankine systems, performance enhancement of STE could achieve a further improvement of the energy efficiency of ORC system. The gas leakages through the axial and radial Clearances have a great effect on the overall performance of STE. The present work proposed a three-dimensional numerical technique available for modeling the radial leakage flows through the axial Clearances at the tip and root of scroll wrap. The radial leakage flow patterns of both axial Clearances are investigated. Asymmetrical distribution of the radial leakage flow through the axial Clearances at both sides of working chambers are revealed. Leakage flow difference between the top and bottom axial leakage Clearances is comparatively discussed. The effects of radial leakage on the flow fields in the working chambers are also analyzed. The results show the radial leakage flows occur at the axial Clearances of both the scroll segments between asymmetrical working chambers and those between symmetrical working chambers. Radial leakage flows through the top and bottom axial Clearances are approximately symmetrical about the meshing line. Pressure distribution in the axial Clearance passage is uneven along the scroll involute direction, especially in the axial Clearance passages between asymmetric chambers. Pressure distortion occurs in the downstream of the axial Clearance passage between asymmetric working chambers nearby the mesh point of the scroll wraps. Radial leakage flow leads to the secondary vortex flows and non-uniform pressure distributions in the working chambers.
Sven Mansson - One of the best experts on this subject based on the ideXlab platform.
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Clearance of iohexol chromium 51 ethylenediaminetetraacetic acid and creatinine for determining the glomerular filtration rate in pigs with normal renal function comparison of different Clearance techniques
Academic Radiology, 1996Co-Authors: Bo Frennby, Gunnar Sterner, Torsten Almen, Chunming Chai, Boanders Jonsson, Sven ManssonAbstract:RATIONALE AND OBJECTIVES: We wanted to improve determination of the glomerular filtration rate (GFR) with plasma Clearance techniques because the alternative-renal Clearance techniques-may involve inaccurate urine sampling or risk of urinary tract infection when bladder catheterization becomes necessary. Therefore, we compared the renal and plasma Clearances of iohexol and chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), as well as endogenous creatinine Clearance, in 19 normal pigs using different techniques. METHODS: After an intravenous bolus injection of the GFR markers, 16 plasma samples were used to plot the marker concentrations versus time for 4.5 hr. Urine was collected during nine 30-min periods. Plasma Clearance was calculated by dividing the dose of marker with the area under the plasma concentration curve (AUC) from the time of injection to infinity using one-compartment (ClAUC-slope) and three-compartment (ClAUC-3comp) models. The renal Clearance was calculated by dividing the amount of marker excreted in the urine in a period with the AUC in the same period. This AUC was determined by integrating the total area in the period (Clren adv)--our reference method representing the "true" GFR--or by using the arithmetic mean of the plasma concentrations of the marker at the beginning and end of the urine collection period (Clren simple). Creatinine Clearance was determined according to Clren simple. RESULTS: Renal Clearances of iohexol and 51Cr-EDTA were significantly higher than creatinine Clearance (P = .0002). There was no significant difference between the renal Clearances of iohexol and 51Cr-EDTA or between their plasma Clearances. The two mathematical methods of calculating the renal Clearance of iohexol were highly correlated (rs = .99), as were the two methods of calculating its plasma Clearance (rs = .95). Because of the extrarenal Clearance of the markers, the plasma Clearance methods for iohexol and 51Cr-EDTA always overestimated the true GFR. ClAUC-3comp was the method closest to the true GFR. For iohexol, the median overestimation of the GFR was higher with ClAUC-slope when early plasma samples (30-120 min) after injection of the marker were used (5.5 ml.min-1.10 kg-1) than when late samples (180-270 min) were used (4.0 ml.min-1.10 kg-1). After subtracting the median extrarenal Clearances of iohexol and 51Cr-EDTA (previously determined in nephrectomized pigs) from their plasma Clearances (ClAUC-3comp), the median overestimation of the true GFR was reduced from 2.0 to 1.1 ml.min-1.10 kg-1 with iohexol and from 2.1 to 1.3 ml.min-1.10 kg-1 with 51Cr-EDTA. CONCLUSION: GFR determination with plasma Clearance techniques can be improved in three- and one-compartment models by taking late plasma samples and by subtracting the extrarenal plasma Clearance of the species. One-compartment models can be improved by determining a correction formula in the species for the early parts of the decay curve of the plasma concentration of the marker
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extrarenal plasma Clearance of iohexol chromium 51 ethylenediaminetetraacetic acid and inulin in anephric pigs
Academic Radiology, 1996Co-Authors: Bo Frennby, Gunnar Sterner, Torsten Almen, Chunming Chai, Boanders Jonsson, Sven ManssonAbstract:Rationale and Objectives. To improve the measurement of the glomerular filtration rate (GFR), we determined the extrarenal plasma Clearance of the GFR markers iohexol, chromium-51-ethylenediaminetetraacetic acid (51Cr-EDTA), and inulin using 11 anephric pigs. Methods. After an intravenous (IV) bolus injection of the markers, the decay curves of their plasma concentrations were monitored for 29 hr by 16 plasma samples. The area under the curve (AUC; concentration of marker versus time) was calculated according to one- and three-compartment kinetics. The extrarenal Clearance was calculated by dividing the dose of marker by the AUC. Results. In the three-compartment model, the median of the extrarenal Clearances of iohexol, 51Cr-EDTA, and inulin were 0.87 ml·min−1·10 kg−1 (range = 0.62–1.26 ml·min−1·10 kg−1), 0.79 ml·min−1·10 kg−1 (range = 0.61–1.04 ml·min−1·10 kg−1), and 0.83 ml·min−1·10 kg−1 (range = 0.65–1.17 ml·min−1·10 kg−1). The extrarenal Clearance of 51Cr-EDTA was slightly lower than that of iohexol and inulin when measured with the three-compartment model (p = .015). There was no statistically significant difference between the two models of kinetics in calculating Clearance of the same marker. Conclusion. Our results indicate that subtracting the median values of the extrarenal Clearance of the markers from the total plasma Clearance will provide GFR values closer to the “true” GFR. This technique might prove useful in GFR calculations in patients with a very low GFR (e.g., residual GFR in patients on dialysis).
Ibrahim Uzmay - One of the best experts on this subject based on the ideXlab platform.
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effects of balancing and link flexibility on dynamics of a planar mechanism having joint Clearance
Scientia Iranica, 2012Co-Authors: Selcuk Erkaya, Ibrahim UzmayAbstract:Abstract An experimental study is proposed to investigate the effects of balancing and link flexibility on the dynamics of a mechanism with imperfect revolute joints, that is, joints having radial Clearance. A planar slider-crank mechanism, widely used in vehicle engines, is used in the experimental investigation. Bearing vibrations are considered to evaluate the reflection of balancing and link flexibility effects on a mechanism having two revolute joints with Clearance. On the other hand, these vibrations are measured to clarify how the balancing and link flexibility feature can decrease the undesired effects of joint Clearances. For this purpose, three accelerometers, an analyzer and a PC are used for measuring the related vibrations on the main frame. The experimental results show that joint Clearance leads to sudden changes in motion characteristics of the mechanism. During small time intervals, these sudden changes cause forces to impact in the joints of the mechanism with Clearance. This also leads to some vibration peaks, and increases the vibration amplitudes. Furthermore, the flexibility feature of the mechanism link has a crucial role in decreasing additional vibration arising from joint Clearance. Also, the undesired effects of Clearance are reduced to some degree by using the balancing.
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experimental investigation of joint Clearance effects on the dynamics of a slider crank mechanism
Multibody System Dynamics, 2010Co-Authors: Selcuk Erkaya, Ibrahim UzmayAbstract:Clearance is inevitable for assembly and mobility in the kinematic joints of mechanisms. Excessive value of this Clearance leads to poor operational characteristics, and these result in losses in kinematic and dynamic performances of mechanism. In this study, effects of joint Clearances on vibration and noise characteristics of mechanism are investigated. An experimental test rig has been set up, and a planar slider-crank mechanism having two joints with Clearance has been used as a model mechanism. Joint Clearance is modeled as a massless virtual link and continuous contact mode between journal and bearing in joint connection is considered in theoretical analyses. Three accelerometers and two microphones have been located at different points to measure the vibrations and noises on system during the mechanism motion. The results obtained for the cases with and without joint Clearance are evaluated for vibration and noise characteristics of mechanism.
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investigation on effect of joint Clearance on dynamics of four bar mechanism
Nonlinear Dynamics, 2009Co-Authors: Selcuk Erkaya, Ibrahim UzmayAbstract:As a result of design, manufacturing and assembly processes or a wear effect, Clearances are inevitable at the joints of mechanisms. In this study, dynamic response of mechanism having revolute joints with Clearance is investigated. A four-bar mechanism having two joints with Clearance is considered as a model mechanism. A neural network was used to model several characteristics of joint Clearance. Kinematic and dynamic analyses were achieved using continuous contact mode between journal and bearing. A genetic algorithm was also used to determine the appropriate values of design variables for reducing the additional vibration effect due primarily to the joint Clearance. The results show that the optimal adjusting of suitable design variables gives a certain decrease in shaking forces and their moments on the mechanism frame.
