scholarly journals A Non-Dimensional Conceptual Design Procedure for the Vaneless Volutes of Radial Inflow Turbines

1991 ◽  
Author(s):  
A. Whitfield ◽  
A. B. Mohd Noor
Keyword(s):  
Mach Number ◽  
Conceptual Design ◽  
Swirling Flow ◽  
Design Procedure ◽  
Area Ratio ◽  
Working Fluid ◽  
Flow Area ◽  
Cross Sectional ◽  
The Absolute ◽  
Inlet Conditions

The requirements for the volute of a radial inflow turbine are that it should collect the working fluid, deliver it to the turbine rotor as efficiently as possible and provide the desired rotor inlet conditions. The overall performance requirements of the turbine leads to the rotor design and the identification of the desired flow conditions at rotor inlet in terms of the magnitude and direction of the absolute Mach number, see Whitfield (1990). The volute must then be designed to ensure that the desired rotor inlet conditions are attained. A non-dimensional conceptual design procedure for a vaneless turbine volute is described. Based on a knowledge of the magnitude and direction of the absolute Mach number at rotor inlet the overall dimensions of the volute in terms of the radius ratio and flow area ratio are first established. The overall design is then developed to provide the variation of the volute centroid radius and area ratio with azimuth angle. A trapezoidal cross-sectional shape is then used to establish the outer dimensions of the volute. The non-dimensional design procedure assumes a one-dimensional compressible flow and as such relies on the empirical specification of the dissipation of angular momentum, the dissipation of energy, and the deviation of the swirling flow from that of a free vortex. The effect of the uncertainties associated with the empirical data on the volute design geometry is assessed.

Design and Performance of Vaneless Volutes for Radial Inflow Turbines: Part 1: Non-Dimensional Conceptual Design Considerations

1994 ◽  
Vol 208 (3) ◽  
pp. 199-211 ◽  
Author(s):  
A Whitfield ◽  
A B Mohd Noor
Keyword(s):  
Mach Number ◽  
Swirling Flow ◽  
Flow Direction ◽  
Experimental Studies ◽  
Design Procedure ◽  
Area Ratio ◽  
Working Fluid ◽  
One Dimensional ◽  
The Absolute ◽  
Inlet Conditions

The requirements for the volute of a radial inflow turbine are that it should collect the working fluid, deliver it to the turbine rotor as efficiently as possible and provide the desired rotor inlet conditions. The design requirements of the turbine leads to the rotor design and the identification of the desired flow conditions at rotor inlet in terms of the magnitude and direction of the absolute Mach number. The volute must then be designed to ensure that the desired rotor inlet conditions are attained. A non-dimensional design procedure for a vaneless turbine volute is described. Based on a knowledge of the flow direction and magnitude of the absolute Mach number at rotor inlet the overall dimensions of the volute in terms of the radius ratio and flow area ratio are first established. The overall design is then developed to provide the variation of the volute centroid radius and area ratio with azimuth angle. A trapezoidal cross-sectional shape is then used to establish the outer dimensions of the volute. The non-dimensional procedure assumes a one-dimensional compressible flow and as such relies on the empirical specification of the dissipation of angular momentum, the dissipation of energy and the deviation of the swirling flow from that of a free vortex. The effect of the uncertainties associated with the empirical data on the volute design geometry is assessed. A complementary experimental investigation to develop and substantiate the required empiricism is presented in Part 2, which follows. As the design procedure is essentially one-dimensional it must be interpreted with a knowledge of the actual three-dimensional flow within a volute passage. Supportive experimental studies will be presented in Part 3 in the next issue.

Analysis of two-phase ejectors with Fabri choking

2002 ◽  
Vol 216 (5) ◽  
pp. 607-621 ◽  
Author(s):  
W E Lear ◽  
G M Parker ◽  
S A Sherif
Keyword(s):  
Single Phase ◽  
Phase Region ◽  
Working Fluid ◽  
Two Phase ◽  
Cross Sectional ◽  
Flow Phenomena ◽  
Mass Flowrate ◽  
Inlet Conditions ◽  
R 134A ◽  
Phase Fluid

A one-dimensional mathematical model was developed using the equations governing the flow and thermodynamics within a jet pump with a mixing region of constant cross-sectional area. The analysis is capable of handling two-phase flows and the resulting flow phenomena such as condensation shocks and the Fabri limit on the secondary mass flowrate. This work presents a technique for quickly achieving first-approximation solutions for two-phase ejectors. The thermodynamic state of the working fluid, R-134a for this analysis, is determined at key locations within the ejector. From these results, performance parameters are calculated and presented for varying inlet conditions. The Fabri limit was found to limit the operational regime of the two-phase ejector because, in the two-phase region, the speed of sound may be orders of magnitude smaller than in a single-phase fluid.

Investigation on the Effects of Various Swirl Generators on Heat Transfer and Fluid Flow in Decaying Swirling Flows

2010 ◽  
Vol 224 (10) ◽  
pp. 2181-2197
Author(s):  
M Ahmadvand ◽  
A F Najafi ◽  
S Shahidinejad
Keyword(s):  
Heat Transfer ◽  
Swirling Flow ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Mean Flow ◽  
Inlet Conditions ◽  
The Individual ◽  
Comparison Of The Results

Influences of three typical vortex generators on flow pattern and ensuing heat transfer augmentation were investigated and compared at similar Re and swirl numbers inlet conditions. Studied swirlers such as propeller swirlers, jet-type swirlers, and rotating honeycombs were installed at the pipe inlet. Reynolds number ranges from 10000 to 30000. Swirlers were set on the swirl numbers 1.4, 0.89, and 0.52, which were obtained by propellers. This study has been carried out under uniform heat flux condition and air was employed as the working fluid. The obtained results provide the individual effects of each swirler configuration on mean flow and turbulence distribution as well as on enhancement of heat transfer. Considering S=1.4, jet-type swirlers pointed 133 per cent Nu enhancement compared to axial flow, whereas propellers and rotating honeycombs approached 105 per cent and 79 per cent, respectively. For S=0.89, relative treatment has been changed and propellers with 70 per cent Nu augmentation demonstrated tip-top performance behind of which other swirlers lined. By decreasing the swirl number, approximately closer heat performances were represented from all swirler configurations. Comparison of the results of various swirlers exhibited that Re and swirl numbers are not generally sufficient to determine the swirling flow characteristics and each swirler confirms an individual flow quality.

Numerical Simulations of Misalignment Effects in Microfluidic Interconnects

2010 ◽  
Vol 1272 ◽  
Author(s):  
Sudheer Rani ◽  
Taehyun Park ◽  
Byoung Hee You ◽  
Steven Soper ◽  
Michael C Murphy ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Area Ratio ◽  
Straight Pipe ◽  
Flow Area ◽  
Cross Sectional ◽  
Area Reduction ◽  
Equivalent Length ◽  
End To End

AbstractNumerical simulations were performed to see the effect of geometrical misalignment in pressure driven flows. Geometric misalignment effects on flow characteristics arising in three types of interconnection methods a) end-to-end interconnection, b) channel overlap when chips are stacked on top of each other, and c) the misalignment occurring due to the offset between the external tubing and the reservoir were investigated. For the case of end-to-end interconnection, the effect of misalignment was investigated for 0, 13, 50, 58, and 75% reduction in the available flow area at the location of geometrical misalignment. In the interconnection through channel overlap, various possible misalignment configurations were simulated by maintaining the same amount of misalignment (75% flow area reduction) for all the configurations. The effect of misalignment in a Tube-in-Reservoir interconnection was investigated by positioning the tube at an offset of 164μm from the reservoir center. All the results were evaluated in terms of the equivalent length of a straight pipe. The effect of reynolds number (Re) was also taken into account by performing additional simulations of aforementioned cases at reynolds numbers ranging from 0.075 to 75. The results are interpreted in terms of equivalent length (Le) as a function of Re and misalignment area ratio (A1:A2), where A1 is the original cross-sectional area of the channel and A2 is the available flow area at mismatch location. Equivalent length calculations revealed that the effect of misalignment in tube-in-reservoir interconnection method was the most insignificant when compared to the other two methods of interconnection

Optimized Ejector-Diffuser Design Procedure for Natural Gas Vapor Recovery

1983 ◽  
Vol 105 (3) ◽  
pp. 388-393 ◽  
Author(s):  
J. C. Dutton ◽  
B. F. Carroll
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Natural Gas ◽  
Compression Ratio ◽  
Ambient Pressure ◽  
Design Procedure ◽  
Area Ratio ◽  
Optimized Design ◽  
Storage Tanks ◽  
Oil Storage

A procedure for designing optimized ejector-diffuser systems for recovering natural gas vapor from oil storage tanks is presented. The system utilizes high pressure gas from the separator to entrain the ambient pressure gas from the tanks and then pumps the mixture to the sales line. The analysis predicts the minimum separator pressure and the optimum nozzle Mach number and ejector area ratio required to accomplish this task. The results of a parametric study suggest that this system is feasible and that the higher the required ejector compression ratio the more critical is the use of an optimized design.

scholarly journals Atrophy patterns in isolated subscapularis lesions

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Gernot Seppel ◽  
Andreas Voss ◽  
Daniel J. H. Henderson ◽  
Simone Waldt ◽  
Bernhard Haller ◽  
...  
Keyword(s):  
Muscle Atrophy ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Control Group ◽  
Sectional Area ◽  
Cross Sectional ◽  
Subscapularis Muscle ◽  
Mri Scans ◽  
The Mean ◽  
The Cross

Abstract Background While supraspinatus atrophy can be described according to the system of Zanetti or Thomazeau there is still a lack of characterization of isolated subscapularis muscle atrophy. The aim of this study was to describe patterns of muscle atrophy following repair of isolated subscapularis (SSC) tendon. Methods Forty-nine control shoulder MRI scans, without rotator cuff pathology, atrophy or fatty infiltration, were prospectively evaluated and subscapularis diameters as well as cross sectional areas (complete and upper half) were assessed in a standardized oblique sagittal plane. Calculation of the ratio between the upper half of the cross sectional area (CSA) and the total CSA was performed. Eleven MRI scans of patients with subscapularis atrophy following isolated subscapularis tendon tears were analysed and cross sectional area ratio (upper half /total) determined. To guarantee reliable measurement of the CSA and its ratio, bony landmarks were also defined. All parameters were statistically compared for inter-rater reliability, reproducibility and capacity to quantify subscapularis atrophy. Results The mean age in the control group was 49.7 years (± 15.0). The mean cross sectional area (CSA) was 2367.0 mm2 (± 741.4) for the complete subscapularis muscle and 1048.2 mm2 (± 313.3) for the upper half, giving a mean ratio of 0.446 (± 0.046). In the subscapularis repair group the mean age was 56.7 years (± 9.3). With a mean cross sectional area of 1554.7 mm2 (± 419.9) for the complete and of 422.9 mm2 (± 173.6) for the upper half of the subscapularis muscle, giving a mean CSA ratio of 0.269 (± 0.065) which was seen to be significantly lower than that of the control group (p < 0.05). Conclusion Analysis of typical atrophy patterns of the subscapularis muscle demonstrates that the CSA ratio represents a reliable and reproducible assessment tool in quantifying subscapularis atrophy. We propose the classification of subscapularis atrophy as Stage I (mild atrophy) in case of reduction of the cross sectional area ratio < 0.4, Stage II (moderate atrophy) in case of < 0.35 and Stage III (severe atrophy) if < 0.3.

Use of Cardiac Magnetic Resonance Imaging Based Measurements of Inferior Vena Cava Cross-Sectional Area in the Diagnosis of Pericardial Constriction

2015 ◽  
Vol 66 (3) ◽  
pp. 231-237 ◽  
Author(s):  
Kate Hanneman ◽  
Paaladinesh Thavendiranathan ◽  
Elsie T. Nguyen ◽  
Hadas Moshonov ◽  
Rachel Wald ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Cardiac Magnetic Resonance ◽  
Inferior Vena ◽  
Vena Cava ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Resonance Imaging ◽  
Cross Sectional ◽  
Aortic Area

Purpose To evaluate the value of cardiac magnetic resonance imaging (MRI)–based measurements of inferior vena cava (IVC) cross-sectional area in the diagnosis of pericardial constriction. Methods Patients who had undergone cardiac MRI for evaluation of clinically suspected pericardial constriction were identified retrospectively. The diagnosis of pericardial constriction was established by clinical history, echocardiography, cardiac catheterization, intraoperative findings, and/or histopathology. Cross-sectional areas of the suprahepatic IVC and descending aorta were measured on a single axial steady-state free-precession (SSFP) image at the level of the esophageal hiatus in end-systole. Logistic regression and receiver-operating curve (ROC) analyses were performed. Results Thirty-six patients were included; 50% (n = 18) had pericardial constriction. Mean age was 53.9 ± 15.3 years, and 72% (n = 26) were male. IVC area, ratio of IVC to aortic area, pericardial thickness, and presence of respirophasic septal shift were all significantly different between patients with constriction and those without ( P < .001 for all). IVC to aortic area ratio had the highest odds ratio for the prediction of constriction (1070, 95% confidence interval [8.0-143051], P = .005). ROC analysis illustrated that IVC to aortic area ratio discriminated between those with and without constriction with an area under the curve of 0.96 (95% confidence interval [0.91-1.00]). Conclusions In patients referred for cardiac MRI assessment of suspected pericardial constriction, measurement of suprahepatic IVC cross-sectional area may be useful in confirming the diagnosis of constriction when used in combination with other imaging findings, including pericardial thickness and respirophasic septal shift.

Assessment of sand stabilization potential of a plant-derived biomass

2016 ◽  
Vol 23 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Dunja Perić ◽  
Paul A. Bartley ◽  
Lawrence Davis ◽  
Ali Ulvi Uzer ◽  
Cahit Gürer
Keyword(s):  
Area Ratio ◽  
Cross Sectional Area ◽  
Experimental Program ◽  
Early Age ◽  
Shear Stresses ◽  
Sectional Area ◽  
Cross Sectional ◽  
Near Surface ◽  
Total Cross Sectional Area ◽  
Dry Sand

AbstractLignin is a coproduct of biofuel and paper industries, which exhibits binding qualities when mixed with water. Lignin is an ideal candidate for a sustainable stabilization of unpaved roads. To this end, an experimental program was devised and carried out to quantify effects of lignin on compaction and early age shear strength behaviors of sand. Samples were prepared by mixing a particular type of coproduct called calcium lignosulfonate (CaL) with sand and water. Based on the extensive analyses of six series of strength tests, it was found that a normalized cohesion increased with an increasing normalized areas ratio. Normalizations were carried out by dividing the cohesion and area ratio by gravimetric CaL content whereby the area ratio was obtained by dividing the portion of the cross-sectional area occupied with lignosulfonate-water (CaL-W) paste by the total cross-sectional area. While the increase in the normalized cohesion eventually leveled out, the cohesion peaked at 6% of CaL. Thus, sand-CaL-water (S-CaL-W) mixes sustained larger shear stresses than dry sand for a range of normal stresses below the limiting normal stress. Consequently, the early age behavior indicates that adding CaL-W to sand is clearly beneficial in the near-surface applications in dry sand.

Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Low Mach Number ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers ◽  
Wide Range ◽  
Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

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