scholarly journals Experimental Investigation of a Forward Swept Rotor in a Multistage Fan with Inlet Distortion

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Aspi R. Wadia
Keyword(s):  
Experimental Investigation ◽  
Flow Distortion ◽  
Two Stage ◽  
Guide Vanes ◽  
Stall Margin ◽  
Second Stage ◽  
Inlet Distortion ◽  
Inlet Guide Vanes ◽  
Current Production ◽  
Stage 1

Previous studies of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep to multistage configurations. The experimental investigation compare two builds of an advanced two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two-stage fan's sensitivity with inlet distortion.

Forward Swept Rotor Studies in Multistage Fans With Inlet Distortion

2002 ◽  
Author(s):  
A. R. Wadia ◽  
P. N. Szucs ◽  
D. W. Crall ◽  
D. C. Rabe
Keyword(s):  
Pressure Ratio ◽  
Flow Distortion ◽  
Two Stage ◽  
Good Efficiency ◽  
Guide Vanes ◽  
Stall Margin ◽  
High Pressure Ratio ◽  
Inlet Distortion ◽  
Inlet Guide Vanes ◽  
Current Production

Previous experimental and analytical studies conducted to compare the performance of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep with respect to aerodynamic performance and stability to multistage configurations. The experimental investigation compares, on a back-to-back test basis, two builds of an advanced good efficiency, high pressure ratio, two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained an already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two stage fan’s sensitivity with inlet distortion.

Aerodynamic Design and Testing of an Imbedded Forward Swept Rotor in a Two-Stage Transonic Fan

2018 ◽  
Author(s):  
A. R. Wadia ◽  
J. D. Niedermeier ◽  
P. N. Szucs ◽  
N. G. Cormier ◽  
D. W. Crall ◽  
...  
Keyword(s):  
Leading Edge ◽  
Aerodynamic Design ◽  
Two Stage ◽  
Stall Margin ◽  
Second Stage ◽  
Inlet Distortion ◽  
Overall Performance ◽  
Stage Matching ◽  
Stage 1 ◽  
Transonic Fan

Previous experimental and analytical studies comparing the performance of transonic swept rotors in single and multistage fans have demonstrated the potential of large improvements in clean inlet performance and substantial improvements in fan sensitivity with inlet distortion with forward swept blading. A two-stage, low-aspect ratio transonic fan investigation was previously conducted in the Air Force’s Compressor Research Facility, in two builds on a back-to-back test basis, using a radial and a forward swept stage 1 blade. While the forward swept stage 1 blade configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion, the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept Rotor 1. To address this measured overall performance shortfall, this paper reports on the design of a new second stage blade tested in the same two-stage fan rig with the forward swept stage 1 blade configuration. The new second stage blade was designed with forward sweep to improve efficiency and operability while replicating the baseline radial Rotor 2’s aerodynamic design conditions within the same flow path. The design point requirements of the forward swept Rotor 2 were selected to preserve the internal stage matching with the radially stacked Rotor 2. As the new stage 2 blade had to fit within the existing radial Rotor 2’s physical envelope, the new blade was designed with forward sweep through lean only, which proved to be quite challenging from a mechanical growth and deflection view point. The first attempt to run the fan rig with the new stage 2 blade resulted in a leading-edge tip rub during a part speed stall event. However, even with this unfortunate event, fan mapping test results with clean inlet from part speed to 97.5 percent design speed showed a significant improvement in overall fan efficiency and stall margin, validating the hypothesis that in the earlier tests stage 2 was indeed the limiting stage that prevented the fan from reaching its overall performance goals. Based on this experience and the test data acquired with unstable leadingedge tip rubs during stall deflections with forward swept airfoils leaned in the direction of rotation, a process was developed to determine the acceptability criteria of such blading.

Aerodynamic Design and Testing of an Imbedded Forward Swept Rotor in a Two-Stage Transonic Fan

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
A. R. Wadia ◽  
J. D. Niedermeier ◽  
P. N. Szucs ◽  
N. G. Cormier ◽  
D. W. Crall ◽  
...  
Keyword(s):  
Leading Edge ◽  
Aerodynamic Design ◽  
Two Stage ◽  
Stall Margin ◽  
Second Stage ◽  
Inlet Distortion ◽  
Overall Performance ◽  
Stage Matching ◽  
Stage 1 ◽  
Transonic Fan

Previous experimental and analytical studies comparing the performance of transonic swept rotors in single and multistage fans have demonstrated the potential of large improvements in clean inlet performance and substantial improvements in fan sensitivity with inlet distortion with forward swept blading. A two-stage, low-aspect ratio transonic fan investigation was previously conducted in the Air Force’s Compressor Research Facility, in two builds on a back-to-back test basis, using a radial and a forward swept stage 1 blade. While the forward swept stage 1 blade configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion, the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1. To address this measured overall performance shortfall, this paper reports on the design of a new second stage blade tested in the same two-stage fan rig with the forward swept stage 1 blade configuration. The new second stage blade was designed with forward sweep to improve efficiency and operability while replicating the baseline radial rotor 2’s aerodynamic design conditions within the same flow path. The design point requirements of the forward swept rotor 2 were selected to preserve the internal stage matching with the radially stacked rotor 2. As the new stage 2 blade had to fit within the existing radial rotor 2’s physical envelope, the new blade was designed with forward sweep through lean only, which proved to be quite challenging from a mechanical growth and deflection view point. The first attempt to run the fan rig with the new stage 2 blade resulted in a leading-edge tip rub during a part speed stall event. However, even with this unfortunate event, fan mapping test results with clean inlet from part speed to 97.5% design speed showed a significant improvement in overall fan efficiency and stall margin, validating the hypothesis that in the earlier tests stage 2 was indeed the limiting stage that prevented the fan from reaching its overall performance goals. Based on this experience and the test data acquired with unstable leading-edge tip rubs during stall deflections with forward swept airfoils leaned in the direction of rotation, a process was developed to determine the acceptability criteria of such blading.

Measured and Predicted Effects of Inlet Distortion on Axial Compressors

1990 ◽  
Author(s):  
J. P. Longley
Keyword(s):  
Fluid Dynamics ◽  
Experimental Investigation ◽  
Linear Model ◽  
Guide Vanes ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Inlet Guide Vanes ◽  
Basic Fluid ◽  
Non Linear ◽  
Made In

Encouraging developments have recently been made both in the understanding and the modelling of compressor flowfields. This paper describes an experimental investigation undertaken to assess the validity of the assumptions made in the simple non-linear model for a bladerow operating in an unsteady or non-uniform flowfield. The results show that the basic fluid dynamics of the problem have been correctly modelled and that meaningful predictions may be made. The measurements also indicate that inlet guide vanes may be more sensitive to incidence variations than had been previously thought. The effects of inter-bladerow gaps are also discussed.

scholarly journals Recess Vane Passive Stall Control

1992 ◽  
Author(s):  
M. Ziabasharhagh ◽  
A. B. McKenzie ◽  
R. L. Elder
Keyword(s):  
Experimental Investigation ◽  
Axial Flow ◽  
Operating Efficiency ◽  
Stall Margin ◽  
Casing Treatment ◽  
Inlet Distortion ◽  
Stall Margin Improvement ◽  
Stage Characteristic ◽  
Stall Control

An experimental investigation has been carried out on the influence of a vaned recessed casing treatment on the stall margin improvement of axial flow fans with different hub to tip ratio, with and without inlet distortion. The inlet distortion tests were conducted on a 0.5 hub to tip ratio fan and significant increases in the flow range with only small drops in operating efficiency were observed. The clean flow tests were conducted on higher hub to tip ratio fans (0.7 and 0.9). In each case the stage characteristic was compared with the results obtained with a solid casing. Significant increases in the flow range, with only modest or no loss in operating efficiency, were observed for optimum configurations at both diameter ratios.

scholarly journals Efficacy of Two-Stage Treatment of Onychomycosis Using a Long-Pulsed Nd:YAG 1064-nm Laser

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Shan Zhong ◽  
Guan-ting Lin ◽  
Jun-ying Zhao
Keyword(s):  
Laser Treatment ◽  
Clinical Efficacy ◽  
Nail Plate ◽  
Efficacy Rate ◽  
Treatment Schedule ◽  
Two Stage ◽  
Second Stage ◽  
Controlled Treatment ◽  
Stage 1

Objectives. Onychomycosis is a fungal infection of the nail bed, nail matrix, and nail plate. Lasers have recently been studied as future clinical options for onychomycosis. We sought to evaluate the efficacy of the long-pulsed Nd:YAG 1064-nm laser on onychomycosis using a two-stage treatment. Methods. A total of 100 affected nails (88 toenails and 12 fingernails from 22 patients) were treated using a long-pulsed Nd:YAG 1064-nm laser. The self-controlled treatment schedule included the first stage (1 session per week for 8 weeks) and the second stage (1 session every 4 weeks for 16 weeks). Patients were followed up with for 12 weeks after the last laser treatment. Direct microscopy, cultures, and clinical assessments were performed at various time points. Results. Of the nails studied, 84% were infected by Trichophyton rubrum, while others were coinfected with T. rubrum and other fugal strains. The mycological clearance rate and the clinical efficacy rate of the nails were 29% and 21% after the first stage, 69% and 35% after the second stage, and 67% and 39% during follow-up, respectively. The second stage of laser treatment significantly improved the mycological clearance and clinical efficacy. Conclusion. Long-pulsed Nd:YAG 1064-nm laser two-stage treatment was effective for onychomycosis, with significantly improved mycological clearance and clinical efficacy. This trial is registered with ChiCTR 1900021669.

The Effect of Inlet Guide Vanes on Inlet Flow Distortion Transfer and Transonic Fan Stability

2013 ◽  
Author(s):  
M. J. Shaw ◽  
P. Hield ◽  
P. G. Tucker
Keyword(s):  
Experimental Data ◽  
Stability Margin ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Computational Fluid Dynamics Cfd ◽  
Inlet Flow Distortion ◽  
Transonic Fan ◽  
Do So

An investigation has been carried out into the effects of variable inlet guide vanes (VIGVs) on the performance and stability margin of a transonic fan in the presence of inlet flow distortion. The study was carried out using computational fluid dynamics (CFD) and validated with experimental data. The capability of CFD to predict the changes in performance with or without VIGVs in the presence of an inlet flow distortion is assessed. Results show that the VIGVs improve the performance and stability margin and do so by reducing the amount of swirl at inlet to the rotor component of the fan.

scholarly journals Non-Axisymmetric Design-Optimization of Inlet Guide Vanes for a Fan with Inlet Distortion

2020 ◽  
Author(s):  
Sandeep Kumar ◽  
◽  
Mark Turner ◽  
Mark Celestina ◽  
◽  
...  
Keyword(s):  
Design Optimization ◽  
Guide Vanes ◽  
Inlet Distortion ◽  
Inlet Guide Vanes

An Experimental Investigation on the Clocking Effect Between Inlet Guide Vanes and Vaned Diffuser in a Centrifugal Compressor Stage

2008 ◽  
Author(s):  
Jiang Hua ◽  
Xi Guang ◽  
Zhang Wei ◽  
WuQi Gong ◽  
ZhiHeng Wang
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Stage Efficiency ◽  
Peak Value

Different circumferential angle positions between stator or rotor vane rows in turbomachinery can lead to different flow structures or stage performances. The clocking effect phenomenon has been detected in axial compressor and turbine by investigators, but rarely reported on centrifugal compressor. The present work is an experimental investigation on the stator clocking effect between inlet guide vanes (IGV) and vaned diffuser in a low-speed centrifugal compressor. The experimental rig consists of a circumferentially rotatable IGV, an unshrouded centrifugal impeller, a vaned diffuser, a volute and etc. The impeller diameter is 796mm, and the rotate speed is about 3100 rpm. At each inlet prewhirl angle of −20°, 0° and +20°, the stage performance curves are measured at three clocking angle positions of 0°, 8° and 16°. The result shows that at the circumferential angles of 0° and 8°, the efficiency curve has a double peak value feature, but at the angle of 16° being the conventional single peak value curve. Further, at the circumferential angles of 0° and 8°, the stage efficiency is bigger 3.6% than that case of the angle being 16°, where the IGV prewhirl angles are 0° and 20°. When the IGV prewhirl angle is changed into −20°, the stage efficiency increases about 2.0% near the first peak value position at the circumferential angles of 0°and 8° than at 16°, however, at the second peak value position, the stage efficiency at the circumferential angle of 0° is bigger about 1.4% than at 8° and 16°. Moreover, the circumferential angle positions between IGV and vaned diffuser have corresponding influence on the pressure ratio.

Numerical Investigation of the Flow Distortion Impact on a Refrigeration Centrifugal Compressor

2016 ◽  
Author(s):  
Feng Shen ◽  
Lei Yu ◽  
William T. Cousins ◽  
Vishnu Sishtla ◽  
Om P. Sharma
Keyword(s):  
Centrifugal Compressor ◽  
Computational Cost ◽  
Major Effect ◽  
Tip Clearance ◽  
Cfd Modeling ◽  
Inlet Pipe ◽  
Flow Distortion ◽  
Guide Vanes ◽  
Stall Margin ◽  
Steady Simulation

The inlet pipe to a centrifugal compressor in a water-cooled chiller can cause complexities in designing a compact unit. Flow distortion caused by the inlet pipe shape and non-uniformity of the flow from the evaporator can affect the compressor performance. Inlet guide vanes (IGVs) used for capacity control may help reduce the distortion by forcing a redistribution of the flow. However, the guide vanes themselves result in increased losses and can introduce flow distortion due to the clearance between the movable vane and stationary housing. In this effort, the influence of the flow distortion on the impeller performance and the losses caused by IGVs were investigated using a commercial code dealing with real gas. The CFD model was first verified by comparison to test data. Further investigation showed that the hub-to-shroud flow distortion, especially shroud side distortion, has a major effect on stage performance. IGVs are necessary for straightening the incoming flow to benefit stall margin but generate high losses themselves. The tip clearance of the IGV decreases the deswirl capability and introduces additional local separation loss. Distortion intensity was calculated according to ARP-1420 methods to justify the usage of the mixing plane in the CFD modeling. The extent of distortion indicated that the steady simulation served as a preferable choice for balancing computational cost & prediction accuracy.

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