Influence of Circumferential Inflow Distortion on the Performance of a Low Speed, High Aspect Ratio Contra Rotating Axial Fan

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Chetan Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Rotational Speed ◽  
Total Pressure ◽  
Flow Behavior ◽  
Axial Fan ◽  
Low Speed ◽  
Overall Performance ◽  
Design Speed ◽  
Inflow Conditions

The influence of circumferential inflow distorted on the performance and flow behavior of a high aspect ratio, low speed contra rotating fan is reported in this paper. The total pressure at the inlet is artificially distorted by means of 90 deg mesh sector with a porosity of 0.70. The performance of the contra rotating fan was studied under different speed combinations of the two rotors under clean and distorted inflow conditions. Detailed flow analyses were conducted under design and off-design conditions. In order to understand the effect of distortion and its extent, the distortion sector was rotated circumferentially at intervals of 15 deg to cover the entire annulus. Detailed measurements of the total pressure, velocity components, and flow angles were carried out at the inlet of the first rotor, between the two rotors, and at the exit of the second rotor. The study reveals a few interesting aspects on the effect of inflow distortion on the performance of a contra-rotating stage. For the design speed combination and lower rotational speed of rotor-2, a reduction in the overall operating range with a shift of the peak pressure point towards higher mass flow rate, was observed. It is observed that the effect of inflow distortion at the inlet of rotor-1 gets transferred in the direction of rotor-1 rotation and spreads across the entire annulus. The opposite sense of rotation of rotor-2 causes the distortion effect to get transferred in the direction of rotation of rotor-2 with an associated reduction in the total pressure near the hub. It is observed that a higher rotational speed of the second rotor has a beneficial effect on the overall performance due to the strong suction by generated higher rotational speed of rotor-2.

Investigations on the Effect of Inflow Distortion on the Performance of a High Aspect Ratio, Low Speed Contra Rotating Fan Stage

2013 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Total Pressure ◽  
Flow Behavior ◽  
Variable Speed ◽  
Low Speed ◽  
Inlet Distortion ◽  
Overall Performance ◽  
Inflow Conditions

In this paper, results from an experimental study on the effect of circumferential inflow distorted on the performance and flow behavior of a high aspect ratio, low speed contra rotating fan, are reported. The total pressure at the inlet is artificially distorted by means of 90° mesh sector having porosity of 0.70. The performance of contra rotating fan was studied under variable speed combinations of rotors under clean and distorted inflow conditions. Detailed flow analyses were conducted under design and off-design conditions. In order to understand the extent of inlet distortion, the distortion sector was rotated circumferentially at intervals of 15° to cover the entire annulus. Detailed measurements of total pressure, velocity components and flow angles were carried out at the inlet of the first rotor, between the two rotors and at the exit of the second rotor. The study reveals a few interesting aspects on the effect of inflow distortion on the performance of a contra-rotating stage. It is observed that a higher rotational speed of the second rotor has a beneficial effect on the overall performance.

Study of the Velocity Flow Field Under Distorted Inflow Conditions for a High Aspect Ratio Low Speed Contra Rotating Fan

2013 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Total Pressure ◽  
Flow Behavior ◽  
Low Speed ◽  
Inlet Distortion ◽  
Velocity Magnitude ◽  
Velocity Flow ◽  
Design Speed ◽  
Inflow Conditions

In this paper, results from an experimental study on the effect of circumferential inflow distortion on the flow behavior of a high aspect ratio, low speed contra rotating fan, are reported. The total pressure at the inlet is artificially distorted by means of (i) 90° sector mesh having porosity of 0.70, (ii) 90° sector mesh having porosity combination of 0.70 and 1/3rd section at the hub region covered by mesh of porosity 0.64 (hub covered combined distortion) and (iii) 90° sector mesh having porosity combination of 0.7 and 1/3rd section at the tip region covered by mesh of porosity 0.64 (tip covered combined distortion). Detailed flow analyses were conducted under design speed combination and design mass flow rate of 6 kg/s. In order to understand the extent of inlet distortion, the distortion sector was rotated circumferentially at intervals of 15° to cover the entire annulus. Detailed measurements of velocity components and flow angles were carried out at the inlet of the first rotor, between the two rotors and at the exit of the second rotor. The study reveals a few interesting aspects on the effect of circumferential and combined distortion inflow distortion on the flow behavior of a contra-rotating stage. The presence of low porosity screen reduces the axial velocity magnitude and generates higher spread of distortion near the localized region of placement of the screen. The pure circumferential distortion has a greater effect on the performance of both the rotors compared to hub and tip covered combined distortion.

Understanding the Flow Behavior in a Low Hub-Tip Ratio, High Aspect Ratio Contra-Rotating Axial Fan Stage

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Total Pressure ◽  
Numerical Study ◽  
Flow Behavior ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Axial Fan ◽  
Stall Margin

This paper discusses the results of a parametric study of a pair of contra-rotating axial fan rotors. The rotors were designed to deliver a mass flow of 6 kg/s at 2400 rpm. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies were carried out on these contra-rotating rotors operating at a Reynolds number of 1.25 × 105 (based on blade chord). The axial spacing between the rotors was varied between 50 to 120 % of the chord of rotor 1. The performance of the rotors was evaluated at each of these spacing at design and off-design speeds. The results from the numerical study (using ANSYS CFX) were validated using experimental data. In spite of certain limitations of CFD under certain operating conditions, it was observed that the results agreed well with those from the experiments. The performance of the fan was evaluated based on the variations of total pressure, velocity components and flow angles at design and off-design operating conditions. The measurement of total pressure, flow angles etc. are taken upstream of the first rotor, between the two rotors and downstream of the second rotor. It was observed that the aerodynamics of the flow through a contra rotating stage is significantly influenced by the axial spacing between the rotors and the speed ratio of the rotors. With increasing speed ratios, the strong suction generated by the second rotor, improves the stage pressure rise and the stall margin. Lower axial spacing on the other hand, changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. The performance is investigated at different speed ratios of the rotors at varying axial spacing.

Effect of Speed Ratio and Axial Spacing Variations on the Performance of a High Aspect Ratio, Low Speed Contra-Rotating Fan

2012 ◽  
Author(s):  
Chetan S. Mistry ◽  
A. M. Pradeep
Keyword(s):  
Aspect Ratio ◽  
Numerical Simulations ◽  
High Aspect Ratio ◽  
Total Pressure ◽  
Experimental Studies ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Stall Margin ◽  
Low Speed

This paper explores the effect of speed ratio and axial spacing between high aspect ratio, low speed contra-rotating pair rotors on their aerodynamic performance. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies are carried out on these contra-rotating rotors operating at a Reynolds number of 1.258 × 105 (based on blade chord). The first and second rotors were designed to develop a pressure rise of 1100 Pa and 900 Pa, respectively, for total mass flow rate of 6 kg/s when both operating at a design speed of 2400 rpm. The performance of the fan was evaluated based on variations of total pressure and flow angles at off-design operating conditions. The measurementsof total pressure rise, flow angles etc. are taken upstream of the first rotor and in between the two rotors and downstream of the second rotor. The performance of the contra rotating stage is mainly influenced by the axial spacing between the rotors and speed ratio of both the rotors. The study reveals that the aerodynamics of the contra-rotating stage and stall margin is significantly affected by both the speed ratio as well as the axial spacing between the rotors. It was found that with increasing the speed ratio, the strong suction generated by the second rotor, improves the stage pressure rise and stall margin. Lower axial spacing changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. This however, is accompanied by an increased noise level. The performance is investigated at different speed ratios of the rotors at varying axial spacing. Detailed numerical simulations have been conducted using ANSYS CFX13© using mixing plane approach between rotors. Numerical simulations are compared with experimental results at off-design conditions. These results are validated using the experimental data. Numerical simulations are expected to provide deeper insight into the flow physics of contra-rotating rotors which may be difficult to capture experimentally.

scholarly journals Experimental Study of the Effect of Radially Distorted Inflow on a Contrarotating Fan Stage

2014 ◽  
Vol 2014 ◽  
pp. 1-14
Author(s):  
Chetan Mistry ◽  
A. M. Pradeep
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Pressure Rise ◽  
The Other ◽  
Operating Range ◽  
Radial Distortion ◽  
Performance Pressure ◽  
Overall Performance ◽  
Inflow Conditions

The paper reports results of a detailed study of hub- and tip-strong radial inflow distortion on the performance of a low speed, high aspect ratio (3.0) contrarotating fan stage. The distortion screen (placed upstream of the first rotor) covers 1/3 of the span of the blade near the hub and the casing for hub-strong and tip-strong inflow distortions, respectively. The performance of the contrarotating fan was investigated under both the radially distorted inflows and compared with the clean inflow conditions under different speed combinations of rotor-1 and rotor-2. The hub-strong radial distortion reduces the overall performance (pressure rise and efficiency) as well as the operating range by about 2 to 4% under the different speed combinations. On the other hand, it is interesting to observe that the tip covered radial distortion not only improves the pressure rise, but also increases the overall operating range by about 6 to 8%. There was, however, a 6 to 8% decrease in efficiency in this case as compared to 12 to 15% for hub-strong radial inflow distortion. The results reveal the physics of the effects of radial inflow distortion on the overall performance of the contrarotating fan stage.

Numerical Analysis to Investigate the Effect of Swept Rotor on the Overall Performance of a Transonic Compressor Stage

2014 ◽  
Author(s):  
Shobhavathy M. Thimmaiah ◽  
Ramesha Gurikelu ◽  
Nisha Sherief
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Stability Margin ◽  
Compressor Stage ◽  
Operating Range ◽  
Transonic Compressor ◽  
Overall Performance ◽  
Design Speed ◽  
The Stability

This paper presents the steady state numerical analyses carried out to investigate the effect of forward and backward swept rotor on the overall performance and stability margin of single stage transonic axial flow compressor. Initially, the analyses were carried out on a radially stacked rotor/baseline configuration and obtained the overall performance map of the compressor stage. These results were compared with the available experimental data for validation. Further, investigations were carried out on geometrically modified rotor with six configurations having 5, 10 and 15° forward and backward sweep. A commercial 3-Dimensional CFD package, ANSYS FLUENT was used to compute the complex flow field of transonic compressor rotors. The flow field structures were studied with the help of Mach number total pressure contours. The results of modified rotor geometry indicated that the peak adiabatic efficiency and the total pressure ratio for all the tested forward and backward swept rotor configurations are marginally higher than that of the baseline configuration at all speeds. The operating ranges of all the swept rotor configurations are found to be higher than that of the baseline configuration. The operating range is broader at lower operating speeds than at design speed condition. Rotor with 10° forward sweep and 5° backward sweep indicated the noteworthy improvement in the operating range against the baseline configuration. The stability margin of 11.3, 6.6, 5.2 and 3.5% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration obtained from 10° forward sweep. Rotor with 5° backward sweep showed the stability margin of 12, 4, 3.9 and 3% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration.

Investigation of a High Aspect Ratio Rectangular Channel With High Blockage Ratio Round-Corner Ribs

2004 ◽  
Author(s):  
Christophe Diette ◽  
Tony Arts ◽  
Olivier Sgarzi ◽  
Emmanuel Laroche
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Large Scale ◽  
Flow Direction ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Internal Cooling ◽  
Liquid Crystal Thermography ◽  
Main Flow Direction

The flow behavior and heat transfer were measured in a large scale, high aspect ratio, turbine blade rib-roughened internal cooling channel. The ribs, installed on one wall, were inclined at 90 deg with respect to the main flow direction and generated a blockage of 20%. The rib corners were rounded to take into account manufacturing aspects. The bulk flow Reynolds number was 20,000. Pressure drop and velocity measurements were first conducted. Liquid crystal thermography was applied to quantify the heat transfer, not only along the ribbed and the smooth opposite walls but also on the rib itself. Numerical simulations were conducted with two flow solvers, IGG/FINE (Numeca) and MSD (ONERA) and compared with measurements. They also supported the analysis of the flow behavior. The influence of round-corner versus sharp edge ribs was numerically evaluated with IGG/FINE.

Machining and Characterization of Double-Helical Grooves on Cylindrical Copper Parts by Wire Electric Discharge Turning

2020 ◽  
Vol 1009 ◽  
pp. 117-122
Author(s):  
Jacob Serah Krupa ◽  
G.L. Samuel
Keyword(s):  
Aspect Ratio ◽  
Electric Discharge ◽  
High Aspect Ratio ◽  
Rotational Speed ◽  
Turbine Blades ◽  
Wire Edm ◽  
Machining Time ◽  
Pitch Distance ◽  
Helical Grooves

In the work, the design and development of a novel Wire-EDM setup with double-wire guide discs is presented. It facilitates sparks to be generated between the workpiece and wire at two locations separated by the helical pitch distance. This sparking causes two helical grooves to be generated simultaneously on the surface of the workpiece when it is given suitable rotational speed and table feed. In this work, machining is carried out on rods of 1.5 mm diameter. Helical groves with helix angles ranging from 35 to 500 were generated and characterized. This method of machining the double helical grooves with a single pass reduces the machining time and eliminates the complexities involved in machining one groove at a time. It was observed that the proposed method is suitable for machining double helical grooves with helix angles in the range of 40 - 50°. The parts produced by the mentioned method can be used as EDM tools for generation of high aspect ratio holes in turbine blades and injection nozzles.

Sign in / Sign up

Export Citation Format

Share Document