scholarly journals Prediction of Performance of a Variable-Pitch Axial Fan with Forward-Skewed Blades

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2353 ◽  
Author(s):  
Xuemin Ye ◽  
Fuwei Fan ◽  
Ruixing Zhang ◽  
Chunxi Li
Keyword(s):  
Total Pressure ◽  
Pressure Rise ◽  
Separation Flow ◽  
Axial Fan ◽  
Point Change ◽  
Variable Pitch ◽  
Tip Leakage ◽  
Through Flow ◽  
Efficiency Increase ◽  
Blade Pitch Angle

For a single-stage variable-pitch axial fan, the aerodynamic performance and through flow with and without blade skewing are examined numerically. Simulated results show that the total pressure rise and efficiency increase by 2.99% and 0.16%, respectively, with the best forward-skewed angle of θ = 3° at the design conditions. At the blade pitch angles of β = 29° and 35°, the total pressure rises and efficiency of the fan with θ = 3.0° under the highest efficiency point change by −0.55%, −0.53% and 1.39%, 2.11%, respectively. At design and off-design conditions, the forward-skewed blades mitigate tip leakage and delay the emergence of separation flow at the blade root, these benefits are higher at the higher blade pitch angle. The θ = 3.0° forward skew effectively raises the stage performance of the impeller and guide vanes.

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.

scholarly journals Innovations in Body Force Modeling of Transonic Compressor Blade Rows

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
David J. Hill ◽  
Jeffrey J. Defoe
Keyword(s):  
Total Pressure ◽  
Body Force ◽  
Computational Cost ◽  
Pressure Rise ◽  
The Body ◽  
Force Model ◽  
Axial Fan ◽  
Compressor Blades ◽  
Time Resolved ◽  
Transonic Compressor

Aeroengine fans and compressors increasingly operate subject to inlet distortion in the transonic flow regime. In this paper, innovations to low-order numerical modeling of fans and compressors via volumetric source terms (body forces) are presented. The approach builds upon past work to accommodate any axial fan/compressor geometry and ensures accurate work input and efficiency prediction across a range of flow coefficients. In particular, the efficiency drop-off near choke is captured. The model for a particular blade row is calibrated using data from single-passage bladed computations. Compared to full-wheel unsteady computations which include the fan/compressor blades, the source term model approach can reduce computational cost by at least two orders of magnitude through a combination of reducing grid resolution and, critically, eliminating the need for a time-resolved approach. The approach is applied to NASA stage 67. For uniform flow, at 90% corrected speed and peak-efficiency, the body force model is able to predict the total-to-total pressure rise coefficient of the stage to within 1.43% and the isentropic efficiency to within 0.03%. With a 120∘ sector of reduced inlet total pressure, distortion transfer through the machine is well-captured and the associated efficiency penalty predicted with less than 2.7% error.

Experimental and Numerical Examinations of a Transonic Compressor-Stage With Casing Treatment

2013 ◽  
Author(s):  
D. Schönweitz ◽  
M. Voges ◽  
G. Goinis ◽  
G. Enders ◽  
E. Johann
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Guide Vane ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Tip Leakage Vortex ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Transonic Compressor

The flow in the blade tip vicinity of the transonic first stage of a multi-stage axial flow compressor with variable inlet guide vane (IGV) and casing treatment (CT) above the rotor is investigated experimentally and numerically with focus on the effects of the CT on flow structures and compressor performance. For the experimental part of this study, conventional performance instrumentation is used to estimate the operating condition of the compressor. Radial distributions of total temperature and total pressure are taken at the leading edges of the stators for comparison with simulations as well as for adjusting the operating conditions of the compressor. The velocity field in the rear part of the first-rotor is determined with Particle Image Velocimetry (PIV) at 90% and 96% radial height using two periscope light sheet probes. The employed PIV setup allows a spatial resolution of 0.7 mm × 0.7mm and thus a similar resolution as the spatial discretization in the simulation. For the numerical part of the study, time-accurate simulations are conducted for the same operating conditions as during experiments. Additional simulations of the same configuration with smooth casing are conducted in order to estimate the effect of the CT on the flow. The examination of PIV measurements and corresponding simulations exposes complex vortical structures originating from the interaction of the rotor bow shock with the IGV trailing edge, CT, IGV wake and the tip leakage vortex. The associated induced velocities together with the general passage flow form a complex flow field with significantly altered blockage compared to a common flow field in the tip vicinity. Position and trajectory of the tip leakage vortex are deduced from interactions between tip leakage vortex and IGV wake / CT. The detailed comparison of the tip region of simulations with and without CT shows that the CT influences pressure rise and flow parameters in a wide radial range due to a radial redistribution of the flow. Correspondingly, a rotor with CT can achieve an increased total pressure rise compared to a rotor with smooth casing, with only minor effects on the efficiency.

Studies on Downstream Stator With Rotor Re-Staggering and Forward Sweeping in a Subsonic Axial Compressor Stage

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
Computational Model ◽  
Flow Rate ◽  
Total Pressure ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Distance ◽  
Compressor Stage ◽  
Numerical Work ◽  
Stagger Angle

The present numerical work studies the flow field in subsonic axial compressor stator passages for: (a) preceding rotor sweep (b) preceding rotor re-staggering (three stagger angle changes: 0°, +3° and +5°); and (c) stator sweeping (two 20° forward sweep schemes). The following are the motives for the study: at the off-design conditions, compressor rotors are re-staggered to alleviate the stage mismatching by adjusting the rows to the operating flow incidence. Fundamental to this is the understanding of the effects of rotor re-staggering on the downstream component. Secondly, sweeping the rotor stages alters the axial distance between the successive rotor-stator stages and necessitates that the stator vanes must also be swept. To the best of the author’s knowledge, stator sweeping to suit such scenarios has not been reported. The computational model for the study utilizes well resolved hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: (1) When the rotor passage is closed by re-staggering, with the same mass flow rate and the same stator passage area, stators were subjected to negative incidences. (2) Effect of stator sweeping on the upstream rotor flow field is insignificant. Comparison of total pressure rise carried by the downstream stators suggests that an appropriate redesign of stator is essential to match with the swept rotors. (3) While sweeping the stator is not recommended, axial sweeping is preferable over true sweeping when it is necessary.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

Robust Compressor Blades for Desensitizing Operational Tip Clearance Variations

2014 ◽  
Author(s):  
Pranay Seshadri ◽  
Shahrokh Shahpar ◽  
Geoffrey T. Parks
Keyword(s):  
Robust Design ◽  
Total Pressure ◽  
Pressure Rise ◽  
Side Surface ◽  
Tip Clearance ◽  
Design Parameters ◽  
Compressor Blades ◽  
Robust Designs ◽  
Multi Objective ◽  
Mean And Variance

Robust design is a multi-objective optimization framework for obtaining designs that perform favorably under uncertainty. In this paper robust design is used to redesign a highly loaded, transonic rotor blade with a desensitized tip clearance. The tip gap is initially assumed to be uncertain from 0.5 to 0.85% span, and characterized by a beta distribution. This uncertainty is then fed to a multi-objective optimizer and iterated upon. For each iteration of the optimizer, 3D-RANS computations for two different tip gaps are carried out. Once the simulations are complete, stochastic collocation is used to generate mean and variance in efficiency values, which form the two optimization objectives. Two such robust design studies are carried out: one using 3D blade engineering design parameters (axial sweep, tangential lean, re-cambering and skew) and the other utilizing suction and pressure side surface perturbations (with bumps). A design is selected from each Pareto front. These designs are robust: they exhibit a greater mean efficiency and lower variance in efficiency compared to the datum blade. Both robust designs were also observed to have significantly higher aft and reduced fore tip loading. This resulted in a weaker clearance vortex, wall jet and double leakage flow, all of which lead to reduced mixed-out losses. Interestingly, the robust designs did not show an increase in total pressure at the tip. It is believed that this is due to a trade-off between fore-loading the tip and obtaining a favorable total pressure rise and higher mixed-out losses, or aft-loading the tip, obtaining a lower pressure rise and lower mixed-out losses.

scholarly journals Genetic Algorithm Optimization of the Volute Shape of a Centrifugal Compressor

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Martin Heinrich ◽  
Rüdiger Schwarze
Keyword(s):  
Numerical Model ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Maximum Efficiency ◽  
Algorithm Optimization ◽  
Cross Sectional ◽  
Design Variables ◽  
Design Speed

A numerical model for the genetic optimization of the volute of a centrifugal compressor for light commercial vehicles is presented. The volute cross-sectional shape is represented by cubic B-splines and its control points are used as design variables. The goal of the global optimization is to maximize the average compressor isentropic efficiency and total pressure ratio at design speed and four operating points. The numerical model consists of a density-based solver in combination with the SSTk-ωturbulence model with rotation/curvature correction and the multiple reference frame approach. The initial validation shows a good agreement between the numerical model and test bench measurements. As a result of the optimization, the average total pressure rise and efficiency are increased by over1.0%compared to the initial designs of the optimization, while the maximum efficiency rise is nearly 2.5% atm˙corr=0.19 kg/s.

Effect of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1—Framework of Technical Approach and Wake–Stator Blade Interactions

1999 ◽  
Vol 121 (3) ◽  
pp. 377-386 ◽  
Author(s):  
T. V. Valkov ◽  
C. S. Tan
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Tip Vortex ◽  
Technical Approach ◽  
Tip Vortices ◽  
Tip Leakage ◽  
Unsteady Interaction ◽  
Flow Approximation ◽  
Stator Blade ◽  
The Impact

In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stators with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-averaged performance of the stator. Detailed interrogation of the computed flow field showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically, there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated nontransitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.

Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

2017 ◽  
Author(s):  
Brian M. T. Tang ◽  
Marko Bacic ◽  
Peter T. Ireland
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Total Pressure ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Turbine Efficiency ◽  
Coolant Injection ◽  
Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

The Behavior of the Casing Boundary Layer With the Presence of Tip Leakage Vortex

2018 ◽  
Author(s):  
Xi Nan ◽  
Feng Lin ◽  
Takehiro Himeno ◽  
Toshinori Watanabe
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Flow Loss ◽  
Produce Flow

Casing boundary layer effectively places a limit on the pressure rise capability achievable by the compressor. The separation of the casing boundary layer not only produce flow loss but also closely related to the compressor rotating stall. The motivation of this paper is to present a viewpoint that the casing boundary layer should be paid attention to in parallel with other flow factors on rotating stall trigger. This paper illustrates the casing boundary layer behavior by displaying its separation phenomena with the presence of tip leakage vortex at different flow conditions. Skin friction lines and the corresponding absolute streamlines are used to demonstrate the three-dimensional flow patterns on and near the casing. The results depict a Saddle, a Node and several tufts of skin friction lines dividing the passage into four zones. The tip leakage vortex is enfolded within one of the zones by the separated flows. All the flows in each blade passage are confined within the passage as long as the compressor is stable. The casing boundary layer of a transonic compressor is also examined in the same way, which results in qualitatively similar zonal flows that enfolds the tip leakage vortex. This research develops a new way to study the casing boundary layer in rotating compressors. The results may provide a first-principle based explanation to stalling mechanisms for compressors that are casing sensitive.

Sign in / Sign up

Export Citation Format

Share Document