Fan Performance Scaling With Inlet Distortions

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
J. J. Defoe ◽  
M. Etemadi ◽  
D. K. Hall
Keyword(s):  
Design Flow ◽  
Flow Coefficient ◽  
Axial Fan ◽  
Fan Performance ◽  
Physical Mechanisms ◽  
Viscous Losses ◽  
Performance Scaling ◽  
Large Distortion ◽  
Stator Blade ◽  
Primary Focus

Applications such as boundary-layer-ingesting (BLI) fans and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. The objectives are to (1) identify the physical mechanisms which govern the fan response to inflow distortions and (2) determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The model does not include viscous losses so that changes in diffusion factor are the primary focus. Distortions in stagnation pressure and temperature as well as swirl are considered. The key findings are that unless sharp pitchwise gradients in the diffusion response, strong radial flows, or very large distortion magnitudes are present, the response of the blade rows for strong distortions can be predicted by scaling up the response to a weaker distortion. In addition, the response to distortions which are composed of nonuniformities in several inlet quantities can be predicted by summing up the responses to the constituent distortions.

Fan Performance Scaling With Inlet Distortions

2016 ◽  
Author(s):  
J. J. Defoe ◽  
D. K. Hall
Keyword(s):  
Design Flow ◽  
Flow Coefficient ◽  
Stagnation Temperature ◽  
Axial Fan ◽  
Fan Performance ◽  
Viscous Losses ◽  
Flow Mechanisms ◽  
Stator Blade ◽  
The Individual ◽  
Pressure Swirl

Applications such as boundary-layer-ingesting fans, and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. Previous work in the literature has shown that the same flow mechanisms contributing to the response of a fan to distortion are at play in incompressible and transonic flows. The objective is to determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The approach has been shown to capture overall stage performance and flow field behavior with distortions having length scales much longer than the blade pitch. The approach requires only knowledge of the blade geometry, but the model does not include viscous losses. As a result, efficiency is not assessed but instead a metric based on changes in diffusion factor is defined which is conjectured to be related to efficiency changes. Distortions in stagnation pressure, swirl, and stagnation temperature are considered. By studying the distortions individually, it is found that the diffusion metric scales linearly with the intensity of the distortions (i.e. the ratio of minimum to maximum values) but that changes in distortion location relative to the fan axis produce nonlinear changes in the diffusion metric. Combinations of distortions are also studied and it is found that the diffusion metric associated with the combined distortion can be predicted using a summation procedure for the metrics associated with the individual constituent distortions. The mechanism found to govern the effectiveness of this summation procedure is the incidence distortions at rotor and stator inlet.

Axial Fan at Reversal Flow

2004 ◽  
Author(s):  
Va´clav Cyrus
Keyword(s):  
Volume Flow Rate ◽  
Axial Flow ◽  
Volume Flow ◽  
Design Flow ◽  
Flow Coefficient ◽  
Flow Rate Ratio ◽  
External Diameter ◽  
Axial Fan ◽  
Aerodynamic Loading ◽  
Reversal Flow

Flow reversal in axial fans is usually performed by the change of revolution direction and by stator vanes turning. Derived relations express the relative position of characteristics curves for reverse and normal flows. The ratio of volume flow rates at these conditions decreases with rotor blade profiles camber (aerodynamic loading) and with flow coefficient. The characteristics of two axial-flow stages A, B with different aerodynamic loading and design flow coefficient were measured on a test rig with external diameter of 600mm. Rotor diffusion factor D at mid-span of stage A and B were DR,m = 0.56 and DR,m = 0.3. Design flow coefficient was φD = 0.6 and 0.4, respectively. Theoretical deductions were confirmed by the experiment. Required volume flow rate ratio (Qrev/Qn ≥ 0.6) was reached only in the case of stage B. Detailed flow fields investigations were carried out in this case with the use of 5-hole conical probes at normal and reverse flows. The mechanism of 3D flows in blade rows could be described in these different fan working regimes.

Increasing Inducer Stability and Suction Performance With a Stability Control Device

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Leading Edge ◽  
High Energy ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Blade Tip ◽  
Rotordynamic Forces ◽  
Suction Performance

An inducer is used as the first stage of high suction performance pump. It pressurizes the fluid to delay the onset of cavitation, which can adversely affect performance in a centrifugal pump. In this paper, the performance of a water pump inducer has been explored with and without the implementation of a stability control device (SCD). This device is an inlet cover bleed system that removes high-energy fluid near the blade leading edge and reinjects it back upstream. The research was conducted by running multiphase, time-accurate computational fluid dynamic (CFD) simulations at the design flow coefficient and at low, off-design flow coefficients. The suction performance and stability for the same inducer with and without the implementation of the SCD has been explored. An improvement in stability and suction performance was observed when the SCD was implemented. Without the SCD, the inducer developed backflow at the blade tip, which led to rotating cavitation and larger rotordynamic forces. With the SCD, no significant cavitation instabilities developed, and the rotordynamic forces remained small. The lack of cavitation instabilities also allowed the inducer to operate at lower inlet pressures, increasing the suction performance of the inducer.

Reynolds Number and Roughness Effects on Turbocompressor Performance: Numerical Calculations and Measurement Data Evaluation

2020 ◽  
Author(s):  
Fabian Dietmann ◽  
Michael Casey ◽  
Damian M. Vogt
Keyword(s):  
Reynolds Number ◽  
Measurement Data ◽  
Theoretical Models ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Roughness Effects ◽  
Flow Channels ◽  
Compressor Performance ◽  
Low Flow Coefficient

Abstract Further validation of an analytic method to calculate the influence of changes in Reynolds number, machine size and roughness on the performance of axial and radial turbocompressors is presented. The correlation uses a dissipation coefficient as a basis for scaling the losses with changes in relative roughness and Reynolds number. The original correlation from Dietmann and Casey [6] is based on experimental data and theoretical models. Evaluations of five numerically calculated compressor stages at different flow coefficients are presented to support the trends of the correlation. It is shown that the sensitivity of the compressor performance to Reynolds and roughness effects is highest for low flow coefficient radial stages and steadily decreases as the design flow coefficient of the stage and the hydraulic diameter of the flow channels increases.

Performance of a Low Speed Axial Fan Under Distortion: An Experimental Investigation

2020 ◽  
Author(s):  
Sumit Tambe ◽  
Ugaitz Bartolomé Oseguera ◽  
Arvind Gangoli Rao
Keyword(s):  
Flow Field ◽  
Symmetry Plane ◽  
Vortex Pair ◽  
Axial Fan ◽  
Low Speed ◽  
Fan Performance ◽  
Fuel Burn ◽  
Flow Phenomena ◽  
Order Of Magnitude ◽  
Distortion Index

Abstract In the pursuit of reducing the fuel burn, future aircraft configurations will feature several types of improved propulsion systems, e.g. embedded engines with boundary layer ingestion, high-bypass ratio engines with short intakes, etc. Depending on the design and phase of flight, the engine fan will encounter inflow distortion of varying strength, and fan performance will be adversely affected. Therefore, investigation of the flow phenomena causing performance losses in fan and distortion interaction is important. This experimental study shows the effect of varying distortion index on four aspects of fan performance: distortion topology, upstream redistribution, performance curve, and flow unsteadiness. A low speed fan is tested under 60° circumferential distortion of varying strength, generated using distortion screens. The flow field in the upstream redistribution region is measured using PIV (planar and stereo). The fan performance is obtained using total pressure measurements. The noise spectra measured by a microphone are used to quantify the unsteadiness in the flow field. The distortion index (DC60) varies linearly with the grid porosity at constant wall thickness and aspect ratio of the grid cells. However, the distortion topology is significantly different as a stream-wise vortex pair appears in distorted flow at higher DC60. The vortices are stronger at higher DC60, but their order of magnitude is much lower than the circulation corresponding to fan itself. The spinner, distortion index and topology significantly affect the upstream redistribution mechanism. The vortex pair redistributes the flow which results in lower asymmetry in the symmetry plane. With increasing distortion, the performance is reduced and the unsteadiness is increased.

Influence of distorted inflows on the performance of a contra-rotating fan

2020 ◽  
pp. 1-18
Author(s):  
M.P. Manas ◽  
A.M. Pradeep
Keyword(s):  
Pressure Rise ◽  
Aircraft Engine ◽  
High Flow ◽  
Flow Coefficient ◽  
Potential Candidate ◽  
Blade Surface ◽  
Axial Fan ◽  
Stall Inception ◽  
Relative Contribution ◽  
Inflow Conditions

ABSTRACT A contra-rotating fan offers several aerodynamic advantages that make it a potential candidate for future aircraft engine configurations. Stall in a contra-rotating axial fan is interesting since instabilities could arise from either or both of the rotors. In this experimental study, a contra-rotating axial fan is analysed under clean or distorted inflow conditions to understand its performance and stall inception characteristics. The steady and unsteady measurements identified the relative contribution of each rotor towards the performance of the stage. The tip of rotor-1 is identified to be the most critical region of the contra-rotating fan. The contribution of rotor-2 to the overall loading of the stage is observed to be relatively less than rotor-1. The penalty due to distortion in the stage pressure rise is mostly felt by rotor-1, while rotor-2 also shows a reduction in performance for distorted inflows. Rotor-2 stalls at a high flow coefficient marking the initiation of partial stall of the stage, and the stall of the whole stage occurs once rotor-1 stalls. A fluid phenomenon that is attached to the blade surface marks the stall of rotor-1, and this fluid phenomenon initially rotates at a speed close to the speed of rotation of the blade. As the stage moves towards the fully developed stall, this fluid phenomenon sheds from the blade surface. The fluid phenomenon thus propagates at a speed much lower than the rotational speed of the blade during fully developed stall.

Steady and Transient Computations of Interaction Effects in a Centrifugal Compressor With Different Types of Diffusers

2010 ◽  
Author(s):  
S. Anish ◽  
N. Sitaram
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Leading Edge ◽  
Design Flow ◽  
Flow Coefficient ◽  
Pressure Recovery ◽  
Maximum Efficiency ◽  
Vaned Diffuser ◽  
Lower Flow ◽  
Transient Simulations

A computational study has been conducted to analyze the performance of a centrifugal compressor under various levels of impeller-diffuser interactions. The study has been conducted using a low solidity vaned diffuser (LSVD), a conventional vaned diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using Reynolds-Averaged Navier-Stokes simulations. A commercial software ANSYS CFX is used for this purpose. The intensity of interaction is varied by keeping the diffuser vane leading edge at three different radial locations. Frozen rotor and transient simulations are carried out at four different flow coefficients. At design flow coefficient maximum efficiency occurs when the leading edge is at R3 (ratio of radius of the diffuser leading edge to the impeller tip radius) = 1.10. At lower flow coefficient higher stage efficiency occurs when the diffuser vanes are kept at R3 = 1.15 and at higher flow coefficient R3 = 1.05 gives better efficiency. It is observed that at lower flow coefficients positive incidence causes separation of flow at the suction side of the diffuser vane. When the flow rate is above design point there is a negative incidence at the leading edge of the diffuser vane which causes separation of flow from the pressure side of the diffuser vane. Compressor stage performance as well as performance of individual components is calculated at different time steps. Large variations in the stage performances at off-design flow coefficients are observed. The static pressure recovery coefficient (Cp) value is found to be varying with the relative position of impeller and diffuser. It is observed that maximum Cp value occurred at time step where Ψloss value is lowest. From the transient simulations it has been found that the strength and location of impeller exit wake affect the diffuser vane loading which in turn influences the diffuser static pressure recovery.

Flow Field Analysis of Inlet Distortion in a Transonic Fan With Straight and Bowed Stator Blade

2007 ◽  
Author(s):  
Peng Sun ◽  
Jingjun Zhong ◽  
Guotai Feng
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Three Dimensional ◽  
Field Analysis ◽  
Navier Stokes ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Flow Loss ◽  
Stator Blade ◽  
Transonic Fan

The performance and stability of a fan in clean and distorted inlet flow can be improved through the use of bowed stator blades. Measurements between the blade rows in transonic and supersonic flow are too complex to provide any useful insights, so 3D flow simulations are required. In this paper, a time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan is carried out using “Fluent-parallel” in a parallel supercomputer. Two sets of simulations are performed. The first simulation focuses on a better understanding of inlet total pressure distortion effects on a transonic fan. The second set of numerical simulation aims at studying the improvements of fan performance made by bowed stator blades. Three aspects are contained in this paper. The first is about the distortion effects on characteristics of the fan stage with straight stator. The effects of bowed stator on fan performance with inlet distortion are demonstrated secondly. One hand bowed stator increases the loss in rotor. On the other hand, it reduces the flow loss in stator. Finally, the patterns of flow loss caused by total pressure distortion with straight/bowed stator are compared. The scale of vortex in stator induced by inlet total pressure distortion is weakened by bowed blades, which decreases the stator loss.

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