scholarly journals Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion

1982 ◽  
Author(s):  
M. M. Al-Mudhafar ◽  
M. Ilyas ◽  
F. S. Bhinder
Keyword(s):  
Experimental Study ◽  
Velocity Profiles ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Inlet Distortion ◽  
Mach Numbers ◽  
Inlet Flow Distortion

The results of an experimental study on the influence of severely distorted velocity profiles on the performance of a straight two-dimensional diffuser are reported. The data cover entry Mach numbers ranging from 0.1 to 0.6 and several inlet distortion levels. The pressure recovery progressively deteriorates as the inlet velocity is distorted.

Effect of Inlet Flow Distortion on Performance of Vortex Controlled Diffusers

1992 ◽  
Vol 114 (2) ◽  
pp. 191-197 ◽  
Author(s):  
R. K. Sullerey ◽  
V. Ashok ◽  
K. V. Shantharam
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Velocity Profiles ◽  
Short Length ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Exit Velocity ◽  
Inlet Velocity ◽  
Vortex Control

The present experimental investigations are concerned with diffusers employing the concept of vortex control to achieve high pressure recovery in a short length. Two types of two-dimensional diffusers have been studied, namely, vortex controlled and hybrid diffusers. Investigations have been carried out on such short diffusers with symmetrically and asymmetrically distorted inlet velocity profiles for area ratios 2.0 and 2.5 and divergence angle of 30 and 45 deg at a Reynolds number of 105. For each of the above configurations, experiments have been carried out for a range of fence subtended angles and bleed rates. The results indicate improvement in diffuser effectiveness up to a particular bleed off for both types of diffusers. It was observed that the nature of exit velocity profiles could be controlled by differential bleed.

Prediction of Engine Performance Under Compressor Inlet Flow Distortion Using Streamline Curvature

2006 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Ioannis Templalexis ◽  
Theodosios Alexander ◽  
Petros Kotsiopoulos
Keyword(s):  
Three Dimensional ◽  
Engine Performance ◽  
Radial Pressure ◽  
Two Dimensional ◽  
Component Level ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Streamline Curvature ◽  
Inlet Flow Distortion ◽  
Inlet Conditions

Traditionally, engine performance has been simulated based on non-dimensional maps for compressors and turbines. Component characteristic maps assume by default a given state of inlet conditions which can not be easily altered in order to simulate two-dimensional or three-dimensional flow phenomena. Inlet flow distortion, for example, is usually simulated by applying empirical correction factors and modifiers to default component characteristics, alternatively, the parallel compressor theory may be applied. The accuracy of the above methods has been rather questionable since they are unable to capture in sufficient fidelity component-level, complex physical processes and analyze them in the context of the whole engine performance. The technique described in this paper integrates a zero-dimensional (non-dimensional) gas turbine modeling and performance simulation system and a two-dimensional, streamline curvature compressor software. The two-dimensional compressor software can fully define the characteristics of a compressor at several operating condition and is subsequently used in the zero-dimensional cycle analysis to provide a more accurate, physics-based estimate of compressor performance under clean and distorted inlet conditions, replacing the default compressor maps. The high-fidelity component communicates with the lower fidelity cycle via a fully automatic and iterative process for the determination of the correct operating point. This study discusses in detail the development, validation and integration of the two-dimensional, streamline curvature compressor software and presents the various loss models used in the code. It also discusses the relative changes in the performance of a two-stage, experimental compressor with different types of radial pressure distortion obtained by running the two-dimensional streamline curvature compressor software independently. Moreover, the performance of a notional engine model, utilizing the coupled, two-dimensional compressor, under distorted conditions is discussed in detail and compared against the engine performance under clean conditions.

Upstream Attenuation and Quasi-Steady Rotor Lift Fluctuations in Asymmetric Flows in Axial Compressors

1973 ◽  
Author(s):  
E. M. Greitzer
Keyword(s):  
Apparent Discrepancy ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Axial Compressors ◽  
Compressor Rotor ◽  
Inlet Flow Distortion ◽  
Asymmetric Flows ◽  
Induced Velocity ◽  
Proper Consideration

This paper examines the quasi-steady lift variations experienced by a compressor rotor working in a circumferential inlet flow distortion. It is shown that for a given axial velocity distortion at the compressor face, the phase and magnitude of the lift fluctuations are strongly dependent not only on the geometry of the specified rotor, but on the total compressor configuration in which the rotor is operated. A simple numerical example is presented to illustrate this point. It is then demonstrated that the differences in the rotor lift fluctuation occur due to the upstream circumferential velocity component which is associated with the upstream attenuation of inlet velocity distortion. It is also pointed out that proper consideration of the circumferential component resioves an apparent discrepancy between two previous analyses of this problem. Finally, arguments are presented concerning the influence of the bound (blading) and downstream shed (wake) vorticity on the flow field upstream of the compressor. For the cases considered, it is shown that the induced velocity field associated with the upstream attenuation of inlet flow distortion is due equally to the bound and shed vorticity.

Prediction of Engine Performance Under Compressor Inlet Flow Distortion Using Streamline Curvature

2006 ◽  
Vol 129 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Ioannis Templalexis ◽  
Theodosios Korakianitis ◽  
Petros Kotsiopoulos
Keyword(s):  
Engine Performance ◽  
Two Dimensional ◽  
Physical Processes ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Streamline Curvature ◽  
Simulation Strategy ◽  
Flow Phenomena ◽  
Inlet Flow Distortion ◽  
Inlet Conditions

Traditionally, engine performance has been simulated based on nondimensional maps for compressors and turbines. Component characteristic maps assume by default a given state of inlet conditions that cannot be easily altered in order to simulate two- or three-dimensional flow phenomena. Inlet flow distortion, for example, is usually simulated by applying empirical correction factors and modifiers to default component characteristics. Alternatively, the parallel compressor theory may be applied. The accuracy of the above methods has been rather questionable over the years since they are unable to capture in sufficient fidelity component-level, complex physical processes and analyze them in the context of the whole engine performance. The technique described in this paper integrates a zero-dimensional (nondimensional) gas turbine modelling and performance simulation system and a two-dimensional, streamline curvature compressor software. The two-dimensional compressor software can fully define the characteristics of any compressor at several operating conditions and is subsequently used in the zero-dimensional cycle analysis to provide a more accurate, physics-based estimate of compressor performance under clean and distorted inlet conditions, replacing the default compressor maps. The high-fidelity, two-dimensional compressor component communicates with the lower fidelity cycle via a fully automatic and iterative process for the determination of the correct operating point. This manuscript firstly gives a brief overview of the development, validation, and integration of the two-dimensional, streamline curvature compressor software with the low-fidelity cycle code. It also discusses the relative changes in the performance of a two-stage, experimental compressor with different types of radial pressure distortion obtained by running the two-dimensional streamline curvature compressor software independently. Moreover, the performance of a notional engine model, utilizing the coupled, two-dimensional compressor, under distorted conditions is discussed in detail and compared against the engine performance under clean conditions. In the cases examined, the analysis carried out by this study demonstrated relative changes in the simulated engine performance larger than 1%. This analysis proves the potential of the simulation strategy presented in this paper to investigate relevant physical processes occurring in an engine component in more detail, and to assess the effects of various isolated flow phenomena on overall engine performance in a timely and affordable manner. Moreover, in contrast to commercial computational fluid dynamics tools, this simulation strategy allows in-house empiricism and expertise to be incorporated in the flow-field calculations in the form of deviation and loss models.

scholarly journals Inlet Flow Distortions in Centrifugal Fans

1984 ◽  
Author(s):  
S. Madhavan ◽  
J. DiRe ◽  
T. Wright
Keyword(s):  
Comprehensive Evaluation ◽  
Performance Degradation ◽  
Centrifugal Fan ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Fan Performance ◽  
Inlet Distortion ◽  
Centrifugal Fans ◽  
Inlet Flow Distortion ◽  
Distortion Parameters

Recent measurements of the performance of a centrifugal fan subjected to inlet flow distortion are presented. Results of axial and multilobed distortion modes are discussed in the context of a previously published study to provide a more comprehensive evaluation of related fan performance degradation. Distortion parameters presented in the previous study are shown to be insufficient for the complete description of inlet distortion and further indicators are proposed.

The Effect of Non-Uniform Aerodynamic Loading on the Blade Responses

2007 ◽  
Author(s):  
Abdelgadir M. Mahmoud ◽  
Mohd S. Leong
Keyword(s):  
Turbine Blades ◽  
Forced Response ◽  
Flow Section ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Bladed Disk ◽  
Aerodynamic Loading ◽  
Bladed Disk Assembly ◽  
Flow Generator ◽  
Inlet Flow Distortion

Turbine blades are always subjected to severe aerodynamic loading. The aerodynamic loading is uniform and Of harmonic nature. The harmonic nature depends on the rotor speed and number of nozzles (vanes counts). This harmonic loading is the main sources responsible for blade excitation. In some circumstances, the aerodynamic loading is not uniform and varies circumferentially. This paper discussed the effect of the non-uniform aerodynamic loading on the blade vibrational responses. The work involved the experimental study of forced response amplitude of model blades due to inlet flow distortion in the presence of airflow. This controlled inlet flow distortion therefore represents a nearly realistic environment involving rotating blades in the presence of airflow. A test rig was fabricated consisting of a rotating bladed disk assembly, an inlet flow section (where flow could be controlled or distorted in an incremental manner), flow conditioning module and an aerodynamic flow generator (air suction module with an intake fan) for investigations under laboratory conditions. Tests were undertaken for a combination of different air-flow velocities and blade rotational speeds. The experimental results showed that when the blades were subjected to unsteady aerodynamic loading, the responses of the blades increased and new frequencies were excited. The magnitude of the responses and the responses that corresponding to these new excited frequencies increased with the increase in the airflow velocity. Moreover, as the flow velocity increased the number of the newly excited frequency increased.

Lip Separation and Inlet Flow Distortion Control in Ducted Fans Used in VTOL Systems

2014 ◽  
Author(s):  
Ali Akturk ◽  
Cengiz Camcı
Keyword(s):  
Angle Of Attack ◽  
Axial Flow ◽  
Vertical Force ◽  
High Angle ◽  
Flow Distortion ◽  
High Angle Of Attack ◽  
Inlet Flow ◽  
Flight Velocity ◽  
Ducted Fan ◽  
Inlet Flow Distortion

This paper describes a novel ducted fan inlet flow conditioning concept that will significantly improve the performance and controllability of ducted fan systems operating at high angle of attack. High angle of attack operation of ducted fans is very common in VTOL (vertical take off and landing) UAV systems. The new concept that will significantly reduce the inlet lip separation related performance penalties in the edgewise/forward flight zone is named DOUBLE DUCTED FAN (DDF). The current concept uses a secondary stationary duct system to control inlet lip separation related momentum deficit at the inlet of the fan rotor occurring at elevated edgewise flight velocities. The DDF is self-adjusting in a wide edgewise flight velocity range and its corrective aerodynamic effect becomes more pronounced with increasing flight velocity due to its inherent design properties. Most axial flow fans are designed for an axial inlet flow with zero or minimal inlet flow distortion. The DDF concept is proven to be an effective way of dealing with inlet flow distortions occurring near the lip section of any axial flow fan system, especially at high angle of attack. In this present paper, a conventional baseline duct without any lip separation control feature is compared to two different double ducted fans named DDF CASE-A and DDF CASE-B via 3D, viscous and turbulent flow computational analysis. Both hover and edgewise flight conditions are considered. Significant relative improvements from DDF CASE-A and DDF CASE-B are in the areas of vertical force (thrust) enhancement, nose-up pitching moment control and recovery of fan through-flow mass flow rate in a wide horizontal flight range.

Inlet Flow Distortion

2018 ◽  
pp. 249-267 ◽  
Author(s):  
Joachim Kurzke ◽  
Ian Halliwell
Keyword(s):  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Flow Distortion

Nacelle Aerodynamic Optimization and Inlet Compatibility

2015 ◽  
Author(s):  
Jingjing Chen ◽  
Yadong Wu ◽  
Zhonglin Wang ◽  
Anjenq Wang
Keyword(s):  
Pressure Loss ◽  
Operating Conditions ◽  
Maximum Pressure ◽  
Aerodynamic Optimization ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Induction System ◽  
Air Intake ◽  
Inlet Flow Distortion ◽  
The Impact

The design of air induction system is targeting to balance the internal and external flow characteristics as well as the structure and aerodynamic integrity. An optimized air intake design that providing velocity and pressure distributions with least drag and maximum pressure recovery could end up at the expense of higher inlet flow distortion and lower stability margin. Indeed, design requirements and considerations at different operating conditions, such as takeoff, and high AOA maneuvers, could be significantly different from that of cruise and level flight. One of the most challenged operating conditions to be certified for FAR33 & FAR25 requirements is ground crosswind condition, when “Engine” is operating statically on the ground with high crosswind presented. It could accommodate inlet separation or distortion resulted from crosswind, and triggers fan or core stall, as well as induces high fan and/or engine vibrations. Studies of engine inlet compatibility become one of the major tasks required during the engine developing phase. This research is a parametric study of using CFD to evaluate operational characteristics of the air induction system. Comparisons of various inlet designs are made and characterized into four categories, i.e., i) Inlet pressure loss, ii) Nacelle drag, iii) Inlet flow distortion, and iv) Inlet Mach distribution. The objective is to assess the impact of air induction design of turbofan upon inlet compatibility. The research introduces the Kriging model and weighting coefficients to optimize internal total pressure loss and external drag using the isolated nacelle model. Bezier equation was used to fit the optimized curves obtained by changing several control points of the baseline configuration of nacelle. To study the impact of asymmetric lip on flow separation in ground crosswind condition, the paper built crosswind model which introduce a inlet boundary as fan face. Comparisons are then made between the original and optimal nacelle, to show correlation between inlet compatibility and air intake profile.

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