Non-axisymmetric complete flow conditioning gauzes

AbstractThis paper presents a novel methodology for the design of a gauze that produces distributions of stagnation pressure, swirl angle, pitch angle and turbulence intensity, tailored in both the radial and circumferential directions. A distortion gauze is made from a large number of small-scale circumferential and radial blades with tailored thickness and camber distributions. By controlling the blade design independently in both the radial and circumferential directions, the target inflow pattern can be achieved. 1D correlations are used to initialise the blades and they are refined using full 3D CFD simulations. The final design is additively manufactured for use in rotating rigs. In this paper, the method has been used to reproduce four target inflow patterns with large variations in stagnation pressure and flow angularity. Two examples model the inlet flow distortion seen at the aerodynamic interface plane of an aft-mounted boundary layer ingesting fan. The final two examples model the inlet distortion at inlet to an axial compressor spool caused by upstream structural struts in a swan neck duct. The gauzes are shown to replicate the structures of the target flow in an experimental test. These kind of flow structures would be extremely difficult or impossible to replicate in an experiment in any other way. Graphical abstract

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Inlet Flow Distortion in Turbomachinery

Journal of Engineering for Power ◽

10.1115/1.3230362 ◽

1980 ◽

Vol 102 (4) ◽

pp. 924-929

Author(s):

B. S. Seidel ◽

M. D. Matwey ◽

J. J. Adamczyk

Keyword(s):

Mach Number ◽

Axial Compressor ◽

Stagnation Pressure ◽

Single Stage ◽

Parameter Study ◽

Stagnation Temperature ◽

Flow Distortion ◽

Inlet Flow ◽

Swirl Angle ◽

Mach Numbers

A single stage axial compressor with distorted inflow is studied. The inflow distortion occurs far upstream and may be a distortion in stagnation temperature, stagnation pressure or both. The blade rows are modelled as semi-actuator disks. Losses, quasi-steady deviation angles, and reference incidence correlations are included in the analysis. Both subsonic and transonic relative Mach Numbers are considered. A parameter study is made to determine the influence of such variables as Mach Number and swirl angle on the attenuation of the distortion.

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Prediction of Inlet Distortion Induced Axial Compressor Flow Field Instability in Mid-Air Refueling

Volume 1: Fora, Parts A, B, C, and D ◽

10.1115/fedsm2003-45393 ◽

2003 ◽

Author(s):

Ningyu Liu ◽

Eddie Yin-Kwee Ng ◽

Hong Ngiap Lim ◽

Tock Lip Tan

Keyword(s):

Incidence Angle ◽

Axial Compressor ◽

Axial Flow ◽

Flow Distortion ◽

Practical Applications ◽

Inlet Distortion ◽

Compressor Inlet ◽

Physical Insight ◽

Flow Compressor ◽

Compressor Efficiency

The propagation of strong distortion at inlet of an axial compressor is investigated by applying the critical distortion line and the integral method. The practical applications, such as flaming of leakage fuel during mid-air refueling process, are implemented to show the details of the numerical methodology used in analysis of the axial flow compressor behavior and the propagation of inlet distortion. From the viewpoint of compressor efficiency, the propagation of inlet flow distortion is further described by a compressor critical performance and its critical characteristic. The simulated results present a useful physical insight to the significant effects of inlet parameters on the distortion extension, velocity, and compressor characteristics. The distortion level, the size of distortion area, and the incidence angle at compressor inlet, and the rotor blade speed are found to be the major parameters affecting the mass flow rate of engine.

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JET ENGINE INLET DISTORTION SCREEN AND DESCRIPTOR EVALUATION

Acta Polytechnica ◽

10.14311/ap.2017.57.0022 ◽

2017 ◽

Vol 57 (1) ◽

pp. 22-31 ◽

Cited By ~ 1

Author(s):

Jiří Pečinka ◽

Gabriel Thomas Bugajski ◽

Petr Kmoch ◽

Adolf Jílek

Keyword(s):

Total Pressure ◽

Basic Flow ◽

Interface Plane ◽

Inlet Channel ◽

Flow Distortion ◽

Turbine Engine ◽

Inlet Distortion ◽

Mass Flow Rates ◽

Total Temperature ◽

The University

Total pressure distortion is one of the three basic flow distortions (total pressure, total temperature and swirl distortion) that might appear at the inlet of a gas turbine engine (GTE) during operation. Different numerical parameters are used for assessing the total pressure distortion intensity and extent. These summary descriptors are based on the distribution of total pressure in the aerodynamic interface plane. There are two descriptors largely spread around the world, however, three or four others are still in use and can be found in current references. The staff at the University of Defence decided to compare the most common descriptors using basic flow distortion patterns in order to select the most appropriate descriptor for future department research. The most common descriptors were identified based on their prevalence in widely accessible publications. The construction and use of these descriptors are reviewed in the paper. Subsequently, they are applied to radial, angular, and combined distortion patterns of different intensities and with varied mass flow rates. The tests were performed on a specially designed test bench using an electrically driven standalone industrial centrifugal compressor, sucking air through the inlet of a TJ100 small turbojet engine. Distortion screens were placed into the inlet channel to create the desired total pressure distortions. Of the three basic distortions, only the total pressure distortion descriptors were evaluated. However, both total and static pressures were collected using a multi probe rotational measurement system.

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Flow Field Coupling Between Compression System Components in Asymmetric Flow

Journal of Engineering for Power ◽

10.1115/1.3446328 ◽

1978 ◽

Vol 100 (1) ◽

pp. 66-72 ◽

Cited By ~ 9

Author(s):

E. M. Greitzer ◽

R. S. Mazzawy ◽

D. A. Fulkerson

Keyword(s):

Total Pressure ◽

Axial Compressor ◽

Nonuniform Flow ◽

Asymmetric Flow ◽

Flow Distortion ◽

Compression System ◽

Field Coupling ◽

Inlet Distortion ◽

System Components ◽

Good Agreement

The coupling between an axial compressor in an inlet distortion and downstream compression system components is studied analytically and experimentally. The analysis is based on a nonlinear multisegment parallel compressor model coupled to a calculation procedure for the asymmetric flowfield downstream of the compressor. It is shown that in the presence of circumferentially nonuniform flow (distortion) there can be a strong interaction between the compressor and its overall environment. The response of the compressor to an inlet total pressure distortion can therefore depend not only on the compressor, as has sometimes been assumed, but also on the other components in the compression system. Further, the alteration in the response as a result of the interaction can be either beneficial or detrimental, depending on the nature of the component. Experiments investigating this coupling have been carried out on a three stage compressor. The experiments, which involved operating the compressor with three quite different downstream components, show clearly the differences that can exist in compressor response to distortion due to the compressor-component coupling. The analytical predictions of these effects are found to be in good agreement with the experimental results.

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Blade Forcing Function and Aerodynamic Work Measurements in a High Speed Centrifugal Compressor With Inlet Distortion

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2009-59911 ◽

2009 ◽

Cited By ~ 6

Author(s):

Albert Kammerer ◽

Reza S. Abhari

Keyword(s):

Failure Modes ◽

Pressure Sensors ◽

Forced Response ◽

Blade Surface ◽

Centrifugal Compressors ◽

Flow Distortion ◽

Unsteady Pressure ◽

Inlet Distortion ◽

Forcing Function ◽

Work Distribution

Centrifugal compressors operating at varying rotational speeds, such as in helicopters or turbochargers, can experience forced response failure modes. The response of the compressors can be triggered by aerodynamic flow non-uniformities, such as with diffuser-impeller interaction or with inlet distortions. The work presented here addresses experimental investigations of forced response in centrifugal compressors with inlet distortions. This research is part of an ongoing effort to develop related experimental techniques and to provide data for validation of computational tools. In this work measurements of blade surface pressure and aerodynamic work distribution were addressed. A series of pressure sensors were designed and installed on rotating impeller blades and simultaneous measurements with blade-mounted strain gauges were performed under engine representative conditions. To the best knowledge of the authors, this is the first publication which presents comprehensive experimental unsteady pressure measurements during forced response for highspeed radial compressors. Experimental data were obtained for both resonance and off-resonance conditions with uniquely tailored inlet distortion. This paper covers aspects relating to the design of fast response pressure sensors and their installation on thin impeller blades. Additionally, sensor properties are outlined with a focus on calibration and measurement uncertainty estimations. The second part of this paper presents unsteady pressure results taken for a number of inlet distortion cases. It will be shown that the intended excitation order due to inlet flow distortion is of comparable magnitude to the second and third harmonics which are consistently observed in all measurements. Finally, an experimental method will be outlined that enables the measurement aerodynamic work on the blade surface during resonant crossing. This approach quantifies the energy exchange between the blade and the flow in terms of cyclic work along the blade surface. The phase angle between the unsteady pressure and the blade movement will be shown to determine the direction of energy transfer between the blade and the fluid.

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Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion

Volume 1: Turbomachinery ◽

10.1115/82-gt-67 ◽

1982 ◽

Cited By ~ 1

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.

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Non-Axisymmetric Stator Design for Boundary Layer Ingesting Fans

Volume 1: Aircraft Engine; Fans and Blowers; Marine; Honors and Awards ◽

10.1115/gt2017-63082 ◽

2017 ◽

Author(s):

E. J. Gunn ◽

C. A. Hall

Keyword(s):

Boundary Layer ◽

Flow Field ◽

Diffusion Factor ◽

Pressure Surface ◽

Inlet Distortion ◽

Design Changes ◽

Final Design ◽

And Diffusion ◽

Stator Design ◽

Additional Loss

In a Boundary Layer Ingesting (BLI) fan system the inlet flow field is highly non-uniform. In this environment, an axisymmetric stator design suffers from a non-uniform distribution of hub separations, increased wake thicknesses and casing losses. These additional loss sources can be reduced using a non-axisymmetric design that is tuned to the radial and circumferential flow variations at exit from the rotor. In this paper a non-axisymmetric design approach is described for the stator of a low-speed BLI fan. Firstly sectional design changes are applied at each radial and circumferential location. Next, this approach is combined with the application of non-axisymmetric lean. The designs were tested computationally using full-annulus unsteady CFD of the complete fan stage with a representative inlet distortion. The final design has also been manufactured and tested experimentally. The results show that a 2D sectional approach can be applied non-axisymmetrically to reduce incidence and diffusion factor at each location. This leads to reduced loss, particularly at the casing and midspan, but it does not eliminate the hub separations that are present within highly distorted regions of the annulus. These are relieved by non-axisymmetric lean where the pressure surface is inclined towards the hub. For the final design, the loss in the stator blades operating with BLI was measured to be 10% lower than for the original stator design operating with undistorted inflow. Overall, the results demonstrate that non-axisymmetric design has the potential to eliminate any additional loss in a BLI fan stator caused by the non-uniform ingested flow-field.

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Toward Future Installations: Mutual Interactions of Short Intakes With Modern High Bypass Fans

Journal of Turbomachinery ◽

10.1115/1.4044080 ◽

2019 ◽

Vol 141 (8) ◽

Cited By ~ 1

Author(s):

Nagabhushana Rao Vadlamani ◽

Teng Cao ◽

Rob Watson ◽

Paul G. Tucker

Keyword(s):

Pressure Fluctuations ◽

Limiting Factors ◽

Small Scale ◽

Flow Distortion ◽

Factors Affecting ◽

Fan Performance ◽

Shock Unsteadiness ◽

Power Spectral ◽

Order Of Magnitude ◽

Underlying Mechanisms

In this paper, we investigate the coupled interaction between a new short intake design with a modern fan in a high-bypass ratio civil engine, specifically under the off-design condition of high incidence. The interaction is expected to be much more significant than that on a conventional intake. The performance of both the intake-alone and rotor-alone configurations are examined under isolation. Subsequently, a comprehensive understanding on the two-way interaction between intake and fan is presented. This includes the effect of fan on intake angles of attack (AoA) tolerance (FoI) and the effect of circumferential and radial flow distortion induced by the intake on the fan performance (IoF). In the FoI scenario, the rotor effectively redistributes the mass flow at the fan-face. The AoA tolerance of the short-intake design has increased by ≈4 deg when compared with the intake-alone configuration. Dynamic nature of distortion due to shock unsteadiness has been quantified. ST plots and power spectral density (PSD) of pressure fluctuations show the existence of a spectral gap between the shock unsteadiness and blade passing, with almost an order of magnitude difference in the corresponding frequencies. In the IoF scenario, both the “large” (O(360 deg)) and “small” scale distortion (O(10–60 deg)) induced by the intake results in a non-uniform inflow to the rotor. Sector analysis reveals a substantial variation in the local operating condition of the fan as opposed to its steady characteristic. Streamline curvature, upwash, and wake thickening are identified to be the three key factors affecting the fan performance. These underlying mechanisms are discussed in detail to provide further insights into the physical understanding of the fan-intake interaction. In addition to the shock-induced separation on the intake lip, the current study shows that shorter intakes are much more prone to the upwash effect at higher AoA. Insufficient flow straightening along the engine axis is reconfirmed to be one of the limiting factors for the short-intake design.

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