Rotor Design to Attenuate Flow Distortion—Part I: A Semiactuator Disk Analysis

1975 ◽  
Vol 97 (1) ◽  
pp. 11-20 ◽  
Author(s):  
C. T. Savell ◽  
W. R. Wells
Keyword(s):  
Wave Length ◽  
Design Parameters ◽  
Transmission Characteristics ◽  
Flow Distortion ◽  
One Dimensional ◽  
Inlet Distortion ◽  
Rotor Design ◽  
Blade Cascade ◽  
Wave Guides ◽  
Parametric Studies

The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady semiactuator disk cascade theory. This method models the blade cascade as one-dimensional wave guides and describes the transmission characteristics of a rotor to be a function of the distortion wave length and the length of the rotor chord, as well as the normal design parameters. Two parametric studies on the response of a loaded rotor to inlet distortions are done for a single rotor operating at off design conditions and a number of rotors operating at their design points. Fourier series representations of arbitrary distortion wave shapes are used for comparison with experimental data.

Rotor Design to Attenuate Flow Distortion—Part II: An Unsteady Thin Airfoil Cascade Analysis

1975 ◽  
Vol 97 (1) ◽  
pp. 37-46
Author(s):  
C. T. Savell ◽  
W. R. Wells
Keyword(s):  
Physical Interpretation ◽  
Wave Length ◽  
Design Parameters ◽  
Flow Distortion ◽  
Inlet Distortion ◽  
Actuator Disk ◽  
Rotor Design ◽  
Thin Airfoil ◽  
Cascade Analysis ◽  
Airfoil Cascade

The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady thin airfoil cascade theory which can account for the distortion wave length, rotor chord and cascade solidity. The model consists of representing each blade by a moving doublet filament of finite length immersed in a compressible stream containing a velocity distortion. The study is limited to an unloaded, flat plate rotor. This model provides a new physical interpretation for the flow adjustments observed ahead of the rotor and for the generation of sound when an inlet distortion is imposed. The analytical results show the influence of solidity and other rotor design parameters on the distortion transfer. They are found to approach the semi-actuator disk results as the solidity tends to infinity.

Momentum exchange impact damper design methodology for object-wall-collision problems

2017 ◽  
Vol 24 (14) ◽  
pp. 3206-3218
Author(s):  
Yohei Kushida ◽  
Hiroaki Umehara ◽  
Susumu Hara ◽  
Keisuke Yamada
Keyword(s):  
Optimal Design ◽  
Design Methodology ◽  
Design Parameters ◽  
Momentum Exchange ◽  
Impact Damper ◽  
One Dimensional ◽  
Practical Design ◽  
Wall Collision ◽  
Damper Design ◽  
And Control

Momentum exchange impact dampers (MEIDs) were proposed to control the shock responses of mechanical structures. They were applied to reduce floor shock vibrations and control lunar/planetary exploration spacecraft landings. MEIDs are required to control an object’s velocity and displacement, especially for applications involving spacecraft landing. Previous studies verified numerous MEID performances through various types of simulations and experiments. However, previous studies discussing the optimal design methodology for MEIDs are limited. This study explicitly derived the optimal design parameters of MEIDs, which control the controlled object’s displacement and velocity to zero in one-dimensional motion. In addition, the study derived sub-optimal design parameters to control the controlled object’s velocity within a reasonable approximation to derive a practical design methodology for MEIDs. The derived sub-optimal design methodology could also be applied to MEIDs in two-dimensional motion. Furthermore, simulations conducted in the study verified the performances of MEIDs with optimal/sub-optimal design parameters.

Performance Modeling of Desiccant Wheels: 1 — Model Development

2008 ◽  
Author(s):  
Chaoqin Zhai ◽  
David H. Archer ◽  
John C. Fischer
Keyword(s):  
Model Development ◽  
Axial Direction ◽  
Performance Model ◽  
Design Parameters ◽  
Residual Water ◽  
One Dimensional ◽  
Operating Variables ◽  
Steady State Operation ◽  
Rotary Speed ◽  
The Impact

This paper presents the development of an equation based model to simulate the combined heat and mass transfer in the desiccant wheels. The performance model is one dimensional in the axial direction. It applies a lumped formulation in the thickness direction of the desiccant and the substrate. The boundary conditions of this problem represent the inlet outside/process and building exhaust/regeneration air conditions as well as the adiabatic condition of the two ends of the desiccant composite. The solutions of this model are iterated until the wheel reaches periodic steady state operation. The modeling results are obtained as the changes of the outside/process and building exhaust/regeneration air conditions along the wheel depth and the wheel rotation. This performance model relates the wheel’s design parameters, such as the wheel dimension, the channel size and the desiccant properties, and the wheel’s operating variables, such as the rotary speed and the regeneration air flowrate, to its operating performance. The impact of some practical issues, such as wheel purge, residual water in the desiccant and the wheel supporting structure, on the wheel performance has also been investigated.

Parametric Studies of Pipe Diffuser on Performance of a Highly Loaded Centrifugal Compressor

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Ge Han ◽  
Xingen Lu ◽  
Shengfeng Zhao ◽  
Chengwu Yang ◽  
Junqiang Zhu
Keyword(s):  
Centrifugal Compressor ◽  
Performance Enhancement ◽  
Detailed Comparison ◽  
Flow Distortion ◽  
Flow Solver ◽  
Beneficial Effects ◽  
Physical Mechanisms ◽  
Parametric Studies ◽  
Compressor Performance ◽  
Highly Loaded

Pipe diffusers with several different geometries were designed for a highly loaded centrifugal compressor originally using a wedge diffuser. Parametric studies on the effect of pipe diffuser performance of a highly loaded centrifugal compressor by varying pipe diffuser inlet-to-impeller exit radius ratio, throat length, divergence angle, and throat area on centrifugal compressor performance were performed using a state-of-the-art multiblock flow solver. An optimum design of pipe diffuser was obtained from the parametric study, and the numerical results indicate that this pipe diffuser has remarkable advantageous effects on the compressor performance. Furthermore, a detailed comparison of flow visualization between the pipe diffuser and the wedge diffuser was conducted to identify the physical mechanism that account for the beneficial effects of the pipe diffuser on the performance and stability of the compressor. It was found that the performance enhancement afforded by the pipe diffuser is a result of the unique diffuse inlet flow pattern. Alleviating flow distortion in the diffuser inlet and reducing the possibility of a flow separation in discrete passages are the physical mechanisms responsible for improving the highly loaded centrifugal compressor performance.

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

2009 ◽  
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.

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.

Numerical Investigation of the Effect of Diffuser and Volute Design Parameters on the Performance of a Centrifugal Compressor Stage

2016 ◽  
Author(s):  
Lei Yu ◽  
William T. Cousins ◽  
Feng Shen ◽  
Georgi Kalitzin ◽  
Vishnu Sishtla ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Gas Flow ◽  
Pressure Rise ◽  
Design Parameters ◽  
Compressor Stage ◽  
Flow Distortion ◽  
Cross Sectional ◽  
Centrifugal Stage ◽  
And Performance ◽  
The Impact

In this effort, 3D CFD simulations are carried out for real gas flow in a refrigeration centrifugal compressor. Both commercial and the in-house CFD codes are used for steady and unsteady simulations, respectively. The impact on the compressor performance with various volute designs and diffuser modifications are investigated with steady simulations and the analysis is focused on both the diffuser and the volute loss, in addition to the flow distortion at impeller exit. The influence of the tongue, scroll diffusion ratio, diffuser length, and cross sectional area distribution is examined to determine the impact on size and performance. The comparisons of total pressure loss, static pressure recovery, through flow velocity, and the secondary flow patterns for different volute designs show that the performance of the centrifugal compressor depends upon how well the scroll portion of the volute collects the flow from the impeller and achieves the required pressure rise with minimum flow losses in the overall diffusion process. Finally, the best design is selected based on compressor stage pressure rise and peak efficiency improvement. An unsteady simulation of the full wheel compressor stage was carried out to further examine the interaction of impeller, diffuser and the volute. The unsteady flow interactions are shown to have a major impact on the performance of the centrifugal stage.

Fan Aerodynamics With a Short Intake at High Angle of Attack

2020 ◽  
Author(s):  
Ben Mohankumar ◽  
Cesare A. Hall ◽  
Mark J. Wilson
Keyword(s):  
Pressure Ratio ◽  
Angle Of Attack ◽  
Radial Pressure ◽  
Separation Mechanism ◽  
Flow Distortion ◽  
Ratio Distribution ◽  
Rotor Design ◽  
Velocity Triangle ◽  
Tip Velocity ◽  
High Work

Abstract Future turbofan engines seek shorter intakes to reduce the cruise fuel burn of a low pressure ratio, large diameter fan. However, shorter intakes increase the level of flow distortion entering the rotor when the aircraft angle of attack (AOA) is high, reducing thrust when critically needed. This paper considers how the fan rotor radial pressure ratio distribution and tip velocity triangle can be designed to improve thrust at high AOA. Full annulus, unsteady CFD is performed on three rotor designs coupled to a short intake. We show that rotor design for high AOA should be guided by three flow mechanisms. Mechanism i) is caused by high Mach number flow over the bottom intake lip, which chokes the rotor leading to high loss. Mechanism ii) is the loss generation in the rotor tip as it passes through an intake separation. Mechanism iii) shows radial flows through the rotor change both the amount and the way work is imparted on the flow. Two comparable rotor design philosophies for high thrust are proposed; high work or low loss. Rotors designed to a mid-high radial pressure ratio distribution impart high work on streamlines that migrate radially towards the hub and exit the rotor at highly cambered sections. Meanwhile, tip-high designs reduce choking losses in the midspan when operating with a separated intake, particularly when the tip velocity triangle is designed to high axial velocity diffusion over high camber. However, such designs suffer with higher tip losses after exiting an intake separation.

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