Preliminary Study of a Centrifugal Compressor With Counter-Rotating Impellers: Design and Performances Study

2020 ◽  
Author(s):  
Abed Cheikh Brahim ◽  
Khelladi Sofiane ◽  
Deligant Michael ◽  
El Marjani Abdel ◽  
Farid Bakir
Keyword(s):  
Centrifugal Compressor ◽  
Degrees Of Freedom ◽  
Numerical Data ◽  
Centrifugal Impeller ◽  
Through Flow ◽  
Aerodynamic Performances ◽  
Preliminary Study ◽  
And Performance ◽  
And Control ◽  
Selection Of

Abstract Turbomachinery with double counter-rotating impellers offer more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more published works are available concerning axial type turbomachines than centrifugal ones. This work deals with a preliminary design and performance analysis applied to two counter-rotating impellers of a centrifugal compressor. We present here the design practice developed based on 0D/1D models, also coupled with optimization and stream-curvature through-flow methods to satisfy the selected design-criteria. An analyze of aerodynamic performances results are made and compared to those available experimental and numerical data of a baseline configuration, composed of one centrifugal-impeller and a volute. The compressor studied here includes a first conventional impeller with an axial inlet and a mixed or centrifugal outlet. The second impeller is designed parametrically and can be considered as a rotating-diffuser with a radial or mixed inlet and outlet. Ultimately, the numerical simulation results of a selection of candidate solutions are discussed.

scholarly journals Experimental Validation of the Aerodynamic Performance of an Innovative Counter-Rotating Centrifugal Compressor

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2582
Author(s):  
Cheikh Brahim ABED ◽  
Sofiane KHELLADI ◽  
Michael DELIGANT ◽  
Abdellatif EL EL MARJANI ◽  
Moisés SOLIS ◽  
...  
Keyword(s):  
Experimental Data ◽  
Centrifugal Compressor ◽  
Degrees Of Freedom ◽  
Experimental Validation ◽  
Design Method ◽  
Pressure Rise ◽  
Design Tool ◽  
Centrifugal Impeller ◽  
Speed Ratio ◽  
And Control

Turbomachinery with double counter-rotating impellers offers more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more publications concerning axial type turbomachines are available than centrifugal ones. This work deals with a design and experimental performance analysis, applied to two counter-rotating impellers of a centrifugal compressor “CRCC”. CRCC was designed with a specifically developed tool based on mean-line approach coupled with optimization algorithms and a stream-curvature through-flow method to satisfy the design criteria. This paper presents an experimental validation of the CRCC design tool and its performances against the baseline “SR”, composed of one centrifugal impeller and a volute for which experimental data are available. CRCC numeric simulations are also validated by experimental data. For a fair comparison between CRCC and SR, the same volute is used for both configurations. The CRCC studied here includes a first conventional impeller with an axial inlet and a radial outlet, while the second impeller is parametrically designed and can be considered a rotating bladed diffuser with a radial inlet and outlet. The obtained results show that CRCC can deliver a pressure rise increase of two compared to SR, along with an increase of isentropic efficiency and also validate the design method of this novel layout. The experimental results also show that the speed ratio of CRCC has a positive effect on the surge and shock margin.

scholarly journals Soft Spherical Tensegrity Robot Design Using Rod-Centered Actuation and Control

2016 ◽  
Author(s):  
Lee-Huang Chen ◽  
Kyunam Kim ◽  
Ellande Tang ◽  
Kevin Li ◽  
Richard House ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Space Exploration ◽  
Robot Design ◽  
The Novel ◽  
Flexible Design ◽  
Spherical Robot ◽  
Potential Benefits ◽  
And Performance ◽  
And Control

This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture. This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system’s behavior and performance.

scholarly journals Using Recommender Systems for Matching Students with Suitable Specialization: An Exploratory Study at King Abdulaziz University

2021 ◽  
Vol 16 (03) ◽  
pp. 316
Author(s):  
Khloud Alshaikh ◽  
Naela Bahurmuz ◽  
Ola Torabah ◽  
Sara Alzahrani ◽  
Zainab Alshingiti ◽  
...  
Keyword(s):  
High School Graduates ◽  
Selection Process ◽  
Accuracy Ratio ◽  
King Abdulaziz University ◽  
Filtering Technique ◽  
Preliminary Study ◽  
And Performance ◽  
Preparatory Year ◽  
Initial Results ◽  
Selection Of

In Saudi Arabia, all high school graduates who want join local universities have to go through a preparatory year before selecting their specific specialization/major. One of the most concerning issues for those fresh undergraduate college students is the selection of their specialization. College specialization selection is critical for them, as their academic and career future will be affected by this decision. An un-suitable specialization selection will have unfortunate consequences, not only on the students' future but also on the university’s resources and budget. This paper sug-gests a solution to this problem by introducing a preliminary study of a recommend-er system (RS), which will recommend the appropriate specialization for the students based on various tests and grades during the preparatory year at King Abdulaziz University (KAU). The proposed system guides students through their specialization selection process based on their abilities. The collaborative filtering technique was used to build the RS and K-fold cross-validation was adopted to evaluate its accura-cy and performance. The results showed the prediction of a specialization for each student with good accuracy ratio. These promising initial results provide a feasible solution to assess this issue further in future studies.

Influence of Swirl Distribution on Blade Shape and Performance of a Centrifugal Impeller

2020 ◽  
Author(s):  
Qin Cui ◽  
Guoliang Qin ◽  
Lei Li ◽  
Cheng Jia ◽  
Yi Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Flow Direction ◽  
Input Parameter ◽  
Vortex Method ◽  
Centrifugal Impeller ◽  
Streamline Curvature ◽  
Design Program ◽  
Blade Shape ◽  
And Performance

Abstract All-over-controlled vortex method is an effective tool to inversely design the 3D impeller of a centrifugal compressor. In this method, swirl distribution is treated as a significant input parameter to control the blade shape, impeller flow field, and compressor performance. It is acknowledged that swirl distribution is prescribed by designers mostly relying on the personal experience at the beginning of design. So how to specify the swirl distribution is still a big challenge for impeller designers. Of the most interest in this paper is to provide a theoretical technique that can be readily applied to specify swirl distribution and reduce the dependence on the designers experience. A judgement criterion rCθ – ωr2 is proposed to design the swirl distribution. Based on the streamline curvature method, a 3D centrifugal impeller design program is developed to design centrifugal impeller. The scale and uniformity of rCθ – ωr2 along flow direction are discussed theoretically to conduct the specifying of swirl distribution. The theoretical analysis is verified by a specific centrifugal compressor case. Then commercial CFD software is used to predict the flow field and the performance of the impeller. The results demonstrate that the scale and distribution uniformity of rCθ – ωr2 have a significant effect on the blade shape and the flow field within the impeller, and possible loss can be reduced. For the new designer, it is possible to preliminarily recognize and eliminate the infeasible swirl distribution, and adjust the unsatisfactory swirl distribution using rCθ – ωr2. Proper blade shape and good impeller performance can be achieved with the help of the judgement criterion rCθ – ωr2.

A Centrifugal Compressor Flow Analysis Employing a Jet-Wake Passage Flow Model

1977 ◽  
Vol 99 (1) ◽  
pp. 141-147 ◽  
Author(s):  
J. H. G. Howard ◽  
C. Osborne
Keyword(s):  
Centrifugal Compressor ◽  
Curve Fitting ◽  
Flow Model ◽  
Flow Analysis ◽  
Stagnation Pressure ◽  
Centrifugal Impeller ◽  
Experimental Measurements ◽  
Suction Surface ◽  
Streamline Curvature ◽  
Through Flow

The streamline curvature through-flow analysis of a centrifugal impeller passage flow has been modified to include a flow model with a wake on the suction surface. With this model, empirically determined or measured impeller conditions can be matched without requiring a distributed stagnation pressure loss within the passage. Its use in impeller design is presented and comparison with experimental measurements from two impellers illustrate the utility of this approach. A brief discussion of experience with the associated forms of curve fitting and streamline smoothing required for the analysis solution is included.

Human Extenders

1993 ◽  
Vol 115 (2B) ◽  
pp. 281-290 ◽  
Author(s):  
H. Kazerooni ◽  
Jenhwa Guo
Keyword(s):  
Degrees Of Freedom ◽  
Experimental Studies ◽  
Mathematical Expression ◽  
Contact Forces ◽  
Degree Of Freedom ◽  
Direct Drive ◽  
Physical Strength ◽  
Dynamics And Control ◽  
And Performance ◽  
And Control

A human’s ability to perform physical tasks is limited by physical strength, not by intelligence. We coined the word “extenders” as a class of robot manipulators worn by humans to augment human mechanical strength, while the wearer’s intellect remains the central control system for manipulating the extender. Our research objective is to determine the ground rules for the control of robotic systems worn by humans through the design, construction, and control of several prototype experimental direct-drive/non-direct-drive multi-degree-of-freedom hydraulic/electric extenders. The design of extenders is different from the design of conventional robots because the extender interfaces with the human on a physical level. The work discussed in this article involves the dynamics and control of a prototype hydraulic six-degree-of-freedom extender. This extender’s architecture is a direct drive system with all revolue joints. Its linkage consists of two identical subsystems, the arm and the hand, each having three degrees of freedom. Two sets of force sensors measure the forces imposed on the extender by the human and by the environment (i.e., the load). The extender’s compliances in response to such contact forces were designed by selecting appropriate force compensators. The stability of the system of human, extender, and object being manipulated was analyzed. A mathematical expression for the extender performance was determined to quantify the force augmentation. Experimental studies on the control and performance of the experimental extender were conducted to verify the theoretical predictions.

Tip clearance effect on through-flow and performance of a centrifugal compressor

2004 ◽  
Vol 18 (6) ◽  
pp. 979-989 ◽  
Author(s):  
Hark-Jin Eum ◽  
Young-Seok Kang ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Compressor ◽  
Tip Clearance ◽  
Through Flow ◽  
And Performance

scholarly journals Soft Spherical Tensegrity Robot Design Using Rod-Centered Actuation and Control

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Lee-Huang Chen ◽  
Kyunam Kim ◽  
Ellande Tang ◽  
Kevin Li ◽  
Richard House ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Space Exploration ◽  
Robot Design ◽  
The Novel ◽  
Flexible Design ◽  
Preliminary Testing ◽  
Potential Benefits ◽  
And Performance ◽  
And Control

This paper presents the design, analysis, and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees-of-freedom in movement and flexible design. However, to take full advantage of these properties, a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable, and power routing systems and increased design difficulty. Here, we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture. This paper presents the novel mechanism design, architecture, and simulations of TT-3, an untethered, fully actuated cable-driven six-bar spherical tensegrity robot. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system's behavior and performance and is evaluated against previous models of tensegrity robots developed at UC Berkeley and elsewhere.

Freezing Degrees of Freedom During Motor Learning: A Systematic Review

Motor Control ◽  
2020 ◽  
Vol 24 (3) ◽  
pp. 457-471 ◽  
Author(s):  
Anderson Nascimento Guimarães ◽  
Herbert Ugrinowitsch ◽  
Juliana Bayeux Dascal ◽  
Alessandra Beggiato Porto ◽  
Victor Hugo Alves Okazaki
Keyword(s):  
Motor Learning ◽  
Control Strategy ◽  
Degrees Of Freedom ◽  
Control Strategies ◽  
System Solution ◽  
Dart Throwing ◽  
The Central Nervous System ◽  
Enormous Variation ◽  
And Control ◽  
Selection Of

According to Bernstein, the central nervous system solution to the human body’s enormous variation in movement choice and control when directing movement—the problem of degrees of freedom (DF)—is to freeze the number of possibilities at the beginning of motor learning. However, different strategies of freezing DF are observed in literature, and the means of selection of the control strategy during learning is not totally clear. This review investigated the possible effects of the class and objectives of the skill practiced on DF control strategies. The results of this review suggest that freezing or releasing the DF at the beginning of learning does not depend on the class (e.g., discrete skill class: football kick, dart throwing; continuous skill class: athletic march, handwriting) or objective of the skill (e.g., balance, velocity, and accuracy), in isolation. However, an interaction between these two skill elements seems to exist and influences the selection of the DF control strategy.

scholarly journals Robust LFT-LPV H∞ Control of an Underactuated Inverted Pendulum on a Cart with Optimal Weighting Functions Selection by GA and ES

2020 ◽  
Vol 14 (4) ◽  
pp. 186-197
Author(s):  
Seif-El-Islam Hasseni ◽  
Latifa Abdou
Keyword(s):  
Degrees Of Freedom ◽  
Inverted Pendulum ◽  
Robust Stabilization ◽  
Evolutionary Strategies ◽  
Parametric Uncertainties ◽  
Weighting Functions ◽  
Cart Model ◽  
External Signals ◽  
And Control ◽  
Selection Of

Abstract This article investigates the robust stabilization and control of the inverted pendulum on a cart against disturbances, measurement noises, and parametric uncertainties by the LFT-based LPV technique (Linear-Fractional-Transformation based Linear-Parameter-Varying). To make the applying of the LPV technique possible, the LPV representation of the inverted pendulum on a cart model is developed. Besides, the underactuated constraint of this vehicle is overcome by considering both degrees of freedom (the rotational one and the translational one) in the structure. Moreover, the selection of the weighting functions that represent the desired performance is solved by two approaches of evolutionary algorithms; Genetic Algorithms (GA) and Evolutionary Strategies (ES) to find the weighting functions’ optimal parameters. To validate the proposed approach, simulations are performed and they show the effectiveness of the proposed approach to obtain robust controllers against external signals, as well as the parametric uncertainties.

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