DESIGN AND ANALYSIS OF A NEW SYMMETRICAL LINEAR ACTUATOR FOR HYDRAULIC AND PNEUMATIC SYSTEMS

1999 ◽  
Vol 23 (3-4) ◽  
pp. 377-396 ◽  
Author(s):  
S. Habibi ◽  
A.A. Goldenberg
Keyword(s):  
Flow Characteristics ◽  
Dynamic Effect ◽  
Input Force ◽  
Symmetrical Design ◽  
Command Input ◽  
Linear Actuators ◽  
Fixed End ◽  
Actuation Systems ◽  
Force Relationship ◽  
Better Than

In this paper, the performance of hydraulic actuation systems is analyzed and, it is observed that the performance of symmetrical (rotary) actuators is significantly better than their linear asymmetrical counterpart. The deficiency of linear actuators, resulting from their asymmetry, manifests itself as an undesirable dynamic effect related to the pressure characteristics of the actuator chambers. Subsequently, a new symmetrical design for linear actuators is proposed. In this design, the active areas of the two pressure chambers are made equal without the need for a dead-space on the fixed end of the piston as required by commercial double rod pistons. The paper discusses the benefits of this new design and demonstrates the advantages of its flow characteristics and its command input/force relationship. The theoretical observations are supported by experiments conducted on a large hydraulic robot. The Workmaster, formerly manufactured by Thorn EMI Robotics.

Flow Field Analysis of Pulse Converter Exhaust Manifold of Diesel Engines

2012 ◽  
Vol 468-471 ◽  
pp. 1693-1696
Author(s):  
Wen Jun Zhong ◽  
Zhi Xia He ◽  
Zhao Chen Jiang ◽  
Yun Long Huang
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Region ◽  
Field Analysis ◽  
Exhaust Manifold ◽  
Recirculation Flow ◽  
Pulse Converter ◽  
Flow Field Analysis ◽  
Better Than

A three-dimensional unsteady flow for the pulse converter exhaust manifold of 8-cylinder diesel engine was numerical simulated to get the flow characteristics of the exhaust manifold. Simulation results show that there are strong eddy flows, low pressure closed recirculation flow region in the exhaust manifold. Afterwards the structure optimization of the exhaust manifold with baffle was put forward and then the unsteady flow in the normal exhaust manifold, the exhaust manifold with baffle of 30 degrees and the exhaust manifold of 15 degrees were simulated and analyzed. It is concluded that the exhaust manifold with baffle is better than that without baffle, the recirculation flow region and the pressure loss in the exhaust manifold with baffle of 30 degrees is smaller than in it with baffle of 15 degree and the flow in the former exhaust manifold is much smoother.

scholarly journals Flow Characteristic and Trapping Characteristics of Cycloid Rotor Pump

2015 ◽  
Vol 9 (1) ◽  
pp. 449-454 ◽  
Author(s):  
Ren Zhenxing ◽  
Liu Chunyan ◽  
Li Yulong
Keyword(s):  
Flow Rate ◽  
Flow Characteristics ◽  
Position Angle ◽  
Gear Pump ◽  
Rotary Pump ◽  
Uniformity Coefficient ◽  
Discharge Pressure ◽  
Instantaneous Flow Rate ◽  
External Gear Pump ◽  
Better Than

To accurately calculate the flow rate of cycloid rotary pump as well as to correctly understand its trapped oil phenomenon, firstly the instantaneous flow rate formula of cycloid rotary pump was established based on the method of swept area, and then it was compared with the two present approximate formulas by an example. Secondly, based on the established flow rate formula and the created trapped oil model in the present literature, the trapped oil pressure of a single cavity near the minimum volume position was simulated. It was pointed that for cycloid rotary pump as an example, the flow non-uniform coefficient was 6.45%, and in contrast, the flow non-uniformity coefficient of external gear pump was 21.2%. Relative to the accurate results, the two present approximate errors of flow rates were 1.93% and 2.90%; and the present approximate error of flow non-uniform coefficient was 7.13%; when the minimum position angle was added by 0.5° or 1° or 2°, relative to discharge pressure of the pump, the corresponding maximum peak of trapped oil pressure increased by 1.6% or 6.0% or 21.7%. The results indicate that the flow characteristics of cycloid rotary pump are better than the external gear pump, the two present approximate errors of flow rate are little but the present approximate error of flow non-uniform coefficient is higher. Also, there is a trapped oil phenomenon in cycloid rotary pump which is not obvious.

Units Commitment Optimization of Pumping Station Based on Velocity Uniformity Analysis

2013 ◽  
Vol 805-806 ◽  
pp. 1720-1723
Author(s):  
Xing Liang
Keyword(s):  
Experimental Data ◽  
Velocity Distribution ◽  
Flow Pattern ◽  
Unit Commitment ◽  
Flow Characteristics ◽  
Optimal Operation ◽  
Operation Strategy ◽  
Turbulent Model ◽  
Pumping Station ◽  
Better Than

The Realizable k-ε turbulent model is employed to simulate the flow pattern in forebay of pumping station, and the precision of simulated results is verified by experimental data. And then the flow pattern of the different unit commitments is simulated to acquire the flow characteristics in forebay, such as circulating flow and velocity distribution, and the velocity uniformity of forebay is analyzed to search the optimal units commitment. The research results show that: under the different unit commitment, the characteristics of flow in forebay is so different that the effect of the diversion piers is not always advantageous; comparing the velocity uniformity, the optimal operation strategy is to try to operate the middle pumps, and the operation strategy of operating pumps on both sides is better than that of opening pumps on one side.

Double-Helix Linear Actuators

2021 ◽  
pp. 1-40
Author(s):  
Andrew P. Sabelhaus ◽  
Kyle Zampaglione ◽  
Ellande Tang ◽  
Lee-Huang Chen ◽  
Adrian Agogino ◽  
...  
Keyword(s):  
Double Helix ◽  
Kinematic Model ◽  
Helix Angle ◽  
Robotic Systems ◽  
Force Transmission ◽  
Force Load ◽  
Transmission Properties ◽  
Tension And Compression ◽  
Linear Actuators ◽  
Fixed End

Abstract Many robotic systems require linear actuation with high forces, large displacements, and compact profiles. This article presents a series of mechanisms, termed double-helix linear actuators (DHLAs), designed for this purpose. By rotating the fixed end of a double-helix linear actuator, its helix angle changes, displacing at the free end. This article proposes two concepts for DHLA designs, differing in their supporting structure, and derives kinematic and geometric models for both. Prototypes of each concept are presented, and for the more promising “continuous-rails” design, hardware tests are conducted that validate the actuator's kinematic model and characterize its force transmission properties. The final prototypes can exert both tension and compression forces, can displace up to 75% of their total length, and show consistent trends for torque vs. force load. These designs have the potential to overcome the force and displacement limitations of other linear actuators while simultaneously reducing size and weight.

Flow and Heat Transfer in Microchannels With Dimples and Protrusions

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Jibing Lan ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Characteristics ◽  
Field Synergy ◽  
Transfer Enhancement ◽  
Rectangular Microchannel ◽  
Field Synergy Principle ◽  
Flow And Heat Transfer ◽  
Better Than

Flow characteristics and heat transfer performances in a rectangular microchannel with dimples/protrusions are studied numerically in this research. The height and the width of the microchannel is 200 μm and 50 μm, respectively. The dimple/protrusion diameter is 100 μm, and the depth is 20 μm. The effects of Reynolds number, streamwise pitch, and arrangement pattern are examined. The numerical simulations are conducted using water as the coolant with the Reynolds number ranging from 100 to 900. The results show that dimple/protrusion technique in mcirochannel has the potential to provide heat transfer enhancement with low pressure penalty. The normalized Nusselt number is within the range from 1.12 to 4.77, and the corresponding normalized friction factor is within the range from 0.94 to 2.03. The thermal performance values show that the dimple + protrusion cases perform better than the dimple + smooth cases. The flow characteristics of the dimples/protrusions in microchannel are similar to those in conventional channel. Furthermore, from the viewpoint of energy saving, dimples/protrusions in microchannel behave better than those in conventional channel. Also from the viewpoint of field synergy principle, the synergy of the dimple + protrusion cases are much better than the dimple + smooth cases. Moreover, the synergy becomes worse with the increase in the Reynolds number and decrease in the streamwise pitch.

Internal Flow Field Analysis of Engine Intake Manifold Based on RE and CFD

2014 ◽  
Vol 1079-1080 ◽  
pp. 930-934
Author(s):  
Cai Yun Wang ◽  
Zhi Xia He ◽  
Qian Wang ◽  
Guo Jun Zhang ◽  
Shuo Wang
Keyword(s):  
Flow Characteristics ◽  
Internal Flow ◽  
Field Analysis ◽  
Intake Manifold ◽  
Engineering Technology ◽  
Air Intake ◽  
Flow Field Analysis ◽  
Processing Software ◽  
Working Performance ◽  
Better Than

The performance of the engine air intake system directly affect the working performance and fuel consumption, where the intake manifold design is the key.In this paper aimed at L91 Engine intake manifold ,firstly theRE(Reverse Engineering)technology was usedto rebuild the3d model of intake manifold.And then the internal flow zoneof the intake manifoldwas meshedin the pre-processing software ICEMand the internal flow fieldwas analyzedin the softwareof Fluent.The numerical model was verified by comparing the simulated and measured results. And then based on the numerical analysis of the internal flow characteristics of the intake manifold, the structure of variable-length intake manifold was come up with and finally was numerically proved to be better than the normal one.

scholarly journals Numerical simulation of the mixing and flow characteristics in lobed mixers

2014 ◽  
Vol 18 (4) ◽  
pp. 1203-1212 ◽  
Author(s):  
Wang Zhi-Wu ◽  
Zhang Kun ◽  
Zheng Longxi ◽  
Chen Xing-Gu ◽  
Li Ping ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Recirculation Region ◽  
Mixing Length ◽  
Mixing Performance ◽  
Gas Ratio ◽  
Better Than

This paper focused on the mixer optimization by numerical simulation. The mixing and flow characteristics inside two different lobed mixers with/without centrum were obtained by three-dimensional CFD simulation. The core flow was the hot rich-methane/O2?l?burnt gas, while the cold air flew by the by-pass. The air/burnt gas flow ratio was improved from 7 to 9 in order to confirm the effect of air/burnt gas ratio on the mixing and flow characteristics. The simulation results indicated that no matter which mixer was used, there were a pair of symmetrical recirculation regions in the mixers, and the total temperature and species distribution turned to be more uniform at the increased mixing length. The mixing performance in the lobed mixer with centrum was slightly better than that of the lobed mixer without centrum, and the length of recirculation region in the lobed mixer with centrum was slightly shorter than that of the lobed mixer without centrum. The air/burnt gas ratio had considerable effect on the mixing and flow characteristics. The mixing performance with air/burnt gas ratio of 9 was much better than that of air/burnt gas ratio 7. Similar mixing performance would attain in the case of air/burnt gas ratio 9 with only half of the mixing length in the case ofair/burnt gas ratio 7. The recirculation region in the case of air/burnt gas ratio 9 occurred ahead of that of air/burnt gas ratio 7, and the former was longer than the latter.

scholarly journals Flow Field Study of Bio-Inspired Corrugated Airfoils at Low Reynolds Number with Different Peak Shapes

2020 ◽  
Vol 12 (3) ◽  
pp. 87-100
Author(s):  
Y. D. DWIVEDI
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Turbulence Modeling ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Geometrical Parameters ◽  
Ansys Fluent ◽  
Modeling Software ◽  
Fluent Software ◽  
Better Than

This study is intended to understand the fluid flow behaviour of a bio inspired corrugated wing obtained from the mid span of the dragonfly wing with different peak shapes of the corrugations. The aerodynamic effect due to variation of the shape of the first peak is studied with triangular and a curved peak shapes. The coordinates of the corrugated wing of the dragonfly were obtained from the existing literature and scaled up 1:50 to do the computational work on it. The corrugated wing was modeled by using a modeling software, the meshing was done by using ICEMCFD with a rectangular block meshing and simulated in Ansys Fluent software at 35000 Reynolds number and angles of attack ranging from 4° to 12°. The k-ε turbulence modeling was deployed to capture turbulence in the tested domain. The boundary conditions and size of the domain were selected as per available experimental wind tunnel setup. The flow characteristics like pressure and velocity of the triangular and curved peaks were obtained computationally and compared with each other having same geometrical parameters. The simulated results showed that the curved peak performed aerodynamically better than the triangular peak. The leading edge vortices were observed in both models trapped in the trough of the first valley with some different intensity. The validation of the computational flow results was done by existing experimental flow visualization in a wind tunnel and both results agree with each other.

Improvement of the Performance of a Centrifugal Compressor by Modifying the Volute Inlet

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Semi Kim ◽  
Junyoung Park ◽  
Kukyoung Ahn ◽  
Jehyun Baek
Keyword(s):  
Radial Velocity ◽  
Mass Flow ◽  
Flow Characteristics ◽  
Total Efficiency ◽  
Swirl Velocity ◽  
Mass Flow Rates ◽  
New Type ◽  
Comparison Of The Results ◽  
Simulated Flow ◽  
Better Than

In centrifugal compressors, the diffuser and the volute have strong influences on the flow discharged from the impeller and thus also on the performance. In particular, a key parameter is the radial velocity at the volute inlet; it determines the swirl velocity, which is dissipated as a loss, i.e., it results in performance degradation. With the aim of reducing the swirl loss, a new type of volute with a modified inlet height was tested in this study. The volute inlet height was modified to 6 mm and 7 mm from the original height of 5 mm. The reliability of our computations was tested by comparison of the results of a model with this original height with experimental data. Flow analyses were conducted not only at the design mass flow rate but also at lower and higher mass flow rates. A higher total-to-total efficiency was obtained as a result of the linear increases of the volute inlet height from the diffuser outlet to 6 mm and 7 mm. Our detailed investigation of the simulated flow fields shows that the flow characteristics for a volute inlet height of 6 mm are better than those for a volute inlet height of 5 mm. These results clearly show that a greater volute inlet height assists in pressure recovery and reduces swirl loss in the volute. However, the volute inlet height of 7 mm results in larger hub separation and more energy loss, and thus in inferior performance. Therefore, the hub separation and the radial velocity at the volute inlet strongly influence the performance.

Experimental and Simulation Research on Flow Characteristics of SCR System in a 100MW Power Station

2014 ◽  
Vol 1051 ◽  
pp. 920-926
Author(s):  
Qian Jun Li ◽  
Dong Ping Zhang ◽  
Fang Zhang ◽  
Xian Feng Liu
Keyword(s):  
Concentration Field ◽  
Flow Characteristics ◽  
Test Plant ◽  
Simulation Research ◽  
Guide Plate ◽  
Practical Engineering ◽  
Simulation Results ◽  
Scr System ◽  
Better Than ◽  
Good Agreement

This work try to optimize the flow field and concentration field of SCR system. Firstly, the original SCR system is simulated by Fluent and two kinds of guide plates are utilized. The simulation results show that the straight guide plate is slightly better than curve guide plate. The relatively standard deviation of velocity and concentration fields and pressure drop agree with the design rules. To verify the simulation results, a 1:10 scale cold plexiglass test plant is established and this plant is simulated correspondingly. The simulation results are in good agreement with experimental results. So the simulation results of original SCR system are credibly and can guide the practical engineering.

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