scholarly journals Effect of chamber diameter of vortex gripper on maximum suction force and flow field

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401983740 ◽  
Author(s):  
Ching Wang ◽  
Jianghong Zhao ◽  
Xin Li
Keyword(s):  
Theoretical Model ◽  
Flow Field ◽  
Pressure Gradient ◽  
Velocity Distribution ◽  
Negative Pressure ◽  
High Speed ◽  
Vortex Chamber ◽  
Experimental Results ◽  
Circumferential Velocity ◽  
Suction Force

The vortex gripper is a non-contact suction device that uses a high-speed rotating airflow to create a negative pressure and suction force. In this research, we studied the effect of the vortex gripper’s diameter on the maximum suction force and internal flow field. First, we proposed a simplified theoretical model of the maximum suction force and predicted the influences of changing the diameter. Then, we obtained the maximum suction forces of the grippers with different diameters through the experiment. Both the theoretical and experimental results show that changing the diameter of the vortex gripper increases the maximum suction force. However, with the increase in the diameter, the prediction of the trend of the maximum suction force is inconsistent with the experimental results. To analyze the difference between the theoretical and experimental results, we further measured the pressure distribution of the vortex gripper and calculated the pressure gradient. The pressure distribution showed that the maximum negative pressure decreases while the diameter increases, and there is a pressure platform, which dominates the central area of the chamber. Next, we indirectly obtained the circumferential velocity distribution based on the relationship between the pressure gradient and circumferential velocity. The results of the circumferential velocity distribution reveal that the high-speed rotating airflow only exists in the area near the inner wall of the vortex chamber, while the circumferential velocity in the central part of the vortex chamber is extremely slow. In addition, the results clarify that the inaccurate assumption of velocity distribution of the simplified theoretical model is the main cause of the theoretical prediction bias.

Experimental Study of Turbulent Macroinstabilities in an Agitated System with Axial High-Speed Impeller and with Radial Baffles

1996 ◽  
Vol 61 (6) ◽  
pp. 856-867 ◽  
Author(s):  
Oldřich Brůha ◽  
Ivan Fořt ◽  
Pavel Smolka ◽  
Milan Jahoda
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
High Speed ◽  
Experimental Results ◽  
Turbulent Regime ◽  
Frequency Of Occurrence ◽  
Visualization Method ◽  
Entire Flow

The frequency of turbulent macroinstability occurrence was measured in liquids agitated in a cylindrical baffled vessel. As it has been proved by preceding experimental results of the authors, the stochastic quantity with frequency of occurrence of 10-1 to 100 s-1 is concerned. By suitable choosing the viscosity of liquids and frequency of impeller revolutins, the region of Reynolds mixing numbers was covered from the pure laminar up to fully developed turbulent regime. In addition to the equipment making it possible to record automatically the macroinstability occurrence, also the visualization method and videorecording were employed. It enabled us to describe in more detail the form of entire flow field in the agitated system and its behaviour in connection with the macroinstability occurrence. It follows from the experiments made that under turbulent regime of flow of agitated liquids the frequency of turbulent macroinstability occurrence is the same as the frequency of the primary circulation of agitated liquid.

Two-dimensional pressure field and backflow in the annular skirt of vortex gripper

2020 ◽  
pp. 095440622097404
Author(s):  
Jianghong Zhao ◽  
Xin Li
Keyword(s):  
Flow Field ◽  
Pressure Distribution ◽  
Local Stress ◽  
Vortex Chamber ◽  
Physical Contact ◽  
Two Dimensional ◽  
Stress Concentrations ◽  
Suction Force ◽  
Maximum Value ◽  
Gap Height

The vortex gripper is a kind of pneumatic noncontact gripper that does not produce a magnetic field and heat. It can grip a workpiece without physical contact, which avoids any unintentional damage such as mechanical scratches, local stress concentrations, frictional static electricity, and surface stains. This study focused on the two-dimensional pressure distribution field on a workpiece surface under the vortex gripper. Theoretical, experimental, and computational fluid dynamics results were combined to study the backflow phenomenon in the annular skirt, which can decrease the gripper’s suction force after the maximum value is reached. First, the pressure distribution in the annular skirt was theoretically modeled. A comparison with the experimental results showed that increasing the gap height between the gripper and workpiece generates a circumferentially asymmetrical flow field in the skirt. Based on this, it was hypothesized that an airflow in the circumferential direction may exist. The experimental data and simulation results were analyzed under large gap height conditions to observe the backflow in detail and it was found that an uneven pressure distribution with positive and negative pressure regions generated by the uneven flow is the root cause of the backflow. Finally, the effect of the backflow on the flow field in two different flow regions (in the annular skirt and inside the vortex chamber) was analyzed and the reason why the suction force of the vortex gripper has a maximum value was determined.

The effect analysis of an engine jet on an aircraft blast deflector

2018 ◽  
Vol 41 (4) ◽  
pp. 990-1001
Author(s):  
Song Ma ◽  
Jianguo Tan ◽  
Xiankai Li ◽  
Jiang Hao
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
High Speed ◽  
Deflection Angle ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Experimental Results ◽  
Exhaust Gases ◽  
The Impact

This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard [Formula: see text]-[Formula: see text] turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the [Formula: see text] deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that [Formula: see text] may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck.

Experimental Investigation of the Characteristics of Dynamic Cutting Process

1977 ◽  
Vol 99 (2) ◽  
pp. 410-418 ◽  
Author(s):  
M. M. Nigm ◽  
M. M. Sadek
Keyword(s):  
Experimental Investigation ◽  
Theoretical Model ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Rake Angle ◽  
Experimental Results ◽  
High Speed Photography ◽  
Cutting Coefficients

The dynamic response of the shear plane and the variations of the dynamic cutting coefficients are experimentally investigated at various values of feed, cutting speed, rake angle, clearance angle, frequency, and amplitude of chip thickness modulation. Wave generating and wave removing cutting tests, in which high-speed photography is used to investigate the geometry of chip formation, are carried out. The theoretical model of dynamic cutting developed in [1] is assessed with reference to these experimental results. A comparison between this model and previous models in relation to the experimental results is also presented.

A Theoretical Model for Flow Instability Inception in Transonic Fan/Compressors

2013 ◽  
Author(s):  
Xiaofeng Sun ◽  
Xiaohua Liu ◽  
Dakun Sun
Keyword(s):  
Theoretical Model ◽  
Flow Field ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Instability ◽  
Computational Cost ◽  
Mean Flow ◽  
Transonic Compressor ◽  
Onset Point ◽  
Transonic Fan

This paper applies a theoretical model, which has been developed recently, to calculate the flow instability inception of axial transonic fan/compressors system. After the mean flow field is computed by steady CFD simulation, a body force approach, which is a function of flow field data, is taken to represent the effects of discrete blades on the flow field and duplicate the physical sources of flow turning and loss. Further by applying appropriate boundary conditions and spectral collocation method, a group of homogeneous equations will yield from which the stability equation can be derived. The singular value decomposition method is adopted over a series of fine grids in frequency domain to solve the resultant eigenvalue problem, and the onset point of flow instability can be judged by the imaginary part of the resultant eigenvalue. The present investigation is to validate the feasibility of calculating the stall onset point for single stage transonic compressor. It is shown that this model is capable of predicting instability inception point of transonic flow with reasonable accuracy, and it is sustainable in terms of computational cost for industrial application. It is shown that this model can provide an unambiguous judgment on stall inception without numerous requirements of empirical relations of loss and deviation angle. It provides a possibility to check over-predicted stall margin during the design phase of new high speed fan/compressors. In addition, the effect of flow compressibility on the stall onset point calculation for transonic rotor is studied.

scholarly journals Application of the Symmetric Model to the Design Optimization of Fan Outlet Grills

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 959 ◽  
Author(s):  
Lin ◽  
Cheng
Keyword(s):  
Wind Speed ◽  
Flow Field ◽  
Velocity Distribution ◽  
Simulation Analysis ◽  
Three Dimensional ◽  
Surface Flow ◽  
Simulation Software ◽  
Experimental Results ◽  
Symmetric Model ◽  
Airflow Rate

In this study, different designs of the opening pattern of computer fan grills were investigated. The objective of this study was to propose a simulation analysis and compare it to the experimental results for a set of optimized fan designs. The FLUENT computational fluid dynamics (CFD) simulation software was used to analyze the fan blade flow. The experimental results obtained by the simulation analysis of the optimized fan designs were analyzed and compared. The effect of different opening pattern designs on the resulting airflow rate was investigated. Six types of fans with different grills were analyzed. The airflow velocity distribution in the simulated flow channel indicated that the wind speed efficiency of the fan and its influence were comparable with the experimental model. The air was forced by the fan into the air duct. The flow path was separately measured by analog instruments. The three-dimensional flow field was determined by performing a wind speed comparison on nine planes containing the mainstream velocity vector. Moreover, the three-dimensional curved surface flow field at the outlet position and the highest fan rotation speed were investigated. The air velocity distribution at the inlet and the outlet of the fan indicated that among the air outlet opening designs, the honeycomb shaped air outlet displayed the optimal performance by investigating the fan characteristics and the estimated wind speed efficiency. These optimized designs were the most ideal configurations to compare these results. The air flow rate was evenly distributed at the fan inlet.

Air Bearing Force Measurement of Pico Negative Pressure Sliders During Dynamic Unload

1999 ◽  
Vol 122 (4) ◽  
pp. 771-775 ◽  
Author(s):  
M. Chapin ◽  
D. B. Bogy
Keyword(s):  
Negative Pressure ◽  
High Speed ◽  
Force Measurement ◽  
Force Transducer ◽  
Experimental Results ◽  
Air Bearing ◽  
Load Beam ◽  
Bearing Force ◽  
Lift Off ◽  
Force Displacement

The air bearing forces of “pico negative pressure” (1.25 × 1.0 mm subambient pressure) sliders during the unload process were investigated experimentally. A high speed vertical load/unload mechanism with a sensitive force transducer was developed to measure the air bearing forces. Force histories were measured at various disk rpm and unload velocities. The force histories showed that the suspension load dimple separated from the load beam during the lifting. This separation was held to an acceptable amount by flexure limitors built into the suspension. Force-displacement curves show the need for control of the gap between the limitor and load beam. A technique was developed to determine critical suspension parameters for use in the CML Dynamic Load/Unload Simulator. Simulation of the force history was then in excellent agreement with experimental results. Both simulation and experimental results showed that the lift-off force decreases with increasing disk rpm. Experimental results also showed that higher unload speeds lead to larger lift-off forces. By selecting the correct disk rpm and unload speed, the lift-off force could be minimized. [S0742-4787(00)00103-X]

scholarly journals Experimental Study of Flow Field and Movement of Sediment over a Ramp

2019 ◽  
Vol 8 (2) ◽  
pp. 79-86
Author(s):  
Binit Kumar ◽  
Subhojit Kadia ◽  
Zulfequar Ahmad
Keyword(s):  
Flow Field ◽  
Velocity Distribution ◽  
High Speed ◽  
Digital Image Analysis ◽  
Flow Direction ◽  
Camera System ◽  
Analysis Techniques ◽  
Sediment Particles ◽  
Very High ◽  
Image Analysis Techniques

Applications of hydraulic structures in low dams and diversion structures in countries like India, where sediment is a serious concern, demands a good expanse of research on the flow field and movement of sediment. The present study was focused on the non-uniformity in the velocity distribution along the flow direction and the movement of sediment over a ramp. The velocity distribution of the flow near and over the ramp was studied with the help of Acoustic Doppler Velocimeter. Experiments were conducted to study the mechanics and kinematics of movement of sediment particles. The movement of sediment particles over the smooth ramp was studied with the help of high-speed camera system. The particle velocity, acceleration, applied force and the angle of velocity vector were processed and analyzed from the captured images using digital image analysis techniques. The path of the movement of sediment particle was tracked. The vector results of the flow pattern indicated a very high amount of increase of the uplift velocity (y – component of the instantaneous flow velocity) component over a ramp. The sediment had very little movement for about 3.8 seconds at the beginning of the ramp and accelerated as it moved along the ramp in the downstream side. The path of the sediment movement over the ramp was found to be inclined by 25.6 to 35.7 degree to the horizontal axis which was almost parallel to the ramp (29.055 degree).

Experimental Study on the Ballast Pick-Up Problem in High Speed Trains

2010 ◽  
Author(s):  
Fermin Navarro-Medina ◽  
Angel Sanz-Andres ◽  
Isabel Perez-Grande
Keyword(s):  
Theoretical Model ◽  
High Speed ◽  
Experimental Results ◽  
Wind Gust ◽  
Experimental Facility ◽  
Proposed Model ◽  
Theoretical Predictions ◽  
High Speed Trains ◽  
Train Speed

A new theoretical approach on the determination of the conditions for the initiation of the motion of the ballast stones due to the wind gust created under the high-speed trains has been recently developed (Sanz-Andres & Navarro-Medina, 2009). This determination is critical to predict the starting of ballast pick-up, because once the motion is initiated a saltation-like chain reaction could take place. Sometimes the flying stones reach an height which is larger than the lowest parts of the train, striking them (and the track surroundings) producing considerable damage that are to be avoided e.g. by limiting the maximum allowed operational train speed. The aim of this contribution is to present the experimental results that have been obtained to check the validity of the proposed model. The experimental facility is a wind tunnel, with a gust generator, with a maximum wind speed of some 20 m/s (65.6 ft/s) and 10 Hz gust frequency. The test section is 0.39 m × 0.54 m (15.4 in × 21.3 in), which is suitable to perform experiments with stone models. It is shown that in the range of parameters explored, the experimental results are in good agreement with the theoretical model predictions. In this contribution the theoretical model is summarized, the experimental facility is described, showing some of its typical performances, the experimental procedure is outlined, and the experimental results are compared with the theoretical predictions.

Numerical Study of Classification of Ultrafine Particles in a Gas-Solid Field of Elbow-Jet Classifier

2005 ◽  
Author(s):  
Shibin Liang
Keyword(s):  
Flow Field ◽  
Ultrafine Particles ◽  
High Speed ◽  
Numerical Study ◽  
Experimental Results ◽  
Speed Flow ◽  
Fluent Software ◽  
Air Classifier ◽  
Different Diameters

Computational fluid dynamics (CFD) is applied to develop a novel submicron air classifier. Based on different inner structure sizes and positions in the elbow-jet classifier, the two-dimensional air flow field has been simulated by the Fluent software. The Coanda-effect plays a paramount role in the separation of ultrafine particles in the high-speed flow field of the elbow-jet classifier. The effects on the features of the Coanda element, i.e. a half-cylinder, have been analyzed and discussed. The trajectories of moving particles with different diameters in the channels and chambers of the classifier have been calculated under the velocity field simulation results obtained by the CFD analysis. The cut sizes of three products at the related outlets of the classifier are obtained based on the trajectories calculation of the particles and compared with the corresponding experimental results. The ground/classified experiment has been conducted by using the products outlet of a vortex jet mill as the particles feed of the elbow-jet classifier. The experimental results show that the external classifier for the vortex jet mill improves the classification of the mill significantly. The combination of the vortex jet mill with the external classifier provides a new choice of the grinding equipment for the multiple size products of fine/medium/coarse powders. A centrifugal channel has been added between the vortex jet mill and the elbow-jet classifier to improve the performance of the air classifier. Both numerical and experimental results show that the pre-distributed feed powders at the exit of the centrifugal channel have a strong effect on the fine powders separation and a less effect on the coarse powders separation.

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