scholarly journals Coupled Fluid–Solid Numerical Simulation for Flow Field Characteristics and Supporting Performance of Flexible Support Cylindrical Gas Film Seal

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 97
Author(s):  
Junfeng Sun ◽  
Meihong Liu ◽  
Zhen Xu ◽  
Taohong Liao ◽  
Xiangping Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Film Thickness ◽  
Fluid Dynamic ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
High Rotational Speed ◽  
Flexible Support ◽  
Flow Field Characteristics

A new type of cylindrical gas film seal (CGFS) with a flexible support is proposed according to the working characteristics of the fluid dynamic seal in high-rotational-speed fluid machinery, such as aero-engines and centrifuges. Compared with the CGFS without a flexible support, the CGFS with flexible support presents stronger radial floating characteristics since it absorbs vibration and reduces thermal deformation of the rotor system. Combined with the structural characteristics of a film seal, an analytical model of CGFS with a flexible wave foil is established. Based on the fluid-structure coupling analysis method, the three-dimensional flow field of a straight-groove CGFS model is simulated to study the effects of operating and structural parameters on the steady-state characteristics and the effects of gas film thickness, eccentricity, and the number of wave foils on the equivalent stress of the flexible support. Simulation results show that the film stiffness increases significantly when the depth of groove increases. When the gas film thickness increases, the average equivalent stress of the flexible support first decreases and then stabilizes. Furthermore, the number of wave foils affects the average foils thickness. Therefore, when selecting the number of wave foils, the support stiffness and buffer capacity should be considered simultaneously.

scholarly journals Influence of Vortex Finder Structure on Separation Performance of Double-Overflow Three-Product Hydrocyclones

Separations ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 79
Author(s):  
Yuekan Zhang ◽  
Jiangbo Ge ◽  
Lanyue Jiang ◽  
Hui Wang ◽  
Junru Yang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Experimental Research ◽  
Separation Efficiency ◽  
Structural Parameters ◽  
Separation Performance ◽  
Insertion Depth ◽  
Flow Field Characteristics ◽  
Vortex Finder ◽  
Fine Classification

In view of the difficulty of traditional hydrocyclones to meet the requirements of fine classification, a double-overflow three-product (internal overflow, external overflow and underflow) hydrocyclone was designed in this study. Numerical simulation and experimental research methods were used to investigate the effects of double-overflow flow field characteristics and structural parameters (i.e., internal vortex finder diameter and insertion depth) on separation performance. The research results showed that the larger the diameter of the internal vortex finder, the greater the overflow yield and the larger the cut size. The finest internal overflow product can be obtained when the internal vortex finder is 30 mm longer than the external vortex finder. The separation efficiency is highest when the internal vortex finder is 30 mm shorter than the external vortex finder.

scholarly journals Optimal Design of Multi-section Proportional Directional Valve Throttle Grooves with Artificial Neural Networks

2018 ◽  
Vol 237 ◽  
pp. 03003 ◽  
Author(s):  
Xiaolu Zhang ◽  
Anlin Wang ◽  
Jiangwei Tang
Keyword(s):  
Optimal Design ◽  
Design Method ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Flow Stability ◽  
Complex Flow ◽  
Physical Test ◽  
Flow Field Characteristics ◽  
Structure Boundary ◽  
Proportional Directional Valve

This paper presents a method for design multi-section proportional directional valve Throttle grooves with ANN method, which aims at getting a better flow stability. There exists a coupling matter during the opening and closing process between the throttling notches, so that it’s difficult to parameterize the complex flow field characteristics Cd and the structure boundary of the spool grooves. However, in this paper, an ANN was built with data from CFD results, while the typical structural parameters (U type, the O-type and C-type), operating parameters was input vectors, the discharge coefficient as output vectors. Meanwhile, all of the needed data is taken from the three-dimensional CFD analysis, which are organized properly and verified by a bench scale test on a rig. Then, with throttling stiffness as optimization objective to evaluate flow stability, an optimal design process is carried out to optimize to optimize the structure of coupling grooves with ANN models and genetic algorithm. Ultimately, the optimized structure is verified better by the physical test on test rig, therefore, the significance of design method is proved.

Numerical Research on Flow Field Characteristics within the Slipstream of a Propeller

2012 ◽  
Vol 224 ◽  
pp. 55-60
Author(s):  
Zhong Zhe Duan ◽  
Pei Qing Liu ◽  
Li Chuan Ma
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Scientific Basis ◽  
Disk Model ◽  
Actuator Disk ◽  
Numerical Result ◽  
Light Load ◽  
Strip Theory ◽  
Flow Field Characteristics ◽  
Numerical Research

Numerical research on three dimensional flow field of a propeller and actuator disk model have been made. Under design conditions (headway 66.889m/s, revolving velocity 2575rpm）, the Slipstream flow field after Propeller is solved by RANS equations with structure mesh. Chosen 12 million mesh through verification of reliability analysis. The numerical result consists of the flow field and vortex field in the propeller slipstream. With comparison to the calculation result of standard strip theory and actuator disk model, it is shown that for light load propeller with the side small contraction of slipstream, in the slipstream cross section after 0.6R away from downstream of propeller rotation plane, the axial, circular and radial induced velocity coefficient by Prandtl’s blade tip corrected standard strip theory result; three dimensional flows numerical simulation and actuator disk model are well consistent. It verified the correctness of standard strip theory and also provided scientific basis for the correction of actuator disk model

scholarly journals Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings

1988 ◽  
Vol 110 (3) ◽  
pp. 315-325 ◽  
Author(s):  
L. T. Tam ◽  
A. J. Przekwas ◽  
A. Muszynska ◽  
R. C. Hendricks ◽  
M. J. Braun ◽  
...  
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Circumferential Velocity ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Lumped Model ◽  
Destabilizing Factors ◽  
Recirculation Zones

A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.

Investigation of the Flow Field on a Transonic Turbine Nozzle Guide Vane With Rim Seal Cavity Flow Ejection

2009 ◽  
Author(s):  
M. Pau ◽  
G. Paniagua
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Numerical Study ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Cavity Flow ◽  
Trailing Edge ◽  
Dynamic Simulations ◽  
Purge Flow

Ensuring an adequate life of high pressure turbines requires efficient cooling methods, such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present work addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process a numerical study was carried out combining computational fluid dynamic simulations (CFD) and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed modeling the purge cavity flow ejected downstream of the stator blade row, at three flow regimes, subsonic M2 = 0.73, transonic M2 = 1.12 and supersonic M2 = 1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase of the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structures modification downstream of the stator.

scholarly journals Three-Dimensional Numerical Analysis of LOX/Kerosene Engine Exhaust Plume Flow Field Characteristics

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Hong-hua Cai ◽  
Wan-sheng Nie ◽  
Xin-lei Yang ◽  
Rui Wu ◽  
Ling-yu Su
Keyword(s):  
Numerical Analysis ◽  
Flow Field ◽  
Chemical Reaction ◽  
Reaction Mechanisms ◽  
Three Dimensional ◽  
Engine Exhaust ◽  
Exhaust Plume ◽  
Flow Field Characteristics ◽  
Chemical Reaction Mechanisms ◽  
Plume Flow

Aiming at calculating and studying the flow field characteristics of engine exhaust plume and comparative analyzing the effects of different chemical reaction mechanisms on the engine exhaust plume flow field characteristics, a method considering fully the combustion state influence is put forward, which is applied to exhaust plume flow field calculation of multinozzle engine. On this basis, a three-dimensional numerical analysis of the effects of different chemical reaction mechanisms on LOX/kerosene engine exhaust plume flow field characteristics was carried out. It is found that multistep chemical reaction can accurately describe the combustion process in the LOX/kerosene engine, the average chamber pressure from the calculation is 4.63% greater than that of the test, and the average chamber temperature from the calculation is 3.34% greater than that from the thermodynamic calculation. The exhaust plumes of single nozzle and double nozzle calculated using the global chemical reaction are longer than those using the multistep chemical reaction; the highest temperature and the highest velocity on the plume axis calculated using the former are greater than that using the latter. The important influence of chemical reaction mechanism must be considered in the study of the fixing structure of double nozzle engine on the rocket body.

PIV Measurements of Recirculation Patterns in a Stirred Tank

2001 ◽  
Author(s):  
Khaled J. Hammad ◽  
George Papadopoulos
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Vertical Axis ◽  
Transitional Flow ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Blade Passage ◽  
Flow Field Characteristics

Abstract Phase-resolved PIV measurements were performed to reveal the detailed flow features within a triple impeller stirredtank. Two tests were performed: low and high rotational speeds, 175 and 575 RPM, respectively. The tests used an optically transparent mixing vessel to measure the 2D flow field characteristics along a vertical plane passing through the tank center. The measurements disclosed interesting in-plane vortical behavior that when measured at two angular positions with respect to the blade passage further indicated the three-dimensional flow behavior. For the low RPM case, a laminar flow nature was apparent, whereby vortical toroidal structures spanned around the stirrer vertical axis. Six such structures were dominant. For the high RPM case and for θ = 0° six dominant vortical structures were apparent. Their r-z plane location and size were different from that for the low RPM case. With blade passage four of these vortical structures appeared to merge into two, suggesting that constant toroidal vortical structures spanning around the stirrer axis were absent from the high RPM case. A switch between six distinct and four distinct in-plane vortical structures as the blades pass through the measurement plane further suggested a transitional flow field at 575 RPM.

Analysis of a Control Valve's Inner Flow Field Characteristics Based on CFD

2013 ◽  
Vol 756-759 ◽  
pp. 4652-4655
Author(s):  
Liang Wang
Keyword(s):  
Flow Field ◽  
Energy Loss ◽  
Three Dimensional ◽  
Control Valve ◽  
Flow Path ◽  
Dynamics Simulation ◽  
Flow Field Characteristics ◽  
Simulation Results

In this paper, the inner flow field characteristics of a control valve were analysed through dynamics simulation and showed by using the three-dimensional visualization. Through the analysis of simulation results, reasons were found for the energy loss, which was, then, reduced by the optimized flow path. Calculations about the optimized positions were carried out, the results of which showed an improvement of flow and a significant decrease in energy loss.

Simulation Research on Micro-Cavity Flow Field Characteristics of Liquid Floating Rotor Gyro

2013 ◽  
Vol 562-565 ◽  
pp. 490-495 ◽  
Author(s):  
Yu Peng Shi ◽  
Fei Tang ◽  
Xiao Hao Wang
Keyword(s):  
Flow Field ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Cavity Flow ◽  
Three Dimensional Model ◽  
Simulation Research ◽  
Resistance Torque ◽  
Flow Field Characteristics ◽  
Micro Cavity

The liquid floating rotor gyro is a gyroscope using electrostatic or electromagnetic forces to levitate rotor, and filling rotor-stator cavities with liquid in order to improve stability of motion. Under influence of the relative surface roughness, rotor velocity, dimension of flow field and fluid nature, flow characteristics of cavity flow field vary under different boundary conditions and geometrical conditions. This paper adopts three-dimensional model and periodic boundary conditions to conduct numerical modeling on cavity flow field. Its results show that, with velocity rising, distribution of flow field speed and pressure manifests partial fluctuations in turbulent-flow-intensive area; resistance torque amid rotor rotation is nonlinearly correlated with velocity, whose rules can be obtained through high-order curve fitting.

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