Numerical Modeling of Upstream Nozzle Effect in Supersonic/Hypersonic Impactors for Nano-Particles

2005 ◽  
Author(s):  
Omid Abouali ◽  
Goodarz Ahmadi
Keyword(s):  
Computer Simulation ◽  
Gas Flow ◽  
Operating Conditions ◽  
Nano Particles ◽  
Navier Stokes ◽  
Correction Coefficient ◽  
Computer Simulation Model ◽  
Computational Domain ◽  
Simulation Results ◽  
Computer Simulation Studies

In this study the performance of supersonic and hypersonic impactors under various operating conditions was analyzed using a computer simulation model. The study was focused on the effect of the nozzle upstream condition on the performance of the supersonic and hypersonic impactors. In our earlier work, the computational domain covered downstream of the nozzle with a sonic boundary condition at the inlet. In the present study, the computational domain included the upstream nozzle where the flow and particles enter with at low velocities. Axisymmetric forms of the compressible Navier-Stokes and energy equations were solved and the gas flow and thermal condition in the impactor were for evaluated. A Lagrangian particle trajectory analysis procedure was used and the deposition rates of different size particles under various operating conditions were studied. For dilute particle concentrations, one-way interaction was assumed and the effect of particles on gas flow field was ignored. The importance of drag and Brownian forces on particle motions in supersonic/hypersonic impactors was analyzed. Sensitivity of the simulation results to the use of different expressions for the drag force was also examined. It was shown that when the upstream nozzle is included in the computational model, the Stokes-Cunningham drag with variable correction coefficient and a constant Cunningham correction factor based on stagnation point properties lead to the same results. Thus these drag laws are most suitable for computer simulation studies of nano-particles in supersonic/hypersonic impactors. The computer simulation results were shown to compare favorably with the experimental data.

Bow Shock Effect on Particle Transport and Deposition in a Hypersonic Impactor

2003 ◽  
Author(s):  
Omid Abouali ◽  
Goodarz Ahmadi
Keyword(s):  
Computer Simulation ◽  
Flow Field ◽  
Particle Transport ◽  
Operating Conditions ◽  
Bow Shock ◽  
Nano Particles ◽  
Correction Coefficient ◽  
Navier Stokes Equation ◽  
Micro Particles ◽  
Simulation Results

Supersonic/hypersonic impactors are used as a collector and/or size separator of nano- and micro-particles. Thin film and fine line pattern deposition by aerosol jets are other applications of deposition of supersonic/hypersonic impactors. At extremely low backpressures, the exiting flow from a nozzle forms a supersonic free jet. The supersonic jet forms a strong normal shock in the front of the impactor plate. The stagnation pressure, backpressure and distance between the nozzle exit and the impactor plate affect the flow field. Due to the rather complicated flow in the impactor, studies of particle motions in supersonic impactors are rather scarce. In this study the airflow and particle transport and deposition in a supersonic/hypersonic impactor are numerically simulated. The axisymmetric compressible Navier-Stokes equation is solved and the flow properties are evaluated. It is assumed that the particle concentration is dilute, to the extent that the presence of particles does not alter the flow field. Deposition of different size particles under different operating conditions is studied. The importance of drag, lift and Brownian forces on particle motions in supersonic impactors is discussed. Sensitivity of the simulation results to the use of different expressions for the drag force is also examined. A strong bow shock on the flowfield has much effect in drag forces on particles. It is shown that the Stokes-Cunningham drag with variable correction coefficient is most suitable for computer simulation studies of nano-particles in supersonic/hypersonic impactors. The computer simulation results are shown to compare favorably with the experimental data.

A Numerical Model for Brownian Motions of Nano-Particles in Supersonic and Hypersonic Impactors

2006 ◽  
Author(s):  
Azam Zare ◽  
Omid Abouali ◽  
Goodarz Ahmadi
Keyword(s):  
Brownian Motion ◽  
Collection Efficiency ◽  
Operating Conditions ◽  
The Body ◽  
Nano Particles ◽  
Navier Stokes ◽  
Computer Simulation Model ◽  
Micro Particles ◽  
Deposition Processes ◽  
Energy Equations

In this paper, transport and deposition processes of nano-particles in supersonic and hypersonic impactors were investigated using a computational modeling approach. Axisymmetric forms of the compressible Navier-Stokes and energy equations were solved and the airflow and thermal condition in the impactor including the upstream nozzle were evaluated. A computer simulation model for solving the Lagrangian particle equation of motion including all the relevant forces was developed. The importance of the accurate modeling of the Brownian motion of nano-particles was further emphasized. The motion of nano- and micro-particles in the supersonic and hypersonic impactors were then simulated and the impactor capture efficiencies under various operating conditions were studied. For dilute particle concentrations, the assumption of one-way interaction was used. Particular attention was given to proper evaluation of the Brownian motion of the nano-particles in the upstream nozzle and in the body of impactor. The simulation results for collection efficiency were found to be in good agreement with experimental data. In particular, the model accurately predicted the loss of the nano-particles in the upstream nozzle due to their Brownian motion.

The Validity of the Compressible Reynolds Equation for Gas Lubricated Textured Parallel Slider Bearings

2012 ◽  
Author(s):  
Mingfeng Qiu ◽  
Brian Bailey ◽  
Rob Stoll ◽  
Bart Raeymaekers
Keyword(s):  
Gas Flow ◽  
Reynolds Equation ◽  
Stokes Equations ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Slider Bearings ◽  
Simplifying Assumptions ◽  
Simulation Results

The Navier-Stokes and compressible Reynolds equations are solved for gas lubricated textured parallel slider bearings under hydrodynamic lubrication for a range of realistic texture geometry parameters and operating conditions. The simplifying assumptions inherent in the Reynolds equation are validated by comparing simulation results to the solution of the Navier-Stokes equations. Using the Reynolds equation to describe shear driven gas flow in textured parallel slider bearings is justified for the range of parameters considered.

Analysis of gas flow over a cylinder at all Knudsen numbers based on non-newtonian constitutive models

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040076
Author(s):  
Zhen-Yu Yuan ◽  
Zhong-Zheng Jiang ◽  
Wen-Wen Zhao ◽  
Wei-Fang Chen
Keyword(s):  
Constitutive Model ◽  
Gas Flow ◽  
Constitutive Relations ◽  
Constitutive Models ◽  
Direct Simulation Monte Carlo ◽  
Navier Stokes ◽  
Dsmc Simulation ◽  
Nonequilibrium Flows ◽  
Simulation Results ◽  
Better Than

This paper is focused on the gas properties over a cylinder from continuum to rarefied regimes based on the non-Newtonian constitutive model. This new constitutive model is first derived from Eu’s nonequilibrium ensemble method, which is intended for accurate description of nonequilibrium flows. Some assumptions and simplifications are made during the establishing progress of the new constitutive model by both Eu and Myong. To verify its accuracy, temperature contours and skin frictions around the cylinder are simulated by this new model. The inflow Mach number is equal to 10 and the Knudsen number ranges from 0.002 to 0.05. All simulation results are compared with Navier–Stokes (NS) and the direct simulation Monte Carlo (DSMC) methods in detail. The comparisons of friction around the surface show that the non-Newtonian constitutive models are better than the linear constitutive relations of NS equations for the prediction of nonequilibrium flow and much more close to DSMC simulation results.

Numerical Research of the Effect of the Outlet Diameter of Diffuser on the Performance and the Radial Force in a Single-Stage Centrifugal Pump

2014 ◽  
Author(s):  
Jiang Wei ◽  
Li Guojun ◽  
Liu Pengfei ◽  
Zhang Lisheng ◽  
Qing Hongyang
Keyword(s):  
Centrifugal Pump ◽  
Radial Force ◽  
Numerical Results ◽  
Operating Conditions ◽  
Single Stage ◽  
Navier Stokes ◽  
Computational Domain ◽  
Ansys Fluent ◽  
Vaned Diffuser ◽  
Unsteady Numerical Simulation

In this paper, a single-stage pump with diffuser vanes of different outlet diameters has been investigated both numerically and experimentally. The influence of the diffuser vane outlet diameter on pump hydraulic performance and on the radial force of the impeller is explored. Pumps equipped with three different diffusers but with impellers and volutes of the same parameters were simulated by 3D Navier-Stokes solver ANSYS-FLUENT in order to study the effect of the outlet diameter of vaned diffuser on performance of the centrifugal pump. Structured grids of high quality were applied on the whole computational domain. Experimental results were acquired by prototype experiments and were then compared with the numerical results. Both experimental and numerical results show that the performance of a pump with a diffuser of smaller outlet diameter is better than of bigger outlet diameter under all operating conditions. The radial force imposed on the impeller obtained by unsteady numerical simulation was analyzed. The results also indicated that an appropriate decrease in the outlet diameter of the diffuser vane could increase the radial force.

Numerical Simulation of Gas Flow Pattern in Cyclone Spray Scrubber

2011 ◽  
Vol 233-235 ◽  
pp. 701-706
Author(s):  
Bing Tao Zhao ◽  
Yi Xin Zhang ◽  
Kai Bin Xiong
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Flow Pattern ◽  
Gas Flow ◽  
Stokes Equations ◽  
Tangential Velocity ◽  
Navier Stokes ◽  
Computational Domain ◽  
Spray Scrubber ◽  
Cfd Method

The numerical simulation of the fluid flow is presented by CFD technique to characterize the flow pattern of cyclone spray scrubber. In this process, the Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. According to the computational results, the tangential velocity, axial velocity and turbulence intensity of the gas flow are addressed in the different flowrate. The results indicate that the CFD method can effectively reveal the mechanism of gas flow in the cyclone spray scrubber.

Steady and Unsteady Modeling for Heat Transfer Predictions of High Pressure Turbine Blade Internal Cooling

2012 ◽  
Author(s):  
Rémy Fransen ◽  
Nicolas Gourdain ◽  
Laurent Y. M. Gicquel
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Cooling System ◽  
Transfer Problem ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Wall Region ◽  
Internal Cooling ◽  
Computational Domain ◽  
Complex Flow

This work focuses on numerical simulations of flows in blade internal cooling system. Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS) approaches are compared in a typical blade cooling related problem. The case is a straight rib-roughened channel with high blockage ratio, computed and compared for both a periodic and full spatial domains. The configuration was measured at the Von Karman Institute (VKI) using Particle Image Velocimetry (PIV) in near gas turbine operating conditions. Results show that RANS models used fail to predict the full evolution of the flow within the channels where massive separation and large scale unsteady features are evidenced. In contrast LES succeeds in reproducing these complex flow motions and both mean and fluctuating components are clearly improved in the channels and in the near wall region. Periodic computations are gauged against the spatial computational domain and results on the heat transfer problem are addressed.

scholarly journals СНИЖЕНИЕ ВИБРОНАПРЯЖЕННОСТИ ПОПАРНО БАНДАЖИРОВАННЫХ РАБОЧИХ ЛОПАТОК ТУРБИНЫ

2020 ◽  
pp. 52-58
Author(s):  
Юрий Петрович Кухтин ◽  
Руслан Юрьевич Шакало
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Stokes Equations ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Turbine Engine ◽  
Exciting Forces ◽  
Working Blades

To reduce the vibration stresses arising in the working blades of turbines during resonant excitations caused by the frequency of passage of the blades of the nozzle apparatus, it is necessary to control the level of aerodynamic exciting forces. One of the ways to reduce dynamic stresses in rotor blades under operating conditions close to resonant, in addition to structural damping, maybe to reduce external exciting forces. To weaken the intensity of the exciting forces, it is possible to use a nozzle apparatus with multi-step gratings, as well as with non-radially mounted blades of the nozzle apparatus.This article presents the results of numerical calculations of exciting aerodynamic forces, as well as the results of experimental measurements of stresses arising in pairwise bandaged working blades with a frequency zCA ⋅ fn, where fn – is the rotor speed, zCA – is the number of nozzle blades. The object of research was the high-pressure turbine stage of a gas turbine engine. Two variants of a turbine stage were investigated: with the initial geometry of the nozzle apparatus having the same geometric neck area in each interscapular channel and with the geometry of the nozzle apparatus obtained by alternating two types of sectors with a reduced and initial throat area.The presented results are obtained on the basis of numerical simulation of a viscous unsteady gas flow in a transonic turbine stage using the SUnFlow home code, which implements a numerical solution of the Reynolds-averaged Navier-Stokes equations. Discontinuity of a torrent running on rotor blades is aggravated with heat drops between an ardent flow core and cold jets from film cooling of a blade and escapes on clock surfaces. Therefore, at simulation have been allowed all blowngs cooling air and drain on junctions of shelves the impeller.As a result of the replacement of the nozzle apparatus with a constant passage area by a nozzle apparatus with a variable area, a decrease in aerodynamic driving force by 12.5 % was obtained. The experimentally measured stresses arising in a pairwise bandaged blade under the action of this force decreased on average by 26 %.

Computer Simulation of the Aerodisperse Systems Hydrodynamics in Granulation and Drying Apparatus

2019 ◽  
pp. 277-321
Author(s):  
Artem Artyukhov ◽  
Nadiia Artyukhova ◽  
Jan Krmela
Keyword(s):  
Computer Simulation ◽  
Fluidized Bed ◽  
Disperse Phase ◽  
Residence Time ◽  
Selection Criteria ◽  
Gas Flow ◽  
Hydrodynamic Conditions ◽  
Two Phase ◽  
Simulation Results

The chapter presents validation of the selection criteria for the construction of the granulation and drying equipment. New forms of the organization of the flows motion in a fluidized bed regime are offered. The steering mechanisms for the motion and the residence time of the disperse phase in a workspace of the apparatus are described. The results of the simulation of the hydrodynamic conditions for the motion of the directional gas flow and the two-phase aerodisperse system are presented. Based on the simulation results, various constructions of the apparatus components are offered. The well-minded construction of the workspace of the apparatus helps to achieve optimized consumption of the heating agent and the minimal residence time of the disperse phase in the apparatus. The computer simulation allowed the authors to offer an algorithm of the optimization calculations of the granulation and drying equipment. New constructive solutions to perform the granulation and the drying processes in the devices with a directional fluidized bed are offered.

scholarly journals Meander-Like Shape Optimization of the Stator-Rotor Platform Cavity

2018 ◽  
Author(s):  
Paht Juangphanich ◽  
Guillermo Paniagua
Keyword(s):  
Geometry Optimization ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Practical Implementation ◽  
Computational Domain ◽  
Optimization Strategy ◽  
Minimum Thickness ◽  
Ansys Fluent ◽  
Driving Mechanisms ◽  
Wide Range

Recent progress in additive manufacturing has enabled opportunities to explore novel stator rim geometries which can be implemented to improve cooling strategies in turbomachinery. This paper presents a simplified stationary geometry optimization strategy to produce enhanced stator-rotor cavity sealing and highlights main driving mechanisms. The stator and rotor rims were designed using a design strategy based on inspiration from the meandering of rivers. A minimum thickness of 2mm was maintained throughout the cavity to ensure a practical implementation. The computational domain comprised of the stator outlet, hub disk leakage cavity, and rotor platform was meshed using NUMECA Int. package, Hexpress. The numerical analysis required 3D Unsteady Reynolds Average Navier-Stokes to replicate vorticial structures using Ansys Fluent. The operating conditions were representative of engine-like conditions, exploring a wide range of massflow ratios from 1 to 3%. The optimization yielded designs that provide 30% reduction in rear platform temperature while minimizing coolant massflow. The applicability of the design was compared against 3D sector in both stationary and in rotation.

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