Numerical Investigation on the Flow Characteristics in a Cover-Plate Pre-Swirl System

2021 ◽  
Author(s):  
Menghua Jian ◽  
Xuesen Yang ◽  
Wei Dong
Keyword(s):  
Reynolds Number ◽  
Numerical Investigation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Circumferential Velocity ◽  
Cover Plate ◽  
Temperature Reduction

Abstract This paper presents a numerical investigation on the flow characteristics in a cover-plate pre-swirl system. The Reynolds-averaged Navier-Stokes equations, coupled with the standard k-ε turbulent model, are adopted and solved. With the inlet total pressure and total temperature being constant, the influences of the temperature reduction and flow resistance by changing pressure ratios and rotational Reynolds numbers were conducted. Flow features in the pre-swirl nozzle, pre-swirl cavity, receiver hole and cover-plate cavity were summarized. The results obtained in this study indicate that the pressure ratio and rotational Reynolds number have a significant influence on the vortex structure of the pre-swirl system. As the air is accelerated by the pre-swirl nozzle, the difference of circumferential velocity between the air and the rotational domain would be reduced, and the static temperature of the air would be decreased. The pressure drop in the pre-swirl system mainly occurs in the pre-swirl nozzle and the pre-swirl cavity. In addition, with the increase of the pressure ratio, the air mass flow rate and the circumferential velocity of the air out of the nozzle increased, thereby leading to an increment in temperature reduction. Moreover, with the increasing of the rotational Reynolds number, the dimensionless mass flow rate and temperature reduction of the pre-swirl system, which are mainly determined by the flow incidence angle of cooling air at the receiver hole, will first increase to a maximum and then decrease.

Thermal and Fluid Dynamic Behavior of a Horizontal Channel With Adiabatic Moving Lower Plate

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Horizontal Channel ◽  
Lower Plate ◽  
Stationary Condition ◽  
Moving Plate ◽  
Plate Velocity

In this study a numerical investigation of mixed convection in air in horizontal parallel walled channels with moving lower plate is carried out. The moving lower plate has a constant velocity and it is adiabatic, whereas the upper one is heated at uniform heat flux. The effects of horizontal channel height, heat flux and moving plate velocity are analyzed. Results in terms of temperature and stream function fields are given and the mass flow rate per unit of length and divided by the dynamic viscosity is reported as a function of Reynolds number based on the moving plate velocity. For stationary condition of lower plate, a typical C–loop inside the horizontal channel is detected. Different flow motions are observed in the channel and the two reservoirs, depending on the heat flux values and the distance between the heated upper stationary plate and lower adiabatic moving plate. The dimensionless induced mass flow rate presents different increase between the Reynolds number lower or greater than 1000.

scholarly journals Development of Hybrid Airlift-Jet Pump with Its Performance Analysis

2018 ◽  
Vol 8 (9) ◽  
pp. 1413 ◽  
Author(s):  
Dan Yao ◽  
Kwongi Lee ◽  
Minho Ha ◽  
Cheolung Cheong ◽  
Inhiug Lee
Keyword(s):  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Jet Pump ◽  
Two Phase

A new pump, called the hybrid airlift-jet pump, is developed by reinforcing the advantages and minimizing the demerits of airlift and jet pumps. First, a basic design of the hybrid airlift-jet pump is schematically presented. Subsequently, its performance characteristics are numerically investigated by varying the operating conditions of the airlift and jet parts in the hybrid pump. The compressible unsteady Reynolds-averaged Navier-Stokes equations, combined with the homogeneous mixture model for multiphase flow, are used as the governing equations for the two-phase flow in the hybrid pump. The pressure-based methods combined with the Pressure-Implicit with Splitting of Operators (PISO) algorithm are used as the computational fluid dynamics techniques. The validity of the present numerical methods is confirmed by comparing the predicted mass flow rate with the measured ones. In total, 18 simulation cases that are designed to represent the various operating conditions of the hybrid pump are investigated: eight of these cases belong to the operating conditions of only the jet part with different air and water inlet boundary conditions, and the remaining ten cases belong to the operating conditions of both the airlift and jet parts with different air and water inlet boundary conditions. The mass flow rate and the efficiency are compared for each case. For further investigation into the detailed flow characteristics, the pressure and velocity distributions of the mixture in a primary pipe are compared. Furthermore, a periodic fluctuation of the water flow in the mass flow rate is found and analyzed. Our results show that the performance of the jet or airlift pump can be enhanced by combining the operating principles of two pumps into the hybrid airlift-jet pump, newly proposed in the present study.

scholarly journals Ballast Flow Characteristics of Discharging Pipeline in Shield Slurry System

2019 ◽  
Vol 9 (24) ◽  
pp. 5402
Author(s):  
Yang Wang ◽  
Yimin Xia ◽  
Xuemeng Xiao ◽  
Huiwang Xu ◽  
Peng Chen ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Slurry Flow ◽  
Volumetric Concentration ◽  
Mass Percentage ◽  
Pipe System ◽  
Pipeline Wall ◽  
Slurry Flow Rate

We adopted two-way coupling of discrete and finite elements to examine the non-spherical ballast flow characteristics in a slurry pipe system during a shield project. In the study, we considered the slurry rheological property and the flake shape of the ballast. A ballast size between 17 and 32 mm under different slurry flow rates and ballast volumetric concentration conditions was investigated for determining the law through which the mass flow rate, detained mass percentage, and ballast distribution state are influenced. The results indicate that increasing slurry flow rate and the ballast volumetric concentration increase the mass flow rate; the influence of the latter is stronger. Increases in both in the slurry flow rate and the ballast volumetric concentration can reduce the detained mass percentage in the slurry discharging pipeline, whereas increasing the ballast size has the opposite effect. The increase in both the slurry flow rate and the ballast size changes the ballast motion state. Experiments verified the numerical lifting model of the ballast in the vertical pipeline. The measurements of the actual pipeline wall thickness verified that the simulation results regarding the ballast distribution were accurate.

Design and Internal Flow Analysis of a Ducted Contra-Rotating Axial Flow Fan

2014 ◽  
Author(s):  
Ali Mohammadi ◽  
Masoud Boroomand
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Optimum Operating ◽  
Axial Flow Fan ◽  
Design Algorithm ◽  
Flow Solver ◽  
Operating Points

This paper presents the design procedure of a ducted contra-rotating axial flow fan and investigates the flow behavior inside it using ANSYS CFX-15 flow solver. This study investigates parameters such as pressure ratio, inlet mass flow rate and efficiency in different operating points. This system consists of two rotors with an outer diameter of 434 mm and an inner diameter of 260 mm which rotate contrary to each other with independent nominal rotational speeds of 1300 rpm. Blades’ maximum thickness and rotational speeds of each rotor will be altered as well as the axial distance between the two rotors to investigate their effect on the overall performance of the system. Designed to deliver a total pressure ratio of 1.005 and a mass flow rate of 1.8 kg/s at nominal rotational speeds, this system proves to be much more efficient compared to the conventional rotor-stator fans. NACA-65 airfoils are used in this analysis with the necessary adjustments at each section. Inverse design method is used for the first rotor and geometrical constraints are employed for the second one to have an axial inlet and outlet flow without using any inlet or outlet guide vanes. Using free vortex swirl distribution method, characteristic parameters and the necessary data for 3D generation of this model are obtained. The appropriate grid is generated using ATM method in ANSYS TurboGrid and the model is simulated in CFX-15 flow solver by employing k-ε turbulence model in the steady state condition. Both design algorithm and simulation analysis confirm the high anticipated efficiency for this system. The accuracy of the design algorithm will be explored and the most optimum operating points in different rotational speed ratios and axial distances will be identified. By altering the outlet static pressure of the system, the characteristic map is obtained.

An Experimental Study of the Flow of R-407C in an Adiabatic Spiral Capillary Tube

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
M. K. Mittal ◽  
R. Kumar ◽  
A. Gupta
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Flow Rates ◽  
Tube Test ◽  
Mass Flow Rates ◽  
R 134A

The objective of this study is to investigate the effect of coiling on the flow characteristics of R-407C in an adiabatic spiral capillary tube. The characteristic coiling parameter for a spiral capillary tube is the coil pitch; hence, the effect of the coil pitch on the mass flow rate of R-407C was studied on several capillary tube test sections. It was observed that the coiling of the capillary tube significantly reduced the mass flow rate of R-407C in the adiabatic spiral capillary tube. In order to quantify the effect of coiling, the experiments were also conducted for straight a capillary tube, and it was observed that the coiling of the capillary tube reduced the mass flow rate in the spiral tube in the range of 9–18% as compared with that in the straight capillary tube. A generalized nondimensional correlation for the prediction of the mass flow rates of various refrigerants was developed for the straight capillary tube on the basis of the experimental data of R-407C of the present study, and the data of R-134a, R-22, and R-410A measured by other researchers. Additionally, a refrigerant-specific correlation for the spiral capillary was also proposed on the basis of the experimental data of R-407C of the present study.

Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)

2019 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Compressor Inlet

Abstract The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work. For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted. The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.

Centrifugal Compressor Performance Prediction Using Gaussian Process Regression and Artificial Neural Networks

2019 ◽  
Author(s):  
Pau Cutrina Vilalta ◽  
Hui Wan ◽  
Soumya S. Patnaik
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Data Augmentation ◽  
Pressure Ratio ◽  
Gaussian Process Regression ◽  
Compressor Performance ◽  
Artificial Neural

Abstract In this paper, we use various regression models and Artificial Neural Network (ANN) to predict the centrifugal compressor performance map. Particularly, we study the accuracy and efficiency of Gaussian Process Regression (GPR) and Artificial Neural Networks in modelling the pressure ratio, given the mass flow rate and rotational speed of a centrifugal compressor. Preliminary results show that both GPR and ANN can predict the compressor performance map well, for both interpolation and extrapolation. We also study the data augmentation and data minimzation effects using the GPR. Due to the inherent pressure ratio data distribution in mass-flow-rate and rotational-speed space, data augmentation in the rotational speed is more effective to improve the ANN performance than the mass flow rate data augmentation.

scholarly journals Numerical and Experimental Study of Microchannel Performance on Flow Maldistribution

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 323 ◽  
Author(s):  
Jojomon Joseph ◽  
Danish Rehman ◽  
Michel Delanaye ◽  
Gian Luca Morini ◽  
Rabia Nacereddine ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Experimental Studies ◽  
Wire Mesh ◽  
Pressure Losses ◽  
Macro Scale ◽  
Flow Maldistribution

Miniaturized heat exchangers are well known for their superior heat transfer capabilities in comparison to macro-scale devices. While in standard microchannel systems the improved performance is provided by miniaturized distances and very small hydraulic diameters, another approach can also be followed, namely, the generation of local turbulences. Localized turbulence enhances the heat exchanger performance in any channel or tube, but also includes an increased pressure loss. Shifting the critical Reynolds number to a lower value by introducing perturbators controls pressure losses and improves thermal efficiency to a considerable extent. The objective of this paper is to investigate in detail collector performance based on reduced-order modelling and validate the numerical model based on experimental observations of flow maldistribution and pressure losses. Two different types of perturbators, Wire-net and S-shape, were analyzed. For the former, a metallic wire mesh was inserted in the flow passages (hot and cold gas flow) to ensure stiffness and enhance microchannel efficiency. The wire-net perturbators were replaced using an S-shaped perturbator model for a comparative study in the second case mentioned above. An optimum mass flow rate could be found when the thermal efficiency reaches a maximum. Investigation of collectors with different microchannel configurations (s-shaped, wire-net and plane channels) showed that mass flow rate deviation decreases with an increase in microchannel resistance. The recirculation zones in the cylindrical collectors also changed the maldistribution pattern. From experiments, it could be observed that microchannels with S-shaped perturbators shifted the onset of turbulent transition to lower Reynolds number values. Experimental studies on pressure losses showed that the pressure losses obtained from numerical studies were in good agreement with the experiments (<4%).

Evaluation of Axial Compressor Characteristics Under Overspray Condition

2013 ◽  
Author(s):  
Chihiro Myoren ◽  
Yasuo Takahashi ◽  
Manabu Yagi ◽  
Takanori Shibata ◽  
Tadaharu Kishibe
Keyword(s):  
Gas Turbine ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Test Facility ◽  
Compressor Performance ◽  
Water Mass Flow Rate

An axial compressor was developed for an industrial gas turbine equipped with a water atomization cooling (WAC) system, which is a kind of inlet fogging technique with overspray. The compressor performance was evaluated using a 40MW-class test facility for the advanced humid air turbine system. A prediction method to estimate the effect of WAC was developed for the design of the compressor. The method was based on a streamline curvature (SLC) method implementing a droplet evaporation model. Four test runs with WAC have been conducted since February 2012. The maximum water mass flow rate was 1.2% of the inlet mass flow rate at the 4th test run, while the design value was 2.0%. The results showed that the WAC decreased the inlet and outlet temperatures compared with the DRY (no fogging) case. These decreases changed the matching point of the gas turbine, and increased the mass flow rate and the pressure ratio by 1.8% and 1.1%, respectively. Since prediction results agreed with the results of the test run qualitatively, the compressor performance improvement by WAC was confirmed both experimentally and analytically. The test run with the design water mass flow rate is going to be conducted in the near future.

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