Flow Rate Coefficient Research Articles

Condensation flow at the wet steam centrifugal turbine stage

This paper investigates spontaneous condensation of wet steam in a centrifugal turbine by means of three-dimensional computational fluid dynamics. The flow field and aerodynamic characteristics of the wet steam in the centrifugal turbine are compared and analyzed by using the equilibrium steam and nonequilibrium steam models, respectively, where the latter applies the classical droplet nucleation theory and neglects velocity slip between the liquid phase and the gaseous phase. The state parameters of wet steam are described here based on the IAPWS’97 formulation. It is concluded that under the design condition, the mass flow rate, wetness fraction, and flow angle of the wet steam centrifugal turbine in the nonequilibrium steam model all change compared with the equilibrium steam model, with values of 4.4%, 0.5%, and 10.57%, respectively. Then the performance variation of the wet steam centrifugal turbine is analyzed under different steam conditions and different outlet back-pressure conditions. The results show that the change law of the mass flow rate, shaft power, and wetness fraction in the centrifugal turbine are basically identical in both models, and the mass flow rate, shaft power, wheel efficiency, and entropy loss coefficient of the centrifugal turbine in the nonequilibrium steam model are all higher than those in the equilibrium steam model, whereas the outlet wetness fraction is lower than that in the equilibrium steam model.

Forced Convection upon Heat Sink of AL-Cu for Design Optimization by Experimental and CFD Analysis for cooling of ICs in CPU.

A heat sink device is used with specific power input at 100V and 20W by the heater attached at the base plate of copper and then obtaining the average temperature of Heat sink by the help of 10 thermocouples .Two specimens of heat sinks were designed and were tested for mass flow rate and heat transfer coefficient. With base of 1.5mm&2.5mmtip thickness and another specimen with dimensions as tip0.5mm and1.00mmbase thickness are used By experimenting and CFD simulations,optimization of heat sink design was done.Then correlation and Validation foe both the specimen was done and were found satisfactory results.

Study of the flow structure in boundary layer bleed channel at the hypersonic speed of external flow

The paper presents the study of the flow structure in a boundary layer bleed channel and calculation of the mass flow rate under the conditions of thick boundary layer incoming. The flow at Mach numbers of M = 3, 4, 6 and angle of attack 6° has been considered. In the framework of the problem, the Reynolds-averaged Navier-Stokes equations added with the k–ω SST turbulence model have been solved. Numerical simulation of the flow in the channel has been carried out using the Roe implicit scheme of the second order of accuracy. Pressure and temperature profiles at the outlet boundary obtained at the simulation of the flow around the inlet forebody have been used to specify the inlet boundary conditions for simulation of the flow through the boundary layer bleed hole. The pressure distribution obtained at numerical simulation of a flow in the boundary layer bleed channel has shown that there is a large high-pressure area caused by the presence of so-called “barrier shock” near the channel back wall. Thus here is a supercritical pressure drop which ensures a sonic flow in the bleed hole. This conclusion has been confirmed by the experimental data obtained for small supersonic speeds. Calculation of the mass-flow rate through exit cross-section of the cylindrical bleed channel has shown that the mass flow rate coefficient decreases 2.5 – 3 times with the Mach number increasing from 3 to 6. The mass flow coefficient also decreases by about 10% due to the change of conditions in the 3D flow before the bleed hole with the moving off from the symmetry plane.

Выбор размеров безлопаточного диффузора центробежной компрессорной ступени на стадии первичного проектирования

The advances in the primary design method of centrifugal compressors of the Universal Modeling Method have led to the need to analyze and revise the recommendations for the optimal size and configuration selection of vaneless diffusers of centrifugal compressor stages. The results of CFD calculations of a family of vaneless diffusers with different relative width, radial length, velocity coefficients and flow angles at the inlet are used to develop new recommendations. The choice of the optimal width of the vaneless diffuser is based on ensuring a non-separable flow in it at the boundary of the surge. The optimal value of the relative radial length of the diffuser is in the range of 1.65–2.0. Considering the above, a formula for selecting the vaneless diffuser outer diameter is proposed depending on the design flow rate coefficient. The developed primary design method of vaneless diffusers is included in the software programs of the Universal Modeling Method and is used in design and research practice.

Experimental study and numerical simulation on in-cylinder flow of small motorcycle engine

This study aimed at experimental and numerically investigating in-cylinder flows of a small motorcycle engine under steady-state conditions. The experiment was conducted in the engine head for a variety of fixed valve lifts at two pressure drops (300 and 600 mmH2O). Besides, this study attempted to analyze the characteristics of in-cylinder flows in a small engine by applying CFD methods. Looking at the results, there was a good agreement between the results of experiment and simulation in terms of flow coefficient, air flow rate and discharge coefficient at two pressure drops. In both horizontal and vertical planes, both increased valve lift and pressure drop delivered increased velocity and vorticity magnitude. An increase in pressure drop at the beginning of valve lift opening appeared to have no effect on the swirl ratio until the valve lift reached 5 mm. However, the swirl ratio got a 25% reduction when the valve lift reached 6.25 mm. An increase in pressure drop at the intake stroke did not deliver a significant effect on the tumble ratio and accumulated air mass. However, the accumulated air mass increased 3.77% at compression stroke. An increase in pressure drop delivered a significant effect on turbulent kinetic energy (TKE), turbulent length scale and turbulent kinematic viscosity. TKE reached its peak (200%) at 470 °CA, while turbulent length scale and turbulent kinematic viscosity reached their peaks at 590 °CA where the intake valve was almost closed. The increase in turbulence in fact produced a more homogeneous in-cylinder air-fuel mixing. Besides, the increase in turbulence directly increased the rate of fire propagation. Further study would be expected to focus on modifying the design of intake port for improving the air flow characteristics of small engines. Then, this study was expected to reduce the number of experiments required for investigating optimized parameters in small engines.

Pengaruh Perubahan Luas Tutupan Lahan Hutan Terhadap Karakteristik Hidrologi DAS Citarum Hulu

The decline in water resources and the occurrence of various hydrological disasters in the Citarum watershed indicate the need to restructure the components inside the watershed, especially land cover in the upper watershed area. This study aims to determine the effect of forest land cover on the hydrological parameters of the upstream Citarum watershed through simulations of the SWAT (Soil and Water Assessment Tool) model. The results showed that the forest cover in the Citarum watershed was only 15.96% of the watershed area and only 4.94% was located in the Upper area. The Flow Rate Coefficient of the upstream Citarum watershed is 31.4, the annual average surface flow and annual erosion are 933.03 mm and 517.9 tons/ha respectively. The simulation from several scenarios shows that a decreasing in forest area can increase discharge and surface runoff, whereas an increase in forest area will increase soil infiltration and evapotranspiration. Decreasing forest area by 10% from existing conditions caused 58% of rainwater to become surface runoff. The large number of discrepancies between the existing conditions and the directions in the RTRWP will require a long time and large costs to adjust so that the short-term alternative that can be done is to convert dryland agricultural cover to the forest to reach forest cover of at least 45% of the land area in the upstream area and can optimize the hydrological function of the watershed.

A New Practical Approach to the Design of Industrial Axial Fans: Tube-Axial Fans With Very Low Hub-to-Tip Ratio

This paper presents a simple but complete design method to obtain arbitrary vortex design tube-axial fans starting from fixed size and rotational speed. The method couples the preliminary design method previously suggested by the authors with an original revised version of well-known blade design methods taken from the literature. The aim of this work is to verify the effectiveness of the method in obtaining high-efficiency industrial fans. To this end, the method has been applied to a 315 mm rotor-only tube-axial fan having the same size and rotational speed, and a slightly higher flow rate coefficient, as another prototype previously designed by the authors, which was demonstrated experimentally to noticeably increase the pressure coefficient of an actual 560 mm industrial fan. In contrast, no constraints are imposed on the hub-to-tip ratio and pressure coefficient. The new design features a hub-to-tip ratio equal to 0.28 and radially stacked blades with aerodynamic load distribution corresponding to a roughly constant swirl at rotor exit. The ISO-5801 experimental tests showed fan efficiency equal to 0.68, which is 6% higher than that of the previous prototype. The pressure coefficient is lower, but still 12% higher than that of the benchmark 560 mm industrial fan.

Analytical and Numerical Study of a Pulsatile Flow in a Porous Tube

Lateral leakage is encountered in many biological and chemical applications such as renal flows and filtration processes. In this paper, we report a comprehensive analytical and numerical method to examine pulsatile flow in a porous-walled tube, with leakage flow rate or permeation coefficient prescribed. In the first scenario, the analytical results have been obtained when the leakage flow rate is small as compared to the axial flow rate. Numerical simulations using ansysFluent were performed for cases where both the pulsatile Reynolds number based on the amplitude of the axial velocity and the leakage ratio (ratio of leakage velocity amplitude to the mean axial velocity amplitude) were varied. The comparison between the analytical and the numerical results indicates that the analytical solution for the axial velocity had an increasing deviation from the numerical results with the increasing pulsatile Reynolds number, or increasing leakage ratio. Interestingly, the analytical radial velocity almost overlapped with its numerical counterpart, for all considered cases. In the second scenario where a permeation coefficient for the leakage is prescribed, an analytical solution was obtained. Importantly, the solution in the second scenario suggests the criteria based on the wall permeability for the application of the analytical method developed herein.

The numerical analysis of mass evacuation in Taipei 101 with control volume model

Issues of safety evacuation of super high-rise buildings for emergencies have been attracting a lot of studies, especially after the disaster of WTC 9/11. In this study, the numerical results and dynamic processes of mass evacuation of a super high rise building are investigated by using the control volume model. The evacuation process of this model is divided into five stages and based on the assumptions of homogeneous flow with merge flow ratio where the exit flows from different floors meet and merge together. The super high-rise building, Taipei 101 is chosen for the object of evacuation simulation building, which is about 508 m tall. Seven scenarios, which content as total building evacuation and phased evacuation, are analyzed by using various values of the parameters which influenced the evacuation process in the building including walking speed, coefficient of flow rate, and merge flow ratio etc. The numerical results of mass evacuation are found to be in good agreement with the result of the National Fire Protection Association (NFPA) first-order approximation and indicate that the evacuation processes are highly dependent on the parameters of walking speed and specific flow. Furthermore, the dynamic characteristics of the evacuation process at each time-step for each floor are presented and discussed.

Forced Convection Upon Heat Sink of AL-Cu for Design Optimization by Experimental and CFD Analysis for Cooling of ICs in CPU

A heat sink device is used with specific power input at 100V and 20W by the heater attached at the base plate of copper and then obtaining the average temperature of Heat sink by the help of 10 thermocouples .Two specimens of heat sinks were designed and were tested for mass flow rate and heat transfer coefficient. With base of 1.5mm&2.5mmtip thickness and another specimen with dimensions as tip0.5mm and1.00mmbase thickness are used By experimenting and CFD simulations,optimization of heat sink design was done.Then correlation and Validation foe both the specimen was done and were found satisfactory results.

CFD simulation of methane flow through an orifice plate

In this paper the effects of errors in the flow rate and discharge coefficient when Methane (CH 4 ) flow through orifice plates with flange tapping has been investigated by the Computational Fluid Dynamics (CFD). The location of vena- contracta was also estimated from CFD simulations. Outcomes of the CFD simulations are in terms of profiles of pressure and velocity. In this study a numerical investigation of the flow characteristics behavior caused by a Methane (CH 4 ) flow through an orifice configuration is reported. This study investigates the following parameters; orifice pressure drop, flow rate and shift in discharge coefficient. In the present work, k-e turbulence model with density based solver has been used to predict velocity fields, pressure loss, shift in flow rate and discharge coefficient around this device. It is observed that the flow is jet-like flow in the core field and the presence of recirculation zone.

Structural Transformations in Composite Nanofiltration Films Caused by the Action of Excess Pressure

Samples of original and working porous composite nanofiltration membranes were investigated by xray scattering, thermal analysis, and study of the specific flow rate and retention coefficient. It was established that mechanical loading due to excess pressure of 1.5 MPa in the OFAM-K membranes leads to conformational changes in the phenylone C-4 macromolecules in the crystalline and amorphous intercrystalline phases, where the calculated degree of crystallinity decreases from 49 to 36%. Investigations by differential-scanning calorimetry indicate homogeneous crystallites with a thermal effect of 7.87 kJ/kg are formed in the working sample of the membrane. The working sample of OPMNP membrane undergoes polymorphous rearrangement of the crystalline phase with a change in the dimensions of the crystalline cell in the direction of the crystal axis (c) and with increase of crystallinity from 44 to 55%, while the amorphous phase becomes looser.

Numerical Investigation of the Effect of Needle Lift and Seat Design on Steady and Transient Flow in Diesel Injector Nozzle

In this study, the flow of fluid in the fuel injector nozzle of a Diesel engine was simulated under steady-state and transient conditions using ANSYS Fluent. At first, a nozzle for which experimental results were available was simulated. Then, validating the results, the $$ k - \varepsilon $$ turbulence model and the Schnerr–Sauer cavitation model were selected for the numerical simulation of a real four-hole fuel injector nozzle. In order to reduce the computational costs, only a quarter of the nozzle was modeled and the flow rate and discharge coefficient were obtained for different pressure differences. Three different seats with various needle lifts were analyzed in the steady-state case. Next, the problem was addressed under transient conditions and the results were compared with the steady-state case. Transient analysis has been performed by using ANSYS Fluent layering dynamic mesh with using UDF code for the needle lift. Ultimately, the impact of the needle lift frequency was investigated on the formation of vapors in the nozzle under transient conditions. The results of the numerical simulation show that, in addition to the discharge coefficient, needle lift, the seat design, and the frequency of the needle lift also affect the location and the size of the cavitation.

Numerical simulation of incompressible turbulent flow in shrouded disk system with radial outflow

The flow behavior inside the shrouded disk system is of importance in appropriate design of turbomachinery cavities and turbine test cell hydraulics dynamometer. The turbulent incompressible flow is analyzed for the shrouded disk system with axial clearance. The flow core behaves as a Batchelor type structure when a weak inflow is imposed on the disk cavity. By increasing the inflow, the central core disappears and the tangential velocity distribution is changed to Stewartson type structure. The central core again reappears by increasing the Reynolds number. The moment coefficient of rotary disk depends on superimposed flow rate coefficient and dimensionless geometrical parameters. Moment coefficient increases with increasing inflow rate while the other parameters remain constant. The coefficient is reduced by increasing the Reynolds number. Moreover, it increases with both increasing rotary and stationary disks axial distance, and decreasing clearance ratio. The experimental results of a cavity with radial clearance are used to validate the accuracy of the simulation. The results of this analysis and its development can be used in the design of turbine test cell hydraulics dynamometers.

Dynamic headspace analysis using online measurements: Modeling of average and initial concentration

Dynamic headspace sampling is an important technique for the analysis of consumer products, the study of biological samples and environmental water analyses. This paper shows the influence of experimental conditions, such as the sampling time, sampling flow rate, headspace volume, liquid volume and Henry coefficient on the measured average concentration values. A corresponding closed expression as function of these variables is introduced in order to quantify the deviation of the initial headspace concentration. The proposed bi-exponential function embeds different current existing models for recovery calculation in dynamic sampling analyses in one single expression. A fully automated and user-friendly Excel® file to investigate or to model the dynamic headspace sampling results is added to everyone's easy use.

Heat transfer analysis for fast filling of on-board hydrogen tank

The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions, mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper, the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature, hydrogen pressure, tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data, the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

A Study on In-Cylinder Flow of Small Engine Using Steady-State Flow Benches

In-cylinder air flow structures are known to strongly impact on the performance and combustion of internal combustion engines (ICE). Therefore, the aim of this paper is to experimentally study an IC engine in-cylinder flow under steady-state conditions. Steady-state flow bench methods can be used to characterize the in-cylinder flow engine. The experiments were carried out on the small cylinder head with pressure difference across the inlet valves of 100 to 300 mmH2O. The experimental results are presented in terms of the measured air flow rate, flow coefficient and discharge coefficient. Moreover, the CFD used to illustrate the evolution of tumble motion in-cylinder engine. The results show that air volume flow rate and flow coefficient increased as the valve lift increases but the coefficient of discharge decrease if valve lift increase. The higher the pressure drop the higher the mass flow rate value. However, the higher the pressure drop the lower the value of flow coefficient and discharge coefficient.

Analysis of tip-leakage flow in an axial fan at varying tip-gap sizes and operating conditions

Detailed and comprehensive analyses of the tip vortex system of a ducted axial fan are performed based on highly resolved large-eddy simulations. Various tip gap sizes, which are typically found in technical fans, and two operating conditions are considered. The Reynolds number based on the tip speed of the blade and the diameter of the fan D0 is Re=9.36×105, the Mach number is M=0.136, and the rotational speed Ω=3000 rpm. The chosen tip clearances s are s/Do=0.001,0.005,0.01 and the design and off-design operating conditions are defined by the flow rate coefficients Φ=0.195 and Φ=0.165, respectively. The conservation equations of a compressible, viscous fluid are integrated on a multi-block structured mesh with 140 × 106 grid points in a rotating frame of reference for a single out of five blades using periodic boundary conditions in the circumferential direction and prescribed undisturbed inflow conditions based on experimental data. The results show that increasing the tip-gap size results in several vortices in the tip-gap region, i.e., tip leakage, separation and induced vortices, which enlarge the diameter and the strength of the main tip vortex and decrease the efficiency of the fan. For the off-design operating condition, the tip-gap vortex for the smallest tip-gap size decays faster than for the design operating condition. Increasing the tip-gap width, changes the direction of the tip-leakage vortex trajectory. The angle between the blade chord and the tip-leakage vortex is decreased at design condition, while the opposite behavior is observed for the off-design condition, in which the tip-leakage vortex moves further away from the suction side of the blade. Furthermore, the interaction between the axial flow and the main tip leakage vortex convecting downstream of the blade leads to an enhanced turbulent mixing at larger tip-gap size. For the largest tip clearance, i.e., s/Do=0.01, spiral vortex breakdown occurs at the design operating condition caused by the interaction of the main tip vortex with the secondary vortex generated in the tip-gap region. At off-design operating conditions, a larger tip-leakage-loss coefficient is obtained due to a more intensive turbulent mixing, where the maximum loss coefficient occurs at around midchord.

Analysis of Cascade Vapour Refrigeration System with Various Refrigerants

Abstract In this paper report the performance analysis of different refrigerants couples in cascade refrigeration system. Refrigerants such as R134a/R23, R410A/R23 and R404A/R170 have been successfully analyzed in the superheating and sub cooling range of 10 °C and 5 °C respectively. The variation in condenser temperature was from 30 to 50 °C in high temperature circuit while evaporator temperature in low temperature circuit varied in the range of -70°C to -50 °C. The compressor efficiency was assumed to be 0.7 throughout the experiment. It has been revealed that there is enhancement in coefficient of performance and flow rate with rise in compressor work and evaporator temperature. From the present study we conclude that the refrigerant pair R134a/R170 was found to have greater coefficient of performance and lower mass flow rate and the pair R404A/R508B was found to have smaller coefficient of performance and greater mass flow rate.

Verification of a simplified mathematical model of centrifugal compressor stages

To calculate the efficiency of a centrifugal compressor, it is sufficient to know the design parameters and similarity criteria: flow rate coefficient, loading factor, relative hub ratio, Mach number. The effect of the inlet nozzle and the diffuser type is also taken into account. The original simplified model was successfully used for calculation of compressors’ candidates in computer programs of the Universal Modelling Method. Recently, the model has undergone significant revision and been remade. The modernized model is used in the program for primary design of centrifugal compressors. The authors verified the new model, comparing the calculated efficiency with the measured efficiency of several dozens of model stages 21CV family and low flow rate model stages. In total, calculations were carried out for more than thirty model stages. The range of design parameters of analysed model stages is quite wide: flow rate coefficient 0.00564 – 0.0676; loading factor 0.384 – 0.742; hub ratio 0.258 – 0.466.