Inlet Diameter Research Articles

DESIGN OF CENTRIFUGAL COMPRESSOR IMPELLER FOR OPTIMAL EFFICIENCY

This research present a case steady namely design of centrifugal air compressor impeller for power station. This compressor is a dynamic compress which depends on a rotating impeller to compress the air. Impeller is the most important part of the centrifugal compressor components. Detail design calculation of centrifugal compressor impeller is described in this research. This study contains a complete set of detail drawing for blade profile of impeller. It can be used at sites which flow rate is 0.1275 m3 /s and 45561 rpm. The required data are collected from Ywama Power Station which is located in Yangon. For the given capacity, the inlet and outlet diameter are 0.054 m and 0.17 m and the number of blade is 19. Keywords: centrifugal compressor, impeller, velocity, diameter, width.

Optimization of the Structural Parameters of a Plastic Centrifugal Pump

The structural design parameters of a plastic centrifugal pump were calculated and modeled, and flow field simulation analysis of the model was performed using CFD, in the framework of an orthogonal design method (or experiment). The inlet mounting angle β1, outlet mounting angle β2, wrap angle ϕ, and impeller inlet diameter D1 of the pump impeller were the four factors assumed for the application of the orthogonal experiment, using the efficiency and Net Positive Suction Head (NPSH) as evaluation indices. Moreover, taking the maximum efficiency and minimum NPSH of the plastic centrifugal pump as the evaluation factors, the parameters of the pump impeller were re-optimized through the Taguchi algorithm (leading to the following optimal combination: inlet diameter 35 mm, inlet angle 26°, outlet angle 27°, and wrap angle 110°). The minimum NPSH and the maximum efficiency have been found to be 0.957% and 61.5%, respectively.

Optimization of the Structural Parameters of a Plastic Centrifugal Pump in the Framework of a Flow Field Analysis

In order to determine the optimal structural parameters of a plastic centrifugal pump in the framework of an orthogonal-experiment approach, a numerical study of the related flow field has been performed using CFX. The thickness S, outlet angle β2, inlet angle β1, wrap angle, and inlet diameter D1 of the splitter blades have been considered as the variable factors, using the shaft power and efficiency of the pump as evaluation indices. Through a parametric analysis, the relative importance of the influence of each structural parameter on each evaluation index has been obtained, leading to the following combinations: β1 19°, β2 35°, S 2 mm, wrap angle 154°, and D1 85 mm (corresponding to the maximum efficiency of 75.48%); β1 19°, β2 20°, S 6 mm, wrap angle 158°, and D1 81 mm (corresponding to the minimum shaft power of 75.48%). Moreover, the grey correlation method has been applied to re-optimize the shaft power and efficiency of the pump, leading to the following optimal combination: β1 19°, β2 15°, S 4 mm, D1 81 mm, and wrap angle 152° (corresponding to the maximum efficiency of 71.81% and minimum shaft power of 2.187 kW).

Dynamic Characteristics Analysis of Pilot Valves with Different Inlet Diameters Installed on the Main Steam Valve Set

Dynamic Characteristics Analysis of Pilot Valves with Different Inlet Diameters Installed on the Main Steam Valve Set

Influence of flow parameters in the dual nozzle CO2-based vortex tube cooling system during turning of Ti-6Al-4V

Dual nozzle vortex tube cooling system (VTCS) is developed to improve the machinability of Ti-6Al-4V where cold-compressed CO2 gas is used as a coolant. The cooling effect is produced by the process of energy separation in the vortex tube and the coolant is supplied into the machining zone to remove the generated heat in machining. In this study, the responses such as cutting force (Fz), cutting temperature (Tm), and surface roughness (Ra) are analyzed by considering coolant inlet pressure, cold fraction, and nozzle diameter as input variables. Further optimization is performed for the input variables using the genetic algorithm technique, and the results at optimum conditions are compared with those of dry cutting. From the results, lower cutting force is observed at lower coolant pressure and cold fraction and higher nozzle diameter. The cutting temperature is minimized by increasing coolant pressure and cold fraction and by decreasing nozzle diameter. A better surface finish is observed at high coolant pressure and cold fraction and lower nozzle diameters. It is observed from the response surface method (RSM) that the coolant pressure is most significantly affecting all the responses. At optimum conditions, the cutting temperature and surface roughness are 35.6% and 66.14%, respectively, lower than dry cutting due to the effective cooling and lubricating action of the CO2 gas, whereas cutting force observed under the VTCS is 18.6% higher than that of dry cutting because of the impulse force of the coolant VTCS and thermal softening of the workpiece in dry cutting.

Simulation and Optimization of the Nozzle Section Geometry for a Suspension Abrasive Water Jet

In order to improve the life cycle and cutting ability of a suspension abrasive water jet nozzle at the same time, hydrodynamics technology, an enumeration method and multiparameter orthogonal optimization are used to optimize the nozzle section geometry, taking the inlet diameter coefficient of the nozzle, the axial length coefficient of the contraction section and the contraction section curve as optimization variables, and selecting the peak velocity and the unit flow erosion rate as the indicators, it is concluded that the optimal contraction section curve is a Widosinski curve, the optimal inlet diameter coefficient of the nozzle is 0.333 and the optimal axial length coefficient of the contraction section is 2.857. Compared with the commercial product single cone nozzle, the performance of the optimal section nozzle improves by 5.64% and the life cycle increases by 43.2%. On this basis, the effects of operating parameters, including inlet pressure, abrasive particle flow rate and abrasive particle size, are further studied. It is determined that the optimal section nozzle has the best performance under the above operating parameters. It is demonstrated that by optimizing the nozzle section geometry, the cutting capacity and life cycle of the nozzle are improved, the performance of the nozzle can be significantly improved and the optimization of the performance of the nozzle is realized.

Volumetric design for ORC-VCC compressor-expander units.

The combination of an ORC (Organic Rankine Cycle) with a VCC (Vapor Compression Cycle) is studied analytically. In this work, the two cycles use the same fluid and operate with a common condenser. Elementary transformations of the fluid between two consecutive points of the system are calculated using a one-dimensional thermodynamic approach considering real fluid properties, the pressure losses and irreversibilities present in the compressor, in the expander and in the pump. The performances and the recommended inlet and outlet diameters of the expander and the compressor are established for various operating conditions and 12 fluids. The system can produce a typical useful cooling capacity of 0.60 kW at 5.5 °C when using a 2 kW heating source at 65 °C and when the condenser temperature is 30 °C. The cooling capacity reaches 1.0 kW if the cold source temperature is 15.5 °C. Results show the required diameters ratios at inputs and outputs of the compressor and the expander. They indicate the situations for which the compressor is smaller than the expander and vice versa. They identify the particular cases in which the compressor and the expander have exactly the same inlet and outlet diameters. This particular case allows using two identical compressors, one working as a compressor, the second as an expander.

A Newly Developed Empirical Predictive Model for the Dispersed Phase (DP) Holdup in Rotating Disc Contactors

Newly novel developed correlations were derived to predict the dispersed phase (DP) holdup in a rotating disc contactor (RDC) extraction column. DP holdup is one of the significant parameters in the design of liquid–liquid contactors and for calculating their production capacity. Despite the availability of quite a large number of holdup prediction correlations for the RDC, most of these correlations are either general in nature or valid for a limited range of operating conditions. This study conducted an experimental and theoretical investigation of the RDC holdup under the influence of varying geometries, including variations in the dispersed phase distributor, speed of the disc, flow rate, and physical characteristics of the system. The analysis revealed that the holdup decreased with an increasing distributor hole diameter and increased with an increasing disc speed and total flow rate. The effect of the physical properties on the holdup was larger than the effect of the disc speed. Using the measurements of over 150 runs, two RDC column holdup predictive models were proposed and evaluated. The first correlation was derived in terms of the distributor hole diameter, operating parameters, system physical properties, and column geometry. The second correlation excluded the column geometry. These correlations, which consider the distributor hole inlet diameter in predicting the DP holdup for an RDC column, were presented for the first time in this study. The predictive capability of these correlations was evaluated via their standard deviation (SD) and mean average percentage error (MAPE). The respective SD and MAPE of the two correlations were 1.7 and 5.2% for the first correlation and 1.6 and 11.4% for the second.

Design and Experiment of Hydraulic Scouring System of Wide-Width Lotus Root Digging Machine

In response to the problems of small working width and low operating efficiency of existing hydraulic scouring lotus root harvesters, a wide-width hydraulic scouring system was designed based on a wide-width self-propelled lotus root harvester. The main parameters of the key components were determined through theoretical analysis of the water flow energy of the hydraulic scouring system pipelines. An experimental study was also carried out on the main factors affecting the working performance of this hydraulic scouring system. Through hydrodynamic simulation tests, the effect of nozzle type and constriction section structure on the turbulence intensity at the nozzle outlet and the pressure loss per unit mass of fluid between the nozzle inlet and outlet sections were compared and analysed. The test yielded conical-cylindrical nozzle geometry parameters for nozzle inlet diameter of 40 mm, shrinkage angle of 30°, nozzle outlet straight section length of 20 mm, nozzle outlet diameter of 16 mm, the nozzle had better flushing performance. Single-factor tests were carried out with nozzle outlet pressure, scouring angle and nozzle height from the mud surface as influencing factors. Based on the optimum effective scour depth, a three-factor, three-level Box–Behnken central combination design test was completed. The primary and secondary factors affecting the effective scouring depth were obtained in the following order: nozzle height from the mud surface, nozzle outlet pressure, and scouring angle. Finally, the performance test of the hydraulic scouring system was completed. Results showed that when the nozzle outlet pressure of 0.30 MPa, the scouring angle of 60° and the nozzle height from the mud surface of 0 mm, the effective scouring depth was 395 mm, the lotus root floating rate was 90% and the damage rate was 5%, which meet the requirements of lotus root harvesting operations.

Computational Modeling of Aortic Stenosis With a Reduced Degree-of-Freedom Fluid-Structure Interaction Valve Model.

In this study, a novel reduced degree-of-freedom (rDOF) aortic valve model is employed to investigate the fluid-structure interaction (FSI) and hemodynamics associated with aortic stenosis. The dynamics of the valve leaflets are determined by an ordinary differential equation with two parameters and this rDOF model is shown to reproduce key features of more complex valve models. The hemodynamics associated with aortic stenosis is studied for three cases: a healthy case and two stenosed cases. The focus of the study is to correlate the hemodynamic features with the source generation mechanism of systolic murmurs associated with aortic stenosis. In the healthy case, extremely weak flow fluctuations are observed. However, in the stenosed cases, simulations show significant turbulent fluctuations in the ascending aorta, which are responsible for the generation of strong wall pressure fluctuations after the aortic root mostly during the deceleration phase of the systole. The intensity of the murmur generation increases with the severity of the stenosis, and the source locations for the two diseased cases studied here lie around 1.0 inlet duct diameters (Do) downstream of the ascending aorta.

Influence of dry ice inlet and outlet positions on cooling characteristics of high heat flux chip

• Radiator models with different dry ice inlet and outlet positions are proposed. • Dry Ice with low temperature and sublimation latent heat is used as a coolant. • Influence of radiators on the temperature field, speed field and cooling time are Simulated. • A radiator model with optimum coupling of velocity and heat transfer is obtained. Based on the cooling characteristics of dry ice on high heat flux chip, a variety of radiator models with different dry ice inlet and outlet positions are proposed in the present study. The influence of these radiator models on temperature field, velocity field, dry ice distribution and chip cooling time are analyzed. The results demonstrate that when the diameter of inlet and outlet is 12 mm and the chip power P 0 = 95W, the average temperature of all models' chip bottom has reached below 50 °C when t = 70 s. The inlet of Model g is located in the center of the upper surface of the radiator and the outlet is located in the center of the side surface, the chip overall temperature of Model g is the most uniform distribution with 90% of the area temperature at 25 °C. Model g combines the advantages of the phase change heat transfer and the jet impingement heat transfer, which can realize the optimal coupling of the flow rate and the heat transfer, ensuring the safety and reliability of the chip more effectively. Moreover, the results of simulation and optimization are in good agreement with the relevant experiments, laying a foundation for further optimization of the structural scale of the radiator and better coupling of the heat flow field of the dry ice cooling system.

Effects of extrusion ratio and direction on extruded Au nanowires investigated using molecular dynamics simulation

The effects of the extrusion ratio (diameter of the extrusion mold inlet divided by that of its outlet) and direction on extruded Au nanowires (NWs) are studied using molecular dynamics simulations based on the embedded-atom method. The effects are investigated in terms of atomic trajectories, common neighbor analysis, flow field, system pressure, and the extruded NW length-pressing ram displacement curve. The simulation results show that for the forward extrusion process, a smaller extrusion ratio leads to a larger diameter of the extruded NW and a smoother cross-sectional profile. Extruded NWs obtained at a smaller extrusion ratio have a higher face-centered cubic fraction and a less disordered structure due to lower system pressure. The adhesion effect between extruded NWs and mold outer walls increases with increasing extrusion ratio, resulting in an uneven appearance of extruded NWs and a decrease in their length. The backward extrusion process can produce amorphous NWs from crystal NWs. The forward extrusion process can produce NWs that are longer than those produced with the backward extrusion process.

Vane induced two phase flow mixing

Micromixers are used for mixing of multiphase fluids in microchannels. Passive micromixers help in mixing of fluids by having a designed periphery in their structure. In the current study, a Y micro-channel section of 25 mm length with an inlet diameter of 2 mm is considered. Vane shaped micromixers are placed inside the channel to mix fluids of two different concentrations. The vanes are positioned at specific places inside the channel to enhance mixing in the stratified flow stream. The presence of vanes during the flow induces mixing of the stratified fluids without requiring additional components. The study is carried out using COMSOL Multiphysics. The mixing index increases with increase in the number of vanes and no considerable change in velocity is observed downstream of the last vane. Further, when the thickness of the vane is increased, it is found that the mixing index also increases.

Development of pumps with improved anti-cavitation characteristics

When considering the creation of pumps with improved anti-cavitation characteristics, the results of an in-depth analysis of the problem of pumping viscous liquids at high temperatures are presented. On the example of the technological process of evaporation of sugar syrup on a film evaporator of the latest type, the problem of the occurrence of cavitation when pumping viscous liquids at high temperatures was revealed. After analyzing the existing machines used for the specified operating conditions, critical design and operating parameters were identified that affect the appearance of cavitation. Namely, the appearance of cavitation is influenced by the reduced diameter of the impeller inlet, the diameter of the impeller inlet, the number of blades, the width of the blades and the rotor speed. To study the level of influence of these parameters, a method of physical modeling was chosen, an experimental stand was designed and manufactured. Studies have been carried out on the operation of the pump with and without a reducer. The work with a two- and three-blade inducer is analyzed, the work with an open and closed impeller, with one and two-level blade system is investigated. As a result of the analysis of experimental data, the optimal design of the hydraulic part with a three-blade reducer and a semi-open impeller with a two-level blade system was chosen. In turn, this made it possible to reduce the compression of the flow at the inlet to the impeller without loss of energy efficiency; the angles of inclination of the inducer and impeller blades were synchronized. The experience gained made it possible to design and manufacture an industrial sample of a cantilever pump with an inducer and a semi-open impeller. Thus, allowing to solve the problem of pumping thick syrup on a film evaporating unit of the Teofipol sugar plant (Khmelnytskyi region, Ukraine), with a cavitation reserve of 1.5 m.

Two-Phase Flow Development of R134a in a Horizontal Pipe: Computational Investigation

To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2.s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

CFD simulation and statistical experimental design analysis of core annular flow in T-junction and Y-junction for oil-water system

One of the big challenges in transporting heavy oils through the pipelines is the high pressure drop due to the effect of viscosity and shear-thinning fluid behaviour of oil. Core annular technique has been applied in industry for transporting heavy oil via pipelines to considerably reduce pressure drop. Several studies have been conducted related to oil-water core annular flow (CAF) within pipelines. However, limited works are found in cases of CAF in widely used T and Y-shaped junction pipes which have important roles for dividing or combining the flow. In this study, a computational fluid dynamic (CFD) approach was applied to simulate the high viscous oil-water CAF through T and Y-shaped junction pipe configurations. The 2k factorial statistical experimental design was applied to investigate the effect of pipe diameter and junction angle on the flow performance through T and Y-shaped junction pipes. Eight cases were run with different junction pipe configuration combinations. By applying the factorial designs method, all possible combinations of factors were able to be investigated with lowest numbers of simulation run. The selected response variables of the flow system were the average values of oil hold up and pressure gradient as well as the standard deviation of pressure from inlet to outlets of pipes. It was observed that the stability of CAF was not achieved at the downstream region. The flow transformed into stratified and slug flow. The most attractive design was measured by the small average of pressure gradient and standard deviation of pressure but with a high value of oil holdup. The T-shaped pipe with smaller inlet diameter combined with larger outlet diameter showed the most considerable effect for a better flow performance.

Numerical studies on ejector in proton exchange membrane fuel cell system with anodic gas state parameters as design boundary

A comprehensive entrainment performance evaluation system of the ejector was built including four indexes. An ejector's Computational Fluid Dynamics (CFD) model was established, and the sensitivity analysis of the entrainment performance to four key geometry parameters of the ejector, namely, the nozzle diameter (Dn), the primary nozzle exit position (NXP), the mixing tube diameter (Dm), and the secondary flow inlet diameter (Ds) was performed. Based on the quantified boundary conditions obtained by the Simulink simulation, the ejector structure was optimized with a new method. It is found that the total recirculation ratio increases but the hydrogen recirculation ratio decreases with the increase of the relative humidity of the secondary flow. The hydrogen recirculation ratio shows a unidirectional increase tendency with the increase of Ds and the decrease of Dn and NXP. The hydrogen recirculation ratio increases firstly and then decreases with the increase of Dm. High hydrogen recirculation ratio with low primary hydrogen flow rate, corresponding to low current operation point of fuel cell system and low sensitiveness to the changing relative humidity are usually incompatible. The hydrogen recirculation ratio with low primary flow rate degrades significantly when Dn increases and Dm is larger than a certain value. The ejector with smaller Ds shows lower sensitiveness to the changes of relative humidity, while the hydrogen recirculation ratio with low primary hydrogen flow rate is not affected badly. When matching with a specific system, it is necessary to balance the ejection performance at low current density operating points and the sensitiveness to the changes of relative humidity in combination with the anodic gas state at each operating point, so as to find the optimal structural parameters. The optimization sequence of structural parameters should follow: Dn is selected firstly, then NXP and Ds are optimized, and finally Dm is chosen.

Heat transfer and pressure drop correlations for direct on-chip microscale jet impingement cooling with alternating feeding and draining jets

Jet impingement cooling with distributed outlet configuration is regarded as an efficient cooling solution for high performance systems. This work develops the Nusselt number Nu¯f-Red and pressure drop k-factor correlations for microscale multi-jet impingement cooling with alternating feeding and draining jets. An extensive design of experiments (DOE) of unit cell modeling-based simulations is used for the correlation fitting. In order to understand the flow and thermal behavior, the impact of single variables including the inlet diameter, outlet diameter, jet-to-target distance and nozzle length is studied systematically. On the other hand, this work firstly shows the predictive model with k-Red, including the impact of nozzle length t/L, cavity height H/L and inlet diameter ratio di/L. Finally, the extracted correlations are experimentally validated, both with experimental data of different jet impingement demonstrators, as well as with the literature experimental data.

SIMULATION OF FLUID FLOW THROUGH A STAINLESS STEEL GLOBE VALVE USING ENGINEERING FLUID DYNAMICS

Globe valves are often used in many practical application of industry with the aim of controlling the fluid flow through the valve. Valve design ensuring an operation capacity plays an important role for engineers. This paper presents the design and simulation of fluid flow through the globe valve using CAD/CAE tools such as Autodesk CFD. Besides, design of experiment technique Box-Behnken is used to integrate the CFD simulation to identify the optimal design parameters of the globe valve. These parameters are inlet pressure, orifice diameter, and outlet clearance. The results showed that the optimal parameters are appropriate to improve the valve design to ensure the maximum fluid flow rate.

스크류원심펌프 임펠러 자오면형상 설계파라미터 최적화

Screw centrifugal pump is a non-clog type pump, which is widely used for drainage and sewage control systems. The screw centrifugal pump combines the advantages of the screw pump and centrifugal pump. Screw centrifugal pump shows the relatively high efficiency and the good solids handing capability. Based on a screw centrifugal pump design method, the parameters of impeller meridional plane shape are investigated for the improvement of pump performance. The design parameters of impeller meridional plane shape, such as impeller inlet and outlet diameters, outlet width, total axial length, blade inlet and outlet angles, and inclination angles, were investigated to examine their effects on the pump performance. Numerical analysis was conducted to determine the essential design variables for the screw centrifugal pump. Furthermore, flow passage shape optimization was conducted to enhance the performance of the screw centrifugal pump.