Outlet Velocity Research Articles

Aerodynamic development and investigation of turbine transonic rotor blade cascades

An intricate nature of the pattern in which working fluid flows over transonic blade cascades generates the need for experimentally studying their characteristics in designing them. Three cascades having identical main geometrical parameters and differing from one another only in the suction side curvature in the outlet area between the throat and trailing edge were tested in optimizing the rotor blade cascade for the reduced flow outlet velocity λ2 ≈ 1. In initial cascade 1, its curvature decreased monotonically toward the trailing edge. In cascade 2, the suction side curvature near the trailing edge was decreased, but the section near the throat had a larger curvature. In cascade 3, a profile with inverse concavity near the trailing edge was used. The cascades were blown at λ2 = 0.7–1.2 and at different incidence angles. The distribution of pressure over the profiles, profile losses, and the outlet angle were measured. Cascade 1 showed efficient performance in the design mode and under the conditions of noticeable deviations from it with respect to the values of λ2 and incidence angle. In cascade 2, flow separation zones were observed at the trailing edge, as well as an increased level of losses. Cascade 3 was found to be the best one: it had reduced positive pressure gradients as compared with cascade 1, and the relative reduction of losses in the design mode was equal to 24%. The profiles with inverse concavity on the suction side near the trailing edge were recommended for being used in heavily loaded turbine stages.

Numerical Analysis and Experimental Verification of an Industrial Cleaner

Cleaner blowers play an important role in the proper functioning of fluffs collection system for industries. In this paper an industrial blower with three different volute geometries is investigated by using Computational Fluid Dynamics (CFD). And then two new volute geometries are modeled and analyzed based on the air flow through the blower. The numerical investigation revealed that the blowers with modified volute geometries have better outlet velocities. For this work, volute is modeled using Solid Works and meshed in ICEM CFD. The post processing is carried out using CFD POST. The results obtained were then validated and compared the experimental values of the different models of the blowers.

Optimization of a Porthole Die for an Aluminum Profile Extrusion Based on Orthogonal Test Method

In the present work, an attempt was made to solve the problem of distortions during the trial extrusion of an automobile shock absorption by means of orthogonal test method and HyperXtrude software based on ALE (Arbitrary Lagrangian Eulerian) method. According to orthogonal test arrangement, nine times simulations were carried out to study the effects of four significant parameters on distortions. Analysis shows that the influence of bearing length on the outlet velocity uniformity is the largest among the four selected factors. The material flow will be held up obviously with bearing length increasing because of the friction enlargement. But once the bearing length is beyond a critical value, its influence on flow resistance will decrease suddenly. The analysis also confirms that the baffle-block height and ram speed also have considerable influence on outlet velocity uniformity. And the impact of welding-chamber height on outlet velocity uniformity is slight and could be ignored. Finally, the die structure was optimized on the basis of the optimal combination of parameters obtained though the results and analysis of the simulation test. Extrudate with high quality were obtained.

Kinetic plots for gas chromatography: Theory and experimental verification

Mathematical kinetic plot expressions have been established for the correct extrapolation of the kinetic performance measured in a thin-film capillary GC column with fixed length into the performance that can be expected in a longer column used at the same outlet velocity but at either the maximal inlet pressure or at the optimal inlet pressure, i.e., the one leading to an operation at the kinetic performance limit of the given capillary size. To determine this optimal pressure, analytical solutions have been established for the three roots of the corresponding cubic equation. Experimental confirmation of the kinetic plot extrapolations in GC has been obtained measuring the efficiency of a simple test mixture on 30, 60, 90 and 120m long (coupled) columns.

Effect of strainer type, spray pressure, and orifice size on the discharge coefficient of standard flat-fan nozzles

The aim of this study was to determine the effect of nozzle strainer type (cylindrical, ball check, slotted, and cup screen type), spray pressure, and nozzle orifice size on the discharge coefficient (Cd) of standard flat-fan nozzles of different nominal sizes (from 02 to 06) and 110° spray angle. The flow rates measured for each nozzle orifice size and strainer type combinations were determined at five different spray pressures (2.0, 3.5, 5.0, 6.5, and 8.0 bars). In the study, size, shape, and area measurements concerned with nozzle geometry were performed and the differences between nozzles of different nominal sizes were revealed. Some of these data were also used to determine the liquid inlet and outlet velocity, discharge coefficient, and minimum spray pressure required for the atomization of nozzles with different strainer types. The liquid inlet and outlet velocity ranged from 4.38 to 11.75 m s-1 and 20.49 to 41.72 m s-1, respectively, depending on the spray pressures. The nozzles used with the cup screen and slotted strainers had identical velocity data as the same nozzles without strainers. The cylindrical and ball check strainers had a limiting effect on liquid inlet and outlet velocity, especially for 04 and 06 sizes. The Cd means of the nozzles with cup screen and slotted strainers, and of those without strainers, ranged from 0.874 to 0.980, and the differences between their means were found to be statistically insignificant for each spray pressure and orifice size. The Cd means of the nozzles with cylindrical and ball check strainers were 0.850-0.961 and 0.811-0.963, respectively. The Cd of the standard flat fan nozzles without strainer had a tendency to decrease with the increasing spray pressure, while the Cd means of the nozzles with ball check strainer moderately increased. For the complete atomization, the minimum pressure requirements of the orifices of 02 and 06 size without strainer were 2.03 and 0.99 bars, respectively, corresponding to flow rates of 0.64 and 1.33 L min-1. The required spray pressure for the nozzle with ball check strainer was found to be higher than that of the other strainer types.

A BIPV/T System Design Based on Simulation and its Application in Integrated Heating System

In order to better master the internal airflow distribution characteristics of photovoltaic thermal (PV/T) collector on air source heat pump (ASHP) system heating performance, CFD software was applied in studying the building-integrated photovoltaic thermal (BIPV/T) sys-tem. A mathematical model of BIPV/T and ASHP integrated heating system was established. Numerical simulation of the system was conducted based on the typical meteorological data in Shenyang area. The influence of the inlet and outlet velocity, internal flow field distribution and temperature field distribution of the BIPV/T system were analyzed on the system thermal efficiency. The relationship between optimal COP and the inlet and outlet velocity of ASHP system was studied. The optimal inlet velocity of the BIPV/T – ASHP integrated system was determined to be 4 m/s, and the COP reached 4.6.

A Study on the Ignition System of a Pilot Flame in a Cannon-type-combustor of a Turbo-engine

We studied a stable pilot flame system for a cannon type combustor of turbo-engines by adding both a frontchamber and a pilot flame chamber with an electric ignition system to the conventional two-stage system with two-stage combustion domains: a primary zone and a secondary zone. The electric ignition period was about 1 second with 2760V(theoretical) generated by Kochcroft-Welton circuit, and the fuel was butane gas. The inlet was 25m/sec and the pressure was about 400Pascal at the inlet of combustor.We set two cases for the outlet configuration: a converging nozzle and a turbine. The outlet temperature was 280C at the outlet velocity of 25m/sec, and the temperature was 230C at the outlet velocity of 12m/sec. A sufficiently large rotational speed and torque was obtained to rotate the compressor and fan of the turbine. Weanalyzed the ignition mechanism by solving two dimensional compressible Navier-Stokes equations and found that the role of the front chamberwas to maintain the pilot flame after the ignition shock. We confirmed experimentally that this system can ignite and preserve a stable pilot flame with quite high probability.

Residual surface topology modeling and simulation analysis for micro-machined nozzle

The performance of the micro nozzle is determined primarily by its machined surface topology. A circular cross-section micro-Laval nozzle is modeled and studied by using numerical simulation in this paper. The geometry of residual height and residual area of machined nozzle surface with flat-end milling cutter and ball-end milling cutter are created. It is found that the ball end milling cutter with large diameter is better than the flat one for nozzle finishing operations. The nozzle velocity performance is also revealed in this research. When residual height increased from 0.6 μm to 9.6 μm for nozzle with throat diameter less than 2 mm, the maximum outlet velocity of nozzle reduced gradually. The maximum outlet velocity of nozzle remains stable for the nozzle with throat diameter greater than 2 mm. The results show that the maximum outlet velocity of nozzle significantly reduces with throat diameter decreasing under constant residual height. Based on the analysis about velocity boundary layer, when residual height changing from 0.6 μm to 9.6 μm, the nozzle with throat diameter is 1 mm, has the boundary layer thickness ranging from 5% to 14% of outlet radius.

Effect of the volute tongue profile on the performance of a low specific speed centrifugal pump

In this study, we investigated the effects of volute tongue geometry variation on the head, efficiency, and radial force of a centrifugal pump. Numerical simulation modeling based on [Formula: see text] turbulence with automatic near wall treatments was used to simulate the turbulent flow. The effect of blade position with respect to the volute tongue on instantaneous pump characteristics was investigated. The parametric studies were done for cutwater gap, tongue shape, and volute tongue angle. Numerical results showed that the large cutwater gap caused lower radial force, especially at high flow rates. Investigations using various volute tongue shapes indicated that the short tongue volute decreased the radial force at design and low flow rates. Considering all aspects, the most satisfactory volute tongue angle was found to be 5° less than the outlet velocity angle of the impeller; yielding about 40% lower radial force than others at the design point.

Outlet Flow Velocity in Circular Culvert

Abstract The outlet flow velocity in the end section of the culvert barrel depends in most cases on the culvert geometry, including the barrel slope, as well as on upstream and downstream channel parameters. Flowing water can create pressure flow or free surface flow in the culvert barrel. In the case of an unsubmerged barrel outlet, the free-surface flow is more frequent than the full flow. Increased velocities can cause channel bed scour and bank erosion downstream of the culvert outlet. Different culvert flow cases in which the barrel outlet is unsubmerged are presented in this paper. The influence of the flow regime on the outlet velocity is also discussed.

Film cooling performance in a low speed 1.5-stage turbine: effects of mainstream Reynolds number and turbulence

The effects of mainstream Reynolds number and turbulence to film cooling performance were investigated experimentally and computationally under rotating conditions in a 1.5-stage turbine. The rotor of the turbine included 18 blades with chord of 124.3 mm and height of 99 mm. A film hole was set in the middle span of the rotor blade surface with injection angles of 28° on the pressure side and 36° on the suction side respectively. The Reynolds number based on the mainstream velocity of the turbine outlet and the chord length of the rotor blade varied from 1.9 × 105 to 2.1 × 105. Measurements were made at three different rotation speeds of 702, 737 and 800 rpm to keep the rotating number consistent at 0.0280 while the blowing ratio varied from 0.5 to 2.0. Air and CO2 worked as coolant to achieve the density ratio of 1.03 and 1.57, respectively. Computational investigation was performed using the hexahedral structured grids and k-e turbulence model. Results showed that the film coverage and cooling effectiveness are enlarged while the film deflection is weakened as the mainstream Reynolds number increases. Furthermore, the mainstream turbulence plays a negative role in the film coverage and cooling effectiveness at lower blowing ratio on both the pressure side and suction side while it promotes the film reattachment at higher blowing ratio on the suction side.

Effect of a rib on rim seal performance

The effect of a rib installed in a rim seal on sealing effectiveness was investigated using three-dimensional Reynolds-averaged Navier–Stokes analysis. A parametric study was performed for a single square rib installed on the surface on the rotor side. A total of 12 cases were tested with different heights, widths, and locations of the rib. The Spalart–Allmaras model was adopted as a turbulence closure model. The Reynolds number based on the axial chord of blade was 500,000 at the mainstream outlet. Ratio of the mainstream outlet velocity to mainstream inlet velocity was kept constant at 3.10. The sealing effectiveness was selected as the performance parameter. Installation of a rib in the rim seal enhances sealing performance regardless of the dimensions and location of the rib, although the effects are relatively small in some cases where the rib is located far from the surface of the rim seal on the rotor side.

Calculation and Analysis of the Surface Heat-Transfer Coefficient and Temperature Fields on the Three-Dimensional Complex End Windings of a Large Turbogenerator

With increased turbogenerator capacity and electromagnetic load, overheating of the complex end parts has become one of the main problems affecting safe and stable turbogenerator operation. In this research, a flow network was built representing the structural and ventilation characteristics of a 330-MW turbogenerator. The fan inlet velocity and pressures (boundary conditions) of each end-region outlet were obtained by the flow network method. The 3-D transient electromagnetic field in the turbogenerator end was calculated, and the eddy current losses (heat sources) of the end parts were obtained by the finite-element method. To study the surface heat-transfer coefficient distribution on the stator-end winding surface, fluid and thermal mathematical and geometric models of the whole turbogenerator end region were given. Using the finite-volume method, the surface heat-transfer coefficient distribution on the complex 3-D stator-end winding surface, fluid-flow distribution, and temperature distribution of the end parts were investigated under rated-load conditions. The calculated temperature results match well with measured data. This research can provide a theoretical basis for calculating the heat-transfer coefficients of the outer surfaces of large turbogenerators.

Analysis on Relation between Mixing Ratio and Outlet Temperature and Velocity in a Cold-Hot-Water Mixer

To study the relation between cold-hot-water mixing ratio and outlet-water temperature of a mixer, the geometrical model of the mixer was built. On the basis of theoretical analysis, the outlet-water temperature with different mixing ratio of cold and hot water was simulated by FLUENT software. The results show that: flow field in mixer can be divided into recirculation zone and convection zone, in which there are different thermal resistances individually, and it result in the nonlinear relation in outlet average temperature and mixing ratio; there is a linear relation between outlet average velocity and mixing ratio, which accords to the mass conservation principle of non-compressible and continuous fluid flow.

Research on Supersonic and Subsonic Field of Externally Pressurized Gas Lubricated Bearing

The flow passage including supply hole of externally pressurized gas was investigated. The outlet velocity of supply hole, bearing number and supply pressure’s relationship were built. According to supply hole’s speed, supersonic or subsonic model was chosen to calculate bearing clearance’s pressure distribution. Bearing number’s effects on pressure’s distribution was also studied. The calculation result shows that at larger bearing number, supply hole’s speed is harder to be chocked. Both in supersonic and subsonic condition, larger bearing number produces lower pressure loss.

Study on flow distribution inside integrated hybrid actuator

A piezoelectric-based hydraulic actuator is a type of piston-cylinder device which is operated by internal flow energy. Recently, an artificial muscle and a micro actuator have been developed using a new smart material and internal flow control. Thus, the actuating velocity of the fabricated integrated hybrid system was investigated using the pumping frequency and load weight. The actuating velocity was then calculated using a developed program, and the numerical result was compared with the experimental result to validate the numerical program. Also, the internal flow rate was measured to analyze the pump efficiency experimentally. The flow rate inside the integrated hybrid actuator calculated using a CFD program for various pumping frequencies was then compared with the experimental results. The maximum outlet velocity was obtained at the pumping frequency of 35 Hz and the velocity decreased from that point due to flow loss.

Internal Flow Field Analysis of Air-Suction Roller-Type Precision Metering Device

In order to analyze the influence of structure parameter of air-suction roller-type precision metering device on the flow velocity and pressure, the flow field was calculation and simulation. Take the compressibility and the viscosity of the real gas into account, the N-S equations, RNG k-ε turbulence model and wall function were applied to measure the flow rate and pressure of the outlet under the conditions of changing the area of the suction holes and the diameter of shaft. The results revealed that compared with the shaft holes area, the diameter of center axis have a marked influence on the flow velocity and pressure of outlet. When the area of suction holes is constant, with the increase of shaft diameter, the outlet velocity increased and pressure decreased; when the diameter of axle is constant, with the shaft holes area increase, the outlet velocity increased and pressure decreased.

Treating Congenital Heart Disease: In Vitro Ultrasound Imaging of a Powered Total Cavopulmonary Connection

Three-staged Fontan surgery is often performed on children suffering from congenital heart disease where only one ventricle is working correctly. The Fontan procedure reroutes blood from the vena cava directly to the pulmonary arteries, creating a circulation known as total cavopulmonary connection (TCPC). A novel cavopulmonary assist device, the viscous impeller pump (VIP), is currently being developed to reduce the workload on the single ventricle. Hemodynamic, or blood flow, efficacy of the VIP previously has been studied using computational fluid dynamics (CFD) and stereoscopic particle imaging velocimetry (SPIV). This study is the first to use ultrasound imaging to visualize complex flow patterns in powered and unpowered in vitro Fontan circulation. The idealized TCPC was modeled with a silicone mold and flowing glycerol seeded with 10-μm glass beads to mimic blood. B-mode, color Doppler (CD), and pulsed-wave Doppler (PW Doppler) images were used to quantify complex flow patterns in the idealized TCPC with (1) no VIP, (2) stationary VIP, and powered VIP at (3) 500 and (4) 2,000 RPM. PW Doppler data showed higher mean velocities and greater variance in the outlets relative to the larger inlets. The ratio of the means of maximum outlet velocity to maximum inlet velocity for no VIP, 0 RPM, 500 RPM, and 2,000 RPM decreased from 1.96 to 1.48, 1.29, and 1.15, respectively. These data indicate that both the placement and rotation of the VIP help improve hemodynamics. Oscillating vortices were observed in the outlets of the powered and unpowered idealized TCPC, agreeing with previous CFD and SPIV studies. The results of this study suggest that measuring complex flow patterns with ultrasound in vivo could be used clinically to optimize positioning and VIP rotation rate during and after implantation.

Numerical study on jet effect in the vertical showerhead MOCVD reactor

Numerical simulations are conducted about jet effects in the vertical showerhead MOCVD reactor. By varying the reactor height, nozzle spacing, jet speed and susceptor rotating speed, the flow, temperature and concentration fields in the reactor are simulated, so as to gain insights into the jet effect in vertical MOCVD reactor. It is concluded that (1) in the reactor chamber below the showerhead, velocity, temperature and concentration are all in periodic fluctuation, and the fluctuations decay gradually from the susceptor center to the edge; (2) the vertical velocity at the susceptor center is larger than that in the edge, the precursor concentration in the center is higher than that in the edge, and the temperature in the center is lower than that in the edge; (3) increasing the reactor height and the susceptor rotating speed, decreasing the nozzle spacing and the jet outlet velocity, the radial fluctuations of both axial jet velocity and precursor concentration will be depressed.

Influence of air stability and metabolic rate on exhaled flow.

The characteristics of contaminant transport and dispersion of exhaled flow from a manikin are thoroughly studied in this article with respect to the influence of two important factors: air stability conditions and metabolic rates. Four cases with the combinations of stable and neutral conditions as well as lower (1.2 met) and higher (2 met) metabolic rates for a breathing thermal manikin are employed. The exhaled contaminant is simulated by smoke and N2 O to visualize and measure the contaminant distribution both around and in front of the manikin. The results show that the microenvironment around the manikin body can be affected by different air distribution patterns and metabolic heating. Under stable conditions, the exhaled contaminant from mouth or nose is locked and stratified at certain heights, causing potentially high contaminant exposure to others. In addition, velocity profiles of the pulsating exhaled flow, which are normalized by mean peak velocities, present similar shapes to a steady jet. The outlet velocity close to the mouth shows decrement with both exhalation temperature and body plume. The velocity decay and concentration decay also show significant dependence on air stability and metabolic level.