Axial Flow Rate Research Articles

Research on digital vibration model of typical components in pipe system

The spatial distribution of pipe system is complex, long span and multi-point elastic support, so vibration analysis of pipe system is required in the pipeline design. This paper takes the pipe system as a typical component, based on the Timoshenko beam model, establishes a dynamic procedure for straight pipe elements that considers the axial flow rate of fluid, the pressure on the pipe wall, the Poisson coupling effect of fluid and pipeline structure, and the axial, transverse and torsional vibration. Through Laplace transform, the frequency simplified dynamic model is established. And the frequency transfer matrix model of straight pipe elements and the boundary constraint matrix of common boundary (such as fixed support) is established. Finally, the frequency domain transfer matrix model of different pipeline elements are set to the overall transfer matrix of the flow pipe system, providing a convenient means for rapid optimization of pipe system vibration.

Experimental study on the discharge characteristics of an air rotating gliding arc

In this study, the discharge characteristics of an air rotating gliding arc (RGA) are investigated by synchronous measurements of a digital oscilloscope and a high-speed camera, and the emission spectrum measurement. The discharge evolution in one complete motion cycle exhibits a ‘breakdown-elongation-extinction’ process accompanied by a jump phenomenon of the arc root and a back-breakdown phenomenon. The discharge evolves from the unstable breakdown mode (U-B), to the transition mode and finally to the stable gliding mode (S-G) by increasing the input voltage or decreasing the tangential and axial gas flow rates. The U-B mode at an input voltage of 120 V is featured by the large reduced electric field and high electron temperature of 1.90 eV, but the arc length and existence time are very short. The S-G mode at an input voltage of 270 V has a relatively low breakdown frequency of 0.33 kHz and an average breakdown current of 1.31 A, implying that the arc steadily glides and rotates along the spiral electrode. The average electron temperature is 0.64 eV in the S-G mode, while the arc length and existence time are longer. The rotational and vibrational temperatures of the N2(C3∏u) state are respectively measured at 2200 K and 4400 K in the U-B mode, and in the S-G mode are 2600 K and 4820 K. From the evolution of emission intensities of measured excited species, it is found that the NOγ band emission intensity generally rises from the U-B mode to the S-G mode since the gas temperature and arc existence time rise, indicating that the S-G mode may be beneficial for the vibrationally promoted Zeldovich reactions. This study could deepen the understanding of arc characteristics in air RGA for selecting a suitable mode to achieve better plasma performance in practical applications.

Comparative analysis of flow factors and crystallinity in conventional extrusion and gas-assisted extrusion

Abstract Two-dimensional models of die-melt and die-gas-melt were created using Polyflow software. The radial and axial directions flow rate, shear rate, pressure, and first normal stress of the specimen were numerically simulated under conventional extrusion and gas-assisted extrusion while taking into consideration the heat transfer on the free surface of the specimen. The crystallinity was determined by combining the simulation data with the crystallization kinetics equation. The computation results are then examined using Origin software. The findings demonstrate that the use of gas-assisted extrusion technology can cause the Vx to decrease or even turn negative by reducing the friction between the melting edge and the die wall. Additionally, it makes Vy , pressure, shear rate, temperature, first normal stress, and crystallinity increasingly steady and aids in reducing or avoiding the Barus effect. The crystallization phenomena can be measured by using the crystallization kinetics equation. The study of extruded parts at the microscopic level will benefit from this application.

IMPROVEMENT OF DIMENSIONS AND CHARACTERISTICS OF THE VORTEX CHAMBER PUMP FOR COAL-WATER MEDIUM DELIVERING

The vortex chamber pump combines the positive characteristics of the centrifugal pump and the jet pump, and its efficiency is much higher than that of the classical jet pump. This pump differs from the vortex injector by having the pump flow into the tangential outlet channel, which is not available in the vortex injector. The traditional bulk material pump in many aspects has certain shortcomings, these shortcomings limit its application scope and use effect, the traditional bulk material pumps mechanical parts and seals rapidly wear, resulting in short service life. Based on solving the Reynolds equations for water flow, the influence of the angle between the tangential channels of the pump on the energy characteristics is analyzed: an increase in the angle to 180° leads to a decrease in the relative efficiency by 30 %, the outlet pressure by 12 %, and the suction flow rate by 14 %. Thus, the design with a zero angle between the tangential active medium inlet and the tangential outlet channels is optimal in terms of energy-saving pumping performance. As the diameter of the vortex chamber increases, there is no significant trend in the efficiency of the pumped fluid be the vortex chamber pump. With the increase in the total supply pressure, the axial inlet flow rate increase is relatively slow, and the outlet flow rate increases in a parabolic trend. The wear of the pump vortex chamber wall depends on the mass flow rate of coal entering the vortex chamber. The larger the mass flow rate of the abrasive medium, the greater the erosion rate density and the mean volume fraction in the vortex chamber of the vortex chamber pump. The smaller the particle diameter of the coal, the larger the erosion rate density and mean volume fraction in the vortex chamber of the vortex chamber pump. Thus, an increase in particle size should be sought, which will result in less wear.

NUMERICAL SIMULATIONS OF LIQUID FILM PRIMARY BREAKUP IN A PINTLE INJECTOR: A PARAMETRIC STUDY

In the present study, numerical simulations have been conducted to investigate the primary breakup of the liquid film in the gas-liquid pintle injector, using the volume of fluid (VOF) method with the adaptive mesh refinement to capture the gas-liquid interface. The film breakup and atomization characteristics in the pintle injector are studied by changing the structure parameters and the momentum ratio. The results show that increasing the radial liquid flow rate to raise the momentum ratio promotes the atomization performance, while decreasing the axial gas flow rate deteriorates the atomization performance. The two methods of altering the momentum ratio both cause the spray angle to increase with the momentum ratio, but the first routine leads to a slower increase. With the increase of opening distance, the velocity of the liquid flow decreases, and the thickness of the liquid film increases significantly, making the film hard to break up. The skip distance negatively influences the film breakup and atomization when the skip distance exceeds one. Moreover, the hollow region of the spray is decreased with a longer skip distance, which is detrimental to fuel combustion.

Effect of initial generating eddy height on temperature, velocity and air entrainment of fire whirl

In this paper, we present an experimental effort to reveal the effect of the initially generated eddy height on the thermal, velocity, and air entrainment properties of the fire vortex plume. Experiments were performed by a fixed-frame facility with variable channel wall height (h), using propane as the fuel (20 cm in burner exit diameter, 50.0–100.0 kW in heat release rate). Results show that the growth rates of centerline excess temperature and axial velocity tend to increase with h in the continuous flame below h. It is found that the radial distribution of excess temperature is always of hump-type and little affected by h at lower levels, while the radial profile of axial velocity changes from the plateau-type into the hump-type as h is increased. In the upper continuous and intermittent flames, the radial profile of excess temperature evolves from the hump type into the unimodal type, and that of axial velocity develops into the unimodal type from the plateau type as h is increased. The growth rates of excess temperature radius and axial velocity radius with the normalized height decrease with h for the continuous and intermittent flames. The axial position corresponding to the significant increase in the growth rate moves upstream with the increase of the heat release rate (Q˙). Under small h, the tangential velocity within the vortex core decreases with height, suggesting that the rotational strength becomes weakened. It is found that the air entrainment is weak at the flame bottom within the initial generating eddy height, and the entrained air is insufficient for complete combustion. The axial mass flow rate increases obviously as the channel wall disappears. With the increase of h, turbulence suppression is enhanced, and its role in flame elongation becomes more significant. The reduction of flame height is probably attributed to the greater turbulent mixing length under lower initial generating eddy height.

Cooling of a synchronous electric motor using an axial air flow

The current work investigates the rate of cooling of an axial air flow through the gap between the stator and the rotor of a four-pole synchronous electric motor. The axial air is passing though the rotor's four longitudinal slots. The stator is considered insulated. The effect of the axial air flow rate, the rotor rotational speed and the slot size on the average Nusselt number has been investigated numerically using ANSYS-CFX. These effects have been studied considering a motor radius ratio (RR) in the range of 0.65–0.85, an axial Reynolds number (Rea) between 1750 and 40,000 and a rotational Reynolds number (Rer) of 1750 up to 35,000.Numerical results have been validated using published experimental data. The maximum deviation was less than 15 %. The present numerical results showed that increasing the axial air flow rate always enhances the rate of cooling. The effect of the axial Reynolds number was found to be more dominant than that of the rotational Reynolds number. Increasing the rotor rotational speed (Rer) enhanced the rate of heat transfer up to a certain limit beyond which a revered effect was observed. Such limit was investigated and found to depend on the motor radius ratio and the relative magnitude of the axial and rotational Reynolds numbers represented by X = Rea/Rer. The enhancement due to increasing Rer was reversed at X = 0.33 and 0.12 when RR was at 0.85 and 0.75, respectively. A new correlation of the average Nusselt number as a function of the axial and rotational Reynolds number has been developed.

The impact of mainstream ingress on the leakage flow and loss in partial shrouded turbines

The vital source of the leakage loss in shrouded LP turbines is the interaction between the leakage flow and mainstream at the exit cavity and downstream of the rotor tip. This paper numerically investigates the effect of the shroud design on the leakage loss. The results show that the mainstream ingress in the exit cavity is the key flow feature affecting the intensity and the resultant loss of the interaction between the two flows, which is highly intenser in partial shrouded turbines than full shrouded turbines and causes three aspects of impact: Firstly, the abundant amount of ingested mainstream raises the pressure in the exit cavity, reducing the axial leakage flow rate through the sealing structure. However, there is circumferential leakage flow at the rotor trailing edge due to the lack of the blockage of the shroud platform. In addition, the ingested mainstream also develops into backflow and a streamwise vortex in the exit cavity, intensifying the mixing of the leakage flow and mainstream. Thirdly, the pressure raise in the cavity promotes the convergence of the cavity outflow at the suction side of the rotor blade, thus expanding the impact region of the leakage flow and increasing the mixing loss downstream. The above impacts result in an efficiency decrease of up to 0.90% in the partial shrouded turbine compared to the full shrouded turbine. Based on the loss mechanisms of mainstream ingress, this paper presents an optimized shroud design, which can effectively reduce the loss in the rotor tip by suppressing the mainstream ingress phenomenon. In this way, the optimized shroud design has improved considerably the aerodynamic efficiency by about 0.50%.

Analytical approach to explore theory of creeping flow with constant absorption

Exploration of entire human body is now possible with the advancement in the field of biotechnology, biosensors and bio-inspired modeling. We model the flow of a fluid between parallel plates for a couple stress fluid in order to incorporate polar effects on the flow. The stream function is used to transform the governing equations to system of ordinary differential equations. The analytical solutions are found for velocity components, pressure distribution, the axial flow rate, the mean pressure drop and the shear stress. The effect of couple stress parameter on the velocity, pressure and the shear stress has been investigated through graphs. We have also used the data from the renal tubule of a rat kidney in our analytical results to study the effect of the couple stress parameter on the mean pressure drop across the slit of the rat’s renal tubule.

Peristaltic mechanism in a micro wavy channel

In this article the peristaltic transport of Williamson fluid in a wavy microchannel has been discussed. Williamson fluid has number of applications in petroleum industry and power engineering. In order to determine the energy distribution, viscous dissipation is reckoned. Here we have considerd the wavelength of the wall motion much larger than the channel width to validate the theory of lubrication. For simplification of Poisson Boltzmann equation, we have applied the Debye-Hunkel linearization which is valid for small surface potential situations with zeta wall potential ≤ 25 mV. In the cases of large surface potentials, it has been found that, in comparison with the exact solution of the Poisson-Boltzmann equation, the linear solution predicts slightly lower values of the potential in the region near the wall. After a small distance from the wall, the difference between the linear solution and the exact solution diminishes. We have considered the Williamson fluid in the absence of body force. However, an external electric field has been employed. The solution of axial velocity, flow rate, pressure rise, heat transfer, mass concentration and stream functions subjected to physical partial slip boundary conditions are calculated. The effects of appropriate parameters like Debye length, Helmholtz-velocity which characterize the EDL phenomenon and external electric field are also examined. The results reveal that the peristaltic pumping varies by applying external electric field. The resulting non-linear problem has been solved analytically through the perturbation technique to analyze the distribution and change in velocity, temperature, pressure, concentration and volumetric flow rate. Results have been found through MATHEMATICA and the effects of important parameters have been discussed graphically.

Continuous process technology for bottom-up synthesis of soluble cello-oligosaccharides by immobilized cells co-expressing three saccharide phosphorylases

BackgroundContinuous processing with enzyme reuse is a well-known engineering strategy to enhance the efficiency of biocatalytic transformations for chemical synthesis. In one-pot multistep reactions, continuous processing offers the additional benefit of ensuring constant product quality via control of the product composition. Bottom-up production of cello-oligosaccharides (COS) involves multistep iterative β-1,4-glycosylation of glucose from sucrose catalyzed by sucrose phosphorylase from Bifidobacterium adeloscentis (BaScP), cellobiose phosphorylase from Cellulomonas uda (CuCbP) and cellodextrin phosphorylase from Clostridium cellulosi (CcCdP). Degree of polymerization (DP) control in the COS product is essential for soluble production and is implemented through balance of the oligosaccharide priming and elongation rates. A whole-cell E. coli catalyst co-expressing the phosphorylases in high yield and in the desired activity ratio, with CdP as the rate-limiting enzyme, was reported previously.ResultsFreeze-thaw permeabilized E. coli cells were immobilized in polyacrylamide (PAM) at 37–111 mg dry cells/g material. PAM particles (0.25–2.00 mm size) were characterized for COS production (~ 70 g/L) in mixed vessel with catalyst recycle and packed-bed reactor set-ups. The catalyst exhibited a dry mass-based overall activity (270 U/g; 37 mg cells/g material) lowered by ~ 40% compared to the corresponding free cells due to individual enzyme activity loss, CbP in particular, caused by the immobilization. Temperature studies revealed an operational optimum at 30 °C for stable continuous reaction (~ 1 month) in the packed bed (volume: 40 mL; height: 7.5 cm). The optimum reflects the limits of PAM catalyst structural and biological stability in combination with the requirement to control COS product solubility in order to prevent clogging of the packed bed. Using an axial flow rate of 0.75 cm− 1, the COS were produced at ~ 5.7 g/day and ≥ 95% substrate conversion (sucrose 300 mM). The product stream showed a stable composition of individual oligosaccharides up to cellohexaose, with cellobiose (48 mol%) and cellotriose (31 mol%) as the major components.ConclusionsContinuous process technology for bottom-up biocatalytic production of soluble COS is demonstrated based on PAM immobilized E. coli cells that co-express BaScP, CuCbP and CcCdP in suitable absolute and relative activities.

Unsteady radiative–convective flow of a compressible fluid: a numerical approach

This article is designed to inspect the thermal effects of an unsteady compressible flow of a viscous fluid through a symmetric channel. Combined effects of convective heat transfer, magnetic field, and radiation are also given special attention in this article. Basic laws of mass, momentum, and energy for compressible flow are employed in the modeling of the current problem. In addition, slip boundary conditions are also implemented in the analysis of the above thermal flow problem. Coupled nonlinear differential equations are solved numerically using explicit finite difference technique. Finally, the influence of different sundry parameters on the axial velocity, flow rate, and heat transfer are visualized through graphs. Time variant behavior of flow rate is calculated. Outcomes of the results reveal that the increment of the flow rate is related to the increase of compressibility parameters. Enhancement in the temperature profiles in the presence of radiation number is also reported. This model is the most general version of peristalsis of compressible flow in view of natural convection and radiation impact with extensive applications in aircraft industry, geophysics, and other industrial situations (cooling of electronic equipment, heat exchangers, and so forth).

Visco-Elastic Fluid Model in an Inclined Porous Stenosed Artery with Slip Effect and Body Acceleration

The present paper analyzes an unsteady magnetohydrodynamic blood flow model of an visco-elastic fluid through an inclined porous stenosed artery with body acceleration and slip effect. Navier-Stokes equations have been used to describe the blood flow model. The governing equation of blood flow is solved by an analytic method by considering blood as an incompressible, visco-elastic fluid, and suspension of RBC’s in plasma. Axial velocity, blood acceleration, flow rate, and shear stress are derived numerically by using the finite Laplace and Hankel transformation and their inverse. The effect of parameters such as the visco-elasticity parameter, Womersley number, Hartmann number, inclination angle, parameter of slip, and body acceleration frequency is analyzed. Axial velocity reduces as the Hartmann number and visco-elasticity parameter enhance and it enhances with the enhancement of the slip parameter and inclination angle. The study is beneficial for finding the effect of slip parameter, porosity factor and Hartmann number when a human body is exposed to MRI and CT scan.

Heat Transport in Rotating Annular Duct: A Short Review

Heat transport in rotating processes finds a wide range of application in which academic issues in the fluid mechanics and heat transfer areas are here reported. This paper discusses successive works from the seminal paper of Taylor (1923) to recent numerical results established from a broad range of methods such as DNS, LES, RANS or LB methods. The flow regimes identification is thus reported in Taylor–Couette geometry. The role of the axial flow rates in the apparition, stabilization and destruction of the large-scale of the turbulent structures is depicted in the case of Taylor–Couette–Poiseuille geometry. In a non-isothermal condition, a discussion is held on the various exponent values found in the scaling relationships relying on the Nusselt number as a function of the Rayleigh or Reynolds numbers according to the regimes of thermal convection.

Numerical Turbulent Flow Analysis through a Rotational Heat Recovery System

Herein, hydrodynamic analysis from a large-eddy simulation in Couette–Taylor–Poiseuille (CTP) geometry is numerically investigated. The present geometry is inspired by a previous experimental work in which heat transport phenomena were investigated in a heat recovery system devoted to a rotary kiln facility. The streamwise and spanwise components of the velocity and the Reynolds stress tensor are firstly validated using an experimental benchmark. The effect of the axial flow rates is studied at a fixed rotational velocity. It is shown that the streamwise velocity component damps the vortex flow organization known in Couette–Taylor (CT) flow. The bulk region and its wall footprint are therefore characterized by various methods (spectral and statistical analysis, Q-criterion). It is shown that the turbulent kinetic energy of the streamwise component in the near-wall region is augmented leading to a multi-scale nature of turbulence.

Numerical simulations of internal flow fields in a nozzle with liquid fertilizer deep machinery

Fertilizing with water jet is a non-contact fertilization technique that uses high pressure water jet for hole-caving and fertilizing. In this article, an automatic liquid fertilizer deep machinery is proposed. The influences of three typical nozzles on the liquid fertilizer deep machinery were investigated via numerical simulations. The feasible water jet nozzle structures were obtained based on analysis and optimization of the main flaws of the four nozzles. A three-dimensional mathematical model of internal flow field in a high-pressure nozzle was established using the ANSYS software. Using the standard k-ε turbulent model, the internal flow field in the nozzle was simulated and the influences of nozzle parameters on the flow rate isogram and axial flow rate at the outlet of the flow field were studied. The results revealed that the axial flow rate at the outlet increased and then decreased as the convergence angle increased. The effects of cylinder section length on the axial flow rate at the outlet were negligible within a certain range. As the outlet diameter increased, the axial flow rate at the outlet decreased.

Analysis of Impact of a Novel Combined Casing Treatment on Flow Characteristics and Performance of a Transonic Compressor

To reduce the negative impacts of stall and surge on compressor performance, a novel combined casing treatment (CCT) structure with axial skewed slots and injection groove is proposed in this paper. The aerodynamic performance, as well as the mechanisms of loss generation, of a transonic axial compressor with NASA Rotor 67 are investigated numerically. The simulation results indicate that, compared with individual casing treatment method, the CCT works effectively with regard to operation performance. The stall margin (SM) is increased by 14.7% with 1.12% decrease in the peak efficiency. The interaction of axial skewed slots and injection groove can be explained by the enhancement of exchange flow in slots and axial motion of fluid. As a result, the leakage flow near the blade tip is eliminated and the flow separation is further suppressed. What is more, an analysis of entropy generation is also conducted. The results reveal that the effect of CCT on loss reduction mainly concentrates in the tip part of the blade, with the loss decrease about 14.46% compared with the original rotor. The best control effect can be expected by appropriate match between geometrical parameters of axial skewed slots and mass flow rate of injection from the parameter analysis.

Spray Entrainment Coefficient Modeling for High Injection Pressure Based on Entrainment Velocity and Force Analysis

Abstract The entrainment coefficient reflects the air–fuel mixing quality, which is one of the foremost concerns for the development of cleaner and higher power-density internal combustion engines. Previous prediction models constructed by the change of axial mass flow rate have lower accuracy under high injection pressure conditions. During modeling in the work, a new construction method based on local entrainment velocity and local entrainment area is developed, and the influences of dilution effect and forces such as flow resistance, lateral pressure, etc. on the local entrainment velocity are considered. With the modified model, its prediction accuracy can be effectively extended to high injection pressure and detailed information about entrainment can be provided for analysis. It is found that, with the increase of injection pressure, the entrainment coefficient rises in the whole flow field. When increasing to high injection pressure, the entrainment coefficient constantly decreases with distance in the far-field, which is consistent with the experiments, but not a constant value predicted by previous models. Besides, the decreased rate of entrainment coefficient rises with the increase of injection pressure. Meanwhile, the increase of ambient pressure also makes the entrainment coefficient rise, but barely influences the decreased rate in the far-field. The large decrease of local entrainment velocity in the far-field caused by strong shear stress and flow resistance can explain the decrease of entrainment coefficient with distance. Overall, the modified model is able to rapidly predict the spray mixing quality over a wider range of operational conditions and provide more detailed entrainment information for analysis.

Effect of pitched short blades on the flow characteristics in a stirred tank with long-short blades impeller

This work focuses on the design improvement of the long-short blades (LSB) impeller by using pitched short blades (SBs) to regulate the flow field in the stirred vessel. After mesh size evaluation and velocity field validation by the particle image velocimetry, large eddy simulation method coupled with sliding mesh approach was used to study the effect of the pitched SBs on the flow characteristics. We changed the inclined angles of the SBs from 30° to 60° and compared the flow characteristics when the impeller was operated in the down-pumping and up-pumping modes. In the case of down-pumping mode, the power number is relatively smaller and vortexes below the SBs are suppressed, leading to turbulence intensification in the bottom of the vessel. Whereas in the case of up-pumping mode, the axial flow rate in the center increased significantly with bigger power number, resulting in more efficient mass exchange between the axial and radial flows in the whole vessel. The LSB with 45° inclined angle of the SBs in the up-pumping mode has the most uniform distributions of flow field and turbulent kinetic energy compared with other impeller configurations.

Thermally developed electrokinetic bi-layer flows of Newtonian and non-Newtonian fluids in a microchannel

In the present study, thermofluidic characteristics of a combined pressure-driven and electrical field mediated thermally fully developed flow of an immiscible Newtonian and a viscoelastic fluid bi-layer in a microchannel have been analyzed. The simplified Phan-Thien–Tanner model with a linear kernel for the stress coefficient function has been utilized to describe the complex fluid rheology for the non-Newtonian fluid. Disparate zeta potentials have been assumed at the interfaces. Accordingly, distinct zeta potential values have been used at the channel walls and interfaces between the fluids to derive the closed-form analytical expressions for the pertinent velocity, stress, and shear viscosity distributions in the fluid layers. For thermally developed flows, the temperature and entropy distributions are obtained along the microchannel for constant wall heat flux boundary conditions. Major findings from our research show that amplification of the viscoelastic parameter designated by the Weissenberg number exhibits an enhancement in the non-dimensional axial velocity, flow rate, and stress magnitudes. Furthermore, the present study indicates that Joule heating and viscous dissipation significantly vary the dimensionless temperature profiles along the fluid bi-layer. The Nusselt number values are found to decrease with the augmentation of the viscoelasticity, Joule heating, and viscous dissipation parameters. The total entropy generation for the fluid layer systems increases with the increasing Joule heating parameter.