Tangential Inlet Research Articles

Study of the short-circuit flow and circulation flow’s impact on separation performance of cyclone separator with volute-helical inlet

Short-circuit flow and circulation flow are important secondary flows in a cyclone, which have a negative impact on separation performance. This work proposed new cyclones (VH cyclone), incorporating volute-helical inlets with five tilt angles based on the characteristics of short-circuit flow and circulation flow, in order to enhance separation efficiency without a significant pressure drop compared to a Lapple-type cyclone with a tangential inlet (TI cyclone). The separation performance and Euler number of six cyclones are obtained by experiments and analytical models. The simulation is utilized to explore characteristics of short-circuit flow and circulation flow, with a focus on the impact of these flow patterns on particle motion. The result shows that proportion of short-circuit flow increases initially and then decreases with the increase of the tilt angle, while circulation flow is continually weakened. The cutoff diameter increases first and then decreases while the trend of Euler number is opposite for new cyclones. By considering both separation performance and Euler number, VH4 cyclone (Tilt angle of volute-helical inlet is 6.5°) exhibits optimal performance, with a cutoff diameter 20.41% lower than that of TI cyclone, while their Euler numbers are similar.

Design of vortex-based cavitation devices/reactors: Influence of aspect ratio, number of inlets and shape

Vortex-based hydrodynamic cavitation devices are being used in a wide range of applications. However, adequate information on the design of such devices is not available. In this work, we have computationally investigated the influence of key design parameters such as the aspect ratio of the vortex chamber, the number of tangential inlets and the shape of the device on resulting flow characteristics and cavitation. Experiments were carried out to validate key findings from the computational studies. These investigations revealed that the aspect ratio of the vortex chamber as six may be considered as optimum. The performance of single and multiple inlet devices was found to be comparable at the same pressure drop (that is at same energy consumption per m3). Scale-up with a geometric similarity led to a reduction in the extent of cavitation for same energy consumption per m3. For facilitating scale-out option, an attempt was made to simplify the configuration of the vortex-based cavitation device. Computational results indicated that the cavitation performance of simplified configuration was not significantly inferior. A case of the formation of liquid–liquid emulsion was taken as a test case for evaluation of a modified cavitation device based on the present investigations. The droplet size distributions of emulsions generated by both the devices indicate that the proposed simplified configuration, which may facilitate fabrication and offer integrated scale-out options, performs almost at par with a complex configuration. The presented results will be useful for optimising designs of vortex-based hydrodynamic cavitation devices/ reactors.

Influence of different inlet modes on hot carrier gas flow in magnesium nitrate pyrolysis furnace

Spray pyrolysis of magnesium nitrate is a way to prepare magnesium oxide solid particles. The gas–solid flow process after the generation of solid particles inside the pyrolysis furnace was studied in this article. Six different inlet modes of hot-carrier gas were designed, and the hot-carrier gas enters the pyrolysis furnace at the same flow rate through the six different inlet modes. The influence of varying inlet methods on the actual running distance of gas flow and the particle sedimentation rate was deeply studied in this article. The longer the distance the hot-carrier gas runs in the pyrolysis furnace, the more conducive it is to full contact with the material. The higher the particle settling rate, the more magnesium oxide particles are collected in the pyrolysis furnace. ANSYS Fluent was used for numerical simulation in this study. The results indicate that when using a tangential inlet, the actual running distance of the hot-carrier gas in the pyrolysis furnace is longer than that of the normal inlet. The actual running distance of the thermal carrier gas at the three tangential inlets is 46.5 m, and that at a single normal inlet is 24.7 m. The former is 88% more than the latter. The sedimentation rate of solid particles at three tangential inlets is 32.24%, and that at a single normal inlet is 12.06%. The former is 167% higher than the latter. The three tangential inlet mode is the best way to increase the actual running distance of the hot-carrier gas and improve the solid particle settling rate in the pyrolysis furnace. The pyrolysis furnace with multiple tangential inlets has two advantages. On the one hand, increasing the running distance of the hot-carrier gas in the furnace is conducive, thereby making the contact between the hot-carrier gas and the material more sufficient. On the other hand, it can increase the capture rate of product particles, improve the product yield, and reduce the dust content of pyrolysis tail gas.

Flow and heat transfer characteristics of an impinging jet augmented with swirl

Jet impingement cooling techniques using conventional nozzles, round jets, and swirling jets are effective heat transfer methods extensively used for various industrial applications. This work proposes a geometrical mechanism that generates augmented swirling and round jets for enhanced heat transfer. The proposed geometry has an axial inlet port and three tangential inlet ports. The total flow is partitioned through these inlet ports using different split ratios (SR), resulting in a single augmented flow comprising swirling and round jets. The impingement heat transfer from a heated flat plate is modelled using steady 3-D RANS based numerical simulations. Also, computations for conventional round jets and swirling jets generated by an in-house developed vane-swirler are performed for the Reynolds number range of 6000–15,000, and for a range of jet-plate distance H = 1.5–4 times the jet diameter D. The optimum conditions for maximum heat transfer for various configurations of jets are presented. From this numerical study, the proposed augmented jet is found to enhance the impingement heat transfer rate at an optimal condition of split ratio (SR-4) and dimensionless jet-plate distance (H/D = 1.5) compared to conventional round jets as well as swirl jets generated by vane swirlers.

Numerical Study on Heat Transfer and Pressure Loss Characteristics of Swirl Cooling in Elliptical Tubes With Tangential Jet Inlets

Abstract The paper presents a numerical study of the heat transfer, pressure loss, and flow characteristics of swirl cooling in elliptical tubes, which are compared to the counterpart of swirl cooling in a circular tube with a diameter of D = 50.0 mm under equal passage Reynolds numbers and equal jet Reynolds numbers. The swirl tubes with two kinds of fixed tube length of 12D and 20D are compared, where there are sequentially arranged three tangential jet inlets over the leading tube length of 12D. The numerical results show that the swirl tubes with the tube length of 12D has a much better heat transfer performance. Under equal passage Reynolds numbers, the elliptical swirl tubes with the tube length of 12D show appreciably higher Nusselt numbers by up to 22.8% and lower pressure loss coefficients by up to 69.0% than the circular tube. Under equal jet Reynolds numbers, the elliptical tubes can reduce the global heat transfer performance modestly by up to 25.6%, but reduce the pressure loss much significantly by up to 70.6%. Mostly due to much less pressure loss, the elliptical tubes have remarkably higher thermal performance in terms of the obtained heat transfer coefficient per unit pumping power for both L1 = 12D and L2 = 20D. The numerical simulations indicate that the suppression of elliptical tubes on the swirling flow development reduces the heat transfer on the wall between the jet inlets, and decreases the wall shear force and the pressure loss in the tube.

Study of Tangential Effusion Cooling of a Combustor Liner

Tangential effusion cooling of a combustor liner has a large difference from traditional effusion cooling on a plate. In this paper, numerical simulation is carried out to study the flow field, heat transfer characteristics and the factors affecting the cooling effectiveness of tangential effusion cooling of a combustor liner. It is found that the cooling film formed by the tangential jet is distributed in a divergent “horsetail” shape and adheres tightly to the inner wall of the liner, which increases the cooling area and effectiveness. Three different tangential inlet cooling hole arrangements and their cooling efficiencies are studied, and several important parameters that affect the cooling effectiveness are summarized. Then, an improved cooling hole arrangement is proposed, and its cooling efficiency is studied and compared with those of the original three arrangements. The results show that the new arrangement significantly improves the comprehensive cooling efficiency and decreases the wall temperature, thus confirming the effectiveness of the improved strategy and providing a theoretical basis for the subsequent cooling design to improve the cooling efficiency for a combustor liner.

Study on the non-premixed combustion characteristics and exergy analysis of H2/Air in vase-shaped micro combustor

The micro thermophotovoltaic system (MTPV) based on H2/Air combustion has the advantages of high energy density, long-lasting and small-scaled. However, there are still some challenges in combustion stability and safety due to short residence time, large heat dissipation, and flashback. For this reason, a non-premixed micro-combustor with tangential inlet and vase shape is proposed in this paper. The tangential inlet can replace the swirler to form a swirling flow and the vase-shaped channel is designed as a gradual expansion and shrinking tube. The effects of the tangential inlet, equivalence inlet velocity, and key parameters of structure on non-premixed combustion characteristics were numerically studied. The energy transfer path and exergy efficiency were analyzed. The results showed that the vase-shaped micro combustor has a higher blow out limit, and much greater exergy and exergy efficiency than the conventional combustor. With the increase of equivalence inlet velocity, the exergy increases while the exergy efficiency greatly decreases. With the decrease in tangential inlet size, the flame temperature and exergy decreased while the exergy efficiency increased significantly. The tangential inlet can promote the mixing effect in the back-flow region, but the exergy and exergy efficiency decrease. The blow out limit increases with the increase of R3/R1 (maximum channel radius/inlet-1 radius) while the efficiency greatly decreases.

Performance Investigation and Optimization of the Primary Separation Part of the Oil-Gas Separator

Oil-gas separators are significant in the safe and reliable operation of the natural gas storage system. The separation efficiency of the conventional primary separation part of the oil-gas separator was not high enough, causing the insufficient performance of the whole separator. Three modification schemes were proposed to optimize the primary separation part of the oil-gas separator, including adding a curved baffle at the entrance, forming a centrifugal separation through the tangential inlet, and forming a cyclone structure by adding an inner cylinder. The separation performance was obtained through the Eulerian–Lagrangian approach numerically. For each scheme, a variety of parameter combinations were designed by the orthogonal array and the structure with the highest separation efficiency was reasonably selected. The separation efficiency of the centrifugal structure was higher than that of the collision structure on the whole. To evaluate the feasibility of the practical application, the three structural schemes were compared coupled with the analytic hierarchy process (AHP) based on the separation efficiency, the pressure loss, the uniformity of filter inlet velocity, and the modification cost. The results showed that the scheme of adding a curved baffle with reasonable structural parameters at the entrance had better comprehensive performance, which could be used as the optimal scheme in improving the oil-gas separator applied in natural gas storage.

Numerical study of the mixing characteristics in an air swirling fluidized bed with monodisperse and multi‐sized particles

AbstractPowder mixers are used in many industries. In the present work, a new type of air swirling mixer was designed and optimized with eight horizontally arranged inlet pipes at the tangential inlet angle of 35°. The mixing of multi‐sized spherical particles (2.0, 3.0, 4.0, and 5.0 mm) was numerically investigated in the air swirling mixer by coupled computational fluid dynamics–discrete element method. The numerical results showed that multi‐sized particles achieved comparable mixing performance to monodisperse particles. The Lacey index for multi‐sized particles increased initially, and then reached a maximum value at 0.824. The upward velocity of the particles, , increased initially, and then decreased to zero along the bed height. The maximum value of occurred at a height of 40 mm. Particle radial velocity was larger near the wall than at the mixer tube centre area. The smallest particles aggregated in three layers. The collision number of the particles reached a maximum at bed height of 120 mm, which was consistent with the position of the maximum stress of the particles against the tube wall.

Influence of Intake Valve Structure Combined with Valve Lift Dissimilitude on Intake Performance of Diesel Engine

For diesel engines equipped with a combined spiral/tangential inlet, the main object of the valve structure and valve lift dissimilitude strategies is the valve, the changes of both will alter the motion state of the in-cylinder airflow, which has an important impact on the formation and combustion of the mixture. In order to investigate the flow performance of valve structure and valve lift dissimilitude, this paper used computational fluid dynamics (CFD) numerical simulation and multi-parameter regression methods to optimize the dual intake valve structure and obtained three valve structures with better intake performance first. Then, the optimized intake valve structure models were combined with the valve lift dissimilitude schemes to conduct steady-flow tests for the intake port. Through the reasonable combining of the two, the intake performance of the original engine was further improved. The results show that the valve structure has a relatively small influence on the intake mass, while it has a greater effect on the formation of the swirl in the cylinder, increasing the swirl ratio by 8.0%. The optimized valve structure model was combined with the valve lift dissimilitude scheme. It was found that the valve structure with optimal intake mass combined with the dissimilitude scheme of the largest valve lift of the spiral inlet could increase the flow coefficient by a maximum of 1.9%. The valve structure of the optimal swirl ratio combined with the dissimilitude scheme of the largest valve lift of the tangential inlet could increase the swirl ratio by a maximum of 9.7%. This study can guide diesel engines with combined intakes to increase the intake mass and improve the intake performance.

Hydrodynamic instability of premixed tubular flame stabilized in stretched rotating flow

The paper analyzes the hydrodynamic instability of a cylindrical flame stabilized in a converging rotating gas flow simulating the flow in a cyclone combustion chamber. The analysis was carried out within the framework of a two-dimensional model describing the gas flow with radial and tangential supply of combustible gas through the walls of a cylindrical chamber. In the stationary case, the gas flow in combustion products and the combustible mixture is described by the solution for a rotating tornado-shaped vortex. The rotation of the gas creates a centrifugal force, which has a stabilizing effect on the flame perturbations. The dependences of the perturbations growth rate on the wave vector of perturbations, the radial and tangential inlet gas velocities, and other parameters of the problem are obtained. The analytical criterion of neutral stability separating regions of stable flame with respect of any perturbations and flame instability in the plane of radial and tangential velocities is obtained. In the absence of rotation and at the large flame radii, the model converts into the Landau- Darrieus model of flame hydrodynamic instability.

Numerical simulation analysis of heat and mass transfer of saline wastewater in a falling film evaporation tube based on different inlet modes.

Falling film evaporation technology is widely used in the treatment of salt-containing wastewater in coal chemical industry. However, there is still a lack of research on the inlet method of vertical falling film evaporation tubes. In this paper, the heat and mass transfer processes of saline wastewater under vertical and tangential inlets were investigated using numerical simulations. On this basis, the differences in flow and heat transfer processes between saline wastewater and pure water under tangential inlet were investigated. The results showed that the flow velocity of saline wastewater with a falling film evaporation tube in a tangential inlet mode was larger. Meanwhile, the turbulence in this way was more intense and the fluid temperature in the vertical tube was higher. Saline wastewater has higher temperature and smaller liquid volume fraction than pure water liquid membrane in the range of 193-1,000 mm from the inlet. The use of tangential inlet method to treat salt-containing wastewater has higher evaporation efficiency and is a very effective way to guide the improvement of heat transfer efficiency.

Shale gas hydraulic fracturing flowback fluid treatment using a modified vortex flocculation reactor: Effects of the axial and tangential inlet angles

Flocculation technology has been widely applied in treating shale gas hydraulic fracturing flowback fluid. To improve flocculation efficiency, we designed a series of vortex flocculation reactors with variable axial and tangential inlet angles. It was found that a flow field beneficial to flocculation would be formed when the axial and tangential inlet angles were 45° and 30°, respectively. Under this condition, the turbulent dissipation rate of the flow field was high near the inlet and decreased step by step from the bottom to the top of the reactor. The flocs were denser and more resistant to shearing and oscillations. Moreover, this reactor exhibited superior chemical oxygen demand and turbidity removal rates of 78.21% and 88.10%, respectively, which increased by 28.08% and 23.69%, when compared with the traditional reactor (both axial and tangential inlet angles were 0°). This study is a reference for developing and optimizing high-performance vortex flocculation reactors.

Numerical analysis on the impact of axial grooves on vortex cooling behavior in gas turbine blade's leading edge

In this article, a novel design for the vortex chamber with the axial grooves used for cooling the turbine blades leading edge is presented. The vortex chamber has nine tangential inlets that make a vortex in the chamber and an axial groove located along with the chamber. In addition to enhance the flow turbulence, these grooves cause an increasing heat transfer by cutting the thermal boundary layer and reformation. For this purpose, a 3D model based on Reynolds-averaged Navier–Stokes (RANS) equation was simulated in Ansys Fluent software. After comparing different turbulent models and experimental data, results showed Reynolds stress model (RSM) mode presents the best accuracy. Grooves with different sizes, positions, and numbers are used to investigate the vortex structure and the heat transfer mechanism. This study revealed that a chamber with grooves has a higher heat transfer in comparison with chambers without grooves. The best performance is achieved in a chamber with three grooves, where the average Nusselt number is increased by more than 4%. In this method, pressure difference between the inlet and outlet in the chamber with and without grooves are not very significant, and the highest friction factor happened in the case with three grooves.

Self-cleaning performance of three bottom drain modes in circular culture tank: Experimental and numerical study

This work investigated the self-cleaning performance of three drain modes in circular bottom drain water tanks with tangential inlet. Removal experiments in center, eccentric and center-eccentric combined (dual) drain modes were carried out in a miniature tank with a diameter of 0.44 m and a depth of 0.215 m for a hydraulic retention time of 30 min using two artificial bio-wastes mimicking fish fecal and uneaten feed matters. The experiments were simulated by using the Eulerian model of FLUENT. The correlations between the numerical solutions and the experimental data confirm the adequate reproduction of the bio-waste removal behavior. It was confirmed that the self-cleaning performance of the center drain is four times greater than that of the eccentric drain under the same water supply condition. Since the water drainage speeds of the dual-drain were less than those of the other two drains under the same water supply condition, the order of precedence for self-cleaning performance was the center drain, dual-drain, and eccentric drain. According to numerical experiments in the full-size tank with a diameter of 9.15 m and a depth of 1.83 m for hydraulic retention times of 30 and 55 min, the above order was kept constant, but the self-cleaning performance of the center drain was reduced by 1.04 times of that in the eccentric drain. The numerical experiments of all possible dual, triple and quadruple bottom drain modes in the full-size tank with one center drain and three eccentric drains showed that an increase of the eccentric drains causes a decrease of the drainage speed and thus does not lead to a noticeable improvement in self-cleaning performance. Numerical experiments in a medium-size tank showed that the above order was also kept constant. The reason why the self-cleaning performance of the center-eccentric combined drain is lower than that of the center drain is that its reduced drainage speed does not have kinetic energy enough to push the bio-wastes up to the height of the outlet. The center drain has the best self-cleaning performance in the circular tanks with tangential inlet and if the drainage speed is not sufficiently increased, the multiple drain system might have negative effect on self-cleaning performance.

A varying-swirl design concept for dry powder inhalers

The de-agglomeration potential of a dry powder inhaler (DPI) strongly affects its aerosol performance. Typically, a swirling flow is employed for the entrainment and de-agglomeration of drug powder into the inhalation air flow. Here, we propose a novel design concept that passively modifies the DPI swirling-flow, and thereby the de-agglomeration process, in order to achieve higher lung deposition. The essence of this design is a varying inner cross-section of the pipe-shaped device, realised in the form of converging and diverging circular sections placed after the tangential inlets in the device. An improved aerosol performance was shown for this device, with the fine particle fraction reaching 68.4% of the emitted dose, compared with 66.8% from that of the baseline device. This was found to be a direct effect of the modified flow characteristics generated within the device and thereafter emerging from its mouthpiece. These flow characteristics were determined from computational fluid dynamics simulations and particle image velocimetry measurements.Adaptations of this DPI design concept were achieved through the use of a honeycomb grid placed either after the device tangential inlets, or at the device mouthpiece exit. When placed after the inlets, a 10.4% reduction in the fine particle fraction was observed, as the air flow was straightened due to the influence of the grid which significantly reduced the flow-swirl before the flow entered the converging–diverging sections. Whereas, when placed at the mouthpiece exit, the flow-straightening effect of the grid resulted in reduced lateral spreading of the emitted aerosol but did not significantly affect throat deposition.

Catalytic reverse-flow oxidation process in reactors of various designs: Axial, side and tangential gas inlet

The study was dedicated to the mathematical modeling of the catalytic reverse-flow process in reactors of different design, e.g. in reactors with axial, side or tangential arrangement of reaction gas inlet/outlet streams. The oxidation of volatile organic compounds in the fixed adiabatic catalyst beds was considered, using toluene as an example contaminant. Three-dimensional fluid dynamics modelling performed by means of Comsol Multiphysics software showed the existence of the significant gradients of temperature, concentrations of reactants and fluid velocities along the bed radius; such gradients are neglected in the conventional one-dimensional models, usually used for simulation of reverse-flow processes. The spatial distribution of these parameters may be asymmetric in the reactors with asymmetric design. It was shown that efficiency of both toluene conversion and heat regeneration significantly decrease in reactor with side feeding of inlet mixture, finally resulting in lower thermal stability of the process with the significant (∼20%) decline of the maximum possible duration of the cycles between flow reversals compared to reactor with axial gas feeding. Vice versa, the tangential arrangement of gas inlet provides the visible (∼10%) increase of maximum cycle duration. Application of 3D modelling approach to development and optimization of catalytic processes becomes especially important in case of reverse-flow reactors where negative influence of various spatial non-uniformities may impose more significant influence on process parameters.

Experimental Analysis of Tangential-Vane Swirl Atomizer Spray Angle

A swirl atomizer is a widely applied spray-generating device. The swirling motion of a swirl atomizer is induced either by a tangential inlet or a swirl-generating vane. The swirling effect produces a spray with a wide angle which is important in various applications such as gas cooling, diesel engine combustion, and automatic hand sanitizer. An intense swirling mechanism was reported to significantly affect the spray angle. An attempt was made by combining tangential inlet and swirl-generating vane in a single embodiment to create a more intense swirling effect. The experiment was conducted with pipe flow in transition and turbulence regimes. The shadowgraph technique was applied to acquire the spray images. The images were processed using image processing software. It was found that the combined swirling mechanism produces a wider spray angle compared to the individual tangential inlet swirl atomizer. It was also found that the swirling intensity has a bigger effect on the spray angle than the Reynolds number.

A Numerical Study on Swirling Hot Air Anti-Icing with Various Surface Structures on the Internal Wall

Swirling hot air is a promising heat transfer enhancement technology for anti-icing applications in aircrafts, where the swirling flow is accompanied by pretty high turbulence and a quite thin boundary layer. It is of interest to investigate the compound heat transfer characteristics of the swirling air configuration combined with surface structures on the internal wall. This paper carries out a series of numerical computations to obtain the Nusselt number and pressure loss data in such a swirling air heat transfer system with four kinds of surface structures (trenches, ribs, dimples and bulges) on the wall and with different tangential inlet jets placed along the tube. At a tube Reynolds number from 10,000 to 50,000, the results show that the surface dimples and bulges are conducive to improving the Nusselt number, but the surface trenches and ribs show a Nusselt number deterioration relative to the smooth swirl tube. Among the four investigated surface structures, the surface bulges perform best, which can enhance the Nusselt number by up to 15.0%, increase the total heat transfer quantity by up to 17.3% and reduce the hot air pressure loss by up to 15.6%. Furthermore, the circumferential velocity distribution and swirl number are introduced to describe the flow fields. The surface trenches and ribs lead to less of a reduction in the circumferential velocity and swirl intensity, while the surface dimples and bulges could significantly suppress the in-tube swirl intensity.

Analytical solutions for vortex flow at the tangential inlet of a vertical dropshaft

Vertical dropshafts with tangential intake structures are often used in urban drainage systems to route surface flow into underground systems. Vortex flow driven by a tangential inlet is the typical flow pattern in the vertical dropshaft. However, analytical solutions of the key hydraulic transition from chute flow to vortex flow have not been investigated, and theoretical guidelines of the vortex dropshaft are not available. In the present study, a series of theoretical analytical solutions are proposed to determine the circumferential flow generated at the vertical dropshaft inlet. The contraction ratio of the tapering chute, dropshaft size, and flow depth at the joint section determines the vortex flow performance in the vertical dropshaft. Based on the free surface drop height, theoretical criteria are proposed to describe the spiral movement intensity in the vertical dropshaft. Systemic experiments for different vortex dropshaft models are tested, and the experimental observations agree with the theoretical analysis. The present investigation provides a general reference for a tangential dropshaft inlet design that can smoothly route rotational flow down a vertical dropshaft.