Flow Swirlers Research Articles

Study on characteristics of phase-isolation caused by different classic axial flow swirlers in upward vertical gas-liquid two-phase flow

The characteristics of phase-isolation of annular flow caused by axial flow swirler are very critical for separation efficiency of axial inlet separator and accuracy of phase-isolation based measurement method. However, there are lack of comparative study among different types of swirlers and research focusing on characteristics of phase-isolation. In this paper, the phase-isolation characteristics caused by four different classic axial flow swirlers with the same main structural parameters were firstly experimentally studied in upward vertical gas-liquid two-phase flow. Five flow patterns were proposed after obvious evolution in phase distribution at downstream of the swirler, including gas-column flow, swirling annular flow, central bubble flow, central bubble-column flow, and variable diameter gas-column flow. According to the different phase-isolation characteristics, flow patterns downstream of the swirler were divided into stable phase-isolation, quasi-phase-isolation, and non-effective phase-isolation. The corresponding flow pattern maps were also obtained respectively. The experimental results also show that the swirler with good phase-isolation performance generally requires a larger pressure drop as the cost. Finally, the flow in the swirlers was studied numerically. It is found that although the outlet angle of the swirlers is the same, different types of swirlers will result in flow with different deflection angle, and eventually cause the different phase-isolation performance.

Распределение температуры на оси камеры расширения при различных схемах работы вихревой трубы

The change in air temperature along the axis of the expansion chamber in the zones of the nozzle inlet and the flow swirler in the direct-flow, counter-flow, three-flow and single-flow vortex tubes has been investigated. It has been established that in all cases, the cooling of air in the vortex tube occurs in the zone of the swirling device, and its heating - in the zone of unwinding of the flow. The change in air temperature in the axial zone along the length of the expansion chamber occurs due to heat exchange between the heating and cooling zones.

Исследование движения несжимаемого газа в вихревом теплогенераторе

The article presents the results of the performed analytical and experimental studies of the hydrodynamics of the translationalrotational motion of a viscous incompressible gas flow in the working space of a vortex heat generator of variable geometry, analytically determined the dependences of the effect of device performance, confuser opening angles, confuser channel width on the hydrodynamic parameters of the device and, as a consequence, its energy efficiency. The degree of energy efficiency of the swirler screw for the operation of a vortex heat generator at various loads on the working path has been experimentally estimated, according to the Euler number EUc. It has been proven that the energy efficiency of its operation is on average 35% higher when the swirler screw is installed. The influence of the geometry of the nozzle on the axial symmetry and smoothness of the flow of incompressible gas in the vortex chamber is investigated. It was found that the specified indicator is most satisfactory for a nozzle with a rectangular cross-section. The distribution of the temperature field of a moving incompressible gas along the height of the vortex chamber is investigated depending on the taper angle. The distribution of angular velocities along the axis of the flow swirler is investigated at various values of productivity. It was found that the angular velocity decreases according to the law of potential fluid flow. A mathematical model has been developed to optimize the operating modes and parameters of the vortex heat generator. A software block was built based on the mathematical package MathCAD version 11 for the implementation of the developed mathematical model. An optimal design of a vortex heat generator with a variable geometry of the working space has been developed, which has been tested in laboratory conditions. Laboratory studies have proven its high energy efficiency at the level of modern standards and the feasibility of using the device for heating buildings and structures in industry and the domestic sector. Keywords: incompressible gas, hydrodynamics of an incompressible gas flow, vortex motion, mathematical model, equation of motion, continuity equation, vortex heat generator, thermal energy, cavitation, turbulence, vortex zone, MathCAD package.

The calculation of the rates in the swirling flow for the confuser section

The advantages of using aconfuser section in the outlet part of the vortex spillwayare shown in the paper; they may be more rational in terms of ensuring cavitation-free operation of the flow swirler. An analytical method for calculating the aerated swirling flow in the confuser section of the vortex spillway is presented, as well as its correspondence to experimental results, which allow us to quickly and accurately conduct the distribution analysis of axial and tangential rates in the swirling flow along the length of the confuser at different taper angles.

Relief flow swirlers to control wax deposition formation inside downhole equipment

The present study describes problems of wax deposition formation on the surface of oil field equipment. In particular, the problem of wax deposition prevention inside tubing walls is considered. Wax prevention techniques and wax removal techniques were analyzed and the main advantages and disadvantages of these techniques were highlighted. The technique for controlling wax deposits by means of fluid swirl is proposed, which is carried out using a process module for controlling downhole deposits based on a flow swirl. Simulation flow modeling in the direct-flow swirler was performed. The simulation was carried out with the help of SolidWorks Flow Simulation program for different profiles of flow section, number of turns, and swirling pitch. An increase in temperature due to a fluid swirl and a significant pressure gradient in the wall layers of the tubing after the swirler were revealed.

Using Flow Swirlers to Enhance Heat Transfer in Apparatuses of Wet Regeneration of Waste-Gases Heat

The paper presents results of experimental study of the effect of air-droplet flow swirling on evaporation of moisture contained in the flow. The tests were conducted in a round 30 mm tube within the range of Reynolds number (15-50)103 at the wall heat flux ranged from 14 to 23 kW/m2 and water-spraying density 10-20 g/(m s). It was demonstrated that the swirling inserts enhance droplet deposition from the flow core to the wall and recover the evaporated liquid film at a length equal to several tube calibers. Followed by dried zones appearing at the wall again. This is due to the processes of liquid film rupture and liquid entrainment accompanying liquid deposition enhancement. The overall effect of the flow swirling appeared to be less effective than it was anticipated.

Substantiation of counter­vortex spillway structures of hydrotechnical facilities

The construction and reconstruction of waterworks sets a number of scientific and engineering tasks that require a new approach to their solution. One of the promising areas for solving these and a number of other problems is the use of swirling water flows in hydrotechnical facilities. The article presents the results of physical simulation of spillway counter-vortex systems. The model had a damping chamber diameter of 0.15 m and was tested at a head up to 8 mH 2 O and a flow rate up to 0.11 m 3 /s. As a result of the conducted experiments, the values of the flow coefficient of the entire system were obtained. The water-carrying capacity was determined for several modes of operation of the model by means of a combination of switching valves that brought water to the inlet nozzles of the model. In addition, a change in the mode of operation of the model was carried out by changing the vacuum in the near-vortex zone of the counter-vortex flow in a wide range. A self-similarity of the flow coefficient by the head and the Reynolds number has been established. The physical modelling has made it possible to formulate a well-grounded approach to the hydraulic calculation of counter-vortex spillway systems. One of the most important issues studied experimentally in the process of the described hydraulic tests was the determination of the energy damping capacity of counter-vortex spillways, reflecting their effectiveness. The energy damping capacity was determined by the energy damping factor, reduced to the general head in the model. The article presents the main schemes of local water flow swirlers for the formation of a counter-vortex flow, which can be used in hydrotechnical practice. Some of their geometric and hydraulic characteristics are considered. A simplified scheme of hydraulic calculation of a counter-vortex spillway structure for various types of swirlers and constructive solutions of a spillway system (an open type or an underground tunnel) is proposed. The authors compared the efficiency of the proposed method for damping the energy of the spillway flow and the hydraulic scheme with a sudden expansion of the flow according to the Borda formula. The counter-vortex method of damping the energy of the transit flow has a much higher efficiency in comparison with sudden expansion. The study suggests directions for further research on complex counter-vortex flows.

EFFECT OF VARYING THE DOUBLE RADIAL SWIRLER CONFIGURATION ON THE FLUID DYNAMIC AND EMISSIONS PERFORMANCES IN A CAN COMBUSTOR

The main purpose of this article is to present the fluid dynamic and combustion performances of a can combustor applying double radial flow swirler. Analysis was conducted using Computational Fluid Dynamics simulation (CFD) and compared with experimental works conducted by previous researchers. Air pollution, in the form of gaseous emissions from gas turbine generator reportedly increasing every year. Design modifications was identified and used in this study where air swirler been proven able to reduce the formation rate of gaseous emission such as NOx and CO during combustion. Swirler in a burner is a device that serves to improve the air and fuel mixture in the main combustion zone. Swirlers, presently studied are from a combination of two radial swirlers with different vane angle (primary and secondary) such as 30o/40o, 30o/50o and 30o/60o. Application of Ansys Fluent 14 CFD solvers was used in this study. Turbulent flow model used was from Reynolds Average Navier-Stokes (RANS) type involving k-ϵ. The fuel used is diesel. The parameters studied were wall temperature distribution along the combustor, the volume of NOx and volume of CO in the main combustion zone. Results from this study showed that the combination of 30o/60o generates the lowest gaseous emissions production rate. The highest average percentage error obtained by simulation studies compared to the actual experimental values for NOx was 22% and CO was 17.8%. Comparison between simulation and actual study proves that the simulation method can be used for preliminary decision and able to be used as benchmark to determine which is the best swirler configuration.

Influence of the inlet flow swirler construction on hydrodynamics and efficiency of work

The object of research is construction of a vortex dust collector. To solve the problem of increasing the efficiency of dust cleaning in a vortex apparatus with revealing the features of the mechanism and the destructive forces of the process, the features of the hydrodynamic regime of rotation of the gas-dust flow in the zone of the swirler and immediately after it are used. The influence of the swirler construction and the location of its installation in the gas duct for feeding the gas-dust flow on the efficiency of the vortex apparatus is studied. It is shown that the aerodynamic processes that determine the nature of the flow rotation and its flow in the flue after the swirler reach the maximum possible angular velocity of the gas flow rotation in the separation chamber for this construction. It is proved that the swirler construction under the appropriate conditions allows a swirling flow leaving the duct to the separation chamber to reach the maximum possible angular velocity of the gas flow rotation for the given construction. The characteristic regimes of the gas-dust flow in the duct are established immediately after the swirler from its construction. It is shown that for a traditional vane swirler with a swirling flow in one direction, the most effective blade inclination angle corresponds to 45°. Its installation must be carried out in the duct from the end outlet to the separation chamber below by 1 . 4 ¸ 1 . 6 of the swirler diameter. Before the gas-dust flow flows into the separator, the flow is agglomerated with dust particles. At the exit of the gas-dust flow from the end of the flue to the separation space, the maximum value of the angular velocity of the flow in the separator is ensured. It is established that the blade vortex, which provides for the organization of coaxial turbulent flows in the flue, twisted in opposite directions, will allow more efficient agglomeration of dust particles. A basic construction of the vortex dust collector is developed, which makes it possible to increase the cleaning efficiency with a vortex device to 98–99 %.

A canonical geometry to study wall filming and atomization in pre-filming coaxial swirl injectors

A coaxial twin counter-rotating air swirl prefilming injector with necessary optical access, is developed to visualize and quantify its internal fluid dynamics. This research injector consists of a simplex nozzle arranged at the center of two coaxial counter-rotating radial air flow swirlers, and two transparent coaxial tubes are attached, one each to the primary and secondary air swirl paths. Spray from the simplex nozzle is swirled by the primary air and impinges on the inner tube—the prefilmer, undergoes filming, and convects to the tube tip to form a liquid rim, which is sheared by the counter-rotating swirl into finer droplets. Stage-wise phase Doppler particle analyzer measurements indicate the final spray to be much finer than the simplex nozzle spray after undergoing the above processes. Time resolved laser induced fluorescence (TR-LIF) imaging techniques are applied to visualize the wall filming and primary atomization inside the injector. The simplex nozzle spray velocity under the influence of air swirl flow is measured using stereo-particle image velocimetry. The precessing vortex core from the primary swirl imparts a precessing motion to the simplex spray, which in turn induces a non-uniform filming on the prefilmer. The droplet impingement on the prefilmer leads to splashing and crater formation on the surface. The crater size distribution is obtained and compared to the droplet size of the injector spray before impingement. The film thickness variation on the prefilmer surface and the rim thickness are estimated from planar LIF experiments along with a long distance microscope. The thickness of the liquid rim is identified as a major factor in determining the final droplet size at the injector exit. These are correlated to SMD at the injector exit at different air flow rates.

Investigation of the effect of using tube inserts for the intensification of heat transfer

In this work, heat transfer in channels containing inserts of different shapes was investigated using computational fluid dynamics (CFD) modeling techniques taking a gaslight water heater as an example. Three types of devices inserted in the water heater tube (flow swirlers) were investigated: star-shaped, coiled wire, and classic ones in the form of twisted tapes. In the present study, the RNG k-ɛ turbulence model is used to model the turbulent flow regime. This numerical simulation has been performed over a Reynolds number range of 5800–18500. In the studied range of Reynolds number the maximum thermal performance factor was obtained by the starry inserts with A star/A inlet = 0.50. The results have exposed that also the use of all tube inserts leads to a considerable increase in heat transfer and pressure drop over the smooth tube. In addition, the results revealed that both heat transfer rate and friction factor in the tube equipped with starry insert were significantly higher than those in the tube fitted with the coiled wire inserts and classic twisted tape.

On choice of a swirler for the impulse combustion chamber

In this paper, some problems on implementation of an air-fuel mixture combustion process in the flame tube with a GTE impulse combustion chamber flow swirler are considered. When the peripheral swirler is placed in the flame tube head of this chamber, a number of 3-D reverse flow zones are formed to effectively mix up the air-fuel mixture providing its steady-state combustion. As a result, the thrust impulse is increased and a level of atmospheric emissions of NOx, CO, and some other detrimental compounds is significantly decreased.

Analyzing the effectiveness of wall flow swirlers

Results obtained from multicase thermal-hydraulic calculations of different heat transfer intensifiers are presented. The possibilities of saving fuel and materials in manufacturing heat exchangers for thermal and nuclear stations and during their operation due to the use of these intensifiers are shown. The objectives of further investigations are formulated.

A simple model of heat exchange and friction in the channels with spiral near-wall flow swirlers

A model, constructed on the basis of modern concepts, for thermohydraulic calculation of the heat exchanger channels with the heat exchange intensifiers is proposed. Urgent problems of the further investigations in this field are formulated.

Co-firing of eucalyptus bark and rubberwood sawdust in a swirling fluidized-bed combustor using an axial flow swirler

Co-combustion of eucalyptus bark (as shredded fuel) and rubberwood sawdust was conducted in a swirling fluidized-bed combustor using a 22-vane axial flow swirler. During the co-firing tests, the fuel blend feed rate was maintained at about 60kg/h, while the mass/energy fraction of the blended fuels was variable. Excess air supply ranged from 20% to 80% for each fuel option via variation of primary air, while secondary air was injected tangentially into the bed splash zone at a constant flowrate. For comparison, tests with pure rubberwood sawdust at similar operating conditions were performed as well. Temperature and concentrations of O2, CO and NO were measured along radial and axial directions in the combustor as well as at stack. For all fuel firing options, the radial and axial temperature profiles in the reactor were found to be weakly dependent on operating conditions. However, the gas concentration profiles exhibited apparent effects of fuel properties, excess air and secondary air injection, which resulted in variable emission characteristics of the combustor. For the sawdust energy fraction in the fuel blend of about 0.85, CO and NO emissions can be controlled at acceptable levels (both complying with the national emission limits) by maintaining excess air between 50% and 55%. Under such conditions, the co-combustion of high-moisture eucalyptus bark and rubberwood sawdust in the proposed combustor occurs in a stable regime with high, 99.6%, combustion efficiency.

Velocity measurements in a pump volute with a non-rotating impeller

A Plexiglas laboratory pump with rectangular cross sections was tested and volute velocities were measured with a laser velocimeter. First, the pump with a four bladed rotating impeller was run at three flowrates. Second, the rotating impeller was replaced with a 32-bladed non-rotating impeller with forward facing blades that imparted a swirl to the flow under forced circulation that simulated the rotating impeller case. Velocity measurements in the discharge region and flow visualization in the entire volute indicate that the proper general flow characteristics were achieved with the flow swirler but the unsteady ‘jet-wake’ regions were eliminated. Thus similitude was attained between the rotating and non-rotating impellers allowing study of volute flow characteristics without rotating impeller effects. Two non-rotating impellers were used to provide data for comparison to future steady state theoretical analyses. One produced a flow field that represented 121% of the nominal capacity and the other represented 160% of the nominal capacity. Detailed velocity traverses were made in the volute region for both swirlers. Circumferential non-uniformities (up to 275% from the mean) were found and were largest for the 160% simulated capacity. These are not due to rotating impeller effects and are attributed to the mismatch between the exit angle of the swirler and the volute. Radial non-uniformities in velocity were also seen (up to 22%) and the largest variations were observed for 121% simulated capacity. Finally, axial variations up to 30% were observed and these also were largest for 121% simulated capacity.