Swirl Motion Research Articles

Experimental studies on a novel swirling fluidized-bed combustor using an annular spiral air distributor

This work reports studies on hydrodynamics as well as combustion and emission characteristics of a conical swirling fluidized-bed combustor (SFBC) using an annular spiral air distributor as the swirl generator. In the experimental study on a ‘cold’ SFBC model, hydrodynamic regimes and characteristics of an air–sand bed were investigated for variable bed particle size and static bed height. Depending on the superficial air velocity, the bed exhibited four operational regimes. Based on the results from the ‘cold’ hydrodynamic study, optimum bed characteristics (sand particle size and bed height) and the range of primary air were determined prior to the combustion tests. In the second part of this work, a conical SFBC was tested for firing 80 kg/h rice husk. During the combustion tests, swirl motion of a fluidized bed was induced by primary air injected into the bed through the air distributor and, also, sustained by tangential injection of secondary air into the bed splash zone. Radial and axial temperature and gas (O 2, CO, NO) concentration profiles in the reactor were obtained for 20–80% excess air. Effects of operating conditions on formation and decomposition of major gaseous pollutants (CO and NO) in the reactor are discussed. Both CO and NO were found to be reduced significantly in the bed splash zone, resulting in quite low CO and moderate NO emissions from the reactor. High combustion efficiency, 99.4–99.5%, is achievable when burning rice husk in the proposed conical SFBC at 80 kg/h feed rate and excess air of 40–80%.

Numerical and experimental study of electromagnetically driven vortical flows

The paper reports on numerical and experimental investigations of electromagnetically driven vortical flows of an electrically conductive fluid in a generic setup. Two different configurations of permanent magnets are considered: a 3-magnet configuration in which the resulting Lorentz force is focused in the wall-boundary layers, and a 2-magnet configuration which creates a centrally located intensive swirling motion. For both configurations the intensity of the Lorentz force could be varied by variation of the electrode DC current between 0.5 and 10 A. A comparative assessment of measured (PIV) and numerically calculated (LES with electromagnetically extended subgrid closure) velocity fields showed good agreement for both configurations. It is demonstrated that the newly designed setup can be used for fundamental studies of the interactions between fluid flow, turbulence and electromagnetic fields and provide detailed insights into the underlying physics of these interactions. This in turn can be used to optimise magnetic control of flow, turbulence and heat transfer in various configurations of practical relevance.

Mixing of Small Solid Particles Using a Swirl Motion of a Bubbling Jet in a Cylindrical Vessel

When air is injected vertically upwards into a water-filled cylindrical vessel through a J-shaped lance, two types of swirl motions of the water in the vessel appear under specific conditions: shallow-water wave type and deep-water wave type. The swirl motions are similar to the rotary slashing. The deep-water wave type of swirl motion has high mixing ability. Small solid particles placed on the bottom of the cylindrical vessel can be lifted up into the bath through an effect of the swirl motion. The lifting behaviors of the particles can be classified into two types depending on the aspect ratio of the bath.

粒子浮上を伴う円筒容器内旋回気泡噴流の基本特性

A swirl motion of a bubbling jet in a cylindrical vessel is useful for bath mixing. This paper describes the mixing of small solid particles initially settled on the bottom of a water-filled cylindrical bath. The bubbling jet is generated by injecting air through a J-shaped lance placed on the bath centerline. Experiments are made on the patterns of swirl motion, the occurrence condition of the deep-water wave type swirl motion accompanied by lifted-up particles, the amplitude and the period of the swirl motion. The measured values are compared with empirical and theoretical equations proposed previously for the bottom blown bath.

Some Aspects of the Amplitude of Swirl Motion of a Cylindrical Bath Induced by a Liquid Jet

Some Aspects of the Amplitude of Swirl Motion of a Cylindrical Bath Induced by a Liquid Jet

Ejection of Small Sedimentary Particles into a Cylindrical Bath by Swirl Motion of bubbling Jet

Ejection of Small Sedimentary Particles into a Cylindrical Bath by Swirl Motion of bubbling Jet

Swirl Motion of a Water Jet in a Water Bath of Linearly Increasing Depth

Swirl Motion of a Water Jet in a Water Bath of Linearly Increasing Depth

CFD Analysis of VVT/VVA on the Gas Exchange and Fuel-Air Mixing in a Diesel Engine

A three-dimensional simulation was carried out for investigating effects of negative valve overlap (NVO) on gas exchange and fuel-air mixing processes in a diesel homogeneous charge compression ignition (HCCI) engine with early fuel injection. It was found that the case with longer NVO produced a stronger swirl motion and a more significant vortex below the intake valve due to the high annular jet flow through the valve curtain area during the intake stroke. However, there was not much difference in the values of swirl ratio, tumble ratio and turbulence intensity between different NVOs at the end of compression stroke. It was also seen that enlarged NVO not just increased in-cylinder temperature but also improved the temperature homogeneity. With increased NVO, there is a bigger spray shape and more droplets exist in gaps of sprays. This demonstrates that stronger turbulence intensity and higher temperature homogeneity with higher NVO improve fuel vaporization and air-fuel mixing.

Model Experiments on Transient Swirl Motion of a Wastewater Jet Generated by J-Shaped Lance

Model Experiments on Transient Swirl Motion of a Wastewater Jet Generated by J-Shaped Lance

선박용 엔진의 흡기포트 형상에 따른 텀블 및 내부 유동 특성에 관한 수치적 연구

Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. The combustion phenomena of reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. To know this relationship definitely, this paper describes analytical results of the tumble motion, swirl motion, turbulence intensity, turbulence inside the cylinder of marine engine. 3-D computation has been performed by using STAR-CD solver and es-ice.

과부하 원형맨홀에서의 손실계수 산정을 위한 실험적 연구

도시 우수 배수 시스템에서 우수 관거는 개수로 흐름 상태로 가정하여 설계되었기 때문에 맨홀에서의 에너지 손실은 일반적으로 중요하게 고려되지 않았다. 그러나 과부하흐름에서 에너지 손실은 관거의 배수능력을 저하시켜 도심지역의 침수피해를 가중시키는 요인이 된다. 그러므로 과부하 맨홀 내에서의 수두 손실을 분석할 필요가 있다. 본 연구에서는 맨홀에 대한 문헌조사 및 현장조사를 실시하여 실험장치 제작과 실험조건을 선정하였다. 선정된 실험조건인 인버트 형상 조건(CASE A, B, C), 단차 조건(CASE I, II, III) 및 실험 유량(<TEX>$1.0\;{\sim}\;5.6\;{\ell}/sec$</TEX>)을 변화시키면서 실험을 실시하였다. 맨홀 직경(<TEX>$D_m$</TEX>)과 유입관경(<TEX>$D_{in}$</TEX>)의 비(<TEX>$D_m/D_{in}$</TEX>)가 증가할수록 손실계수가 증가하였으며, 맨홀 수심(<TEX>$h_m$</TEX>)과 유입관거 직경(<TEX>$D_{in}$</TEX>)의 비(<TEX>$h_m/D_{in}$</TEX>)가 <TEX>$1.0{\sim}1.5$</TEX>일 때 손실계수가 가장 크게 산정되었다. 또한, CASE A, B, C의 평균 손실계수는 각각 0.45, 0.37, 0.3으로 산정되었다. 맨홀에 U자형 인버트를 설치하면, 원형 맨홀에서 에너지 손실을 저감시킬 수 있다. 또한 산정된 맨홀에서의 손실계수는 과부하흐름을 고려한 우수 관거 설계에 활용될 수 있다고 판단된다. Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus which can be changed the invert type(CASE A, B, C) and step height(CASE I, II, III) was installed for this study. The range of the experimental discharges were from <TEX>$1.0{\ell}/sec$</TEX> to <TEX>$5.6\;{\ell}/sec$</TEX>. As the manhole diameter ratio(<TEX>$D_m/D_{in}$</TEX>) increases, head loss coefficient increases due to strong horizontal swirl motion. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios(<TEX>$h_m/D_{in}$</TEX>) were from 1.0 to 1.5. The average head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is most effective for energy loss reduction at circular manhole. This head loss coefficients could be available to design the urban sewer system with surcharge flow.

Swarming and Swirling in Self-Propelled Polar Granular Rods

Using experiments with anisotropic vibrated rods and quasi-2D numerical simulations, we show that shape plays an important role in the collective dynamics of self-propelled (SP) particles. We demonstrate that SP rods exhibit local ordering, aggregation at the side walls, and clustering absent in round SP particles. Furthermore, we find that at sufficiently strong excitation SP rods engage in a persistent swirling motion in which the velocity is strongly correlated with particle orientation.

Measures to Overcome Low-Load Misfiring of 2-Stroke Cycle Spark Ignition Engine by Direct Injection Stratified Charge Combustion

2-stroke cycle spark ignition engine with direct injection was studied to avoid inherent misfiring in low load region by using stratified charge combustion. The three mixture formation concepts of spray-guided, wall-guided and air-guided were introduced to achieve stratified charge combustion and the stable combustion was obtained in three concepts. The most stable ignitability was achieved by spray-guided concept and the second was wall-guided concept. In the case of air-guided concept stable combustion was obtained with swirl motion that was generated by the closure of half part of scavenging port. Decreasing delivery ratio within no smoke and stable combustion regions was found to cause the reduction of NOx emission.

Swirl Motion of a Mercury Jet Appearing in a Cylindrical Vessel in Transient Period

Swirl Motion of a Mercury Jet Appearing in a Cylindrical Vessel in Transient Period

Computational fluid dynamics simulation of in-cylinder flows in a motored homogeneous charge compression ignition engine cylinder with variable negative valve overlapping

In-cylinder air motion is one of the most important factors that control the degree of mixture preparation and thus is fundamental to improvements in the combustion process and overall engine performance. The major aim of this paper is to elucidate, through a predictive study, the main features of in-cylinder flow fields in a motored homogeneous charge compression ignition (HCCI) engine cylinder with variable negative valve overlapping (NVO). A commercial finite-volume computational fluid dynamics (CFD) package was used in the programme of simulation. The computational model was validated through a qualitative comparison between CFD results and the available experimental data. Thus one of the main developments presented in this study is the investigation of the intake process of the HCCI engine with various valve strategies, and it is perhaps the first time (to the current authors' best knowledge) that a direct comparison has been made of the results obtained in the same HCCI NVO motored engine using modelling and experimental approaches. The comparison illustrated a fair agreement between both sets of results, with some differences. A parametric predictive study of the effects of variable valve timings on the in-cylinder air motion has then been carried out. Three different sets of valve timings have been applied to the intake and exhaust valves to generate NVO of 70, 90, and 110 degrees of crank angle (°CA). The NVO was controlled by adjusting the times of exhaust valves closing (EVC) and intake valves opening (IVO) while keeping the times of exhaust valves opening (EVO) and intake valves closing (IVC) unchanged. The predicted results show a noticeable modification of the strength and the global direction of the in-cylinder charge motion as a result of increasing the magnitude of NVO. Modifications of in-cylinder swirl and tumble motions obtained by applying higher degrees of NVO are expected to have a considerable effect on the air-fuel mixture preparation process as well as the actual in-cylinder conditions at the end of the compression stroke.

Quantification of Volumetric In-Cylinder Flow of SI Engine Using 3-D Laser Doppler Velocimetry ( II )

Simultaneous 3-D LDV measurements of the in-cylinder flows of three different engine setups were summarized for the quantification of the flow characteristics in each vertical or horizontal plane, and in entire cylinder volume. The ensemble averaged-velocity, tumble and swirl motions, and turbulent kinetic energy during the intake and compression strokes were examined from the measured velocity data (approximately 2,000 points for each engine setup). The better spatial resolution of the 3-D LDV allows measurements of the instantaneous flow structures, yielding more valuable information about the smaller flow structures and the cycle-to-cycle variation of these flow patterns. Tumble and swirl ratios, and turbulent kinetic energy were quantified as planar and volumetric quantities. The measurements and calculation results were animated for the visualization of the flow, and hence ease to analysis.

Effect of Sludge on a Swirl Motion of Bubbling Jet in a Cylindrical Bath

Effect of Sludge on a Swirl Motion of Bubbling Jet in a Cylindrical Bath

PTV investigation of phase interaction in dispersed liquid–liquid two-phase turbulent swirling flow

An investigation of dispersed liquid–liquid two-phase turbulent swirling flow in a horizontal pipe is conducted using a particle tracking velocimetry (PTV) technique and a shadow image technique (SIT). Silicone oil with a low specific gravity is used as immiscible droplets. A swirling motion is given to the main flow by an impeller installed in the pipe. Fluorescent tracer particles are applied to flow visualization. Red/green/blue components extracted from color images taken with a digital color CCD camera are used to simultaneously estimate the liquid and droplet velocity vectors. Under a relatively low swirl motion, a large number of droplets with low specific gravity tend to accumulate in the central region of the pipe. With increasing droplet volume fraction, the liquid turbulence intensity in the axial direction increases while that in the wall-normal direction decreases in the central region of the pipe. In addition, the turbulence modification in the present flow is strongly dependent on the droplet Reynolds number; however, the interaction of droplet-induced turbulences is significant due to vortex shedding, particularly at high droplet Reynolds numbers and higher droplet volume fraction.

제3세대 LPLI 엔진 연소실내 스월유동 및 희박연소 특성 해석

The intake swirl motion, as one of dominant effects for an engine combustion, is very effective for turbulence enhancement during the compression process in the cylinder of 2-valve engine. Because the combustion flame speed is determined by the turbulence that is mainly generated from the mean flow of the charge air motion in intake port system. This paper describes the experimental results of swirl flow and combustion characteristics by using the oil spot method and back-scattering Laser Doppler velocimeter (LDV) in 2-valve single cylinder transparent LPG engine using the liquid phase LPG injection. For this, various intake port configurations were developed by using the flow box system and swirl ratios for different intake port configurations were determined by impulse swirl meter in a steady flow rig test. And the effects of intake swirl ratio on combustion characteristics in an LPG engine were analyzed with some analysis parameters that is swirl ratio, mean flow coefficient, swirl mean velocity, fuel conversion efficiency, combustion duration and cyclic variations of indicated mean effective pressure(IMEP). As these research results, we found that the intake port configuration with swirl ratio of 2.0 that has a reasonable lean combustion stability is very suitable to an 11ℓ heavy-duty LPG engine with liquid phase fuel injection system. It also has a better mean flow coefficient of 0.34 to develope a stable flame kernel and to produce high performance. This research expects to clarify major factor that effects on the design of intake port efficiently with the optimized swirl ratio for the heavy duty LPG engine.

Numerical simulation of three-dimensional flow field with strong swirl in vortex tube

In order to understand the flow behavior inside the tube distinctly, a three-dimensional physical model of vortex tube is constructed according to flow's movement characteristic and three-dimensional flow field with strong swirl inside the tube is simulated by the usage of practical "Realizable κ–e" turbulent numerical model. From the simulated velocity field, the distributions of tangential, axial and radial velocity as well as the recirculating flow patterns are investigated. In addition, the strategy of non-dimensional comparisons between numerical results and previous experimental data is applied to validate numerical data indirectly. Satisfactory agreements are observed between them. The numerical results show that flow motion inside the vortex tube presents extraordinary complicated behavior. The swirling flow inside the vortex tube consists of two regions with an outer region of quasi-free vortex flow sur-rounding an inner region of quasi-forced vortex flow. From view of the composition of axial and swirl motion, the flow inside the tube consists of periphery flow and inner flow. With radial and swirl motion considered, the helical flow exits inside the vortex tube. There is also a recirculating flow inside the tube when the composite motion of radial and axial movement are analyzed. The peripheral and inner flows exchange heat and mass through the enveloping surface of zero axial velocity in the form of recirculating flow because the enveloping surface of zero axial velocity is the interface between peripheral and inner flow.