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An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles. 相似文献
3.
The effects of swirl intensity on non-reacting and reacting flow characteristics in a flat flame burner (FFB) with four types
of swirlers were investigated. Experiments using the PIV method were conducted for several flow conditions with four swirl
numbers of 0, 0.26, 0.6 and 1.24 in non-reacting flow. The results show that the strong swirling flow causes a recirculation,
which has the toroidal structures, and spreads above the burner exit plane. Reacting flow characteristics such as temperature
and the NO concentrations were also investigated in comparison with non-reacting flow characteristics. The mean flame temperature
was measured as the function of radial distance, and the results show that the strong swirl intensity causes the mean temperature
distributions to be uniform. However the mean temperature distributions at the swirl number of 0 show the typical distribution
of long flames. NO concentration measurements show that the central toroidal recirculation zone caused by the strong swirl
intensity results in much greater reduction in NO emissions, compared to the non-swirl condition. For classification into
the flame structure interiorly, the turbulence Reynolds number and the Damkohler number have been examined at each condition.
The interrelation between reacting and non-reacting flows shows that flame structures with swirl intensity belong to a wrinkled
laminar-flame regime. 相似文献
4.
The purpose of this paper is to investigate the effects of slits and swirl vanes on the turbulence augmentation in the flow
fields of a gun-type gas burner using an X-type hot-wire probe. The gun-type gas burner adopted in this study is composed
of eight slits and swirl vanes located on the surface of an inclined baffle plate. Experiment was carried out at a flow rate
of 450 //min in burner model installed in the test section of subsonic wind tunnel. Swirl vanes play a role diffusing main
flow more remarkably toward the radial direction than axial one, but slits show a reverse feature. Consequently, both slits
and swirl vanes remarkably increase turbulence intensity in the whole range of a gun-type gas burner with a cone-type baffle
plate. 相似文献
5.
An experimental study was performed for measuring velocity and turbulence intensity in a circular tube for Re=10,000, 15,000 and 20,000, with swirl and without swirling flow. The velocity fields were measured using PIV techniques and swirl motion was produced by a tangential inlet condition. Some preliminary measurements indicated that over the first 4 diameter, two regions of flow reversal were set up (the so called 2-cell structure). At the highest Reynolds numbers, the maximum values of the measured axial velocity components had moved toward the test tube wall and produce more flow reversal at the corner of the tube. As the Reynolds number increased, the turbulence intensity of swirling flow at the tube inlet also increased. 相似文献
6.
An experimental study was performed to investigate heat transfer characteristics of turbulent swirling flow in an axisymmetric
annuli. The static pressure, the local flow temperature, and the wall temperature with decaying swirl were measured by using
tangential inlet conditions and the friction factor and the local Nusselt number were calculated for Re=30000-70000. The local
Nusselt number was compared with that obtained from the Dittus-Boelter equation with swirl and without swirl. The results
showed that the swirl enhances the heat transfer at the inlet and the outlet of the test tube. 相似文献
7.
Shin Hyuk Joo Kwang Min Chun Younggy Shin 《Journal of Mechanical Science and Technology》2000,14(12):1412-1420
The objectives of the study are to investigate the effect of swirl on the flame propagation and to propose a flame propagation model that predicts the behavior of the flame front in the presence of significant swirl flow field by analyzing flame images pictured with a high speed digital video at idle. The velocity distribution of the charge in the cylinder was measured using an LDV measurement system. From the experimental results and analyses, a new flame propagation model is proposed in which flame frontal locations can be traced by superposing the convective flow field and the uniform expansion speed of the burned gas, and the proposed model reveals that the increase of the flame propagation speed in the presence of swirl motion within 1 ms after ignition is mainly due to the flame stretch, and mainly due to increased turbulence intensity later than 1 ms after ignition. 相似文献
8.
Jang-kweon Kim 《Journal of Mechanical Science and Technology》2001,15(7):895-905
This paper presents vector fields, three dimensional mean velocities, turbulent intensities, turbulent kinetic energy and Reynolds shear stresses measured in the X-Y plane of the gas swirl burner with a cone type baffle plate by using an X-type hot-wire probe. This experiment is carried out at the flow rates of 350 and 450 ℓ/min which are equivalent to the combustion air flow rate necessary to release 15,000 kcal/hr in a gas furnace. The results show that the maximum axial mean velocity component exists around the narrow slits situated radially on the edge of a burner. Therefore, there is some entrainment of ambient air in the outer region of a burner. The maximum values of turbulent intensities occur around the narrow slits and in front of a burner up to X/R=1.5. Moreover, the turbulent intensity components show a relatively large value in the inner region due to the flow diffusion and mixing processes between the inclined baffle plate and the swirl vane. Consequently, the combustion reaction is expected to occur actively near these regions. 相似文献
9.
Jang-Kweon Kim 《Journal of Mechanical Science and Technology》2008,22(1):180-189
Mean velocities and turbulence characteristics in the swirling flow of a gun-type gas burner (GTGB) were measured with a triaxial
hot-wire probe (T-probe) and compared with previous data measured with an X-type hot-wire probe (Xprobe). Vectors and axial
mean velocity data obtained by the measurement of the two types of probes in the horizontal plane and in the cross section
differ in magnitude, but have very similar shape in overall distribution. Axial mean velocity components show especially wide
differences around the slits and outer part of the swirl vanes within the range of X/R=2. Also, various turbulence intensities
appear in a similar trend to axial mean velocity components within the range of X/R=2. The radial component of turbulence
intensity around the slits and the outer part of swirl vanes above the range of X/R=2 has an opposite phenomenon. On the whole,
the T-probe’s measurements appear smaller than the X-probe’s. This shows that the X-probe is better than the T-probe, especially
on the swirling flow because it is much easier to use. 相似文献
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Abstract In the present work, the various parameters affecting the variation of the surface diffusion coefficients, determined by the novel methodology of reversed‐flow gas chromatography (RF‐GC), for CO adsorption on a well‐studied Pt/SiO2 catalyst, are under investigation. These are the adsorption energy, ?, the lateral interaction energy, β, the surface coverage, θ and the surface concentration of the adsorbate, c s *. The magnitude of surface diffusion coefficient values, determined by RF‐GC, is comparable to those obtained by other experimental techniques, ascertaining the potential of the method. Physicochemical parameters giving information for the surface mobility, such as adsorption energies, local isotherms, local surface concentration of the adsorbate, and energy distribution functions can be determined in a single kinetic run. 相似文献
12.
Jong-Chan Kim Kwang-Hee Yoo Hong-Gye Sung 《Journal of Mechanical Science and Technology》2011,25(10):2703-2710
To conduct a comprehensive study on the flow characteristics and acoustic oscillation in a gas turbine combustor, a 3D large-eddy
simulation (LES) was implemented. The formulation consists of the Favre-filtered conservation equations of mass, momentum,
and energy. The subgrid-scale dynamics are modeled using a compressible flow version of the Smagorinsky model. To investigate
the dominant coherent structure, the proper orthogonal decomposition (POD) method was used for post-processing. The combustor
of concern is the LM6000, lean-premixed dry low-NOx annular combustor, developed by General Electric Aircraft Engines (GEAE).
Four important characteristics of swirl flow are visualized: vortex breakdown, procession and dissipation of vortical structures,
recirculation zones, and helical waves immediately downstream of the swirl injector. It is shown that the turbulent motion
of swirl flow directly affects acoustic oscillation through the cycle and spectral analysis. The four most dominant acoustic
modes are extracted from the flow field by the POD analysis. The transverse modes in the y and z directions are dominant in
all four modes, since the pressure fields are significantly affected by swirl flow. 相似文献
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14.
Sam-Goo Lee 《Journal of Mechanical Science and Technology》2008,22(12):2509-2515
The experimental objective was to compare disintegration characteristics from the internal mixing pneumatic nozzles under
the different operating conditions in terms of swirl angles. For this investigation, supplied air pressures and nozzle configuration
ratios were fixed. This experimental comparison is of fundamental importance to the understanding and modeling of turbulent
atomization because the axisymmetric swirling flows involve relatively complex interactions. For the measurement, four internal
swirl mixing nozzles with axisymmetric holes at swirl angles of 15°, 30°, 45°, and 60° to the central axis were employed,
which is responsible for the enhancement of mixing in pneumatic jets. To illustrate the swirl phenomena quantitatively, the
distributions of mean velocities, turbulence intensities, and SMD (Sauter mean diameter, or D32) variations with different configuration ratio were comparatively analyzed. It indicated that the atomization characteristics
are performed well in the case of 30° of swirl angle, and that turbulence intensities are gradually degenerated with the increase
of radial distances, showing a slight increment of SMD at downstream region. In particular, measurements showed that nozzle
configuration is one of the significant geometrical parameters affecting the spray trajectories.
This paper was recommended for publication in revised form by Associate Editor Jun Sang Park 相似文献
15.
针对不同连接方式下角座阀内介质的流动特性开展数值模拟和实验研究。采用RNG k-ε湍流模型, 结合标准壁面函数法, 计算阀内流场。通过流量系数的实验数据和计算结果对比, 验证了数学模型和计算方法的准确性。在此基础上, 对正接和反接方式下角座阀内的流动核心区域、速度场和压力场进行对比分析。结果表明:正接方式下, 角座阀具较高的流通能力, 阀芯附近流动核心区域的面积更大, 并且在阀门出口下侧存在较大的漩涡, 会导致流阻增加。两种连接方式下, 阀芯中央截面处均出现二次流, 其中正接方式具有更高的流动不稳定性。 相似文献
16.
水平管气液衰减螺旋流的流型及压降发展 总被引:1,自引:0,他引:1
气液衰减螺旋流在工业中应用广泛,但是对其中的关键问题,衰减影响下的螺旋流发展运动规律认识不清。通过室内试验研究空气-水两相流在内径25 mm、长4 m的水平管中流型和压降沿流向的变化规律。通过可视化试验获得叶片式起旋器下游不同位置处的螺旋流流型,测量下游沿流向不同区间的压降波动信号。试验发现,在离心力作用下,螺旋流中气液相界面发生重构,形成螺旋流中特有流型。但是由于离心力的衰减,导致螺旋流流型不断变化,逐渐转变成非旋流流型。流动压降沿流向逐渐降低,最终趋于非旋流压降;不同螺旋流流型的维持距离不同,同时也受来流气液相雷诺数的影响。基于流型及压降分析,获得起旋器下游不同位置处的螺旋流流型图。 相似文献
17.
Suk-Young Lee Ku-Seob Jeong Chung-Hwan Jeon Young-June Chang 《Journal of Mechanical Science and Technology》2005,19(2):704-715
In this study, to investigate m-cyhnder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined
with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment,
and also turbulent characteristics of m-cyhnder flow field were investigated by 2-frame cross-correlation particle image velocimetry
(PIV) method In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics
were showed according to OCV or SCV figures The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy
than a baseline engine, especially around the wall and lower part of the cylinder Above all, SCV B type was superior to the
others About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV
installed one because flow impinged on the cylinder wall It should be concluded, from what has been said above, as swirl component
was added to existing tumble flow adequately, it was confirmed that turbulent intenstty was enlarged, flow energy was conserved
effectively through the experiment In other words, there is a suggestion that flow characteristics as these affected to m-cyhnder
combustion positively 相似文献
18.
涡轮流量传感器在旋转来流中的特性研究 总被引:8,自引:2,他引:6
本文对涡轮流量传感器在旋转来流中的特性进行了理论和实验研究。利用涡轮流量传感器的数学模型,给出了涡轮转速、仪表常数与来流旋转角之间的理论关系式。计算了来流旋转强度及上游直管段长度变化时,仪表常数的变化情况。设计了能获得不同来流旋转强度的旋转发生器,并获得了大量的实验数据。实验结果与理论计算值在较大的流量范围内甚为吻合。 相似文献
19.
Seong-Yeon Yoo Kee-Young Yoon Kyung-Am Park 《Journal of Mechanical Science and Technology》1997,11(5):574-581
Flow characteristics of a swirl generator are studied using an open circuit flow loop, and influence of upstream swirl on the discharge coefficients of sonic nozzles is investigated using a high pressure gas flow standard measurement system. The open circuit flow loop consists of swirl generator, testsection, sonic nozzle, suction fan and LDV system. The gas flow measurement system comprises two compressors, storage tank, temperature control loop, sonic nozzle testsection, weighing tank, gyroscopic scale and data acquisition system. Experiments are performed at various nozzle throat diameters, inlet pressures and angles of swirl generator. As the angle of swirl generator becomes larger, axial velocities decrease near the wall and rapidly increase in the pipe core, and swirl velocities increase to form swirl flow. Influence of upstream swirl on discharge coefficients becomes greater as the intensity of swirl increases and as the nozzle throat diameter is enlarged. Variation trend with Reynolds number, however, is very similar each other regardless of swirl intensity. 相似文献
20.
Soft abrasive flow(SAF) finishing can process the irregular geometric surfaces, but with the matter of low processing efficiency. To address the issue, an improved SAF finishing method based on turbulent kinetic energy enhancing is proposed. A constrained flow passage with serration cross-section is constructed to increase the turbulence intensity. Taking the constrained flow passage as the objective, a two-phase fluid dynamic model is set up by using particle trajectory model and standard k-ε turbulence model, and the flow field characteristics of the flow passage are acquired. The numerical results show that the serration flow passage can enhance the turbulence intensity, uniform the particles distribution, and increase the particle concentration near the bottom wall. The observation results by particle image velocimetry(PIV) show that the internal vortex structures are formed in flow passage, and the abrasive flow takes on turbulence concentrating phenomenon in near-wall region. The finishing experiments prove that the proposed method can obtain better surface uniformity, and the processing efficiency can be improved more 35%. This research provides an abrasive flow modeling method to reveal the particle motion regulars, and can offer references to the technical optimization of fluid-based precision processing. 相似文献