AERATED FLOW CHARACTERISTICS IN STEPPED CHANNELS FOR NONUNIFORM FLOW REGION

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

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LES and RANS Analysis of the End-Wall Flow in a Linear LPT Cascade: Part I — Flow and Secondary Vorticity Fields Under Varying Inlet Condition

Volume 2B: Turbomachinery ◽

10.1115/gt2018-76233 ◽

2018 ◽

Cited By ~ 6

Author(s):

R. Pichler ◽

Yaomin Zhao ◽

R. D. Sandberg ◽

V. Michelassi ◽

R. Pacciani ◽

...

Keyword(s):

Boundary Layer ◽

Secondary Flow ◽

Flow Characteristics ◽

Flow Region ◽

Secondary Flows ◽

Wall Boundary Layer ◽

Wall Boundary ◽

Wall Flow ◽

End Wall ◽

The Impact

In low-pressure-turbines (LPT) around 60–70% of losses are generated away from end-walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Experimental and numerical studies have shown how the strength and penetration of the secondary flow depends on the characteristics of the incoming end-wall boundary layer. Experimental techniques did shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving CFD allowed to dive deep into the details of the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 LPT profile at Re = 120K and M = 0.59 by benchmarking with experiments and investigating the impact of the incoming boundary layer state. The simulations are carried out with proven Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) solvers to determine if Reynolds Averaged models can capture the relevant flow details with enough accuracy to drive the design of this flow region. Part I of the paper focuses on the critical grid needs to ensure accurate LES, and on the analysis of the overall time averaged flow field and comparison between RANS, LES and measurements when available. In particular, the growth of secondary flow features, the trace and strength of the secondary vortex system, its impact on the blade load variation along the span and end-wall flow visualizations are analysed. The ability of LES and RANS to accurately predict the secondary flows is discussed together with the implications this has on design.

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A Functional Scaling Relationship for Laminar to Turbulent Flow Regimes

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-16012 ◽

2011 ◽

Author(s):

George Papadopoulos

Keyword(s):

Turbulent Flow ◽

Stokes Equations ◽

Initial Conditions ◽

Flow Characteristics ◽

Flow Region ◽

Flow Regimes ◽

Transitional Flow ◽

Turbulent Regime ◽

Flow Profile ◽

Scaling Relationship

A dimensional analysis that is based on the scaling of the two-dimensional Navier-Stokes equations is presented for correlating bulk flow characteristics arising from a variety of initial conditions. The analysis yields a functional relationship between the characteristic variable of the flow region and the Reynolds number for each of the two independent flow regimes. A linear relationship is realized for the laminar regime, while a nonlinear relationship is realized for the turbulent regime. Both relationships incorporate mass-flow profile characteristics to fully capture the effects of initial conditions on the variation of the characteristic variables. The union of these two independent relationships is formed utilizing the concept of flow intermittency to further expand into a generic scaling relationship that incorporates transitional flow effects to fully encompass solutions spanning the laminar to turbulent flow regimes. The results of the analysis are discussed within the context of several flow phenomena (e.g. pipe flow, jet flow & separated flow) resulting from various initial and boundary conditions.

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Aerated flow characteristics of skimming flow over stepped chutes

Journal of Hydraulic Research ◽

10.1080/00221686.2013.861364 ◽

2013 ◽

Vol 51 (6) ◽

pp. 735-736

Author(s):

Robert M. Boes ◽

Jill Lucas ◽

Willi H. Hager

Keyword(s):

Flow Characteristics ◽

Aerated Flow

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Aerated flow characteristics of skimming flow over stepped chutes

Journal of Hydraulic Research ◽

10.1080/00221686.2012.702859 ◽

2012 ◽

Vol 50 (4) ◽

pp. 427-434 ◽

Cited By ~ 23

Author(s):

Masayuki Takahashi ◽

Iwao Ohtsu

Keyword(s):

Flow Characteristics ◽

Aerated Flow

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Squealer Tip Leakage Flow Characteristics in Transonic Condition

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4025918 ◽

2013 ◽

Vol 136 (4) ◽

Cited By ~ 21

Author(s):

Wei Li ◽

Hongmei Jiang ◽

Qiang Zhang ◽

Sang Woo Lee

Keyword(s):

Flow Characteristics ◽

Leading Edge ◽

Flow Region ◽

Suction Side ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Cavity Depth ◽

Tip Leakage ◽

Flow Flux ◽

Subsonic Region

The over-tip-leakage (OTL) flow characteristics for a typical squealer tip of a high-pressure turbine blade, which consists of subsonic and transonic flow, have been numerically investigated in the present study, in comparison with the corresponding flat tip results. For the squealer tip employed, flow choking behavior still exists above the tip surface, even though the Mach number is lower and the transonic region is smaller than that for the flat tip. Detailed flow structure analysis shows that most of the fluid entering the squealer cavity is from the frontal leading edge region. The fluid migrates along the cavity and is ejected at various locations near the suction side rim. These fluids form a large subsonic flow zone under the supersonic flow passing over the tip gap which reduces the OTL flow flux. The squealer design works even in the presence of choked OTL flow. Comparisons between results from three different cavity depths with and without relative casing motion suggest that the over-tip-leakage flow flux has much dependence upon the cavity depth for the subsonic region, but is less sensitive to the depth for the transonic tip flow region. Such behavior has been confirmed with and without the existence of relative casing motion.

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Flow Field Analysis of Pulse Converter Exhaust Manifold of Diesel Engines

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.468-471.1693 ◽

2012 ◽

Vol 468-471 ◽

pp. 1693-1696

Author(s):

Wen Jun Zhong ◽

Zhi Xia He ◽

Zhao Chen Jiang ◽

Yun Long Huang

Keyword(s):

Unsteady Flow ◽

Three Dimensional ◽

Flow Characteristics ◽

Flow Region ◽

Field Analysis ◽

Exhaust Manifold ◽

Recirculation Flow ◽

Pulse Converter ◽

Flow Field Analysis ◽

Better Than

A three-dimensional unsteady flow for the pulse converter exhaust manifold of 8-cylinder diesel engine was numerical simulated to get the flow characteristics of the exhaust manifold. Simulation results show that there are strong eddy flows, low pressure closed recirculation flow region in the exhaust manifold. Afterwards the structure optimization of the exhaust manifold with baffle was put forward and then the unsteady flow in the normal exhaust manifold, the exhaust manifold with baffle of 30 degrees and the exhaust manifold of 15 degrees were simulated and analyzed. It is concluded that the exhaust manifold with baffle is better than that without baffle, the recirculation flow region and the pressure loss in the exhaust manifold with baffle of 30 degrees is smaller than in it with baffle of 15 degree and the flow in the former exhaust manifold is much smoother.

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Flow Characteristics of Discharge Flow Region in a Stirred Vessel with Aeration.

KAGAKU KOGAKU RONBUNSHU ◽

10.1252/kakoronbunshu.18.495 ◽

1992 ◽

Vol 18 (4) ◽

pp. 495-501

Author(s):

Kohei Ogawa ◽

Shiro Yoshikawa ◽

Hirohisa Shiode

Keyword(s):

Flow Characteristics ◽

Flow Region ◽

Discharge Flow ◽

Stirred Vessel

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AERATED FLOW CHARACTERISTICS ON STEPPED CHANNELS

PROCEEDINGS OF HYDRAULIC ENGINEERING ◽

10.2208/prohe.52.787 ◽

2008 ◽

Vol 52 ◽

pp. 787-792

Author(s):

Masayuki TAKAHASHI ◽

Youichi YASUDA ◽

Iwao OHTSU

Keyword(s):

Flow Characteristics ◽

Aerated Flow

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Heat Transfer and Flow Characteristics of an Oblique Turbulent Impinging Jet Within Confined Walls

Journal of Heat Transfer ◽

10.1115/1.2822523 ◽

1995 ◽

Vol 117 (2) ◽

pp. 316-322 ◽

Cited By ~ 16

Author(s):

K. Ichimiya

Keyword(s):

Heat Transfer ◽

Temperature Distribution ◽

Flow Characteristics ◽

Local Heat Transfer ◽

Flow Region ◽

Turbulent Heat Transfer ◽

Working Fluid ◽

Turbulent Heat ◽

Transfer Coefficients ◽

Impingement Surface

Experiments were conducted to determine the turbulent heat transfer and flow characteristics of an oblique impinging circular jet within closely confined walls using air as a working fluid. The local temperature distribution on the impingement surface was obtained in detail by a thermocamera using a liquid crystal sheet. A correction to the heat flux was evaluated by using the detailed temperature distribution and solving numerically the three-dimensional equation of heat conduction in the heated section. Two-dimensional profiles of the local Nusselt numbers and temperatures changed with jet angle and Reynolds number. These showed a peak shift toward the minor flow region and a plateau of the local heat transfer coefficients in the major flow region. The local velocity and turbulent intensity in the gap between the confined insulated wall and impingement surface were also obtained in detail by a thermal anemometer.

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