Experimental Studies for Hypersonic Vehicle Design and Code Validation of Unsteady Flow Characteristics associated with "Free Flight" Shroud and Stage Seperation, and Mode Switching

An experimental study was conducted in a 0.6m by 0.6m wind-tunnel to analyze effects of boundary-layer thickness on unsteady flow characteristics inside a rectangular open cavity at subsonic and transonic speeds. The sound pressure level (SPL) distributions at the centerline of the cavity floor and Sound pressure frequency spectrum (SPFS) characteristics on some measurement positions presented herein was obtained with cavity length-to-depth ratio (L/D) of 8 over Mach numbers (Ma) of 0.6 and 1.2 at a Reynolds numbers (Re) of 1.23 × 107 and 2.02 × 107 per meter under different boundary-layer thickness to cavity-depth ratios (δ/D). The experimental angle of attack, yawing and rolling angles were 0°. The results indicate that decrease in δ/D leads to severe flow separation and unsteady pressure fluctuation, which induces increase in SPL at same measurement points inside the cavity at Ma of 0.6. At Ma of 1.2, decrease in δ/D results in enhancing compressible waves. Generally, decrease in δ/D induces more flow self-sustained oscillation frequencies. It also makes severer aerodynamic noise inside the open cavity.

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Quantitative Experimental Study of SiO2-Water Nanofluids on Backward-Facing Step Flow under Low Reynolds Number

Materials Science Forum ◽

10.4028/www.scientific.net/msf.916.221 ◽

2018 ◽

Vol 916 ◽

pp. 221-225

Author(s):

Ji Zu Lv ◽

Liang Yu Li ◽

Cheng Zhi Hu ◽

Min Li Bai ◽

Sheng Nan Chang ◽

...

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Reynolds Number ◽

Volume Fraction ◽

Pure Water ◽

Experimental Studies ◽

Flow Characteristics ◽

Thermal Engineering ◽

Heat Transfer Medium ◽

Step Flow

Nanofluids is an innovative study of nanotechnology applied to the traditional field of thermal engineering. It refers to the metal or non-metallic nanopowder was dispersed into water, alcohol, oil and other traditional heat transfer medium, to prepared as a new heat transfer medium with high thermal conductivity. The role of nanofluids in strengthening heat transfer has been confirmed by a large number of experimental studies. Its heat transfer mechanism is mainly divided into two aspects. On the one hand, the addition of nanoparticles enhances the thermal conductivity. On the other hand, due to the interaction between the nanoparticles and base fluid causing the changes in the flow characteristics, which is also the main factor affecting the heat transfer of nanofluids. Therefore, a intensive study on the flow characteristics of nanofluids will make the study of heat transfer more meaningful. In this experiment, the flow characteristics of SiO2-water nanofluids in two-dimensional backward step flow are quantitatively studied by PIV. The results show that under the same Reynolds number, the turbulence of nanofluids is larger than that of pure water. With the increase of nanofluids volume fraction, the flow characteristics are constantly changing. The quantitative analysis proved that the nanofluids disturbance was enhanced compared with the base liquid, which resulting in the heat transfer enhancement.

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Modeling Cyclic Variability in Spark-Assisted HCCI

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2906176 ◽

2008 ◽

Vol 130 (5) ◽

Cited By ~ 34

Author(s):

C. Stuart Daw ◽

K. Dean Edwards ◽

Robert M. Wagner ◽

Johney B. Green

Keyword(s):

Control Strategies ◽

Experimental Studies ◽

Mode Switching ◽

Load Range ◽

Gasoline Engines ◽

Cyclic Variability ◽

Hcci Combustion ◽

Quantitative Understanding ◽

Low Dimensional ◽

High Degree

Spark assist appears to offer considerable potential for increasing the speed and load range over which homogeneous charge compression ignition (HCCI) is possible in gasoline engines. Numerous experimental studies of the transition between conventional spark-ignited (SI) propagating-flame combustion and HCCI combustion in gasoline engines with spark assist have demonstrated a high degree of deterministic coupling between successive combustion events. Analysis of this coupling suggests that the transition between SI and HCCI can be described as a sequence of bifurcations in a low-dimensional dynamic map. In this paper, we describe methods for utilizing the deterministic relationship between cycles to extract global kinetic rate parameters that can be used to discriminate multiple distinct combustion states and develop a more quantitative understanding of the SI-HCCI transition. We demonstrate the application of these methods for indolene-containing fuels and point out an apparent HCCI mode switching not previously reported. Our results have specific implications for developing dynamic combustion models and feedback control strategies that utilize spark assist to expand the operating range of HCCI combustion.

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Investigation on Unsteady Flow Characteristics of a SCO2 Centrifugal Compressor

Applied Sciences ◽

10.3390/app7040310 ◽

2017 ◽

Vol 7 (4) ◽

pp. 310 ◽

Cited By ~ 9

Author(s):

Yuqi Wang ◽

Dongbo Shi ◽

Di Zhang ◽

Yonghui Xie

Keyword(s):

Unsteady Flow ◽

Centrifugal Compressor ◽

Flow Characteristics

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Configuration trade and code validation study on a conical hypersonic vehicle

10.2514/6.1988-4505 ◽

1988 ◽

Cited By ~ 4

Author(s):

PETER COVELL ◽

RICHARD WOOD ◽

STEVEN BAUER ◽

IRA WALKER

Keyword(s):

Validation Study ◽

Hypersonic Vehicle ◽

Code Validation

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Numerical study of unsteady flow and exciting force for swept turbomachinery blades

Thermal Science ◽

10.2298/tsci160205199z ◽

2016 ◽

Vol 20 (suppl. 3) ◽

pp. 669-676

Author(s):

Di Zhang ◽

Ma Jiao-Bin ◽

Qi Jing

Keyword(s):

Boundary Layer ◽

Unsteady Flow ◽

Pressure Fluctuation ◽

Numerical Study ◽

Flow Characteristics ◽

Aerodynamic Performance ◽

Rotor Blades ◽

Stable Operation ◽

Straight Blade ◽

Excitation Force

The aerodynamic performance of blade affects the vibration characteristics and stable operation of turbomachinery closely. The aerodynamic performance of turbine stage can be improved by using swept blade. In this paper, the RANS method and the RNG k-? turbulence mode were adopted to investigate the unsteady flow characteristics and excitation force of swept blade stage. According to the results, for the swept blade, the fluid of boundary layer shifts in radial direction due to the influence of geometric construction. It is observed that there is similar wake development for several kinds of stators, and the wake has a notable effect on the boundary layer of the rotor blades. When compared with straight blade, pressure fluctuation of forward-swept blade is decreased while the pressure fluctuation of backward-swept blade is increased. The axial and tangential fundamental frequency excitation force factors of 15?forward-swept blade are 0.139 and 0.052 respectively, which are the least, and all excitation force factors are in the normal range. The excitation factor of the forward-swept blade is decreased compared with straight blade, and the decreasing percentage is closely related to the swept angle. As for backward-swept blades, the situation is the other way around. Additionally, the change of axial excitation factor is more obvious. So the vibration reduction performance of forward-swept blade is better.

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Unsteady flow characteristics regarding hump instability in the first stage of a multistage pump-turbine in pump mode

Renewable Energy ◽

10.1016/j.renene.2018.04.069 ◽

2018 ◽

Vol 127 ◽

pp. 377-385 ◽

Cited By ~ 28

Author(s):

Jun Yang ◽

Giorgio Pavesi ◽

Xiaohua Liu ◽

Tian Xie ◽

Jun Liu

Keyword(s):

Unsteady Flow ◽

Flow Characteristics ◽

Pump Mode ◽

Pump Turbine ◽

Multistage Pump

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CFD TECHNOLOGY FOR HYPERSONIC VEHICLE DESIGN

Computational Structural Mechanics & Fluid Dynamics ◽

10.1016/b978-0-08-037197-9.50009-7 ◽

1988 ◽

pp. 39-46

Author(s):

GERALD C. PAYNTER

Keyword(s):

Hypersonic Vehicle ◽

Vehicle Design

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Hydrodynamics of an in-pond raceway system with an aeration plug-flow device for application in aquaculture: an experimental study

Royal Society Open Science ◽

10.1098/rsos.182061 ◽

2019 ◽

Vol 6 (7) ◽

pp. 182061 ◽

Cited By ~ 1

Author(s):

Wuhua Li ◽

Xiangju Cheng ◽

Jun Xie ◽

Zhaoli Wang ◽

Deguang Yu

Keyword(s):

Water Flow ◽

Plug Flow ◽

Experimental Studies ◽

Three Dimensional ◽

Flow Characteristics ◽

High Water ◽

Secondary Flows ◽

Commercial Application ◽

Flow Device ◽

Intensive Aquaculture

An in-pond raceway system (IPRS) is an effective intensive aquaculture practice for regions with high water consumption and limited land resources. Water flow and dissolved oxygen (DO) are important for sustainable aquaculture. Several innovations have been made in IPRS design and operation to increase water exchange and DO concentration; one of these is the aeration plug-flow device (APFD). The APFD is commonly used in China as the only power source for water recirculation in aquaculture ponds. Understanding of the hydrodynamics of the system is necessary to improve the design of the IPRS with APFD. To this end, we performed experimental studies on a model system. We measured three-dimensional velocity at various locations using an Acoustic Doppler Velocimeter. Velocity distribution and turbulence characteristics were assessed, and plug-flow characteristics were analysed. Two patterns of velocity and turbulence in horizontal sections were observed: near the APFD, the water flow was intensively pushed downstream and simultaneously recirculated; farther away, the reflux area gradually decreased and the velocity and turbulence distribution trended towards uniform. Secondary flows occurred in different directions, which improved the diffusion of materials and DO retention. The system is effectively self-circulating, and the plug-flow capability may be scaled up for commercial application.

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