Internal Flow Mechanism of Cone-straight Nozzle

To investigate the pre-stall behavior of an axial flow compressor rotor, which was experimentally observed with spike-type stall inception, systematic experimental and whole-passage simulations were laid out to analyze the internal flow fields in the test rotor. In this part, emphases were put on the analyses of the flow fields of whole-passage simulation, which finally diverged, and the objective was to uncover the flow mechanism of short length scale disturbance (or spike) emergence. The numerical result demonstrated that the test rotor was of spike-type stall initiation. The numerical probes, arranged ahead of the rotor to monitor the static pressure variation, showed that there first appear two pips on the curves. After one rotor revolution, there was only one pip left, spreading at about 33.3% rotor speed. This propagation speed was almost the same as that of the spike observed in experiments. The further analysis of the flow field revealed a concentrated blockage sector on the flow annuls ahead of rotor developed gradually with the self-adjustment of flow fields. The two pins on monitoring curves corresponded to two local blockage regions in near-tip passages, and were designated as B1 and B2, respectively. The correlation between the tip secondary vortices (TSVs) in the preceding and native passages was the flow mechanism for propagation of B2 and B1, thereby leading to their spread speed approximate to the active period of the TSV in one passage. Furthermore, the self-sustained unsteady cycle of TSVs was the underlying flow mechanism for the occurrence of the so-called “tip clearance spillage flow” and “tip clearance backflow.” Because B2 was the tip-front of the blockage sector, TSVs associated with its propagation became stronger and stronger, so that the “tip clearance backflow” induced by it was capable of spilling into the next passage below the blade tip. This phenomenon was regarded as the threshold event where B2 started to evolve into a spike. The distinctive flow feature during the development stage of the spike was the occurrence of a separation focus on the suction side in the affected passages, which changed the self-sustained unsteady cycle of the TSV substantially. A three-dimensional vortex originating from this focus led to a drastic increase in the strength of the TSV, which, in turn, led to a rapid increase in the “tip clearance backflow” induced by the TSV and the radial extent of spillage flow.

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Internal flow mechanism in a supersonic expander-rotor

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/09544100211023675 ◽

2021 ◽

pp. 095441002110236

Author(s):

Zhenyu Huang ◽

Jingjun Zhong

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Flow Structure ◽

Internal Flow ◽

Leading Edge ◽

Wave Structure ◽

Oblique Shock ◽

Expansion Wave ◽

Oblique Shock Wave ◽

Flow Mechanism

This article proposes a numerical investigation into the internal flow structure in the supersonic expander-rotor (SER). In order to reveal internal flow mechanism, the significant influencing factors in the flow structure are identified, and the solutions to improving the integrated performance of the SER are developed. According to the numerical results, the wave structure of the expansion wave and the oblique shock wave is what characterizes the flow in the mainstream region of the SER. In addition, the expansion wave and the oblique shock wave impose control on the pattern of static pressure distribution in the 3-D channel and then the 3-D flow structure. The formation and breakdown of the tip leakage vortex are the main form that the motion of vortex takes in the SER. The concentration, recirculation, and separation of the boundary layer; the low energy fluid mixing with mainstream; and the interaction between the oblique shock waves and the boundary layer are the crucial motion tracing near the endwall. Compared with the traditional turbines, the flow structures in the tip region of the SER are relatively simpler; the essential motion tracing is the airflow near the leading edge of the strake wall moving from the PS through the tip gap to the SS as a result of the transverse pressure difference.

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Numerical Simulation of Torque Converter With Different Pump Blade Camber

Volume 3A: Fluid Applications and Systems ◽

10.1115/ajkfluids2019-5394 ◽

2019 ◽

Author(s):

Zhifang Ke ◽

Cheng Liu ◽

Wei Wei ◽

Qingdong Yan ◽

Xianglu Meng

Keyword(s):

Internal Flow ◽

Torque Converter ◽

Flow Fields ◽

Hydrodynamic Performance ◽

Maximum Efficiency ◽

Speed Ratio ◽

Main Function ◽

Flow Mechanism ◽

Entrance Angle ◽

The Difference

Abstract The main function of the torque converter pump is to transfer mechanical power into fluid dynamic energy. It has been proved that the pump blade shape, especially pump blade camber peak, is crucial to torque converter hydrodynamic performance. However, it remains unclear how this parameter affects internal flow characteristics, and how it leads to the difference in performance. Thus, the relationship between the pump blade camber and the performance of torque converter and the flow mechanism were explored in this study. Torque converters with different pump blade camber were tested. Meanwhile, the corresponding numerical models were also established and their internal flow fields were investigated through steady-state simulations. The influence of the pump blade camber on the hydrodynamic performance was studied using both numerical and experimental methods, and the flow mechanism was also revealed and elaborated by exploring the numerical flow fields. The results from both experiments and simulations showed that larger pump blade camber peak led to higher pump capacity, higher maximum efficiency and lower stall torque ratio. The flow field simulation revealed that larger pump camber peak would lead to higher total pressure in pump channel. And the pressure distribution between the suction and pressure surface showed a similar pattern; however, their difference, especially near the leading and tailing edge, depends on the camber peak. Besides, higher camber peak blade absorbed more power, also induced more complex vortex, but there always existed the most efficient speed ratio when pump efficiency can reach to peak, at this moment, the difference between angle of attack and entrance angle reach the zero, which can be used to guide the design of pump blade.

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Internal flow Mechanism and Experimental Research of low Pressure Axial fan with Forward-Skewed Blades

Journal of Hydrodynamics ◽

10.1016/s1001-6058(08)60061-x ◽

2008 ◽

Vol 20 (3) ◽

pp. 299-305 ◽

Cited By ~ 15

Author(s):

Yang Li ◽

Jie Liu ◽

Hua Ouyang ◽

Zhao-Hui Du

Keyword(s):

Experimental Research ◽

Internal Flow ◽

Low Pressure ◽

Flow Mechanism ◽

Axial Fan

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Internal flow mechanism in filter cakes

AIChE Journal ◽

10.1002/aic.690150320 ◽

1969 ◽

Vol 15 (3) ◽

pp. 405-409 ◽

Cited By ~ 82

Author(s):

Mompei Shirato ◽

Masao Sambuichi ◽

Hiroo Kato ◽

Tsutomu Aragaki

Keyword(s):

Internal Flow ◽

Flow Mechanism ◽

Filter Cakes

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Investigation of the natural ventilation of wind catchers with different geometries in arid region houses

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.3.2020.12.0557 ◽

2020 ◽

Vol 14 (3) ◽

pp. 7109-7124

Author(s):

Nasreddine Sakhri ◽

Younes Menni ◽

Houari Ameur ◽

Ali J. Chamkha ◽

Noureddine Kaid ◽

...

Keyword(s):

Arid Region ◽

Natural Ventilation ◽

Reduction Rate ◽

Internal Flow ◽

Climatic Conditions ◽

Maximum Pressure ◽

Ventilation Technique ◽

Window Position ◽

The One ◽

Flow Velocities

The wind catcher or wind tower is a natural ventilation technique that has been employed in the Middle East region and still until nowadays. The present paper aims to study the effect of the one-sided position of a wind catcher device against the ventilated space or building geometry and its natural ventilation performance. Four models based on the traditional design of a one-sided wind catcher are studied and compared. The study is achieved under the climatic conditions of the South-west of Algeria (arid region). The obtained results showed that the front and Takhtabush’s models were able to create the maximum pressure difference (ΔP) between the windward and leeward of the tower-house system. Internal airflow velocities increased with the increase of wind speed in all studied models. For example, at Vwind = 2 m/s, the internal flow velocities were 1.7, 1.8, 1.3, and 2.5 m/s for model 1, 2, 3, and 4, respectively. However, at Vwind = 6 m/s, the internal flow velocities were 5.6, 5.5, 2.5, and 7 m/s for model 1, 2, 3, and 4, respectively. The higher internal airflow velocities are given by Takhtabush, traditional, front and middle tower models, respectively, with a reduction rate between the tower outlet and occupied space by 72, 42, 36, and 33% for the middle tower, Takhtabush, traditional tower, and the front model tower, respectively. This reduction is due to the due to internal flow resistance. The third part of the study investigates the effect of window (exist opening) position on the opposite wall. The upper, middle and lower window positions are studied and compared. The air stagnation or recirculation zone inside the ventilated space reduced from 55% with the lower window to 46% for the middle window and reached 35% for the upper window position. The Front and Takhtabush models for the one-sided wind catcher with an upper window position are highly recommended for the wind-driven natural ventilation in residential houses that are located in arid regions.

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Experimental and Numerical Analysis of a Motorcycle Air Intake System Aerodynamics and Performance

International Journal of Automotive and Mechanical Engineering ◽

10.15282/ijame.17.1.2020.10.0565 ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

M. A. Abd Halim ◽

N. A. R. Nik Mohd ◽

M. N. Mohd Nasir ◽

M. N. Dahalan

Keyword(s):

Combustion Process ◽

Three Dimensional ◽

Engine Performance ◽

Internal Flow ◽

Rapid Expansion ◽

Navier Stokes ◽

Turbulent Fluctuation ◽

Ansys Fluent ◽

Induction System ◽

Acceleration And Deceleration

Induction system or also known as the breathing system is a sub-component of the internal combustion system that supplies clean air for the combustion process. A good design of the induction system would be able to supply the air with adequate pressure, temperature and density for the combustion process to optimizing the engine performance. The induction system has an internal flow problem with a geometry that has rapid expansion or diverging and converging sections that may lead to sudden acceleration and deceleration of flow, flow separation and cause excessive turbulent fluctuation in the system. The aerodynamic performance of these induction systems influences the pressure drop effect and thus the engine performance. Therefore, in this work, the aerodynamics of motorcycle induction systems is to be investigated for a range of Cubic Feet per Minute (CFM). A three-dimensional simulation of the flow inside a generic 4-stroke motorcycle airbox were done using Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) solver in ANSYS Fluent version 11. The simulation results are validated by an experimental study performed using a flow bench. The study shows that the difference of the validation is 1.54% in average at the total pressure outlet. A potential improvement to the system have been observed and can be done to suit motorsports applications.

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