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Characteristics of the recirculation zone in a cylindrical confined space and its suppression by an annular orifice plate

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Building Simulation 2023年第8期16卷 1391-1408页

作者： Yu Zhou Wan-Rong Ren Mengfan Quan Lei Jia Manning Wang Yi Wang State Key Laboratory of Green Building in Western China Xi'an University of Architecture and TechnologyXi'an 710055China School of Building Services Science and Engineering Xi’an University of Architecture and TechnologyNo.13 Yanta RD.Xi’an 710055China

The accumulation of pollutants in the recirculation zone can worsen *** is critical to reduce recirculation zones to improve the ventilation efficiency of ***,the variation rule of the recirculation zone in a cylindrical confined space(CCS)is unclear,and there are few solutions to suppress or eliminate the recirculation zone at *** this paper,an annular deflector orifice plate for suppressing the recirculation zone was developed based on the structural characteristics of the *** device is simple in structure and can be used *** experiments and numerical simulations,the variation rule of the recirculation zone length and the influence of structural parameters of the device on the vortex suppression were ***,empirical formulas for calculating the length of the recirculation zone in the CCS were *** addition,it was proved that placing the annular orifice plate inside the CCS effectively reduced the recirculation zone and improved the ventilation *** to the system without the annular orifice plate,the dimensionless length of the recirculation zone was decreased by 76.3%,and the time to completely discharge the pollutants from the CCS was decreased by 16.7%.Finally,parameters of the annular orifice plate that form the best vortex suppression effect were proposed:the porosity range was 40%–50%,uniform in shape with equal ring spacing,and placed more than one inlet diameter away from the *** results help guide the ventilation design of CCS.

关键词： cylindrical confined space recirculation zone vortex suppression orifice plate

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Experimental Investigations of the Flow Field Structure and Interactions between Sectors of a Double-Swirl Low-Emission Combustor

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Journal of Thermal Science 2020年第3期29卷 43-51页

作者： FAN Xiongjie XU Gang LIU Cunxi WANG Jianchen LIN Yuzhen ZHANG Chi Key Laboratory of Light-duty Gas-turbine Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics Collaborative Innovation Center of Advanced Aero-EngineSchool of Energy and Power EngineeringBeihang UniversityBeijing 100191China

In this paper,the flow field characteristics of a double-swirl low-emission combustor were analyzed by using Particle Imaging Velocimetry(PIV)technology in an optical three-sector combustor test *** interactions between sectors and the flow field structure were *** results illustrated that there was a big difference between the flow field structures of the middle sector and the side sector under the same pressure drop,which was mainly induced by the interactions between *** interactions made the swirl intensity of the middle sector weaker than that of the side sector,which made the recirculation zone of the middle sector be smaller than that of the side *** the increase of swirler pressure drop,the jet velocity at the exit of the swirler,the jet expansion angle,the width of the recirculation zone and the recirculating speed of the central axis became larger,enhancing the interactions between air streams from middle sector and side *** flow velocity in the central plane between sectors was small,especially the radial velocity,mainly because of the loss of the swirl intensity by the interactions between flow field of adjacent *** expansion angle determined the position of the vortex in the primary recirculation zone;the axial and radial position of the vortex move downstream and radial outward with the increase of the jet expansion *** results of the mechanism of flow field organization in this study can be used to support the design of new low-emission combustor.

关键词： combustor recirculation zone Particle Imaging Velocimetry(PIV) pressure drop

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Understanding of tip clearance flow structure in high speed mixed flow compressor

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Propulsion and Power Research 2023年第3期12卷 356-379页

作者： Hemant Kumar Chetan S.Mistry Department of Aerospace Engineering Indian Institute of TechnologyKharagpurWest Bengal 721302India

This paper addresses the necessity to make a physical interpretation of a highly complex three-dimensional tip clearance flow field study for high-speed mixed-flow compressor having stage exit static pressure to inlet total pressure ratio of 3.8 with 39,836 rpm rotor *** four different tip configurations namely the constant(l Z 0.016 and 0.019)and variable(l Z 0.011(inlet)-0.019(exit)and 0.019(inlet)-0.022(exit))tip clearances were numerically analysed using available experimental *** numerical investigation reveals that in contrast to the classic jet-wake pattern,two anomalous velocity profiles formed at the impeller exit which results in pressure losses in the vaneless *** the impeller inlet,the tip leakage flow rolls up to discrete tip leakage vortex structure for each tip clearance *** results in the formation of a region of momentum deficit,recirculation zone,which gets weakened as it moves *** tip clearance configuration is observed to profoundly influence the extent and vorticity of the tip leakage *** the splitter blade passage,the tip leakage flow and Coriolis flow interact with passage flow,resulting in the formation of two secondary passage vortices that move downstream along the pressure and suction surface of the splitter *** tip clearance configuration directly influences the impeller exit jetwake pattern by modulating the secondary passage vortices trajectory and ***,off-design analysis for tip clearances l Z 0.016 and l Z 0.019,depict distinctive tip leakage vortex *** operating near the stall conditions(80%of design mass flow rate),l Z 0.019 exhibits bubble shape tip leakage vortex breakdown occurring near the impeller *** result in a substantial change in the tip leakage vortex nature;expansion of the recirculation zone and early weakening of the vorticity in the tip leakage *** is observed that vortex breakdown plays a vital role in characte

关键词： recirculation zone Vortex breakdown Tip leakage flow Mixed-flow compressor Jet-wake flow Vaned-diffuser

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Instability of wave complex resulting from oblique detonation decoupling

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Acta Mechanica Sinica 2022年第5期38卷 11-19,I0001页

作者： Honghui Teng Xuechen Xi Kuanliang Wang Pengfei Yang School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China

Oblique detonation wave(ODW)has been investigated widely for application in ramjet-type engines,but there are less works concerning its instability in a confined ***,a wave complex induced by ODW decoupling has been observed,and this study investigates the instability of this wave complex featuring a recirculation *** results show that the wave complex with recirculation zone oscillates,but the oscillations are found to be periodic rather than random,never reported *** dependence of the period and frequency on the corner location and angle are analyzed in detail,with very irregular motion tracks of recirculation zone *** quantitative analysis by Fast Fourier transformation reveals two origins of instability:one is the basic oscillation of the recirculation zone associated with the movement of surrounding wave complex;the other is self-excitation inside the recirculation zone,which makes its motion tracks more complicated than the external wave configuration.

关键词： Oblique detonation Expansion corner recirculation zone Instability

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Influence of Ship Motion on Flow Field over Modified Simple Frigate Shapes

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Transactions of Nanjing University of Aeronautics and Astronautics 2021年第3期38卷 520-534页

作者： LI Tong WANG Yibin ZHAO Ning Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China

When the frigate moves forward,due to the ship motion such as pitching and rolling,the flow over the flight deck becomes very complex,which may seriously threaten the taking off and landing of the ship-borne *** flow fields over the different modified simple frigate shape(SFS)models,consisting of the hangar and flight deck,were numerically studied by changing the ratio of hangar height and length in the static state and pitching *** different models,the contours of velocity and pressure above the flight deck,as well as the variations of velocity components of the observation points and line in static state and pitching state were compared and *** results show that the size of recirculation zone and the location of the reattachment point have distinct differences for diverse models,and reveal the tracks of recirculation zone’s center and reattachment position in a pitching *** addition,the velocity components at two observation positions also change periodically with the periodic ***,the deviations of the velocity components in static state and pitching state are relatively large,therefore,the flow fields in static state cannot be used to simulate that in pitching state correctly.

关键词： computational fluid dynamics simple frigate shape ship airwake pitching recirculation zone

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Cold Gas-particle Flows in a New Swirl Pulverized-coal Burner by PDPA Measurement

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Tsinghua Science and Technology 2000年第1期5卷 100-104页

作者：李志强李荣先周力行 Department of Engineering Mechanics Tsinghua University Beijing 100084 China

A new type of swirl burner has been developed to stabilize pulverized\|coal combustion by burning different types of coal at different loads and to reduce NO x formation during combustion. The burner uses a device to concentrate the coal powder in the primary\|air tube that divides the primary coal\|air into two streams with different pulverized\|coal concentrations. This paper reports the measurement of gas\|particle flows at the exit of the different swirl burners using a 3\|D Phase Doppler Particle Anemometer (PDPA). The effect of different geometrical configurations on the two\|phase flow field is studied. The results that give the two\|phase flow fields and particle concentrations show the superiority of the new swirl burner. 

关键词： swirl burner Phase Doppler Particle Anemometer (PDPA) recirculation zone gas\|particle flows

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