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Your search keyword '"Siyin Zhou"' showing total 2 results
Start Over Author "Siyin Zhou" Topic atmospheric pressure Publication Year Range Last 50 years
2 results on '"Siyin Zhou"'

1. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

Author

Chao Yang, Wansheng Nie, Siyin Zhou, Penghui Zhou, Tao Shao, Xueke Che, Hou Zhiyong, Haobo He, and Tian Xihui

Subjects
Physics::Fluid Dynamics, Physics, Flow visualization, Flow control (fluid), Nuclear magnetic resonance, Particle image velocimetry, Atmospheric pressure, Electric potential, Mechanics, Condensed Matter Physics, Plasma actuator, Flow measurement, Voltage
Abstract

Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

Published
2014

2. Experimental study on the diffusive flame stabilization mechanism of plasma injector driven by AC dielectric barrier discharge.

Author

Siyin Zhou, Lingyu Su, Tianyi Shi, Tikai Zheng, Yiheng Tong, Wansheng Nie, Xueke Che, and Jiafeng Zhao

Subjects
*ATMOSPHERIC pressure, *FLAME, *HEAT release rates, *GLOW discharges, *INJECTORS, *PLASMA temperature, *JETS (Fluid dynamics)
Abstract

A plasma injector element was designed to experimentally study the mechanism of methane-air diffusive flame stabilized by a discharge plasma. The air plasma was generated within the annulus gap of the injector by alternating current dielectric barrier discharge. The discharge voltage, current and photographs were recorded first. Three internal effects of the plasma on combustion were later investigated separately through several diagnostic methods, including optical emission spectrometry (OES), infrared thermography, thermocouple, infrared thermometer, schlieren imaging, photos and CH* chemiluminescence. Finally, the return on investment (ROI) was calculated. The results showed that a large number of filamentary micro discharge paths occur within the discharge gap. These discharge paths rotate anticlockwise at high speed and act as a virtual ‘fan’ to induce the flow jet. The velocity of the induced jet increases with increasing discharge voltage. The original jet expansion angle is enlarged by the radial velocity component of the induced jet, resulting in the mixing enhancement of the air and methane. The plasma rotational temperature (the first negative system ) obtained from OES is close to the discharge gas temperature measured by infrared thermography, indicating that the discharge gas temperature can be approximately represented by the rotational temperature. According to the measured temperature of the injector and the jet, the impact of the thermal effect of the plasma on flame stabilization is negligible. Due to the plasma, the height of the flame center and its representative length are generally reduced as the voltage rises, and the methane-air mixture becomes ignitable, and a stable flame can be reached under the conditions in which direct ignition fails. The combustion is enhanced with increasing heat release rate of the flame by the plasma. This finding revealed that the ROI of plasma-assisted flame stabilization is lower under a higher flowrate and a larger equivalence ratio for unstable flame situations. [ABSTRACT FROM AUTHOR]

Published
2019
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