CAJ | 학술논문

为提高小型便携式风力灭火机的灭火射程和风量，提出了通过空气引射增大其出口空气流量，减缓风速衰减的方法。以其接收室收敛角θ，混合室直径Dm以及喷嘴位置S为变量，建立了240个不同尺寸参数组合的计算流体动力学（CFD）模型并进行了模拟和计算，基于其计算结果，用响应曲面法详细分析并揭示了各结构尺寸对亚音速空气引射性能的影响规律。研究了不同尺寸参数下混合室内部压力场的变化，从机理上探讨了各参数对距离风机中心2.5 m处风速和引射系数交互作用及影响的原因。结果表明：Dm与θ对距离风机中心2.5 m处风速影响很大，Dm与θ两者之间的交互作用很强；而S对距离风机中心2.5 m处风速影响较小，且与其他参数的交互性很弱。确定最佳参数组合即当θ为36.25°，Dm为144 mm，S为90 mm时，距离风机中心2.5 m处风速可达最优值，经试验测定该最优值为36.4 m/s。
위제고소형편휴식풍력멸화궤적멸화사정화풍량，제출료통과공기인사증대기출구공기류량，감완풍속쇠감적방법。이기접수실수렴각θ，혼합실직경Dm이급분취위치S위변량，건립료240개불동척촌삼수조합적계산류체동역학（CFD）모형병진행료모의화계산，기우기계산결과，용향응곡면법상세분석병게시료각결구척촌대아음속공기인사성능적영향규률。연구료불동척촌삼수하혼합실내부압력장적변화，종궤리상탐토료각삼수대거리풍궤중심2.5 m처풍속화인사계수교호작용급영향적원인。결과표명：Dm여θ대거리풍궤중심2.5 m처풍속영향흔대，Dm여θ량자지간적교호작용흔강；이S대거리풍궤중심2.5 m처풍속영향교소，차여기타삼수적교호성흔약。학정최가삼수조합즉당θ위36.25°，Dm위144 mm，S위90 mm시，거리풍궤중심2.5 m처풍속가체최우치，경시험측정해최우치위36.4 m/s。
A portable pneumatic extinguisher is an effective device that has been widely used for forest and grassland fire extinguishing in China. In order to enhance the effective range and rate of discharge of portable pneumatic extinguishers, a new method to weaken air velocity attenuation by increasing the flow rate using an air ejector was proposed and investigated in this study. This research belongs to the category of subsonic air ejector. First, the turbulivity of air jet“c”has been updated to the value of 0.106 by experiments. It is necessary to use this factor for the calculation of air velocity where 2.5 m downstream from the centrifugal fan which defined as u2.5. Experimental and the CFD (Computational Fluid Dynamics) methods are applied to investigate the influence on the performance of the air ejector. Three parameters were characterized:converging angle of entraining chamberθ;diameter of the mixing chamber Dm and the nozzle position (NXP) S. Up to 240 different models were established and meshed by Gambit 2.3, and then simulated and calculated by Fluent 6.3 with the turbulence model of RNG k-epsilon. Consequently, 240 different results containing the flow rate of nozzle outlet cross-section mp, the entrainment flow rate me, the flow rate of the mixing chamber outlet cross-section mc, and the air velocity of a mixing chamber outlet cross-section uc were acquired. Based on this data, the response surfaces for u2.5 and entrainment ratio that are used to investigate the interaction between Dm,θand S to u2.5 and entrainment ratio were established. The results indicated that the parameters Dm andθhave a great influence on u2.5 and entrainment ratio. It was also demonstrated that the interaction between Dm andθis significant. However, parameter S gave a relatively delicate influence on u2.5 and entrainment ratio, and also the interaction with the other parameters was weak. In addition, to find out the mechanism of interaction between Dm andθ, three groups of different pressure fields have been investigated and compared as well. It indicates that a high value ofθ(whenθ<36.25°) could create a relatively significant negative pressure zone in the mixing chamber, which requires a larger Dm to provide sufficient air input, and as a consequence u2.5 and entrainment ratio increase accordingly. Because of the negative pressure zone nearby the nozzle outlet, the effective power of the centrifugal fan and engine are both increased. The optimum value of θ is 36.25°, and when Dm equals to 144 mm, u2.5 could reach the maximum value. The maximum u2.5, which was gained by experiments using an ejecting pneumatic extinguisher, was 36.4 m/s. Meanwhile, the value of u2.5 could keep adding up as Dm continued to increase, but the range of Dm has been limited by the design and practical applicability of the portable pneumatic extinguisher.