BASIC STUDY ON THE PERFECT PUSH-PULL LOCAL VENTILATION SYSTEM OF TOXIC GAS.

本研究的目的是建立推拉式通风系统，将浮力射流中的污染物或有毒气体完美地捕获到拉风罩开口中，并尽可能减少驱动通风系统中安装的机器所需的能量。在这一年里，首先改进了喷嘴几何形状，提供了平面空气射流通过矩形喷嘴的二维流动，并利用流动显示技术得到了从喷嘴完美释放的各种气流速度下通过二维湍流推拉流场边界捕获浮力射流中污染物或有毒气体的气流速度极限。在二维推拉流动的湍流结构上，用I型热线风速仪测量了从喷嘴到排气罩不同位置的气流平均速度和脉动分量。平均速度和涡轮…的发展在喷嘴喷出的恒定速度下，分别研究了诱导风量极限以下和以上两种情况下的ULENCE强度分布。在二维湍流推拉流场中，考虑了不同位置风速对吸力的影响。取得的结果如下。喷嘴附近的发展射流区域与排气罩附近的吸力区域有明显的差异。在发展射流区域，平均速度分布由顶帽分布发展为高斯分布，下游相对湍流强度增大，峰值位置由半速点变为0.75倍半速点。计算结果与传统的平面射流从喷嘴排入静止环境的结果相吻合。在吸力区，平均速度分布从内区的高斯特征分布扩展到由吸力引起的外部旋转流场的速度分布。湍流强度在内区呈平坦分布，向外区逐渐减小。较少

THIS STUDY IS UNDERTAKEN IN ORDER TO ESTABLISH THE PUSH-PULL VENTILATION SYSTEM TO CAPTURE THE POLLUTANTS OR TOXIC GAS OF BUOYANT JET INTO THE PULL HOOD OPENING PERFECTLY AND TO DECREASE THE ENERGY USED TO DRIVE MACHINES INSTALLED IN THE VENTILATION SYSTEM AS LITTLE AS POSSIBLE. FIRSTLY IN THIS YEAR, NOZZLE GEOMETRIES WERE IMPROVED TO PROVIDE THE PLANE AIR JET ISSUING THROUGH THE RECTANGULAR NOZZLE TWO-DIMENSIONALLY AND UNIFORMLY.NEXT, THE LIMIT OF AIR FLOW RATE INDUCED THROUGH THE BOUNDARIES OF THE TWO-DIMENSIONAL TURBULENT PUSH-PULL FLOW FIELD TO CAPTURE THE POLLUTANTS OR TOXIC GAS IN THE BUOYANT JET FOR THE VARIOUS AIR JET FLOW RATES ISSUING FROM THE NOZZLE PERFECTLY WERE OBTAINED USING THE FLOW VISUALIZATION TECHNIQUES.ON THE TURBULENCE STRUCTURE OF THE TWO-DIMENSIONAL PUSH-PULL FLOW, MEAN VELOCITY AND FLUCTUATING COMPONENTS IN THE FLOW WERE MEASURED AT VARIOUS LOCATIONS FROM THE NOZZLE TO THE EXHAUST HOOD BY I-TYPE HOT WIRE ANEMOMETER. THE DEVELOPMENT OF THE MEAN VELOCITY AND TURB … More ULENCE INTENSITY PROFILES WAS INVESTIGATED UNDER THE CONSTANT SPEED OF AIR JET ISSUING FROM THE NOZZLE FOR TWO CASES UNDER AND ABOVE THE LIMIT OF INDUCTION AIR FLOW RATE, RESPECTIVELY. AND THE INFLUENCE ON SUCTION OF THE AIR SPEED PULLED INTO THE EXHAUST HOOD WAS CONSIDERED AT THE VARIOUS LOCATIONS IN THE TWO-DIMENSIONAL TURBULENT PUSH-PULL FLOW FIELD. THE RESULTS OBTAINED ARE AS FOLLOWS. THERE ARE DISTINCT DIFFERENCES BETWEEN THE DEVELOPING JET REGION NEAR THE NOZZLE AND THE SUCTION REGION NEAR THE EXHAUST HOOD. IN THE DEVELOPING JET REGION, MEAN VELOCITY PROFILE DEVELOPS FROM THE TOP-HAT PROFILE TO THE GAUSSIAN CHARACTERISTIC DISTRIBUTION, AND RELATIVE TURBULENCE INTENSITY INCREASES DOWNSTREAM AND THE LOCATION OF THE PEAK VALUE CHANGES FROM THE HALF-VELOCITY POINT TO 0.75 TIMES THE HALF-VELOCITY POINT. THE RESULT AGREES WITH THE CONVENTIONAL RESULT OF THE PLANE JET EXHAUSTING FROM THE NOZZLE INTO QUIESCENT SURROUNDINGS. IN THE SUCTION REGION, ON THE OTHER HAND, MEAN VELOCITY PROFILE SPREADS FROM THE GAUSSIAN CHARACTERISTIC PROFILE IN THE INNER ZONE INSIDE THE HALF-VELOCITY POINT TO THE VELOCITY DISTRIBUTION OF THE EXTERNAL IRROTATIONAL FLOW FIELD CAUSED BY THE SUCTION. THE TURBULENCE INTENSITY SHOWS FLAT DISTRIBUTION IN THE INNER ZONE, AND DECREASES GRADUALLY TOWARDS THE EXTERNAL FLOW FIELD. Less