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

本研究是为了建立推拉式通风系统，将浮喷的污染物或有毒气体完美地捕获到拉式通风罩开口中，并尽可能减少通风系统中安装的机器的驱动能量。首先，在这一年，改进了喷嘴的几何形状，使平面气流通过矩形喷嘴二维均匀地发出。其次，通过二维湍流推拉流场的边界，利用流动可视化技术完美地获得了在喷管发出的不同气流流速下，为捕获浮力射流中的污染物或有毒气体而诱导的气流流速极限。在二维推拉流的湍流结构上，利用i型热线风速仪测量了从喷管到排气罩的不同位置的平均速度和流动中的波动分量。摘要研究了喷管出风速度恒定时，平均速度和涡顶气流强度分布的变化规律，并对两种情况分别进行了分析。并考虑了二维湍流推拉流场中不同位置拉入排气罩的风速对吸力的影响。所得结果如下：喷管附近的显影射流区与排气罩附近的吸力区存在明显的差异。在发展射流区，平均速度分布由顶帽型向高斯特征分布发展，下游相对湍流强度增大，峰值位置由半速点向0.75倍半速点变化。该结果与传统的平面射流从喷口向静态环境中喷射的结果一致。而在吸力区域，平均速度分布由半速度点内部区域的高斯特征分布向吸力引起的外无旋流场的速度分布扩散。湍流强度在内区呈平缓分布，向外流场逐渐减小。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