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

本研究的目的是建立一种推压式通风系统，以将浮力射流的污染物或有毒气体完美地捕获到通风罩开口中，并尽可能减少用于驱动通风系统中安装的机器的能量。本年度首先对喷嘴几何形状进行了改进，使通过矩形喷嘴喷出的平面空气射流具有二维和三维的特性。其次，通过二维湍流推流边界诱导的空气流量的极限利用流场显示技术，得到了不同流量的空气射流在浮力射流中捕捉污染物或有毒气体的理想流场本文用I型热线风速计测量了从喷嘴到排气罩不同位置的二维推流湍流结构、平均涡度和脉动分量。平均湿度与涡轮的发展 ...更多信息 在喷嘴喷出的气流速度恒定的情况下，分别在低于和高于诱导气流速度极限的两种情况下，绘制了光强分布图。并考虑了在二维湍流推压流场中不同位置处抽气速度对吸气量的影响。获得的结果如下。喷嘴附近的喷射区域和排气罩附近的吸入区域之间存在明显差异。在急流区，平均涡度廓线由顶帽型向高斯型转变，相对湍流强度向下游增大，峰值位置由半涡度点向0.75倍半涡度点变化。计算结果与传统的平面射流从喷管中喷出进入静止环境的结果一致。另一方面，在吸气区，平均涡度分布从半涡度点内部区域的高斯涡度分布扩展到吸气引起的外部无旋流场的涡度分布。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