二相流噴嘴之研究

Abstract

本研究首先設計與製作一二相氣液噴射系統架構，使噴嘴的出口速度達氣液混合液的聲速，並設計三個不同噴嘴出口的角度，來比較出口擴張對推力的影響。由量測不同空氣流量下所產生的推力發現：(1)二相氣液噴射系統噴入壓縮空氣可以增加推力、(2)研究中以半錐角22.5度的噴嘴出口效果最佳，最大推力在有噴入壓縮空氣1300L/min時可達沒有壓縮空氣的3倍。 第二部分是將設計與製作一二相流噴嘴於自由流場中進行拖行實驗，試著以壓縮空氣做為推進的動力來源，其效果為何？實驗過程中同樣噴入不同的空氣流量，來量測推力的變化。實驗結果顯示，噴入的壓縮空氣並沒有產生推力的現象。 第三部分是以水上摩托車為載具，設計適用的二相流噴嘴進行實體測試，利用微泡所產生的膨脹效應，進一步對噴嘴內的流體加速以提高噴水推進系統的推力。實驗結果顯示，在加入的空氣流量與水上摩托車的噴流量一樣時，可以增加約90% 的推力，同時顯示速度越高時，所增加的推力越大。

A two phase gas-water nozzle experimental system was designed to study the effect of injecting compressed air in the waterjet system. The speed of the nozzle exit can reach the sound speed of gas-water mixture in the designed system. Also three nozzles with different exit angle were designed to study the effect of nozzle expansion on the thrust produced by the two phase jet. The test results show that the two phase nozzle with injecting compressed air does increase the thrust produced by the waterjet. The nozzle with half exit angle 22.5 is the best nozzle in this study. And, the measured maximum thrust with injecting compressed air is three times the thrust produced by waterjet without injecting compressed air. A two phase gas-water nozzle experimental system was also design to study the effect of injecting compressed air in the towing tank. The test results show that the two phase nozzle with injecting compressed air does not produced thrust. A two phase nozzle system was also designed for a jet ski. The resistance and thrust of the jet ski with two phase nozzle were measured in the towing tank. The test results show that the two phase nozzle with injecting the compressed air also increases the thrust produced by the jet ski. A 90% thrust increase was obtained in this study.