A Comparative Study On The Theory And Experiment Of Jet Fragmentation

Plane liquid film jet, circular liquid jet, annular liquid film jet are the study of the three major forms of liquid jet, the study of the theory of the scholars from all over the world have made great progress. My supervisor Prof.Cao Jianming and his team are also on the research of above three kinds of jet and they have obtained certain achievement. Scholars study the jet are based on breakup model established by the linear stability theory, Prof.Cao Jianming and his graduate Xiong Wei also did much calculation on the basis of it, and had get the linearization dimensionless criterion of plane liquid film jet, and get the linearization dimensionless criterion of circular liquid jet with his graduate Hou Jie, and had get the linearization dimensionless criterion of annular liquid film jet with his graduate Ren Huan and Guo Guangxiang. These criterions expressed the relationship between the dimensionless wave growth rate and wave number. By this relationship and jet breakup empirical formulas proposed by previous scholars, we can get the theoretical breakup length. The trend of breakup length will change completely differently, if the jet stays in different regions such as laminar flow region, transition region, turbulent region, atomization region, so the jet breakup length in different stages has differently empirical formula. In this paper we use the constant pressure water jet test platform, and measure the breakup length under the corresponding operating points of plane liquid film jet, circular liquid jet, annular liquid film jet. Compared with theoretical breakup length and analyse gap, in the end we modify experience breakup formula in corresponding region put forward by the predecessors, make it more close to the theoretical breakup length in corresponding region. In the way of deriving breakup length, we found the initial wave amplitude 0? is also an important unknown parameter, previous scholars estimated this parameter when they needed use it, in fact we need to measure it. Therefore we exploratorily established measurement method of the initial wave amplitude, and successfully measured the the initial wave amplitude in tne corresponding points, and summarize the changing rule of the initial wave amplitude in this paper.The final experiment shows these poits:(1)The plane liquid film jet experiment is conducted in the laminar flow phase, the breakup length increases with the increase of liquid jet velocity. The theoretical breakup length received by original jet breakup empirical formula havs the same trend with the really experimental date, the gap is very small. We add a correction coefficient to the original experience formula and make it more close to the experimental breakup length. Then wen found that the initial wave amplitude is not a stable value, it will change if the experimental satuation changes. In the end we sthdy the change rule of the initial wave amplitude.(2)The circular liquid jet experiment is conducted in the transitional phase, The breakup length decreases with the increase of liquid jet speed. The theoretical breakup length received by original jet breakup empirical formula is smaller than really experimental breakup length, but the change trends are basically same, with the increase of liquid jet velocity, the breakup length decreases. We modify the original and get the date which is close to real date. Then we coduct an additional test and study the change of the initial wave amplitude.(3) the annular liquid film jet experiment was conducted in the transitional phase,breakup length decreases with the increase of jet velocity. We contrast the theoretical breakup length received by original jet breakup empirical formula and the real experimental date, and find the theoretical dates are smaller, but they have almost close trend, with the increase of the inner ring interference airflow breakup length change shorter. By means of adding a correction factor to original breakup formula, the theoretical value is closer to the experimental value. And we study its change of the initial wave amplitude, and find the initial wave amplitud’s variation is small.