Experimental Study On The Atomization Characteristics Of Impinging Jets Of Power-law Fluid

Doublet like-on-like impinging jet has been widely used in liquid rocket engine because it has good atomization and mixing characteristics under different injection pressure and it is easy to manufacture and maintenance. Power-law fluid is a new kind of propellant. Making the propellant gelled can make it have the advantage of both the liquid propellant and the solid propellant. However it has been recognized that the rheological properties of power-law fluid make it difficult to atomize into fine drops and its atomization characteristics is different from Newtonian fluid. Therefore, to study the atomization characteristics of power-law fluid is of great significance. It can help to control the atomization quality optimize the combustion process.This paper review the study of Newtonian fluid and power-law fluid of impinging jets at home and abroad. It is found that there is little quantitative study of atomization characteristics of power-law fluid. Based on the shortcomings of current research, the content and the experimental scheme of the paper were determined.Design and improve the doublet like-on-like impinging jet atomization experiment system. Based on the original pressure and flow measurement control system, pressure measurement system, injection system and the azimuth control system, we built the power-law fluid transport system and air disturbance system. As a result, the whole experiment system can meet the experiment requirement. PIV was debugged to measure the velocity field of spray. Three kind of mass concentration carbopol were prepared. The rheological properties was measured and the rheological parameters of the power-law fluid constitutive equation was obtained.We conducted the experiment of atomization characteristics of power-law fluid and analyzed the break regime, the liquid sheet characteristics, the size of the droplets and the velocity field of spray. Results indicates that: different power-law fluid have different breakup regime. The sheet length-width ratio increases with increasing viscosity. The surface wave length decreases with increasing inject weber number. The breakup length increases with increasing weber number first and then decreases. The spray angle increases linearly with increasing weber number until reaches the convergence value which is slightly larger than impinging angle. The SMD of droplets decreases with increasing weber number until reaches the convergence value which is slightly larger than that of Newtonian fluid. And the power-law fluid needs larger pressure to atomize completely. The velocity field of spray is symmetrical, the axial velocity of droplets near the center axis is the largest and the radial velocity is smallest.We studied the influence of jet parameters on atomization characteristics. The result indicates that: when the two jets impinged at eccentricity, the chain sheet can be found. And the length of the link decreased with the increasing eccentricity. When the jet length is different, the fishbone regime can be found. With the increasing impinging angle, the sheet length-width ratio and the breakup length decreases and the spray angle increases. The impinging angle has little influence on the convergence of SMD. Adding airflow disturbances can improve quality of atomization by increasing the strength of surface wave and make the breakup regime develop faster. The width of sheet decreases but the uniformity of spray becomes bad. The strength of power-law fluid containing metal particles becomes smaller. The breakup length of this fluid changes slightly with weber number and the max length decreased obviously. Besides, this fluid atomize completely in lower inject pressure. The SMD convergence of droplets of this fluid is almost same while the SMD reach convergence faster.