关键词: 喷射器, 引射率, 旋流, 计算流体力学, 动量传递, 混合

Abstract:

Ejector is a common fluid supercharging equipment, and its mixing efficiency is low. To solve this problem, a new type of swirling ejector was proposed, which adds three-dimensional disturbing elements to the ejector driving nozzle to enhance momentum exchange efficiency. As a research object, its performance in air condition was studied experimentally and numerically. Compared with the traditional ejector, it can significantly improve the performance of ejector equipment. Under the sup-sonic condition, the three-dimensional disturbing elements cannot affect the mass flow of driving fluid, and the experimental measurement of the critical pressure point (P_RC) is unchanged, so that the boosting performance is guaranteed. The entrainment ratio (E_R) of the critical region increased to 5%. The numerical calculation results are in good agreement with the experimental ones. The flow field analysis of the numerical calculation shows that the spoiler elements installed at the tail of the ejector driving nozzle is useful. On the one hand, it can make the fluid mixing boundary increase. The petal-shaped fold appears, and the increase of the number of teeth can make more area of fluid mixing increases. On the other hand, the thickness of mixing area increases to 39.28%, the disturbing elements can make the axial velocity of driving fluid change into circumferential and radial velocity, the peak value of circumferential velocity changes from 0 to 5.5—20m/s, and the radial velocity increases from 25m/s to 30—47m/s. Swirling flow and radial turbulence make the ejector into three-dimensional momentum exchange. Under the sub-sonic condition of the momentum-enhanced elements, the entrainment ratio decreases, but the critical pressure point decreases, so that the supercharging capacity loses.

Key words: ejector, entrainment ratio, swirling flow, computational fluid dynamics (CFD), momentum transfer, mixing