Structure parameters of DTH reverse circulation drill bit secondary ejector device

Key words:  DTH hammer  reverse circulation  drill bit  ejector device  structure parameter

Abstract:

The secondary ejector device can effectively improve the reverse circulation effect of the hollow through DTH hammer drilling technology. In order to determine the structure size, the influence of the four structure parameters on the the ejector coefficient n was studied by computational fluid dynamics (CFD) simulation. The structure parameters are the secondary injector hole diameter d, the center hole diameter D, the injector hole angle θ, and the distance h from the injector hole to the reverse circulation drill bit bottom. And the CFD results were verified by the experimental method. The results show that with the secondary ejector device structure parameters d, D, θ and h changing, the reverse circulation effect changes. And there is a structure parameter combination to achieve the best reverse circulation effect. Considering the impact effects of the four parameters, the more reasonable structure parameters are as follows:d=11 mm, D=44 mm, θ=30 °, h=180 mm. In addition, the laboratory experiment results agree well with the numerical simulation results, which shows that CFD simulation can be used to optimize the structure parameter, and the above structure parameters are reasonable.