Yingxin Yang

Prediction Method and Experimental Study of Cone/Bit Speed Ratio of Roller Cone Bit

Based on fundamental theory and proceeding from major factor influencing the cone/bit speed ratio, the calculation model for calculating the average cone/bit speed ratio is to be derived. To contrast verify model calculated results with experimental results, they are closely coincide with each other. And further amend the model associating with tooth row and cone structural characters and drilling environment to make the cone/bit speed ratio more reasonable than calculation model. The cone/bit speed ratio calculation model is simple. The parameter in the model is precise and it is easy to get and convenient to calculate practically. The cone/bit speed ratio calculation model provides roller cone bit design, analysis and rock breaking mechanism research with effective theoretical foundation. The model is of high value for application.

Kinematic and bottom-hole pattern analysis of a composite drill bit of cross-scraping:

For improving the drilling efficiency of polycrystalline diamond compact drill bit, a novel polycrystalline diamond compact drill bit is presented with a new rock-breaking method named as cross-scraping. In the novel polycrystalline diamond compact drill bit which is referred to as a composite drill bit, polycrystalline diamond compact cutters are mounted on rotary wheels as major cutting elements, and as a result, mesh-like scraping tracks are formed in the outer radial area of the bottom-hole. Rock-breaking method of the composite drill bit causes both shearing and fracture failure of the bottom-hole rock, which will greatly increase the rock-breaking efficiency and will prolong the bit service life. By analyzing the complex motion of cutters on the composite drill bit, velocity and acceleration models of the cutters, as well as wheel/bit speed ratio model of the bit are established in accordance with the geometric relationship between cutters and bit body in a compound coordinate system. In simulation examples, motion tracks, velocity and acceleration features of the cutter and especially the bottom-hole pattern are analyzed. Further, indoor experiments are conducted to test the mesh-like bottom-hole pattern and rock-breaking features, which have proved the accuracy of the analysis model of the composite drill bit.

DESIGN AND TRIAL OF INTELLIGENT SLIDING BEARING SYSTEM

A patented intelligent sliding bearing system of roller cone bit is invented to monitor radial wear and to stop the running of bearing automatically when the wear reaches the predetermined limit so as to prevent the wear-induced cone loss by early warning. In this paper, the basic operating mechanism of new bearing is stated and discussed. A series of tests are conducted to investigate the mechanical features and the reliability of the new bearing system. The performance of the system is proven to be adequate by the test results.