Pneumatic Hammer Mechanism Computer Simulation

To drilling costs at present being with high, the deep and complicated-formation well's ROP being with low and being aptly to produce deviation problem ,the high WOB problem of horizontal well and large-diameter surface hole etc, the paper comprehensively analyses the application prospect, development and the relevant literature of the DTH hammer at home and abroad. Because the DTH hammer has. the advantages such as the lower RPM, the lower WOB, controlling deviation easier, and the littler quantity of the circulation leakage and the drill collar, it avoids the complex and costly combination of BHA, and it reduce cyclic stresses and wear, widely improve the ROP and reduce the drilling time and costs, especially in the surface of the large-diameter well.Through analyzing the DTH hammer structure, the paper emphasizes the following three questions: firstly, the bit impacts the drilling time and costs directly, and the paper discusses the development and history of the bit particularly, analyses the advantage and disadvantage of different end shapes of the bit and analyses flat-bottomed bit and how to improve the application effect of roller flat-bottomed bit. It gives the theory basis for the way how to select DTH hammer bit.Secondly, according to the principle of the kinematics, dynamics, gas dynamics and thermodynamics, the paper sets up the mathematics and dynamics modal, which includes gases equation, gasses energy balance differential equation, gas flow equation, gasses adiabatic equation and the deducing of the performance parameter of mathematical expression, for the purpose to describe the working process of the DTH hammer. It suppose the emulational condition through analyzing the principle of the DTH hammer, emulates the working process of the DTH hammer according to difference finitude theory, and draws the pressure-time curve, velocity-time curve, velocity-displacement curve and time-displacement curve which indicate the inside motivity process of the DTH hammer. The computer computes the final performance parameter of the DTH hammer according to the DTH hammer recipating several cycling and the results tending to stabilization, and outputs the results which includes the periods, single impact energy, impact frequance, impact velocity, piston's journey, impact power, gas-consuming and available thermal power.Finaly, the paper discusses the performance of the DTH hammer is influenced by its performance parameter which is related with many factors such as air supply pressure, piston mass, back pressure, distribution journey, structure journey, fore-and-aft gas cell area, fore-and-aft gas cell longness and fore-and-aft gas cell entrance area etc. Owing to spatial confined, the paper enumerates air supply pressure and backpressure which influence the working parameter of the DTH hammer only.