Study And Simulation Analysis On A New Type Of DTH Hammer

The percussion and rotation drilling is the most effective method of hard rock, pebbles gravel and broken formation drilling. The percussion and rotation drilling is used very widely because of its characteristics, such as high efficiency, excellent quality and security. Combining with other advanced boring method, multi-technics percussion and rotation drilling technique is formed. Its application fields are expanding, and it is playing a more important role in every fields of drilling engineering. At present, the technique is used widely in geological exploration and engineering of different formation.Under some conditions, there are various problems of whole-hole rotation in trenchless drilling, tunnel tubular shed construction, directional drilling and seafloor sampling drilling construction.In allusion to above problems, through general and detailed researches to DTH hammer and pneumatic rock drill, this paper uses the former people's researchment thought for reference, exploringly applies the elements of pneumatic rock drill to DTH hammer. Combining DTH hammer with pneumatic rock drill, use the high-pressure of pneumatic rock drill to drive DTH hammer. Setting the rotational mechanisn of rock drill into DTH hammer, this paper designs a new type of DTH Hammer with self-propelled round drill which can transfer the direct movement of the piston to the rotation movement of the aiguille. The new type of DTH hammer can adequately utilize the energy of return stroke of the piston and achieve self-propelled round of the aiguille It fully utilizes the energy of the constringent air to realize percussion and rotation. Such combination uses the respective advantages of DTH hammer and pneumatic rock drill and conquers their disadvantages. It makes a great signality to geological explorations and and engineering constructions.Comparing to the tranditional DTH hammer, this new type of DTH hammer uses the energy of the constringent air of the air compressor,transfers the linear movement of the piston to the rotation movement of the aiguille though a special structure. It realizes percussion and rotation movement of the aiguille.The operational principle and structural charactrristics of this new type of DTH hammer are introduced in this paper. The improved design of DTH hammer and design of key parts and suits are elaborated.Original working pattern of DTH hammer is changed, and the drill rotates when the piston returns. The drill turns when the friction between the DTH hammer and the bottom of the hole is small with the aid of bounce force. So the rotation of the rdill uses energy of teturn motion of the piston efficiently. So the high impact work and less time are obtained. Creative design of upper joint, long air distribution seat, screw, and special-purpose piston of the new type of DTH hammer is done.Relative theories of the DTH hammer with self-propelled round drill are studied by using some equations, such as air state equation, acceleration differential equation, and velocity differential equation, displace differential equation of piston, air flow equation, impact frequency equation, resistance equation of piston return, impact energy equation, and air consumption equation, etc.According to the mathematical model, advanced software MATLAB are used to simulate and calculate the DTH hammer, and then respective parameters of the DTH hammer are obtained. From the results of simulation, when the piston finish its impact stroke, the last impact velocity of the piston exceeds 6.7m/s, and the impact work reach 92N?m. Impact frequency is 26Hz, and the largest air consumption is 2.5m3/s.Compared with general DTH hammer, the conclusions we get are as follows: In the return stroke of the piston, the largest velocity of the piston is 4.6m/s, and the angular velocity of the DTH hammer is 3.685r/s. The largest linear velocity of the DTH hammer is 2.08m/s.Compared with conventional DTH hammer, the pressure of two chambers, acceleration, and velocity changed slowly. Velocity of the piston and rotary speed of the drill are all reasonable.So the the notch wheel and pawl mechanism of the DTH hammer is reasonable, and it can meet the requirements of use.The new type of DTH hammer uses the energy of the constringent air of the air compressor to realize the percussion and self rotation, so it expands the application fields of tranditional DTH hammer. The elements of the DTH hammer with self-propelled round drill is feasible, and the structure design is reasonable.The emulational analysis and the intensity calculation proves the the diversified parameter of the DTH hammer is correct. So it can be used in trenchless drilling, large-caliber purdah engineering, tunnel tubular shed construction, directional drilling and seafloor sampling drilling engineeringes, and makes a great signality to geological explorations and and engineering constructions.