| The current drilling working in oil field is mainly concentrated in deep wells and ultra deep wells. Due to high temperature, high pressure and large formation stress in deep Wells and ultra deep wells, in order to prevent the high pressure fluid of the formation from overflowing, the density of drilling fluid must be large enough. Adapting to the condition of high temperature and high pressure, high steep and complex ground and high density drilling fluid, turbodrill has been widely used in oil field drilling. However, because of the large axial hydraulic load of thrust bearing, which affects the working life of thrust bearing, thereby the service life of the turbodrill is shorten, which will lead to a low work efficiency. Therefore, it has an important theoretical significance and application value to reduce or eliminate the turbodrill hydraulic load and to improve turbodrill service life.Aiming at a reduced working life issue produced by large turbodrill axial load, Refering to the research status of domestic and foreign turbine drill, hydraulic balance system, multi-stage centrifugal hydraulic balance systems and related hydraulic balance system, this paper proposed a balance device in the design of turbine section. Due to the large size turbodrill’obvise influence on hydraulic balance system, this paper designed the larger size φ240 turbine drill, especially the turbine stator and rotor structure. This paper drew the the general assembly drawing of turbine section, and checked the turbine shaft, the spline and the housing. This paper used the Bezier curve for turbine blade design, obtained a requirement of 184 stages by CFD simulation analysis. Therefore, there are two turbine, each part placed 92 turbines sections, in the design of the turbodrill.This paper proposed two kinds of balance devices, the disc and drum balance device and the drum balance device.The high pressure fluid inside the turboshaft flows into the cavity of balance device. According to φ240 turbodrill performance parameters of the CFD simulation analysis, two disc and drum balance devices or two drum balance devices are needed in a turbine section. The main components of the disc and drum balance device and the drum balance device were designed and Fluent was used to analyze balance force, pressure drop and discharge of 100 kinds of the disc and drum balance device model under the condition of different axial clearance (0.1,0.2,0.3,0.4, 0.5,0.6,0.7,0.8,0.9,1.0 mm) and radial clearance (0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8, 0.9,1.0 mm). The balance force, pressure drop and discharge of 10 kinds of the drum balance device model are analyzed by Fluent under the condition of different radial clearance (0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0 mm). Through analysing and comparing the disc and drum balance device and the drum balance device, the disc and drum balance device was selected as balance device in the hydraulic balance system due to its high efficiency.The forced surfaces of the balance cavity are analyzed to study the influence of forced surface on balance force under the condition of different axial clearance and radial clearance. The eccentric motion analysis was carried out on the thrust bearing to avoid the radial friction. This paper studied the regression analysis of balance force, discharge caused by the variation of axial gap. The main conclusions and results are as follows:I The choice of balance device and gap size optimization:(1) The disc and drum balance device was chosen to use in the hydraulic balance system due to its high efficiency. In the process of working, there is a large leakage and energy loss, low efficiency in the drum balance device because the gap between the drum and the drum base is large. However, the disc and drum balance device can improve the hydraulic balance efficiency by adjusting radial clearance and axial clearance. Thus the disc and drum balance device was chosen to use in the hydraulic balance system.(2) The radial gap size of the disc and drum balance device is determined to be 0.5 mm or 0.6 mm. In order to avoid radial friction, the radial clearance should be greater than or equal to 0.5 mm by calculating the eccentric movement of the centralizer bearing. Through regression analysis, the radial clearance should be greater than or equal to 0.7 mm. Along with the increase of axial clearance, balance force curve has a downward trend, which can not produce a good balance effect. Therefore, the radial clearance can choose 0.5 mm or 0.6 mm.(3) The axial clearance of the disc and drum balance device should be designed as far as possible to be near zero clearance. When the axial clearance ranges from 0.4 to 1.0 mm, due to the large axial clearance, while the radial clearance equals to 0.5,0.6mm, the device work as the drum balance device, low efficiency. The axial clearance should be as far as possible to to be near zero.II Balance force, pressure drop, leakage of the disc and drum balance device:(1) Simulation results of balance force in the disc and drum balance device accord with the theoretical value. When the radial clearance equals to 0.5 or 0.6 mm, the disc and drum balance device can balance the axial hydraulic load of turbodrill. According to the curve regression analysis of the balance and leakage influenced by various axial clearance, both radial clearance can produce balance force of 81.39496608kN. The simulation analysis accords with theoretical caculation.(2) In order to ensure the leakage is as little as possible, the axial clearance must be controlled as small as possible. Due to the obvise influence of the axial clearance on the leakage, in order to reduce the leakage as much as possible, the axial gap should be near to zero. |
