Abstract
The article discusses the possibility of improving the design of the turbine of a hydraulic drilling machine for drilling wells in very hard rocks and at considerable depths (5000–12,000 m). The analysis of the results of studies on the technical and technological characteristics of downhole drilling motors showed that it is impossible to ensure stable operation due to the limitation on the operating temperature, while with an increase in the flow rate of the drilling fluid, they do not provide the required power on the spindle shaft, and cannot reach high-speed drilling. In such conditions, turbodrills with a significant change in the profile of the stator and rotor blades and a reinforced support unit are most suitable. The paper presents an invariant mathematical model, which made it possible to determine the optimal geometric parameters based on preselected boundary conditions and the main performance characteristics of the turbine being developed. The results obtained were tested by the finite element method, which showed a convergence of 12.5%. At the same time, zones with the lowest and highest flow rates were identified. Additionally, this paper presents a comparative analysis of the obtained hydraulic turbine with turbodrills of the TSSH-178T and Neyrfor TTT 2 7/8 brands. In comparison with the domestic turbodrill, the developed turbine design shows a 13-fold reduction in its length and a 3-fold reduction in torque, provided that the maximum power is increased by 1.5 times. In comparison with the foreign analog, there is a decrease in length by 8.5 times, an increase in torque by 5 times, and in maximum power by 6.5 times.
Highlights
It is required to create an invariant model that allows for the identification of the optimal operating ranges, as well as to develop the geometric parameters of the turbine, enabling the required power to be generated at increased spindle shaft speeds [32,33]
The main factor by which we can achieve the set indicators is the geometry of the blades of the rotor–stator working pair, in view of obtaining the maximum indicators of torque and power [37,38]. This is why we focused on changing the geometry in further calculations
From the solution described above, we obtained the angle of inclination of the rotor blade (12.18 n) and the angle of inclination of the stator blade (12.18 n)
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. There are high-speed turbodrills in Russia, the rotational speed of which does not exceed 1300 rpm (revolutions per minute), for example, turbodrills developed by VNIIBT-Drilling Instrument These include models of turbodrills T-4 3/4, T-6 3/4, and TSSh-178T [19,20]. There are turbodrills whose rotational speed reaches 2500 rpm, for example, Neyrfor TTT 2 1/8 [21] and Neyrfor TTT 2 7/8 [22], developed by Schlumberger [23,24] These turbodrills have a significant limitation associated with their diameter, the small working area of the blades, due to which the hydraulic energy of the drilling fluid flow is converted into the rotation of the turbodrill shaft [25,26]. From the above technical limitation, it follows that it is necessary to develop a turbodrill with a rotation speed equal to 2500 rpm, and with the possibility of increased mechanical drilling speed in hard and abrasive formations, reducing the drilling time and reducing economic costs, while maintaining high reliability [27,28]
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