Effect of the structure of backward orifices on the jet performance of self-propelled nozzles
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ORIGINAL PAPER
Effect of the structure of backward orifices on the jet performance of self‑propelled nozzles Bi‑Wei Fu1 · Si Zhang1 · Shao‑Hu Liu1 Received: 29 April 2020 © The Author(s) 2020
Abstract Self-propelled nozzle is a critical component of the radial jet drilling technology. Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance. To improve the working performance of the nozzle, the numerical simulation model is built and verified by the experimental results of propulsive force. Then the theoretical model of the energy efficiency and energy coefficient of the nozzle is built to reveal the influence of the structural parameters on the jet performance of the nozzle. The results show that the energy efficiency and energy coefficient of the backward orifice increase first and then decrease with the angle increases. The energy coefficient of forward orifice is almost constant with the angle increases. With the increase in the number and diameter, energy efficiency and energy coefficient of the forward orifice gradually decrease, but the backward orifice energy coefficient first increases and then decreases. Finally, it is obtained that the nozzle has better jet performance when the angle of backward orifice is 30°, the number of backward orifice is 6, and the value range of diameter is 2–2.2 mm. This study provides a reference for the design of efficiently self-propelled nozzle for radial jet drilling technology. Keywords Radial jet drilling technology · Self-propelled nozzle · Propulsive force · Energy efficiency · Cavitation model List of symbols Fj Propulsive force, N f Friction force, N Ff Viscous force, N FT Diverter resistance force, N mn Nozzle quality, kg an Accelerated velocity, m/s2 Fp Recoil force generated by the forward jet, N Fr Recoil force generated by the backward jets, N Fw Impact on the internal and external wall of the nozzle, N F Axial recoil force, N S Cross-sectional area of the orifice, m2 q′ Flow of backward orifice, m3/s v′ Average velocity, m/s v Axial average velocity of the cross-sectional area of backward orifice, m/s
Edited by Xiu-Qiu Peng * Bi‑Wei Fu [email protected] 1
School of Mechanical Engineering, Yangtze University, Jinzhou 434023, Hubei, China
v1 Forward jet velocity, m/s v2 Backward jet velocity, m/s S1 Cross-sectional area of the forward orifice, m2 S2 Cross-sectional area of the backward orifice, m2 Lh Length of the high-pressure hose, m dh Inner diameter of the high-pressure hose, m Pi Inlet pressure, Pa vi Inlet velocity, m/s C1 Energy coefficient of the forward orifice C2 Energy coefficient of the backward orifice uj Velocity component in the j direction, m/s ṁ + Source terms represent the effect of evaporation during the phase change ṁ − Source terms represent the effect of condensation during the phase change pv Vapor pressure, Pa p Mixture pressure, Pa Nb Bubble number density g Acceleration of gravity, m/s2 Fx Body force, N k Turbulence kinetic energy, m2/s2 u+
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