Design and Output Performance Model of Turbodrill Blade Used in a Slim Borehole
Small-diameter turbodrills have great potential for use in slim boreholes because of their lower cost and higher efficiency when used in geothermal energy and other underground resource applications. Multistage hydraulic components consisting of stators and rotors are key aspects of turbodrills. This study aimed to develop a suitable blade that can be used under high temperature in granite formations. First, prediction models for single- and multi-stage blades were established based on Bernoulli’s Equation. The design requirement of the blade for high-temperature geothermal drilling in granite was proposed. A Φ89 blade was developed based on the dimensionless parameter method and Bezier curve; the parameters of the blade, including its radial size, symotric parameters, and blade profiles, were input into ANASYS and CFX to establish a calculation model of the single-stage blade. The optimization of the blade structure of the small-diameter turbodrill enabled a multistage turbodrill model to be established and the turbodrill’s overall output performance to be predicted. The results demonstrate that the design can meet the turbodrill’s performance requirements and that the multistage model can effectively improve the accuracy of the prediction.
Design and Development of Turbodrill Blade Used in Crystallized Section
Turbodrill is a type of hydraulic axial turbomachinery which has a multistage blade consisting of stators and rotors. In this paper, a turbodrill blade that can be applied in crystallized section under high temperature and pressure conditions is developed. On the basis of Euler equations, the law of energy transfer is analyzed and the output characteristics of turbodrill blade are proposed. Moreover, considering the properties of the layer and the bole-hole conditions, the radical size, the geometrical dimension, and the blade profile are optimized. A computational model of a single-stage blade is built on the ANSYS CFD into which the three-dimensional model of turbodrill is input. In light of the distribution law of the pressure and flow field, the functions of the turbodrill blade are improved and optimized. The turbodrill blade optimization model was verified based on laboratory experiments. The results show that the design meets the deep hard rock mineral exploration application and provides good references for further study.
Slurry flow modelling by CFD
An attempt has been made in the present study to develop a generalized slurry flow model using CFD and utilize the model to predict concentration profile. The purpose of the CFD model is to gain better insight into the solid liquid slurry flow in pipelines. Initially a three-dimensional model problem was developed to understand the influence of the particle drag coefficient on the solid concentration profile. The preliminary simulations highlighted the need for correct modelling of the inter phase drag force. The various drag correlations available in the literature were incorporated into a two-fluid model (Euler-Euler) along with the standard k-e turbulence model with mixture properties to simulate the turbulent solid-liquid flow in a pipeline. The computational model was mapped on to a commercial CFD solver FLUENT6.2 (of Fluent Inc., USA). To push the envelope of applicability of the simulation, recent data from Kaushal (2005) (with solid concentration up to 50%) was selected to validate the three dimensional simulations. The experimental data consisted of water-glass bead slurry at 125 and 440-micron particle with different flow velocity (from 1 to 5 m/s) and overall concentration up to 10 to 50% by volume. The predicted pressure drop and concentration profile were validated by experimental data and showed excellent agreement. Interesting findings came out from the parametric study of velocity and concentration profiles. The computational model and results discussed in this work would be useful for extending the applications of CFD models for simulating large slurry pipelines.