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.
Finite element analysis of surface indentation on turbo-drill thrust ball bearing
ABSTRACT In harsh drilling conditions (e.g. abrasive drilling fluid), turbo-drill thrust ball may suffer from raceway surface indentation under the high axial load. The indentation can cause early failure of the bearing components. This paper establishes a micro-scale finite element model (FEM) to discuss the raceway surface indentation resulted from solid particle. For the sake of simplicity, the interaction between steel ball and solid particle as the latter is pressed into the raceway surface was depicted by axial and circumferential displacements. The distribution of stress and strain in solid particle and raceway surface was obtained from the finite element analysis. Through the discussion on solid particle ellipticity and the effect of friction coefficient on indentation features, it is learned that the variation in ellipticity has a slight impact on indentation depth, but a marked effect on raceway surface deformation; the friction coefficient has a significant impact on indentation edge shape and bottom centre of indentation. The simulation results provide a valuable reference for prevention of bearing raceway indentation.
Surface roughness monitoring by singular spectrum analysis of vibration signals
Abstract This study assessed two methods for enhanced surface roughness (Ra) monitoring based on the application of singular spectrum analysis (SSA) to vibrations signals generated in workpiece-cutting tool interaction in CNC finish turning operations i.e., the individual analysis of principal components (I-SSA), and the grouping analysis of correlated principal components (G-SSA). Singular spectrum analysis is a non-parametric technique of time series analysis that decomposes a signal into a set of independent additive time series referred to as principal components. A number of experiments with different cutting conditions were performed to assess surface roughness monitoring using both of these methods. The results show that singular spectrum analysis of vibration signal processing discriminated the frequency ranges effective for predicting surface roughness. Grouping analysis of correlated principal components (G-SSA) proved to be the most efficient method for monitoring surface roughness, with optimum prediction and reliability results at a lower analytical-computational cost. Finally, the results show that singular spectrum analysis is an ideal method for analyzing vibration signals applied to the on-line monitoring of surface roughness.