Design Optimization of Valveless DTH Pneumatic Hammers by a Weighted Pseudo-Gradient Search Method

[+] Author and Article Information
L. E. Chiang

Dept. of Mechanical Engineering, P. Universidad Católica de Chile, 4860 Vicuna Mackenna Ave., Santiago, Chile

E. B. Stamm

Drillco Tools, 1387 Américo Vespucio Ave., Santiago, Chile

J. Mech. Des 120(4), 687-694 (Dec 01, 1998) (8 pages) doi:10.1115/1.2829332 History: Received June 01, 1997; Revised July 01, 1998; Online December 11, 2007


A design methodology for Down-The-Hole (DTH) pneumatic hammers used for rock drilling is proposed which renders an optimal design for a given set of constraints. A generic non-linear dynamic model developed by the authors is used to compute the hammer performance. This model consists of a set of six differential equations plus a set of twenty non-linear polynomial equations. In addition there are parameter range restrictions given by fabrication and operational standard procedures. In any given application, magnitudes such as power, impact energy, frequency, efficiency and mass flow may be sought for optimality. However these magnitudes must be computed by integration after solving the dynamic model over an entire cycle, thus traditional optimization methods for non-linear equations that are based in gradient information are not suitable. Hence a method that uses secant information is used to approximate the gradient of the space of design variables. Several prototypes using this optimization method have been designed and field tested. The results are in agreement with predicted values.

Copyright © 1998 by The American Society of Mechanical Engineers
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