Stories from the Field,Fundamental Questions and Solutions - Measurement While Drilling Signal Analysis, Optimization and Design - page 21

U. S. Patent 4,785,300 or Chin and Trevino (1988) solved the problem by
placing the rotor downstream as indicated in Figure 1.4a. The rotor, now “stable
open,” is augmented with special tapered sides. Torques required to turn, stop
or speed up the rotor are much lower than those associated with upstream rotors.
From a telemetry standpoint, this means faster position modulation requiring
less torque and power, or, much higher data rate. Of course, mechanical
considerations are a small part of the problem. Downhole signal enhancement
and surface noise removal are equally important, as noted earlier. In our
research, all are addressed and fine-tuned to work in concert to provide a fully
optimized system.
Figure 1.4c. Velocities for erosion and pressure analysis.