Techniques for improving the performance of two-stage pneumatic injectors

Effects of barrel roughness on the performance of two-stage pellet injectors were studied experimentally and numerically. It was found that a 50% roughness reduction (from 0.5 to 0.25um) allows a 6-8% increment of pellet speed for assigned conditions in the pump tube. Further improvements were obtained by inserting a resonating cavity of appropriate shape and size between pump tube and barrel. The advantages of this configuration consist of a reduction of temperature levels and a further 6-8% increment of pellet speed.