A Comparative Study of Helicopter Engine Air Particle Separator Technologies

An investigation into the efficacy of helicopter engine sand filters is conducted. Engine Air Particle Separation devices are broadly split into three categories: Vortex Tube Separators, Integrated Particle Separators, and Inlet Barrier Filters. The first two are inertial separators that scavenge particles by centrifugal force; the latter traps particles on its surface, but all three are designed with the aim or removing all particles from the engine bound air. Each technology is different, which gives rise to varying levels of efficacy. The current work uses low order analytical and numerical models to explore these differences and introduces a metric for quantifying the quality of air-particle separation performance. The vortex tube separators exhibit a high efficiency and low pressure drop, but require auxiliary power to operate and experience considerable drag at high forward speeds. Inertial particle separators do not achieve the high separation efficiencies of the vortex tubes or barrier filters, but have a large mass flow to frontal area ratio, hence low drag. Inlet barrier filters are highly efficient at removing particles and improve in this over time due to the accumulation of particles, but at the expense of a temporally increasing pressure drop. The new metric is a quality factor that can be used to directly compare separation technologies for helicopter. Its application is demonstrated by the inlet barrier filter which, when clean, is the best performing device, but over time deteriorates in quality due to the accumulation of particles.