Salt Survey Comparison of Pressurized vs Ambient Deck Air Intakes on JEFF (B) Hovercraft
Abstract
A survey was conducted on AALC JEFF (B) hovercraft to measure salt- spray loadings to an engine (No. 6) which was pressurized from the bag plenum as compared to the loading to an engine (No. 5) drawing ambient deck air. The average deck ambient salt loading in the small (1-50 micrometers) size range was 2 PPM as compared to 4 PPM in the bag plenum. An average 0.25 PPM salt in air entered No. 6. Wash water salinity indicated that the unpressurized engines had 1/10 the loading of the pressurized engine on this mission and 2/3 on more 'normal' missions (without frequency periods of idling to change salt samplers). Leakage bypassing the filters had been improved by a factor of 20 since early craft missions, but still dominated over inlet filter design as a source of salt loading to the unpressurized engines. Pressurization eliminated salt due to leakage, but still gave more loading of both salt and sand as compared to the unpressurized inlets. The pattern of paint stripping by spray and sand in the lift fan volute provided graphic evidence that proper selection of the source location for lift fan pressurized air could provided much cleaner engine air Temperature rise with pressurization was found to be lower than expected. If the pressure loss through the intake filter could also be reduced using cleaner lift fan air (permitting fewer filter elements), then the overall engine performance could be improved over previous predictions with a pressurized system. With any type of system, agglomerator or barrier type filter pads are required in order to minimize salt loading by 1-50 micrometers droplets, but with ambient air these pads should all be downstream of the spin tubes in order to avoid blockage by sand.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 02, 1981
- Accession Number
- ADA095564
Entities
People
- F. K. Lepple
- R. E. Ruskin
- R. K. Jeck
Organizations
- United States Naval Research Laboratory