Testing volcanic-ash ingestion by a jet engine: approximating distal ash-cloud conditions

An experiment to test volcanic-ash ingestion by a jet engine is being planned for 2014 by a consortium of U.S. Government agencies and engine manufacturers, working under NASA's Vehicle Integrated Propulsion Research Program. This experiment will demonstrate the capabilities of advanced jet engine health management sensor technology for detecting and diagnosing incipient engine faults before they become a safety impact and to minimize loss of engine performance. The primary objective is to determine effects (physical, chemical, performance) on jet engines after hours of exposure to ash concentrations (1 and 10 mg/m³) representative of distal ash clouds (100's to >1000 km from a volcanic source), an aviation environment of great interest during explosive volcanic eruptions. A natural volcanic ash, collected from ground deposits of a previous explosive eruption will be used and candidate ash sources are being evaluated. Data from previous ash/aircraft encounters, as well as recent published data from airborne measurements of the Eyjafjallajökull ash cloud, suggest the ash used should be composed primarily of silicic glass particles of andesitic to rhyolitic composition (SiO₂ of 57-74%) with lesser mineral crystals, a few tens of microns in size. Collected ash will be commercially processed to < 63 microns in size (a practical limit with respect to handling and cost) with the expectation that the ash particles will be further pulverized in the engine during the test. Approximately 500 kg of processed ash will be needed for an 80 hour test (nominally planned). Although volcanic ash clouds commonly contain volcanic gases such as sulfur dioxide, this phase of testing will not include volcanic gas or aerosol interactions as these present complex physical and chemical processes beyond the scope of the planned experiment.