Erosion And Deposition Comparison Of Biochar, Pumice, And Arizona Test Dust On Titanium Coupons

A study was conducted to determine the different behavior between sand, volcanic ash, and wildfire ash when ingested by an aircraft engine, with a focus on erosion and deposition. In the field of ingestion research, sand and volcanic ash have been studied numerous times, but no studies have been conducted on wildfire ash. As wildfires become more prevalent and dangerous, it is important to begin to characterize the damage wildfire ash particles can cause as aircrafts fly through ash clouds. Arizona Test Dust (ATD) was used to simulate sand, pumice for volcanic ash, and biochar for wildfire ash. A comparison was made to both validate the testing procedure and set up as well as determine where the biochar fit with well-known particulates. Preliminary testing suggested improvements to the testing procedure were needed to eliminate large particles and clogging of the injector. These preliminary tests also showed interesting results of deposition with biochar which was further investigated in this study. To address the concerns that were presented during the preliminary testing, the particulates were milled down then separated into to the desired size range of 50-150 microns using a sieve shaker. Additionally, the rig was modified to better accommodate biochar. Then, the particulates were fed into a free jet at 9 g/min flowing at Mach 0.65 before impacting a titanium coupon, used to simulate a compressor blade. The surface roughness of each coupon was measured before and after testing to characterize the erosion and deposition caused by each particulate. A visual inspection was conducted on each coupon before and after testing using a 3D profilometer. The surface roughness showed the largest increase on coupons exposed to ATD, then pumice and finally biochar. These results indicate that ATD is the most erosive, then pumice, and biochar causes the least erosion. The visual inspection confirmed these results and showed the greatest deposition with biochar. There was some deposition with ATD and little to know deposition with pumice. Overall, this study validated the testing procedure and rig, especially for the use of biochar allowing for future studies to use this rig and further explore the deposition caused by biochar. This study indicates that aircraft with prolonged exposure to wildfire ash should have additional inspections completed to check for harmful deposition.