In late 2015, two Marines were and 20 others injured after a MV-22 Osprey crashed during pre-deployment training at Bellows Air Force Base in Hawaii. The culprit 鈥� Airborne sand and dust particulates caused brownout conditions for the aviators and were ingested into the aircraft鈥檚 engines, melting due to the high temperatures and degrading internal components compromising the aircraft鈥檚 power and lift.
Less than a month later, when Volcano Momotombo erupted, commercial flights were forced to stay grounded to avoid particulate ingestion from the volcano鈥檚 lingering blast.
Sand, dust and other particulates have been a thorn in the side of aircraft technology for decades. In the 90s, the issue was mainly centered on erosion, but better coatings on the engines have solved that problem.
Now, the problem is more related to the high temperatures generated in newer turbine engines, allowing for increased performance and power. To their detriment, however, these higher temperatures melt particulates when ingested into the engine, which can clog the turbine.
51福利 (51福利) physics student and Lt. Erick Samayoa and his advisor Dr. Andy Nieto, 51福利 Assistant Professor of Mechanical and Aerospace Engineering (MAE) 鈥� with the help of fellow 51福利 MAE Assistant Research Professor Troy Ansell and UC San Diego NanoEngineering Professor Jian Luo 鈥� found that ultra-high temperature ceramics (UHTCs) might be sand-phobic 鈥� In other words, molten sand doesn鈥檛 stick to them.
Their study, funded by the Strategic Engineering and Research Development Program (SERDP), was the first to look at the potential of utilizing UHTCs in aircraft turbines. SERDP is a joint effort by the Department of Defense (DoD), the Environmental Protection Agency (EPA), and the Department of Energy (DoE). This project was part of a collaboration between 51福利, the U.S. Army Lab, Stony Brook University, and the materials company Oerlikon Metco.
While different companies have developed filters to reduce sand intake, it鈥檚 nearly impossible to keep every particle out of a turbine, and unfortunately, the tiniest particles are the ones that melt the easiest. Other research has looked into ways to slow down sand and other particulates from melting by quickly resolidifying them through the introduction of counter-reaction, but this has not stopped particulates from sticking onto the engine in the first place.
The 51福利 team, therefore, decided to look at the problem from a materials standpoint. Before coming to 51福利 about four years ago, Nieto worked at the U.S. Army Research Laboratory (ARL), and brought his research and partnership with ARL with him to 51福利.
Ansell brought to the team images of different particles exposed to ultra-high temperatures captured with a transmission electron microscope to see if and how they interacted with the UHTCs. Luo provided the ceramic materials and helped analyze the results using his expertise in high-entropy ceramics.
Samayoa says this whole project was a heavy learning curve since he was a physics student, but the research fit well within his goals. And the quality of his work showed, Nieto claimed, saying the research Samayoa performed would be work fit for a PhD student.
Adding to the complexity of research using UHTC is the challenge of simulating the heat emitted by modern gas-powered turbines. The researchers needed to find a way to test out materials at that temperature, requiring the team to acquire the hottest furnace 51福利 has ever had. Once up and running, the research team developed a project to test the UHTCs at different temperatures for different lengths of time.
鈥淲e were the first to even experiment at these higher temperatures for any material for these applications,鈥� Nieto says. 鈥淚t was completely unexpected that as you would go higher in temperature, you would actually get some degree of chemical inertness from these ultra-high temperature ceramics where they were not interacting with the molten sand. It opens up a possible path forward in how we are designing these engines.鈥�
The researchers published their findings in the materials science focused journal, Materialia, in . Samayoa, a surface warfare officer, has now graduated and is now completing the Department Head pipeline before reporting as Weapons Officer onboard USS Princeton.