MAE professor studying lubricants for electrified aircraft as part of NASA project

Wednesday, December 4, 2024

Media Contact: Tanner Holubar | Communications Specialist | 405-744-2065 | [email protected]

As unmanned aircraft evolve, so do the technical aspects that allow them to function.  

A research project in the College of Engineering, Architecture and Technology will delve into energy-efficient lubricants for electrified aircraft, especially for electrified vertical takeoff and landing (eVTOL) vehicles. The project is a one-year NASA Oklahoma EPSCoR Rapid Response Research project. 

Dr. Pranjal Nautiyal, assistant professor in the School of Mechanical and Aerospace Engineering, is science-investigator on the project while Dr. Andy Arena, professor and Cunningham Chair of MAE, is principal investigator.  

Nautiyal said the project's goal is to develop low-viscosity lubricants that help improve the flying range and performance of these aircraft. This would reduce energy loss in the aircraft's power trains.  

A challenge with low-viscosity lubricants is that they form a thinner fluid film between moving parts, which results in more metal-to-metal contact.  

"This can lead to higher friction, more surface damage and ultimately, mechanical failures," Nautiyal said. "To solve this, we introduce additives called friction modifiers to the lubricants. These additives form protective and lubricious thin films on surfaces in motion, reducing friction and wear. In electrified aircraft, electrical currents can affect how these additives work, which we don't fully understand yet. This project aims to investigate how electric fields impact the formation and behavior of these protective films, which will ultimately enable the design of improved lubricants for electric aircraft." 

Dr. Pranjal Nautiyal

With it being a rapid response research project, it is intended to be part of NASA's effort to quickly advance the technology for electrified aircraft, especially its eVTOL program. Research is underway to develop lubricants that help mitigate friction and wear, as well as cooling the components of the motor.  

The low-viscosity lubricants being studied are hydrocarbon-based and water-based. Hydrocarbon-based lubricants are traditionally used in aircraft. Water-based lubricants are not widely used, but they show immense promise for cooling electric motor components.  

Nautiyal was inspired to pursue this research project for two reasons: the scientific standpoint and the challenge posed by the reliability of these types of vehicles. He said his research team researches tribology, the study of friction, wear and lubrication.  

"The mechanisms of friction and lubrication traditionally were thought of as being influenced by mechanical stresses and temperatures," Nautiyal said. "Now it seems that electric currents can also have an important role to play in that." 

Aircraft with electrified power trains are challenging due to electric currents causing damage to gears and bearings, such as electrical pitting, spark tracking, frosting and fluting failure. It is expected that as electrified aircraft continue to develop higher power capabilities, these problems will only become more challenging.  

"This is why it's important to study how lubricants perform in electrified environments, something that hasn't been thoroughly explored before," Nautiyal said.  

Two types of friction modifiers, one an oil-soluble molecule and one a water-soluble liquid will be studied during this project. These will be added to low-viscosity synthetic fluids.  

"Using a specialized in-situ tribometer, we will examine how electric fields influence the growth and friction-reducing properties of the protective films formed by these additives," he said. "We'll also analyze the nanoscale structure and chemical composition of these films to better understand the mechanisms behind their formation under electrified conditions." 

Nautiyal sees this project as something that will enable a host of new technologies in electric vehicles and aircraft. He said this project, the first for Nautiyal working with NASA, is exciting because the organization is at the forefront of the development of electrified aircraft.  

"We are working very tightly with our NASA collaborator," Nautiyal said. "In fact, when the solicitation came out, cooling and lubrication technologies were one of the listed topics. So, they really cared about understanding lubricants for eVTOLs. We will be getting their feedback as we pursue the experiments, and when we see any surprising results, if we must pivot, we will be working with them closely." 

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