Jim Heidmann of Glenn Research Center (Cleveland, OH) and Jason Welstead of Langley Research Center (Hampton, VA) have led NASA efforts to develop all-electric and hybrid-electric designs for large passenger aircraft. Using low-carbon propulsion technology, they are exploring how planes can be redesigned and configured.
NASA Tech Briefs: How is a hybrid aircraft like a hybrid car?
Jim Heidmann: In the approaches we’re considering, there are both gas turbine and electric power sources to draw from powering the vehicle. There are many ways you can configure the aircraft to take advantage of both those power sources. That’s what we mean by hybrid gas electric propulsion, and getting away from pure gas turbine power generation for aircraft.
NTB: How is the electricity generated?
Heidmann: In most configurations, you have a battery, like you would in a hybrid car. The battery can then be charged in different ways, in flight or on the ground. You have power distribution systems that can, depending on the configuration, distribute the power from the gas turbine and from the battery (or fuel cell) to the propulsors, which are the fans that propel the vehicle through the air.
NTB: What type of redesign is needed to make hybrid aircraft possible?
Jason Welstead: When you say “hybrid,” there are different levels. The lowest level is turboelectric, which is when all the energy is provided through hydrocarbons, and that energy is converted through a turbogenerator. You can have thrust from turbofans, but also have electric power coming from the turbofan and being distributed to other propulsors. Then, you can have combinations of turboelectric with batteries or solid oxide fuel cells. Finally, you can have full all-electric vehicles.
Heidmann: With a traditional gas turbine turbofan engine, the propulsor, or fan, is closely coupled to the core, or gas generator, where you’re burning the fuel. These concepts allow you to start to decouple the propulsor from the gas generator, from the power generation source, so you can get very creative in terms of where you put the propulsors.
NTB: Why is it so important to have a hybrid plane?
Heidmann: Ultimately, if you can get to all-electric, where you no longer have the gas turbine and you’re no longer burning fuel on the vehicle, then you have the opportunity to reduce carbon impact on the environment, because you are using cleaner energy sources for power. Hybrid is a step in that direction.
Welstead: The distribution of power through electrical means can also enable a fundamental change in the architecture, which will heavily contribute to a step change in fuel benefit. With the advances in the electrical systems, the fundamental way that we design aircraft is really starting to shift. These systems are real. These are no longer items that are way off on the horizon.
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