Chapter 14: Hydrogen Engines

Flashcards covering key concepts from the hydrogen engines lecture notes.

What are the two main ways hydrogen can power aircraft engines?

Hydrogen fuel cells powering an electric motor, and hydrogen used in combustion engines (burned inside a piston or gas turbine).

Hydrogen is the most abundant element and is estimated to make up what percentage of all matter in the universe?

About 75%.

Under what condition would emissions from a hydrogen engine be minimal?

If the hydrogen is produced with renewable energy.

What are the two ingredients required for a hydrogen fuel cell?

Hydrogen stored on the aircraft and oxygen from the outside air.

What are the byproducts of the hydrogen fuel cell reaction?

Heat and water; no emissions.

How can the electricity produced by a hydrogen fuel cell be used in an aircraft?

To power an electric motor or to charge a smaller on-board battery.

How does hydrogen combustion compare to conventional fossil fuels in engines?

It has different burning characteristics requiring design modifications, but the general principles apply.

Which hydrogen usage method is less environmentally friendly and why?

Hydrogen combustion, because it still produces some emissions.

What is the main storage challenge for hydrogen in aircraft?

It takes up far more space than aviation fuel, and is often stored in the fuselage.

What is one way to reduce the storage volume of hydrogen and what is the drawback?

Store it as a liquid to reduce volume, but it requires cryogenic temperatures (~-420°F / -250°C) and may need reconversion to gas before use.

What factors determine the environmental impact of producing hydrogen?

Whether hydrogen is produced using renewable energy (lower lifecycle emissions) or fossil fuels (higher emissions).

Where is hydrogen typically stored in aircraft, and why does this matter?

In the fuselage rather than the wings, reducing space available for passengers or cargo.

What is the goal of this chapter on hydrogen engines?

To provide a general overview of how hydrogen-powered aircraft engines may operate and discuss the challenges involved.