Monterey, CA – At the Naval Post Graduate School's Rocket Propulsion Lab, there are several projects underway that could help the Navy reduce its use of fossil fuels. Some are several years out, like a pulse detonation combustor that could one day replace jet engines. Lab Director Christopher Brophy says by detonating fuel in a controlled way, it's 20% more efficient. "Now the challenge is doing it reliably, repeatedly and not having your combustion chamber be destroyed in the process," said Brophy. Then there's a project just days away from being installed on a ship. "We actually have been tasked to take existing gas turbine injectors that are in an operational engine, and run biofuel blends through the injectors, and see how they spray the fuel differently compared to what we're using right now," said Brophy. Brophy says something as small as the fuel spraying differently could burn a hole in the combustion chamber and the engine will fail. That would be a big problem since the injectors are set to be installed in a ship that will run on a 50/50 blend of bio and traditional fuel.
The push to use alternative fuels comes from Secretary of Navy Ray Mabus. He set the Navy's goal to get at least half its energy from non fossil fuel sources by 2020. On a recent visit to NPS, Secretary Mabus said energy security is national security. "It's a vulnerability because we buy too much fossil fuel from either potentially or actually volatile places on earth because we are susceptible to price and supply spikes," said Secretary Mabus. He adds that every time the price of a barrel of oil goes up $1.00, it adds $30-million to the Navy's annual fuel costs. Since many of the Navy's ships, jets and helicopters are equipped to take traditional fuel, it's looking for a direct replacement. "Today biofuel is a good bit more expensive. But one of the things that the Navy can do is bring a market," said Secretary Mabus.
At the Rocket Propulsion Lab, researchers experiment with biofuel and synthetic fuel.
Lab Director Brophy says they know 50/50 biofuel blends work while100% biofuel doesn't. So the question is, how high can you go? "Ultimately the Navy would like to increase that fraction of biofuel to 60%,70%, 80%," said Brophy. Researchers experiment with those various blends in a table top combustion chamber. With each test, they're looking to see if the blends behave the same as the fuel already in use. "We want the fuel to be nearly identical to how the pilot flies when he's running conventional fuels. He doesn't want to have to think about, well I have to run this engine at a more rigid throttle setting than a normal fuel. It should be a complete drop in replacement for an existing fuel," said Brophy.
With less than nine years to achieve the reduction in use of fossil fuels, Knox Millsaps thinks the goal is attainable. He chairs the department overseeing the Rocket Propulsion Lab. Millsaps points to the Navy's Great Green Fleet that is set to sail in 2016. "This would be sailing around the world on biofuels, 50/50 blends of biofuels. So if the Navy switched all their fuels to 50/50 blends you would just right there have a 50% reduction in the amount of fossil fuels, fossil drive fuels you use," said Millsaps. With the Great Green Fleet researchers will be able to see what long term effect if any the new fuel has on the existing systems. Also in support of the Navy's goal, this Fall NPS will begin offering degree and certificate programs focused on energy.