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NRL's model of a Rotating Detonation Engine  (Source: nrl.navy.mil)
Currently, the Navy has 129 ships with 430 gas-turbine engines that burn $2 billion of fuel annually

The U.S. Navy is working on new technology for its gas-turbine engines in order to decrease fuel consumption without sacrificing performance.

The answer, according to the Naval Research Laboratory (NRL), is equipping current gas-turbine engines with Rotating Detonation Engine (RDE) technology. These engines could not only efficiently provide propulsion for Navy planes and ships, but also create electricity for an all-electric propulsion system.

The Navy currently uses gas-turbine engines that are based on the Brayton thermodynamic cycle, where air is compressed, combined with fuel, combusted at a constant pressure and expanded. This allows for propulsion or generating electricity, just like the RDEs. However, the Brayton cycle is less efficient than the detonation cycle.

Dr. Kazhikathra Kailasanath, head of NRL's Laboratories for Computational Physics and Fluid Dynamics, noted the following in a 2011 paper for the NRL Review:

The challenge with detonation engines is realizing the efficiency of the detonation cycle. Concepts such as oblique detonation-wave engines have failed to be able to recover the efficiency of this detonation cycle, because much of the energy of the inflow is bound up in kinetic energy, which does not increase the pressure and thus does not improve the efficiency. Pulse detonation engines have taken a different approach by creating an unsteady process that removes the requirement of having high velocity inflow. This creates a whole new set of issues, such as rapid initiation of detonations and the requirement of efficient detonators.

The rotating detonation engine takes a different approach toward realizing the efficiency of the detonation cycle. By allowing the detonation to propagate azimuthally around an annular combustion chamber, the kinetic energy of the inflow can be held to a relatively low value, and thus the RDE can use most of the compression for gains in efficiency, while the flow field matches the steady detonation cycle closely.

Currently, the Navy has 129 ships with 430 gas-turbine engines that burn $2 billion of fuel annually. By equipping engines with RDE technology, power could be increased by 10 percent while fuel consumption would decrease by 25 percent. The Navy could also save $300-$400 million annually.

Source: U.S. Navy



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RE: .
By Solandri on 11/3/2012 5:46:49 PM , Rating: 5
quote:
Why do you think the public is so nervous about nuclear power? Every time they start to become convinced that its safe there is another nuclear accident.

The "problem" with nuclear power is that it's an incredibly concentrated power source. A single nuclear reactor replaces about 7 coal plants, or about 5,000-15,000 wind turbines. And a nuclear plant typically has 2-4 reactors.

But when it comes to the consequences of accidents, people think in terms of 1 nuclear reactor = 1 coal plant = 1 wind turbine. Just like people equate 1 airplane crash = 1 car crash and are afraid to fly even though they're more likely to die while riding a car.

If you normalize for the amount of power generated, nuclear turns out to be the safest power source man has ever invented. Yes a single wind turbine is safer than a nuclear reactor. But the 10,000 wind turbines needed to equal the nuclear reactor's power output turn out to be cumulatively more dangerous.

The only other power source which is comparable to nuclear in terms of energy density is hydro. A hydroelectric dam on a large river has a generating capacity similar to or even exceeding a nuclear plant with multiple reactors. This is the reason the worst power generation accident in history (est. 170,000 killed, 6 million buildings destroyed, 11 million people evacuated) was the failure of series of hydroelectric dams. But water is something we deal with every day, while nuclear decay is just an abstract concept. So people fear nuclear while they have no problem with the more dangerous hydro.


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