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George Furey
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Nissan is putting a small 4 cylinder Cummins diesel in their Titan pickup. Not sure if you consider that a (good) small truck.
Peter, Definitely makes more sense now, didnt know the expansion ratio was so high on atkinson cycle engines. If only there was some way the to reduce the knocking effect then you could have a completely customizable engine i.e. you could control pretty much every variable. Would it be possible to design an engine using more conventional expansion ratios and "throttle" it by keeping the intake valve open longer at lower loads, thereby reducing throttling losses? That way it would be a normal engine at full load but would benefit by expanding the gases more when not using full throttle. Maybe I'm being redundant here, is this how that BMW works to reduce throttling losses? An analogy is that it would be similar to direct injection, use stoichiometric mode at high loads (for optimized power) and use stratified charge combustion for low loads(optimized fuel efficiency). Wouldn't this technology be especially good for highway cruising? (low fairly steady loads)
Peter, Some good points, however I still would think that once this design gets to stage II or even stage III prototyping the size could be significantly reduced. I can't predict what going to happen though so we will have to wait and see where this technology goes. As for my point on Atkinson cycle operation I still do not see why with a completely variable system you couldnt induce atkinson operation during part load conditions and switch back to regular otto cycle when the driver demands more power. From examining the engine used in the Prius, the only major difference is that the intake valve is held open for an extended period during the compression cycle, making the compression ratio smaller than the expansion ratio for increased efficiency. What I dont understand is why you couldn't program the valve-train to go back to normal otto cycle operation when more power is demanded, effectively increasing the power density over atkinson cycle and giving you the best of both worlds. Harvey, I know our best engineers will solve the energy density issue with batteries beyond lithium ion because the theoretical densities I have seen are just astounding. The problem I see with quick charging the very large batteries that are smaller than todays is charging efficiency and grid capacity. Lets say you have a battery with two times the capacity and one half the size of todays battery and you charge it in the same time as a battery from today. You're effectively putting four times the amount of energy in the same volume. Amplify this effect because people want their batteries charged very quickly and I could see the batteries getting very hot. How do you charge these compact batteries quickly without destroying them or requiring a massive cooling system? Lastly charging rate at your home is limited by the 240V hookup that most homes have. You can only put so much current through the wires before you trip a breaker somewhere in the system. Wouldnt very high charging rates require rewiring entire neighborhoods to handle at least 480V service?
@Harvey I myself would love to see the transition to electric vehicles however considering the orders of magnitude in energy density improvement batteries need before they can replace gasoline, combined with the rate at which the vehicle fleet replaces itself, I have to agree with SJC that the ICE is going to be here for many years to come, especially in heavy duty applications. @3peacesweet I thought the exact same thing, combining this technology with direct injection would allow for engines that are efficient at nearly all load and speed conditions. The top efficiency islands could be expanded to cover the majority of the engine map. This would have the side effect of reducing the advantage hybrids have over traditional drivetrains. Controlling valve lift and dwell timing could allow you to greatly increase the expansion ratio at part load and act like an atkinson cycle engine. At full load you could also get more HP, a disadvantage in Atkinson engines. You could also reduce throttle pumping losses as in the system Fiat uses @Peter XX Agreed this actuator is much too large to be viable in many engines, however you consider that the whole valvetrain would be replaced with several of these the increased size isn't much more. Also you have to consider that the model in the picture is based off of an experimental benchtop model in the earliest stages of prototyping. I have a strong feeling that a production model could be made much smaller. As for the competition, Fiat pulled off this feat on their multi-air engines, at least on the intake side, however as you said it still requires a camshaft. @GDB "Test results showed that the actuator was able to traverse an 8mm stroke distance in 3 milliseconds with consistent switching trajectories and very soft landings." I bet they probably went without springs to reduce the inertia of the moving parts, decreasing the amount of energy required to actuate the valve. Lower inertia also means you can rev to higher RPMs as long as the actuator can keep up. I would also imagine that if you were to have very high rate springs capable of closing very quickly the power requirements to overcome the spring force would be much higher than without a spring. Removing the spring also allows for the "soft landings" described in the article, possibly allowing for even lighter valves with even lower inertia
Nick- There an old article on here that used the OPOC in a helicopter. I agree power density is one of the main strengths of this engine.
Very interesting technology, depending on how they shape the lens they could create multiple ignition events in various places within the cylinder. My only concern is, what happens when the "window" gets dirty or covered in soot?
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Apr 20, 2011