50% Efficiency Boost From New Fuel Injection System

chudnall notes a Technology Review story on a new gas engine injection system that promises increased efficiency of up to 50%. "The key is heating and pressurizing gasoline before injecting it into the combustion chamber, says Mike Rocke, Transonic's vice president of business development. This puts it into a supercritical state that allows for very fast and clean combustion, which in turn decreases the amount of fuel needed to propel a vehicle. The company also treats the gasoline with a catalyst that 'activates' it, partially oxidizing it to enhance combustion."

Re:Not just "similar" to a diesel

[0100010001010011]

Yep, sounds exactly what it is.

Transonic's injection system varies from direct injection in two ways: it uses supercritical fluids and doesn't require a spark to ignite the fuel. The supercritical fluid mixes quickly with air when it's injected into the cylinder.

Not sure what is considered 'super critical' but diesel fuel under 180 MPa/26,000 psi is pretty super critical to me.

Once the fuel is injected into the piston, the heat and pressure are enough to cause the fuel to combust without a spark (similar to what happens in diesel engines), which also helps provide fast, uniform combustion. Ignition can be timed to happen just when the piston is reaching the optimal point, so it can convert as much of the energy in the gasoline into mechanical movement as possible, without wasting energy by heating up the combustion chamber walls, as happens in conventional technologies. The company has developed proprietary software that lets the system adjust the injection precisely depending on the load put on the engine.

So it sounds exactly like a diesel engine or VW's TSI gasoline engine. [wikipedia.org]

Running Very Lean Re:Same old snake oil

[AJ Mexico]

It's been known for a long time that engines will run very efficiently if you run them very lean. In TFA, you will see that's what these guys are doing. The problem is that the engine then runs very hot, and the thing wears out in short order, or you have to make it out of unobtanium. They are also using unusually high pressures and temperatures. In the fine print, you will see they still have some work to do on verifying that the engines will last very long under this treatment.

So, yes, it will get great miles/gallon, but probably not very many miles/engine.

NOx and emissions?

[Matt_Bennett]

With the increased temperature of ignition, how does this perform with respect to emissions? Since the atmosphere is mostly Nitrogen, and with higher combustion temperature, the greater the NOx. I scanned TFA, but there doesn't seem to be anything on how this technology performs WRT combustion byproducts (by this, I mean beyond CO2 and H20).

This reminds me of articles in Popular Science during the 70's touting columnist (and notable mechanic) Smokey Yunick and his super efficient engine that also used pre-heating of the intake charge, but I think the technology of fuel injection hadn't moved far enough to get to this level of direct injection.

Sounds like something else...

[sackvillian]

This article [technologyreview.com] describes a very similar process from a New York company that uses supercritical diesel fuel -- and they report much more sensible efficiency gains of up to 10%. They've only tested in a lab setting so far though.

I found the article because I was looking for the supercritical points of gasoline, which is a complex mixture of many different hydrocarbons, making the critical points very tricky to estimate. Turns out they are 720K and 60Mpa, from the article above. Their system achieves temperatures this high (almost 400 degrees higher than normal fuel system operations) using exhaust heat. Given that higher temperatures mean improved efficiency, I'd buy the 10% they propose -- though I remain very skeptical abut the 50% proposed in this article.

Vapor...

[Scyth3]

This sounds exactly like what Smokey Yunick claims to have engineered back in the day. http://www.legendarycollectorcars.com/featured-vehicles/other-feature-cars/smokey-yunicks-hot-vapor-fiero-51-mpg-and-0-60-in-less-than-6-seconds-see-and-hear-it-run-in-our-exclusive-video/ [legendaryc...orcars.com] Basically it uses hot gas vapor to improve fuel efficiency. It basically doubled the mileage of the Fiero's iron duke motor. Link to diagram: http://farm4.static.flickr.com/3190/2738903116_71abf7785c.jpg [flickr.com]

Partially oxidizing?

[Nerdposeur]

I don't even understand what it means to "partially oxidize" the fuel ahead of time. Isn't oxidizing fuel, by definition, burning it, since fire is an oxidation reaction? If so, why isn't "pre-oxidized fuel" like "pre-eaten food?" In other words, wouldn't it mean wasting fuel?

Surely my pathetic chemistry knowledge is at fault here, right?

Re:I'm sceptical

[Wiarumas]

I don't think its that unbelievable. Its just a matter of scaling. A 50% boost to 15MPG is 23MPG. 20MPG is 30MPG. I've seen cold air intakes add 1-5 MPG on certain cars that get MPG in the 15-30MPG range. So, I don't think its too outrageous of claim. Might not be the holy grail of fine tuning a Prius to get another 30MPG, but I'm sure it probably will increase it MPG at least somewhat. In the end, its all about ROI. Will this tack on another 4k to the sticker price, or can this be implemented without too much hassle? And repair cost? Is it durable? Etc.

Re:I'm sceptical

[bkaul01]

Modern gasoline engines running at their peak thermal efficiency points are at about 35%. Diesels are typically in the 40% range. But those thermal efficiency numbers are a bit tricky ... it's not even theoretically possible to get any work out of an engine using a thermodynamic cycle that's 100% efficient - the ideal Carnot cycle would be on the order of 70-80% across the same temperature difference. In the real world, something on the order of 50% thermal efficiency is probably attainable. Right now, we're working to push Diesels towards 45%, and it's requiring things like waste heat recovery systems - running a bottoming cycle to recover some of the wasted exhaust energy. There are a variety of more advanced cycles and combustion modes being actively researched too.

Generally speaking, a gasoline engine's peak efficiency is achieved when it's wide-open and running at peak load. At other operating conditions, the efficiency is lower due to a variety of factors. One of the ways we're looking at improving low-load operation is by using what's called HCCI (homogeneous charge, compression ignition) combustion - like diesel, compression ignition is used, but like gasoline engines, the fuel and air are premixed. It sounds like that's what they're probably using here, with the supercritical injection being used to help enhance and control the ignition process (a big difficulty with HCCI).

I don't buy that they could increase the peak thermal efficiency by anywhere near 50%, or that they could increase the thermal efficiency at a given operating condition by that much through supercritical injection alone. If they're comparing HCCI to traditional stoichiometric SI combustion, though, it could get close to that at low-load points where the throttled SI engine is at its worst efficiency points. The supercritical injection isn't the direct cause of that gain, but an enabling technology to help facilitate HCCI operation. All else being equal (i.e. same combustion regimes, etc.), the injection technology could only have an impact on the fuel/air mixing and thus the combustion efficiency (i.e. how much of the fuel is burned completely), which is already well over 90%; there's just not much room for improvement there.

Even if it doesn't increase the peak thermal efficiency of the engine at all, though, it could make a significant difference in vehicle fuel economy by increasing the efficiency at low-load, off-peak conditions. Most of the FTP and NEDC drive cycles (US and Europe, respectively) are at low speed conditions, with quite a bit of idling and cruising, but very little hard acceleration. Increasing the low-load efficiency of the engine will have a disproportionate effect even if the peak efficiency remains unaffected.