Transonic Combustion - SAE Paper 2

[TStaples]

thread71-267518

Since the prior thread is closed, I'm posting this in a new thread referencing the original thread. I previously posted that when new technical information became publicly available, I would link it here.

On October 25, 2010, Transonic Combustion presented an SAE technical paper detailing it's novel new injection ignition combustion process at the Society of Automotive Engineers 2010 Powertrain Fuels and Lubricants Meeting in San Diego CA.

Link:

http://papers.sae.org/2010-01-2110

-Tony Staples

http://www.tscombustion.com

 

[dicer]

Okay and?
What do you know about it?

 

[dgallup]

So it's a diesel:

"Spark ignition gasoline engine efficiency is limited by a number of factors; these include the pumping losses that result from throttling for load control, spark ignition and the slow burn rates that result in poor combustion phasing and a compression ratio limited by detonation of fuel. A new combustion process has been developed based on the patented concept of injection-ignition known as Transonic Combustion or TSCi™; this combustion process is based on the direct injection of fuel into the cylinder as a supercritical fluid. Supercritical fuel achieves rapid mixing with the contents of the cylinder and after a short delay period spontaneous ignition occurs at multiple locations. Multiple ignition sites and rapid combustion combine to result in high rates of heat release and high cycle efficiency. The injection-ignition process is independent from the overall air/fuel ratio contained in the cylinder and thus allows the engine to operate un-throttled. Additionally, the stratified nature of the charge under part load conditions reduces heat loss to the surrounding surfaces, resulting in further efficiency improvements. The short combustion delay angles allow for the injection timing to be such that the ignition and combustion events take place after TDC. This late injection timing results in a fundamental advantage in that all work resulting from heat release produces positive work on the piston. Other advantages are the elimination of droplet burning and increased combustion stability that results from multiple ignition sources."

How long does it take from when I stick the key in until there is sufficient supercritical fluid available to start the engine?

 

[SomptingGuy]

Still waiting for a vehicle report.

I got 65.7 mpg out of my diesel on a 300 mile run last week. Beat that with a gasoline, unthrottled or otherwise.

- Steve

 

[TStaples]

Dave,

Since startup heating is entirely electrical, it takes a few seconds to get enough heat buildup. It's on par with Diesel glow plugs. Once the engine is running, recovered waste heat takes over a large portion of the fuel heating.

You are partially correct. TSCi(tm) utilizes compression ignition, but the injection techniques, the cylinder geometries, and the characterisitics of supercritical gasoline are different enough that it's called Injection Ignition, instead of Compression Ignition. It's definitely a close relative. It's easier to say what it isn't. It's not quite Diesel, and not quite HCCI, but with similarities to both.

The whole point is that our technology allows for better than Diesel engine efficiency, while burning gasoline. The better than Diesel efficiency comes primarily from additional waste heat recovery from the exhaust, used to pre-heat the fuel, and from the mixing/burn characterisitcs of supercritical gasoline.

We cannot switch the whole world over to Diesel fuel. When barrels of oil are refined, you get a mixture of Diesel fuel and gasoline, in the middle distillate range. U.S. refineries are optimized for an approx. 60% gasoline/40% Diesel ratio. Europe's refineries are approx. 50-50. If you built all new refineries, you could make about 60% Diesel/40% gasoline, but since refineries cost in the billions of dollars, that is not a casual investment. You have to have a more efficient solution for all that gasoline.

-Tony Staples

http://www.tscombustion.com

 

[btrueblood]

What steps are taken to prevent coking of the preheated fuel? What issues, if any, are there in shut down of the system, with heated, pressurized fuel left in the injection line?

 

[TStaples]

btrueblood,

Your questions are in areas that are very technically sensitive, and we have spent a lot of time and money addressing those areas. As I posted in the original thread, I cannot share proprietary information. I can only share what is already public.

The correct way to disseminate automotive technical information is to publish it in appropriate journals where it can be peer reviwed. For powertrain technology, SAE is the proper place to publish. As per my earlier link, the paper is available to the public, via SAE.

-Tony Staples

http://www.tscombustion.com

 

[BrianGar]

How are you getting around the crank case oil mist that is recirculated into the intake from crudding up the intake port and valves like on the Vw Fsi heads? You no longer have the fuel mist passing over valve with direct injection, something, after seeing a few Fsi heads, Vw seem to have totally over looked.
This may not be your worry since you are concentrating on the injection part, but it will be someone's worry.

BG.

 

[TStaples]

BrianGar,

We are not building engines at TSC. We are focused on delivering a combustion system to the OEM's who build engines. What you are describing is an engine architectural issue on GDI and Diesel engines.

-Tony Staples

http://www.tscombustion.com

 

[BrianGar]

I understand that. Just making a point. An engine with a very clever set of injectors is useless if the ports are 50% restricted. And what I describe is an architecture issue granted, but It did not exist until GDI came along.

 

[TStaples]

Not all GDI engines suffer from this quite like the VW FSI engines do. BMW have an oil separator that utilizes a cyclonic swirl to condense the oil, and let it drip back to the pan, instead of allowing the mist to go directly to the intake. These separators introduce other potential problems (i.e. water freeze in the internal passages of the separator at cold temps,) but it is being done.

-Tony Staples

http://www.tscombustion.com

 

[black2003cobra]

Tony,

Thanks for posting the additional information, and link.

Regarding the similarities to HCCI, I wondered if you could comment on how this system compares to some of the general advantages/disadvantage of HCCI.

For example, with HCCI the homogeneous lean mixture leads to advantages of lower combustion temperatures, and hence, lower NOX emissions. Low PM emissions are also a benefit. In terms of disadvantages, HCCI seems to only operate over a limited load range (major disadvantage), suffers from difficulties in control (heat release chemistry), and noise (from the fast burn). Please comment on exhaust treatments required.

I believe the Nissan MK diesel HCCI system used late injection, as well. (About 20 deg after TDC.) How does this compare?

Regarding the load range issue, reportedly Honda’s gasoline HCCI system used an SI and HCCI mode to cover the load range. Any comments? (Yes...the load range question again.)

You mention using gasoline instead of diesel. So a low octane is preferred, I assume, to make it easier to ignite? Any further comments on fuel requirements?

Sorry for all the questions.

Thanks,
Eric

 

[WhizzMan]

How are you dealing with the increased peak pressures? You are essentially creating an engine that is pinging because of hot spots. This must be extremely hard on big end bearings.

 

[BrianPetersen]

Well, a diesel engine "pings", too; they're just built strongly enough to take it. If this is meant for a normally aspirated engine with compression ratio comparable to a normal diesel engine, the peak pressures may not be all that far out of range. If it's designed to have ignition and combustion predominantly at or after TDC rather than a portion of it before, that also helps with the peak pressures.

 

[TStaples]

Eric,

This is a simplistic way to look at it: Our technology enables the engine to run in something similar to HCCI mode at all speed/load points. Since we use no spark plug, there is no SI mode.

As for all the other questions, those are areas we discuss in detail only with the OEM engineers under NDA. You are generally correct with your observations of the potential advantages and disadvantages. However, there are ways to manage the injection pulse(s) to minimize noise and durability issues. As for fuel, in a perfect world, TSCi equipped engines would love nothing better than low octane gasoline (lower than what is typically at the pump now). And yes, we have had dialog with several major oil refiners, and they are very interested in supporting this. Lower octane gasoline is much cheaper/easier for them to produce.

-Tony Staples

http://www.tscombustion.com

 

[TStaples]

Brian,

You are correct. TSCi equipped engines need to be a bit more robust than today's gasoline engines, but not quite as beefy as today's Diesels. Interestingly, GDI engines are increasing in CR Ratio and beefiness, to handle the higher peak pressures of turbocharging/DI. Mazda has announced a new Sky-G GDI engine coming out at 14:1 CR. It will obviosly be beefier than SI engines of just a few years ago. We see that as converging right where we need to be.

-Tony Staples

http://www.tscombustion.com

 

[black2003cobra]

Tony,

It has been reported that use of gasoline (instead of diesel) in HCCI mode helps further reduce NOx emissions and smoke via an increase in engine ignition delay (time between start of injection and 50% burn), which tends to help with the (high) load problem. Do you find this to be the case?

One still wonders about dealing with HC and CO emissions with the lower temperatures though. Will work on developing catalysts with lower light-off temps be required?

Do your systems use double injection, or just single?

Thanks again,
Eric

 

[HRHtex]

This idea has always sounded reasonable (unlike most similar new engine ideas being promoted) but it still needs practical demonstration and less theory and discussion.

 

[BrianPetersen]

I suspect that the practical demonstrations are well under way ... away from prying eyes and internet discussions!

If this technology works as promised, whoever brings it to market first stands to gain a lot, and it's in their interest NOT to give competitors any tips.

Doesn't stop us uninvolved folks from speculating on their own, as we don't have any NDA's to respect.

Personally, as a resident of a northern country, I wonder how they deal with cold starting. It's obvious how spark-ignition deals with this, and having had a few VW diesels in the family including two currently, we're all familiar with the moment of silence memorial to the late Rudolf Diesel when it's -30 C outside, before cranking the beast to life. (The glow plug delay is down to a couple of seconds on the newest models, though - it's not a big deal)

If they're running in lean-burn mode, the NOx challenge will be interesting - although Mazda is claiming that their upcoming Sky-D engine will meet Tier 2 bin 5 without NOx aftertreatment, so if it can be done in that application, there's hope - as long as the regulators don't get any *further* brilliant ideas about how far NOx can be reduced regardless of cost or side effects.

 

[tbuelna]

btrueblood hit the nail on the head. This supercritical fuel injection system proposed by Transonic will have long-term issues with deposits in the high-pressure pump and injector nozzle components. Current 4-stroke, high pressure CR diesel injectors require careful liquid-cooling of the nozzle and pintle to prevent accumulation of fuel deposits and loss of operating clearances in these very close tolerance parts.

The basic principles behind the TSC injector are sound. Reduced ignition delay and close to constant volume combustion conditions are beneficial for NOx, SFC and BTE. And I'm sure it works quite well under laboratory conditions, with fixed speeds and loads. But in the real world of engines, I'd doubt that it would survive.

Just my opinion.
Terry