The Holy Grail of internal combustion engines. A job for Myth Busters!!!

[Henry W]

I just ran upon this and I feel this seems like wishful thinking to me.

Henry

Homogenous Charge Compression Ignition (HCCI) – Holy Grail of Future
Internal Combustion Engines
Date Published: 2 Sep 2009

By Avijit Ghosh, Industry Manager, Frost & Sullivan Automotive Practice


Background

According to President Obama, CAFE will increase to a unified national standard of 35.5 mpg by 2016. CAFE will increase by five percent each year, upon the 2011 standard, until 2016.

The new CAFE standards will incorporate California's strict emissions rules and will increase the national mpg average of cars and light trucks to 42 mpg and 26 mpg, respectively, to achieve an overall average of 35.5 mpg by 2016. Current CAFE standards require 27.5 mpg for cars and 24 mpg for light trucks. These new CAFE standards will create significant challenges for US vehicle manufactures.

One of the most important potential OEM reactions to reformed CAFE is the need to change the technology content in engines to increase the fuel efficiency of the vehicle. HCCI technology, when used in combination, could be tremendously effective in meeting the mandated fuel economy increases, and thus could prove to be the holy grail of future IC engines.

Introduction

An HCCI engine ignites an air/fuel mixture by compressing it in the cylinder at low temperature, instead of using a spark plug. The ignition is spontaneous and does not propagate as a flame front. In a gas engine, the ignition is generated from a spark plug, and in a diesel engine, there are multiple flame fronts.

The concept of HCCI technology was introduced three decades back, but advancements took place in the past couple of years when major automakers and research groups across the world started working on building prototypes.

Why HCCI?

HCCI's primary advantage is more favorable fuel consumption, or better MPG, and generating inherently low emissions. The power produced in an HCCI engine is similar to spark ignition (SI) gasoline engines.
An HCCI engine, when combined with other advanced technologies, can provide up to 15 percent greater fuel economy than a comparable, non-HCCI engine by using the compression combustion process that operates at a much lower temperature than diesel combustion.
HCCI combustion takes place at lower temperatures helping to reduce NOx emissions. A diesel HCCI set up emits 30 percent of the NOx that a conventional diesel engine emits, which reduces the necessity of exhaust aftertreatment. By comparison, gas engines have inherently lower NOx emissions, and therefore still more aftertreatment is required for diesels to reduce NOx to the level of gasoline engines.
The technology is compatible with a wide variety of fuels, such as biofuels, diesel, gasoline, and E85 (ethanol). GM's findings reveal that ethanol is a suitable fuel for auto ignition that offers high octane with no smoke-producing tendency. In addition, ethanol produces easier combustion with low carbon accumulation.
Challenges

Despite several advantages, this technology needs to address the following challenges:

The biggest challenge in HCCI technology is controlling the temperature, pressure, and air/fuel mixture quantity to manage the combustion process efficiently without noise or imparting any damage to the engine.
An HCCI engine is best used with individual valve actuators; in other words, it is a camless valve train with each valve infinitely variable in timing and lift. However, this is an expensive, complex, and difficult-to-control technology. Therefore, camless engine technology has not made a mark in the market place.
Difficulty in controlling ignition timing and combustion duration
Has a narrow operating window under light to moderate loads. Can produce noise at high loads when transitioned from in and out of auto ignition, and causes misfire or partial burn at low loads
Vulnerable to temperature variations across the cylinders
Diesel HCCI technology needs to address the NOx emission issue, as EPA regulations are enforced for large and small diesel engines
Currently, auto ignition in HCCI technology occurs only at 4 to 5 bar, or 60 psi BMEP. But a modern engine at wide open throttle should operate at 200-300 psi.
Gasoline HCCI Engine

GM engineers say that gasoline HCCI engines will have 15 percent greater fuel efficiency than comparable conventional gasoline engines making the same HP. GM's first-generation HCCI production unit, likely introduced by 2012, is expected to start operating at stoichiometric mixtures and spark ignition mode at very light loads. It will then transition to HCCI mode at higher loads and intermittently run in spark ignition mode.

Compression ratios can be varied by valve timing in HCCI and modern gasoline engines. There are mechanical means of producing different compression ratios, by a variable length piston stroke, but these are very complex.

Diesel HCCI Engine

Diesel engines can achieve a 20 to 30 percent greater fuel economy than gasoline engines of comparable HP because of a higher compression ratio needed to ignite the air/fuel mixture and reduced throttling losses. Therefore, diesel HCCI engines could be more fuel efficient than gasoline HCCI engines. Also, diesel HCCI produces low NOx at low PM, whereas in a conventional diesel engine there is a trade off between NOx and PM.

In addition to a higher compression ratio, higher thermal efficiency, and reduced throttling losses, a diesel HCCI will generate greater mileage from the high volumetric energy density of the fuel; this adds a 10 -12 percent improvement in MPG just from the fact that diesel fuel is more carbon-rich.

HCCI is also referred to as "controlled auto ignition," but experimenters have found that auto ignition is possible only at low to moderate loads. As the load increases, it switches over to spark ignition, which does not work with diesel fuel. Thus, a different fuel is required for an HCCI engine to function effectively. Octane gasoline is possibly the right fuel and experimenters are aiming to run HCCI engines with a conventional diesel fuel.

One drawback is the fact that diesel engines are roughly three times more expensive than gasoline. To combat this, and net the best of both worlds, an HCCI technology is being researched at GM that could combine the characteristics of both the gasoline and diesel engine.

Where is the HCCI technology heading?

As part of GM's August 2007 Powertrain technology show, the company brought a Saturn Aura and an Opel Vectra, each equipped with a 2.2L HCCI EcoTec four-cylinder engine. Initially, this engine could work in HCCI mode, but only for a short period of time. Thereafter, it continued to work in the basic spark ignition mode. The transition from the HCCI mode to spark ignition was accompanied with a ringing sound for two power cycles post transition.

In 2009, a mixed-mode HCCI engine with an external EGR system was developed that is capable of operating from idle up to 60 mph. Vehicles with fuel-efficient HCCI engines will likely be available at a much lower cost than a hybrid vehicle. GM forecasts low volume production of HCCI engines by 2012.

HCCI promises to be the cleanest gasoline engine. GM has further broadened the operating range of its 2.2L Ecotec HCCI engine currently being tested on a Chevrolet Malibu. This engine's speed/load map in HCCI mode now extends down to idle (800 rpm), which is around 200 rpm lower than its previous HCCI test. The upper limit is confined within 3000 rpm, as it produces higher combustion noise. More work is necessary in this area.

HCCI technology could be an advantageous option for extended-range electric vehicles such as the upcoming Chevrolet Volt, during part-load operation when the ICE is charging the battery.

The electronics within HCCI are considered to be the most sophisticated within the internal combustion engine family. The HCCI engine will have complete onboard diagnostics capability and assured 150,000-mile emissions compliance.

HCCI engines need to have an in-cylinder pressure sensor for each cylinder. Today, all engine prototypes have lab grade pressure sensors that cost around $1,000 each. These sensors are accurate but are not designed for a long life. So the key to commercialization is to have one in-cylinder pressure sensor that will last for the life of the engine.

The HCCI engines need to be properly controlled. As load becomes uneven, the HCCI cylinder needs to adjust accordingly. Researchers are in the process of developing sensors and controllers that will keep temperatures constant throughout the engine or compensate for temperature differences by adjusting pressure ratios within the cylinders.

Coordinating ignition in the cylinders is a challenge. This is because they are at different temperatures, and although they may have a one percent difference in their compression ratios, the difference greatly increases when a high volume of air/fuel mixture is compressed. In addition to temperature variations and different compression ratios, the other factors that affect combustion timing are the air:fuel ratio and intake pressure. These factors need to be synchronized to increase power and efficiency. Researchers are trying to design sensors that will communicate cylinder pressure and temperature to the engine. As soon as the engine knows that some of its cylinders need to be adjusted, either in temperature or pressure, in line with their neighbors, it will take steps to re-adjust them.

The EGR flow needs to be closely controlled in HCCI engines. At some point within the engine operating range, up to 60 percent of the cylinder charge is unburnable EGR. So, if so much oxygen is displaced, engine power will reduce but emissions output should be low as well. At low operating load, this is not a problem.

Conclusion

Technical breakthroughs are needed. Despite the company's financial crisis, GM prioritized the HCCI technology and is speedily moving towards production. It can be anticipated that gasoline HCCI is not likely to be ready for the market by 2012, and maybe even 2015. However, diesel-fuel HCCI or HCCI-like diesel engines (with no SI assist) will possibly be introduced by 2012.

For more information, please contact David Escalante, Corporate Communications, at 210.477.8427 or david.escalante@frost.com.

[Crofter]

Henry, I am not surprised that "noise" is one of the problems to be overcome! It appears to be a very sensitive balancing act of burning a charge just on the verge of detonation. I wonder what they are using for piston rings? I like the bit about varying the piston stroke!

Somehow I just dont think there is one of those engines in my future.

[Wizard]

Google and look up on youtube about Fiat's Multiair.  Chrysler engines will get these too, soon.

Cheers, Wizard

[Randybee1]

Standard gasoline cars could get 60 mpg right now but the fact is Detroit/Japan decided along time ago that the consumer wanted a little car that put out some God awful horse power.. like 260 -360 hp. Its amazing actually,these little cars with tiny engines putting out that much horsepower. If the auto makers wanted to, they could dedicate themselves and come up with a 60+mpg car rather easily, they just choose not to! Right now they are playing "the game" with the government.. If you want a high mileage car.. its gonna cost ya!

And lets not forget the government is to blame too. I have an '86 Volkswagon Jetta (diesel). It gets 50.5 mpg. The new Jetta's get something like 36 mpg. Why is that?? Shouldn't the efficiency have gotten better in 25 years time?

Randy B

[Crofter]

When they get really serious about mpg and forget about wanting 250 ponies in a car it will happen.

I get an honest 60 miles per imperial gallon on my VW golf diesel if I keep the speed limit (summer time) They could easily drop 400pounds of weight and a third of the power and get close to 100 mpg. Hell my first wheels, a 1950 ford had only 80 horsepower. I dont remember mileage but gas was only 33 cents an imperial gallon.

What is disgusting with the new vehicles is all the complexity of electronics and plumbing stuffed under the hood. Some of them are looking at 4 hours to change the spark plugs that cost 25 bucks a pop. They certainly try to lock you into the dealer.

[LowGear]

I've been stymied for most of my adult life.  I grew out of V8s by the time I got out of the Army.  What is it with so many "Johnny Dark Race Car Drivers"?  I dream of an auto ad that brags about mileage, safety and no stupid "zoom - zoom".

This school boy machismo is one of the big reasons that we're hostage to the oil cartels.  I used to drive a Dented Datsun Diesel named, of course, Dudley.  Under powered - only to the hot dogs doing 70 or better on the freeways.  I wonder if someone will take this new technology,HCCI or it's intellectual sisters, stop worrying about zero to sixty statistics and start defining extraordinary automobiles by how many miles or kilometers they can go on a gallon of gasoline.  Do you know how many people live in India and China?  You know most of them want a car.  Man, that syrup is going to get really expensive when the whole planet is mainlining.

Casey

[TimSR2]

Anybody remember Smokey Yunick' s Adiabatic Engine.......?  or was that just snake oil.

[vdubnut62]

I remember the adiabatic lil feller, in a Plymouth Horizon IIRC. It was turbocharged, except that Smokey called it a "homogenizer" and claimed that it just kept the super hot combustible vapors from backing out of the combustion chamber. I can't remember what the efficiency increases or the real world mileage claims were though. I can't remember what kind of engine temps he ran either, but it did have a small cooling system, I think.
But the car did exist.
Snake oil? Could have been, I was in my early teens, and pretty gullible.
Ron

[mobile_bob]

Smokey was my hero, and yes the engine existed
he did development work for gm, ford and mopar for years.

my only regret was he passed away before i could manage to make a pilgrimage to meet him.

the grandam buick turbo's were developed by him for gm iirc

bob g

[rcavictim]

I've still got a couple of engine building books he authored here in a box of such things which I haven't looked at in almost 30 years.  One covers the SB Chevy.  That fellow wasn't afraid to experiment with his ideas.

[wiebe]

My toyota starlet from 1997? is getting 17 km /liter [40miles the gallon?]
Its a 4 banger 1,3 liter gas engine and has 75 hp.
Top speed something like 100mph And 900kg.dont no the weigt in us .

And its not the most ecomomic car here over in the netherlands .

Last time i was in USA NH there were a few toyota aygo/yaris in new hampshire there having better mpg.
Are they more expensive in the US then here in europe ?

Greetings wiebe.

[AdeV]

We have plenty of 60-70mpg'ers over here in Blighty - although our gallon is a little larger than yours, probably to the tune of about 5 miles worth - but they're all ghastly little shitboxes which couldn't pull the skin off a rice pudding. The second biggest barrier to economy on the roads, IMHO, is people simply don't know how to drive economically. Even in their little diesel rattle can. Momentum is the key - or, more specifically, maintaining it. Minimum braking for corners, gentle acceleration out of the corners. Keep the speed up.... the problem is, those little super-economical cars are also horribly unstable in corners, so the drivers have to slow down (but are usually incompetent and slow down far too much); then they have to rag the arse off their 1.3cc (0.05 cubic inch) engine to try to build up any kind of speed again; only to hit the next corner......

The problem is, those of us who have cars which could maintain corner speed, can't because there's some idiot in a tin can getting in the way!

[/rant]

[vdubnut62]

My Wife's Camry is surprisingly large. She was very surprised when I brought it home, her comment was" it's huge!"
In her defense, she had been driving a Chevy S10 Blazer that was pretty much the same size, but the way it was laid out, the Camry has much more usable room. The car has 225000 miles on it now, still gets 35mpg with 4 adults on the interstate at 75 mph with the air conditioner on. It has a 2.7 liter(I think) or maybe 2.4 I'm not sure this late. What it does have is fuel injection, 16 valves and variable valve timing. It is also surprisingly powerful. I don't think an American car from the late 70's or early 80's with an engine 5 liters or under, could as we say in TN "Shine it a light to go by". I don't know how fast it will go, with 4 of us in it I chickened out at 110.
I am pretty impressed.
Now I am very sure, using the same technology, a smaller lighter vehicle COULD be designed that would get upwards of 50 or maybe even 60 mpg. But what is the trade off? I shudder every time I see a Smart Car out on the interstate highway. They just LOOK dangerous. Now with a proper DI diesel power plant, I'm sure that thing could easily achieve 55-60 mpg, and in town it would be great.
Just not on the expressway. I have seen far too many crashes involving tiny cars where the occupants didn't make it. I personally would love to have a practical electric car to bebop around back and forth to the grocery and work, but I can't and will not spend 30 grand on a car with a 75 mile range!
Yes we have a way to go yet to get the compromises worked out, in the meantime we at our house will still drive the old Toyota.
Ron

[cognos]

I had a 1982 Toyota 1 Ton 4X4 (called a HiLux everywhere else in the world) small pickup... it was a 4 speed manual with a 4 cylinder engine, 80 HP if I recall... thing got great mileage, drove quite well for a vehicle the felt like it had cement blocks for shock absorbers, and I drove it 25 miles to work and back every day for 6 years at 135 km/hr (around 80 mph), and it had plenty of power. Also had posi-trac 4WD, wouldn't turn a corner on dry pavement, but it would climb a tree if necessary... I probably pulled 50 pine stumps with it. It had 300,000 km/180,000 miles on it when I bought it, had 600,000 on it when I sold it (to my cousin, it was still a great truck, and he later sold it to a neighbor, and it had over 1,000,000 km/600,000 miles on it...)

Have a look at one now, they're no longer work trucks, they're for redneck wannabes to cruise the strip in with huge stereos, huge engines, fancy tires and rims, delicate sheet metal, etc. - and low MPG. Lots of style, not much substance. The truck, not their drivers - but I wonder sometimes...

My wife and I recently bought a Honda Fit. Sort alike a mini-minivan. She gets 45-50 MPG gas - I get less because I like driving it quickly (but safely, and not aggressively... ). As far as handling, it handles any move that it could reasonablty be expected to perform on the road with ease - and I do know a good handling car, I've been to Porsche Driving School, numerous Skip Barber schools, Skid School, Defensive Driving School, and numerous Club Days at the track... anybody says it is a poor handling car doesn't know how to drive. Like most people.
And it's very comfortable to drive, even for long distances.
It has a HUGE cargo capacity. Has four seats, they fold down, and it will hold 8' lumber. With snow tires on it, it easily climbs our 200' snowy, icy driveway - with an 11° grade... it's a great car, it would fit the bill for 80% of everybody who owns a car, I'd bet...

Our more "socially active" aquaintances hate it. Even the pretender who drives a Prius. It's a pisswinder. "Oh, why'd you buy such a little car?" I'm sure we won't be invited to some of the more upscale events this year...

(I still have a 4X4 truck, but it's a Nissan. Gets terrible mileage, low 20's - but it is really only used around town. We take the Honda if we're travelling.)

Point is - MPG will go up in vehicles only when it becomes unfashionable - and socially unacceptable - to drive to the mall for a hairdo in a Hummer. When a BMW 7-series used to drive 2 miles from home to the yacht club is looked down upon by that crowd. When low 0-60 times and ridiculous top speeds start to mean real legal trouble for the boy-racer/moron set (happening in Ontario with the 50KM/hr over the speed limit racing laws).

It's not an engineering problem - it's a human problem.

[mobile_bob]

the best i have is a '83 toyota pickup with an anemic diesel, however i love the little bugger
it likes 55mph although if pressed it will do 70 easy enough.

it gets right at 35mpg which is adequate for what i have in it and what i intend to use it for.

for  around town, now that i am buying a house in town, a small electric would do me just fine.
maybe i will stuff a changfa in some tiny little car and use it to put around with.  i guess with a water cooled
engine i could also have a heater/defroster.

now thinking about it, it seems like a good idea to me

i have a r185 changfa watercooled 9hp in my collection, i would have to fit it with a starter but i suppose maybe
if i am choosy about what little car maybe i can find one with the starter mounted on the bellhousing of the transaxle
and make it work.

9hp and a automatic, in a sub 2k lb car?

might have to get out the tinsnips and cut away all the unnecessary sheet metal, carpets, radio, backseat, bumpers etc to
cut the weight down as far as possible.

i could probably get away with it in small town kansas

i wonder how many mpg i could get?

any bets?

i know, i know, i could make up an electomagnetic hook/catch to attach to the back of a semi trailer and let him drag me along for the ride... sorta like drafting?

nah, too old to get away with that i suppose.



bob g