Green Car Congress  
Go to GCC Discussions forum About GCC Contact  RSS Subscribe Twitter headlines

« SAFT providing Li-ion cells for KERS systems for 5 of 12 competing F1 teams | Main | Nanocrystal tandem catalysis a promising approach towards designing high-performance, multifunctional nanostructured catalysts; energy applications »

Print this post

Toyota targeting thermal efficiency of more than 45% for next-generation gasoline engines for hybrids

11 April 2011

Among the R&D projects Toyota Motor is exploring to further lower fuel consumption and emissions are two concepts on a pathway to deliver gasoline engines featuring more than 45% thermal efficiency for application in its future hybrid vehicles, according to Koichi Nakata of Toyota in his presentation today at SAE 2011 High Efficiency IC Engines Symposium in Detroit.

The engine used in the first- and second-generation Prius (the 1.5L 1NZ-FXE) had a thermal efficiency of about 37%; the thermal efficiency of the new 1.8L unit in the third-generation Prius (2ZR-FXE) has a thermal efficiency of about 38%. Toyota is targeting a thermal efficiency of more than 40% with what Nakata called its Future Concept 1, followed by thermal efficiency of more than 45% in Future Concept 2 (which is based on concept 1).

In the 2ZR engine (third-generation Prius), some of the main technologies Toyota applied are the Atkinson cycle with variable valve timing to control intake valve timing, cooled EGR, and lowered friction. (In the 1NZ engine, Toyota reduced friction 21.1% compared to an engine for a comparable conventional vehicle; the 2ZR engine in the newest Prius drops that another 26.8%, in large part by the removal of parasitic loads via the hybrid system (e.g., no alternator).

Concept 1 is a cooled EGR stoichiometric spark-ignited direct-injection concept, featuring a long stroke design (stroke/bore=1.5) and cooled EGR with an EGR ratio of more than 30%. The long-stroke design (lengthening the stroke while maintaining displacement), reduces heat loss and also increases piston speed, creating more turbulence. A high tumble ratio intake port (TTR=3.0) and a high-energy ignition system (100 mJ) also contribute to improved combustion. Toyota is continuing to reduce friction.

Concept 2 is a turbocharged lean burn concept, built on the base of concept 1. It also uses the long stroke design, with a high tumble ratio and a higher-energy ignition system (150 mJ).

The high tumble ratio intake port extends the lean limit from 19 to 23, Nakata said. In addition, the lean limit is also increased by using a spherical face on the piston. Furthermore, the high discharge current in the ignition system also gives a higher lean limit.

Nakata said that the engine team has currently delivered a 42.4% thermal efficiency in concept 1 and 43.7% thermal efficiency in concept 2.

Work is ongoing, focused on increasing the expansion ration and decreasing pumping loses. Toyota is also considering a variable super high expansion ratio cycle for further improvements. Nakata suggested that such an engine applied in a hybrid would result in total lifecycle greenhouse gas emissions comparable to that of an electric vehicle.

April 11, 2011 in Engines, Fuel Efficiency, Hybrids | Permalink | Comments (46) | TrackBack (0)

TrackBack

TrackBack URL for this entry:
http://www.typepad.com/services/trackback/6a00d8341c4fbe53ef014e876f7cfc970d

Listed below are links to weblogs that reference Toyota targeting thermal efficiency of more than 45% for next-generation gasoline engines for hybrids:

Comments

In charge-sustaining mode, the ICE will still generate so much heat that you have to cool (just as for a conventional car). If the ICE is never running (EV mode only), you need of course no cooling at all. Insulation might be beneficial if there is kind of a driving mode in between those but I have difficulties to envision how often this could happen. For example, you could run in charge-sustaining mode when you start at home in a rural area, switch to EV mode in the city and then go back to charge-sustaining mode again on the return trip (and charge batteries back home). In that case, insulation would reduce ICE heat losses and friction for the return trip. Insulation is also a good idea if the car is parked for a longer period. In the latter case, a conventional car would probably benefit more, since the ICE is, most likely, bigger than in a PHEV. BMW has been experimenting with insulation but has not commercialized anything yet. Heat storage of latent (salt) or sensible heat (hot coolant) from the cooling water was tested in the 1990´s. BMW had a heat store in production; VW as well, but not for so many vehicles as BMW. Heat store of catalyst heat was proposed by a US federal lab.

Current emission and fuel consumption norms do not give much “credit” to insulation and heat store, since the soak period before the test is too long to provide any large benefit of insulation and/or heat store. The reduction of FC in real life could probably amount to about a few per cent.

Fuel cells do not have combustion, which I favor. As far as cooling, there was talk of a ceramic engine that could run at much higher temperatures. Once the heat is created by loses and not turned into mechanical energy, it is difficult.

In charge-sustaining mode, the ICE will still generate so much heat that you have to cool (just as for a conventional car). If the ICE is never running (EV mode only), you need of course no cooling at all. Insulation might be beneficial if there is kind of a driving mode in between those but I have difficulties to envision how often this could happen. For example, you could run in charge-sustaining mode when you start at home in a rural area, switch to EV mode in the city and then go back to charge-sustaining mode again on the return trip (and charge batteries back home). In that case, insulation would reduce ICE heat losses and friction for the return trip. Insulation is also a good idea if the car is parked for a longer period. In the latter case, a conventional car would probably benefit more, since the ICE is, most likely, bigger than in a PHEV. BMW has been experimenting with insulation but has not commercialized anything yet. Heat storage of latent (salt) or sensible heat (hot coolant) from the cooling water was tested in the 1990´s. BMW had a heat store in production; VW as well, but not for so many vehicles as BMW. Heat store of catalyst heat was proposed by a US federal lab.

Current emission and fuel consumption norms do not give much “credit” to insulation and heat store, since the soak period before the test is too long to provide any large benefit of insulation and/or heat store. The reduction of FC in real life could amount to a few per cent.

Roger,

H2 is here today and so are batteries. Neither one is ready for the scenario you outlined. My point is that if there is a solar panel on every roof and a wind turbine on every acre of farmland then just use the electricity!

Why would you possibly want to spend the energy to convert it back and forth to H2 and then pay for fuel cells to utilize it and create electricity again? The whole scenario makes no sense.

CelsoS,

>>This "thermal efficiency" of the ICE is at steady load in the best BSFC region.

Thanks for clarifying this. And thanks for the links and further elaboration.

What this means that the car as a whole does not achieve anything near 37% (or 43%) thermal on the standard EPA course or the corresponding Euro course.

Whether we can use the in improvements (peak) thermal efficiency to guesstimate improvements in EPA cycle mpg is not clear. It depends on the engine region of operation during the whole course, including also on/off duty cycle during same. It seems like a somewhat reasonable estimation technique, though, as long as the battery technology (and hence duty cycle) did not change.

Ai vin,

The Prius already has a built-in thermos flask to keep the cooling water warm after you stop the car. This is known technology, and generally a good idea. Especially for start/stop operation.

The Prius engine thermal efficiency map shows it is >34% for a wide range of rpms and throttle openings.

Being a hybrid it can keep the engine in the sweet spot most of the time, or all of the time for GM's Volt.

Greenpleasem

>>Toyota gets it.

They do, but you can get get even better than 37% peak or 44% oeak by using a (clean) diesel engine.

I'm hugely disappointed that Toyota is seliing large amounts of highly efficient clean diesel vehicles in Europe, but NONE here. It does not take that much extra effort to pass California emissions for a clean diesel engine. Toyota undoubtedly knows how to do it. VW, Audi, BMW and Mercedes already do.

Make a Toyota Diesel-Electric Hybrid along the lines of the Peugot 3008 for <$30k, and I would be very excited to by one. Just eliminate the sport/performance of the Peugot and make it a commuter car and we will have 70mpg soon. VW is doing the same concept, and Citroen, too,

http://www.greencar.com/articles/peugeot-3008-hybrid4-offers-200-hp-demand-all-wheel-drive.php


The all electric path will eventually be used world wide. Capturing and converting solar and wind energy to electricity will be done on a very large scale. Storing and distributing this clean energy will be one of the most sustainable avenue for most transportation vehicles in the not too distant future. Other sources of e-energy will complement the above for a long time.

This end game goal will be achieved within a few decades. Meanwhile, we will see alternative short term solutions such as improved ICEVs, HEVs and PHEVs but all those vehicles will have to go when very quick charge extended range BEVs arrive.

you can get get even better than 37% peak or 44% oeak by using a (clean) diesel engine.

I'm hugely disappointed that Toyota is seliing large amounts of highly efficient clean diesel vehicles in Europe, but NONE here.

Yeah, I keep hearing stories about DIYers who replaced the gasoline engine in their Prius or Insight and were getting 80-100 MPG.

High compression engines would be a good fit for natural gas and would help make up for its lower energy density.

A 70mpg Prius with 10-15 miles EV range would be pretty hard to beat

Peter XX,

Just when is "Peak Oil" supposed to hit?

It cannot be before 2500 AD just utililyzing currently known but untapped sources. What makes you think it is immannet or any sooner, other than amorphous Doomsday publications with little or no scientific research behind them.

Stan Stan Stan - don't confuse "peak oil" with reserves.
"The world is not running out of oil itself, but rather its ability to produce high-quality cheap and economically extractable oil on demand. After more than fifty years of research and analysis on the subject by the most widely respected & rational scientists, it is now clear that the rate at which world oil producers can extract oil is reaching the maximum level possible. This is what is meant by Peak Oil. With great effort and expenditure, the current level of oil production can possibly be maintained for a few more years, but beyond that oil production must begin a permanent & irreversible decline. The Stone Age did not end because of the lack of stones, and the Oil Age won't end because of lack of oil. The issue is lack of further growth, followed by gradual, then steep decline. Dr King Hubbert correctly predicted peaking of USA oil production in the 1970's on this basis. In fact oil production in 33 out of 48 out countries has now peaked, including Kuwait, Russia and Mexico."

@Anne,
Yes, it's true that solar and wind electricity will be harnessed in large proportions in rural areas, but H2 does not have to be produced in rural or remote areas. The electricity thus produced can be transmitted to the urban areas where H2 can be produced and stored at or nearer the points of distribution. It is far more efficient and cost-effective to transport high-voltage electricity than to transport H2. With higher demands for H2 eventually, there will be a time when it will be economically feasible to build dedicated H2 pipelines.

While BEV's are simple and more efficient than FCV or H2-ICE-HEV, in colder climates BEV's won't hold charge well and can't warm the cabin enough... and in hot climates, BEV's battery life will be compromised.

@DaveD,
Now then, you've wondered, why bother to convert electricity to H2 instead of using it directly?

The reason for this is the intermittency of solar and wind energy. When the sun is strong and the wind is blowing hard, there will be times in the future that we will receive more renewable energy than we can use at the moment. You would advocate to store the excess electricity in batteries and in physical means such as pumped hydrostatic or compressed air...However, these type of energy storage is very limited in capacity and can be expensive in locations where geography is not favorable.

The most efficient way to do with excess renewable energy is to make chemical fuels for use months or years later, just as the photosynthetic organisms have done it for billions of years...except that photosynthesis is less than ~1% efficiency, while solar PV to H2 can achieve 10-15% efficiency, easily one or two order magnitude more efficient that what nature has been doing!!!

solar PV to H2 can achieve 10-15% efficiency

Well good, just so long as you know it's efficiency is that low.

The problem is that with an efficiency this low PV to H2 becomes the solution you go to when nothing else works. Yes, batteries have limited capacity and pumped hydro is limited in location but where you do have batteries or favorable geography you're going to WANT to use those first.
http://www.electricitystorage.org/ESA/technologies/

In my view H2 would be much more justifiable if it was used in synergy; http://www.w2agz.com/PMG%20SuperGrid%20Home.htm

Some locations can use Compressed Air Energy Storage. CAES can use spent natural gas wells and other formations to store renewable energy for night time use.

When you use natural gas to make fuels, you could use more carbon, that is where biomass comes in. Gasify the biomass and use natural gas to extend the yields then put the synthetic gasoline in pipelines and rail cars blended with cellulose ethanol. Just put the plants in the farm belt where the cellulose is.

A couple of errors in the writeup.
The 2ZR-FXE engine adds variable exhaust valve timing.

The previous 1NZ-FXE engine already had intake timing which dates from 1997. In essence Toyota jumped from an engine still being used in the Yaris, incidently, to that currently used by the Corolla. The FXE suffix denotes atkinson camshafting. which their non-hybrids don't have.

Mention of the parasitic load caused by the generator is a typo. Probably confusion with Honda Civic Hybrid which still retains a conventional alternator system.

In fact it is more notable that the new Prius has replaced the belt driven water pump with an electrically driven one, the absence of the V pulley on the end of the crankshaft thus making the 2ZR-FXE the first beltless engine.

Things they should try is better thermal management with motorised grille shutters - also helping aerodynamics since the parasitic cooling of the radiator by vehicle motion causes unnecessary drag when the engine is cold.

Fiat is going to two cylinder 900cc engines with the Aria concept outlined here in Sept 2007. That engine now in production. The turbo version was said to produce 106Hp unkown whether it's being optioned at this time.

@greenplease, you mean Torlon engine block, not Torlan.

Yeah if a plastic engine block can reduce costs that would be great as long as it's reliable and cam handle the heat and compression ratios of direct injection and all that.

Lean burn engine for concept#2. Sounds awesome, like the 5th gen Civic VX and 6th gen Civic HX and 1st gen Honda Insight except better!

But, how will they manage to keep the car SULEV emissions rated? Some very special catalytic converters, wide band o2 sensors.. For instance with the 2000-2006 Insight hybrid, the manual transmission version had the lean burn and was ULEV rated, the CVT version was SULEV rated because it had a non-lean burn engine.
In Japan the CVT still had lean-burn but that's not the USA.

If they can keep the emissions in tune, and make the emissions system reliable (expensive to repair!), It'll be a winner, and hypermilers will put in scangauges to try to extend lean burn mode as much as possible.

Here's to hoping. It looks like Atkinson + Lean burn + short range plug-in = win. Reliability and manufacturing costs are key

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Green Car Congress © 2014 BioAge Group, LLC. All Rights Reserved. | Home | BioAge Group