SJTU team proposes new dual-fuel combustion mode: intelligent charge compression ignition (ICCI); high efficiency, low NOx
13 July 2020
A team at Shanghai Jiao Tong University (SJTU) is proposing a new combustion mode—intelligent charge compression ignition (ICCI)—for ultra-high efficiency and low emissions simultaneously. A paper on ICCI is published in the journal Fuel.
ICCI aims to realize flexible and controllable in-cylinder charge stratification fed by two complementary fuels: gasoline and diesel. To enable this dual-fuel combustion mode, the team utilized two common-rail direct-injection systems independently on a modified single-cylinder engine, each injection system being controlled by its own on-limits electronic control unit, respectively.
Li et al.
In general, a majority of gasoline fuel is injected early to create a premixed background charge, while the rest of the fuels are alternately injected at compression stroke to create controllable reactivity stratification. During the injection process, diesel and gasoline are multi-stratified and mixed with the piston stroking upward. Eventually, before the fuel ignition happening, the ideal stratification completed, which means that the concentration and reactivity in the cylinder were adjusted towards the optimal conditions. The injection timing, fuel split ratio and fuel split number can be changed with the engine operating condition variation, modulating the in-cylinder stratification in real-time. The ignition timing and combustion rate are controllable so that the high thermal efficiency and low NOx emissions could be obtained.
—Li et al.
Experimental results showed that high indicated thermal efficiency close to 50% and low NOx emissions well below 0.12 g/kWh were simultaneously achieved at 85% gasoline ratio.
Based on the optimal gasoline ratio, multi-injection strategies of ICCI mode can further improve thermal efficiency and emissions, the team said.
They also compared ICCI with other combustion modes, including reactivity-controlled compression ignition (RCCI); G85 dual direct injection (DDI); G85; and G70 single direct injection (DI) strategies were carried out. In the similar operating conditions, ICCI combustion got better performance compared with other combustion modes, achieving about 2% increased indicated thermal efficiency in comparison to RCCI or DDI mode and near zero NOx emissions compared with DI combustion.
The relationship between ITE, combustion efficiency, CA50 and combustion duration with the variation of gasoline ratio. Li et al.
Slightly more specifically:
Compared with ICCI mode, single-fuel DI strategies fuel with G70 and G85 have the unacceptable cyclic variation and combustion noise more than 4% and 2 MW/m2, respectively, and still had relatively high NOx emissions within the range of 3–15 g/kWh. G85 DDI strategies obtained lower ITE less than 45% and higher CO and THC emissions more than 10 g/kWh compared with ICCI mode. ICCI mode also had better PM emissions than other single-fuel combustion mode.
ICCI mode and RCCI mode both obtained extremely low NOx emissions less than 0.6 g/kWh. ICCI broke through the limitations cause by PFI in dual-fuel combustion. Therefore, it has a higher ITE than RCCI along with lower CO emissions. However, RCCI had better PM emissions than ICCI in the present experiment.
During the fuel ratio adjustments of ICCI mode, it was found that with the gasoline ratio increasing, the combustion phasing was delayed, while NOx emissions decreased but CO and HC emissions increased. At 8 bar IMEP, the best optimal target in the experiments was the condition of 85% gasoline ratio with the highest efficiency of 49% and relatively low NOx emissions of 0.1 g/kWh simultaneously.
ICCI has a large potential based on the further optimization in the future, the team concluded.
Resources
Zilong Li, Guan Huang, Yaoyuan Zhang, Wenbin Zhao, Jing Li, Zhuoyao He, Yong Qian, Xingcai Lu (2020) “Dual fuel intelligent charge compression ignition (ICCI) combustion: Efficient and clean combustion technology for compression ignition engines,” Fuel, Volume 279, 118565 doi: 10.1016/j.fuel.2020.118565
Could this be a candidate for a serial hybrid EV?
(or just a range extender)
As I have said many times, the problem with EVs is excessive battery sizing. Then tend to get sized by your budget to 60+ kWh while 20 kWh would probably be enough to cover 90% of your journeys.
So if you could fit a range extender, you could stay with the smaller battery (and make 3-6x the number of PHEVs compared to pure EVs).
Looks like this solves the NOx problem which simplifies the exhaust treatment and makes the system cheaper and more likely to happen.
Posted by: mahonj | 13 July 2020 at 08:15 AM
this is RCCI. They continue to rip it off and try to claim its something new. ITS NOT. Im so tired of it.
Posted by: RFH | 13 July 2020 at 05:50 PM
I have a Chevy Volt with a range extender. I love it! I often use all the 50 miles of battery range on my drives for work. I like to fiddle with the hold button and I've gotten up to 60 miles of battery range and 60 mpg on an 100 mile drive by using only the battery to accelerate (something that Chevy could easily do with software if they put their mind to it). But I know that range extenders are a bit of a gimmick. Because I use the full charge of the battery on my regular 50 mile commutes I will wear the battery down quickly and soon will be driving mostly on gasoline or need to replace the battery. It makes more sense to have the life of the battery last at least the life of the car. The Volt weighs as much as battery powered only equivalent car. Once the Tesla 15 minute fast charge is widely available, the advantage of being able to fill up quickly with gas will vanish.
Posted by: Tom Paine | 13 July 2020 at 08:24 PM
Thanks Tom, good to hear from owners.
Posted by: SJC_1 | 13 July 2020 at 08:57 PM
Thomas Paine stated: "It makes more sense to have the life of the battery last at least the life of the car. "
Reply: While the revolutionary Thomas Paine was well known for his "Common Sense" pamphlet, the later-day Thomas Paine is notably lacking in common sense. Well, Tom, NO known battery in existing cars can last for the life of the car, EXCEPT for the hybrid traction battery in the Prius and other Toyota's hybrids. The lead-acid batteries typically last for 5-7 years and must be replaced, even though it is has VERY shallow duty cycle and is always kept at optimal charge level, while the car can last for 15-20 years, so existing non-hybrid gasoline cars must go through FOUR battery changes. during its life span. Li-ion batteries last around 10 years, and so is the warranty of these new Li-ion batteries. A current BEV or PHEV using Li-ion batteries will probably need at least ONE battery change during its lifespan.
Fortunately, changing battery packs can be very quick, as Tesla has demonstrated with its battery swapping, and Nio cars in China routinely having their batteries swapped in THREE minutes at hundreds of battery swapping stations in China for extended-range driving.
So, after 10 years, would you rather spend a small sum of money to change the 18-kWh battery pack of the Volt, or spend a huge sum of money to change the 75-kWh battery pack of the Model 3? There is such a thing as Calendar-Life-Aging which cause battery degradation even if the battery is rarely used and is always kept in optimal charge level, which keep practical life span of current Li-ion batteries to around 10 years, even if rarely used.
Posted by: Roger Pham | 13 July 2020 at 10:39 PM
Currently automotive Li-ion batteries are known to be capable of 3,000 charging/discharging cycles if each cycle is kept to within 80% of its rated capacity. So, if the Volt's battery is cycled to 80% roughly once daily, then it will hold up for about TEN (10) years, which sorta coincide with its calendar lifespan. So, it would make more sense to spend $5,000 to change the 18-kWh battery pack of the Volt rather than to spend $20,000 to change the 75-kWh battery pack of the Model 3 Long Range.
Posted by: Roger Pham | 13 July 2020 at 10:52 PM
I hope you are right that my Volt battery will last 10 years. My last 2 cars, a 1995 Civic and a 2000 BMW 323, I kept for 20 and 17 tears respectively and both had well over 200k miles.
But assuming the 3000 charging cycle life of Lion batteries, the 50 miles of driving electric on the Volt for 300 days a year would indeed last 10 years. But the Model 3 longe range has a range of 322 miles so driving 50 miles 300 days a year would only use 46 cycles of the battery per year so assuming the 3000 charging cycle life of it's batteries it would theoretically take 65 years for the battery to need to be replaced! In reality I think Lion batteries in cars last anywhere from 500 to 2000 charging cycles. And with the 50 miles per day of charging you could keep the Tesla battery well below the maximum and minimum charge allowed by the manufacturers allowing the Tesla battery to get more cycles of life than the Volt.
Posted by: Tom Paine | 14 July 2020 at 08:57 PM
Tom, you again have ignored the calendar life issue completely. Calendar life means battery aging even WITHOUT any cycling at all. Calendar life applies to ALL types of batteries. Calendar life is shortened for Li-ion batteries when kept fully charged, when kept at very low charge, and when kept at high temperatures above 104 degree F or 40 degree C, even in the absence of use. In those conditions, calendar life of Li-ion battery is just a few years even when NOT cycled at all..
Optimally-kept Li-ion batteries can last for over 10 years with careful usage of keeping the charging cycles at under 80% of capacity and at moderate temperatures.
Lead-acid batteries don't age nearly as well. All of my UPS battery power back up devices using Lead-acid batteries will need to have the battery changed in about 5 years, even when the batteries are NOT cycled at all. The batteries just went bad even when kept at optimal charge level all the times.
For more details on the Calendar Aging issue, refer to this link:
https://www.researchgate.net/publication/325738076_Calendar_Aging_of_commercial_Li-ion_cells_of_different_chemistries_-_A_review
So, it is most economical to have a small Li-ion battery pack with just enough capacity for daily driving, and change it every 10 years...instead of having a battery pack 5 times larger than what you need for daily driving, and still having to change it every 10 years, due to calendar aging. GM charged around $5,000 for a new Volt's battery pack, while the Model 3 battery pack will cost above $20,000.
Posted by: Roger Pham | 15 July 2020 at 12:48 PM