Fuels that do not produce hazardous exhaust gases

February 15, 2016
Studies at the bioliq pilot plant focus on how high-quality fuels can be produced from biomass. Credit: KIT

Modern combustion engines become increasingly economical and clean. Engine developers, however, are now facing the technical conflict of whether fuel consumption or exhaust gas emission is to be further reduced. This Gordian knot might be cut by chemists' and engineers' further development of sophisticated fuels that help optimize combustion in the engine. This development work under the OME project is funded by the Federal Ministry of Food and Agriculture (BMEL) via the FNR, the central project-coordinating agency in the area of renewable resources, with EUR 800,000 for a duration of three years.

Parallel optimization of , exhaust gas emission, and user comfort results in a technical conflict. Stricter requirements relating to exhaust gas quality have caused engines and the exhaust gas cleaning system to become increasingly complex. "Further development of diesel and gasoline fuels now offers the chance of preventing the formation of hazardous exhaust gases directly at their origin, i.e. during combustion in the engine," Jörg Sauer, Head of the KIT Institute of Catalysis Research and Technology, explains. "A promising concept for diesel fuels is the use of oxymethylene ethers."

Oxymethylene ethers (OME) are synthetic compounds of carbon, oxygen, and hydrogen (CH3O(CH2O)nCH3). Due to their high oxygen concentration, pollutant formation is suppressed in the combustion stage already. As diesel fuels, they reduce the emission of carbon black and nitrogen oxides. Still, economically efficient production of OME on the technical scale represents a challenge. The OME project will therefore focus on new and efficient processes for the production of the chemical product OME.

OME might be produced from renewable resources, as is shown by the bioliq project of KIT. In this way, these substances would not only contribute to reducing pollutants, but also to decreasing carbon dioxide emission of traffic. The carbon/oxygen/hydrogen ratio of OME is very similar to that of biomass. Production with a high energy and atom efficiency is possible. "Apart from the systematic variation of reaction parameters, such as pressure, temperature and concentration, efficient methods for the processing of OME have to be developed in order to guarantee high fuel quality," Jakob Burger of the Chair for Thermodynamics of TU Kaiserslautern explains.

Little is known about the effects of OME during engine combustion and other aspects of the use in vehicles. Comprehensive studies of engine tests will focus on these aspects of application and contribute to revealing the potentials of enhancing efficiency of OME use. These studies are to provide detailed insight into the relationships between the chemical OME structure and combustion properties. The objective is to demonstrate a highly simplified treatment process without particulate filters and catalytic treatment. "When using OME, fuel may be considered an active substance. This opens up a considerable potential of facilitating the trade-off between consumption and emissions and securing sustainable mobility," Georg Wachtmeister, Head of the Institute of Internal Combustion Engines of TU München, says.

The OME project is executed by KIT as coordinator in cooperation with TU Kaiserslautern and TU München. The project with a total budget of EUR 800,000 is scheduled for a duration of three years and funded by the Fachagentur Nachwachsende Rohstoffe e.V., the central project-coordinating agency of the Federal Ministry of Food and Agriculture (BMEL) in the area of .

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1 / 5 (3) Feb 15, 2016
Will we get to condensing engines, like we have for furnaces? That would allow us to trap and carry much of the nasty components with the vehicle.
Uncle Ira
4 / 5 (4) Feb 15, 2016
Will we get to condensing engines, like we have for furnaces?.

Hey glam-Skippy, did you know condensing engines have been around since the 1700's? Yes indeedy-roo Cher. That is the steam engine we all love to read about if you are into the history of the industrial age. I really love the history about the first steam ships and first railroads. But it was for pumping water out of mines that it got it's start.
1 / 5 (4) Feb 15, 2016
Cute. We were talking about ICE, not ECE.

And show me one which condenses its combustion gases.
Uncle Ira
4.2 / 5 (5) Feb 15, 2016
Cute. We were talking about ICE, not ECE.

And show me one which condenses its combustion gases.

What is with you Skippy? I was interested with what you said, did not down vote you and mentioned that I was interested in condensing engines. You get all snippidty with me. Why you are in the bad grumpy mood all day every day? I hope when I get old I don't have that to look forward to all day.
3.7 / 5 (3) Feb 15, 2016
How about if we go to no emissions? Solar thermal panels can be used to store summer heat for warmth even in the winter with 98% efficiency.

Solar electric for vehicles and house electricity, solar thermal for heating.

Everyone wins except the oil industry.
3.7 / 5 (3) Feb 16, 2016
That would allow us to trap and carry much of the nasty components with the vehicle.

You can only condense that which becomes liquid at room temperature. The pollutants like NOx are gaseous at NTP, so cannot be reasonably condensed.

Furthermore, the point of a condensing boiler is that there's water in the exhaust which condenses at 100 degrees C, which is still useful for household heating. For a car engine, 100 C is thermodynamically useless because the relatively small temperature difference between the condenser and the environment only allows the recovery of 5-6% of the energy by any practical means.

So for the price of carrying a massive and complex exhaust cooling heat exchanger - which btw. introduces back-pressure and pumping losses onto the engine - you may improve the fuel efficiency by a couple percents - an amount you most likely lose many times over by the increased pumping losses and the additional weight.

3.7 / 5 (3) Feb 16, 2016
The problem of the condenser was btw. the issue why stirling engines never became a thing in cars.

The difference between a stirling engine and regular engine is that the regular engine uses the combustion gasses as the working fluid, whereas the stirling engine - much like the steam engine - transfers the combustion heat into a separate working fluid.

That means the stirling engine needs a heat exchanger to get the heat out of the working fluid (gas, really) to maintain the temperature difference between the hot and cold ends of the thermodynamic cycle.

So the heat exchanger has to deal with all the heating power going through the engine, which is 3-4 times the amount that the engine can extract into useful work. For a 20 kW engine, the heat exchanger has to dump 80 kW heat. That severly limits how much heat you can put through, thus making it very difficult to build a car sized stirling engine with reasonable performance, because the heat exchanger becomes huge.

3.7 / 5 (3) Feb 16, 2016
Besides, if you have a heat exchanger for condensing the exhaust gasses, you need airflow to cool it, which means you have to put up some sort of radiator grille or air intake on the car to divert air through it, or most likely a fan.

So you either introduce more air drag to the body of the vehicle, or you use some of the engine power to blow air through a radiator, which means you increase fuel consumption one way or another.

So if the condenser did help you scrub the exhaust of nasties, it would do so at the expense of fuel economy - exactly the problem as outlined in the first paragraph of the article.
3 / 5 (2) Feb 16, 2016
When you see pictures of stirling engines, they're usually very low power tabletop toys, or the actual radiator is left out of the picture. Here's one where the radiator relative to the engine is visible:


That gives you an idea of the size of radiator required to deal with the amount of heat coming out of a car's exhaust, because in a stirling engine the whole point is to put all the heat from the burner exhaust through the engine and then out through the radiator.

That engine is a 10-20 kW generator set, and yet it has a radiator as big as the engine itself. A 100 kW car engine would be all radiator.
3 / 5 (2) Feb 19, 2016
Eikka, please don't confuse gkam with physics and math, it gives him a rash that can only be cured by telling us his experiences. Have a good day.

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