Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MIT researchers work toward spark-free, fuel-efficient engines

24.07.2007
In an advance that could help curb global demand for oil, MIT researchers have demonstrated how ordinary spark- ignition automobile engines can, under certain driving conditions, move into a spark-free operating mode that is more fuel-efficient and just as clean.

The mode-switching capability could appear in production models within a few years, improving fuel economy by several miles per gallon in millions of new cars each year. Over time, that change could cut oil demand in the United States alone by a million barrels a day. Currently, the U.S. consumes more than 20 million barrels of oil a day.

The MIT team presented their latest results on July 23 at the Japan Society of Automotive Engineers (JSAE)/Society of Automotive Engineers (SAE) 2007 International Fuel and Lubricants Meeting.

Many researchers are studying a new way of operating an internal combustion engine known as “homogeneous charge compression ignition” (HCCI). Switching a spark-ignition (SI) engine to HCCI mode pushes up its fuel efficiency.

In an HCCI engine, fuel and air are mixed together and injected into the cylinder. The piston compresses the mixture until spontaneous combustion occurs. The engine thus combines fuel-and-air premixing (as in an SI engine) with spontaneous ignition (as in a diesel engine). The result is the HCCI's distinctive feature: combustion occurs simultaneously at many locations throughout the combustion chamber.

That behavior has advantages. In both SI and diesel engines, the fuel must burn hot to ensure that the flame spreads rapidly through the combustion chamber before a new “charge” enters. In an HCCI engine, there is no need for a quickly spreading flame because combustion occurs throughout the combustion chamber. As a result, combustion temperatures can be lower, so emissions of nitrogen pollutants are negligible. The fuel is spread in low concentrations throughout the cylinder, so the soot emissions from fuel-rich regions in diesels are not present.

Perhaps most important, the HCCI engine is not locked into having just enough air to burn the available fuel, as is the SI engine. When the fuel coming into an SI engine is reduced to cut power, the incoming air must also be constrained-a major source of wasted energy.

However, it is difficult to control exactly when ignition occurs in an HCCI engine. And if it does not begin when the piston is positioned for the power stroke, the engine will not run right.

“It's like when you push a kid on a swing,” said Professor William H. Green, Jr., of the Department of Chemical Engineering. “You have to push when the swing is all the way back and about to go. If you push at the wrong time, the kid will twist around and not go anywhere. The same thing happens to your engine.”

According to Green, ignition timing in an HCCI engine depends on two
factors: the temperature of the mixture and the detailed chemistry of the fuel. Both are hard to predict and control. So while the HCCI engine performs well under controlled conditions in the laboratory, it is difficult to predict at this time what will happen in the real world.

Green, along with Professor Wai K. Cheng of the Department of Mechanical Engineering, and colleagues in MIT's Sloan Automotive Laboratory and MIT's Laboratory for Energy and the Environment have been working to find the answer.

A large part of their research has utilized an engine modified to run in either HCCI or SI operating mode. For the past two years, Morgan Andreae (MIT PhD 2006) and graduate student John Angelos of chemical engineering have been studying the engine's behavior as the inlet temperature and type of fuel are changed.

Not surprisingly, the range of conditions suitable for HCCI operation is far smaller than the range for SI mode. Variations in temperature had a noticeable but not overwhelming effect on when the HCCI mode worked. Fuel composition had a greater impact, but it was not as much of a showstopper as the researchers expected.

Using the results of their engine tests as a guide, the researchers developed an inexpensive technique that should enable a single engine to run in SI mode but switch to HCCI mode whenever possible. A simple temperature sensor determines whether the upcoming cycle should be in SI or HCCI mode (assuming a constant fuel).

To estimate potential fuel savings from the mode-switching scheme, Andreae determined when an SI engine would switch into HCCI mode under simulated urban driving conditions. Over the course of the simulated trip, HCCI mode operates about 40 percent of the time.

The researchers estimate that the increase in fuel efficiency would be a few miles per gallon. “That may not seem like an impressive improvement,” said Green. “But if all the cars in the US today improved that much, it might be worth a million barrels of oil per day-and that's a lot.”

This research was supported by Ford Motor Company and the Ford-MIT Alliance, with additional support from BP.

Elizabeth A. Thomson | MIT News Office
Further information:
http://www.mit.edu

More articles from Automotive Engineering:

nachricht 3D scans for the automotive industry
16.01.2017 | Julius-Maximilians-Universität Würzburg

nachricht Improvement of the operating range and increasing of the reliability of integrated circuits
09.11.2016 | Technologie Lizenz-Büro (TLB) der Baden-Württembergischen Hochschulen GmbH

All articles from Automotive Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>