Focus on Research
Andre L. Boehman,
director of the Penn State Combustion
Laboratory and assistant professor of fuel science, collects
particulate matter to measure total mass emissions from an
exact duplicate of the engine used to run the staff shuttle at University Park.
Photo: Greg Grieco
Coal-derived fuel is found to burn cleaner
By A'ndrea Elyse Messer
Public Information
The chemical that replaced fluoro-chloro carbons in spray cans also may serve as a replacement utility fuel and may even substitute for diesel fuel in the future, according to researchers.
Dimethyl ether (DME) is normally produced by dehydration of methanol, but DME production from natural gas and from coal-derived syngas may open up this clean fuel for broader use, the researchers suggest.
In a study of the emissions produced when burning DME as a substitute for n-butane or propane, researchers found that DME had lower carbon monoxide emissions and the same or lower nitric oxide emissions than either of these commercially available fuels.
"In China and India, propane and butane are used in great quantities for utility purposes such as cooking," said Andre L. Boehman, director of the Penn State Combustion Laboratory and assistant professor of fuel science. "Switching to a fuel that generally has lower emissions and is coal-derived could make cleaner fuel available from local resources."
The researchers, who also included Christopher Frye, graduate student in fuel science and Peter J. A. Tijm of Air Products and Chemicals, Allentown, Pa., found that in a series of tests, carbon monoxide emissions were lower when burning DME than for either butane or propane. They also found that in most cases nitric oxide emissions were lower, but that even in the worst case, nitric oxide emissions were no higher than when burning butane and propane.
"We concluded that in terms of its comparative carbon monoxide and nitric oxide emissions, DME is a viable alternative utility fuel," said Boehman.
With a favorable emission profile, Boehman is now investigating DME as a replacement fuel in diesel engines. While burning DME produces fewer emissions than burning diesel fuel, DME has very poor lubricating properties.
"Diesel engines rely on the lubricating properties of diesel fuel to lubricate the fuel injection system and other components," said Boehman. "DME has no natural lubricating properties and we will need to add a lubricating additive for diesel engine use."
Boehman and his team are planning to test DME-blend fuel in a Defender model, Champion motor coach with an International Corp. chassis and a Navistar engine. The shuttle bus, which seats 22 passengers and is accessible to those with a handicap, was purchased jointly by Penn State's fleet services and Boehman's grants. The motor coach is in daily use as a faculty/staff shuttle bus.
The researchers have begun to determine the baseline characteristics of the motor coach when run on standard diesel fuels. At the same time they are testing a variety of DME fuel blends on a test-bed engine.
Once the baseline and laboratory fuel tests are completed sometime next year, the researchers will adapt the motor coach for use with the DME fuel and will evaluate engine response, emissions and wear under normal usage.
Mechanical forces found
to exert
larger role in blood vessel health
Cholesterol, dietary fat, drugs and other chemical bio-regulators may get most of the media attention, but engineers have shown that mechanical forces, including shear stress, stretch and pressure, can play unsuspected but equivalent roles in some aspects of cardiovascular health and disease.
John Tarbell, distinguished professor of chemical engineering, and associates in Penn State's Biomolecular Transport Dynamics Laboratory, recently showed that there is a one-to-one correspondence between certain effects of shear stress, the frictional force exerted by blood flow, and a growth factor that stimulates the production of new blood vessels.
The Penn State group compared the effects of shear stress with that of vascular endothelial growth factor (VEGF) in laboratory tests with both human and bovine blood vessel tissue. VEGF is multifunctional and, in addition to promoting the growth of new blood vessels, it affects the ability of the cells on the interior surface of blood vessels, the endothelium, to allow fluid to pass through to the cells beneath.
The researchers showed that shear stress and VEGF not only cause similar changes in endothelium transport properties but also do so by the same chemical signaling pathways.
Tarbell, who directs Penn State's Biomolecular Transport Dynamics Option for graduate study in the Life Sciences Consortium, said his group also investigates the effects of fluid flow as it passes across blood vessel walls. This transmural flow is a million times slower than blood flow and amounts to a "seepage" through the wall's tissue matrix. Nevertheless, even though the flow is slow, Tarbell and his associates have shown that it exerts shear stress that affects vessel function. For example, they have found that shear stress from transmural fluid flow stimulates the contraction of smooth muscle cells, which lie deep within the vessel wall. This may, in turn, contribute to the overall vessel contraction in response to an increase in blood pressure.
"Holiday effect" may be
on
permanent holiday for investors
'The holiday effect' -- a phenomenon that once helped stock traders to make a killing in the market before holidays -- appears to have taken a holiday of its own, according to researchers.
Roger Vergin, professor of business administration at Penn State Great Valley, and John McGinnis, finance professor at Penn State Altoona, recently published their study of the preholiday market from 1987 to 1996 in the journal Applied Financial Economics. Their research shows that incredible preholiday market increases from 1928 to 1975, which caused the Standard and Poors 500 to jump a total of 778 percent on fewer than 20 days per year, look to be a thing of the past.
From 1987 to 1996, the study indicates that the S&P 500 saw a modest average increase of .04 percent on the days immediately preceding holidays that shut down the market. The New York Stock Exchange, NASDAQ and AMEX composites showed similar increases.
The holidays considered in the research include President's Day, Easter, Memorial Day, July 4, Labor Day, Thanksgiving, Christmas and New Year's Day. Vergin said he believes the earlier trend was the product of "preholiday euphoria."
"People felt good about having a day off, and became more optimistic, and it seems to have affected their buying patterns," said Vergin.
He said the current trend, which more closely mirrors the average day on Wall Street, is simply a case of investors catching on to the ramifications of the holiday effect.
"Once patterns are detected, enough people react to them so that they are eliminated," said Vergin.