Mechanical Engineering Design, March 2005 -- News and Notes

mechanical engineering design

news & notes

hybrids and hydrogen

Alternative vehicles are making some headway at Ford. As a follow-up to its prize-winning Escape hybrid, Ford Motor Co. plans to expand its hybrid vehicle lineup over the next few years. Ford also has its first customer for new hydrogen-powered vehicles, which will hit the roads next year.

The expanded hybrid lineup will include a Mercury Mariner, available late this year; a Ford Fusion, set for 2008; a Mercury Milan, also due in 2008, and a test fleet of Mazda Tribute hybrids to be introduced late this year and enter full-scale production in two years.

The Ford Escape hybrid was introduced last year and was named the 2005 North American Truck of the Year at the North American International Auto Show in Detroit.

All the hybrids will be designed to shut off the gasoline engine automatically and operate in electric-only mode when the vehicle is traveling at low speeds or when it's stopped.

Ford will deliver hydrogen-powered buses next year.

Ford has announced that the State of Florida will be its first customer for hydrogen-powered E-450 buses, which will debut next year. The Dallas/Fort Worth International Airport is working with Ford on plans to use the V-10 hydrogen-powered buses in its fleet next year, as well.

The hydrogen-powered internal combustion engine buses are equipped with a 26-gallon-equivalent fuel tank. Holding hydrogen pressurized at 5,000 pounds per square inch, the tank has an expected range of 150 miles.

Since there is no carbon in the hydrogen used as fuel, there is no carbon monoxide, carbon dioxide, or unburned hydrocarbons in the exhaust and no particulate emissions, according to a spokesperson from ISE Corp., the San Diego company that developed a prototype hydrogen bus for Ford.

Ford used the buses to shuttle reporters around Detroit during the recent North American International Auto Show.

Ford's will not be the first hydrogen-fueled buses. In Iceland, hydrogen-powered internal combustion engine buses made by DaimlerChrysler are already on the roads. Iceland has an official goal of making the country oil-free by shifting cars, buses, trucks, and ships over to hydrogen by about 2050.

— Gayle Ehrenman

bronze age

Large gas turbines used in electric power generation plants depend on equal flows of liquid fuel to be delivered to all of the combustors. This critical job is done by flow dividers, small gear pumps that separate the single flow of fuel from the fuel pump into a number of equal smaller flows. Yet these devices have an Achilles' heel: They are prone to corrosion and wear, which may lead to failure.

Finding materials that resist deterioration has been a major challenge, but a new design is taking a stab at it. The flow mechanism eliminates a traditional material, cast iron, and combines parts of stainless steel and bronze.

Flow dividers are passive devices that operate from the energy of the flow from the main fuel pump. These identical, highly precise spur gears are coupled together to rotate at equal speeds. When liquid fuel flows into the flow divider, it exerts pressure on the inlet side of the gears, which causes them to rotate and meter the fuel at identical flow rates.

To achieve highly accurate fuel metering, flow dividers are built with very tight running clearances, as small as 0.001 inch. The tight clearances make the gears susceptible to fouling. When fuel is not filtered properly, particulate matter traveling in the fuel stream can lodge between the gear and the faceplate. Excessive friction between the mating surfaces can cause adhesion and surface deterioration.

Liquid fuels may also contain contaminants that can attack flow divider materials. Water entrained in liquid fuel may separate and settle when the unit remains idle for extended periods and lead to rust on some surfaces.

Simple maintenance techniques can help minimize corrosion problems, but are often not adhered to by end users, according to Bill Flavelle, a senior project engineer at the Roper Pump Co. in Commerce, Ga. Flow divider housings have traditionally been made of cast iron, which has low cost and certain desirable mechanical properties. It is easy to machine, and it resists wear and galling when paired with stainless steel gears that operate at relatively low loads and high speeds, he said. The downside of cast iron is that it is susceptible to corrosion.

Flavelle recently redesigned the company's line of flow dividers for gas turbine applications to address problems of corrosion and fuel-borne particulates. The new design eliminates cast iron, in favor of a combination of stainless steel and bronze. Flow element faceplates are made of stainless steel and incorporate replaceable bronze wear plates on both sides of the pumping gears. Gear cases are also made of bronze. Housings, gears, and bearings are made of corrosion- and wear-resistant stainless steel.

Flavelle explained that the materials are unaffected by water, minimizing the problem of corrosion. They are also durable and wear-resistant, and should make the flow dividers less susceptible to failure from particulates. Bronze wear plates also will not gall against stainless steel flow element gears. He said the new flow dividers have shown no wear after 6,000 hours of lab testing.

— John DeGaspari

this car feels your pain

Swiss car designer Rinspeed and Bayer MaterialScience have pushed the boundaries of the concept car. Rather than just refining the look of a current vehicle, or adding a bigger, beefier engine, they've made the car more touchy-feely.

The Senso concept car, to be presented this month at the Geneva Auto Show, is supposed to "sense" the driver and adjust accordingly. The idea is that the car will adjust its interior environment to the driver's condition, to make sure that the driver stays relaxed and awake. The goal is to reduce the risk of an accident. One way the car does this is through the use of innovative lighting.

The Senso uses a sophisticated system of sensors developed by the Universities of Zürich and Innsbruck, coupled with a new 3-D-formable electroluminescent film from Bayer MaterialScience and Swiss electronics specialist Lumitec for the lighting.

The Senso car adjusts to the driver's condition.

The film forms the "smart" outer skin of the plastic component. Beneath this is a multilayer electrode system that produces cold light when a voltage is applied. These flat, readily moldable light-generating plastic parts produce a bright, uniform light while using hardly any energy (there's no bulb or light-emitting diode involved) and have a very long service life, according to Bayer.

The film could be used to provide lighting on the dashboard, as well as on other surfaces in the cabin. The system uses biometric data and other information to adjust the lighting to an appropriate level for the driver, so the driver will suffer less eyestrain, yet not be lulled to sleep by an overly dark cabin.

No details have been released on exactly how the Senso's interior lighting will work. The Senso is designed to be environmentally friendly and powerful, as well. Its six-cylinder, 250-horsepower Porsche Boxer S engine runs on natural gas.

No plans for a production vehicle have been announced.

— Gayle Ehrenman

clean fun in the snow

A dozen teams from universities across the snowy northland of North America are due to gather—quietly—in Houghton, Mich., this month for the Clean Snowmobile Challenge.

The design competition, sponsored by the Society of Automotive Engineers, calls for teams of engineering students to take stock snowmobiles and redesign them to reduce emissions and noise, and to maintain or improve performance.

The sleds will be judged at Michigan Technological University's Keweenaw Research Center, which houses vehicle testing grounds and a winter driving track.

In 2004, the University of Wisconsin's hybrid gas-electric sled took the gold. Michigan Tech placed second.

"I think Wisconsin will be the one to beat again," said Jay Meldrum, director of the Keweenaw Research Center. "And McGill is coming back with their electric sled, so we'll have a very interesting challenge this year."

McGill University is in Montreal.

Teams will put their sleds through a series of performance and emissions tests, including an endurance run. Ergonomic tests that measure rider comfort are new this year. The driver sits on an accelerometer—which Meldrum likened to a whoopee cushion—that can record vibration. The less vibration, the higher the snowmobile will score.

— Jean Thilmany

briefly noted

The Center for Biophysical Science and Engineering at the University of Alabama at Birmingham has been awarded a five-year NASA contract for up to $48 million to develop crew robotics and vehicle equipment for work in space.

SolidWorks Corp., of Concord, Mass., has teamed with Stereo-Graphics of San Rafael, Calif., a manufacturer of electronic stereoscopic visualization hardware, to add a new feature to its software. Users of SolidWorks will be able to see their solid models in stereoscopic 3-D with CrystalEyes electronic eyewear from StereoGraphics. It will be available for download early this year.

The Belgian Federal Government has agreed to co-finance the development of LMS Virtual Lab for Aerospace, a dedicated simulation suite for aircraft and space system development, according to LMS International in Leuven, Belgium.

ImpactXoft of San Jose, Calif., has released a new version of its IX SPeeD Suite, a design environment for simultaneous product development. This version includes specialized 3-D design toolsets for those working in the electronics and electrical, and the consumer goods markets.

Return to Index