Ford Motor Co. projects hydrogen fuel-cell vehicles will hit the mass market in a big way in about 10 years. In the meantime, the company is rolling out vehicles that provide a substantial glimpse into the future. The 2005 Escape Hybrid is the world's first full hybrid SUV with a high-voltage storage battery which can drive on electric power alone. It uses a combination of gasoline and electric power to deliver 36 mpg in city driving. It can travel more than 400 city miles on a single tank of gasoline, without compromising performance or versatility. The hybrid system also meets the strictest emissions standards. The drive system combines a 70-kW permanent-magnetic electric motor (equivalent to 94 hp) and 28-kW generator with a modified Zetec four-cylinder engine that runs on the Atkinson cycle, which is up to 10% more efficient than a conventional four-stroke Otto-cycle. The Atkinson cycle - also called the 'fivestroke cycle' - works like this: intake, backflow (partial expulsion to eliminate pumping losses), compression, expansion, and exhaust. The combustion chamber volume is adapted to maintain a constant compression ratio to avoid knock while increasing the expansion ratio to optimize efficiency. Engineers convert the Zetec I-4 engine to an Atkinson cycle by changing the intake camshaft to one with a very late valve closing and installing pistons that decrease combustion clearance volume. These changes result in a higher, 12.3:1 compression ratio. A planetary gear set acts as an electronically controlled continuously variable transmission (eCVT) and varies the distribution of power between the gasoline engine, electric motor, and the vehicle's wheels. The Escape Hybrid does not need to plug in to recharge. Energy normally dissipated as heat during braking gets recaptured as electric energy and stored in the 330-V nickel-metal-hydride battery pack located beneath the rear load floor. The hybrid storage battery consists of 250 D-sized cells in a sealed enclosure. The Focus Fuel Cell Vehicle (FCV) combines hybrid-electric vehicle technology with an advanced fuel cell to create highly efficient, zero-emission power. The Focus FCV uses a fuel-cell engine from Ballard Power Systems, Burnaby, B.C. with the addition of a Sanyo battery pack and a brake-by-wire electrohydraulic series regenerative braking system. Both of these technologies also are found on the Escape Hybrid. In addition, the Focus FCV has an advanced hydrogen storage tank, which can handle 5,000 psi of hydrogen. The driving range of the four-passenger Focus FCV is between 184 and 200 miles at a top speed governed at 80 mph. The Ballard Mark 902 fuel-cell system has better power density than earlier cells. The 900 Series also was designed in a smaller package to be compatible with the overall system requirements of vehicles. The stack is more reliable and designed for better manufacturability and service than previous-generation devices. It delivers 85 kW, equivalent to 117 hp. In comparison, the base Ford Focus sedan with a gasoline engine has 110 hp. The hybridized Focus FCV's battery pack is made up of 180 individual D-sized batteries packaged between the rear seat and the hydrogen fuel tank. The battery is used during launch and assists the fuel-cell system to improve performance and drivability, but cannot power the vehicle by itself. The regenerative braking system works to recapture electric energy as the brakes are applied. This energy is used to charge the battery. Brake-by-wire means there is no mechanical connection between the brake pedal and the brakes during normal operation. This lets the system electronically optimize braking between regeneration and friction for maximum fuel economy and braking performance. Ford has fielded a fleet of 25 Focus FCV engineering vehicles around the globe and plans to produce up to 30 more hydrogen-powered vehicles, while BP will build a network of fueling stations in California, Florida, and Michigan to support them. Ford is developing a 2.3-liter hydrogen engine with Lean NO(x) Trap (LNT) aftertreatment, which has already been shown to meet the stringent Sulev-Bin 2 emissions standards during first tests. Ford engineers are in the process of optimizing its calibration to give performance similar to a gasoline-powered engine. Limited production for real-world demonstration could come within the next two years. Ford's Hydrogen Hybrid Research (H2RV) vehicle combines a 2.3-liter internal-combustion hydrogen engine (H2ICE), boosted by a supercharger, with a patented Modular Hybrid transmission system, which is a full hybrid system using a single 300-V electric motor, upgraded automatic transmission, and modified hydraulics, which can be used interchangeably in various vehicle structures.


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    Title :

    Automakers drive toward a hydrogen-powered future


    Additional title:

    Zukünftige Wasserstoffantriebe für Personenkraftwagen


    Published in:

    Machine Design ; 77 , 4 ; 110-116


    Publication date :

    2005


    Size :

    4 Seiten, 4 Bilder



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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