Technical Innovations
Marine engine from GM Powertrain
 GM Powertrain incorporated the strengths of the Vortec 8100 truck engine into the 2003 Vortec HP3 marine engine, including the emissions and fuel-economy improvements the company has made over the years. |
As part if its 2003 marine engine lineup, GM Powertrain is introducing a high-performance Vortec HP3 8100 V8 that will produce the highest output ever offered by a GM Powertrain production engine. Based on the largest light-truck cylinder block in its lineup, the Vortec HP3 is targeted for the performance recreational marine market. It produces more than 525 hp (390 kW) at 5200 rpm and 560 lb•ft (760 N•m) at 4000 rpm.
The HP3 is GM's third marine powerplant designed from a common 8.1-L architecture. The Vortec HP1 and HP2 marine engines produce 375 and 420 hp (280 and 313 kW), respectively. The Vortec 8100 offered in both the Chevrolet Silverado and GMC Sierra produces 340 hp (255 kW).
Performance features specific to the Vortec HP3 include a virtually seamless, precision-matched intake manifold and cylinder head ports for optimum flow characteristics, providing improved power and torque for hole shots and acceleration maneuvers when boaters need it most. Other features of the HP3 include steel camshaft and crankshaft timing sprockets; a five-bearing crankshaft with four-bolt, cast iron bearing caps; a high-volume oil pump with weld-reinforced shroud, pickup tube, and screen assembly; double roller timing chain; coated cast aluminum; and port and starboard 12-mm drain plugs.
The fuel delivery system includes a 75-mm (3-in) marine throttle body unit with an HP3-specific, 400-kPa (58-psi) fuel rail, providing a pressure increase of more than 30% over the standard Vortec 8100 production engine. The engine's bore and stroke are 4.25 x 4.37 in (107.95 x 111 mm). Computer ignition and fuel management parameters are calibrated to provide the best possible performance characteristics across the entire powerband.
The Vortec HP3's valvetrain features a high-lift and high-duration camshaft; premium race-style valve springs; 1.7:1 ratio roller rocker arms; dedicated rocker arm studs; and an intake and exhaust push rod exclusive to the HP3. Performance is also enhanced with a dedicated HP3-tuned harmonic balancer and individual ignition coils for each of its eight platinum-tipped spark plugs.
The HP3's performance comes from a naturally aspirated design based on a stock truck engine block. Information gained from automotive engine development was applied to the marine engine. In turn, knowledge gained from marine engine development, where conditions are much more severe, was driven back to automotive engine development for improved product quality.
The new engine will also be available with a remote oil cooling system with all connections and system wiring, a dedicated marine fuel system, and a marine-specific alternator, starter, flame arrestor, and 142°F (61°C) thermostat.
HP3s have a 9.1:1 compression ratio and are designed to run on regular unleaded fuel. The engines are manufactured at GM's engine assembly plant in Tonawanda, NY, and then shipped to Innovation Marine in Sarasota, FL, where they are modified, tested, and sealed before being assembled into the race boats.
In the 2002 American Power Boat Association (APBA) Offshore Racing Series, Vortec HP3-powered boats captured first- and second-place finishes in the APBA race in April in Daytona Beach, FL. Three weeks later, in the second APBA race in Marathon, FL, HP3-powered boats went on to capture a first- and two second-place finishes. In the third and most demanding APBA race, held in June on stormy Atlantic seas off Cape Cod, HP3-powered boats took two first- and two second-place finishes.
- Jean L. Broge
Ticona cuts cost, weight from fuel cells
Development work by Ticona, the technical polymers business of Celanese AG, indicates that injection-molded end plates made of glass-reinforced Fortron polyphenylene sulfide (PPS) can produce "significant" cost and weight savings in proton exchange membrane (PEM) fuel cells that integrate the end plates and the adjacent insulating plates into one functional unit.
PEM fuel-cell stacks typically have sets of separate stainless steel or aluminum end plates and insulating plates at both ends of the stack. End plates hold the bipolar plates in a stack together and compress the gaskets between them. Insulating plates have bored manifolds that feed fuel, air, and deionized water (for cooling) to the stack. Even with automated machining, the two sets of plates on each stack can cost $300 to $500, according to Ticona.
Actual savings from integrating the plates is between $100 and $120 per stack, the company said, and the switch from metal to plastic can cut stack weight at least 10 lb (4.5 kg). Injection molding reduces manufacturing time to less than two minutes per plate versus the several hours needed for machined plates.
Fuel Cell Components and Integrators, Inc. believes Fortron PPS is a good candidate material for end plates. "From our experience, it molds well, replicates fine features, and has little warpage compared to other plastics we've evaluated," said Bernie Rachowitz, company President. "In use, it is stiff, strong, and hard, has low creep, and looks and feels like metal."
The material has the purity needed to satisfy known electrochemical demands in fuel cells, according to Ticona, which says tests show it has little effect on the conductivity of fluids in contact with it. Fortron PPS grade 1140L4 generates only a 2 µS/cm change in conductivity in a 50% glycol solution after seven days. Maintaining low conductivity in the end plates and minimizing ionic impurities that might leach into the electrolyte are key to continued fuel stack efficiency, in the view of Ami El Agizy, Ticona Market Development Manager for fuel cells. Fortron PPS has good dimensional stability and retains its mechanical properties at temperatures of over 200°C (393°F). "This is well above the 80°C at which PEM fuel cells now operate and the 150°C projected for the next PEM generation."
The material also has the rigidity needed to tolerate the high stresses that go along with compressing PEM fuel stacks, as well as long-term resistance to deionized water, oxygen, propane, natural gas, and other hydrocarbon fuels, El Agizy added. In addtion, he added, PPS is a good insulator, has a low coefficient of thermal expansion, absorbs little water, and is inherently flame-retardant.
Ticona offers both short- and long-glass-fiber-reinforced PPS grades. Smaller fuel-cell stacks place relatively low stress on the end plates, and short-fiber-reinforced Fortron 1140L4 PPS is useful for these applications. Larger stacks may require Celstran PPS-GF, which contains long glass fibers chemically coupled to the plastic matrix using a patented pultrusion process that fully impregnates them. The fully wetted fibers improve the polymer's mechanical properties.
As part of its fuel-cell activities, Ticona/Celanese is a member of the U.S. Fuel Cell Council (USFCC), an industry association dedicated to fostering the commercialization of fuel cells in the U.S.
- Patrick Ponticel
Ames seeks big results on "small effects" research
 Napolitano (left) and Trivedi place an aluminum alloy single crystal into a furnace to selectivelymelt certain microscopic regions, forming and trapping a dispersion of tiny liquid droplets within the solid. While this melting proceeds rapidly, stabilization of the droplet dispersion may require several weeks. Morris, the theorist, watches the procedure. |
To gain a better understanding of how microstructures develop in materials, scientists at the U.S. Department of Energy's Ames Laboratory at Iowa State University are examining certain properties that exist in metals at the interface between the liquid and solid phases during solidification. The research may one day enable scientists to tailor microstructural development, providing the basis for new and improved materials.
Researchers at Ames have shown that there are many subtle variations in microscopic properties near the liquid-solid interface as the solid is "freezing out." The small variations depend on which crystal face is in contact with the liquid. Difference faces (orientation) give slightly different values for properties such as free energy, mobility, and stiffness (surface tension); these properties play a crucial role in how the microstructure of a metal evolves during solidification.
"There are some properties that are very small," said Rohit Trivedi, an Ames physical metallurgist and an Iowa State University distinguished professor. "For example, the way a snowflake forms depends on very small factors. It turns out that some of these small factors are really the essential ones in determining shape. The same thing is true not only for materials, but for humans, animals, plants—anything that grows."
Innovative experimental techniques developed by Trivedi and Ralph Napolitano, a physical metallurgist and ISU assistant professor, have provided the first reliable measurements of the minuscule variations in free energy at the liquid-solid interface in metallic systems. Computer simulations developed by Ames theoretical physicist James Morris calculate these same quantities and show how the atoms behave at the interface. The combined efforts provide both a direct check between the experiment and the simulation and the opportunity to put forth new solidification theories that may lead to the ability to predict the development of microstructures.
"We're investigating some very specific quantities, such as the variation of interfacial free energy with crystallographic orientation," said Napolitano. "By revealing the essential physical behavior of liqid-solid interfaces, these critical experiments are facilitating significant advancement in the theoretical prediction of microstructures."
 The two-phase structures that form within the droplets during rapid quenching from the liquid state reveal the overall pre-quench equilibrium shapes of the droplets. Trivedi and Napolitano use such cross sections to quantify the deviation from sphericality in the quenched droplets. The deviation is extremely small, but enough to effect big changes in microstructural development. |
In experiments designed to measure small effects on the property of interfacial free energy, Trivedi and Napolitano have developed a technique to selectively melt certain microscopic regions within an aluminum alloy single crystal, forming a dispersion of tiny liquid droplets trapped within the solid. (A single crystal is one in which all the atoms are oriented in a specific direction. The orientation is uniform throughout the material, creating a simple, symmetric structure.) The material is then heated to bring the droplets structures to equilibrium (the condition at which no change occurs in the state of a system unless its surroundings are altered). After rapid quenching, the droplet shapes are measured carefully and their equilibrium shapes determined, providing the necessary link to interfacial properties.
"Thermodynamics tells us how the equilibrium droplet shape is related to the interfacial free energy," Napolitano said. "These measurements provide a direct means for quantifying the subtle variation of this property with respect to crystallographic orientation. The challenge is to accurately measure the degree to which the droplet shapes deviate from being spherical, and they deviate only by a percent or so."
It's the job of Morris to determine the size of the deviation. If the droplet is not perfectly spherical, "We want to measure that," he said. "We don't want it to be influenced by dirt in the system or anything else. The deviation is a very small number, but it's very important—and that's where doing the calculations and modeling the atomic fluctuations of the liquid-solid interface have come in."
- Patrick Ponticel