Brief notes about the world of science and technology at Southwest Research Institute
Institute engineers are testing a novel electromagnetic valve actuator (EVA) system that provides benefits long sought by vehicle manufacturers -- a way to control engine intake and exhaust valves and meet market demands for greater engine performance and improved fuel economy.
"Preliminary test results show that the EVA variable valve timing system gives a 10 percent increase in engine efficiency and a substantial improvement in power at low speeds," says Principal Investigator Daniel Podnar, a senior research engineer in SwRI's Engine and Vehicle Research Division.
In conventional combustion engines, a mechanically driven camshaft is used to operate the valves with fixed values for valve lift, timing, and duration. This system does not allow any operational variation to maintain peak engine efficiency as road or driving conditions change. Most cam-operated valves are tuned to operate at a specific range of engine speeds, typically between 40 and 55 mph, and there are severe penalties in combustion efficiency and fuel economy at other speeds or at partial load.
The EVA system is one of a series of electromagnetic valves patented by Aura Systems of El Segundo, California. The EVA is being tested in a two-cylinder, 18-horsepower, Kohler Command utility engine converted by SwRI to operate on natural gas. The project is part of a multi-year program sponsored by the Defense Advanced Research Projects Agency to develop efficient hybrid vehicles using natural gas auxiliary power units for military and commercial applications.
"The EVA system provides an infinite number of camshaft profiles at the touch of a control," says Project Manager Edward Bass, manager of Advanced Vehicle Technology at the Institute. "This capability allows us to tune and test the benefits of variable valve timing under a variety of operating conditions. For example, Miller cycle operation, in which the intake valve is closed earlier or later than in conventional engines for more efficient throttle-less operation, is one condition being evaluated."
The EVA system places one actuator at each valve site. Two opposing spring coils are also fitted at each site, providing the primary force to open and close the valves, and to reduce power consumption and increase reliability. The spring forces are supplemented by electromagnetic force from the EVA coils. The intake and exhaust valves are independently computer-controlled and timed, making it possible to fine tune air-fuel and exhaust flows to engine needs in a way no camshaft can.
"Use of the EVA system eliminates the need for a lot of parts that are subject to wear such as the camshaft, rocker assembly, pulley, and timing belt," adds Bass. "Hybrid vehicles represent an ideal use for this kind of valve because of the high voltage available, which increases the efficiency of the EVA system. There are, however, numerous applications for EVA systems in a range of vehicles, and we are looking forward to applying this technology to other combustion engines."
SwRI, under subcontract to Raytheon Demilitarization Company, Philadelphia, has been awarded a contract by the U.S. Army Armament, Munitions, and Chemical Command to monitor the destruction of aging munitions stored at the Army's Umatilla Chemical Depot in Oregon. The Institute will receive $43 million of $566.8 million earmarked for the Umatilla plant.
Raytheon will build and operate the demilitarization plant, where chemical agents and explosives will be destroyed in five incinerators. The plant is expected to begin operations in just under five years, after the construction and operational testing phases are complete.
The Institute will provide 80 full-time staff members to continuously monitor the air inside and immediately outside the plant, as well as plant effluent and the plant's perimeter, for the presence of chemical agents.
Dr. Michael G. MacNaughton, director of Environmental Engineering at SwRI, says the Institute's main role will be to protect the health and safety of those working at the plant and those living in the surrounding communities.
"A comprehensive monitoring plan is being prepared for approval by the state's department of environmental quality," he explained. "This plan will establish the type and frequency of samples that will be collected and analyzed to ensure compliance with environmental and safety standards.
"While construction of the demilitarization facility is under way," he continued, "the Institute will draw up a set of detailed operating procedures with which to implement the monitoring plan. After the plant is functional, extensive testing will be conducted to verify that plant operations are safe and effective." The Institute has performed a similar role since 1987 on Johnston Island in the Pacific with the Johnston Atoll Chemical Agent Disposal System (JACADS). Institute personnel provide continuous monitoring, sampling, and chemical analysis services during the incineration of aging weapons stored on the island, an operation which is overseen by the Army and several federal agencies.
Southwest Research Institute has been contracted to provide scientists, engineers, and technical staff to operate the Air Force's new Coatings Technology Integration Office (CTIO) at Wright-Patterson Air Force Base in Dayton, Ohio. The CTIO will operate as a government-owned, contractor-assisted entity within the Wright Laboratory Materials Directorate.
The application and removal of aircraft and associated equipment coating systems generates approximately 75 percent of the Air Force's hazardous waste. The CTIO will address reliability and maintainability of coating systems as a means to better protect aircraft and to reduce the frequency of removal and reapplication of coatings, a process which is both costly and potentially polluting.
"The CTIO's mission to assess and improve coatings as well as their application and removal processes provides an opportunity for SwRI staff members to solve important environmental and technical issues," says Mary Marshall, director of the Microcapsules, Coatings, and Polymers Department in SwRI's Chemistry and Chemical Engineering Division. Recent changes in the preparation and removal of coatings were introduced to comply with new and more demanding environmental regulations.
The CTIO is providing the Air Force with a central source of expertise and technology to evaluate new materials and processes using the best current testing techniques and will provide field support in troubleshooting unique problems with coating systems that hamper mission performance or interfere with adherence to pollution standards. The office will have between 20 and 30 staff members stationed at the 15,000-square-foot facility at Wright-Patterson and the auxiliary facility at Warner-Robins ALC in Georgia.
"SwRI has a long-standing interest in material and surface technology," says Stephen J. Lukezich, SwRI manager of the CTIO. "The Institute also has a tradition of multidisciplinary research that suits this area of technology. My training lies in the field of corrosion, but the CTIO draws on SwRI staff expertise in a number of fields -- chemistry, materials, surface science, mechanical systems, and statistical analysis -- all of which are related to aircraft coating systems."
Institute engineers, in a multiyear project for the Federal Aviation Administration (FAA), are developing a probabilistic damage tolerance design code to predict the safe operating life of gas turbine rotors and disks used in commercial aircraft. The probabilistic code, known as DARWIN (Design Assessment of Rotors with Inspection), incorporates sophisticated risk assessment methods into inspection procedures so a realistic inspection and replacement schedule for rotors and disks can be implemented.
Code development is being managed by SwRI in collaboration with four major turbine manufacturers -- Allied Signal, Allison, General Electric, and Pratt and Whitney. The companies plan to incorporate all or part of the new code in their design systems. The 'safe-life' approach is currently used to predict the service life of critical engine parts. Safe-life methods assume that any material or manufacturing condition that could affect the life of a part, such as a material flaw, is addressed by the rigorous standard testing procedures carried out in manufacturers' laboratories as well as by conservative estimates of mechanical properties.
However, some material and manufacturing flaws that reduce structural integrity can remain undetected. As an example, the crash of a DC-10 at Sioux City in 1989 was eventually traced to just such a defect. Consequently, the industry faces a dilemma with current design practices -- either frequent and expensive inspection and possibly premature replacement of parts, or the risk of catastrophe if a part is left in service too long.
As a result, the Federal Aviation Administration requested the Aerospace Industries Association (AIA) to review available design procedures to see what additional methods could enhance safety, with the outcome that the Rotor Integrity Subcommittee of AIA recommended the program now under way at SwRI.
"The probabilistic design code that the FAA has asked us to develop does not replace traditional safe-life methods but provides an additional tool to minimize risk," says Dr. Gerald R. Leverant, SwRI program director of Power Generation Materials and manager of the FAA program.
The first phase of the program is focusing on the presence of melt-related defects, known as hard alpha, in titanium alloys. Hard alpha refers to small zones in the material microstructure stabilized by the presence of nitrogen, which can be introduced at various stages in the melting history of the alloy. Cracks or voids associated with the zones can initiate the low-cycle fatigue cracks that contribute to disk failure.
Future phases of the program will apply the methodology to other types of titanium flaws and to other widely used rotor metals such as nickel.
Harold R. Simmons, a principal engineer in the Mechanical and Fluids Engineering Division at SwRI, has been elected a Fellow of the American Society of Mechanical Engineers (ASME).
Simmons received the honor in recognition of his innovative diagnostic technology developments used to solve rotating machinery dynamics problems and for his many years of service to ASME.
Simmons came to SwRI in 1974 from Pratt and Whitney Aircraft in West Palm Beach, Florida. Since joining the Institute, he has managed diagnostic and applied research projects to solve machinery dynamics problems for industrial clients. His 33-year career includes rotor design optimization and vibration analysis of jet engines, applied research on squeeze film dampers, multi-plane balancing, measurement of blade tip clearance to control blade rubbing and seal leakage, detection of blade vibration, and in-place balancing of paper mill rolls.
He has contributed more than 40 papers to the technical literature, receiving the 1990 Best Paper Award from the Pipe Line and Applications Committee of the International Gas Turbine Institute (IGTI) and the 1991 John P. Davis Award for the best applications paper, also from IGTI.
An ASME member for 29 years, Simmons is currently chairman of the Controls and Diagnostics Committee of the IGTI. He is also a member of the Vibration Institute. He holds a bachelor's degree in mechanical engineering from the University of Florida and is a registered professional engineer in the states of Texas and Florida.
Published in the Fall 1997 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.