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2000 Progress Report: New Sensor Technology for Reducing Emissions from AutomobilesEPA Grant Number: R828209
Title: New Sensor Technology for Reducing Emissions from Automobiles
Investigators: Taylor, Henry F.
Institution: Texas A & M University
EPA Project Officer: Karn, Barbara
Project Period: May 1, 2000 through April 30, 2003
Project Period Covered by this Report: May 1, 2000 through April 30, 2001
Project Amount: $220,000
RFA: Technology for a Sustainable Environment (1999) RFA Text | Recipients Lists
Research Category: Sustainability , Pollution Prevention/Sustainable Development
Objective:The goal of this project is to demonstrate the feasibility of producing accurate, affordable, and reliable fiber optic sensors for monitoring in-cylinder pressure in automotive engines.
Relevance to Human Health and Protection of the Environment. Reciprocating engines in automobiles (including passenger cars, light trucks, and sport utility vehicles) have for many decades been the world's most important source of air pollution. Recent EPA data indicate that 78 percent of CO emissions and 45 percent of NOx emissions in the United States are attributable to transportation. At least 90 percent of the emissions in the transportation category are produced by reciprocating engines in automobiles?emissions that are targeted by the proposed research.
In spite of enormous efforts to develop practical automobiles driven by batteries or fuel cells, it appears that the reciprocating engine will prevail as the primary power source for automobiles well into the 21st century. Automobile manufacturers in the United States will be required by EPA regulations to continue their efforts to reduce harmful emissions from these engines and to improve their fuel economy. A significant part of these efforts will be directed towards providing better control of the engine using data from new, more sophisticated sensors that monitor each cylinder. Studies have shown that when an engine is balanced (producing the same peak pressure at the same crank angle in each cylinder), emissions are minimized; but, when one or more cylinders is out of balance, emissions increase dramatically.
It is anticipated that when the appropriate technology is available, automotive engines will be balanced by a feedback process in which data from in-cylinder engine pressure sensors are provided to an onboard computer that controls the electronic fuel injectors in each cylinder. Engine control computers and electronic fuel injectors are well established in today's automobiles. The missing link is the in-cylinder pressure sensor.
The fiber Fabry-Perot interferometer (FFPI) engine pressure sensor?the first sensor capable of continuous, reliable pressure measurement in the high-temperature engine environment?will be adapted to meet this need under the proposed EPA project.
Research Progress. The major technological barriers to achieving the goal of this project, which apply to both fiber optic pressure transducers and the monitoring optoelectronic system, are cost, size, and speed of operation. During the first year, means for overcoming each of these barriers have been explored.
The largest part of the first year's effort has been devoted to exploring methods for embedding FFPI pressure sensors in spark plugs. Representing a radical departure from prior fiber optic transducer designs, this type of sensor has a chance to meet a cost goal of less than $5 per cylinder while requiring very little space in the engine compartment. Fabrication of the FFPI sensing elements starts with producing mirrors on the cleaved ends of fused silica (SiO2) fibers by vacuum deposition of a thin TiO2 film in a planar magnetron sputtering system. The mirrors are then integrated into a continuous length of the fiber by joining a coated fiber to an uncoated fiber with an electric arc fusion splicer. The FFPI sensing elements thus formed are then electroplated with nickel to protect them from mechanical damage. To mount the fiber in the spark plug, a narrow longitudinal groove is cut in the steel casing. Next, to protect the fiber by relieving stress at the point where it enters the casing, it is bonded inside a small-diameter stainless steel capillary tube using a high-temperature polyimide. As the final step in sensor fabrication, the FFPI element with its protective coating is bonded into the groove.
Testing of six of these sensors has been carried out in a single-cylinder Ajax engine at the facility of Fiber Dynamics, our industrial partner. Preliminary results show good sensitivity for the spark-plug-mounted sensor, and the variation of signal level with pressure accurately tracks that measured with a reference piezoelectric sensor. The feasibility of using vertical cavity surface-emitting lasers (VCSELs) in the optoelectronic system for monitoring the sensors also has been explored. This type of laser, recently introduced as a light source for fiber optic communication networks, could be the key to achieving an inexpensive optoelectronic system for acquiring the sensor data. Data measured on five developmental lasers donated by Honeywell show a linear power versus current behavior with threshold currents in the 0.5 mA range and a single mode spectral output.
Future Activities:During the second year of the project, work on the methodology for fabricating reliable, high-performance spark-plug-embedded sensors will continue. Tests will be carried out in a four-cylinder gasoline-fueled Onan engine, which is now being prepared for this purpose. New sensors fabricated in fibers that are single mode in the 0.8 mm spectral regime will be tested using the VCSEL lasers. Work on high-speed electronics for use in the signal conditioning unit will be initiated.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 2 publications||2 publications in selected types||All 1 journal articles|
||Bae T, Atkins RA, Taylor HF, Gibler WN. Interferometric fiber-optic sensor embedded in a spark plug for in-cylinder pressure measurement in engines. Applied Optics 2003;42(6):1003-1007.||