A patent issued to engineers in the SwRI Engine and Vehicle Research Division provides technology that will help manufacturers and operators of lean-burn, natural gas engines solve the problem of misfire, which affects engine performance in regions or seasons of high humidity, defined as dew point temperatures above 15°C.
Most natural gas engines operate close to their "lean" limit to maximize engine efficiency and reduce emissions. High humidity, however, reduces the rate of combustion in these highly boosted engines and increases the likelihood of misfire, which raises emission levels of unburned hydrocarbons and carbon monoxide as well as degrades engine driveability and efficiency.
Research leading to the patent evolved from a project to design a prototype low-emission school bus engine powered by natural gas. The project was sponsored by the National Renewable Energy Laboratory, in cooperation with the Deere Power Systems Group, the Blue Bird Corporation, and the CNG Cylinder Company.
"As a result of the extensive engine mapping necessary to determine the successful limits of operation for the school bus engine, we were able to identify a relationship between atmospheric humidity levels and engine performance and emissions characteristics," says Principal Engineer John Kubesh.
"There was some understanding of these problems before testing," he continues. "For example, both the Society of Automotive Engineers and the Environmental Protection Agency use correction factors that take into account the effect of humidity on gasoline and diesel engine performance and emissions measurements, but these corrections are relatively minor in terms of overall performance measurements. The effects of humidity on the performance of natural gas engines are far more profound."
A water injection and atomizer system was constructed in a test cell, and experiments were conducted to measure the effects of different degrees of humidity on the engine, including its lean misfire limit and rate of combustion. As a result, the SwRI team was able to establish that a natural gas engine that has been calibrated for operation in a dry winter climate such as the southwestern United States would have trouble functioning efficiently on the Gulf Coast during the summer months.
An unexpected discovery was that the output of the oxygen sensor was affected by varying humidity levels. In particular, increased humidity caused the electronic control module to "think" the engine was running too rich and trigger a shift to a leaner mode which increased misfire.
An algorithm solves these problems by dictating a series of adjustments to the oxygen sensor calibration and the engine's fueling, spark timing, and boost pressure setpoint tables based on the humidity of the ambient air. The team found that implementing these solutions alleviated many of the misfire problems and, with proper adjustments, could minimize the emissions levels.
"Geographical and seasonal variations in ambient moisture should be taken into account by engine developers when considering a specific engine application," adds Kubesh. "This is a useful piece of information for us as developers and for the natural gas engine industry in general."
Other inventors named in U.S. Patent No. 5,735,245, "Method and Apparatus for Controlling Air/Fuel Mixture in a Lean-Burn Engine," are Staff Engineer Lee G. Dodge and Principal Engineer Daniel J. Podnar.
SwRI and Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI) have announced the formation of a high-technology, industrial inspection company that will employ 26 former SwRI engineers and technicians.
The new firm, IHI Southwest Technologies, Inc. (ISwT), is a wholly owned, San Antonio-based subsidiary of IHI, a Japanese company employing more than 15,000 people. With headquarters in Tokyo, IHI is a worldwide industrial technology firm specializing in aero-engine, space development, power plants, environmental protection, and the development of industrial equipment and facilities throughout the world.
ISwT will provide nondestructive evaluation (NDE) inspection of critical components at nuclear and fossil-fuel power plants worldwide, as well as at petrochemical facilities. ISwT will also expand its activities to include maintenance and repair of nuclear plant facilities.
"NDE research and development will continue to be an Institute strength," says SwRI President J. Dan Bates.
"The field services function has been spun off into a commercial venture, keeping the Institute's primary focus on technology development and transfer rather than on long-term delivery of field services."
SwRI is not involved in the new firm's ownership or management. However, ISwT will lease approximately 15,000 square feet of office and laboratory space on Institute property under a five-year agreement. This property formerly housed the SwRI Nondestructive Evaluation Inspection Services Department, whose equipment also has been sold to IHI.
ISwT President Bruce Jacobs and all but one of the firm's other initial employees previously provided NDE inspection services as employees of the Institute, using tools and technologies that in many cases were developed at SwRI. The Institute will continue the research and development of new NDE technologies.
Contact Jacobs at (210) 522-2032.
A new, lightweight piston engine that burns heavy distillate fuels, such as diesel or jet fuel, has been successfully test flown on an unmanned aerial vehicle (UAV). Flights were conducted by a team including SwRI, Evan Guy Enterprises, Inc. (EGEI), and Mission Technologies, Inc. The flights, conducted at a Mission Technologies facility near D'Hanis, Texas, demonstrated taxiing, takeoff, and flight patterns around the airfield before landing.
UAVs of various sizes are remote-controlled or programmable reconnaissance aircraft that can extend the eyes of the military over the horizon to gather real-time intelligence against an adversary without placing a pilot at risk. Heavy fuel engine (HFE) powerplants can reduce logistical burdens because they can use the same fuel as jet aircraft, tanks, or military trucks. Current, gasoline-powered UAVs require a separate fuel supply to be stored, maintained, and transported along with the aircraft.
Operating smoothly on JP-8 fuel, the new reciprocating HFE developed by EGEI and SwRI produces 25 horsepower with no visible exhaust smoke, indicating complete and efficient combustion. Evan Guy, EGEI president, explains, "The engine is spark ignited to allow lightweight production engines to meet Department of Defense objectives of heavy fuel operation for UAVs."
The engine was flown on Mission Technologies' Merlin UAV, with a takeoff weight of more than 200 pounds. Takeoff and landing were achieved on an unimproved dirt airstrip.
"This flawless HFE flight on a UAV platform clearly demonstrates needed technology to allow tactical UAVs to operate with heavy fuels," says Tom Prescott, Mission Technologies vice president of engineering and production. "To date, UAVs require gasoline fuels with their associated safety and logistics concerns. UAVs can now join the rest of the military's 'single battlefield fuel' inventory," Prescott says.
The new engine also has potential non-aviation applications, such as in motorcycles or ground power units, states Robert Burrahm of the SwRI Engine and Vehicle Research Division.
While the recent test flight involved a single-cylinder, liquid-cooled engine of approximately 25 horsepower, later versions are expected to be air-cooled, with up to four cylinders and 120 horsepower, says Burrahm.
Contact Burrahm at (210) 522-3064 or firstname.lastname@example.org.
Dr. Vijay Jain, a senior research engineer in the Center for Nuclear Waste Regulatory Analyses at SwRI, has been elected a Fellow of the American Ceramic Society (ACerS). Jain was cited by ACerS for his work in the field of nuclear waste vitrification and for his pioneering efforts toward the use of finite element programs for understanding stress behavior in glass and ceramic products with dissimilar materials.
Since joining SwRI, Jain has been responsible for advising and supporting the U.S. Nuclear Regulatory Commission in the development of regulatory guidelines for the privatized vitrification facilities at the Hanford site in Washington state.
Jain is chairman of the ACerS Nuclear and Environmental Division and is a member of the Materials Research Society.
Contact Jain at (210) 522-5439 or email@example.com.
SwRI has been approved by the U.S. Coast Guard (USCG) to perform evaluations according to the International Maritime Organization (IMO) Fire Test Procedures (FTP) Code. Ships that travel in international waters must now meet IMO standards. Prior to July 1998, individual countries could designate their own standards.
Ship manufacturers were required to ensure that their materials and assemblies would comply with the standards of the country in which the ship was registered. IMO establishes one set of international standards for all countries to follow. SwRI is one of two laboratories in the United States that is approved by the USCG to perform the IMO tests and to provide product control services. The latter require follow-up audits of the manufacturing facilities to ensure that the product that reaches the consumer is comparable to that which was evaluated and tested.
"Because these evaluations are critical to ensuring a ship's safety, the USCG must make sure that laboratories they have approved have a good quality control system," says Gladys Finley, manager of the Listing, Labeling, and Follow-up Inspection Services section in the SwRI Fire Technology Department. "The basis of the FTP code is to ensure the safety of people aboard the ships. Because of this, the USCG is very concerned and strict as to who they approve to perform this work."
The IMO requires that the material being installed on a ship be the same or comparable to the material that was tested. SwRI notes how a product is made, initials the prototype, ships it to the testing laboratory, and writes a quality control manual to specify how that product should continue to be manufactured. The Institute then makes periodic unannounced visits to the manufacturing facilities to ensure that the product is being made according to approved procedures.
The Institute tests a variety of materials and assemblies that are used on ships, such as windows, bulkheads, doors, floors, ceilings, and pipes.
Contact Tim Koebke, M.S., at (210) 522-6976 or firstname.lastname@example.org.
NASA has provided $5.3 million to SwRI to build a component that will study the interaction between the solar wind and the upper atmosphere of Mars. The Analyzer of Space Plasmas and Energetic Neutral Atoms (ASPERA) instrument will fly aboard the European Space Agency (ESA) Mars Express spacecraft in June 2003. The Swedish Institute of Space Physics in Kiruna, Sweden, is taking the ESA lead in collaboration with researchers from Finland, Italy, England, Germany, and France. SwRI is a co-investigator and the lead U.S. hardware institution.
SwRI will build the electron spectrometer for the ASPERA instrument package, which also includes an ion composition instrument and an energetic neutral atom (ENA) imager. The ENA instrument will image energetic neutral atoms created by the exchange of charge between energetic ions and Mars' extended neutral atmosphere. The ENA images and in situ plasma data provided by the ASPERA investigation will be used to characterize the immediate space environment of Mars and to study its interaction with the neutral gases of the martian upper atmosphere. Understanding this interaction is of central importance to efforts by planetary scientists to characterize the present state of the martian atmosphere and to reconstruct its history and evolution over the past 3.5 billion years.
"The fact that Earth can maintain life is a unique condition in the solar system," says Dr. David Winningham, ASPERA co-investigator and an Institute scientist in the SwRI Instrumentation and Space Research Division. "Mars Express could tell researchers what variables are needed to first create, then preserve over geological time, oceans and atmospheres."
In the case of the Earth, a strong planetary magnetic field helps maintain the atmosphere by shielding it from the solar wind - the supersonic stream of charged particles that flows from the sun. Without this magnetic shield, ionized gases in the Earth's upper atmosphere would become entrained in the solar wind and swept away, leading to a significant loss of atmospheric material over geologic time.
Unlike Earth, Mars has no intrinsic magnetic field - or at best only a very weak one - leaving its atmosphere unprotected from erosion by the solar wind. Such erosion results both from the "pick up" of ions from the martian ionosphere by the solar wind's magnetic field and from the "sputtering" of neutral atmospheric material by the heavy "pick-up" ions.
ASPERA will acquire data on the charged particles that impinge on the martian atmosphere and on the atmospheric material that is lost as a result of ion pick up and sputtering. Recent theoretical calculations suggest that the oxygen lost by these and other processes over the last 3.5 billion years is equivalent to the amount of oxygen in a global layer of water about 50 meters deep. The ASPERA measurements thus bear directly on the important question of whether liquid water - the primary requirement for life as we understand it - was ever present on Mars in significant amounts.
Contact Winningham at (210) 522-3075 or email@example.com.
Published in the Summer 1999 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Maria Martinez.