Engines, Fuels, Lubricants, and Vehicle Systems

Meeting clients' product performance requirements while adhering to current and anticipated environmental standards is a continuing challenge in engine and vehicle design. The Institute carries out innovative design and development in the areas of engines, engine components, special vehicles, and improved emissions controls. In addition, the Institute performs a full range of fuel and lubricant test services for clients around the world. SwRI holds full ISO 9002 certification for its Automotive Products and Emissions Research Division and continues to pursue future certifications and accreditations, along with client-focused quality improvements.

Engine Design and Development

As China's economy continues to grow, there is a demand for faster and more reliable rail transportation. Dalian Locomotive and Rolling Stock Works, the People's Republic of China's largest locomotive manufacturer, has selected SwRI to design a high output, lightweight, robust engine to be used in a new class of locomotives. This project will extend over three years, with engine design being conducted in San Antonio jointly with Dalian engineers, and prototype development being carried out in China with Institute engineers.

The GasRail USA program, a cooperative government-industry research program aimed at developing a low emissions, natural gas-fueled locomotive, is in its fourth year, and all major laboratory goals have been met. The project's present focus is on integrating the liquefied natural gas fuel system into a passenger locomotive for field testing prior to operation in commuter service in the Los Angeles, California, area in 1998. Final engine calibration is being carried out on a full-size EMD 710 engine installed at SwRI's large engine facility. The engine uses late-cycle high-injection pressure combustion to burn natural gas, achieving a 75 percent reduction in emissions of oxides of nitrogen (NOx) while maintaining near-diesel fuel economy.

An ultra-safe, ultra-low emissions school bus, developed for the National Renewable Energy Laboratory, is undergoing final testing at the Institute's emissions facility. The natural gas engine, modified by SwRI engineers from a John Deere 8.1L engine, achieves emissions levels less than one-half of California ULEV standards with excellent fuel economy.

An ultra-safe, ultra-low emissions school bus, developed by the National Renewable Energy Laboratory with support from the Blue Bird Corporation, John Deere, and CNG Cylinder Corp., is currently being field tested. The natural gas engine developed for this project has completed transient emissions testing that shows emissions levels of less than half of the California ultra-low emissions vehicle (ULEV) standards, plus excellent fuel economy. Engine control technology developed for this engine includes knock sensing, misfire detection, humidity compensation, and advanced wastegate control. The bus also incorporates safety features such as seat belts, wide aisles, improved driver view, and a collision warning system.

For the past two years, SwRI has been conducting an internal research program to investigate homogeneous charge compression ignition (HCCI) of diesel fuel. The goal is to convert a multi-cylinder compression ignition engine to operate in HCCI mode. This mode significantly decreases engine emissions of particulates and NOx when compared to conventional combustion. Researchers have overcome several challenges with this design, such as high hydrocarbon production, limited operating range, and the high intake temperatures required for fuel vaporization. Currently, they are working to mitigate a slight increase in fuel consumption. However, results show a 98.8 percent reduction in engine-out NOx emissions for diesel-fueled HCCI over a direct-injection diesel configuration of the same engine, without producing soot.

SwRI's rapid prototyping electronic control system (RPECS), a PC-based tool (both hardware and software) used for real-time embedded powertrain control system development, continues to evolve. New applications of RPECS include integrated engine/transmission control, hybrid vehicle supervisory and subsystem control, and integrated engine/test cell control for development and automated mapping activities. More than a dozen such systems have been or are being developed for delivery to clients. In addition, RPECS systems are being used in SwRI internal research project applications. Refinements continue in the areas of analog and digital signal conditioning, hardware design, and graphical user interfaces.

SwRI has developed a dedicated ethanol-fueled (85 percent denatured ethanol/15 percent gasoline) passenger vehicle that meets California's ULEV standards, considered the tightest current emissions standards in the world for spark-ignition engines. Using air-assist fuel injectors, an exhaust gas ignition system, and the RPECS engine control system developed at SwRI, this vehicle maintains excellent driveability and efficiency, while attaining ultra-low emissions.

Engineers continue to use the spray model TESS^TM (Trajectory and Evaporation of Spray Systems^TM), developed at SwRI, for solving a variety of spray problems such as estimating fuel spray trajectories past intake valves in gasoline engines, determining evaporation rates of water sprayed in-cylinder to control emissions in natural gas engines, and approximating congealing rates for molten plastic materials used in the production of plastic parts. Spray behavior is complicated by the fact that a given spray consists of droplets that typically vary in size by a factor of 100. This range of sizes results in a wide distribution of drop trajectories and evaporation rates. Use of the TESS^TM model allows engineers to account for this variability. SwRI also has developed a computer model called ALAMO_ENGINE to estimate how changes in engine design parameters and operating conditions affect the production of NOx, which is a major contributor to photochemical smog in urban areas. This computer model has dramatically reduced the time and costs required for evaluating engine design innovations at SwRI and many diesel engine companies throughout the world.

Emissions Control

Snowmobile engine emissions are of concern in environmentally sensitive areas such as Yellowstone National Park. Results of a study recently completed by SwRI will assist policy makers in determining which types of fuels, lubricants, and equipment are acceptable for use in national parks and forests. The Montana Department of Environ-mental Quality contracted with the Institute to determine potential emissions benefits of bio-based fuels and lubricants in snowmobile engines. Emissions and fuel consumption were measured using a five-mode test cycle developed by SwRI from analysis of snowmobile field operating data. Results indicated that the use of gasohol (10 percent ethanol) reduced hydrocarbons, carbon monoxide, and particulates, but slightly increased NOx emissions, while maintaining equivalent engine power as compared to the reference gasoline in the tests. Also, it was found that particulate emissions could be reduced significantly with a low-smoke lubricant.

The Environmental Protection Agency (EPA) will require automobile manufacturers to develop their own vehicle service accumulation durability driving cycles for emission certification, rather than use an EPA-specified common schedule. These new cycles, which must be approved by the EPA, will demonstrate the durability of emission control systems by operating the cars for 100,000 miles, or by combining a vehicle driving schedule with an accelerated aging of the catalytic converter on an engine test bench. Institute engineers and statisticians have devised a protocol to gather needed information from private owners. The process involves statistically analyzing data to develop and validate the necessary cycles, then gaining EPA approval for the test cycles. It continues with a telephone survey of drivers, extensive engine and exhaust data collection, bench aging of catalytic converters, and standard EPA chassis dynamometer emission tests to validate the durability cycle that is developed. SwRI is already providing this test service to an overseas vehicle manufacturer.

To assess and further control pollution from heavy-duty trucks and buses, emissions data should be collected during operations as similar to actual service conditions as possible. For regulatory purposes, EPA procedures currently determine engine emissions only over a prescribed operating cycle. Institute engineers have developed the Mobile Vehicle Emissions Sampling System (MVESS) to test engine exhaust while a vehicle is operated over a variety of road conditions not easily simulated in the laboratory. The MVESS was designed and assembled under contract to the Pennsylvania Transportation Institute of Pennsylvania State University to estimate emissions from over-the-road buses while operating on a closed-loop track. The system uses a computer program developed by SwRI to calculate and control accumulation of representative samples of raw exhaust from the operating vehicle.

In conjunction with the EPA and the Engine Manufacturers Association, SwRI collected engine data from a backhoe/loader, a crawler tractor, and an agricultural tractor during actual field operation. The data were used to develop engine test cycles that were statistically representative of actual vehicle operations. The test cycles are currently being used on a new SwRI-developed transient engine testing and control system.

SwRI's universal tractor axle dynamometer is used to perform drivetrain endurance and clutch life tests on a variety of tractor models.

The Institute has been selected to develop an American Society for Testing and Materials (ASTM) Sequence VII Oil Protection of Emission System Test (OPEST). This test will qualify oils for emission system compatibility in internal combustion engines as part of the GF-3 engine oil specification proposed for the year 2001. The cooperative program involves several participants from the automotive and oil industries. To complement this project, SwRI has designed and built a synthetic gas reactor that measures catalyst performance of small samples using a precise mixture of simulated engine exhaust gases. The basic OPEST procedure is expected to be completed by the end of 1997.

SwRI engineers have developed a new burner-based catalyst bench test apparatus that extends research investigations into how fuels, lubricating oils, and additives can degrade or cause premature failure of engine catalysts.

An SwRI internal research project simplifies studies of how fuels, lubricating oils, and additives affect automotive catalysts. A new bench apparatus combines an air supply with a burner that heats the air and provides exhaust gas constituents to the catalyst. An oil injection system and a computerized control/data acquisition system complete the compact apparatus. Early tests of the new device will help determine how the phosphorus content of lube oil affects catalyst degradation.

SwRI is working with fuel and additive companies to develop fuels to control combustion chamber deposits that interfere with engine efficiency. Institute engineers have automated data collection by linking a thickness measurement tool to a laptop computer. The system provides precise, repeatable measurements comparing the ability of various fuels and additives to limit these deposits.

Fuels and Lubricants Research

In studies of how deposit formation affects driveability, vehicle octane requirement, and acceleration, the Institute continues to evaluate various types of vehicles for a number of clients. Vehicles are evaluated for driveability using Institute-developed procedures in addition to standardized Coordinating Research Council (CRC) and Society of Automotive Engineers (SAE) procedures. Trained raters assign numeric values based on the operation of the vehicle. A standardized CRC procedure defines evaluations to assess the octane requirement and to measure vehicle performance in relation to hesitations, surge, and stumble. Acceleration tests also are carried out according to a standardized SAE procedure. Deposit buildup in the engine can affect performance by degrading driveability, acceleration, and dependability.

The Institute has participated extensively in developing new tests for a $4 million test matrix funded by the lubrication industry in preparation for establishing a new, heavy-duty diesel engine oil category. The matrix is intended to determine the precision of new types of tests and provide guidelines to determine which tests should be run when different base oils are used with the same additives. The proposed new diesel-engine oil performance category, currently known as PC-7, will represent a significantly more robust minimum performance level for diesel engine oils and fulfills requests from major diesel engine manufacturers for lubricants to meet the requirements of their next-generation engines. It is expected that the American Petroleum Institute will recognize this new performance category and provide the consumer language for labeling.

A universal hydraulic test stand has been developed by SwRI engineers for nonstandard investigations involving hydraulic fluid and components. A variable-speed drive allows operation at speeds up to 3,000 rpm, clockwise or counterclockwise. The electric motor is capable of up to 400 horsepower. A computerized system for data acquisition and control monitors in-line fluid density, mass flow, drive torque, and real-time viscosity measurements while also controlling fluid pressure, motor speed, and operating temperature. Virtually any type of hydraulic pump can be installed to evaluate hydraulic fluid or equipment performance under various conditions.

U.S. Army TARDEC Fuels and Lubricants Research Facility

This year marks 40 years of continuous operation of the U.S. Army Tank-Automotive Research, Development, and Engineering Center (TARDEC) Fuels and Lubricants Research Facility (TFLRF). This government-owned, Institute-operated laboratory functions as a dedicated in-house facility for TARDEC, the Department of Defense organization responsible for the military ground fleet. The TFLRF investigates problems related to fuels, lubricants, and other functional fluids, and provides rapid responses to problems during worldwide operation of combat vehicles.

The Institute has developed a method for providing rapid fuel analysis using advanced statistical techniques and near-infrared (NIR) spectroscopy. This and traditional, complementary techniques are being incorporated into a prototype mobile laboratory to provide rapid fuel analysis wherever the U.S. Army operates. The analytical capabilities incorporated by the Institute into the mobile NIR laboratory provide most of the capabilities of a fixed fuels laboratory within a compartment of an Army high-mobility multipurpose wheeled vehicle.

With the continuing emphasis on higher engine efficiency and lower exhaust emissions from aviation gas turbine engines, internal engine temperatures and pressures continue to increase. One result is increased surface temperatures within engine fuel atomizers, which can lead to higher fuel temperatures and increased fuel-derived deposit formation. TFLRF scientists are conducting studies of the mechanisms through which jet fuels form deposits on surfaces, including the role of fuel composition, flow conditions, and heat flux. This work is supporting advanced turbine engine development and also has led to a characteristic time model of deposit formation that can be incorporated into future fuel system design codes.

Through grants from the National Aeronautics and Space Administration (NASA) and additional funding from the Institute, TFLRF has been investigating the mechanisms, kinetics, and chemistry of fuel deposit formation in jet fuels. This work has identified specific chemical reactions that occur for the formation of deposit precursors. An understanding of these chemical processes could lead to a new approach to using additives for fuel-deposition control in aircraft.

The vapor space above distillate or kerosene fuels often has been assumed to be too fuel-lean to burn. Nevertheless, TFLRF has developed analytical techniques to determine quickly the lean flammability limit of vapors from such fuels and to generate vapor mixtures of controlled flammability. These new capabilities, along with previously developed expertise in the role of spark energy on the probability of ignition, have been used by an automotive manufacturer and U.S. government agencies, including the U.S. Air Force and Navy, to study the explosive potential of fuel tank designs and to improve instruments for monitoring flammability limits.

Environmentally sound disposal of used engine oil is becoming increasingly difficult for the U.S. Army. TFLRF has investigated several alternatives, including recycling, re-refining, and burning in a variety of applications. TFLRF is participating in a project to evaluate the effect of blending used oil with fuel and consuming it in the engines of tactical vehicles. While this approach has been popular in commercial trucking fleets, few measurements exist of its long-term impacts on engine durability, emissions, efficiency, and maintenance. TFLRF is conducting both laboratory-based diesel engine durability tests and fuel-quality degradation studies. It is also monitoring a test fleet operating at the U.S. Army National Training Center, Fort Irwin, California. This study will determine the environmental and financial impacts of this method of disposal.

Vehicle Systems Design and Development

A regenerative active suspension system was designed, fabricated, and installed on a large passenger bus to provide increased ride quality and better handling. A multi-section variable pump assembly sends and recovers oil to and from individual hydropneumatic suspension struts without the use of energy wasting control valves. Tests show the SwRI-developed system requires only seven horsepower to maintain chassis control, while recovering more than 75 percent of activation energy during demanding maneuvers. The bus was delivered to the client for additional development and testing. This system was recognized with a 1997 R&D 100 award. The awards, presented by R&D Magazine, recognize the 100 most significant technical achievements of the year.

To meet performance, emissions, and fuel economy goals, engineers at SwRI are developing computer software tools that simulate advanced vehicle powertrains. This software development effort is part of a cooperative research and development program between the U.S. Council for Automotive Research (USCAR), a consortium of U.S. auto manufacturers and the federal government. The joint initiative, called the Partnership for a New Generation of Vehicles (PNGV), was formed to develop a vehicle that achieves up to 80 miles per gallon, or about three times the fuel efficiency of today's baseline vehicles. The goal further challenges engineers to maintain or improve current performance, size, utility, and cost of ownership. The new vehicle must also meet or exceed federal safety and emissions requirements. Configurations covered in the simulation include conventional, series hybrid, and parallel hybrid vehicles.

In another program in support of the PNGV, the Institute is cooperating with the EPA to develop hybrid hydraulic vehicle technologies to improve vehicle efficiency. These projects include developing a lightweight, high-pressure, hydraulic accumulator to store hydraulic energy generated during vehicle braking. This accumulator is made of composite materials to reduce weight and improve energy density. In another program, the Institute is developing more efficient pump motors by reducing internal losses. Other areas of this technology are being supported by testing hydraulic components, fabricating special components, and developing control systems.

As the demand for more fuel-efficient vehicles increases, improvements in powertrain efficiency are becoming a critical area for vehicle manufacturers' research and development activities. SwRI engineers are focusing research efforts on continuously variable transmission (CVT) technology. SwRI is conducting efficiency testing of push-type belt transmissions for automotive applications, investigating shift logic used in belt-sheave CVTs, and testing various high-pressure pumps used in CVTs. SwRI has performed analytical studies of all mechanical CVT types available including belt, chain, toroidal, nutating (oscillating), and epicyclic designs, and is extending its scope to include hydrostatic and electrical motors and their various electronic drives.

In an internal research project, SwRI staff members are investigating models for a novel configuration of a parallel hybrid vehicle. A unique drivetrain combines power from a small conventional engine and an electric motor to provide vehicle performance similar to present day conventional vehicles, but with up to three times the fuel economy. Simulation results using the federal test procedure driving profile indicate fuel economy of 70 miles per gallon achieved with a control system that operates both power sources at maximum efficiency. A fully functional computer model has been developed and tested. SwRI is preparing to put a parallel hybrid prototype on a test stand to evaluate fuel economy, vehicle performance, and reliability.

Particle contamination is a major factor in reduced performance of engines and vehicle components and can lead to marginal operation or failure under severe operating conditions. Engine and vehicle component designers, while aware of the problems caused by contamination, have lacked the tools to study the effects. SwRI engineers are developing and upgrading the technology and equipment to establish test protocols that measure the effects of contamination on expected service life, and are working to quantify and accelerate these procedures. Recent projects include the development of specific test protocols and analysis models to correlate laboratory testing with field conditions. Radioactive tracer technology also will be used to measure real-time wear in operating engines.

SwRI designed, integrated, and tested several types of auxiliary power units (APU) for military and commercial projects under a contract with the Defense Advanced Research Projects Agency (DARPA). Hybrid APUs, which extend the range of batteries in electric-drive vehicles, typically include three major components: an engine, an electrical generator, and a controller. This program investigated rotary engines, gas turbines, direct and indirect injection diesels, and compressed natural gas spark-ignition engines. The generators were homopolar DC, wound-field synchronous AC, and permanent magnet brushless DC devices. Control systems developed by SwRI have incorporated strategies for low emissions and high efficiency.

SwRI engineers are investigating improvements in the storage life of battery packs to make electric vehicles more cost-effective. Thermal gradients within an individual battery module adversely affect battery life and can lead to thermal strains on electrode materials, accelerated corrosion, and reduced cycle life. In a project for the Sacramento Municipal Utility District and DARPA, thermal imaging is allowing the designer to detect, isolate, and display continuous temperature distribution within advanced batteries and battery pack systems. Data from this thermal imaging study will provide a basis for more sophisticated analyses, such as finite element analysis, that will assist designers in maximizing the performance and life of cooling and heating systems for battery packs.

1997 Annual Report SwRI Home