Engines, Fuels, Lubricants, and Vehicle Systems

In response to increasingly rigorous requirements for reduced emissions and improved fuel efficiency in the U.S. and abroad, the Institute continues its significant involvement in all phases of engine and vehicle subsystem design and development, alternative fuels research, and fuel and lubricant testing.

Engine Design and Development

Institute research in engine design, modeling, and analysis continues to expand as manufacturers seek to improve engine power and reliability, reduce costs, and extend the lifetime of vehicles and components. Institute engineers routinely use a variety of advanced analysis techniques, refine computer codes to make them more accurate, and develop new software programs to allow performance modeling and evaluation of the whole engine. In a recent project for a client requiring a radical power upgrade of a large engine, SwRI staff undertook a complete design analysis to ensure that the engine was sufficiently robust to withstand the increased load.

Finite element stress analyses of engine cranks allow Institute engineers to identify regions of high stress around the crank fillets, where cracking and failure is most likely to occur if the part is not properly designed.

The Institute is a leader in using computational fluid dynamics (CFD) in engine applications, including analyses of intake port, manifold, coolant, fuel, and lubricant flows. CFD analysis is also being used to help manufacturers predict various critical parameters in bearing design. As combustion engines become lighter, but retain equal or greater horsepower, engine bearings are subject to increased loading and significant deformation. The Institute-developed dynamic bearing model is the first to rapidly assist clients in predicting problems that can arise from bearing deformation, oil film leakage, oil film cavitation zones, and crankshaft wear.

In another innovative program, SwRI has developed a comprehensive gas exchange model that allows engine designers to optimize fundamental engine proportions and to refine intake and exhaust systems design. The flexible software easily simulates virtually any engine configuration.

Institute engineers have designed and built an engine control system that rapidly evaluates the complex control and diagnostic algorithms needed to test and modify engines under development. The flexible system is equally successful for all fuels as well as a variety of cylinder, ignition, and fuel-delivery configurations. The Rapid Prototyping Engine Control System gives engineers a tool to effectively replace original equipment manufacturer and off-the-shelf control systems, for which the control algorithms are generally proprietary. The system is being used in a number of Institute projects, including one sponsored by the U.S. Department of Energy (DOE) and the National Renewable Energy Laboratory to develop an ultra-safe school bus powered by natural gas.

Future heavy-duty diesel engine emissions standards require significant reductions in both oxides of nitrogen (NO_x) and particulate matter (PM). Exhaust gas recirculation has been found to be an effective method of reducing NO_x emissions, but generally results in an increase in PM, caused by poor fuel-air mixing towards the end of the combustion cycle. The Institute is investigating the emissions benefits of enhancing late combustion fuel/air mixing by introducing a hot, energetic jet into the combustion chamber from a late-secondary fuel charge, thereby reducing NO_x and PM simultaneously. The project is sponsored by the Institute's Clean Heavy Duty Diesel Engine (CHDDE) cooperative industry research program and the California Energy Commission's Clean Diesel Program.

Seventeen heavy-duty diesel engine manufacturers from around the world are members of the CHDDE program conducted by SwRI. The first four-year phase of the program is complete, and satisfactory progress has been made toward meeting the program goal of developing diesel engine emissions control technology. In particular, NO_x levels of 2.5 grams per brake horsepower-hour (gm/bhp-hr) and PM levels of 0.1 gm/bhp-hr have been demonstrated — with minimal impact on fuel consumption and engine durability. A second four-year program (CHDDE-II) will begin in late 1995, with goals of 1.0 gm/bhp-hr NO_x and 0.035 gm/bhp-hr PM.

The Institute is in the last year of a five-year Ultra-Low Emissions Engine (ULEE) cooperative industry research program aimed at meeting California's ultra-low emissions vehicle (ULEV) standards for passenger cars. The 11 program participants from the U.S., Asia, and Europe include automobile manufacturers and automotive component suppliers. Results to date include improved control and test algorithms, novel forms of exhaust aftertreatment such as a fast light-off port system, and an in-depth study of the effects of atomization on fuel to enhance combustion and reduce emissions during cold starts.

SwRI is in the sixth year of a Gas Research Institute-sponsored program to examine various gas engine technology advancements. Progress during the past year includes the development of an NO_x model for more accurate predictive emissions monitoring; the design and development of a fast-acting gaseous metering valve for stationary or liquid natural gas engines fueled under low supply pressures (patent pending); the design of a long life spark plug with titanium diboride electrodes (patent pending); a comparison of light-duty passenger car emissions when fueled with gasoline, reformulated gasoline, and natural gas over a standard test cycle and also under heavy acceleration and load; and the use of wide-range oxygen sensors to gather data on cylinder pressure and NO_x levels to improve engine control and reduce emissions.

Under the sponsorship of the Southern California Gas Company and the South Coast Air Quality Management District, SwRI has developed a patented innovative engine design known as the hybrid rich-burn/lean-burn engine. The ultimate goal is to develop a stationary gas compressor with exhaust emissions containing less than 5 parts per million (ppm) NO_x on a 15-percent exhaust-gas oxygen basis. The engine requires some cylinders of a multicylinder engine to be fueled with rich natural gas-air mixtures; the remaining cylinders operate on an extremely lean mixture of natural gas and air while being supplemented with exhaust from the combustion-rich cylinders.

Initial testing was carried out on a single-cylinder research engine to characterize the two combustion events, and results showed that NO_x levels as low as 8 ppm (corrected to 15 percent oxygen) can be achieved while maintaining good combustion stability and thermal efficiency. The design is being evaluated using a full-size engine capable of producing 500 horsepower. The engine has been converted to the hybrid design and will undergo process testing over the next year before being field tested in California.

The Institute is completing the second year of a cooperative industry research program called GasRail USA. Its goal is to demonstrate that the use of natural gas fuel in locomotive engines will provide significant advantages over diesel fuel in terms of exhaust emissions and operating costs. Program participants hope to achieve a 75-percent reduction in NO_x emissions compared with baseline diesel locomotives, using a combustion system that provides the most favorable tradeoffs between power output, fuel economy, and exhaust emissions. Several competing combustion technologies will be evaluated to provide a quantitative comparison of the systems tested on the same engine. At program completion, two low-emission natural gas locomotive engine technologies are expected to be developed — one for California passenger locomotives with an emphasis on low emissions, and the other for widespread freight applications where reduced operating costs are most important.

SwRI engineers are gathering vehicle performance data on engine system durability for a fleet of modified Blue Bird TC/2000 buses. The buses, powered by John Deere 8.1-liter compressed natural gas engines, average daily mileage accumulations of 750 miles.

The Institute is exploring ways to understand how the piston and piston rings in a reciprocating engine are lubricated. This process is important because it affects engine variables such as friction, oil consumption, reliability, and durability. Oil consumption is particularly significant, because it indicates how well engine lubrication is carried out. In general, low oil consumption over long-term engine operation is a good indication of efficient design. The Institute has developed an on-line oil consumption measurement system using a sulphur dioxide tracer technique that can be used under steady-state and transient operating conditions.

Conventional diesel engines inject fuel under high pressure towards the end of the compression cycle, and combustion is controlled by the rate at which the fuel and air mix; this results in the formation of pollutants such as NO_x and PM. In an internal research project, Institute engineers have developed an advanced combustion system in which diesel fuel and air are premixed and ignited by compression. The challenge has been to achieve successful ignition over a wide range of engine operating conditions while preventing uncontrolled, explosive combustion. The system has the potential of simultaneously reducing NO_x and PM to near zero levels.

Emissions Control

In conjunction with John Deere and the Blue Bird Bus Corporation, the Institute is developing a fully electronically controlled ultra-safe school bus powered by natural gas. institute engineers are testing the engine to evaluate control strategies and other features.

The Institute has extended its emissions measurement capabilities with the acquisition of a Horiba modal analysis system. While SwRI already has the capability to monitor pre- and post-catalyst emissions on a concentration (percentage or ppm) basis, the Horiba system allows emissions monitoring on the basis of mass, measured continuously on a second-by-second or mode-by-mode basis (acceleration, deceleration, idle, and cruise), providing a powerful tool with which to analyze the effects of new technologies on emissions levels.

Institute facilities to evaluate the performance of catalytic converters were recently expanded to allow heat and vibration tests at temperatures up to 1,050 C and acceleration forces up to 75 g's.

The Institute has expanded its capabilities to evaluate and develop catalysts to meet changing emissions and durability standards. Durability is measured through a number of tests. For example, to assess their resistance to vibration, catalysts are traditionally subjected to acceleration forces up to 75 g's and temperatures up to 1,050 C, which stress the packaging design as well as the catalyst itself. Institute engineers have also developed accelerated aging cycles that subject the catalyst and its housing to the equivalent of 100,000 road miles in only 60 hours.

Updated facilities that have the capability to precisely control exhaust conditions, temperatures, and flow rates have recently been completed to evaluate new catalysts. Small catalytic samples can be evaluated in a mini- reactor system, eliminating the costly process of preparing a full-sized catalyst for some purposes. In addition, the use of mini-catalysts allows multiple formulations to be evaluated simultaneously, further reducing time and cost.

The Institute is working with engine manufacturers to certify that nonroad engines meet new emissions standards established by the U.S. Environmental Protection Agency (EPA). The standards are for engines operating at or below 19 kW, which power utility and garden equipment, and engines at or above 37 kW, which power farm, construction, and industrial equipment. Regulations for spark-ignited marine engines are also being developed. The Institute can test engines not only to North American standards, but also with test procedures established by the European Economic Community and the International Organization for Standardization.

The Institute conducts compliance and parametric emissions tests of stationary and mobile engines in the field. SwRI's mobile laboratory can be fitted to sample and rapidly analyze a variety of unregulated as well as regulated pollutants.

Institute engineers are pursuing the reduction of cold-start emissions by investigating the use of a gasoline-fueled burner for accelerated catalytic heating. Catalysts can reduce emissions efficiently once light-off temperature is reached, but until that point unburned hydrocarbons and carbon monoxide pass uncatalyzed through the engine and can supply as much as 90 percent of the total emissions generated during the test cycle. The Institute is also evaluating other promising technologies to provide supplemental heat to catalysts, including electrically heated catalysts and exhaust gas combustors. In a recent test, a gasoline-fueled system developed at SwRI, fitted to the exhaust system of a 3.8-liter vehicle, raised the temperature of the catalyst to light-off in 10 seconds and reduced by half the time required to convert hydrocarbon emissions.

A two-year consortium program is under way to investigate plasma and corona discharge technologies for the simultaneous reduction of PM and NO_x from diesel engine exhaust. Initial experiments with plasma technology sponsored by an internally funded research program produced encouraging results for the control of both pollutants. Previous aftertreatment technologies have focused on either PM or NO_x emissions, and success in the control of one has often led to increases in the other. Any technology that provides for simultaneous control of both pollutants would benefit heavy-duty diesel manufacturers. Program goals are to define the problems of the technology, determine its operational feasibility, and screen other methods used to reduce emissions in heavy-duty diesels.

Fuels and Lubricants Research

Around-the-clock testing of cars and light trucks at speeds up to 100 miles per hour will be possible on 12 newly installed mileage accumulation dynamometers, each with its own PC-based control system that regulates vehicle speed and load and ensures test repeatability.

The Institute has installed 12 mileage accumulation dynamometers in a fully instrumented facility that accommodates cars and light trucks, where testing can be conducted 24 hours a day at speeds up to 100 mph. New instrumentation ensures test repeatability and makes it possible to test prototype vehicles more accurately using a PC-based test stand system that controls load and speed. Speed profiles are generated by driving a vehicle carrying a data collection device over a designated course. The profile is then used by the computer to duplicate the same driving cycle on the dynamometers. This approach eliminates variations in driving style that result from on-road testing and enhances test standardization.

The Institute has developed an innovative computer-controlled instrument for the petroleum and refining industry known as the Automatic On-Line Reid Vapor Pressure-Vapor/Liquid Ratio Measurement Apparatus. The instrument allows 24-hour unattended on-line sampling with self-calibration checks. A patent application is pending.

SwRI has developed an innovative, automatic, computer-controlled instrument for the petroleum and refining industry known as the Automatic On-Line Reid Vapor Pressure-Vapor/Liquid Ratio Measurement Apparatus. A patent application has been filed for the apparatus, which automatically measures the vapor pressure and vapor-to- liquid ratio of oxygenated gasoline and other volatile petroleum products, with no modifications other than required software changes. The new instrument features 24-hour on-line sampling and operator-selectable self-calibration checks, a unique capability that ensures reliable unattended operation. For the petroleum industry, the apparatus will provide more efficient, accurate results that relate directly to refinery short- and long-term cost savings.

Institute engineers are implementing a data assurance system that will allow clients access to a computerized network of data loggers that monitor and control client test requirements. The new system offers clients tighter control of test parameters and provides an exceptional degree of accuracy in results. In addition, clients will be provided with printouts to confirm that tests are being performed within specified guidelines.

Intake valve deposits and valve stickiness can cause serious engine problems, such as compression loss. The Institute screens gasoline additives for their effects on deposit levels using a test stand equipped with a 6,500-watt generator.

As emissions requirements for gasoline- and diesel-fueled vehicles become increasingly stringent, fuel quality and fuel effects on emissions have become more important. To support industry as it responds to the new requirements, the Institute has developed several test procedures now being used by fuel suppliers. The procedures are used to evaluate fuels for both North American and European standards and to simulate both transient and steady-state driving conditions. Sophisticated instrumentation is included to detect abnormal knock as well as a fuel's deposit-forming potential.

For the DOE, SwRI has completed the first year of a three-year project to examine the best way to integrate coal liquids into the existing petroleum refining industry. Institute staff projected the makeup of a typical refinery 10 to 15 years in the future, the earliest time when coal liquids could be available as a fuel source. Two coal liquid sources were developed, one a direct liquid from bituminous coal and the other an indirect liquid from sub-bituminous coal. At the DOE Alternative Fuels Center located at SwRI, both liquids were distilled into naphthas, kerosenes, and heavy distillates for refinery processing. The specification-grade fuels made for this project will undergo testing to determine the effects of the coal components on engines and emissions.

U.S. Army TARDEC Fuels and Lubricants Research Facility

The Institute has staffed and operated the U.S. Army Tank-Automotive Research, Development, and Engineering Center (TARDEC) Fuels and Lubricants Research Facility (TFLRF), formerly known as the U.S. Army Belvoir Fuels and Lubricants Research Facility, since it opened in 1957 on SwRI grounds. The TFLRF functions as a dedicated in-house facility, with capabilities that are augmented as needed by the Institute's large and diverse staff. Multidisciplinary teams can be easily organized to investigate military problems related to fuels, lubricants, and engines. Research at the TFLRF gives the Army and Department of Defense unique capabilities, ranging from proof-of-concept to validation testing, as well as rapid response to field problems in the areas of combat mobility fuels and powertrain lubricants and fluids.

The Institute, working with the International Snowmobile Manufacturing Association, is determining engine operating parameters for snowmobiles under a variety of conditions to support development of a field test cycle.

Over the past year, the Institute continued to examine the effects of fuel composition and additives on injection system performance using the SwRI-developed Scuffing Load Wear Test. Field complaints associated with the new low- sulphur diesel and jet fuels in military equipment were also investigated, and a survey of lubricity characteristics continued. The Institute also completed an investigation of the exhaust emissions characteristics of military engines using low-sulphur diesel fuel or aviation kerosenes, and a program was initiated to investigate the application of natural gas as a fuel for peacetime use in diesel tactical vehicles.

The first year of a cooperative industry research program to examine problems of fuel filtration was completed, during which the critical particle size that can cause damage to rotary injection fuel pumps was determined. This information will be compared to data generated in the coming year on new-generation, high-pressure injection systems. Program members include filtration companies and equipment, pump, and engine manufacturers.

Next-generation aircraft gas turbines must improve efficiency while reducing exhaust emissions. The technology to meet these goals requires fuel to take on a more important role as a coolant for avionics and engine systems. The TFLRF is investigating the problems associated with a higher temperature fuel environment including deposition, heat transfer, and endothermic chemical reactions.

Vehicle Systems Design and Development

Reciprocating engines can produce torsional fluctuations that propagate throughout the vehicle frame, producing unacceptable vibrations. SwRI engineers are assisting manufacturers in assessing the effects of mounting compression springs in the clutch to reduce undesirable vibrations.

The Institute assists transmission and vehicle manufacturers in evaluating the efficiency of transmission assemblies as well as pumps and torque converters. The Institute has conducted benchmark testing of more than 60 preproduction and production transmission models for comparative purposes. In a related study, engineers are investigating whether significant improvements can be made in the area of torque loss by changing transmission sensor configurations.

An automatic transaxle is an assembly of clutches, gears, pumps, and torque converter subsystems operating at different speeds within the transaxle housing. Transmission fluid circulates in the housing, passing through and over components with varying temperatures. These thermal variations can significantly affect transmission efficiency. To quantify temperatures throughout the transaxle, Institute engineers installed sensors at several axial and radial positions to measure temperatures under a variety of operating conditions and to produce thermal maps with associated fluid flows. Understanding the fluid flow through a particular transmission will help engineers control temperatures.

Statistical analysis is an increasingly important aspect of transportation research. The Institute is analyzing survey data using random samples of U.S. drivers operating vehicles in commercial and non-commercial settings, to determine which improvements in vehicle component design are needed to reliably extend warranty periods to at least 100,000 miles. Information on annual miles driven, frequency of acceleration and trailer towing, and miles driven on steep grades is being summarized in distributional form to characterize vehicle component performance.

Institute engineers use the Cummins L-10 diesel injector deposit test to evaluate fuels and fuel additives. This procedure is the only known injector deposit test for direct-injection diesel engines.

Under a Presidential directive known as the Partnership for a New Generation of Vehicles, the Institute is cooperating with the EPA on programs to develop hydraulic hybrid vehicle technology to improve vehicle efficiency. One such program involves the development of a lightweight high-pressure hydraulic accumulator to store hydraulic energy generated during vehicle braking. The accumulator is made with composite materials that reduce weight and improve specific energy density. In another program, the Institute is developing more efficient hydraulic motors by reducing the losses associated with fluid compressibility within the motor.

Radioactive tracer technology makes it possible to measure engine wear on a real-time basis. SwRI pioneered the technology to study ring and bearing wear as a function of engine operating conditions and lubricant composition. Prior to testing, the engine's rings and rod bearings are irradiated in a nuclear reactor to produce artificial radioisotopes that individually characterize each component's wear surface. The parts are then reinstalled in the engine for specific tests. The radioisotopes act as detectable tracers when irradiated wear particles abrade from the rings and bearings and circulate in the lubrication system. The amount of radioactivity present is proportional to the mass of wear particles in the oil at the time of measurement. With this technology, it is possible to measure ring and bearing wear simultaneously without disassembling the engine for inspection and measurement.

An internal research project is in progress to investigate the structural design of polymer electrolyte membrane fuel cells. The cells have considerable potential for use in portable generators and for providing power at remote sites, but have encountered problems with uneven heat distribution that can result in premature failure and inefficient operation. Project goals are to solve these problems and reduce their associated costs by developing an improved cell architecture.

As part of an Advanced Research Projects Agency program in cooperation with seven commercial coalitions, the Institute is developing and testing components and systems for electric and hybrid-electric vehicles. Here, a technician monitors an electric vehicle in a temperature-controlled room to evaluate the effects of temperature on range and other operating characteristics.

The Advanced Research Projects Agency, in cooperation with seven commercial coalitions throughout the U.S., is developing and testing components and systems for electric and hybrid-electric commercial vehicles. The Institute is contributing to this effort by developing auxiliary power units that operate on natural gas, thus extending the range of purely electric vehicles. Three engine technologies are being investigated — reciprocating, rotary, and turbine. Reciprocating piston engines are the most mature technology in this power range and have demonstrated good efficiency and low emissions, but provide the least amount of power for a given weight. Rotary and turbine engines are being investigated because they are able to generate even higher power for a given engine density, and they can provide significant reductions in scale and emissions.

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