Engines, Fuels, Lubricants, and Vehicle Systems

The internal combustion engine and vehicle systems continue to evolve for several reasons, including competition and client demand. Perhaps the greatest catalysts today, however, are environmental regulatory requirements. The Institute offers internationally recognized research and testing capabilities for engines, fuels, lubricants, and vehicle systems, and provides not only product testing, but also support in the design and development of new systems. To increase support, a 50,000-square-foot addition for emissions research and evaluation is under way.

The Institute develops and conducts thermal cycling tests of catalytic converters for exhaust system suppliers and automobile manufacturers to evaluate the converters' ability to continue reducing emissions over the life of a vehicle.

Engine Design and Development

An SwRI-developed technique for rating the ignition quality of diesel fuels has been incorporated into a new automated apparatus to accurately determine the cetane number of such fuels. The Institute delivered a prototype to Advanced Engine Technology Ltd. (AET). A production version of the apparatus - called the Ignition Quality Tester (IQT) - that rapidly tests a large number of fuels to determine their ignition delay was developed by AET and is now commercially available. The IQT performs a similar function as the industry-accepted cetane engine test, American Society for Testing and Materials (ASTM) D 613, but is more accurate and provides a statistically significant number of data points in a shorter time and with a smaller amount of test fuel. When adopted as an ASTM and Institute of Petroleum (IP) test method, the IQT will reduce the cost of qualifying a fuel for widespread use.

Stationary prime movers have been continually targeted by strict air quality mandates, but emission-reduction methods for these large, natural gas-fueled engines cannot meet future oxides of nitrogen (NO_x) limits of 5 to 36 parts per million. In an internally funded effort, SwRI developed a pre-engine catalyst that converts a portion of the natural gas fuel normally inducted by the cylinders to syngas. Syngas, formally known as synthesis gas, is a high hydrogen-content gas created during an intermediate stage in stream-reforming processes. Engine emissions and performance tests using the natural gas/syngas mixture generated by the catalyst showed that NO_x was reduced to 10 parts per million while maintaining stable combustion at a brake thermal efficiency of 30 percent. The Institute is proposing this low-emission technology for use in stationary and on-road engines.

The SwRI-developed Rapid Prototyping Electronic Control System^TM (RPECS^TM), a computer-based tool for real-time powertrain control development, provides integrated control of conventional and hybrid powertrains and vehicles. Using RPECS, engineers also control vehicle subsystems such as the suspension or antilock brakes. More than 40 test cell and vehicle-based systems have been developed for approximately 20 clients. Refinement continues and is nearing completion of a compact and robust version that will allow convenient in-vehicle installation and permit use in a severe test cell environment.

A scanning mobility particle sizer and an electrical low-pressure impactor help SwRI engineers to better understand issues required for robust measurement and characterization of exhaust particles produced during steady-state and transient engine operations. New emissions standards will further limit particulate matter as well as other pollutants.

Institute engineers are developing model-based control techniques for a variety of applications, including control of engine airflow, estimation of exhaust gas recirculation (EGR) flow, and control of spark-ignition and direct-injection engines. In this continuing series of projects, algorithms are developed using experimental powertrain hardware, models, and simulations. Engineers use sophisticated software programs to model and optimize powertrain components. Control algorithms are developed initially in the simulation environment before being transferred to the actual hardware for refinement and verification.

In October 1999, SwRI initiated a four-year cooperative research program called Clean Diesel III to develop low-emission technologies for diesel engines. Today the consortium has more than 20 members from eight countries representing light- and heavy-duty engine manufacturers, component suppliers, and petroleum companies. The NO_x and particulate matter goals for Clean Diesel III are 0.20 gram per horsepower-hour (g/hp-hr) and 0.01 g/hp-hr, respectively. Six different technology areas are being investigated at SwRI to meet these ambitious emission goals.

SwRI engineers are developing a new approach to integrated machinery system simulation. By correctly characterizing the complex behavior of mechanical systems with multiple components and dependent interactions, machinery problems beyond the scope of current analysis methods can be resolved. Finite element analysis, nonlinear dynamics, and dynamically loaded lubrication technologies are being integrated into a comprehensive system to simulate a specific gas engine or compressor. The resulting model will verify this method for use with other machinery and improve the predictability and reliability of new engine designs. Further efforts of this internally funded project may result in commercial development and licensing.

Emissions Control

Recent work at the Institute identified a new emissions control mechanism for improving catalyst conversion efficiency. The suggested mechanism was labeled "phased perturbation," and involves independently controlling the fuel delivered to each bank of a dual-bank engine (in addition to individual cylinder fuel control), which allows the two banks to have an adjustable, relative air/fuel (A/F) perturbation phase shift. An internal research project was initiated to create an engine fuel controller capable of producing an A/F phase shift, and then to study the impact of phasing on catalyst conversion efficiency. Phased perturbation produced significant improvements in catalyst conversion efficiency for hydrocarbons (HC), carbon monoxide (CO), and NO_x. Further development of phased perturbation would provide an additional engine calibration tool to augment EGR, spark timing, and improved A/F ratio control, particularly useful for improving control of NO_x, a major reduction target in upcoming regulations. 

Cleaner and more fuel-efficient cars, light trucks, and sport utility vehicles incorporate new control strategies such as those under way at SwRI. These vehicles are being evaluated in the SwRI emissions laboratory.

As part of a consortium, SwRI conducted on-vehicle measurements of catalytic converter temperature, exhaust gas pressure, and vibration on six vehicles with various engine and exhaust system designs. Measurements were made on a chassis dynamometer under varied driving conditions. Increasingly stringent emissions requirements have led to exhaust catalysts being placed closer to the engine to promote faster warm-up. Vehicle data were obtained and analyzed to better understand the physical environments of such modern catalytic converter systems.

To put the development of a new Mack diesel engine T-10 test category on a fast track, SwRI teamed with an original equipment manufacturer and an additive company. SwRI was the sole testing laboratory for the new round of test development, which included EGR tests. This unifying concept enhanced the decision-making process and has more clearly defined the technical objectives of the procedure development. The Mack T-10 test evaluates lubricant performance in piston ring wear, liner wear, and bearing corrosion. EGR tends to increase particulate emissions and specific fuel consumption at higher loads, but researchers at SwRI are working to overcome these negative effects so that EGR can be successfully used in diesel engines.

For the California Air Resources Board (CARB), SwRI engineers have demonstrated the potential for substantial emissions reductions in spark-ignited marine engines by using EGR and automotive-type catalysts. While most of the engines powering stern-drive and inboard pleasure craft are automotive derivatives, they employ water-cooled exhaust systems that limit application of conventional aftertreatment technologies. A current study will help develop a marine engine exhaust system designed to protect the catalyst from water. Another pollutant of concern is the particulate matter (PM) emitted by two-stroke marine outboard and personal watercraft engines. Difficulty in measuring marine engine particulate has prevented CARB from addressing this issue. SwRI is currently developing a suitable technique and will use this methodology to characterize particulate emissions from a number of marine engines.

A 23,000-gallon test tank and a Universal Data Acquisition and Control System console developed and built by the Institute are used to examine lubricant-related issues in two- and four-stroke outboard engines.

The population of diesel trucks, vans, and sport utility vehicles with gross vehicle weight ratings of more than 8,500 pounds has been increasing, along with their overall contribution to emissions. The Environmental Protection Agency (EPA) has data for only a few such vehicles, mostly from previous tests at SwRI. To provide better emission inventory estimates, six additional vehicles selected by the EPA were tested over a series of light-duty transient driving cycles. This work expanded the EPA's database to include more model years, manufacturers, and emissions results.

Current emissions rates are typically estimated based on laboratory measurements because on-road test methods can be cumbersome and costly. An on-board emissions measurement system developed by the EPA, called "ROVER," provides a relatively simple and inexpensive means of determining in-use vehicle exhaust emissions on the road. SwRI engineers independently determined how well ROVER measures in-use vehicle exhaust emissions. These evaluations were conducted in the laboratory and on a test track over specified driving cycles, and on the road during a variety of real-world driving situations. Four diesel- and four gasoline-fueled, late-model, light heavy-duty trucks from different manufacturers were tested. The system's ability to measure carbon dioxide and NO_x emissions correlated with laboratory measurement methods under most driving conditions. In addition, SwRI provided the EPA with recommendations to improve the system's operation.

Specially trained rating technicians, working under stringent lighting and environmental conditions, and using rating guidelines and manuals provided by the Coordinating Research Council (CRC), assign numerical values to the amount of deposits and distress on engine parts following tests of fuels, lubricants, and additives. These rating technicians attend semi-annual, week-long workshops to verify their "calibration" with a pool of international rating experts. Here, a rating technician in SwRI's Deposit and Distress Rating Area inspects a piston from a multi-cylinder diesel engine.

Fuels and Lubricants Research

One of the newest additions to SwRI's testing program is a fluid test rig for a continuously variable transmission (CVT), developed cooperatively with General Motors and Van Doorne's Transmissie b.v. (VDT). This rig will evaluate new generations of CVT fluids using VDT-developed methodology and hardware. CVTs allow an automobile engine to operate in the optimum speed range for desired performance, increasing fuel efficiency and reducing emissions.

In support of a petition to include a Fischer-Tropsch-derived diesel fuel as an alternative fuel, SwRI researchers conducted testing to provide a client with experimental data from the generation, collection, and analysis of combustion emission samples. Testing was performed on heavy-duty, heavy light-duty, and light-duty vehicles. Measurements included regulated emissions, detailed hydrocarbon speciation, greenhouse gases, diesel particulate characterization, and air toxics. If the petition is successful, this synthesized substitute for petroleum diesel would be the first to be designated an "alternative fuel."

The Institute custom designs fleet programs, locating and procuring vehicles to meet client needs. For a lubricant program, SwRI conducted fleet evaluations according to MIL-PRF-2105E. SwRI arranged for the use of seven one-half-ton shuttle vans, averaging 100,000 miles of operation per year. Following the protocol specified in the MIL specification, oil samples were taken at 10,000-mile intervals and analyzed. At the conclusion, visual ratings of drivetrain components were obtained. Performance of the lubricant was based on both the analyses and visual ratings.

In a client-sponsored project in support of EPA requirements for registering designated fuels and fuel additives, SwRI assisted in the generation, collection, and analysis of combustion emission samples. A stable water-in-fuel emulsion was tested on a 1999 Detroit Diesel heavy-duty diesel engine. Emissions measurements included regulated emissions, speciation of vapor-phase and semi-volatile hydrocarbon compounds, alcohols, ethers, aldehydes, and ketones. Polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons were also measured. The emulsion produced a substantial improvement in NO_x and PM emissions from this engine. 

EGR reduces NO_x in engines, but it also increases particulate levels and acid contamination of crankcase oil. PM thickens oil, plugs oil filters, increases wear, and decreases durability. Increased acid levels deplete the oil's detergency at a higher rate and can lead to higher levels of corrosion in bearings and other critical engine parts. A new oil to address these problems, designated PC-9, is under development. SwRI is working with heavy-duty engine manufacturers to develop new EGR tests for the PC-9 category. Researchers also are working with Cummins Engine Company to develop the M-11 EGR test, and with Caterpillar, Inc. to develop the 1-Q test. In June 2000, ASTM voted to prove the T-10 and M-11 using full-scale precision testing. Upon acceptance by the American Chemistry Council, the tests will be officially online and oil marketers and additive companies can register engine tests that will ultimately lead to American Petroleum Institute licensing and commercial sales.

U.S. Army TARDEC Fuels and Lubricants Research Facility

The U.S. Army Tank-Automotive Research, Development, and Engineering Center (TARDEC) Fuels and Lubricants Research Facility (TFLRF) is a government-owned laboratory located on the SwRI grounds and staffed and operated by Institute personnel. The laboratory has functioned as a dedicated, in-house component of TARDEC, the Department of Defense organization responsible for military ground vehicle fleets. TFLRF assists the military and other federal agencies in investigating and solving problems in fuels, lubricants, and functional fluid technologies and in providing rapid response to problems during worldwide operation of combat vehicles.

Air Force efforts to improve jet fuel's thermal stability resulted in a new formulation designated as JP-8+100, for use in fighters and other small aircraft. TFLRF studied the likelihood and possible effects on Army aviation and ground equipment, which run on JP-8, being inadvertently fueled with the new fuel. The study showed that aircraft misfueling with JP-8+100 was probable, but would not adversely affect operations. Even though ground vehicle misfueling was less likely, significant filter plugging or equipment failure could result. These results prompted the Army to prohibit the use of JP-8+100 in Army equipment.

Using an SwRI-developed, laboratory-scale combustor rig fabricated from engine hardware, and with support from BetzDearborn, Inc., engineers are studying the effects of jet-fuel composition and JP-8+100 thermal stability additive technology on particulates in jet engine exhaust. A jet fuel treated with this type of additive technology could result in near-term improvement of air quality in and around airports without waiting for improved engine designs to be placed into service.

In studies funded by the Department of Energy and the Coordinating Research Council, TFLRF evaluated options for light-duty diesel engine emissions reduction through fuel or lubricant modification. Project activities include investigating oxygen-containing compounds for use in diesel fuel, evaluating the effect of various diesel fuel reformulations on the emission of polyaromatic hydrocarbons, and evaluating the effect of lubricant reformulation options on diesel engine particulate and gas phase emissions.

Fuel is the largest logistical load in battlefield support, and the Army has focused on reducing total combat fuel demand. To decrease the need for fuel on the battlefield, the TFLRF is improving the lubricant contribution to vehicle drivetrain efficiency. In the first phase of this study, engineers are using the SwRI-developed vehicle performance software and bench-scale lubricant characterizations to assess the logistical fuel savings from low-friction powertrain lubricants.

Under contract with the U.S. Navy, SwRI is developing automated systems for the Marine Corps to improve fuel logistics on the battlefield. Fuel automated quantity sensors (FAQS) gather fuel inventory data from remote locations, while the onboard vehicle-to-refueler communication (OVRC) system provides automated refueling control and transaction processing. Designed to improve the accuracy and timeliness of battlefield refueling, OVRC provides wireless communication between the vehicle and the refueling system, transmitting information such as the vehicle's identification number and operating parameters. The transaction record is then forwarded to a remote monitoring station to be used to forecast future logistics support. FAQS and OVRC can be incorporated into a single unit that uses a satellite-tracking system for communication.

Vehicle Systems Design and Development

Contaminants cause premature abrasion wear of bearings, piston rings, and other friction-sensitive equipment and, along with small particles, may lead to blockages, lockups, and failures involving valves, pumps, seals, and fuel injectors. Using contamination analysis, testing, modeling, and simulation methodologies, SwRI engineers help manufacturers design components that meet allowable contamination levels, identify key contamination-sensitive parameters and components, obtain realistic service-life estimates, and achieve targeted service lives. A variety of industry-approved and Institute-developed techniques, including radioactive tracer technology (RATT®) for real-time wear measurement, are used to quickly obtain meaningful wear results.

The hybrid electric vehicle (HEV) shows promise for meeting the fuel economy and emission requirements of the 21st century. Development of these vehicles has been hampered by the lack of a design methodology that combines simulation, design, and high-current testing into a single environment. To meet this need, SwRI is developing an advanced, reconfigurable HEV control system demonstrator that can integrate high-fidelity models with high-power hardware such as an engine, battery pack, or fuel cell. The integrated test system can be applied to other real-time control system development programs that require energy transfer among mechanical, hydraulic, and electrical components.

During an internal research project intended to enhance the performance of a proton exchange membrane fuel cell, engineers noted that the addition of a metallic layer within the membrane enabled the cell to accept and store additional electrical energy, such as might result from regenerative braking. The metallic layer in the membrane can then release this added energy in a single pulse, similar to that of a capacitor. This energy capture and release capability corresponds to the power requirements of a hybrid electric vehicle as it brakes to a stop and then accelerates. Because the fuel cell does not have to be sized to store peak power requirements, it may be considerably downsized with only minor changes in cell architecture. Using the metallic layer as a third electrode may offer a novel method of electrically controlling the cell operation and allow a direct method of sensing membrane hydration.

SwRI scientists are developing a variety of accelerated-life testing methods for vehicle components and subsystems. In this contamination sensitivity evaluation, staff members introduce controlled amounts of contaminant into the fuel delivery subsystem assemblies as they undergo severe laboratory testing. Using analytical tools, realistic testing, and simulation methods jointly developed by SwRI and industry, scientists quickly predict the real-world performance and longevity of the component.

Under contract with the U.S. Army Tank-Automotive and Armaments Command (TACOM) National Automotive Center, SwRI is helping to design and simulate the performance, emissions, and fuel economy of future trucks. The Institute is developing capabilities to simulate conventional diesel, hybrid electric, and fuel cell propulsion systems. Engineers are evaluating transient power requirements, fuel consumption, and battery charge status in a variety of driving profiles. Also included in the study are the effects of accessory loads and temperature on vehicle subsystems, fuel economy, transient heat rejection loads, and sizing of all subsystems as a function of a worst-case terrain profile.

SwRI, in cooperation with a U.S. automobile manufacturer, is developing a simulation tool to evaluate vehicle performance characteristics such as fuel consumption and acceleration. The simulation package can be used to develop control strategies for future vehicles and to perform trade-off studies. The tool, which is intended to become a commercial, off-the-shelf product, features a graphical user interface and a database to contain simulation data and results. Anticipated add-on toolboxes to the software include hardware-in-the-loop capabilities, hybrid vehicle models, heavy-duty vehicle models, and co-simulation with other third-party software.

In a project for the U.S. Army TACOM, Institute engineers developed specifications for an emissions test cell capable of testing diesel engines up to 750 horsepower through the EPA's transient test cycle. The Institute evaluated hardware produced by at least three manufacturers for each system to determine the components that provided optimum system performance. This evaluation included review and comparison of accuracy, repeatability, environmental effects, and durability.

SwRI engineers use RATT to study and measure real-time wear in vehicle engines and powertrains. Using this proven technology, SwRI studies engine wear, fuel and lubricant formulation, component design, and material properties. In a recent study of piston ring and bearing wear resulting from partially stressed and debris-contaminated oil, test results showed less wear than when testing with clean oil under similar conditions. This surprising result could enable extended oil-drain intervals, if verified in light- and heavy-duty diesel engines. In another project, RATT was used to evaluate metal deposition occurring in engine coolant systems.

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