|This electronic brochure highlights our
capabilities and activities in the area of Gas and Large Engine Development.
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Tom E. Boberg, Southwest Research Institute.
Gas and Large Engine Development
For 30 years, Southwest Research Institute (SwRI) has pioneered
the use of natural gas as an alternative engine fuel. Natural gas is abundant, has a
favorable anti-knock quality, and produces lower regulated exhaust emissions than
conventional fuels. Emphasis on clean air, lower energy costs, and reduced dependence on
imported foreign oil provides incentive for increased use of this clean fuel.
The Institute has extensive experience converting diesel and
gasoline engines to operate on natural gas. Heavy-duty diesel engines are converted using
lean-burn combustion technology to maintain high thermal efficiency and achieve low
emissions, both with and without exhaust aftertreatment. Light-duty gasoline engines use
optimized stoichiometric combustion systems with electronic controls and three-way
Using this large engine test facility, SwRI
investigates methods of converting diesel locomotive engines to run on natural gas. The
Institute has six locomotive engines available for research and development efforts.
To assist in the development process, engineers have designed
special instrumentation to measure parameters such as valve recession, piston temperature,
flame propagation, and instantaneous oil consumption. To verify engine integrity,
converted engines are durability and field tested, with remote monitoring available.
Clients, ranging from individuals to multinational
corporations, use SwRI to develop innovative technologies using natural gas in vehicular
and stationary engine applications. Engineering expertise includes engine systems
development, control systems, combustion technology, and testing.
Engine Systems Development
SwRI engineers have converted dozens of diesel- and
gasoline-powered vehicles to run on natural gas. Conversions combine combustion, control,
and exhaust aftertreatment systems to provide optimum power and driving cycle efficiency
while reducing emissions. Transient emissions tests are conducted in the Institute's
The Institute has developed lean-burn, turbocharged,
natural gas-fueled heavy-duty engines that match the power and efficiency levels of their
diesel counterparts while producing lower emissions. Special electronic control systems
regulate fuel metering, spark timing, boost pressure, and engine speed.
Hybrid electric vehicles utilize auxiliary power units
(APU) to extend vehicle driving range. Comprised of an engine and generator, APUs provide
power to maintain battery charge and augment batteries during peak power demands. This
utility engine, converted to operate on natural gas for an APU application, incorporates
the latest technology in controls and exhaust aftertreatment.
SwRI develops advanced electronic engine control systems that
reduce emissions, improve fuel economy, and enhance driveability. Flexible PC-based
laboratory development systems are used in-house and produced for sale to engine
manufacturers. Environmentally hardened control systems are designed and produced for
prototype and production vehicles.
Institute engineers rapidly develop highly flexible,
hardened PC-based control systems for use in demonstration vehicles.
With Gas Technology Institute (GTI) funding, SwRI has
developed a revolutionary natural gas conversion system, known as TranslatorTM,
for electronically controlled fuel-injected gasoline engines. Unlike other electronic
conversion systems, this system uses the original manufacturers' electronic control
modules, utilizing desirable design features built into vehicles.
Using a variety of engine models and diagnostic methods, SwRI
designs and develops unique combustion systems that capitalize on the favorable combustion
characteristics of natural gas. Engineers develop an appropriate combustion system --
prechamber, open chamber, direct-injection, or dual fuel -- for the engine size and
A focused research program investigating open-chamber,
spark-ignited combustion systems has included basic research on how parameters such as
engine geometry, equivalence ratio, spark timing, and fuel composition affect performance.
For combustion analysis, SwRI combines optical spark plug and
ionization head gasket probes (SPION) with cylinder pressure measurement equipment to
study flame development, growth, and completion. The cycle-to-cycle data help characterize
cold-start cycle variability, lean misfire limits, knock, and rough idle. Using this
technology, the Institute determines how spark energy, air motion, turbulence, fuel,
composition, and EGR affect flame development.
To evaluate durability, reliability, and performance, SwRI
conducts laboratory and field tests on prototype and demonstration gas engines. Staff
members have developed a suite of advanced instruments and technology to perform tests
unique to these specialized engines.
The Institute developed the compressed natural gas
(CNG) engine and the CNG storage system for this Mack refuse truck. The vehicle was
equipped with an SwRI data logger that allowed remote monitoring during the vehicle's
one-year field test.
SwRI developed a PC-based data logger that records up
to 128 channels of data, which are monitored and downloaded remotely via a built-in
cellular telephone. Using this device, engineers can troubleshoot field demonstration
vehicles or remote stationary engines without leaving the office. The system has been used
in city transit busses, utility trucks, refuse haulers, and locomotives.
SwRI engineers are specialists in developing natural gas-fueled
engines, using advanced engine electronic control system and exhaust aftertreatment
Gas engine development projects are aided by the extensive
facilities found in the Design and Development Department. Forty test cells accommodate engines
from 2 to 6,000 hp, with both absorption and motoring dynamometers available. Natural gas
fuel is available from an LNG storage facility capable of supplying 6,000 psi, 99 percent
pure methane gas or from an eight-inch, 100 psi gas utility pipeline. A gas compressor
rated at 5,000 psi and 250 scfm provides CNG for engine testing and NGV refueling. Gas
composition is constantly measured using a gas chromatograph, which provides real-time
correction of heating value, stoichiometric fuel-air ratio, and fuel density.
Using the latest tools and techniques, SwRI accelerates the
development process. Test cell data acquisition systems acquire and process large amounts
of performance and combustion data. A PC-based engine control system developed at SwRI
speeds control algorithm development and engine calibration. The Institute also conducts
complete gaseous and particulate emissions measurements, including EPA-recognized
Gas Technology Institute
For more than a decade, SwRI has conducted gas engine research for
the Gas Technology Institute (GTI), developing basic natural gas engine technology. Research
reports on the following topics are available through GTI.
This brochure was published in September 1994. For more information about gas
and large engine
Tom E. Boberg, Principal Engineer, Engine, Emissions and Vehicle Research Division, Southwest Research
Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-6267, Fax
- Exhaust Oxygen Sensors
- Open Chamber Combustion
- Low-Hydrocarbon Prechambers
- Catalytic Converters
- Piston Temperature Measurements
- Valve and Valve Seat Wear
- Long-Life Spark Plugs
- Gaseous Metering Valves
- Gas Composition Effects
- Multi-Point Fuel Injection
- Natural Gas Lube Oils
- LNG Weathering
- Knock/Misfire Sensors
- Portable Emissions Analyzers
- High-Propane-Content Natural Gas Fuel
- Natural Gas Compressor Improvements
- Stratified Charge Glow Plug Ignition
- NOx Emissions Sensors
- Stoichiometric Control System Development
- Lean-Burn Control System Development
- NOx Modeling
Gas Engine Durability
Engine, Emissions and Vehicle Research Brochures
SwRI Technical Divisions