Diesel Engine Combustion Research

The combination of superior fuel economy and durability has made diesel engines popular worldwide. Because these engines can emit large amounts of ozone-forming constituents and particulates, they are subject to increasingly stringent regulations that require continual improvements in the combustion process.

Southwest Research Institute (SwRI) helps engine manufacturers and suppliers meet these regulations and emissions standards. SwRI's Engine, Emissions and Vehicle Research Division has achieved certification to ISO 9001, ensuring compliance with stringent quality control procedures and standards in design, development, and research. With more than 50 years of service to the automotive and engine manufacturing industry, SwRI engineers offer expertise in a wide range of diesel-related technologies, including:

• Base engine design
  
• Fuel injection system development
  
• Fuel properties evaluation
  
• Electronic control system development
  
• Aftertreatment system design

Experienced Institute staff members improve diesel combustion and reduce emissions caused by light-, medium-, and heavy-duty engine applications including:

• On-highway
  
• Off-highway
  
• Marine
  
• Stationary
  
• Locomotive

SwRI provides a comprehensive range of services, including:

• Combustion research
  
• Diagnostic evaluation
  
• Engine testing
  
• Modeling
  
• Rating development
  
• Cold Start development

Combustion Research

SwRI engineers investigate, design, and develop improved diesel engine combustion systems, reducing gaseous and particulate emissions over specified test cycles by using advanced technologies involving:

• Combustion chamber designs
  
• Variable-rate fuel injection systems
  
• Advanced turbocharging concepts
  
• Diluents, such as exhaust gas recirculation or water injection
  
• Electronic control system development
  
• Model-based control
  
• Variable valve timing strategies
  
• Aftertreatment integration
  
• Fuel property evaluation
  
• Homogeneous charge compression ignition (HCCI)

Using sophisticated computational models, SwRI staff members simulate the interaction of fuel spray with a piston crown.

Diagnostic Evaluation

Engineers refine the combustion and fuel injection processes by analyzing the measured crank-angle resolved cylinder pressure and fuel injection signals. Using the resulting data, SwRI determines combustion-related parameters, including:

• Maximum cylinder pressure and pressure rise rate
  
• Combustion duration
  
• Fuel injection timing, duration, and rate
  
• Injection centroid
  
• Fuel injection stability
  
• Cycle work
  
• Heat release rate
  
• Cumulative heat release

Institute engineers monitor combustion and fuel injection processes on production and prototype engines. Using SwRI-developed or commercially available data acquisition systems, staff members measure a wide range of engine parameters, such as:

• Cylinder pressure
  
• Needle lift
  
• Fuel line pressure at pump and nozzle
  
• Rocker arm and push rod loads
  
• Solenoid current
  
• Intake and exhaust manifold pressures
  
• Valve motion

Prototype and existing engine designs are assessed using advanced analytical techniques such as:

• Computational fluid dynamics code
  
• Cycle simulation codes, including VIPRE™ and ALAMO_ENGINE
  
• Fuel jet performance, including JETMIX

Engine Testing

With more than 30 developmental steady-state engine dynamometer test stands, SwRI conducts sophisticated emissions reduction programs for future engines. The Institute also has transient-capable test stands and light-duty chassis dynamometers supported by certification-quality equipment. Up-to-date instrumentation in SwRI's engine laboratories is used to evaluate engines ranging from small generator engines to large marine and locomotive powerplants. SwRI measures a wide range of engine parameters, including:

• Performance
  
• Gaseous emissions
  
• Particulate emissions via full or partial dilution
  
• Smoke or opacity
  
• Tapered element oscillating microbalance--real-time particulate indicator
  
• Particulate size distribution
  
• Heat rejection
  
• Turbocharger performance
  
• Fuel injector performance

A high-pressure, high-temperature, static gas apparatus evaluates spray characteristics of diesel fuel injection systems and the resulting combustion. The SwRI-developed apparatus operates at air pressures up to 8.3 MPa and temperatures up to 550°C

SwRI staff members evaluate the degree of emissions reduction on a heavy-duty engine. Using the information gained from these evaluations, engineers design and prototype more efficient engines.

Modeling and Design

Modeling: Computer-generated combustion models are essential to achieving low emissions while meeting other engine constraints such as maximum cylinder pressure, exhaust temperature, and compressor pressure ratio. Engineers use simulations in development programs that vary parameters such as:

• Injection and valve timing
  
• Valve overlap
  
• Compression ratio
  
• Boost pressure
  
• Air/fuel ratio

Using the Institute-developed JETMIX code, engineers simulate diesel engine parameters such as:

• Hole size
  
• Injection pressure
  
• Number of holes
  
• Chamber density effects

Design: To refine an existing engine or design a new engine, engineers use sophisticated solid modeling techniques to produce prototype components and assemblies, including:

• Intake and exhaust ports
  
• Manifolds
  
• Piston bowls
  
• Cylinder head assemblies
  
• Complete engines

Related Capabilities

SwRI provides a comprehensive range of measurement and analytical capabilities to support development of a next-generation engine or to calibrate a change on an older engine. SwRI offers services including:

• Rating development/fuel system calibration
  
• 24-hour/day durability assessment
  
• Diesel fuel effect studies
  
• Alternative fuel studies
  
• Cold-start development
  
• Control algorithm development
  
• Engine mapping/reverse engineering
  
• Real-time oil consumption measurement with SO₂ techniques
  
• Wear mapping with radioactive techniques
  
• ASTM-complementary fuel ignition test

This SwRI-patented exhaust gas recirculation valve, with feedback and electronic control, is used to evaluate low NOx emissions by prototype heavy-duty engines.

The contribution from various sources to total particulates demonstrates the need for continued reductions in the oil contribution to particulate. *Volatile Organic Fraction

The SwRI-developed Rapid Prototyping Electronic Control System (RPECS) is a full-authority controller, commercially available as a rapid algorithm development tool.

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