Combustion System Materials

Homogeneous Charge Compression Ignition (HCCI) engines appear promising for transportation as well as stationary engines because of the potential for increased efficiency and reduced emissions.  Rapid heat release, unthrottled operation, and reduced radiant heat losses are responsible for increased efficiency and highly dilute operation is responsible for reduced NOx and particulate emissions.  Power density, however, is currently limited by the peak pressures and the rate of pressure rise that are allowed for a given application and engine design.  The materials used for bearings, piston crowns, head gaskets, top of liner, valves/valve seats, turbo-machinery, other air handling and EGR equipment, and even engine blocks may limit the operating conditions.  An investigation of advanced materials for use with HCCI engines is ongoing and includes an investigation of high-temperature exhaust valves.

Milestone:  Evaluate microstructural evolution and causes related to the failure of two additional solder joint compositions identified through interactions with industrial partners, when subjected to stress testing conditions.  (9/09)

Related Agreements:

• High-Strength Materials for HCCI Engines

High-Strength Materials for HCCI Engines

Homogeneous charge compression ignition (HCCI) engines appear promising for transportation as well as stationary engines because of the potential for increased efficiency and reduced emissions.  Rapid heat release, unthrottled operation, and reduced radiant heat losses are responsible for increased efficiency and highly dilute operation is responsible for reduced NOx and particulate emissions.  Power density, however, is currently limited by the peak pressures and the rate of pressure rise that are allowed for a given application and engine design.  The materials used for bearings, piston crowns, head gaskets, top of liner, valves/valve seats, turbo-machinery, other air handling and EGR equipment, and even engine blocks may limit the operating conditions.  An investigation of advanced materials for use with HCCI engines appears warranted.

Goal:  To identify and catalog the materials operating conditions in the HCCI engines and utilize computational design concepts and other techniques to develop advanced materials for such applications.

Objectives:  (1) Interactions with designers of HCCI engines and manufacturers of engine components in order to identify the components that will be affected by the new operating conditions resulting from the HCCI design and mixed-mode or mode switching to conventional combustion; (2) identify the highest priority component(s) that are critical to the implementation of the HCCI concept; (3) identify key properties that need to be improved in materials used in the critical components; (4) apply computational design concepts to develop high-performance materials that would mitigate the material barrier for use of HCCI engine concepts.

Based on discussions with various companies, exhaust valves were identified as one of the highest priority components. Valve materials are needed to operate at temperatures up to 1600°F, higher than the current value of 1400°F.  During FY 2006, several candidate Ni-based alloys with the potential to have required high temperature properties at 1600°F have been identified for further testing and evaluation. In FY 2007, detailed evaluation of microstructure and high temperature mechanical properties of these alloys were carried out to develop a database on the relationship between composition of alloys, microstructure, and their high temperature fatigue properties. Based upon this database and the experimental validation completed in FY 2007 and FY 2008, one new alloy composition will be identified with the potential for improved performance using computational modeling techniques. In FY 2009, mechanical property data and microstructural information will be obtained on the promising alloy/alloys and the best alloy from existing and new alloy/s will be down selected for component fabrication/testing in FY 2010.

Milestone:  Evaluate fatigue properties of the most promising alloy/s identified in FY 2007 and select best alloy for component fabrication/testing.   (9/09)

Contacts:

• G. Muralidharan, Oak Ridge National Laboratory, 865-574-4281, muralidhargn@ornl.gov
• Bruce Bunting, Oak Ridge National Laboratory, 865-946-1512, buntingbg@ornl.gov

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