2011 IR&D Annual Report

Causal Investigation of Heavy-Duty Diesel Engine Structural Limitations
to Peak Cylinder Pressure, 03-R8116

Principal Investigators
Marc C. Megel
Mark A. Tussing
Barry E. Westmoreland

Inclusive Dates:  11/17/06 – 01/28/11

Background — Advances in emissions technology, fuel economy and power levels of modern heavy-duty diesel engines have increased operating peak combustion pressures to levels at or near the structural limits of the engines' designs. The relationship between design parameters and structural performance for geometrically complex engine components, like cylinder heads or cylinder blocks, is not well understood. Future improvements in the performance of the existing fleet of heavy-duty diesel engines will require an increase in the structural capability of the engine design. This project was targeted at gaining a clear understanding of the relationship between the structural performance and the key design parameters for heavy-duty diesel cylinder heads.

Approach — The approach consisted of conceptual design of a 250-bar capable production-intent cylinder head using computer-aided design solid modeling in addition to casting flow and solidification analysis related to the producibility of key novel features. Cylinder head layout was based on three key requirements. First, the feature geometry had to incorporate those characteristics previously identified in an extensive design-of-experiments analysis as being necessary for 250-bar operation. Second, the geometry needed to be compatible with a specific on-highway, heavy-duty diesel engine manufactured by a major domestic engine manufacturer with whom SwRI has partnered. Finally, the resulting design needed to be producible using available production techniques and materials.

Accomplishments — In Phase 3 of this three-part project, SwRI completed tooling design, casting, machining and hydraulic fatigue rig testing of two first-prototype cylinder heads designed in Phase 2. Test results successfully demonstrated 250-bar cylinder pressure capability with no cracking observed in the high-stress regions. Figure 1 shows the prototype cylinder head undergoing fatigue testing and Figure 2 shows a post-test section used for crack inspection.

Figure 1. First Prototype Cylinder Head Hydraulic Fatigue Rig under Test
Figure 1. First Prototype Cylinder Head Hydraulic Fatigue Rig under Test.

Figure 2. Post Fatigue Test Cylinder Head Section for Crack Inspection
Figure 2. Post Fatigue Test Cylinder Head Section for Crack Inspection.

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 9 technical divisions.