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

Principal Investigators
Marc Megel
Mark Tussing
Barry Westmoreland

Inclusive Dates:  11/17/06 – Current

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 design of the engines. 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 is 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 consists of a conceptual design of a 250-bar capable production-intent cylinder head using computer-aided design (CAD) 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 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 has completed tooling design, casting and machining of a first prototype cylinder head design from Phase 2. The prototype parts have been delivered to SwRI and are currently installed on a hydraulic fatigue test rig to demonstrate component durability at 250-bar cylinder pressure. Figure 1 shows the prototype cylinder head casting, and Figure 2 shows the machined final part prior to fatigue testing, which should be completed by February 2011. Machining of the parts on a production manufacturing line within a major heavy duty diesel OEM demonstrated successful completion of the third and final requirement for this next-generation design, which was to utilize available production techniques and material.

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