Determination of the Cylinder Head Valve Bridge Temperatures in the Concept Phase Using a Novel 1D Calculation Approach 2010-01-0499

The steady increase of engine power and the demand of lightweight design along with enhanced reliability require an optimized dimensioning process, especially in cylinder head valve bridge, which is progressively prone to cracking. The problems leading to valve bridge cracking are high temperatures and temperature gradients on one hand and high mechanical restraining on the other hand. The accurate temperature estimation at the valve bridge center has significant outcomes for valve bridge thickness and width optimization.

This paper presents a 1D heat transfer model, which is constructed through the cross section of the valve bridge center by the use of well known quasi-stationary heat convection and conduction equations and reduced from 3D to 1D via regression and empirical weighting coefficients. Several diesel engine cylinder heads with different application types and materials are used for model setup and verification. Calculated values with the 1D model are compared with the 3D finite element analysis results for exhaust-exhaust and exhaust-intake valve bridges, where estimated results lie in a +/- 6°C error interval showing a reasonable approximation. The proposed calculation method is further used to derive the sensitivity of the valve bridge temperatures on the valve bridge thickness and width, which serves as a basis for dimensional optimization under predefined temperature limits of the cylinder head material, even in the concept phase.