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Determination of the Cylinder Head Valve Bridge Temperatures in the Concept Phase Using a Novel 1D Calculation Approach
Abstract:
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.