STUDY ON STRUCTURE OPTIMIZATION AND EVALUATION INDEX OF COOLING CAPACITY IN A BI-LAYER COOLANT JACKET OF CYLINDER HEAD

To solve problems such as thermal overload in the cylinder head of a 6-cylinder heavy-duty diesel engine and the thermal cracks in the valve-bridge of the engine. Structure of the coolant jacket was optimized from monolayer to bi-layer, and structures of upper nozzles were also optimized using the orthogonal experimental design method in this paper. At present, the cooling capacity of the coolant jacket in cylinder head is mainly judged by the coolant velocity. In this paper, the coolant heat transfer coefficient (HTC) was adopted as the criterion to evaluate the heat transfer process in cylinder head. Both of the velocity and HTC were used as the evaluation indexes to obtain the optimum schemes respectively. To determine which evaluation index fits the actual heat transfer process better, and which optimized schemes should be adopted, the temperatures in the bottom of the cylinder head were measured. The experimental results show that it is better to evaluate the cooling capacity of coolant jackets by HTC. HTC reflects the actual heat transfer process much better than velocity.Copyright © 2010 by ASME