항공기용 굴곡전열면 판형 열교환기 구조해석에 관한 연구

Abstract

Development of a new heat exchanger is required in order to decrease further the amount of fuel consumption and pollutant emission in the advanced aero engine. Due to the weight constraints of the new heat exchanger used in the aero-engine, structural optimal design of the heat exchanger should be done for the application of HX to the aero engine.

The objective of this paper is to develop the analysis method in order to predict the thermo-mechanical performance for matrix part of the cross-corrugated heat exchanger on thermo-mechanical load and to find optimum shape of the structure. The thermo-mechanical analysis is carried out to estimate stress level of the matrix because temperature differences between hot and cold gases of HX are causing large thermal stresses and large thermal expansion.

Full model using the solid element needs a lot of elements and requires longer computational time, whereas shell element model and sub model require less number of elements and computational time. Thus, compromised analysis technique used is sub-model using shell element which requires lower memory and computational time. A FE sub-model using solid element is considered for the detailed analysis in the brazing region. Stress distribution of cross-corrugated heat exchanger obtained by using full shell model is generally similar to that obtained by using solid model. Therefore, shell element can be used to carry out the structural analysis in the full model and multi-layer model.

Thermo-mechanical analysis is performed to understand the effect of brazing area at the contact part on the stress distribution. Abnormal peak stress occurs at the point contact part. However, there is no abnormal peak stress in the solid brazed model. Accordingly, abnormal stresses can be ignored in shell model as a result of brazing part analysis.

Based on the analysis technique using the sub model, parametric analysis is carried out in order to optimize heating surface of cross-corrugated heat exchanger. The first parameter considered is plate thickness whose values are 0.1, 0.2, and 0.3 mm, respectively. The second parameter is pitch/height ratio about corrugated section whose values are 2.2, 2.6, and 3.0. The last parameter is intersection angle between upper layer and lower layer whose values are 30°, 60° and 90°, respectively. We can find optimum structural configuration of cross-corrugated heat exchanger based on thermo-mechanical loading.