Keywords: exhaust gas recirculation cooler, fluid-structure interaction, error estimation, ADINA.

Exhaust gas recirculation (EGR) is a key technology in the development of efficient and low emission combustion engines. The main idea of this technology is to recirculate a portion of the exhaust gas to the engine cylinders in order to reduce the total amount of nitrogen oxides (NOx) in the exhaust gas. An important part of the EGR circuit is the EGR cooler which cools the hot exhaust gas prior to being reintroduced into the cylinders. This paper focuses on vibration analysis of tube-type coolers where arising from natural engine vibrations single tubes in the cooler are forced to vibrate which can lead to tube clashes against the cooler housing and hence to a failure of the engine.

This paper shows how vibrations of cooler tubes can be analyzed using transient fluid-structure interaction (FSI) analyses. The basis of the analysis is to use real engine test data which describe the vibrations of the cooler inlet and outlet arising from natural engine vibrations. The novelty of the presented approach is to employ a four step procedure for three-dimensional FSI analysis of EGR coolers. First, based on measurements in the frequency domain, a time signal is obtained using the inverse Fourier transform for which a fully three-dimensaional coupled FSI analysis is performed. The response of the structural part of the FSI model in the time domain is again transformed into the frequency domain using the Fourier transform which yields a frequency spectrum of the response.

The maximum tube vibrations are observed to be in good agreement with engine measurements. The results are also compared with the results obtained from structural dynamic analysis and from an analysis using the classical added mass concept where it is shown that the new approach leads to much more accurate results.

A practical approach for controlling the numerical error in transient fluid-structure interaction analyses is employed using the concept of goal-oriented error estimation as presented for steady-state FSI problems in [1]. The new approach is practical and leads to accurate and robust results in the test problem considered using different types of fluid elements of standard finite element software [2].

1

T. Grätsch, K.J. Bathe, "Goal-oriented error estimation in the analysis of fluid flows with structural interactions", Computer Methods in Applied Mechanics and Engineering, 195(41-43), 5673-5684, 2006. doi:10.1016/j.cma.2005.10.020

2

K.J. Bathe, H. Zhang, "A Flow-Condition-Based Interpolation Finite Element Procedure for Incompressible Fluid Flows", Computers & Structures, 80, 1267-1277, 2002. doi:10.1016/S0045-7949(02)00077-9

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