Comparison of Finite Element analysis and experimental results of a combustion chamber type TMF panel test

Abstract

The inner liner of a regeneratively cooled wall of a main stage rocket combustion chamber is extremely loaded by the high temperature of the hot gas and the pressure difference between the coolant and the hot gas. A cyclic operation of such a chamber usually causes a LFC failure of the wall structure after a very low number of cycles. For the tests presented in this paper, cyclic laser heating is (as replacement for the hot gas) applied to an actively cooled small section of the hot gas wall of the real engine -the so called TMF panel.Optical measurements during such TMF panel tests provide essential validation data for CFD, thermal, structural and fatigue life analyses: The 2d measurement of the thermal field of the heat loaded structure provides -together with the measurement of the temperature, pressure and mass flow rate of the coolant of the TMF panel -data for the combined validation of the CFD analysis of the coolant flow and the thermal analysis of the wall structure. The measurement of the deformation of the thermally loaded structure providestogether with the already determined temperature distribution and the above mentioned pressure measurements of the cooling channels -data for the validation of the structural analysis of the thermally loaded structure. Counting the number of laser loading cycles (laser on-off) until the TMF panel fails (by cracks appearing on the laser loaded side of the cooling channels) provides data for the validation of (either post processing or damage parameter based) fatigue life analyses of thermally loaded structures.

Comparison of damage parameter based Finite Element fatigue life analysis results to combustion chamber type TMF panel test results

“…From the results of the uniaxial LCF tests, a damage threshold relative decrease of 27 % by increasing the temperature from = 700 K to 900 K was determined. Furthermore, the simulated wall thickness increase in the vicinity of the two fins is quite similar to the experimental observations and also similar to the numerical results of Riccius [1].…”

“…A similar Finite Element mesh as shown in [1] is used. For numerical analysis efficiency reasons, only half of the domain of the TMF panel is modeled.…”

“…The actively cooled inner liner is usually made of copper-base alloys and its behavior is mainly governed by low cycle fatigue and creep at elevated temperatures. A cost-efficient experimental setup with a cut-out model of an actively cooled combustion chamber wall (the so-called TMF-panel) was developed at the German Aerospace Center (DLR) in Lampoldshausen for validating numerical fatigue life prediction analyses [1]. In the present work, a numerical visco-plastic model coupled with ductile isotropic damage based on the work of Tini [2] is used as a user-defined material (USERMAT) in the Finite Element program package ANSYS.…”

Pressure Drop Measurement of Porous Materials: Flashback Arrestors for a N2O/C2H4 Premixed Green Propellant

“…4 However, the available heat flux of 20 MW/m 2 is assumed to be sufficient for creating validation data for fatigue life analyses of combustion chamber and nozzle throat structures. 1 Finally, small white speckle marks on the surface of the TMF panel allow the measurement of the 3D displacement field with a stereo camera system before, during and after the laser loading.…”

“…A cost-efficient experimental setup with a cut-out model of an actively cooled combustion chamber wall (the so-called TMF panel) was developed at the German Aerospace Center (DLR) in Lampoldshausen for validating numerical fatigue life prediction analyses. 1 In the present work, a numerical viscoplastic model coupled with isotropic damage based on the work of Tini 2 is used as a user-defined material in the finite element program package ANSYS. In addition to the work of Thiede, 3 the crack-closure effect is implemented to consider the different stiffness behavior in tensile and compressive direction due to the influence of damage.…”