A first step into the blanching modelling of Liquid Rocket Engines: taking into account the roughness increase of the chamber wall

Whereas pure oxidation of a copper based liquid rocket combustion chamber wall results (due to the brown color of copper oxide) in a darkening of the hot-gas side of this chamber wall, blanching (on the contrary) leads to a lighter color. This is a result of a cyclic oxidation and reduction of the chamber wall material. The most important influence of blanching is the roughness increase of the chamber wall. The strong effect of this roughness increase is exemplarily considered for the main combustion chamber of a 10 MPa chamber pressure, 1 MN vacuum thrust reference engine. A thermally fully coupled CFD analysis of the hot-gas flow and thermal FE analysis of the heat conduction in the chamber wall and CFD analysis of the coolant flow is applied to a chamber wall model of this reference engine. By running this analysis for both: initial (small) roughness as well as blanching-caused (strongly increased) roughness, the severe thermal influence of blanching can be assessed. Finally, the blanching-caused decrease of the fatigue life of the chamber wall of the reference engine is shown

TMF test based validation of numerical methods for the analysis of heat-loaded walls

The creation of validation data for CFD, thermal, structural and life time analyses of actively cooled thermally loaded wall structures of rocket engines by means of Thermo- Mechanical Fatigue (TMF) - tests is discussed in this paper. During a TMF test, only a small section of the hot gas wall of the real engine (the so called TMF panel) is tested. For such a TMF panel, realistic cooling conditions similar to a full scale rocket engine are chosen. 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 provides (together 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) life time analyses of thermally loaded structures

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

The potential of in situ melt pool monitoring (MPM) for parameter development and furthering the process understanding in Laser Powder Bed Fusion (LPBF) of CuCr1Zr was investigated. Commercial MPM systems are currently being developed as a quality monitoring tool with the aim of detecting faulty parts already in the build process and, thus, reducing costs in LPBF. A detailed analysis of coupon specimens allowed two processing windows to be established for a suitably dense material at layer thicknesses of 30 µm and 50 µm, which were subsequently evaluated with two complex thermomechanical-fatigue (TMF) panels. Variations due to the location on the build platform were taken into account for the parameter development. Importantly, integrally averaged MPM intensities showed no direct correlation with total porosities, while the robustness of the melting process, impacted strongly by balling, affected the scattering of the MPM response and can thus be assessed. However, the MPM results, similar to material properties such as porosity, cannot be directly transferred from coupon specimens to components due to the influence of the local part geometry and heat transport on the build platform. Different MPM intensity ranges are obtained on cuboids and TMF panels despite similar LPBF parameters. Nonetheless, besides identifying LPBF parameter windows with a stable process, MPM allowed the successful detection of individual defects on the surface and in the bulk of the large demonstrators and appears to be a suitable tool for quality monitoring during fabrication and non-destructive evaluation of the LPBF process

Dependency of Surface Temperature on Coolant Mass Flow and Heat Flux in Rocket Combustion Chambers

This paper presents the simulation and experimental results of the dependency of the surface temperature of a heat transfer test (HTT) panel representing liquid rocket engine combustion chamber geometry on the coolant mass flow rate and heat flow rate. The HTT panel is made of a high-conductivity copper material. This material is appropriate for the inner liner of lowly loaded regeneratively cooled combustion chambers like upper stages. In the experimental setup the HTT panel uses only a small section of the actual combustion chamber geometry, typically five cooling channels. The panel is heated by a high power diode laser providing realistic amounts of heat flux. For safety and cost reasons supercritical nitrogen is used as coolant instead of hydrogen or methane. Within the experiment differ ent combinations of surface temperature, heat flux and mass flow rate were examined, in total 24 different test conditions. Subsequently a coupled steady state thermal fluid-structureinteraction analysis was conducted in ANSYS and validated with the experimental data. ANSYS CFX was used to analyze the nitrogen coolant fluid flow with a Shear Stress Turbulence (SST) model. ANSYS Mechanical was used for the thermal finite element analysis. The relevant thermophysical parameters like heat conductivity, diffusivity and heat capacity were measured for temperatures above 273 K. For lower temperatures these parameters were determined theoretically. The results gained in this study will be used for the accurate modeling of the heat transfer in a thermomechanical fatigue life analysis by adding a dedicated structural Finite Element (FE) Analysis in ANSYS Mechanical. The accurate modeling of thermomechanical fatigue is particularly important for reusability of rocket engines. Furthermore the results of the validated numerical simulation are useful for the estimation of heat transfer in new developments of liquid rocket engines, particularly upper stages

Overview of the In-Space Propulsion (ISP-1) Project

The intent of this publication is to provide an overview of the progress of the ISP1 project over the 2011-2012 period. In the frame of the European FP7 Collaborative Project, Focused Research Project Theme 7, the In-Space Propulsion (ISP-1) project GA# 218849 was initiated in 2009 with the objective of improving the knowledge and the techniques which are necessary for future space missions relying on cryogenic propulsion. The ISP-1 program is structured into five main work packages which deal with various technological issues associated to the development of a Low Thrust Cryogenic Propulsion system. It concentrates on liquid oxygen, liquid hydrogen, and liquid methane propellants. The subject addressed by the work packages are the LOX-methane combustion, the hydrogen embrittlement, the material compatibility and tribology in liquid oxygen, the energy management of low thrust propulsion system, and the development of electrically driven cryogenic turbopumps. The scientific and technological goals assigned to each work package can be summarized as: - LOX/CH4 Combustion studies and test focused on low thrust LOX/CH4 space propulsion with an emphasis on low pressure liquid injection - Compatibility and tribology analysis and tests addressing both technological aspects (Foil bearings in cryogenic conditions , material for bearing retainer, graphite against a hard surface for dynamic seals) and more fundamental aspects (feasibility of CH4 tribological tests, theoretical analysis of local contact conditions) of tribology. - Hydrogen embrittlement studies and tests with the objective of testing new materials in a High pressure and medium range temperature environment - Heat Accumulators studies and tests, focused on energy management techniques, with testing of a low temperature accumulator - The Propellant Electric Pumps design and tests, to be concluded by the testing of a demonstrator pump in LN2 The work packages of project ISP1 rely on a combination of analysis and test, of theoretical activities which can serve as a basis for PhD theses or more application oriented activities such as the design and testing of a demonstrator pump or a demonstrator accumulator. These work packages are focused on technologies which are considered as the critical points of future cryogenic space propulsion systems. By increasing the technological readiness level of these technologies, these activities pave the way for the development of future propulsion systems and constitute an asset with respect to possible future international cooperation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Focused research on RLV-technologies: the DLR project AKIRA

DLR has organized a multidisciplinary research project on technologies critical for the realization of RLV-stages called AKIRA. The research topics are efficient RLV-stage return, reusable cryogenic tank insulation technologies, and structural technologies in RLV-stages and reusable engines. The paper provides an overview of all ongoing activities and summarizes major research results achieved over the successful mid-term review of November 2018 up to early 2019

DLR-Projekt AKIRA: Ausgewählte Kritische Technologien und Integrierte Systemuntersuchungen für RLV Anwendungen (Zwischenbericht)

Das Projekt wird sowohl Systemseitig als auch auf Subsystemebene kritische RLV-Technologien untersuchen. Auf der Systemseite werden verschiedene Stufendesigns und Rückkehroptionen untersucht werden, unter anderem Fly-Back Booster, In-Air-Capturing, Toss-back mit vertikaler Landung (ähnlich SpaceX), sowie Konzepte die eine Rückführung von Teilkomponenten einer Stufe vorsehen (z. B. Airbus ADELINE). Aus diesen Konzepten werden sinnvolle Konfigurationen ausgewählt. Für jedes ausgewählte Konzept ist eine Systemvorstudie durchzuführen, und die Vorteile und Nachteile, technischen Herausforderungen und Wirtschaftlichkeitsfragen sind herauszuarbeiten. Auf dieser Basis sind die Konzepte schließlich einer vergleichenden Bewertung zu unterziehen. Ein zweiter Teilbereich der Systemanalyse wird die Definition von zwei Referenzkonfigurationen umfassen, deren Hauptaufgabe die Bereitstellung repräsentativer Randbedingungen für die technischen Arbeiten in den anderen Arbeitspaketen ist. Die Referenzkonfigurationen wurden bei RY-SRT entworfen und stellen Vertreter zweier unterschiedlicher Kategorien von RLVSystemen dar