Effects of Compounds in Liquefied Methane on Rocket Engine Operation

Methane (CH4) is a promising rocket fuel for various future space mission scenarios. It has advantages in terms of cost, performance, and environmental friendliness. Currently, there is no clear definition on standards and specifications for liquefied methane or similar liquids such as liquefied natural gas (LNG) for their use as rocket fuel. However, those regulations are necessary for the commercial, safe, and proper operation of methane rocket engines. Composition and impurities of liquefied methane gas mixtures obtained from natural gas or biogenic sources depend on location of the natural gas source (Europe, Asia, or America), its extraction method and treatment, used cleaning methods or conditions of the gasification process, and biomass sources. In the present work, effects of impurities (N2, CO2, C2H6) within liquid natural gas/liquid methane on the methalox rocket engine operation behavior are analyzed. Regarding the cold cryogenic side, phase diagrams are discussed and critical temperatures for the fuel side are outlined. Carbon dioxide is identified as a rather problematic pollutant. The combustion processes are investigated with several numerical simulations (1D and 2D CFD). The results indicate a minor influence on the overall combustion temperature and a minor but potentially relevant influence on the pressure within the combustion chamber. Additionally, the results indicate that with respect to temperature and pressure, no complex NOx nitrogen chemistry is required

Modification of a cryogenic rocket combustor informed by transcritical oxygen-methane combustion modelling

A priori modelling of transcritical injection and combustion of cryogenic oxygen and methane was used to prepare the geometry and operating conditions of experiments with a single-injector research rocket combustor at conditions relevant for main- and upper-stage rocket engines. The choice of Reynolds averaged Naiver Stokes solver, a two-dimensional, axisymmetric domain, and flamelet combustion model 4th International Seminar on Non-Ideal Compressible Fluid Dynamics minimised computational resources, allowing a parametric study to be performed. Varying the relative injection flow rates of the shear coaxial injector and cooling film in the model allowed the interaction of the two streams to be minimised later in the experiment. Prediction of the length of the diffusion flame was used to adapt the length of the combustion chamber in the experiment to minimise incomplete combustion

Simulation of Single-Injector Methane Rocket Combustor Using Different Numerical Codes

A single-injector methane combustion chamber is simulated using two different computational fluid dynamic codes: TAU and Fluent, density-based and pressure-based solvers, respectively. The simulated test case is the capacitively-cooled rocket combustor fed with gaseous methane and oxygen and operated at pressure of 19 bar. The aim of the simultaneous simulations is to compare the performance of the two algorithms of solving the Navier–Stokes equations: density-based and pressure-based. Earlier the densitybased and pressure-based approaches have not been compared at rocket engine conditions. The simulations were carried out using the same mesh and as much as possible similar setups. Both simulations, TAU and Fluent, agree with each other and with the experimental data well. The Fluent pressure-based solver has showed much faster convergence than the TAU density-based solver due to a larger pseudo-time step and the really two-dimensional setup

REST HF-10 Test Case: Numerical Simulation of a Single Coaxial LOX-CH4 Injector with Forced Mass Flow Oscillations Using the DLR TAU-Code

Combustion instabilities are high-pressure acoustic oscillations that often develop spontaneously and may lead to catastrophic failure of a liquid rocket engine. In order to investigate this phenomenon, the Rocket Engine Stability initiative (REST) was founded by CNES, ONERA, DLR and CNRS. Supporting current and future engine developments, the REST community has worked towards a better understanding of highfrequency instability phenomena. The advancement of numerical simulation methods created new opportunities to simulate combustion instabilities and allowed for a deeper understanding of processes in rocket engines that are difficult to observe experimentally. Numerical simulations were used to investigate the coupling between different internal processes like pressure oscillations and heat release fluctuations. With Prometheus as the engine of a future European launcher vehicle, predicting instabilities and flame dynamics in methane-oxygen (CH4-O2) combustion became an important step in developing reliable, efficient and reusable rocket engines. In order to support these developments numerically, the REST community proposed a representative single injector test case designed for fundamental research. The test case consists of a hexagonal combustion chamber with periodic boundary conditions and a representative injector geometry. The injector was designed within the frame of the "Sonderforschungsbereich Transregio 40", a research program founded by the German Research Foundation (DFG), and is intended to be suitable both for LOx-CH4 and LOx-H2 rocket engines. The chamber pressure is set to be 100 bar and instabilities are introduced by modulating the inlet mass flows for methane and the oxygen injector up to +-10 % of their nominal values at different frequencies. The main goal of this test case is to compare the different numerical codes and modeling approaches (different turbulence modeling, different combustion modeling) between the members of the REST community and various codes. This paper presents the current status of the DLR contribution to the test case. All simulations are conducted with the DLR in-house Code TAU. The combustion is modeled using a real-gas flamelet model whereas the turbulence is modeled using a 2-layer k-epsilon RANS model. In addition to the URANS simulations, Detached-Eddy simulation (DES) results for all test case load points are presented and compared to the URANS results. It is shown that the URANS simulations greatly overestimates the dense LOx core lengths while the DES results give more reasonable values. Investigations of the flame response to the longitudinal mass flux oscillations showed only a small effect for an excitation of the O2 inflow at 5 kHz while there is a stronger flame response for the other excited cases. We also present results for numerical grid resolution sensor and a grid convergence study indicating that the chosen mesh resolution allows for grid-converged results for this test case

LiberTEM/LiberTEM: 0.2.1

LiberTEM is an open source platform for high-throughput distributed processing of large-scale binary data sets using a simplified MapReduce programming model. The current focus is pixelated scanning transmission electron microscopy (STEM) and scanning electron beam diffraction data. It is designed for high throughput and scalability on PCs, single server nodes, clusters and cloud services. On clusters it can use fast distributed local storage on high-performance SSDs. That way it achieves very high aggregate IO performance on a compact and cost-efficient system built from stock components. LiberTEM is supported on Linux, Mac OS X and Windows. Other platforms that allow installation of Python 3 and the required packages will likely work as well. The GUI is running in a web browser. InstallationThe short version: $virtualenv -p python3.6 ~/libertem-venv/$ source ~/libertem-venv/bin/activate (libertem) $ pip install libertem[torch] Please see our documentation for details! Deployment as a single-node system for a local user is thoroughly tested and can be considered stable. Deployment on a cluster is experimental and still requires some additional work, see Issue #105. Applications Virtual detectors (virtual bright field, virtual HAADF, center of mass , custom shapes via masks) Analysis of amorphous materials Strain mapping Custom analysis functions (user-defined functions) Please see the applications section of our documentation for details! The Python API and user-defined functions (UDFs) can be used for more complex operations with arbitrary masks and other features like data export. There are example Jupyter notebooks available in the examples directory. If you are having trouble running the examples, please let us know, either by filing an issue or by joining our Gitter chat. LiberTEM is suitable as a high-performance processing backend for other applications, including live data streams. Contact us if you are interested! LiberTEM is evolving rapidly and prioritizes features following user demand and contributions. In the future we'd like to implement live acquisition, and more analysis methods for all applications of pixelated STEM and other large-scale detector data. If you like to influence the direction this project is taking, or if you'd like to contribute, please join our gitter chat and our general mailing list. File formatsLiberTEM currently opens most file formats used for pixelated STEM. See our general information on loading data and format-specific documentation for more information! Raw binary files Thermo Fisher EMPAD detector files Quantum Detectors MIB format Nanomegas .blo block files Gatan K2 IS raw format Gatan DM3 and DM4: See Issue #291 Please contact us if you would like to process such data! FRMS6 from PNDetector pnCCD cameras (currently alpha, gain correction still needs UI changes) FEI SER files (via openNCEM) HDF5-based formats such as Hyperspy files, NeXus and EMD Please contact us if you are interested in support for an additional format! LicenseLiberTEM is licensed under GPLv3. The I/O parts are also available under the MIT license, please see LICENSE files in the subdirectories for details

REST HF-10 test case: Synthesis of the Contributions for the Simulation of Excited Methane Flames under Real Gas Conditions

The REST (Rocket Engine Stability iniTiative) test case HF-10 is a numerical test case for the calculation of a liquid oxygen-methane (LOx-CH4) coaxial flame at 100 bar. The participants of the 4th REST modelling workshop from both industrial and scientific institutions were invited to use their respective commercial or in-house codes and models to simulate the test case. One steady state and three excited calculations were requested. The approaches used by the participants were LES, DES and URANS with different chemistry models and different numerical schemes. Hence, comparing the results is expected to unveil the influence of these aspects. Important differences in flame structure and dynamics are visible and highlight the particularities and capabilities of the modelling