1,722,069 research outputs found
A detailed chemistry solver on adaptive curvilinear meshes and its application to rotating detonation simulations
No full textThe rotating detonation engine (RDE) has drawn increasing interest in recent years due to its potential for high thermal efficiency and pressure-gain properties. The simulations of RDE have primarily focused on premixed injection and its wave structure, as the premixing assumption allows for the use of simplified chemistry models. However, a fully premixed RDE may lead to potential flashback issues during actual experiments. Another common simplification present in the simulation of RDEs is the adiabatic wall boundary condition. As the duration of operation increases to hundreds of seconds, the need of a cooling system has become more urgent. Simulations addressing these challenges require a three-dimensional solver capable of accurately and efficiently handling detailed chemistry and boundary flows.In this work, a three-dimensional solver is developed based on the Adaptive Mesh Refinement in Object-oriented C++ (AMROC) framework. The adaptive mesh refinement technique enables dynamic mesh refinement based on a user-defined threshold. Initially proposed for Cartesian meshes, the adaptive mesh technique is extended and implemented on curvilinear meshes in this study. This novel combination of a stretched body-fitted mesh and the dynamic adaptive mesh reduces the total number of meshes required for an RDE simulation. The developed solver is verified and validated with different benchmark tests. The results show that the present solver achieves second-order accuracy and ensures conservation across the multi-level hierarchy. In addition, the solver demonstrates the capability for robust and accurate simulation of high-speed reacting flows, including unsteady shock-induced combustion and curved cellular detonation.Finally, the solver is applied to investigate the effects of partial premixing on RDE performance. Hydrogen fuel is blended into the air stream at different bypass flow rates. An increase in bypass flow rate results in improved RDE performance, as indicated by higher detonation velocity, thrust, and specific impulse. The effects of cooling walls are also studied, and the results confirm that introducing a cooling wall during the operation process still preserves the number of detonation heads and the macro structure on the middle plane. The adiabatic case overestimates the detonation velocity without considering the heat loss on detonation. The cooling walls play a crucial role in suppressing parasitic and commensal combustion waves near the walls, leading to a reduction in low-pressure heat release. Moreover, the walls experienced unequal heat loads, primarily influenced by the internal combustion zones and the channel width. These findings enhance the understanding of partial premixing and cooling walls on RDE from the numerical aspect
A three-dimensional solver for simulating reactive flow on curvilinear parallel adaptive meshes
No full textA generic solver in a parallel Cartesian adaptive mesh refinement framework is extended to simulate reactive flows on structured curvilinear meshes. A second-order accurate finite volume method is used with a grid-aligned Riemann solver for inviscid thermally perfect gas mixtures. Detailed, multi-step chemical kinetic mechanisms are employed with a splitting approach. The prolongation and restriction operators are modified to implement the adaptive mesh refinement algorithm on a mapped mesh. The developed solver is verified with a multispecies shock tube problem and is then used to simulate rotating detonation waves in an annular combustion chamber. The results show that the new solver can simulate high-speed reactive flows efficiently.<br/
High-resolution simulation of air-breathing rotating detonation engines
No full textRotating detonation engines (RDEs) use one or multiple spinning detonations to burn propellants in an annular combustion chamber. RDEs are of great interest for hypersonic propulsion as detonation combustion involves a gain in total pressure. Yet, the complex energetic interplay between the leading shock wave and the combustion front in a detonation wave and its propagation speed of around 2000m/s make the experimental investigation of RDEs quite challenging. Numerical simulations are therefore of crucial importance for predicting stable RDE operation at the design stage. Here, we conduct predictive 3D numerical simulations of non-premixed detonation combustion in RDEs using our parallel bock-structured finite volume adaptive mesh refinement framework AMROC, which solves the thermally perfect multi-component Navier-Stokes equations with a detailed chemical model as governing equations on body-fitted curvilinear meshes with dynamic mesh adapation following the detonation fronts. After validating the methodology for a hydrogen-air RDE with available experimental data, we implement constant temperature wall boundary conditions and demonstrate that the number of detonation waves remains unchanged, and that the average detonation velocity deficit rises only slightly, confirming that RDEs can be cooled considerably without significantly affecting the detonation efficiency. Finally, we present simulations with different back pressures of a cooled prototype RDE combustion chamber intended for a laboratory turbine engine running on ethylene and air. The ethylene-air simulations demonstrate that despite a considerably reduced detonation velocity in this very realistic configuration, gains in total pressure at the outlet of 13.3\% and 18.1\% can still be measured, which demonstrates the benefit of the RDE concept for turbine engines quite clearly
Simulations of ethylene-oxygen rotating detonation waves under different local equivalence ratio
No full textParallel adaptive simulation of rotating detonation engines
No full textThe rotating detonation engine is a promising realization of pressure gain combustion for propulsion and power generation systems. A rotating detonation engine running on ethylene-oxygen is simulated by using AMROC with a second-order accurate finite volume method and approximate Riemann solvers. Multi-step chemical kinetic mechanisms are employed with a splitting approach. The rotating detonation is studied in a 2-D unwrapped chamber with premixed and non-premixed injections and is then simulated in a 3-D annular chamber. The results show that using the adaptive mesh refinement method can simulate rotating detonation problems efficiently
Parallel Adaptive High-Resolution Simulation of Rotating Detonation Engines in 3D
No full textSimulations of rotating detonation engines are still dominated by solvers on uniform or statically refined meshes. Here, we demonstrate the application of 3D parallel block-structured adaptive mesh refinement to this problem class. The computations employ a generic shock-capturing curvilinear high-speed combustion solver within the parallel adaptive mesh refinement framework AMROC. The ability to not only capture the rotating waves effectively, but to resolve sub-scale phenomena down to the cellular structures, intrinsic to detonation propagation, demonstrates the potential of the approach
A three-dimensional solver for simulating detonation on curvilinear adaptive meshes
No full textA generic solver in a parallel Cartesian adaptive mesh refinement framework is extended to simulate detonations on three-dimensional structured curvilinear meshes. A second-order accurate finite volume method is used with grid-aligned Riemann solvers for thermally perfect gas mixtures. Detailed, multi-step chemical kinetic mechanisms are employed and numerically incorporated with a splitting approach. The adaptive mesh refinement technique is applied to a mapped mesh using modified prolongation and restriction operators. The flux along the coarse-fine interface is considered in a correction procedure to ensure the conservation of the solver. The numerical accuracy, conservation and robustness of the simulations are verified and validated with suitable benchmark tests. The new solver is then used to simulate detonation problems in non-Cartesian geometries. A simulation is conducted of the three-dimensional detonation propagation in a 90-degree pipe bend. A detonation in a round tube is also simulated in a Galilean frame of reference. Both a rectangular mode and a spinning mode are observed in the simulations. In addition, the fundamental problem of detonation wave/boundary layer interaction is studied. The results show that the new solver can simulate high-speed reactive flows efficiently by the combined use of a curvilinear mapping with mesh adaptation
High-resolution numerical simulation of rotating detonation waves with parallel adaptive mesh refinement
No full textSimulations of rotating detonation engines are still dominated by solvers on uniform or statically refined meshes. Here, simulations of premixed rotating detonation waves are conducted using the block-structured adaptive mesh refinement (SAMR) technique. The studied configurations include both a two-dimensional unrolled model with a discretely injected hydrogen-air mixture and a three-dimensional annular model with non-premixed and partially premixed hydrogen-air mixtures. The computations employ a generic solver within the parallel Cartesian adaptive mesh refinement framework AMROC, which has been extended to accommodate curvilinear meshes. A second-order accurate finite volume method for the Navier–Stokes equations is utilized, along with grid-aligned Riemann solvers for thermally perfect gas mixtures. Detailed, multi-step chemical kinetic mechanisms are employed and incorporated with a splitting approach. A study into mesh dependency is undertaken, providing an assessment of the influence of local mesh refinement and adaptation criteria on the simulation results. The analysis reveals the formation of a multi-wave structure and transient heat release patterns, indicating the presence of an irregular cellular structure with enhanced local heat release as the detonation propagates through the injection jets. The ability to resolve sub-scale phenomena down to the cellular structures, intrinsic to detonation propagation, demonstrates the benefit of the SAMR approach. Further simulations are conducted to investigate the effects of partial premixing on rotating detonation. Additionally, a workload distribution analysis demonstrates how the on-the-fly partition strategy in AMROC alleviates computational imbalances. Parallel scaling tests exhibit linear acceleration in solving rotating detonation engine problems, highlighting the efficiency of the parallel adaptive mesh refinement technique in capturing the primary features of these simulations
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