Effects of Chemical Reaction Models on Simulations of Scramjet Nozzle Flow

The chemical non-equilibrium flow of supersonic combustion ramjet (scramjet) nozzle is numerical simulated with different chemical kinetic models to research the effects on numerical results of the nozzle performance. The numerical results show that total temperature is increased due to the recombination of dissociation compositions and the combustion of the residual fuel. The effect of the combustion of the residual fuel is more obvious in this paper, and the effect to the performance of the nozzle is noticeable. The species of the compositions in the models influence the quantity of heat sending out when it get equilibrium, so the 9-species chemical kinetic models are more suitable in the simulation of the scramjet nozzle chemical non-equilibrium flows.

Hybrid MPI + OpenMP Parallelization of Scramjet Simulation with Hypergraph Partitioning

As one of the most significant methods to study hypersonic flight vehicle, the numerical simulation of supersonic combustion ramjet has drawn an ever increasing attention at present. Nevertheless, the traditional serial simulation cannot satisfy the practical needs because of high calculation precision, avaricious memory overhead and overlong computation time. In this paper, we study on a general algorithm for scramjet simulation, and bring about parallelization by using a hypergraph partitioning algorithm and a two level hybrid parallel model. The whole computing domain is decomposed into several sub-domains based on hypergraph partitioning, and each sub-domain is assigned to a MPI process. A single step of computation operates in the inter loop level, where a compiler directive is used to split MPI process into several OpenMP threads. Finally, speedup and parallel efficiency of our hybrid program testing on a China-made supercomputer with 4 to 256 cores is compared with pure MPI program. And, the hybrid program exhibits better parallel performance than the pure MPI program in the main, roughly as expected. The result indicates that our hybrid parallel strategy is effective and practical in scramjet simulation.

Parallel Simulation of Scramjet with Multilevel Hypergraph Partitioning

As one of the most considerable methods to study hypersonic flight vehicle, the numerical simulation of supersonic combustion ramjet (scramjet) has drawn an ever increasing attention at present. Nevertheless, the traditional serial simulation is ungratified for current research requirements because of high calculation precision, avaricious memory overhead and overlong computation time. Meanwhile, the efficiency of parallel simulation using the domain decomposition method is not very satisfactory. In this paper, we study on a general algorithm for scramjet design, and subdivide the computing domain by using a multilevel hypergraph partitioning algorithm. In order to reduce computation while enhancing the degree of parallelism, overlapping communication with computation and non blocking communication is adopted to decrease the communication time when dealing with global communication. Finally, experimental results testing on a China-made supercomputer show the smallest value of parallel efficiency is more than 48% when the number of processors is 256. In conclusion, the result indicates that our parallel algorithm is simple, effective and practical in scramjet simulation.

Investigation of the Formation of Microbubbly Liquid Fuel

There are several obstacles encountered during combustion in Supersonic Combustion Ramjet (SCRAMJET) engines such as mixing, ignition, and flame holding. In order to overcome these difficulties, a new type of fuel is generated with the use of combination of two methods namely an effervescent (barbotage) and thermal pyrolysis of the fuel. In the first step of the process, during effervescent method, small gas bubbles are introduced into liquid fuel to improve the spraying characteristics of the fuel. At the second stage, long-chain hydrocarbons are broken down into short-chain hydrocarbons that burn faster. An experimental facility has been designed and developed to study the underlying physics in each process.

SFGP 2007 - Pyrolysis of Supercritical Endothermic Fuel: Evaluation for Active Cooling Instrumentation

Hypersonic flight is expected to be achieved in the coming years by use of Supersonic Combustion RAMJET (SCRAMJET). One of the main issues is the thermal management of the overall vehicle and more specifically the cooling of the engine. In order to simulate the behaviour of an actively cooled SCRAMJET by use of supercritical endothermic fuel, a one-dimensional transient numerical model has been developed with heat and mass transfer, fluid mechanics and detailed pyrolysis chemistry. A dedicated experimental test bench is now available since 2006 at the LEES laboratory of Bourges to study supercritical fuel pyrolysis under steady-state and transient conditions. It aims to provide understanding of coupled phenomena, validation data for the numerical code and evaluation of onboard and real-time measurement methods for industrial use. A brief overview of the numerical code and a presentation of the experimental bench are proposed in this paper. Experimental results are discussed and a comparison is provided between numerical and experimental data. Discrepancies are shown to be lower than a few percent in terms of molar chemical compositions. This is due to uncertainties on experimental temperature measurement and to 2-D effects, which are not taken into account by the modelling. The numerical code appears to be of great importance in accessing unmeasured data and providing new understanding of coupled phenomena. Experimental and numerical tools are proved to be efficient to test future measurement methods under extreme conditions, especially at supercritical states.