• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.59-63
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• 2010

Seven different size of orifice were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The initial flame development and flame propagation were analyzed by the mass fraction burn and combustion enhancement rate. The combustion pressures were measured to calculate the mass fraction burn and the combustion enhancement rates. In addition, the flame propagations were visualized by the shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burned fraction were increased when using the torch-ignition device. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage.

• International Journal of Automotive Technology
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• v.5 no.4
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• pp.221-238
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• 2004

Wall interactions of direct injection spray were investigated using laser-sheet imaging, shadowgraphy, wetted footprint and phase Doppler interferometry techniques. A narrow-cone high-pressure swirl injector is used to inject iso-octane fuel onto a plate, which has three different impact angles inside a pressurized chamber. Heated air and plate conditions were compared with unheated cases. Injection interval was also varied in the heated case to compare dry- and wet- wall impingement behaviors. High-speed macroscopic Mie-scattering images showed that presence of wall and air temperature has only minor effect on the bulk spray structure and penetration speed for the narrow-cone injector tested. The overall bulk motions of the spray plume and its spatial position at a given time are basically unaffected until a few millimeters before impacting the wall. The surface properties of the impact surface, such as the temperature, the presence of a preexisting liquid film also have a small effect on the amount of wetting or the wetted footprint; however, they have strong influence on what occurs just after impact or after a film is formed. The shadowgraph in particular shows that the plate temperature has a significant effect on vapor phase propagation. Generally, 10-20% faster horizontal vapor phase propagation is observed along the wall at elevated temperature condition. For impingement onto a preexisting film, more splash and evaporation were also observed. Contrary to some preconceptions, there is no significant splashing and droplet rebounding from surfaces that are interposed in the path of the DI gasoline spray, especially for the oblique impact angle cases. There also appears to be a dense spray front consists of large sac spray droplets in the oblique impact angle cases. The bulk of the spray is not impacted on the surface, but rather is deflected by it The microscopic details as depicted by phase Doppler measurements show that the outcome of the droplet impaction events can be significantly influenced. Only droplets at the spray front have high enough Weber numbers for wall impact to wet, splash or rebound. Using the sign of vertical velocity, the time-resolved downward droplets and upward droplets are compared. The Weber number of upward moving droplets, which seldom exceeds unity, also decreases as the impact angle decreases, as the droplets tend to impact less and move along the wall in the deflected spray plume.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.343-351
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• 2016

Cryogenic spray characteristics of a nitrogen swirl injector operating in supercritical environment have been numerically investigated. By comparing the equation of states(EOS) used for supercritical condition, SRK EOS was applied to predict the nitrogen thermodynamic property under supercritical environment. A Chung's method was implemented for the calculation of viscosity and conductivity and Takahashi's correlation based on Fuller's Theorem was implemented for the calculation of diffusion coefficient. By injecting the nitrogen with 5 bar differential pressure into 50 bar chamber filled with nitrogen, numerical simulation has been conducted. The dynamic Smagorinsky sub-grid scale (SGS) model has been compared with the algebraic Smagorinsky SGS model using FFT frequency analysis. The instability at the liquid film and gas core inside injector and the propagation of pressure oscillation into the injector has been investigated. The spreading angle of swirl injector obtained by numerical calculation has been validated with experimental result.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.166-170
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• 2010

Six different size of torch-ignition device were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The torch-ignition device was designed six different volumes and same orifice size. The combustion pressures were measured to calculate the mass burn fraction and combustion enhancement rate. In addition, the flame propagations were visualized by shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burn fraction were increased when using the torch ignition device. And the combustion duration were decreased. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition device the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage. And the initial flame propagation was effected torch-ignition volume.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.1-14
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• 2019

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.