• 한국분무공학회지
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• 제12권2호
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• pp.101-107
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• 2007

The purpose of this study is to analyze spray and evaporation characteristics of DME fuel at the high pressure and temperature. For the numerical analysis of dimethyl ether(DME) fuel spray characteristics, hybrid breakup model was applied to the DME spray and its breakup process. In order to obtain experimental results for comparison with the predicted ones, the visualization of the spray evolution process was executed by using a Nd:YAG laser. Also, the numerical investigation was conducted by the two hybrid models for primary and secondary breakup of the DME spray. The primary breakup model was used the Kelvin-Helmholtz(KH) breakup model. In the secondary breakup process, Rayleigh-Taylor(RT) and Drop Deformation Breakup(DDB) model was applied. The results of this study provide the macroscopic characteristics of the spray such as spray tip penetration and cone angle, and prediction accuracy of the two hybrid model.

• 한국분무공학회지
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• 제14권3호
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• pp.109-116
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• 2009

The purpose of this study is the experimental and numerical investigation on the DME spray characteristics in the combustion chamber according to the injection timing in a common-rail injection system. The visualization system consisted of the high speed camera with metal halide lamp was used for analyzing the spray characteristics such as spray development processes and the spray tip penetration in the free and in-cylinder spray under various ambient pressure. In order to observe the spray characteristics as a function of injection timing, the piston head shape of re-entrant type was created and the fuel injected into the chamber according to various distance between nozzle tip and piston wall in consideration of injection timing. Also, the spray and evaporation characteristics in the cylinder was calculated by using KlVA-3V code for simulating spray development process and spray tip penetration under real engine conditions. It was revealed that the high ambient pressure of 3 MPa was led to delay the spray development and evaporation of DME spray. In addition, injected sprays after BTDC 20 degrees entered the bowl region and the spray at the BTDC 30 degrees was divided into two regions. In the calculated results, the liquefied spray tip penetration and fuel evaporation were shorter and more increased as the injection timing was retarded, respectively.

• 동력기계공학회지
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• 제3권3호
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• pp.36-43
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• 1999

Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.270-278
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• 2002

In order to reduce the exhaust emissions of a spark ignition engine, it is important not only to improve the catalyst conversion efficiency, but also to directly reduce the engine-out exhaust emissions during a cold starting of the engine and warm up periods. The purpose of this study is to evaluate feasibility of a glow plug for an early fuel evaporator. In order to promote atomization, gasoline is injected on the glow plug with room temperature(20$\^{C}$) and high temperature(250$\^{C}$). To analyze the spray behavior characteristics, a PMAS is used to measure the SMD and the dropsize distribution of an impinging spray and a free spray. Results show that the evaporation rate of the impinging spray on the high temperature surface of the glow plug was higher than that of the free spray on the room temperature surface.

• 대한기계학회논문집B
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• 제33권5호
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• pp.373-380
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• 2009

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

• 한국연소학회지
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• 제13권3호
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• pp.17-23
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• 2008

The spray combustion and spray cooling depends on droplet evaporation. So, evaporation model for spray has been requested and lots of investigation has been done and various reliable models have been developed also for last few decades. In the present study, One dimensional quasi-steady spherically symmetric droplet evaporation model for micro-gravity is developed. The gas phase was assumed as steady state and the thermophysical properties are calculated as a function of temperature, pressure and composition and the properties used in the model was validated by NIST web data and overall evaporation history results was compared with experimental results by Nomura and Qasim and gave satisfactory agreements. Through this model, diverse phenomenon was investigated, especially regarding the effects of ambient pressure and temperature. The effects of pressure for the droplet evaporation time were studied. The high pressure increased the droplet surface temperature and made effect on the evaporation time depend on atmospheric temperature. The role of the ambient temperature was investigated and explained. The basic investigation for the evaporation process according to variation of droplet diameter and surface temperature were also investigated and the well-known phenomena, like D-square-law, were reported, too.

• 대한기계학회논문집B
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• 제24권6호
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• pp.852-859
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• 2000

The emission in the exhaust gas from diesel engine is effected by the fuel spray characteristics. The spray of D.I. diesel engine impinges on a piston cavity and a cylinder wall. It is very important to know exactly the distribution and behavior of the spray inside cylinder. The objective of this study is to develop more accurate evaporation model. The EPISO code was used to analyze the flow characteristics in the engine. The Wakil model and the Faeth model are applied to the EPISO code to analyze the behavior of impinging spray. And also experimental and numerical analysis were carried out. The spray behavior characteristics were investigated by changing injection pressure, ambient pressure and temperature. The behavior of impinging spray was strongly effected by the change of ambient pressure and temperature. The effects of evaporation and rebounding droplet should be considered.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.8-22
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• 1995

Three dimensional numerical study of non-evaporating and evaporating spray characteristics was performed in a quiescent and motoring condition of direct injection diesel engine. The calculation parameter was breakup model. The breakup models used were Reitz & Diwakar model and TAB model. The modified k-${\varepsilon}$ turbulence model considering the compressibility effect due to the compression and expansion of piston was used. The calculation results of the spray tip penetration and tip velocity using the TAB model showed similar trends comparing with the experimental data. Although the evaporation rate was not nearly affected with the breakup model at the higher injection pressure, in the low injection case, the evaporation rate result using the TAB model became higher than that of R&D model. The evaporation rate was increased with the injection pressure due to the vigorous interaction with the gas field.

• 대한기계학회논문집B
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• 제29권12호
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• pp.1360-1368
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• 2005

This study investigates the characteristics of spray, such as evaporation rate and spray trajectory, for a 4-hole injector which is applied to a 4-valve motorcycle gasoline engine. Three dimensional, unsteady, compressible flow and spray within the intake-port and cylinder have been simulated using the VECTIS code. Spray characteristics were investigated at 6000 rpm engine speed. Furthermore, we visualized fuel behavior in the intake-port using a CCD camera synchronized with a stroboscope in order to compare with the analytical results. Boundary and intial conditions were employed by complete 1-D simulation of the engine using the WAVE code. Fuel was injected into the intake-port at two time intervals relative to the position of the intake valves so that the spray arrived when the valves were closed and fully open. The results showed that the trajectory of the spray was directed towards the lower wall of the port with injection against the closed valves. With open valve injection, a large portion of the fuel was lifted by the co-flowing air towards the upper half of the port and this was confirmed by simulation and visualization.

• 한국분무공학회지
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• 제28권1호
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• pp.32-42
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• 2023

In this study, spray characteristics of n-heptane and propane were investigated under different injection pressure using various imaging techniques such as Mie-scattering, DBI (diffuse back-illumination), and Schlieren imaging techniques. NI compact RIO system was used to control a test injector. Spray penetration length, length-to-width ratio and number of black pixels were calculated by using MATLAB software to compare spray characteristics of each fuel. Longer spray penetration length and higher length-to-width ratio were observed in propane spray because of flash boiling caused by high saturated vapor pressure. Spray collapse occurred in propane spray due to the high plume-to-plume interaction. Moreover, rapid evaporation occurred in propane spray, so that nozzle tip wetting could not be observed. Rapid evaporation of propane also caused fewer residual droplets compared to n-heptane spray. Therefore, propane is advantageous in reducing the generation of soot emission from large droplets that are not atomized. However, additional evaluation should be conducted considering combustion efficiency and the possibility of deposits by nozzle tip icing during fuel injection.