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Drop Interaction in a Burning Drops Stream
( Wei Dong Hsieh ),( Chun Kuei Chen ),( Ta Hui Lin ),( Shuhn Shyurng Hou ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
In a spray combustion flow field, a burning drop may interact with other drops flowing in parallel streams or along the same flow stream. Many studies on drop interaction in parallel streams were reported. However, upstream/downstream interaction of drops along a burning drops stream has not been well studied literately. To understand such interesting phenomena, we established an experimental system to examine a burning dodecane drops stream with variable drop inter-spaces in a high-temperature oxygen-rich environment. Effects of the drop inter-space (s/di) and the oxygen concentration ΩO2) in the hot environment on the interaction of burning drops were investigated in the study. Drop inter-spaces were chosen to be 2.5, 5, 10, 30 and 100. Oxygen concentrations of 21%, 25% and 30% in the hot environment were considered. The flame propagation and interactions between the burning drops in the stream were performed. Results showed that the diffusion flame enclosing the drops stream is narrowed with the increase of ΩO2 whereas effect of ΩO2 is not obvious when s/di>30. The overall flame length was longer for lower s/di due to flame propagating across the drops. Evaporation rates remains constant when s/di>30 indicating a weak interaction of drops along the same stream.
( Chih Chun Hsieh ),( Tao Chih Chang ),( Dong Yih Lin ),( Ming Che Chen ),( Wei Te Wu ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5
The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten arc welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of δ→σ + γ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.
( Chih Chun Hsieh ),( Dong Yih Lin ),( Wei Te Wu ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5
The dispersion strengthening behavior of the σ phase in 304 modified stainless steel as hot-rolled at 1073 K has been investigated in this study. The morphology, quantity and chemical composition of the σ phase were analyzed using optical microscopy (OM), X-ray diffractometry (XRD), ferritscope (FS), and image analysis (IA). The amounts of σ phase in the stainless steels increased gradually at 1073 K as the reduction ratio increased from 0% to 75%. The XRD analyses showed that a higher reduction ratio enhanced the conversion of δ-ferrite (110) to σ phase (542). The σ phase was precipitated homogeneously at the recrystallized ferrite grains when the reduction ratio was increased from 0% to 75%.
Experimental Simulations on Combustion Chamber Deposits of Spray Flames
( Ta Hui Lin ),( Wei Dong Hsieh ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
Combustion chamber deposits are usually observed in various internal combustion devices. They result in negative effects on the operation and performance of these devices. Study of deposits formed in the internal combustion devices is not easy and usually time-consuming. Therefore, we proposed an experimental method to simulate the deposit formation on the combustion chamber wall by considering a spray flame impinging onto a stagnation plate. Using this method, deposits can be readily generated on the stagnation plate, and it is easy to extract them for further chemical or physical analysis. In this paper, we first focused on the gasoline deposits, and later on the diesel deposits, generated on the water-cooled stagnation plate. The comparisons of gasoline deposits from the stagnation spray flames and from actual CFR engine tests exhibited good qualitative correlations. Concerning the diesel deposits, they had great difference with the gasoline deposits in the appearance. However, the effect of the cooling water (the wall temperature) and deposit growth history for the diesel deposits were basically similar to those of the gasoline deposits. This method may be used as a preliminary test on understanding deposit formation or for fuel formula developing. However, further studies are needed to justify its applicability to real engine CCD simulation.