Investigation of Soot Formation in Diesel-GTL Fuel Blends

( U. B. Azimov ),( E. A. Roziboyev ),( K. S. Kim ) 한국액체미립화학회 2007 한국액체미립화학회 학술강연회 논문집 Vol.2007 No.-

LARGE-EDDY SIMULATION OF AIR ENTRAINMENT DURING DIESEL SPRAY COMBUSTION WITH MULTI-DIMENSIONAL CFD

U. B. AZIMOV,K. S. KIM 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.6

Large-Eddy Simulation (LES) was used to perform computations of air entrainment and mixing during diesel spray combustion. The results of this simulation were compared with those of Reynolds Averaged Navier Stokes (RANS) simulations and an experiment. The effect of LES on non-vaporizing and vaporizing sprays was evaluated. The validity of the grid size used for the LES analysis was confirmed by determining the subgrid-scale (SGS) filter threshold on the turbulent energy spectrum plot, which separates a resolved range from a modeled one. The results showed that more air was entrained into the jet with decreasing ambient gas temperatures. The mass of the evaporated fuel increased with increasing ambient gas temperatures, as did the mixture fraction variance, showing a greater spread in the profile at an ambient gas temperature of 920 K than at 820 K. Flame lift-off length sensitivity was analyzed based on the location of the flame temperature iso-line. The results showed that for the flame temperature iso-line of 2000oC, the computed lift-off length values in RANS matched the experimental values well, whereas in LES, the computed lift-off length was slightly underpredicted. The apparent heat release rate (AHRR) computed by the LES approach showed good agreement with the experiment, and it provided an accurate prediction of the ignition delay; however, the ignition delay computed by the RANS was underpredicted. Finally, the relationships between the entrained air quantity and mixture fraction distribution as well as soot formation in the jet were observed. As more air was entrained into the jet, the amount of air-fuel premixing that occurred prior to the initial combustion zone increased, upstream of the lift-off length, and therefore, the soot formation downstream of the flame decreased.

INSTANTANEOUS 2-D VISUALIZATION OF SPRAY COMBUSTION AND FLAME LUMINOSITY OF GTL AND GTL-BIODIESEL FUEL BLEND UNDER QUIESCENT AMBIENT CONDITIONS

Azimov, U.B.,Kim, K.S.,Jeong, D.S.,Lee, Y.G. 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.2

An experimental study has been performed on spray combustion and two-dimensional soot concentration in diesel (ULSD), GTL and GTL-biodiesel fuel jets under high-pressure, high-temperature quiescent conditions. Instantaneous images of the fuel jets were obtained with a high-speed camera. It was confirmed that by blending GTL with 20% rapeseed biodiesel, certain fuel properties such as kinematic viscosity, density, surface tension, volatility, lower heating value and others may be designed and improved to be more like those of conventional diesel fuel but with considerable decrease in the amount of sulfur, PAH, cold filter plugging point, etc. The results showed that the spray tip penetration increased and the spray cone angle decreased when 20% biodiesel fuel was added to GTL fuel. Autoignition of the GTL-biodiesel blend occurred slightly earlier than that of diesel fuel. Experiments under high-pressure, high-temperature conditions showed that higher injection pressure induced a lower soot formation rate. The integrated flame luminosity, which serves as an indicator of soot concentration in the fuel jet, was slightly higher for the GTL-biodiesel blend than for pure GTL fuel due to the slightly higher sulfur content of pure biodiesel fuel.

Investigation of Soot Formation in Diesel-GTL Fuel Blends under Quiescent Conditions

U. B. AZIMOV,E. A. ROZIBOYEV,김기성,정동수,이용규,윤정의 한국자동차공학회 2008 International journal of automotive technology Vol.9 No.5

In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O2 concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixingcontrolled combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O2 concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O2 concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the formation of soot and NOx within a wide range of diesel engine loads. In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O2 concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixingcontrolled combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O2 concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O2 concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the formation of soot and NOx within a wide range of diesel engine loads.

EVALUATION OF LOW-TEMPERATURE DIESEL COMBUSTION REGIMES WITH n-HEPTANE FUEL IN A CONSTANT-VOLUME CHAMBER

U. B. AZIMOV,김기성,정동수,이용규 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.3

The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot simultaneously Various LTC regimes that yield specific emissions have been investigated by a great number of experiments. To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC, and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code. The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced. The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot simultaneously Various LTC regimes that yield specific emissions have been investigated by a great number of experiments. To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC, and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code. The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced.

COMPUTATIONAL AND EXPERIMENTAL STUDIES OF GTL SPRAY AND COMBUSTION

K.S. Kim(김기성),U.B. AZIMOV,D.S.JEONG(정동수),Y.LEE(이용규) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

This paper describes the work performed on GTL(Gas to Liquid) spray and combustion in the environments similar to diesel engine combustion. We have used STAR-CD code developed by CD-adapco Group for simulating diesel spray and combustion phenomena. Computations of spray, temperature, NOx and soot emissions distribution were performed. For comparison, we performed the visual investigation of the sprays and flames in a simulating vessel of diesel combustion. For this work, we constructed a rapid charging combustion vessel (RCCV) where high pressure and hot air is rapidly charged to simulate the environment of a diesel engine combustion chamber. As a fuel, we used GTL (Gas to Liquid) which is synthesized from natural gas and has the potential of less soot emission and SOx.

진동연소기의 NOx 저감 효과 연구

강상구(Sang-Koo Kang),U.B. Azimov,김기성(Ki-Seong Kim) 한국연소학회 2007 한국연소학회지 Vol.12 No.4

The NOx emission characteristics were studied in an oscillating combustion burner equipped with a specially designed proportioning valve. The effects of various parameters on the NOx emission which are important in oscillating combustion were investigated. Also, the effects of coincident application of flue gas recirculation(FGR) were evaluated. The results show that oscillating combustion is an efficient tool for reducing NOx in the burner. Up to 53% of NOx reduction could be acquired in low frequency and small duty ratio conditions. The coincident application of FGR further reduced the NOx emission up to 74%. Thus, this study assured that oscillating combustion technology with FGR could be a fascinating method for NOx reduction in industrial burners.

고정밀 레이저 거리 계측기 개발에 관한 연구

배영철,김이곤,박종배,김천석,조의주,서종주,아지모프,구영덕,Bae, Young-Chul,Kim, Yi-Gon,Park, Jong-Bae,Kim, Chun-Suk,Cho, Eui-Joo,Seo, Jonh-Joo,Azimov, U.B.,Koo, Young-Duk 한국정보통신학회 2006 한국정보통신학회논문지 Vol.10 No.12

본 논문에서는 빛의 세기에 크게 영향을 받지 않고 정밀한 거리 계측과 측정 속도를 대폭 개선할 수 있는 기술로서 5m 단위의 거리 계측에는 비행 펄스 시간 방법을 사용하고, 1mm 단위의 계측에는 헤테로다인 방법을 적용하여, 장거리계측이 가능하게 함과 동시에 측정오차 1mm 이내, 측정 거리 1km 이내의 고정밀의 거리 계측이 가능한 방법을 개발하고 그 유용성을 검증하였다. In this paper, we propose a development technique of high precision laser finder ranger within instrument distance 1km, instrument error less than 1 m by using pulse time of flight method in the 5m unit instrument and heterodyne method in the within Am unit. These propose methods can be more advanced to measurement velocity and more highly precision distance instrument not affected the strength of light. We also validate this usefulness.