• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.451-458
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• 2009

This experimental study was conducted to investigate macroscopic characteristics of the flash boiling spray with tow component mixing fuel. Homogeneous Charge Compression Ignition (HCCI) is a newer combustion method for internal combustion engines to reduce nitrogen oxide and particulate matter simultaneously. But it is difficult to put this combustion method to practical use in an engine because of such problems as instability of combustion in low load operating conditions and knocking in high load operating conditions. In HCCI, combustion characteristics and exhaust emissions depend on conditions of air/fuel mixture and chemical reactions of fuel molecules. The fuel design approach is achieved by mixing two components which differ in properties such as density, viscosity, volatility, ignitability and so on. We plan to apply the fuel design approach to HCCI combustion generated in a real engine, and examine the possibility of mixture formation control using the flash boiling spray. Spray characteristics of two component fuel with a flash boiling phenomenon was investigated using Shlieren and Mie scattering photography. Test fuel was injected into a constant volume vessel at ambient conditions imitated injection timing BTDC of a real engine. As a result, it was found that a flash boiling phenomenon greatly changed spray structure, especially in the conditions of lower temperature and density. Therefore, availability of mixture formation control using flash boiling spray was suggested.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.22-28
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• 2021

Combustion characteristics were examined experimentally for a swirl-stabilized double cone premixed burner nozzle used for industrial gas turbines for power generation. An original model and a variant with a different fuel injection pattern are tested to compare their combustion characteristics such as NOx, CO and stability in pressurized conditions with single burner-flame and in an ambient multi-flame conditions with multi-burners. Test results show that NOx emissions are smaller for the variant, whose number of fuel holes is reduced with the same total area of fuel holes, in ambient and pressurized single-flame conditions with single burner, which results from enhanced fuel/air mixing due to a higher penetration of fuel into the air stream. The multi-burnerflame test results show that NOx emissions are smaller for the variant due to reduced flame interactions, which, on the contrary, slightly reduces the stability margin. On-site test results fromin an actual power plants also show that NOx emissions are reduced for the variant, compared with the original one, which is in agreement with the lab test results stated above.

• Journal of ILASS-Korea
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• v.2 no.2
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• pp.24-34
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• 1997

This paper describes the investigation of combustion characteristics of gasoline-methanol blend in constant volume combustion chamber. A constant volume combustion chamber was used to elucidate a basic combustion characteristics and the premixer was installed to control temperature and equivalence ratio. And the maximum pressure, combustion duration and flame propagation according to the evaporation rate were measured to determine the optimal temperature range for evaporating a blend fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion were deteriorated by decreasing surrounding temperature of fuel. These experimental results indicate that the combustion characteristics such as combustion chamber pressure and combustion were deter orated by decreasing surrounding temperature of fuel injected. It was also found that the overall gasification process for methanol blend fuel was influenced by a combustion chamber temperature rather than a premixer temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.453-456
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• 2011

An experimental investigation of the heat transfer characteristics of stretched premixed flames using Synthetic gas has been performed. Hydrogen and carbon mon-oxide which could be extracted from coal gasification process are the main fuel of synthetic-gas. Heat flux at the stagnation point was increased as global strainrate was increased, then the heat flux was decreased when a global strainrate reached a sudden point. Heat flux at the stagnation point is also affected by nozzle to impingement distance. Heat flux was increased as nozzle to impingement place distance was increased. This study is a foundation study of practical use of secondary gases from coals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1257-1264
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• 2011

This paper presents 3D simulation by STAR-CCM+ for lean premixed combustion in a stationary gas turbine combustor with separate pilot and main nozzles. The constant for the source term in the flame area density transport equation was modified to account for a low global equivalence ratio and validated against measurement data. A Partially-premixed Coherent Flame Model(PCFM) involves propagation of a laminar premixed flame with the predicted flame surface density and equilibrium assumption in the burned gas with spatial inhomogeneity. The conditions for cooling by radiation and convection are considered for accurate determination of the heat flux on the wall. A parametric study is of the pilot-fuel-to-total-fuel-ratio is carried out. A chemical reactor network (CRN) was constructed on the basis of the 3D simulation results and compared against measurements of NOx.

• 한국가시화정보학회:학술대회논문집
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• 2005.04a
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• pp.115-154
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• 2005

SI 엔진의 연소특징은 비정상 난류 예혼합 화염이며 여기서 내부 유동은 직접 화염 전파에 영향을 미치며 난류와 거시적 유동의 패턴 모두 중요한 역할을 한다. 내연기관 연소에서 난류는 매우 중요한 역할을 하고 통상 엔진 속도($\approx$흡입유동 속도)에 비례하며 그 주요 역할은 고속 운전 시 해당 사이클 내에 연소가 완료되는 데 기여하지만 출력저하, 제어 및 측정 그리고 사이클 변동과 관련하여 실질적으로 난류 제어를 통한 엔진 성능 개선은 사실상 불가능하다. 실물 엔진의 성능 파라미터로 주로 유동의 거시적 거동이 사용되며 이 유동과 연료 분사계가 혼합기 분포 상태와 화염 전파 방향을 결정하여 최종적으로 엔진의 성능을 지배한다. 따라서 가시화를 통한 연소 진단도 이 현상에 주목할 필요가 있으며 거시적 파라미터를 성능에 연관하는 다양한 기법이 존재하고 이들은 매우 풍부한 데이터베이스를 통해 비교적 정확한 성능의 예측을 가능하게 하고 이 점에 주목한 엔진만 성공을 거두었다. 이 거시적 현상에 주목하여 가시화를 통해 성층화 현상을 실험적으로 해석한 예를 제시하였다. SI 엔진 가시화에서 기법보다 중요한 것은 현상의 이해이다. 이를 위해 성공적 가시화 진단을 위해서는 우선 현상에 대한 모델링이 필요하고 이 모델에서 가시화를 통해 규명 가능한 현상을 추출해 내는 것이다.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.201-207
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• 1999

The combustion characteristics for the low NOx 50 kW-class gas turbine combustor have been experimentally investigated. In order to achieve the premixing and the lean burn combustion, the geometries of the primary zone including premixed chamber were modified from conventional combustor. The centerline profiles of CO and NO concentration, and temperature were measured for the premixed combustors with or without dilution holes in the liner. The effects of the pilot fuel injection rate and air dilution on flame stabilization and pollutant (CO, NO) emission are discussed in detail.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.145-153
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• 1987

Stability limits of a double concentric jets flame and the structure of recirculation zone formed behind a thick burner rim were investigated. To control the flame stability, swirled secondary air flow ranging 0.13-0.71 of swirl number, and air, fuel, and mixture gas injection from an injection coaxial slit set on burner rim were examined. Flame stability limits, flame shapes, lengths of recirculation zone, temperature distributions, residence times, air ratios in the recirculation zone were measured. The following results were obtained. (1) Lean limits were considerably widened by a strong swirl because the recirculation zone was enlarged. (2) At fuel injection as well as mixture injection, lean limits were also extended. But, air injection had no effect on stability limits. (3) Injected gas seems to diffuse into the recirculation zone through its outer boundary surrounded the secondary air. Therefore, chemical structure in the recirculation zone with air injection coincides with that without injection. (4) Injection position had no effect on flame stability limits.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.179-188
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• 2011

Experiments were conducted in a constant-pressure combustion chamber to investigate the effects of hydrocarbon addition on cellular instabilities of syngas-air flames. The measured laminar burning velocities were compared with the predicted results computed using reliable kinetic mechanisms with detailed transport and chemistry. The cellular instabilities that included hydrodynamic and diffusional-thermal instabilities of the hydrocarbon-added syngas-air flames were identified and evaluated. Further, experimentally measured critical Peclet numbers for fuel-lean flames were compared with the predicted results. Experimental results showed that the laminar burning velocities decreased significantly with an increase in the amount of hydrocarbon added in the reactant mixtures. With addition of propane and butane, the propensity for cell formation was significantly diminished whereas the cellular instabilities for methane-added syngas-air flames were not suppressed.