• 대한기계학회논문집B
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• 제29권2호
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• pp.263-270
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• 2005

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from $0.79{\sim}{\infty}$, on NOx emissions and chemiluminescence of excited $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ radicals in laminar partially premixed flames. the signal from the electronically excited state of $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ was detected through a band pass filter with a photo multiplier tube, which are processed to the intensity ratio ($C_2^{\ast}/CH^{\ast},\;C_2^{\ast}/OH^{\ast},\;and\;CH^{\ast}/OH^{\ast}$) to reveal the correlation with local equivalence ratio. And measurements of NOx emission were made to investigate the relationship between visible flame appearance, chemiluminescence, and EINOX. The results demonstrated that (1) the flames at ${\phi}<1.59$ exhibited classical double flame structure, at ${\phi}>4.76$, the flames exhibited diffusion flame structure, and the intermediate flames at $1.59<{\phi}<4.76$ was a merged flame, (2) the $OH^{\ast}$ peak was located inside the $CH^{\ast}\;and\;C_2^{\ast}$ radical for all measured conditions and the emission intensity ratio of $C_2^{\ast}/CH^{\ast}\;and\;C_2^{\ast}/OH^{\ast}$ were identified as good marker for local equivalence ratio over a range of ${\phi}=0.79{\sim}1.2\;and\;CH^{\ast}/OH^{\ast}\;is\;0.79<{\phi}<1.9$. However, it was difficult to predict the equivalence ratio in partially premixed flames using this system for ${\phi}>2.38$, (3) the minimum NOX emission index (EINOx) is obtained for a equivalence ratio of 3.19 in the intermediate flames.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.481-489
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• 1998

The effects of recirculated exhaust gas on the characteristics of fuel economy combustion and exhaust emissions have been experimentally investigated by a four-cylinder four cycle indirect injection water-cooled and marine diesel engine operating at several loads and speeds. in order to reduce the soot contents in the recirculated exhaust gas to intake system of the engine a novel diesel soot removal system with a cylinder-type scrubber which has 6 water injectors(A water injector has 144 nozzles in 1.0 mm diameter) is specially designed and manufactured for the experiment system The experiments in this study are performed at the fixed fuel injection timing of $15.3^{\circ}$ BTDC regardless of experimental conditions, The brake specific fuel consumption rate is slightly fluctuated with EGR in the range of experimental conditions, The maximum value of premixed combustion for the rate of heat release is decreased with EGR at engine load 25% and the ignition is slightly delayed with EGR at engine load 100% NOx emissions are markedly decreased with EGR especially at high loads while soot emissions are increased as the EGR rate rises.

• 대한환경공학회지
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• 제31권6호
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• pp.442-448
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• 2009

예혼합 분무화염의 유적군 연소 기구를 평가하기 위하여 레이저 가시화법, MICRO (multi-color integrated Cassegrain receiving optics) 및 PDA (phase Doppler anemometer) 광학계측 시스템을 이용하여 동시 시계열 계측을 실시하였다. 또한 유적군의 군연소수를 실험적으로 산출하여 이론해석에 적용하였을 경우 실제로 관찰되는 군연소 형태와 일치하는지에 대하여 검토하였다. 유적군 단면화상에 의해 확인된 모든 유적군에 대하여 실험적으로 군연소수 $G_c$를 산출한 결과 주로 내부 군연소와 외부 군연소로 분류되었으며 이론해석과 일치하였다. 또한 실제 관찰된 군연소 형태와 그 유적군의 군연소수를 이론해석에 적용한 경우에 군연소 형태가 일치하는 경우와 일치하지 않는 경우가 있었다. 일치하지 않는 원인은 군연소수를 유적의 기하학적 배치만으로 결정한 것이나 현상의 3차원성이 측정 결과에 영향을 미친 것이라고 생각되어진다.

• 한국항공우주학회지
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• 제38권2호
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• pp.160-168
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• 2010

공명 주파수의 음파로 가진된 비예혼합 분류화염에서 가진 강도에 대한 영향을 실험적으로 조사하였다. 이를 위해 Mie 산란광 단면법, PLIF, PIV 등 광학적 가시화 방법이 사용되었다. 가진된 분류화염의 부상경로는 연료유량 및 가진 강도에 따라 크게 세 가지 영역으로 구분되는데, 비교적 큰 가진 강도에서 부상될 때 화염기저가 마치 난류화염처럼 부상되는 영역I과 작은 가진 강도에서 쉽게 부상되는 영역II 그리고 이 두 영역들 사이에서 부상된 화염기저가 부분 예혼합의 분젠화염과 같은 형태로 과도기적 영역이 존재함을 알았다. 본 연구에서는 영역I과 II로 구분되는 부상경로 차이에 대한 이해를 높이고자 가진 위상에 따른 노즐과 화염기저간의 유동 혼합과 속도 분포 특성을 아세톤 PLIF와 PIV 시스템을 사용하여 조사하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3264-3269
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• 2007

Combustion instability is a serious obstacle for the lean premixed combustion of gas turbines, and can even cause fatal damage to the combustor and the entire system. Thus, improved understanding of the mechanisms of combustion instability is necessary for designing and operating gas turbine combustors. In this study, in order to understand the instability phenomena, an experimental study was conducted in a rearwardstep dump combustor with LPG and air. The fluctuations of pressure and heat release were measured by piezoelectric pressure sensor and High speed Intensified Charge Coupled Device (ICCD) camera respectively. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The unmixedness of the fuel and air can be controlled by changing the mixing distance ($L_{fuel}$). It is found that the unmixedness of the fuel and air affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.

• Journal of Advanced Marine Engineering and Technology
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• 제10권3호
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• pp.107-118
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• 1986

The presenet research attempts to examine the combustion characteristics and the structure of the flame in turbulent premixed flames and thus enhance the combustion performance that leads to the design of the effective combustion system (untilizing LNG). Following experimental investigations for several stabilized premixed flames were attempted to identify the interactive mechanism between flame structures and flow fields; Visualization by Schlieren method, measurement of flow velocity by LDV, detection of ion current by ion probe, measurement of fluctuating temperature by thermocouple having compensation circuit, average values with respect to time of fluctuating amount for flow velocity, temperature, ion current, etc., variable RMS values, PDFs, autocorrelation, crosscorrelation, spatial macroscale, power spectra, and velocity scale. Continuing the authors published studies whose flame dominated by coherent structures and the characteristics of combustion reaction for irregular three dimensional flame and stabilized flame by step were investigated with obtained experimental quantities. Results of this research are following : The most turbulent flames support the structure of a Wrinkled laminar flame or laminar flamelets. It also observed that combustion reaction is related to small tubulence microscales of the turbulent flow fields closly.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제21회 KOSCO SYMPOSIUM 논문집
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• pp.160-167
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• 2000

We investigated a uniform temperature zone, produced by double flame structure of a coflow CH4/air partially premixed flame, to be used as a temperature calibration source for laser diagnostics. A broadband N2 CARS(coherent anti-Stokes Raman spectroscopy) system with a modeless laser was used for temperature measurement. When the stoichiometric ratio was 1.5, we found the uniform temperature zone in radial direction of the flame of which the averaged temperature was 2110 K with standard deviation 24 K. In the stoichiometric ratio range between 2.0 and 2.5, we found very stable temperature-varying zones in vertical direction at the center of the flame. The size of the zone was approximately 15 mm and it covered a temperature range from 300 K to 1900 K. We also suggest that this zone can be used as a calibration source for 2-D PLIF(planar laser induced flurescence) temperature measurement.

• 한국연소학회지
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• 제17권2호
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• pp.17-23
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• 2012

In this study, thermoacoustic analysis model was developed in order to predict both eigenfrequencies and initial growth rate of combustion instabilities for lean premixed gas turbine combustors. As a first step, a model combustor and nozzle were selected and analytical linear equations for thermoacoustic waves were derived for a given combustion system. Then, methods showing how the equations can be used for analysis of the combustion instability were suggested. It was found that the prediction results showed a good agreement with the measurements. However, there were some limitation in growth rate predictions, which were related with over-simplification of flame structure, acoustic boundary conditions, and temperature distribution in the combustor.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.172-179
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• 2001

Experimental studies have been carried out to find out the characteristics of the heat transfer, combustion emission and noise in the boilers without any extra firing zone for complete combustion of fuel. For the experiments a burner of premixed type and some heat exchangers were designed and manufactured. Also test facilities including a data acquisition system and various measuring devices were set up in order to measure automatically the various temperatures and flow rates of water and combustion gas. Various experiments were performed to find out the heat transfer characteristics as well as combustion emission and noise. In general, the burner which has uniform holes in the burner nozzle plate generates big combustion noise . whistling. The noise reduction method is discussed in this study. Many experimental data such as noise level, the amount of pollutant emission and heat transfer rate for different combination of heat exchangers are given as comparison bases for numerical studies.

• 대한기계학회논문집
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• 제13권1호
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• pp.135-139
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• 1989

본 연구에서는 이러한 예혼합기체의 유한두게의 고온기체에 의한 점화현상을 일차원 평면적으로 다룸에 있어 점화를 일으키는 고온기체의 두께와 기체의 물리적 성질의 비를 나타내는 Lewis수의 영향을 알아 보고자 한다.