Hyouck Ju Kim

Combustion Characteristics of a Premixed Burner in a Stirling Engine for a Domestic Cogeneration System

최근 에너지 자원의 고갈과 지구 온난화 문제가 심각하게 인식되면서 장기적으로는 신재생 에너지의 개발이 단기적으로는 에너지의 합리적 이용이 대책으로 제안되고 있다. 에너지의 합리적 이용 방안으로서 가용 에너지 및 엑서지의 개념에 바탕을 둔 계단식 열에너지 이용을 고려할 수 있다. 즉, 연료를 연소함으로써 발생한 고온의 열에너지는 1 차적으로 전기 에너지로 변환하고 냉난방을 위해 필요한 열은 변환 후에 발생하는 배열을 이용하면 가용에너지가 높은 연소 가스를 직접 열로서 활용하는 것보다 에너지를 합리적으로 활용할 수 있다. 위와 같은 에너지 이용방식을 열병합 발전이라고 하고 시스템을 소형화하여 에너지 수용가에서 직접 전기 및 열에너지를 생산하여 활용할 경우, 고압 송전을 위한 변압 과정이나 송배전 과정에서 발생하는 에너지 손실을 줄일 수 있을 뿐 아니라 에너지 수요에 맞추어 에너지를 생산함으로써 에 Key Words: Stirling Engine(스털링 엔진), Burner(버너), Premixed Combustion(예혼합 연소), Surface Combustion (표면 연소) 초록: 화석 에너지 고갈에 따라 에너지의 합리적 이용이 요구되면서 가용 에너지를 고려한 열에너지의 계단식 활용이 적극적으로 검토되고 있다. 이와 같은 배경에서 1 kW 급의 스털링 엔진을 기반으로 한 열병합발전 시스템이 분산 에너지 시스템을 구축하는 단위로서 제안되었다. 1 kW 의 용량은 가정용에 적합하며, 가정에서 활용하기 위해서는 공간을 작게 차지하도록 하면서도 소음과 유해가스의 배출을 철저하게 차단해야 한다. 이러한 조건들을 충족시키며 효율이 높은 시스템을 개발하기 위하여 슬롯 형태의 예혼합 버너를 제안하였고 버너의 연소 특성을 파악하기 위하여 일련의 실험을 수행하였다. 본 연구에서는 화염의 형상을 촬영하여 연소부하 및 공기비에 따른 연소 모드를 관찰하였고 배가스를 분석하여 연소 모드에 따른 배기 특성을 연구하였다. Abstract: The availability of thermal energy has been widely recognized recently, and the cascade usage of thermal energy from combustion has been encouraged. Within this framework, a 1-kW-class Stirling-engine–based cogeneration system has been proposed as a unit of a distributed energy system. The capacity has been designed to be adequate for domestic usage, which requires high compactness as well as low emissions and noise. To develop a highly efficient system satisfying these requirements, a premixed slot-type short-flame burner has been proposed, and a series of experiments has been performed to understand its combustion characteristics. Flame images have been captured to observe the dependence of the flame mode on the combustion load and air/fuel ratio. The exhaust gas has been sampled and analyzed to study the emission characteristics for each flame mode.

Combustion Characteristics of Non-premixed VIStA Burner in Once-Through-Type Boiler

A modified VIStA (vortex inertial staged air) burner was developed and used in a once-through-type boiler. For safety, the combustion in this burner is of the non-premixed type. An air damper is installed to control the distribution of air to each combustion chamber. The effects of the air-fuel ratio and air distribution on NOx formation were investigated. The newly modified VIStA burner gives NOx reduction effect by maximum 20% in the combustion chamber of a boiler, while it yields more uniform flame than the conventional burner.

Combustion Characteristics of a VIStA Burner Dividing Flame in a Once-Through Type Boiler

A modified VIStA (Vortex Inertial Staged Air) burner has been developed and applied to a once-through type boiler. The secondary air is supplied through a swirler instead of nozzles, which stabilizes the flame and reduces carbon monoxide (CO) emissions. However, the modification increases the emission of nitrogen oxides (NOx). To balance emissions of the two pollutants, a divided flame was adopted. An air damper was installed to control the distribution of air to each combustion chamber, and three types of flame dividers were studied. The effects of the air-fuel ratio and combustion load on the NOx formation were investigated. The divided flame was found to reduce the NOx emission up to 25%, while keeping the CO to less than 10 ppm.

Drying Characteristics of a Radiative Industrial Dryer Adopting a Mat-Type Premixed Catalytic Burner

A catalytic burner that utilizes the thermal energy from fossil fuels without the emission of nitrogen oxides () has been developed. For this purpose, the newly developed burner has two features: firstly, it is in the shape of a flat mat so as to maximize its heating surface, and secondly, it adopts premixed combustion so that it can be used in a closed space. In the present study, the burner was used in a radiation-type industrial dryer. This dryer yields thermal energy in the form of thermal radiation in the infrared regime, which has been proved to be effective for drying organic substances under low-moisture conditions. Analysis of the experimental data has proved that the thermal efficiency of the dryer is better correlated to the moisture than to the dry rate

Combustion and heat transfer characteristics at the combustion chamber of an oxy-fuel boiler for CO2 capturing: a numerical simulation

A 0.5 MW class-oxy-fuel boiler was developed to capture CO2 from the exhaust gas. Flue gas recirculation (FGR) was adopted to make it possible to retrofit existing facility by changing its burner. A co-axial burner was devised to support three combustion modes, which are conventional air combustion, oxy-fuel combustion and oxy-fuel combustion with FGR. Numerical simulations were conducted for the three combustion modes to study the detailed physics inside the combustion chamber of the boiler. The temperature field obtained from the simulation reproduces the flame structures in general, while the results under-predict the spanwise mixing for the air and FGR modes. The FGR combustion yields similar heat transfer characteristics with the conventional air combustion, which implies the possibility to have a CO2-free boiler by retrofitting the burner while keeping other parts of the boiler.