• 한국수소및신에너지학회논문집
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• 제21권5호
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• pp.452-459
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• 2010

This study is aimed to investigate changes of combustion characteristics and heat efficiency when syngas from gasification process using low-rank fuel such as waste and/or biomass is applied partially to an industrial boiler. An experimental study on syngas co-combustion was performed in a 0.7 MW (1 ton steam/hr) water tube boiler using heavy oil as a main fuel. Three kinds of syngas were used as an alternative fuel: mixture gas of pure carbon monoxide and hydrogen, syngas of low calorific value generated from an air-blown gasification process, and syngas of high calorific value produced from an oxygen-blown gasification process. Effects of co-combustion ratio (0~20%) for each syngas on flue gas composition were investigated through syngas injection through the nozzles installed in the side wall of the boiler and measuring $O_2$, $CO_2$, CO and NOx concentrations in the flue gas. When syngas co-combustion was applied, injected syngas was observed to be burned completely and NOx concentration was decreased because nitrogen-containing-heavy oil was partially replaced by the syngas. However, heat efficiency of the boiler was observed to be decreased due to inert compounds in the syngas and the more significant decrease was found when syngas of lower calorific value was used. However, the decrease of the efficiency was under 10% of the heat replacement by syngas.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.201-208
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• 2019

Recently, a fuel reforming plant for supplying high purity hydrogen is being applied to submarines. Since steam reforming is an endothermic reaction, it is necessary to continuously supply heat to the reactor. A fuel reforming plant for a submarine needs a multi-stage burner (MSB) to acquire heat and convert the combustion gas to $CO_2+H_2O$. The MSB has problems that the combustion imbalance occurs during start-up due to the temperature restriction of the combustion gas. This problems can be solved by burning $H_2O$ together with fuel and $O_2$. In this study, the simulation results of MSB were analyzed to determine the optimum flow rate of $H_2O$ supplied to the 6-stage burner. When the flow rate of $H_2O$ was low, combustion was concentrated on the burner#6 in comparison with the burner#1-#5. This combustion concentration improved as the supply amount of $H_2O$ increased. As a results, it was necessary to supply at least 4.9 kmol/h of $H_2O$ (per 1 kmol/h of fuel) to burner#1 in order to maintain the combustion gas temperature of each stage at $750^{\circ}C$ and to convert the final stage burner gas composition to $CO_2+H_2O$.

• 한국추진공학회지
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• 제23권2호
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• pp.60-67
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• 2019

하이브리드로켓의 저주파수 연소불안정(LFI) 특성을 이해하기 위해, 주연소실의 연소 당량비 변화가 500 Hz대역의 압력 및 열방출 진동의 위상변화에 미치는 영향에 대해 직접수치해석을 수행하였다. 주연소실의 당량비 변화는 후연소실로 유입되는 연소가스의 온도 및 조성 변화로 모사하였다. 수치해석 결과, 후향 계단 하류에 와류 생성과 함께 추가적인 연소가 나타나며, 와류가 이동함에 따라 연소 압력 및 반응률의 진동이 관찰되었다. 또한, 유입유동의 온도가 변화하면 압력파의 전파속도도 함께 변화하므로 압력 및 반응률 진동 사이의 위상차가 천이하게 됨을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.906-913
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• 2003

Lean premixed combustion has been considered as one of the promising solutions for the reduction of NOx emissions from gas turbines. However, unstable combustion of lean premixed flow becomes a real challenge on the way to design a reliable, highly efficient dry low NOx gas turbine combustor. Contrary to a conventional diffusion type combustion system, characteristics of premixed combustion significantly depend on a premixing degree of combusting flow. Combustion behavior in terms of stability has been studied in a model gas turbine combustor burning natural gas and air. Incompleteness of premixing is identified as significant perturbation source for inducing unstable combustion. Application of a simple convection time lag theory can only predict instability modes but cannot determine whether instability occurs or not. Low frequency perturbations are observed at the onset of instability and believed to initiate the coupling between heat release rate and pressure fluctuations.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.153-158
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• 2003

Catalytic Combustion used to be applied to specific conditions because of the characteristics different from flame combustion. However, many researches are focused on widening the applicant range of catalytic combustion with the competences of catalytic combustion. The development of many catalytic combustion appliances is one of the trials to overcome the restrictions of reaction and maximize the merits. In this research, past developments of appliances are depicted and new conceptual system will be introduced - sequential system. Sequential catalytic combustion system is composed of units - existing catalytic heat exchangers. This system is performed with parallel in composition and serially in operation. First, the burden of the preheating can be dramatically reduced. Second, stable operation control is expected. Lastly, Capacity expansion is flexible.

• 한국연소학회지
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• 제10권3호
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• pp.17-24
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• 2005

A sub-millimeter scale catalytic combustor with a simple plate-shaped combustion chamber was fabricated. A porous ceramics support coated with platinum catalyst was placed in the chamber. The combustor has a gallium arsenide window on the top that is transparent to infrared ray. The temperature distribution in the combustion chamber was measured using infrared thermal imager while hydrogen-air premixture is steadily supplied to the combustor. The area where the catalytic reaction took place broaden for higher flow rate and lower equivalence ratio made activated area in the combustion chamber broaden. The amount of coated platinum catalyst did not affect the reaction. Stop of reaction, which is similar to flame quenching of conventional combustion, was investigated. Large content of heat generation and broad activated area are essential criteria to prevent stop of reaction that has a bad effect on the combustor performance.

• 한국기계가공학회지
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• 제11권5호
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• pp.109-114
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• 2012

The combustion characteristics using forced pulsating flow were experimentally investigated with confined premixed flames stabilized by a reward-facing step. The intermittent combustion has many merits, for instance, such as high load combustion, high heat transfer, low emission gas, compared with those of continuous combustion. For these purposes, data processing of binary image was conducted to reveal the differences between intermittent and continuous combustion. As the results, it was possible to calculate the reaction zone using OH-emission band and, therefore, showed that forced pulsating flow was useful in combustion technology.

• 대한기계학회논문집
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• 제18권2호
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• pp.397-404
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• 1994

Smoke is emitted in diesel engines because fuel injected into the high-temperatured and high-pressured combustion chamber burns with its mixture with insufficient oxygeny. In consideration of air pollution, above all, it is necessary to illuminate the cause of smoke emission in diesel engines. The smoke emission, which is characteristic of diffusion combustion in diesel engines, results from pyrolysis of fuel not mixed with air. Therefore the smoke emission is dependent on diffusion combustion quantity, which is in turn controlled by engine parameter. The study aims at making clear and interpreting the interdependence of smoke emission in diesel engines with heat released within combustion chamber, camparing diffusion combustion quantity according to each engine parameter (air fuel ratio, injection timing, and engine speed), and showing the relation between smoke emission and fraction of diffusion combustion through experiment.

• 한국분무공학회지
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• 제22권4호
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• pp.197-202
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• 2017

The objective of this study is to investigate the effects of low-temperature combustion (LTC) on the correlations of combustion characteristics and reduction of exhaust emissions in a small DI diesel engine with biodiesel fuel. In order to analyze the combustion, exhaust emission characteristics and distribution of nano size particles for biodiesel were investigated. In addition, to evaluate the effect of LTC on the combustion and emission characteristics, 30 and 50% of cooled-EGR rates were investigated. From these results, it revealed that the influence of LTC on the combustion characteristics showed that the ignition delay significantly increased and reduces peak heat release rate of premixed combustion by lowering reaction rate. With 50% EGR and advanced injection timing, soot and $NO_x$ emissions were simultaneously reduced.

• 한국추진공학회지
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• 제16권5호
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• pp.37-46
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• 2012

로켓엔진 연소실에서 막냉각을 고려한 열전달 해석을 위한 모델을 수립하였다. 연소실 내에서의 대류, 복사, 막냉각 효과는 로켓엔진을 위한 경험식을 사용하였으며, 벽 외부는 일반적인 대류, 복사 식을 적용하였다. 또한 벽 내부는 유한체적의 격자를 구성하여 시간전진법에 의해 비정상 열해석을 수행하였다. 연소압 50 기압의 액체산소/케로신 엔진을 예로 해석하였으며, 이 경우 4% 유량의 막냉각까지는 벽온도를 낮추는데 크게 기여하였으나, 그 이상의 공급은 막냉각 유량에 비해 효과가 미비함을 확인하였다.