• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.54-60
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• 2017

In order to identify the characteristics of the flame transfer function gain, cold-flow transfer function was introduced, which is the part of the combustion instability research. Nitrogen and carbon dioxide was used to obtain the cold-flow transfer function and input/output variables was measured by hot wire anemometry. Density and fluid flow rate affect the cold-flow transfer function gain and peak frequency. In addition, acoustic resonance frequency affects the peak frequency of gain in the fuel feeding line.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.5
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• pp.343-348
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• 2009

The present study has experimentally investigated the effects of $CO_2$ diluted oxygen on the structure of swirl-stabilized flame in a lab-scale combustor. The methane fuel and oxidant mixture gas ($CO_2$ and $O_2$) were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for various amount of carbon dioxide addition to the methane fuel and various swirl strengths. The effects of carbon dioxide addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using chemiluminescence techniques to provide information about flow field. The results show that the hot combustion zone increases at the upstream reaction zone because of an increase in the recirculation flow for an increase in swirl intensity. The hot combustion zone is also increased at the downstream zone by recirculation flow because of an increase in swirl intensity which results in higher centrifugal force. The OH and CH radical intensities of reaction zone decrease with carbon dioxide addition because the carbon dioxide plays a role of diluted gas in the reaction zone.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.1979-1983
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• 2008

The effects of carbon dioxide addition to oxygen have been investigated with swirl-stabilized premixed methane flame in a laboratory-scale pre-mixed combustor. The methane fuel and oxydant mixture gas ($CO_2$ and $O_2$) were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for different amount of carbon dioxide addition to the methane fuel and different swirl strengths. The effects of carbon dioxide addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using chemiluminescence techniques to provide information about flow field. The results show that the flame area increases at upstream of reaction zone because of increase in recirculation flow for increase in swirl intensity. The flame area is also increased at the downstream zone by recirculation flow because of increase in swirl intensity which results in higher centrifugal force. The OH and CH radical intensity of reaction zone decrease with carbon dioxide addition because the carbon dioxide plays a role of dilution gas in the reaction zone.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.2
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• pp.12-16
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• 1987

세계각국에서는 원류의 소비절약과 대체연료의 개발에 발차를 기하는 등 유류파동에 휘말리지 않 으려고 노력하고 있다. 그러한 노력의 일찬으로 기존기한을 크게 개조 및 수정하지 않는 범위 에서 메타놀 등의 알콜류에 대한 연국가 활발히 진행되고 있다. 그 예로서 가솔린에 10-20%의 알콜을 혼합하면 안티노크성이 증가되고 기관의 운전이 원활하다는 것이 오래전부터 알려져 있 었다. 자동차의 배출가스문제가 제기되면서 이와 같은 종류으 혼합연료를 배기대책에 이용하는 것이 검토되었다. 더욱이 가솔린이나 경유에 알콜 등의 함산소화합물, 기타 첨가제를 혼합하여 연소를 개신하고 배출가스를 저장하는 가능성에 대한 연구가 많이 진행되었다. 지금까지의 연 구에서는 알콜, 에테르 등 항산소화합물의 일부가 적당하게 이용됨에 따라 순수가 솔린만을 사 용하는 것 보다도 배출가스의 점에서 유리하다고 알려졌다. 또 최근에는 석유자원을 절약하는 보조연료로서 또 장래의 대체연료로서 그 평가의 관점이 바뀌고 있다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3452-3457
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• 2007

Experiments were carried out in an atmopheric pressure, lab-scale gas turbine combustor to see the effect of partial premixing on unstable flame structure and $NO_X$ emission characteristics. The swirl angle is 45 deg., fuel-air mixing degrees were varied 0, 50, and 100% respectively at equivalence ration ranging from 0.53 to 0.79. The evaluation of phased-locked OH chemiluminescence images were acquired with an ICCD. $NO_X$ emission characteristics were also investigated at each experimental condition. The effect of the fuel-air mixing degree on the flame structure was obtained from phase-locked $OH^*$ images. And it was obtained from local heat release characteristics that the information about the region which the combustion instability was amplified or damped. It also could be confirmed that ${\sigma}$ has greatly influence on $NO_X $emission characteristics at lean regimes. It would be expected that it could provide invaluable data for understanding the mechanism of combustion instability

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.1-9
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Because this concept reduced NOx and smoke emissions simultaneously. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and intake air temperature affect the mixture formation. The purpose of this study is to investigate characteristics of combustion and mixture formation according to injection timing and intake air temperature in a common rail direct injection type HCCI engine using an early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection timing and intake air temperature affect the mixture formation and in turn affects combustion in the PCCI engine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.633-640
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• 2011

In this study, the stabilization of an edge flame and the intensity variation of a diffusion branch were investigated using a multi-slot combustor under conditions of high temperature and small fuel-concentration gradient (FCG). The combustor consists of three narrow channels: a quartz channel and two side-heating combustors. For the accuracy of this experimental study, quantitative analysis was carried out for each boundary condition. Stable edge flames could be observed under high-temperature conditions by controlling the FCG and fuel dilution ratio. Moreover, it was found that the intensity of the diffusion flame was increased by increasing the temperature of the mixture. On the contrary, the intensity of the diffusion flame was decreased by increasing the dilution ratio. It was also found that a propane flame is more sensitively affected by these experimental parameters than a methane flame.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.155-160
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• 2001

The low NOx characteristics have been investigated to develop the combustor for micro turbine. The lean premixed combustion technology was applied to reduce the NOx emission. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of $450\sim650K$ were supplied to the combustor through the air preheater. The temperature and emissions of NOx and CO were measured at the exit of combustor, The exit temperature and NOx were increased and CO was decreased with increasing inlet air temperature. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The NOx was decreased with decreasing the equivalence ratio. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.4. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The NOx was decreased and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1309-1316
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• 2003

A premixed-compression-ignition engine has been studied to improve the efficiency and to decrease exhaust emissions. However those systems have some difficulties for controlling combustion process. Radical is an activated chemical species formed by a chemical chain reaction between reactant and product. When the chain reactions occur, the energy bond of species is broken easily by the released radicals. The combustion chamber of the premixed-compression-ingnition engine is consist of a main chamber with lean premixture and a subchamber with rich premixture. Those are connected by narrow cylinderical connections. With ignition start in the subchamber, many different kinds of radical is jetted into the main chamber. The premixed gas in main chamber is quickly burned up by the radical ignition in multi-pionts. In this paper, the combustion phenomena in a constant volume combustor having a radical injector are numerically analyzed. The some constants in the reaction rate equation are adjusted by the experimental results tested in the same geometrical chamber. The code is applied on the two combustors in a wide range of equivalence ratio. The results show that the burning time is much shorter in the combustor having radical injector.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.4
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• pp.276-282
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• 2008

The effects of hydrogen enrichment to methane have been investigated with swirl-stabilized premixed hydrogen-enriched methane flame in a laboratory-scale pre-mixed combustor. The hydrogen-enriched methane fuel and air were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for different amount of hydrogen addition to the methane fuel and different swirl strengths. The hydrogen addition effects and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using micro-thermocouple, particle image velocity meter (PIV) and chemiluminescence techniques to provide information about flow field. The results show that the flame area increases at upstream of reaction zone because of increase in ignition energy from recirculation flow for increase in swirl intensity. The flame area is also increased at the downstream zone by recirculation flow because of increase in swirl intensity which results in higher centrifugal force. The higher combustibility of hydrogen makes reaction faster, raises the temperature of reaction zone and expands the reaction zone, consequently recirculation flow to reaction zone is reduced. The temperature of reaction zone increases with hydrogen addition even though the adiabatic flame temperature of the mixture gas decreases with increase in the amount of hydrogen addition in this experiment condition because the higher combustibility of hydrogen reduces the cooler recirculation flow to the reaction zone.