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가스터빈용 희박 예혼합 연소기 내부에 와류 발생기(vortex generator)를 장착하여 그에 따른 연료/공기혼합 및 NOx 배출 특성 변화를 조사하였다. 이를 위해 수치해석적 방법을 채택하여 연소기내 유동특성, 연료/공기 혼합도, 배기가스(NOx), 화염형상을 분석하였다. 와류 발생기를 장착한 경우, 연소기 내부에서 와류 발생기에 의한 나사산 형상으로 인해 와류가 형성되며 이는 연소기 전면부까지 유지되었다. 또한 연소기 내부 면적 차로 인해 압력섭동이 발생하였다. 이와 더불어 연소기 전면부 기준 상류지역의 연료와 공기의 혼합도가 증가됨으로서 연료 과농지역이 감소하게 되며 이로 인해 전반적인 NOx 발생량의 감소 효과를 볼 수 있었다. 화염 형상의 변화로부터 와류 발생기의 영향으로 선회수는 다소 감소할 것으로 예상되며, 이는 와류 발생기로 인한 유속의 반복적 증감에 의한 결과라고 판단된다.
The oxy-fuel combustion is CO₂ capture technology that uses mixture of pure O₂ and recirculated exhaust as oxidizer. Currently some Oxy-fuel power plants demonstration project is underway in worldwide. Meanwhile research project for converting 125 MWe Young-Dong power plant to 100 MWe oxy-fuel power plants is progress. In this paper, 1 D process analytical approach was applied for conducting process design and operating parameters sensitivity analysis for oxy-fuel combustion of Young-Dong power plant. As a result, appropriate gas recirculation rates was 74.3% that in order to maintain normal rating superheater, reheater steam temperature and boiler heat transfer patterns. And boiler efficiency 85.0%, CPU inlet CO₂ mole concentration 71.34% was predicted for retrofitted boiler. The oxygen concentration in the secondary recycle gas is predicted as 27.1%. Meanwhile the oxygen concentration 22.4% and moisture concentration 5.3% predicted for primary recycle gas. As the primary and secondary gas recirculation increases, then heat absorption of the reheater is tends to increases whereas superheater side is decreased, and also the efficiency is tends to decrease, according to results of sensitivity analysis for operating parameters. In addition, the ambient air ingression have a tendency to lead to decline of efficiency for boiler as well as decline of CO₂ purity of CPU inlet.
In order to measure the burning velocity of LFG and compare it to methane at engine-like conditions, LFG assuming a ratio of CH₄ to CO₂ as 60:40 was used. The flame propagation was observed by ignition at initial pressure of 10 bar and initial temperature of 50 ℃ in a constant volume combustion chamber. The combustion velocity was calculated using the CHEMKIM library and the GRI mechanism and compared with the experimental results. For stable ignition of the mixture of LFG and air, an ignition circuit using a 24V battery power and a mechanical distributor was constructed. This work reveals that the burning velocity of LFG compared with methane is 67.4% at equivalence ratio of 0.7 compared to that of 65.5% at 1.0.
The effect of non-thermal plasma (NTP) on lean premixed flame in a model gas turbine combustor has been investigated experimentally by adopting a dielectric barrier discharge (DBD) technique. The plasma reactor had eight spikes electrodes with alternating current (AC) power supply to generate and keep a constant distribution of streamers. To identify the effect of flame on plasma generation, the streamer generation characteristics in lean premixed flame were first investigated. The results indicated that the existence of flame significantly enhances the plasma generation by the increase in the reduced electric field intensity due to high-temperature burnt gas and the abundance of positive and negative ions and electrons in the flame region. Flame liftoff heights and liftoff equivalence ratio were measured as functions of applied various voltages and frequencies. The results showed that the streamers extended the stabilized the flames and lean flammable limit in terms of all conditions of equivalence ratio by high streamers.
Hydrogen enriched LNG flame is tested to understand hydrogen effect on the flame such as temperature, flame speed, emissions (NOx, CO), and extinction at lean premixed (ф=0.4~0.6) various pressure (p=1~25 bar) conditions using CHEMKIN-Pro with GRI 3.0 detailed chemistry. Hydrogen flame temperature is much higher than that of LNG, which may affect high NOx emission production. The flame speed increases with the addition of H₂, so a design speed change should be considered to prevent flashback at the nozzle. The addition of H₂ reduces CO emissions and increases NOx emissions, but can be overcome with a lower equivalent ratio due to the increased flame stabilization due to the addition of H₂. Extinction stretch rate gradually increases with hydrogen addition which shows that enriched hydrogen LNG premixed flame could be sustainable in high turbulent condition which means more stable than LNG itself flame. Even though in 100% H₂ operating condition, gas turbine operating condition shows similar combustion air and exit flue gas flow rate with LNG which means the compressor and turbine may not need major modification.