• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.99-108
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• 2004

Fundamental combustion characteristics, such as the combustion potential, burning velocity and flame stability, for the practical utilization of LFG(Landfill gas) and LFG-blended fuels were experimentally investigated. The combustion potentials(CP) of LFG-blended fuels calculated from the previously suggested formulae were compared with burning velocities obtained by present experiments. The results showed that the previous formulae fur CP of LFG-blended fuels were not agreed with the experimental burning velocity, and these formulae should be revised. To provide an useful information needed to design the combustion devices, a triangular diagram was suggested for the maximum burning velocity of the mixture of CH$_4$, LPG and LFG. From the investigation of the burning velocity and the flame stability in a practical combustor, it was noted that the LFG-blended fuels, of which heating values or Wobbe indices were adjusted to that of natural gas, could be used as an alternative fuel of natural gas.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.119-122
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• 2007

The present study employs experimental approach to identify combustion stability characteristics of fuel-rich gas generators. The gas generator of interest, fueled by LOx and Jet A-1, experienced combustion instability coupled to a longitudinal resonant mode of the combustion chamber at about 1200 Hz. The occurrence of instability is strongly associated with acoustic boundary condition at the exit .and axial location of maximum heat release. As a result, stretching heat release zone in the axial direction by increase of the fuel nozzle diameter has dramatically stabilized combustion.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.35-41
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• 2014

The wood pellet, which is one of the woody biomass energy, has very high economic efficiency and combustion efficiency during their combustion. The existing pellet burner have many problems such as low combustion efficiency, flame stabilization, ash problem and ignition time etc. We developed cyclonic wood pellet burner aim to 20,000kcal/hr boiler and measured temperature profiles and exhaust gases in order to investigate the flame stability and optimum combustion condition at any air flow conditions. As results, we confirmed the reappearance and the isotropy of the experimental results in the burner. At the first air flow inlet condition of excess air ratio ${\alpha}=0.02$, second air flow $490{\ell}/min$ had the best combustion condition when pellet supplied 30g. This result means that we need much air supply only for the swirling of second air flow. So we tested various second air flux at first air excess air ratio ${\alpha}=0.7$ condition. At this condition, we could find out that we don't need much second air and total air flux compared to the former condition. We will continuously test this work of air flow distribution, and swirl effect of first air flow, and ash elimination.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.24-33
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• 2020

In this study, model combustion tests were conducted to investigate the combustion instability characteristics of swirl coaxial injectors for a liquid rocket engine. To examine the effects of the combustion chamber resonant frequency and the injector mixing conditions, pressure fluctuations in the combustion chamber were measured by changing the combustion chamber length, injector recess length, and propellant mixture ratio. From the test results, the variation in the pressure fluctuations for each experimental condition was confirmed and the combustion stability was evaluated by stability mapping. It was found that the longitudinal mode and Kelvin-Helmholtz instabilities occurred due to the change in the combustion chamber and recess lengths.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.99-106
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• 2005

The SRT(stability rating test) technique, which is indispensable for the development of a LRE(liquid rocket engine), essentially requires a development of a combustion test sequence as well as artificial perturbation devices. For the development of an indigenous SRT technique, several combustion tests of sub-scale LRE were performed to search a proper combustion test sequence. At first, a pressure-wave inducing device which is used for adapting pulse gun was designed and a cooling gas supply system for the pressure-wave inducing device was set up to prevent a malfunction of pulse gun. Through the several combustion tests which included cooling procedure of a pressure-wave inducing device, a proper combustion test sequence was found out. It did not make any significant disturbance at normal combustion process. Finally, an indigenous SRT technique has been developed successfully.

• Journal of the Korean Society of Combustion
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• v.13 no.3
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• pp.1-8
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• 2008

A flame stability diagram in a partially premixed flame is typically expressed using the axis coordinates of heat input rate and equivalence ratio. These diagrams are inadequate for identifying changes in combustion conditions and flame stability when a reference fuel is substituted with other fuels under identical operating conditions. This study proposes a new type of diagram and validates it experimentally. In this new diagram, the axis coordinates are air flow rate and Wobbe fuel flow rate, defined as the fuel flow rate multiplied by the square root of the relative density. The diagram was validated in trials using various fuels, including $CH_4$, $C_{3}H_{8}$, and LFG-$C_{3}H_{8}$ mixed fuels, in a domestic gas-range and an gas interchangeability test burner. The results of these trials show that the new diagram can provide information useful for assessing gas interchangeability of combustion conditions and flame stability when one fuel is substituted with another under identical operating conditions.

• Journal of the Korean Society of Combustion
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• v.11 no.2
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• pp.1-6
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• 2006

This report presents a study of the development of an advanced coal nozzle used in burners to reduce unburned carbon (UBC) in a tangential coal-fired boiler. To understand the mechanism of UBC reduction, experiments using conventional burners were carried out to evaluate the effects of air injection velocity, coal fineness and over fired air (OFA) on combustion efficiency. It was confirmed that ignition of pulverized coal particles close to the burner is helpful toward the complete burn of residual carbon in fly ash. These efforts indicated the additional results that UBC was strongly dependent on the primary air velocity and coal fineness; especially that UBC dramatically decreased when the weight fraction of pulverized coal under $75{\mu}m$ was over 85 %. New coal nozzles, modified from conventional nozzles, were prepared and tested to improve the combustion efficiency. Some of these nozzles offered relatively lower unburned carbon than those of conventional burners and are referred to as HPFS (High Performance Flame Stability) coal nozzles.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.42-49
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• 2021

As a measure of susceptibility on the combustion instability, thermo-acoustic instabilities in rocket combustion system was considered for the estimation of the operational stability margin. Growth rate, which governs the asymptotic stability behavior of the system, was determined from the dynamic data measured during combustion tests in order to understand the dynamic characteristics of combustor system. Frequency transform technique was first applied to determine the system parameters such as growth rate and/or damping coefficient for an interested mode from the time series pressure data, and the PDFs of pressure amplitude were extracted from the amplitude envelope of pressure oscillation for the stochastic analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.26-33
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• 2000

In-cylinde flow and mixture formation are key contributors to both idle stability and combustion stability at part load condition in SI engine. The real time measurements of air-fuel ration and in- cylinder residual gas fraction are particularly important to obtain a better understanding of the mechanisms for combustion and emissions especially during cold start and throttle transient condition. This paper reports the cycle resolved measurements of residual gas fraction and equivalence ration near speak plug with value timing change and their effects on combustion characteristics at part load. The results showed that the effect of intake value opening on the residual gas fraction was smaller than that of exhaust valve closing because of the decreases of exhaust gas reverse flow from exhaust port. The variation of equivalence ratio near spark plug increased with the increase of value overlap and it closely related with heat release rate and combustion stability

• Journal of Power System Engineering
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• v.20 no.4
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• pp.12-18
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• 2016

Typical boiler system consists of combustion chamber and heat exchanger in one housing, therefore the size of boiler system is large and the heat exchanging efficiency becomes low. At these boiler systems, because the combustible mixture fires as free flame in the combustion chamber, consequently the combusted hot gas heats the heat exchanger only as conductive and convective heat transfer. The present Porous Ceramic Burner concept is that combustion process is occurred at the gaps of the porous ceramic materials, and the heat exchanger is placed in the same porous materials. Therefore we can reduce the boiler size, and we can also use radiative heat transfer from ceramic material with conductive and convective heat transfer from combusted gas throwing the porous materials. The purpose of this study is to search the flame stability ranges at different fuel flow rate and excess air ratio burning in the $Al_2O_3$ ceramic balls. We found out the stable excess air ratio range on given combustion intensity. And we can get clean porous ceramic combustion results compared with free flame.