• Journal of the Korean Society of Combustion
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• v.12 no.4
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• pp.22-30
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• 2007

The NOx emission characteristics were studied in an oscillating combustion burner equipped with a specially designed proportioning valve. The effects of various parameters on the NOx emission which are important in oscillating combustion were investigated. Also, the effects of coincident application of flue gas recirculation(FGR) were evaluated. The results show that oscillating combustion is an efficient tool for reducing NOx in the burner. Up to 53% of NOx reduction could be acquired in low frequency and small duty ratio conditions. The coincident application of FGR further reduced the NOx emission up to 74%. Thus, this study assured that oscillating combustion technology with FGR could be a fascinating method for NOx reduction in industrial burners.

• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.37-44
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• 2009

An experimental study was conducted to reduce NOx emission in RT(radiant tube)burner by using oscillating combustion processes in RIST. A solenoid valve gives the various oscillating conditions, such as oscillation frequency, duty ratio of fuel flow. In this study, we used commercial software, CFD-ACE+ to predict combustion and NOx emission characteristics for various experimental oscillation conditions. The effect of oscillation frequency and duty ratio on NOx emission will be discussed in terms of flow field, temperature and equivalence ratio distributions in detail.

• Journal of the Korean Society of Combustion
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• v.9 no.3
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• pp.36-43
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• 2004

The flame patterns were investigated in an oscillating combustion burner equipped with a specially designed proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a hot wire anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rapidly changed, so the valve seemed appropriate for the oscillating combustion burner application. Mushroom shape and highly wrinkled structure were typical features of the flames in the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.130-137
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• 2004

The flame patterns were investigated in an oscillating combustion burner equipped with a proportioning valve. The proportioning valve is driven by a solenoid and has an elastomer part which controls the valve opening area. For characterizing the valve, nozzle exit velocities were measured with a Hot Wire Anemometry. The flame patterns were investigated by direct photographing methods using a high speed camera and a digital camera. The results show that the nozzle exit velocities could be controlled diversely and rose up and fell down abruptly, so the valve seemed appropriate for the application for the oscillating combustion burner. Mushroom shaped and highly wrinkled flames were a typical features of the oscillating combustion burner. As the oscillating intensity of the fuel flow increased, the flame length was shortened.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.100-106
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• 2008

An experimental study was carried out in a small-scale test furnace to investigate the performance, such as $NO_X$ emission, enhancement of heat transfer, uniformity of temperature, and etc, of oscillating combustion applied in radiant tube burner system. A premixed type burner and a cyclic oscillating control valve were designed and used. The fuel, used commercial LPG in this study, was only oscillated using the cyclic oscillating control valve. As oscillating combustion was applied in radiant tube burner system, it is found that $NO_X$ emission, compared to no oscillation, could be reduced by 38% at $90{\sim}120rpm\;(1.5{\sim}2.0Hz)$. However, as oscillating frequency was increased, effect of abatement of $NO_X$ emission is gradually reduced. From the measurement of furnace heating time from $100^{\circ}C$ to $720^{\circ}C$, heat transfer is increased by 11.5% at the oscillation of 120rpm. Temperature distribution of radiant tube surface is more uniform at oscillation of 120rpm with decrease of the peak temperature and increase of low temperature. From these results, it is confirmed that oscillating combustion is useful in radiant tube burner system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.539-545
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• 2011

Combustion characteristics of industrial radiant tube (RT) burners with forced oscillating combustion technology are investigated using a real-scale (125,000 kcal/h) industrial RT burner facility in both laboratory and field tests. Three different types of industrial RT burners using a by-product gas from the iron-and-steelmaking process are examined in a laboratory facility equipped with a W-type RT. During the field tests, an industrial RT burner is characterized in a large facility equipped with multiple RTs. Their performance and emission controls are investigated under diverse operating conditions. The feasibility of the forced oscillating combustion technology is evaluated by the extent of $NO_x$ reduction and the efficiency improvement. These improvements are able to save energy, extend the RT lifetime, and enhance productivity. The operating conditions that achieve the best performance and emission control for each RT burner are determined.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1219-1226
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• 2017

This paper presents the hybrid stepping machine for linear oscillating generators. The focus of the work is the suggestion of the improved model through the comparison of proposed models ; new flux concentrating PMs mover of the hybrid stepping generator is proposed based on the symmetrical and non-symmetrical stator cores of the surface mounted PMs mover, and non-slanted PMs and slanted PMs of the flux concentrating PMs mover. It is achieved using equivalent magnetic circuit considering leakage elements. Finally, this study suggests new hybrid stepping structure of linear oscillating generator.

• Journal of the Korean Society of Combustion
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• v.13 no.4
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• pp.8-15
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• 2008

When a circular cylinder is placed at the center of a slot burner nozzle, once stable Woflhard-Parker type laminar lean premixed flame is changed to an oscillating flame with self-induced noise. The wrinkled flame surface showed the same pattern and frequency of the Karman vortex street at the downstream of a circular cylinder. The interaction of flame with Karman vortex street is observed to be responsible for flame oscillation. The measured flame oscillation frequency is very similar to the estimated Karman vortex shedding frequency based on the St-Re relationship of the flow past circular cylinder, which could be considered as a strong evidence for the interaction between laminar pre-mixed flame and a Karman vortex street. As Reynolds number increases oscillation frequency decreases and the self-induced noise level increases as well as the flame front is more severly wrinkled. This result suggests that the flame/vortex interaction becomes more active at higher Re.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.720-727
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• 2019

Resonating thermal lags of solid fuel with heat transfer oscillations generated by boundary layer oscillation is the primary mechanism of the occurrence of the LFI (Low Frequency Combustion Instability) in hybrid rocket combustion. This study was experimentally attempted to confirm that how the boundary layer was perturbed and led to the LFI. Special attention was also made on oxidizer swirl injection to investigate the contribution to combustion stabilization. Also the overall behavior of fluctuating boundary layer flow and the occurrence of the LFI was monitored as swirl intensity increased. Fluctuating boundary layer was successfully monitored by the captured image and POD (Proper Orthogonal Decomposition) analysis. In the results, oscillating boundary layer became stabilized as the swirl intensity increases. And the coupling strength between high frequency p', q' diminished and periodical amplification of RI (Rayleigh Index) with similar frequency band of thermal lag was also decreased. Thus, results confirmed that oscillating axial boundary layer triggered by periodic coupling of high frequency p', q' is the primary mechanism to excite thermal resonance with thermal lag characteristics of solid fuel.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1820-1831
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• 2003

Characteristics of self-excited combustion oscillation are experimentally studied using confined premixed flames stabilized by a rearward-facing step. A new idea to suppress combustion oscillation was applied to the flames. The characteristics of unsteady combustion were examined, which is driven by forced pulsating mixture supply that can modulate its amplitude and frequency. The self-excited combustion oscillation having weaker flow velocity fluctuation intensity than that of the forced pulsating supply can be suppressed by the method. The effects of the forced pulsation amplitude and frequency on controlling self-excited combustion oscillations were also investigated comparing with the steady mixture supply. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations, and it also exhibits desirable performances, from a practical point of view, such as high combustion load and reduced pollutant emissions of nitric oxide.