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한풍규(Poonggyoo Han),박주현(Juhyun Park) 한국자동차공학회 2021 한국 자동차공학회논문집 Vol.29 No.5
This paper deals with the methodology for detecting misfired cycles by using the discrete Fourier transform-based frequency analysis. This methodology discriminates single or dual cylinder misfires at first, and then it identifies misfired cylinders for misfired cycles. In general, the highest amplitude of DFT exists at lower harmonic modes than the number of cylinders during misfires. However, because it is located at the same harmonic mode with the number of cylinders at high speed conditions even though misfires take place, origin shift should be introduced in order to identify the misfired cycles even at a high speed operating condition. New origin can be located at the averaged real and imaginary values of the transformed engine rpm on the complex plane during normal combustion cycles. Based on this new origin of the complex plane, the circle of threshold can be derived as a boundary for detecting misfires at each harmonic mode. Single cylinder misfires can be detected when transformed engine rpms are located outside this circle of threshold at both the first and second harmonic modes. In case of opposing dual cylinder misfires, misfires can be detected when transformed engine rpms are located outside this circle of threshold at the first harmonic mode and inside it at the second harmonic mode. On the contrary, the transformed engine rpms of the non-opposing dual cylinder misfires are inside it at the first harmonic mode and outside it at the second harmonic mode. In other words, the misfire detection criteria of a non-opposing dual cylinder misfire are vice versa of the opposing dual cylinder misfire. The misfired cylinders of single cylinder and opposing dual cylinder misfires can be identified by their phases at the first harmonic mode, and those of the non-opposing dual cylinder misfire can be done by them at the second harmonic mode.
한풍규(Poonggyoo Han),오명환(Myunghwan Oh),김영수(Youngsoo Kim) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.11
차세대 초고속 공기흡입식 추진기관의 제작 소요 기술을 분류하였으며, 현대로템(주)에서 보유하고 있는 액체로켓엔진과 국내에 기확보되어 있는 가스터빈 및 항공기용 애프터버너의 제작기술을 차세대 초고속 공기흡입식 추진기관 제작에 적용 또는 응용이 가능한 지를 검토하였다. The manufacturing technology used for next generation high-speed air-breathing engines, such as ramjet engine, scramjet engine and so on, was classified and reviewed to check up if pre-occupied manufacturing technology in Hyundai Rotem and other Korean companies in the field of liquid rocket engines, gas turbines and afterburners can be applied for fabricating next generation air-breathing engines.
엔진속도의 Post Oscillation 영향을 받지 않는 실화 진단 지표에 관한 연구
한풍규(Poonggyoo Han) 한국자동차공학회 2020 한국 자동차공학회논문집 Vol.28 No.2
Immediately after misfires occur in the gasoline engines of automobiles, engine speed fluctuates significantly. This phenomenon is called post oscillation due to misfires. The engine roughness method, which is currently used in misfire diagnoses in many cars, cannot detect misfires during post oscillation. So, this study aims to present a new misfire detection index that is not affected by post oscillation. The new misfire detection index, called gap slope, is defined as the difference between the two slopes of an engine speed trend line and an engine speed inclination line at all cylinders per cycle. Here, the engine speed trend line is a line that connects the engine speeds of the first and the final teeth per cycle. The engine speed inclination line connects the engine speeds of two specified teeth at all cylinders in the cycle, and its slope reflects the amount of velocity increase due to fuel combustion at the cylinders. Thus, gap slope is defined as the magnitude in the change of the engine angular acceleration per cylinder. Though engine speed vastly fluctuates during post oscillation, it increases and decreases repeatedly at the cylinders regardless of large fluctuations. Thus, this gap slope index can detect misfires during post oscillation. On the other hand, the process of calculating the gap slope index includes the detrend effect by the engine speed trend line, and, thus, it does not require a detrend process by linear regression. Moreover, gap slope is considered hardly affected by machining tolerance, torsional vibration, and difference in air-fuel mixture amount distributed to cylinders. Therefore, misfire detection through the gap slope index becomes much simpler and faster.
심창열(ChangYeul Shim),남궁혁준(HyuckJoon Namkoung),한풍규(PoongGyoo Han),김영수(YoungSoo Kim) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11
본 연구에서는 일반적으로 연소기 엔진 지상연소시험 설비용으로 사용되는 연소식 히터가 설계되었다. 본 연소식 히터는 출구성능과 열구조적인 안정성을 고려하여 설계가 되었으며, 설계 단계에서 열전달을 고려한 복합(conjugated) 열유동해석과 열구조해석이 수행되었다. 연소실의 복합 열유동해석 결과를 본 연소식 히터의 전 시스템 열유동해석에 적용하여 히터 출구에서의 성능조건을 충족시켰으며 복합 열유동해석에서 구한 열전달계수 값을 열구조해석에 적용하여, 히터 구조체의 열구조적 안정성을 검토하였다. In this paper, we designed the vitiated heater for ground combustion test of engine. This heater is designed with considering outlet performance and thermal-structure stability. We also performed conjugated thermal flow analysis in considering with heat transfer at the design-stage and thermal structure analysis. Finally, we evaluated the thermal structure stability of this heater by approving the result from conjugated thermal analysis and satisfied the performance condition of heater outlet.
김동준(Dongjun Kim),임지혁(Ji-Hyuk Im),길태옥(Taeok Khil),한풍규(Poonggyoo Han),윤영빈(Youngbin Yoon) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.7
분사조건과 주위기체 압력에 따라 스월 인젝터의 분무각과 분열길이를 측정함으로써, 스월 인젝터의 분무 및 분열특성에 대한 연구를 수행하였다. 분사조건으로 축방향 We 수(We₁)를 1554까지 주위기체 압력을 4.0㎫까지 증가시켰다 We₁과 주위기체 밀도(ρ)가 증가함에 따라 공기역학적 힘이 증가하여 원추형 액막 표면의 교란이 증가하게 되고, 따라서 분열이 빨리 일어난다. 결과에 따르면 주위 기체 밀도에 따른 분무각의 변화가 분열이 일어나기 전과 후가 다르게 나타났다. 분열이전에는 분무각이 주위기체 밀도 변화에 관계없이 거의 일정하였으나, 분열이 일어나게 되면 분무각이 감소하게 된다. 또한 측정된 분열길이를 선형불안정이론과 비교해 보았는데, 액막두께의 감쇠를 고려한 수정된 이론이 측정 결과와 상당히 유사한 결과를 얻을 수 있었다. The spray and breakup characteristics of swirling liquid sheet were investigated by measuring the spray angle and breakup length as the axial Weber number We₁ was increased up to 1554 and the ambient gas pressure up to 4.0㎫. As We₁ and ambient gas density increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces, and thus the liquid sheet disintegrated near from the injector exit. The measured spray angles according to the ambient gas density were different before and after the sheet breaks. Before the liquid sheet breaks, the spray angle was almost constant, but once the liquid sheet started to breakup, the spray angle decreased. And the breakup length decreased because of the increase of the aerodynamic force as the ambient gas density and We₁ increased. Lastly, the measured breakup length according to the ambient gas density and We₁ was compared with the result by the linear instability theory. We found that the corrected linear instability theory considering the attenuation of sheet thickness agrees well with our experimental results.