• Title/Summary/Keyword: Rayleigh Index

Search Result 43, Processing Time 0.018 seconds

Effects of Partial Premixing on Flame Structure and NOx Emission Characteristics in an Unstable Gas Turbine Combustor (불안정 가스 터빈 연소기에서 부분 예혼합이 화염구조와 NOx 배출 특성에 미치는 영향)

  • Lee Jae-Ho;Lee Jong-Ho;Kim See-Hyun;Chang Young-June;Jeon Chung-Hwan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2005.11a
    • /
    • pp.437-444
    • /
    • 2005
  • Experiments were carried out in an atmospheric pressure, lab-scale gas turbine combustor to see the effect of partial premixing on unstable flame structure and Nox emission characteristics. The swirl angle is 45 deg., fuel-air mixing degrees were varied 0, 50 and 100% respectively at equivalence ratio ranging from 0.53 to 0.79. The evolution of phased-locked OH chemiluminescence images were acquired with an ICCD. NOx 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 NOx emission characteristics at lean regimes. It would be expected that it could provide invaluable data for understanding the mechanism of combustion instability.

  • PDF

Study of Retrieving the Aerosol Size Distribution from Aerosol Optical Depths (에어로졸 광학깊이를 이용한 에어로졸 크기분포 추출 연구)

  • Kim, Dukhyeon
    • Korean Journal of Optics and Photonics
    • /
    • v.29 no.4
    • /
    • pp.139-148
    • /
    • 2018
  • In this study, aerosol size distributions were retrieved from aerosol optical depth measured over a range of 10 wavelengths from 250 to 1100 nm. The 10 wavelengths were selected where there is no absorption of atmospheric gases. To obtain the solar spectrum, a home-made solar tracking system was developed and calibrated. Using this solar tracking system, total optical depths (TODs) were extracted for the 10 wavelengths using the Langley plot method, and aerosol optical depths (AODs) were obtained after removing the effects of gas absorption and Rayleigh scattering from the TODs. The algorithm for retrieving aerosol size distributions was suggested by assuming a bimodal aerosol size distribution. Aerosol size distributions were retrieved and compared under various arbitrary atmospheric conditions. Finally, we found that our solar tracking spectrometer is useful for retrieving the aerosol size distribution, even though we have little information about the aerosol's refractive index.

Analysis of Communication Performance According to Detection Sequence of MMSE Soft Decision Interference Cancellation Scheme for MIMO System (다중 입출력 시스템 MMSE 연판정 간섭 제거 기법의 검출 순서에 따른 통신 성능 분석)

  • Lee, Hee-Kwon;Kim, Deok-Chan;Kim, Tae-Hyeong;Kim, Yong-Kab
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
    • /
    • v.12 no.6
    • /
    • pp.636-642
    • /
    • 2019
  • In this paper, we analyzed BER (Bit Error Rate) communication performance according to the detection order of MMSE (Minimum Mean Square Error) based soft decision interference cancellation. As the detection order method, antenna index order method, absolute value magnitude order method of channel elements, absolute value sum order method of channel elements, and SNR (Signal Noise Ratio) order method are proposed. BER performance for the scheme was measured and analyzed. As a simulation environment, 16-QAM (Quadrature Amplitude Modulation) modulation is used in an uncoded environment of an M×M multiple-input multiple-output system, and an independent Rayleigh attenuation channel is considered. The simulation results show that the performance gain is about 1.5dB when the SNR-based detection order method is M=4, and the performance gain is about 3.5dB when M=8 and about 3.5dB when M=16. The more BER performance was confirmed, the more the detection order method of the received signal prevented the interference and error spreading occurring in the detection process.