• Title/Summary/Keyword: Light-off

Search Result 746, Processing Time 0.026 seconds

A Study for Fast Light-Off of a Catalyst During Cold Start (냉시동시 촉매의 예열시간 단축에 관한 연구)

  • Cho, Y.S.;Lee, Y.S.
    • 한국연소학회:학술대회논문집
    • /
    • 1998.10a
    • /
    • pp.69-77
    • /
    • 1998
  • In order to meet the stringent emission regulations, fast light-off of a catalyst is essential to reduce the HC and CO emissions during cold start. Cranking Exhaust Gas Ignition (CEGI) method developed in this study showed that the catalyst reaches the light-off temperature in a few seconds after cold start. The CEGI system cuts off the ignition signal for a few seconds during the cranking period. so the unburned fuel-air mixture bypasses the combustion chamber and flows through the exhaust manifold. When the unburned mixture reaches two glow plugs installed upstream of the catalyst, it burns and releases the thermal energy to heat up the catalyst. Results from the FTP-75 tests showed that the exhaust emissions with the CEGI reduced by 47.7% for THC and by 88.6% for CO in the cold-transient phase of the test.

  • PDF

Calculation and Regulation Proposal of Light Pollution from Road Lightings (도로조명의 빛공해 계산 및 규제안 제안)

  • Cho, Sook-Hyun;Lee, Min-Wook;Choi, Hyeon-Seok;Kim, Hoon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.25 no.12
    • /
    • pp.21-26
    • /
    • 2011
  • This is a study to establish regulations against light pollution for lighting on roads. Many kinds of light pollution by luminaire on roads was calculated and analyzed by applying the classification method of luminaires(Cut-off classification of IDA-IESNA, BUG Rating Classification) and the calculation method of Upward Lighting Ratio of CIE among measures to prevent light pollution that international lighting organizations suggest. As a result of the analysis, it was found that the regulation by Cutoff of IESNA and ULR classification of CIE could be one for scattered light of light pollution compared to BUG classification but is not sufficient for the regulation of light tresspass or glare. BUG classification by each lighting zone was suggested as threshold value of the light pollution regulation considering domestic conditions.

Indoor Localization Technology Survey

  • Kim, Cheong-Mi;Jang, Beakcheol
    • Journal of the Korea Society of Computer and Information
    • /
    • v.21 no.1
    • /
    • pp.17-24
    • /
    • 2016
  • In this paper, we introduce indoor localization technologies categorizing them into ON/OFF switch and senor based, wireless communication based, and image based technologies. Then we describe several representative techniques for each of them, emphasizing their strengths and weaknesses. We define important performance issues for indoor localization technologies and analyze recent technologies according to the performance issues. Our analyses show that ON/OFF switch based technologies are difficult to install, but accurate and not limited by light. Wireless communication technologies are not limited by light nor distance (space) and do not need additional device. Image based technologies do not need additional device but are limited by light, and their accuracies are affected by light. We believe that this paper provide wise view and necessary information for recent indoor localization technologies.

Flicker Prevention Using Byte-Inversion in OOK Modulated Visible Light Data Transmission (OOK변조된 가시광 데이터전송에서 바이트반전을 이용한 플리커 방지)

  • Lee, Junho
    • Journal of IKEEE
    • /
    • v.24 no.2
    • /
    • pp.579-585
    • /
    • 2020
  • In this study, we used byte-inversion transmission method to prevent the flicker of lighting source in a visible light data communication link. In the transmitter, the non-return-to-zero (NRZ) signal with 9.6 kbps was on-off keying (OOK) modulated with a 100 kHz square wave carrier and byte-inversion signal was added after each byte to make the average optical power of the light-emitting diode (LED) constant. In the receiver, we used a band-pass filter to eliminate the interference of the 120 Hz noise which was induced from the adjacent light lamps, and an OOK demodulator to recover the original NRZ signal This scheme is useful in constructing wireless data networks using the illumination of visible light lamps.

Theoretical and numerical study to investigate characteristics of light-off and steady state of methane autothermal reactor for efficient light-off, high hydrogen yield and selectivity (시동 특성, 수소 생산 및 선택성 향상을 위한 자열개질기의 이론 및 수치해석적 연구)

  • Lee, Shin-Ku;Bae, Joong-Myeon
    • Proceedings of the KSME Conference
    • /
    • 2007.05b
    • /
    • pp.3353-3358
    • /
    • 2007
  • The present paper is devoted to investigate dynamic effect and steady-state performance of methane autothermal reformer theoretically and numerically. In order to simplify the complicated phenomena in the system, axisymmetric heterogeneous reactor model is developed. As autothermal reaction takes places on catalyst surface between bulk gas and catalyst, volume averaging method is incorporated using porous medium approach. To understand the start-up process which occurs in the reactor is highly important. Therefore, in this paper we get various goverining equations to find out transient and steady solutions and time scale for start-up introducing dimensionless variables. Start-up is a significant issue in reforming reaction for automobile system and fueling of SOFC-based auxiliary power units. This paper deals with characteristics of heat and mass transfer and predicted light-off time in the reformer as oxygen to carbon ratio ($O_2$/C) and amount of feeding gas.

  • PDF

Numerical Study on the Effect of Changes of Geometric Shape of Diesel Particulate Filter on Light-Off Characteristics and Transient Thermal Behavior during Regeneration (디젤입자상물질필터의 기하학적 형상변화가 재생과정 중 활성화 특성 및 비정상 온도거동에 미치는 영향에 관한 수치적 연구)

  • Jeong, Soo-Jin;Lee, Sang-Jin;Kim, Woo-Seung;Lee, Chun-Beom
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.14 no.4
    • /
    • pp.68-76
    • /
    • 2006
  • The minimization of maximum DPF wall temperature and the fast Light-off during regeneration are the targets for the high durability of the DPF system and the high efficiency of regeneration. In order to predict transient thermal response of DPF, one-channel numerical modeling has been adopted. The effect of the ratio of length to diameter(L/D), cell density, the amount of soot loading on temporal thermal response and regeneration characteristics has been numerically investigated under two different running conditions: city driving mode and high speed mode. The results indicate that the maximum wall temperature of DPF increase with increasing 'L/D' in 'High speed mode'. For 'City driving mode', the maximum wall temperature decreases with increasing 'L/D' in the range of $'L/D{\geq}0.6'$. The maximum temperature decreases with increasing cell density because heat conduction and heat capacity are increased. It is also found that the effect of amount of soot loading on light-off time is negligible.

Numerical Analysis of Thermal and Flow Characteristics for an Optimum Design of Automotive Catalytic Converter (자동차용 촉매변환기의 최적설계를 위한 열 및 유동특성에 대한 수치적 연구)

  • Jeong, Soo-Jin;Kim, Woo-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.7
    • /
    • pp.841-855
    • /
    • 1999
  • In the present work, the effect of a flow maldistribution on the thermal and conversion response of 8 monolith catalytic converter is Investigated. To achieve this goal, a combined chemical reaction and multi-dimensional fluid dynamic mathematical model has been developed. The present results show that flow uniformity within the monolith brick has 8 great impact on light-off performance of the catalytic converter. In the case of lower flow uniformity, large portions of the monolith remain cold due to locally concentrated high velocities and CO, HC are unconverted during warm-up period, which loads to retardation of light-off. It has been also found that the heat-up pattern of the monolith ill similar to the flow distribution profile, In the early stage of the reaction. It may be concluded that flow maldistribution can cause a significant retardation of the light-off and hence can eventually worsen tho conversion efficiency of automotive catalytic converter.

CHANGE OF CATALYST TEMPERATURE WITH UEGI TECHNOLOGY DURING COLD START

  • CHO Y.-S.;KIM D.-S.
    • International Journal of Automotive Technology
    • /
    • v.6 no.5
    • /
    • pp.445-451
    • /
    • 2005
  • Most of the pollutants from passenger cars are emitted during the cold-transient phase of the FTP-75 test. In order to reduce the exhaust emissions during the cold-transient period, it is essential to warm up the catalyst as fast as possible after the engine starts, and the Unburned Exhaust Gas Ignition (UEGI) technology was developed through our previous studies to help close-coupled catalytic converters (CCC) reach the light-off temperature within a few seconds after cold-start. The UEGI system operates by igniting the unburned exhaust mixture by glow plugs installed upstream of the catalyst. The flame generates a high amount of heat, and if the heat is concentrated on a specific area of monolith surface, then thermal crack or failure of the monolith could occur. Therefore, it is very important to monitor the temperature distribution in the CCC during the UEGI operation, so the local temperatures in the monolith were measured using thermocouples. Experimental results showed that the temperature of CCC rises faster with the UEGI technology, and the CCC reaches the light-off temperature earlier than the baseline case. Under the conditions tested, the light-off time of the baseline case was 62 seconds, compared with 33 seconds for the UEGI case. The peak temperature is well under the thermal melting condition, and temperature distribution is not so severe as to consider thermal stress. It is noted that the UEGI technology is an effective method to warm up the catalyst with a small amount of thermal stress during the cold start period.

Characterizing light pollution in national parks during peak and off-peak tourist seasons using nighttime satellite images (야간위성영상을이용한국립공원탐방성수기와비수기의빛공해특성분석)

  • Cho, Woo;Sung, Chan-Yong;Ki, Kyong-Seok
    • Korean Journal of Environment and Ecology
    • /
    • v.28 no.4
    • /
    • pp.484-489
    • /
    • 2014
  • In this paper, we examined factors that influenced light pollution in Korean national parks during peak and off-peak tourist seasons. Cloud-and moonlight-free nighttime satellite images that were collected during October 2012(for peak season) and January 2013(for off-peak season) by the Day and Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor were used to estimate the levels of light pollution in 19 national parks (excluding the Bukhansan and Mudeungsan National Parks). Bootstrapping regression analyses were conducted to examine the effects of socioeconomic and policy factors on light pollution in the study national parks for peak and off-peak tourist seasons, separately. The characteristics of light pollution in the national parks varied by season. During the peak tourist season, light pollution in the national parks were affected more by night lights nearby the parks than those within in the parks, while in the off-peak season, light sources in the parks were more important. Scattering of light emitted from hotels and other recreational facilities outside the parks that led to the sky glow effect can be attributed to the greater impact of night lights nearby the parks during the peak season. This result suggests that regulating light pollution nearby the park areas is needed to mitigate light pollution in the national parks, especially in a peak tourist season.

Dimming Control in Visible Light Communication Using Subcarrier Modulation of Manchester Code (맨체스터 코드의 부반송파 변조를 이용한 가시광통신의 조명제어)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
    • /
    • v.28 no.3
    • /
    • pp.191-197
    • /
    • 2019
  • In this study, we propose a dimming control method for a visible light communication (VLC) system, in which the subcarrier on-off keying (OOK) modulation of Manchester code is used for data transmission. In the VLC transmitter, non-return-to-zero (NRZ) code data is transformed to Manchester code, which is OOK modulated with a subcarrier. Manchester code is used for flicker-free lighting; the duty factor is changed for dimming control, and the subcarrier is used for preventing the adjacent noise light interference. In the experiments, the dimming control was carried out from about 8%-92% of the continuous wave (CW) LED light. This configuration is simple and effective in constructing a VLC system for indoor wireless sensor networks with flicker-free illumination and dimming control capability without adjacent noise light interference.