• 제목/요약/키워드: Light-off

검색결과 745건 처리시간 0.024초

저온활성촉매변환기의 체적변화가 활성화 성능에 미치는 영향에 관한 수치적 연구 (Numerical Study on the Effect of Volume Change of Light-Off Catalyst on Light-Off Performance)

  • 정수진;김우승
    • 한국자동차공학회논문집
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    • 제8권6호
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    • pp.87-100
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    • 2000
  • HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the light-off catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically consider three-dimensional, unsteady compressible reacting flow in the light-off and under body catalyst to examine the impact of a light-off catalyst on thermal response of the under body catalyst and tail pipe emission. The effect of flow distribution on the temperature distribution and emission performance have also been examined. The present results show that flow distribution has a great influence on the temperature distribution in the monolith at the early stage of warm-up process and the ultimate conversion efficiency of light-off catalyst is severly deteriorated when the space velocity is above $100,000hr^{-1}$.

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A STUDY ON A CATALYTIC CONVERTER OBD BEFORE LIGHT-OFF

  • Yun, Seung-Won;Son, Geon-Seog;Lee, Kwi-Young
    • International Journal of Automotive Technology
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    • 제3권1호
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    • pp.33-40
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    • 2002
  • Increasingly stringent emission regulations of EU and CARB (California Air resource Board) require mandatory OBD (On Board Diagnostics) far the catalytic converters of a vehicle. It demands that MIL(Malfunction Indication Light) should be tuned on to inform the driver of catalytic converter failures. Currently dual oxygen sensor method Is widely used for the converter OBD. However, since it works only alter converter light-off, it has a serious limitation when applied to TLEV or more stringent emission regulations where more than 85% of total emission is coming out before converter light-off. In addition, a recent development in catalyst material. coating technology and additive catalysts leads to a much improved OSC (Oxygen Storage Capacity) after converter light-off, current methods are very difficult to determine levels of converter aging. Therefore, it is desired to develop an OSC detecting method before converter light-off to diagnose converter failures with higher reliability. In this study, OSCs of converters are measured by an absolute measuring method and a dynamic measuring method, and some of fundamental ideas are suggested about converter OBD before converter light-off. The converters are aged with two different aging methods; those are a furnace aging and an engine bench aging: to represent aging conditions in actual field applications. Dual oxygen sensor method at the lower temperature than light-off is also studied at a model gas bench with the converters. It is fecund that there is a certain point in temperature lower than light-off where difference due to aging level becomes maximum, thus a proper dynamic method to effectively monitor catalytic converters could be implemented fur the range lower than light-off temperatures. With this result, the aging level of converters is examined at an engine bench.

자동차용 촉매변환기의 활성화 성능 향상을 위한 횡방향 가변 셀 밀도법의 수치적 평가: 활성화 촉매변환기를 중심으로 (Numerical Evaluation of a Radially Variable Cell Density Strategy for Improving Light-off Performance: Focusing on Light-off Catalyst)

  • 정수진;김우승
    • 한국자동차공학회논문집
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    • 제10권1호
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    • pp.115-124
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    • 2002
  • The optimum design of auto-catalyst needs a good compromise between the pressure drop and flow distribution in the monolith. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. However, there has been no study of evaluating the usefulness of this method on light-off catalyst. We have computationally investigated the effectiveness of variable cell density technique applied to the light-off catalyst using a three-dimensional integrated CFD model. in which transient chemical reacting calculations are involved. Computed results show that variable cell density technique can reduce the accumulated emissions of CO and HC during the early 100sec of FTP cycle by 86.78 and 80.87%, respectively, The effect of air-gap between the monoliths has been also examined. It is found that air-gap has a beneficial effect on reducing pressure drop and cold-start emissions.

냉간시동시 자동차용 저온활성촉매의 성능 향상을 위한 수치적 설계 (Numerical Design of Light-off Auto-Catalyst for Reducing Cold-Start Emissions)

  • 정수진;김우승
    • 대한기계학회논문집B
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    • 제24권9호
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    • pp.1264-1276
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    • 2000
  • Light-off catalyst has been used for minimization of cold-start emissions. Improved cold-start performance of light-off catalyst needs the optimal design in terms of flow distribution, geometric surface area, precious metal loading, cell density and space velocity. In this study, these influential factors are numerically investigated using integrated numerical technique by considering not only 3-D fluid flow but also heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading of depositing high active catalyst at upstream of monolith is beneficial during warm-up period but its effect is severely deteriorated when the space velocity is above 100,000 $hr^{-1}$ To maximize light-off performance, this study suggests that 1) a light-off catalyst be designed double substrate type; 2) the substrate with high GSA and high PM loading at face be placed at the front monolith; and 3) the cell density of the rear monolith be lower to reduce the pressure drop.

가시광통신체계에서 난반사 조명을 고려한 인코딩 스킴 (An Encoding Scheme Considering Diffused Lights In a Visual Light Communication System)

  • 은성배;김동규;차신
    • 한국멀티미디어학회논문지
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    • 제22권2호
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    • pp.186-193
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    • 2019
  • Visible light communication technology is being studied and developed in various ways due to advantages such as high transmission speed, excellent positioning and higher security. However, existing visible light communication systems have difficulties in entering the market because they use special transmitters and receivers. We will overcome the difficulty if we develope a VLC system that uses a conventional LED light as a transmitter and a smartphone camera as a receiver. What matters is that LED lights include a scatter filter to prevent glareness for human eyes, but the existing VLC(Visual Light Communication) method can not be applied. In this paper, we propose a method to encode data with On / Off patterns of LEDs in the lighting with $M{\times}N$ LEDs. We defined parameters like L-off-able and K-seperated to facilitate the recognition of On / Off patterns in the diffused Lights. We conducted experiments using an LED lighting and smart phones to determine the parameter values. Also, the maximum transmission rate of our encoding technique is mathematically presented. Our encoding scheme can be applied to indoor and outdoor positioning applications or settlement of commercial transactions.

엔진 문전 조건이 촉매 온도에 미치는 영향 (Parametric Study of Engine Operating Conditions Affecting on Catalytic Converter Temperature)

  • 이석환;배충식;이용표;한태식
    • 한국자동차공학회논문집
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    • 제10권3호
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    • pp.61-69
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    • 2002
  • To meet stringent LEV and ULEV emission standards, a considerable amount of development work was necessary to ensure suitable efficiency and durability of catalyst systems. The main challenge is to cut off the engine cold-start emissions. It is known that up to 80% of the total hydrocarbons(THC) are exhausted within the first five minutes in case of US FTP 75 cycle. Close-Coupled Catalyst(CCC) provides fast light-off temperature by utilizing the energy in the exhaust gas. However, if some malfunction occurred at engine operation and the catalyst temperature exceeds 1050$\^{C}$, the catalytic converter is deactivated and shows the poor conversion efficiency. This paper presents effEcts of engine operating conditions on catalytic converter temperature in a SI engine, which are the indications of catalytic deactivation. Exhaust gas temperature and catalyst temperature were measured as a function of air/fuel ratio, ignition timing and misfire rates. Additionally, light-off time was measured to investigate the effect of operating conditions. It was found that ignition retard and misfire can result in the deactivation of the catalytic converter, which eventually leads the drastic thermal aging of the converter. Significant reduction in light-off time can be achieved with proper control of ignition retard and misfire, which can reduce cold-start HC emissions as well.

The effects of short persistent CCFL in Blinking Back Light Unit to reduce blur on TFT-LCD

  • Han, J.M.;Bae, K.W.;Kim, S.Y.;Kim, Y.H.;Lim, Y.J.
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.694-697
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    • 2003
  • In applying LCD to TV application, one of the most significant factors to be improved is image sticking on the moving picture. LCD is different from CRT in the sense that it's continuous passive device, which holds images in entire frame period, while impulse type device generate image in very short time. To reduce image sticking problem related to hold type display mode, we made an experiment to drive LCD like CRT. We made articulate images by turn on-off backlight, and we realized the ratio of Back Light on-off time by adjusting between on time and off time for video signal input during 1 frame (16.7ms). Conventional CCFL (cold cathode fluorescent lamp) cannot follow fast on-off speed, so we evaluated new fluorescent substances of light source to improve residual light characteristic of CCFL. We realized articulate image generation similar to CRT by blinking drive. As a result, reduced image sticking phenomenon was validated by naked eye and response time measurement.

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냉시동시 미연 배기가스 점화 기술을 이용한 촉매 온도 상승 효과에 관한 연구 (A Study of Catalyst Temperature Rise Effect by using UEGI(Unburned Exhaust Gas Ignition) Technology during Cold-Start)

  • 김충식;천준영;최진욱;김인탁;엄인용;조용석
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집B
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    • pp.335-340
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    • 2000
  • Most vehicle's exhaust emissions come from the cold transient period of the FTP-75 test. In this study, UEGI technology was developed to help close-coupled catalytic converter (CCC) reach light-off temperature within a few seconds after cold-start. In the UEGI system, unburned exhaust mixture is ignited by four glow plugs installed upstream of the catalyst. Experimental results showed that the temperature of CCC rises faster with the UEGI technology, and the CCC reaches light-off temperature earlier. Under the conditions tested, the light-off time of the baseline case was 62 seconds and that of the UEGI case was 33 seconds.

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유동특성을 고려한 촉매변환기의 활성화(Light-off) 성능에 관한 연구 (A Study of Light-off Performance of Catalytic Converter with the Effect of Flow Characteristics)

  • 정수진;김우승
    • 한국자동차공학회논문집
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    • 제7권5호
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    • pp.107-120
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    • 1999
  • Catalytic converters are the most fascinating and complicated chemical reactors. They are most often operated in the transient state with respect to composition, flow rate, temperature, etc. The mathermatical model developed in this work accounts for simultaneous heat and mass transfer, chemical reaction, and multi dimensional flow characteristics to analyze the light-off performance of monolithic catalytic converter with comparable mass flow rate. To validate the mathematical model, comparison between experimental and numerical results has been performed. The numerical results show a good agreement with experimental data. It is forund that inflow rate shows major effect on the characteristics of termal response of catalytic converter.

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Making Thoughts Real - a Machine Learning Approach for Brain-Computer Interface Systems

  • Tengis Tserendondog;Uurstaikh Luvsansambuu;Munkhbayar Bat-Erdende;Batmunkh Amar
    • International Journal of Internet, Broadcasting and Communication
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    • 제15권2호
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    • pp.124-132
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    • 2023
  • In this paper, we present a simple classification model based on statistical features and demonstrate the successful implementation of a brain-computer interface (BCI) based light on/off control system. This research shows study and development of light on/off control system based on BCI technology, which allows the users to control switching a lamp using electroencephalogram (EEG) signals. The logistic regression algorithm is used for classification of the EEG signal to convert it into light on, light off control commands. Training data were collected using 14-channel BCI system which records the brain signals of participants watching a screen with flickering lights and saves the data into .csv file for future analysis. After extracting a number of features from the data and performing classification using logistic regression, we created commands to switch on a physical lamp and tested it in a real environment. Logistic regression allowed us to quite accurately classify the EEG signals based on the user's mental state and we were able to classify the EEG signals with 82.5% accuracy, producing reliable commands for turning on and off the light.