• Title, Summary, Keyword: Idle stability

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Spray Characteristics of the Pressure Swirl Injector for the APU Gas Turbine Engine (APU 가스터빈엔진 압력식 스월인젝터의 분무특성)

  • Choi, Chea-Hong;Choi, Seong-Man;Lim, Byeong-Jun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.359-364
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    • 2007
  • Spray characteristics of the APU gas turbine engine were investigated. In order to understand blow out phenomena of the APU engine, we performed fuel spray test. In the test, four operating conditions such as sea level idle, sea level max power, 20,000 feet idle, 20,000 feet max power were used as spray experimental conditions. PDPA(phase Doppler Particle Analyzer) was used for measuring the particle diameter and velocity. Also spray visualization was performed by using ND-YAG sheet laser beam. From the test result, in the case of 20,000 feet idle condition, SMD is about 100 ${\mu}m$ and maximum particle velocity is about 10 m/s. For the flame stability, spray quality should be improved at 20,000 feet idle condition.

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Effects of Engine Control Variables on Exhaust Gas Temperature and Stability during Cranking Operation of an SI Engine (가솔린기관의 시동시 기관 제어변수가 배기가스온도 및 시동성에 미치는 영향에 관한 실험적 연구)

  • Cho, Yong-Seok;An, Jae-Won;Park, Young-Joon;Kim, Duk-Sang;Lee, Seang-Wock
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.64-70
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    • 2007
  • Raising exhaust gas temperature during cold-start period is very crucial to improve emission performance of SI engines because it enhances the performance of catalyst in the early stage of engine start. In this study, control variables such as ignition timing, idle speed actuator(ISA) opening and fuel injection duration were extensively investigated to analyze variations in exhaust gas temperature and engine stability during cranking period. Experimental results showed that spark timing affected engine stability and exhaust gas temperature but the effects were small. On the other hand, shortened injection duration and increased ISA opening led to a significant increase in exhaust gas temperature. Under such conditions, increase in cranking time was also observed, showing that it becomes harder to start the engine. Based on these observations, a pseudo fuel-air ratio, defined as a ratio of fuel injection time to degree of ISA opening, was introduced to analyze the experimental results. In general, decrease in pseudo fuel-air ratio raised exhaust gas temperature with the cost of stable and fast cranking. On the contrary, an optimal range of the pseudo fuel-air ratio was found to be between 0.3 to 0.5 where higher exhaust gas temperatures can be obtained without sacrificing the engine stability.

Cycle-to-Cycle Fluctuations in a Spark Ignition Engine at Low Speed and Load

  • Han, Sung Bin;Hwang, Sung Il
    • Journal of Energy Engineering
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    • v.22 no.2
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    • pp.205-210
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    • 2013
  • Cycle-to-cycle variation has long been recognized as limiting the range of operating conditions of spark ignition engines, in particular, under lean and highly diluted operation conditions. At a part load, some of the cycles tend to knock, while others may have incomplete combustion by the time the exhaust valve opens. An experimental study has been performed in order to evaluate the relative contribution of several relevant parameters on the cyclic variability in spark ignition engines. In general, the stability of engine operation is improved with fuel injector according to the optimal injection timing, but the stability of engine operation at idle is not improved compared with a practical gasoline engine. In this study, we investigated the relationship of the effect of operating conditions for the stability at low speed and load.

An Advanced Embedded SRAM Cell with Expanded Read/Write Stability and Leakage Reduction

  • Chung, Yeon-Bae
    • Journal of IKEEE
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    • v.16 no.3
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    • pp.265-273
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    • 2012
  • Data stability and leakage power dissipation have become a critical issue in scaled SRAM design. In this paper, an advanced 8T SRAM cell improving the read and write stability of data storage elements as well as reducing the leakage current in the idle mode is presented. During the read operation, the bit-cell keeps the noise-vulnerable data 'low' node voltage close to the ground level, and thus producing near-ideal voltage transfer characteristics essential for robust read functionality. In the write operation, a negative bias on the cell facilitates to change the contents of the bit. Unlike the conventional 6T cell, there is no conflicting read and write requirement on sizing the transistors. In the standby mode, the built-in stacked device in the 8T cell reduces the leakage current significantly. The 8T SRAM cell implemented in a 130 nm CMOS technology demonstrates almost 100 % higher read stability while bearing 20 % better write-ability at 1.2 V typical condition, and a reduction by 45 % in leakage power consumption compared to the standard 6T cell. The stability enhancement and leakage power reduction provided with the proposed bit-cell are confirmed under process, voltage and temperature variations.

Performance Improvement of Wireless Positioning System Using IC-IPDL Method (IC-IPDL 기법을 이용한 무선 측위 시스템의 성능 개선)

  • 김상헌;정양석;윤대희;이충용
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.2A
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    • pp.124-129
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    • 2002
  • We propose a wireless positioning system using IC-IPDL method that exploits the modified-IPDL method and the interference cancellation techniques to improve hearability. In the proposed system, IPDL method is modified to maintain the transmission of CPICH for stability of CDMA network Simultaneously in mobile CPICH is cancelled out using the interference cancellation techniques for improving hearability. The simulation results showed that the proposed location system has a compatible performance to the standard IPDL method though CPICH exists during idle period.

The Study of the Design and Control for the Hydrogen Recirculation Blower Noise and Vibration Reduction (수소 재순환 블로어 소음 진동 저감을 위한 설계 및 제어에 관한 연구)

  • Bae, Ho June;Ban, Hyeon Seok;Noh, Yong Gyu;Jang, Seok Yeong;Lee, Hyun Joon;Kim, Chi Myung;Park, Yong Sun
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.5
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    • pp.509-515
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    • 2014
  • At the fuel processing system (FPS) of fuel cell vehicle, hydrogen recirculation blower (HRB) is used for the recirculation of remained hydrogen after reaction. In this paper, noise and vibration improvement of HRB is studied by changing design and control. It is checked the campbell diagram and critical speed for stability of rotor, and housing stiffness is improved using simulation of frequency response function (FRF). A method is suggested that can decrease the unbalance amount of the rotor and impeller which main source of noise and vibration. In order to reduce the noise during deceleration of blower, electrical braking is applied and tested the risk impact of durability. Founded the optimum switching frequency of the motor control, and reduced the idle rpm by increasing of aerodynamic performance. The superiority of paper is proved by measurement of the improved product's noise and vibration.

The Study for Idle Fuel Consumption of a Hydrogen-Blended Natural Gas Engine (수소 혼합 천연가스 연료 엔진의 아이들 연비에 관한 연구)

  • Lee, Sun-Youp;Kim, Young-Min;Lee, Jang-Hee
    • Journal of Energy Engineering
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    • v.19 no.3
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    • pp.171-176
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    • 2010
  • Using a hydrogen blended compressed natural gas (HCNG) as a fuel for IC engines has a significant meaning in terms of achieving a reduction of automotive exhaust emissions as well as preparing for an upcoming hydrogen economy by constructing hydrogen infrastructure. In addition, a HCNG engine has higher thermal efficiency than a CNG engine, which is another advantage that makes HCNG fuel considered as a future alternative for natural gas. Therefore, in this study, idling operation of a 11 litre HCNG bus engine was investigated in terms of fuel consumption rate and emissions characteristics. The results show that fuel consumption rate was decreased more than 20% by use of HCNG and all the emissions were significantly reduced in idling condition.

In-cylinder Flame Visualization and Flame Propagation Characteristics of SI Engine by using Optimal Threshold Method (Optimal Threshold 법을 이용한 가솔린 기관의 실린더 내화염 가시화 및 화염 전파 특성에 관한 연구)

  • 김진수;전문수;윤정의
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.5
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    • pp.96-104
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    • 2000
  • It is well known that combustion stability under idle and part-load conditions directly affect fuel economy and exhaust emission. In practice, there have been a lot of studies so that a significant improvement in combustion stability has been achieved in this research field. However, applying published results to the development process of mass production engine, there are still many problems which are solved previously. In this study, initial flame behavior and flame propagation characteristic were investigated statistically in order to optimize combustion chamber shapes in the development stage of mass production S.I. engine. To the purpose, the authors applied the flame image capturing system to single cylinder optical engine. The captured flame images were effectively analyzed by using the image processing program which was developed by the authors and adopted new threshold algorithm instead of conventional histogram analysis. In addition, the cylinder pressure was also measured simultaneously to compare evaluated flame results with cylinder pressure data in terms of the combustion characteristics, combustion stability, and cycle-to-cycle combustion variability.

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Computational fluid analysis of Aircraft Exhaust Duct for Verification of Structural Stability (항공기용 배기덕트의 구조적 안정성 검토를 위한 전산유동해석)

  • Lee, Changwook;Kim, Woncheol;Park, YongSuk;Yang, Yongjun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.606-608
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    • 2017
  • The computational fluid analysis was carried out to investigate structural stability of exhaust duct for turboprop engine. In order to calculate the thrust and shear force acting on the flight condition of the aircraft, the flow in the exhaust duct and the flow in the direction of the exhaust duct flange were analyzed by Fluent software to obtain thrust, shear force and bending moment. As a result of the analysis, it was confirmed that the allowable loads set idle engine manual were not exceeded.

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The Effect of Split Injections on the Stability of Idle Combustion and Emissions Characteristic in a Gasoline Direct Injection Engine (GDI 엔진의 분할 분사가 아이들 연소 안정 및 배출물 특성에 미치는 영향)

  • Roh, H.G.
    • Journal of ILASS-Korea
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    • v.19 no.4
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    • pp.221-226
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    • 2014
  • This paper described the effect of split injections on the stability of combustion and emission characteristics in a direct injection gasoline engine at various operating conditions. In order to investigate the influence of direct injection gasoline engine, the fuel injection timing was varied direct fuel injection at various fuel pressure. The experimental apparatus consisted of GDI engine with 4 cylinder, EC dynamometer, injection control system, and exhaust emissions analyzer. The emission and combustion characteristics were analyzed for the fuel injection timing and fuel injection pressure strategies. It is revealed that CO and HC emissions are dramatically decreased at advanced injection timing. Also, engine performance is increased at increase fuel injection pressure.