• Title/Summary/Keyword: CNG직접분사식엔진

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A Study on Expansion of Lean Limit for Heavy-Duty DI Engine with Compressed Natural Gas (대형 직접분사식 CNG기관의 희박한계 확장에 관한 연구)

  • Quoc, Tran Dang;Lee, Kwang-Ju;Lee, Jong-Tai
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.5
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    • pp.735-740
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    • 2011
  • 본 연구에서는 직접분사식 CNG기관의 희박한계를 보다 확장하여 고효율 및 저배기 공해를 실현시키고자 실린더 내에 고압의 천연가스를 직접분사함과 동시에 흡입과정 중 흡기관 내에 소량의 저압천연가스를 보조분사하는 경우의 희박한계 확장 및 제반특성에 대해 검토하였다. 그 결과, 흡기보조분사가 없을 경우 희박한계가 ${\lambda}$ = 1.4 까지였으나, 흡기보조분사율이 5~15% 정도에서는 희박한계가 ${\lambda}$ = 1.5 까지 확장되었다. 이는 흡기보조분사에 따른 혼합기의 혼합율 향상에 기인한 것으로 해석하였다. 연소기간은 줄어들었지만, 흡기보조분사의 효과는 주연소기간에서 조기연소기간보다 강하게 나타났다.

Numerical Study of Combustion Characteristics in CNG DI Engine using Gaseous Sphere Injection Model (기체구 분사 모델을 이용한 CNG DI 엔진의 연소특성 수치해석)

  • Choi, Mingi
    • Journal of ILASS-Korea
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    • v.24 no.4
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    • pp.171-177
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    • 2019
  • This paper describes numerical study of combustion characteristics in CNG(compressed natural gas) DI(direct injection) engine using gaseous sphere injection model. Simulations were conducted using KIVA-3V Release 2 code. Gaseous sphere injection model, which is modified model of liquid fuel injection, was used to simulate the CNG direct injection. Until now, a very fine mesh smaller than the injector nozzle has been required to resolve the gas-jet inflow boundary. However, the gaseous sphere injection model simulates gaseous fuel injection using a coarse mesh. This model injects gaseous spheres as in liquid fuel injection and the gaseous spheres evaporate together without the latent heat of evaporation. Therefore, it does not require a very fine mesh and reduce calculation time. Combustion simulation were performed under various injection timings and injection pressures.

Mixing and Combustion Characteristics of a CNG and Air according to Fuel Supply Conditions in a DI Engine (직분식 엔진에서 연료공급 조건에 따른 CNG와 공기의 혼합 및 연소특성)

  • Kang, Jeong-Ho;Park, Jong-Sang;Yeom, Jeong-Kuk;Chung, Sung-Sik;Ha, Jong-Yul
    • Journal of ILASS-Korea
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    • v.13 no.1
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    • pp.1-8
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    • 2008
  • It was investigated how fuel injection timing - early injection and later injection - in conjunction with throttle open rate effect the fuel-air mixing characteristics, Engine power, combustion stability and emission characteristics on a DI CNG spark Engine and control system that had been modified and designed according to the author's original idea. It was verified that the combustion characteristics were changed according to fuel injection timings and Engine conditions determined by different throttle open rates and rpm. It was found that the combustion characteristics greatly improved at the complete open throttle rate with an early injection timing and at the part throttle rate with a late injection timing. Combustion duration was governed by flame propagation duration in a late injection timing and by an early flame development duration in an early injection timing. As the result, we discovered that combustion duration is shortened, lean limit is improved, air-fuel mixing conditions controlled, and emissions reduced through control of fuel injection timing according to change of the throttle open rate.

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The Effect of Fuel Injection Timing on Combustion and Power Characteristics in a DI CNG Engine (직분식 CNG 엔진에서 연료 분사시기의 변화가 연소 및 출력 특성에 미치는 영향)

  • Kang, Jeong-Ho;Yoon, Soo-Han;Lee, Joong-Soon;Park, Jong-Sang;Ha, Jong-Yul
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.193-200
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    • 2007
  • Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.