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首页> 外文会议>SAE World Congress Experience >Infrared Borescopic Evaluation of High-Energy and Long-Duration Ignition Systems for Lean/Dilute Combustion in Heavy-Duty Natural-Gas Engines
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Infrared Borescopic Evaluation of High-Energy and Long-Duration Ignition Systems for Lean/Dilute Combustion in Heavy-Duty Natural-Gas Engines

机译：重型天然气发动机贫液燃烧的高能和长持续时间点火系统的红外Borscopic评价

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Natural gas (NG) is attractive for heavy-duty (HD) engines for reasons of cost stability, emissions, and fuel security. NG cannot be reliably compression-ignited, but conventional gasoline ignition systems are not optimized for NG and are challenged to ignite mixtures that are lean or diluted with exhaust-gas recirculation (EGR). NG ignition is particularly challenging in large-bore engines, where completing combustion in the available time is more difficult. Using two high-speed infrared (IR) cameras with borescopic access to one cylinder of an HD NG engine, the effect of ignition system on the early flame-kernel development and cycle-to-cycle variability (CCV) was investigated. Imaging in the IR yielded strong signals from water emission lines, which located the flame front and burned-gas regions and obviated image intensifiers. A 9.7-liter, six-cylinder engine was modified to enable exhaust-gas recirculation and to provide optical access. Three ignition technologies were studied: a conventional system delivering 65 mJ of energy to each spark, a high-energy conventional system delivering 140 mJ, and a Bosch Controlled Electronic Ignition (CEI) system. CEI uses electronics to extend the ignition event, yielding sparks up to 5 ms in duration with up to 300 mJ of energy. Air/fuel equivalence ratios, λ, as high as 1.6 (with minimum EGR) and EGR fractions as high as 23% (stoichiometric) were tested; ignition delay, engine-out emissions, fuel consumption and image-derived parameters were compared. In most lean or dilute cases, the 140-mJ system yielded the lowest CCV. The imagery provided information about the early stages of ignition and combustion, where pressure measurements are not reliable. Image-based metrics also revealed that early flame kernels located further from the head yielded better combustion, showing that borescopic IR imaging can provide guidance for future engine design.
机译：天然气（NG）是用于重载（HD）引擎的成本稳定，排放和燃油安全原因的吸引力。 NG不能可靠压缩点火，但传统的汽油点火系统并不对NG优化，面临的挑战是点燃混合物是贫或具有排气再循环（EGR）稀释。 NG点火在大缸径发动机特别具有挑战性的，其中可利用的时间完成燃烧更困难。使用两个高速红外（IR）摄像机和borescopic访问高清NG发动机的一个汽缸，点火系统对早期火焰内核开发和周期到周期变化（CCV）的影响进行了研究。成像在IR产生从水发射线强信号，其位于所述火焰前缘和燃烧气体的区域和消除图像增强器。阿9.7升六缸发动机被修改，以使排气再循环和提供光接入。三个点火技术进行了研究：一个常规系统中传送的能量为65mJ每一个火花，一个高能量的以往的系统中传送140毫焦，和一个受控博世电子点火（CEI）系统。 CEI使用电子延长点火事件，产生火花高达时间为5毫秒的能量高达至300mJ。空气/燃料的当量比，λ，高达1.6（用最小的EGR）和EGR分数高达23％（化学计量）进行测试;点火延迟，发动机排出的排放，燃料消耗和图像导出的参数进行比较。在大多数贫或稀的情况下，140-MJ系统产生最低的CCV。该图像提供了关于点火和燃烧的早期阶段，其中压力测量是不可靠的信息。基于图像的度量还透露，早期火焰内核进一步从头部位于产生更好的燃烧，这表明borescopic IR成像可提供用于未来发动机设计指导。

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