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首页> 外文会议>ASME Internal Combustion Engine Division Technical Conference >A REDUCED CHEMICAL KINETIC MECHANISM FOR CFD SIMULATIONS OF HIGH BMEP, LEAN-BURN NATURAL GAS ENGINES
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A REDUCED CHEMICAL KINETIC MECHANISM FOR CFD SIMULATIONS OF HIGH BMEP, LEAN-BURN NATURAL GAS ENGINES

机译：高BMEP，瘦燃烧天然气发动机的CFD模拟化学动力学机制

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Recent developments in numerical techniques and computational processing power now permit time-dependent, multi-dimensional computational fluid dynamic (CFD) calculations with reduced chemical kinetic mechanisms (approx. 20 species and 100 reactions). Such computations have the potential to be highly effective tools for designing lean-burn, high BMEP natural gas engines that achieve high fuel efficiency and low emissions. Specifically, these CFD simulations can provide the analytical tools required to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. To accurately model the transient, multi-dimensional chemically reacting flows present in these systems, chemical kinetic mechanisms are needed that accurately reproduce measured combustion data at high pressures and lean conditions, but are of sufficient size to enable reasonable computational times. Presently these CFD models cannot be used as accurate design tools for application in high BMEP lean-burn gas engines because existing detailed and reduced mechanisms fail to accurately reproduce experimental flame speed and ignition delay data for natural gas at high pressure (40 atm and higher) and lean (0.6 equivalence ratio (Φ) and lower) conditions. Existing methane oxidation mechanisms have typically been validated with experimental conditions at atmospheric and intermediate pressures (1 to 20 atm) and relatively rich stoichiometry. These kinetic mechanisms are not adequate for CFD simulation of natural gas combustion in which elevated pressures and very lean conditions are typical. This paper provides an analysis, based on experimental data, of the laminar flame speed computed from numerous, detailed chemical kinetic mechanisms for methane combustion at pressures and equivalence ratios necessary for accurate high BMEP, lean-burn natural gas engine modeling. A reduced mechanism that was shown previously to best match data at moderately lean and high pressure conditions was updated for the conditions of interest by performing sensitivity analysis using CHEMKIN. The reaction rate constants from the most sensitive reactions were appropriately adjusted in order to obtain a better agreement at high pressure lean conditions. An evaluation of this adjusted mechanism, "MD19", was performed using Converge CFD software. The results were compared to engine data and a remarkable improvement on combustion performance prediction was obtained with the MD19 mechanism.
机译：在数字技术和计算处理能力的最新进展，已允许时间依赖性，多维计算流体动力学（CFD）具有降低的化学动力学机理计算（约20种，100个反应）。这样的计算有潜力成为设计的稀薄燃烧，高BMEP天然气引擎，实现了高燃油效率，低排放的高效工具。具体地，这些CFD模拟可以提供分析工具需要设计高度优化的天然气发动机部件，如活塞，进气口，预燃室中，燃料系统和点火系统。为了精确建模瞬时，多维化学反应流存在于这些系统中，化学动力学机制是需要的在高压和在贫燃条件精确地再现测量燃烧的数据，但具有足够的尺寸，以使合理的计算时间。目前这些CFD模型不能被用作准确的设计工具，用于在高BMEP应用贫油燃烧汽油发动机因为现有详细和降低的机制失效在高压下精确地再现天然气实验火焰速度和点火延迟数据（40个大气压或更高）和稀（0.6当量比（Φ）和降低）的条件。现有甲烷氧化机制通常被验证在大气压和中间压力（1至20大气压），相对浓于化学计量的实验条件。这些动力机制不足以天然气燃烧的CFD模拟在升高的压力和非常瘦的条件是典型的。本文提供了一个分析，根据实验数据，从众多计算的层流火焰速度，在压力和必要的准确的高BMEP当量比为详细甲烷燃烧化学反应动力学机制，稀薄燃烧天然气发动机模型。这是在适度倾斜和高压条件先前显示最佳匹配数据减小的机制用于感兴趣通过利用CHEMKIN灵敏度分析的条件更新。从最敏感的反应的反应速率常数，以获得在高压贫燃条件更好的协议进行了适当调整。使用收敛CFD软件进行调整这一机制，“MD19”的评价。结果进行比较，以发动机数据和燃烧性能预测的显着的改善与MD19机构获得。

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