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首页> 外文会议>ASME Internal Combustion Engine Division technical conference >MODELING THE FORMATION OF POLLUTANT EMISSIONS IN LARGE-BORE, LEAN-BURN GAS ENGINES
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MODELING THE FORMATION OF POLLUTANT EMISSIONS IN LARGE-BORE, LEAN-BURN GAS ENGINES

机译：对大口径，稀燃气体发动机中污染物排放的形成进行建模

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This paper discusses chemical kinetic modeling used to analyze the formation of pollutant emissions in large-bore, lean-burn gas reciprocating engines. Pollutants considered are NO_x, CO, HCHO, and UHC. A quasi-dimensional model, built as a chemical reactor network (CRN), is described. In this model, the flame front is treated as a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR), and reaction in the burnt gas is modeled assuming a batch reactor of constant-pressure and fixed-mass for each crank angle increment. The model treats full chemical kinetics. Engine heat loss is treated by incorporating the Woschni model into the CRN. The mass burn rate is selected so that the modeled cylinder pressure matches the experiment pressure trace. Originally, the model was developed for large, low speed, two-stoke, lean-burn engines. However, recently, the model has been formatted for the four-stroke, open-chamber, lean-burn engine. The focus of this paper is the application of the model to a four-stroke engine. This is a single-cylinder non-production variant of a heavy duty lean-burn engine of about 5 liters cylinder displacement. Engine speed is 1500 RPM. Key findings of this work are the following. 1) Modeled NO_x and CO are found to agree closely with emission measurements for this engine over a range of relative air-fuel ratios tested. 2) This modeling shows the importance of including N_2O chemistry in the NO_x calculation. For X = 1.7, the model indicates that about 30% of the NO_x emitted is formed by the N_2O mechanism, with the balance from the Zeldovich mechanism. 3) The modeling shows that the CO and HCHO emissions arise from partial oxidation late in the expansion stroke as unburned charge remaining mixes into the burnt gas. 4) Model generated plots of HCHO versus CH_4 emission for the four-stroke engine are in agreement with field data for large-bore, lean-burn, gas reciprocating engines. Also, recent engine tests show the correlation of UHC and CO emissions to crevice volume. These tests suggest that HCHO emissions also are affected by crevice flows through partial oxidation of UHC late in the expansion stroke.
机译：本文讨论了用于分析大口径稀薄燃烧气体往复式发动机中污染物排放形成的化学动力学模型。所考虑的污染物为NO_x，CO，HCHO和UHC。描述了建立为化学反应器网络（CRN）的准维度模型。在此模型中，将火焰锋面视为完全搅拌反应器（PSR），然后处理为活塞流反应器（PFR），并对燃烧气体中的反应进行建模，并假设每个曲柄均具有恒压和固定质量的间歇式反应器角度增量。该模型处理完整的化学动力学。通过将Woschni模型纳入CRN，可以处理发动机的热量损失。选择质量燃烧率，以使模型化的气缸压力与实验压力轨迹相匹配。最初，该模型是为大型，低速，二冲程，稀薄燃烧发动机开发的。但是，最近，该模型已针对四冲程，开放式室，稀薄燃烧发动机进行了格式化。本文的重点是该模型在四冲程发动机上的应用。这是约5升气缸排量的重型稀薄燃烧发动机的单缸非生产型。发动机转速为1500 RPM。这项工作的主要发现如下。 1）在所测试的相对空燃比范围内，发现建模的NO_x和CO与该发动机的排放测量值非常吻合。 2）该模型显示了在NO_x计算中包括N_2O化学的重要性。对于X = 1.7，模型表明排放的NO_x约30％是由N_2O机理形成的，其余的则来自Zeldovich机理。 3）模型显示，CO和HCHO排放源于膨胀冲程后期的部分氧化，这是因为未燃烧的电荷残留物混入燃烧的气体中。 4）四冲程发动机的HCHO对CH_4排放的模型生成图与大口径，稀薄燃烧，气体往复式发动机的现场数据一致。另外，最近的发动机测试表明，UHC和CO排放与缝隙体积之间存在相关性。这些测试表明，在膨胀冲程后期，UHC的部分氧化会导致裂隙流，从而影响HCHO的排放。

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