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Scalar dissipation rate based multi-zone model for early-injected and conventional diesel engine combustion

机译：基于标量耗散率的早期喷射和常规柴油机燃烧的多区域模型

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Low-temperature combustion (LTC) concepts, such as Homogeneous Charge Compression Ignition (HCCI) or Premixed-Charge Compression Ignition (PCCI), have the potential of simultaneous reducing nitrogen oxides (NO.), soot, and unburned hydrocarbons (uHC). However, the successful implementation for internal combustion engines is difficult. Control strategies need to be employed to ensure appropriate combustion phasing over wide ranges of operating conditions. Model-based engine control is particularly successful when physics-based models are employed. Multi-zone combustion models represent potential candidates for efficiently computing combustion in PCCI diesel engines. Multi-zone models were originally developed for HCCI gasoline engine combustion and did not account for mixing between zones due to the relatively homogeneous mixture while later developments considered small inhomogeneities. However, for diesel or PCCI combustion, this is not justified due to noticeable fuel stratification. Therefore, a novel mixing model for multi-zone modeling accounting for mass and energy exchange between zones is presented in this work. The model is derived from the representative interactive flamelet (RIF) model and thus depends on the scalar dissipation rate as well as the mixture fraction in each zone. The multi-zone model can be used as a stand-alone model after performing a number of non-reactive computational fluid dynamics (CFD) simulations to train an empirical, engine-specific model for the scalar dissipation rate. With the stand-alone model, cost-efficient parameter studies can be performed, with further model reduction, the use in model-based control algorithms is also possible. For validation of the stand-alone multi-zone model, experiments were conducted with a four-cylinder diesel engine. 105 operation conditions including variations in start of injection (SOI), injected fuel mass (FMI), and external exhaust gas recirculation (EGR) were selected to assess the model performance. CFD simulations applying the RIF model were carried out for representative cases to further assist in validating and analyzing the new multi-zone model. Predictions of the multi-zone model regarding indicated mean effective pressure (IMEP), combustion phasing (CA(50)), and emissions of nitrogen monoxide as well as unburned hydrocarbons are compared against experimental data and results from numerical simulations. Overall good agreement over various operating conditions was found demonstrating the capability of the multi-zone model to adequately capture PCCI diesel engine combustion. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：低温燃烧（LTC）概念，例如均质充气压缩点火（HCCI）或预混合充气压缩点火（PCCI），具有同时还原氮氧化物（NO。），烟灰和未燃烧碳氢化合物（uHC）的潜力。然而，内燃机的成功实施是困难的。需要采用控制策略来确保在宽范围的运行条件下进行适当的燃烧定相。当使用基于物理的模型时，基于模型的引擎控制特别成功。多区域燃烧模型代表了有效计算PCCI柴油机燃烧的潜在候选者。多区域模型最初是为HCCI汽油发动机燃烧而开发的，由于混合物相对均匀，因此并未考虑区域之间的混合，而后来的发展则认为较小的不均匀性。但是，对于柴油或PCCI燃烧，由于明显的燃料分层，因此不合理。因此，在这项工作中提出了一种新的用于多区域建模的混合模型，该模型考虑了区域之间的质量和能量交换。该模型是从代表性交互式火焰（RIF）模型中得出的，因此取决于标量耗散率以及每个区域中的混合比例。在执行了许多非反应性计算流体动力学（CFD）仿真以训练标量耗散率的经验性，引擎特定模型之后，该多区域模型可以用作独立模型。使用独立模型，可以进行具有成本效益的参数研究，并通过进一步简化模型，也可以在基于模型的控制算法中使用。为了验证独立的多区域模型，使用四缸柴油机进行了实验。选择了105种运行条件，包括喷射开始（SOI），喷射燃料质量（FMI）和外部废气再循环（EGR）的变化，以评估模型性能。针对代表性案例进行了使用RIF模型的CFD模拟，以进一步帮助验证和分析新的多区域模型。将多区域模型关于指示平均有效压力（IMEP），燃烧阶段（CA（50））和一氧化氮以及未燃烧碳氢化合物排放的预测与实验数据和数值模拟结果进行了比较。发现在各种操作条件下的总体良好一致性证明了多区域模型能够充分捕获PCCI柴油机燃烧的能力。 （C）2016年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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