Issues on clean diesel combustion technology using supercritical fluids: Thermophysical properties and thermal stability of diesel fuel
Issues on clean diesel combustion technology using supercritical fluids: Thermophysical properties and thermal stability of diesel fuel
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发表时间：
2011
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通讯作者：
Ronghong Lin
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作者：
Ronghong Lin
利用超临界流体的清洁柴油燃烧技术旨在提高燃油经济性和减少有害排放。该新工艺涉及超临界燃料/稀释剂混合物的制备、喷射和燃烧。这种新工艺的设计和开发需要对燃料特性有深入的了解。目前的研究试图解决三个燃料属性相关的问题：燃料替代品，扩散性和热稳定性。燃料代用品常用于发动机研究，以模拟真实的燃料特性。在这项工作中，十个柴油燃料代用品进行了调查，这些代用品预测柴油燃料的性能进行了评估。结果发现，没有一个能够预测所有感兴趣的属性，包括挥发性，临界点，密度，粘度，热容量和热导率。不同的替代品，建议不同的属性的预测。采用泰勒扩散法测定了柴油和替代化合物在超临界CO2中的扩散系数，温度和压力分别为373.15 K和30 MPa。结果用Wilke-Chang、Scheibel、He-Yu、12/D T相关系数和12/D T D12相关系数进行相关。结果表明，He-Yu关联式的预测能力最强，而12/DT关联式的拟合能力最好，AAD %<8%。对样品进样、检测器线性、移动的相平均速度和色谱柱方向引起的实验不确定度进行了广泛讨论。提出了一个无量纲参数φ来表征注入体积的影响，并在现有研究结果的基础上推广了一个新的D12-U模式图来描述移动的相平均速度对扩散率测量的影响。采用间歇和连续热应力试验研究了温度、停留时间和CO2对柴油高温热稳定性的影响。结果表明，柴油的热安定性随温度和停留时间的增加而降低。发现400 - 420 ° C是超临界燃料输送和燃烧可以工作的最佳温度范围。10wt%CO2的存在由于增强的溶剂容量而减少了固体沉积物的积累。然而，二氧化碳不太可能具有化学防止燃料焦化的能力。不同的尺寸，形貌和结构的固体沉积物观察到在300 - 440 ° C，这意味着不同的存款形成机制。柴油超临界流体清洁燃烧技术研究中的几个问题--柴油的热物理性质和热稳定性
The clean diesel combustion technology using supercritical fluids is aimed to both improve fuel economy and reduce harmful emissions. This novel process involves preparation, injection and combustion of supercritical fuel/diluents mixtures. Design and development of this new process require a deep understanding of fuel properties. The current study has attempted to address three fuel property related issues: fuel surrogates, diffusivity and thermal stability. Fuel surrogates are often used in engine research to mimic real fuel properties. In this work, ten diesel fuel surrogates were investigated, and the ability of these surrogates to predict diesel fuel properties was evaluated. It was found that none of them were able to predict all properties of interest including volatility, critical points, density, viscosity, heat capacity, and thermal conductivity. Different surrogates are suggested for predictions of different properties. Diffusion coefficients of diesel fuel and surrogate compounds in SCCO2 were determined using the Taylor dispersion method at temperatures and pressures up to 373.15 K and 30 MPa, respectively. Results were correlated by Wilke-Chang, Scheibel, He-Yu, 12 / D T and T D12 correlations. It was found that the He-Yu correlation had the best prediction capability, while the 12 / D T correlation gave overall best fit for experimental data with AAD% < 8%. Experimental uncertainties caused by sample injection, detector linearity, mobile phase mean velocity, and column orientation were extensively discussed. A dimensionless parameter φ was proposed to characterize the effect of the injection volume, and a new D12-U pattern diagram was generalized based on current results to describe the impact of mobile phase mean velocity on diffusivity measurements. The effects of temperature, residence time and CO2 on thermal stability of diesel fuel at high temperatures were investigated by both batch and continuous thermal stressing experiments. Results showed that thermal stability of diesel fuel decreased as temperature and residence time increased. 400-420 o C was found to be the optimal temperature range where supercritical fuel delivery and combustion could work. The presence of 10 wt% CO2 reduced accumulation of solid deposits due to enhanced solvent capacity. However, CO2 was not likely to have the ability to chemically prevent fuel coking. Solid deposits of different sizes, morphologies and structures were observed at 300 440 o C, which implies different deposit formation mechanisms. ISSUES ON CLEAN DIESEL COMBUSTION TECHNOLOGY USING SUPERCRITICAL FLUIDS: THERMOPHYSICAL PROPERTIES AND THERMAL STABILITY OF DIESEL FUEL