CO_2捕集过程中钙基吸收剂吸碳反应本征动力学

本文通过严格控制实验条件,消除内扩散和外扩散的影响,对两种CaO质量分数均为75%的合成钙基吸收剂进行了本征动力学实验。通过晶粒模型分析,找到了完全由表面反应控制的本征动力学阶段,分析其本征反应动力学特性,得到本征反应速率常数k_s和活化能E,并与早期的研究结果进行了对比分析。研究表明:两种合成吸收剂的活化能均小于石灰石吸碳反应的活化能;合成吸收剂的吸碳反应速率与石灰石分解CaO的吸碳反应速率具有相同的数量级。本研究同时得到了反应动力学控制阶段吸碳反应速率与驱动力CO_2分压之间的关系。     

3,7-二硝基亚氨基-2,4-二氮杂双环[3,3,0]辛烷的放热分解反应动力学

在程序升温条件下 ,用DSC研究了标题化合物的放热分解反应动力学 .用线性最小二乘法、迭代法以及二分法与最小二乘法相结合的方法 ,以积分方程、微分方程和放热速率方程拟合DSC数据 .在逻辑选择建立了微分和积分机理函数的最可几一般表达式后 ,用放热速率方程得到相应的表观活化能 (Ea)、指前因子 (A)和反应级数 (n)的值 .结果表明 :该反应的微分形式的经验动力学模式函数、Ea 和A值分别为 (1-α) 0 .44、2 30 .4kJ/mol和 10 18.16s-1.借助加热速率和所得动力学参数值 ,提出了标题化合物放热分解反应的动力学方程 .该化合物的热爆炸临界温度为 30 2 .6℃ .上述动力学参数对分析、评价标题化合物的稳定性和热变化规律十分有用 .     

传递函数在石灰石分解研究中的应用

本文应用高温气固悬浮试验台架对石灰石的分解动力学过程进行了研究,并利用试验系统的传递函数对检测数 据进行了修正,从而获取了石灰石在反应器中的真实动态分解数据。试验结果表明采用传递函数对试验数据进行修正是必 要的,所得结果对于工业应用以及设计具有一定的参考价值。     

钾基CO2吸收剂再生反应特性

通过热重分析试验研究了钾基 CO2 吸收剂的再生反应特性.深入分析了气氛、分解终温和升温速率对再生转化率和分解反应速率的影响.通过热分析方法求取了反应动力学参数.研究发现,其分解终温最佳值为 200℃;CO2 和H2O 在分解终温较低时对反应过程的影响较大;升温速率对反应的影响程度在其高于 10℃/min 后明显减弱;KHCO3分解反应的表观活化能为 90～120 kJ/mol.本文为干法 K2CO3/KHCO3 循环脱除 CO2 的研究提供了一定的基础数据.     

基于反应动力学的GaN LED参数退化模型的研究

加速实验中, 参数退化模型描述了参数的退化规律, 参数退化规律对应于器件退化机理, 而退化机理又对应于内部的物理化学反应. 因此, 本文基于反应动力学中物理化学反应的温度效应速率模型及反应量浓度随时间的变化规律, 研究并建立了GaN LED参数退化模型. 本模型尝试从物理机理上解释参数退化过程中的退化规律, 包括单调上升或单调下降退化规律、先上升后下降或先下降后上升等非单调退化规律, 解决了实验后拟合方法不能建立非单调退化模型的问题. 然后对GaN LED进行加速实验, 确定模型参数. 同时对GaN LED的退化规律进行分解, 并且量化了GaN LED两种退化规律的退化比例及时间常数. 关键词： 参数退化模型 反应动力学 加速实验 GaN LED     

细胞色素P450 2E1催化下乙醛羟基化反应动力学同位素效应的理论研究

采用建立在Eyring绝对反应速率理论基础上的计算模型,对细胞色素P4502E1催化下乙醛羟基化反应动力学同位素效应进行了理论研究.计算表明,乙醛羟基化反应的动力学同位素效应大小约为5.0(Wigner量子校正后约为7.0左右),远比烷烃羟基化反应的动力学同位素效应要小的多.这个反应对温度比较敏感,所以反应存在明显的量子隧穿现象.文中还对动力学同位素效应给出了相应的过渡态构型方面的解释.     

全内反射紫外光谱原位研究稀土离子萃取的界面反应动力学

研究稀土离子的萃取动力学行为特性有利于了解其萃取过程微观机制,但以往传统的萃取动力学研究方法无法原位获取萃取反应过程的油水两相界面分子层次微观信息。本文提出一种全内反射紫外光谱的方法,原位研究稀土离子在油/水相界面的萃取反应动力学。采用拟一级反应动力学模型对稀土离子紫外吸光度值随时间的变化进行了拟合,得到了表观反应速率常数。研究成果为进一步深入研究离子在界面的微观动态行为奠定了基础。     

生石灰颗粒中温脱硫过程数值计算

本文采用晶粒模型对中温条件下单颗粒石灰石脱硫过程进行数值模拟。利用已有文献数据、电子显微镜及TGA实验数据确定模型中化学反应动力学以及物性参数。计算结果与TGA实验结果符合较好,表明脱硫模型可直接应用于中温条件下石灰石脱硫过程的数值预报与分析。     

用含时波包方法将SVRT模型应用到F+CD4→CD3+DF反应中

为了实现量子动力学含时波包方法对多原子反应体系的研究,采用美国纽约大学张增辉教授提出的一个半刚性振转子的模型,对F+CD4反应及其同位素反应物反应在MJ1势能面上进行了含时波包动力学的研究.所用到的势能面的反应势垒66meV.实验和理论研究表明在反应中C-D键不影响反应碰撞,它只是一个旁观者.对C-D键作为常数处理使得计算大大简化了.计算了给定初始态的这些反应的积分反应截面和速率常数.从得到的数值结果可以看出,积分截面随着碰撞能有一个很大的起伏,这一般来讲是与动力学振荡有关系.速率常数同已有的理论以及实验结果进行了比较,得到了比较合理的结论.     

强流电子束泵浦XeCl准分子激光动力学模型

强流电子束泵浦XeCl准分子激光动力学模型由三部分组成,即电子束能量沉积的计算;电子温度、电子反应速率的计算和化学/激光动力学。这个模型可以准确地预报小信号增益、吸收等激光特征量的时间变化规律。 该模型是在文献[1]、[2]、[3]报导的动力学模型的基础上提出的。采用四阶龙格_库塔法在VAX—11/780机器上进行数值求解。 计算给出XeCl准分子激光反应过程中各种粒子浓度、小信号增益、吸收、输出光强、激发速率以及平均电子能量随时间的变化规律。计算结果表明本征效率是激发速率,电流密度和工作气体(Ne/Xe/HCl)的各分压比的函数。 该模型可为高功率准分子激光器的研制提供设计参数和最佳实验条件。     

Dissipation,mass exchange and the microscopic time scale of heavy-ion collisions

The time scale provided by the nucleon exchange mechanism in heavy-ion reactions is employed to study kinetic energy damping. The experimental kinetic energy lost per nucleon exchanged in Kr- and Xe-induced reactions is observed to decrease linearly with the total kinetic energy loss. These results, which are consistent with energy dissipation and nucleon exchange occuring on a similar time scale, are compared with the predictions of a one-body dissipation mechanism and a diffusion model.     

Spectral uncertainty quantification, propagation and optimization of a detailed kinetic model for ethylene combustion

The ability of a reaction model to predict the combustion behavior of a fuel relies on the rigorous quantification of the kinetic rate parameter uncertainty. Although the accuracy of a detailed kinetic model may be ensured, in principle, by a multi-parameter optimization, the inherent uncertainties in the fundamental combustion targets used for optimization cause the resulting optimized model to be characterized by a finite kinetic parameter space. In this work, spectral expansion techniques are developed and employed to quantify these uncertainties, using an as-compiled, detailed, H₂/CO/C₁-C₄ kinetic model for ethylene combustion as an example. Uncertainty was quantified for both the as-compiled model and the optimized model, and propagated into a wide variety of combustion experiment and conditions. Application of the spectral uncertainty method in mechanism reduction is also discussed.     

Kinetic investigation on sono-degradation of Reactive Black 5 with core–shell nanocrystal

The experimental data of sonocatalytic degradation of Reactive Black 5 (RB5) as an azo dye by core–shell nanocrystals (CdS–TiO₂) were applied to the proper kinetic models. In this work, two kinetic models were proposed and fitted properly to the data. In the first one, the heterogeneous reaction was considered similar to the Langmuir–Hinshelwood (L–H) mechanism and the kinetic rate parameters were determined. In this model, short time of sonication with initial concentration changes has been applied and the contribution of the reaction intermediates has been neglected in degradation. Hence, this model may not be valid for longer reaction times where the reaction intermediates effects prevail. In the second one, two first-order reactions in series provided the most convincing rate form for the sonodegradation of dyes adsorbed on the synthesized nanocomposite. In these series reactions, the first step is the conversion of colored dye to colored intermediate, and the second step is the conversion to colorless product(s). The obtained results were in good agreement with the proposed kinetic models. The rate constants of degradation of catalyzed reaction were higher than that obtained without catalyst, solar and UV irradiation.     

An experimental and kinetic modeling study of a four-component surrogate fuel for RP-3 kerosene

Detailed high-fidelity kinetic models of fuels are of great significance by providing guidance for the improvement of the combustion performance in engines and promising the reduction of design cycle of new concept combustors. However, the kinetic modeling works on Chinese RP-3 kerosene, the most widely used civil aviation fuel in China, are meager to date. In this study, a kinetic model, including a surrogate fuel and its combustion kinetic mechanism, were developed to describe the combustion of RP-3. Firstly, a surrogate comprised of components n-dodecane, 2,2,4,6,6-pentamethylheptane (PMH), n-butylcyclohexane and n-butylbenzene (22.82/31.30/19.19/26.69 mol%) was proposed based on the combustion property target matching method. These components are all within the typical molecular size (C10-C14) of jet fuels and thereby can potentially improve the ability of the surrogate in emulating the properties that depend on molecular size. Experiments were then carried out in a heated rapid compression machine and a heated shock tube to evaluate the performance of the surrogate in reproducing the combustion behavior of the target fuel over wide conditions. It is found that the surrogate can reproduce the autoignition characteristics of RP-3 very well. A chemical kinetic mechanism was developed to describe the oxidation of this surrogate. This mechanism was assembled using a published n-butylbenzene sub-mechanism and our previous sub-mechanisms for the other pure components, and was assessed against the present experimental data. The results showed that the simulations agreed well with the experimental data under the investigated conditions, demonstrating that the composition of the surrogate and its mechanism are appropriate to describe the combustion of RP-3. The first-stage ignition negative temperature coefficient behavior and the evolution of key radicals were investigated using the kinetic model.     

DME/LPG混合燃料HCCI燃烧模拟

根据碳氢燃料化学反应系统具有层次结构的特性,本文通过分析二甲醚(DME)与液化石油气(LPG)的详细化学反应机理,构建了反映DME／LPG混合燃料均质压燃(HCCI)燃烧的详细化学反应机理．采用该机理应用单区燃烧模型对DME／LPG混合燃料HCCI燃烧的化学反应动力学过程进行了数值计算．计算结果与试验结果对比表明,所构建的DME／LPG混合燃料氧化的详细化学反应机理能够准确预测DME／LPG混合燃料的两阶段放热特性,对低温和高温着火始点的预测很好;但高温反应过程预测欠佳,高温反应机理需要改进．     

Self-consistent multidimensional electron kinetic analysis forinductively coupled plasma sources

Based upon the kinetic equations coupled with electromagnetic analysis for the recently developed inductively coupled plasma sources (ICPS), a self-consistent electron kinetic model is presented for 2-D (r, z) in a cylindrically symmetric configuration space and 2-D (ν _∂, ν_z) in the velocity space, The EM model is based on the mode analysis, while the kinetic analysis gives the perturbed Maxwellian distribution of electrons by solving the Boltzmann-Vlasov equation. The kinetic analysis shows that the RF energy in an ICPS is extracted by a collisionless dissipation mechanism, once the electron thermovelocity is close to the RF phase velocities determined by the reactor height and mode indexes. In this context, the effect of varying the reactor geometry is reported in terms of the electron energy distribution function. The analytical results are compared to the experimental data of Barnes et al. (see Appl. Phys. Lett., vol.62, no.21, p.2622-4 (1993)), which shows qualitative agreements in many aspects     

LES modelling of turbulent non-premixed jet flames with correlated dynamic adaptive chemistry

Large eddy simulations (LES) for turbulent flames with detailed kinetic mechanisms have received growing interest. However, a direct implementation of detailed kinetic mechanisms in LES modelling of turbulent combustion remains a challenge due to the requirement of huge computational resources. An on-the-fly mechanism reduction method named correlated dynamic adaptive chemistry (CoDAC) is proposed to overcome this issue. A LES was conducted for Sandia Flame-D, with the reaction mechanism of GRI-Mech 3.0 consisting of 53 species and 325 reactions. The reduction threshold used in LES was obtained a priori by using auto-ignition model and partially stirred reactor (PaSR) with pairwise mixing model. LES results with CoDAC are in good agreement with experimental data and those without reduction. The conditional mean of the number of selected species indicates that a large size of locally reduced mechanism is required in the reaction zone where CH₄ is destructed. A computational time analysis shows that the PaSR model predicts better than the auto-ignition model on the wall time reduction with CoDAC in LES.     

A detailed chemical kinetic model of high-temperature ethylene glycol gasification

In recent experimental investigations, ethylene glycol is used as a model substance for biomass-based pyrolysis oil in an entrained flow gasifier. In order to gain a deeper insight into process sequences and to conduct parametric analysis, this study describes the development and validation of a detailed chemical kinetic model of high-temperature ethylene glycol gasification. A detailed reaction mechanism based on elementary reactions has been developed considering 80 species and 1243 reactions for application in CFD software. In addition to mechanism validation based on ignition delay times, laminar flame speeds and concentration profiles, simulation results are compared to experimental data of ethylene glycol gasification under complex turbulent reactive flow conditions.     

Cluster dynamics and cluster size distributions in systems of self-propelled particles

Systems of self-propelled particles (SPP) interacting by a velocity alignment mechanism in the presence of noise exhibit rich clustering dynamics. Often, clusters are responsible for the distribution of (local) information in these systems. Here, we investigate the properties of individual clusters in SPP systems, in particular the asymmetric spreading behavior of clusters with respect to their direction of motion. In addition, we formulate a Smoluchowski-type kinetic model to describe the evolution of the cluster size distribution (CSD). This model predicts the emergence of steady-state CSDs in SPP systems. We test our theoretical predictions in simulations of SPP with nematic interactions and find that our simple kinetic model reproduces qualitatively the transition to aggregation observed in simulations.