热声斯特林发电系统的实验研究

本文介绍了一台由热声斯特林发动机及其驱动的直线发电机组成的热声斯特林发电系统原理样机.一方面为满足发电机与发动机间体积流率和相位的匹配要求,另一方面为了能在直线发电机活塞处获得较好的压力波与体积流率间相位关系、提高直线发电机的电功输出能力,装置保留了发动机原有的锥形谐振管.初步实验以氦气为工质,在2.5MPa平均压力、64Hz工作频率下,获得了97W的电功.本文还分析了该热声发电系统的效率,得出直线发电机声电转换效率超过了0.8.然而由于谐振管耗散了大量的声功,目前整机的热电转换效率还较低.     

Understanding the effect of inhomogeneous fuel–air mixing on knocking characteristics of various ethanol reference fuels with RON 100 using rapid compression machine

We investigated the effect of inhomogeneous mixing of a fuel–air mixture in a spark-ignition engine on knocking characteristics and the dependency of the effect on the fuel, especially for various ethanol reference fuels with a fixed RON of 100. We assumed that a locally lean spot and rich spots exist in the end gas owing to inhomogeneous mixing and calculated their thermodynamic states with a multizone spark-ignition engine simulation. Subsequently, the ignition delay around the state was measured using a rapid compression machine at varying temperatures and equivalence ratios. The obtained results were processed to calculate ξ, which is the ratio of sound speed to auto-ignition propagation speed, and $?$, defined as the time required for acoustic front to exit the hot spot divided by the excitation time. Then, we analyzed the knocking occurrence and intensity from the locally lean spot and rich spots based on Zel'dovich and Bradley's ξ–$?$ theory. Our results show that the lean spot has a shorter ignition delay than the stoichiometric mixture (ξ?>?0) regardless of the ethanol content, whereas the rich spot does not (ξ?<?0), implying that only the lean spot can initiate knocking. This is because the temperature of the lean spot is higher than the surrounding mixture owing to its higher specific heat ratio and less charge cooling effect. In addition, the knocking intensity from the lean spot is found to be maximized with ERF0, showing the largest ${\xi }^{?2}$ value. Further analysis was conducted by dividing ξ into the effect of the temperature gradient, ξ_T, and that of the equivalence ratio gradient, ξ_?. Consequently, we found that the magnitude of ξ_T is related to the activation energy of the fuel, while that of ξ_? is determined by the dependency of the pre-heat release characteristics of the fuel on the equivalence ratio.     

Investigation of the structure of detonation waves in a non-premixed hydrogen–air rotating detonation engine using mid-infrared imaging

The structure of detonation waves propagating through the annular channel of an optically accessible non-premixed rotating detonation engine (RDE) are investigated using mid-infrared imaging. The RDE is operated on hydrogen–air mixtures for a range of air mass flow rates and equivalence ratios. Instantaneous images of the radiation intensity from water vapor are acquired using a mid-infrared camera and a band-pass filter (2.890?±?0.033?µm). The instantaneous mid-infrared images reveal the stochastic nature of the detonation wave structure, position and angle of oblique and reflected shock waves, presence of shear layer separating products from the previous and current cycles, and extent of mixing between the reactants and products in the reactant fill zone in front of the detonation wave. The images show negligible signal directly in front of the detonation waves suggesting that there is minimal mixing between the reactants and products from the previous cycle ahead of the detonation wave for most operating conditions. The mid-infrared images provide insights useful for improving fundamental understanding of the detonation structure in RDEs and benchmark data for evaluating modeling and simulation results of RDEs.     

ESR and calculations on electronic structure of phenalenyl and phenalenyl derivative radicals

Calculations on electronic structure of the perinaphthenyl radical and phenalenyl derivative radicals responsible for the composition of the ESR spectrum of marine diesel under heating were performed to obtain support for the experimental ESR results. The parameters calculated were the hyperfine coupling constants (A), which were then used for comparison with the experimental data. The energy‐minimized structures were obtained using the density functional theory method. In all cases, the symmetry system was taken into account in theoretical calculations. The differences between experimental and theoretical values were below 7% for nearest hydrogens in molecules, named hyperfine coupling constant A (first neighbors) and 18% for farthest hydrogens atoms named hyperfine coupling constants A′ (second neighbors), for all structures analyzed. Copyright © 2014 John Wiley & Sons, Ltd.     

Investigation and optimization of the recovery of coal fines using oil agglomeration process: Use of waste oils from different sectors

The high cost of the bridging liquid subdues the implementation and commercialization of oil agglomeration process. To overcome this problem, waste oils from different sectors were used in this present study. The performance of the process was assessed based on the responses like ash rejection and organic matter recovery. The aim of the present study was to investigate the usage of waste oils from different sectors and to optimize and analyze the behavioral pattern showcased by different variables (pulp density, oil dosage, agglomeration time and oil type) using response surface methodology (Box-Behnken design). Experimental investigation shows that the optimum pulp density, oil dosage, agglomeration time and oil type condition obtained as 3%, 15%, 15?min and waste engine oil, respectively. At optimum condition, the % ash rejection and % organic matter recovery obtained as 63.94% and 81.8%, respectively.     

柴油溶剂中脂肪酶催化高酸值废油脂酯化制备生物柴油

采用0＃柴油作为反应溶剂,利用固定化脂肪酶催化高酸值废油脂与甲醇酯化反应制备生物柴油。来源于Candida antarctica的固定化脂肪酶Novozym435在0＃柴油溶剂中具有极高的催化活性。以酸价高达157×10-3的废油脂为原料,废油脂质量比10%的Novozym435,甲醇与废油脂初始摩尔比2∶1,0＃柴油与废油脂质量比5∶1,摇床摇速170r/min,50℃下反应2h甲酯化率可达95.10%。0＃柴油作为反应溶剂有效地溶解了高酸值废油脂和甲醇,降低了反应体系的黏度和消除了甲醇对Novozym435的负面影响,提高了Novozym435的稳定性。同时,0＃柴油溶剂对未脱胶废油脂中残留的对脂肪酶有害的磷脂等胶类物质具有一定的稀释作用。该工艺省却了溶剂蒸馏的繁琐工序,直接得到脂肪酸甲酯和石化柴油的混合燃料。     

Hysteretic behavior induced by an electroacoustic feedback loop in a thermo-acousto-electric generator

An active control method of the spatial distribution of the acoustic field is applied in a thermo-acousto-electric generator. An auxiliary acoustic source is used to force the self-sustained thermoacoustic oscillation in order to control the thermoacoustic amplification. The auxiliary source consists of a loudspeaker, located inside the loop-tube close to the main ambient heat exchanger, and supplied with a delayed signal through an electric feedback loop, comprising a phase-shifter and an amplifier, connected to a reference microphone. Experiments are performed on a prototype engine working with air at a static gauge pressure of 5 bars. Experimental results demonstrate how it is possible to tune the acoustic oscillations in order to increase the global performance of the generator, compared to the case without control, as well as the existence of a hysteretic behavior induced by the electroacoustic feedback loop itself, which leads to a discrepancy between the onset heat input and the offset one.     

A new green system of HPW@MOFs catalyzed desulfurization using O2 as oxidant

A series of crystalline compounds were obtained from simple one-step hydrothermal reaction of copper nitrate, benzentricaboxylate and different Keggin polyoxometalates. Phosphotungstic acid immobilized in host matrix was selected for the first time as a recyclable and efficient catalyst in oxidative desulfurization process, under eco-sustainable conditions supported by the green oxidant O₂ and the green extracting agent distilled water. The efficiency of desulfurization with air was studied and it is possible to use air as green oxidant in desulfurization. Moreover, the catalyst is effective for the desulfurization of real diesel.     

Deep desulfurization of diesel by selective oxidation using amphiphilic paradodecatungstate catalyst

An amphiphilic paradodecatungstate catalyst, [(C₁₈H₃₇)₂N(CH₃)₂]₉[NaH₂W₁₂O₄₂] was prepared and characterized by Fourier transform infrared spectroscopy, UV–visible spectrum, differential thermal analysis, and thermogravimetric analysis. The amphiphilic catalyst exhibits very high catalytic activity that dibenzothiophene (DBT) in model diesel can be oxidized into dibenzothiophene sulfones using hydrogen peroxide as an oxidant. The reactivity of sulfur compounds decreased in the order of DBT > 4,6-DMDBT > BT > 5-MBT. The reaction rates of these sulfur compounds are sensitive to the electron density on sulfur atoms and the steric hindrance of the substituted groups of sulfur compounds. The sulfur level of a commercial diesel after desulfurization can drop from 200 ppm to about 12 ppm.     

关于教材中热力学第二定律的若干逻辑问题

指出了一些物理化学教材在叙述热力学第二定律时存在的若干逻辑问题,表明它们违反了逻辑学中的同一律、不矛盾律和充足理由律。并从历史的角度简述了Carnot循环和Carnot机效率公式的由来。