废气再循环对二甲醚/天然气双燃料均质压燃燃烧过程和排放特性的影响

在一台单缸直喷式柴油机上研究了冷却废气再循环(EGR)对二甲醚(DME)／天然气(CNG)双燃料均质压燃(HCCI)燃烧过程和排放的影响．结果表明，EGR率加大，着火时刻滞后，放热速率降低，燃烧持续期延长，DME比例加大，着火始点提前，放热率峰值上升，燃烧持续期缩短，EGR率增大，发动机“失火”和爆震燃烧的DME比例增大，但“失火”和爆震燃烧之间的DME比例区间变宽，EGR可以拓宽HCCI发动机的工况范围．对应不同比例的EGR，有一个热效率最佳的DME比例区域．HC排放和CO排放随EGR率的增高而增加，随DME比例的增大而降低．NO。排放在不发生爆震的情况下保持在极低的水平．因此，控制DME比例和EGR率是控制DME／CNG双燃料HCCI发动机燃烧过程、性能和排放的关键。     

废气再循环对二甲基醚均质压燃燃烧过程影响的试验研究

在一台单缸发动机上进行了废气再循环(EGR)对二甲基醚(DME)均质压燃(HCCI)燃烧过程影响的试验研究。结果表明，EGR比例小于20％对运行最大负荷工况范围影响不大；采用高比例EGR可以拓宽DME均质压燃运行工况范围，随着EGR率增大，HCCI运行的最大负荷工况增大，着火燃烧时刻推迟，燃烧放热率降低，缸内最大爆发压力降低，发动机热效率增大；EGR率小于75％，HC排放略有降低或相当，EGR率为75％时，HC排放显著增加；EGR率大于25％，随着EGR率增加，CO排放增大，小负荷工况尤其明显，在中高负荷工况，EGR率对CO排放影响较小。     

甲醇缸内直喷热氛围燃烧的试验研究

在单缸直喷式柴油机上进行了二甲醚(dimethyl ether,DME)气道喷射和甲醇缸内直喷的甲醇热氛围燃烧试验研究．结果表明,该燃烧方式呈现分布式放热规律,燃烧过程可分为DME低温放热、高温放热和甲醇扩散燃烧 3个阶段．随负荷的增加,实现稳定燃烧的最小DME比例减小．随DME比例减小,DME高温放热和甲醇燃烧滞后．在稳定燃烧的情况下,随DME比例的增大,燃烧效率和热效率降低,HC和NOx排放呈上升趋势,而CO排放先升高后降低．综合考虑,采用最小比例DME有利于提高其热效率、降低排放．此时热效率、HC排放与原柴油机相当, NOx降低约50％,但CO排放相对原柴油机有较大幅度的增加．     

甲醇/二甲醚双燃料发动机全负荷范围优化策略的研究

在不同燃烧方式研究的基础上,提出了甲醇/二甲醚(DME)双燃料发动机在全负荷范围内实现高效清洁燃烧的优化策略.即在低负荷工况,采用单一DME加大比例废气再循环(EGR)的HCCI(Homogeneous Charge Compression Ignition)燃烧以获得相对高的热效率;在中高负荷工况,采用甲醇/二甲醚双燃料HCCI燃烧方式实现高效低Nox排放的清洁燃烧;在大负荷工况,采用甲醇晚喷实现DME气道喷射与甲醇缸内直喷复合燃烧方式以保证高的功率输出.     

DME预混比和柴油供油提前角对PCCI发动机性能影响

在一台2105柴油机上采用进气道预混DME一缸内直喷柴油的复合方式实现PCCI燃烧,研究了DME预混比和柴油供油提前角对预混合压燃(premixed charge compression ignition,PCCI)发动机燃烧、排放特性和燃油经济性影响。研究结果表明:随DME预混比增加,PCCI发动机燃烧始点逐渐前移,缸内压力峰值增大,放热过程由两阶段放热变成三阶段放热,且放热率曲线整体前移,NO_x、碳烟排放和当量燃油消耗率均降低,而CO和HC排放及有效热效率均逐渐升高;随柴油供油提前角增大,PCCI发动机燃烧始点相应提前,缸内压力峰值逐渐增大,放热过程由三阶段放热变成两阶段放热,NO_x排放大幅升高,碳烟排放明显下降,CO和HC排放及当量燃油消耗率先下降后增加,而有效热效率则先升高后降低,     

喷射参数对二甲醚PPCCI发动机燃烧与排放特性的影响

在一台6缸增压电控共轨二甲醚发动机上进行试验,研究了预喷时刻、预喷燃料量、喷射压力、主喷时刻等喷射参数对二甲醚部分预混合充量压缩燃烧(PPCCI)发动机燃烧与排放特性的影响。试验结果表明:随预喷时刻提前,缸内压力峰值降低,二甲醚发动机缸内燃烧由两阶段放热转变为PPCCI三阶段放热,氮氧化物(NOx)排放显著降低,HC和CO排放升高;随预喷射燃料量增加,缸内压力峰值及预混合燃烧的冷焰反应和热焰反应速率明显增大,NOx排放逐渐降低,HC和CO排放显著升高;随喷射压力降低,预混合燃烧热焰反应速率增加,主喷扩散燃烧始点推迟,扩散燃烧放热率峰值和NOx排放明显降低,HC和CO排放升高;随主喷时刻推迟,预喷预混合燃烧几乎没有变化,主喷扩散燃烧延后,缸内压力峰值和放热率峰值降低,NOx排放显著降低,HC和CO排放升高。     

甲醇质量比对防爆柴油机预混合引燃模式燃烧特性的影响

针对甲醇、聚甲氧基二甲醚和F-T柴油的各自优势,为提高能量转化效率,在改造后的CY25防爆柴油机上研究甲醇质量比对甲醇/聚甲氧基二甲醚、甲醇/F-T柴油预混合引燃模式燃烧特性的影响。研究结果表明:随着甲醇质量比的增加,甲醇/聚甲氧基二甲醚燃烧模式的比油耗增大,有效热效率降低;在甲醇质量比小于60%时,随着甲醇质量比的增加,甲醇/F-T柴油燃烧模式的比油耗减少,有效热效率升高;随着甲醇质量比的增加,两种预混合引燃模式的燃烧相位均后移,与单燃料原机燃烧模式相比,甲醇/聚甲氧基二甲醚燃烧模式下的缸内压力峰值和瞬时放热率峰值的最大升幅分别为9.5%和142%,甲醇/F-T柴油燃烧模式下的缸内压力峰值和瞬时放热率峰值的最大升幅分别4.24%和99.7%。     

EGR对GDI汽油机燃烧和排放特性的影响

通过改变EGR率,在一台GDI汽油机上进行了EGR对燃烧和排放特性影响的试验.结果表明:加入EGR后,燃烧持续期增大;且随EGR率增加,着火时刻先提前后延迟;放热率曲线峰值逐渐降低且后移,放热过程迟缓,缸内压力和缸内温度逐渐降低,压力峰值前移.此外,EGR率增加导致NOx排放逐渐降低,最高降低比例达80%以上,THC和CO排放逐渐增加,最大增加比例分别约为25%和7%.GDI汽油机排气颗粒物呈核态和积聚态的双峰分布;积聚态颗粒物峰值数密度随EGR率升高逐渐降低,核态颗粒物峰值数密度和颗粒物总数量浓度在加入EGR后均明显增加,核态和积聚态颗粒物峰值粒径受EGR的影响较小.     

预混合比例实时优化控制正庚烷复合HCCI燃烧

在一台单缸柴油机上试验研究了预混合比例对正庚烷复合HCCI燃烧的影响,并在各个负荷下实现预混合比例的优化控制.结果表明:复合HCCI燃烧呈现三阶段放热模式,并且随着预混合比例的增大,复合HCCI燃烧第2阶段高温反应着火提前,燃烧持续期缩短,第3阶段扩散燃烧滞燃期缩短,同时缸内最高压力和最大压力升高率均升高.复合HCCI的NOx排放与直喷相比显著降低,且随预混合比例的增大先降低后升高.同时,复合HCCI的CO排放随预混合比例增大先增大后减小,而HC则随预混合比例增大而增大.通过预混合比例优化控制,复合HC-CI燃烧能够显著拓展负荷范围,并且保持较高的热效率.     

内外部EGR控制二甲醚发动机的燃烧与排放

在一台改造过的2-135柴油机上通过气道引入二甲醚和CO2,模拟实现了内外部EGR控制二甲醚发动机燃烧与排放的试验研究.结果表明,燃烧过程包括二甲醚HCCI燃烧和缸内喷雾的预混及扩散燃烧;燃烧方式主要受内外部EGR率的影响而呈现不同的放热特征.缸内直喷燃烧采用较大供油提前角时,在较小内外部EGR率下可使NOx排放控制在50 x 10-6以下;在较小供油提前角和微量内外部EGR率下可实现二甲醚发动机两级预混合低温燃烧模式,NOx排放接近于零.采用适当的内外部EGR率,二甲醚发动机经济性与NOx排放可获得较好的折中.     

Effect of corrosion inhibitors on hydrogen uptake by Al from NaOH solution

Corrosion rate, hydrogen permeation rate (hydrogen uptake) and stress corrosion cracking of Al were studied in NaOH solutions, pure and with the addition of H₃BO₃, EDTA, KMnO₄ and As₂O₃. The presence of the studied species in electrolyte and the implantation of Al surface with B⁺ ions inhibited corrosion. Hydrogen uptake was found to be promoted or inhibited by means of studied species, depending on the method of their introduction into the base solution and on the applied polarization. The observed different influence of corrosion inhibitors on the hydrogen uptake was associated with the different chemical composition and structure (revealed by XPS analysis) of the surface films, formed on Al under the various conditions. Under similar polarization conditions, the presence of H₃BO₃ in the base solution similarly affected the hydrogen uptake by Al and the susceptibility to stress corrosion cracking of the metal.     

废气再循环与燃料辛烷值对均质压燃发动机性能和排放影响的试验研究

在一台单缸直喷式柴油机上研究了废气再循环（EGR）对不同辛烷值燃料均质压燃（HCCI）发动机性能和排放特性的影响。结果表明，混合气较稀，EGR对指示热效率影响较小，其影响和燃料辛烷值有关；混合气变浓，EGR对指示热效率的影响增大。不同辛烷值燃料最高指示热效率出现在高EGR率、混合气较浓的区域，并且靠近爆震燃烧边界，辛烷值为60的燃料最高指示热效率最高，并且覆盖的工况区域最宽。高EGR率区域，EGR对HC排放的影响十分明显，EGR率升高，HC排放急剧增大，而且随着燃料辛烷值增大，这种趋势越明显；CO排放与缸内燃烧温度有较大的相关性，EGR率升高，CO排放升高。NOx排放出现急剧升高的“拐点”是判断HCCI爆震燃烧的一个重要判据，EGR率增大，“拐点”出现的混合气浓度增大，在正常工作范围内，NOx排放极低，EGR对NOx排放几乎没有影响。     

生物合成聚羟基脂肪酸酯（PHA）的研究进展

聚羟基脂肪酸酯（PHA）是微生物细胞在碳氮失衡的情况下合成的一种聚酯,具有优异的生物降解性和相容性以及多种材料学性能,是一类可替代传统塑料的新型生物塑料。目前生物合成PHA主要以微生物发酵为主,其次还有转基因植物法和活性污泥法等。本文对PHA的生产现状及其生物合成路径和方法的研究进展进行了综述。     

Performance analysis of the tracking of the global extreme on multimodal patterns using the Asymptotic Perturbed Extremum Seeking Control scheme

This paper presents the capability of the Asymptotic Perturbed Extremum Seeking Control (aPESC) scheme to track the Global Extreme on multimodal patterns. The multimodal patterns are simulated based on power characteristics generated by a photovoltaic (PV) array under Partial Shading Conditions (PSCs). The aPESC scheme is tested to evaluate the performance of locating, searching and tracking of the Global Maximum Power Point (GMPP). The following performance indicators such as the searching resolution, tracking accuracy, tracking efficiency, and tracking speed are used to compare the performance of the GMPP tracking (GMPPT) algorithms. The aPESCH1 scheme proposed has been implemented in MATLAB/Simulink package to evaluate the performance indicators mentioned above. The results prove that the proposed aPESCH1 scheme is effective and simple to be implemented.     

Impact of FACTS devices on exercising market power in deregulated electricity market

In power system studies, congestion in transmission lines and utilization of flexible alternating current transmission system (FACTS) devices are closely associated. These devices are very important due to their role in power delivery system enhancement. It is to be noted that the generation companies can exercise their market power which depends on the line flows, line constraints, generators’ location and its share to the individual loads. This issue cannot be overlooked as it creates monopoliness which is against the deregulated market policy. The objective of this paper is to study the impact of market power when FACTS devices like thyristor controlled switching capacitor (TCSC) and thyristor controlled phase angle regulator (TCPAR) are used under steady state operation. The market power is determined using nodal must-run share (NMRS) index for the standard IEEE 14-bus system with and without the above FACTS devices and the results obtained are compared. All the above simulations are conducted in a MATLAB 7.9-R2009b environment.     

The effect of using two PCMs on the thermal regulation performance of BIPV systems

Building Integrated Photovoltaics (BIPVs) is one of the most promising applications for Photovoltaics (PVs). However, when the temperature in the BIPV increases, the conversion efficiency deteriorates. A PV/PCM system using Phase Change Materials (PCM) for BIPV thermal control has been experimentally and numerically studied previously. One of the main barriers for this application is how to improve the low thermal conductivity of the PCM in order to achieve a quick thermal dissipation response with longer thermal regulation in PVs. Although the metal fins inserted inside the PCM can improve the heat transfer, the thermal regulation period declines as the volume of the PCM is substituted by the metal mass of the PV/PCM system. A modified PV/PCM system integrated with two PCMs with different phase transient temperatures for improving the heat regulation needs to be investigated. The use of combinations of PCMs, each with a set of different phase transient temperatures, is expected to enhance the thermal regulation effect of the PV/PCM system and lengthen the thermal regulation time in PVs. In this study a developed PV/PCM numerical simulation model for single PCM application has been modified to predict the thermal performance of the multi-PCMs in a triangular cell in the PV/PCM system. A series of numerical simulations tests have been carried out in static state and realistic conditions in UK. The thermal regulation of the PV/PCM system with a different range of phase transient temperature PCMs has been discussed.     

电动车最大效率节能控制技术的研究

根据电动车电驱动系统的基本行性,从提高效率,节约能源的角度出发,综述了电动力用感应电动机驱动系统最大效率节能控制的研究现状,并指出了目前最大效率节能控制技术上的一些问题,然后分析了感应电动机驱动系统最大效率节能控制的关键问题,最后给出了作者在电动车最大效率节能控制技术的一些研究成果。     

Study on hydrogen storage properties of LaNi3.8Al1.2−xMnx alloys

Effects of the Mn substitution on microstructures and hydrogen absorption/desorption properties of LaNi_3.8Al_1.2−xMn_x (x = 0.2, 0.4, 0.6) hydrogen storage alloys were investigated. The pressure-composition (PC) isotherms and absorption kinetics were measured in a temperature range of 433 K ≤ T ≤ 473 K by the volumetric method. XRD analyses showed that with the increase of the Mn content in the LaNi_3.8Al_1.2−xMn_x alloys, the lattice parameter a was decreased, c increased and the unit cell volume V reduced. It was found that the absorption/desorption plateau pressure was increased and the hydrogen storage capacity was enhanced with the increase of Mn content. The absorption/desorption plateau pressure of the alloys was linearly changed with the Mn content x and the lattice parameter a, while the hydrogen storage capacity was linearly increased with the increase of c/a ratio. It was also found that the slope factor S_f was closely correlated with the lattice strain of the alloys.     

Effect of pressure and sample type on decomposition of ammonium perchlorate

Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and high pressure DSC (HP-DSC) have been used to study the thermal decomposition of ammonium perchlorate samples in the form of 2-mm monocrystals, 265- and 3-μm powders, and pellets pressed at 4 and 7 tons. HP-DSC runs have been performed to determine the effect of pressure on decomposition. TGA and DSC techniques have been employed to examine the effect of sample type on the kinetics of the process. The effects have been evaluated as changes in the temperature, reaction heat, and rate of decomposition. Isoconversional kinetic analysis has been carried out to detect changes in the effective activation energy of the process. These measurements and calculations show sublimation and decomposition for ammonium perchlorate to be highly dependent on sample preparation and applied pressure. This calculation finds that the activation energy for the early stages of sublimation/decomposition for all samples starts at ∼120 kJ mol⁻¹, which is followed by a dramatic drop to ∼60 kJ mol⁻¹ at 20% mass loss. The activation energy for the later stages of sublimation/decomposition varies with sample type ranging from ∼95 to 145 kJ mol⁻¹.