Approbation of an innovative method of pretreatment of dark fermentation feedstocks

According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen.     

Enhanced heat transfer in rectangular duct with punched winglets

Thermal performance of a heat exchanger duct with punched winglets(PWs) mounted on the upper duct wall has been examined for Reynolds number(Re) ranging from 4100 to 25,500. In the present experiment, two types of PWs: punched delta-and elliptical-winglets(P-DW and P-EW) with four punched-hole sizes were tested at a fixed attack angle, optimal relative pitch and height. Also, data of solid delta-and elliptical-winglets(DW and EW) were included for comparison. The investigation has shown that the P-DW yields higher thermal-performance enhancement factor(η) than the P-EW. Although the solid DW and EW with no punch have the highest heat transfer and friction loss, the PWs yield better η than the solid ones. For PWs, the P-DW with smaller hole size has the peak heat transfer and friction loss around 5.7 and 40 times over the smooth duct, respectively but the optimum η of 2.17 is seen for the one with a certain hole size. The PWs provide η at about 5%–8% above the solid winglets.     

Hydrogen mixing augmentation mechanism induced by the vortex generator and oblique shock wave in a scramjet engine

The mixing process between the fuel and the incoming air is extremely important for the engineering implementation of the scramjet engine. In the current study, the vortex generator coupled with the oblique shock wave is utilized to promote the hydrogen mixing process in a supersonic crossflow. The configurations of the vortex generator are put into investigation, namely typical ramp, split ramp and ramp vane. Some parameters are provided to evaluate the flow field properties quantitatively. The obtained results predicted by the three-dimensional Reynolds-average Navier-Stokes (RANS) equations show that the method of shock wave/jet shear layer interaction coupled with the vortex generator can effectively improve the mixing efficiency. Different vortex generator structures all have great effect, especially for Case SR (split ramp), with the mixing efficiency raised by 36.27%. The streamwise vorticity plays an important role in the mixing process.     

涡流空气分级机叶片间流场的数值模拟研究

根据等速旋转坐标系中的动量方程和连续方程,运用PHOENICS程序对转子叶片间流场进行数值模拟,通过数值模拟的结果分析了转速、风量及转子结构对分级性能的影响。     

基于MSP430系列单片机热量表的设计

介绍了热量表的技术要求及控制核心,对以MSP430系列单片机作为控制核心的热量表的硬件结构及主程序进行了研究。     

海洋独立支撑钢管桩的涡振研究

对在水流、波浪力作用下海洋独立支撑结构所产生的涡振进行非线性研究.该研究的目的是通过改变独立支撑结构自振频率来控制结构产生的涡振,以避免结构产生涡振破坏.提出涡振概念;分析独立支撑结构1产生涡振条件、作用荷载、涡振频率以及振动方程的解.结果表明通过改变独立支撑结构EI值或采取一些特殊措施,增加结构的自振频率,来避免其在施工过程中产生的涡振破坏,对实际工程具有重大理论价值.     

腰轮流量表计量过程中窜流现象研究

对某计量偏差问题进行探讨,提出腰轮流量表计量过程中天然气窜流现象。分析天然气在腰轮流量表内反向流动产生的原因、判断方法以及预防措施,提出了腰轮流量表设计和安装的建议。     

基于气体超声波流量计的间歇激励和信号处理

为了提高气体超声波流量计系统的响应速度,提出一种新的基于相邻峰值最大差值的气体超声流量计信号处理方法。为了进一步提高该信号处理方法的测量精度,又提出一种新的间歇式激励方法。采用间歇式激励方法能得到相邻峰值差值较大的回波信号,并且在不同流量下,相邻峰值最大差值的相对位置始终保持不变。在实际测量中,通过回波信号中相邻峰值最大差值的位置,确定回波信号的到达时刻,进而计算出超声波传播时间,得到气体流量。将间歇式激励方法和基于相邻峰值最大差值的信号处理方法在硬件系统上进行实时实现,并进行标定实验,结果验证了激励方法配合信号处理方法的高效性。     

流型频繁切换下科氏质量流量计驱动特性研究

在科氏质量流量计测量过程中,流量管振动幅值的控制很重要。当单相流与气液两相流频繁切换的情况发生时,使用当前的控制方法流量管会出现振动幅值大幅衰减和超调的问题。为此,设计了一套实验方案,进行实验,分析了出现该问题的原因。针对该问题,提出变驱动周期的方法和变积分限幅值的方法,在所研制的数字式科氏质量流量变送器上实时实现,并进行实验验证。实验结果表明,变驱动周期的方法有效地降低了单相流切换到气液两相流时流量管振动幅值衰减的程度,变积分限幅值的方法很好地解决了气液两相流切换到单相流时流量管振动幅值大幅超调的问题。     

基于回波峰值拟合的气体超声流量计信号处理

针对从气体超声波流量计回波信号中难以确定到达时刻,而仪表又要求具有较高实时性的问题,提出一种基于回波上升段峰值拟合的气体超声流量计信号处理方法,以及拟合峰值范围的确定方法。首先根据拟合峰值范围,在回波信号的上升阶段,选取若干个峰值点,对各峰值点进行最小二乘拟合,得到特征直线,将该直线与X轴的交点作为特征点,确定回波信号的到达时刻,进而计算出超声波传播时间,得到气体流量。研制实现基于回波上升段峰值拟合的气体超声流量计,进行标定实验,以验证方法和仪表的有效性。