秸秆颗粒冷态压缩成型过程的比能耗回归分析

对5种秸秆颗粒冷态压缩成型过程进行开式试验研究,将其压缩成型过程分为松散、过渡、压紧和推移4个阶段,回归了不同阶段的压力方程,采用Matlab软件计算出整个压缩成型过程中的比能耗值。以小麦秸秆为例,采用二次回归通用旋转组合设计,建立了压缩速度、物料含水率2个因素与比能耗的数学模型,结果表明,压缩速度的影响比含水率大,且二者均为负效应。     

解捆状玉米秸秆常温压缩成型试验研究

文章以解捆状玉米秸秆为原料,在含水率、成型套筒长径比不同的情况下,在柱塞液压式成型机上进行单因素试验,并利用体视显微镜观察成型块的微观结构,分析成型状态。试验结果表明:在常温状态下,解捆状玉米秸秆可以被压缩成型;当含水率为15%、成型套筒长径比为4.5时,成型效果最好,所得成型块的松弛密度为0.74 g/cm3;含水率相同,成型套筒长径比增大,成型压力随之增大;成型套筒长径比相同,随着含水率的增加,成型压力先增大后减小。     

生物质燃料的成型工艺及微观成型机理研究

为研究生物质物料粒度、含水率,成型模具长径比、开口锥度以及保压孔长度对成型燃料品质的影响,以玉米秸秆为研究对象,通过自行设计的不同尺寸的模具制备成型棒料,以成型棒料的松弛密度作为品质评价标准。当成型模具锥度为10°、长径比为5∶1、保压孔长度为30 mm,物料粒度为3.5 mm、含水率为16%时,成型燃料的品质最好,对成型设备的优化具有指导意义。同时,利用环境扫描电子显微镜对成型棒料的微观形貌进行观测,对比分析了不同成型条件下成型棒料的微观形貌,从微观角度研究了生物质燃料的成型机理,研究结果旨在为成型机成型孔的优化设计提供理论参考。     

秸秆冷态压缩成型微观结构变化的实验研究

采用扫描电子显微镜,在不同压缩成型条件下对3种秸秆冷态压缩成型前后微观结构变化进行实验研究,通过秸秆原料和颗粒燃料在纵横截面微观结构变化的对比分析,得出秸秆冷态压缩成型的微观结合方式,总结出压缩成型条件对秸秆微观结构的影响规律。实验结果表明:当压缩速度取40mm/min、秸秆原料为玉米秸秆时,冷态压缩成型效果最佳。     

木屑颗粒燃料冷态压缩成型参数试验研究

对杉木屑进行不同成型直径、含水率及压缩速度条件下的冷态压缩成型试验,分析多个影响因素对木屑成型试样的松弛密度、抗压强度及比能耗的影响。通过单因素影响试验分析表明,在含水率为16%和成型直径为10 ~ 12 mm时能获得较好的成型参数,压缩速度为40 mm/min时,可获得较大的松弛密度和抗压强度,但比能耗相对较大。通过设计三因素三水平正交试验,运用多指标综合加权评分法对试验结果进行分析,权重系数综合考虑松弛密度、抗压强度和比能耗的重要与次要程度,结果表明：木屑最佳成型因素水平组合为成型直径10 mm、含水率16%、压缩速度40 mm/min,此时木屑试样松弛密度、抗压强度和比能耗分别为0.91 g/cm³、315 N和30.20 J/g,综合加权评分值最高。     

生物质冷态压缩特性曲线分析

在不同含水率、不同压缩速度条件下,对6种不同的生物质原料进行了冷态压缩成型试验,并绘制出生物质成型压力一密度关系曲线.发现同一种生物质在含水率不同时的压力一密度曲线各不相同,但有一共同交点.在该交点前后水分对密度的影响相反.压缩速度对成型密度影响较大,在相同条件下,压缩速度越大,生物质成型密度越小.     

模辊式生物质压块成型模孔受力分析及参数影响研究

针对模辊式生物质压块成型机的成型模孔,通过理论分析和ANSYS仿真,研究了秸秆物料在模孔中的受力变化规律以及模孔参数对压强的影响,并建立了正交异性物料挤压成型的压强数学模型。通过正交试验,验证了模孔参数对压块成型的影响,并确定了玉米秸秆成型的最优参数组合。结果表明:秸秆物料在模孔内所受最大压强随锥角、长径比的增大而增大;物料在模孔中的成型过程可分为压缩、成型、保型3个阶段;在试验范围内,模孔的长径比、锥角、物料含水率及粒度均对秸秆压块的松弛密度影响显著,且影响顺序为长径比含水率粒度锥角;以松弛密度为评价指标时,最优参数组合为长径比6∶1、含水率15%、粒度5 mm、锥角10°。     

生物质颗粒燃料冷成型技术试验研究

对环模生物质颗粒燃料成型机影响成型的各主要因素进行了分析及试验研究,给出不同生物质原料、粒度、含水率、环模孔长径比等因素与颗粒成型率及吨料电耗的关系,找出生物质颗粒燃料的最佳成型条件。     

秸秆颗粒成型机吨料电耗影响因素的试验研究

对影响环模秸秆颗粒冷态成型机吨料电耗的主要因素进行了正交试验研究,得出了秸秆粒度、含水率、环模孔长径比三因素与吨料电耗的数学模型,并进行了三因素及两因素间的交互效应分析,通过Matlab软件编程计算,得出吨料电耗最低时的各因素最优组合,即:粒度为6mm,含水率为16%,环模孔长径比为5.2时,吨料电耗为102.33kW·h·t~(-1)。     

生物质稻壳压缩成型过程建模及优化

在生物质压缩成型燃料的品质指标中,除燃烧特性外,松弛密度是成型燃料的一个重要性能指标,它直接决定了成型燃料的使用、运输要求和贮藏条件。文章以生物质稻壳为研究对象,考虑稻壳成型过程中含水率和成型温度对松弛密度的影响,依据最小二乘支持向量机建立了稻壳压缩成型过程模型,并进行了验证。在此基础上,建立了压缩成型过程的优化目标函数,旨在寻找成型燃料松弛密度最大时,含水率和成型温度两个控制量应满足的优化目标值。结果表明,该模型具有较好的拟合效果,可有效模拟稻壳压缩成型过程特性,且当稻壳含水率为6.631 4%,成型温度为140.991 5℃时,成型燃料松弛密度可达到最大值1.281 6 g/cm3。     

隔膜特性对氢气电化学压缩能耗的影响

文章选取Nafion 211和Nafion 117膜作为电化学压缩隔膜,通过仿真建模方法研究了隔膜特性对电化学压缩机压缩性能的影响。研究结果表明:隔膜欧姆阻抗对电压效率影响显著,隔膜气密性对电流效率影响显著;与Nafion 117膜相比,将Nafion 211膜应用于电化学压缩机时,电化学压缩机能够获得更高的能量效率,当工作电流为0.5 A/cm^2,压缩比为3时,等温压缩效率最高可达到50%。将以Nafion 211膜为隔膜,工作电流为2 A/cm^2的电化学压缩机用于制氢厂的管束车充装,当气源压力为2 MPa,管束车压力由5 MPa充装至20 MPa时,平均能量效率为35%,综合平均电耗为2 kW·h/kg,比目前常用的机械往复式压缩机的电耗降低了30%以上。     

Automatic high-pressure H2 generation up to 40 MPa through HCO3−/CO32− enhanced Al–H2O reaction

For the practical application, storage, and transportation of hydrogen energy, compressed high-pressure H₂ is generally required, which consumes large amounts of energy. In this research, an automatic high-pressure H₂ production system based on the HCO₃^? enhanced Al–H₂O reaction is established, in which, over 40 MPa H₂ at 300 °C (25 MPa at 25 °C) is successfully obtained without using any compressing facilities. Energy balance calculation reveals that although this reaction requires a high temperature, it is highly exothermic (145.9 MJ/kg H₂). Since heating the reactants to the desired reaction temperature only needs an energy of 55.3 MJ/kg H₂, the energy requirement of this reaction can be self-supported. In addition, waste Al-can is further tested for the high-pressure H₂ generation to realize a waste material recovery simultaneously, and over 40 MPa H₂ at 300 °C can also be obtained with the addition of Na₂CO₃. This research proposes a new way of automatic high-pressure H₂ production from renewable resources, which can promote the practical large-scale hydrogen energy utilization.     

Computational Analysis of a Variable Ejector Flow

The present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. The variable ejector is a facility to obtain specific recirculation ratio under a given operating pressure ratio by varying the ejector throat area ratio. The numerical simulations are carried out to provide an understanding of the flow characteristics inside the variable ejector. The sonic and supersonic nozzles are adopted as primary driving nozzles in the ejector system, and a movable cone cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio. The numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged Navier-Stokes equations. The results show that the variable ejector can control the recirculation ratio at a fixed operating pressure ratio.     

增压直喷汽油发动机早燃现象改善的研究

低速大负荷早燃现象是制约增压直喷汽油发动机低速性能提升的主要因素之一,早燃易导致发动机火花塞烧蚀、活塞熔顶等质量问题,所以在发动机设计开发过程中必须对早燃问题加以优化改善。阐述了早燃产生的机理,更换不同机油、改变压缩比以及空燃比进行试验,结果表明：更换机油以及改变空燃比能够降低早燃频次,改变压缩比对早燃无影响。     

Parametric study on the heat transfer characteristics in a circular tube with helical tape insert under laminar flow conditions

In the present study, the effect of a helical coiled tape on the heat transfer characteristics in a tubular heat exchanger has been studied. Numerical analysis is carried out in a tubular heat exchanger with a helical coiled tape insert under laminar flow conditions. The heat transfer characteristics, like Nusselt number (Nu) and friction factor (f), have been determined. Numerical modeling is undertaken and validated using analytical results. To study the parametric variation, simulation is carried out for different width ratios (WR) and twist ratios (TRs). It is observed that Nu increases as the WR is increased and the TR is reduced. The thermohydraulic performance index (THPI) is measured and found to be higher for a combination of a higher WR and a higher TR. From the tested values, it is seen that for a combination of WR = 3 and TR = 1.25, the maximum THPI was observed. It is concluded that both the tape width and pitch will significantly influence the thermohydraulic characteristics in a tubular heat exchanger with a helical tape insert inserted.     

Influence of equivalence ratio and H2 blended ratio on explosion propagation characteristics of DME/H2 blended gas in closed narrow space

To reveal the explosion risk and propagation law of dimethyl ether (DME)/hydrogen (H₂) blended gas, the explosion propagation characteristics of DME/H₂ blended gas under different equivalence ratio (Φ) and hydrogen blended ratio (λ) was investigated based on experimental research and theoretical analysis. The results show that the peak overpressure (P_p), the peak pressure rise rate (dP/dt)_p and the peak shock wave propagation velocity (V_p) show an increasing and then decreasing trend with the increase of Φ, and reach the maximum at Φ = 1.0. The effect of a little addition of H₂ on the explosion hazards of blended gas is small, but when λ > 10%, the explosion hazards increase significantly. The magnitude of increase of P_p, (dP/dt)_p and V_p is different with the increase of λ. Compared with the enhancement effect on P_p and (dP/dt)_p, the enhancement effect on V_p is more obvious with the continuous blend of H₂. Comprehensive analysis of the thermodynamic and chemical kinetic parameters of H₂, the chemical kinetic parameters of H₂ play a dominant role in the explosion risk of hydrogen-blended gases.     

太阳光谱选择性吸收涂层制备工艺探讨

探讨粘结层、吸收层、减反射层的制备工艺及基底粗糙度状态对太阳选择性吸收涂层性能的影响。采用磁控溅射法,以SS/AlN涂层为例,制备太阳光谱选择性吸收涂层,并测试性能。结果表明：合适的制备工艺可以提高膜层的结合力和涂层的整体性能,胶带粘贴无脱落,吸收比96%,500℃发射比10.5%,并证实基底的粗糙度对涂层的发射率基本无影响。