内混式气液雾化喷嘴雾滴粒径的实验研究

雾滴粒径是衡量喷嘴雾化性能的一个重要指标，为了提高喷嘴的雾化效果，对一种新型的内混式气液雾化喷嘴进行了测试。实验采用4组不同几何结构参数的喷头，研究了气孔直径、气孔数、气液流交角和喷孔直径等喷嘴结构及气压、气液比、混合室压力等工况参数对MMD（质量中值粒径）的影响；并且进一步对实验结果进行了定性和定量分析，得出具有较好雾化性能的喷嘴结构和工况参数，为喷嘴的结构优化和使用提供了依据。     

海洋温差能向心透平的气动设计及性能研究

通过对7.5 kW海洋温差能向心透平的蜗壳、喷嘴和叶轮进行气动设计,模拟研究了透平在设计工况及非设计工况下的气动性能。采用经验参数及遗传算法优化方法对透平的一维参数进行设计,得到一维设计结果,并据此对蜗壳、喷嘴和叶轮进行三维设计,得到透平的气动结构造型。利用CFD技术模拟研究了透平的三维流场及性能,得到透平在设计工况及非设计工况下的性能,模拟结果表明:在设计工况下,透平效率为86.5%;在非设计工况下,透平效率随着叶轮转速的增加而增大,但增加至设计转速后,透平效率增加幅度较小;随着进口温度的升高,透平效率逐渐增大;当进口压力为设计工况压力时,透平效率存在最大值;非设计工况下的透平功率基本与叶轮转速、进口压力和进口温度均呈正相关;设计工况下的最佳喷嘴-叶轮相对径向间隙为0.05,可变喷嘴叶片安装角为35～40°。     

四级轴流涡轮变工况数值分析

采用FINE／Turbo软件包,对一个四级轴流空气涡轮两种转速下的不同流量工况进行了全三维数值模拟,与实验数据进行了涡轮效率、压比以及级间参数分布的比较。结果表明,计算与实验结果在各种工况下的性能符合良好。本文还对设计流量及小流量工况下透平内的流动情况进行分析和比较,研究这两种典型工况下叶片表面极限流线图谱、间隙流动特征等的差异。分析表明,在小流量工况下,与通道涡对应的分离线住置和展向尺度都与设计工况存在显著差别,动叶顶部间隙涡的再附形式以及叶片压力面极限流线图谱也发生了较大变化。     

机械过冷CO2引射制冷系统性能研究

利用R134a机械过冷系统对CO2引射制冷系统（ERS）气体冷却器出口工质进行冷却,实验研究了在不同过冷度、排气压力及蒸发温度下机械过冷CO2引射制冷系统（MSERS）的性能,并与ERS系统性能进行了对比分析。结果表明,MSERS系统的COP随着过冷度及排气压力的变化存在最大值,最佳过冷度约为16℃,而最佳排气压力约为8.5Mpa;随着蒸发温度升高,MSERS系统的引射比及COP均增大,且引射比随蒸发温度增大的速度在低蒸发温度工况下比较小。MSERS与ERS系统性能的对比表明,在实验蒸发温度范围内MSERS系统的COP大于ERS系统,且在低蒸发温度工况下MSERS系统COP的改善幅度更大;在蒸发温度小于1℃的工况条件下MSERS系统的引射比比ERS系统的引射比提高了约2.5%～6.0%;在不同的一级节流阀前温度工况下,MSERS系统制冷量比ERS系统提高了约27.2%～35.5%,COP增大了约6.2%～17.6%。     

花瓣形喷嘴对喷射器性能影响的数值研究

提出采用花瓣形喷嘴提高气流混合效率的方法来提升喷射器性能。采用FLUENT软件对喷射器流场进行数值模拟,对比分析了不同运行参数下花瓣形喷嘴和圆形喷嘴的喷射器性能。研究表明:在设计工况下,花瓣形高压喷嘴喷射器的临界背压提高了5%,引射比最多提高了13. 3%;另外,在高压压力越大或低压压力越小时,新型喷射器的引射效果要明显好于传统的圆型喷嘴喷射器;在研究工况下,新型喷射器在临界工况下的引射比最多提高了13. 5%,临界背压最多提高5%。     

微型燃气轮机燃烧室热力性能的实验研究

对一微型燃气轮机燃烧室在不同负荷下的热力性能进行了实验研究,得到了该燃烧室在不同负荷下燃烧效率,出口温度分布,总压保持系数及NOx排放浓度等燃烧室性能指标参数的变化情况.结果表明,该燃烧室在各个实验负荷工况下均具有优异的性能,同时随着负荷的增加,压力损失增大,NOx排放浓度降低.     

导流片结构对物流分配性能影响的实验研究

通过板翅式换热器物流分配问题的实验研究发现,不合理的导流片结构造成板翅式换热器内部物流分配极不均匀,以及在横向与纵向上物流分配不均匀的程度也不相同。同时提出了具有补液腔的新型导流片结构,并定义了新型导流片的结构参数。实验结果表明,采用新型的导流片可以有效的改进换热器内部物流分配不均匀的问题,同时还发现在实验的条件下结构参数为0．2的导流片具有最佳的导流性能,通过实验研究得到了不同导流片结构的物流分配不均匀特性与流体雷诺数之间的关系式。     

缸内直喷CNG发动机喷射方向对燃烧过程影响模拟研究

燃烧过程是决定发动机性能的关键因素之一,应用CFD软件分析研究天然气喷射方向对一台缸内直喷CNG发动机燃烧过程及排放的影响。结果表明,不同的喷射方向决定了混合气在气缸内的浓度分布。在所模拟工况下,存在一个最佳的喷射方向,此时平均指示压力高,发动机的性能较好。     

电弧炉炼钢出钢过程在线喷粉水模拟优化研究

通过水模拟实验研究不同试验方案下的熔池混匀时间,分析喷枪角度、喷枪枪位、喷枪流量对出钢过程中钢包熔池搅拌效果,确定最佳的喷吹工艺参数,为现场生产提供理论指导。     

轿车发动机的调节技术

为了使经常在变工况下工作的轿车发动机的性能得到最佳发挥，发动机的某些参数必须随发动机的工况变化而相应变化。而传统的发动机设计和参数选择都是采用折衷办法设计固定结构参数的发动机，难免使某些性能方面付出牺牲。调节技术可以使其性能得到最佳发挥，本文介绍了轿车发动机的调节技术及其应用实例。     

Theoretical and experimental studies on optimum heat rejection pressure for a CO2 heat pump system

The experimental and simulation researches have been conducted to investigate the relationships between optimum heat rejection pressure and other related operating parameters for a transcritical CO₂ heat pump system with two throttle valves. It proved that it is relatively reliable to control the heat rejection pressure of the CO₂ system with two expansion valves in series. The experimental results also show similar trends with those from simulation, under widely different operating conditions. Thus both the simulation and experimental results meet here: for a transcritical CO₂ cycle, there exists an optimal heat rejection pressure, under which the system can reach the maximum heating coefficient of performance (COP). Furthermore, the research also reveals that the optimal heat rejection pressure mainly depends on the refrigerant outlet temperature of gas cooler whereas the evaporating temperature and the performance of the given compressor have smaller effect on the optimum heat rejection pressure. Based on the experimental data, a correlation of the optimal heat rejection pressure with respect to mainly involved parameters is obtained for specific conditions.     

Optimization of assembly clamping pressure on performance of proton-exchange membrane fuel cells

The compression induced by the assembly of proton-exchange membrane (PEM) fuel cells causes partial deformation of the gas-diffusion layers (GDLs) and affects the characteristics of the porous media and, consequently, influences the performance of PEM fuel cells. The objective of the present study is: (1) to develop a three-dimensional model to investigate the effect of assembly clamping pressure on the GDL properties and thus on the performance of PEM fuel cells, and (2) to determine the optimum clamping pressures when the cell is operated under different operating voltages. The optimum clamping pressures under different operating voltages are explored by using a global searching method, namely, the simultaneous perturbation stochastic algorithm (SPSA) method. The simulation results indicate that a clamping pressure of 1 or 1.5 MPa improves the fuel cell performance when the cell is operated under high operating voltages, and causes the cell performance to decrease when it is operated under low-voltage conditions. The optimum clamping pressures increase when the operating voltage increases.     

泡沫陶瓷填料湿化器加湿性能实验研究

温化器是湿空气透平(HAT)循环的关键部件,其性能优劣对于循环的性能有着重要的影响.对采用新型SiC泡沫陶瓷填料的湿化器在加压条件下的湿化性能进行了实验研究,分析了水气比、进口水温、操作压力以及进口空气温度对湿化过程的影响,研究表明,提高水气比或进口水温会使进出口空气温差、含湿量差相应增加,湿化器节点温差增大.操作压力...     

Experimental study on the performance of the thermoacoustic refrigerating system

This study is on the performance of the thermoacoustic refrigerating system with respect to some critical operating parameters. Experiments were performed on the system under various operating conditions. The experimental setup consists of the thermoacoustic refrigerating system with appropriate valves for the desired controls, instrumentation and the electronic data acquisition system. The resonator was constructed from aluminum tubing but it had plastic tube lining on the inside to reduce heat loss by conduction. Significant factors that influence the performance of the system were identified. The cooling produced increases with the temperature difference between the two ends of the stack. High pressure in the system does not necessarily result in a higher cooling load. There exists an optimum pressure and an optimum frequency for which the system should be operated in order to obtain maximum cooling load. Consequently, for the thermoacoustic refrigeration system, there should be a related compromise between cooling load, pressure and frequency for best performance.     

控制循环锅炉水冷壁流量偏差影响因素数值分析

1引言控制循环锅炉是一种重要类型的锅炉,已在我国一批电厂投运。控制循环锅炉的主要特点是在下降管和上升管之间加装循环泵,以提高循环回路的运动压头。机组运行时,管屏中每个管子受热是不同的,结构也不完全相同。在相同压差下,受热强的管子,管内的平均比容大,流量小,而受热弱     

基于遗传算法的汽油机朗肯循环余热回收系统的优化

为了更加高效利用汽油机排气余热,分析了某款汽油机排气余热回收潜力,建立了基于蒸发器和活塞式膨胀机的汽油机-朗肯循环联合余热回收系统模型。利用遗传算法,同时考虑膨胀机输出功、排气利用率、蒸发器效率和膨胀机绝热效率,以膨胀机输出功和系统总效率为优化目标,以蒸发压力和膨胀机转速为优化变量,对汽油机4个工况下朗肯循环系统的最佳运行参数进行了研究。结果表明,在整个发动机转速范围内,排气最大可利用效率均高于46%,转速越高则排气品质越高。在不同工况下存在最优的膨胀机转速和蒸发压力。经过优化,在选取的4个工况下,功率提高率均在6%以上,最高达到7.08%。     

Mathematical modeling of gasification of high‐ash Indian coals in moving bed gasification system

Simulation of gasification of high‐ash Indian coal in an updraft moving bed gasification system is presented in this paper. A steady one‐dimensional numerical model, which takes into account of drying, devolatilization, combustion and gasification processes, is used to solve the mass and energy balances in the gasification system. The results from the model have been validated against the experimental data available in literature for various types of coals. The predicted product gas composition, its calorific value and the exit temperature are in agreement with the reported results. The validated model is used to study the effect of input parameters such as oxygen content in air stream, steam flow rates and the pressure of the gasification system. Results indicate that the value of oxygen mole fraction around 0.42 in the oxidizer stream can provide optimum performance in oxygen‐based gasification systems. There is a range of steam‐to‐coal ratio that is dependent on the oxygen content in oxidizer stream. For air‐based systems, this value is around 0.4 and for oxygen‐based systems it is 1.5. The gasification performance improves with operating pressure significantly. An operating pressure of around 8 bar and higher, based on the application, can be used for achieving the required performance with high‐ash coals. The model is useful for predicting the performance of high‐ash Indian coals in a moving bed gasification system under different operating parameters. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation and optimization of solar desiccant wheel performance

This paper presents the evaluation and optimization of a solar desiccant wheel performance. A numerical model is developed to study and discuss the effect of the design parameters such as wheel thickness, wheel speed, regeneration to adsorption area ratio, wheel porosity, and the operating parameters such as air flow rate, inlet humidity ratio of the air and regeneration air temperature on the wheel performance. It is also used to draw the performance curves of the desiccant wheel to quantify the optimum design parameters for certain operating conditions.Also, an open test loop for the desiccant wheel is constructed with appropriate control devices and measuring instruments. A perforated plate solar air heater of 2 m² area, together with an electric heater, is used as a source of energy to regenerate the desiccant material. The experimental tests are used to validate the numerical model and to evaluate the performance of the solar system and the desiccant wheel under actual conditions of Cairo climate (30° latitude).Comparison between numerical and experimental results shows good agreement between them, especially at low flow rates of air. Numerical results show that there is a maximum value of each design parameter at each operating condition, and above that no remarkable changes in the wheel performance are noticed. The results also show that there is an effective range of the air flow rate, due to which wheel performance becomes inefficient. This range is found to be between 1 and 5 kg/min. The performance curves of the wheel, which help to determine the humidity reduction ratio, are drawn for wheel speeds between 15 and 120 rev/h, dimensionless wheel thickness between 0.15 and 0.5, air flow rate equal to 1.9 and 4.9 kg/min, and regeneration temperature equal to 60 and 90 °C. These curves show that there is an optimum value of the wheel speed for each wheel thickness to obtain the best wheel performance for certain operating conditions.Experimental results show that the perforated plate solar air heater of 2 m² area can share about 72.8% of the total regeneration energy required at 1.9 kg/min air flow rate and 60 °C the regeneration air temperature. This value decreases to about 13.7% at a flow rate equal to 9.4 kg/min and regeneration temperature equal to 90 °C. The perforated plate solar air heater area required to completely fulfill the regeneration energy during the daytime is also calculated.     

基于CFX的混流泵内流场数值模拟

基于三维不可压缩流体的N-S方程和RNGκ-ε湍流模型,采用流体计算软件ANSYS-CFX计算了额定转速下190～300L/s流量范围内9个工况点的某混流泵内部流动,研究了小流量工况、最优工况和大流量工况等工况下叶片压力面、吸力面的静压分布及各断面翼型附近的相对流速分布;通过分析混流泵内部流动速度和叶片表面静压分布,揭示了其内部流动的主要特征。预测了泵的水力性能,并与泵模型性能试验结果进行了对比。结果表明,最优工况时数值模拟与试验结果吻合较理想,满足工程实际的需要。     

Studies on thermal performance of certain wood burning cook stoves and design of a high efficiency cook stove

Wood is a major cooking fuel in rural areas of many developing countries and is burnt in vessel mounted stoves. Multipot chimney type cookstoves were introduced about forty years ago to overcome problems of smoke and to increase the conversion efficiency. Although widely propagated, there is still scope to improve the design of these stoves based on a critical evaluation of performance and an understanding of the basic principles of heat transfer, fluid mechanics and heat release. This paper describes in detail the results of thermal performance studies conducted on three widely propagated stove versions with respect to all operating variables. Based on the analysis, certain broad guidelines were arrived at for design of a proper stove. Another widely propagated version was taken up for detailed optimisation study in the light of such guidelines resulting in the development of a high efficiency design. The performance of the optimized unit is compared with the original version. This study leads to the conclusion that except for pot placement schemes and geometric shapes, the wide variety of stoves (over 60) being propagated under various trade names are not really different and the optimum parameters depend only on the fuel burning rate desired.