制冷工质压力对红外用波纹管J-T制冷器制冷性能的影响研究

通过具体实验研究了制冷工质压力对波纹管自调式J-T制冷器制冷性能的影响。实验工况内的结论如下:在一定的压力范围内(11 MPa≤P≤23 MPa),随着工质压力的增大,应用该款制冷器的红外系统的启动时间逐步缩短,但启动加快的速率会随工质压力的增大而减小。当工质压力增大到一定程度(23 MPa≤P≤27 MPa)时,启动时间将趋于稳定。在一定的压力范围内(11 MPa≤P≤15 MPa),随着工质压力的增大,应用该款制冷器的红外系统的蓄冷时间逐步加长;但工质压力增大到一定程度(15 MPa≤P≤27 MPa)时,蓄冷时间将趋于稳定。在一定的压力范围内(11 MPa≤P≤27 MPa),随着工质压力的增大,制冷器启动时的最大流量呈线性增大趋势,运行时的稳定流量呈逐步增大趋势。本文实验研究的过程方法和研究结果具有工程借鉴意义。

超微气流粉碎设备动态参数研究

研究了超微气流粉碎机工质压力、进料压力、进料量等动态参数对物料粉碎效果的影响,得到了这些参数与粉体粒径及其分布之间的变化关系,为优化超微气流粉碎设备的设计与粉碎过程提供了依据。

基于单螺杆膨胀机的发动机排气余热回收系统

针对发动机排气余热的特点,设计了有机朗肯循环(ORC)排气余热回收系统,采用单螺杆膨胀机作为动力输出装置,采用R245fa作为工质,提出了发动机排气余热利用率的概念和计算方法。结合发动机的试验数据,分析了ORC工质蒸发压力和发动机转速对ORC系统性能的影响,确定了适用于ORC系统的工质蒸发压力的最佳值。研究结果表明,当工质蒸发压力为3.0 MPa时,ORC系统能够在发动机全转速范围内正常工作,并且ORC系统的净输出功率最高可达12.1 kW,热力学第一定律效率最高可达11.27%,热力学第二定律效率最高可达25.8%,发动机排气余热利用率最高可达8.9%,发动机排气余热回收效果明显。

内燃机车柴油机冒黑烟的原因分析及处理

针对内燃机车柴油机在实际运用中．发生冒黑烟的现象进行了分析．阐述了产生的原因、解决方案和处理措施。

超临界锅炉控制系统设计

超临界锅炉是将锅炉内工质压力提高到临界点以上,一般在22.115MPa至26MPa之间,使其发电效率大幅提高,同时具有较高的环保效果和经济性,本文在超临界锅炉发电技术的基础上,通过设计超临界锅炉的启动系统和汽温控制系统,来减少工质流失和热量损失,适应快速变化的锅炉负荷,提高锅炉的控制精度和稳定性。

变工况下船舶多种余热利用系统性能评估

余热回收是提高船舶能效的重要途径之一,但单一余热利用方法诸如温差发电(TEG)和有机朗肯循环(ORC)等余热利用能力有限且难以实现船舶多种余热回收。基于此,文章提出了一种基于TEG-ORC联合循环的船舶多种余热利用系统。在完成系统设计的基础上,结合具体工况开展试验研究,分析了输出功率、热效率、发电成本、主机烟气余热利用量等主要性能参数随TEG/ORC底循环比、ORC工质蒸发压力的变化规律,并对系统性能进行评估。结果表明,联合循环系统在实现船舶多种余热利用的同时提升了余热利用性能。

Customer participation in the service encounter

This paper considers the role of service customers in those service encounters where the customer participates in the service production and delivery process, and the customer factors, motivations and incentive mechanism to participate in service delivery are analyzed. This study explores the relationship between service quality and service customer participation in the service encounter and the effect of customer participation on service providers＇ job stress. Finally, the management implications about customer participation in the service encounter from the findings are discussed.

Research on technological parameters of pressure forming with hot granule medium on AA7075 sheet

Hot granule medium pressure forming （HGMF） process is a new process in which granule medium replaces the medium in existing flexible-die hot forming process, such as liquids, gases or viscous medium. Hot forming of light alloy sheet parts can be realized based on the properties of granule medium, such as withstanding high temperature and pressure, filling well, sealing and loading easily. In this work, the forming of AA7075 cylindrical parts by HGMF process is taken as an example to establish the constitutive relation and forming limit diagram （FLD） of AA7075 sheet which is related to temperature by hot uniaxial tensile test of sheet metal. Based on the assumption that granule medium is applied to extended Drucker-Prager linear material model, the finite element model of HGMF process is established and the effect of technological parameters, such as forming temperature, blank-holder gap and drawing ratio, on the sheet metal formability, is studied. The limit drawing ratio curve of AA7075 cylindrical parts at forming temperature of 175-300 ℃ is obtained by HGMF process test, and the limit drawing ratio reaches the maximum value of 1.71 at 250 ℃. The results of numerical simulation are consistent with the results of process test, and the forming force, distribution of wall thichness and form of instability are predicted correctly, which provides reference for the application of HGMF process.

Effect of fissure water on mechanical characteristics of rock mass

In view of the effect of fissure water in fractured rock mass on the strength of rock mass in engineering projects, we pre-pared specimens of cement mortar to simulate saturated rock mass with continuous fractures of different slope angles. By exerting static and dynamic loads on the specimens, the mechanical characteristics of rock mass with fissure water under these loads can be analyzed. Our experimental results indicate that the static compressive strength of saturated fractured rock mass is related to the slope angle. The lowest compressive strength of fractured rock mass occurs when the slope angle is 45°, while the highest strength occurs when the specimen has no fractures. Fissure water can weaken the strength of rock mass. The softening coefficient does not vary with the slope angle and type of load. The hydrodynamic pressure of fractured rock mass gradually increases with an increase in dynamic load. For a 0° slope angle, the hydrodynamic pressure reaches its highest level. When the slope angle is 90°, the hydro-dynamic pressure is the lowest.

Improving the Shape Accuracy by Simulating the Short-Stroke Honing Process

This study represents an approach to investigate a force controlled short-stroke honing process and especially the dependency between the type of finishing tool and the resulting shape accuracy. Based on a finite element analysis and a validation with special pressure measurement films, the contact mechanisms between the finishing tool and the workpiece are analyzed. In order to achieve a high surface quality without reducing the shape accuracy, the influence of different finishing tools with an individual material behavior on the resulting shape accuracy have been analyzed. With a variation of the geometry of the finishing tool as well as of the workpiece, different loading cases between the tool and the workpiece are considered in the finite element simulation. These results, combined with experimental investigations with different finishing films lead to an improvement of the surface quality without reducing the shape accuracy.

CO_2跨临界热泵气体冷却器性能影响因素研究

将某二氧化碳跨临界热泵(选用双级冷却套管式气体冷却器)作为研究对象,采用实验方法,在设定条件下,分别改变气体冷却器冷却水进水温度、二氧化碳质量流量、压缩机排气压力,分析这3个参数对气体冷却器输出热功率、工质压力降的影响。