正交试验法在微小型喷射器实验研究中的应用

在研究应用于小型太阳能喷射制冷系统的微小型喷射器实验中,根据已有理论和实际知识,决定选取结构参数,即等截面混合段长度、混合段进口到喷嘴出口距离,及引射流体压力作为试验因子,利用正交试验方法设计实验提高实验效率,以较少试验次数获得足够全面的实验结果。文中还探讨了评价试验对象性能的合理指标。     

自动脱螺纹注塑模液压马达脱螺纹与推板推出动作关系的工程分析

针对自动脱螺纹注塑模具中液压马达脱螺纹速度与弹簧驱动的推板推出速度可能存在不同步的问题,对液压马达脱螺纹动作规律进行了论述,对弹簧驱动的推板推出动作规律进行了运动学分析,通过对这两种动作规律的比较得出了一个结论,即在实际工程应用中选用的液压马达多为低速马达的情况下,液压马达轴向脱螺纹速度总是制约弹簧驱动的推板推出速度,从而实现了一种制约同步。根据这个结论,为避免出现塑件螺纹损坏的情况,在模具结构允许的情况下,应尽量选择劲度系数较低的推板弹簧。     

Performance analysis of a supersonic ejector cycle working with R245fa

A supersonic ejector chiller for industrial use is currently being developed and tested as part of a project cooperation between Frigel s.p.a and DIEF (Department of Industrial Engineering, University of Florence). The refrigerator was built following a “ready to market” setup criterion and is intended for applications on the industrial refrigeration market or in air conditioning. The plant has a nominal cooling power of 40 kW and is powered by low temperature heat (from 90 up to 100 °C). The ejector is equipped with a movable primary nozzle and 9 static pressure probes along the mixing chamber/diffuser duct. The working fluid is R245fa. An extensive numerical campaign was performed to analyze the internal dynamics of the ejector. All the simulations were carried out by accounting for the real gas properties of the refrigerant. Comparison with experimental data resulted in close agreement both in terms of global and local parameters. Analyses showed that in order to achieve an accurate matching with the experimental data, it is necessary to correctly account for the surface roughness of the ejector. This is especially true for off-design operating conditions.     

First and second law investigations of a new solar‐assisted thermodynamic cycle for triple effect refrigeration

This investigation is persuaded for the first and second law analyses of a new solar‐driven triple‐effect refrigeration cycle using Duratherm 600 oil (Duratherm Extended Life Fluid, NY, USA) as the heat transfer fluid is performed. The proposed cycle is an integration of ejector, absorption, and cascaded refrigeration cycles that could produce refrigeration output of different magnitude at different temperature simultaneously. Both exergy destruction and losses in each component and hence in the overall system are determined to identify the causes and locations of the thermodynamic imperfection. The effects of some influenced parameters such as hot oil outlet temperature, refrigerant turbine inlet pressure, and the evaporator temperature of ejector and cascaded refrigeration cycle have been observed on the first and second law performances. It is found that maximum irreversibility occurs in central receiver as 52.5% and the second largest irreversibility of 25% occurs in heliostat field. The second law efficiency of the solar driven triple effect refrigeration cycle is 2%, which is much lower than its first law efficiency of 11.5%. Analysis clearly shows that performance evaluation based on the first law analysis is inadequate and hence, more meaningful evaluation must be included in the second law analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

下喷式液气喷射器内流体力学的数值模拟

本文用STAR-CCM+软件研究下喷式液气喷射器内的流体力学.结果表明,混合管直径一定,随面积比的增加,混合管入口的压力先增高后减低,空气抽吸量存在一个最大值,此时对应面积比约为4.在模拟的喉径比范围内,混合管人口处的压力较低,但存在一个最大的压力降,对应喉管长度为0,空气抽吸量随喉径比而变,也存在一个最大值.喷射器结...     

喷射式液液混合器与静态混合器复合应用研究

喷射式液液混合器和静态混合器都是混合过程强化的重要设备。合理设计具有喷射式混合器、静态混合器的复合结构的新混合器,可以解决生产上的难题。新混合器能直接进行两种不同压力流体的混合,使压力较低流体混合后的压力有所提高,保证较好的混合效果,降低能耗,提高经济效益,简化流程。降低投资。     

化妆粉盒底壳注射模设计

介绍了化妆粉盒底壳注射模结构,为保证塑件顺利脱模,用一个滑块同时完成塑件3个方向的抽芯动作,开、合模动作灵活可靠。模具定模型腔板和动模型芯均采用循环水冷却方式,塑件注射成型后能充分冷却,既缩短了成型周期,又提高了塑件质量。     

电脑键盘注射模设计

介绍了1副电脑键盘注射模,针对塑件的7个横向通孔需要侧向抽芯的特点,采用3组斜导柱加滑块机构进行外侧抽芯、4组分体式斜推杆进行内侧抽芯,大大减小了模具外形尺寸。模具浇注系统及定距分型机构设计合理,冷却充分,塑件推出平衡,较好地保证了模具寿命和塑件精度。     

齿条-齿轴-齿条斜向抽芯压铸模

尺寸较小、带有斜向孔的铸件,其斜孔抽芯机构和推件位置的设计是模具设计的难点.为此,文中给出了齿条齿轴一齿条料向抽芯机构和推杆、推管同时推件机构,在保证模具结构紧凑的同时,保证了铸件的成形质量.分析了铸件工艺性,设计了模具结构,论述了模具工作过程.     

船用喷射制冷机组的研究及发展现状

船用喷射制冷机组可以有效利用船舶上低品位热能,实现能源的节约和高效利用。简述了喷射制冷的原理,进行了热力学分析,对船用蒸汽喷射制冷机组及余热回收式喷射制冷机组的研究及发展现状进行了分析,并对太阳能等新型喷射制冷机组船用化进行了展望。