Effects of process parameters on semi-solid squeeze casting performance of aluminum alloy scrolls for scroll compressors

The aluminum alloy scroll is one of the key parts of the scroll compressors widely used in the air-conditioning,refrigeration,and heat pump systems.In this work,the semi-solid squeeze casting(SSSC)process was used to fabricate the aluminum alloy scroll.The effects of process parameters including the pouring temperature,mold temperature,and squeezing velocity on the filling and solidification behaviors of the alloys were investigated through simulations based on the power law cut-off(PLCO)material model.Results show that there is a significant increase in the flow velocity of the slurry,and the area of the high-speed region enlarges with the increase of the pouring temperature.The homogeneity of the temperature and velocity fields in the slurry is improved with an increase in mold temperature.Both the filling time and its variation rate decrease with an increase in squeezing velocity.The maximum solidification time exhibits a linear variation with the increase in pouring temperature.The shrinkage area is decreased by increasing the mold temperature.The optimal process parameters of the SSSC process were obtained from simulation analysis,which are the pouring temperature of 595°C,mold temperature of 350°C,and squeezing velocity of 0.3 m·s-1.Moreover,the qualified scroll casting was fabricated using the SSSC process under the optimal process parameters.

Flow characteristics of tangential leakage in a scroll compressor for automobile heat pump with CO_(2)

Tangential leakage loss reduction has great significance on improving the performance of scroll compressors.In this study,the flow field of a scroll compressor working with CO_(2) was numerically investigated.The development characteristics of the tangential leakage flow in different working chambers were carried out,which was obtained by analyzing the field quantities distributions.The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration,in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors.Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream.Owing to little reverse pressure gradient,the tangential leakage flow maintained the typical jet form in the suction chambers.By contrast,the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber.The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage.With the increase of the radial clearance,the volumetric efficiency declined and the discharge temperature increased rapidly.In terms of flow control of the tangential leakage,the increase of sidewall roughness by 2μm could achieve the same effect as the decrease of the radial clearance by 4μm,while the volumetric efficiency increased by almost 5%and average discharge temperature decreased by 5K.

Structural dynamic analysis of the orbiting scroll wrap in the scroll compressor

A deep analysis of orbiting scroll wraps was conducted in this paper by using ANSYS and SolidWorks. Through the modal analysis, the involute of the circle profile orbiting scroll wrap demonstrated a large span in natural frequencies, which led to more superiority in avoiding structural resonances. Based on the dynamic harmonic analysis, loads of frequency changes were gained and the stress and strain distribution of the orbiting scroll wrap in the most dangerous working conditions were obtained, which determined the segments with maximum stress and strain-displacement properties. Two paths defined to elucidate further the structural characteristics of the exhaust chamber provided evidence for the initial correction of orbiting wraps. The results of the present study offer a theoretical basis for the design and manufacture of scroll wraps, and providing a new way to evaluate different scroll wraps.

Leakage Model of Axial Clearance and Test of Scroll Compressors

Leakage clearance plays an important role in guaranteeing high efficiency of scroll compressors.In view of the shortcomings of the existing leakage models of axial clearance of scroll compressors,a modified Fano flow model and a turbulence model are presented based on the flow characteristics of fluid in the leakage passage under actual working conditions.Firstly,according to the Fano flow energy equation and the turbulence theory,two kinds of leakage models,Fano flow model and turbulence model,of axial clearance are established.Then,the established models are verified through an experimental platform established to measure the axial clearance leakage in the working process of a scroll compressor,and the measured values are compared with the values obtained from the two theoretical models.Finally,the effect of such factors as pressure difference,clearance amount,spindle speed on the axial clearance leakage is analyzed.Results show that the two established models can precisely reflect the variation law of axial clearance leakage of scroll compressor under different working conditions.In particular,the Fano flow model is more suitable for predicting the clearance leakage when the spindle speed is low(less than 3500 r/min)and the clearance is small(less than 0.025 mm),whereas the turbulence model is suitable for high spindle speed(more than 3500 r/min)and large clearance(more than 0.025 mm).

Research on the natural meshing mechanism and testing analysis of scroll profiles for refrigeration scroll compressor

In the design theory of scroll profiles for refrigeration scroll compressor,a mechanism principle of scroll profiles based on the center of natural temporal involutes and meshing region is presented,by which the performance characteristics of the various involutes are studied. Profiles type selection is very important for scroll compressor. Through analyzing the characteristic geometry,natural meshing mechanism is discovered in the study of scrolls. And a novel method for scroll profiles based on natural meshing mechanism is proposed. The result shows that the meshing region angle of odd regular polygon involutes is half of the characteristic-geometry exterior angle,and that of even regular polygon involutes is equal to the exterior angle to the moment. The corresponding meshing region angle is reduced increasingly with the increase of the edge number of characteristic geometry. The performance characteristics of scroll compressor tend towards the best correspondingly. Aiming at the existing problems of profile design for scrolls,we developed a novel methodology to study scroll profile. Originality research was done for the further study of scroll profile. It is the fundamentality factor representing essence character of scroll profiles function itself.

Air-source heat pump coupled with economized vapor injection scroll compressor and ejector:Design and experimental research

Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation temperature of -20oC,and an experimental setup was established to test the prototype.The measured results demonstrated that the heating EER(energy efficiency ratio)of the EVIe could reach about 4%higher than that of the system without the ejector when the heating capacity remained nearly constant.The design method is helpful to development of a heat pump system coupled with scroll compressor and ejector.

Performance analysis of a single-stage scroll compressor used in a drying heat pump over a wide condensing temperature range(30–80°C)

This study presents the performance of a new single-stage scroll compressor used for the heat pump drying of thermally sensitive materials over a wide temperature range.The performance of the new compressor was predicted by an ARI standard 540map-based compressor model and verified by a semi-open drying heat pump system constructed for this purpose.A comparison of the experimental data with the predicted data proved that the new scroll compressor used in the drying heat pump works well,can supply a wide range of condensing temperatures(30–80°C)(without auxiliary heating),and has a minimum coefficient of performance(COP)above 2.0,even in the worst condition.

基于功率流有限元法的涡旋压缩机振动特性研究

针对涡旋压缩机内部振动传递路径复杂,采用传统的传递函数法往往不能真实地描述振动产生与传递的本质问题,引入功率流有限元法从能量角度分析振动传递特性,进行涡旋压缩机内部振动产生、传递与空间分布的可视化研究。在分析涡旋压缩机的动力拓扑关系基础上建立激励源,提取与振动响应模型并进行仿真分析;利用实体试验和响应分析结果对比进行模型有效性分析;在验证后的模型上定义8个能量输出面,分析谐波与激励作用下上支撑和下支撑的振动能量传递特性,并且计算节点的功率流矢量确定振源的空间分布。结果表明,涡旋压缩机曲轴在运转到280°时,振动频率在1 000 Hz与1 890 Hz时振动能量传递率较高,上支撑能量分布均匀并集于自身,下支撑能量集中于支脚并向外传递。研究方法和研究成果对于涡旋压缩机振动分布及传递、振动控制和优化设计等方面具有一定借鉴意义。

涡旋膨胀机研究进展及展望

随着“双碳”目标的提出,涡旋膨胀机作为回收低品位能量的机械装置备受关注。首先,对近年来涡旋膨胀机的理论研究成果进行了综述,主要包括型线理论、热动力学和计算流体力学(CFD)仿真。然后,对涡旋膨胀机在有机朗肯循环(ORC)中的应用进行了总结,梳理了涡旋膨胀机在跨临界CO_(2)制冷循环中的应用研究成果。最后,对涡旋膨胀机未来的研究方向进行了展望。结果表明:变壁厚涡旋膨胀机因其可以在不增加泄漏线长度的情况下增加内容积比,因此将成为未来型线优化的主要方向;CFD仿真已成为重要的研究工具;润滑油是影响涡旋膨胀机性能的关键因素,提高润滑油的黏度有利于提升效率,而过量的润滑油则会使其性能下降;工作压力是影响涡旋膨胀机性能的最主要的因素,过膨胀、欠膨胀以及泄漏现象都会使其性能下降。此外,涡旋膨胀压缩一体机集成了膨胀机和压缩机两个功能单元于一个机壳中,显著简化了系统结构并提高了能量回收效率,是提升新能源车用CO_(2)热泵空调系统性能的有效途径。基于当前的研究成果和行业需求,提出涡旋膨胀机未来应继续深入研究和优化型线设计、减少泄漏、优化工作压力等,以满足日益增长的能量回收和环境保护需求。

涡旋压缩机径向柔性机构动力学仿真分析

以偏心滑块式径向柔性机构为研究对象,从机构学角度对机构的避让功能进行分析,确定了机构限位范围;利用ADAMS软件对柔性机构转子系统的动态特性进行了仿真分析,得到动涡旋质心的运动轨迹,确定机构限位参数对动涡盘质心运动规律之间的关系,优化主轴承受力,为空调涡旋压缩机的振动分析和性能提升奠定基础。

涡旋压缩机平衡铁结构对阻力矩的影响研究

针对涡旋压缩机平衡铁随主轴旋转时产生的阻力损失问题,提出了圆角结构及机翼型结构平衡铁。运用Fluent有限元分析软件,结合滑移网格技术对平衡铁工作区域模拟,研究了3种不同结构平衡铁所受的压差阻力矩和摩擦阻力矩,对比分析了不同结构产生的阻力矩大小。结果表明:压差阻力矩占总阻力矩的90%以上,总阻力矩随转速的增大而增大;相对于样机平衡铁,前后端面为圆角的平衡铁总阻力矩减小了30%~50%之间;机翼型平衡铁总阻力矩减小了55%~65%之间。

汽车空调涡旋压缩机排气孔优化研究

针对汽车空调涡旋压缩机排气孔处气体流动变化产生的流动损失问题,对排气孔结构进行优化,以期降低流动损失并提高排气压力。通过三维动网格模型对不同排气孔结构的涡旋压缩机排气过程进行瞬态仿真,发现腰果形排气孔更大的截面积使其拥有更好的开启特性,可有效降低排气损失,提高排气稳定性。在对腰果形排气孔采取进一步扩压式优化后,发现其可以更加有效地降低排气速度并提高排气压力。

微小型压缩空气储能系统用涡旋压缩机流动特性研究

以空气为工质,基于计算流体动力学方法,对无油空气涡旋压缩机在变工况运行条件下进行了三维非稳态数值模拟。研究发现:动静涡旋齿之间存在的径向间隙,会使得压缩机工作腔内温度、流速和压力的分布不规律;增大转速,不但可以增加涡旋压缩机的质量流量,而且还可以减小切向泄漏量,进而提高压缩机的工作效率;排气压力过大,会降低涡旋压缩机的基本输出性能;在低转速下,过高的排气压力会使得压缩机排气口出现“净回流”现象。

涡旋压缩机排气孔流动特性研究

为了研究排气孔结构对短型线涡旋压缩机性能的影响,以一款排量为38 cm3的涡旋压缩机为例,建立了三维非稳态数值计算模型,并通过试验对模型进行了验证,误差在9.5%以内。利用此模型,分别研究了排气孔大小和形状对压缩机性能的影响。结果表明,当采用圆形排气孔时,随着孔径由5.2 mm增大到9.0 mm时,压缩机功耗降低了5.82%,总质量流量增加了1.09%,排气过程中压力波动以及上、下腔之间压力不平衡性逐渐增强;当采用腰形、圆弧形以及复合形的排气孔时,相比5.2 mm圆形孔,压缩机功耗有一定程度降低,总质量流量少量增加,排气过程中压力波动和上、下腔内压力不稳定性变化不明显,其中排气孔形状为复合形时,性能提升最明显,压缩机功耗降低了5.81%,总质量流量提升了1.26%;相比总质量流量,压缩机排气孔的改变对功耗影响更大。研究结果可为涡旋压缩机排气孔的结构优化提供参考。

电动汽车涡旋压缩机补气特性的数值研究

为研究短型线的汽车空调涡旋压缩机的补气特性,以一款排量为38 cm^(3)/r的电动汽车补气式涡旋压缩机为例,建立了三维非稳态数值计算模型,并通过实验数据验证了模型的准确性,误差在9.5%以内。通过模型分别研究补气压力和补气温度对涡旋压缩机性能的影响,结果表明:在补气过热度不变的情况下,随着补气压力的升高,压缩机排气温度先减小后逐渐增加,制热量呈增加趋势,当转速为5000 r/min和6000 r/min时,制热量最大增幅分别为20.5%和17.1%,制热COP先上升后下降,2种转速下有补气时制热COP的最大值较无补气时分别增加3.9%和2.3%,压缩机效率均先增大后减小,容积效率逐渐降低;在补气压力不变的情况下,随着补气温度的增加,排气温度略有增加,压缩机功耗、制热量及制热COP几乎保持不变;相较于补气温度,补气压力对压缩机性能的影响更大。

一种异步式压缩机涡旋盘的变形和疲劳强度分析

涡旋压缩机工作时,因涡旋盘工作环境及受力较为复杂,其容易产生变形和应力,导致密封性变差和疲劳破坏,影响到涡旋压缩机的工作效率及可靠性。针对这一问题,基于有限元理论,对一种微小型异步式涡旋压缩机进行了数值模拟研究(在多种载荷作用下),分析了其实际工况下的变形应力和疲劳寿命分布规律。首先,分析了异步吸排气涡旋压缩机的构造原理,划分了该涡旋盘的结构化网格,并赋予其材料、连接、约束和载荷等要素,由此建立了该涡旋盘的有限元计算模型;然后,分析了该涡旋盘在气体温度载荷、气体压力载荷、惯性力载荷及多载荷耦合作用下的变形和应力分布规律,并进行了模拟结果的可靠性分析;最后,计算了该涡旋盘在常温常压工况下的疲劳寿命,并研究了其在变载荷工况下的疲劳寿命变化。研究结果表明:温度载荷是引起涡旋盘变形和应力的主要因素;高吸气温度下,涡旋盘疲劳寿命随吸气温度和吸气压力的升高而线性减小,且前者的影响更加明显;低吸气温度下,涡旋盘疲劳寿命在较高的吸气压力下出现迅速下降的趋势。

涡旋压缩机吸气过程流场特性研究

针对涡旋压缩机吸气过程产生的预压缩现象,为了探明其产生机理和对压缩过程的影响以及流场的变化规律,基于计算流体动力学原理,在不同曲轴转速条件下,运用三维动网格技术对涡旋压缩机内部流场进行数值模拟计算。结果表明:吸气腔与两侧进气流道的流场分布均不对称,不同曲轴转角时进气流道、吸气腔等位置产生强度不同的涡流区;随着曲轴转速的提升,吸气过程预压缩现象发生时曲轴转角提前约10~21°不等,引起吸气腔内压力升高23.5%~29.0%,使得实际吸气量与理想吸气量不再相等,涡旋齿尾部涡流现象随之加剧。

基于CFD仿真的涡旋压缩机吸气带油分析

低背压涡旋压缩机吸气侧引入较低温的润滑油进入压缩过程,可对压缩过程的径向和轴向间隙进行密封,有利于能效水平的提高。为了进行吸气带油结构的设计并研究其影响规律,采用压缩仿真和供油仿真研究了吸气带油孔位置和供油量的设计方法,分析了吸气带油对于径向和轴向间隙中泄漏量的影响规律。结果发现吸气带油结构可以有效实现功能,降低了轴向和径向间隙的泄漏速度,使得冷量增加。通过整机测试发现在性能工况下吐油量增加约0.48%,冷量增加了约1%,能效平均增加约0.58%,验证了仿真方法的有效性,可为涡旋压缩机吸气过程的优化设计提供参考。

具有油背压机构的涡旋压缩机动涡盘轴向平衡研究

涡旋压缩机在工作过程中,轴向气体力会导致径向泄漏,同时会加重动涡盘与机架之间的摩擦磨损。如何有效地平衡轴向气体力尤为重要。针对此问题,应用Fluent滑移网格技术模拟偏心质量块在旋转过程中对背压腔内润滑油的搅动,通过监视器对背压腔上表面压力积分得到背压力随主轴转角变化的数据,分析不同转速工况及不同背压阀开启压力条件下背压力如何变化。结果表明,背压力随主轴转角变化而周期性变化,背压阀开启压力与背压力关系成近乎线性正相关,主轴转速越高,背压力振幅越大。根据背压力与轴向气体力随主轴转角变化均为相同周期变化,提出了在错角优化基础上结合背压阀调控优化方案,有效地降低了动盘受轴向合力的振幅与平均值,为涡旋压缩机轴向平衡提供了新的优化思路。

基于制冷剂泄出的双温热泵特性研究

为满足生产生活中双温供暖供热的需求,提出了一种基于制冷剂泄出的双温热泵系统。建立基于制冷剂泄出的涡旋压缩机数理模型和系统模型并进行数值模拟验证,计算分析系统在不同泄出口位置、泄出口大小、蒸发温度、高温冷凝温度、中温冷凝温度下系统各项性能参数的变化趋势,并与传统双温热泵系统进行对比分析。结果表明,压缩机中间泄出口打开越早压缩机耗功越少、泄出口越大系统节能效果越明显,较传统双温热泵系统制热性能系数在不同工况下都有显著提高,最高可提升16%。所提模型为制冷剂泄出式双温热泵、补气增焓热泵系统的理论分析提供了更有效方法,为涡旋压缩机性能优化和双温热泵系统的研究、设计及系统性能的提升提供了理论参考。