冰箱直线压缩机行程不稳定波动的机理分析

直线压缩机冰箱制冷系统的实验研究显示,在初始启动调节后供电参数保持不变的过程中,直线压缩机行程出现了不稳定波动现象。最大的活塞行程波动率约为3. 8%,输入功的波动率约为21. 3%,波动周期约为220 s。通过建立的直线压缩机动态仿真模型,对该不稳定现象进行解耦分析,结果表明:吸气压力的波动对直线压缩机行程的影响较大,排气压力的波动对其影响很小,但行程的波动对排气压力有一定的影响。直线压缩机启动过程中行程的反复调节引起了排气压力出现较大的波动,经过一段稳定运行后,该波动传递到直线压缩机的吸气端,从而引起了所述的不稳定波动。     

冰箱直线压缩机不稳定波动的机理分析

直线压缩机冰箱制冷系统的实验研究显示,在初始启动调节后供电参数保持不变过程中,直线压缩机出现了不稳定波动现象。最大的行程波动率约为3.8%,输入功的波动率约为21.3%,波动周期约为220 s。通过建立的直线压缩机动态仿真模型,对该不稳定现象进行解耦分析,结果表明：吸气压力的波动对直线压缩机行程的影响较大,排气压力的波动对其影响很小,但行程的波动对排气压力有一定的影响。直线压缩机启动过程中行程的反复调节引起了排气压力出现较大的波动,经过一段稳定运行后,该波动传递到直线压缩机的吸气端,从而引起了所述的不稳定波动。     

螺杆式制冷压缩机故障分析

螺杆式制冷压缩机(以下简杯螺杆机)由于结构紧凑,体积小,运行平稳,安全可靠,与活塞式制冷压缩机比较.它具有排气温度低.可在较高压缩比下运行,对湿行程不敏感,能量可在15—100%范围内无级调节,机器易损件少等优点,所以越来越多地被运用于各制冷系统中。但由于螺杆机机型在国内     

国外制冷系统中防排气压力超高装置

对引进意大利制冷系统的技术资料进行分析时,发现制冷压缩机在排气超高压保护中除了有高压保护继电器、高温保护继电器以外还设置了排气温度调节控制器。见制冷系统流程图所示。排气温度调节控制器由三个部分组成:压力式感温元件,温度调节器;执行元件电磁阀(24V)。控制原理请见方框图。     

直线压缩机喷射补气特性分析

本文针对直线压缩机的喷射补气特性开展研究,基于直线压缩机电磁学模型、动力学模型和小孔进气模型,建立了喷射补气式直线压缩机及压缩腔仿真模型并进行了实验验证,研究了补气压力和参数调节对压缩机运行参数的影响。结果表明：喷射补气使吸气阀滞后开启和提前关闭,低压吸气量减小,排气量增大。在吸气压力为62.5 kPa、排气压力为765 kPa条件下,补气压力为200 kPa时,吸气量降低61%,排气量提升50%;补气压力为400 kPa时,低压无吸气,排气量相比于200 kPa补气时提升60%。给定供电参数条件下,喷射补气使自由活塞行程、偏移量与余隙容积增大,固有频率有一定的提高;定余隙容积运行时,随着补气压力的提升,气体力等效刚度和等效阻尼均增大。固定频率下,行程增大时吸气量随之增大,而补气流量达一定值后基本保持不变;频率调节时,压缩机在固有频率附近吸、补气量存在最大值,驱动频率较高时补气对吸气量的降低影响减弱。     

某型往复式制冷压缩机吸/排气噪声源在自由场中的辐射特性研究

往复式制冷压缩机在制冷冰箱领域广泛应用,是产生噪声的源头。为了研究往复式压缩机的噪声特性,首先通过对工作过程中的吸/排气流场特性进行了数值模拟,将流场声源信息导入声学软件LMS Virtual.Lab中,基于喷射噪声理论对壁面压力脉动引起的偶极子声源和湍流四极子声源在排气过程中的变化规律及辐射特性进行研究,最后得到压缩机吸/排气噪声辐射指向性。为实现低噪声制冷压缩机的研制提供了理论依据。     

无油直线压缩机动态特性实验研究

成功研制了1台蒸气压缩制冷系统用的无油线性压缩机,基于无油线性压缩机在不同工况进行实验研究,分析不同压比和行程下吸排气压力对压缩机工作特性的影响。结果表明,压缩机的谐振频率受到活塞行程、吸排气压力的共同作用。随着排气压力的升高或吸气压力的降低以及行程的减小,谐振频率会逐渐增大。在排气压力不变,压缩比从2增加到4时,随着吸气压力的降低,压缩机的输入功率和流量、容积效率逐渐减小;在吸气压力不变,压缩比从2增加到4时,随着排气压力的升高,压缩机的输入功率逐渐增大,流量和容积效率随之减小。     

R32和R22过热度对转子式压缩机制冷系统影响的对比

利用变频滚动转子式压缩机制冷循环实验台,研究了R32和R22制冷系统过热度对系统性能的影响。定量分析了R32制冷系统在过热状态下的一些规律,并且通过对比工况1#下R32和R22的系统参数,分析了R32优于R22的原因,研究了R32商用空调最佳过热度的调节范围。结果表明:R32制冷系统各项参数变化趋势与R22基本一致,R32制冷系统具有较好的制冷效果;在工况1#下,相比R22制冷系统,R32系统的制冷量提高约为42%,COP提高6.8%,系统压比增加7%左右,系统性能更稳定;在空调工况下,R32系统过热度控制在4℃以内,具有较好的节能效果。     

充注量对小型CO2制冷系统影响的实验研究

为了研究充注量对小型二氧化碳制冷系统的影响,利用一套展示柜二氧化碳制冷系统,进行了不同充注量的实验。讨论了充注量对二氧化碳制冷系统吸排气压力、运行功率、吸排气温度的影响。同时,结合本系统,对假临界现象进行了分析,结果表明:充注量不足,蒸发、冷凝压力低,压缩机吸、排气温度高,系统COP较低;充注量过多,系统运行功率高,系统制冷系数降低;系统运行一段时间后,回热器热侧出口达到假临界温度,吸、排气温度产生突降;随着充注量的增加,吸、排气温度突降点前移。本研究可为跨临界二氧化碳制冷系统最佳充注量的确定及如何维持系统高效运行提供理论指导。     

氟利昂经济器螺杆制冷压缩机组常见故障及处理

氟利昂经济器螺杆制冷压缩机组在实际操作及运行过程中出现压缩机不能正常启动,机组振动大,声音异常,制冷量不足,压缩机能量调节及内容积比调节机构不动作,压缩机轴封泄漏,排气温度过高,冷凝压力过高以及油路系统故障。对这些故障进行分析,给出简单的解决方法。     

The effect of clearance control on the performance of an oil-free linear refrigeration compressor and a comparison between using a bleed flow and a DC current bias

A moving magnet type oil-free linear compressor has been designed for applications such as electronics cooling. A control system using a solenoid operated valve was developed for DC offset and axial clearance control. Operation of the linear compressor with a fixed clearance of 0.8 mm was compared with a zero DC offset operation. The fixed clearance operation requires a higher power input.The mean piston position can be controlled by using a DC bias on the drive voltage or by using a bleed flow from the compressor body to the suction side of the compressor. Using a DC bias on the drive voltage induces a higher power loss than using a bleed flow when there is a small radial clearance between the piston and cylinder. This provides evidence that the piston control in a refrigeration system with capacity control should be for a zero DC offset using a bleed flow.     

跨临界二氧化碳压缩机热力性能仿真与分析

针对跨临界二氧化碳半封闭式往复式活塞压缩机建立了一个通用数学模型,既包括热力学模块,也包括机械模块。热力学模块主要描述气缸内部的气体压缩过程。机械模块包括运动学模型和曲轴连杆机构模型,考虑了轴承上的功耗损失。采用一台压缩机样机对模型进行了不同运行工况下的实验验证,结果显示压缩机流量和耗功的最大误差分别不超过5%和8%。通过仿真分析了变结构和变工况条件下的压缩机性能,结果表明:在不同的运行工况下,存在最佳缸径行程比;容积效率和等熵效率都随着转速的增加而下降;吸排气阀门内径存在最佳值;对于容积效率的影响,吸气阀间隙比排气阀间隙更大,活塞与汽缸间隙比活塞环与汽缸间隙更大。     

滚动转子式压缩机吸气状态与排气温度的实验研究

利用变频滚动转子式压缩机实验台,研究了压缩机吸气带液对系统性能和排气温度的影响,以寻求降低压缩机排气温度有效、安全的方法。结果表明:在大部分空调工况和运转频率下,当吸气干度约为0.95~0.98时,系统制冷量和COP达到最大值,且压缩机的排气温度显著降低至吸气压力对应的饱和等熵压缩排气温度。考虑到运行的安全性,吸气干度合适的范围为0.95~0.98。     

Piston position sensing and control in a linear compressor using a search coil

Linear compressors with clearance seals are well established for cryocoolers using either a Stirling cycle or pulse tube. However, both piston stroke and piston offset require detection and control in valved compressors. In order to manufacture linear compressor in large scale, then a simple, robust, and cheap control system is required with a minimum of sensors and actuators. This work introduces an approach to sensing the position of the piston using a search coil. The piston stroke is detected by calculating the peak-to-peak flux linkage in relation to the measured drive voltage and current. The piston offset is proportional to an integrated modulus of the back electromotive force (emf) of the search coil. Two PID (proportional-integral-derivative) controllers were developed to control the piston stroke by adjusting the drive voltage and a solenoid valve and bleed flow to control the piston offset. Experimental results validate the proposed compressor control technique.     

Instability of automotive air conditioning system with a variable displacement compressor. Part 2. Numerical simulation

A test system is built first in order to investigate the instability of the automotive air conditioning (AAC) system with a variable displacement compressor (VDC), and hunting phenomena caused by the large external disturbance in the AAC system with a VDC and a thermal expansion valve, and in the AAC system with a VDC and a fixed-area throttling device are investigated experimentally in part 1 of this paper. The experimental results indicate that there also exist the hunting phenomena in the AAC system with a fixed-area throttling device. The system stability is found to be dependent on the direction of the external disturbance, and the system is apt to cause hunting when the condensing pressure decreases excessively since it may cause two-phase state at the throttling device inlet and make a large disturbance to the system. The piston stroke length will oscillate only when the oscillation amplitudes of forces acting on the wobble plate are great enough, otherwise the piston stroke length will be kept invariable, and then the system instability rule is also suitable for the AAC system with a fixed displacement compressor. From the experimental results, it is concluded that the two-phase flow at the throttling device inlet or at the evaporator outlet is the necessary condition but not sufficient condition for system hunting. Finally, a new concept, conservative stable region, is proposed based on the experimental results and theoretical analysis.     

Modeling the stiction effect in automatic compressor valves

The stiction effect is a source of thermodynamic losses in compressor suction and discharge systems. Deformation of the lubricant film between the valve and the seat delays the valve opening, as larger pressure differences between the cylinder and the discharge or suction chambers are needed to overcome the stiction force. A model is presented for the dynamic behavior of a ring-shaped lubricant oil film between a discharge valve and the seat. The valve is allowed to move under the action of an external force due to the time-dependent pressure difference between the cylinder and the discharge chamber. The main contributions of the model are the consideration of a finite oil amount between the valve and the seat and relationships for calculating the film thickness initial condition. At typical conditions of discharge systems of domestic refrigeration compressors, viscous effects are the dominant component in the oil stiction force under dynamic conditions.     

无油线性压缩机的频率特性和活塞偏移特性研究

针对线性压缩机随工况和热负荷变化而引起共振频率和活塞中心位置偏移量改变的问题,建立了关于压缩机共振频率的线性等效模型和傅里叶变换计算模型。两种模型用来预测线性压缩机的共振频率,后者同时用来计算活塞中心位置偏移量,模型中考虑了不同行程、不同排气压力对共振频率的影响以及不同行程、不同排气压力和不同运行频率对活塞中心位置偏移量的影响。为了验证模型的有效性,搭建了用来测量线性压缩机共振频率和活塞中心位置偏移量的测试系统,并将测量结果与模型所计算结果进行对比,结果表明,线性等效模型相比于傅里叶变换计算模型能更加准确的预测线性压缩机的共振频率;线性压缩机的共振频率随着行程的增加而逐渐减小,随着排气压力的增加而逐渐增加。实验表明,线性压缩机活塞中心位置偏移量随行程的增加而几乎不变,随着排气压力的增加而逐渐增加。傅里叶变换计算模型针对不同行程下活塞中心位置偏移量预测值高于实际值;但在不同排气压力或不同行程下的活塞偏移量可用该模型计算压缩机在上止点位置的偏移量来进行预测,误差不大于10%。     

Numerical modeling of startup and shutdown transients in reciprocating compressors

Several phenomena that affect energy consumption, noise level and reliability of compressors are associated with transient effects that occur during the compressor startup and shutdown. This paper presents a simulation methodology, experimentally validated, developed to analyze the compressor in such transients. Because the time scale associated with the compressor thermal behavior is much larger than that related to the mechanical physics, a thermal equilibrium condition has been considered herein for convenience. Results for valve displacement, piston motion, pressure in the compression chamber and resistive torques are provided to illustrate the application of the methodology and to assist an understanding of the physical aspects that affect the compressor performance throughout the startup and shutdown. It is observed that the dynamics of suction and discharge valves are greatly affected. Moreover, the model is employed to estimate the minimum voltage required for the compressor startup as a function of the equalized pressure and the auxiliary coil actuation time.