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。     

滑板喷射型准二级滚动转子压缩机性能

本文提出一种将补气结构设置于滑板上的新型滚动转子压缩机结构,该结构能保证吸气结束后补气口才向压缩腔打开,避免了补气回流至吸气管导致的容积效率降低。通过建立数值模型,对该新型结构进行了模拟研究。结果显示:该新型结构可完全避免喷射过程中喷射制冷剂回流至吸气腔;与传统结构补气单缸滚动转子压缩机相比,带有新型喷射结构的单缸滚动转子压缩机的容积效率提升2.6%~3.7%。     

变频螺杆压缩机经济器的变工况实验研究

为提高带经济器的变频螺杆压缩机效率,本文实验研究了压缩机排气压力、电机频率、经济器补气压力、容积效率等参数对压缩机效率的影响,得出压缩机排气压力和电机频率对经济器补气压力的变化规律。当冷凝温度为40℃,蒸发温度为5℃时,电机频率从200 Hz降至50 Hz,经济器补气压力上升了88.3 k Pa;当排气压力提高30%,经济器补气压力仅上升了4.9 k Pa,压缩机的容积效率仅降低约2%。结果表明:与压缩机排气压力相比,电机频率对补气压力和容积效率的影响较大。     

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。     

带经济器的螺杆式压缩机性能试验

为研究带经济器的螺杆式压缩机在不同补气状态下的性能,以压缩机的理论压缩过程为基础,设计不同压比、不同吸气压力和不同补气压差的测试工况,并进行相应试验。结果表明,在吸气压力一定的工况下,压比越大,补气压差增大对于制冷量和性能系数的提升作用越明显;在压比一定的工况下,吸气压力越低,补气压差增大对于制冷量的提升作用越明显;当压比低于2.5时,尽管中间补气可以提升压缩机的制冷量,但压缩机的性能系数呈下降趋势。     

冰箱直线压缩机运行不稳定的实验研究

本文进行了直线压缩机冰箱系统的制冷实验,分析了直线压缩机运行的不稳定特性。结果表明:冰箱制冷过程中直线压缩机定频运行,会出现三种不同的不稳定状态:启动调节不稳定、外部扰动不稳定和电磁阀调节不稳定。启动过程中,供电参数的调节以及吸排气压力的变化引起的不稳定状态,随着电参数保持不变和吸排气压力趋于稳定,启动过程的不稳定现象也逐渐消失。当供电参数和制冷工况保持稳定时,制冷系统的随机扰动也会使直线压缩机产生一定的不稳定振荡,行程最大振幅约0.3 mm,电流和输入功的最大波动约为平均值的10%,直线压缩机对外部扰动具有自修复性。电磁阀调节过程对直线压缩机的稳定性影响较大,行程最大振幅约2.2 mm,压缩机存在极大的撞缸可能性。因此非常有必要结合制冷系统的运行工况,进行直线压缩机本体结构和控制系统的优化设计,保证直线压缩机在冰箱调节过程中安全可靠的运行。     

基于变频压缩机的跨临界CO_2热泵热水器名义工况的试验研究

搭建基于变频压缩机的跨临界CO_2热泵热水器试验台。在系统制冷剂充注量为950 g,测试工况为名义工况的前提下,分析电子膨胀阀开度和压缩机运行频率对系统参数,包括压缩机吸气温度和压力,排气温度和压力,系统制热量和制热性能系数COP_h的影响。试验结果表明:随着电子膨胀阀开度的增大,压缩机吸气温度降低,吸气压力升高,而排气温度和排气压力趋势性走低,中间偶有起伏;制热量随着电子膨胀阀开度的增大逐渐降低,制热性能系数COP_h在电子膨胀阀一定开度范围内存在一个最优值;压缩机吸气温度受频率的影响较小,吸气压力则随着频率的增加而降低,排气温度和排气压力均随频率的增加而升高;制热量随着频率的升高而增大,制热系数COP_h最大值出现在低频率范围。     

变容量双级压缩热泵系统实验研究

通过改变压缩机频率,实现低高压压缩机理论输气量不同配比,对变容量双级压缩热泵系统进行实验研究,分析系统中间压力、中间温度和制冷剂循环量等参数随低高压压缩机理论输气量比的变化规律。实验结果表明:该系统在较低蒸发温度时,通过增大低高压压缩机理论输气量比可有效提高系统制热量,但系统制热COP改善较小;随蒸发温度的降低,系统制热COP最优值所对应的低高压压缩机理论输气量比将遵循增大的规律。同时指出该系统在蒸发温度0℃,冷凝温度40℃,低高压压缩机理论输气量比为2.82时,系统中间压力已接近冷凝压力,系统失去中间喷射的补气增焓效果。该研究为双级压缩系统性能的研究及其优化设计提供了有力的参考。     

无油线性压缩机变容量制冷性能实验研究

无油线性压缩机具有结构简单紧凑、效率高和寿命长等优点,在航空航天热控领域具有巨大的发展潜力。针对实验室研制的无油线性压缩机进行变容量制冷性能研究,分析行程和余隙容积变化对压缩机的制冷性能受的影响。实验结果表明,在冷凝温度为48℃,蒸发温度为10℃,热沉温度维持15℃,行程从6.5 mm增加到8.9 mm时,压缩机的制冷量会随行程的增大而增大。在行程为8.9 mm时,最大制冷量为180 W;系统的COP和压缩效率会随着行程的增大先增大后减小,在行程为7.9 mm时,具有最高COP和压缩效率,分别为1.78%和30.6%。在冷凝温度为55℃,蒸发温度为10℃,热沉温度稳定在15℃,系统的余隙长度从0.1 mm增加到1.1 mm时,随着余隙长度的增加,压缩机的制冷量、COP和压缩效率会逐渐降低。电机效率会随着余隙容积的增加先升高后降低,在余隙长度为0.9 mm时,电机效率为78.4%。     

A novel linear electromagnetic-drive oil-free refrigeration compressor using R134a

A new type of oil-free moving magnet linear compressor with clearance seals and flexure springs has been designed for incorporation into a vapour compression refrigeration system with compact heat exchangers for applications such as electronics cooling. A linear compressor prototype was built with a maximum stroke of 14 mm and a piston diameter of 19 mm. An experimental apparatus was built to measure the compressor efficiencies and coefficient of performance (COP) of a refrigeration system with the linear compressor, using R134a. The resonant frequency for each operating condition was predicted using the discharge pressure, suction pressure and stroke. Refrigeration measurements were conducted for different strokes under each pressure ratio with a fixed condenser outlet temperature of 50 °C and evaporator temperature ranging from 6 °C to 27 °C. The results show that the COPs are around 3.0 for tests with a pressure ratio of 2.5 (evaporator temperature of 20 °C).     

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%。     

Thermodynamic analysis on the performance of a variable speed scroll compressor with refrigerant injection

A thermodynamic model for a variable speed scroll compressor with refrigerant injection was developed using continuity, energy conservation and real gas equation. The model included energy balance in the low-pressure shell compressor, suction gas heating, motor efficiency, and volumetric efficiency considering gas leakages as a function of compressor frequency. The developed model was verified by comparing the predicted results for the no injection condition with the experimental data. The deviations of the predicted from the measured values were within 10% for approximately 90% of the experimental data. Based on the model, mass flow rate, suction gas heating, cooling capacity and power consumption of the compressor were estimated and analyzed as a function of frequency. The effects of refrigerant injection on the performance of the compressor were also discussed as a function of frequency, injection conditions, and injection geometry.

Résumé

A thermodynamic model for a variable speed scroll compressor with refrigerant injection was developed using continuity, energy conservation and real gas equation. The model included energy balance in the low-pressure shell compressor, suction gas heating, motor efficiency, and volumetric efficiency considering gas leakages as a function of compressor frequency. The developed model was verified by comparing the predicted results for the no injection condition with the experimental data. The deviations of the predicted from the measured values were within 10% for approximately 90% of the experimental data. Based on the model, mass flow rate, suction gas heating, cooling capacity and power consumption of the compressor were estimated and analyzed as a function of frequency. The effects of refrigerant injection on the performance of the compressor were also discussed as a function of frequency, injection conditions, and injection geometry.     

Testing and modelling of an automotive wobble plate compressor

Wobble plate compressors are well used in air conditioning for high-class automobiles. They allow continuous control by automatic adjustment of the piston stroke, to keep the low pressure above a certain limit. Here an externally controlled wobble plate compressor is analyzed experimentally through its isentropic and volumetric effectivenesses and control characteristics. Compressor effectivenesses depend mainly on the compressor speed and pressure ratio: there is obtained, for example, isentropic and volumetric effectivenesses of 0.65 and 0.8 for a pressure ratio of 4 at 1000 rpm and 0.4 and 0.35 for the same pressure ratio at 4000 rpm. This degradation is attributed to the increasing of the supply pressure drop. The “lubricant” (oil + dissolved refrigerant) mass flow rate is obtained by minimization of the residuals of the thermal balances on the compressor, condenser and evaporator. Here an important oil-flow circulation is obtained: between 9.5% and 12.5% of the refrigerant flow rate. A special displacement sensor is used to measure instantaneous piston stroke and to relate it to overall compressor performance. This measurement is then compared with the results obtained with a semi-empirical model, which is able to predict, in part load, the compressor displacement. The model predicts the displacement ratio with deviations that vary between −14.5% and +8.1%.     

罗茨水蒸气压缩机性能实验研究

压缩机是蒸气压缩蒸发系统的核心设备,会显著影响系统的能耗和运行稳定性.本文搭建了基于罗茨压缩机驱动的蒸气压缩蒸发实验台,蒸发温度为80～100℃,蒸发压力为46.60～101.64 kPa,压缩机压升为17.86～36.03 kPa,蒸发量为125.72～424.85 kg/h,实验研究了吸气流量、压缩比功、容积效率和...     

Effects of vapor injection techniques on the heating performance of a CO2 heat pump at low ambient temperatures

The objective of this study is to investigate the effects of vapor injection techniques on the heating performance of a CO₂ heat pump. The performances of the flash tank vapor injection (FTVI), sub-cooler vapor injection (SCVI) and FTVI with a suction line heat exchanger (FTSX) cycles were measured and analyzed with variations of the outdoor temperature, compressor frequency, and injection mass flow rate. At the outdoor temperature of −15 °C and compressor frequency of 55 Hz, the heating capacity and COP of the optimized SCVI cycle were 12.1% and 12.7% higher than those of the optimized FTVI cycle, respectively, because the total mass flow rate in the SCVI cycle was higher than that in the FTVI cycle by the large temperature and pressure differences in the sub-cooler of the SCVI cycle. In addition, the optimum injection flow rate ratios in the vapor injection CO₂ cycles yielding the maximum COP were determined at various compressor frequencies.     

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。     

螺杆式压缩机内置活塞式进气控制阀分析

对内置活塞式进气控制阀在螺杆式压缩机上的应用原理及其作用进行阐述,进气控制阀的压损、吸气侧的筒直径及其弹簧力大小是影响阀打开力大小的3个主要因素。阀打开力与阀的压损、阀体吸气侧筒的直径平方几乎呈正比关系,弹簧力是阻碍阀打开的因素,弹簧力减小的数值就是阀打开力增大的数值。在进气控制阀的设计上,对螺杆式压缩机的性能和进气控制阀可靠性必须综合考虑,进气控制阀设计参数选择要合适,在确保阀打开可靠的前提下,阀的压损一般控制在25-30 kPa范围内。     

A study on the linear compressor characteristics of the Stirling cryocooler

The purpose of this study is to analyze the characteristics of the linear compressor for Stirling cryocooler. To ensure high performance and long life of the free piston, free displacer Stirling cryocooler, the operating parameters of the linear compressor should be optimized. The experimental results show the operating frequency of the linear compressor has significant effect to the input power characteristics, and the compressor with higher charging pressure of working fluid has high pressure ratio. For the high performance of the linear compressor, compressor has uniform magnetic force with different stroke, and the optimal operating frequency with respect to the charging pressure.