Experimental Study on Inducement and Development of Flow Instabilities in a Centrifugal Compressor with Different Diffuser Types

A centrifugal compressor is a typical compressed air energy storage device. In order to ensure the safety of the compressed energy storage process in the compressor, the internal unsteady flow phenomena need to be closely monitored, especially some serious ones like stall and surge. It is necessary to explore the mechanism of flow instabilities under different conditions. A centrifugal air compressor was tested with a vaneless diffuser and a variable vaned diffuser with five different vane setting angles, respectively. Various diffuser types resulted in various modes of flow instabilities prior to surge. The vaneless region between the impeller and the diffuser was focused on. Multiple high-speed sensors were arranged along the circumferential direction. The pressure signals at all these positions were being measured and collected in real time as the compressor was slowly throttled into surge. This paper emphasizes on the influence of matching between the impeller and the diffuser on the flow instability. The experimental results showed that the diffuser vane setting angle affected the stall characteristics. Due to the asymmetry of the volute, the circumferential pressure distribution was always severely distorted prior to surge. A high-pressure region appeared near the volute tongue, and a low-pressure region was formed away from the volute tongue. In the case of the vaned diffuser with non-design installation angle and the vaneless diffuser, the rotating stall signal was originated in the low-pressure region and propagated circumferentially. However, in the case of the vaned diffuser with the design installation angle, the circumferential high-pressure region became the most sensitive region for the generation of stall, and another form of instability occurred there. Both the inducement and development of these flow instabilities have been studied. The dynamic experimental research on the compressor matching different types of diffusers could be a good case supplement.     

丙烯酸装置循环气压缩机叶片损伤分析与修复

某石化公司丙烯酸装置循环气压缩机在运行过程中,一级叶片突然发生断裂,导致机组停机。采用宏观检查、扫描电子显微镜、能谱分析等方法对断裂叶片进行检验和检测,将断裂叶片的材质、裂纹及断口特征检测结果与疲劳断裂特征和机组运行状况进行对比,确定压缩机叶片的断裂系其达到疲劳寿命所致,提出采用激光熔覆方法对压缩机叶片进行修复,介绍了修复工艺操作程序要点,可为同类故事的处理提供参考。     

空压机润滑油系统可靠性试验研究

对空压机润滑系统进行分析,提出了一种润滑油压力调节机构,保证了空压机在高油温时油压正常,为空压机运动件提供充分润滑,从而提高空压机运行的可靠性。实验证明了该机构是可靠的,为空压机润滑系统设计提供了参考依据。     

来流马赫数影响高负荷扇形扩压叶栅气动性能的研究

为研究亚音速高负荷扇形扩压叶栅NACA0065-K48的变工况性能,采用数值方法研究了来流马赫数对叶栅气动性能和流场结构的影响,来流马赫数的取值范围为0.3～0.8。计算结果表明:随着来流马赫数的增大,叶栅静压比不断提高,但总压损失先减后增,马赫数在0.5～0.7范围内叶栅具有较好的综合气动性能。扇形叶栅下角区分离程度大于上角区的不平衡流动现象会随着马赫数的增大而加剧,通道涡则是这一发展趋势的主导,且马赫数达到0.7之后,下角区通道涡与集中脱落涡趋于融合。此外,下端壁分离螺旋点的形成与发展是控制下角区分离程度和损失大小的关键。     

往复式活塞压缩机中间喷液制冷系统的(火用)分析

通过对往复式活塞压缩机进行改造，在单级活塞压缩系统的基础上搭建了一种中间喷液冷却的准两级压缩系统并在蒸发温度为-20 ℃的工况下进行实验测量，根据实验数据对单级活塞压缩系统和新型中间喷液冷却活塞压缩系统的COP、〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗损失和〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗效率进行计算。结果表明：加入中间喷液冷却系统后，系统的COP由1.27提升至1.36，单位制冷量由155.1 kJ/kg提升至176.7 kJ/kg；单级活塞压缩系统〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗损失较大的部分是压缩机和膨胀阀，分别占压缩机输入〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗的16.2%和14.8%，加入中间喷液冷却系统后压缩机部分的〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗损失明显降低，仅占压缩机输入〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗的3.6%，冷凝器及膨胀阀的〖HT5”，7”〗火〖KG-*3〗用〖HT5”〗损比也有所下降。     

VRF制冷系统变吸气状态下频率与阀开度的同步调节

针对变流量制冷(Variable Refrigerant Flow,VRF)系统变吸气状态下带液量的精确控制以及控制元件所引起的滞后或超调现象,以变频滚动转子式制冷系统为研究对象,分别通过恒定频率不同阀开度与恒定阀开度不同频率两个实验,建立其单独控制下的拟合模型,得到其在不同工况下的同步控制方法。结果表明:过热度随阀开度的增大而减小,在过热度为6 K以下,即阀开度为27.8%～30%时,过热度控制难度上升,提高冷冻水温度可改善这一状况;过热度随频率的降低而减小,在过热度为5 K以下,即频率为44.5～46.5 Hz时,控制难度上升;吸气干度随阀开度增大而下降,随频率降低而减小;在某一工况下,以系统质量流量为控制目标,可以拟合得到频率与阀开度的关系式,实现同步控制,在变吸气状态可以精确控制吸气干度,不损坏压缩机,并使系统迅速达到稳定状态。     

Thermodynamic analysis of natural gas reciprocating compressors based on real and ideal gas models

The accurate modelling and investigating effects of various parameters of the reciprocating compressors are important subjects. In this work, based on first law of thermodynamics, conversation of mass and real and ideal gas assumptions, a theoretical analysis has been constructed to simulate natural gas reciprocating compressors. For computing the thermodynamic properties of natural gas based on real gas model, the AGA8 equation of state has been used. Numerical results validated with previous measured values and showed a good agreement. The effects of important parameters such as: angular speed, clearance and pressure ratio have been studied on the performance of the compressors. The results reveal the in-control volume temperature for ideal gas is more than real gas model but the mass flow rate and work for real gas is higher than ideal gas model. On the other hand, the indicated work that required for compression is greater for ideal gas model.     

Development of high pressure membraneless alkaline electrolyzer

A technology for cyclic generation of hydrogen and oxygen using electrodes made of variable valency material that does not need the use of separating ion-exchange membranes is presented. The technological solution enables to fabricate electrolyzers for uninterrupted producing high-pressure hydrogen with reduced energy intensity of the production. The total work for compressing 1 m³ of hydrogen and 0.5 m³ of oxygen has been estimated. Results of investigation of influence of discrete supply of DC current to the electrolysis cell, in order to improve the processes of gas evolution and to simplify the power systems of the electrolysis plant, have been considered. There is also considered an electrolysis installation equipped with a thermosorption compressor in which LaNi₅ is used as a hydride-forming compound. The comparative characteristics of the developed electrolyzer and the currently used hydrogen generators are given.     

浅谈蒸汽压缩机防喘振控制方式

在制盐及废水处理的蒸发结晶工艺系统(MVR)中,由于蒸汽压缩机工况区较窄,容易出现液击、频繁喘振、振动值超过极限导致跳车等状况。为解决这些问题,本文在DCS上通过控制蒸汽压缩机出口压力和温度、设置防喘振预警控制程序及喘振画面报警等措施,以及增加回流管线等方式,在蒸汽压缩机喘振情况出现时,DCS通过喘振预警程序及喘振报警画面等方式发出信号,当喘振信号出现时能自动开启喘振阀门,或以人工手动开启喘振阀门,避免了蒸汽压缩机液击和喘振等状况的出现。     

基于声学有限元的柴油机增压器压气机气动噪声研究

为研究船用低速柴油机增压器压气机气动噪声,采用计算流体动力学和声学有限元的混合计算方法进行了数值预测。通过试验对压气机计算模型进行了验证。在3个工况下对压气机非定常流场进行了计算,其中压力脉动被用作声学计算中的声源信息;采用声学有限元方法对压气机气动噪声进行了预测。结果表明:计算流体力学和声学有限元的混合计算方法具有较高的计算精度,可以用于压气机气动噪声数值预测;压气机进口气动噪声主要谱成分为离散单音噪声和宽频噪声;离散单音噪声在叶片通过频率处有明显的指向性,存在两个突出峰值。