Investigation of Efficiency Deterioration Causes in Process Centrifugal Compressor Operation

The high operating efficiency of centrifugal compressor is a basic requirement to maintain the gas productivity and machine availability. However, there are several factors influencing the stage efficiency in the operating environment leading to a deterioration in the compressor performance in addition to its impact on the mechanical integrity of the internal components. These variables can be classified into three main groups which are suction parameters variation, flow profile distortion, and compressor component damage. The determination of the root cause will help for a proper maintenance plan and to reduce the machine downtime. Hence, this paper will introduce a new approach to identify the inefficient compressor operation causes based on the available operation data. The investigated case is a three-stage gas transport centrifugal compressor driven by 2.9 MW two-shaft gas turbine. The outcomes from the conducted optimisation are compared with the measured discharge parameters and the findings from the internal inspection observation to emphasize the outcomes from the derived approach.     

Dämpfung von Rotating Stall in Radialverdichterstufen

In part load span centrifugal compressors incline rotating stall in the impeller, which often causes transient pressure oscillations and surge. Operation in part load span with transient processes has to be avoided, because it can endanger the compressor and the plant by vibrations. Active devices like an upstream or downstream side channel stage can influence flow and unsteady gas pressure oscillations in centrifugal compressor stages and shift rotating stall to lower flow or entirely avoid it. This article shows experimental results for characteristic lines and unsteady gas pressure oscillations in centrifugal compressor stages, which where coupled with an downstream side channel stage. The enforced turbulent eddy flow with unsteady gas pressure oscillation in side channel stages diminishes unsteady gas pressure oscillation in the centrifugal compressor stage and limits pressure gradient as well as the maximum reachable value of gas pressure oscillation at rotating stall.     

基于多重分形的离心压缩机出口动态压力非线性特征研究及其在喘振识别中的应用

以800 kW离心压缩机系统的工作状态从平稳到喘振阶段的出口动态压力为分析对象,从多重分形角度研究了多重分形谱参数与出口动态压力之间的关系,着重研究了系统在喘振状态表现出的复杂非线性特征.通过控制系统出口防喘振阀的开度得到离心压缩机在不同工况下的出口动态压力.研究系统出口动态压力的结构函数在不同权重因子下的尺度特征和多...     

Optimising the refrigeration cycle with a two-stage centrifugal compressor and a flash intercooler

The optimisation of a refrigeration process with a two-stage centrifugal compressor and flash intercooler is presented in this paper. The two-stage centrifugal compressor stages are on the same shaft and the electric motor is cooled with the refrigerant. The performance of the centrifugal compressor is evaluated based on semi-empirical specific-speed curves and the effect of the Reynolds number, surface roughness and tip clearance have also been taken into account. The thermodynamic and transport properties of the working fluids are modelled with a real-gas model. The condensing and evaporation temperatures, the temperature after the flash intercooler, and cooling power have been chosen as fixed values in the process. The aim is to gain a maximum coefficient of performance (COP). The method of optimisation, the operation of the compressor and flash intercooler, and the method for estimating the electric motor cooling are also discussed in the article.     

相似理论在高温气冷堆氦气压气机中的应用

根据相似理论推导出在不同工质条件下进行压气机模化试验的决定性相似准则数并加以敏感性分析,研究发现马赫数小于0．5时,绝热指数对模拟性能试验引起的偏差很小;在几何相似的基础上,只需使流量系数φ和压头系数ψ相等就能保证运动相似,从而保证模型与原型流动相似。研究发现氦气轮机部分工况下的低雷诺数会降低压气机气动性能和稳定性。在确定了压气机模化试验参数的基础上,由氦气压气机设计工况推导出使用空气进行模拟试验时压气机的特性曲线图,为氦气压气机的试验与优化设计提供了理论依据。     

Influence of the new refrigerant thermodynamic properties on some refrigerating turbocompressor characteristics

Comparison of the main geometrical and operating parameters of centrifugal compressors working with various refrigerants is realised in this paper. The interdependence between the centrifugal compressor pressure ratio, compression work, impeller peripheral speed, Mach number, compressor capacity, impeller diameter and width, speed of rotation, and refrigerant molecular mass, normal boiling temperature and specific volumetric cooling capacity for various refrigerants are shown and discussed. The flow phenomena in the turbocompressor flow field, caused by high Mach number and high pressure ratio, are analysed. Some theoretical observations for the influence of the substitute of the refrigerant on the turbocompressor performance characteristics are presented. The possibilities for the replacement of the refrigerant in the existing refrigerating machines are discussed.     

离心式空压机防喘振控制策略的研究

压缩空气系统是火力发电机组中非常重要的公用系统,其主要作用是为机组自动控制系统中的气动执行机构、吹扫及冷却系统提供安全可靠的气源。因此,空压机的运行工况直接关系到机组的安全稳定运行。但是,喘振是离心式空压机的固有属性,如何避免离心式空压机在运行过程中发生喘振,使空压机运行在稳定工况区是空压机控制系统需要解决的问题。本文采用OMRONCJ系列PLC控制器,对系统压力和流量采用双PID控制,利用入口门、旁路门“快开慢关”原则,有效的避免了喘振的发生。该控制系统已经在华能国际上安电厂应用,运行结果良好。     

动磁式直线冰箱压缩机的设计方法

建立了动磁式压缩机理论数学模型,采用描述函数法对非线性气体力进行了线性化,分析了压缩机系统振动特性.从制冷量和制冷性能系数(COP值)要求出发,提出了一套动磁式直线冰箱压缩机理论设计新方法,从而合理确定压缩机主要结构和性能参数,保证压缩机系统高效运行.样机设计和性能仿真分析表明.此种设计方法是可行的.     

两级蒸发对跨临界CO_2引射制冷系统影响的实验研究

两级蒸发引射制冷循环中通过二级蒸发器不仅能调节引射器出口干度还能提高系统效率。通过改变第二蒸发器冷冻水流量对两级蒸发引射制冷系统进行实验研究,并与改变引射器面积比的调控效果进行比较。结果表明:在实验工况范围内,气冷器压力、第一蒸发器压力和压缩机流量都随第二蒸发器冷冻水流量的增加而增大;而且引射器面积比越大,气冷器压力越高而蒸发器压力和压缩机流量越低。同时,系统引射系数随第二蒸发器冷冻水流量的增加而降低,而制冷量和COP则升高,尤其是在小引射系数下,系统制冷量和COP提高的更为明显。本研究为引射循环提供了另外一种良好的调控思路。     

MVR系统中离心式蒸汽压缩机与蒸发器的匹配特性研究

为了保证机械式蒸汽再压缩（mechanical vapor recompression, MVR）系统的运行经济性和稳定性,对MVR系统中离心式蒸汽压缩机与蒸发器的匹配特性进行研究。针对蒸发器换热系数在新投、工作和结垢工况下的变化,提出了蒸发器运行温阻特性线的概念,并将其与离心式蒸汽压缩机的温升特性线叠加,从而开展离心式蒸汽压缩机与蒸发器的匹配分析。通过分析发现,离心式蒸汽压缩机的设计流量偏大或蒸发器的换热面积过小会导致匹配不足,易发生喘振,从而影响MVR系统的运行稳定性。而离心式蒸汽压缩机的设计流量偏小或蒸发器的换热面积过大会导致匹配过度,致使MVR系统的运行经济性差,甚至可能造成MVR系统无法建立热力自循环。结果表明,离心式蒸汽压缩机在MVR系统启动过程中会出现不稳定的喘振现象,可以通过系统参数的临时调节或采取辅助措施来避开不稳定区。设计时应保证离心式蒸汽压缩机的喘振裕度大于20%,蒸发器换热面积的设计裕度为30%;MVR系统运行时实际蒸发温度与设计温度的偏差应控制在±5 ℃以内。研究结果可为MVR系统的设计和调试提供参考。     

离心式冷水机组变工况运行性能分析研究

以单级离心式制冷压缩机的性能曲线为基础,分析了单级离心式冷水机组的变工况运行性能,在给定的非标准工况下,综合比较了压缩机-换热器-膨胀节流装置在各种配置下的运行性能.从数据对比,说明电子膨胀阀对于离心式冷水机组的变工况运行适应性最好,手动/半自动可调膨胀节流孔板可兼顾变工况性能与制造成本,而固定式膨胀节流装置从综合能效比来讲运行经济性较差.     

Les hélico compresseurs ou compresseurs à visHelical or screw compressors

In the first part of the paper the patenting of the helical compressor at the end of the last century by a Swedish engineer as a type of air and gas blower, modified some 50 years later by another Swedish engineer as an air and gas compressor, is discussed. Decade by decade, the machine was developed by the Swedish firm SRM and by their licenced manufacturers machining the screw compressor in Sweden, Germany, France, Scotland, etc. At the present time this type of compressor seems to be fully developed and occupies a first class position in the range of positive displacement machines.Recently, a new type of screw compressor has been patented by a French engineer, this machine having only one main rotor and two small satellites, compared with the early type which had only two main rotors. These two types of compressors are now competing on the refrigeration market all over the world.In the second part of the paper, all the improvements made during the 50 yeats of development are examined in detail. In the beginning, the screw compressor was designed as an oil free compressor and was not very well adapted to the refrigerating plants, this type of oil free compressor still being used for the compression of pure gases. The first improvement was the oil injected screw compressor allowing the machine to support high compression ratios and large pressure differences and some time later, to be fitted with a sliding valve for the purpose of volume adaptation. One other modification to the profile of the rotors results in greater compressor efficiency allowing it to work with higher compression ratios; for example, in the case of low temperatures such as are used for the freezing of food products.This is not a good solution for saving energy, and the performance has been improved by creating a complementary orifice designed as a superfeed port. This increases the global efficiency of the whole circuit with a screw compressor.The same improvements were carried out on the mono rotor screw compressors and now the two types of compressors are competing with the same auxiliaries imposed by the special lubrication of this type of machine. Some comparisons are made with reciprocating and centrifugal compressors.     

氧气透平压缩机氮气试车新方法

利用现有中压氮气管网氮气作为氧气透平压缩机的密封气和工作介质,对其进行正式开车前的试车,从而节省调试时间以确保项目顺利进行。详细介绍了氮气试车的气体流路、试车过程及试车过程中的参数。     

A sorption compressor with a single sorber bed for use with a Linde-Hampson cold stage

A sorption compressor cell basically consists of a container that is filled with an adsorbent. When such a cell is thermally cycled, a pressure difference is created by the subsequent adsorption and desorption of the gas. As a consequence, a single sorption compressor cell inherently provides an intermittent flow. A Joule-Thomson expansion stage requires a more or less continuous flow. The standard way to obtain a continuous flow out of a sorption compressor is to use three or more compressor cells that are operated out of phase. This paper presents an alternative compressor concept that uses only one compressor cell, two buffer volumes and two check valves. Such a compressor is easier to construct and to operate and has a higher reliability at the expense of a slight variation in the cooler’s cold-end temperature. The principle was demonstrated using a sorption compressor cell that is filled with Maxsorb [The Kansai Coke & Chemicals Co. Ltd., 1-1 Oh-Hama, Amagasaki, Japan 660] activated carbon, is equipped with a gas-gap heat switch, and uses xenon as the working fluid. A flow of 0.52 mg/s was achieved with a low pressure of 1.39 bar and a high pressure of 17.0 bar, giving a theoretical cooling power of 42 mW at 172 K. A sensitivity analysis on several control parameters has been performed experimentally.     

Numerical Simulation and Technological Parameter Optimization for Quenching Process of a Gas Turbine Compressor Disk Based on Metallo-Thermo-Mechanics

Thermal, mechanical and microstructural phenomena are involved in the process of steel quenching. Based on the coupled metallo-thermo-mechanics theory, a calculation model has been developed in this study to simulate the quenching process of a gas turbine compressor disk by finite element method. The thermal physical and mechanical properties were treated as a functions of temperature. Moreover, a series of subroutines were developed on the MARC software platform. Consequently, simulated results on temperature, internal stress and distortion during the quenching were illustrated. With the aid of the simulated results, an optimum quenching scheme was proposed. The quenching process simulated in this study appears to be a promising tool in design of heat-treatment processing parameters for gas turbine compressor disks.     

Vibration Modal Analysis of Compressor Blade based on ANSYS

Compressor is an important part of aero engine. In the environment of high temperature and high pressure,compressor blade will suffer from several physical and chemical processes,such as centrifugal force,aerodynamic force vibration and oxidation. These processes will lead compressor blade to fatigue fracture,and at the same time,make negative effects on the engine' s overall performance. Based on the software ANSYS15. 0,we made strength analysis and modal analysis of compressor blade in this paper. As a result,we got its natural frequencies,relevant modal parameters and vibration mode cloud pictures. After analyzing the influence that centrifugal force made on modal parameters,we predicted the expected damage of the blade. Eventually the analysis results will provide the basis for overall performance evaluation,structural crack detection,fatigue life estimation and strength calculation of aircraft engine compressor.     

An aerodynamic investigation of a centrifugal compressor for HCFC123

A centrifugal compressor was investigated experimentally to improve HCFC123 compression performance. A CFC11 compressor working with HCFC123 shows lower adiabatic head rise, efficiency and volume flow. Another CFC11 compressor working with HCFC123 and a modified impeller shows a result comparable to that when CFC11 is compressed. A tandem impeller is designed to compensate for the volume flow increase for HCFC123. This impeller sufficiently absorbs the volume flow increase and also improves efficiency.     

Optimization of refrigeration system with gas-injected scroll compressor

Gas refrigerant injection has been proven as an effective method to improve the performance of the scroll compressor and its refrigeration system under high compression ratio working conditions. Much research on the injected scroll compressor and its system has been conducted, but the universal control and design method is still lacking. A model of the refrigeration system with a gas-injected scroll compressor is developed in this paper. With this model, the effects of gas injection on the system and component parameters are investigated. Based on the identified evaporator characteristics and thermodynamic analysis, a set of general principles for the design and operation of the refrigeration or heat pump system with a gas-injected scroll compressor is proposed.     

Theoretical study of a novel refrigeration compressor – Part II: Performance of a rotating discharge valve in the revolving vane (RV) compressor

A new refrigeration compressor, named ‘Revolving Vane (RV) compressor’, has been introduced in Part I of this paper series. For a first time in refrigeration compressors, a rotating discharge valve is employed in the RV compressor mainly due to the rotation of the entire cylinder. This paper presents a theoretical investigation on the dynamic behavior of a reed-type discharge valve undergoing rotatory motion, with the primary objective of elucidating the applicability of such valves in refrigeration compressors. Under the application of the Euler–Bernoulli beam theory, a mathematical model of the rotating valve is formulated and the transient response of the valve under centrifugal loads in addition to pressure forces is analyzed. Results have shown that under careful design considerations, the performance as well as the reliability of the rotating discharge valve can be enhanced as compared to a non-rotating valve that has been used in all refrigeration compressors currently.     

Characterization of a vapor injection scroll compressor as a function of low,intermediate and high pressures and temperature conditions

The interest in two stage cycles has increased in the last years and some compressor manufacturers have commercialized compressors adapted to work in these conditions. Nevertheless, the information supplied by them usually is limited to certain design conditions defined by the application and extrapolation to other conditions is not straightforward. In this article a test campaign of an injection scroll compressor is presented. This test campaign was divided in two parts, on the first one a wide range of evaporating and condensing pressures for the intermediate conditions recommended by the manufacturer were measured, and the compressor behavior was systematically compared with single stage compressor of the same volume. On the second part an experimental study of the influence of the intermediate conditions on the performance have been done. The study has included the evaluation of the separate influence of intermediate gas superheat, intermediate pressure and wet injection.