离心空压机喘振与控制

由于离心式空压机结构简单,排气量大,效率高,目前广泛应用于冶金、化工以及空分等行业。但离心式空压机在运行过程中,对气体的压力、流量以及温度变化较为敏感,容易发生"喘振"现象。离心空压机喘振具有较大的危害性,是造成空压机损坏的主要原因之一。因此,研究和预防喘振的发生,弄清和掌握喘振的机理,采取有效控制措施避免喘振的发生是离心空压机控制中的重要任务。     

Active surge control for variable speed axial compressors

This paper discusses active surge control in variable speed axial compressors. A compression system equipped with a variable area throttle is investigated. Based on a given compressor model, a fuzzy logic controller is designed for surge control and a proportional speed controller is used for speed control. The fuzzy controller uses measurements of the change of pressure rise as well as the change of mass flow to determine the throttle opening. The presented approach does not require the knowledge of system equilibrium or the surge line. Numerical simulations show promising results. The proposed fuzzy logic controller performs better than a backstepping controller and is capable to suppress surge at different operating points.     

中央空调压缩机无位置传感器正弦波变频控制器的开发

为了改善定频空调压缩机启停频繁、噪声大及效率低等缺点,开发了基于永磁同步电机无位置传感器正弦波控制的中央空调压缩机变频控制器.控制器采用通用单片机,依据矢量控制理论,通过估计转子磁链成功实现了转子位置和转速的在线检测.压缩机在中低速时使用单位电流最大转矩控制方法,提高了压缩机及空调整机的效率;高速时利用弱磁控制,提高了压缩机的转速.软件算法在中央空调变频压缩机上得到验证.空调运行时,压缩机的电压和电流正弦度好,转速波动小,效率高于另一种国外方案.实验结果表明,该变频控制器实现了空调的变频节能,可以在空调制冷系统中应用.     

Surge detection methods using empirical mode decomposition and continuous wavelet transform for a centrifugal compressor

The occurrence of surge in a centrifugal compressor results in large oscillations in pressure and flow. To avoid damaging the compressor because of surge, we develop several surge detection methods in this study. Considering the incipient surge phenomenon, the Empirical mode decomposition (EMD) and the Morlet Continuous wavelet transform (CWT) methods are selected. Both methods are validated through experimental data collected from surge tests conducted on the three-stage Ingersoll-Rand Centac centrifugal compressor at Toyota Motor Manufacturing in Kentucky, USA. For incipient surge detection, the EMD-based method can determine the threshold 1 sec earlier than the Morlet CWT-based method. Therefore, the EMD method can be used to implement the incipient surge detection scheme on the tested centrifugal compressor for safety considerations.     

百万吨乙烯装置丙烯压缩机组设计的技术难点及解决方案

针对丙烯压缩机组设计过程中遇到的技术难点——ANTI-STONEWALL阀门流量计算等,通过分析乙烯装置丙烯流程中防喘振、防阻塞控制的特点,同时考虑多种因素影响,对常规算法进行补充,提出区别以往常规的独特流量计算方法,设计与实现了ANTI-STONEWALL阀门流量及其控制算法的解决方案。     

Analytical design of an industrial two-term controller for optimal regulatory control of open-loop unstable processes under operational constraints

This paper proposes a novel optimization-based approach for the design of an industrial two-term proportional-integral (PI) controller for the optimal regulatory control of unstable processes subjected to three common operational constraints related to the process variable, manipulated variable and its rate of change. To derive analytical design relations, the constrained optimal control problem in the time domain was transformed into an unconstrained optimization problem in a new parameter space via an effective parameterization. The resulting optimal PI controller has been verified to yield optimal performance and stability of an open-loop unstable first-order process under operational constraints. The proposed analytical design method explicitly takes into account the operational constraints in the controller design stage and also provides useful insights into the optimal controller design. Practical procedures for designing optimal PI parameters and a feasible constraint set exclusive of complex optimization steps are also proposed. The proposed controller was compared with several other PI controllers to illustrate its performance. The robustness of the proposed controller against plant-model mismatch has also been investigated.     

Study on flow fields in high specific speed centrifugal compressor with unpinched vaneless diffuser

Performance of centrifugal compressors strongly depends on their internal flow fields. CFD has become indispensable tool for getting the information about flow fields in centrifugal compressors. CFD codes are usually validated by some representative data or compared with calculated results by other CFD codes, in order to ensure their accuracies. However, learning their accuracies for all types of centrifugal compressor’s specifications requires continuous works that compare experimental data obtained in developmental processes of various types of centrifugal compressors with CFD results. A prediction of a performance and a flow field of a centrifugal compressor by CFD is relatively accurate when the impact of separation and secondary flow on that flow field is weak, i.e. near design condition. Centrifugal compressors are deemed to have a wide operating range alongside high efficiencies at design points. Hence the prediction accuracy of CFD at off design conditions, where the impacts of separation and secondary flow on the flow field are strong, is critical for the design of the centrifugal compressors. This study therefore investigated the prediction accuracy of CFD using a centrifugal compressor whose geometry was intentionally changed to have a distorted flow field over a whole operating range, i.e. from choke to surge.     

Coordinating IMC-PID and adaptive SMC controllers for a PEMFC

For a Proton Exchange Membrane Fuel Cell (PEMFC) power plant with a methanol reformer, the process parameters and power output are considered simultaneously to avoid violation of the constraints and to keep the fuel cell power plant safe and effective. In this paper, a novel coordinating scheme is proposed by combining an Internal Model Control (IMC) based PID Control and adaptive Sliding Mode Control (SMC). The IMC-PID controller is designed for the reformer of the fuel flow rate according to the expected first-order dynamic properties. The adaptive SMC controller of the fuel cell current has been designed using the constant plus proportional rate reaching law. The parameters of the SMC controller are adaptively tuned according to the response of the fuel flow rate control system. When the power output controller feeds back the current references to these two controllers, the coordinating controllers system works in a system-wide way. The simulation results of the PEMFC power plant demonstrate the effectiveness of the proposed method.     

Numerical simulation investigation on centrifugal compressor performance of turbocharger

In this paper, the mathematical model of the flow filed in centrifugal compressor of turbocharger was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using CFX. Meanwhile, the influences of grid number and distribution on compressor performance were investigated, and numerical calculation method was analyzed and validated, through combining with test data. The results obtained show the increase of the grid number has little influence on compressor performance while the grid number of single-passage is above 300,000. The results also show that the numerical calculation mass flow rate of compressor choke situation has a good consistent with test results, and the maximum difference of the diffuser exit pressure between simulation and experiment decrease to 3.5% with the assumption of 6 kPa additional total pressure loss at compressor inlet. The numerical simulation method in this paper can be used to predict compressor performance, and the difference of total pressure ratio between calculation and test is less than 7%, and the total-to-total efficiency also have a good consistent with test.     

Adaptive flow optimization of a turbocharger compressor to improve engine low speed performance

To improve the engine overall performance, an adaptive flow optimization procedure is proposed in this paper to synthesize turbocharger compressor optimum designs. Two objective functions are involved in the adaptive optimization. They are the traditional compressor design and the compressor design with consideration of improving engine overall performance. The two-step decomposition approach is chosen to generate optimum designs. The optimized designs not only satisfy turbomachinery and engine constraints but also have optimum objective function values in the two fields. Performance sensitivity analysis of compressor main design variables is performed for the flow optimization design process. A centrifugal compressor is redesigned for a turbocharged gasoline engine, as an example, based on the adaptive flow optimization process. The calculating results show a more than 5% increase of isentropic efficiency in comparison with the base line compressor, resulting in a more than 19% increase of engine torque at low speed conditions.     

离心压缩机喘振特性及喷射扩稳研究

以某单级离心压缩机为研究对象,搭建工况动态特性实时监测系统,通过控制排气调节阀的开度展开喘振实验研究,在此基础上,设计和实现离心压缩机的主动控制喷射扩稳,通过小孔喷射高速气流实现喘振裕度的提升.研究表明:出口压力脉动幅度大大高于进口压力脉动,进气管道流动进入深度喘振的起始时刻要落后于排气管道进入深度喘振的起始时刻;机匣...     

叶片断裂破坏与气动非定常脉动的关联分析

在离心压气机实际的工况运行中,流量通常在一个区间内变化,如果流量超出稳定工作范围,在叶轮流道中可能会引起旋转失速甚至喘振等非稳定性流动现象,极易引发叶片的疲劳断裂[1].本文基于某型压气机在实际运行中发生叶片叶顶断裂事故,利用CFD软件NUMECA进行数值计算分析,主要从气动方面分析其在各个流量下的流动情况.从非定常流动特征方面深入分析其破坏机理.结果表明在一定的流量下,流场中的压力脉动非常强烈,极有可能引发叶片的疲劳破坏.本研究为压缩机叶片的疲劳破坏机理力学分析提供了可靠的理论依据和坚实的数据基础.     

涟钢3万m~3/h制氧机组的控制系统

以FOXBRO集散控制系统（DCS）在涟钢3万m3/h制氧机组中的应用为例,介绍了集散控制系统在制氧工艺流程中的应用及其先进性,重点针对利用集散控制系统实现的制氧机组空压机防喘振控制、分子筛切换的顺序控制、氧压机3种停车方式的顺序控制及防喘振控制,同时对一些常见的控制过程中的问题,作了简单的介绍。     

正弯静叶对某多级压气机变工况特性的影响研究

对某13级轴流压气机的内部流场进行了全三维数值模拟数值分析。针对原型压气机变工况运行时静叶吸力面角区位置流动分离较为严重的情况,进行正弯优化设计,探讨正弯叶片的引入在全工况范围内对压气机前三级的流动特性带来的影响,并重点分析改型前后近喘振点的流场特征。结果表明,适当的弯叶片可以抑制角区闭式分离的发生和发展,从而恢复角区的扩压能力,并获得整个流场的改善,最终提高压气机的压比、效率和喘振裕度,同时级间匹配良好,变工况性能明显优于原型。     

基于TS3000系统的延迟焦化富气压缩机防喘振控制探讨

介绍了TS3000基本软硬件配置以及三冗余原理,论述了压缩机发生喘振的原理,压缩机防喘振控制的3种基本方法。介绍了九江石化延迟焦化装置富气压缩机防喘振控制的原理和实现方式,分析了防喘振阀的动作过程,总结了该套系统在实际应用中的效果。     

Prediction of Critical Multiphase Flow Through Chokes by Using A Rigorous Artificial Neural Network Method

Passing the flow through a choke valve is one of the most important and valuable techniques in oil production. Liquid flow rate is an important factor to assess oil wells from an operational and economic point of view. There are some validated models that predict the flow rate of single phase fluid in a wellhead condition. However, the fluid is mostly multi-phase and lies in the critical condition when passing through the choke valve. A large number of scholars have made abortive attempts to develop a universal method to predict this flow rate. Based on the available empirical equations, the liquid rate depends on upstream pressure, gas-liquid ratio, and the bin size of the choke valve. To fill the current gap, this paper seeks to develop a model that can predict the multiphase flow behavior of choke valve in critical conditions by means of Radial Basis Function (RBF) neural network coupled with Genetic Algorithm (GA), as the optimizer. The model was developed using 221 training and 55 testing data points. The obtained results were then compared with the field data and, accordingly, the eligibility of the selected method was verified. Moreover, the dependency of input parameters on the liquid rate was evaluated using the Pearson and Spearman methods to show the effectiveness of each input parameter. While upstream pressure and gas-liquid ratio showed an inverse relationship, the choke bin size showed a direct relationship with the liquid rate.     

打磨修理对跨声速压气机性能的影响研究

为了控制航空发动机压气机叶片损伤继续发展,通常采用孔探打磨进行修理。为研究其带来的影响,选取跨声速压气机Rotor37为研究对象,构建了不同叶高的叶片前缘打磨修理模型,采用数值模拟方法,研究了打磨修理对跨声速压气机气动性能的影响,结果表明:叶片前缘打磨修理使压气机整体性能下降,压比减小,效率降低,使堵塞点流量减小,而对失速流量点基本没有影响;不同叶高的打磨修理中心对压气机气动性能影响趋势一致影响幅度相当,但打磨叶高的不同造成压气机内部流场变化;叶片前缘打磨后,打磨处激波前马赫数增加,激波强度增大,影响效果随着叶高的增加而增加;压气机进口因为叶片打磨而造成相对动能在叶片打磨处附近降低。     

车用低压质子交换膜燃料电池电堆的半经验模型

首先介绍质子交换膜燃料电池建模的现状,然后结合车用情况采用半经验方法进行建模,主要从理论基础出发,简化电堆模型,从中推导出浓差项,提出浓差阻力的概念.根据车用低压电堆的工作条件,采用断电法来获取不同温度下电堆的欧姆损失,用线性拟合方法获得欧姆损失表达式.在保证其他操作条件不变的情况下,改变空气过量系数,通过比较电堆电压的变化情况,采用实数编码的遗传算法对试验数据进行拟合,获得浓差阻力系数的表达式.在获得欧姆、浓差损失的基础上,推导出电堆的活化损失表达式.最终获得车用低压质子交换膜燃料电池电堆的半经验模型,并采用建立的模型对20组不同温度和过量空气系数下的电堆输出电压进行计算,计算结果与实际测量值比较吻合,说明建模方法相当有效,模型精度达到系统优化和控制的要求.     

Experiment and surge analysis of centrifugal two-stage turbocharging system

To study a centrifugal two-stage turbocharging system’s surge and influencing factors, a special test bench was set up and the system surge test was performed. The test results indicate that the measured parameters such as air mass flow and rotation speed of a high pressure (HP) stage compressor can be converted into corrected parameters under a standard condition according to the Mach number similarity criterion, because the air flow in a HP stage compressor has entered the Reynolds number (Re) auto-modeling range. Accordingly, the reasons leading to a two-stage turbocharging system’s surge can be analyzed according to the corrected mass flow characteristic maps and actual operating conditions of HP and low pressure (LP) stage compressors.     

制氧空压机喘振原因分析与解决对策

为了研究三制氧空压机喘振问题原因,采用排除和比对测试方法,在空压机喘振停机后热态及冷态情况分别做了调节阀在100%~50%行程范围内动作情况和气动薄膜调节阀全开和全关行程时间测试、DCS控制信号突变实验,获得一级导叶机械部件在45.5%至43.5%阀位范围内存在卡滞现象和二级导叶机械限位与空压机最初投运时防喘振实验报告中限位不符的结果,排除空压机喘振是仪表故障引起的可能性,得到空压机两次喘振停机原因分别为一级导叶卡滞及二级导叶限位开度太小的结论,最终提出解决对策。