多级离心式压缩机故障停机反转特性研究

发布时间：2018-04-03 10:01

本文选题：反转　切入点：故障停机　出处：《上海交通大学》2012年硕士论文

【摘要】：离心式压缩机在国民经济各部门中有着重要的地位,相对于容积式压缩机而言,其具有流量大、工艺性能好、结构简单等特点,因此在化工、能源以及冶金等领域有着广泛的应用。近年来,随着设计、制造与控制技术的进步,石化企业大型乙烯装置陆续建成,被称为乙烯装置“心脏设备”的裂解气离心式压缩机也在市场的主导下向大型化趋势发展。在实际生产运行中,压缩机系统中储存的高压工艺气体量显著增加,发生故障停机跳车时,高压气体不能及时排出,导致压缩机各段进出口压力不能迅速达到平衡,工艺气体将从离心式压缩机出口通过压缩机内部流到入口,气体膨胀产生动力,反向推动力可能使压缩机在停机过程中出现反转。压缩机反转将对干气密封及其他零部件造成破坏,严重影响了乙烯装置的平稳、高效运行。本文首先以国内多家石化企业的大型乙烯装置裂解气离心式压缩机为例,对乙烯装置的工艺流程及裂解气压缩机的作用进行了简要介绍。与此同时,分析了正常停机过程与故障停机反转过程中离心式压缩机的运动规律与动力学特性,并对反转过程中压缩机各段的压力平衡过程进行了较为深入的探讨,最终获得故障停机反转过程中系统压力平衡与运动的共性规律。针对离心式压缩机反转造成的破坏,分析了干气密封与可倾瓦轴承的结构及工作原理,给出了产生破坏的原因及部分改造措施。基于对离心式压缩机故障停机过程的分析与共性规律的总结,本文建立了针对简化系统的离心式压缩机正常停机过程与故障停机反转过程动力学模型。与此同时,建立了故障停机反转过程中压缩机各段压力平衡模型。而后,以实际乙烯装置裂解气压缩机故障停机反转过程数据为参考,利用编制的程序对正常停机与故障停机反转过程进行仿真计算,从而对所建立的模型进行了验证。结果表明,离心式压缩机故障停机过程中出现反转,是由于在惰走过程结束后,压缩机各段进出口压力仍没有达到平衡,高压工艺气体从出口通过压缩机内部流到入口,产生了反向推力矩,利用本文中所建立的系统模型得到的计算结果与实际停机过程记录数据较为吻合。针对离心式压缩机故障停机过程中内部流动复杂等特点,本文还对压缩机停机及反转过程进行了数值模拟,计算了不同转速下的流动情况,获得了上述过程中压缩机内部的流动规律及压力分布,分析了轴向推力、转矩等参数随转速的变化趋势并且再次验证了前述动力学模型的可靠性。现场数据验证及CFD计算均表明：理论模型能够较好的模拟结构相近的离心式压缩机故障停机反转过程,进而为压缩机系统改造与控制策略调整提供依据,消除实际生产运行中压缩机反转隐患。因此,本文进行的分析及所建立的理论模型具有一定的现实意义与工程应用价值。
[Abstract]:Centrifugal compressor plays an important role in various departments of the national economy. Compared with the volumetric compressor, it has the characteristics of large flow rate, good process performance, simple structure, and so on, so it is widely used in chemical industry.Energy and metallurgy are widely used.In recent years, with the development of design, manufacture and control technology, large scale ethylene plants in petrochemical enterprises have been built one after another. The centrifugal compressor of cracking gas, known as the "heart equipment" of ethylene plant, is also developing to a large scale under the market.In the actual production and operation, the quantity of high pressure process gas stored in the compressor system has been increased significantly, and the high pressure gas can not be discharged in time when there is a failure to stop and jump, which results in the pressure of inlet and outlet of the compressor being unable to reach balance rapidly.Process gas will flow from the outlet of the centrifugal compressor to the inlet of the compressor, and the gas expansion will generate power. The reverse propulsion may cause the compressor to reverse during the shutdown process.The reverse of compressor will destroy the dry gas seal and other parts and seriously affect the smooth and efficient operation of ethylene plant.Taking the cracking gas centrifugal compressor of large scale ethylene plant in many domestic petrochemical enterprises as an example, the technological process of ethylene plant and the function of cracking gas compressor are briefly introduced in this paper.At the same time, the movement law and dynamic characteristics of centrifugal compressor during normal shutdown and fault shutdown reversal are analyzed, and the pressure balance process in each section of compressor is discussed deeply.Finally, the common rules of system pressure balance and motion are obtained.In view of the damage caused by the reverse of centrifugal compressor, the structure and working principle of dry gas seal and tilting pad bearing are analyzed, and the causes of failure and some measures of improvement are given.Based on the analysis of the fault shutdown process of centrifugal compressor and the summary of the common law, the dynamic model of the normal shutdown process and the fault shutdown reversal process of the centrifugal compressor is established in this paper.At the same time, the compressor pressure balance model is established.Then, with reference to the data of the reverse process of the fault shutdown of the cracking gas compressor of the actual ethylene plant, the simulation calculation of the normal shutdown and the reverse process of the fault shutdown is carried out by using the program compiled, and the established model is verified.The results show that the reverse of the centrifugal compressor during failure shutdown is due to the fact that the inlet and outlet pressure of the compressor is still not balanced after the idle walk, and the high pressure process gas flows from the outlet to the inlet of the compressor through the inside of the compressor.The reverse thrust torque is generated, and the calculated results obtained by using the system model established in this paper are in good agreement with the actual data recorded in the shutdown process.In view of the complex internal flow in the process of centrifugal compressor fault shutdown, this paper also carries out numerical simulation of the compressor shutdown and reverse process, and calculates the flow situation at different rotational speeds.The flow law and pressure distribution in the compressor are obtained. The variation trend of axial thrust torque and other parameters with rotating speed is analyzed and the reliability of the above dynamic model is verified again.Field data verification and CFD calculation show that the theoretical model can well simulate the reverse process of the centrifugal compressor fault shutdown with similar structure, and provide the basis for the compressor system transformation and control strategy adjustment.Eliminate the hidden danger of compressor inversion in actual production operation.Therefore, the analysis and the theoretical model established in this paper have certain practical significance and engineering application value.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH452

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