往复压缩机管线的振动分析方法探究

随着石化行业装置的大型化,往复压缩机的管线振动问题成为困扰整机性能的关键。通过对相关规范的技术领会,对往复压缩机运动特性、管线振动产生的机理、振体特性等的研究,提出利用DIG-MO和CAESARII分析软件对压缩机管线的振动进行综合分析,实现了设计阶段对产品质量进行预期验证的目的。

离心压缩机的喘振机理及实例分析

阐述了离心式压缩机的工作原理和喘振机理,介绍了压缩机入口流量、压力、转速和入口介质相对分子质量等几个主要因素对喘振的影响,以及对喘振现象的判断和解决方法。控制工艺参数在合理范围内,机组调整负荷时,协调压缩机的性能曲线及管网特性曲线的变化,使工作点在工作区,可保证机组的稳定运转。

轴流压缩机动叶片模态分析方法研究

基于某轴流压缩机第1级动叶片,在精确建立其几何模型的基础上,通过有限元仿真方法提取了前10阶固有频率及模态振型的计算值,然后通过试验测试方法对其进行了模态测试,得到了前10阶固有频率及模态振型的实测值,并将理论计算结果和实际测试结果进行了对比。

高温高速下大涡旋压缩机皮带故障原因分析

通过对高温高速下使用大排量涡旋压缩机空调系统的故障原因分析,提出使用压缩机和皮带时需注意的事项。

掺氢天然气管道输送工艺特性

将氢气掺入现役天然气管道中混输是实现氢气大规模、长距离、低成本储运的有效方法,但是氢气的掺入会对天然气管道水力特性和安全等方面造成较大影响。为此,采用SPS软件对不同混氢比(均为摩尔分数)的天然气管道输送工况和泄漏工况进行仿真计算,探究掺氢对天然气管道水力特性、离心压缩机运行特性、泄漏后截断阀压降速率及泄漏量的影响。结果表明,掺入氢气会降低天然气管网的输气效率和压缩机性能,可通过增大压降的方式确保管道输气效率不变;在相同天然气需求下,随混氢比的增大,管道动态压力波动减小;掺氢天然气管道泄漏后,随着混氢比的增加,压降速率和泄漏量均增大,管线截断阀压降速率阈值设定值也要相应增大。该研究成果为确定天然气管道最大混氢比的研究奠定了一定基础,为天然气管道掺氢输送工艺的确定提供了有效借鉴。

A fault diagnosis method of reciprocating compressor based on sensitive feature evaluation and artificial neural network

A method combining information entropy and radial basis function network is proposed for fault automatic diagnosis of reciprocating compressors.Aiming at the current situation that the accuracy rate of reciprocating compressor fault diagnosis which depends on manual work in engineering is very low,we apply information entropy evaluation to select the sensitive features and make clear the corresponding relationship of characteristic parameters and failures.This method could reduce the feature dimension.Then,a complete fault diagnosis architecture has been built combining with radial basis function network which has the fast and efficient characteristics.According to the test results using experimental and engineering data,it is observed that the proposed fault diagnosis method improves the accuracy of fault automatic diagnosis effectively and it could improve the practicability of the monitoring system.

Non-axisymmetric Flow Characteristics in Centrifugal Compressor

The flow field distribution in centrifugal compressor is significantly affected by the non-axisymmetric geometry structure of the volute.The experimental and numerical simulation methods were adopted in this work to study the compressor flow field distribution with different flow conditions.The results show that the pressure distribution in volute is characterized by the circumferential non-uniform phenomenon and the pressure fluctuation on the high static pressure zone propagates reversely to upstream,which results in the non-axisymmetric flow inside the compressor.The non-uniform level of pressure distribution in large flow condition is higher than that in small flow condition,its effect on the upstream flow field is also stronger.Additionally,the non-uniform circumferential pressure distribution in volute brings the non-axisymmetric flow at impeller outlet.In different flow conditions,the circumferential variation of the absolute flow angle at impeller outlet is also different.Meanwhile,the non-axisymmetric flow characteristics in internal impeller can be also reflected by the distribution of the mass flow.The high static pressure region of the volute corresponds to the decrease of mass flow in upstream blade channel,while the low static pressure zone of the volute corresponds to the increase of the mass flow.In small flow condition,the mass flow difference in the blade channel is bigger than that in the large flow condition.

Effect of Double Air Injection on Performance Characteristics of Centrifugal Compressor

In the operation of a centrifugal compressor of turbocharger, instability phenomena such as rotating stall and surge are induced at a lower flow rate close to the maximum pressure ratio. In this study, for the suppression of surge phenomenon resulting in the extension of the stable operating range of centrifugal compressor to lower flow rate, the compressed air at the compressor exit was re-circulated and injected into the impeller inlet by using the double injection nozzle system. The experiments were performed to find out the optimum circumferential position of the second nozzle relative to the fixed first one and the optimum inner diameter of the injection nozzles, which are able to most effectively reduce the flow rate of surge inception. Moreover, in order to examine the universality of these optimum values, the experiments were carried out for two types of compressors.

Unsteady Behavior of Leading-edge Vortex and Diffuser Stall in a Centrifugal Compressor with Vaned Diffuser

The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge(i.e., the leading-edge vortex(LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading-edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor.

Investigation on Inlet Recirculation Characteristics of Double Suction Centrifugal Compressor with Unsymmetrical Inlet

The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method,mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions,the circumferential non-uniform distributions of the inlet recirculation,the recirculation velocity distributions of the upstream slot of the rear impeller.The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions..In design speed,the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range,but in the small flow range,the recirculation flow rate of the rear impeller is smaller than that of the front impeller.In different working conditions,the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different.The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change.The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller,but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller,the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute.In the design flow and small flow conditions,the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different,and the recirculation velocities distribution forms at both sides of the mean line are different.The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct.

Numerical Investigation of Rotating Stall in Centrifugal Compressor with Vaned and Vaneless Diffuser

This study presents a numerical simulation of the stall and surge in a centrifugal compressor and presents a description of the stall development in two different cases.The first case is for a compressor with vaneless diffuser and the second is for a compressor with vaned diffuser of the vane island shape.The main aim of this study is to compare the flow characteristics and behavior for the two compressors near the surge operating condition and provide further understanding of the diffuser role when back flow occurs at surge.Results showed that for a location near the diffuser entrance,the amplitude of the static pressure fluctuations for the vaneless diffuser case is higher than that for the vaned diffuser case near surge condition.These pressure fluctuations in the case of the vaneless diffuser appear with a gradual decrease of the mean pressure value as a part of the surge cycle.While for the case of the vaned diffuser,the pressure drop during surge occurs faster than the case of the vaneless diffuser.Also,results indicated that during surge in the case of vaneless diffuser,there is a region with low velocity and back flow that appears as a layer connecting all impeller passages near shroud surface and this layer develops in size with time.On the other hand,for the case of vaned diffuser during surge,the low velocity regions appear in random locations in some passages and these regions expand with time towards the shroud surface.Results showed that during stall,the impeller passages are exposed to identical impact from stall cells in the case of vaneless diffuser while the stall effect varies from passage to another in the case of the vaned diffuser.

Numerical Investigation of Base-Setting of Stator's Stagger Angles for a 15-stage Axial-Flow Compressor

A 15-stage axial-flow compressor utilized in steel industry was studied in this paper. All the stator's stagger angles of the compressor are variable to ensure the multistage compressor operate effectively within a wide range of flow rate and meanwhile satisfy the demand for sufficient pressure ratio, adiabatic efficiency and stall margin. Three in all different base-settings of stator's stagger angles were presented and commercial CFD software was applied to obtain the overall performance characteristics. The results showed that both of the optimized base-settings improved the performances both in summer and winter conditions, although the adiabatic efficiency was somewhat decreased. Taking incidence angle and stage loading into consideration, differences among the three cases were analyzed in detail. On the basis of numerical computations, the performance could be effectively improved through adjusting the base-setting of stator's stagger angles.

Unsteady Behavior of Surge and Rotating Stall in an Axial Flow Compressor

Unsteady behaviors as well as unsteady cascade flow fields of a single-stage axial flow compressor were experi- mentally investigated by detail measurements of unsteady performance characteristics and casing wall pressure and internal flow velocity fluctuations. The main feature of the test compressor is a capacity tank connected di- rectly to the compressor outlet in series through slits and a concentric duplex pipe, and also jet nozzles in order to inject compressed air toward the rotor tip region. Research attention is focused on the post-stall characteristics of surge and rotating stall which occur simultaneously. When the compressor was connected to the capacity tank, surge was generated with rotating stall in accordance with the capacitance increment of whole compressor system The surge behavior changed irregularly with throttling valve installed behind the compressor, and several types of surge cycles were observed. In addition, the surge cycle changed by jet injection to the rotor tip region. The re- suits suggested that the blockages of the cascade flow which were generated by a stall cell play an important role in deciding the surge behaviors.