Rotor Manufacturing Research Articles

A general mathematical model for manufacturing Roots pump rotors using conical milling cutters

The rotors are the key components in the Roots pump, and the rotor manufacture time will decide the pump price. In special cases, such as when one rotor shaft has two stages, respectively, with claw-type and Roots profiles, the traditional forming method is unsuitable for manufacturing the Roots rotor stage. Instead, more suitable manufacturing methods, such as planning or end-mill milling, can be applied. However, these two methods take time and effort. Therefore, this study proposes a general mathematical approach for Roots rotor manufacturing using the conical milling cutter as the key tool, which can reduce manufacturing time. The contact points and meshing angles between the rotor and the conical milling cutter can be calculated based on contact conditions. Then, a 3D conical milling cutter surface is obtained based on the cutter profile as a straight line, and the conical cutter is designed and considered to avoid undercutting in the rotor cutting process. The generated Roots rotor can be obtained by applying cutting simulation from the proposed mathematical model. The normal deviations of the rotor can be found by comparing the generated rotor profile to the datum rotor profile. In addition, the influence of axis errors of the conical milling cutter on the tooth profiles of the Roots pump rotor is investigated and discussed. The experimental results based on the proposed mathematical model are obtained and expressed to confirm the practicability of the proposed method.

Selection of a biocomposite material as an alternative for the manufacture of the rotor of a gravitational vortex turbine

In this research study, a polymeric matrix biocomposite reinforced with natural fibers was evaluated as an alternative for the manufacture of impeller blades for a gravitational vortex turbine. Laminates were manufactured using the manual impregnation method, combining unsaturated polyester resin with three layers of fique fiber. Density tests were conducted along with the mechanical properties of the biocomposite, and they were compared with conventional materials such as aluminum, stainless steel, and fiberglass, commonly used in the construction of impellers. As a result of the tests, it was determined that bio composites present advantages such as: low cost, environmental sustainability and lower density compared to traditional materials. Finally, a prototype rotor for a gravitational vortex turbine was manufactured with the material proposed in the present study. In conclusion, the findings suggest that the developed biocomposite has the potential as an alternative to replace conventional materials in the manufacture of hydraulic rotors.

In Vitro and In Vivo Testing of Stereolithography (SLA)-Manufactured Haemocompatible Photopolymers for Blood Pump

A major medical problem of state-of-the-art heart ventricular assist devices (LVADs) is device-induced thrombus formation due to inadequate blood-flow dynamics generated by the blood pump rotor. The latter is a highly complex device, with difficulties during conventional manufacturing through milling or casting. Therefore, the additive manufacturing technology relying on stereo-lithography (SLA) capable of producing parts of significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as novel and flexible technology for that type of application. However, as yet state-of-the-art SLA is not suitable to produce fully safe blood-contacting devices. Therefore, the present experiment covered chemical, mechanical, rheological, tribological, and complex biocompatibility characterization in accordance with i.a. ISO 10993 standards, including hemolysis and an acute thrombogenicity blood test on fresh animal blood (both as innovative laboratory tests to avoid animal usage in preclinical studies) with a special focus on testing demonstrators of miniaturized blood pump rotors. The conducted tests indicated acceptable biocompatibility of the material and a slight improvement in biocompatibility with surface modification. Additionally, a high biocompatibility of the tested materials was confirmed. Based on studies and simulations, stereolithography (SLA) as an additive manufacturing technology with significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as a novel and flexible technology basis in the 4DbloodROT project to enable future manufacturing of rotors with exceptional biomimetic complexity.

Ceramic and Metal Additive Manufacturing of Monolithic Rotors From SiAlON and Inconel and Comparison of Aerodynamic Performance for 300W Scale Microturbines

Abstract The gas turbine industry is continuously developing and testing new materials and manufacturing methods to improve the performance and durability of hot section components, which are subjected to extreme conditions. SiAlON and Inconel 718 are especially desirable for turbomachinery applications due to their high strength and high-temperature capabilities. To demonstrate the viability of additive manufacturing for small-scale turbomachinery for 300W scale microturbines, a monolithic rotor with a design speed of 450,000 RPM containing radial turbine and compressor was developed considering additive manufacturing constraints. The geometry was manufactured from SiAlON and Inconel 718 using lithographic ceramic manufacturing and selective laser melting, respectively. The additive manufacturing and thermal process parameters as well as material characterization are described in detail. Surface and computerized tomography scans were conducted for both rotors. While the metallic rotor showed undesirable printing artifacts and a large number of defects, the ceramic part achieved a level of relative precision and surface quality similar to large-scale production via casting. To compare turbomachinery performance, an aerodynamic test facility was developed allowing to measure pressure ratios and efficiency of small compressors. The rotors were tested in engine-realistic speeds, achieving a compressor rotor pressure ratio of 2.2. The ceramic part showed superior efficiency and pressure ratio compared to the Inconel rotor. This can be explained by lower profile and incidence losses due to a higher fidelity physical representation of the model geometry and better surface finish.

Performance Improvement of Permanent-Magnet-Synchronous Motors through Rotor Shape Optimization of Marine Blowing System with High-Speed Rotation

Currently, research is being carried out on the performance improvement of permanent-magnet-synchronous motors (PMSM) used in air conditioning and blowing systems for marine, as well as structural research, regarding their high-speed operation. Surface-mounted permanent magnet (SPM) motors used in marine propulsion and air-conditioning systems have the advantages of easy rotor manufacturing and a simple structure. However, owing to the structural characteristics associated with attaching a permanent magnet to the surface of the rotor, there is a risk of permanent magnet scattering when turning a rated load at high speed, and the rotor assembly is directly affected by the heat generated in the stator winding. Therefore, in this study, additional protrusions were proposed to prevent rotor scattering during high-speed operations. Additionally, optimization was performed to reduce the torque ripple at the rated load and the total harmonic distortion (THD) of the no-load-induced electromotive-force waveform generated by the protrusion. Consequently, the risk of scattering at high speeds was improved by securing the bonding force of the permanent magnet using the proposed structure, and the THD and torque ripple were reduced compared with those of the basic model through optimization. In addition, rotor structural stress analyses were conducted to solve the problem of scattering at high speeds and eigenmode analysis.

A General Double-Input Synchronous Signal Processor for Imbalanced Vibration Mitigation in AMB-Rotor Systems

Imbalanced vibration is an urgent yet challenging problem in active magnetic bearings (AMBs) rotor manufacturing due to the rotor mass imbalance effect. The virtue of active control in AMB systems lies in enabling substantial online mitigation of imbalanced vibrations. However, in practice, due to the lack of speed sensors in most of the existing AMB-rotor systems, efficient rotational speed feedback is still on the way. As a remedy, this article proposes a rotational speed sensor-free synchronous signal processor (SSP) with the double inputs: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$</tex-math> </inline-formula> -and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$</tex-math> </inline-formula> -axes direction displacement measurements of radial AMBs. The proposed SSP is capable of estimating the rotational speed and accordingly generating synchronous signals of the imbalanced vibrations by filtering noise in both directions. Such signals are afterward implemented as a feedforward compensator for eliminating the periodical imbalance effects. With the assistance of the Lyapunov theory, the conditions of the proposed SSP method together with the feedforward imbalance compensator are derived to guarantee the stability of the closed-loop AMB-rotor system. Extensive experimental results substantiate the effectiveness and superiority of the proposed SSP method in terms of imbalanced vibration suppression.

Aero-Engine Rotor Assembly Process Optimization Based on Improved Harris Hawk Algorithm

Multi-stage disc rotor assembly is an important part of the aero-engine rotor manufacturing process. To solve the problem that excessive unbalance of assembly affects the vibration of the whole machine, this paper presents an optimization method for aero-engine rotor assembly balance based on an improved Harris Hawk algorithm. Firstly, the assembly sequence model of the single-stage disc blade and the phase assembly model of a multi-stage disc of the engine rotor is established. Secondly, by using the initial population generation based on dynamic opposing learning and the escape energy function of the non-linear logarithmic convergence factor, the search mechanism of the whale optimization algorithm is introduced in the global exploration, and the adaptive weight strategy and mutation strategy of the genetic algorithm is introduced in the development to improve the algorithm. Then, the effectiveness of the algorithm is verified by experiments and compared with particle swarm optimization, genetic algorithm, and Harris Hawk algorithm, the unbalance of the optimal blade assembly sequence is reduced by 91.75%, 99.82%, and 83.39%, respectively. The algorithm comparison and analysis are carried out for all disc-blade assembly optimization of the rotor. The optimal unbalance of the improved Harris Hawk optimization algorithm is reduced by 79.71%, 99.48%, and 54.92% on average. The unbalance of the algorithm in this paper is the best. Finally, the improved Harris Hawk algorithm is used to find the best assembly phase, and the optimized unbalanced force and moment are reduced by 84.22% and 98.05%, respectively. The results of this study prove that the improved Harris Hawk algorithm for aero-engine rotor assembly balance optimization can effectively reduce the unbalance of rotor disc blade assembly and rotor unbalance and provide a powerful solution for solving engine vibration.

Unbalance Prediction of Low Pressure Rotor Based on Mechanism and Data Fusion

The assembly, as the core part of low-pressure rotor manufacturing, is of great importance to ensure its unbalance. Low-voltage rotor assembly is a multi-process process influenced by the quality of part machining, assembly process, and assembly quality, resulting in unbalance that is difficult to predict during the assembly process. The unbalance measurement in the assembly process is important for the subsequent process optimization. Therefore, in order to achieve the prediction of unbalance measurement in the assembly process, this paper proposes an unbalance measurement prediction method based on mechanism and data fusion. Firstly, through research and analysis, the influencing factors of unbalance are determined, the low-pressure rotor blade sequencing mechanism model is established, and the blade sequencing optimization is realized by using reinforcement learning. Then, since the unbalance is formed after all the processes are completed and the subsequent work steps in the assembly process have not been carried out yet, the actual process parameters cannot be obtained, the semi-physical simulation method is used to combine the actual data of the assembled work steps with the theoretical data of the unassembled work steps to build a prediction model of the unbalance based on the BRNN (bidirectional recurrent neural network) network to achieve the prediction of the unbalance measurement in the assembly process. Finally, the model was validated using actual assembly process data, which proved the feasibility and effectiveness of the method.

End-Ring Wear in Deep-Well Submersible Motor Pumps

Wear of end ring is to date an unreported and uninvestigated failure that very frequently takes place in deep-well submersible motor pumps. This article first analyses the particularities of these induction motors, especially their unusual rotor manufacturing process. Failure mechanism related to the end-ring wear is described, showing several examples of damaged rotors in a motor repair shop. Then, the difficulties of its diagnosis through conventional rotor asymmetry indicators are described, caused by the subtlety of this fault and the very easy appearance of false negatives. The end-ring wear detection through a multicomponent approach is researched through simulation, laboratory results, and the diagnosis of two-field motors showing that new fault alarm levels need to be defined. To perform this last step and for the first time in the technical literature, two induction motors working in a deep borehole have been continuously monitored (one measure every six operating hours) for almost one year.

Corrosion Behaviour of Nodular Cast Iron Used for Rotor Manufacturing in Different Wastewaters

Submersible drainage sump pumps work in a highly corrosive environment, forming films with corrosive reaction products on the surface. Pump rotors are high-demand parts, so they are made of quality materials with good wear and corrosion resistance properties such as nodular graphite cast iron. This paper analyses the corrosion behaviour of cast iron used in the manufacture of rotors in three types of wastewaters, with variable pH. Nodular graphite cast iron samples were immersed in wastewater for 30, 60, and 90 days and tested by linear polarisation and electrochemical impedance spectroscopy (EIS). Also, the layers of reaction products formed on the surface of the material were analysed by SEM and EDS. The results showed that nodular cast-iron immersed in wastewater with acidic pH showed intense corrosion, the oxide layer formed on its surface is unstable. Also, the final structure of the product layer is that of a tri-layer with cations and anions absorbed from the corrosion media: the double-electric layer directly connected to the metal surface, an internal layer consisting of ferrous compounds and ferric compounds that control the diffusion of oxygen, an outer layer, and a compact crust of ferric compounds. The change in the pH of the wastewater has a major influence on the corrosion rate of the cast iron, which increases from 356.4 µm/year in DWW-1 (6.5 pH) to 1440 µm/year in DWW-2 (3 pH) and 1743 µm/year DWWW-3 (11 pH) respectively. As can be seen, the experimental study covers the problem of the corrosion behaviour of the pump rotor in various types of wastewaters this aspect is particularly important for the good use of wastewater pumps and to predict possible deviations for the operation of the equipment within the treatment plants.

A novel installation parameter optimization design method of forming tool for screw rotor

Characterized by a complex contour profile involving arc, cycloid, and involute, the screw rotor is usually manufactured by a forming tool. The finished surface quality and efficiency of the screw rotor are determined by the cutting performance of the forming tool. However, the machining performance of the forming tool is closely related to the structure shape of cutting edge, which is then determined by the installation parameters of the forming tool. Therefore, to make the cutting performance of forming tool controllable, it is essential to investigate the relationship between the cutting performance of the forming tool and its installation parameters at the design stage. In this paper, a novel installation parameter optimization design method of forming tool for screw rotor is presented. A parametric optimization program is designed to finalize the range of installation parameters satisfying the spatial meshing relation and machining equipment parameters. The profile characteristics of forming tool under different center distances and mounting angles have been investigated. For validation, several screw rotors were ground in experiments and the resulted profile errors were analyzed. The results show that the cost of precision grinding of screw rotor can be significantly reduced, without compromise of machining quality. As such, the proposed design method could serve as a promising platform to facilitate screw rotor manufacture.

Determination of COG Based on Propagation of Positioning and Orientation Errors in Aero-Engine Rotors

The ultra-precision measurement of the center of gravity (COG) of aero-engine rotor runs through the whole engine manufacturing process and this link is the premise of accurate control of aero-engine dynamic characteristics. A Multi-point weighing method is commonly used for measurement of COG, and the measurement accuracy is affected by the accuracy of the pressure sensor and by the positioning accuracy of the coordinate system, especially the precise positioning of coordinate system. This paper proposes a measurement model based on propagation control of the positioning and orientation errors, which can compensate and eliminate the spatial cumulative errors introduced by the measurement, and improve the measurement accuracy of COG of rotors by tracing the measurement errors to the machining errors of the measurement device and rotors. The results show that the measurement model of COG proposed in this paper eliminates the spatial cumulative errors, improves the positioning accuracy of the rotor coordinate system, and finally allows the ultra-precision measurement of COG of rotors. The results and experience obtained in this paper can be applied to the measurement and control of COG during rotor manufacturing, assembly and operation.

A Systematic Framework for Quantifying Production System-Specific Challenges in Life Cycle Inventory Data Collection

Understanding the environmental impacts of production setups and process parameters is a necessity for process optimization and new process development within sustainable manufacturing. Previous research studies have focused on developing standard methodologies and frameworks for parametrically modelling the life cycle inventories of unit manufacturing processes. However, these approaches do not fully account for the challenges associated with implementing life cycle inventory models in real-world production setups. Therefore, the time- and cost-intensiveness associated with constructing such models limit their use for identifying sustainability-focused process improvements in complex, real-world production processes. To address the above challenges, this paper proposes a framework to identify process inventory data that have a significant influence on process resource consumption, taking into consideration the difficulties and variabilities in measuring these data. The overarching goal is to identify feasible process improvements from the perspective of process monitoring for sustainable manufacturing. The application of the proposed framework is presented using a case study on a real-world through-feed centerless grinding production process for rotor manufacturing. This study reveals grinding time is the most sensitive process parameter among the other time-related parameters. The manual nature of the process, lack of a data acquisition system, non-standardized sequence of operation, and inability to capture in-process measurements without disrupting real-time production significantly contributes to the difficulty and variability of measuring grinding time.

Integrated approach to the technology of manufacturing electrostatic gyro rotors

Technological solutions based onthe integrated approach are presented, which optimize the manufacturing process and satisfy the requirements imposed on spherical rotors of electrostatic gyros. System modelingis used to study the main stages of defining the rotor functional parameters and to constructa system of models that determines the coordinated processes of diffusion welding, precision sphere lapping and rotor weight correction. The practical results of rotor manufacturing and the prospects for accuracy enhancing are provided.

Application of New Materials to Increase the Reliability of Centrifugal Separators

The urgent task of increasing the durability and reliability of centrifugal separators under the corrosion and erosion impacts of the processed media with a high content of chlorine ions and abrasive inclusions predetermined the transition to the manufacture of rotor parts from corrosion-resistant high-plastic steels of the austenitic and austenitic-ferritic class instead of previously used high-strength low-plastic steels of austenitic-martensitic class. Application of high-plastic corrosion-resistant steels with high fracture toughness characteristics excludes the possibility of brittle fracture of rotors. However, these steels have a low yield point, which makes it necessary to conduct hardening for highly loaded body parts of rotors in the field of centrifugal forces. Hardening ensures the elastic work of the rotor parts during operation, creates residual stress fields, partially compensating for the stresses arising in the operating mode. Based on the results of the study, steels of the austenitic-ferritic class are recommended for the manufacture of separator rotors with the provision of the necessary structural safety margins.

Prospects for the creation of high-temperature heatresistant alloys based on refractory matrices and natural composites

The paper presents the scientific, technical and technological aspects in the field of creating new high-temperature materials for parts of the hot section of gas turbine engines (GTE) with operating temperatures exceeding those existing in GTE. More refractory metallic materials for the creation of new high-heat-resistant alloys used for the manufacture of rotor and nozzle blades and other parts of promising gas turbine engines based on NiAl-Ni3Al, Co-Cr-Re, Pt-Al, Nb-Si, Mo-Si-B systems have been investigated. It is shown that, depending on the composition of the selected matrix, the working temperature of heat-resistant alloys increases to 1300-1500°С, which is significantly higher than the existing nickel heat-resistant alloys.

Technological and Operational Aspects That Limit Small Wind Turbines Performance

Small Wind Turbines (SWTs) are promissory for distributed generation using renewable energy sources; however, their deployment in a broad sense requires to address topics related to their cost-efficiency. This paper aims to survey recent developments about SWTs holistically, focusing on multidisciplinary aspects such as wind resource assessment, rotor aerodynamics, rotor manufacturing, control systems, and hybrid micro-grid integration. Wind resource produces inputs for the rotor’s aerodynamic design that, in turn, defines a blade shape that needs to be achieved by a manufacturing technique while ensuring structural integrity. A control system may account for the rotor’s aerodynamic performance interacting with an ever-varying wind resource. At the end, the concept of integration with other renewable source is justified, according to the inherent variability of wind generation. Several commercially available SWTs are compared to study how some of the previously mentioned aspects impact performance and Cost of Electricity (CoE). Understanding these topics in the whole view may permit to identify both tendencies and unexplored topics to continue expanding SWTs market.

INCREASE DURABILITY AND RELIABILITY OF CENTRIFUGAL SEPARATORS BY USING NEW MATERIALS

The urgent task of increasing the durability and reliability of centrifugal separators under the conditions of corrosive erosion of treated media with a high content of chlorine ions and abrasive inclusions predetermined the transition to the manufacture of rotor parts from corrosionresistant, high-plastic steels of the austenitic and austenitic-ferrite class instead of the previously used high-strength and low-elastic steel martensitic class. The use of highly ductile corrosion-resistant steels with high fracture toughness characteristics eliminates the possibility of brittle fracture of rotors. However, these steels have a low yield strength, which makes it necessary to conduct hardening rotors for highly loaded body parts in the field of centrifugal forces. Hardening provides elastic operation of rotor parts during operation, creates fields of residual stresses that partially compensate for stresses arising in the operational mode. In this work, the stress-strain state and the bearing capacity of the rotor of a separator of a self-unloading type with a diameter of 500 mm, made of parts that have passed the hardening cycle, are investigated. Three variants of the rotor of the same design were investigated, differing in the materials of the body parts, for which austenitic steel grades 06X17H13M3-VD, ALIII-23-43-02 and austenitic-ferritic grades 10X26H5M, ALIII-23-24 were used. The stress-strain state of the rotor was investigated by the numerical finite element method for an axisymmetric problem. When choosing a design scheme, the following assumptions are made: the rotor is an axisymmetric design with an axisymmetric load; initial stresses are not taken into account; the load from the influence of the medium being treated is perceived by the rotor body parts (excluding the internal piston). The boundary conditions for the rotor are determined based on the analysis of the interaction of the hub with the shaft (the landing of the rotor on the shaft is carried out with the hub fixed in the axial direction). During the loading process, the residual deformation was determined by steps by the strain gauging method, and the diameters of the parts were also measured with a micrometer with an accuracy of ± 0.01 mm. Strain gages were glued at the circuits of the concentrators: holes for the cover stopper relative to the base, unloading windows, holes in the tightening rings, as well as on the ends of the base and the tightening ring. Thus, based on the results of the study, it can be recommended for the manufacture of rotors of separators of steel of austenitic-ferrite class, providing the necessary safety margins of structures.

Increasing service life and reliability of centrifugal separators by applying new materials

This paper analyzes stress-strain behavior and bearing capacity of a rotor in a self-discharging separator, diameter 500 mm, manufactured from parts that underwent a hardening cycle. Three variants of the rotor were studied having the same design but differing in body materials: austenitic steels 06X17H13M3-BД, ALIII-23-43-02 and austenitic-ferritic steel 10X26H5M, ALIII-23-24. Research results allow recommending austenitic-ferritic steel for manufacture of separator rotors, as they provide necessary margin of safety for the design.

Algorithm for predicting the vibrational state of a turbine rotor using machine learning

A machine learning algorithm has been developed to solve the problem of predicting a vibrational state in order to improve the turbine rotor assembly processes using its digital twin. The digital twin of the rotor includes a parametric 3D model specially created in the CAD module of the NX program and a design project in the ANSYS system in which the working conditions of the rotor are simulated. The parameters of vibration acceleration and the reaction force of the rotor supports at critical speeds depending on geometric errors were calculated. To reduce the complexity of the calculations, neural network architectures were chosen to predict the parameters of the vibrational state depending on the geometric errors of the rotors. The novelty of the work lies in the creation and use of the original numerical model of balancing, taking into account the rotor manufacturing tolerances.