Rotor Profile Research Articles

Analysis and numerical simulation of claw vacuum pumps with novel three-claw rotors

The rotor profiles of the claw vacuum pump mainly determine its working performance. The composition curves of the existing three-claw rotor profiles are complicated, and the compressed gas remaining in the carryover is recompressed, resulting in a remarkable increase of power consumption. For solving those problems, a sinusoidal curve was used to smoothly connect the addendum and dedendum arcs, and a novel three-claw claw rotor and its parametric equations were obtained. A novel discharge port was designed to avoid the secondary-compression of the gas in the carryover. The working process and the internal flow field of the new three-claw vacuum pump (TCVP) were revealed through numerical simulations. The mass flow rate at the proposed discharge port was also analyzed. Study results show that the proposed claw rotor has considerable advantages of simple profile, high internal volume ratio and small relative carryover. The designed discharge port realizes complete gas discharge without secondary-compression of the gas in the carryover. It is revealed that part of gas in the chamber formed by the separation of the compression chambers can flow back to the suction chamber in the compression process.

Dual-convolutional neural network based aerodynamic prediction and multi-objective optimization of a compact turbine rotor

With the development of neural network technology, surrogate models and dimensionality reduction strategies based on machine learning have become the research hotspots of aerodynamic shape optimization recently. In order to further improve the accuracy and interpretability of the traditional surrogate models, this research establishes a deep learning model, named Dual Convolutional Neural Network (Dual-CNN) for the aero-engine turbines. The aerodynamic performances are predicted and the pressure, temperature fields are reconstructed for multiple rotor profile conditions. The prediction of efficiency is compared with the accuracy of Gaussian Process Regression (GPR) and Artificial Neural Network (ANN) models. The results show that the proposed Dual-CNN model can accurately reconstruct the fields, thus interpreting the mechanism for the change of aerodynamic performance. Dual-CNN is more accurate than GPR and ANN in predicting efficiency and torque, whose error is within an acceptable range of optimization. Then, efficiency and torque are selected as the objective functions to perform a gradient-based multi-objective optimization by the automatic differentiation method and a Pareto solution is obtained. The trained Dual-CNN provides rapid and accurate prediction of performance without CFD calculation in the optimization. Finally, the sensitivity to train size is analyzed for the Dual-CNN model, which indicates that the sampling of 1500 cases for eight design variables in this dataset enables Dual-CNN to achieve favorable effect of field reconstruction and performance prediction.

Analysis and construction of a parabolic rotor profile for Roots vacuum pumps

Rotor profile is a critical factor affecting the performance of Roots vacuum pumps. Hence, research on rotor profiles of Roots vacuum pumps is important. The rotor profiles are mainly composed of arcs, involutes, cycloids, epicycloid, and combined curves. Moreover, the two rotor profiles form a pair of conjugate curves. To obtain a parabolic rotor profile, transformations of three coordinate systems are established to derive equations and analyze the parabolic curve and its conjugate curve. Additionally, the parameters of the parabolic rotor profile are discussed to determine their ranges and the relationship between the performance of a parabolic rotor profile and the independent parameters. The results indicate that the area efficiency of the parabolic rotor profile is greater than the area efficiency of the arc rotor profile for the same ratio of the top circle radius to pitch circle radius.

A comprehensive method for controlling the electrical runout of the rotor for a geared centrifugal compressor

The internal high-speed geared rotor is the most important component of centrifugal compressors. The electrical runout error of the rotor including mechanical and electrical ones can greatly affect the working performances of the centrifugal compressors. To overcome this problem, this work proposes a practical comprehensive method for controlling the electrical runout of the rotor of a geared centrifugal compressor. An elastic-plastic deformation calculation method based on the slice approach is presented to determine the applied load range calculation for controlling the cross-sectional deviation of the rotor profile. In this method, the demagnetism and remanence detection should be provided to obtain a small residual magnetism value before the mechanical runout detection. A combined method including cold extrusion processing and slight impact processing is proposed to reduce the electrical runout of the rotor. A case study is carried out to validate the proposed method. To avoid the effect of the rotation precision and clearance of the support system on the detection results, a rigid support system is used to detect the mechanical runout of the rotor. Note that single cold extrusion or impact processing cannot completely eliminate the electrical runout. Finally, the results show that the proposed combined method can be a helpful approach in controlling the electrical runout of the rotors.

Geometric Design of the Limaçon-to-Circular Fluid Processing Machine

Abstract A limaçon machine is a rotary positive displacement device, in which the housing and rotor are constructed of limaçon of Pascal curves. Previous works have been published to investigate the working of these machines in two applications: gas expanders and compressors. This article presents a theoretical investigation into the potential of modifying the rotor profile of the limaçon machines to simplify the machine’s manufacturing process and to reduce production cost. The proposed modification will produce new characteristics for the housing–rotor interaction. An outcome that motivates the need to obtain new mathematical models to investigate the housing–rotor interference and describe the volumetric relationship of the new machine. This article also employs an optimization approach to design the best machine for a given set of operating conditions, i.e., expander, compressor, and pump. The outcome of this study confirms the validity of the proposed modification and its potential to produce a limaçon machine with favorable characteristics.

A universal rotor design method for twin-rotor fluid machines with a parameterized sealing line considering inter-lobe clearances

The sealing line is a major leakage path affecting various performances of twin-rotor fluid machines (TRFMs). The rotor profile generation methods using a sealing line proposed previously are improvable further. A key factor, inter-lobe clearance, can be considered at the initial design stage of rotor profile; and a more universal model suitable for opened and closed sealing lines can be studied further to generate varied rotor profiles for different applications. Therefore, this study proposes a parameterized sealing line (PSL) with predefined inter-lobe clearance as a universal method, named the gap-distributed sealing line (GDSL) method, to generate the rotor profile for varied twin-rotor fluid machines. The PSL with opened or closed forms is predefined by explicit equations to generate different rotor profiles more flexibly. The inter-lobe clearance is directly given and distributed along the PSL to form a pair of rotor profiles with a gap. Additionally, the proposed method is also used to generate a conical rotor profile. The results presented in the numerical examples verify the flexibility and practicability of the proposed method.

Comprehensive experimental and numerical assessment of a drag turbine for river hydrokinetic energy conversion

Nile River is considered as an auspicious area; in particular along with Upper Egypt, to produce electrical energy from the water current which called hydrokinetic energy. This sort of renewable energy is admitted deeply as a unique and uncommon solution for the electric power demand in the remote areas on the rivers’ sides. The hydrokinetic energy of the river stream can be extracted by a submerged vertical axis turbine due to its specific advantages. The main objective of this work is to investigate experimentally the performance of two different Savonius rotor profiles inside an irrigation canal in Toshka, Aswan, Egypt. Furthermore, the rotor with the optimum performance is investigated numerically by adding two shielding plates to further enhancements. The results indicate that the rotor with better fullness has better operating characteristics with a power coefficient 0.1285 at a tip speed ratio of 0.61 that is higher than the other rotor profile by 12%. Moreover, the two shielding plates increased the net average power coefficient at a tip speed ratio at 0.7 for the optimum rotor profile by 84% compared with the conventional design.

Thermal Analysis of Bajaj Pulsar Disc Brake

The disc brake is a device that used for reducing speed or discontinuing the cycle of the vehicle. many times, using the brake for vehicle starts to heat producing during braking process, such that disc brake undergoes breakage due to high temperature. Disc brake design is done through creo 4.0 and analysis is completed by using ANSYS18.1 workbench. The main purpose of this project is to study the Thermal analysis of the Materials for the Cast Iron, Stainless steel and aluminium alloy at various disc rotor profiles. A comparison between the three materials and profile for the Thermal values at maximum speed of the vehicle.

A new design of the Lobe pump is based on the meshing principle of elliptical gear pairs

The paper presents a new rotor design of an external coupling Lobe pump driven by pair of elliptical gears. The new rotor is a four-tooth elliptical gear with tooth profile is a improve cylocid curve. The improve cylocid curve is the locus of the fixed point on the generation circle, when the circle a pure rolling without slipping on the elliptical centrode of the rotor. The conditions of the rotor addendum and dedendum profiles are also considered. The limited supply angle addendum and dedendum rotor profiles are determined through an iterative algorithm when the generation circle makes a pure rolling without slipping on the ellipse base of the rotor. From there, we proceed to determine the pump design parameters according to the characteristic design parameters forming the rotor profile. The flow rate of the pump is determined by the area of the pockets on a cross-section perpendicular to the pump shaft. On that basis, a Matlab program is written from the mathematical model established by the paper to calculate the rotor design. In addition, the paper also investigates the effect of the coefficient l (semi-major axis divided semi-minor axis of the elliptical centrode ) on the average flow and axis distance. Survey results show that the design at l = 0.5 flow is 52.17% larger and the axis distance is reduced by 21.43% when compared to the traditional design at l = 1. This is the advantage of the new design proposed by this study.

Influence of curtain plates on the aerodynamic performance of an elliptical bladed Savonius rotor (S-rotor)

The S-rotor is a drag driven wind turbine, having lesser performance coefficients. Its various geometric and aerodynamic parameters have been optimized to improve its performance. Several rotor profiles and augmentation methods have also been progressed to improve its performance further. The augmentation method reduced the negative drag generated in the S-rotor. Very recently, the elliptical bladed profile has shown higher performance than the other profiles. Hence, in this study, the elliptical bladed profile has been considered along with the curtain plates augmenter before the rotor blades. The 2D unsteady numerical analysis is conducted through the SST k–ω turbulence model. The simulations are also performed for the elliptical profile without the curtain plates for direct comparison. From the 2D unsteady results, it was found that the elliptical bladed profile with curtains plates has higher aerodynamic performance (CDavg = 2.60 and CLavg = 0.65) than the elliptical profile without curtains (CDavg = 1.43 and CLavg = 0.95). Hence, there is an improvement of CDavg by 81.81% in the elliptical profile with curtain plates than the profile without the curtain plates.

An analytical model for precision milling of screw rotor using a disk-like form-milling cutter with multiple inserts

In screw rotors manufacturing, milling machining can be conducted by using a disk-like form-milling cutter. Design method of a disk-like form-milling cutter with multiple inserts applied on screw rotors machining for twin-screw compressors were presented in this study. An analytical calculation procedure of insert arrangement on the cutter body profile was constructed. Subsequently, the screw rotor cutting simulation was performed by considering the actual cutting conditions based on a horizontal CNC milling machine’s established coordinate system. Finally, the simulated rotor profile could be obtained and the normal deviation was evaluated.

Effectiveness enhancement of non-contact vacuum pumps working process

Three options of rotor profiles of Roots vacuum pump are considered: elliptic, circular, and involute. Rotor profiles are drawn in the same housing and are analyzed from point of view of backward leakage minimization through inter-rotor channel and geometric pumping speed increase. It is shown that coefficient of working volume use is only 3% higher for involute profile. Averaged over one revolution conductance of rotor mechanism channels is minimal for elliptic rotor profile. For inter-rotor channel it is 14% less than for involute profile. The presented approach makes it possible to choose the optimal rotor profile of Roots pump for particular purpose.

A novel method for rotor profile optimization of high temperature screw expanders employed in waste heat recovery systems

High temperature expanders have always been employed in industrial waste heat recovery systems, where twin-screw expanders were frequently adopted. However, the significant thermal deformation of rotors contributes to much technical difficulty on the designation and manufacturing of high temperature twin-screw expanders. The profile should be optimized with consideration of its thermal deformation in high temperature working conditions. In this article, a novel method for twin-screw expander profile optimization is developed. The thermal deformation of rotors is considered with meshing pair rules and interlobe clearance presetting. Theoretical analysis on interlobe clearance is made any steam inlet temperature from 20°C to 400°C, while experimental facility was built to figure out its reliability at high temperature. The optimized profile proved the effectiveness of this method. The clearance decreases significantly, decreasing from 1.28 mm at the working temperature of 20°C to 0.16 mm at 400°C. The testing results illustrated that the significant thermal deformation of rotors causes much interlobe abrasion once the operating temperature reached 400°C. With clearance of 0.1 mm and the radius correction angle of 0.0758°, the screw expander was proved to be reliably working at 400°C.

A study on the rotor profile and internal clearances of the gerotor pump used in lubricating system of gas turbine engine

Gerotor pump is widely used in lubrication systems of a gas turbine engine where compactness and reliability is of key importance. In this work, the characteristic of the pump is studied for its application in the lubrication system. The rotor profile geometry of the Gerotor pump and its effect on the flow characteristics such as specific flow rate and flow irregularities is studied. The effect of the rotor geometry on the wear characteristics have also been taken into account by considering Hertz contact stress and the relative sliding velocity between the rotors. A Gerotor pump having fixed geometrical parameters designed based on mathematical 1D model using MatLab and AMESim software used for the profile generation and studying the theoretical flow characteristics. This work is further extended by studying the various internal leakages of the pump. The predicted flow rates obtained from Amesim software were then compared with the experimental results and found close match within 5% deviation. Hence, this methodology can be used to estimate performance and wear parameters. This study can assist pump designers to select geometrical parameters and internal clearances of gerotor pump as per their requirements.

A geometric study of different curves for the rotor profiles of a twin-screw compressor

This paper presents the results of comparisons among some patented solutions for profiling the contours of the rotors in twin-screw compressors. Referring to a base case where all the generating curves are circumferences, patents suggesting to replace arcs of circumference with arcs of conic sections, i.e. parabola, ellipse and hyperbola, but even a straight line segment, are presented and guidelines for rotor profile construction are reported. After setting the size of the compressor, attention is paid to the inter-lobe area, as the sum of the area between two consecutive lobes in the male rotor and of the area of the groove in the female rotor. Actually, this area is strictly related to the volume displacement. Limited to the current case study, the profile including an elliptic segment seems to be the preferable solution for higher inter-lobe area, then for higher displacement, though a number of considerations should be necessary for a broader context.

Free energy-extraction using Savonius hydrokinetic rotor with dual splitters

Hydrokinetic energy is a broadly available form of low-grade energy in countries like India, where irrigation canals are available in huge areas. To utilize this energy, hydrokinetic turbines are used. Out of many hydrokinetic turbines, efforts are made to improve Savonius hydrokinetic turbine's performance in the present work. The Savonius rotor profile is modified by providing a dual splitter-like shape on the blade's concave side. The two cases were selected for finding the optimum splitter position of both the splitter. The upper (top) splitter kept fixed and radially placed the second splitter in the first case. In the second case, the lower (bottom) splitter fixed and moving another splitter radially. Validated Computational analysis was done to analyze performance after modification. The fluid material was taken as water with standard properties. The improvement was observed for the specific position of splitters by 7.3% from conventional design.

Design methodology and performance analysis of conical rotors for dry screw vacuum pumps

Abstract The conical rotor, as an alternative internal compression structure, has shown the potential to enhance the performance of screw vacuum pumps further. In view of no available literature examining the design of them, to fill this gap, mathematical models for the generation and analysis of conical rotors were established in this paper. The generation process was based on a design implementing a rotor profile cluster and a conical helix. The analysis model reflected the geometric characteristics and thermodynamic performance of conical rotors. The effect of key parameters in conical rotors was investigated, and the difference between conical rotors and variable-pitch rotors was revealed. Results showed that with the increase in the conical angle the internal volume index enlarged while both the specific power and pumping speed decreased. To achieve greater internal compression, more rotor stages were needed. The rotor performance could be improved by changing the distribution of the tooth width angle for the rotor profile cluster at a certain inlet pressure. In comparison with the variable-pitch rotor, the specific power was lower for the conical rotor at a close pumping speed.

Error compensation method for milling single-threaded screw rotors with end mill tools

Form milling using end mill tools is commonly employed to manufacture single-threaded screw rotors, especially for profiles where a side mill tool is inapplicable. In practical applications, position deviation and wear of the cutter mainly affect the machining accuracy of screw rotors. Therefore, this study proposes a method to compensate for machining errors through profile correction and position adjustment of the end mill tool for single-threaded screw rotor milling. The milling process is simulated by an established coordinate system of a multi-axis computerised numerical control milling machine. The effect of end mill tool profile and position on the rotor profile deviation can be analysed and collected to form sensitivity matrices. Based on these matrices and the Levenberg–Marquardt algorithm, profile deviation is greatly reduced after several closed-loop iterative compensations. In the presented examples, a fault in an end mill tool profile calculated by the Holroyd Profile Management System is successfully solved. Improvements in rotor profile deviations are investigated by considering different combinations of end mill tool position parameters and by performing end mill tool profile correction.

Rotor segment split and its optimization of axial-field dual-rotor segmented switched reluctance machine

Switched reluctance machine (SRM) produces vibration and acoustic noise due to the significant torque ripple. The widespread use of SRM is thus limited. For the discussed axial-field dual-rotor segmented switched reluctance machine (ADS-SRM), this paper describes a proposal for a new rotor profile featured by the rotor segment splits. These splits minimize the undesired torque ripple. The effects of each geometric parameter, such as split width and split offset, are investigated using finite-element method (FEM). After optimizing the rotor-segment geometry, the approximately flat-top torque profile is achieved. The motion-coupled analysis further validates the effectiveness of this novel technique. It is found that, by incorporating the optimization of the turn-on and turn-off angles, the torque-ripple coefficient decreases by about 73%, from 0.995 to 0.27. However, the average torque decreases by only 4.2%.

Development and Testing of a Roots Pump for Hydrogen Recirculation in Fuel Cell System

In this paper, the development and testing of a Roots pump with a new rotor profile for hydrogen recirculation in the fuel cell system are presented. The design method of the rotor profile, port position, and structure of the pump is presented. A prototype of a three-lobe Roots pump with helical rotors was fabricated, and its performance was experimentally tested. The measured data show that the effect of the pressure difference on the flow rate and volumetric efficiency of the Roots pump is the most significant, while the effect of suction pressure is limited. It is concluded that the leakage rather than flow resistance is the key factor, which has a major influence on volumetric and isentropic efficiency. The comparison of the performance is also given by the measured results of the same Roots pump working with air, helium, and hydrogen. Finally, the successful integration of the Roots pumps into three PEM fuel cell systems is reported and the optimal operating parameters of the Roots pump in the systems under various loads are also presented. It is found that the performance of the Roots pump integrated into the fuel cell system is better than that measured with pure hydrogen on the test rig. The performance maps composed of all the measured data of the Roots pump are very helpful for the optimal design and operation of the fuel cell system.