Rotor Profile Research Articles

Research and clearance analysis on of steam twin-screw expander employed in indutrial waste heat recovery

In actual factories, screw expanders frequently operate under partial loads.To address the lack of theoretical research and the risks of errors in engineering design associated with steam pressure differential power generation under these conditions,a simulation of the twin-screw expander's working process was developed. The rotor profile was designed, geometric variables such as rotor mesh clearance were calculated, and models for leakage and heat transfer were established. A suction pressure correction model was proposed for the suction process under partial loads, along with correction parameters to simplify simulations.Experimental results demonstrate that the twin-screw expander operates stably under highly fluctuating conditions, demonstrating excellent variable load performance.As the load decreases, the loss of suction pressure reduces the expander's pressure differential, leading to lower leakage and improved efficiency. When the load is reduced from 100 % to 65 %, the volumetric efficiency increases from 78.87 % to 84.76 %, and the isentropic efficiency rises from 66.81 % to 74.25 %.Compared to experimental data, the flow calculation error of the suction pressure correction model presented in this study is controlled within 3 %.This model addresses performance calculations under partial loads, ensuring that theoretical models better align with real-world applications and supporting accurate selection of twin-screw expanders.This model enables appropriate selection of expanders to reduce pressure losses and enhance economic efficiency.

Meshing pair geometry of the intersecting-axis internally geared screw compressor

The Intersecting-Axis Internally Geared Screw Compressor (IISC) is an emerging advanced positive displacement machine showing the potential to greatly broaden the application of screw compressor technology. The core component of the IISC is an internally geared meshing pair with the intersecting-axis gearing, while its design methodology has not been disclosed yet. To fill the gap, this paper established the geometry model for the meshing pair and discussed the influence of its core parameters on geometric performance. First, the generation model of meshing pairs was presented, and the complete parameters set of meshing pairs was defined. The established model was verified by a meshing pair manufactured by 3D printing and CNC techniques. Next, the geometric analysis model of IISCs was established such as working volume and leakage channels, which was verified by commercial 3D software. Using the analysis model, the mesh pair parameters (rotor profile, cone angle, wrap angle, and L/D ratio) were discussed to reveal the design methodology of IISCs. Finally, the variable-pitch technology was discussed, and a novel variable-pitch method was proposed to further enhance the performance of IISCs. This paper could effectively guide the design of IISCs to further promote the development of the screw compressor technology.

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.

Measurement and machining error assessment method for cycloid pump rotor profile based on STEP

Abstract The contour shape and machining precision of the rotor of an cycloid pump directly determine the sealing performance of the pump cavity. Precise measurement of contour machining errors is a crucial step in the manufacturing process. However, rotor contour curves are often designed by enterprises based on actual engineering needs, leading to inconsistency between the measured baseline contour and the designed contour, thus failing to accurately reflect the actual machining condition of the rotor. Therefore, this paper proposes a method for measuring the contour of the cycloid pump rotor and evaluating machining errors based on the standard for the exchange of product (STEP) files necessary for product design in manufacturing. Firstly, utilizing NX/OPEN API functions, contour coordinate points and unit normal vectors are obtained from the rotor’s STEP design data. Subsequently, by planning the process of measuring the closed continuous contour of the rotor, the transformation between the workpiece coordinate system and the measurement coordinate system is achieved to position the tested rotor, followed by analyzing the influence of different starting points on error measurement and evaluation determines the optimal starting point. Finally, a measurement sampling point strategy is established to collect data points of the actual machining contour of the rotor. By achieving the best matching between the actual machining contour and the measured baseline contour, a contour deviation calculation model is established. Utilizing gauge blocks enables accurate assessment of pitch deviation, radial runout, and tooth-to-tooth distance deviation, resulting in assessment results that better fit the actual meshing situation of the rotor. Experimental results verifies consistency between the measurements of the one-dimensional probe and Gleason measurements. This theory and method not only expand the measurement range of the one-dimensional probe but also provide more accurate and efficient guidance for the flexible machining of the rotor.

Fault diagnosis of new type screw compressor of helium liquefier by vibration signal

A diagnostic method for screw compressor faults using vibration signals was introduced and applied to a new type of helium oil-injected screw compressor in the 80L/h helium liquefier. The study revealed that the destruction of the oil film due to impurity particles could lead to rotor rubbing and poor meshing, compromising the reliability of these compressors. Based on frequency-domain analysis, the major vibration occurred at the meshing frequency of screw rotors and a series of its harmonics. The vibration of the characteristic frequency of bearing parts also indicated that the bearing had slight wear in the early stage. The vibration waveform’s time domain diagram exhibited clear clipping, and the axis trajectory shew disorder, which were common characteristic of rotor rubbing. When compressing helium with low molecular weight, the meshing clearance, tooth tip clearance, and end clearance of the rotor were significantly lower than those of traditional refrigerants or air media. Additionally, the thermal gap caused by thermoelastic deformation was smaller due to the large adiabatic index of helium. Therefore, rubbing faults between rotors and between rotors and casing were more likely to occur. The article recommended establishing a vibration signal monitoring system, optimizing the design of helium screw rotor profiles, and setting up reliability standards for screw compressor operation, such as limiting the vibration speed to ≤ 8 mm/s. Additionally, attention should be given to cleaning gas pipelines in cryogenic engineering and monitoring compressor vibration and noise signals during operation to prevent rotor damage due to particle impurities.

Optimization of rotor profile design and analysis of transient flow fields in an asymmetric singular double claw vacuum pump

The claw vacuum pump is widely used in vacuum industries due to its high-performance, compact structure, and oil-free operation. This study delves into the rotor profile and internal flow field characteristics of an asymmetric singular double claw vacuum pump. Theoretical profile equations for the male-female rotor of claw vacuum pumps were given, and a three-dimensional transient simulation of the internal flow field was carried out using the dynamic mesh reconstruction method. The simulation result was also verified by experiments. Analysis shows that: the radial clearance significantly affects the volumetric efficiency of the claw vacuum pump, with a larger effect than the axial clearance; the maximum instantaneous temperature corresponds to radial clearance, leading to maximum thermal deformation concentrated at the claw tip; thermal deformation is the predominant factor contributing to maximum deformation; the smaller the coefficient of thermal expansion, the less the rotor material affects the claw vacuum pump clearance. Based on these insights, we have innovatively optimized two elements of the theoretical claw vacuum pump rotor profile, i.e., the curvature of the cusp B and three optimized configurations of the complex EH section. The optimization results provide a solid theoretical basis for advancing the design and practical application of this pump type.

Optimization of Savonius rotor blade performance using Taguchi method: Experimental and 3D-CFD approach

The Savonius hydrokinetic turbine (HKT) is both cost-effective and reliable, providing clean energy with minimum environmental impact. The efficiency of the Savonius rotor can be improved by modifying the blade profile to increase the effective torque. However, past research works reported that modifying the blade profile is quite challenging due to small Cp improvement and design constraint. Therefore, the present study proposes a newly developed blade profile blueprint, akin to parameterizable designs such as the modified Bach and Benesh profiles but offering more shape versatility. This new blueprint is optimized with a systematic design of experiment (DOE) using a 3D computational fluid dynamics (CFD) simulation to maximize the Cp. The best design is determined statistically using the Taguchi method and analysis of variance (ANOVA). The optimized rotor profile enhances Cp by approximately 10.9 % compared to the conventional Savonius rotor at the optimal TSR (best Cp = 0.159) and 16.7 % improvement at a higher TSR value of 0.9 (Cp = 0.158). Moreover, the optimized rotor outperforms the Fibonacci rotor (Fibonacci blade profile) by 27 % in terms of efficiency. A thorough CFD analysis suggests that the optimized blade profile has a greater lift generated at the convex side of the advancing blade due to its streamlined shape, which delays the flow separation further up to the root of the blade. The confirmation test (experiment) is also performed to verify the Cp improvement of the optimized rotor, and the results herein concluded that the present CFD prediction is accurate and consistent with the experimental values.

Rotor profile improvement by optimizing meshing curve for helical roots blowers in HFCV application

This paper introduced a novel design and optimization method of the Roots profile to enhance the performance of helical Roots blowers in Hydrogen Fuel Cell Vehicle applications. The proposed profile was generated based on defined meshing curves, and thus the shape of meshing curves can be explicitly optimized. First, the mathematical models for Roots profile generation based on meshing curves were presented. Next, the influence of the shape of meshing curves on the geometric performance of Roots rotors was investigated, and the meshing curve was further optimized using a genetic algorithm. Finally, the CFD method was employed to identify the specific performance enhancement brought by the optimized Roots profile. Results showed that the proposed profile design method could flexibly adjust the shape of meshing curves so as to intuitively control the spatial leakage channels formed by helical rotors. The optimized profile boosted the volumetric and adiabatic efficiency of the Roots blower up to 2.87%, and 1.89%, respectively, compared to the original one. The leakage analysis indicated that the performance improvement was attributed to the reduction of the leakage rate caused by the blow-hole and contact line. The conclusions obtained could effectively support the development of high-efficiency helical Roots blowers.

Design and testing of the fuel cell twin-screw air compressor

The oil-free dry air compressor plays a crucial role in the fuel cell system, particularly in commercial buses where twin-screw air compressors have proven effective. A novel rotor profile of the twin-screw dry air compressors has been developed, which simplifies the profile curve and yields excellent performance results with a volume flow of 11.99 m³/min and corrected specific power of 3.54 kW/(m³/min).

The Side-Cutter Position Adjustment Method for Enhancing Milled Rotor Profile Accuracy using ANN and NSGA-II

The Side-Cutter Position Adjustment Method for Enhancing Milled Rotor Profile Accuracy using ANN and NSGA-II

Archimedes Screw Pump Efficiency Based on Three Design Parameters using Computational Fluid Dynamics Software – Ansys CFX

Utilization of Archimedes screw pumps as water lifting pumps has become widespread in past decade due to frequent occurrences of floods in Malaysia. The problem of insufficient drainage in various urban areas exacerbates the impact of heavy rainfall, prompting efforts to mitigate this issue with minimal maintenance cost and low impact to the environment. Thus, this study is aiming to study the design parameters of screw pump to obtain the optimal efficiency of the Archimedes screw pump specifically for flood mitigation in Malaysia. The main design parameters affecting pump’s efficiency are rotor profile, pitch length, length of the pump, rotational speed, inclination angle, and material selection. However, only three design parameters were considered in the study, that are the angle of inclination, the number of blades, and the angular velocity of the rotating pump. These three design parameters are selected as many previous findings focusing on varying angle of inclination with number of blades with constant rotational speed. Thus, this study will find the highest efficiency when these three design parameters are integrated with variation of rotational speeds at 25, 30 and 40 RPM. Basically, screw pump is designed using SOLIDWORKS and simulations with specific boundary conditions are conducted using the ANSYS-CFX software, which utilizes computational fluid dynamics (CFD) techniques. These boundary conditions are based on previous study by Rosly et al in 2016. The inlet flow rate of 0.002 m3/s and diameter of the screw pump are constant while the other three main parameters are varying within the acceptable ranges which are reported from prior studies. The outcomes found that the highest torque is generated by a single rotating blade at 5.65 Nm which rotates at 30 RPM at 30° angle of inclination. Meanwhile, the highest efficiency of 24.04% is obtained with a single rotating blade at 40 RPM with 20° angle of inclination. Based on the findings, it is concluded that these three main design parameters of screw pump may not be sufficient to obtain the optimal efficiency for the specific boundary conditions used in the simulation study. Thus, several combinations of design parameters should be considered in the future to increase the screw pump’s efficiency.

Numerical Investigation on Aerodynamic Performance of Helical Savonius Rotor Inspired by Natural Shapes

There have been extensive studies conducted on Horizontal Axis Wind Turbines (HAWT) at relatively moderate to high wind speed regions. However, such detailed investigations for Vertical Axis Wind Turbines (VAWT), specifically for low wind speed terrains are amply reported. This motivates us to conduct research to explore possibilities in improving performance of VAWT in low wind speed terrains, which is attempted in the present work. This is required due to the fact that most of regions do not have sufficient extractable wind energy due to low speeds. VAWTs can perform at such low wind speed, but are less efficient. Improving efficiency of VAWT will solve the purpose. Hence, the present study is aimed at finding the performance characteristics of VAWT for low Wind speed configurations. Various parameters affecting power generation are investigated. Numerical analyses on various configurations are conducted to study the effects of twist angle, free stream velocity, number of blades. Computational results obtained have been in good agreement with the established results for semi-circular Savonius rotor profile. The results suggest that for low wind speed terrains, there is a need to explore the combination of lift and drag type of profiles, which could be used for the utilization of available wind power. Hence, naturally inspired shapes (profiles) were investigated for the possible solution of combined lift and drag type wind turbines at low speeds. The blade shape for such combined lift and drag type wind turbine were deduced from the available literature. It is well established that the naturally inspired shapes as noted in sea conch follow golden ratio in its contours. The present study provides an insight on the characteristic curves of VAWT for low wind speed terrains, effects of various geometric and flow parameters suitable for low wind speed terrains.

Computational study of a newly developed parabolic blade profile of a Savonius wind rotor

Computational study of a newly developed parabolic blade profile of a Savonius wind rotor

Designing the working surfaces of rotary planetary mechanisms

Purpose. To design a method for smoothing the working surfaces of stator and rotor with the use of computer simulation to eliminate the impact of the rotor on the stator when they interact. Methodology. Special and general methods of research have been used: interpolation of the point series – to determine the contour nodes of the rotor and the stator of the rotary-planetary machine; formation of B-splines – to construct a point series whose coordinates are structurally determined; technology of automated formation of curves in CAD-system SolidWorks – for modelling of functional surfaces of a planetary-rotary compressor. Findings. Algorithms for formation of the contours representing curves defined analytically or constructively with a given accuracy have been developed. The obtained contours are used in the CAD system as linear elements of the surface model. The developed method has been tested in the simulation of functional surfaces of a planetary-rotary compressor. Optimization of the body shape and rotor profiles in order to increase the productivity of the rotary-planetary machine has been carried out. Originality. The developed algorithms make it possible to determine the original point series belonging to any curve and provide a given interpolation accuracy when forming a B-spline contour or second-order curve arcs. Computer models of the body surfaces of the rotor are formed on the basis of the gear ratio of the planetary-rotary mechanism and the rotor dimensions. In order to increase the performance of the compressor, the working surfaces of the rotor have been optimized. The maximum volume of the working chamber was increased by increasing the radius of the moving gear of the planetary-rotary mechanism. In order to prevent the rotor from jamming during compressor operation, the rotor contour was changed. Practical value. The method for modelling the surfaces of complex shape in CAD-system has been developed on the basis of creating contours which with given accuracy represent lines from the surface determinant. This method makes it possible to form computer models of complex surfaces on the basis of a framework consisting of curves absent in CAD libraries.

Analysis of disc brake with composite materials

While braking, frictional heat raise temperatures at the disc/pad interface. Due to which rotor's surface may experience early wear, thermally elastic instability, brake fluid vaporization, and thermally stimulated vibrations as a result of an excessive temperature increase brought on by frictional heat. In order to increase braking effectiveness and improve vehicle stability, an investigation on the use of various materials for the disc brake rotors of two different vehicle types, one of which is solid and the other of which is vented is carried out. The disc brake is modelled using modelling software CATIA and Finite element analysis (FEA) is carried out using ANSYS 14.5, the toolis able to analyse the temperature distribution, stress variation, and deformation over the rotor's profile of the disc brake rotor. After considering the impacts of temperature distribution, Vonmises stresses, and deformation. In this work analysis of disc brake is done with three materials (Aluminium Metal matrix composite, Mild steel and cast iron) used for vented with and without holes type disc brakes. Conferring to the results, Aluminium MMC is observed to be the optimum material for disc brakes where the deformation is minimum at mode shape 3 at frequency 597.1 Hz when compared to other mode shapes.

Contour-Line Optimization and Performance Analysis of Yin-Yang Rotor in Twin-Screw Compressor

To investigate the influence of the profile design of the Yin and Yang rotor on the performance of the twin-screw compressor such as outlet flow, exhaust pressure and turbulence intensity. In this paper, the Yin and Yang rotor profile optimization is carried out based on a type of twin-screw compressor, and the optimization profile and the original profile are numerically simulated, and the performance curves of the two groups of profile parameters are obtained. The results show that the optimized profile has better performance parameters under the same flow condition, that is, it is more stable in operation and has better vibration and noise index in operation.

Numerical modelling of hook and claw-type vacuum pump performance based on cut cell Cartesian method

Vacuum pump is widely used in aviation, chemical, semiconductor and other fields because of its superior performance. In order to study the internal flow characteristics and pump performance, 1-D Chamber Model method and the CFD modelling method based on static grid are commonly used, such methods ignore many important three-dimensional transient flow details. However, in numerical modelling of three-dimensional transient flow field for hook and claw-type vacuum pump with cusps in the rotor profile, the generation of flow field grid is always a challenge. The body-fitted mesh method is difficult to generate effective dynamic grid for such kind of fluid domain, which usually leads to the divergence of calculation. In order to solve these problems, the cut cell Cartesian method is proposed to simulate the three-dimensional transient flow field in hook and claw-type vacuum pump. Firstly, the mathematical basis of the cut cell Cartesian method was introduced in detail, in which the immersed boundary method (IBM) was combined with the generation process of adaptive Cartesian volume mesh. Aiming at modelling the hook and claw-type vacuum pump, firstly, the profile design method of hook and claw-type vacuum pump was derived, and the geometric model of the calculation domain was established. The transient flow field characteristics of the vacuum pump with different inter-lobe clearance sizes were analyzed, and the velocity, pressure, vortices and temperature characteristics inside the vacuum pump were obtained. The influence of clearance variation on the performance of the vacuum pump was discussed. The feasibility and accuracy of the method were verified by a study case of a two-stroke reciprocating piston pump. The research provides a good reference for dynamic grid generation and precise numerical simulation of hook and claw-type vacuum pump.

Geometric design and performance analysis of conical-rotor screw vacuum pump with adjustable flow field clearances

Structure rotor takes a great effect on the performance of screw vacuum pump. An optimized design for conical rotor profiles with adjustable flow field clearances is proposed. Mathematical models of cross-section profiles and helix of conical rotor are established. Meshing model can generate directly by the profiles with stable circumferential clearance, tooth clearance, tooth side clearance and radial clearance. Effects of offset distance involute, deflection angle of epicycloid, the radial offset distances of addendum and dedendum circles on the clearances are analyzed. Mathematical models for working chamber volume, tooth width, pumping speed and shaft power of the vacuum pump are established. Furthermore, the calculated pumping speed and shaft power are verified by comparing the experimental measured results. Effects of rotor structure parameters on the geometric characteristics and working performance of the vacuum pump are revealed as well as the comparisons with the fixed-pitch and variable-pitch cylindrical screw vacuum pumps. Results show that shaft power of the conical rotor pump are smaller than those of the two cylindrical pumps under similar actual pumping speeds, resulting in superior performances.

Research on Optimization of Profile Parameters in Screw Compressor Based on BP Neural Network and Genetic Algorithm

In order to accurately calculate the geometric characteristics of the twin-screw compressor and obtain the optimal profile parameters, a calculation method for the geometric characteristics of twin-screw compressors was proposed to simplify the profile parameter design in this paper. In this method, the database of geometric characteristics is established by back-propagation (BP) neural network, and the genetic algorithm is used to find the optimal profile design parameters. The effects of training methods and hidden layers on the calculation accuracy of neural network are discussed. The effects of profile parameters, including inner radius of the male rotor, protection angle, radius of the elliptic arc, outer radius of the female rotor on the comprehensive evaluation value composed of length of the contact line, blow hole area and area utilization rate, are analyzed. The results show that the time consumed for the database established by BP neural network is 92.8% shorter than that of the traditional method and the error is within 1.5% of the traditional method. Based on the genetic algorithm, compared with the original profile, the blow hole area of the screw compressor profile optimized by genetic algorithm is reduced by 54.8%, the length of contact line is increased by 1.57% and the area utilization rate is increased by 0.32%. The CFD numerical model is used to verify the optimization method, and it can be observed that the leakage through the blow hole of the optimized model is reduced, which makes the average mass flow rate increase by 5.2%, indicating the effectiveness of the rotor profile parameter optimization method.

Исследование перетеканий в двухроторном вакуумном насосе типа Рутс с эллиптическим профилем роторов при молекулярном режиме течения газа

A Roots-type two-rotor vacuum pump with the rotors’ elliptical profile was designed, developed and manufactured. Its channels conductivity was measured experimentally at various angles of the rotors’ rotation and pressures. Experimental conductivity of the channels was determined in the flow molecular regime. Using the angle factor method implemented in the COMSOL Multiphysics package calculated values of the channel conductivity were obtained for a two-rotor vacuum pump. Deviations in calculated data from the experimental data were not exceeding 10%. Verification and validation of analytical expressions for conductivity of the non-contact pump slot channels demonstrated possibility of their application in mathematical models of the working process of the two-rotor vacuum pumps.