Gate Rotor Research Articles

Resonance Analysis of Single Screw Expander Based on Compressed Air Energy Storage System

As an important technology to achieve energy restructuring, electricity storage plays an important role in the mission of carbon neutrality in today’s society. Compressed air energy storage is one of the most promising technologies for medium- and small-scale power storage. Single screw expander as an important energy conversion equipment in the compressed air energy storage, the stability of its performance is the key to ensure the normal operation of the energy storage system. In this study, based on the resonance problem of single screw expander in variable speed operation and the modal parameters of internal key components structure, the research is carried out. The results show that: The single screw expander can cause a large resonance damage when the rotational speed is working under 1950 – 2380 rpm. The natural modal frequencies of gate rotor, screw rotor and main shaft are not the cause of resonance. Through the work of this study, the influence of internal key components structure on resonance is eliminated, and the next research direction is defined.

Performance Improvement of Single Screw Compressor by Meshing Clearance Adjustment Used in Refrigeration System

The single screw compressor (SSC) is widely used in air compression and refrigeration systems due to its many advantages. The meshing clearance between the screw groove and gate rotor teeth flank has a significant influence on the compressor performance. In this paper, mathematical calculation models describing the internal working process of the SSC are established in order to evaluate the thermal dynamic characteristics of the compressor under varying meshing clearance heights. The refrigerating capacity, volume efficiency and adiabatic efficiency of the SSC are calculated and discussed. Three prototypes, with different meshing clearance heights, were manufactured to study the internal influence mechanisms. The theoretical model was verified using experimental data and the calculation results strongly agreed with the experimental results. Results demonstrate that comparisons of volume efficiency and adiabatic efficiency between the measured and calculated results exhibited deviations of 3.64%–7.98% and 5.92%–9.4%, respectively. Based on the models, analysis under varying meshing clearance heights and working conditions was performed. Taking into account working performance, actual manufacturing conditions and manufacturing cost limitations, a meshing clearance height range from 0.01 mm to 0.08 mm is suggested. This study can provide important theoretical data and experimental support for the design, manufacturing and optimization of single screw compressors.

Modal Analysis of Variable Structure of Gate Rotor of CP-type Single-screw Structure

Single screw technology, due to its superiority of structure, has been widely used in many fields of gas compression, refrigeration, power and so on at present. However, specialized research on the dynamics of single screw structure has not been systematic or in-depth yet. As for single screw compressors and expanders, the dynamics of the gate rotor are the key factors influencing its performance, and the variable-structure modal analysis of the gate rotor is an important task to study its dynamic characteristics. In this paper, the modal parameters of the CP-type single-screw structure gate rotor are compared by modal simulation and modal experiment, and the accuracy of the finite element method is verified. And mainly carried out the simulation modal analysis of the gate rotor variable structure. The results show that the change of structural parameters is an important factor affecting the natural frequency of the gate rotor mode. The variable structure modal analysis can be used to provide reference for the structural optimization of the gate rotor.

Performance evaluation of a novel single-screw compressor and expander design

Single-screw machines have seen significant development and improvement over the last decades and they are currently employed as both compressors and expanders in several applications. The correct functioning of the machine heavily relies on the meshing between the gate rotors and the central rotor which is directly linked to the precision of the manufacturing process to avoid unexpected wear of the tooth profiles. It is well known that the wear of the gate rotor tooth profiles over time is one of the limiting factors with respect to twin-screw machines. To this end, a number of studies have been reported in the literature about improved tooth profiles. For instance, the conventional straight-line profile has been replaced by multi-column tooth flank designs to enlarge the contact surface. However, the manufacturing process is still based on CNC machines with associated challenges.In a previous study, the authors proposed and modeled a new tooth profile design to overcome the aforementioned limitations. In particular, 3D printing technique was utilized to manufacture the non-conventional tooth design. A geometry model has also been developed to calculate the sealing lines, groove volume curves, and surface areas of the new design.In this work, a detailed mechanistic model of the single-screw machine is exercised to compare the conventional straight-line profile with the newly proposed tooth profile. Particular emphasis is given to the effect of seal lines on the leakage flows. Furthermore, the design implications of the new tooth profile on internal volume ratio, porting, and displacement are also discussed.

Grid Generation for CFD Analysis and Design of a Variety of Twin Screw Machines

A detailed study of the fluid flow and thermodynamic processes in positive displacement machines requires 3D CFD modeling in order to capture their real geometry, including leakage gaps. However, limitations in the conventional computational grids, used in commercial software packages, exclude their use for classical twin screw machines. The screw compressor rotor grid generator (SCORG) is a customized grid generation tool developed to overcome these limitations. This paper shows how it can be further extended to include non-conventional rotor designs, such as those with variable lead or profile variation and even internally geared machines with conical rotors. Other arrangements possible with this improvement include multiple gate rotors to increase volumetric displacement or dual lead, high wrap angle rotors for very high-pressure differences and vacuum applications. A case study of a water-injected twin screw compressor is included to demonstrate its use for both detailed flow analysis and design.

싱글 스크류 압축기의 게이터 로터 설계

싱글 스크류 압축기의 게이터 로터 설계

Theoretical and experimental analyses of the internal leakage in single-screw expanders

A single-screw expander (SSE) is a type of volumetric expander that can be applied to power generation, which is beneficial for energy conservation and environment protection. Investigating the SSE leakage characteristics is necessary because leakage has a significant influence on the SSE performance. This study provides theoretical and experimental analyses of the SSE internal leakage with compressed air as the working fluid. Both mathematical model of different leakage paths and leakage model have been established. The simulation model was verified by experimental data at internal volume ratios of 2.95 and shows a maximum deviation of 3.63%. Results show that fitting clearance height and rotational speed could clearly influence the volumetric efficiency and power output. The diameters of both the screw and the gate rotor could also significantly influence the volumetric efficiency. The volumetric efficiency decreased with the increase in internal volume ratio.

Internally geared screw machines with ported end plates

It is possible to design cylindrical helical gearing profiles such that an externally lobed inner gear rotates inside an internally lobed outer gear while maintaining continuous lines of contact between the gears. The continuous contact between the inner and outer rotors (analogous to the main and gate rotors in a conventional screw machine) creates a series of separate working chambers. In this type of machine the rotors have parallel axes of rotation, and if both rotors are free to rotate about their own axes, these axes can be fixed in space.The use of ported end plates is proposed to control the period during which fluid is allowed to enter or leave the working chambers of the internally geared screw machine. As with conventional screw machines, these internally geared rotors can then be used to achieve compression or expansion of a trapped mass of fluid, and the machine geometry can be designed in order to optimise performance for particular applications.This paper describes the geometrical analysis of some simple rotor profiles and explores the effect on rotor torques for particular applications of this novel screw configuration.

Static Finite Element Analysis on Cast Shell of a 100 kW Single Screw Expander

In the process of shell design of a 100kW single screw expander, the fundamental research on the screw chamber walls thickness is still lacking. Thin wall may cause deformation and the damage possibility of the inlet passage. Thick wall will increase the weight of the expander and led to assembly problem and transportation inconvenience. In this paper, static finite element analysis on cast shell of the 100 kW single screw expander was carried out. By calculating stress distribution and deformation of the expander shell under 1.5 times of the design pressure, the authors find the thickness of gate rotor chamber walls and inlet passage walls as 15 mm is acceptable, but the thickness of screw chamber walls should be at least 35 mm.

Modeling and Manufacture of a PC-Type Single-Screw Compressor Rotor

This study aimed to effectively design, manufacture and simulate a single-screw compressor. In this paper, a mathematical model of a pc-type single-screw compressor was developed. The pc-type single-screw compressor was assembled using two gate rotors, a screw rotor and a frame. First, the mathematical model of a conical tooth was designed and a gate rotor equation was obtained through coordinate transformation. Then, the coordinate systems between the gate rotor and the screw rotor were set up. Using a homogeneous coordinate transformation matrix, the family of gate rotor surfaces was obtained. Based on gear theory, the equations of meshing between the gate rotor and screw rotor were determined. Substituting the equation of meshing into the family of gate rotor surfaces, the gate rotor and the screw rotor were generated and their geometrical model illustrated using a software package. Based on the developed mathematical models, the contact lines and stress analysis between the gate rotor and screw rotor were displayed. An edge contact between the gate and screw rotors was found, indicating the necessity of a plastic or a composite material to encircle the conical surface. A computer-aided manufacturing software package was used to simulate the manufacture of the screw rotor.

IDENTIFICATION OF MULTI-CRACKS IN THE GATE ROTOR SHAFT BASED ON THE WAVELET FINITE ELEMENT METHOD

In order to have fault identification for the gate rotor shaft with multiple cracks effectively, the quantity identification method of the gate rotor shaft with multiple cracks based on wavelet finite element method is established and the frequency test of the gate rotor shaft based on blind source separation algorithm is analyzed. Firstly the wavelet finite element was established by combining the Daubechies wavelet theory and the traditional finite element theory and then the vibration equations of intact and cracked wavelet finite element were obtained, which were applied to compute the changing rate of the natural frequencies for the cracked gate rotor shaft. Then natural frequencies fitting curve surface of the cracked gate rotor shaft with were acquired based on the wavelet finite element method and the identification procedure of the cracks was confirmed and the gate rotor shaft with two different cracks was analyzed and the results showed that the wavelet finite element could predict the multi-cracks correctly.

The Application of Wavelet Finite Element Method on the Crack Recognition of the Gate Rotor Shaft of the Single Screw Compressor

The Application of Wavelet Finite Element Method on the Crack Recognition of the Gate Rotor Shaft of the Single Screw Compressor

Vibration Analysis for the Gate Rotor of the Single Screw Compressor Based on Wavelet Finite Element

The gate rotor was a main part of the single screw compressor. In order to study the vibration characteristics of the gate rotor, wavelet finite element was used to have vibration analysis for it. The Daubechies wavelet plate element was used for meshing depending on transverse deforming theory. The Daubechies wavelet plate element was established by using Daubechies wavelet as shape function, and the finite elment formulation was deduced finally. The top six natural frequencies and mode shapes of the gate rotor were acquired. The results were close to that calculated by ANSYS software. And the correctness of wavelet finite element method was verified. Through calculating the vibration properties of the gate rotor offered the theory instruction for designing and using it.

Two-dimensional localisation and clearance evaluation of screw rotors

Twin screw compressors have been widely used in industry owing to their advantages. Owing to machining imperfections, it is necessary to apply clearance between main and gate rotors, which will still provide minimum clearance with lowest leakage. The aim of this study is to develop a method to analyse clearance distribution between rotors with theoretical, modified design and machined profiles. In order to evaluate contact point on rotors, a localisation algorithm was developed. The clearances were then calculated along sealing line that was originally derived from theoretical profile. The validity of the method was verified by computer simulation and experiments.

The Study of Meshing Performance for Single Screw Compressor Based on Contact Analysis

In order to increase transmission performance and lubricating condition for meshing pair of the single screw compressor, the contact analysis for the single screw compressor is analyzed. The equations of the former tooth surface of the gate rotor, the back tooth surface of the gate rotor, the top tooth surface of the gate rotor and transition surface between two tooth of gate rotor are constructed respectively. The tooth surface equation of the screw rotor is deduced through using the tooth surface equation of the gate rotor and transform matrix depending on conjugated theory, the contact line equation is moreover acquired. The calculation formula of inducing method curvature is deduced, the inducing method curvature of some points on contact line with the rotation degree of the gate rotor changing is calculated. The computing results show that the contact surface is osculating, which is favor to increase contact strength of the tooth surface. The distribution rules for contact lines of the former tooth surface and back tooth surface of gate rotor is gained through calculation, which provide theory basis for manufacturing screw rotor.

STUDY OF A SINGLE SCREW COMPRESSOR WITH A CONICAL TEETH GATE ROTOR

From a geometric viewpoint, a mathematical model of a single screw compressor with a conjugate pair of meshing conical teeth gate rotor is a conjugate problem. Coordinate transformation and envelope theory are applied to determine the sets of spatial points of the contacting surfaces that define the main rotor of a single screw compressor. Envelope theory and analytical procedure are used to derive mathematical models of a gate rotor and a main rotor. Stress analysis for the single screw compressor mechanism is performed. PowerMILL software package is used to simulate the manufacture of a main rotor. A numerical example with a compressor ratio of 11:6 is presented to demonstrate the application of the mathematical models developed in this paper.

MODELING AND MANUFACTURING OF PP-TYPE SINGLE SCREW COMPRESSOR

A geometric model and a mathematical model of a PP-type single screw rotor with planar gate rotor are derived from the gate-rotor generation process and gear theory. The teeth of gate rotor are planar. Based on the inverse envelope concept, the cutter required for machining the single screw rotor can be obtained using an inverse envelope of a one-parameter family of screw surfaces. The surface of the proposed screw rotor is analyzed using the developed mathematical model. A surface analysis, including stress analysis, of the design and manufacture of the screw compressor is presented. Finally, a numerical example demonstrates the geometric model of the PP-type single screw rotor with a compression ratio of 11:6.

Profile generation and analysis for a pp-type single-screw compressor

The precision design of the screw rotor and the gate rotor is the foundation to promoting the operational reliability of a pp-type single-screw compressor. The purpose of the present paper is to determine the mathematical model of a single-screw rotor with conical gate rotors. A simple method by gear theory to determine the profiles of a screw rotor and a gate rotor have been studied. The mathematical model of the screw rotor is defined as the envelope to the family of gate rotor surfaces. As an example, the pp-type single-screw compressor for a compressor ratio of 11:6 is demonstrated with the aid of the proposed mathematical model. Based on the developed geometrical models, the contour of von Mises stress distributions of a screw rotor and four gate rotors on the proposed mechanism is presented. Using rapid prototyping (RP) and manufacturing technology, the proposed pp-type single-screw compressor with conical teeth of a gate rotor was designed. The RP primitives provide an actual full-size physical model that can be analyzed and used for further development. The results from these mathematical models should have practical applications in the design of pp-type single-screw mechanisms.

A mathematical model of a cc-type single-screw compressor

In this paper, a method is proposed for determining a basic profile of a cc-type single-screw compressor including the gate rotor and the screw rotor. The cc-type has a cylindrical screw and two cylindrical gate rotors. Based on this method, a mathematical model of the meshing principles of a cc-type screw rotor meshed with a gate rotor, that has either straight edge teeth or conical teeth, is presented. The inverse envelope concept is used to determine the cutting-edge curve of a gate rotor. Based on this concept, the required cutter for machining a cc-type screw rotor can be obtained by the envelope of a one-parameter family. The obtained screw rotor is an envelope to the family of the gate rotor's surfaces. The obtained envelope becomes the generating surface. The inverse envelope can be used to obtain the envelope to the family of generating surfaces. Then the profile of a gate rotor cutting-edge curve can be easily obtained. The surface analysis including contact lines is shown for the design and manufacture of a screw compressor. As an example, the cc-type single-screw compressor with a compressor ratio of 11:6 was determined with the aid of the proposed mathematical model. Using rapid prototyping (RP) and manufacturing technology, a cc-type single-screw rotor with a gate rotor was designed. The RP primitives provide an actual full-size physical model that can be analysed and used for further development. Results from these mathematical models should have applications in the design of cc-type single-screw compressors.

A mathematical model of the rotor profile of the single-screw compressor

This paper presents a method for determining the basic profile of a single-screw compressor including a gate rotor and a screw rotor. The inverse envelope concept for determining the cutting-edge curve of the gate rotor is presented. Based on this concept, the required cutter for machining the screw rotor can be obtained by an envelope of the one-parameter family of obtained screw rotors. The obtained screw rotor is an envelope of the family of gate rotor surfaces. Let the obtained envelope of the one-parameter family of gate rotor surfaces become the generating surface. The inverse envelope can be used to obtain the envelope of the family of generating surfaces. Then, the profile of the gate rotor with the cutting-edge curve can be easily obtained. The proposed method shows that the gate rotor and the screw rotor are engaged along the contact line at every instant. This is essential to reduce the effect of leakage on compressor performance. In this paper, a mathematical model of the meshing principle of the screw rotor with the gate rotor is established. As an example, the single-screw compressor for a compressor ratio of 11:6 is determined with the aid of the proposed mathematical model. Results from these mathematical models should have applications in the design of single-screw compressors.