scholarly journals Improving Performance of Cantilevered Momentum Wheel Assemblies by Soft Suspension Support

2013 ◽  
Vol 20 (4) ◽  
pp. 737-748 ◽  
Author(s):  
Weiyong Zhou ◽  
Dongxu Li
Keyword(s):  
Rotational Speed ◽  
Ball Bearings ◽  
Rigid Support ◽  
High Rotational Speed ◽  
Trade Off ◽  
Jeffcott Rotor ◽  
Speed Range ◽  
Before And After ◽  
In Series ◽  
Large Disturbance

This paper focuses on improving the performance of the rigid support cantilevered momentum wheel assemblies (CMWA) by soft suspension support. A CMWA, supported by two angular contact ball bearings, was modeled as a Jeffcott rotor. The support stiffness, before and after in series with a linear soft suspension support, were simplified as two Duffing's type springs respectively. The result shows that the rigid support CMWA produces large disturbance force at the resonance speed range. The soft suspension CMWA can effectively reduce the force on the bearing (also disturbance forces produced by the CMWA) at high rotational speed, and also reduce the nonlinear characteristic of the stiffness. However, the instability of the soft suspension CMWA will limit the maximum rotational speed of the CMWA. Thus, a "proper" stiffness of the soft suspension system is a trade-off strategy between reduction of the force and extension of the speed range simultaneously.

Conceptual Design of a Novel Three-Speed Geared Motor

2013 ◽  
Vol 284-287 ◽  
pp. 629-633
Author(s):  
Yi Chang Wu ◽  
Chia Ho Cheng
Keyword(s):  
Rotational Speed ◽  
Integrated Design ◽  
Gear Train ◽  
Bldc Motor ◽  
Direct Drive ◽  
High Rotational Speed ◽  
Brushless Dc ◽  
Speed Range ◽  
Structural Assembly ◽  
Driving Torque

The purpose of this paper is to develop a novel three-speed geared motor that integrates a basic epicyclic-type gear train with an exterior-rotor brushless DC (BLDC) motor to form a compact structural assembly. Unlike existing gear motors, the proposed device provides three speed ratios including an under drive, a direct drive, and an over drive, and is operated with a single clutch-to-clutch shaft. It provides a wider speed range than the traditional geared motor. Such an integrated design can be appropriately employed in high driving torque and low rotational speed applications or high rotational speed and low driving torque applications.

scholarly journals Pengaruh Modifikasi Belitan Stator Motor Induksi Satu Phasa Starting Kapasitor Pada Mesin Bor Meja Terhadap Arus dan Daya listrik serta Putaran Motor

2020 ◽  
Vol 12 (2) ◽  
pp. 34-43
Author(s):  
Muhammad Naim
Keyword(s):  
Induction Motor ◽  
Double Layer ◽  
Rotational Speed ◽  
Wire Diameter ◽  
Stator Winding ◽  
Drilling Machine ◽  
High Rotational Speed ◽  
Rotor Rotation ◽  
In Series ◽  
Winding Wire

A 1-phase 4-pole starting capacitor induction motor which is used as an activator of the table drilling machine has a more complicated construction because it has a  centrifugal switch which is connected in series with the capacitor for its initial start and a high rotational speed of the stator field, which is 1500 rpm. While a 3-phase 6-pole induction motor has a much simpler construction because it does not require a centrifugal switch and a capacitor for its initial start with a low rotational speed of the stator field, which is 1000 rpm. This study discusses the effect of modifying the stator winding in a 1-phase 4-pole starting capacitor induction motor on the table drilling machine into a stator winding of 3-phase 6-pole induction motor on the rotation of the rotor. Modifications are carried out on the stator winding of a 1-phase induction motor by changing the number of phases, number of poles, type of winding, wire diameter and number of windings per groove. Modifications are carried out on the windings to obtain a 3-phase 6-pole 24-groove induction motor with 200 windings per groove, a wire diameter of 0.5 mm, and a winding type of spiral double layer. In our trials without a load on the induction motor the rotor rotation decreased by 33.71% from 1498 rpm to 993 rpm, and with a load decreased by 36% from 1450 rpm to 927 rpm.

Performances of HSK Tool Interfaces under High Rotational Speed

CIRP Annals ◽  
2001 ◽  
Vol 50 (1) ◽  
pp. 281-284 ◽  
Author(s):  
T. Aoyama ◽  
I. Inasaki
Keyword(s):  
Rotational Speed ◽  
High Rotational Speed

Rolling Bearing Parametric Excitation of a Jeffcott Rotor System

2020 ◽  
Author(s):  
Ghasem Ghannad Tehrani ◽  
Chiara Gastaldi ◽  
Teresa Maria Berruti
Keyword(s):  
Parametric Excitation ◽  
Rotational Speed ◽  
Input Parameter ◽  
Equations Of Motion ◽  
Harmonic Balance Method ◽  
Rolling Bearing ◽  
Mean Value ◽  
Hertzian Contact ◽  
Rolling Bearings ◽  
Jeffcott Rotor

Abstract Rolling bearings are still widely used in aeroengines. Whenever rotors are modeled, rolling bearing components are typically modeled using springs. In simpler models, this spring is considered to have a constant mean value. However, the rolling bearing stiffness changes with time due to the positions of the balls with respect to the load on the bearing, thus giving rise to an internal excitation known as Parametric Excitation. Due to this parametric excitation, the rotor-bearings system may become unstable for specific combinations of boundary conditions (e.g. rotational speed) and system characteristics (rotor flexibility etc.). Being able to identify these instability regions at a glance is an important tool for the designer, as it allows to discard since the early design stages those configurations which may lead to catastrophic failures. In this paper, a Jeffcott rotor supported and excited by such rolling bearings is used as a demonstrator. In the first step, the expression for the time–varying stiffness of the bearings is analytically derived by applying the Hertzian Contact Theory. Then, the equations of motion of the complete system are provided. In this study, the Harmonic Balance Method (HBM) is used to as an approximate procedure to draw a stability map, thus dividing the input parameter space, i.e. rotational speed and rotor physical characteristics, into stable and unstable regions.

The Coupling Characteristic of HSK Tool-Holder/Spindle Interface for High-Speed NC Machine Tool

2014 ◽  
Vol 590 ◽  
pp. 121-125 ◽  
Author(s):  
Wen Kai Jie ◽  
Jian Chen ◽  
Deng Sheng Zheng ◽  
Gui Cheng Wang
Keyword(s):  
Machine Tool ◽  
Rotational Speed ◽  
High Speed ◽  
Nonlinear Finite Element Method ◽  
High Rotational Speed ◽  
Tool Holder ◽  
Nc Machine Tool ◽  
Machine Tool Accuracy ◽  
Nc Machine ◽  
Coupling Characteristic

The coupling characteristic of the tool-holder/spindle interface in high speed NC machine has significant influence on machine tool accuracy and process stability. With the example of HSK-E63, based on nonlinear finite element method (FEM), the coupling characteristic of the tool-holder/spindle interface under high rotational speed was investigated, the influence of interference, clamping force and rotational speed on the contact stress and the sectional area of clearance were discussed in detail. The results can be used as theoretical consideration to design and optimize the high speed tool-holder/spindle interface.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

scholarly journals Multi-machine transient stability by using static synchronous series compensator

2020 ◽  
Vol 11 (3) ◽  
pp. 1249
Author(s):  
Nur Ashida Salim ◽  
Nur Diyana Shahirah Mohd Zain ◽  
Hasmaini Mohamad ◽  
Zuhaila Mat Yasin ◽  
Nur Fadilah Ab Aziz
Keyword(s):  
Power System ◽  
Transient Stability ◽  
Single Phase ◽  
Power Transmission ◽  
System Stability ◽  
Phase System ◽  
Proportional Integral ◽  
Before And After ◽  
In Series ◽  
Static Synchronous Series Compensator

<span lang="EN-US">Transient stability in power system is vital to be addressed due to large disturbances that could damage the system such as load changes and voltage increases. This paper presents a multi-machine transient stability using the Static Synchronous Series Compensator (SSSC). SSSC is a device that is connected in series with the power transmission line and produces controllable voltage which contribute to a better performance in the power system stability. As a result, this research has observed a comparison of the synchronization of a three-phase system during single-phase faults before and after installing the SSSC device. In addition, this research investigates the ability of three different types of controllers i.e. Proportional Integral (PI), Proportional Integral Derivation (PID), and Generic controllers to be added to the SSSC improve the transient stability as it cannot operate by itself. This is because the improvement is too small and not able to achieve the desired output. The task presented is to improve the synchronization of the system and time taken for the voltage to stabilize due to the fault. The simulation result shows that the SSSC with an additional controller can improve the stability of a multi-machine power system in a single phase fault.</span>

scholarly journals Turbomachine Design for Supercritical Carbon Dioxide Within the sCO2-HeRo.eu Project

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Alexander Hacks ◽  
Sebastian Schuster ◽  
Hans Josef Dohmen ◽  
Friedrich-Karl Benra ◽  
Dieter Brillert
Keyword(s):  
Rotational Speed ◽  
Mechanical Design ◽  
Integrated Design ◽  
Mechanical Analysis ◽  
High Rotational Speed ◽  
Through Flow ◽  
Compressor Impeller ◽  
Final Design ◽  
Manufacturing Techniques ◽  
Future Work

The paper aims to give an overview over the keystones of design of the turbomachine for a supercritical CO2 (sCO2) Brayton cycle. The described turbomachine is developed as part of a demonstration cycle on a laboratory scale with a low through flow. Therefore, the turbomachine is small and operates at high rotational speed. To give an overview on the development, the paper is divided into two parts regarding the aerodynamic and mechanical design. The aerodynamic design includes a detailed description on the steps from choosing an appropriate rotational speed to the design of the compressor impeller. For setting the rotational speed, the expected high windage losses are evaluated considering the reachable efficiencies of the compressor. The final impeller design includes a description of the blading development together with the final geometry parameters and calculated performance. The mechanical analysis shows the important considerations for building a turbomachine with integrated design of the three major components: turbine, alternator, and compressor (TAC). It includes different manufacturing techniques of the impellers, the bearing strategy, the sealing components, and the cooling of the generator utilizing the compressor leakage. Concluding the final design of the TAC is shown and future work on the machine is introduced.

Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part I — Flow Structure Analysis

2020 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Stability Limit ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
High Rotational Speed ◽  
Lower Accuracy ◽  
The Stability ◽  
Computational Resources

Abstract High-speed centrifugal compressor requirements include a wide operating range between choking and stall especially for turbocharging applications. The prediction of the stability limit at different speeds is still challenging. In literature, several studies have been published on the phenomena that trigger the compressor instability. However, a comprehensive analysis of criteria that can be used in the first steps of centrifugal compressors design to predict the stability limit is still missing. In previous work the authors have already presented a criterion, so called “Stability Parameter”, to predict the surge line of centrifugal compressors based on a simplified CFD approach that does not require excessive computational resources and that can be efficiently used in the preliminary design phases. The above methodology has demonstrated its accuracy for centrifugal compressors with vaned diffuser, but a lower accuracy has been detected for vaneless diffusers. Before proceeding to identify additional criteria focused on compressors with vaneless diffuser, an in-depth fluid dynamics analysis has been necessary. This analysis has been also carried out through fully 3D unsteady simulations to allow identifying the real phenomena linked to the trigger of the instability of centrifugal compressors. It has been found how these phenomena are strongly related to the rotational speed, in particular have been shown the key role of the volute at high rotational speed.

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