Coupled Torsion-Lateral Stability of a Shaft-Disk System Driven Through a Universal Joint

2002 ◽  
Vol 69 (3) ◽  
pp. 261-273 ◽  
Author(s):  
H. A. DeSmidt ◽  
K. W. Wang ◽  
E. C. Smith
Keyword(s):  
High Speed ◽  
Linear Time ◽  
Parametric Instability ◽  
Disk System ◽  
Lateral Instability ◽  
Worst Case ◽  
Stable Case ◽  
Rotor Shaft ◽  
Periodic Linear ◽  
The Stability

Understanding the instability phenomena of rotor-shaft and driveline systems incorporating universal joints is becoming increasingly important because of the trend towards light-weight, high-speed supercritical designs. In this paper, a nondimensional, periodic, linear time-varying model with torsional and lateral degrees-of-freedom is developed for a rotor shaft-disk assembly supported on a flexible bearing and driven through a U-joint. The stability of this system is investigated utilizing Floquet theory. It is shown that the interaction between torsional and lateral dynamics results in new regions of parametric instability that have not been addressed in previous investigations. The presence of load inertia and misalignment causes dynamic coupling of the torsion and lateral modes, which can result in torsion-lateral instability for shaft speeds near the sum-type combinations of the torsion and lateral natural frequencies. The effect of angular misalignment, static load-torque, load-inertia, lateral frequency split, and auxiliary damping on the stability of the system is studied over a range of shaft operating speeds. Other than avoiding the unstable operating frequencies, the effectiveness of using auxiliary lateral viscous damping as a means of stabilizing the system is investigated. Finally, a closed-form technique based on perturbation expansions is derived to determine the auxiliary damping necessary to stabilize the system for the least stable case (worst case).

Coupled Torsion-Lateral Stability of a Shaft-Disk System Driven Through a Universal Joint

2001 ◽  
Author(s):  
Hans A. DeSmidt ◽  
K. W. Wang ◽  
Edward C. Smith
Keyword(s):  
High Speed ◽  
Linear Time ◽  
Parametric Instability ◽  
Perturbation Expansions ◽  
Disk System ◽  
Lateral Instability ◽  
Worst Case ◽  
Stable Case ◽  
Rotor Shaft ◽  
Periodic Linear

Abstract Understanding the instability phenomena of rotor-shaft and driveline systems incorporating universal joints is becoming increasingly important because of the trend towards light-weight, high-speed supercritical designs. A non-dimensional, periodic, linear time-varying model with torsional and lateral degrees-of-freedom is developed for a rotor shaft-disk assembly supported on a flexible bearing and driven through a U-Joint and stability is investigated with Floquet Theory. It is shown that the interaction between torsional and lateral dynamics results in new regions of parametric instability that have not been addressed in previous investigations. The presence of load inertia and misalignment causes dynamic coupling of the torsion and lateral modes, which can result in torsion-lateral instability for shaft speeds near the sum-type combinations of the torsion and lateral natural frequencies. The effect of angular misalignment, static load-torque, load-inertia, lateral frequency-split, and auxiliary damping on the stability of the system is studied over a range of shaft operating speeds. Also, the effectiveness of auxiliary lateral viscous damping as a means of stabilizing the system is investigated. Finally, a closed-form technique based on perturbation expansions is derived to determine the auxiliary damping necessary to stabilize the system for the least stable case (worst case).

Numerical and Experimental Investigation of the CeCOST Swirl Burner

2018 ◽  
Author(s):  
Erdzan Hodzic ◽  
Senbin Yu ◽  
Arman Ahamed Subash ◽  
Xin Liu ◽  
Xiao Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Combustion Process ◽  
Stability Limit ◽  
Swirl Burner ◽  
Current Configuration ◽  
Stable Case ◽  
Eddy Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

Clean technology has become a key feature due to increasing environmental concerns. Swirling flows, being directly associated with combustion performance and hence minimized pollutant formation, are encountered in most propulsion and power-generation combustion devices. In this study, the development process of the conceptual swirl burner developed at the Swedish National Centre for Combustion and Technology (CeCOST), is presented. Utilizing extensive computational fluid dynamics (CFD) analysis, both the lead time and cost in manufacturing of the different burner parts were significantly reduced. The performance maps bounded by the flashback and blow-off limits for the current configuration were obtained and studied in detail using advanced experimental measurements and numerical simulations. Utilizing high speed OH-chemiluminescence, OH/CH2O-PLIF and Large Eddy Simulation (LES), details of the combustion process and flame-flow interaction are presented. The main focus is on three different cases, a stable case, a case close to blow-off and flashback condition. We show the influence of the flame on the core flow and how an increase in swirl may extend the stability limit of the anchored flame in swirling flow burners.

Statistical Analysis of Damper Seal Clearance Divergence and Impact Upon Rotordynamic Stability

2004 ◽  
Author(s):  
Joseph Tecza ◽  
Thomas Soulas ◽  
Thomas Eldridge
Keyword(s):  
Response Surface ◽  
High Speed ◽  
Statistical Technique ◽  
Design Parameters ◽  
Stable Operation ◽  
Worst Case ◽  
Compressor Design ◽  
Design Values ◽  
The Stability ◽  
The Impact

Rotordynamic stability in a high-speed, high-pressure centrifugal compressor is achieved through introducing stabilizing forces and managing destabilizing forces. It becomes the original equipment manufacturer’s (OEM) responsibility to provide sufficient stabilizing influence to ensure acceptable operational behavior. A variety of mechanisms exist to provide stability: damper bearings, de-swirl elements on seals, shunt holes and damper seals are commonly provided by the compressor manufacturer to combat instability. The application of damper seals provides a significant increase in rotordynamic stability if designed properly. A previous case study (Camatti, et. al. [1]) presented the detrimental effect of damper seal clearance divergence and seal gas pre-swirl upon predicted stability. Accurate prediction of rotordynamic stability requires knowledge of the destabilizing influences, and evaluation of the variation possible in the stability promoting elements. In particular, the damper seal can be strongly influenced by the presence of divergence in the seal-to-rotor clearance and can result in unexpected at-load behavior. One approach to ensure stable operation is to perform a “worst case” evaluation. However, this often results in excessive compromise (large seal clearance and impact on aerodynamic performance) to “eliminate” the possibility of unstable operation. A different and new approach is to define an acceptable envelope of probability. This study presents a statistical evaluation of the impact of damper seal clearance divergence, along with other compressor design parameters, and provides a method for ensuring stable operation regardless of manufacturing or operational variation. The logarithmic decrement is evaluated as a function of compressor design values and a statistical response surface is created. From the response surface and defined variation in design values, a measure of probability for instability can be obtained. Allowable parameter variation can be restricted to ensure stable operation. Three case studies will be presented where the potential for instability exists and the risk quantified using this statistical technique. Additionally, in one of these cases, test results are presented to support the analytical work.

Predicting the Effect of Vibration on Machining Distortion in High-Speed Milling Aerospace Monolithic Components

2010 ◽  
Author(s):  
Q. H. Song ◽  
X. Ai ◽  
Z. Q. Liu
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Coordinate Measuring Machine ◽  
Stable Case ◽  
Machining Distortion ◽  
Stable Conditions ◽  
Unstable Case ◽  
Measuring Machine ◽  
The Stability ◽  
Monolithic Components

Based on the stability lobe diagram of two degrees of freedom milling system obtained by using the numerical method, two kinds of cutting conditions (stable and unstable) are selected to perform the cutting tests of aeronautical monolithic components. Cutting distortion and secular distortion are measured and analyzed by using the MISTRAL 775 coordinate measuring machine (CMM), respectively. Influences of chatter on machining distortion are investigated. It is shown that, both machining distortion and secular distortion are smaller in stable case; in unstable case, machining distortion is also smaller, while secular distortion is very large, and torsion occurs in the workpiece end with larger box. Therefore, workpiece need be machined in stable conditions for subsequent assembly work, especially aeronautical monolithic components.

Application of Floquet Theory to On-Off Valve Controlled Pneumatic Actuators

1992 ◽  
Vol 114 (2) ◽  
pp. 299-305 ◽  
Author(s):  
Cengiz Kunt ◽  
Rajendra Singh
Keyword(s):  
Dynamic Response ◽  
Transient Response ◽  
Floquet Theory ◽  
Linear Time ◽  
Computational Technique ◽  
Valuable Insight ◽  
Pneumatic Actuators ◽  
Periodic Linear ◽  
Straightforward Solution ◽  
The Stability

A periodic linear time varying (LTV) model for on-off valve controlled pneumatic actuation systems, was described in an earlier paper by the authors. Based on this LTV model formulation, Floquet’s Theorem is invoked to characterize dynamic response of the system. A new computational technique called the expanded state space method is developed to calculate the frequency response of the LTV system with staircase coefficient variations. This technique is computationally superior to the straightforward solution scheme. Floquet Theory is also used to assess the nature of transient response. A single acting cylinder system controlled by an on-off valve is considered to illustrate the stability and transient response issues. Computer simulation based on the nonlinear model is used to obtain detailed results. It is shown that application of the Floquet Theory provides valuable insight into the dynamic response of the class of actuators considered.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

Dynamic Performance of High-Speed Electric Multiple Unit within Multi-Body System Simulation

2019 ◽  
Vol 12 (4) ◽  
pp. 339-349
Author(s):  
Junguo Wang ◽  
Daoping Gong ◽  
Rui Sun ◽  
Yongxiang Zhao
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Dynamic Performance ◽  
Body System ◽  
High Speed Railway ◽  
Evaluation Indexes ◽  
Actual Operation ◽  
Multiple Unit ◽  
The Stability ◽  
Multi Body

Background: With the rapid development of the high-speed railway, the dynamic performance such as running stability and safety of the high-speed train is increasingly important. This paper focuses on the dynamic performance of high-speed Electric Multiple Unit (EMU), especially the dynamic characteristics of the bogie frame and car body. Various patents have been discussed in this article. Objective: To develop the Multi-Body System (MBS) model of EMU, verify whether the dynamic performance meets the actual operation requirements, and provide some useful information for dynamics and structural design of the proposed EMU. Methods: According to the technical characteristics of a typical EMU, a MBS model is established via SIMPACK, and the measured data of China high-speed railway is taken as the excitation of track random irregularity. To test the dynamic performance of the EMU, including the stability and safety, some evaluation indexes such as wheel-axle lateral forces, wheel-axle lateral vertical forces, derailment coefficients and wheel unloading rates are also calculated and analyzed in detail. Results: The MBS model of EMU has better dynamic performance especially curving performance, and some evaluation indexes of the stability and safety have also reached China’s high-speed railway standards. Conclusion: The effectiveness of the proposed MBS model is verified, and the dynamic performance of the MBS model can meet the design requirements of high-speed EMU.

A High-Speed Temperature Sensor with Low Supply Sensitivity for SoC Thermal Monitoring

2018 ◽  
Vol 27 (07) ◽  
pp. 1850116
Author(s):  
Yuanxin Bao ◽  
Wenyuan Li
Keyword(s):  
Temperature Sensor ◽  
Conversion Rate ◽  
High Speed ◽  
Supply Voltage ◽  
Ring Oscillator ◽  
Temperature Sensitive ◽  
Cmos Process ◽  
Digital Code ◽  
Thermal Monitoring ◽  
Worst Case

A high-speed low-supply-sensitivity temperature sensor is presented for thermal monitoring of system on a chip (SoC). The proposed sensor transforms the temperature to complementary to absolute temperature (CTAT) frequency and then into digital code. A CTAT voltage reference supplies a temperature-sensitive ring oscillator, which enhances temperature sensitivity and conversion rate. To reduce the supply sensitivity, an operational amplifier with a unity gain for power supply is proposed. A frequency-to-digital converter with piecewise linear fitting is used to convert the frequency into the digital code corresponding to temperature and correct nonlinearity. These additional characteristics are distinct from the conventional oscillator-based temperature sensors. The sensor is fabricated in a 180[Formula: see text]nm CMOS process and occupies a small area of 0.048[Formula: see text]mm2 excluding bondpads. After a one-point calibration, the sensor achieves an inaccuracy of [Formula: see text][Formula: see text]1.5[Formula: see text]C from [Formula: see text]45[Formula: see text]C to 85[Formula: see text]C under a supply voltage of 1.4–2.4[Formula: see text]V showing a worst-case supply sensitivity of 0.5[Formula: see text]C/V. The sensor maintains a high conversion rate of 45[Formula: see text]KS/s with a fine resolution of 0.25[Formula: see text]C/LSB, which is suitable for SoC thermal monitoring. Under a supply voltage of 1.8[Formula: see text]V, the maximum energy consumption per conversion is only 7.8[Formula: see text]nJ at [Formula: see text]45[Formula: see text]C.

scholarly journals Influence of Whey Protein Micro-Gel Particles and Whey Protein Micro-Gel Particles-Xanthan Gum Complexes on the Stability of O/W Emulsions

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2301
Author(s):  
Man Zhang ◽  
Bin Liang ◽  
Hongjun He ◽  
Changjian Ji ◽  
Tingting Cui ◽  
...  
Keyword(s):  
Oxidative Stability ◽  
Whey Protein ◽  
High Speed ◽  
Xanthan Gum ◽  
Physical Stability ◽  
Theoretical Support ◽  
Gel Particles ◽  
Oil In Water ◽  
The Stability ◽  
The Impact

Appropriate pretreatment of proteins and addition of xanthan gum (XG) has the potential to improve the stability of oil-in-water (O/W) emulsions. However, the factors that regulate the enhancement and the mechanism are still not clear, which restricts the realization of improving the emulsion stability by directional design of its structure. Therefore, the effects of whey protein micro-gel particles (WPMPs) and WPMPs-XG complexes on the stability of O/W emulsion were investigated in this article to provide theoretical support. WPMPs with different structures were prepared by pretreatment (controlled high-speed shear treatment of heat-set WPC gels) at pH 3.5–8.5. The impact of initial WPC structure and XG addition on Turbiscan Indexes, mean droplet size and the peroxide values of O/W emulsions was investigated. The results indicate that WPMPs and XG can respectively inhibit droplet coalescence and gravitational separation to improve the physical stability of WPC-stabilized O/W emulsions. The pretreatment significantly enhanced the oxidative stability of WPC-stabilized O/W emulsions. The addition of XG did not necessarily enhance the oxidative stability of O/W emulsions. Whether the oxidative stability of the O/W emulsion with XG is increased or decreased depends on the interface structure of the protein-XG complex. This study has significant implications for the development of novel structures containing lipid phases that are susceptible to oxidation.

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