Comparison Between the Effects of Zero and Non-Zero Flow Acceleration on the Entropy Wave Decay: An Experimental Study

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
S. M. Hosseinalipour ◽  
E. Rahmani ◽  
A. Fattahi
Keyword(s):  
Hot Spot ◽  
Theoretical Models ◽  
Fast Response ◽  
Effective Length ◽  
Combustion Instabilities ◽  
Convergent Nozzle ◽  
Flow Acceleration ◽  
Wave Decay ◽  
Accelerated Flow ◽  
Effective Length Method

Abstract Entropy wave, as the convecting hot spot, is one of the sources of combustion instabilities, which is less explored through the literature. Convecting in a highly turbulent flow of a combustor, entropy waves may experience some levels of dissipation and deformation. In spite of some earlier investigations in the zero acceleration flow, the extent of the wave decay has not been clear yet. Further, there exist no results upon the wave decay in non-zero accelerated flows. This is of crucial importance, as the wave passes through the end nozzle of the combustor or gas turbine stages. The current experiment, therefore, compares the wave decay in both flow of constant and variable bulk velocity, meaning, respectively, a uniform pipe and a convergent nozzle. The comparison will aid the theoretical models to reduce complexity by simplifying the relations of non-zero acceleration flow to those of no acceleration, as followed by the earlier effective-length method. Reynolds number and inlet turbulence intensity are considered as the governing hydrodynamic parameters for both investigated flows. The entropy wave is generated by an electrical heater module and detected using fast-response thermocouples. The results show that the entropy wave variation is point-wise and frequency-dependent. The accelerated flow of the nozzle is generally found to be more dissipative in comparison with the zero acceleration flow.

scholarly journals Perturbation Analysis of a Multiple Layer Guided Love Wave Sensor in a Viscoelastic Environment

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4533 ◽  
Author(s):  
Tao Wang ◽  
Ryan Murphy ◽  
Jing Wang ◽  
Shyam S. Mohapatra ◽  
Subhra Mohapatra ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Liquid Layer ◽  
Perturbation Analysis ◽  
Love Wave ◽  
Low Cost ◽  
Maxwell Model ◽  
Theoretical Models ◽  
Fast Response ◽  
Liquid Environment

Surface acoustic wave sensors have the advantage of fast response, low-cost, and wireless interfacing capability and they have been used in the medical analysis, material characterization, and other application fields that immerse the device under a liquid environment. The theoretical analysis of the single guided layer shear horizontal acoustic wave based on the perturbation theory has seen developments that span the past 20 years. However, multiple guided layer systems under a liquid environment have not been thoroughly analyzed by existing theoretical models. A dispersion equation previously derived from a system of three rigidly coupled elastic mass layers is extended and developed in this study with multiple guided layers to analyze how the liquid layer’s properties affect the device’s sensitivity. The combination of the multiple layers to optimize the sensitivity of an acoustic wave sensor is investigated in this study. The Maxwell model of viscoelasticity is applied to represent the liquid layer. A thorough analysis of the complex velocity due to the variations of the liquid layer’s properties and thickness is derived and discussed to optimize multilayer Surface acoustic wave (SAW) sensor design. Numerical simulation of the sensitivity with a liquid layer on top of two guided layers is investigated in this study as well. The parametric investigation was conducted by varying the thicknesses for the liquid layer and the guided layers. The effect of the liquid layer viscosity on the sensitivity of the design is also presented in this study. The two guided layer device can achieve higher sensitivity than the single guided layer counterpart in a liquid environment by optimizing the second guided layer thickness. This perturbation analysis is valuable for Love wave sensor optimization to detect the liquid biological samples and analytes.

Design and Compiling of Laser Propagation Simulation Software in Atmospheric Environment

2012 ◽  
Vol 490-495 ◽  
pp. 2136-2140
Author(s):  
Tong Gang Zhao ◽  
Zhi Qiang Zhang
Keyword(s):  
Theoretical Model ◽  
Rayleigh Scattering ◽  
Hot Spot ◽  
Theoretical Models ◽  
Mie Scattering ◽  
Simulation System ◽  
Simulation Software ◽  
Atmospheric Environment ◽  
Laser Propagation ◽  
Atmospheric Propagation

As development of laser technology, the characteristic of laser atmospheric propagation is always hot spot in laser domain. Using theoretical models of laser atmospheric propagation, a simulation system is researched by implementing a scientific method of software development. This simulation system can simulate the radiate property of laser propagation in atmosphere, and demonstrate the course of laser propagation. This theoretical model of atmospheric propagation is based on Lambert-Beer law, combined with other classic theoretical model such as Rayleigh scattering and Mie scattering. Multiple scattering theories are used when simulating the laser propagation in smoke or fog. In calculation, the atmosphere is divided into layer. An appropriate model will be selected for calculation in each layer in order to enhance the stimulation precision. Lastly, the figure of light spot is drawn along with transmission space. Laser atmospheric propagation is demonstrated.

Demonstration of Active Control of Combustion Instabilities on a Full-Scale Gas Turbine Combustor

2001 ◽  
Author(s):  
C. E. Johnson ◽  
Y. Neumeier ◽  
M. Neumaier ◽  
B. T. Zinn ◽  
D. D. Darling ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Active Control ◽  
Fast Response ◽  
Dominant Mode ◽  
Broadband Noise ◽  
Full Scale ◽  
Operating Conditions ◽  
Combustion Instabilities ◽  
Gas Turbine Combustor ◽  
Airflow Distribution

This paper presents the results of an investigation of active control of combustion instabilities in a natural gas, high-pressure, full-scale gas turbine combustor that was retrofitted with an Active Control System (ACS). The combustor test rig simulates the geometry, inlet airflow distribution, and pressurization of a can-type combustor that exhibits dynamic flame instabilities at some off-design operating conditions. Two essential features of the investigated ACS are 1) a real-time mode observer that identified the frequencies, amplitudes and phases of the dominant modes in the pressure signal and 2) a fast response servo valve that can modulate a large portion of the gaseous fuel. Two active control configurations were studied. In the first configuration, the actuator was mounted on one of two premixed fuel stages, and in the second configuration it was mounted on the inlet to the stabilizing diffusion stage. In both configurations, the ACS damped combustion instabilities, attenuating the dominant mode by up to 15dB and reducing the overall broadband noise by 30-40%. NOx emissions were also reduced by approximately 10% when control was applied. Finally, this study demonstrated the importance of having a fast multiple-mode observer when dealing with complex combustion processes with inherently large time delays.

Development and Application of a Fast-Response Total Temperature Probe for Turbomachinery

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Martin C. Arenz ◽  
Björn Weigel ◽  
Jan Habermann ◽  
Stephan Staudacher ◽  
Martin G. Rose ◽  
...  
Keyword(s):  
Hot Spot ◽  
Fast Response ◽  
High Temporal Resolution ◽  
Test Bed ◽  
Low Pressure Turbine ◽  
Temperature Probe ◽  
Measuring Surface ◽  
Measurement Principle ◽  
Total Temperature ◽  
Insight Into

The measurement of unsteady total temperature is of great interest for the examination of loss mechanisms in turbomachinery with respect to the improvement of the efficiency. Since conventional thermocouples are limited in frequency response, several fast-response total temperature probes have been developed over the past years. To improve the spatial resolution compared to these existing probes and maintaining a high temporal resolution, a new fast-response total temperature probe has been developed at the Institute of Aircraft Propulsion Systems (ILA), Stuttgart, Germany in cooperation with Berns Engineers, Gilching, Germany. The design of the probe allows a sensitive measuring surface below 1 mm2. A detailed insight into the design of the probe, the measurement principle, the calibration process, and an estimation of the measurement uncertainty is given in the present paper. Furthermore, to prove the functionality of the probe, first experimental results of a simple test bed and of area traverses downstream of the first rotor of a two-stage low pressure turbine are presented. It is shown, that the new probe is capable of detecting rotor characteristic effects as well as rotor-stator-interactions. In addition, a hot-spot is investigated downstream of the first rotor of the turbine, and the findings are compared to the effects known from the literature.

STABILITY AND SIMULATION-BASED DESIGN OF STEEL SCAFFOLDING WITHOUT USING THE EFFECTIVE LENGTH METHOD

2003 ◽  
Vol 03 (04) ◽  
pp. 443-460 ◽  
Author(s):  
S. L. CHAN ◽  
A. Y. T. CHU ◽  
F. G. ALBERMANI
Keyword(s):  
Bending Moment ◽  
Nonlinear Problems ◽  
Second Order ◽  
Effective Length ◽  
Analysis And Design ◽  
Order Analysis ◽  
Effective Length Factor ◽  
Highly Nonlinear ◽  
Reliable Design ◽  
Effective Length Method

A robust computer procedure for the reliable design of scaffolding systems is proposed. The design of scaffolding is not detailed in design codes and considered by many researchers and engineers as intractable. The proposed method is based on the classical stability function, which performs excellently in highly nonlinear problems. The method is employed to predict the ultimate design load capacities of four tested 3-storey steel scaffolding units, and for the design of a 30 m×20 m×1.3 m 3-dimensional scaffolding system. As the approach is based on the rigorous second-order analysis allowing for the P-δ and P-Δ effects and for notional disturbance forces, no assumption of effective length is required. It is superior to the conventional second-order analysis of plotting only the bending moment diagram with allowance for P-Δ effect since it considers both P-Δ and P-δ effects such that section capacity check is adequate for strength and stability checking. The proposed method can be applied to large deflection and stability analysis and design of practical scaffolding systems in place of the conventional and unreliable effective length method which carries the disadvantages of uncertain assumption of effective length factor (L e /L).

Development and Application of a Fast-Response Total Temperature Probe for Turbomachinery

2016 ◽  
Author(s):  
Martin C. Arenz ◽  
Björn Weigel ◽  
Jan Habermann ◽  
Stephan Staudacher ◽  
Martin G. Rose ◽  
...  
Keyword(s):  
Hot Spot ◽  
Fast Response ◽  
High Temporal Resolution ◽  
Test Bed ◽  
Low Pressure Turbine ◽  
Temperature Probe ◽  
Measuring Surface ◽  
Measurement Principle ◽  
Total Temperature ◽  
Insight Into

The measurement of unsteady total temperature is of great interest for the examination of loss mechanisms in turbomachinery with respect to the improvement of the efficiency. Since conventional thermocouples are limited in frequency response, several fast-response total temperature probes have been developed over the past years. To improve the spatial resolution compared to these existing probes and maintaining a high temporal resolution, a new fast-response total temperature probe has been developed at the Institute of Aircraft Propulsion Systems (ILA) in cooperation with Berns Engineers. The design of the probe allows a sensitive measuring surface below one square millimeter. A detailed insight into the design of the probe, the measurement principle, the calibration process, and an estimation of the measurement uncertainty is given in the present paper. Furthermore, to prove the functionality of the probe, first experimental results of a simple test bed and of area traverses downstream of the first rotor of a two-stage low pressure turbine are presented. It is shown, that the new probe is capable of detecting rotor characteristic effects as well as rotor-stator-interactions. In addition, a hot-spot is investigated downstream of the first rotor of the turbine and the findings are compared to effects known from literature.

Passive Discrete Variable Stiffness Joint (pDVSJ-II): Modeling, Design, Characterization, and Testing Toward Passive Haptic Interface

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad I. Awad ◽  
Irfan Hussain ◽  
Dongming Gan ◽  
Ali Az-zu'bi ◽  
Cesare Stefanini ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Variable Stiffness ◽  
Fast Response ◽  
Low Energy ◽  
Effective Length ◽  
Haptic Interface ◽  
Discrete Variable ◽  
Low Energy Consumption ◽  
Instantaneous Switching ◽  
Different Levels

In this paper, the modeling, design, and characterization of the passive discrete variable stiffness joint (pDVSJ-II) are presented. The pDVSJ-II is an extended proof of concept of a passive revolute joint with discretely controlled variable stiffness. The key motivation behind this design is the need for instantaneous switching between stiffness levels when applied for remote exploration applications where stiffness mapping is required, in addition for the need of low-energy consumption. The novelty of this work lies in the topology used to alter the stiffness of the variable stiffness joint. Altering the stiffness is achieved by selecting the effective length of an elastic cord with hook's springs. This is realized through the novel design of the cord grounding unit (CGU), which is responsible for creating a new grounding point, thus changing the effective length and the involved springs. The main features of CGU are the fast response and the low-energy consumption. Two different levels of stiffness (low, high) can be discretely selected besides the zero stiffness. The proposed physical-based model matched the experimental results of the pDVSJ-II in terms of discrete stiffness variation curves, and the stiffness dependency on the behavior of the springs. Two psychophysiological tests were conducted to validate the capabilities to simulate different levels of stiffness on human user and the results showed high relative accuracy. Furthermore, a qualitative experiment in a teleoperation scenario is presented as a case study to demonstrate the effectiveness of the proposed haptic interface.

Effective lengths of laterally continuous, laterally unsupported steel beams

1985 ◽  
Vol 12 (3) ◽  
pp. 603-616 ◽  
Author(s):  
Calvin D. Schmitke ◽  
D. J. Laurie Kennedy
Keyword(s):  
Bending Moment ◽  
Effective Length ◽  
Steel Beams ◽  
Lateral Torsional Buckling ◽  
Limit States ◽  
Torsional Buckling ◽  
Resistance Factors ◽  
New Methods ◽  
Fundamental Equations ◽  
Effective Length Method

Laterally unsupported steel beams of sufficient length may fail by elastic or inelastic lateral–torsional buckling. The fundamental equations governing elastic lateral–torsional buckling, taking into account such parameters as the shape of the bending moment diagram, the level of application of the load, and the effect of end restraints to lateral movement and to twist, are reviewed. Provisions in the current CSA Standard CAN3-S16.1-M84 are discussed. The methods currently available for dealing with the interactive lateral–torsional buckling of laterally continuous beams are evaluated statistically. Two new methods for considering this interaction, called the iterated effective length method and the equivalent beam method, are presented. A statistical evaluation of these methods shows that they are in reasonable agreement with available test data. Resistance factors for use in limit-states design are developed for the existing methods discussed as well as for the new methods. Key words: beam, bending moment, buckling, effective lengths, elastic, inelastic, lateral–torsional buckling, laterally continuous, steel.

scholarly journals Nonlinear mechanical model of the shaft of a roll forming mill and parameter identification

2021 ◽  
Vol 112 (11-12) ◽  
pp. 3363-3375
Author(s):  
Matthias Lamprecht ◽  
Emin Koçbay ◽  
Martin Leonhartsberger ◽  
Yury Vetyukov ◽  
Friedrich Bleicher
Keyword(s):  
Continuous Process ◽  
Theoretical Models ◽  
Element Model ◽  
Rolling Process ◽  
Metal Sheet ◽  
Effective Length ◽  
Roll Forming ◽  
Beam Model ◽  
Compliant Part ◽  
Final Profile

AbstractRoll forming is a continuous process in which a moving metal sheet passes through numerous pairs of opposing forming rolls. The shafts of the roll forming mill are equipped with these rolls and must be set up and aligned to achieve the required final profile of the sheet. The practically relevant task of predicting the profile geometry of this incremental rolling process with varying characteristics of the metal sheet entering the mill requires an accurate description of the stiffness behavior of the shaft with rolls, which is the most compliant part of the roll forming mill. In this paper, the measured force-deflection characteristic of the shaft without rolls is compared with predictions of various theoretical models, followed by the adoption of the shear deformable beam model of the shaft with nonlinear elastic supports in the bearings. The coefficients of the cubic stiffness characteristics of the rotational springs as well as the effective length between the supports are identified based on the experimental data for the deflections, measured along the shaft for various loading levels. The theoretical predictions are obtained via the nonlinear finite element model of the shaft. The model thus provided shows high accuracy compared with the measurements. The paper’s results serve as a foundation for models to predict the stiffness of shafts with rolls.

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