On combustion generated noise

1971 ◽  
Vol 49 (2) ◽  
pp. 399-414 ◽  
Author(s):  
Warren C. Strahle
Keyword(s):  
Fluid Mechanics ◽  
Experimental Work ◽  
Power Output ◽  
Turbulent Flames ◽  
Experimental Results ◽  
Combustion Noise ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Spectral Content ◽  
Past Experimental Work

Upon review of past experimental results and theoretical efforts it is apparent that the mechanism by which combustion noise is generated is not well understood. A theory of combustion noise is developed in this paper which follows rigorously from the principles of fluid mechanics. Lighthill's approach, used in his studies of aerodynamic noise, is closely followed in the present work. The sound radiated from open, turbulent flames is found to depend strongly upon the structure of such flames; at present their structure is not well known. However, meaningful bounds and scaling rules for the sound power output and spectral content are derived based upon the present limited knowledge. A framework is developed which explains past experimental work and the origin of combustion noise.

Probabilistic Feature Attention as an Alternative to Variables in Phonotactic Learning

2021 ◽  
pp. 1-56
Author(s):  
Brandon Prickett
Keyword(s):  
Experimental Work ◽  
Experimental Results ◽  
Phonological Acquisition ◽  
Novel Approach ◽  
Free Model ◽  
Cast Doubt ◽  
Feature Attention ◽  
Phonotactic Learning ◽  
Past Experimental Work ◽  
Algebraic Representations

Abstract Since Halle (1962), explicit algebraic variables (often called alpha notation) have been commonplace in phonological theory. However, Hayes and Wilson (2008) proposed a variable-free model of phonotactic learning, sparking a debate about whether such algebraic representations are necessary to capture human phonological acquisition. While past experimental work has found evidence that suggested a need for variables in models of phonology (Berent et al. 2012, Moreton 2012, Gallagher 2013), this paper presents a novel mechanism, Probabilistic Feature Attention (PFA), that allows a variable-free model of phonotactics to predict a number of these phenomena. Additionally, experimental results involving phonological generalization that cannot be explained by variables are captured by this novel approach. These results cast doubt on whether variables are necessary to capture human-like phonotactic learning and provide a useful alternative to such representations.

Comparing the Seismic Performance of Beam-Column Joints with and without SFRC when Subjected to Cyclic Loading

2012 ◽  
Vol 626 ◽  
pp. 85-89 ◽  
Author(s):  
Kay Dora Abdul Ghani ◽  
Nor Hayati Hamid
Keyword(s):  
Energy Dissipation ◽  
Cyclic Loading ◽  
Seismic Performance ◽  
Experimental Work ◽  
Concrete Beam ◽  
Steel Fiber ◽  
Precast Concrete ◽  
Experimental Results ◽  
Column Joint ◽  
Initial Cracks

The experimental work on two full-scale precast concrete beam-column corner joints with corbels was carried out and their seismic performance was examined. The first specimen was constructed without steel fiber, while second specimen was constructed by mixed up steel fiber with concrete and placed it at the corbels area. The specimen were tested under reversible lateral cyclic loading up to ±1.5% drift. The experimental results showed that for the first specimen, the cracks start to occur at +0.5% drifts with spalling of concrete and major cracks were observed at corbel while for the second specimen, the initial cracks were observed at +0.75% with no damage at corbel. In this study, it can be concluded that precast beam-column joint without steel fiber has better ductility and stiffness than precast beam-column joint with steel fiber. However, precast beam-column joint with steel fiber has better energy dissipation and fewer cracks at corbel as compared to precast beam-column joint without steel fiber.

Definition of the yield point in plasticity and its effect on the shape of the yield locus

1966 ◽  
Vol 1 (4) ◽  
pp. 331-338 ◽  
Author(s):  
T C Hsu
Keyword(s):  
Yield Point ◽  
Experimental Work ◽  
Strain Curve ◽  
Yield Locus ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Proportional Limit ◽  
Stress Strain ◽  
Small Section ◽  
Definition Of

Three different definitions of the yield point have been used in experimental work on the yield locus: proportional limit, proof strain and the ‘yield point’ by backward extrapolation. The theoretical implications of the ‘yield point’ by backward extrapolation are examined in an analysis of the loading and re-loading stress paths. It is shown, in connection with experimental results by Miastkowski and Szczepinski, that the proportional limit found by inspection is in fact a point located by backward extrapolation based on a small section of the stress-strain curve, near the elastic portion of the curve. The effect of different definitions of the yield point on the shape of the yield locus and some considerations for the choice between them are discussed.

Maximizing Human Power Output by Suitable Selection of Motion Cycle and Load

1970 ◽  
Vol 12 (3) ◽  
pp. 315-329 ◽  
Author(s):  
J. Y. Harrison
Keyword(s):  
Mechanical Properties ◽  
Experimental Work ◽  
Power Output ◽  
Factors Affecting ◽  
Human Power ◽  
Input Motion ◽  
Ergometer Cycling ◽  
Selection Of

In this paper various factors affecting human power output are discussed, including the mechanical properties of muscle, the geometry of the input motion and the kinematics of the input motion. A mulitpurpose ergometer, designed and built to take account of these factors is described. Two basic motions are possible on the ergometer: cycling and rowing. The rowing motions may be made with any combination of seat and feet either sliding or fixed. In the rowing motions, during a single to and fro cycle, prescribed variations in velocity of the input links can be forced on a subject. Experimental work, which is described, showed that there are considerable differences in the effectiveness of the various ways of working, and that one in particular, a modified rowing motion, allowed the production of greater average amounts of power for periods up to two minutes than have so far been recorded and published (to the author's knowledge).

A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan

2012 ◽  
Author(s):  
Jian-Cheng Cai ◽  
Da-Tong Qi ◽  
Yong-Hai Zhang
Keyword(s):  
Pressure Fluctuation ◽  
Sound Radiation ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Structural Noise ◽  
Tonal Noise ◽  
Fan Noise ◽  
Blade Passing Frequency ◽  
Dipole Sources

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.

SMILE Project — The Effect of Warm Pre-Stress in RPV Assessment: Synthesis of Experimental Results and Analyses

2006 ◽  
Author(s):  
Dominique Moinereau ◽  
Anna Dahl ◽  
Ste´phane Chapuliot ◽  
David Lidbury
Keyword(s):  
Fracture Mechanics ◽  
Beneficial Effect ◽  
Experimental Work ◽  
Brittle Failure ◽  
Short Description ◽  
Experimental Results ◽  
Numerical Analyses ◽  
Local Approach ◽  
Model Following ◽  
Cracked Cylinder

Within framework of 5th EC European SMILE project, some R&D actions have been conducted to demonstrate, to model and to validate the beneficial warm pre-stress (WPS) effect regarding the risk of brittle failure in a RPV assessment. An important experimental work has been conducted including classical WPS type experiments on CT specimens on usual RPV steels, and one PTS type transient on a large cracked cylinder. All experimental results confirm the beneficial effect of warm pre-stress, with a significant increase of the materials resistance regarding the risk of brittle failure. The experiments have been analyzed using fracture mechanics, including both engineering methods (Chell, Haigh, Wallin) and more refined analyses based on local approach to fracture (‘modified Beremin’ model). Following a short description of WPS concept, the paper summarizes the main experimental results and presents a synthesis of mechanical analyses involving engineering approaches and numerical analyses.

A Duct Optimization Study for a Vertical Axis Hydro-current Turbine Model

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
M. Alidadi ◽  
V. Klaptocz ◽  
G. W. Rawlings ◽  
Y. Nabavi ◽  
S. Calisal
Keyword(s):  
Power Output ◽  
Numerical Optimization ◽  
Vertical Axis ◽  
Experimental Results ◽  
Maximum Power Output ◽  
Numerical Predictions ◽  
Optimization Study ◽  
Current Turbine ◽  
Turbine Model ◽  
Good Agreement

A numerical optimization study is used to design a duct for a model of vertical axis hydro-current turbine. The effects of this duct on the power output and torque fluctuations of the turbine model are then examined numerically and experimentally. Relatively good agreement was obtained between the experimental results and numerical predictions especially at higher tip speed ratios. Experimental results show an 85% increase in the maximum power output when the turbine is placed inside the duct. The numerical and experimental torque curves for the turbine also show substantial reductions in the torque fluctuations as a result of ducting.

Study on the Combustion Noise Characteristic of Low Speed Diesel Engine

2014 ◽  
Vol 945-949 ◽  
pp. 750-753 ◽  
Author(s):  
Li Qi Yan ◽  
Hui Jun Ge
Keyword(s):  
Diesel Engine ◽  
Vibration Control ◽  
Combustion Engine ◽  
Combustion Noise ◽  
Aerodynamic Noise ◽  
Power Device ◽  
Response Analysis ◽  
Cylinder Pressure ◽  
Real Condition ◽  
Low Speed

In recent years, the Low speed two stroke diesel engines are widely used as the main power device of big ship for its so many advantages such as the high power, better economical efficiency and good maintenance. However, the problem of diesel strong vibration and noise becomes a more and more serious at the same time. Because of the Construction Features of marine two-stroke low-speed diesel engine, the structure has to be suffered different kind of forces when it runs. In considering the source of vibration, the whole noise can be divided into combustion noise、machinery noise and aerodynamic noise. The combustion noise caused by cylinder pressure is the most important part of diesel noise. In this paper, the cylinder pressure curves are tested. The internal combustion engine dynamics and the equivalent node load are used in the calculation procedure to achieve the real condition simulation. The loading program is made to simulate the change of cylinder pressure and the move of piston. The transient response of the diesel engine is calculated. The characteristics of diesel caused by cylinder pressure are analyzed.The response analysis can be used to the vibration control.

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