The Mechanisms Whereby Double Helical Offset-Toothed Synchronous Belt Produces Lower Noise Than Straight-Toothed Synchronous Belt: A Theoretical Investigation

2016 ◽  
Author(s):  
Jianhua Guo ◽  
Yu Wang ◽  
Qingming Hu ◽  
Shan Li ◽  
Ze He ◽  
...  
Keyword(s):  
Standing Wave ◽  
Sound Field ◽  
Experimental Investigations ◽  
Sound Power ◽  
One Dimensional ◽  
Impact Noise ◽  
Helical Angle ◽  
The One ◽  
The Impact ◽  
Lower Noise

Recent experimental investigations demonstrate that the level of noise generated by double helical synchronous belt (DHSB) is lower than that by straight-toothed synchronous belt (STSB). The present study is to theoretically elucidate the mechanisms whereby DHSB produces lower noise. In the theoretical analysis, a model DHSB is divided into several parallel narrow DHSBs with equal width. Let each narrow DHSB’s helical angle be 0° so each narrow DHSB becomes a narrow STSB. The theory of the one-dimensional sound field is then applied to obtain the standing wave solution of impact sound pressure. The sum of impact sound pressures by the narrow STSBs derived from one pair (left- and right-handed) of helical teeth of the model DHSB represents transmission impact noise. Computational results reveal that the power of impact sound at the damping-frequency decreases as the helical tooth’s angle increases. In addition, the impact sound power decreases as the degree of tooth’s offset of a double helical offset-toothed synchronous belt (DHOTSB) increases. Impact sound power is in the following order from high to low: STSB » DHSB > DHOTSB. In experimental investigations, the noise was in the following order from high to low: STSB » DHSB > DHOTSB, consistent with theoretical prediction. Also, the sound power at high frequency was markedly attenuated in DHSB or DHOTSB, the impact noise is the major sources of noise. Thus, the reduced noise in DHSB and DHOTSB can be explained by the one-dimensional standing wave sound field theory.

Reduction of Impact Noise at the Design Stage: A Specific Case Study

1972 ◽  
Vol 186 (1) ◽  
pp. 391-399
Author(s):  
M. A. Salter ◽  
B. Downs ◽  
G. R. Wray
Keyword(s):  
Experimental Approach ◽  
Design Stage ◽  
Experimental Investigations ◽  
Theoretical Treatment ◽  
Impact Noise ◽  
Design Changes ◽  
Machine Cycle ◽  
Mechanism Of Impact ◽  
The Impact

A case study is made on the tack driving assembly of a boot and shoe lasting machine, and relates to the impact noise occurring during part of the machine cycle. Much of the noise is radiated due to vibrations at several frequencies of the tack driver lifting lever, which is excited by the direct application of impacts during the tack driving process. An experimental approach in applying noise reduction principles to various components of the assembly has been preferred to a more complex theoretical treatment, since the identification of the mechanism of impact noise generation and its subsequent abatement is directly relevant to most machine designers faced with the possibility of impact noise problems in other types of machinery. Small design changes, based on the knowledge gained from the experimental investigations, have resulted in noise reductions from 10 to 14 dB being achieved.

scholarly journals Analytical Model to Compare and Select Creep Constitutive Equation for Stress Relief Investigation during Heat Treatment in Ferritic Welded Structure

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 688
Author(s):  
Mengjia Hu ◽  
Kejian Li ◽  
Shanlin Li ◽  
Zhipeng Cai ◽  
Jiluan Pan
Keyword(s):  
Heat Treatment ◽  
Constitutive Equation ◽  
Analytical Model ◽  
Stress Relief ◽  
Treatment Temperature ◽  
Hole Drilling ◽  
One Dimensional ◽  
Welded Structure ◽  
The One ◽  
The Impact

The one-dimensional analytical model was promoted to help select the creep constitutive equation and predict heat treatment temperature in a ferritic welded structure, along with neglecting the impact of structural constraint and deformation compatibility. The analytical solutions were compared with simulation results, which were validated with experimental measurements in a ferritic welded rotor. The as-welded and post weld heat treatment (PWHT) residual stresses on the inner and outer cylindrical surfaces were measured with the hole-drilling method (HDM) for validation. Based on the one-dimensional analytical model, different effects of Norton and Norton-Bailey creep constitutive equation on stress relief during heat treatment in a ferritic welded rotor were investigated.

scholarly journals A Mathematical Model for Transport in Poroelastic Materials with Variable Volume:Derivation, Lie Symmetry Analysis, and Examples

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 396
Author(s):  
Roman Cherniha ◽  
Joanna Stachowska-Pietka ◽  
Jacek Waniewski
Keyword(s):  
Solute Transport ◽  
Lie Symmetry ◽  
Transport Processes ◽  
Experimental Investigations ◽  
One Dimensional ◽  
Poroelastic Media ◽  
Poroelastic Materials ◽  
Dimensional Version ◽  
The One ◽  
Symmetry Method

Fluid and solute transport in poroelastic media is studied. Mathematical modeling of such transport is a complicated problem because of the volume change of the specimen due to swelling or shrinking and the transport processes are nonlinearly linked. The tensorial character of the variables adds also substantial complication in both theoretical and experimental investigations. The one-dimensional version of the theory is less complex and may serve as an approximation in some problems, and therefore, a one-dimensional (in space) model of fluid and solute transport through a poroelastic medium with variable volume is developed and analyzed. In order to obtain analytical results, the Lie symmetry method is applied. It is shown that the governing equations of the model admit a non-trivial Lie symmetry, which is used for construction of exact solutions. Some examples of the solutions are discussed in detail.

scholarly journals A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

2020 ◽  
pp. 146808742092158
Author(s):  
Alberto Broatch ◽  
Pablo Olmeda ◽  
Xandra Margot ◽  
Josep Gomez-Soriano
Keyword(s):  
Heat Transfer ◽  
Combustion Engine ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Insulation Material ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Dimensional Modeling ◽  
The One ◽  
The Impact

This article presents a study of the impact on engine efficiency of the heat loss reduction due to in-cylinder coating insulation. A numerical methodology based on one-dimensional heat transfer model is developed. Since there is no analytic solution for engines, the one-dimensional model was validated with the results of a simple “equivalent” problem, and then applied to different engine boundary conditions. Later on, the analysis of the effect of different coating properties on the heat transfer using the simplified one-dimensional heat transfer model is performed. After that, the model is coupled with a complete virtual engine that includes both thermodynamic and thermal modeling. Next, the thermal flows across the cylinder parts coated with the insulation material (piston and cylinder head) are predicted and the effect of the coating on engine indicated efficiency is analyzed in detail. The results show the gain limits, in terms of engine efficiency, that may be obtained with advanced coating solutions.

Influence of the combustion chamber geometry on the scavenging of a four-stroke internal-combustion engine during the valve overlap period

2016 ◽  
Vol 230 (14) ◽  
pp. 1873-1890
Author(s):  
Nicolas-Ivan Hatat ◽  
David Chalet ◽  
François Lormier ◽  
Pascal Chessé
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
One Dimensional ◽  
Digital Testing ◽  
The One ◽  
Small Engines ◽  
Variable Valve ◽  
Valve Overlap ◽  
The Impact

The performance of an internal-combustion engine is directly related to the fuel quantity that can react with the oxygen in the air during the exothermic oxidation step, also called combustion. Thus, the amount of fuel introduced is intrinsically linked to the air volume that can be admitted into the cylinder (air filling of the cylinder). Hence keeping the air in the cylinder is one of the most important concepts to predict in simulations. Nevertheless, the phenomenon of air filling depends on many parameters. Also, the discharge coefficients, and the impact of the piston presence near the valves on the flow, during valve overlap are investigated. For this, a digital flow bench is constructed to reproduce a series of tests carried out on a flow test bench functioning as a result of the reduction in the pressure. In this paper, the engine studied is a 125 cm3 single-cylinder four-stroke atmospheric type with two valves. Thus, the idea of this paper is to treat the case of engines with large valve overlaps as small engines or engines with variable valve timing. First, traditional tests through a single valve are performed. The forward and reverse directions are systematically tested to ensure proper operation of the digital testing, and to determine the differences between tests and simulations in the case of conventional configurations. Then, the flow through the entire cylinder head, i.e. the intake valve–cylinder with piston–exhaust valve system, is tested and studied. The aim is to compare the results obtained by the tests and the simulations during the valve overlap period. Significant differences were highlighted between the rates measured in one-dimensional simulations and in the tests. It was noteworthy that the one-dimensional code overestimated the mass passing through the system during valve overlap by about one fifth of the estimated mass passing through the system from the results obtained with the test rig.

Numerical Solution for Two-Dimensional Elastic Wave Propagation in Finite Bars

1967 ◽  
Vol 34 (3) ◽  
pp. 725-734 ◽  
Author(s):  
L. D. Bertholf
Keyword(s):  
Experimental Data ◽  
Wave Propagation ◽  
Elastic Wave ◽  
Numerical Solutions ◽  
Step Change ◽  
Two Dimensional ◽  
One Dimensional ◽  
Elastic Bar ◽  
The One ◽  
The Impact

Numerical solutions of the exact equations for axisymmetric wave propagation are obtained with continuous and discontinuous loadings at the impact end of an elastic bar. The solution for a step change in stress agrees with experimental data near the end of the bar and exhibits a region that agrees with the one-dimensional strain approximation. The solution for an applied harmonic displacement closely approaches the Pochhammer-Chree solution at distances removed from the point of application. Reflections from free and rigid-lubricated ends are studied. The solutions after reflection are compared with the elementary one-dimensional stress approximation.

Theoretical and experimental investigations of the reflexion of normal shock waves with vibrational relaxation

1967 ◽  
Vol 30 (1) ◽  
pp. 51-64 ◽  
Author(s):  
N. H. Johannesen ◽  
G. A. Bird ◽  
H. K. Zienkiewicz
Keyword(s):  
Shock Wave ◽  
Vibrational Relaxation ◽  
Experimental Investigations ◽  
Rayleigh Line ◽  
Dimensional Problem ◽  
Density Measurements ◽  
Wave Characteristic ◽  
One Dimensional ◽  
The One ◽  
Theoretical Results

The one-dimensional problem of shock-wave reflexion with relaxation is treated numerically by combining the shock-wave, characteristic, and Rayleigh-line equations. The theoretical results are compared with pressure and density measurements in CO2, and the agreement is found to be excellent.

The Dissipation Function-Based Efficiency for Turbomachinery: Part 1 — The Efficiency of a Cooled Turbine Row

2014 ◽  
Author(s):  
Chong M. Cha
Keyword(s):  
Aerodynamic Performance ◽  
Dissipation Function ◽  
Second Law ◽  
Efficiency Measure ◽  
One Dimensional ◽  
Specific Heats ◽  
Gas Streams ◽  
The One ◽  
The Impact ◽  
Mixing Problem

The effect of coolant addition or “mixing loss” on aerodynamic performance is formulated for the turbine, where mixing takes place between gas streams of different compositions as well as static temperatures. To do this, a second law efficiency measure is applied to a generalization of the one-dimensional mixing problem between a main gas stream and a single coolant feed, first introduced and studied by Hartsel [1] for the turbine application. Hartsel’s 1972 model for mass-transfer cooling loss still remains the standard for estimating mixing loss in today’s turbines. The present generalization includes losses due to the additional contributions of “compositional mixing” (mixing between unlike compositions of the main and coolant streams) as well as the effect of chemical reaction between the two streams. Scaling of the present dissipation function-based loss model to the mainstream Mach number and relative cooling massflow and static temperature is given. Limitations of the constant specific heats assumptions and the impact of fuel-to-air ratio are also quantified.

Longitudinal Impact of Semi-Infinite Elastic Bars: Plane Any Time Solution

2013 ◽  
Vol 81 (5) ◽  
Author(s):  
M. A. Malkov
Keyword(s):  
Analytical Solution ◽  
Exact Analytical Solution ◽  
The Other ◽  
Longitudinal Impact ◽  
Infinite Plane ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
Contact Surfaces ◽  
The One ◽  
The Impact

Using the Sobolev–Smirnov method, we have found the exact analytical solution of a longitudinal impact of semi-infinite plane elastic bars for any time after the impact. After collision, there are loading waves from contact surfaces of bars and unloading waves from lateral surfaces. Then the unloading waves reach the opposite surface of the bars and create the reflected loading waves. These loading waves reach the other surface of the bars and generate new unloading waves. The number of waves grows exponentially. The sum of waves tends to the wave of the one-dimensional approximation.

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