Molecular Tagging Velocimetry and Its Application to In-Cylinder Flow Measurements

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Ravi Vedula ◽  
Mayank Mittal ◽  
Harold J. Schock
Keyword(s):  
Internal Combustion Engines ◽  
Measurement Techniques ◽  
Quantitative Description ◽  
Experimental Studies ◽  
Small Scale ◽  
Flow Measurements ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Intake Stroke ◽  
Cylinder Flows

This review article provides an overview of the experimental studies of in-cylinder flows using various flow measurement techniques with a focus on molecular tagging velocimetry. It is necessary to understand the evolution of large-scale and small-scale turbulence as prepared during the intake stroke with a cycle resolved quantitative description. Due to the difficulty in obtaining these descriptions, either by modeling or experimentally, they are often characterized with somewhat ambiguous notions of bulk swirl and tumble measurement methods. During the intake stroke, in-cylinder flows are formed in such a manner as to provide advantageous spatial and temporal behavior for mixture formation later during the compression stroke. Understanding the details of how these flows influence fuel-air mixing, the initiation of ignition, combustion, and subsequent flame propagation processes is the primary motivation for the development of the methods described in this paper. The authors provide an introduction to fundamental flow motion inside the engine cylinder and measurement techniques, e.g., hot-wire anemometry, laser Doppler anemometry, and particle image velocimetry. Furthermore, molecular tagging velocimetry is discussed in detail in terms of (i) different mechanisms, (ii) procedure and data reduction methods to obtain the desired flow properties such as velocity, vorticity, and turbulent intensities, and (iii) applications to flow studies in internal combustion engines. Finally, the significance of experimental investigations of in-cylinder flows is discussed along with possible future applications.

scholarly journals A theoretical verification of the integral fluctuation theorem for accelerated colloidal systems in the long-time limit

2021 ◽  
Author(s):  
Yash Lokare
Keyword(s):  
Steady State ◽  
Time Scales ◽  
Numerical Study ◽  
Quantitative Description ◽  
Experimental Studies ◽  
Fluctuation Theorem ◽  
Nonequilibrium Steady States ◽  
Small Scale ◽  
Colloidal Systems ◽  
Long Time

A quantitative description of the violation of the second law of thermodynamics in relatively small classical systems and over short time scales comes from the fluctuation-dissipation theorem. It has been well established both theoretically and experimentally, the validity of the fluctuation theorem to small scale systems that are disturbed from their initial equilibrium states. Some experimental studies in the past have also explored the validity of the fluctuation theorem to nonequilibrium steady states at long time scales in the asymptotic limit. To this end, a theoretical and/or purely numerical model of the integral fluctuation theorem has been presented. An approximate general expression for the dissipation function has been derived for accelerated colloidal systems trapped/confined in power-law traps. Thereafter, a colloidal particle trapped in a harmonic potential (generated by an accelerating one-dimensional optical trap) and undergoing Brownian motion has been considered for the numerical study. A toy model of a quartic potential trap in addition to the harmonic trap has also been considered for the numerical study. The results presented herein show that the integral fluctuation theorem applies not only to equilibrium steady state distributions but also to nonequilibrium steady state distributions of colloidal systems in accelerated frames of reference over long time scales.

On the analysis of the integral fluctuation theorem for accelerated colloidal systems in the long-time limit

2021 ◽  
Author(s):  
Yash Lokare
Keyword(s):  
Steady State ◽  
Time Scales ◽  
Numerical Study ◽  
Quantitative Description ◽  
Experimental Studies ◽  
Fluctuation Theorem ◽  
Nonequilibrium Steady States ◽  
Small Scale ◽  
Colloidal Systems ◽  
Long Time

Abstract A quantitative description of the violation of the second law of thermodynamics in relatively small classical systems and over short time scales comes from the fluctuation-dissipation theorem. It has been well established both theoretically and experimentally, the validity of the fluctuation theorem to small scale systems that are disturbed from their initial equilibrium states. Some experimental studies in the past have also explored the validity of the fluctuation theorem to nonequilibrium steady states at long time scales in the asymptotic limit. To this end, a theoretical and/or purely numerical model of the integral fluctuation theorem has been presented. An approximate general expression for the dissipation function has been derived for accelerated colloidal systems trapped/confined in power-law traps. Thereafter, a colloidal particle trapped in a harmonic potential (generated by an accelerating one-dimensional optical trap) and undergoing Brownian motion has been considered for the numerical study. A toy model of a quartic potential trap in addition to the harmonic trap has also been considered for the numerical study. The results presented herein show that the integral fluctuation theorem applies not only to equilibrium steady state distributions but also to nonequilibrium steady state distributions of colloidal systems in accelerated frames of reference over long time scales.

scholarly journals A Theoretical Analysis of the Integral Fluctuation Theorem for Accelerated Colloidal Systems in the Long-Time Limit

2021 ◽  
Author(s):  
Yash Lokare
Keyword(s):  
Steady State ◽  
Time Scales ◽  
Numerical Study ◽  
Quantitative Description ◽  
Experimental Studies ◽  
Fluctuation Theorem ◽  
Nonequilibrium Steady States ◽  
Small Scale ◽  
Colloidal Systems ◽  
Long Time

A quantitative description of the second law of thermodynamics in relatively small classical systems and over short time scales comes from the fluctuation-dissipation theorem. It has been well established both theoretically and experimentally, the validity of the fluctuation theorem to small scale systems that are disturbed from their initial equilibrium states. Some experimental studies in the past have also explored the validity of the fluctuation theorem to nonequilibrium steady states at long time scales in the asymptotic limit. To this end, a theoretical and/or purely numerical model of the integral fluctuation theorem has been presented. An approximate general expression for the dissipation function has been derived for accelerated colloidal systems trapped/confined in power-law traps. Thereafter, a colloidal particle trapped in a harmonic potential (generated by an accelerating one-dimensional optical trap) and undergoing Brownian motion has been considered for the numerical study. A toy model of a quartic potential trap in addition to the harmonic trap has also been considered for the numerical study. The results presented herein show that the integral fluctuation theorem applies not only to equilibrium steady state distributions but also to nonequilibrium steady state distributions of ideal colloidal systems in accelerated frames of reference over long time scales.

Micro-Scale Velocity Measurements Using Molecular Tagging Velocimetry: Methodology and Uncertainty

2002 ◽  
Author(s):  
B. R. Thompson ◽  
D. Maynes ◽  
B. W. Webb
Keyword(s):  
Correlation Method ◽  
Velocity Profiles ◽  
Line Center ◽  
Flow Measurements ◽  
Measured Velocity ◽  
Molecular Tagging Velocimetry ◽  
Molecular Tagging ◽  
Micro Scale ◽  
Inside Diameter ◽  
New Applications

Micro-scale fluidic devices are now being designed and manufactured for a host of new applications, and it is certain that new applications will emerge. There is, therefore, a need for increased understanding of the momentum transport phenomena at this scale to aid in the understanding, and design and optimization of such devices. This need is behind the development of new techniques for making flow measurements at the micro-scale. Molecular Tagging Velocimetry (MTV) is a laser-based non-intrusive technique for obtaining detailed measurements of velocity profiles. This paper reports on the extension of the method to microtubes of inside diameter of order 100 µm. Fully developed velocity profile measurements are reported here for a Reynolds number of about 140 in a capillary of inside diameter 148 µm. Two image analysis techniques were compared—the line center method, and the correlation method. It was found that the correlation method produced better results and smaller overall uncertainty. Volumetric flow rate determined from integration of the measured velocity profiles agree with accumulation measurements made over a specified time interval to within 3%; the agreement was usually 1–2%. This work reports on the difficulties encountered in applying MTV at these physical scales, the influence of measurement and analysis parameters on results, and the uncertainty associated with measurements.

On the spatial length scales of scalar dissipation in turbulent jet flames

2008 ◽  
Vol 596 ◽  
pp. 103-132 ◽  
Author(s):  
P. VAISHNAVI ◽  
A. KRONENBURG ◽  
C. PANTANO
Keyword(s):  
Thin Sheet ◽  
Measurement Techniques ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Scalar Dissipation ◽  
Small Scale ◽  
Computational Domain ◽  
Length Scales ◽  
Jet Flame ◽  
True Value

Spatial length scales of the rate of dissipation, χ, of fluctuations of a conserved scalar, Z, are inferred numerically using a DNS database of a turbulent planar jet flame. The Taylor-scale Reynolds numbers lie in the range of 38 to 58 along the centreline of the simulated jet flame. Three different methods are used to study the spatial length scales associated with χ. First, analysis of the one-dimensional dissipation spectra shows an expected Reδ−3/4 (Kolmogorov) scaling with the outer-scale Reynolds number, Reδ. Secondly, thin sheet-like three-dimensional scalar dissipation structures have been investigated directly. Such structures were identified within the computational domain using level-sets of the χ-field, and their thicknesses were subsequently computed. The study shows, in accordance with experimental studies, that the captured dissipation-layer thickness also shows a Kolmogorov scaling with Reδ. Finally, spatial filters of varying widths were applied to the instantaneous Z field in order to model the averaging effect that takes place with some experimental measurement techniques. The filtered scalar dissipation rate was then calculated from the filtered scalar field. The peaks in the instantaneous filtered χ-profiles are observed to decrease exponentially with increasing filter width, yielding estimates of the true value of χ. Unlike the dissipation length scales obtained from the spectral analysis and the level-set method, the length-scale estimates from the spatial-filtering method are found to be proportional to Reδ−1. This is consistent with the small-scale intermittency of χ which cannot be captured by techniques that just resolve the conventional Batchelor/Obukhov–Corrsin scale. These results have implications when considering resolution requirements for measuring scalar dissipation length scales in experimental flows.

DIESEL ENGINE OPERATION IN USE OF FUEL WITH ADDITIVES

2018 ◽  
pp. 18-24
Author(s):  
Petar Kazakov ◽  
Atanas Iliev ◽  
Emil Marinov
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Diesel Fuel ◽  
Internal Combustion Engines ◽  
Experimental Studies ◽  
Combustion Engines ◽  
Engine Operation ◽  
Factors Affecting ◽  
Operating Modes ◽  
Positive Effects

Over the decades, more attention has been paid to emissions from the means of transport and the use of different fuels and combustion fuels for the operation of internal combustion engines than on fuel consumption. This, in turn, enables research into products that are said to reduce fuel consumption. The report summarizes four studies of fuel-related innovation products. The studies covered by this report are conducted with diesel fuel and usually contain diesel fuel and three additives for it. Manufacturers of additives are based on already existing studies showing a 10-30% reduction in fuel consumption. Comparative experimental studies related to the use of commercially available diesel fuel with and without the use of additives have been performed in laboratory conditions. The studies were carried out on a stationary diesel engine СМД-17КН equipped with brake КИ1368В. Repeated results were recorded, but they did not confirm the significant positive effect of additives on specific fuel consumption. In some cases, the factors affecting errors in this type of research on the effectiveness of fuel additives for commercial purposes are considered. The reasons for the positive effects of such use of additives in certain engine operating modes are also clarified.

scholarly journals Photoisomeric molecular tagging velocimetry with CCVJ

2021 ◽  
Vol 6 (4) ◽  
Author(s):  
Markus J. Schmidt ◽  
Benno Käslin ◽  
Thomas Rösgen
Keyword(s):  
Molecular Tagging Velocimetry ◽  
Molecular Tagging
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