<p>This paper presents the study of the flow field in a flameless combustion chamber using PIV for different combustion regimes. Three representative reactive flow test cases from the literature were chosen to validate the experimental test bench and measurement techniques. The streamlines of mean velocity magnitude indicated the main recirculation structure in the combustion chamber, which is responsible for the dilution of the fresh reactants with the combustion products in the reactive flow. Measured normalized Reynolds stress components indicate higher turbulence intensity for the flameless case when compared to the conventional regime. The Large-eddy PIV methodology was applied for the first time in a reactive flow under flameless combustion regime to estimate the turbulent kinetic energy dissipation rate, making it possible to calculate the Kolmogorov time scale based on the estimated <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40430_2024_5345_Article_IEq1.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="11" /> </InlineMediaObject> <EquationSource Format="TEX">$\varepsilon$</EquationSource> <EquationSource Format="MATHML"><math> <mi>ε</mi> </math></EquationSource> </InlineEquation>. A discussion on the fundamentals of the turbulent combustion for the three regimes is presented by an analysis of the turbulent combustion diagram based on the experimental results. The conventional combustion regime develops with the thickened-wrinkled flame structure since its Karlovitz number is <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40430_2024_5345_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="103" /> </InlineMediaObject> <EquationSource Format="TEX">$1<Ka<100$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo><</mo> <mi>K</mi> <mi>a</mi> <mo><</mo> <mn>100</mn> </mrow> </math></EquationSource> </InlineEquation>. The flameless case, with <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40430_2024_5345_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="73" /> </InlineMediaObject> <EquationSource Format="TEX">$Ka>100$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>K</mi> <mi>a</mi> <mo>></mo> <mn>100</mn> </mrow> </math></EquationSource> </InlineEquation>, indicates a higher interaction of the reaction zone structure with the smaller scales of turbulence compared to the conventional regime.</p>

Experimental turbulence assessment of the reactive flow field in a flameless combustion chamber operating in three regimes

期刊论文
发表日期：

2025年1月4日

查看全文

Helio Henrique Santomo Villanueva,
Guenther Carlos Krieger

摘要

This paper presents the study of the flow field in a flameless combustion chamber using PIV for different combustion regimes. Three representative reactive flow test cases from the literature were chosen to validate the experimental test bench and measurement techniques. The streamlines of mean velocity magnitude indicated the main recirculation structure in the combustion chamber, which is responsible for the dilution of the fresh reactants with the combustion products in the reactive flow. Measured normalized Reynolds stress components indicate higher turbulence intensity for the flameless case when compared to the conventional regime. The Large-eddy PIV methodology was applied for the first time in a reactive flow under flameless combustion regime to estimate the turbulent kinetic energy dissipation rate, making it possible to calculate the Kolmogorov time scale based on the estimated $\varepsilon$ $ε$ . A discussion on the fundamentals of the turbulent combustion for the three regimes is presented by an analysis of the turbulent combustion diagram based on the experimental results. The conventional combustion regime develops with the thickened-wrinkled flame structure since its Karlovitz number is $1<Ka<100$ $1 < K a < 100$ . The flameless case, with $Ka>100$ $K a > 100$ , indicates a higher interaction of the reaction zone structure with the smaller scales of turbulence compared to the conventional regime.