Effect of nozzle dimensions and fuel type on flame lift-off length

Taşkıran, Özgür Oğuz; Ergeneman, Metin

doi:10.1016/j.fuel.2013.03.005

Cited by 21 publications

(7 citation statements)

References 12 publications

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“…These indicate that the lift-off position is not sensitive to the unsaturation level. This is in line with the results obtained by Taskiran et al and Persson et al, who found that the effects of fuel type on LOL are marginal.…”

Section: Resultssupporting

confidence: 93%

Numerical Analysis of the Effects of Biodiesel Unsaturation Levels on Combustion and Emission Characteristics under Conventional and Diluted Air Conditions

Cheng

Gan

et al. 2018

Energy Fuels

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This work presents a numerical analysis of spray combustion and associated emissions formation for methyl esters of soybean (SME) and coconut (CME) in a constant volume bomb and a light-duty diesel engine. SME and CME were used to represent biodiesel fuels with high and low unsaturation levels, respectively. In the constant volume bomb, diesel engine-like conditions were used, where two ambient oxygen (O2) levels of 15% and 21% (by mole fraction) were specified to study the effects of exhaust gas recirculation on the combustion and soot formation of biodiesel fuels. As the ambient O2 level increased to 21%, the lift-off length (LOL) was reduced by 25%, while the maximum soot volume fraction (SVF) at quasi-steady state was 4 times higher. The effects of unsaturation levels were next investigated under 21% ambient O2 level. When the unsaturation level was increased, the ignition delay (ID) periods and LOL did not vary significantly as a relative difference of less than 10% was observed between both. A higher local equivalence ratio (φ) and hence maximum SVF were observed in the SME combustion. A higher adiabatic flame temperature (T) of approximately 40 K was also recorded in the SME test case. Additionally, higher soot formation and oxidation rates were found for SME. In the diesel engine cases at 21% ambient O2 level, the φ–T distributions and in-cylinder peak pressures predicted for SME and CME were identical. Meanwhile, the peak soot formation rate predicted for SME was increased by 7% as compared to that of CME. Similarly, the peak soot oxidation due to O2 calculated for SME was 30% higher than that of CME, while the oxidation rates due to hydroxyl (OH) were similar for both fuels. For the tested conditions, the rates of production of acetylene (C2H2) and nitrogen oxides (NO x ) were increased by 43% and 12%, respectively, as a result of the increase in unsaturation level.

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Section: Resultssupporting

confidence: 93%

Numerical Analysis of the Effects of Biodiesel Unsaturation Levels on Combustion and Emission Characteristics under Conventional and Diluted Air Conditions

Cheng

Gan

et al. 2018

Energy Fuels

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“…12 as a function of ambient density and injection pressure (left and right part respectively). Several researches [14,15,18,27] support the influence of this two parameters in LOL. Gas density, being a parameter that enhances the evaporation and mixing processes, causes a reduction in lift-off length.…”

Section: Lift-off Lengthmentioning

confidence: 99%

“…This technique has been also employed for ignition delay measurements under the knowledge of the light intensity characteristics of each combustion phase [14,15]. Furthermore, several authors have underlined the effect of air-fuel mixture on soot formation, which can be associated with lift-off length [16][17][18][19]. It has been determined that ambient oxygen concentration rises products effective temperature, which continues increasing reactant temperatures and consequently reducing the ignition delay time [20].…”

Section: Introductionmentioning

confidence: 99%

Experimental study of the injection conditions influence over n-dodecane and diesel sprays with two ECN single-hole nozzles. Part II: Reactive atmosphere

Payri

Salvador

Gimeno

et al. 2016

Energy Conversion and Management

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a b s t r a c tThe second part of this experimental analysis, presented in this paper, seeks to go deep on the characterization of the Spray C and Spray D nozzles from the Engine Combustion Network, investigating the penetration of fuel spray at reacting conditions alongside characteristic parameters of combustion such as ignition delay and lift-off length. Both ECN mono-orifice injectors have similar nozzle flow capacity but different conicity degrees and corner sharpness, being Spray C more susceptible to cavitate. Schlieren imaging technique was employed to quantitatively measure reactive penetration and ignition delay, while lift-off length was identified through OH ⁄ chemiluminescence. As in the inert part of this research, n-dodecane and commercial diesel were selected for the tests, thereby the effect of the fuel properties in the measured parameters was analyzed. Also, once again the concept of R-parameter, defined as the penetration derivative respect to the square root of time was calculated to delve into the penetration behavior. The experiments were performed in a constant pressure-flow facility able to reproduce engine-like thermodynamic conditions. Results revealed that R-parameter evolution can be divided in four stages: an inert zone, a 'bump', a 'valley' part and a quasi-steady one that overlaps the previous inert part. Those stages are highly governed by ambient temperature and oxygen concentration. Nozzle geometry and fuel properties demonstrated to have a noteworthy influence on all measured parameters.

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“…A larger spray angle would imply, on the one hand, leaner local equivalence ratios, with the subsequent expected reduction in soot formation, and on the other hand, the possibility to develop the spray combustion closer to the nozzle tip, reducing heat transfer losses to the combustion chamber walls. Taskiran and Ergeneman provided evidence for this behavior on a nozzle with divergent orifices, 35 with a reduction in liquid length and lift-off length. Nevertheless, purely divergent orifices act as a diffuser, so lower outlet velocities are expected, with a negative impact on spray atomization.…”

Section: Introductionmentioning

confidence: 92%

Numerical analysis of flow characteristics in diesel injector nozzles with convergent-divergent orifices

Salvador

Morena

Carreres

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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The geometry of diesel injector nozzles is known to significantly affect the characteristic spray behavior and emissions formation. In this paper, a novel nozzle concept, consisting on orifices with convergent-divergent shape, is investigated through CFD techniques. Three of these nozzles, characterized by different degrees of conicity, are compared to a nozzle with cylindrical orifices, which acts as a baseline. An Homogeneous Equilibrium Model (HEM), validated against experimental data in previous works by the authors, is used to calculate the eventual cavitation formation inside these orifices. Additionally, the characteristics of the flow at the orifice outlet are analyzed for the four aforementioned nozzles in terms of their stationary mass flow, effective outlet velocity and area coefficient. The results show that convergentdivergent nozzles exhibit high cavitation intensity, located in the transition between the convergent and the divergent sections. This high cavitation intensity tends to compensate for the expected velocity decrease induced by the divergent shape, producing effective velocity values similar to those achieved by the cylindrical nozzle in many of the simulated conditions. The characteristics of the flow, together with the higher spray opening angles expected due to the divergent section of the nozzle, may improve atomization and fuel-air mixing processes.

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Effect of nozzle dimensions and fuel type on flame lift-off length

Cited by 21 publications

References 12 publications

Numerical Analysis of the Effects of Biodiesel Unsaturation Levels on Combustion and Emission Characteristics under Conventional and Diluted Air Conditions

Numerical Analysis of the Effects of Biodiesel Unsaturation Levels on Combustion and Emission Characteristics under Conventional and Diluted Air Conditions

Experimental study of the injection conditions influence over n-dodecane and diesel sprays with two ECN single-hole nozzles. Part II: Reactive atmosphere

Numerical analysis of flow characteristics in diesel injector nozzles with convergent-divergent orifices

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