Soot Formation in Diesel Fuel Jets Near the Lift-Off Length

2006 ◽  
Vol 7 (2) ◽  
pp. 103-130 ◽  
Author(s):  
L M Pickett ◽  
D L Siebers
Keyword(s):  
Heat Release ◽  
Diesel Fuel ◽  
Soot Formation ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Entrainment Rate ◽  
Fuel Type ◽  
Fuel Jet ◽  
Air Mixing ◽  
Lift Off

Soot formation in the region downstream of the lift-off length of diesel fuel jets was investigated in an optically accessible constant-volume combustion vessel under quiescent-type diesel engine conditions. Planar laser-induced incandescence and line-of-sight laser extinction were used to determine the location of the first soot formation during mixing-controlled combustion. OH chemiluminescence imaging was used to determine the location of high-heat-release reactions relative to the soot-forming region. The primary parameters varied in the experiments were the sooting propensity of the fuel and the amount of fuel-air premixing that occurs upstream of the lift-off length. The fuels considered in order of increasing sooting propensity were: an oxygenated fuel blend (T70), a blend of diesel cetane-number reference fuels (CN80), and a #2 diesel fuel (D2). Fuel-air mixing upstream of the lift-off length was varied by changing ambient gas and injector conditions, which varied either the lift-off length or the air entrainment rate into the fuel jet relative to the fuel injection rate. Results show that soot formation starts at a finite distance downstream of the lift-off length and that the spatial location of soot formation depends on the fuel type and operating conditions. The distance from the lift-off length to the location of the first soot formation increases as the fuel sooting propensity decreases (i.e. in the order D2 < CN80 < T70). At the baseline operating conditions, the most upstream soot formation occurs at the edges of the jet for D2 and CN80, while for T70 the soot formation is confined to the jet central region. When conditions are varied to produce enhanced fuel-air mixing upstream of the lift-off length in D2 fuel jets, the initial soot formation shifts towards the fuel jet centre and eventually no soot is formed. For all experimental conditions, the observed location of soot formation relative to the heat-release location (lift-off) suggests that soot formation occurs in a mixture of combustion products originating from partially premixed reactions and a diffusion flame. The results also imply that soot precursor formation rates depend strongly on fuel type in the region between the lift-off length and the first soot formation.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2005 ◽  
Vol 127 (1) ◽  
pp. 187-196 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven nonpremixed turbulent flames.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

2001 ◽  
Author(s):  
Lyle M. Pickett ◽  
Dennis L. Siebers
Keyword(s):  
Diesel Fuel ◽  
Direct Injection ◽  
Flame Structure ◽  
Air Entrainment ◽  
Flame Length ◽  
Turbulent Flames ◽  
Orifice Diameter ◽  
Jet Flame ◽  
Fuel Jet ◽  
Lift Off

Abstract The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty, direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven, non-premixed turbulent flames.

Spray Combustion Characteristics of Single/Multi-Component Surrogate Fuel for Aviation Kerosene

2022 ◽  
Author(s):  
Wenjin Qin ◽  
Dengbiao Lu ◽  
Lihui Xu
Keyword(s):  
Soot Formation ◽  
Mean Field ◽  
Combustion Characteristics ◽  
Spray Combustion ◽  
Aviation Kerosene ◽  
Eddy Simulation ◽  
Air Mixing ◽  
Flow Field Characteristics ◽  
Lift Off ◽  
Surrogate Fuel

Abstract In this research, n-dodecane and JW are selected as single and multi-component surrogate fuel of aviation kerosene to study the Jet-A spray combustion characteristics. The spray combustion phenomena are simulated using large eddy simulation coupled with detailed chemical reaction mechanism. Proper orthogonal decomposition method is applied to analyze the flow field characteristics, and the instantaneous velocity field are decomposed into four parts, namely the mean field, coherent field, transition field and turbulent field, respectively. The four subfields have their own characteristics. In terms of different fuels, JW has a higher intensity of coherent structures and local vortices than n-dodecane, which promotes the fuel-air mixing and improves the combustion characteristics, and the soot formation is significantly reduced. In addition, with the increase of initial temperature, the combustion is more intense, the ignition delay time is advanced, the flame lift-off length is reduced, and soot formation is increased accordingly.

scholarly journals Numerical Steady and Transient Evaluation of a Confined Swirl Stabilized Burner

2021 ◽  
Vol 6 (4) ◽  
pp. 46
Author(s):  
Federica Farisco ◽  
Luisa Castellanos ◽  
Jakob Woisetschläger ◽  
Wolfgang Sanz
Keyword(s):  
Heat Release ◽  
Gas Turbines ◽  
Numerical Data ◽  
Operating Conditions ◽  
Main Reaction ◽  
Combustion Model ◽  
Ansys Fluent ◽  
Lean Premixed Combustion ◽  
Flamelet Generated Manifold ◽  
Lift Off

Lean premixed combustion technology became state of the art in recent heavy-duty gas turbines and aeroengines. In combustion chambers operating under fuel-lean conditions, unsteady heat release can augment pressure amplitudes, resulting in component engine damages. In order to achieve deeper knowledge concerning combustion instabilities, it is necessary to analyze in detail combustion processes. The current study supports this by conducting a numerical investigation of combustion in a premixed swirl-stabilized methane burner with operating conditions taken from experimental data that were recently published. It is a follow-up of a previous paper from Farisco et al., 2019 where a different combustion configuration was studied. The commercial code ANSYS Fluent has been used with the aim to perform steady and transient calculations via Large Eddy Simulation (LES) of the current confined methane combustor. A validation of the numerical data has been performed against the available experiments. In this study, the numerical temperature profiles have been compared with the measurements. The heat release parameter has been experimentally and numerically estimated in order to point out the position of the main reaction zone. Several turbulence and combustion models have been investigated with the aim to come into accord with the experiments. The outcome showed that the combustion model Flamelet Generated Manifold (FGM) with the k-ω turbulence model was able to correctly simulate flame lift-off.

Optimized Intake Manifold Designs and Their Effects on the Operation and Emissions of a Gas-to-Liquid Diesel Engine

2020 ◽  
Author(s):  
Y. M. Abdellatif ◽  
A. T. Saker ◽  
A. M. Elbashir ◽  
S. F. Ahmed
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Diesel Fuel ◽  
Alternative Fuels ◽  
The Other ◽  
Intake Manifold ◽  
Outlet Angle ◽  
Air Mixing ◽  
Gas To Liquid ◽  
No Emissions

Abstract Two simultaneous strategies have been used in this work to reduce the diesel engine emissions. First, using novel manifold designs to generate strong turbulence and improve the fuel-air mixing inside the cylinder. The second strategy is the usage of alternative fuels, namely Gas-To-Liquid (GTL) fuel and its blends with diesel fuel. In this study, six new spiral-helical manifolds designs have been tested, which could be divided into two groups. The first group is m(2.6,30,1t), m(2.6,30,2t), m(2.6,330,3t) and m(2.6,30,4t) which contains manifolds that have the same inner diameter (2.6 cm), same outlet angle (30°), but different number of spiral turns (1t, 2t..etc). The second group is m(2.1,30,3t), m(2.6,30,3t) and m(2.9,30,3t) which contains the same parameters but different inner diameters. It should be mentioned that the outlet angle of all manifolds has been tested in previous investigations [18, 52] and 30° showed the best performance. The results of the current study showed that the highest pressure and heat release achieved by manifold m(2.6,30,1t) for the blended diesel-GTL fuel. It was observed that the heat release rate decreases with the increase in number of turns. The lowest pressure raise rate was recorded for the combination of m(2.6,30,1t) and diesel fuel. Same combination also reduced the pressure raise rate (dP/dθ) by about 24% compared to the normal manifold. The bsfc for all fuels and m(2.6,30,1t) were almost the same as the normal manifold. For the emissions, NO emissions were reduced by about 25% compared to normal manifold when m(2.6,30,4t) and GTL are used. On the other hand, the normal manifold recorded the least NO emissions for the other fuels. The manifold m(2.6,30,1t) recorded slightly higher NO emissions compared to the normal manifold for all fuels. The total particulate matters (PM) were the lowest for m (2.6,30,1t) and normal manifold in case of diesel fuel. In general, It was found that the combination of m(2.6,30,1t) with diesel fuel gave the optimum performance among all manifolds, while using m (2.6,30,4t) with GTL fuel produced low emission levels.

scholarly journals Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions

2020 ◽  
Vol 10 (16) ◽  
pp. 5460
Author(s):  
José V. Pastor ◽  
José M. García-Oliver ◽  
Carlos Micó ◽  
Alba A. García-Carrero ◽  
Arantzazu Gómez
Keyword(s):  
Vegetable Oil ◽  
Diesel Fuel ◽  
Ignition Delay ◽  
Soot Formation ◽  
Imaging Techniques ◽  
Detection Threshold ◽  
Combustion Characteristics ◽  
Engine Combustion ◽  
Lift Off ◽  
Oxygenated Fuels

The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH∗ chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME1 and a blend of oxymethylene ethers, identified as OMEx) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OMEx sprays have similar behavior in terms of global combustion metrics. In the case of OME1, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME1 and OMEx was below the detection threshold in all tested conditions.

scholarly journals Effect of Primary Variables on A Confined Plunging Liquid Jet Reactor

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 764 ◽  
Author(s):  
Bader S. Al-Anzi
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Liquid Jet ◽  
Entrainment Rate ◽  
Activated Sludge Process ◽  
Gas Entrainment ◽  
Air Entrainment Rate ◽  
Aeration Process

The effects of operating conditions including a novel downcomer geometry on the gas/air entrainment rate, Qa, were investigated for a local vertical confined plunging liquid jet reactor (CPLJR) as an alternative aeration process that is of interest to Kuwait and can be used in various applications, such as in wastewater treatment as an aerobic activated sludge process, fermentation, brine dispenser, and gas–liquid reactions. Operating conditions, such as various downcomer diameters (Dc = 45−145 mm), jet lengths (Lj = 200–500 mm), nozzle diameters (dn = 3.5–15 mm), and contraction angles (Ɵ =20–80°), were investigated. A newly designed downcomer with various mesh openings/pores (Dm = 0.25ʺ (6.35 mm)–1ʺ (25.4 mm)) was also investigated in the current study. The air entrainment results showed that these were the primary parameters for the measured air entrainment rate in confined systems. The highest gas entrainment rates were achieved when the ratio of the downcomer diameter (Dc) to the nozzle diameter (dn) was greater than approximately 5, as long as the liquid superficial velocity was sufficient to carry bubbles downward. Furthermore, a downcomer with mesh openings (Dm) less or equal to 0.5ʺ (12.7 mm) provided a higher entrainment rate than that of conventional downcomer (without a mesh).

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