Investigation on the Ignition Conditions From a Comparison Between Reacting and Non-Reacting Diesel Spray Experiments

2002 ◽  
Author(s):  
T. Kim ◽  
J. B. Ghandhi
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Equivalence Ratio ◽  
Ignition Delay Time ◽  
Ignition Time ◽  
Liquid Core ◽  
Injection Pressure ◽  
Lift Off ◽  
Injection Pressures

Natural luminosity images from reacting diesel sprays were acquired in a combustion-type constant-volume spray chamber. Using an ambient condition of 15 kg/m3 and 1000 K, the effects of peak injection pressures (60, 90 and 150 MPa) and nozzle hole sizes (140, 158 and 200 μm) were investigated. From high-speed natural luminosity cinematography, macroscopic reacting spray characteristics such as flame lift-off height and ignition delay time were obtained. For increasing injection pressures the ignition delay time decreased, and the flame lift off height increased. For increasing hole diameter the ignition time delay decreased, and the flame lift-off height decreased. The authors’ previous results of the fuel concentration measurement from non-reacting spray experiments were used to ascertain the local equivalence ratio for the reacting spray during the ignition and initial flame development period. The first detection of the luminosity (believed to be chemiluminescence) signal was found to occur in fuel-rich vapor regions near the boundary of the liquid core with an equivalence ratio near 2 and a temperature of approximately 800 K. These conditions were found to be independent of injection pressure and nozzle diameter for the condition tested (15 kg/m3 and 1000 K ambient), suggesting that this is a kinetically controlled process.

Experimental Study and Modeling of Autoignition of Natural Gas/Air-Mixtures Under Gas Turbine Relevant Conditions

2005 ◽  
Author(s):  
Andreas Koch ◽  
Clemens Naumann ◽  
Wolfgang Meier ◽  
Manfred Aigner
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
Evaluation Procedure ◽  
Ignition Process ◽  
Ignition Delay Times ◽  
Delay Times

The objective of this work was the improvement of methods for predicting autoignition in turbulent flows of different natural gas mixtures and air. Measurements were performed in a mixing duct where fuel was laterally injected into a turbulent flow of preheated and pressurized air. To study the influence of higher order hydrocarbons on autoignition, natural gas was mixed with propane up to 20% by volume at pressures up to 15 bar. During a measurement cycle, the air temperature was increased until autoignition occurred. The ignition process was observed by high-speed imaging of the flame chemiluminescence. In order to attribute a residence time (ignition delay time) to the locations where autoignition was detected the flow field and its turbulent fluctuations were simulated by numerical codes. These residence times were compared to calculated ignition delay times using detailed chemical simulations. The measurement system and data evaluation procedure are described and preliminary results are presented. An increase in pressure and in fraction of propane in the natural gas both reduced the ignition delay time. The measured ignition delay times were systematically longer than the predicted ones for temperatures above 950 K. The results are important for the design process of gas turbine combustors and the studies also demonstrate a procedure for the validation of design tools under relevant conditions.

scholarly journals Effect of Cu(NO3)2 and Cu(CH3COO)2 Activating Additives on Combustion Characteristics of Anthracite and Its Semi-Coke

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5926
Author(s):  
Kirill Larionov ◽  
Konstantin Slyusarskiy ◽  
Svyatoslav Tsibulskiy ◽  
Anton Tolokolnikov ◽  
Ilya Mishakov ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
Early Stage ◽  
Copper Acetate ◽  
Gas Analysis ◽  
Copper Salts ◽  
Activating Additives ◽  
On Line

The process of anthracite and its semi-coke combustion in the presence of 5 wt.% (in terms of dry salt) additives of copper salts Cu(NO3)2 and Cu(CH3COO)2 was studied. The activating additives were introduced by an incipient wetness procedure. The ignition and combustion parameters for coal samples were examined in the combustion chamber at the heating medium temperatures (Tg) of 600–800 °C. The composition of the gaseous combustion products was controlled using an on-line gas analyzer. The fuel modification with copper salts was found to reduce the ignition delay time on average, along with a drop in the minimum ignition temperature Tmin by 138–277 °C. With an increase in Tg temperature, a significant reduction in the ignition delay time for the anthracite and semi-coke samples (by a factor of 6.7) was observed. The maximum difference in the ignition delay time between the original and modified samples of anthracite (ΔTi = 5.5 s) and semi-coke (ΔTi = 5.4 s) was recorded at a Tg temperature of 600 °C in the case of Cu(CH3COO)2. The emergence of micro-explosions was detected at an early stage of combustion via high-speed video imaging for samples modified by copper acetate. According to the on-line gas analysis data, the addition of copper salts permits one to reduce the volume of CO formed by 40% on average, providing complete oxidation of the fuel to CO2. It was shown that the introduction of additives promoted the reduction in the NOx emissions during the combustion of the anthracite and semi-coke samples.

scholarly journals High-Speed Imaging and Measurements of Ignition Delay Times in Oxy-Syngas Mixtures With High CO2 Dilution in a Shock Tube

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
High Speed Imaging ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Syngas Combustion ◽  
End Wall

In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2 cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% to 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (ϕ), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (θ), hydrogen to carbon monoxide, from 0.25, 1.0, and 4.0. The study was performed at 1.61–1.77 atm and a temperature range of 1006–1162 K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed nonhomogeneous combustion in the system; however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.

Experimental and Kinetic Modeling of Kerosene-Type Fuels at Gas Turbine Operating Conditions

2006 ◽  
Vol 129 (3) ◽  
pp. 655-663 ◽  
Author(s):  
P. Gokulakrishnan ◽  
G. Gaines ◽  
J. Currano ◽  
M. S. Klassen ◽  
R. J. Roby
Keyword(s):  
Low Temperature ◽  
Gas Turbine ◽  
Ignition Delay ◽  
Delay Time ◽  
Equivalence Ratio ◽  
Ignition Delay Time ◽  
Flow Reactor ◽  
Fuel Oil ◽  
Stirred Reactor ◽  
Lean Conditions

Experimental and kinetic modeling of kerosene-type fuels is reported in the present work with special emphasis on the low-temperature oxidation phenomenon relevant to gas turbine premixing conditions. Experiments were performed in an atmospheric pressure, tubular flow reactor to measure ignition delay time of kerosene (fuel–oil No. 1) in order to study the premature autoignition of liquid fuels at gas turbine premixing conditions. The experimental results indicate that the ignition delay time decreases exponentially with the equivalence ratio at fuel-lean conditions. However, for very high equivalence ratios (>2), the ignition delay time approaches an asymptotic value. Equivalence ratio fluctuations in the premixer can create conditions conducive for autoignition of fuel in the premixer, as the gas turbines generally operate under lean conditions during premixed prevaporized combustion. Ignition delay time measurements of stoichiometric fuel–oil No. 1∕air mixture at 1 atm were comparable with that of kerosene type Jet-A fuel available in the literature. A detailed kerosene mechanism with approximately 1400 reactions of 550 species is developed using a surrogate mixture of n-decane, n-propylcyclohexane, n-propylbenzene, and decene to represent the major chemical constituents of kerosene, namely n-alkanes, cyclo-alkanes, aromatics, and olefins, respectively. As the major portion of kerosene-type fuels consists of alkanes, which are relatively more reactive at low temperatures, a detailed kinetic mechanism is developed for n-decane oxidation including low temperature reaction kinetics. With the objective of achieving a more comprehensive kinetic model for n-decane, the mechanism is validated against target data for a wide range of experimental conditions available in the literature. The data include shock tube ignition delay time measurements, jet-stirred reactor reactivity profiles, and plug-flow reactor species time–history profiles. The kerosene model predictions agree fairly well with the ignition delay time measurements obtained in the present work as well as the data available in the literature for Jet A. The kerosene model was able to reproduce the low-temperature preignition reactivity profile of JP-8 obtained in a flow reactor at 12 atm. Also, the kerosene mechanism predicts the species reactivity profiles of Jet A-1 obtained in a jet-stirred reactor fairly well.

Ignition and Oxidation of 50/50 Butane Isomer Blends

2009 ◽  
Author(s):  
Nicole Donato ◽  
Christopher Aul ◽  
Eric Petersen ◽  
Christopher Zinner ◽  
Henry Curran ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Ignition Time ◽  
Pressure Rise ◽  
Time Data ◽  
Kinetics Modeling ◽  
Time Sensitivity ◽  
Wide Range

One of the alkanes found within gaseous fuel blends of interest to gas turbine applications is butane. There are two structural isomers of butane, normal butane and iso-butane, and the combustion characteristics of either isomer are not well known. Of particular interest to this work are mixtures of n-butane and iso-butane. A shock-tube experiment was performed to produce important ignition delay time data for these binary butane isomer mixtures which are not currently well studied, with emphasis on 50–50 blends of the two isomers. These data represent the most extensive shock-tube results to date for mixtures of n-butane and iso-butane. Ignition within the shock tube was determined from the sharp pressure rise measured at the endwall which is characteristic of such exothermic reactions. Both experimental and kinetics modeling results are presented for a wide range of stoichiometry (φ = 0.3–2.0), temperature (1056–1598 K), and pressure (1–21 atm). The results of this work serve as validation for the current chemical kinetics model. Correlations in the form of Arrhenius-type expressions are presented which agree well with both the experimental results and the kinetics modeling. The results of an ignition-delay-time sensitivity analysis are provided, and key reactions are identified. The data from this study are compared with the modeling results of 100% normal butane and 100% iso-butane. The 50/50 mixture of n-butane and iso-butane was shown to be more readily ignitable than 100% iso-butane but reacts slower than 100% n-butane only for the richer mixtures. There was little difference in ignition time between the lean mixtures.

Understanding the Effect of Oxygenated Biofuels Addition on Combustion Characteristics of Gasoline

2018 ◽  
Author(s):  
Shrabanti Roy ◽  
Saeid Zare ◽  
Omid Askari
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
Equivalence Ratio ◽  
Ignition Delay Time ◽  
Combustion Characteristics ◽  
Wide Range ◽  
Oxygenated Fuels ◽  
Laminar Burning Speed

The change in laminar burning speed and ignition delay time of iso-octane with the addition of oxygenated fuels are investigated. As oxygenated fuels, ethanol and 2,5 dimethyle furan (DMF) are used. To confirm the process and mechanism a detailed validation is done on laminar burning speed and ignition delay time. Further, three different blending ratios of 5%, 25% and 50% for both ethanol/iso-octane and DMF/iso-octane are investigated separately. Wide range of equivalence ratio from 0.6–1.4 is considered in calculating laminar burning speed. Ignition delay time is measured under various temperatures from 650 K to 1100 K. Results of each blending are compared with the pure fuels. A comparison is also done between the effects of these two oxygenates. It has found that for each blending case presence of DMF brings larger change in the behavior of iso-octane than ethanol. This observation refers to further study on comparison of these two oxygenates.

High-Speed Imaging and Measurements of Ignition Delay Times in Oxy-Syngas Mixtures With High CO2 Dilution in a Shock Tube

2017 ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
High Speed Imaging ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Syngas Combustion ◽  
End Wall

In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% – 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (ϕ), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (θ), hydrogen to carbon monoxide, from 0.25, 1.0 and 4.0. The study was performed at 1.61–1.77 atm and a temperature range of 1006–1162K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed non-homogeneous combustion in the system, however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.

Identification of significant design factors for diesel spray combustion control through comprehensive experiments with various multi-hole nozzle internal geometries

2021 ◽  
pp. 146808742098375
Author(s):  
Naoki Watanabe ◽  
Naoki Kurimoto ◽  
Kazufumi Serizawa ◽  
Mutsumi Yoshino ◽  
Scott Skeen ◽  
...  
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
Ignition Delay Time ◽  
Orifice Diameter ◽  
Diesel Spray ◽  
Spray Combustion ◽  
Lasso Regression ◽  
Design Factor ◽  
Lift Off ◽  
Design Factors

It is well known that nozzle internal geometries affect the characteristics of diesel spray and combustion. However, despite a number of studies, the effects are difficult to generalize. It is also not clear which spray features are more important for combustion than others. To investigate these subjects, a comprehensive dataset on diesel spray combustion was obtained with 20 variations of multi-hole injector nozzle. The 20 variations had different combinations of orifice diameter, orifice length, sac length and orifice hub-to-tip ratio, which cover the large range of existing production injectors. Vapor penetration, vapor width, ignition delay time, ignition distance and lift-off length were quantified using schlieren and excited-state hydroxyl radical (OH*) chemiluminescence imaging for an isolated plume emerging from these different nozzles. The experiments were conducted with Japanese diesel fuel in a constant-volume diesel spray combustion facility at Sandia National Laboratories. The results were analyzed with response surface and Lasso regression analysis to identify significant design factors for spray combustion. Orifice diameter has large effects on spray combustion. Orifice length, sac length, orifice hub-to-tip ratio and their interactions have effects on spray combustion, but each effect is smaller than the effect of orifice diameter. Vapor penetration is a significant design factor for ignition delay time, ignition distance and lift-off length, while vapor width is not. Lift-off length is well-explained by ignition distance and ignition delay time. Ignition distance should be taken into consideration as a significant design factor for lift-off length as well as ignition delay time.

scholarly journals Effects of Pressure and Coal Rank on the Oxy-Fuel Combustion of Pulverized Coal

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 265
Author(s):  
Dingyi Qin ◽  
Qianyun Chen ◽  
Jing Li ◽  
Zhaohui Liu
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Bituminous Coal ◽  
Ignition Delay Time ◽  
Reaction System ◽  
Fuel Combustion ◽  
Release Time ◽  
Anthracite Coal ◽  
Combustion Technology

Pressurized oxy-fuel combustion technology is the second generation of oxy-fuel combustion technology and has low energy consumption and low cost. In this research, a visual pressurized flat-flame reaction system was designed. A particle-tracking image pyrometer (PTIP) system based on a high-speed camera and an SLR camera was proposed. Combining the experimental system and data-processing method developed, the ignition and combustion characteristics of a single coal particle between 69 and 133 μm in size were investigated. The results indicated that at atmospheric pressure, the ignition delay time of ShanXi (SX) anthracite coal was longer than that of ShenHua (SH) bituminous coal, while that of PRB sub-bituminous coal was the shortest. As the pressure rose, the ignition delay time of the PRB sub-bituminous coal and SX anthracite coal showed a continuous increasing trend, while the ignition delay time of SH bituminous coal showed a trend of first increasing and then decreasing. Moreover, pressure also affects the pyrolysis process of coal. As the pressure increases, it became more difficult to release the volatiles produced by coal pyrolysis, which reduced the release rate of volatiles during the ignition stage, and prolonged the release time and burning duration time of volatiles.

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