Combustion of Nonane and JP8 Droplets With Additives in Low Convection

2003 ◽  
Author(s):  
J. H. Bae ◽  
C. T. Avedisian
Keyword(s):  
Atmospheric Pressure ◽  
Quantitative Measurement ◽  
Soot Formation ◽  
Droplet Diameter ◽  
Burning Process ◽  
Initial Droplet ◽  
Approximate Order ◽  
Scale Variable ◽  
Glycol Methyl Ether ◽  
Thermal Stability Of

The combustion of nonane and JP8 droplets was studied in an environment to promote spherically symmetric droplet flames. Measurements of the droplet, flame and soot ‘shell’ or ‘cloud’ diameters were made to examine how the burning process and sooting dynamics were influenced by three miscible additives: hexanol, tripropylene glycol methyl ether (TPM), and an additive that had been previously developed to improve thermal stability of JP8, called as ‘+100’. The experimental results presented for nonane were used to compare with JP8 for a comparatively simple fuel. The initial droplet diameters ranged from 0.4mm to 0.7mm to allow quantitative measurement of the influence of droplet diameter on the droplet burning process. Spherical symmetry was promoted by carrying out the experiments in microgravity. The burning conditions were room temperature air at atmospheric pressure. Soot formation was found to be massive for JP8 compared to nonane, with thick dark soot clouds that accumulated significant soot as burning progressed. With hexanol and TPM mixed with JP8, soot formation was noticeably reduced. Soot trends in the approximate order of JP8 > JP8+100 > JP8+100 / TPM (90/10, v/v) > JP8+100 / TPM (80/20) > JP8+100 / hexanol (50/50) > nonane are noted for the fixed initial droplet diameter. Significant droplet heating was found for JP8 compared to nonane, due to the higher liquid thermal diffusivity of nonane compared to JP8 and the lower product of density and specific heat of nonane compared to JP8. A distinct influence of initial droplet diameter on the subsequent evolution of droplet diameter after ignition was found for nonane in that larger droplets burned slower than smaller droplets for the range of initial droplet diameters examined. The evolution of soot shell diameter was independent of additive concentrations for JP8 and still distinct from nonane. A new scale variable is presented which collapses the various ‘standoff’ diameters (soot shell and flame) onto a single curve for a given fuel.

Effects of Initial Diameter on Burning of Nonane Droplets in a Non-Buoyant and Buoyant Ambience: Burning Rate, Soot Formation and Flame Structure

2001 ◽  
Author(s):  
J. H. Bae ◽  
C. T. Avedisian
Keyword(s):  
Burning Rate ◽  
Droplet Size ◽  
Soot Formation ◽  
Droplet Diameter ◽  
Flame Structure ◽  
Large Droplet ◽  
Droplet Combustion ◽  
Small Droplet ◽  
Burning Process ◽  
Initial Droplet

Abstract The results from nonane droplet combustion experiments conducted at 1g and μg are analyzed and compared in the following aspects: the burning rate, soot formation, flame structure. By varying the initial droplet diameter, we observe and discuss the effect of Do on droplet burning. The μg experiments were performed in a drop tower and a drag shield was used to create a low buoyant environment All experiments were fiber-supported and used the same experimental instruments. The droplet size between 0.40 to 0.95mm was examined in the experiments. Results showed that droplet burning is nonlinear in both a buoyant and a non-buoyant environment for the initial droplet diameters examined. Soot formation, which is influenced by Do may strongly affect the droplet burning process in both environments. The large droplet produces more soot and bums slowly whereas the small droplet bums fast because there is less soot.

The effect of initial diameter in spherically symmetric droplet combustion of sooting fuels

1994 ◽  
Vol 446 (1927) ◽  
pp. 255-276 ◽  
Keyword(s):  
Burning Rate ◽  
Rate Constants ◽  
Soot Formation ◽  
Droplet Diameter ◽  
Droplet Surface ◽  
Spherically Symmetric ◽  
Low Gravity ◽  
Initial Droplet ◽  
Initial Diameter ◽  
Burning Rates

The effect of initial droplet diameter on the burning rate of sooting fuels – n-heptane and 1-chloro-octane – was examined experimentally at low gravity. A 1.2s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fibre-supported droplets were burned, and both techniques gave matching results for droplets of similar initial diameter. Burning rate constants for both fuels were measured for a large number of droplets ranging from 0.4 to 1.1 mm in initial diameter. Results showed that burning rate constants decreased monotonically as the initial droplet diameter was increased above 0.6 mm for both fuels. This decrease was considered to be due to the observed increase in soot formation and accumulation in a shell-like structure inside the flame of the larger droplets. The increased collection of soot inside the larger droplet flames reduced the proportional heat release from the flame and may have acted as a barrier to heat transfer from the flame to the droplet. Flame-to-droplet diameter ratio increased monotonically with time, thus suggesting that quasi-steady combustion was not achieved. The flames and soot shells for 1-chloro-octane droplets with their lower burning rates remained closer to the droplet surface than similarly sized n-heptane droplets.

An Experimental Study of the Vaporization Characteristics of Diesel-Benzyl Azides Blend Droplets

2013 ◽  
Author(s):  
Kai Han ◽  
Geng Fu ◽  
Changlu Zhao ◽  
Bolan Liu ◽  
Shibo Ma
Keyword(s):  
Experimental Study ◽  
Ambient Temperature ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Droplet Diameter ◽  
Video Camera ◽  
Initial Droplet ◽  
High Speed Video Camera ◽  
Combustion Duration ◽  
Suspended Droplet

An experimental study of diesel-benzyl azides blend droplets vaporization characteristics was carried out to study the reasons of diesel-benzyl azides blend shortened combustion duration using suspended droplet device and a high-speed video camera. Experiments were performed at atmospheric pressure, ambient temperature range 480–933 K, and initial droplet diameter of 0.98, 1.42, 1.88 mm. The results show a shorten in diesel-benzyl azides blend droplet lifetime by 10% compared to diesel droplet at 1.42 mm initial droplet diameter and 933 K ambient temperature companion to puffing. The above results support the original idea of designing diesel-benzyl azides blend where the energy released by the decomposition of azides improves the vaporization and the release of nitrogen leads to the breakup of the droplet. In addition, it is observed that the blend lifetime decrease with increasing ambient temperature compared to diesel droplet lifetime. More nitrogen is released and the expansion of bubbles is more violent with increasing initial droplet diameter.

scholarly journals Autoignition Behavior of an Ethanol-Methylcellulose Gel Droplet in a Hot Environment

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2168 ◽  
Author(s):  
Donggi Lee ◽  
Jonghan Won ◽  
Seung Baek ◽  
Hyemin Kim
Keyword(s):  
Ambient Temperature ◽  
Ignition Delay ◽  
Atmospheric Pressure ◽  
Droplet Diameter ◽  
Experimental Studies ◽  
Sudden Increase ◽  
Pure Ethanol ◽  
Initial Droplet ◽  
Hot Environment ◽  
Ignition And Combustion

Autoignition of an ethanol-based gel droplet was experimentally investigated by adding 10 wt % of methylcellulose as gellant to liquid ethanol. Experimental studies of the ignition behavior of the gel droplet were found to be quite rare. The initial droplet diameter was 1.17 ± 0.23 mm. The gel droplet was suspended on a K-type thermocouple and its evaporation, ignition and combustion characteristics were evaluated and compared with pure ethanol at an ambient temperature of 600, 700, and 800 °C under atmospheric pressure conditions. The gel droplet exhibited swelling and vapor jetting phenomena. Before ignition, a linear decrease in droplet diameter followed by a sudden increase was repeatedly observed, which was caused by evaporation and swelling processes, respectively. Major droplet swelling was detected just before the onset of ignition at all temperatures. But no further swelling was detected after ignition. For the gel droplet, the ignition delay accounted for 93% of the droplet lifetime at 600 °C, and 88% at 700 °C, but only 31% at 800 °C. Its average burning rate was also evaluated for all temperatures. At 800 °C, the gellant layer no longer exerts any influence on the combustion of the gel droplet.

scholarly journals Droplet Characteristics of Rotating Packed Bed in H2S Absorption: A Computational Fluid Dynamics Analysis

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 724
Author(s):  
Wang ◽  
Wu ◽  
Yang ◽  
Wang ◽  
Liu ◽  
...  
Keyword(s):  
Residence Time ◽  
Droplet Diameter ◽  
Packed Bed ◽  
Droplet Velocity ◽  
Radial Position ◽  
Selective Absorption ◽  
Rotating Speed ◽  
Initial Droplet ◽  
Rotating Packed Bed ◽  
Computational Fluid Dynamics Analysis

Rotating packed bed (RPB) has been demonstrated as a significant and emerging technology to be applied in natural gas desulfurization. However, droplet characteristics and principle in H2S selective absorption with N-methyldiethanolamine (MDEA) solution have seldom been fully investigated by experimental method. Therefore, a 3D Eulerian–Lagrangian approach has been established to investigate the droplet characteristics. The discrete phase model (DPM) is implemented to track the behavior of droplets, meanwhile the collision model and breakup model are employed to describe the coalescence and breakup of droplets. The simulation results indicate that rotating speed and radial position have a dominant impact on droplet velocity, average residence time and average diameter rather than initial droplet velocity. A short residence time of 0.039–0.085 s is credited in this study for faster mass transfer and reaction rate in RPB. The average droplet diameter decreases when the initial droplet velocity and rotating speed enhances. Restriction of minimum droplet diameter for it to be broken and an appropriate rotating speed have also been elaborated. Additional correlations on droplet velocity and diameter have been obtained mainly considering the rotating speed and radial position in RPB. This proposed formula leads to a much better understanding of droplet characteristics in RPB.

The evaporation and combustion of levitated arrays of two, three and five droplets at a hot surface

1988 ◽  
Vol 418 (1855) ◽  
pp. 365-382 ◽  
Keyword(s):  
Droplet Diameter ◽  
Flame Height ◽  
Linear Arrays ◽  
Initial Droplet ◽  
Surface Temperatures ◽  
Droplet Array ◽  
Burning Rates ◽  
Hot Surface

The interactions between droplets in several geometrical arrays in Leidenfrost evaporation and combustion on a hot surface were studied. Comparisons between evaporation and burning times of isolated droplets, two- and three-droplet linear arrays, and a five-droplet array (a centre droplet surrounded by four droplets) were made. The liquids studied were water, n -heptane, and n -hexadecane at 0.101 MPa and at surface temperatures above their respective Leidenfrost values. A range of centre distance to initial droplet diameter ratios, L / d 0 , were studied (2 < L / d 0 < ∞). The evaporation or burning rates of droplets in binary arrays were found to be identical to those of isolated droplets ( L / d 0 → ∞). The flames around each droplet, however, merged as the droplets were brought closer together. In three- and five-droplet arrays more significant interactions were observed, with the edge droplets in the arrays burning faster than the centre droplets. The results are explained on the basis of flame-height measurements for the arrays. In pure evaporation, though, the droplets evaporated without regard for their neighbours.

Droplet Burning and Evaporation Times for Distillate and Residual Fuel Oils

1980 ◽  
Author(s):  
P. C. T. de Boer
Keyword(s):  
Gas Turbine ◽  
Constant Velocity ◽  
Droplet Diameter ◽  
Diffusion Constant ◽  
Gas Mixture ◽  
Residual Oil ◽  
Gas Turbine Combustor ◽  
Initial Droplet ◽  
Fuel Oils ◽  
Industrial Gas Turbine

Estimates are given of the burning and evaporation times of No. 2 distillate and No. 6 residual oil droplets, under conditions typical of industrial gas turbine combustors. Account is taken of the temperature dependence of the specific heat, the diffusion constant, and the thermal conductivity of the gas mixture surrounding the droplet. Detailed calculations are presented of the factor by which the droplet lifetime is reduced as a result of convection, for the case that the droplet is released in a gas moving at constant velocity. This factor is on the order of four for the conditions of interest. Using estimates of initial droplet diameter based on data reported by Jasuja, it is found that the ratio of characteristic droplet burning time to characteristic droplet residence time in a typical industrial gas turbine combustor is much smaller than 1 for distillate oil, but may be on the order of 1 for residual oil.

scholarly journals Thermal behavior of Pd@SiO2 nanostructures in various gas environments: a combined 3D and in situ TEM approach

Nanoscale ◽  
2018 ◽  
Vol 10 (43) ◽  
pp. 20178-20188 ◽  
Author(s):  
Walid Baaziz ◽  
Mounib Bahri ◽  
Anne Sophie Gay ◽  
Alexandra Chaumonnot ◽  
Denis Uzio ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Behavior ◽  
Atmospheric Pressure ◽  
Electron Tomography ◽  
Core Shell ◽  
In Situ Tem ◽  
Environmental Tem ◽  
First Time ◽  
Thermal Stability Of

The thermal stability of core–shell Pd@SiO2 was for the first time monitored by using in situ Environmental TEM at atmospheric pressure coupled with Electron Tomography on the same particles.

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