Additives to reduce coking in endothermic heat exchangers

Wickham, David; Alptekin, Gökhan; Engel, J.R.; Karpuk, M.E.

doi:10.2514/6.1999-2215

Cited by 21 publications

(23 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Formations of alloys [13][14][15][16][17], partial passivation of the active sites with sulfur, tin or bismuth [14,15,[18][19][20] are some examples of strategies employed for achieving this goal. Moreover, in order to avoid sintering which changes the active sites and accelerates coke formation, shells out of silica, [21,22] tin oxide [23] and zirconia [24] have been formed around the active catalysts by employing techniques such as chemical vapor deposition, dendrimer encapsulation or grafting.…”

Section: Introductionmentioning

confidence: 99%

Alumina coated nickel nanoparticles as a highly active catalyst for dry reforming of methane

Baktash

Littlewood

Schomäcker

et al. 2015

Applied Catalysis B: Environmental

120

View full text Add to dashboard Cite

Section: Introductionmentioning

confidence: 99%

Alumina coated nickel nanoparticles as a highly active catalyst for dry reforming of methane

Baktash

Littlewood

Schomäcker

et al. 2015

Applied Catalysis B: Environmental

120

View full text Add to dashboard Cite

“…Liquid hydrocarbon (HC) fuels, on the other hand, have not been very useful for supersonic airbreathing applications because they are far less reactive, although they are obviously much easier to store and handle. Recently, endothermic catalytic cracking of HC fuels has also been investigated [1][2]. Difficult and competing objectives remain, however, to achieve ignition and robust combustion in relatively small subsonic cavity flameholders -so as to (a) generate rapid reaction with sufficient initial heat release, (b) avoid excessive internal drag and loss of net thrust, and (c) achieve needed "endothermic" heat soak in active cooling channels without the formation and deposition of significant carbon residues [2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, endothermic catalytic cracking of HC fuels has also been investigated [1][2]. Difficult and competing objectives remain, however, to achieve ignition and robust combustion in relatively small subsonic cavity flameholders -so as to (a) generate rapid reaction with sufficient initial heat release, (b) avoid excessive internal drag and loss of net thrust, and (c) achieve needed "endothermic" heat soak in active cooling channels without the formation and deposition of significant carbon residues [2][3][4][5][6][7][8]. Thus catalytically cracked fuel vapor and entrained air must mix, diffuse and react long enough in a subsonic cavity to achieve ignition with robust "incipient flameholding," to supply radicals and adequate enthalpy to the overriding supersonic flow, with minimal loss of initial kinetic energy.…”

Section: Introductionmentioning

confidence: 99%

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Pellett¹,

Convery²,

Wilson³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

View full text Add to dashboard Cite

Opposed Jet Burner (OJB) tools have been used extensively by the authors to measure Flame Strength (FS) extinction limits of laminar H 2 /N 2 -air and (recently) hydrocarbon (HC)-air Counterflow Diffusion Flames (CFDFs) at one atm. This paper details normalization of FSs of N 2 -diluted H 2 and HC systems to account for effects of fuel composition, temperature, pressure, jet diameter, inflow Reynolds number, and inflow velocity profile (plug, contoured nozzle; and parabolic, straight tube). Normalized results exemplify a sensitive accurate means of validating, globally, reduced chemical kinetic models at ~ 1 atm and the relatively low temperatures approximating the loss of non-premixed "idealized" flameholding, e.g., in scramjet combustors.Laminar FS is defined locally as maximum air input velocity, U air , that sustains combustion of a counter-jet of g-fuel at extinction. It uniquely characterizes a fuel. And global axial strain rate at extinction (U air normalized by nozzle or tube diameter, D n or t ) can be compared directly with computed extinction limits, determined using either a 1-D Navier Stokes stream-function solution, using detailed transport and finite rate chemistry, or (better yet) a detailed 2-D Navier Stokes numerical simulation. The experimental results define an "idealized flameholding reactivity scale" that shows wide ranging (50 x) normalized FS's for various vaporized-liquid and gaseous HCs, including, in ascending order: JP-10, methane, JP-7, n-heptane, n-butane, propane, ethane, and ethylene. Results from H 2 -air produce a unique and exceptionally strong flame that agree within ~1% of a recent 2-D numerically simulated FS for a 3 mm tube-OJB. Thus we suggest that experimental FS's and/or FS ratios, for various neat and blended HCs w/ and w/o additives, offer accurate global tests of chemical kinetic models at the Ts and Ps of extinction.In conclusion, we argue the FS approach is more direct and fundamental, for assessing, e.g., idealized scramjet flameholding potentials, than measurements of laminar burning velocity or blowout in a Perfectly Stirred Reactor, because the latter characterize premixed combustion in the absence of aerodynamic strain. And FS directly measures a chemical kinetic characteristic of non-premixed combustion at typical flameholding temperatures. It mimics conditions where gfuels are typically injected into a subsonic flameholding recirculation zone that captures air, where the effects of aerodynamic strain and associated multi-component diffusion become important.

show abstract

“…The coke formed deteriorates the performance of the engine, such as the blockage of oil circuit and even the flameout of the engine, which is a bottleneck for hypersonic flight [2][3][4]. Wickham et al studied the formation of filamentous carbons in supercritical cracking of fuels and analyzed the effect of metals [5]. John et al found that the coke deposition is correlated with the aromatic compounds formed during the cracking reaction [6].…”

Section: Introductionmentioning

confidence: 99%

Formation of coke in thermal cracking of jet fuel under supercritical conditions

Zhu

et al. 2008

Front. Chem. Eng. China

View full text Add to dashboard Cite

Continuous-flow reactor experiments were carried out to study coke formation from thermal cracking of home-made jet fuel RP-3 under supercritical conditions. The mechanism and precursor of coke forming were analyzed. The starting cracking temperature of RP-3 fuel was determined to be 471.8uC by differential scanning calorimetry (DSC). Temperature-programmed oxidation and scanning electron microscopy (SEM) characterizations of the stressed tubes showed that there are three different coke species including chemisorbed carbon, amorphous carbon and filamentous coke in the solid deposits. More than 90% of coke deposits are carried away by the supercritical fluid, which has strong capabilities of extraction for coke deposits and their precursors. There were 17.1 wt-% of iron and 11.1 wt-% of chromium found on the coke surface detected by energy dispersive spectroscopy (EDS) which suggests carburetion on alloy. RP-3 fuel and its cracking liquids were analyzed by GC-MS,which showed that the content of alkyl benzene and alkyl naphthalene increased evidently in cracking liquids.

show abstract

Additives to reduce coking in endothermic heat exchangers

Cited by 21 publications

References 1 publication

Alumina coated nickel nanoparticles as a highly active catalyst for dry reforming of methane

Alumina coated nickel nanoparticles as a highly active catalyst for dry reforming of methane

Opposed Jet Burner Approach for Characterizing Flameholding Potentials of Hydrocarbon Scramjet Fuels

Formation of coke in thermal cracking of jet fuel under supercritical conditions

Contact Info

Product

Resources

About