Combustion-related Properties Research Articles

Research on the Combustion Properties of Propellants with Low Content of Nano Metal Powders

AbstractA comparison of various experimental results for combustionrelated properties evaluation, including burning rates, deflagration heat, flame structures and thermal decomposition properties, of AP/RDX/Al/HTPB composite propellants containing nano metal powders is presented. The thermal behavior of n‐Al (nano grain size aluminum) and g‐Al (general grain size aluminum i.e., 10 μm) heated in air was also investigated by thermogravimetry. The burning rates results indicate that the usage of bimodal aluminum distribution with the ratio around 4 : 1 of n‐Al to g‐Al or the addition of 2% nano nickel powders (n‐Ni) will improve the burning behavior of the propellant, while the usage of grading aluminum powders with the ratio 1 : 1 of n‐Al to g‐Al will impair the combustion of the propellant. Results show that n‐Al and n‐Ni both have a lower heating capacity, lower ignition threshold and shorter combustion time than g‐Al. In addition n‐Al is inclined to burn in single particle form. And the thermal analysis results show that n‐Ni can catalyze the thermal decomposition of AP in the propellant. The results also confirm the high reactivity of n‐Al, which will lead to a lower reaction temperature and rather higher degree of reaction ratio as compared with g‐Al in air. All these factors will influence the combustion of propellants.

Effect of Biodiesel Utilization of Wear of Vital Parts in Compression Ignition Engine

The combustion related properties of vegetable oils are somewhat similar to diesel oil. Neat vegetable oils or their blends with diesel, however, pose various long-term problems in compression ignition engines, e.g., poor atomization characteristics, ring-sticking, injector coking, injector deposits, injector pump failure, and lube oil dilution by crank-case polymerization. These undesirable features of vegetable oils are because of their inherent properties like high viscosity, low volatility, and polyunsaturated character. Linseed oil methyl ester (LOME) was prepared using methanol for long-term engine operations. The physical and combustion-related properties of the fuels thus developed were found to be closer to that of the diesel oil. A blend of 20 percent was selected as optimum biodiesel blend. Two similar new engines were completely disassembled and subjected to dimensioning of various vital moving parts and then subjected to long-term endurance tests on 20 percent biodiesel blend and diesel oil, respectively. After completion of the test, both the engines were again disassembled for physical inspection and wear measurement of various vital parts. The physical wear of various vital parts, injector coking, carbon deposits on piston, and ring sticking were found to be substantially lower in case of 20 percent biodiesel-fuelled engine. The lubricating oil samples drawn from both engines were subjected to atomic absorption spectroscopy for measurement of various wear metal traces present. AAS tests confirmed substantially lower wear and thus improved life for biodiesel operated engines.

Modelling and validation of the formation and oxidation of cenospheres in a confined spray flame

Oil combustion generated particulates are mainly soot formed during gas-phase reactions and cenospheres, consisting of ash and unburnt carbon, formed by the liquid-phase pyrolysis. Both kinds of particulates may lead to fouling, augment emissions and change the heat transfer process inside industrial furnaces. In this work, a model to predict the formation, oxidation and spatial distribution of cenospheres is presented and it is developed based on experimental results and on the governing physical mechanisms. This model was coupled to the standard dual eulerian–lagrangian framework to predict two-phase flows combustion. The gas-phase combustion-related properties are calculated by means of time-averaged eulerian conservation equations, in addition to the k–ε turbulence model. The droplets and cenospheres balance equations are solved in a lagrangian fashion, with a stochastic approach to turbulent dispersion. The gaseous turbulent-diffusion flame is modelled using a clipped-Gaussian pdf to account for fluctuations of scalar properties. Chemistry is assumed to be fast. Radiation is modelled by the discrete transfer method. In order to validate the model, the whole procedure was applied to the prediction of a cylindrical laboratory furnace, oil-fired by an industrial-type burner, where experimental data are available. The comparison of predictions against experimental values showed good agreement and, therefore, the validity of the model. The study has proved that the reduction of particulate emissions is achievable through control of aerodynamics, combustion and the quality of atomization. © 1997 by John Wiley & Sons, Ltd.

Physical properties of low molecular weight triglycerides for the development of bio-diesel fuel models

To aid the improvement of fuel properties of oils, basic physical and combustion-related properties of low molecular weight triglycerides are described. These properties include density, viscosity, heat capacity, surface tension and vapor pressure. Fuel injection atomization factors were determined for these triglycerides. Properties of tributyrin (C4:0), tricaproin (C6:0), tricaprylin (C8:0) and tricaprin (C10:0) indicate that these triglycerides are potential components in future diesel fuels derived from plant oils.

COMBUSTION PERFORMANCE RELATED PROPERTIES OF AVIATION TURBINE FUELS

Abstract In recent years the hydrogen content of Aviation Fuels has generated considerable interest. Various investigators have suggested correlation of hydrogen content with combustion related properties of aviation turbine fuel (ATF). A suitable threshold value of hydrogen content 13.8 %wt is being considered as a waiver of Specification sueh as specific energy, aniline gravity product, smoke point, aromatic content, naphthalenes and luminometer number. In the present paper relationship between the Hydrogen content and. combustion related properties have been examined and improved correlations of hydrogen content with several combustion related properties have been developed by incorporating a characterizationfactor in the equations. The supporting threshold value of a hydrogen content of 13.8 %wt is verified with 25 data points for waiving of combustion properties such as specific energy, aniline gravity product, smoke point and aromatic content from aviation turbine fuel.

Charcoal and fuel value of agroforestry tree crops

Charcoal was produced from short rotation tropical species ofLeucaena leucocephala andTectona grandis. The combustion-related properties, moisture content, specific gravity and percentage element composition of carbon, hydrogen, oxygen, nitrogen, sulphur and ash in wood and charcoal from the two species were determined. The gross heat of combustion of wood and charcoal was also determined. There were significant differences in the moisture content, specific gravity and percentage element composition between wood and charcoal from the two species. The carbon and ash content of charcoal were higher than those of wood. The average heat of combustion of charcoal 25.25 MJKg−1 was higher than that of wood 13.75 MJKg−1.

Is liquid hydrogen safer than liquid methane?

This paper compares the physical and combustion-related properties of the liquid state of hydrogen (LH2) and methane (LCH4). This type of comparison is important for studying the safe use of these chemicals as aircraft fuels, although it cannot yield definite conclusions because the actual effect on safety depends on the conditions of the accident.