Combustion Of Liquid Hydrocarbons Research Articles

The Influence of Hydrogen Addition to Diesel Fuel Spray Combustion for Different Atomization Conditions

The negative effects of hydrocarbon fuels are widely highlighted by increasing global warming and declining quality of human health. Therefore, it is important to reduce the level of emissions from liquid hydrocarbon combustion. Hydrogen addition to the combustion chamber is one of the proven methods to improve emssions level. In this research, an experiment was conducted on diesel fuel spray combustion with hydrogen addition. The effect of additional hydrogen was observed on CO, CO2, NO and THC exhaust gas emissions. A small hydrogen fraction (0~3 vol %) was added to the rich premixed spray combustion. The results show that increasing the hydrogen fraction reduced the emission indexes of CO and THC, and increased the emission index of CO2. Increasing the hydrogen fraction caused an increase in the emission index of NO, but the actual physical amount was insignificant. Increasing the atomizing air flow rate reduced the CO and THC emission indexes, but increased the CO2 and NO emission indexes.

Experimental study of the mild combustion of liquid hydrocarbons

A strong exhaust gas recirculation combined with air preheating generates relatively low maximum flame temperatures allowing for a better control of the furnace temperature and a lower pollutant production. While the sustainability of this combustion technology (named mild or flameless combustion) for different gaseous fuels has been extensively studied, much less information are available for liquid fuels. Consequently, this work has focused on the investigation of the sustainability of mild combustion for liquid hydrocarbons using a dual-nozzle laboratory-scale burner. Pure liquid n-octane has been used as a reference fuel, while mixtures involving also other hydrocarbons commonly found in practical fuels have been investigated to start collecting information on surrogate fuels. It has been found that the dual-nozzle configuration allows sustaining mild combustion conditions by directly injecting different liquid hydrocarbons in a mild combustion environment previously attained using a gaseous fuel. Similar results for gaseous alkanes (namely, methane and LPG) have been obtained, while using liquid hydrocarbons (namely, n-octane, n-octane/ i-octane and n-octane/ i-octane/ n-decane) have led to somewhat different results, even if similar to each other. In particular, the mild combustion region in the T avg– K V space enlarges when using liquid hydrocarbons with respect to gaseous ones. However, in this region very low amounts of NO x , CO, as well as negligible PAH and soot precursors have been found, therefore supporting the idea that a dual-nozzle mild combustion burner can create a suitable environment for NO x , PAH and soot depression for a wide range of liquid wastes and low-BTU liquid fuels.

Kinetics of liquid hydrocarbon combustion using the DSC technique

TGA/DSC techniques were applied to the combustion of crude oil in the presence of solid particles of various specific surface areas. The major physical and chemical transitions observed were classified into three groups, namely distillation, liquid hydrocarbon combustion and coke combustion. This paper deals with the peak associated with the liquid hydrocarbon combustion. Kinetic study revealed that the liquid hydrocarbon combustion peak consisted of two types of combustion reactions which could not be modelled with a single power-law-type kinetic model. Oxygen concentration of the purging gas was varied and its effect on the DSC curve was monitored. It was noticed that at low oxygen concentration, i.e. in the range of 5 to 10%, two distinct peaks emerged. Kinetic analysis of each peak produced a power-law kinetic model for each reaction. The kinetic model was first-order with respect to oxygen partial pressure for both peaks. The order of reaction with respect to the hydrocarbon content was unity for the first peak and 1.5 for the second peak. Optimization of all the data produced a reaction order with respect to the surface area of −0.57 for the first peak and −0.2 for the second peak.

Mechanism and theoretical interpretation of pulsating combustion of liquid hydrocarbons between 250°C and 400°C

Multiple secondary cool flames (MSCF) are a general phenomenon in the oxidation of liquid fuels and are shown to have many features in common with chemical oscillatory reactions. It has been established that two factors are necessary for the occurrence of periodicity, namely, an exothermic surface reaction of order higher than unity with respect to the fuel and a sufficiently high temperature gradient from the gas phase to the surface. The use of a heat balance for the surface layer then allows the dependence of the periodicity of MSCF on experimental conditions to be explained.

Combustion of Liquid Hydrocarbons in a High-speed Airstream

A theoretical formulation and experimental results of the high-speed mixing, ignition, and combustion characteristics of liquid fuels injected directly into a high-velocity airstream are presented. Experiments were performed in a direct connect constant area combustor supplied by a Mach 2 air stream at a static pressure level of 1 atmosphere and at total temperatures ranging from ambient (530°R) to approximately 3300°R. The fuel was liquid hexane and was injected laterally into the supersonic flow through piloted and nonpiloted injector configurations. It was found that autoignition and stable combustion occurs for air total temperatures above about 2600°R. Furthermore, the liquid fuel was effectively ignited and burned stably below this autoignition level by employing a small reacting pilot j et. Minimum pilot size and energy requirements were then established. It was found that the pilot mass flows needed for ignition and sustained combustion were small compared to the main fuel and air flow rates. Comparison with theory indicates combustion efficiencies up to 93% were obtained.