Micro combustion
Encyclopedia
Micro Combustion is the sequence of exothermic
Exothermic
In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...

 chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species at micro
Micro
Micro is a prefix in the metric system denoting a factor of 10-6 . Confirmed in 1960, the prefix comes from the Greek , meaning "small".The symbol for the prefix is the Greek letter μ...

 level. The release of heat can result in the production of light in the form of either glowing or a flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

. Fuels of interest often include organic compounds (especially hydrocarbons) in the gas, liquid or solid phase.

The development of miniaturized products such as microrobots, notebook computers, micro-aerial vehicles and other small scale devices is becoming increasingly important in our daily life. There is a growing interest in developing small scale combustor
Combustor
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the combustor or combustion chamber is fed high pressure air by the compression system. The...

 to power these micro devices due to their inherent advantages of higher energy-density, higher heat and mass transfer coefficients and smaller recharge
Recharge
Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface...

 times compared to electrochemical batteries . Energy-density of hydrocarbon fuels is 20-50 times higher than the most advanced Li-ion concept based electrochemical batteries. Concept of micro heat engine was proposed by Epstein and Senturia in 1997. Since then, substantial amount of work has been done towards the development and application of such small scale devices to generate power through the combustion of hydrocarbon fuels. Micro combustors are an attractive alternate to batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

  as they have large surface area to volume ratio, due to which, significant amount of heat is transferred through the walls which leads to flame quenching. However, the increased rate of heat transfer through solid walls is advantageous in the case of steam reformers used for Hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 production .

B. Khandelwal et al.. have experimentally studied the flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

 stability limits and other characteristics in a two staged micro combustor. They found out that staged combustor leads to higher flame stability limits, in addition to that they also offer higher temperature profiles which would be helpful in utilizing the heat produced by combustion. Maruta et al. have experimentally studied the flame propagation characteristics of premixed methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 air mixtures in a 2.0 mm diameter straight quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 channel with a positive wall temperature gradient along the flow direction. This was a simple one-dimensional configuration to study flame stabilization characteristics in microchannels. Other researchers have studied the flame stabilization behavior and combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 performance in Swiss roll
Swiss roll
A Swiss roll or jelly roll is a type of sponge cake roll. The thin cake is made of eggs, flour and sugar and baked in a very shallow rectangular baking tray, called a sheet pan. The cake is removed from the pan and spread with jam or buttercream, rolled up, and served in circular slices.The...

 combustor , micro-gas turbine engines , micro thermo photovoltaic system , free piston knock engine , micro-tube combustor , radial channel combustors and various other concepts of micro combustors  .

Major problem of micro
Micro
Micro is a prefix in the metric system denoting a factor of 10-6 . Confirmed in 1960, the prefix comes from the Greek , meaning "small".The symbol for the prefix is the Greek letter μ...

 combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

is high surface to volume ratio. As the surface to volume ratio increases heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 loss to walls of combustor
Combustor
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the combustor or combustion chamber is fed high pressure air by the compression system. The...

 increases which leads to flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

 quenching.
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