LIQUID NITROGEN AS A NON- POLLUTING FUEL
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ABSTRACT:
Our paper examines the capability of several energy conversion process to provide sufficient energy in a world where the non-renewable resource are getting depleted. Moreover pollution caused by them is increasing at a rapid rate. One such efficient and non-polluting means of running the vehicles is the use of liquid nitrogen. To use liquid nitrogen as a non-polluting fuel, a multiple reheat open Rankine and a closed Brayton cycle are used.
INTRODUCTION:
In 1997, the University of North Texas (UNT) and University of Washington (UW) independently developed liquid nitrogen powered vehicles in which the propulsion systems in these vehicles are cryogenic heat engines in which a cryogenic substance is used as a heat sink for heat engine.
Cryogenic:
Cryogenic can be defined as the branch of the physics that deals with the production of and study of effects and very low temperature.
Cryogenic Engineering:
It is mainly concerned with temperatures found in range of –150oC to absolute zero (-273.15oC).
Various Cryogenic Fluids:
Liquid Helium
Liquid Nitrogen
Cryogenic Heat Engine:
It is a engine which uses very cold substances to produce useful energy. A unique feature of an cryogenic heat engine is that it operates in an environment at the peak temperature of the power cycle, thus, there is always some heat input to the working fluid during the expansion process.
Liquid Nitrogen :
Liquid Nitrogen is the cheapest, widely produced and most common cryogenic liquid. It is mass produced in air liquefaction plants. The liquefaction process is very simple in it normal, atmospheric air is passed through a dust precipitator and pre-cooled using conventional refrigeration techniques. It is then compressed inside large turbo pumps to about 100 atmospheres. Once the air has reached 100 atmospheres and has been cooled to room temperature it is allowed to expand rapidly through a nozzle into an insulted chamber. By running several cycles the temperate of the chamber reaches low enough temperatures the air entering it starts to liquefy. Liquid nitrogen is removed form the chamber by fractional distillation and is stored inside well-insulated Dewar flasks.
Principle of Operation :
The principle of running the LN2000Car is like that of steam engine, except there is no combustion involved. Instead liquid nitrogen at –320oF (-196oC) is pressurized and then vaporized in a heat exchanger by ambient temperature of the surroundings air. This heat exchanger is like the radiator of a car but instead of using air to cool water, it uses air to heat and boil liquid nitrogen. The resulting high pressure nitrogen gas is fed to an engine that operates like a reciprocating steam engine, converting pressure to mechanical power. The only exhaust is nitrogen, which is major constituent of our atmosphere.
Analysis of CooLN2 Car Performance:
A single-cylinder reciprocating expander that runs on compressed nitrogen gas with the exhaust gas released into the atmosphere was considered. When compressed gas flowed into the expanders cylinder, isobaric work was done on the moving piston by the gas.
The net isobaric expansion work done during a single cycle is gauge pressure of the gas multiplied by the volume of the gas that flows into the cylinder.
Conclusion :
In a real sense, the more such vehicles are used, the cleaner the air will become if the liquefaction process is driven by non-polluting energy sources. In addition to the environmental impact of these vehicles, refueling using current technology can take only a few minutes, which is very similar to current gas refueling times.