Alternative fuel

CRYOGENIC LIQUID NITROGEN (An Alternative Fuel)

CRYOGENIC LIQUID NITROGEN

(An Alternative Fuel)

ABSTRACT

Now the world is filled with automobiles of various types from a small two-wheeler to huge trucks, but the soul of those engines are the fuels what we are using. From the olden days onwards we use only the fossil fuels, we are using still now but the major disadvantage of those fuels are the pollution caused by them and their availability. Now our world is under the pressure of pollution, though there may be many reasons for pollutions, the major amount was contributed by automobiles and this fossil fuel are non-renewable resource and we know that this would available only for 30-40 years. So our scientists are searching for renewable resource as fuel for engines and moreover pollution free.

This paper deals about using liquid nitrogen as a fuel for the future world. Yes of course using of nitrogen which is very abundant (78%) in our atmosphere. The technique of liquefying the nitrogen gas by the process of “CRYOGENISIS” and using it as a fuel. The major advantage of using this fuel is pollution free (ZERO EMISSION VEHICHLE). Since the exhaust of this engine is again a nitrogen gas. So within few years we can see the automobiles that are propelled by liquid nitrogen and we can make a pollution free world

CRYOGENIC AND ITS DEVELOPMENT:

Cryogenics

The branches of physics and engineering that involve the study of very low temperatures, how to produce them, and how materials behave at those temperatures.

The upper limit of cryogenic temperatures has not been agreed on, but the National Institute of Standards and Technology has suggested that the term cryogenics be applied to all temperatures below -150°C (-238°F or 123° above absolute zero on the Kelvin scale). Some scientists regard the normal boiling point of oxygen (-183°C or -297°F), as the upper limit. Cryogenic temperatures are achieved either by the rapid evaporation of volatile liquids or by the expansion of gases confined initially at pressures of 150 to 200 atmospheres. The expansion may be simple, that is, through a valve to a region of lower pressure, or it may occur in the cylinder of a reciprocating engine, with the gas driving the piston of the engine. The second method is more efficient but is also more difficult to apply. Pioneering work in low-temperature physics by the British chemists Sir Humphrey Davy and Michael Faraday, between 1823 and 1845, prepared the way for the development of cryogenics. Davy and Faraday generated gases by heating an appropriate mixture at one end of a sealed tube shaped like an inverted V. The other end was chilled in a salt-ice mixture.. The combination of reduced temperature and increased pressure caused the evolved gas to liquefy. When the tube was opened, the liquid evaporated rapidly and cooled to its normal boiling point. By evaporating solid carbon dioxide mixed with other, at low pressure, Faraday finally succeeded in reaching a temperature of about 163 K (about -110°C/-166°F).If a gas initially at a moderate temperature is expanded through a valve, its temperature increases. But if its initial temperature is below the inversion temperature, the expansion will cause a temperature reduction as the result of what is called the Joule-Thomson effect. The inversion temperatures of hydrogen and helium, two primary cryogenic gases, are extremely low, and to achieve a temperature reduction through expansion, these gases must first be pre-cooled below their inversion temperatures.

PROPERTIES OF LIQUID NITROGEN

Liquid nitrogen is inert, colorless, odorless, non-corrosive, nonflammable, and extremely cold. Nitrogen makes up the major portion of the atmosphere (78.03% by volume, 75.5% by weight). Nitrogen is inert and will not support combustion; however, it is not life supporting. Nitrogen is inert except when heated to very high temperatures where it combines with some of the more active metals, such as lithium and magnesium, to form nitrides. It will also combine with oxygen to form oxides of nitrogen and, when combined with hydrogen in the presence of catalysts, will form ammonia.

Physical Properties

· Molecular Weight: 28.01

· Boiling Point @ 1 atm: -320.5°F (-195.8°C, 77^oK)

· Freezing Point @ 1 atm: -346.0°F (-210.0°C, 63^oK)

· Critical Temperature: -232.5°F (-146.9°C)

· Critical Pressure: 492.3 psia (33.5 atm)

· Density, Liquid @ BP, 1 atm: 50.45 lb/scf

· Density, Gas @ 68°F (20°C), 1 atm: 0.0725 lb/scf

· Specific Gravity, Gas (air=1) @ 68°F (20°C), 1 atm: 0.967

· Specific Gravity, Liquid (water=1) @ 68°F (20°C), 1 atm: 0.808

· Specific Volume @ 68°F (20°C), 1 atm: 13.80 scf/lb

· Latent Heat of Vaporization: 2399 BTU/lb mole

· Expansion Ratio, Liquid to Gas, BP to 68°F (20°C): 1 to 694

PRODUCTION OF LIQUID NITROGEN

STIRLING PROCESS

This is the most famous process by which liquid nitrogen was generated. Here air is sucked in and compressed through compressor so that water is rejected out, and then through pressure swing adsorption the excess amount of oxygen and its wastes are removed and the remaining nitrogen is sent into cryogenerator and it is compressed as liquid nitrogen and stored in tanks.

A practical Stirling liquid nitrogen compressor which compresses the nitrogen at cryogenic temperature. The sketch and its specifications are given below

STORAGE OF NITROGEN

The nitrogen is stored in Dewar flask which is a vacuum flask

Dewar flask

A glass vessel used for keeping liquids at temperatures differing from that of the surrounding air. This is done by reducing to a minimum the transfer of heat between the liquid and the air. A Dewar flask consists of a double-walled flask, with the space between the two walls exhausted to a very high vacuum, to minimize transfer of heat by convection and conduction. The inner surfaces of the walls are silvered to reduce transfer of heat by radiation; areas of contact between the two walls are kept at a minimum to keep down conduction of heat.

CRYOGENIC HEAT ENGINE

Another version of an air-powered car is being developed by researchers at the University of Washingtonusing the concept of a steam engine, except there is no combustion. The Washington researchers use liquid nitrogen as the propellant for their LN2000 prototype air car. The researchers decided to use nitrogen because of its abundance in the atmosphere -- nitrogen makes up about 78 percent of the Earth's atmosphere -- and the availability of liquid nitrogen. There are five components to the LN2000 engine:

Ø A 24-gallon stainless steel tank

Ø A pump that moves the liquid nitrogen to the economizer.

Ø An economizer that heats the liquid nitrogen with leftover exhaust heat.

Ø A heat exchanger that boils the liquid nitrogen, creating a high pressure gas .An expander, which converts nitrogen's energy into usable power.

The liquid nitrogen, stored at -320 degrees Fahrenheit (-196 degrees Celsius), is vaporized by the heat exchanger. The heat exchanger is the heart of the LN2000's cryogenic engine, which gets its name from the extremely cold temperature at which the liquid nitrogen is stored. Air moving around the vehicle is used to heat the liquid nitrogen to a boil. Once the liquid nitrogen boils, it turns to gas in the same way that heated water forms steam in a steam engine

Nitrogen gas formed in the heat exchanger expands to about 700 times the volume of its liquid form. This highly pressurized gas is then fed to the expander, where the force of the nitrogen gas is converted into mechanical power by pushing on the engine's pistons. The only exhaust is nitrogen, and since nitrogen is a major part of the atmosphere, the car gives off little pollution. However, the cars may not reduce pollution as much as you think. While no pollution exits the car, the pollution may be shifted to another location. As with the evolution car, the LN2000 requires electricity to compress the air. That use of electricity means there is some amount of pollution produced somewhere else. Some of the leftover heat in the engine's exhaust is cycled back through the engine to the economizer, which preheats the nitrogen before it enters the heat exchanger, increasing efficiency. Two fans at the rear of the vehicle draw in air through the heat exchanger to enhance the transfer of heat to the liquid nitrogen.

PRACTICAL CAR LN2000

The University of Washington discovered a car that runs with liquid nitrogen as a fuel

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Researchers at the University of Washington are developing a new zero-emission automobile propulsion concept that uses liquid nitrogen as the fuel. The principle of operation is like that of a steam engine, except there is no combustion involved. Instead, liquid nitrogen at –320° F (–196° C) is pressurized and then vaporized in a heat exchanger by the ambient temperature of the surrounding 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 the major constituent of our atmosphere.

LN2000 MODEL AND SPECIFICATION

The LN2000 is an operating proof-of-concept test vehicle, a converted 1984 Grumman-Olson Kubvan mail delivery van. The engine, a radial five-cylinder 15-hp air motor, drives the front wheels through a five-speed manual Volkswagen transmission. The liquid nitrogen is stored in a thermos-like stainless steel tank, or Dewar, that holds 24 gallons and is so well insulated that the nitrogen will stay liquid for weeks. At present the tank is pressurized with gaseous nitrogen to develop system pressure but a cryogenic liquid pump will be used for this purpose in the future. A preheated, called an economizer, uses leftover heat in the engine's exhaust to preheat the liquid nitrogen before it enters the heat exchanger. Two fans at the rear of the van draw air through the heat exchanger to enhance the transfer of ambient heat to the liquid nitrogen. The design of this heat exchanger is such as to prevent frost formation on its outer surfaces.

As with all alternative energy storage media, the energy density (W-hr/kg) of liquid nitrogen is relatively low when compared to gasoline but better than that of readily available battery systems. Studies indicate that liquid nitrogen automobiles will have significant performance and environmental advantages over electric vehicles. A liquid nitrogen car with a 60-gallon tank will have a potential range of up to 200 miles, or more than twice that of a typical electric car. Furthermore, a liquid nitrogen car will be much lighter and refilling its tank will take only 10-15 minutes, rather than the several hours required by most electric car concepts. Motorists will fuel up at filling stations very similar to today's gasoline stations. When liquid nitrogen is manufactured in large quantities, the operating cost per mile of a liquid nitrogen car will not only be less than that of an electric car but will actually be competitive with that of a gasoline car.The process to manufacture liquid nitrogen in large quantities can be environmentally very friendly, even if fossil fuels are used to generate the electric power required. The exhaust gases produced by burning fossil fuels in a power plant contain not only carbon dioxide and gaseous pollutants, but also all the nitrogen from the air used in the combustion. By feeding these exhaust gases to the nitrogen liquefaction plant, the carbon dioxide and other undesirable products of combustion can be condensed and separated in the process of chilling the nitrogen, and thus no pollutants need be released to the atmosphere by the power plant. The sequestered carbon dioxide and pollutants could be injected into depleted gas and oil wells, deep mine shafts, deep ocean subduction zones, and other repositories from which they will not diffuse back into the atmosphere, or they could be chemically processed into useful or inert substances. Consequently, the implementation of a large fleet of liquid nitrogen vehicles could have much greater environmental benefits than just reducing urban air pollution as desired by current zero-emission vehicle mandates.

GAS FLOW DIAGRAM

Air motor

A pneumatic motor is a machine which converts energy of compressed air into mechanical work. In industrial applications linear motion can come from either a diaphragm or piston actuator. As for rotary motion, either a vane type air motor (USA) or piston air motor (USA) is used. Rotary motion vane type air motors are used to start large industrial diesel or natural gas engines. Stored energy in the form of compressed air, nitrogen or natural gas enters the sealed motor chamber and exerts pressure against the vanes of a rotor. Much like a windmill, this cause the rotor to turn at high speed. Reduction gears are used to create high torque levels sufficient to turn the engine flywheel when engaged by the pinion gear of the air motor or air starter.A widespread application of small pneumatic motors is in hand-held tools, powering ratchet wrenches, drills, sanders, grinders, cutters, and so on. Their overall energy efficiency is low, but due to compactness and light weight, they are often preferred to electric tool

POWER TRAIN OF NITROGEN-POWERED CAR

NITROGENS ECONOMY

Nitrogen is more economic and in mass production for producing 1gallon of n2 (4litres) it costs Rs4/-. And moreover for electric vehicles 1000 pounds of lead are used and it costs more than this . Currently, most road vehicles are powered by internal combustion engines burning fossil fuel. If transportation is to be sustainable over the long term, the fuel must be replaced by something else produced by renewable energy. The replacement should not be thought of as an energy source; it is a means of transferring and concentrating energy, a "currency"Liquid nitrogen is generated by cryogenic or Stirling engine coolers that liquefy the main component of air, nitrogen (N₂). The cooler can be powered by renewable generated electricity or through direct mechanical work from a hydro or wind turbines. Liquid nitrogen is distributed and stored in insulated containers. The insulation reduces heat flow into the stored nitrogen. Heat from the surrounding environment boils the liquid. Reducing inflowing heat reduces the loss of liquid nitrogen in storage. The requirements of storage prevent the use of pipelines as a means of transport. Since long-distance pipelines would be costly due to the insulation requirements, it would be costly to use distant energy sources for production of liquid nitrogen. Petroleum reserves are typically a vast distance from consumption but can be transferred at ambient temperatures. Liquid nitrogen consumption is in essence production in reverse. The Stirling engine or cryogenic heat engine offers a way to power vehicles and a means to generate electricity. Liquid nitrogen can also serve as a direct coolant for refrigerators, electrical equipment and air conditioning units. The consumption of liquid nitrogen is in effect boiling and returning thenitrogen to the atmosphere.

THREATS FOR OTHERS

FOR ELECTRIC CARS

The cost of production of 1 gallon of liquid nitrogen costs approx about Rs. 2/- (4 cents) whereas an electric car requires 7 cents.Refilling of the tank requires just 10-15 min, while an electric car requires an considerable amount.Extremely non pollutant whereas, lead-acid batteries used in electric cars pose threats in increasing metal pollution.

FOR HYDROGEN CAR

More over nitrogen is safer than hydrogen since this is less combustible than hydrogen and the liquification process is simple rather than hydrogen. The engine design is simple and the avilablity is more

CONCLUSION

SO due to the nitrogen abundance and its property of inertness and zero emissions we would see the world filled with car that would be propelled by nitrogen everlasting.

The scope of cryogenics has expanded widely from basic military and space applications to various civil applications. Already Infrared sensors are being increasingly used for fire detection alarm systems, energy conservation thermo graphic analysis, astronomical observations, and medical thermo graphic analysis for early Cancer detection.

The future developments are expected to lead towards disposable miniature 80 K cryogenics. Ever since the introduction ofcryogenic nitrogen, it has found applicability in practically all fields because of its higher efficiency as compared to cryogenics based on other refrigerating cycles

Cryogenics offer immense scope for the researchers and scientists for challenging ideas for new developments. Thus we conclude that the cryogenic nitrogen are playing a very important role in the researches and applications of its liquefaction, preservation and super cooling processes.