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COMPRESSED AIR VEHICLE (CAV) (A Practical approach with design) Sai Chakradhar. Kommuri, Student, Department of Mechanical Engineering, QISCET, Ongole. Email i.d:saichakradharkommuri@gmail.com contact:8143691783
Tunnel and other Gotthardbahn.
ABSTRACT: A Compressed air car is a car that uses a motor powered by compressed air. The car can be powered solely by air, or combined (as in a hybrid electric vehicle). Compressed air as a source of energy in different uses in general and as a nonpolluting fuel in compressed air vehicles has attracted scientists and engineers for centuries. Efforts are being made by many developers and manufacturers to master the compressed air vehicle technology in all respects for its earliest use by the mankind. The present paper gives a brief introduction to the latest developments of a compressed-air vehicle along with an introduction to various problems associated with the technology and their solution. While developing of compressed air vehicle, control of compressed air parameters like temperature, energy density, requirement of input power, energy release and emission control have to be mastered for the development of a safe, light and cost effective compressed air vehicle in near future.
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In 1903, the Liquid Air Company located in London England manufactured a number of compressed-air and liquefiedair cars. The major problem with these cars and all compressed-air cars is the lack of torque produced by the "engines" and the cost of compressing the air.
INTRODUCTION Compared to batteries, compressed air is favourable because of a high energy density, low toxicity, fast filling at low cost and long service life. These issues make it technically challenging to design air engines for all kind of compressed air driven vehicles. To meet the growing demand of public transportation, sustainable with environmental consciousness, people are in the search for the ultimate clean car with zero-emissions. Many concept vehicles were proposed that run on everything from solar power to algae, but most of them are expensive and require hard-to-find fuels .Compressed air vehicle project in the form of light utility vehicle (LUV) (i.e., air car in particular) has been a topic of great interest for the last decade and many theoretical and experimental investigations.
HISTORY OF CAV: Compressed air has been used since the 19th century to power mine locomotives and trams in cities such as Paris (via a central, citylevel, compressed), and was previously the basis of naval torpedo propulsion. During the construction of the Gotthardbahn from 1872 to 1882, pneumatic locomotives were used in the construction of the Gotthard Rail
COMPRESSED TECHNOLOGY
AIR
Mankind has been making use of uncompressed airpower from centuries in 1
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different application viz., windmills, sailing, balloon car, hot air balloon flying and hang gliding etc. The use of compressed air for storing energy is a method that is not only efficient and clean, but also economical and has been used since the 19th century to power mine locomotives, and was previously the basis of naval torpedo propulsion. The laws of physics dictate that uncontained gases will fill any given space. The easiest way to see this in action is to inflate a balloon. The elastic skin of the balloon holds the air tightly inside, but the moment you use a pin to create a hole in the balloon's surface, the air expands outward with so much energy that the balloon explodes. Compressing a gas into a small space is a way to store energy. When the gas expands again, that energy is released to do work. That's the basic principle behind what makes an air car go. The air compressors are built into them. The principle of compressed-air propulsion is to pressurize the storage tank and then connect it to something very like a reciprocating engine of the vehicle. Instead of mixing fuel with air and burning it in the engine to drive pistons with hot expanding gases, compressed air vehicles (CAV) use the expansion of compressed air to drive their pistons. Thus, making the technology free from difficulties. The air is compressed at pressure about 150 times the rate the air is pressurized into car tyres or bicycle. The tanks must be designed to safety standards appropriate for a pressure vessel. The storage tank may be made of steel, aluminium, carbon fibre, Kevlar or other materials, or combinations of the above. The fibre materials are considerably lighter than metals but generally more expensive. Metal tanks can withstand a large number of pressure cycles, but must be checked for corrosion periodically. A company has stated to store air in tanks at 4,500 pounds per square inch (about 30 MPa) and hold nearly 3,200 cubic feet (around 90 cubic
metres) of air. The tanks may be refilled at a service station equipped with heat exchangers, or in a few hours at home or in parking lots, plugging the vehicle into an on-board compressor. The cost of driving such a car is typically projected to be around Rs. 60 per 100 km, with a complete refill at the "tank-station" at about Rs. 120 only. The compression, storage and release of the air together are termed as the Compressed Air Technology. This technology has been utilized in different pneumatic systems. This technology has been undergoing several years of research to improve its applications.
WORKING The air-powered car runs on a pneumatic motor that is powered by compressed air stored on board of the vehicle. Once compressed air is transferred into the on board storage tank, it is slowly released to power the car’s pistons The engine that is installed on the compressed air car, uses compressed air which is stored in the car’s tank. The compressed air drives the piston down as the power stroke. At the end of the power stroke, the compressed air is released through the exhaust valves and the exhaust is only air. The motor then converts the air power into mechanical power. That power is then transferred to the wheels and becomes the source of power for the car. ( i.e. the pistons were connected to the wheels through the HERO HONDA bike’s 4 speed transmission.). This modified engine was mounted on a rectangular crossectional frame and a body that looked like a curious crossbreed of a car.
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Modifying the cam shaft of the engine. 1.
COMPRESSED AIR TANK Compressed air tank is one of the most important part of these cars. These tanks hold 0.05m3 of air to 30 bars. It is similar to the tanks used to carry the liquid gas. The tank enjoys the same technology developed to containing natural gas. These tanks do not explode in case of accidents since there are no metals in them if made of carbon fibre. So the selection of material for the storage tank matters much in safety.
PROPERTIES OF AIR CAR ENGINE The properties of air car engine are:
2. ENGINE SPECIFICATIONS Made: HERO HONDA Model: CD100 Stroke: 4 stroke No. of cylinders: Single cylinder Displacement: 110 cc
1. Approximately 0.05 mt3 of compressed air is stored in mild steel tank in the vehicle. 2. The engine is powered by compressed air, stored in the tank at 30bar. In order to reduce weight, The tank can be made of carbon fibre. 3. The expansion of this air pushes the piston and creates movement. The atmospheric temperature is used to reheat the engine and increase the road coverage. 4. The air condition system can be made use of the expelled cold air.
3. THE CHASSIS Based on design principles in aeronautics, engine has put together highly-resistant, yet light, chassis, zinc rods welded together. Using these rods enables us to build a more shockresistant chassis than regular chassis, allowing quick assembly and a more secure. This system helps to reduce manufacture time.
We only need a simple piston-cylinder arrangement with an intlet and an exhaust. But as we know a normal two stroke engine contained several ports and it also had the spark plug which we didn’t require. So, due to the presence of ports in a two stroke engine, it is difficult to get required output from the engine. So, several modifications had to be done on the four stroke engine to suit our purpose.
The
modifications
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4. AIR FILTER The engine works with air taken from the atmosphere. Air is compressed by the off-board compressor or at service stations equipped with a high-pressure compressor. Before compression, the air must be filtered to get rid of any impurities that could damage the engine. Carbon filters are used to eliminate dirt, dust, humidity and other particles which, unfortunately, are found in the air in our cities.
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Providing a suitable connector at the cylinder head. Removing the spark plug from the cylinder head. 3
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improve the mileage and efficiency. In case of leakage or accident, there won’t be any fire. Engine vibrations were very less and sound pollution was also very low. Operating cost is ten times less than that of gasoline engine.
5. REFILLING As these energies are so easy to store Filling stations are setup as for petrol and diesel. The filling of tank of an air car nearly takes 3 to 4 minutes for cars. Either, we can set up a filling equipment too in our house, which is quite cheaper. 6. SPECIAL FEATURES There is absolutely no fuel required and no combustion in the engine cylinder. There is no pollution at all as only air is taken in and air is ejected out. No Heat is generated, as there is no combustion. No engine cooling system is required, like water Pump, radiator, and water Circulating pipes. It was measured practically that the engine exhaust is a cooled air; its temperature was measured as low as 5 degrees Celsius. No air conditioning system in the car is required if used, the exhaust chilled and clean air can be recirculated partly in the car to cool it. The atmospheric temperature can fall down, as the exhaust is a clean and chilled air, so the problem of pollution can be permanently eradicated. Very less maintenance is required as there won’t be any soot formation. Very low cost materials can be used, as there is no heat involvement. Weight of the engine can be reduced in the absence of cooling system and because of lightweight material, which will
7. EMISSION OUTPUT Since the compressed air is filtered to protect the compressor machinery, the air discharged has less suspended dust in it, though there may be carry-over of lubricants used in the engine. The car works when gas expands.
ADVANTAGES Compressed-air vehicles are comparable in many ways to electric vehicles, but use compressed air to store the energy instead of batteries. Their potential advantages over other vehicles include:.
Compressed-air technology reduces the cost of vehicle production by about 20%, because there is no need to build a cooling system, fuel tank, Ignition Systems or silencers. The engine can be massively reduced in size. The engine runs on cold or warm air, so can be made of lower strength light weight material such as aluminium, plastic, low friction Teflon or a combination. Low manufacture and maintenance costs as well as easy maintenance. Compressed-air tanks can be disposed of or recycled with less pollution than batteries. Compressed-air vehicles are unconstrained by the degradation problems associated with current battery systems.
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The air tank may be refilled more often and in less time than batteries can be recharged, with re-filling rates comparable to liquid fuels. Lighter vehicles cause less damage to roads, resulting in lower maintenance cost. The price of filling air powered vehicles is significantly cheaper than petrol, diesel or biofuel. If electricity is cheap, then compressing air will also be relatively cheap.
specialized equipment at service stations may fill the tanks in only 3 minutes.
Tanks get very hot when filled rapidly. SCUBA tanks are sometimes immersed in water to cool them down when they are being filled. That would not be possible with tanks in a car and thus it would either take a long time to fill the tanks, or they would have to take less than a full charge, since heat drives up the pressure.
Early tests have demonstrated the limited storage capacity of the tanks; the only published test of a vehicle running on compressed air alone was limited to a range of 7.22 km (4 mi).
A 2005 study demonstrated that cars running on lithium-ion batteries outperform both compressed-air and fuel cell vehicle more than threefold at same speeds.[10] MDI has recently claimed that an air car will be able to travel 140 km (87 mi) in urban driving, and have a range of 80 km (50 mi) with a top speed of 110 km/h (68 mph) on highways, when operating on compressed air alone.
DISADVANTAGES The principal disadvantage is the indirect use of energy. Energy is used to compress air, which – in turn – provides the energy to run the motor. Any conversion of energy between forms results in loss. For conventional combustion motor cars, the energy is lost when oil is converted to usable fuel – including drilling, refinement, labor, storage, eventually transportation to the end-user. For compressed-air cars, energy is lost when electrical energy is converted to compressed air.
When air expands, as it would in the engine, it cools dramatically (Charles's law) and must be heated to ambient temperature using a heat exchanger similar to the Intercooler used for internal combustion engines. The heating is necessary in order to obtain a significant fraction of the theoretical energy output. The heat exchanger can be problematic. While it performs a similar task to the Intercooler, the temperature difference between the incoming air and the working gas is smaller. In heating the stored air, the device gets very cold and may ice up in cool, moist climates.
POSSIBLE IMPROVEMENTS Compressed-air vehicles operate to a thermodynamic process as air cools down when expanding and heats up when being compressed. As it is not possible in practice to use a theoretically ideal process, losses occur and improvements may involve reducing these, e.g., by using large heat exchangers in order to use heat from the ambient air and at the same time provide air cooling in the passenger compartment. At the other end, the heat produced during compression can be stored in water systems, physical or chemical systems and reused later.
Refueling the compressed-air container using a home or low-end conventional air compressor may take as long as 4 hours, while the 5
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It may be possible to store compressed air at lower pressure using an absorption material within the tank. Absorption materials such as Activated carbon, or a metal organic framework is used to store compressed natural gas at 500 psi instead of 4500 psi, which amounts to a large energy saving.
cost effective and economical for deriving. The storage of compressed air (initially as well as during journey) with all benefits like no heating, high energy density and provisions to make use of cooling produced during adiabatic expansion during the energy release have to be taken care off in a much more controlled manner. Electric-powered cars and bikes already available on the market put a strong competition to compressed air car not only in terms of cost but also their environment friendly role. The technology still looks distant but that has not deterred inventors from working on it.
CONCLUSION It’s important to remember that while vehicles running on only compressed air might seem like a distant dream, but they still have public interest due to their environmental friendly nature. Efforts should be to make them light, safe,
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