3rd Year in Mechanical Engineering
Siddharth Institute of Engineering & Technology, Puttur
Email I.D: bhargavi1093[MENTION=183148]gmail[/MENTION].com
Abstract – Light utility vehicles are becoming very popular means of independent transportation for short distances. Cost and pollution with petrol and diesel are leading vehicle manufacturers to develop vehicles fuelled by alternative energies. Engineers are directing their efforts to make use of air as an energy source to run the light utility vehicles. The use of compressed air for storing energy is a method that is not only efficient and clean, but also economical. The major problem with compressed air cars was the lack of torque produced by the "engines" and the cost of compressing the air. Recently several companies have started to develop compressed air vehicles with many advantages and still many serious bottlenecks to tackle. Gasoline is already the fuel of the past. It might not seem that way as you fill up on your way to work, but the petroleum used to make it is gradually running out. It also pollutes air that's becoming increasingly unhealthy to breathe, and people no longer want to pay the high prices that oil companies are charging for it. Automobile manufacturers know all of this and have spent lots of time and money to find and develop the fuel of the future. Air never runs out. Air is non-polluting. Best of all, air is free. Thus Air Driven cars are an eco-friendly engine which operates with compressed air. An Air Driven car uses the expansion of compressed air to drive the pistons of an engine. It is a pneumatic actuator that creates useful work by expanding compressed air. There is no mixing of fuel with air as there is no combustion. It makes use of Compressed Air Technology for its operation The Compressed Air Technology is quite simple. If we compress normal air into a cylinder the air would hold some energy within it. This energy can be utilized for useful purposes. When this compressed air expands, the energy is released to do work. So this energy in compressed air can also be utilized to displace a piston.
Keywords - Compressed air, pollution free, no heat generation, chassis construction, air powered car
One cannot accurately claim that compressed air as energy and locomotion vector is recent technology. At the end of the 19th century, the first approximations to what could one day become a compressed air driven vehicle already existed, with the arrival of the first pneumatic locomotives.
In fact, two centuries before that Dennis Pippin apparently came up with the idea of using compressed air (Royal Society London, 1687). In 1872 the Mekarski air engine was used for street transit, consisting of a single stage engine. It represented an extremely important advance in terms of pneumatic engines, due to its forward thinking use of thermodynamics, which ensured that the air was heated, by passing it through tanks of boiling water, which also increased its range between fill-ups. Numerous locomotives were manufactured and a number of regular lines were opened up (the first in Nantes in 1879). In 1892, Robert Hardie introduced a new method of heating that at the same time served to increase the range of the engine.
We know that world is facing fuel crisis now. All kinds of conventional fuel sources of fuel are on the verge of exhaustion. Gasoline which has been the main source of fuel for the history of cars is becoming more and more expensive and impractical. These factors are leading car manufacturers to develop car fuelled by alternative energy. The cost is not only the problem it is also damaging the environment eventually. Out of all alternatives air powered car is one possible alternative. Air powered Cars run on compressed air instead of gasoline. This car is powered by 2 gas cylinder engines. Compressed air is stored in glass or fiber tank at a pressure of approximately 4351 psi. This would most likely be the evolution of zero pollution cars.
Compressed Air Technology is now widely preferred for research by different industries for developing different drives for different purposes. The Compressed Air Technology is quite simple. If we compress normal air into a cylinder the air would hold some energy within it. This energy can be utilized for useful purposes. When this compressed air expands, the energy is released to do work. So this energy in compressed air can also be utilized to displace a piston. This is the basic working principle of the Air Driven Engine. It uses the expansion of compressed air to drive the pistons of the engine. So an Air Driven Engine is basically a pneumatic actuator that creates useful work by expanding compressed air. This work provided by the air is utilized to supply power to the crankshaft of the engine. In the case of an Air Driven Engine, there is no combustion taking place within the engine. So it is non-polluting and less dangerous. It requires lighter metal only since it does not have to withstand elevated temperatures.
II. COMPRESSED AIR TECHNOLOGY
Mankind has been making use of uncompressed airpower from centuries in 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 uncont*ained 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 steam 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, both technical and medical, of using ammonia, petrol, or carbon disulphide as the working fluid. Manufacturers claim to have designed engine that is 90 percent efficient. 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 fiber, Kevlar or other materials, or combinations of the above. The fiber 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.
Compressed air is regarded as the fourth utility, after electricity, natural gas, and water. Compressed air can be used in or for:
· Pneumatics, the use of pressurized gases to do work.
· Vehicular transportation using a compressed air vehicle
· Scuba diving
· To inflate buoyancy devices.
· Cooling using a vortex tube.
· Gas dusters for cleaning electronic components that cannot be cleaned with water.
· Air brake (rail) systems
· Air brake (road vehicle) systems
· starting of diesel engines (an alternative to electric starting)
· compressed air breathers (such as Suisse Air)
· Pneumatic air guns
· Pneumatic screwdrivers
It uses the expansion of compressed air to drive the pistons in a modified piston engine. Efficiency of operation is gained through the use of environmental heat at normal temperature to warm the otherwise cold expanded air from the storage tank. This non-adiabatic expansion has the potential to greatly increase the efficiency of the machine.
The only exhaust gas is cold air (−15 °C), which may also be used for air conditioning in a car. The source for air is a pressurized glass or carbon-fiber tank holding air at around 3,000 lbf/in² (20 MPa). Air is delivered to the engine via a rather conventional injection system. Unique crank design within the engine increases the time during which the air charge is warmed from ambient sources and a two stage process allows improved heat transfer rates.
The properties of air car engine are:
· Approximately 90m3 of compressed air is stored in fiber tank in the vehicle.
· The engine is powered by compressed air, stored in a carbon-fiber tank at 30MPa. The tank is made of carbon fiber in order to reduce its weight.
· The engine has injection similar to normal, but uses special crankshaft and piston, which remains at top dead centre for about 700 of crankshaft rotation.
· 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.
· The air condition system makes use of the expelled cold air.
We only needed a simple piston-cylinder arrangement with an outlet 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, several modifications had to be done on the engine to suit our purpose. The modifications comprised of:
· Closing the transfer port
· Closing the inlet port
· Removing the spark plug from the cylinder head
· Providing an inlet at the place of the spark plug
· Providing a suitable connector at the cylinder head.
III. COMPRESSED AIR TANK
Compressed air tank are one of the most important part of these cars. These tanks hold 90m3 of air to 300 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.
IV. BRAKE POWER RECOVERY
The MDI vehicles will be equipped with a range of modern systems. For example, one mechanism stops the engine when the car is stationary (at traffic lights, junctions etc). Another interesting feature is the pneumatic system which recovers about 13% of the power used.
V. THE BODY
The car body is built with fibre and injected foam, as are most of the cars on the market today. This technology has two main advantages: cost and weight. Nowadays the use of sheet steel for car bodies is only because of cost - it is cheaper to serially produce sheet steel bodies than fibre ones. However, fibre is safer (it doesn´t cut like steel), is easier to repair (it is glued), doesn´t rust etc.
VI. THE AIR FILTER
The engine works with both air taken from the atmosphere and air pre-compressed in tanks. Air is compressed by the on-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.
This represents a true revolution in automobiles - it is the first time that a car has produced minus pollution, i.e. it eliminates and reduces existing pollution rather than emitting dirt and harmful gases. The exhaust pipe on the cars produces clean air, which is cold on exit (between -15º and 0º) and is harmless to human life. With this system the air that comes out of the car is cleaner than the air that went in.
VII. THE CHASSIS
Based on its experience in aeronautics, engine has put together highly-resistant, yet light, chassis, aluminium rods glued together. Using rods enables to build a more shock-resistant chassis than regular chassis. Additionally, the rods are glued in the same way as aircraft, allowing quick assembly and a more secure join than with welding. This system helps to reduce manufacture time.
VIII. Electrical system
Guy Nègre, inventor of the MDI Air Car, acquired the patent for an interesting invention for installing electrics in a vehicle. Using a radio transmission system, each electrical component receives signals with a microcontroller. Thus only one cable is needed for the whole car. So, instead of wiring each component (headlights, dashboard lights, lights inside the car, etc), one cable connects all electrical parts in the car. The most obvious advantages are the ease of installation and repair and the removal of the approximately 22 kg of wires no longer necessary. What more, the entire system becomes an anti-theft alarm as soon as the key is removed from the car.
IX. Distribution and valves
To ensure smooth running and to optimize energy efficiency, air engines use a simple electromagnetic distribution system, which controls the flow of air into the engine. This system runs on very little energy and alters neither the valve phase nor its rise. No clutch is necessary. The engine is idle when the car is stationary and the vehicle is started by the magnetic plate, which re-engages the compressed air. Parking manoeuvres are powered by the electric motor. The P04 engine is equipped with patented variable- volume butts and a dynamic variable-volume volumetric reducer. The engines can be equipped with and run on dual energies - fossil fuels and compressed air - and incorporate a reheating mechanism between the storage tank and the engine. This mechanism allows the engine to run exclusively on fossil fuel, which permits compatible autonomy on the road. While the car is running on fossil fuel, the compressor refills the compressed air tanks. The control system maintains a zero-pollution emission in the city at speeds up to 60 km/h.
X. THE SOLENOID VALVE
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid coil. Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas.
For controlling the air flow in and out of the engine we use a 3/2 pilot operated normally closed valve. The symbol of the 3/2 valve is as shown:
The specifications of the valve are the following:
· Orifice: 12mm.
· Operating pressure range: 2-10bar
· Flow rate: 3000Litres/minute
· Coil width: 32mm.
· Voltage: 24V DC
· Duty cycle: Continuous
XI. REFILLING OF AIR
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.
XII. 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 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.
XIII. ADVANTAGES OF AIR DRIVEN ENGINE
· less costly and more effective
· The air engine is an emission-free piston engine that uses compressed air as a source of energy.
· Simple in construction. The engine can be massively reduced in size
· Easy to maintain and repair.
· No fire hazard problem due to over loading. Air, on its own, is non-flammable.
· Low manufacture and maintenance costs
· Comparatively the operation cost is less.
· Light in weight and easy to handle. 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
· Compressed-air tanks can be disposed of or recycled with less pollution than batteries.
· Compressed-air engines are unconstrained by the degradation problems associated with current battery systems.
· 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
· The price of filling air tanks is significantly cheaper than petrol, diesel or bio fuel. If electricity is cheap, then compressing air will also be relatively cheap
· Quick response is achieved.
XIV. RUNNING COST ANALYSIS
Preliminary analysis based on the prototype calculations shows that around three cubic meter of air at a pressure more than 30bar can give a mileage equivalent to one liter of petrol. In India one-liter petrol is Rs 52, and cost of production of one cubic meter of air at a pressure of 50bar is Rs 3. Hence air of Rs 9 can give the mileage of Rs 52 of petrol. However if air is mass compressed and produced the cost will further come down.
The air car which is the result of a long research and development is a clean, easy to drive, high performance car. The end product is a light weight vehicle that can reach speeds up to 220 km/h (even though the legal limit is 120), a product that does not pollute like twentieth century vehicles and does not take a lifetime to pay off. Essentially, MDI has developed a modern, clean, and cheap car that meets most people’s needs.
The principle advantages for an air powered vehicle are:
· Fast recharge time
· Long storage lifetime (electric vehicle batteries have a limited useful number of cycles, and sometimes a limited calendar lifetime, irrespective of use).
· Potentially lower initial cost than battery electric vehicles when mass produced.
The emission benefits of introducing this zero emission technology are obvious. At the same time the well to wheels efficiency of these vehicles need to be improved.
I deem it a rare privilege presenting the paper titled “Air Car” under the guidance of my faculty (Siddharth Institute of Engineering & Technology, Puttur).
I also convey my thanks to Koneru Lakshmaiah College of Engineering for giving me this valuable opportunity.
I specially thank my parents for their best co operation & guidance.