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ABSTRACT
A compressed air engine is primarily an engine that uses the energy stored compressed air to do work. Here the expansion of compressed air stored at high pressure in a storage tank occurs in the engine cylinder to move a piston doing mechanical work. The main application of this engine is in automobile industry where the potential energy of the compressed air is converted into kinetic energy of the linear motion of piston and rotary motion of the crank and the crank shaft. this motion is transferred to the wheels using usual transfer mechanisms .As the working fluid is compressed air there is no requirement of any other fuel other than some amount of electrical energy for compression of air in an electric compressor .The engine is free of emissions at the tail pipe as the only exhaust is air and is environmental friendly. Even though it is below its counter parts in power, comfort and performance, its supporters believe that altered versions of this engine are to dominate the automobile industry in future.
INTRODUCTION
At first glance the idea of running an engine on air seems to be too good to be true. Actually, if we can make use of air as an aid for running an engine it is a fantastic idea. As we all know, air is all around us, it never runs out, it is non-polluting and it is free. An Air compressed Engine makes use of Compressed Air Technology for its operation. 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 compressed Engine. It uses the expansion of compressed air to drive the pistons of the engine. So an Air compressed 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 compressed 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. As there is no combustion taking place, there is no need for mixing fuel and air. Here compressed air is the fuel and it is directly fed into the piston cylinder arrangement. It simply expands inside the cylinder and does useful work on the piston. This work done on the piston provides sufficient power to the crankshaft
LITERATURE REVIEW
COMPRESSED AIR TECHNOLOGY
Air can be compressed into small volumes and can be stored in suitable containers at high pressures. Such air compressed into containers is associated with an amount of energy. When the stored compressed air is released freely it expands thereby releasing the energy associated with it. This energy released can be utilized to provide useful work. 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:
1. Pneumatics, the use of pressurized gases to do work.
2. vehicular transportation using a compressed air vehicle
3. scuba diving
4. To inflate buoyancy devices.
5. Cooling using a vortex tube.
6. Gas dusters for cleaning electronic components that cannot be cleaned with water.
7. air brake (rail) systems
8. air brake (road vehicle) systems
9. starting of diesel engines (an alternative to electric starting)
10. compressed air breathers (such as Suisse Air)
11.pneumatic air guns
12.pneumatic screwdrivers
COMPONENTS
Receiver tank
Air compressor
FOURSTROKE ENGINE
CAM SHAFT
PRESSURE VALVE
HISTORY
In fact, two centuries before that Dennis Papin[6]apparently came up with the idea of using compressed air (Royal Society London, 1687). In 1872 the Mekarski[6] air engine was used for street transit, consisting of a single stage engine. Numerous locomotives were manufactured and a number of
regular lines were opened up (the first in Nantes in 1879). In 1892, Robert Hardie[6] introduced a new method of heating that at the same time served to increase the range of the engine which in turn helped to increase the distance that could be traveled at a stretch. One of its new features was regenerative braking. By using the engine as a compressor during deceleration, air and heat were added to the tanks, increasing the range between fill-ups. However, the first urban transport locomotive was not introduced until 1898, by Hoadley and Knight[6], and was based on the principle that the longer the air
is kept in the engine the more heat it absorbs and the greater its range. As a result they introduced a two stage engine. Charles B. Hodges will always be remembered as the true father of the compressed air concept applied to cars, being the first person, not only to invent a car driven by a compressed air engine but also to have considerable commercial success with it. After twelve years of research and development, Guy Negre has developed an engine that could become one of the biggest technological advances of this century. A French engineer by profession, he has designed a low consumption and low pollution engine for urban motoring that runs on compressed air technology. “air car” from Motor Development International is a significant step for zero emission transport, delivering a compressed air-driven vehicle that is safe, quiet, has a top speed of 110 km/h and a range of 200 km. Guy Nègre is the head of Research and Development at Moteur Development International (MDI) cars, where the Zero Emission Vehicle (ZEV) prototype has been in production since 1994.
Receiver tank
The air is compressed slowly in the compressor. But since the pneumatic system needs continuous supply of air, this compressed air has to be stored. The compressed air is stored in an air receiver as shown in Figure 6.1.2. The air receiver smoothens the pulsating flow from the compressor. It also helps the air to cool and condense the moisture present. The air receiver should be large enough to hold all the air delivered by the compressor. The pressure in the receiver is held higher than the system operating pressure to compensate pressure loss in the pipes. Also the large surface area of the receiver helps in dissipating the heat from the compressed air. Generally the size of receiver depends on,
• Delivery volume of compressor.
• Air consumption.
• Pipeline network
• Type and nature of on-off regulation
• Permissible pressure difference in the pipelines
Compressor:
It is a mechanical device which converts mechanical energy into fluid energy. The compressor increases the air pressure by reducing its volume which also increases the temperature of the compressed air. The compressor is selected based on the pressure it needs to operate and the delivery volume.The compressor can be classified into two main types
a. Positive displacement compressors and
b. Dynamic displacement compressor
Positive displacement compressors include piston type, vane type, diaphragm type and screw type
Diaphragm compressor
These are small capacity compressors. In piston compressors the lubricating oil from the pistons walls may contaminate the compressed air. The contamination is undesirable in food, pharmaceutical and chemical industries. For such applications diaphragm type compressor can be used. the construction of Diaphragm compressor. The piston reciprocates by a motor driven crankshaft. As the piston moves down it pulls the hydraulic fluid down causing the diaphragm to move along and the air is sucked in. When the piston moves up the fluid pushes the diaphragm up causing the ejection of air from the outlet port. Since the flexible diaphragm is placed in between the piston and the air no contamination takes place.