Essay: VALVE TIMING OPTIMIZATION AND CAM REDESIGN FOR COMPRESSED AIR ENGINE

ABSTRACT
In “VALVE TIMING OPTIMIZATION AND REDESIGN OF CAM FOR COMPRESSED AIR ENGINE”. We will try to optimize the timing of inlet and exhaust valve. We will also work on the modified design of CAM-FOLLOWER for compressed air engine (C.A.E) where the engine will run on highly pressurized (Compressed) air. Now a days cost of fuel is major problem for everyone. Moreover pollution occurs by various gasoline fuels is also other major problem to globe. So this whole project will helpful as alternative fuel to the gasoline and diesel which is ENVIRONMENT FRIENDLY as well as ECONOMIC.
 
2. LITERATURE REVIEW
The basic principle of compressed air engine is slightly different from the engines which run on gasoline fuel. In petrol engines, petrol burns itself & produces in the gases which are used to move the piston [1] cylinder arrangement same principle is used in CAE but instead of using petrol only compressed air is used to displacement piston. In CAE compressed air tank is the energy storage medium similar to a fuel tank is gasoline operated vehicles. Compressed air tank is used to supply necessary amount of air to the engine which is required foe engine operation to run the vehicle efficiency the energy. Density of fuel used will be high but in fact compressed air is having less energy density as compressed to conventional fuels &rechargeable batteries. But it is possible to increase energy density of air by with greater storage tank pressure. Various gas lows explain how
Compressed air behaves. Boyles low state that if volume of air halves during compression then pressure is doubled. Also, Charles low state that volume of gas changes in direct proportion to temperature.
1. Stage First-
Compressed air provided by compressor having capacity to produced compressed air up to 10 bar .Air is injected at TDC by injector at the cylinder head. The injected air immediately acquires passage above the piston at that time inlet valve remain open and exhaust valve get closed.
2. Second Stage-
In second stage exhaust valve get opens and inlet valve get closed. So it causes expelling the air to the atmosphere through outlet and piston will move from Bottom Dead Centre to Top Dead Centre.
Original Engine Specifications
For this experiment we use four stroke single cylinder petrol engine made by Hero-Honda Private Limited. It having robust construction and also light weight.
1. Company Name-Hero Honda Private Limited
2. Engine type-Single Cylinder Four Stroke Petrol Engine
3. Power-9.65Hp (7.0Kw) @8000RPM
4. Gearbox-Four Speed
5. Final Drive-Chain
The significant part of experimentation was concentrated on one aspect, Running the engine at different pressures and observing different speed in RPM. The engine was successfully tested at majorly two pressures at 4 bar and 3 bar respectively without load. The pressure required to start the engine is 4bar while engine will be shut off below pressure 1.5bar.
Sr. No. Pressure in Bar Speed in RPM
1. 3-4 bar 1650(Average)
2. 2-3 bar 1600(Average)
Table No.2.1: Pressures & RPM speed
From above table it is clear that engine will gives about 4000RPM at pressure of 10bar without load.
The engine is filled only by the air at high pressure when the [3] piston is at TDC. The pneumatic engine can be simply done by modification of the design of the classic two-stroke engine. The engine does not require the inlet port delivering the air to the crankcase. The crankcase has a vent which causes only small compression of the air. However, the crankshaft is made traditionally with rolling bearing. The lubrication takes place at lower temperatures of the charge and elements. The oiling of the bearings and the cylinder surface is ensured by a small oil pump or by oil drop valve in a close cycle. The schematic idea of the pneumatic two-stroke engine is shown in below figure. The engine has any transfer ports, because delivering of the air is not from the crankcase. Only one exhaust port is used for the gas exchange in the cylinder. The engine has an injector or pneumatic valve controlled by the electronic unit. The bottle of certain volume contains the air at high pressure. The pressure of stored air in the bottle or tank (about 300bar) is reduced by pressure
regulator to smaller injection pressure about 20-30 bar. The pressure is controlled by the sensor and the air is delivered by the pipe of small diameter (about 5-8 mm) to the valve.[2] The air volumetric flow rate through the valve is rather high in comparison to the liquid fuel injection. The use of the electromagnetic stem valve requires high voltage and high electric power. For that case the electromagnetic pneumatic valve used in industry is better solution. The air flow control should enable the high pressure in the cylinder ATDC and on the other hand the opening of the pneumatic valve lasts very short (about 40-60 0deg CA) and for this reason the natural frequency of the moving elements in the valve should be high.
Fig 2.1: two-stroke pneumatic engine
For each mode, the optimum opening timing for charging valve has been determined with a constant closure at TDC. In the specific case of the 2-stroke mode, Inlet Valve Closure and Opening timings were optimized too. The criterion used was to maximize the air sent to the air tank, without worrying about Indicated Work. Indeed, during pneumatic pump mode, energy can be considered without any cost, as there is more energy available than can be stored during each braking phase. Table 1 shows the optimized timings, expressed in crank angle, and Figure 10 displays the effect of the opening timing in the specific case of 4-stroke pneumatic pump mode. (Reference angle is for end exhaust/start inlet TDC.)
4-stroke 4-stroke exhaust-off
2-stroke full variable
Inlet open -10° 710° 35°
Inlet close 190° 190° 190°
Charging open 310° 310° 310°
Charging close 360° 360° 360°
Exhaust open 530° x x
Exhaust close 10° x x
Table No.2.1: Pneumatic pump optimum angles
Table 2 displays the indicated work, the pumped air mass sent to the air tank, and the Specific Pump Consumption (SPC) defined [7] by Equation for each simulated mode. It can be seen that the lower the SPC is; the best the conversion from mechanical energy to pneumatic potential energy.
2.1 Pneumatic Components
2.1.1 CAM Nomenclature
Fig 2.1.1: CAM Nomenclature
Trace point: A theoretical point on the follower, corresponding to the point of a fictitious knife-edge follower. It is used to generate the pitch curve. In the case of a roller follower, the trace point is at the center of the roller.
Pitch curve: The path generated by the trace point at the follower is rotated about a stationary cam.
Working curve: The working surface of a cam in contact with the follower. For the knife-edge follower of the plate cam, the pitch curve and the working curves coincide. In a close or grooved cam there is an inner profile and an outer working curve.
Pitch circle: A circle from the cam center through the pitch point. The pitch circle radius is used to calculate a cam of minimum size for a given pressure angle.
Prime circle (reference circle): The smallest circle from the cam center through the pitch curve.
Base circle: The smallest circle from the cam center through the cam profile curve.
Stroke or throw: The greatest distance or angle through which the follower moves or rotates.
Follower displacement: The position of the follower from a specific zero or rest position (usually it’s the position when the follower contacts with the base circle of the cam) in relation to time or the rotary angle of the cam.
 
2.1.2 VALVE
In four stroke the “Poppet Valve” performed the opening of the cylinder to inlet or exhaust manifold at the correct moment. Generally the face of valve is ground at 45 degree but in some cases it is ground at 30 degree also. It is not important to have a same angle of face in inlet and exhaust valve of same engines. To make it in right order, the valve may be reground after some use. There is some margin provided to avoid sharp edges. The groove, retain the valve spring which aids in keeping the valve pressed against the seat when closed and thus seal the combustion space tightly. In close position, the valve face, fits the accurately matched ground seat in the cylinder block. Generally replaceable ring inserts are used for exhaust valve seat. The inlet valves are made from plain nickel, nickel chrome or chrome molybdenum. Whereas exhaust valves are made from nickel chrome, silicon chrome steel, high speed steel, stainless steel, high nickel chrome, tungsten steel and cobalt chrome steel. A poppet valve (also called mushroom valve is a valve typically used to control the timing and quantity of gas flow into an engine. It consists of a hole, usually round or oval, and a tapered plug.
Fig 2.1.2: VALVE
The poppet valve is fundamentally different from slide and oscillating valves; instead of sliding or rocking over a seat to uncover a port, the poppet valve lifts from the seat with a movement perpendicular to the port. The main advantage of the poppet valve is that it has no movement on the seat, thus requiring no lubrication. Poppet valves are used in most piston engines to open and close the intake and exhaust ports in the cylinder head. The valve is usually a flat disk of metal with a long rod known as the valve stem attached to one side. The stem is used to push down on the valve and open it, with a spring generally used to return it to the closed position when the stem is not being depressed. At high revolutions per minute (RPM), the inertia of the spring makes it too slow to return the valve to its seat between cycles, leading to \’valve float\’. In this situation desmodromic valves are used which, being closed by a positive mechanical action instead of by a spring, are able to cycle at the high speeds required in, for instance, motorcycle and auto racing engines
2.1.3 PISTON AND CYLINDER
A piston is a component of reciprocating engines among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. The piston of an air compressed air is acted upon by the pressure of the expanding compressed air in the space at the top of the cylinder. This force then acts downwards through the connecting rod and onto the crankshaft. The connecting rod is attached to the piston by a swiveling gudgeon pin. This pin is mounted within the piston: unlike the steam engine, there is no piston rod or crosshead. The pin itself is of hardened steel and is fixed in the piston, but free to move in the connecting rod. A few designs use a \’fully floating\’ design that is loose in both components. All pins must be prevented from moving sideways and the ends of the pin digging into the cylinder wall.
Fig 2.1.3: PISTON
Gas sealing is achieved by the use of piston rings. These are a number of narrow iron rings, fitted loosely into grooves in the piston, just below the crown. The rings are split at a point in the rim, allowing them to press against the cylinder with a light spring pressure. Two types of ring are used: the upper rings have solid faces and provide gas sealing; lower rings have narrow edges and a U-shaped profile, to act as oil scrapers. There are many proprietary and detail design features associated with piston rings. A cylinder is the central working part of a reciprocating engine the space in which a piston travels. A cylinder\’s displacement, or swept volume, can be calculated by multiplying its cross-sectional area (the square of half the bore by pi) and again by the distance the piston travels within the cylinder (the stroke). The engine displacement can be calculated by multiplying the swept volume of one cylinder by the number of cylinders.
2.1.4 CRANK SHAFT
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating motion into rotary motion or vice versa. Crank shaft consists of the shaft parts which revolve in the main bearing, the crank pins to which the big ends of the connecting rod are connected, the crank webs or cheeks which connect the crank pins and the shaft parts.
Crank shafts can be divided into two types: 1. Crank shaft with a side crank or overhung crank. 2. Crank shaft with a center crank. A crank shaft can be made with two side cranks on each end or with two or more center cranks. A crank shaft with only one side crank is called a single throw crank shaft and the one with two side cranks or two center cranks as a multi throw crank shaft.
.
Fig 2.1.4: CRANK SHAFT
The overhung crank shaft is used for medium size and large horizontal engines. Its main advantage is that only two bearings are needed, in either the single crank or two crank, crank shafts. Misalignment causes most crank shaft failures and this danger is less in shafts with two bearings than with three or more supports. Hence, the number of bearings is very important factor in design. To make the engine lighter and shorter, the number of bearings in automobiles should be reduced. For the proper functioning, the crank shaft should fulfill the following conditions: 1. enough strength to withstand the forces to which it is subjected i.e. the bending and twisting moments. 2. Enough rigidity to keep the distortion a minimum. 3. Stiffness to minimize. And strength to resist, the stresses due to torsional vibrations of the shaft. 4. Sufficient mass properly distributed to see that it does not vibrate critically at the speeds at which it is operated. 5. Sufficient projected areas of crank pins and journals to keep down the bearing pressure to a value dependent on the lubrication available. 6. Minimum weight, especially in aero engines.
The crank shafts are made much heavier and stronger than necessary from the strength point of view so as to meet the requirements of rigidity and vibrations. Therefore, the weight cannot be reduced appreciably by using a material with a very high strength. The material to be selected will always depend upon the method of manufacture i.e. cast, forged, or built up. Built up crank shafts are sometimes used in aero engines where light weight is very important.
In industrial engines, 0.35 carbon steel of ultimate tensile strength 500 to 525 MPa and 0.45 carbon steel of ultimate tensile strength of about 627 to 780 MPa are commonly used. In transport engines, alloy steel e.g. manganese steel having ultimate strength of about 784 to 940 MPa is generally used. In aero engines, nickel chromium steel having ultimate tensile strength of about 940 to 1100 MPa is generally used.
Failure of crank shaft may occur at the position of maximum bending; this may be at the center of the crank or at either end. In such a condition the failure is due to bending and the pressure in the cylinder is maximal. Second, the crank may fail due to twisting, so the connecting rod needs to be checked for shear at the position of maximal twisting. The pressure at this position is the maximal pressure, but only a fraction of maximal pressure.
 
3. WORKING
3.1 Operation of Pneumatic System
Pneumatic systems are designed to move loads by controlling pressurized air in distribution lines and pistons with mechanical or electronic valves. Air under pressure possesses energy which can be released to do useful work. Examples of pneumatic systems: dentist’s drill, pneumatic road drill, automated production systems.
Pneumatics is a section of technology that deals with the study and application of pressurized gas to produce mechanical motion. Pneumatic systems used extensively in industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically powered compressor powers cylinders, air motors, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to a electric motors and actuators. Pneumatics also has applications in dentistry, construction, mining, and other areas.
Fig 3.1: Pneumatic System
Compressor is the power source of a pneumatic system. It is usually driven by a motor or an internal combustion engine. The compressed air is first stored in a strong metal tank called reservoir. Before entering the cylinders and valves, the compressed air has to pass through the air treatment devices, including air filter to remove dust and moisture, pressure regulator to adjust pressure, and lubricator to spray lubrication oil.
3.2 Valve Timing
The timing gear is connected by chain, gears or a belt to the crankshaft at one end and the camshaft on the other. The timing gear is marked with tiny increments all around its perimeter.
The marks correspond to degrees of timing from the straight-up timing position of the camshaft and crankshaft In order to set an engine\’s timing gear to the correct inclination, the mechanic must confer with the engine manufacturer as well as the camshaft manufacturer. The purpose of timing an engine with the timing gear is to ensure that the valves are opening and closing at the correct time to best fill the cylinder with an air/fuel mixture as well as to release all of the spent fumes from the exhaust cycle of the cylinder. A mere few degrees off on the timing gear can be the difference in an engine that performs perfectly and an engine that will not run correctly. A poor running engine will make less power and use more fuel than a properly-timed engine.
While the timing gear rotates a full 180 degrees, the timing marks are concerned with just a few degrees before and after top dead center of the piston\’s rotation. Top dead center is when the piston is at its absolute highest point of travel within the cylinder or at the top of the stroke at the dead center of when the crankshaft is neither traveling up nor down in the cylinder. The timing gear is used to measure the amount of rotation in degrees in relation.
Fig 3.2: Valve Timing
3.3 Pressure angle
The angle at any point between the normal to the pitch curve and the instantaneous direction of the follower motion. This angle is important in cam design because it represents the steepness of the cam profile.
Fig 3.3: Pressure angle
3.4 Comparison of Valve Timing Diagrams
Suction stroke: Fuel and air mixture introduced into the intake manifold. Inlet valve remains open and Exhaust valve closed as per Valve timing diagram. The piston moves from T.D.C to B.D.C.
Compression: The charge is compressed in the compressed stroke by moving the piston B.D.C to T.D.C. In this stroke both valves are in closed position.
Expansion/Power stroke: The charge is combusted in the combustion chamber which gives power to the engine by means of operating the piston again from T.D.C to B.D.C. In this stroke both valves are in closed position.
Exhaust stroke: The exhaust stroke occurs when spent gases are expelled from the combustion chamber and released to the atmosphere. The exhaust stroke is the final stroke and occurs when the exhaust valve is open and the intake valve is closed.
Fig 3.4.1: Four Stroke Engine Valve Timing Diagram
The working of compressed air engine partially similar with general 4-stroke engine.
Actually there are two strokes:
1. Suction cum Power Stroke
2. Exhaust Stroke
Fig 3.4.2: Compressed Air Engine Valve Timing Diagram
3.5 Advantages and Disadvantages
ADVANTAGES:-
1. Air, on its own, is non-flammable, abundant, economical, transportable, storable and, most importantly, non-polluting.
2. The mechanical design of the engine is simple and robust.
3. Transportation of the fuel would not be required due to drawing power off the electrical grid.
4. This presents significant cost benefits. Pollution created during fuel transportation would be eliminating.
5. Compressed-air tanks can be disposed of or recycled with less pollution than batteries.
6. The tank may be able to be refilled more often and in less time than batteries can be recharged, with refuelling rates comparable to liquid fuels.
DISADVANTAGES:-
1. When air expands, as it would in the engine, it cools dramatically (Charles law) and must be heated to ambient temperature using a heat exchanger similar to the intercooler used for internal combustion engines. This might be problematic if the kit is employed on a full scale automobile.
2. Refuelling the compressed air container using a home or low-end conventional air compressor may take as long as 4 hours (although the specialized equipment at service stations may fill the tanks in only minutes).
3. 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 vehicle 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.
4. The limited storage capacity of the tanks will severely hinder the distance possible to cover with even a fully charged cylinder.
 
3.6 Plan of work
 
4. CALCULATIONS
Considering the calculations of the CAM for the two-stroke compressed air engine as below:
Data for the CAM design are given below:
(1) Inlet cam:
Base Diameter (d1): 50mm
Outer-Stroke (θ1): 120°
Return-Stroke (θ2): 120°
Dwell: 60° & 60°
Stroke length (l): 5mm
Roller Diameter: 20mm
 
(2) Exhaust cam:
Base Diameter (d1): 60mm
Outer-Stroke (θ1): 100°
Return-Stroke (θ2): 100°
Dwell: 80° & 80°
Stroke length (l): 5mm
Roller Diameter: 20mm
 
(3) Final cam:
Base Diameter (d1): 60mm
Outer-Stroke (θ1): 120°
Return-Stroke (θ2): 120°
Dwell: 60° & 60°
Stroke length (l): 50mm
Roller Diameter: 20mm
4.2 Future Plan of work
5. SELECTION OF CAM AND MATERIAL
5.1 SELECTION OF CAM
5.1.1 Roller cam follower
– It can be transfer power efficiently between the cam and follower .
– reducing friction and minimizing wear between them.
– the gravity constraint cam it is simple and effective and can be used with rotating disk or and end cams if the weight follower system is enough constant with cam profile.
5.1.2 Wedge or knife edge cam follower
– knife edge is only theoretical because knife edge follower is never used because of very High . ( wire length 15:29)
– Wear out very fast .
– The sliding motion takes place between the contacting surface ( i.e. the knife edge and cam surfaces)
– It is seldom used in practice because small area of contacting surfaces result excessive wear.
5.1.3 flat cam followers
– side thrust between the follower and guide is much reduced in case.
– friction taken place is higher.
– the only side thrust is due to friction between the contact surfaces of the follower the cam.
– used in where space is limited such as in cams which operate values of automobiles
Engines.
– High surfaces stresses produced.
5.1.4 spherical faced follower
– Minimize these surfaces stresses in this case.
– Nearly point contact occurs between meeting surface of cam & followers.
 
5.2 SELECTION OF CAM MATERIAL
For the improvement of the invention of conventional stand to an automated stand, it requires the material such as wood, iron, steel, copper or other semi conductor. Materials are selected such that it should be effective during the operating conditions, it can be easily available in the markets, it should have optimal price in the market, it should have resistivity from atmosphere or heat generation. The material must have proper machining and mechanical properties with efficient working as per requirement.
The table below will give the information about the list of material with its ultimate tensile strength which gives us idea about the material strength for lifting and carry the load of the two wheeler vehicle.
Name of Material Ultimate tensile strength Ultimate shear strength
Carbon steel 276 MPa 186 MPa
Alloy steel 758 MPa 366 MPa
Stainless steel 515 MPa 552 MPa
Aluminum 310 MPa 207 MPa
 
6 :- IMPLIMENTATION
 First we completed our optimization for new cam valve timing(compressed air engine).after that we decided to make the prototype or we can say modification in present splendor’s engine.so we went to the engine market(KABADI MARKET) to brought a engine.
Fig 6.1: kabadi market
 We got an engine from the kabadi market of Ahmedabad and after that we saw that the engine is required to services and washing.
 So we opened that engine and do services in one garage and got knowledge of construction and working of that engine deeply by the mechanics.
Fig 6.2: engine
Fig 6.3: engine head
 We did service that engine and remove the things which we did not useable for our goal like cam, timing chain, magnet, etc.
 And all exhaust hole filled up with packing so our entire air will not come out of that area.
Fig 6.4: Removable CAM
Fig 6.5: Removable parts
 When engine was in good condition to used then we started a practical on that. But when we did this practical during that time we find a problem of exhaust air.
 So we thought upon that solving problem and then we were guided by that our guide to Added a one extra mechanism of DCV with timing switch which shows in below figure.
Fig 6.6: 24V AC DCV
Fig 6.7: Timing switch with roller follower
 This both things connected with each other and this whole mechanism connected with 12V DC battery.
 And all this things are connected with air pipes. These connected the air compressor to DCV inlet and through DCV outlet connect the engine inlet.
 In the engine we make a spark plug as an air inlet so we remove spark plug also.
Fig 6.8: Air compressor
 After all we connected all this mechanism with its requirement and then started the practical and we got success readings.
 In this our project doing this type of work…first connect the all mechanism and then start the compressor to fill the air in the engine.
 That air enter in the DCV inlet and passed through this DCV enter in the engine with 8-10 bar pressure.
 So the piston will move with its pressure and timing switch is pressed when the inlet valve is open.
 This all are the our project working.
 
7:- SPECIFICATION OF PARTS
NO Parts name Specification
1 Engine Company:- Hero Honda
Model:- Splendor
Type:-4 stroke single cylinder, air cooled
Displacement:- 97.2
Maximum power:- 6.15 KW @8000rpm
Maximum torque:- 0.82kg-m @5000rpm
Bore x stroke:- 50.0 x 49.5mm
Compression ratio:- 9.9:1
Starting:- kick start
Ignition:- dc digital-cdi
Valve train:- poppet valve
Ideal speed:- 1400rpm
Clutch:- Multiplate wet
Gear box:- 4 speed constant mesh
2 Cam Material:- Wooden cam
3 3/2 DCV Model:- 3V210-0
company – Techno
pressure- 0.15-0.8Mpa
Circuit – 24V AC
4 Limit switch 10A , 250V~
16A , 250V~
5 pipe Dimension:- 6mm
Special ideal for Pneumatic pipe
8 :- PROJECTS COSTING
NO Parts Rupees(RS)
1 Engine 2900
2 3/2 dcv 650
3 Pipe 150
4 Limit switch 50
5 Lathe work 750
6 Engine clean 1000
TOTAL 5500
9. CONCLUSION
1. The model designed by us is a small scale working model of the compressed air engine. When scaled to higher level it can be used for driving automobiles independently with other engines like I.C. engines.
2. Utilization of non-conventional energy sources such as compressed air engine we can set a milestone in the field of green technology because it is the demand of the time to adopt green technology
3. Compressed air technology allows for engines that are both non-polluting and economical.
4. Unlike electric and hydrogen powered vehicles compressed air vehicles are not expensive and do not have limiting driving range.
5. Compressed air vehicles are easy to get around in cities and have performance rate that stands up to current standards.
6. After ten years of research and development, the compressed air vehicle will be introduced worldwide.
7. 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.
 
10. FUTURE SCOPE
On the market for 10 years or so, the air-powered car is struggling to find a space among other clean car technologies. Will the arrival of the new AIRPod model from the company Motor Development International (MDI) change the future of this kind of vehicle? An initiative that should be welcomed at a time when technological innovations are dramatically, and permanently, changing the face of the automotive sector.
The latest developments in the history of the air-powered car, whereas its future on the market did appear less than certain, the launch of a new model from the company MDI has now opened up new opportunities in France and worldwide.
Let’s come back to the history of Motor Development International (MDI), founded in 1991 by Luxemburger Guy Nègre. For more than 10 years, the company has been trying to make a name for itself with an engine for urban vehicles that is capable of functioning on compressed air.
Air-powered cars are non- polluting and run thanks to an on-board compressor connected to a socket in order to produce air. The compressed air is then sent into a cylinder in order to propel a piston linked to a crankshaft.
Such a system also permits the use of bi-energy sources. As with hybrid models the cars can increase their range with the use of Petrol.
Compressed Air Engine will be make revolution in automobile industry. This engine having many advantages than the conventional engines .With some modifications it will give better performance than the conventional engines. This engine having minimum disadvantages and cheap. So in future compressed air engine will be give the better option for the conventional engines.