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CONTENTS

1. Introduction

1.1 Abstracts 3

1.2. Compressed air engine basics 4

1.3. History 5

1.4. Applications 6

1.5. Advantages 7

1.6. Disadvantages 8

2. Literature Review

2.1. Description of Mechanical Components 10-19

2.2. Description of Valve Mechanism Implemented 20-25

2.3. Study of Compressed Air Engine and its Working 26-28

3. Design and Fabrication

3.1. Design of Piston Cylinder 30

3.2. Design of Connecting Rod 30-32

3.3. Design of Crank Shaft 33-35

3.4. Design of Valve Mechanism 36

3.5. Design of Cam and Follower 37

3.6. Fabrication of Model 38-51

4. Problems Faced 52

5. Solutions Adapted 53

6. Conclusion 54

7. References 55

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Chapter 1: Introduction

1.1. Abstract

1.2. Compressed Air Engine Basics

1.3. History

1.4. Applications

1.5. Advantages

1.6. Disadvantages

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1.1 Abstracts:

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.

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1.2 Compressed Air Engine Basics:

A Compressed-air engine is a pneumatic actuator that creates useful work by expanding

compressed air. A compressed-air vehicle is powered by an air engine, using compressed air,

which is stored in a tank. 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.

They have existed in many forms over the past two centuries, ranging in size from hand held

turbines up to several hundred horsepower. For example, the first mechanically-powered

submarine, the 1863 Plongeur, used a compressed-air engine.

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 cargo.

Some types rely on pistons and cylinders, others use turbines. Many compressed air engines

improve their performance by heating the incoming air, or the engine itself. Some took this a

stage further and burned fuel in the cylinder or turbine, forming a type of internal combustion

engine.

One manufacturer claims to have designed an engine that is 90 percent efficient. Compressed

air propulsion may also be incorporated in hybrid systems, e.g., battery electric propulsion

and fuel tanks to recharge the batteries. This kind of system is called hybrid-pneumatic

electric propulsion. Additionally, regenerative braking can also be used in conjunction with

this system.

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1.3 History:

a) The first compressed-air vehicle was devised by Bompas, a patent for a locomotive being

taken out in England in 1828. There were two storage tanks between the frames, with

conventional cylinders and cranks. It is not clear if it was actually built. (Knight, 1880)

b) The first recorded compressed-air vehicle in France was built by the Frenchmen Andraud

and Tessie of Motay in 1838. A car ran on a test track at Chaillot on the 9th July 1840, and

worked well, but the idea was not pursued further.

Fig: 1.1

c) In 1848 Barin von Rathlen constructed a vehicle which was reported to have been driven

from Putney to Wands worth (London) at an average speed of 10 to 12 mph.

d ) At the end of 1855, a constructor called Julienne ran some sort of vehicle at Saint-Denis in

France, driven by air at 25 atmospheres (350 psi), for it to be used in coal mines.

e) Compressed air locomotives were use for haulage in 1874 while the Simplon tunnel was

being dug. An advantage was that the cold exhaust air aided the ventilation of the tunnel.

f) Louis Mékarski built a standard gauge self-contained tramcar which was tested in February

1876 on the Courbevoie-Etoile Line of the Paris Tramways Nord (TN), where it much

impressed the current president and minister of transport Maréchal de Mac Mahon. The

tramcar was also shown at the exhibition of 1878 as it seemed to be an ideal transport

method, quiet, smooth, without smoke, fire or the possibility of boiler explosion.

g) The compressed-air locos were soon withdrawn due to a number of accidents, possibly

caused by icing in the pipes of the brakes, which were also worked by compressed air.

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1.4 Applications:

The compressed air engine can be used in many vehicles. Some of its applications to be used

as engine for vehicles are:

a) Mopeds Jem Stansfield, an English inventor has been able to convert a regular scooter to a

compressed air moped. This has been done by equipping the scooter with a compressed air

engine and air tank.

b) Buses MDI makes Multi CATs vehicle that can be used as buses or trucks. RATP has also

already expressed an interest in the compressed-air pollution-free bus.

c) Locomotives Compressed air locomotives have been historically used as mining

locomotives and in various areas.

d) Trams Various compressed-air-powered trams were trialed, starting in 1876 and has been

successfully implemented in some cases.

e) Watercraft and aircraft currently, no water or air vehicles exist that make use of the air

engine. Historically compressed air engines propelled certain torpedoes.

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1.5 Advantages:

The advantages are well publicised since the developers need to make their machines

attractive to investors. 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:

a) Much like electrical vehicles, air powered vehicles would ultimately be powered through

the electrical grid, which makes it easier to focus on reducing pollution from one source, as

opposed to the millions of vehicles on the road.

b) Transportation of the fuel would not be required due to drawing power off the electrical

grid. This presents significant cost benefits. Pollution created during fuel transportation

would be eliminated.

c) 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.

d) Air, on its own, is non-flammable.

e) High torque for minimum volume.

f) The mechanical design of the engine is simple and robust.

g) Low manufacture and maintenance costs as well as easy maintenance.

h) Compressed-air tanks can be disposed of or recycled with less pollution than batteries.

i) Compressed-air vehicles are unconstrained by the degradation problems associated with

current battery systems.

j) The tank may be able to be refilled more often and in less time than batteries can be

recharged, with re-fuelling rates comparable to liquid fuels.

k) Lighter vehicles would mean less abuse on roads. Resulting in longer lasting roads.

l) The price of fuelling air-powered vehicles will be significantly cheaper than current fuels.

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1.6 Disadvantages:

Like the modern car and most household appliances, 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, labour, storage, eventually transportation to the end-user. For compressed-air

cars, energy is lost when electrical energy is converted to compressed air.

a) 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. 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.

b) Refuelling the compressed air container using a home or low-end conventional air

compressor may take as long as 4 hours though the specialized equipment at service stations

may fill the tanks in only 3minutes.

c) 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.

d) 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.

e) A 2005 study demonstrated that cars running on lithium-ion batteries out-perform both

compressed air and fuel cell vehicles more than three-fold at same speeds. MDI has recently

claimed that an air car will be able to travel 140km in urban driving, and have a range of 80

km with a top speed of 110km/h on highways, when operating on compressed air alone.

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Chapter 2: Literature Review

2.1 Description of Mechanical Components

2.2 Description of Valve Mechanism Implemented

2.3 Study of Compressed Air Engine and its Working

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2.1 Description of Mechanical Components:

Various Mechanical parts used in engine are:

1. Crank shaft

2. Connecting rod

3. Piston

4. Cylinder

5. Valves

6. Roller bearing

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2.1.1 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.

Fig. 2.1.1 Crank Shaft

Crank shafts can be divided into two types:

1. Crank shaft with a side crank or overhung crank.

2. Crank shaft with a centre crank.

3. A crank shaft can be made with two side cranks on each end or with two or more centre

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 centre cranks as a multi throw 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 fulfil 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.

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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 525MPa and 0.45

carbon steel of ultimate tensile strength of about 627 to 780MPa 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 about940 to 1100 MPa is generally used.

Failure of crank shaft may occur at the position of maximum bending; this may be at the

centre 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.

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2.1.2. Connecting rod:

Connecting rod is a part of the engine which is used to transmit the push and pull from the

piston pin to the crank pin. In many cases, its secondary function is to convey the lubricating

oil from the bottom end to the top end i.e. from the crank pin to the piston pin and then for

the splash of jet cooling of piston crown. The usual form of connecting rod used in engines

has an eye at the small end for the piston pin bearing, a long shank, and a big end opening

which is usually split to take the crankpin bearing shells. The connecting rods of internal

combustion engine are mostly manufactured by drop forging. The connecting rod should

have adequate strength and stiffness with minimum weight. The materials for connecting rod

range from mild or medium carbon steel to alloy steels.

In industrial engines, carbon steel with ultimate tensile strength ranging from550 to 670 MPa

is used. In transport engines, alloy steel having a strength of about 780 to 940 MPa is used

e.g., manganese steel. In aero engines, nickel chrome steel having ultimate tensile strength of

about 940 to 1350 MPa is most commonly used.

For connecting rod of low speed horizontal engines, the material may be some times steel

castings. For high speed engines, connecting rod may also be made up of duralumin

and aluminium alloys.

The usual shape of connecting rod is:

Rectangular

Circular

Tubular

I section

H section

In low speed engines, the section is usually circular with flattened sides, or rectangular, the

larger dimension being in the plane of rotation. In high speed engines, lightness of connecting

rod is a major factor. Therefore tubular, I-section or H-section rods are used.

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Fig.2.1.2 Connecting Rod

The length of the connecting rod depends upon the ratio of connecting rod length and stroke

i.e. l/r ratio; on l/r ratio depends the angularity of the connecting rod with respect to the

cylinder centre line. The shorter the length of the connecting rod l in respect to the crank

radius r, the smaller the ratio l/r, and greater the angularity. This angularity also produces a

side thrust of the piston against the liner. The side thrust and the resulting wear of the liner

decreases with a decrease in the angularity. However, an increase of l/r ratio increases the

overall height of the engine. Due to these factors, the common values of l/r ratio are 4 to

5.The stresses in the connecting rod are set up by a combination of forces.

The various forces acting on the connecting rod are:

1. The combined effect of gas pressure on the piston and the inertia of the reciprocating parts.

2. Friction of the piston rings and of the piston.

3. Inertia of the connecting rod.

4. The friction of the two end bearings i.e. of the piston pin bearing and the crank pin bearing.

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2.1.3 Piston

A piston is a component of reciprocating engines, reciprocating pumps, gas

compressors and pneumatic cylinders, 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. In a pump, the function is reversed and force is

transferred from the crankshaft to the piston for the purpose of compressing or ejecting

the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and

uncovering ports in the cylinder wall.

Types of Piston:

1. Trunk pistons

2. Crosshead pistons

3. Slipper pistons

4. Deflector pistons

Fig.2.1.3 Piston

Pistons are cast from aluminium alloys. For better strength and fatigue life, some racing

pistons may be forged instead. Early pistons were of cast iron, but there were obvious

benefits for engine balancing if a lighter alloy could be used. To produce pistons that could

survive engine combustion temperatures, it was necessary to develop new alloys such as Y

alloy and Hiduminium, specifically for use as pistons.

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2.1.4 Cylinder

A cylinder is the central working part of a reciprocating engine, the space in which

a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine

block, which is typically cast from aluminum or cast iron before receiving precision machine

work. Cylinders may be sleeved (lined with a harder metal) or sleeveless (with a wear-

resistant coating such as Nikasil).

A cylinder's displacement, or swept volume, can be calculated by multiplying its cross-

sectional area (the square of half the bore bypi ) 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.

Presented mathematically,

Fig.2.1.4 Cylinder

A piston is seated inside each cylinder by several metal piston rings fitted around its

outside surface in machined grooves; typically two for compressional sealing and one

to seal the oil. The rings make near contact with the cylinder walls (sleeved or

sleeveless), riding on a thin layer of lubricating oil; essential to keep the engine from

seizing and necessitating a cylinder wall's durable surface.

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2.1.5 Valve:

A valve is a device that regulates, directs or controls the flow of a fluid (gases, liquids,

fluidized solids, or slurries) by opening, closing, or partially obstructing various

passageways. Valves are technically valves fittings, but are usually discussed as a separate

category. In an open valve, fluid flows in a direction from higher pressure to lower pressure.

The simplest, and very ancient, valve is simply a freely hinged flap which drops to obstruct

fluid (gas or liquid) flow in one direction, but is pushed open by flow in the opposite

direction. This is called a check valve, as it prevents or "checks" the flow in one direction.

Valves have many uses, including controlling water for Irrigation, industrial uses for

controlling processes, residential uses such as on / off & pressure control to dish and clothes

washers & taps in the home. Even aerosols have a tiny valve built in. Valves are also used in

the military & transport sectors.

Valves are found in virtually every industrial process, including water & sewage processing,

mining, power generation, processing of oil, gas & petroleum, food manufacturing, chemical

& plastic manufacturing and many other fields.

Types (General):

1. BALL

2. BUTTER-FLY

3. GATE

4. GLOBE

5. NEEDLE

6. PLUG

7. SPHERICAL

8. FIXED CONE

9. NON-RETURN (CHECK) VALVE

Fig.2.1.5 Valve

Valves may be operated manually, either by a handle, lever, pedal or wheel. Valves may also

be automatic, driven by changes in pressure, temperature, or flow. These changes may act

upon a diaphragm or a piston which in turn activates the valve, examples of this type of valve

found commonly are safety valves fitted to hot water systems or boilers.

More complex control systems using valves requiring automatic control based on an external

input (i.e., regulating flow through a pipe to a changing set point) require an actuator. An

actuator will stroke the valve depending on its input and set-up, allowing the valve to be

positioned accurately, and allowing control over a variety of requirements.

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2.1.6. Bearing:

The concept behind a bearing is very simple: Things roll better than they slide. The wheels on

your car are like big bearings. If you had something like skis instead of wheels, your car

would be a lot more difficult to push down the road. That is because when things slide,

the friction between them causes a force that tends to slow them down. But if the two

surfaces can roll over each other, the friction is greatly reduced.

Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and

outer metal surface for the balls to roll against. These balls or rollers "bear" the load, allowing

the device to spin smoothly.

Working of a Bearing:

As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are

rolling they have a much lower coefficient of friction than if two flat surfaces were rotating

on each other.

Ball bearings tend to have lower load capacity for their size than other kinds of rolling-

element bearings due to the smaller contact area between the balls and races. However, they

can tolerate some misalignment of the inner and outer races.

Compared to other rolling-element bearings, the ball bearing is the least expensive, primarily

because of the low cost of producing the balls used in the bearing.

Types of Bearings:

There are many types of bearings, each used for different purposes. These include ball

bearings, roller bearings, ball thrust bearings, roller thrust bearings and tapered roller thrust

bearings.

Cut away view of a ball bearing cut away view of various bearings:

Fig.2.1.6(a) Ball bearing Fig.2.1.6(b) Roller Thurst bearing

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Fig.2.1.6(c) Roller bearing Fig.2.1.6(d) Ball Thrust Bearing

Fig2.1.6 (e) Tapered Roller bearing

Bearing Used:

In the compressed air engine being fabricated by us, in place of bearings BUSH are used as it

made the fabrication process more simple and the project work less costly.

Hence the bush used in place of bearing is the cut section of pipe pieces used for making

bench and stools, and on filing it from inside by a round file we used the pipe as bush in place

of bearing in our compressed air engine.

Fig.2.1.6(f) Bush bearing Fig.2.1.6(g) Bush used

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2.2 Description of Valve Mechanism Implemented:

Valve mechanism implemented in current compressed air vehicles are SOLENOID

VALVES.

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 may have two or

more ports: in the case of a two-port valve the flow is switched on or off; in the case of a

three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid

valves can be placed together on a manifold.

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.

Solenoids offer fast and safe switching, high reliability, long service life, good medium

compatibility of the materials used, low control power and compact design.

A solenoid valve has two main parts: the solenoid and the valve. The solenoid converts

electrical energy into mechanical energy which, in turn, opens or closes the valve

mechanically. A direct acting valve has only a small flow circuit, shown within section E of

this diagram. This diaphragm piloted valve multiplies this small flow by using it to control

the flow through a much larger orifice.

Solenoid valves may use metal seals or rubber seals, and may also have electrical interfaces

to allow for easy control. A spring may be used to hold the valve opened or closed while the

valve is not activated.

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The solenoid valve described above is not been used in our project, though its very effective

and precise mechanism the reason why we didn’t implement the solenoid valve in our

compressed air engine are:-

The solenoid valve is an electrically operated device.

It need electric power source such as battery and dynamo.

It has some complicated electronic system which needs programming.

It is also a costly device.

MECHANICALLY OPERATED VALVE MECHANISM:-

The mechanically operated valve mechanism is a cam follower type valve mechanism which

is being used in our compressed air engine. The various parts are as follows:-

2.2.1-Cam

2.2.2-Follower

2.2.3-Push rod

2.2.3-Valve Actuator:-

a. Reciprocating part

b. Stationary part

2.2.1 Cam:

A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming

rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel (e.g. an

eccentric wheel) or shaft (e.g. a cylinder with an irregular shape) that strikes a lever at one or

more points on its circular path. The cam can be a simple tooth, as is used to deliver pulses of

power to a steam hammer, for example, or an eccentric disc or other shape that produces a

smooth reciprocating (back and forth) motion in the follower, which is a lever making contact

with the cam.

The most commonly used cam is the plate cam which is cut out of a piece of flat metal or

plate. Here, the follower moves in a plane perpendicular to the axis of rotation of the

camshaft.

Fig 2.2.1 Cam

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2.2.2 Cam Follower:

A cam follower, also known as a track follower, is a specialized type of roller or needle

bearing designed to follow cams. Cam followers come in a vast array of different

configurations, however the most defining characteristic is how the cam follower mounts to

its mating part; stud style cam followers use a stud while the yoke style has a hole through the

middle.

While cam and followers appear to be very similar to roller bearings in construction they

have quite a few differences. Standard ball and roller bearings are designed to be pressed into

a rigid housing, which provides circumferential support. This keeps the outer race from

deforming, so the race cross-section is relatively thin. In the case of cam followers the outer

race is loaded at a single point, so the outer race needs a thicker cross-section to

reduce deformation.

Fig. 2.2.2 Cam Follower

2.2.3 Push Rod:

A push rod is a part of an internal combustion engine that rests in the top of a valve lifter and

goes up into the rocker arm. As the lifter follows the cam lobe, the push rod actuates the

rocker arm and moves the valve, opening and closing it to allow fuel and air in and exhaust

out of the combustion chamber. The push rod, being hollow, also channels oil up from the

lifter and out of the rocker arm. This oil cools the valve spring as well as lubricates the rocker

arm.

On some vehicles, the push rod operates within the constraints of a valve guide. On these

applications, the push rod must be hardened to withstand the contact of rubbing the guide

plate. If the push rod is not hardened, it would be ground thin and would bend. By hardening

the rod, it can tolerate the friction with no ill effects or damage.

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2.2.4 Valve Actuator:

Valve actuator used in our project is the pressure distributor which actuates by the action of

cam via push rod. It has two parts, one is the stationary part which acts as the junction for the

inlet outlet manifolds and the reciprocating part which follows the cam and actuates the

mechanical valve according to the valve timing.

The Stationary Part:

The stationary part is a junction of eight ports for inlet outlet manifold.

The stationary part is machined from a cuboidal metal piece of 30x30x150 mm. This contains

a hole of 13.5mm dia upto 136 mm depth in which the reciprocating part of the valve actuator

reciprocates with maximum displacement of 16mm and actuates the mechanical valve.

The stationary part contains 8 ports and their functions are as follows:-

PORT1- Inlet for cylinder 1

PORT2- Exhaust for cylinder 1

PORT3- Exhaust for cylinder 2

PORT4- Inlet for cylinder 2

PORT5- Inlet from pressure cylinder

PORT6- Exhaust to atmosphere from cylinder 2

PORT7- Exhaust to atmosphere from cylinder 1

PORT8- Inlet from pressure cylinder

Fig. 2.2.4 (a) Stationary part of valve actuator

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Reciprocating Part:

Reciprocating part is the front portion of push rod which have several grooves for actuation

of different ports in the stationary part of valve mechanism. The grooves are positioned in

such a manner that it actuates the different valves in different time according to the

movement of the cam.

Valve activity according to crank angle:-

Crank Angle

Inlet cyl.1

Exhaust cyl.1

Inlet cyl.2

Exhaust cyl.2

00

Closed

closed

closed

closed

900

Open

closed

closed

open

1800

Closed

closed

closed

closed

2700

Closed

open

open

closed

Fig. 2.2.4 (b) Reciprocating part of Mechanical Valve

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 25

Valve Position at different crank angle:-

Fig. 1- At 00 Crank angle

Fig. 2- At 900 crank angle

Fig. 3-At 1800

Crank Angle

Fig. 4- At 2700 Crank angle

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2.3. Study of the Compressed Air Engine and its Working:

A compressed-air vehicle is powered by an air engine, using compressed air, which is stored

in a tank. 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.

Compressed air propulsion may also be incorporated in hybrid systems, e.g., battery electric

propulsion and fuel tanks to recharge the batteries. This kind of system is called hybrid-

pneumatic electric propulsion. Additionally, regenerative braking can also be used in

conjunction with this system.

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 first air cars will have air compressors built into them. After a brisk drive, you'll be able

to take the car home, put it into the garage and plug in the compressor. The compressor will

use air from around the car to refill the compressed air tank

Unfortunately, this is a rather slow method of refueling and will probably take up to two

hours for a complete refill. If the idea of an air car catches on, air refueling stations will

become available at ordinary gas stations, where the tank can be refilled much more rapidly

with air that's already been compressed. Filling your tank at the pump will probably take

about three minutes.

The first air cars will almost certainly use the Compressed Air Engine (CAE) developed by

the French company, Motor Development International (MDI). Air cars using this engine will

have tanks that will probably hold about 3,200 cubic feet (90.6 kiloliters) of compressed air.

The vehicle's accelerator operates a valve on its tank that allows air to be released into a pipe

and then into the engine, where the pressure of the air's expansion will push against the

pistons and turn the crankshaft. This will produce enough power for speeds of about 35 miles

(56kilometers) per hour. When the air car surpasses that speed, a motor will kick into operate

the in-car air compressor so it can compress more air on the fly and provide extra power to

the engine. The air is also heated as it hits the engine, increasing its volume to allow the car

to move faster.

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India's Tata Motors will likely produce the first air car in the marketplace in the next few

years. Tata Motors' air car will also use the CAE engine. Although Tata announced in August

2008 that they aren't quite ready to roll out their air cars for mass production, Zero Pollution

Motors still plans to produce a similar vehicle in the United States. Known collectively as the

Flow AIR, these cars will cost about $17,800. The company, based in New Paltz, N.Y., says

that it will start taking reservations in mid-2009 for vehicle deliveries in 2010. The company

plans to roll out 10,000 air cars in the first year of production. MDI also recently unveiled the

joystick-driven Air Pod, the newest addition to its air car arsenal. Although the Air Pod

generates a top speed of only 43 mph, it's also extremely light and generates zero emissions.

Major automobile makers are watching the air car market with interest. If the first models

catch on with consumers, they'll likely develop their own air car models. At present, a few

smaller companies are planning to bring air cars to the market in the wake of the MDI-based

vehicles.

These include:

K'Airmobiles

French company K'Air Energy has built prototypes of an air-fuelled bicycle and light road

vehicle based on the K'air air compression engine

Air Car Factories SA

This Spanish company has an air car engine currently in development. The company’s owner

is currently involved in a dispute with former employer MDI over the rights to the

technology.

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Working of Compressed Air Engine:

Fig. Assembly view of compressed air engine

At initial position consider the piston 1 to be at TDC position while piston2 is at

BDC.

In above position inlet manifold of piston2 opens while outlet manifold of piston1

opens.

High compressed air is feed in piston2 from compressed air cylinder at the same time

air from piton1 is released into atmosphere as exhaust, in this process piston 1 moves

from TDC to BDC releasing exhaust into atmosphere and Piston 2 moves from BDC

to TDC i.e. expansion or power stroke is going on in Piston 2.

Above same procedure is repeated again with piston1 and piston2.

The compressed air engine acts as a two stroke engine as in every rotation of crank

power stroke is obtained and the power is obtained at the crank shaft.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 29

Chapter3: Design and Fabrication

3.1. Engine Specifications

3.2. Design of Piston Cylinder

3.3. Design of Connecting Rod

3.4. Design of Crank Shaft

3.5. Design of Cam and Follower

3.6. Fabrication of Model

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3.1. Engine Specification:

Cylinder:-

Bore dia. =38mm

Stroke length =160mm

Cylinder length =180mm

Cylinder thickness =1.5 mm

Cylinder material =Medium Carbon Steel

Cylinder material property (young’s modulus) E =210GPa

Cylinder head thickness =2mm

Piston:-

Piston material = sulphurised rubber

Piston dia = 38mm

Connecting rod:-

Rod section = circular section

Rod dia. = 12mm

Rod length = 200mm

Rod material = cast iron

Crank shaft:-

Shaft dia. = 16mm

Crank radius = 80mm

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3.2. Design of Piston Cylinder:

Designing a piston cylinder for the following requirements:

Power: = 90W

Working Pressure: 5 Bar = 5x 105 N/m

2

Step 1: Finding the appropriate Length of Stroke:

Bore Dia: 38 mm = 0.038m

Speed of Engine: 60rpm

Length of Stroke:

Power (P) = Pressure (p) x Volume x Speed of Engine

90 = 5x105 x 3.14/4 x0 .038

2 x Ls x60

Ls = 160mm

Step 2: To select the thickness of cylinder:

For thin cylinder t/d ratio should be smaller than 1/15

i.e. t/d < 1/15

where,

t : Thickness of cylinder wall

d: Bore Dia

In case of the bore dia being 38 mm, the thickness of the cylinder wall to be taken as thick

cylinder should be smaller than 2.5 mm. We consider the thickness to be 1.5mm.

Hence the design is appropriate according to thin cylinder.

Therefore,

Outer Diameter (d0) = 38 + 2 x 1.5 = 41 mm

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Step 3: Thickness of Cylinder Head:

The thickness of the cylinder cap or cylinder head secured firmly to the cylinderis given by,

T = Di ×[ 𝑃𝑖

6 σt]1/2

Where,

σt: Allowable working stress on the cover plate for Cast Iron,

σt = 20.6 MN/m2

So, T = Di ×[ 𝑃𝑖

6 σt]1/2

T =0.159 cm

T = 1.59 mm

Taking factor of safety 1.5 the cylinder head thickness taken is 2mm.

hence the design is safe.

Step 4: Design of Piston :

The piston used for compressed air engine is of high strength rubber of 800psi which means it

has a strength of about 5.52 N/m2, and the pressure to which the piston is acted upon is of 5

bar, hence the piston head is safe under design parameters.

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3.3 Design of connecting rod:

CASE I:

As the cylinder is to be used as pneumatic cylinder, there should be negligible clearance

between the cylinder and the piston as this could lead to leakage of air. So the diameter

of piston is taken to be same as that of the bore dia. of the cylinder.

So,

Dia of piston = 38mm

And,

Dia of piston rod is given as

d = di ×[ 𝑃𝑖

σt∗]1/2

Now,

For σt* Using Cast Iron as the material for piston rod

σut = 450 MN/m2

σt = 1/8 x 450

= 56.25 MN/m2

And, for double acting cylinder, the factor of safety is taken as 10.So, Actual working tensile

stress in piston rod,

σt* =σt/10

= 56.25 / 10

= 5.62 MN/m2

Therefore,

Dpr = di ×[ 𝑃𝑖

σt∗]1/2

= 11.32mm

According to design calculation the piston rod diameter is 11.32mm, and the actual piston rod

dia. taken is 12mm hence the dimension is safe under design parameters.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 34

CASE II:

Section of rod:

In the plane of motion, the ends of the rod are direction free and so freely hinged at the piston

pin and crank pin. Hence for buckling about the neutral axis xx, the strut is freely hinged. In

the plane, perpendicular to the plane of motion, for buckling about the axis yy , the strut is

fixed ended due to the constraining effect of the bearings at piston and crank pins, therefore ,

for buckling about axis yy, the rod is four times as strong as for buckling about axis xx. But

the rod should be equally strong in both the planes,

Fig 3.3 section of connecting rod

Since area of section of Connecting rod is circular,

Therefore, moment of Inertia of the connecting rod about XX-axis & YY-axis would be

same.

i.e. Ixx = Iyy

Now, Moment of Inertia of the circular section about XX-axis:

Ixx = π×d4/64

Ixx = π×124/64

Ixx = 1017.87 mm4

Ixx = Iyy = 1017.87mm4

Area of section = π x 122

/4

= 113.097 mm2

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 35

And, K2

xx = Ixx/A

= 1017.87 / 113.097

= 8.99 mm2

The connecting rod is subjected to buckling load, hence the buckling load acting on the

connecting rod is given by Euler’s buckling Equation ,

Where,

F = Euler load

E = young’s modulus

I = Moment of Inertia

K = Column effective length factor, whose value depends on the conditions of end

support of the column, as follows.

For both ends pinned (hinged, free to rotate), = 1.0.

For both ends fixed, = 0.50.

For one end fixed and the other end pinned, = 0.699....

For one end fixed and the other end free to move laterally, = 2.0.

L =Length of connecting rod

In our project the both ends of connecting rod are hinged

Hence K =1.0

And,

F = π2×1.8×105×1017.87 /200

2

F = 4.5 x 104

N

Therfore the compressive stress on the connecting rod is

σc = F/ Area

= 4.5 x 104

/ 113.09

= 397.88 N/mm2

As the material of connecting rod is of cast iron having strength 450 N/mm2.

Hence the design is safe.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 36

3.4. Design of Crank Shaft:

Crank shaft is subjected to the twisting load acting on it due to the rotation of the crank and

resistance of wheel against movement of crank.

Hence finding the twisting moment on the crank shaft,

Power output of engine is = 93 W

Power P = 2π x N x T

60

Where,

P = power

N= rpm

T= torque

95 = 2π x 120 x T

60

T = 7.4 Nm

We also know from Torsional Formula,

T = ι = Gθ

J r l

Therefore shear stress ι = T x r

J

= 7.5 x 0.008

6.4 x 10-9

= 9.3 x 10 6 N/m

2

Hence the design is safe under torsional load.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 37

3.5 Design of Cam and Follower:

In our project on fabrication of Compressed Air Engine we have used mechanical valve

instead of solenoid valve and hence to actuate the mechanical valve a linear deflection of

16mm is required to reciprocate the reciprocating part of the mechanical valve.

To fulfill the above requirement a cam and follower arrangement is given.

Cam is fabricated from a piece of steel plate, which was first machined to form a circular disc

of 6mm thickness and for the required linear deflection of 16mm, eccentricity in the circular

disc is given so that it can fulfill the requirement of mechanical valve on rotation of the crank

shaft.

Calculation For Eccentricity:

Dia. Of Cam circle = 36mm

Linear displacement required =16mm

The eccentric centre divides the cam circle

diameter into two parts,

let first part be X.

Then, other part will be X+16.

Now,

X + (X + 16) =36

X =10mm Fig. Cam

Which means that the eccentric centre should be 10mm radially away from circumference of

the cam circle.

Since radius of the cam circle is 18mm.

Therefore the eccentric point should be 18 – 10 = 8mm away from the centre point of the cam

circle, so as to achieve 16mm linear displacement in the mechanical valve.

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3.6 Fabrication of model:

Fabrication of model involves the following steps.

STEP 1: Crank shaft of dia. 16mm is taken and cut into a length of 300mm

STEP 2: Crank piece having hole at the centre is inserted inside the crank shaft

Crank Shaft

Crank

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STEP 3: Insert the Cam inside the shaft:

STEP 4: Insert another crank for cylinder 2:

CAM

CRANK 1 CRANK 2

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STEP 4: Insert the buses which are used in place of bearings:

STEP 5: After arranging all elements at predefined position as per design, all

elements are welded:

BUSHES

WELDED JOINTS

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STEP 6: Insert sleeves to be used to connect connecting rod with the crank:

STEP 7: Now cut the intermediate portion of the Crank:

SLEEVES

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STEP 8: Place Sprocket at the extreme end of the crank shaft for the purpose of

power transmission:

STEP 8: After fixing all elements of Crank weld it to the frame:

SPROCKET

FRAME

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STEP 9: Take a long piece of pipe to be used as cylinder for engine:

STEP 10: Cut the pipe from the mid so as to obtain 2 pieces for 2 cylinders:

CYLINDER 1 CYLINDER 2

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STEP 11: Weld a metal plate at one end of the cylinder

Make 2 holes at its curved surface near closed end

Weld another bush at its bottom to be hinged:

STEP 12: Weld piston with the connecting rod:

INLET PORT

EXHAUST PORT

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STEP 13: Take the stationary part of valve machined from a metal piece and

drill eight holes as per the dimensions:

STEP 14: Weld eight 1 inch thin pipe pieces at every port of the valve:

STATIONARY PIECE OF VALVE

COPPER PIPES

GAS WELDED JOINTS

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STEP 15: Machine the reciprocating part of the valve as per Design:

STEP 16: Weld the follower with the valve:

FOLLOWER

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STEP 17: Assemble both the cylinders and the valve on the frame:

STEP 18: Insert both the piston as well as the reciprocating part of valve inside

the stationary part

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STEP 19: Weld four legs to the frame :

STEP 20: Assemble the flywheel to the frame:

FLYWHEEL

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STEP 21: Connect the flywheel to the sprocket via. Chain drive

STEP 22: Fix the Compressed air tank to the Frame:

CHAIN DRIVE

COMPRESSED AIR TANK

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STEP 23: Mount the Pressure gauge and the outlet valve on cylinder:

STEP 24: Connect the valve to the cylinder through pressure pipes:

PRESSURE GAUGE

VALVE

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STEP 26: Connect all the remaining supply lines to the system:

Thus, all the required steps leads to a final working model of COMPRESSED AIR ENGINE.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 52

Chapter 4: Problems Faced

4.1. Non-availability of components of desired specification in market as per the design.

4.2. Due to many no. Of parts in crank, the fabrication process becomes difficult and the

required alignment was not obtained and hence the crank movement is not free,

resulting into failure of whole crank assembly.

4.3. Problem of leakage from mechanical valve which has been fabricated manually on

lathe.

4.4. Air leakage from piping used to connect the junction from compressed air source to

valves and from valves to cylinders.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 53

Chapter 5: Solutions Adopted

5.1. As the components required are not available in the market as per the desired

specification, each and every component are machined out by performing various

machining operations on Lathe machine, Grinding machine, sensitive Drilling machine

and shaper machine.

All the fabrication work is performed either by Electric Arc Welding, Gas Welding and

fastening other components by nut and bolt.

5.2.To overcome the problem of misalignment and jamming of the crank, the whole crank

was replaced by a new crank which was fabricated on a single 16mm shaft which acts as

the crank shaft and after joining the complete crank arrangement, the intermediate portion

of the crank shaft was removed out by cutting it with hexsaw.

5.3.To fix the problem of leakage from the clearance between the reciprocating and stationary

part of the mechanical valve, various grooves with appropriate spacing and depth is

provided on the reciprocating part and it was then sealed by winding the sewing thread

around the grooves so as to fill the clearance and make the valve leak proof. Greasing is

also done in the reciprocating part to fill the gap and also to provide smooth operation of

the valve.

5.4.To fix the leakage from all the ports and piping sealing tape is used in all the joints and

then the joints are tightened with GI wire.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 54

Chapter 6: Conclusion

The values noted down are used for calculating the mechanical efficiency, indicated power

brake power; etc. Since this proto type was designed for low speed, the output power; applied

load was also kept low. The prime aim being to test the concept of application of compressed

air engine. Hence the obtain result may not be the exact measure of its potential, since it

wasn't very professionally designed. 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 or combined (hybrid) with other engines like I.C. engines

This is a revolutionary engine design which is eco friendly, pollution free, but also very

economical. This redresses both the problems of fuel crises and pollution. However excessive

research is needed to completely prove the technology for both its commercial and technical

viability. It can be seen that the indicated power is increasing for increase of load. As load is

increased, the speed falls down, to maintain it constant injection pressure has to be increased.

As the injection pressure has to be increased, the indicated mean effective pressure

gets increased; hence the indicated power is increased upon the application of the load.

Though the applied load was small, however, the developed power was

in proportion to the applied load. As load was applied the speed was reduced, to maintain it

constant, the inlet air pressure has to be increased.

Main advantages of Compressed Air Engine are :-

1. Zero emission.

2. Use of renewable fuel.

3. Zero fuel cost (the cost is involved only in the compression of air).

But the Compressed Air Engine (C.A.E.) has some disadvantages, which are:

1. Less power output

2. High pressure of compressed air may lead to bursting of storage tank.

3. Probability of air leakage.

Compressed Air Engine is a product that does not pollute like twentieth century vehicle and

doesn’t take a lifetime to payoff.

BANSAL INSTITUTE OF SCIENCE AND TECHNOLOGY Page 55

Chapter 7: References

Sharma P.C. & Aggarwal D.K., Machine Design, S.K. Kataria & Sons, Ed. 11

th

Reprint.

Mahadevan & Reddy, Design Data Handbook, CBS Publishers, Ed. 3rd

.

Mechanical Engineering and Design, Tata McGraw Hill, Ed. 3rd

.

Wiki Foundation Wikipedia Website.

How Stuff Works Website.

Engineering Hobbyist Website.

Youtube Website.