A

Seminar report on“A STUDY OF AIR ENGINE AND A CRITICAL REVIEW”

Submitted in partial fulfilment for the award of Degree of Bachelor of Technology of Rajasthan Technical University, Kota

2011-15

Submitted to: Submitted by:

Mr. Deepak Sharma Ankit Bhardwaj

(ASST. PROF. M.E.) PGI/ME/11/040

Mr. Satish Sharma 11ESDME018

(ASST. PROF. M.E.)

DEPARTMENT OF MECHANICAL ENGINEERING

POORNIMA GROUP OF INSTITUTIONS

SITAPURA, JAIPUR (RAJ)-302022

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CERTIFICATE

This is to certify that the seminar entitled “A STUDY OF AIR ENGINE AND A

CRITICAL REVIEW”, has been carried out by Ankit Bhardwaj under my

guidance in partial fulfilment of the degree of bachelor of engineering in

Mechanical Engineering of Rajasthan Technical University, Kota, during the

academic session 2011 - 2015. To the best of my knowledge and belief this work

has not been submitted elsewhere for the best award of any other degree. The work

has been found satisfactory and is approved for submission.

(Sign By Guide) (Sign By HOD)

Mr. Deepak Sharma Mr. Naval Jain

Deptt. of M.E. Deptt. of M.E.

PGI, Jaipur PGI, Jaipur

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ACKNOWLEDGEMENT

I ACKNOWLEDGE THE GREAT TIMELY AND VOLUNTARY HELP AND GUIDANCE

FROM THE FOLLOWING PERSONALITIES WITHOUT WHOSE HELP THE SEMINAR

COULD NOT HAVE BEEN COMPLETED SUCCESFULLY.

1. First of all I wish to express my thanks to the Poornima Group of Institutions ,

Mr. N.K. Jain(H.O.D) and Mr. Deepak Kumar (Asst. Prof.) for providing all sorts

of helping order to make this training possible.

2. I would also like to acknowledge my colleagues, who was always with me

during the seminar and helped for the successful transformation of an idea into

seminar.

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ABSTRACT

 In the present energy scenario the fossil fuel sources are fast depleting and their combustion

products are causing global environmental problems. There are couples of option of alternative

fuel such as solar power, tidal power, geo-thermal power, etc. and one of them is Compressed

Air.  Compressed Air Powered Engine is an alternative technology which uses compressed air to

run the engine and thus eliminates the use of fossil fuels. Exhaust temperature of it will be

slightly less than atmospheric temperature (i.e. 20-25°C) and thus helps in controlling global

warming and reducing temperature rise caused due to other means.

                Air Engine can be used to produce power to run automobile, generators etc. This paper

review contains study of a compressed air engine. This engine does not require any of the fossil

fuels like petrol, diesel, CNG, hydrogen etc. to run engine and no power is required to start the

engine, only, compressed air valve is to be opened. It is pollution free and 100% eco-friendly.

There are several technical benefits of using this engine, like as no combustion takes place inside

the cylinder, working temperature of engine is very close to ambient temperature. This helps in

reducing wear and tear of the engine components. Also there is no possibility of knocking. This

in turn results in smooth working of engine. One more technical benefit is that there will not be

any need for installing cooling system or complex fuel injection systems. This makes the design

simpler.

Based on the principle of gas expansion, a new structure of reciprocating air-powered engine is

proposed which is basically a modification of a conventional SI engine.

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PREFACE

Present seminar deals with the study of alternative fuel for automobile engines with a special

emphasis on compressed air driven engine. It includes construction and operation of the

pneumatic piston engines. Advantages of the Compressed Air Powered Engine are also

discussed.

This paper summarizes five selected papers on Air Powered Engine or related topics. This paper

is basically a comparative study of the compressed air engine with other conventional engines.

We start with the scarcity and effects of fossil fuels and need for an alternative fuel. Properties of

a compressed air are listed and behavior is highlighted. Then basic principle of the engine and

working is described. In the last chapter conversion of a conventional SI engine to an air

powered engine is shown.

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CONTENTS

Title Page

CERTIFICATE………………………………………………………………………...2

ACKNOWLEDGEMENT........................................................................................3

ABSTRACT............................................................................................................ .4

PREFACE................................................................................................................ 5

CONTENTS............................................................................................................. 6

LIST OF FIGURES................................................................................................. 8

ABBREVIATIONS................................................................................................... 9

SYMBOLS................................................................................................................10

1. INTRODUCTION AND OVERVIEW

1.1 Background......................................................................................................11 1.2 Air Vehicle vs Electric Vehicle.........................................................................12 1.3 Air Vehicle: Status in World.............................................................................12 1.4 Air Vehicle: Status in India...............................................................................13

2. FOSSIL FUELS: A BLACK PAST

2.1 Scarcity of Fossil Fuels.....................................................................................14 2.2 Influence of Fossil Fuel of Environment............................................................16 2.3 Influence of Fossil Fuel of Economy.................................................................16 2.4 Search for an Alternative Fuel......................................................................... 17 2.5 Fossil Fuel: Context to India......................................................................... 17

3. COMPRESSED AIR: A GREEN FUTURE

3.1 Compressed Air............................................................................................... 19 3.2 Basic Principle: Thermodynamic Analysis........................................................ 19 3.3 Availability....................................................................................................... 20 3.4 Compressed Air to Fuel a Car......................................................................... 20 3.5 Advantages of Compressed Air as a Fuel........................................................ 20

3.5.1 Technical Benefits............................................................................... 203.5.2 Economic Benefits............................................................................ .213.5.3 Environmental Benefits....................................................................... 22

3.6 Disdvantages of Compressed Air as a Fuel...................................................... .23

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4. COMPRESSED AIR ENGINE

4.1 Construction....................................................................................................244.1.1 Pneumatic Cylinder..............................................................................25

4.1.2 Pneumatic Solenoid Valve and Working…………………....……......25 4.1.3 Compressor…………………………………………………………..25 4.1.4 Crank Shaft…………………………………………………………...26 4.2 Working of Air Engine.......................................................................................26 4.3 Issues with Compressed Air Technology Implementation...................................28

4.3.1 Air Storage & Refueling.......................................................................28 4.3.2 Input Energy …………………………..…………………....…….......29 4.3.3 Temperature Change …………….………………………………........29 4.3.4 Multistage Compression ….…………………………………………...30

4.3.5 Energy Released……… ….……………………………………….......31

5. CONVERTING A CONVENTIONAL IC ENGINE INTO AN AIR POWERED ENGINE

5.1 Necessary Changes............................................................................................33 5.2 Operation...........................................................................................................35 5.3 Comparison between Old and New Engine.........................................................36 5.3.1 Difference in Working..........................................................................36 5.3.2 Advantage of Air Powered Engine over Conventional Engine...............37

6. CONCLUSION.....................................................................................................38

REFERENCES.........................................................................................................40

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LIST OF FIGURES

Figure Title Page

1.1 MDI Main Engine Configuration.....................................................................12

1.2 Model of Air Car by TATA Motor...................................................................13

2.1 Various Losses using Fossil Fuels....................................................................18

3.1 Various Losses of Energy in Air Engine....................................................................23

4.1 Layout of Air Engine.......................................................................................24

4.2 Complete Cycle of a Two Stroke Air Engine....................................................27

4.3 Multistage Compression Requirement for Air Compression.............................31

4.4 Energy released as a function of compression pressure at constant volume of

compressed air.................................................................................................32

5.1 A Conventional SI Engine................................................................................33

5.2 The Air Powered Engine...................................................................................35

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ABBREVIATIONS

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BDC Bottom Dead Center

CFM Cubic Feet per Minute

CNG Compressed Natural Gas

DC Direct Current

IC Internal Combustion

MDI Motor Development International

PLC Programmable Logic Controller

PSI Pounds per Square Inch

SI Spark Ignition

TDC Top Dead Center

SYMBOLS

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P Pressure

T Temperature

V Volume

CHAPTER 1

INTRODUCTION AND OVERVIEW

1.1 Background

Fossil fuels (i.e., petroleum, diesel, natural gas and coal) which meet most of the world's

energy demand today are being depleted rapidly. Also, their combustion products are causing

global problems, such as the greenhouse effect, ozone layer depletion acid rains and pollution

which are posing great danger for environment and eventually for the total life on planet. These

factors are leading automobile manufactures to develop cars fueled by alternatives energies.

Hybrid cars, Fuel cell powered cars, Hydrogen fueled cars will be soon in the market as a result

of it. One possible alternative is the air powered car. Air, which is abundantly available and is

free from pollution, can be compressed to higher pressure at a very low cost, is one of the prime

option since atmospheric pollution can be permanently eradicated. Compressed air utilization in

the pneumatic application has been long proven. Air motors, pneumatic actuators and others

various such pneumatic equipment are in use. Compressed air was also used in some of vehicle

for boosting the initial torque. Turbo charging has become one of the popular techniques to

enhance power and improve the efficiencies of the automotive engine that completely runs on

compressed air.

Climate change and energy security require a reduction in travel demand, a modal shift,

and technological innovation in the transport sector. Through a series of press releases and

demonstrations, a car using energy stored in compressed air produced by a compressor has been

suggested as an environmentally friendly vehicle of the future.

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1.2 Air Vehicle vs Electric Vehicle

During literature survey it is observed that compressed air vehicles has many potential

advantages over electric vehicles which includes no degradation problems of batteries, time

required for refueling the tank, easy disposal of compressed air tank without causing any

pollution as with the batteries. Hence in order to overcome the above stated problems there is a

need of eco-friendly vehicles using compressed air as a working medium in future.

1.3 Air Vehicle: Status in World

The first compressed air vehicles were built by Andraud and Tessié du Motay in Paris between

1838 and 1840. Since then the idea has been tried again and again, but has never reached

commercialization. Currently, related researches of compressed air are carried out all over the

world. The French company MDI has developed a partial commercial production of the air

powered car. MDI plans to sell this clean fuel vehicle and a compressed air hybrid in Europe for

less than 15,000 dollars in near future.

1.4 Air Vehicle: Status in India

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Figure 1.1 MDI Main Engine Configuration

In January 2007, Tata Motors and Motor Development International (Luxembourg)

signed a license agreement that enables Tata Motors to produce and sell compressed air cars

using MDI technology in India. In 2008, India’s largest car manufacturer also announced that it

would begin production of world’s first commercial vehicle to run on nothing but compressed

air.

The agreement with MDI covered two phases of activity encompassing the technology

transfer and proof of the technical concept in the first phase, and in the second phase completing

detailed development of the compressed air engine into specific vehicle and stationary

applications.

The first phase of this program - proof of the technical concept in Tata Motors vehicles - has now

been successfully completed with the compressed air engine concept having been demonstrated

in two Tata Motors vehicles.

In the second phase of the development, the two companies are working together to complete

detailed development of the technology and required technical processes to industrialize a market

ready product application over the coming years.

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Figure 1.2 Model of Air Car by TATA Motor

CHAPTER 2

FOSSIL FUELS: A BLACK PAST

2.1 Scarcity of Fossil Fuels

Fossil fuels, as the name suggests, are very old. Although humans probably used fossil fuels in

ancient times, as far back as the Iron Age, it was the Industrial Revolution that led to their wide-

scale extraction. About 100 years ago, the major source of energy shifted from recent solar to

fossil fuel (hydrocarbons). Technology has generally led to a greater use of hydrocarbon fuels,

making civilization vulnerable to decreases in supply. The current study made in the year 2004,

predicts that if the oil is consumed at the current rates, then by 2020, we will be consuming 80%

of the entire available resource.

Latest studies and projections available indicate that the crises of fossil fuel in near future is

inevitable and alternative to fossil fuel must be looked for. Some of the studies made in this

regard are detailed ahead.

i. When the wells run dry, We use more oil than we find, and if producers are fixing their

figures the end could be closer than thought, by Adam Porter, The Guardian [2005 May

25]

"Predicting the end of the age of oil can be a sticky business. The Association for the

Study of Peak Oil and Gas (Aspo), a collection of industry figures, politicians and

academics, this week held its annual meeting at the Gulbenkian Museum in Lisbon..."

ii. Peaking of World Oil Production: Impacts, Mitigation, & Risk Management, by Robert

L. Hirsch, SAIC, Roger Bezdek, MISI, Robert Wendling, MISI for the National Energy

Technology Laboratory of the US Department of Energy [2005 February]

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"The peaking of world oil production presents the U.S. and the world with an

unprecedented risk management problem. As peaking is approached, liquid fuel prices

and price volatility will increase dramatically, and, without timely mitigation, the

economic, social, and political costs will be unprecedented. Viable mitigation options

exist on both the supply and demand sides, but to have substantial impact, they must be

initiated more than a decade in advance of peaking."

iii. Expert says Saudi oil may have peaked, by Adam Porter [2005 February 22] : "As oil

prices remain above $45 a barrel, a major market mover has cast a worrying future

prediction. Energy investment banker Matthew Simmons, of Simmons & Co

International, has been outspoken in his warnings about peak oil before. His new

statement is his strongest yet, 'we may have already passed peak oil."

iv. U.S. Energy Policy: A Declaration of Interdependence, by David J. O'Reilly Chairman

and CEO, ChevronTexaco Corporation [2005 February 15] "Simply put, the era of easy

access to energy is over. In part, this is because we are experiencing the convergence of

geological difficulty with geopolitical instability... We are seeing the beginnings of a

bidding war for Mideast supplies between East and West."

v. New Oil Projects Cannot Meet World Needs This Decade, by Oil Depletion Analysis

Centre [2004 November 16] "World oil supplies are all but certain to remain tight

through the rest of this decade, unless there is a precipitous drop in demand, according to

the results of a study by the London-based Oil Depletion Analysis Centre (ODAC). "The

study found that all of the major new oil-recovery projects scheduled to come on stream

over the next six years are unlikely to boost supplies enough to meet the world’s growing

needs."

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2.2 Influence of Fossil Fuel on Environment

It is observed that with increasing pace of civilization, uses of transport have become essential

part of life and increasing in geometrical progression. This is leading to very hazardous condition

due to high rate of pollution. Many of the environmental problems our generation faces today

result from our fossil fuel dependence. These impacts include global warming, air quality

deterioration, oil spills, and acid rain.

Emissions from an individual car are generally low, relative to the smokestack image many

people associate with air pollution. But in numerous cities across the country, the personal

automobile is the single greatest polluter, as emissions from millions of vehicles on the road add

up. Driving a private car is probably a typical citizen’s most “polluting” daily activity. Gasoline

and diesel fuels are mixtures of hydrocarbons, compounds which contain hydrogen and carbon

atoms. In a “perfect” engine, oxygen in the air would convert all the hydrogen in the fuel to

water and all the carbon in the fuel to carbon dioxide. Nitrogen in the air would remain

unaffected. In reality, the combustion process cannot be “perfect,” and automotive engines emit

several types of pollutions like CO, NOx, SO2, Volatile Organic Compounds,O3 etc.

2.3 Influence of Fossil Fuel on Economy

Oil, the master energy resource, is the driver of economic growth. But our financial system is

wired for economic growth. This is the challenge. It is structural change that is needed. Over the

last 150 years relatively cheap oil has enabled economic growth to happen. It has transformed

agricultural methods, enabled world population to grow, and powered transport. So now, not

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only are we required to adapt to life with less oil, but the very enabler of economic growth is

becoming more and more unaffordable.

Our economy may well recover somewhat, but that recovery will lead to increased oil use, which

leads to increased prices, which will lead to another economic contraction. And this cycle will

repeat – with each subsequent recovery being weaker than the last. So no amount of optimism or

wishful thinking can bring back economic growth. Future economic growth will be impeded by

the depletion of critical, natural resources, the increased costs of extraction and its associated

negative environmental impacts, and ever mounting debt. This is not a temporary phenomenon, it

is the start of a long series of cyclical recessions, and it signifies the end of growth. It is a great

disruption to our normal patterns.

2.4 Search for an Alternative Fuel

Many research works are being carried out to find the alternative to fossil fuel. Alternative fuels,

known as non-conventional or advanced fuels, are any materials or substances that can be used

as fuels, other than conventional fuels. Conventional fuels include: fossil fuels (petroleum (oil),

coal, and natural gas). Some well-known alternative fuels include biodiesel, bioalcohol

(methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells), hydrogen,

non-fossil methane, non-fossil natural gas, vegetable oil, propane, and other biomass sources.

Compressed Air is one of the important and freely available alternative fuel.

2.5 Fossil Fuel: Context to India

India is developing country. Still per capita income of average person is very low to meet out the

minimum requirement of person. Maximum population of country is still living in villages.

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There transport is still either bi-cycle or Motor Bike. Current hike of fossil fuel is going

tremendously high up to 30-40 % every year. With this pace up to 2010 prices may go double

than what is today and by 2030-40, it may fetch to Rs.1000 per litre. A time will come when

common person would not be able to purchase fuel to even run the Motor-Bike. It is not only due

to rate of increase of vehicles in India. It is worldwide problem that 80 % of fossil fuel is being

consumed in transport with increasing mobility of persons to day and daily consumable materials

are being transported through Road Transport. Thus it is need of day to explore possibility of

alternative for fossil fuel to make environment free from emission & make children healthy.

With high rate of consumption of fossil fuel it also necessary to make sustainable energy or in

other words of erstwhile PRESIDENT of INDIA Dr. APJ Abdul Kalam make INDIA energy

freedom by 2030, which he has spoken in his speech on the eve of 14th Aug.’2005 of

Independence day. So we need a focus on Alternative Fuel Research.

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Figure 2.1 Various Losses using Fossil Fuels

CHAPTER 3

COMPRESSED AIR: A GREEN FUTURE

3.1 Compressed Air

Compressed air is a gas, or a combination of gases, that has been put under greater pressure than

the air in the general environment. Current applications using compressed air are numerous and

diverse, including jackhammers, tire pumps, air rifles, and aerosol cheese. According to

proponents, compressed air also has a great deal of potential as a clean, inexpensive, and

infinitely renewable energy source. Its use is currently being explored as an alternative to fossil

fuels.

3.2 Basic Principle: Thermodynamic Analysis

Compressed air is clean, safe, simple and efficient. There are no dangerous exhaust fumes of or

other harmful by products when compressed air is used as a utility. It is a non-combustible, non-

polluting utility. When air at atmospheric pressure is mechanically compressed by a compressor,

the transformation of air at 1 bar (atmospheric pressure) into air at higher pressure (up to 414

bar) is determined by the laws of thermodynamics. They state that an increase in pressure equals

a rise in heat and compressing air creates a proportional increase in heat. Boyle's law explains

that if a volume of a gas (air) halves during compression, then the pressure is doubled.

Charles' law states that the volume of a gas changes in direct proportion to the temperature.

These laws explain that pressure, volume and temperature are proportional; change one variable

and one or two of the others will also change, according to this equation:

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(P1 V1) / T1 = (P2 V2)/T2

Compressed air is normally used in pressure ranges from 1 bar to 414 bar (14 to 6004 PSI) at

various flow rates from as little as 0.1 m (3.5 CFM - cubic feet per minute) and up.

3.3 Availability

Air is natural source and available freely in atmosphere, which can be stored after compressing it

to desired pressure. This is the only source which can be stored at very high pressure and can be

retained without any loss after lapse of passage of time, which can drive so many domestic

appliances such as vacuum cleaner, mixy and pumps, running Power generator when electric

power is off instead of using inverter to have clumsy arrangements of battery etc.

3.4 Compressed Air to Fuel a Car

It is hard to believe that compressed air can be used to drive vehicles. However that is true, and

the “air car”, as it is popularly known, has caught the attention of researchers worldwide. It has

zero emissions and is ideal for city driving conditions. MDI is one company that holds the

international patents for the compressed air car.

A proved fact: “Research by MDI shows that an Air Powered Car can travel 171 km by using

electricity costing about Rs. 80-100 which would cost about Rs. 570 for a normal S.I. engine car

giving an average of 15 kmpl.”

3.5 Advantages of using Compressed Air as a Fuel

3.5.1 Technical Benefits

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Air Powered Engine is an alternative technology which uses compressed air to run

the engine and thus eliminates the use of fossil fuels. Exhaust temperature of it will

be slightly less than atmospheric temperature (i.e. 20-25°C) and thus helps in

controlling global warming and reducing temperature rise caused due to other

means. As we are going to convert the already existing conventional engine into an

air powered one, this new technology is easy to adapt. Another benefit is that it

uses air as fuel which is available abundantly in atmosphere.

Apart from above other technical benefits are as follows:

i. The temperature of the engine while working will be slightly less than the

ambient temperature.

ii. Smooth working of the engine due to very less wear and tear of the

components.

iii. There is no possibility of knocking.

iv. No need of cooling systems and spark plugs or complex fuel injection

systems.

3.5.2 Economic Benefits

Some major economic benefits of Air Engine are listed below

i. No use of expensive fossil fuels as the free air is compressed and taken to use.

ii. For this reason people can easily shift to the new technology.Compressors use electricity

for generating compressed air which is relatively much cheaper and widespread.

iii. Smooth working will lead to less wear & tear, so lesser maintenance cost.

iv. Compressed air is most sustainable. It has no volatility or temperature or much weather

effect .Once compressed air is stored through compressor, it will be available at any time

without any loss of Pressure.

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3.5.3 Environmental Benefits

Compressed air may be definitely as an alternate for running light vehicle, which is presently

creating emission due to use of fossil fuel and ultimately effects public health hazard. The major

benefits of Air Engine in the direction of environmental safety are as follows:

i. As the exhaust temperature of this engine will be slightly less than the

atmospheric temperature (i.e. 15-25oC). So this will help in cooling the

environment.

ii. And if this technology is widely used than it will help in controlling global

warming. These are some green bytes associated with this technology.

iii. Exhaust gases leaving the engine will be only air having low temperature. So

this will eliminate the problem of harmful emissions, in conventional engines.

This gives us environmental benefit of using this engine.

iv. Also as there will be no thermal radiations produced, radar can’t detect these

vehicles. So this will help our army too.

3.6 Disadvantages of using Compressed Air as a Fuel

Apart from the benefits listed above, there are some disadvantages which are as follows:

i. The principal disadvantage is the indirect use of energy. For conventional combustion

motor cars, the energy is lost when chemical energy in fossil fuels is converted to

mechanical energy, most of which goes to waste as lost heat. For compressed-air cars,

energy is lost when chemical energy is converted to electrical energy (if electricity is

produced from chemical sources), when electrical energy is converted to compressed air,

and when the compressed air is converted into mechanical energy (fig 5.1).

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ii. Compressed air vehicles likely will be less robust than typical vehicles of today which

poses a danger to users of compressed air vehicles sharing the road with larger, heavier

and more rigid vehicles.

iii. Compressed air has a low energy density comparable to the values of electrochemical

lead-acid batteries. While batteries can somewhat maintain their voltage throughout their

discharge and chemical fuel tanks provide the same power densities from the first to the

last litre, the pressure of compressed air tanks falls as air is drawn off.

iv. Cars powered alone by compressed air have a limited speed range but can have

comparable speeds to present day vehicles by converting them into hybrid cars, for e.g.

compressed air plus electric car.

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Figure 3.1 Various Losses of Energy in Air Engine

CHAPTER 4

COMPRESSED AIR ENGINE

4.1 Construction

The construction of compressed air engine mainly consist of pneumatic cylinder, pneumatic

solenoid valve, compressor and crank shaft.

A typical layout of an Air engine is as shown in figure 4.1.

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The main components of the Compressed Air Engine are as follows-

4.1.1 Pneumatic Cylinder

Pneumatic cylinders are mechanical devices which produce force, often in combination with

movement, and are powered by compressed gas. To perform their function, pneumatic cylinders

impart a force by converting the potential energy of compressed gas into kinetic energy. This is

achieved by the compressed gas being able to expand, without external energy input, which itself

occurs due to the pressure gradient established by the compressed gas being at a greater pressure

than the atmospheric pressure. This air expansion forces a piston to move in the desired

direction. Once actuated, compressed air enters into the tube at one end of the piston and, hence,

imparts force on the piston. Consequently, the piston becomes displaced by the compressed air

expanding in an attempt to reach atmospheric pressure.

4.1.2 Pneumatic Solenoid Valve and Working

The term solenoid usually refers to a coil used to create magnetic fields when wrapped around a

magnetic object or core. In engineering terms, the solenoid describes transducer mechanisms

used to convert energy into motion. Solenoid valves are controlled by the action of the solenoid

and typically control the flow of water or air as a switch. If the solenoid is active (current is

applied), it opens the valve. If the solenoid is inactive (current does not exist), the valve stays

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Figure 4.1 A layout of Air Engine

closed. The action of the pneumatic solenoid is controlled by the use of pneumatics. The opening

or closing of a valve is referred to as "changing state."

4.1.3 Compressor

A gas compressor is a mechanical device that increases the pressure of a gas by reducing its

volume. Compressors are similar to pumps: both increase the pressure on a fluid and both can

transport the fluid through a pipe. As gases are compressible, the compressor also reduces the

volume of a gas.

Compressed air Piston range operates between 0.75 kW to 420 kW (1hp to 563 hp) producing

working pressure at 1.5 bar to 414 bar (21 to 6004psi). Compressed air Vane compressors

operate between 1.1 kW to 75 kW (1.5 to 100hp), producing working pressures of 7 to 8 and 10

bar (101 to 145psi).

4.1.4 Crank Shaft

The crankshaft translates reciprocating linear piston motion into rotation. To convert the

reciprocating motion into rotation, the crankshaft has "crank throws" or "crankpins", additional

bearing surfaces whose axis is offset from that of the crank, to which the "big ends" of the

connecting rods from each cylinder attach.

4.2 Working of Air Engine

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 use the expansion of compressed air to drive their

pistons. The complete cycle of a two-stroke air engine is as shown in figure 4.2.

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When the piston is at the top position (Fig. 4.2a) its spindle opens the ball valve, the compressed

air fills the space of cylinder. The air exerts pressure on surface of the piston, causing its

movement down and rotate the crankshaft (Fig. 4.2b). The valve closes when piston is moving

down, but the air is still expanding and exerts a force on the piston. In the lower turning point

(Fig. 4.2c) piston is opening outlet window and releasing air outside. Exhaust temperature of it

will be slightly less than atmospheric temperature (i.e. 20-25°C) and thus helps in controlling

global warming and reducing temperature rise caused due to other means.

The shaft is starting to move by inertia (Fig. 4.2d) then pushes the piston to the top and closing

the off window. In the cylinder are small amounts of air, so the piston moves upwards until it

will again open the ball valve and the cycle repeats.

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Figure 4.2 Complete cycle of a two stroke air engine

4.3 Issues with Compressed Air Technology Implementation

Compressed air cars are not yet available in most places but the technology behind them

is being perfected so that they can be introduced into the market. These cars can be powered

solely by air or by a combination of air and fuel, such as diesel, ethanol, or gasoline which is

how a hybrid electric vehicle runs. Compressed air car engines are fueled by a tank of

compressed air, instead of an engine that runs with pistons and an ignited fuel air mixture.

Basically, compressed air cars are powered by the expansion of compressed air. Vehicles that run

on compressed air sound like a fantastic idea on paper, but bringing this technology to the

masses have proven, well, a difficult road to travel because of some inherited technical problems

with compressed air. The present article gives a brief report to highlight such problems so that

some methods can be designed to counter to improve the efficiency of compressed air vehicle.

4.3.1 Air Storage & Refueling

The cars are designed to be filled up at a high-pressure pump and thus the tanks must be

designed to safety standards appropriate for a pressure vessel. The storage tank may be made of

metal or composite materials. 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. It may be possible to store compressed air at lower

pressure using an absorption material within the tank.

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The Tata/MDI air car version had 4,350 psi in its tanks, which would require stations to install

new high-tech air pumps, a difficult investment for station owners. As thought by engineers and

designers, the storage tank would be made up of carbon fiber to reduce the car’s weight and

prevent an explosion, in case of a direct collision.

Carbon-fiber tanks are capable of containing air pressure up to 4500 psi, something the steel

tanks are not capable of. For fueling the car tank with air, the compressor needs to be plugged

into the car, which would use the air that is around to fill the compressed air tank. This could be

a slow process of fueling; at least until air cars are commonly used by people, after which high-

end compressors would be available at gas stations that would fuel the car in no time at all.

4.3.2 Input Energy

Compressed air to very large pressures is extremely expensive to produce and it is very

inefficient to use. Of the energy required to produce compressed air, less than 20% of input

energy is left for use. That means 80% of what is paid for is used up before compressed air is put

in the distribution system. In order to use air storage in vehicles or aircraft for practical land or

air transportation, the energy storage system must be compact and lightweight. Energy density is

the engineering term that defines these desired qualities. Compressed air has a low energy

density. In 300 bar containers, about 0.1 MJ/L and 0.1 MJ/kg is achievable, comparable to the

values of electrochemical lead-acid batteries. While batteries can somewhat maintain their

voltage throughout their discharge and chemical fuel tanks provide the same power densities

from the first to the last litre, the pressure of compressed air tanks falls as air is drawn off.

It is important to take into consideration that the energy needed to compress the air into

the tanks comes from the electrical grid. Such electric grids are generally supported with use of

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fossil fuels. However, efforts are going on to make use of non-conventional sources of energy

like solar and wind to compress air.

4.3.3 Temperature Change

In adiabatic process of compression of air, the heat of compression is retained, that means, there

is no heat exchange resulting in zero entropy change, so the compressed air becomes very hot.

Compressed air would experience a temperature rise due to the energy that has been added to the

gas by the compressor which can be controlled with isothermal or adiabatic compression

processes. In an isothermal compression process, the gas in the system is kept at a constant

temperature throughout. This necessarily requires removal of heat from the gas. This heat

removal can be achieved by heat exchangers (intercooling) between subsequent stages in the

compressor. To avoid wasted energy, the intercoolers must be optimized for high heat transfer

and low pressure drop. Naturally this is only an approximation to an isothermal compression,

since the heating and compression occurs in discrete phases. Some smaller compressors can

approximate isothermal compression even without intercooling, due to the relatively ratio of

surface area to volume and the resulting improvement in heat dissipation from the compressor

body itself.

An adiabatic process is one where there is no heat transfer between the fluid and the

surroundings: the system is insulated against heat transfer. If the process is furthermore internally

reversible (smooth, slow and frictionless, to the ideal limit) then it will additionally be isentropic.

An adiabatic storage system does away with the intercooling during the compression process,

and simply allows the gas to heat up during compression, and likewise to cool down during

expansion. This is attractive, since the energy losses associated with the heat transfer are

avoided, but the downside is that the storage vessel must be insulated against heat loss.

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4.3.4 Multistage Compression

Power requirement can be controlled through multistage compression of air. The compression

generates heat, the compressed gas is to be cooled between stages making the compression less

adiabatic and more isothermal. The inter-stage coolers typically result in some partial

condensation that is removed in vapor-liquid separators. By cooling the compressed air between

each stage, the compression curve moves to near isothermal. The work done by the compressor

is less if it is multi-staged. A multi-stage compressor is one in which there are several cylinders

of different diameters. The intake of air in the first stage gets compressed and then it is passed

over a cooler to achieve a temperature very close to ambient air. This cooled air is passed to the

intermediate stage where it is again getting compressed and heated. This air is again passed over

a cooler to achieve a temperature as close to ambient as possible. Then this compressed air is

passed to the final or the third stage of the air compressor where it is compressed to the required

pressure and delivered to the air receiver after cooling sufficiently in an after-cooler.

Figure 4.3 Multistage Compression Requirement for Air Compression

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4.3.5 Energy Released

Compressed air is more expensive than many other utilities when evaluated on a per unit energy

delivered basis. Therefore, energy released by the compressed air is very important and thus are

Figure 4.4 Energy released as a function of compression pressure at constant volume of compressed air

the factor like volume of compressed air, compressed air pressure and expansion flow rate under

isothermal or adiabatic conditions of expansion on which it depends. Figure 4.4 shows the

typical control characteristics of energy release by the compressed air on its isothermal or

adiabatic expansion as a function of compressed air pressure, volume of compressed air and flow

rate. Applying best energy release management and control practices, the desired energy can be

achieved.

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CHAPTER 5

CONVERTING A CONVENTIONAL IC ENGINE INTO ANAIR POWERED

5.1 Necessary Changes

The normal 4 stroke SI engine is shown as:

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Figure 5.1 A conventional SI engine

To convert a conventional IC engine into an Air Powered one, few components are to be

replaced.

First of all replace the spark plug with a pulsed pressure control valve which can create required

pressure. Now the pulsed air firing in this valve is controlled by controlling the supply of

electrical signal to the plunger. For this we require an electronic timing circuit which can control

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the flow of electrical supply to the plunger of this valve. This can be achieved by using PLC

circuit. Now speed of the engine will be controlled by controlling this input signal.

Now fuel tank is to be replaced with air vessel, as it requires pressurized air as input. And two

things are to be taken care while designing air vessel:

1. First is its strength to withstand high internal pressure, which exists due to compressed

air. For this outer body of it should be made of a material, having high strength, like

carbon fiber.

2. Second is its capacity to store air and its weight. Now replace cam with a modified cam.

This is to be done, so that both the inlet and outlet valves open and close at the same

time. Main advantage of doing this is to achieve better scavenging system. Also this will

result in conversion of 4 stroke engine into 2 stroke air engine, which in turn gives us the

benefit of low mean effective pressure requirement in addition to other operational

benefits.

The new Air Powered engine, after modifications would look like as follows:

35Figure 5.2 The Air Powered Engine

5.2 Operation

Initial torque is supplied from the DC exciter motor, and then the engine

operation starts.

Stage 1: When the piston is in the TDC, compressed air is injected through

the pulsed air firing valve, which pushes the piston to BDC.

Stage 2: Due to the motion of the engine and its inertia, the piston moves

back to TDC, pushing the air out of the valves.

The plunger of the pulsed firing valve is controlled by a timing circuit which is specifically a

PLC programmed circuit. It supplies the electronic signals by which the plunger moves so that it

opens and closes the pulsed firing valve.

5.3 Comparison between the Old and New Engine

5.3.1 Difference in Working

On comparing it with the working of normal SI 4 stroke engine, we can say

that:

i. “Stage 1” of the air engine comprises of the combined operation of

“Suction stage” and

“Power stage” of the normal 4 stroke SI engine.

ii. “Stage 2” of the air engine comprises of the combined operation of the

“Compression stage” and “Exhaust stage” of the normal 4 stroke SI

engine.

5.3.2 Advantages of Air Powered Engine over Conventional Engine

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i. Air, on its own, is non-flammable, abundant, economical, transportable,

storable and, most importantly, nonpolluting.

ii. Compressed air technology reduces the cost of vehicle production by

about 20%, because there is no need to build a cooling system, fuel

tank, spark plugs or silencers.

iii. High torque for minimum volume. The mechanical design of the engine

is simple and robust.

iv. Low manufacture and maintenance costs as well as easy maintenance.

Lighter vehicles would mean less abuse on roads, thus, resulting in

longer lasting roads.

v. The price of fueling air powered vehicles will be significantly cheaper

than current fuels.

vi. When the air is being compressed at reasonable speeds, it heats up.

The heat given off during compression could be reclaimed for space

heating or water heating,

vii. 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.

Compressed-air vehicles are comparable in many ways even to electric

vehicles and their potential advantages over electric vehicles include:

viii. Compressed-air vehicles are unconstrained by the degradation

problems associated with current battery systems

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ix. 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.

x. Compressed-air tanks can be disposed of or recycled with less pollution

than batteries.

xi. The tank may be able to be refilled more often and in less time than

batteries can be recharged, with refueling rates comparable to liquid

fuels.

xii. The tanks used in a compressed air motor have a longer lifespan in

comparison with batteries, which, after a while suffer from a reduction

in performance.

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CHAPTER 6

CONCLUSION

With the use 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. On the whole, the technology is just about modifying the

engine of any regular IC engine vehicle into an Air Powered Engine. The Air

Powered Engine technology is cheaper in cost and maintenance, can be

easily adapted by the masses and it doesn’t cause any kind of harm to the

environment. Instead, its widespread use will help mankind in controlling the

serious problem of global warming.

Cars powered by compressed air are an alternative to hybrid vehicles

and to cars powered only by electricity from fuel cells or lithium-ion

batteries. The greatest advantage of air vehicles is their low price – the

simplest MDI model costs less than $ 5; 300. For comparison, the most

popular hybrid car – the Toyota Prius Luna (bottom of the range) costs $

34,000 in 2011.

One feature where the compressed air vehicle outclasses other cars is its

light weight (due to its composite tank and simple structure), which easily

translates into energy needs. By contrast, other energy-saving solutions are

equipped with a heavy pack of battery or fuel cells.

Moreover, these expensive batteries have to be replaced every few

years at great cost and with due care given to eco-friendly disposal. A

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compressed air tank will suffice for the entire lifetime of the vehicle and is

safe even during accidents (according to [8] the composite material does not

explode but only cracks allowing the reservoir pressure to fall slowly without

causing any danger).

One major drawback of pneumatic motor vehicles is their poor range,

resulting from the limited size of the compressed air tank (low density

energy). This disadvantage is only slightly o

set by the small mass of the vehicle. Filling up the 200 liter tank to a

pressure of 350 bar at the assumptions adopted previously cost $ 2.74 (in

reality, less), which like-for-like is about one-quarter the cost of a gasoline-

powered car. This volume of air enables the AIRONE MDI to go about 80 to

135 km (according to [7]). In its simplest configuration, air motor efficiency is

very low, due to the need to cool the compressed air before it goes into the

tank. The best way to improve the efficiency of this engine is to use ambient

heat to warm the working medium and engine cylinders.

Compressed air for vehicle propulsion is already being explored and

now air powered cars are being developed as a more fuel-efficient means of

transportation. Some automobile manufacturers are further exploring

compressed air hybrids and compressed fluids to store energy for vehicles

which might point the way for effective air powered vehicles design.

Unfortunately there are still some serious problems to be sorted out, like lack

of starting torque and cost of compressing air, before air powered vehicles

become reality for common use but there is a hope that with the

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developments in science and technology which are also in agreement with

the environment, air-powered vehicles will definitely see light of the day.

If the compressed air technology is implemented in the light transport

vehicles such as: motorbikes

etc., it will practically generate zero pollution and compressed air engine

technology will reduce the emission up to 50-60% as presently 80 % of

pollution is generated due to the transport sector.

Thus compressed air is definitely going to be the most attractive and

efficient clean energy option for 21st century. It surely is the “Futuristic Mode

of Transport”. “Let’s move from a Black Oil Past to a Green Air

Future…”

REFERENCES

1. Wojciech SZOKA, Dariusz SZPICA, Adaptation Of Classic Combustion Engines To

Compressed Air Supply, Acta mechanica et automatica, vol.6 no.1, 2012.

2. Patel B. S., Barot R. S., Air Powered Engine, National Conference on Recent Trends in

Engineering & Technology, May 2011.

3. Lal Abhishek, Design and Dynamic Analysis of Single Stroke Compressed Air Engine,

International Journal of Renewable Energy Research Vol.3, No.2, 2013.

4. Yadav JP and Singh Bharat Raj, Study and Fabrication of Compressed Air Engine, S-

JPSET : ISSN : 2229-7111, Vol. 2, Issue 1, 2011.

5. Singh B.R. and Singh Onkar, Study of Compressed Air as an alternative to fossil fuel for

Automobile Engines, International Conference on Challenges and Strategies for

Sustainable Energy and Environment, UP, India, June 2006.

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6. Szabłowski Łukasz, Milewski Jarosław, Dynamic analysis of compressed air energy

storage in the car, Journal of Power Technologies 91 (1) 23–36, 2011.

7. Verma S.S., Latest Developments of a Compressed Air Vehicle: A Status Report, Global

Journal of Researches in Engineering Automotive Engineering, Global Journals Inc.

(USA) Volume 13 Issue 1 Version 1.0, 2013.

8. MDI. Analyse comparative. Technical report, 2009.

9. Air car: compressed air technology

//www.aircarcompressedairtechnology.com/indexeng.php (accessed on 2nd August,

2014).

10. MDI Technology, //www.thefuture.net.nz/mdi_tech.htm,(accessed on 2nd August, 2014)

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