Self-Study Programme 262 Natural gas an alternative fuel for motor vehicles.pdf

Service Training

Self-study programme 262

Natural gas - an alternative fuel

for motor vehicles

Design and function

Within the process of reducing harmful emissions

caused by traffic in built-up cities and the rising

costs of petrol and diesel fuel, more emphasis is

being placed on natural gas as an alternative

power source to drive motor vehicles.

In this day and age, Volkswagen offers the Golf

BI FUEL as a series production vehicle with bivalent

natural gas drive (vehicle can be driven with

natural gas or petrol).

The Transporter ’91

can be equipped with a

retrofit option for bivalent natural gas powered

operation.

➤

Gas as a power source to drive vehicles is not a

modern invention. It has a long history. Even the

first internal combustion engine - the patent for

which was applied for by Nikolaus Otto in 1876 -

was developed in the Deutz AG gas engine

factory.

Please note that there will be country-specific

differences with regards to legal requirements.

With this self-study programme we would like to

introduce you to the special features of the bivalent

natural gas drive system for Volkswagen vehicles

(centred around the framework conditions in

Germany).

Within the scope of further motor vehicle engine

development, gas technology, as well as other

drive concepts, was always a source upon which

engineers could fall back on - mostly in times of

emergency.

This lead to vehicles being equipped with

storage tanks, in which town gas or a mixture of

propane/butane was filled, or the gas was

generated directly in gas generators from wood

or anthracite while the vehicle was in motion.

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NEW

Warning

Note

The self-study programme represents the design

and function of new developments!

The contents will not be updated.

For instructions on testing, adjusting and repairs,

please refer to the relevant service literature.

At a glance

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Natural gas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Natural gas compared with other fuels. . . . . . . . . . . . . . . . . . . . . . . . . 8

Supply of natural gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Comparison and laws affecting its use . . . . . . . . . . . . . . . . . . . . . . . . . 14

Engine technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

The Transporter ‘91

bivalent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

The Golf BI FUEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

➤

Natural gas storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

The different methods of storing natural gas fuel. . . . . . . . . . . . . . . . 20

The gas tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

The tank test intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Natural gas components in Golf BI FUEL . . . . . . . . . . . . . . . 26

Overview of components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Natural gas supply in Golf BI FUEL . . . . . . . . . . . . . . . . . . . . 28

System overview of natural gas supply . . . . . . . . . . . . . . . . . . . . . . . . 28

Flow chart of natural gas supply system . . . . . . . . . . . . . . . . . . . . . . 30

High pressure side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

From high pressure to low pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

The low pressure side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

The technical safety concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Engine management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

The system overview of sensors and actuators . . . . . . . . . . . . . . . . . 54

The system functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

The function chart, Transporter ‘91

bivalent . . . . . . . . . . . . . . . . . 62

The function chart, Golf BI FUEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

➤

Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

The legal requirements in Germany . . . . . . . . . . . . . . . . . . . . . . . . . . 66

The diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Associated special tools and workshop equipment . . . . . . . . . . . . . . 70

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Explanation of highlighted terms

Test your knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Introduction

Natural gas

At the start of the 90s, public interest was

centred more and more around motor vehicle

traffic as the main cause of pollution and

excessive noise in built-up cities. Only terms such

as “summer smog” and “acid rain” are referred

to.

The lower the carbon content of an energy

source, the lower the carbon related emissions,

such as carbon dioxide, carbon monoxide and

soot particles.

Natural gas can be used as a fuel directly in

internal combustion engines without any

chemical changes necessary. In this way, there is

a considerable saving in costs compared to the

measures necessary in processing oil to petrol

and diesel. However, it may be necessary to

clean or dry the natural gas depending on the

source from which is was extracted.

For the emissions of gas components nitrogen

oxide (NO x ), hydrocarbons (HC), carbon

monoxide (CO), carbon dioxide (CO 2 ) and soot

particles, strict limit values were established.

The use of alternative fuels, such as natural gas,

makes an effective contribution towards

improving the environmental situation.

The availability of natural gas resources is

greater than that of mineral oil. This way there

is a means of interchanging the exclusive

dependence on oil.

Natural gas is created under similar conditions

to that of oil and is produced as a by-product of

oil extraction.

It is also found in single geological deposits.

It is lighter than air and mixes well with the air.

It burns “softly”.

For reasons of safety, the odourless natural gas

is supplemented with strong smelling additives in

Germany.

This makes it possible to detect natural gas by

smell even in the smallest of quantities.

As a flammable gas, natural gas is the most

environmentally compatible fossil energy source.

It comprises in essence of 80 - 99 % methane

(CH 4 ). The rest is built up of carbon dioxide,

nitrogen oxide and low value hydrocarbon

additions.

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Number of gas powered vehicles

The number of gas powered vehicles was calculated using international natural gas powered vehicle

statistics, as of the second half of 2003.

Number of gas powered vehicles world-wide

approx. 2,837,000

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The number of vehicles world-wide is currently

about 665 million.

Approx. 2.8 million of these are registered as

natural gas powered vehicles.

The leading countries here are those with high

natural gas deposits, such as Argentina with

approx. 951,000 gas powered vehicles.

In Europe, Italy is way ahead of other countries

with 434,000 vehicles, thanks to a good natural

gas infrastructure.

In Germany, currently about 20,000 vehicles run

on natural gas. Half of these are Volkswagen

models which were specially converted for this

purpose.

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