Cng & Lpg Engines

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Outline

Introduction

Why CNG and LPG?????

CNG fuel properties CNG vehicle development

LPG fuel properties

LPG vehicle development

Advantages and Disadvantages

Future Scope


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Introduction

"It's not that easy being green.


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Introduction

Designing, developing andmarketing "green" cars has notbeen an easy task.

Fossil fuels still account foralmost 75 percent of the world'senergy consumption.

Soaring prices of petrol

Increase in harmful emissionsand environmental problems.

Need for a low cost and cleansolution.


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Why CNG and LPG???

Availability

Environmental compatibility.

CNG and LPG can be used inconventional diesel and gasolineengines.

CNG and LPG are cheaper than gasolineor diesel.


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Natural gas

Natural gas is produced from gaswells or mainly obtained withcrude oil production.

Comes from the decay of ancientorganisms, but it naturally takes agaseous form.

It is often dissolved in crude oil at

the high pressures existing in areservoir.


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Compressed Natural gas (CNG)

CNG requires a larger volume to store the

same mass of natural gas and the use of very

high pressure on about 200 bar.

Compressed natural gas is non-toxic and will

not contaminate groundwater if spilled.

Compressed natural gas is a largely available

form of fossil energy and therefore non-

renewable.

Natural gas consists primarily of methane

and other hydrocarbon gases


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CNG: Composition

Natural gas (NG) is made upprimarily of methane (CH4) butfrequently contains trace amounts ofethane, propane, nitrogen, carbondioxide, hydrogen sulphide, andwater vapour.


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CNG: Fuel Characteristics

Properties CNG Gasoline Diesel

Ignition Limits 24-6.7 21-7 100-20

Stoichometric

Ratio

17.2 : 1 14.7 : 1 14.5 : 1

Auto-IgnitionTemperature (F)

842 572 446

Lower calorificvalue(kJ/kg)

45800 42100 43100

Octane rating 130 85-95 30

Peak FlameTemperature (F)

3423 3591 3729


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CNG: Engine Development

The First Natural Gas Vehicle 1860

The first internal combustion engine (ICE) vehicle to run on natural gas was

created by Etienne Lenoir in 1860!


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CNG: Engine Working


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CNG: Engine working

Storage cylinders:

Gas is compressed to 25 Mpabefore

being pumped into high-pressure, tube-

shaped cylinders that are attached to the

rear, top or undercarriage of the vehicle.

More lightweight cylinders have been

developed

Integrated Storage Systems (ISSs):

-fibreglass shell

-impact-absorbing foam


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CNG: Engine working

Main shut off valve:

When engine needs fuel, CNG

leaves storage cylinder and leaves

and passes through master

manual shut off valve.


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CNG: Engine working

Pressure regulator:

Three-stage pressure reductionfrom about 20 Mpa to slightly aboveatmospheric pressure.


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CNG: Engine working

Solenoid valve:

Solenoid valve lets the gasfrom the regulator intothe fuel injectors.

This same solenoid valve

shuts off the natural gaswhen engine is stopped


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CNG: Engine working

FUEL METERING

CNG then flows throughventuri carburettor or fuelinjection system to thecombustion chambers.


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CNG: Performance characteristics


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LPG Third most popular fuel after Petrol and Diesel.

Used in many countries like Turkey, South Korea, Japan,

Australia, Italy and many more in public and private

transport Sector.


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LPG: Fuel Characteristics


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Fuel Injection System

Components-

LPG storage Tank.

Vacuum Fuelock

Filter.

Pressure Regulator.

Carburetor.


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LPG Storage Tank

Storage Pressure- 7.5-10

bar.

Pressure vessel designed

to hold pressure of 45 bar.

Separate Filler and

Extraction Valve.


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Vacuum Fuelock Filters

Functions-

It prevents dirty fuel fromreaching the Carburetor.

It shuts off the fuel flow

automatically, regardless of the

ignition being on or off.


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Pressure Regulator/Vaporisor

Functions-

Reduce fuel pressure in two

stages. Convert the fuel from a

liquid to a vapor

Meter the fuel output in

relation to a negativepressure signal (vacuum)from the carburetors.


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CarburetorsFunctions-

The air valve carburetors consist of a

mixer, throttle body and an optional

air horn.

The air horn enables the

connection of an air hose or air filter

assembly.

The throttle valve controls

delivery of the air-fuel mixtureinto the engine intake manifold

based on the operators

command(foot pedal).


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LPG Engine Performance

In the case of using LPG in SI engines, the burning rate of fuel is

increased, and thus, the combustion duration is decreased.

As a consequence of this, the cylinder pressures and

temperatures predicted for LPG are higher than those obtained

for gasoline.

Thus ,Volumetric Efficiency

Hence, Power output and Efficiency Consequently SFC


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LPG Engine Performance

The volumetric efficiency is

thus improved by employing

heat removal system from the

heated intake air.

This results in increase in

power output by almost 8%

as compared with same size of

gasoline engine.


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CNG Engines: Applications

In traditional gasoline internal combustion engine cars that have been

converted into bi-fuel vehicles (gasoline/CNG).

CNG is starting to be used also in pickup trucks, transit and school buses,

and trains.

CNG can be used in Otto-cycle (gasoline) and modified Diesel cycle

engines.

One successful trip with CNG in dual fuel mode was conducted on 23.4.05

by INDIAN RAILWAYS.


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Advantages

High possible power output

High octane number

Higher compression ratio


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Advantages

No possibility of fouling of spark plug

Lower maintenance costs

High auto ignition temperature:

Safe

No spill and evaporation losses:

Increased life of lubricating oils

Easy mixing with air for combustion


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Advantages

Low pollution content as compared to petrol : An engine

running on petrol for 100kms emits 22,000 grams of CO2,

while covering the same distance on CNG emits only

16,275 grams of CO2.


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Disadvantages Greater storage space . More number of equipment for gas supply.

Cost of conversion is still the biggest setback. Savings in fuel and

maintenance costs, however, can offset the initial cost.

Refuelling.


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LPG: Advantages

Power, acceleration, payload and cruise speed

Refueling

High octane rating


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LPG Engine Emissions Use of LPG reduces the content of pollutants like CO, NOx , and HC

in the Exhaust.

0

2

4

6

8

10

12

14

5hp 6hp 13hp 18hp

Gasoline

LPG

HC+NOx Emissions

g/kw/h

0

50

100

150

200

250

300

350

5hp 6hp 13hp 18hp

Gasoline

LPG

CO Emissions

g/kw/h


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LPG: Disadvantages

In cold conditions Starting could be a problem.

One gallon of LPG contains less energy than a gallon of

gasoline.

LPG is generally higher priced.

Refueling stations.


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Future Scope

More petrol and diesel vehicles will beconverted to NGVs(Natural gas vehicles).

100% conversion of heavy duty vehicles

will take place within a decade.

Smaller fuel tanks will come up.

Use of Liquefied Natural Gas (LNG) for

storing will be used by maintaining

cryogenic conditions in the tank.

Better CNG and LPG dedicated engine

designs.

Low emissions meeting the strictpollution norms.

Cleaner environment!!!!


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Cng & Lpg Engines

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