COMPRESSED NATURAL GAS VEHICLES

Compressed natural gas or liquid petroleum gas or auto gas can be used as a fuel source to power or run automobile vehicles. CNG or LPG or autogas in its composition consist of either propane or butane gas alone or it is a mixture of propane and butane gas .CNG or LPG or autoGas, has an octane rating of between 90 and over 100.it has energy content of about 25.5 megajoules per litre (for pure propane) and 28.7 mega joules per litre (for pure butane) depending upon the actual fuel composition.it can be satisfactorily used as fuel source with virtually any petrol engine.

CNG or LPG or Autogas is widely used as a “green” fuel, as its use reduces CO2 exhaust emissions  by around 15% compared to petrol.

CNG or LPG or Autogas is the third most popular automotive fuel in the world, with approximately 16 million of 600 million passenger cars powered using the fuel, representing less than 3% of the total market share. Approximately half of all CNG or LPG autogas-fueled passenger vehicles are in the five largest markets (in descending order): Turkey, South Korea, Poland, Italy, and Australia. While other gas producers like Nigeria are try to catch up by launching an ambitious energy programme to shift the dependence of its automobile industry from petrol to CNG by the turn of the century.

In fact, compressed natural gas (CNG) vehicles operate with little change to the configuration of the petrol engine. The basic difference is the device elements in the fuel supply line, en route from gas storage tank to the internal combustion engine. However in general, the CNG fuel supply system supply gas under high pressure to the fuel line via a pressure regulator, which reduces the supply gas pressure to the level compatible with the engine fuel injection system. Thereafter the gas is mixed with air in the combustion chamber of engine, prior to ignition by a spark plug.

However there are four basic types of the CNG or LPG supply system,
(1) LPG Liquid Phase Direct Injection (LPDI) has liquid LPG injected directly into the combustion chamber. LPDI is the most advanced LPG system for cars.

(2) LPG Liquid Phase Injection (LPI) systems inject liquid directly into the intake manifold.

(3)  LPG Vapor Phase Injection (VPI) the gas exits the converter under pressure and is injected into the intake manifold.

(4) LPG Converter-and-Mixer Systems is the oldest style LPG system. Liquid fuel converts into vapor and is then mixed with air before going into the intake manifold.

 

KEY COMPONENT OF A COMPRESSED NATURAL GAS VEHICLE

The key components of a compressed natural gas vehicle are;

(1)Battery: The battery provides electricity to start the engine and power vehicle electronics/accessories.

(2)Electronic control module (ECM): The ECM controls the fuel mixture, ignition timing, and emissions system; monitors the operation of the vehicle; safeguards the engine from abuse; and detects and troubleshoots problems.

(3)Exhaust system: The exhaust system channels the exhaust gases from the engine out through the tailpipe. A three-way catalyst is designed to reduce engine-out emissions within the exhaust system.

(4)Fuel filler: A nozzle from a fuel dispenser attaches to the receptacle on the vehicle to fill the tank.

(5)Fuel injection system: This system introduces fuel into the engine’s combustion chambers for ignition.

(6)Fuel line: A metal tube or flexible hose (or a combination of these) transfers fuel from the tank to the engine’s fuel injection system.

(7)Fuel tank (compressed natural gas): Stores compressed natural gas on board the vehicle until it’s needed by the engine.

(8)High pressure regulator: Reduces and regulates the pressure of the fuel exiting the tank, lowering it to an acceptable level required by the engine ‘s fuel injection system.

(9)Internal combustion engine (spark-ignited): In this configuration, fuel is injected into either the intake manifold or the combustion chamber, where it is combined with air, and the air/fuel mixture is ignited by the spark from a spark plug.

(10)Manual shut off: Allows the vehicle operator or mechanic to manually shut off the fuel supply.

(11)Natural gas fuel filter: Traps contaminants and other byproducts to prevent them from clogging critical fuel system components, such as fuel injectors.

(12)Transmission: The transmission transfers mechanical power from the engine and/or electric traction motor to drive the wheels.

ADVANTAGES OF COMPRESSED NATURAL GAS ENGINES

(1) CNG or LPG or Autogas engines have lower running costs.

(2) CNG or LPG or Autogas is typically less expensive than petrol or diesel.

(3) Engine oil and spark plugs need changing less often with CNG or LPG or Autogas vehicles, thereby reducing the service costs.

(4) Environmental benefits of LPG vehicles include reduced particulate, CO2 and NOx emissions.

(5)Octane ratings over 100 allow for higher compression ratios, which can increase power output.

DISADVANTAGES

The benefit or advantages of CNG or LPG or Autogas Vehicles over petrol vehicles far outweighs it disadvantages. Despite CNG being widely used as a fuel for cars, its availability calls for question. The automobile industry has adopted petrol as fuel standard for automobiles with a wide network of petrol service stations all over the world to the detriment of gas stations. However, some CNG fuel-systems are designed to run on both petrol and CNG. This type of petrol and CNG hybrid vehicles are more competitive, since they can benefit from the advantages of both petrol and CNG system.

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