Technical Info

The Diesel Engine:

Internal combustion engines use fuel and air to combust, generating the force that moves each piston in its cylinder, thus powering the vehicle.

Since Otto invented the modern four-stroke cycle engine in 1876, liquid fuels, namely petrol and diesel, have become the preferred fuels, due to their physical properties of high energy content, ease of storage and handling. Relatively, only a small quantity of fuel is required and stored onboard to give the vehicle an acceptable range.

In conventional petrol engines the liquid fuel is premixed with air in the carburettor, while in diesel and fuel-injection engines, the fuel is injected into the combustion chamber by injectors. Pressure fed via a fuel pump, the fuel is 'atomised' or turned into a fine spray through an injection nozzle.

Air flow into and out of the cylinder is controlled by valves. The atomised liquid fuel changes to a gaseous state known as ' vaporisation ' and its molecules attach to the air oxygen molecules, 'volatilisation '. Liquid fuels cannot burn until they are volatilised. During the compression stroke the valves close and the containment of the cylinder is compressed. Due to the density and composition of petrol or diesel, the compression causes a quantity of the vaporised and volatilised fuel to return into an un-combustible liquid state.

In a petrol engine, ignition of the air/fuel mixture is accomplished by a spark plug. In the diesel, combustion takes place automatically as soon as the fuel is injected. The volatilised fuel ignites and the force of the explosion drives the piston. This first explosion powers the vehicle. The release of heat from this first explosion vaporises and volatilises additional liquid fuel and re-ignites due to the auto-ignition temperatures, resulting in waves of combustion. The combustion wave explosions generate sufficient heat to release NOx emissions from the dissociated atmospheric nitrogen. The ambient air is typically composed of 20% oxygen, required for combustion, 78% nitrogen and 2% of N2 compounds.

The remaining un-burnt fuel hydrocarbons that are not burnt-up are released to the atmosphere as undesirable emissions. The emissions of hydrocarbons and NOx have caused severe damage to our environment, ozone layer and the health and welfare of humans, plants, and animals. The engine efficiency of petrol engines range from 25% to 30% and some diesels can achieve efficiencies up to 42%. This means that only a small percentage of the energy in the fuel is converted to mechanical power. The remainder is wasted into the atmosphere or as heat into the vehicle's cooling system.  Typically diesel engines burn 70 - 75% of the diesel that is injected into the combustion chamber. It is this unburnt and wasted diesel that allows the D-Gas System to work.

How the D-GAS Technology works:

LPG vapour fuel is injected into the engine's intake manifold, homogeneously mixing to the engine's intake of atmospheric air. The liquid diesel fuel is injected into the cylinders as before.

Under the compression cycle, the air mixed with the LPG fuel heats to hotter temperatures due to the alternate fuel's higher 'heat of vaporization'. The increased temperatures during the compression cause the diesel fuel to stay in a gaseous state and forces more droplets of diesel fuel to vaporize and volatize. Compression of the LPG/AIR mixture never reaches the auto-ignition point, so pre-ignition is not a concern.

Ignition, as previously, is accomplished automatically as diesel fuel is injected into the engine. In addition to the increased vaporisation and pre-combustion temperatures, the gaseous fuel, due to its 'stoichometric flame speed' (of 0.43 of LPG propane), higher volatility and higher auto-ignition temperature (high octane), causes a quicker and more spontaneous combustion resulting in increased power and economy without engine modification. The wasted 25 - 30% is now turned into an energy producer.  This is where the extra economy and power is obtained from.  More power from the same amount of injected diesel.

The power increases are also due in part to the increase in volumetric efficiency from the requirement for less oxygen in the air/fuel/alternate fuel mixture charge and maintains the engine's existing stoichometric ratios. Although the gaseous alternate fuel should increase the temperature of combustion of the fuel mixture over dedicated liquid fuel combustion, this has not been measurable and is believed to be negligible.  In deed, in practice, customers notice a DECREASE in engine temperatures. 

Since the diesel liquid fuel is virtually vaporised and volatilised pre-combustion, and since combustion is more rapid and complete, there is one explosion consuming the fuel and releasing its energy. No 'combustion waves' but A COMBUSTION WAVE. An audible quieting of the diesel knock can be verified with a stethoscope and by ear. Since there are no additional explosions (combustion waves), excess heat is not generated in after waves of combustion, reducing the formation of NOx and the engine's cooling system is not strained dissipating the excess heat. Cooling system temperatures remain as before, because of thermostats, electronic cooling fans, etc. Engine oil temperatures can decrease by up to 20 - 25 degrees Celsius with the D-GAS System in operation. Exhaust with 'lower' hydrocarbons and NOx emissions are released to the atmosphere.

As virtually no fuel is present in the exhaust gas, there is no after burn in the exhaust. Exhaust temperatures can decrease on vehicles fitted with the D-GAS System and an increased vapour content of the exhaust is observable, a further indication of more efficient combustion.

Additionally, the properties of the LPG dissolves carbon and tar deposits in the combustion chamber after a period of operation. Combustion chamber deposits are responsible for significant increases in emission, heat generation and inefficient combustion. Our dual fuel system operation cleans the combustion chamber even in older or high mileage vehicles and returns them to a cleaner more efficient condition.

Fuel savings are generated because the combustion is more complete with less energy being wasted to heat or turned into harmful emissions. Less liquid diesel fuel is required to maintain the same power levels, yet torque is increased, providing more satisfactory engine performance, improved acceleration, and greater load hauling capabilities. The System works equally well with any diesel engine whether it be using a electronic or mechanical injection pump or two stroke.

The D-GAS - Diesel Emissions System Boost:

The D-GAS System is an add-on fuel saving system which increases economy and lowers exhaust emissions. The system injects a small measured quantity of LPG fuel simultaneously with the existing use of the diesel fuel. The D-GAS System is defined as 'DUAL FUEL', a system that allows a vehicle to run on two fuels at the same time.

Equipping a vehicle with a D-GAS System involves no modifications to the engine or to any part of the fuel or ECU or fuel control systems. The System is fully automatic and will not cause an engine to stop if the system fails.

The D-GAS system comprises the following APA approaved components:

·   A reservoir/tank to store the LPG fuel onboard the vehicle. Since only a small amount of fuel is needed, the capacity of LPG required to increase the vehicle range between refueling is small, for example, a typical passenger car only requires a 15 to 30 lt LPG reservoir which has little or no effect on the vehicle's cargo capacity and presents no safety concern of additional fuel storage.

·   A filling valve to refuel the LPG tank is fitted close to the LPG cylinder.

·   A fuel supply pipe from the reservoir or tank to a vapouriser and then to a second electrical safety shut off valve in the engine bay and then on to the D-GAS control system.

· Injectors and supply line are fitted to the engine intake manifold.

·   A digital fuel level display gauge with on/off switch is installed inside the cab.

Vehicle Standard (Australian Design Rule 80/02 - Emission Control for Heavy Vehicles) 2006

For more information on our D-GAS System, raising the emissions rating on your heavy vehicle fleet or in calculating the savings for your fleet, contact us on 1800 48 78 82

 

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