Specialty Products > GFS® Diesel Dual Fuel System

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Overview

The Gaseous Fuel System™ is an innovative technology that enables operators of heavyduty diesel vehicles to substantially reduce operational costs and lower emissions. This is achieved by substituting diesel fuel with lower cost, cleaner burning natural gas. The Gaseous Fuel System™ is comprised of patented and proprietary technologies that allow diesel engines to safely operate on gas percentages ranging from 50% to 70% of the total fuel requirement. Engines converted to Gaseous Fuel™ operation exhibit diesel-like performance in such critical areas as power, response and efficiency. A key feature of the Gaseous Fuel System™ is its ability to switch fuel modes without interruption in vehicle operation.
In the event the on-board gas supply is exhausted, the Gaseous Fuel System™ will automatically switch the engine to 100% diesel operation. Conversion to Gaseous Fuel™ operation does not require modification of the engine and can typically be completed in a matter of hours. Typical applications include heavy-duty trucks, buses, refuse haulers, earth moving equipment and locomotives. The Gaseous Fuel System™ is compatible with both compressed natural gas (CNG) and liquid natural gas (LNG) fuel storage systems.

Characteristics

1. Air-Fuel Ratio / LEL
   Operation in Gaseous Fuel mode does not appreciably change engine air-fuel ratio. At maximum allowable gas substitution rates (80%), the gas concentration in the intake air is typically less than 3.0% by volume, which is substantially below the 5.0% Lower Explosive Limit (LEL) of methane. Due to the lean condition of the air-gas charge, the possibility of ignition in the engine air-intake system due to backfire or other causes is minimized.
2. Combustion Process
   Combustion in Gaseous Fuel mode follows the normal compression-ignition (CI) sequence. The air-gas mixture is admitted to the combustion chamber through the OEM intake valve and then compressed during the compression cycle. The high auto-ignition temperature of the lean air-gas mixture prevents ignition of the charge until the diesel injector is activated. The injected diesel fuel provides the necessary ignition source for the air-gas mixture which then combusts at a similar speed and pressure compared to 100% diesel operation. Although the injected diesel fuel acts as an ignition source for the air-gas mixture, it is also providing a portion of the total energy needed for combustion, based on the set gas-diesel mixture.
3. Engine Governing
   The Gaseous Fuel System allows the original engine governing system to control engine speed. No interface or tie-in is required between the Gaseous Fuel System and the engine governor. The Gaseous Fuel System is compatible with electro-mechanical and hydro-mechanical governors as well as some electronic injection based governing systems (contact us for details).
4. Engine Performance
   Conversion to GFS Gaseous Fuel typically results in similar performance levels in terms of engine stability, HP, torque and response.
5. Gas-Diesel Ratio
   Vehicle duty cycle is the most important variable for determining average gas-diesel ratio. In addition to duty cycle, gas composition, charge-air temperature as well as ambient conditions (temperature & altitude) may also play a factor relative to the knock limit of the airgas mixture. In general, moderate to heavy engine loading (over the road conditions) will typically yield gas ratios between 60-75% (assumes high quality natural gas). Lower average engine loads (stop and go / high traffic conditions) will typically limit gas ratio to between 50-60%.
6. Engine Lube Oil
   Unless otherwise indicated by gas composition, no changes in engine lube oil specification are required for Gaseous Fuel operation. Natural gas burns with minimum particulate residues so that engine oil may be kept cleaner during Gaseous Fuel operation. This can possibly lead to longer average intervals between lube oil and oil filter changes and extended periods between engine overhauls. No changes should be made to the OEM’s recommended service intervals without complete engine oil and wear analysis and consultation with the OEM.
7. Engine Operating Temperatures
   Engine heat rejection rates while operating in Gaseous Fuel mode are largely similar to 100% diesel performance. Engine exhaust gas temperature, coolant temperature, oil temperature and manifold air temperature levels remain within the limits set by the engine manufacturer.
8. Engine Efficiency
   Because the Gaseous Fuel System utilizes a low restriction air-gas mixing device and maintains the excess-air operation of the diesel engine, net fuel efficiency (specific fuel consumption) is normally equivalent to 100% diesel operation. For each unit of diesel fuel displaced during Gaseous Fuel operation, a calorically equivalent unit of natural gas will be needed to maintain engine power.
9. Emissions
   Gaseous Fuel operation will typically reduce production of nitrogen oxides, sulfur oxides, reactive hydrocarbons, carbon dioxide and particulates. Exhaust opacity levels (visual emissions) are also typically reduced. For emissions sensitive applications, 2-way oxidation catalysts are recommended. Please contact us for specifications.