Converting Diesel Engines to Bi-Fuel


Existing and new diesel engines can be retrofitted to run on Dual Fuel Natural Gas and Diesel with the ability to operate on 100% Diesel Fuel if Natural Gas is interrupted. The system is used to lower exhaust emissions, extend diesel fuel tank run-time, reduce fuel expenses and prolong engine life and maintenance.

Applications: Peak shaving, prime power, co-generation, distributed generation diesel powered electric generators. Sources of gas can be from standard pipelines, oil fields, offshore platforms, landfills, digester or other sources of methane gas.

Technology: The Exclaim Dual Fuel system is based on a fumigation principle first observed by Mr. Rudolph Diesel, the inventor of the Diesel engine. Natural gas enters the engine with normal combustion air through the air filter, before the turbo charger. A significantly reduced amount of diesel fuel continues into the engine, which serves as a pilot ignition source for the natural gas. Our control system maintains the proper balance of natural gas, diesel and air to meet the engine’s BTU power requirements. Applications using controls for dual-fuel fumigation technologies are subject toU.S. patent, with foreign patents pending.

Results: The Exclaim fumigation system does not add spark plugs or change other specifications within the engine, so factory warranties remain in effect. Engines maintain full rated horsepower/kW at factory recommended operating temperatures. Emissions such as NOx can be lowered by as much as 60%. Oil changes can be extended approximately 3 times normal. Black exhaust smoke (particulates) can become clear.

THE SYSTEM

The Exclaim Dual Fuel System operates by blending diesel fuel and natural gas in the combustion chamber. This is achieved using a pilot-ignition, fumigated gas-charge design, whereby natural gas is premixed with engine intake-air and delivered to the combustion chamber via the air-intake valve. The air-gas mixture is ignited when the diesel injector sprays a reduced quantity of diesel fuel into the chamber. This diesel “pilot” acts as the ignition source for the primary air-gas combustible. Because of the high auto-ignition temperature of natural gas, the air-gas mixture will not ignite during the compression stroke, as there is not enough heat present to facilitate combustion.

Because the existing air-intake and diesel injection systems are utilized by the Dual Fuel System, no engine modifications are required for installation.

The various components of the Bi-Fuel System are installed externally of the engine, and at no time is the engine disassembled during installation.

All OEM engine specifications for injection timing, valve timing, compression ratio, etc., remain unchanged after installation. The Dual Fuel System requires a low pressure natural gas supply (approximately 2 – 5 psi) with a flow rate of approximately 8 scfh/kW (i.e. 500 kW=5,000 scfh).

INSTALLATION

The Exclaim Dual Fuel System is installed by trained technicians, with the installation normally taking anywhere from a few hours to a few days depending on the size of the generator. During nearly all of the installation process, the generator can be utilized for emergency power with little or no starting delay if the system is applied at the customers’ job site. Actual downtime of the generator is limited to only a few minutes, and rental back-up power is normally not required during installation of the System.

After installation of the Exclaim Dual Fuel System hardware, the generator is then operated under various load settings (normally with the use of a resistive load bank) while the System is checked and calibrated. After this “tune-in” process is completed, the generator is fully tested in Dual Fuel mode to assure proper operation of the system and generator during light, medium, heavy and transient loads. Finally, the generator is tested in 100% diesel mode to verify that its 100% diesel performance has not been affected by installation.

PERFORMANCE

Installation of the Exclaim Dual Fuel System in no way compromises the performance of the generator relative to the rated load of the machine. A generator with a 1000 kW stand-by rating which has been retrofitted to Dual Fuel will still provide 1000 kW of power in both 100% diesel and Dual Fuel modes.

In other words, the generator is not de-rated after installation of the system. Similarly, there is no decrease in generator load response or stability while operating in either fuel mode.

Outside links to OEM engines manufacturers who also support Dual Fuel/Bi-Fuel technology for generators:
Cummins Generators Dual Fuel Website
Caterpillar Dynamic Gas Blending