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Bi-Fuel System

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  • Applications & Key Technologies

    Gaseous Fuel System™

  • Overview
  • Gas Operating Characteristics
  • Gas Supply
  • Gas Control Components
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    Glossary

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    Gaseous Fuel Systems

  • Gas Train
  • High Pressure Regulator
  • Low Pressure Regulator
  • Gas Solenoid Valve
  • Gas Pressure Transducer
  • Air-Gas Mixer
  • Electronic Control System
  • Diesel Fuel Control
  • Aneroid Control Valve
  • Diesel Control Valve
  • Gases Fuel System

    Components Overview

    Gas Train

    The Gaseous Fuel System requires precise regulation and control of the fuel supply gas. In order to ensure nominal operation, the Gaseous Fuel System is supplied with a specialized "gas train" consisting of a high pressure gas regulator, low pressure gas regulator, electrically activated gas solenoid valve and gas pressure transducers.

    The gas train is designed to accept high pressure supply gas in the range of 2,400 ~ 3,600 psi (165 ~ 247 bar) and supply regulated gas to the engine at slightly negative pressure.

    High Pressure Regulator

    The High Pressure Regulator (HPR) is a single stage regulator designed for high pressure CNG use. The HPR is engine coolant heated to prevent freezing and has dual outlet ports for installation flexibility.

    The HPR is rated up to 3,600 psi (247 bar) inlet and provides a regulated outlet pressure of 150 psi ± 20 psi (10.30 bar ± 1.40). The HPR is supplied with an external pressure relief valve calibrated to open if outlet pressure exceeds 400 psi (27.50 bar). The HPR has been approved by UL, AGA and CGA.

    Low Pressure Regulator

    The Low Pressure Regulator (LPR) is a two stage regulator consisting of a cast aluminum housing containing working diaphragms, an adjustable pressure set-point spring and a pre-loaded counter spring.

    The regulator operates according to the differential pressure between the inlet port and outlet port in order to maintain the set delivery pressure. The regulator detects changes in engine vacuum (at the outlet port) as engine load increases or decreases and adjusts gas flow rate in order to maintain the set outlet pressure. The LPR supplies gas to the engine at approximately atmospheric pressure. The HPR has been approved by UL, AGA and CGA.

    Gas Solenoid Valve

    The Gas Solenoid Valve (GSV) is a DC powered, normally closed, two-way gas control valve. Although typically installed downstream of the HPR, the GSV is rated to accept the maximum system pressure of 3,600 psi (247 bar). The gas solenoid valve is supplied 12 volts DC from the GFS primary controller. When the GSV is energized, gas is supplied to the engine. When the GSV is de-energized, the engine is immediately switched to 100% diesel mode. The GSV has been approved by UL, AGA and CGA.

    Gas Pressure Transducer

    The gas train includes a Gas Pressure Transducer (GPT) for monitoring CNG fuel pressure. The GPT is installed upstream of the HPR regulator using the supplied adaptor fittings. Depending on GFS kit model, the GPT may be rated for 2,400, 3,000 or 3,600 psi operation (165, 206 or 247 bar).

    Air-Gas Mixer

    The Air-Gas Mixer (AGM) blends engine intake-air with an appropriate quantity of natural gas as required for combustion. The AGM is installed upstream of the turbo-compressor inlet and downstream of the engine air cleaner housing. The patented GFS Air-Gas Mixer is a "fixed venturi" design and therefore does not have a moveable air-throttle.

    Air entering the AGM is diverted around a gas diffuser section, causing a turbulent, low pressure area to form. This low pressure area draws natural gas from the diffuser section gas reservoir through a radial pattern of precision machined gas outlet orifices.

    Gas is introduced into the turbulent airflow area immediately downstream of the gas diffuser section, allowing for a high degree of mixing action of the two media. The Gaseous Fuel System Air-Gas Mixer provides for a high degree of air-gas blending with a minimum of airflow restriction.

    The AGM design includes an integral Gas Power Valve (GPV). The GPV is a proprietary flow metering device that allows for precise adjustment of gas flow to the engine. The GPV utilizes a needle and seat type flow adjustment, comprised of an adjustable threaded gas screw and seat.

    Once set, the gas screw position sets a fixed and limiting orifice inside the power valve body, thereby controlling the maximum flow of gas available across the engine load range. By using the adjustable gas screw, the operator is able to set the desired gas-diesel ratio.

    The CAD designed AGM is constructed of aerospace quality materials that have been CNC machined and then assembled using a state-of-art welding process.

    The AGM is mil-spec anodized for surface hardness and corrosion protection. The GFS Air-Gas Mixer comes standard in 4", 5", and 6" O.D. (101.6, 127, 154.4 mm O.D.).

    Electronic Control System

    The Gaseous Fuel System is supplied with an Electronic Control System (ECS) that monitors engine exhaust gas temperature and monitors/displays CNG supply pressure and level.

    Based on sensor inputs and factory-set limits, the ECS will activate or deactivate gaseous fuel mode as required. Depending on the model of Gaseous Fuel System, the ECS will be configured for either 2,400 3,000 or 3,600 psi (165, 206 or 247 bar) operating pressure.

    The controller sub-kit is supplied with the necessary sensors, displays and wiring harnesses. The ECS monitors engine exhaust gas temperature (EGT) using a K-type thermocouple and CNG supply pressure with a pressure transducer.

    The ECS is provided with indicator lights that provide a quick visual status of the Gaseous Fuel System. If a fault is detected by the control system, Gaseous Fuel operation is suspended and the engine is reverted to 100% diesel operation.

    Factory programmed setpoints include high engine EGT and low pressure CNG limits.

    In the event engine EGT exceeds a value of approximately 1200 deg. F (650 deg. C), the ECS will automatically revert the engine to 100% diesel operation and illuminate the amber EGT fault lamp.

    In the event CNG supply pressure drops below approximately 250 psi (1724 kPa), the ECS will automatically revert the engine back to 100% diesel operation and illuminate a red lamp.

    Both high EGT and low CNG conditions result in a latching fault condition - the ECS must be reset to clear the fault condition by removing the DC power supply (typically achieved by cycling the vehicle's key from "run" to "off" and back to "run").

    Diesel Fuel Control

    In order to allow substitution of natural gas for diesel fuel, it is necessary to physically limit the amount of diesel fuel available to the engine injection system. Depending on engine fuel system configuration, the Gaseous Fuel System will include one of the following devices:

    • Aneroid Control Valve

      For engine fuel systems that reference MAP (turbo boost pressure) using an aneroid, the Gaseous Fuel System utilizes an "Aneroid Control Valve" (ACV).

      The ACV is a three-way, 12 volt, DC-powered valve that is installed between the engine airintake manifold and the air-inlet port on the OEM fuel aneroid (or pressure transducer in some cases).

      When activated by the ECS, the ACV diverts the turbo boost "signal" (air pressure) such that the aneroid controller maintains the diesel rack in a retarded position. This has the effect of reducing engine HP by up to 80% and allowing for the substitution of natural gas for diesel fuel.

      When de-activated by the ECS, the ACV allows the normal turbo boost signal to reach the fuel aneroid, thereby restoring full engine power for 100% diesel mode.

    • Diesel Control Valve

      For engine fuel systems that do not employ an aneroid fuel controller, the Gaseous Fuel System utilizes a Diesel Control Valve (DCV).

      The DCV is a three-way, 12 volt, DC-powered, adjustable flow control valve. For engines equipped with in-line injection pumps, the DCV is installed immediately upstream of the injection pump fuel inlet.

      For engines equipped with fuel rails (such as the Cummins PT system), the DCV is installed after the pressure pump and before the inlet to fuel rail.

      When activated by the ECS, the DCV decreases the flow of fuel to the injection pump or fuel rail and decreases engine HP by up to 80% allowing for the substitution of natural gas for diesel fuel.

      When de-activated by the ECS, the DCV allows for unrestricted fuel flow, thereby restoring full engine power for 100% diesel mode.

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