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Gas Engines

Bi-Fuel System

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    Gaseous Fuel System™

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    Glossary

    Conversion

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    Gaseous Fuel Systems

  • Commissioning
  • Commissioning Methods
  • Chassis Dynamometer
  • On-Road Commissioning
  • Gases Fuel System

    Commissioning

    Unless otherwise requested by the operator, the commissioning process normally involves adjusting the Gaseous Fuel System controls to allow for the maximum possible gas ratio (minimum possible diesel fuel consumption) while simultaneously maintaining the engine in a safe operating range.

    The commissioning process can generally be divided into three distinct phases involving:

    1. Testing of the engine to confirm baseline performance,
    2. Reduction of engine h.p. using either the Aneroid Control Valve or the Diesel Control Valve (no gas)
    3. Recovery of engine h.p. to the baseline level established in step 1 above using natural gas.
    Since fuel consumption is typically linear compared to engine load, it is possible to estimate the gas-diesel ratio by comparing peak engine h.p. values in steps 2 and 3 above (when using a chassis dynamometer).

    For example, an engine which makes 250 h.p (at the wheels) is de-rated to a maximum of 75 h.p. (step 2).

    Using gas, the engine h.p. is set back to 250 wheel h.p. in Gaseous Fuel mode (step 3).

    In this case, the approximate gas ratio at peak engine power is 70% (with 30% diesel pilot), since 70% of the engine h.p. was recovered using natural gas (250 h.p. x 0.30% = 75 h.p.).

    In most cases, maximum gas ratio will be limited by one or more of the following factors:

    • Engine Exhaust Gas Temperature (EGT)
    • Engine Knock
    • Engine Stability
    • Engine Durability
    Commissioning Methods

    Preferably, engines should be commissioned in Gaseous Fuel mode using a chassis dynamometer. This method has several benefits including the ability to more precisely set the gas-diesel mixture as well as the ability to fully test the engine across the load / speed range.

    In the event that a chassis dynamometer is not available, the engine may be commissioned "on-road" if necessary.

    On-road commissioning generally takes longer to complete (compared to chassis dynamometer method) and normally requires that the vehicle be placed in service to confirm operating gas-diesel ratio and engine characteristics, since it is typically difficult to simulate loaded conditions.

    Commissioning Process - Chassis Dynamometer

    The commissioning process requires that the vehicle be operated at high speeds and power loadings on the chassis dynamometer.

    In order to monitor engine EGT during the commissioning process, the use of a hand-held, infrared temperature monitor is recommended (range >1200 F/ 650 C). EGT should be monitored at the turbine inlet (turbocharged engines) as well as at each cylinder exhaust port to confirm proper temperature balance between cylinders. It is also possible to utilize the ECS EGT thermocouple to monitor engine EGT using a hand-held temperature monitor (compatible with K-type thermocouples).

    The commissioning process will require extended operation of the vehicle on the chassis dynamometer (dyno). Adequate cooling of the engine and vehicle must be maintained (using a fan or other means) to prevent overheating of the engine and/or drive train.

    Notes Regarding On-Road Commissioning

    In the event that a chassis dynamometer is not available, the engine may be commissioned in Gaseous Fuel mode.

    In order to replicate this process, it will be necessary to devise a method to consistently load the engine / vehicle.

    As an example, engine performance (power) may be inferred by comparing the relative time it takes the vehicle to cover a particular straight distance, or alternately, the time it takes to climb a particular hill or grade. Note that unlike the chassis dynamometer method, the on-road method does not provide empirical data relative to engine h.p. or torque therefore making an accurate estimate of gas-diesel ratio somewhat more difficult.

    In addition, it is often more difficult to monitor other engine parameters. In most cases, a vehicle commissioned on-road will need to be placed in service (or otherwise operated for a significant time/distance) in order to confirm actual operating gas-diesel ratio and general performance in Gaseous Fuel mode.
     

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