We have Diesel/Dual Fuel Engine-Generators, with a new "Micro Pilot" fuel oil injection system, a modern common rail high pressure system, with electronically controlled injections. The engines are rated at 2500 kW, 400 RPM, 17 x 22 B&S, inline 8 cylinder engines, direct coupled to their generators. The engines can burn 100% Diesel Oil (No 2 oil) with their original fuel injection system, jerk pumps etc. (one jerk pump for each cylinder), but when in "Dual Fuel" mode, getting proper fuel injection quantity with the original (and BIG) fuel oil jerk pumps is difficult, as the original jerk pumps are rated at more than 100% fuel flow, 50x to 100x what is needed here. The turndown to such a small fraction of oil injection is not practical when the big Jerk pumps are asked to meter out 1%-2% percent fuel flow. To get acceptable ignition across all 8 cylinders, the big jerk pumps' fuel rack needs to be turned up into the vicinity of 35% capacity, so we are burning on the order of 20 to 30 times the theoretical fuel oil requirement, just to assure no misfires, etc. This makes for lousy emissions, as well as an expensive amount of fuel oil being required, hence the change-out to the "micro-Pilot" system was commissioned.

When operating on digester gas in the "Micro Pilot" mode, about 1% to 2% of the engine energy is derived from injection of fuel oil, which acts like a "spark plug" to ignite the air/digester gas fuel mixture. So the range of "micro pilot" fuel flow has a maximum oil injection rate equivalent to what is needed for a 25 kW to 50 kW diesel engine of 8 cylinders and 400 RPM operation.

The HP fuel pump puts out about 15,000 – 20,000 psi, and requires about 8-10 horsepower, which is taken from the engine's camshaft/accessory gearbox at 1100rpm. However the pump experiences full torque reversals sometimes, say 100% average torque, +/- 200%. The pump drive gear (18 teeth, 4.61 inch pitch diameter, about 3 inches thick) would experience "backlash slamming" due to the gear clearances, and frequent torque reversals.

Is there criteria as to how gears can withstand this type of treatment?