Application of a thermal efficiency maximizing control strategy for ignition timing and equivalence ratio on a natural gas-fueled Hercules G1600

A two dimensional optimization process which simultaneously adjusts the spark timing and equivalence ratio of a lean-burn, natural gas, Hercules G1600 engine has been demonstrated. The optimization process adds small synchronous disturbances to the spark timing and air flow while the fuel injected per cycle is held constant for four cycles. The engine speed response to these disturbances is used to determine the corrections for spark timing and equivalence ratio. The control process, in effect, uses the engine itself as the primary sensor adapting to changes in fuel composition, operating conditions, engine wear, or other factors which may not be easily measured.