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The ignition of single fuel droplets in air is modeled according to the time-varying conditions within the droplet and the boundary layer around the droplet. Ignition is hypothesized when some point in the boundary layer has experienced a sufficiently severe history in terms of pressure, temperature, equivalence ratio, and time to auto ignite. Experiments were conducted with a wide variety of fuels to validate the model. A critical size concept for ignition was predicted by the model and substantiated by the experiments.

A nondimensional representation for a four stroke spark ignition engine was obtained that included the transient charging and exhaust effects. Two basic advantages accrued from this approach; the design and operating parameters that evolved from the nondimensional approach are truly basic in nature, which makes the computer solution more universally applicable to all engines. The inclusion of the transient effects made the representation more realistic and of particular value in the study of engine breathing problems. The effect of valve timing, cam design, valve dimensions, and inlet temperature on engine performance were studied with the computer model.