Fig. 3. Load control strategies in hydrogen operation. The number
of ‘‘spheres’’ represents the density. Thus, in the left figure the density
of mixture entering the cylinder is lower, because of the throttle
resistance. The dark gray areas denote fuel, the light gray areas air.
In the two figures on the left, fuel and air are evenly distributed,
while in the right-hand figure fuel is concentrated around the injector
(stratified operation).