A system for controlling an air flow rate into a vehicle engine room may include a fan shroud in which a cooling fan including a fan motor and a fan blade is mounted, a radial portion which is provided in the fan shroud while corresponding to an operation area of the fan blade, including a shutter hub positioned to a center thereof and a plurality of radial units disposed to the shutter hub and including a plurality of radial shutters selectively unfolded from the shutter hub to external circumference directions or selectively folded to the shutter hub direction, and a radial unit operating portion unfolding the plurality of radial units from the shutter hub to the external circumference directions or folding the plurality of radial units to the shutter hub direction.

A cooling system for a heavy road vehicle provided with a hybrid propulsion system includes a mechanical propulsion system and a hydraulic propulsion system. The cooling system includes a pump and a first cooling circuit including a gearbox cooling circuit a hydraulic propulsion system cooling circuit and a first radiator for cooling of a coolant flowing in the first cooling circuit. The radiator is connected in series with and located upstream of the gearbox cooling circuit and the hydraulic propulsion system cooling circuit. The cooling system is designed such that the hydraulic propulsion cooling circuit and the gearbox cooling circuit are connected in parallel.

A cooling system for a heavy road vehicle provided with a hybrid propulsion system includes a mechanical propulsion system and a hydraulic propulsion system. The cooling system includes a pump and a first cooling circuit including a gearbox cooling circuit a hydraulic propulsion system cooling circuit and a first radiator for cooling of a coolant flowing in the first cooling circuit. The radiator is connected in series with and located upstream of the gearbox cooling circuit and the hydraulic propulsion system cooling circuit. The cooling system is designed such that the hydraulic propulsion cooling circuit and the gearbox cooling circuit are connected in parallel.

A vehicle has a front grille, engine, engine compartment, power storage device, temperature sensor, shutter, heater and controller. The device can be electrically charged from an external power supply. The temperature sensor detects engine coolant temperature. The shutter is disposed in a transfer pathway of air drawn into the engine compartment via the front grille, and is switched between closed and open states. The heater is able to generate heat when receiving the electric power, raising the coolant temperature. The controller starts the engine when the coolant temperature is lower than a startup threshold value, drives the heater when the coolant temperature is lower than a first threshold value equal to or higher than the startup threshold value, until the coolant temperature becomes equal to or higher than the first threshold value, and drives the shutter to place the shutter in the closed state while the heater is driven.

An outdoor unit has a frame that carries a ground grooming or working implement, a traction drive, and a cooling fan, all of which comprises loads on a prime mover. A power management controller automatically reduces an operational speed of the traction drive when prime mover droop is present. The cooling fan cools two cooling fluids. The controller stores data representing variable fan speeds for cooling each cooling fluid in both normal and above normal temperature ranges and for use when prime mover droop is present. The controller uses the highest fan speed required for cooling the cooling fluids in the normal range unless the droop fan speed is lower in which case the lower droop fan speed is used but only to the extent that the lower droop fan speed is not lower than the highest fan speed required for cooling the cooling fluids in the above normal temperature range.

An outdoor unit has a frame that carries a ground grooming or working implement, a traction drive, and a cooling fan, all of which comprises loads on a prime mover. A power management controller automatically reduces an operational speed of the traction drive when prime mover droop is present. The cooling fan cools two cooling fluids. The controller stores data representing variable fan speeds for cooling each cooling fluid in both normal and above normal temperature ranges and for use when prime mover droop is present. The controller uses the highest fan speed required for cooling the cooling fluids in the normal range unless the droop fan speed is lower in which case the lower droop fan speed is used but only to the extent that the lower droop fan speed is not lower than the highest fan speed required for cooling the cooling fluids in the above normal temperature range.