View source for Hybrid Hydraulic System

A hybrid hydraulic vehicle (HHV) is one that typically includes an internal combustion engine (ICE) which is coupled to a hydraulic pump which powers a hydraulic pump motor.  Energy is stored in one or more accumulators in the form of compressed air, typically nitrogen.  The vehicle is propelled when the pump motor is provided hydraulic power either directly from the pump motor or from the accumulator.  Air in the accumulator is compressed by the hydraulic pump or by the pump motor when it operates in reverse during regenerative braking.

The two main advantages of a hybrid hydraulic system are: 1.  It allows for a small ICE to be used which, along with an accumulator, provide power and hence acceleration equal to that of a much larger engine.  Because the smaller engine in a HHV is not coupled directly to the drivetrain, it can be run with its throttle fully open at its speed of optimum efficiency at all times, thereby making it more efficient thaoperating condition of maximum efficiency at all times all the timeoperated at a wide open throttle condition all the timein smaller engine can be operated at the constant speed and load where it produces highest efficiency engine burns less fuel than a larger engine with comparable acceleration and ther  2.  

 and stores with one or more accumulators and storage tankswhich are used to store a significant amount of energy in the form a compressed gas.  Gas in an accumulator is compressed by pumping hydraulic fluid into the accumulator.  Energy is released from an accumulator by allowing the gas to expand and push out some of the hydraulic fluid.  A hybrid hydraulic vehicle (HHV) is one that typically uses a relatively small internal combustion engine in a hybrid hydraulic system to propel the vehicle.

The two main functions of the accumulator in a HHV are 1: To store energy provided by a small engine which drives a hydraulic pump so that a larger amount of power than can be produced by the engine alone can be produced for moderate amounts of time. and 2: To store vehicle kinetic energy which is reclaimed during the braking process.  Both of these functions allow for very high fuel economy to be achieved by a HHV.

The accumulator typically has the form of a pressure tank with a bladder inside which separates the gas and the hydraulic fluid.  To be continued...