Energy Efficiency Analysis of Multi-Pressure Hydraulic System
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High fuel consumption, particle emissions and low energy efficiency are one of the key issues associated with the excavators. In construction machinery excavators are considered main contributors for CO2 emission, which ultimately have adverse environmental impacts. In this research work, prime mover (electric motor) downsizing is achieved through multi-pressure system. It can be derived that also diesel engine downsizing is possible, which will ultimately contribute to meet these environmental challenges. Multi-pressure system is a new approach towards the hydraulic hybridization of off-road machines. It is an ultimate replacement of conventional load sensing system. Load sensing is commonly used in off-road machinery as hydraulic power transmission system. Research reveals that huge power losses occur in load sensing system when multiple actuators are working together in a machine because each actuator has different power requirements. In load sensing system actuator is directly coupled with prime mover hence it is dimensioned according to peak power requirements due to which it is bigger in size. The exclusive feature of multi-pressure system is that it has locally integrated pressure source to the actuator. The system has six power sources for a single actuator. These six power sources are one pump, one accumulator and four pressure transformers. These power sources are connected through on/off valves with actuator. One cycle of swing operation is performed in this research work. Input electrical energy consumption, mechanical energy consumption of motor and hydraulic energy consumption of pump is determined. Later, the evaluated afore-mentioned energy consumption comparison is made with energy consumption of load sensing system for the same operation. It has been revealed from analysis that multi-pressure system is remarkably energy efficient compared to Load Sensing System. However, experimental results show that there are some controllability issues at lower velocities. The controller needs to be improved when the actuator has low velocity.