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Mohamed Allam

Energy efficient multi-pressure system in excavators

Doctoral Student

Energy losses of conventional valve controlled hydraulic systems is one of the main contributors for the poor fuel efficiency and high emissions of non-road mobile machinery (NRMM) such as an excavator. Excavators contribute to more than half of the harmful emissions produced by NRMM where only a small portion of the chemical energy input to the machine is used as useful work, the rest is either consumed by poor engine efficiency, auxiliaries, pump and throttling losses. Furthermore, current hydraulic systems do not offer the possibility of energy regeneration through boom potential or swing kinetic energies where both are lost as heat energy. Therefore, it is necessary to introduce a system that is capable of reducing the energy losses of the hydraulics while simultaneously improving the operation of the diesel engine and pump to properly address all the loss mechanisms of excavators.


This research introduces a novel hydraulic system implemented on the work functions of a 20-ton excavator which aims at reducing the throttling losses significantly compared to the state-of-the-art LS systems currently implemented in NRMM. The research concentrates on the experimental study of the excavator’s efficiency and controllability enabled by the novel system while improving the operability of the diesel engine and the pump.

Academic supervisor
Matti Linjama
Mikko Huova
Industry partner
Kim Heybroek

Volvo Construction Equipment

Energy losses of conventional valve controlled hydraulic systems is one of the main contributors for the poor fuel efficiency and high emissions of non-road mobile machinery (NRMM) such as an excavator. Excavators contribute to more than half of the harmful emissions produced by NRMM where only a small portion of the chemical energy input to the machine is used as useful work, the rest is either consumed by poor engine efficiency, auxiliaries, pump and throttling losses. Furthermore, current hydraulic systems do not offer the possibility of energy regeneration through boom potential or swing kinetic energies where both are lost as heat energy. Therefore, it is necessary to introduce a system that is capable of reducing the energy losses of the hydraulics while simultaneously improving the operation of the diesel engine and pump to properly address all the loss mechanisms of excavators.


This research introduces a novel hydraulic system implemented on the work functions of a 20-ton excavator which aims at reducing the throttling losses significantly compared to the state-of-the-art LS systems currently implemented in NRMM. The research concentrates on the experimental study of the excavator’s efficiency and controllability enabled by the novel system while improving the operability of the diesel engine and the pump.

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