Enhancing Hydraulic Efficiency: A Four-Chamber Cylinder System for Energy Conservation and Stability in Mobile Machinery

Hydraulic systems are essential to many industrial machinery applications because they power everything from excavators and construction equipment to manufacturing processes. At the core of a hydraulic system is the principle of fluid dynamics where a fluid is used to transmit force and the basic components of a hydraulic system include a pump which moves the fluid; a series of valves which control the flow and direction of the fluid; an actuator such as a cylinder or motor which converts the fluid power into mechanical force; and the hydraulic fluid itself, which is typically oil. When the pump forces the fluid through the system, the pressurized fluid flows to the actuator, which then performs work, such as lifting, pushing, pulling or rotating. One of the primary challenges facing traditional hydraulic systems is their inherent energy inefficiency. For instance, centralized hydraulic systems which rely on a diesel engine driving variable hydraulic pumps to generate high-pressure fluid are particularly vulnerable to energy losses. These losses occur at multiple points in the system including the engine itself which operates with relatively low efficiency and the hydraulic pumps which also suffer from energy dissipation. Additionally, throttling losses where energy is lost due to the regulation of flow through control valves further exacerbate the inefficiency. These combined losses are significant and can amount to as much as 80% of the total energy input which leads to high fuel consumption and increased operational costs. Furthermore, the wasted potential and kinetic energy which could otherwise be captured for reuse contributes to the overall inefficiency and environmental impact of these systems. Decentralized pump-controlled systems, which employ the close-circuit volume regulating way, are countermeasures to eliminate the throttling losses and recover potential/kinetic energies. However, the flow asymmetry inherent in traditional pump-controlled hydraulic cylinders especially those with single-rod designs is another challenge. These cylinders produce asymmetric flow during operation which must be compensated for by additional systems such as low-pressure charging circuits supplied by accumulators. However, these compensatory systems introduce their own set of problems including added complexity, increased system weight and further energy losses due to the need for charge pumps and check valves which will result in inefficient cumbersome system and difficult to optimize for varying load conditions. Another critical issue in traditional pump-controlled hydraulic systems is speed limitation where in decentralized hydraulic architectures, the speed of hydraulic actuators is constrained by the available hydraulic power and the design of the system’s components. This limitation becomes particularly problematic in applications requiring rapid and responsive actuation, such as in mobile machinery used for construction and earthmoving. The inability to achieve higher speeds without compromising force output or energy efficiency restricts the operational capabilities of these machines, limiting their productivity and effectiveness in demanding environments.

To overcome these challenges, researchers have previously tried a few strategies to enhance the energy efficiency and performance of hydraulic systems. For example, one promising approach that was tried is the integration of energy storage systems with the aim to capture and reuse potential and kinetic energy that would otherwise be lost. Hydraulic energy regeneration systems (HERS) for example use accumulators to store hydraulic energy in a hydro-pneumatic form and allow for shorter energy transmission chains and more efficient energy recovery compared to electric energy regeneration systems. However, HERS still suffer from issues like flow asymmetry and limited speed capabilities which have yet to be fully resolved. With the pressure to move toward more sustainable and cost-effective solutions, there is an urgent need to address these inefficiencies especially in mobile hydraulic systems where energy conservation and performance optimization are important. To this account, a new study published in Journal of Energy Storage and conducted by Professor Ruqi Ding, Engineer Hongzhi Yin from East China Jiaotong University, together with Min Cheng from Chongqing University, Professor Bing Xu from Zhejiang University proposed a novel solution that could address the inefficiencies of current hydraulic systems while overcoming the limitations of existing decentralized pump-controlled systems, as well as energy storage and reutilization methods. The researchers proposed and analyzed a decentralized variable electric motor and fixed pump system that incorporates a four-chamber hydraulic cylinder which is a design that promises to significantly improve energy efficiency, mitigate flow asymmetry, and expand the operational speed range of hydraulic actuators.

The research team evaluated the velocity range of the hydraulic cylinder. They simulated and tested the four-chamber system under both high-speed and medium-force conditions. The results demonstrated that the four-chamber cylinder could achieve a 66% increase in speed compared to the two-chamber system while maintaining stable pressure and symmetrical flow. This expanded velocity range is crucial for applications requiring rapid yet controlled movements, highlighting the four-chamber system’s superior adaptability. The energy consumption of the systems was another critical focus of the experiments. The researchers measured the peak power required by the pump during the operation of both the four-chamber and two-chamber cylinders. They showed that the additional energy storage chamber in the four-chamber cylinder reduced peak power demands by 20%, and overall energy consumption was decreased by 21.6%. This significant reduction in energy usage underscores the efficiency of the four-chamber system, particularly in scenarios where energy conservation is vital for reducing operational costs and environmental impact. Moreover, the authors examined the pressure stability. The pressure fluctuations in the four-chamber cylinder were found to be substantially lower than those in the two-chamber system. Specifically, the pressure variation during transitions between lifting and lowering operations was reduced by nearly half, resulting in smoother and more stable system performance. This improvement in pressure stability is important to ensure the reliability and longevity of hydraulic systems, especially in demanding industrial applications. Furthermore, the researchers conducted experimental tests that mirrored real-world operating conditions. Their experiments showed that the four-chamber cylinder system maintained consistent performance throughout various load cycles and delivered significant energy savings. The system’s energy consumption during lifting and lowering operations was reduced by 24.9%, and the peak power required was lowered by 34.4%. These results validate the four-chamber system’s potential to revolutionize hydraulic machinery by offering both enhanced energy efficiency and superior operational stability. In conclusion, the authors clearly demonstrated the advantages of the innovative approach of the four-chamber hydraulic cylinder system and provided a more energy-efficient, stable, and versatile solution for mobile machinery.  In a statement to Advances in Engineering, integrating the authors’ system can lead to significant reductions in energy consumption and operational costs as well as improved system stability, reliability, and velocity range which will benefit the economic aspects of machinery operation and contribute to environmental sustainability by reducing emissions associated with energy waste.