Digital Hydraulic Transformer for Load Leveling
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Solution Overview
Problem
Mobile machinery hydraulic systems experience significant energy losses during decelerations due to throttling, leading to inefficiencies in prime mover operation, which is often sized for peak power requirements rather than average loads.
Innovation Solution
A hydraulic system incorporating a transformer and accumulator that efficiently stores energy during low loading periods and releases it during high loading periods, allowing the prime mover to operate consistently and optimizing efficiency by using a variable displacement pump and high-speed valve sets to manage hydraulic fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the prime mover is sized to satisfy peak power requirements, then the system can meet maximum load demands, but the prime mover does not operate at peak efficiency under average working loads
Solution Approach 1:
An energy storage device (flywheel or capacitor) is introduced as an intermediary between the prime mover and the hydraulic pump. This intermediary absorbs excess energy during low-demand periods and releases it during peak demands, allowing the prime mover to operate at a constant, optimized speed while still meeting variable power requirements.
Solution Approach 2:
The system changes the operating parameters of the prime mover by decoupling its speed from the variable power demands through the energy storage device. The prime mover maintains a constant optimal speed, while the energy storage device handles the variable power requirements, thus optimizing efficiency.
2Ease of operation
If throttling is used to control hydraulic fluid flow during decelerations, then the hydraulic system can control active components, but substantial energy loss occurs
Solution Approach 1:
The system converts the harmful effect of throttling (energy loss) into a beneficial process by using the energy storage device to capture the energy that would otherwise be lost during decelerations. The flywheel or capacitor absorbs the kinetic energy from the hydraulic motor during deceleration, converting it into rotational energy or electrical energy for later use.
Solution Approach 2:
The mechanical throttling control mechanism is replaced with an energy storage-based control system. Instead of using throttles to dissipate energy, the system uses the inertial energy storage device to manage power flow, eliminating the energy waste associated with throttling.
3Loss of energy
If a hydraulic transformer with multiple valve sets is used to manage fluid flow, then energy recovery and load leveling are achieved, but device complexity increases
Solution Approach 1:
Multiple valve functions are merged into a single integrated hydraulic transformer component. The transformer combines the functions of energy recovery, load leveling, and flow control in one device, reducing the number of separate components and valves needed in the system.
Solution Approach 2:
The hydraulic transformer is designed as a multi-functional device that simultaneously performs energy recovery from regenerative braking, load leveling through energy storage, and hydraulic flow management. This universal component replaces what would otherwise require multiple separate systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the prime mover to be sized for average power requirements, reducing energy losses and improving overall efficiency by recovering energy from decelerations and leveling the load on the prime mover, thus enhancing operational consistency.
Implementation Method 1
relative rotation about a single axis between the plurality of fluid chambers and the common drive member is coupled with hydraulic fluid flow through the hydraulic transformer
Implementation Method 2
systems and methods for leveling the load on a hydraulic systems prime mover by efficiently storing energy during periods of low loading and efficiently releasing stored energy during periods of high loading
Data Source
AI summary
A hydraulic system that includes a rotating group with a plurality of fluid chambers and a plurality of valve sets that valve a corresponding one of the fluid chambers is disclosed. The hydraulic system may function as a hydraulic transformer. The hydraulic system may transfer energy between a high pressure fluid supply (e.g., from a pump), an accumulator, a hydraulic component (e.g., a hydraulic cylinder, a hydraulic motor, and/or a hydraulic pump-motor), and/or an input/output shaft. The hydraulic system may include a single rotating group with a common axis. Each of the valve sets may include a first valve that fluidly connects to the pump, a second valve that fluidly connects to a tank, a third valve that fluidly connects to the accumulator, and a fourth valve that fluidly connects to the hydraulic component. The valves may have a valving period set to less than half or one-third of a rotational period of the rotating group. The valves may have a frequency of greater than 100 Hertz and may be digitally controlled.