Thermal Condition Monitoring
Using Caspar FSTI to build a digital twin in combination with simple temperature sensors.
To prepare today's fluid power systems for the future digitalization of the industry, it is necessary to improve the information available regarding the current condition of crucial components of the system. Positive displacement machines, which constitute the core of any hydraulic system, play a vital role in this process. Future smart systems will require more information about the current state of the pump such as power usage and efficiency. Current condition monitoring approaches utilize an array of sensors that need to be sampled at high frequency. The transmission, storage, and post processing of this vast amount of data requires an enormous number of resources, especially if exercised at scale. Previous work conducted at the Institute of Mechatronics Engineering at TU Dresden has demonstrated that measuring the temperature in the lubricating gaps can allow for a deeper insight into the tribological mechanisms in these interfaces. Not only can the gap height, viscous friction and leakage be determined from this information, but also crucial information such as wear level and expected component lifespan can be derived from temperature levels with adequate reference models [1]–[4]
The cylinder block is the heart of the rotating kit, connecting all moving parts while housing the displacement chamber and pistons. Two of the three main bearings are directly associated with the cylinder block, and the third, the slipper/swash plate bearing, is indirectly related via the leakage path through and the forces acting on the piston. Caspar FSTI is able to predict both efficiency and temperature of parts and oil.
By combining Caspar FSTI simulation results and temperature measurements, an innovative thermal condition monitoring approach can be achieved. Caspar FSTI provides the digital twin: Temperature trends vs. efficiency for a whole suite of different boundary conditions - including part tolerances and wear in. The temperature sensors - which can have a very low sample rate and reasonable accuracy of ±0.5K - can provide the necessary input for the model. Currently a pressure sensor is needed for reference, however the newest results indicated that simply installing 3 temperature sensors - Inlet, Outlet, Block - are sufficient to predict the entire pump efficiency. Stay tuned!
Meanwhile you can watch the latest presentation about the topic or read my paper here.
Watch the presentation form the 2024 IFK conferences about Thermal Analysis in Piston Pumps using Caspar FSTI as a digital twin
Simulation predicts pump efficiency. Caspar FSTi successfully predicts gap losses. By adding shaft bearing, and setting system losses, the absolute efficiency can be predicted.
The Cylinder Block reflects overall pump efficiency as demonstrated by simulated temperature field with and without valve plate gap influence
Simulation results for two different pumps: Caspar FSTI predicts all gap losses and correlates pump losses with cylinder block surface temperature
Confirmed by measurement: Surface Temperature can be linked directly to total, hm. and volumetric efficiency
Comparison between predicted (right) and measured (left) efficiency vs. block temperature trend. The slope for 100 bar matched very accurately at 200bar+ the shaft bearing and control system losses will need to be accounted for to match efficiency.
Confirmed: The cylinder block temperature can be used for instantaneous efficiency feedback, whereas other temperature data is too slow to react.
Transient Information can be used to predict steady state. Then the data can be compared to the digital twin, which is build using Caspar FSTI at steady state
Measurement set up for validation, using an advanced custom built telemetric system
Caspar FSTI predicts absolute temperature and hot spots very accurately. Minor differences are due to thermal boundary conditions.
Set up including external temperature monitoring
Modeling wear is crucial to predict correct efficiency and temperature
thermal impact of slipper wear on swash plate surface
Caspar FSTI can wear. Here: Slipper wear was predicted at various operating conditions.
Impact of wear on the slipper fluid film - measured and simulated slipper sealing land wear - a perfect match
Caspar FSTI considers changes in fluid properties with temperature and pressure