Hydraulic Test Bed Research Articles

A Novel Wavelet Packet Transform-Fuzzy Pattern Recognition-Based Method for Leakage Fault Diagnosis of Sail Slewing Hydraulic System

When the wind direction changes, rotating the sail to keep it at the optimal angle of attack can effectively utilize offshore wind resources to improve the ship’s energy efficiency. The hydraulic system usually drives the slewing of the sail onboard. The functioning, as well as the safety of hydraulic system will be directly affected in case of leakage failure occurs. Therefore, the leakage fault diagnosis is essential to improve the sail-assisted effect as well as the reliability of the sail slewing system. In this paper, a novel wavelet packet transform (WPT)–fuzzy pattern recognition (FPR) based leakage fault diagnosis method is proposed. In order to analyze the different leakage fault features of the hydraulic system, a simulation model is established, and its effectiveness is verified by the hydraulic testbed. Then, the sensitive feature of flow and pressure signal for different leakage faults is extracted by a WPT-based method. On this basis, an FPR-based leakage fault diagnosis method is proposed. The diagnosis results show that the proposed method has an accuracy of 94% for nine leakage fault modes. This work contributes to realizing the greenization of the shipping industry by improving the utilization rate of offshore wind resources.

Thermal cycling aging of encapsulated phase change material – Compressed expanded natural graphite composite

A paraffin-Compressed Expanded Natural Graphite (CENG) composite encapsulated in aluminium shell has been thermally aged in a packed bed heat storage tank.A hydraulic test bed has been settled in order to impose 8500 thermal cycles where the material underwent a phase change at each cycle. The PCM phase change provokes an expansion of the composite structure that might affect the effective thermal conductivity and then the heat transfer rate of the Thermal Energy Storage (TES). This performance has been monitored all along the cycling test showing a non-significant change in heat transfer rate, despite a delamination of the composite within the capsule. This phenomenon has been explained by the delamination that affects mainly the thermal conductivity in the axial direction while the heat transfer from the PCM to the aluminium shell occurs essentially on the planar direction. Indeed, the thermal conductivity in planar direction is approximatively six times higher than on the axial direction. A DSC analysis on new and aged samples showed that the phase change temperatures remained the same and the latent heat magnitude decreased by less than 10%. A FTIR analysis confirms the chemical stability of the PCM-CENG composite after 8500 cycles.

Magnetic-Capacitive Wear Debris Sensor Plug for Condition Monitoring of Hydraulic Systems

This paper presents a new and efficient sensor for monitoring the presence of wear debris received by the storage tank in hydraulic systems. The proposed sensor plug employs a magnetic approach to attract the ferrous debris in the storage tank. A capacitive sensing scheme is employed in the same sensor plug to sense the presence of the debris accumulated on the plug. This combination of the magnetic and capacitive features in a single sensor for debris monitoring is new and it helps to realize a very sensitive sensor. The proposed sensor is designed in an ingenious way that the permanent magnet that is used to form the magnetic field in the vicinity of the sensor, to attract the debris towards the sensor, itself serves as one of the electrodes of the capacitive sensor. This approach improves the sensitivity and keeps the number of components in the sensor minimum. A prototype of the proposed sensor has been developed and tested. In the prototype, the change in capacitance of the sensor is measured using a high-resolution capacitance-to-digital converter. The sensor was tested after integrating it in a hydraulic test bed which has a controlled debris injection facility to the hydraulic circuit. The output of the sensor was found to be very sensitive to the typical ferrous debris that was introduced in the system. The proposed low-cost sensor will find applications in debris monitoring of underwater and land-based hydraulic systems.

Design and Implementation of the Integrated Test Platform for the Hydraulic Components

In this paper, a new type of hydraulic test bed is developed which can be used for performance testing of hydraulic valves, hydraulic motor and hydraulic pump. The composition structure diagram of hydraulic system, power supply system, and the signal flow diagram of data acquisition system were designed. The characteristics of the LabWindows/CVI development tools and the usage of Prodave MPI/IE 6 network communication tools were introduced, also the database storage and access technology in LabWindows/CVI environment. It was proved through the practical application that the test bed is reliable and has the merit of higher precision and automation level, and simple operation.

Design of Performance Testing Bed for Hydraulic Products of Engineering Machinery

Hydraulic test platform is a very important testing tool for hydraulic products of engineering machinery. In this paper, a new type of hydraulic test bed is developed which can be used for performance testing of hydraulic valves, hydraulic motor and hydraulic pump. The composition structure diagram of hydraulic system, power supply system, and the signal flow diagram of data acquisition system were designed. The communication between sensors and computer via RS232 were researched. At last, the hydraulic test software is developed by using Labwindows/CVI and Simense PLC.

Detection and Isolation of Leakage and Valve Faults in Hydraulic Systems in Varying Loading Conditions, Part 2: Fault Detection and Isolation Scheme

AbstractLeakages and valve faults are among the most common faults in hydraulic systems. This paper studies the real-time detection and isolation of certain leakage and valve faults based on the results obtained in part one. In the first part, the mathematical model of a hydraulic test bed was analysed with Global Sensitivity Analysis to facilitate a systematic and verified approach to model-based condition monitoring. In this paper, an Unscented Kalman Filter-based Fault Detection and Isolation scheme for leakage and valve faults of a generic servo valve-controlled hydraulic cylinder is devised. Compared to existing literature, the leakage and valve faults are decoupled from cylinder static and dynamic loading which makes the results generic and applicable to any servo valve-controlled hydraulic cylinder. Moreover, a more comprehensive set of fault patterns for the detection and isolation of leakages and valve faults with experimental and simulation results are presented. We show that detecting an extern...

FRACTOGRAPHIC ANALYSIS OF FATIGUE CRACK GROWTH IN ENGINE COMPRESSOR DISKS OF Ti‐6Al‐3Mo‐2Cr TITANIUM ALLOY

Abstract—Fractographic features related to fatigue crack growth in a Ti‐6Al‐3Mo alloy are studied using compressor disks tested on a hydraulic test bed and which simulate operational multiaxial cyclic loading conditions. The hold‐time of a cycle results in the formation of a fracture relief which reflects mainly the two‐phase (α+β) lamellar structure of the titanium alloy and a fragmentary fatigue striation formation. Correlation between the number of fatigue striations on the fracture surface and the number of applied blocks of loading (imitating the service conditions of compressor disks) has been obtained. The hold‐time duration of the cycle does not affect the crack growth rate and the formation of the fracture relief in this material. An analytic expression is suggested to describe the relationship between fatigue striation spacing, δ, and the stress intensity factor KcI as applied to quarter‐ellipse‐shaped cracks; it is of the form δ= C[f(τ, FCi)KcI]4, where f(τ, FCi) accounts for the hold‐time, τ, and the programmed loading together with their influence on the fatigue crack growth behaviour. The particular threshold value of stress intensity factor (KcI) is established at 20 MPa m. The work indicates that the role of τ manifests itself via a considerable acceleration of crack growth.