Laboratory Test Rig Research Articles

Sliding Response of Grade 5 Titanium Alloy at Different Speed and Load Levels

Titanium grade 5 alloy is being very distinct because of light weight and higher strength. These alloys are extensively used in aerospace industries. Response of these Titanium alloys under different load level and speed level during contact is required to be studied. The literature survey indicates inadequate studies on effect of load and speed during relative motion. Experiments have been conducted using Pin-On-Disc test rig in laboratory to simulated field conditions. Two load levels of 1.5kg and 3kg and three speed levels of 500,1000 and 1500rpm were maintained during experiments. Pin surface have been studied under Scanning Electron Micrograph [SEM] for understanding wear behaviour. The coefficient of friction was found to be more sensitive to the speed of sliding. At speed of 1500 rpm, irrespective of normal load, two distinct sliding phases, i.e., phase I and phase II have been observed as sliding progressed. Oxidation of wear debris, at lower speed and phase I of sliding takes place.

Partial Rub Detection Based on Instantaneous Angular Speed Measurement and Variational Mode Decomposition

During their lifetime, rotating machines experience various problems. Among others, rotor–stator rubbing is one of the most common problems encountered. Therefore, this paper proposes a two-step procedure for rotor–stator partial rub detection. The first step applies the instantaneous angular speed (IAS) measurement. In this paper, the IAS signal is measured at low to moderate sampling rates as an analog signal from the zebra tape encoder. The correction of encoder segment non-uniformity is also briefly presented in the paper. As a means of coping with the nonlinear signal of the partial rub, the variational mode decomposition (VMD) is proposed in the paper, as the second step of the detection procedure. The VMD is a relatively new method with promising results for machinery fault detection. The partial rub detection tool was tested on the laboratory test rig under three different rotor operating conditions; firstly, for constant rotor speed without rubbing, secondly for rotor running at near critical constant speed with light rotor–stator rubbing, and finally under the condition which describes capabilities of the proposed rubbing detection procedure during variable rotor speed operation. The measurements were taken with an optical phase sensor pointed at the zebra tape encoder. The results are presented in the shape of rotor orbits, IAS signals, FFT spectra of IAS signals and VMD spectrograms of IAS signals. It can be concluded that VMD spectrogram of IAS signal yields a clear detection criterion for light partial rotor–stator rubbing by the presence of 1/2×, 3/2× and 5/2× fractional harmonics. Depending on the analyzed conditions of partial rubbing, at least one of the mentioned fractional harmonics should appear.

An electrostatic measuring technique for monitoring particle size in dilute pneumatic transport

The goal of this research is to establish the applicability of an electrostatic measuring technique for monitoring the quality of a coal-milling process in direct-firing systems. Such systems are used in large steam boilers fired with low-rank coal where the pulverized coal is transported pneumatically from the mills to the burner nozzles via ducts with large cross-sections. The electrostatic measuring method, in connection with intrusive rod-type sensors, was studied because it provides good spatial sensitivity and cost effectiveness. A laboratory test rig was constructed, where the pulverized coal carried by ambient air was employed for the experiments emulating the pneumatic transport of coal particles in direct-firing systems. The test rig enables an extensive variation of the most influential parameters, like the mass-flow, the velocity and the size of the particles. A linear, multi-regression analysis of the results of the experiments was carried out and the appropriate regression model enabling a determination of the mean diameter of the particles using the electrostatic signal was chosen. Based on the results of the study the electrostatic measuring technique can be used for monitoring the size of pneumatically transported particles. The appropriate regression model needs to be chosen for each particular application to describe the dependency of the acquired electrostatic signal on the influential parameters of the pneumatic transport.

Performance Analysis of Forced Commutated Controlled Series Capacitor Rectifier for More Electric Aircraft

The forced commutated controlled series capacitor (FCSC) rectifier has been recently proposed to power stand-alone variable-voltage variable-frequency generation systems, such as the full authority digital electronic control (FADEC) system, in more electric aircraft. The employment of this rectifier helps to meet increasing power demand requirements while maintaining low current harmonic levels without the need for bulky filters. The FCSC rectifier is controlled to maintain resonance with line frequency variation by inserting variable capacitive reactance in series with the variable-frequency generator's inductive reactance. Unity power factor operation with nearly pure sinusoidal converter input currents is thus achieved, for better utilization of the generator. The FCSC rectifier operation with a variable dc on-board load is analyzed in this paper, including a description of the principle modes of operation of the circuit. The enhancement in circuit's output voltage and output power achieved by replacing the conventional diode bridge rectifier with the FCSC rectifier is also demonstrated. Both rectifiers are analyzed numerically using Saber/Synopsys over a wide range of operating voltages and frequencies. Results are experimentally verified using 1-kW laboratory test rig.

Model of Dynamic Modes of an Asynchronous Drive Taking into Account Motor Steel Saturation and Variables of Power Source

A model of squirrel cage induction motor has been developed and implemented in the MATLAB/Simulink software. The proposed model takes into account saturation of magnetic core at high currents in windings of electric motor, as well as current displacement in rotor conductors and internal resistance of power source. The model structure allows to simulate steel saturation according to dependences of physical machine. An equation with coefficients obtained by approximation of experimental data has been proposed for simulation of mutual inductance between stator and rotor as a function of mutual induction flux linkage. The model has been verified in the MATLAB/Simulink environment and on a laboratory test rig by experimental validation of predicted data. The developed model can be used for investigation into dynamic modes of an asynchronous motor. Various drive starting modes have been simulated; in addition, together with electric and mechanic variables, the model determines energy performances. The model has been applied in practice to detect the possibility of using starting currents and voltages of a motor for experimental determination of power source variables.

Application of vibration monitoring to the detection of early misalignment and rub failures in a tidal turbine

Research on tidal turbines has been mainly focused on the design for greater energy efficiency for the last ten years. However, achieving a reliable operation is becoming more and more crucial in current studies. This work presents a continuous monitoring of those turbines based on vibrations controls the control, this technique allows implementing predictive maintenance strategies. The vibration response is analysed in a laboratory test rig. That vibration can be produced by a phenomenon as frequent as a misalignment of the shaft as well as their consequences in the early production of partial rub of the rotor/stator. The response obtained shows that one can easily detect a vibration signal with a misalignment in the shaft of 50 μm. Also, the rub of the shaft/seal is detected with the increase of the dynamic stiffness of the system from 12,87 to 14,30 KN/m. Additionally, the resonance frequency also increases its value from 2400 to 2500 rpm. The application of this early detection on the watertight seal of a tidal turbine, would potentially avoid severe hazards in these equipment.

A METHOD FOR THE DETERMINATION OF THE KINETIC FRICTION COEFFICIENT IN FRICTION PAIRS BASED ON DIRECT ACCELERATION MEASUREMENT OF AN OBJECT ON AN INCLINED PLANE

The paper presents and experimentally verifies a method for the determination of the kinetic friction coefficient of friction pairs. The method involves a direct acceleration measurement of an object sliding down an inclined plane and the determination of the momentary friction force based on acceleration. The laboratory test rig was presented and the theoretical foundations of the method were discussed in detail. The laboratory experiments were conducted for the following material pairs: steel-cast iron, steel-bronze, and for various inclined plane angles. The experiments results were presented, acceleration vs. time curves were plotted, and friction coefficients were determined. These values were compared to the values known from literature [L. 1–3]. The uncertainly analysis of kinetic friction coefficient determination was conducted. The method effectiveness and accuracy was verified, noting the sources of possible measurement errors and the ways to eliminate them.

Modeling, Analysis, and Validation of Controller Signal Interharmonic Effects in DFIG Drives

This paper presents the development of a doubly fed induction machine (DFIG) harmonic model in matlab /Simulink, which is used to examine the spectral content of DFIG controller signals and improve the understanding of their behavior and spectral nature. The reported DFIG harmonic model has the capability of representing the effects of higher order time and space harmonics and thus, allows detailed analysis of the controller signals embedded spectral effects. The model consists of a wound rotor induction machine (WRIM) harmonic model coupled with a stator flux oriented controller model. The WRIM space harmonic effects are represented using the conductor distribution function approach to enable the calculation of winding inductances as a harmonic series. In addition, analytical expressions are derived to define the possible spectral content in the controller signals of DFIGs. Both the reported DFIG harmonic model and the analytical expressions are validated by comparison with measurements taken from a purpose built vector-controlled DFIG laboratory test rig. The findings confirm the capability of the developed DFIG harmonic model in representing the controller signals embedded spectral effects, as well as the accuracy of the reported analytical expressions, and enables a much improved understanding of the spectral nature of the DFIG controller signals.

Optimal design for real-time quantitative monitoring of sand in gas flowline using computational intelligence assisted design framework

Abstract Global demand for oil and gas is still increasing rapidly. The direct consequence of this is the increased operating pressure amid concerns over increasing sand production. According to the Society of Petroleum Engineers (SPE), 70% of the world's hydrocarbon reserves are contained in reservoirs situated on unconsolidated formations. Given the reality of these formations, sand production will certainly be a problem of significant concern particularly during the later life of the fields when they become more ‘mature’. However, to monitor sand and optimise its production for improved recovery and safety, life extension and economy of the fields and ensured reliability, the automatic detection and prediction of sand flow characteristic measurements; sand flow rate (SFR), sand concentration (SC), line pressure drop (PD), and gas velocity (GV), has become an important research topic of great interest. Despite this importance, discussion of the topic is still lacking in the literature. This paper proposes a novel and robust architecture of intelligent real-time sand flow characteristic measurement using an acoustic sensor and computational intelligence assisted design (CIAD) framework. It fully incorporates acoustic signal processing and analysis, prediction algorithms and optimisation algorithms in the design. Acoustic features based on acoustic signal processing techniques are extracted to reduce the dimensionality of the acoustic signals. A classical Artificial Neural Network (ANN) is used to model the non-linear relationships between the acoustic signal characteristics and the flow characteristics measurands. In addition, the ANN algorithm adapts its weights and biases using the Grey Wolf Optimiser (GWO) through minimisation of the cost function during the training phase. Preliminary results obtained on a laboratory test rig demonstrate that an acoustic sensor coupled with CIAD may provide simple and robust practical solution to the measurement problem of particle-laden gas flow characteristics in real-time.

Detection of erosive cavitation on hydraulic turbines through demodulation analysis

Erosive cavitation in hydraulic turbines affects severely the runner structure, increasing maintenance costs and reducing the remaining useful life of the component. Actual vibro-acoustic techniques used to detect this kind of cavitation in hydraulic turbines are based on analysing high-frequency vibrations in different parts of the unit. Particularly, the demodulation of high frequency bands has proven to give relevant results regarding the erosive cavitation behaviour. However, demodulation is not absolutely conclusive since the excitation and the transfer function from the excitation to the measuring point, which depend on every particular prototype, are partially unknown. In this paper, the demodulation method to detect erosive cavitation in hydraulic turbines is reviewed and analysed in detail. To do so, first, an experimental study in a test rig in laboratory has been carried out. This test rig is based on a rotating disk instrumented with a piezoelectric patch and with different sensors, such as accelerometers and acoustic emission sensors, in the rotating and stationary parts. Different excitation patterns simulating erosive cavitation have been applied to the rotating disk. These patterns include pseudo-random excitations of different frequency bands modulated by one low carrier frequency, which model the erosive cavitation characteristics. In this way, it is possible to understand how mechanical vibrations similar to those produced by erosive cavitation are transmitted in such complex systems involving fluid and solid mediums. The knowledge obtained in the test rig helps to interpret the results obtained with demodulation analysis in prototypes. Particularly, in this paper these conclusions have been used to analyse erosive cavitation in a real Francis turbine.

Innovative mechanism to identify robot alignment in an automation system

Robotic applications are commonly used in industrial automation systems. Such systems are often comprised of a series of equipment, including robotic arms, conveyors, a workspace, and fixtures. While each piece of equipment may be calibrated with the highest precision, their alignment in relation to each other is an important issue in defining the accuracy of the system. Currently, a variety of complex automated and manual methods are used to align a robotic arm to a workspace. These methods often use either expensive equipment or are slow and skill-dependent.This paper presents a novel low-cost method for aligning an industrial robot to its workcell at 6 degrees of freedom (DoF). The solution is new, simple and easy to use and intended for the SMEs dealing with low volume, high complexity automated systems. The proposed method uses three dial indicators mounted to a robot end effector and a fixed measurement cube, positioned on a workcell. The robot is pre-programmed for a procedure around the cube. The changes on the dial indicators are used to calculate the misalignment between the robot and the workcell. Despite simplicity of the design, the solution is supported with complex real-time mathematical calculations and proven to identify and eliminate misalignment up to 3 mm and 5 degrees to an accuracy of 0.003 mm and 0.002 degrees: much higher than the precision required for a conventional industrial robot.In this article, the authors describe a proposed solution, validate the computation both theoretically and through a laboratory test rig and simulation.

Experimental investigation and modeling of diffusion dialysis for HCl recovery from waste pickling solution

Hydrochloric acid recovery from pickling solutions was studied by employing a batch diffusion dialysis (DD) laboratory test-rig equipped with Fumasep membranes. The effect of main operating parameters such as HCl concentration (0.1–3 M) and the presence of Fe2+ (up to 150 g/l) was investigated to simulate the system operation with real industrial streams. The variation of HCl, Fe2+ and water flux was identified. When only HCl is present, a recovery efficiency of 100% was reached. In the presence of FeCl2, higher acid recovery efficiencies, up to 150%, were observed due to the so-called “salt effect”, which promotes the passage of acid even against its concentration gradient. A 7% leakage of FeCl2 was detected in the most severe conditions. An original analysis on water flux in DD operation has indicated that osmotic flux prevails at low HCl concentrations, while a dominant “drag flux” in the opposite direction is observed for higher HCl concentrations.A comprehensive mathematical model was developed and validated with experimental data. The model has a time and space distributed-parameters structure allowing to effectively simulate steady-state and transient batch operations, thus providing an operative tool for the design and optimisation of DD units.

Application of gain-scheduled vibration control to nonlinear journal-bearing supported rotor

Bearing reaction forces are commonly approximated by linear coefficients at a given rotational speed, although they are, in reality, considerably nonlinear in some situations. Therefore, a precise numerical simulation is highly desirable before experimental tests, usually resorting to integration of classical Reynolds equation, a well-known numerically time consuming. Due to faults or unusual demands, controllers can be applied to avoid failure. However, control action changes the machine dynamic behavior. This paper investigates the performance of a faster simulation method using a high order Taylor force approximation, by means of nonlinear coefficients, in situations that differs from the one in which the force was originally identified. This is accomplished using the force generated by a gain-scheduled static H∞ controller. The proposed controller aims to stabilize fluid-induced instability and attenuate unbalance vibration at critical speed of a journal bearing supported rotor. A polynomial fit is applied to express the hydrodynamic bearings coefficients according to rotor rotational speed. The resultant polynomial system is then used in linear matrix inequalities from a two-stage method in order to synthetize a controller linearly dependent on rotational speed. Furthermore, the control efficiency is verified under the influence of bearing nonlinearities. The numerical simulations were compared with experimental data measured in a laboratory test rig. The results reveal that the control is effective in reduce vibration amplitudes especially in critical speed and fluid induced instability, and that the nonlinear coefficients are promising for approximating journal motion for both uncontrolled and controlled systems.

Challenges of friction reduction of engine plain bearings – Tackling the problem with novel bearing materials

Abstract This study specifically focuses on the friction properties of bearing materials. By means of laboratory test rigs using ring on disc and bearing segment systems extensive investigations under mixed friction conditions and start stop operation were carried out in this area. One the one hand, commonly used bearing products including bimetal and trimetal bearings with various coatings are studied resulting in elucidation of the underlying mechanisms of the friction performance. On the other hand, based on the conclusions thereof, novel bearing coatings are introduced and are verified regarding friction performance. The results emphasize the changing behaviour of the friction characteristics of bearing materials. Furthermore, the outstanding mixed friction capabilities of the herein proposed novel bearing coatings are documented.

Determination of cleaning mechanisms by measuring particle size distributions

Knowledge of the dominant removal mechanism (diffusive vs. convective mass transport) is important for understanding, modelling and predicting cleaning behavior of food soils. The size of the detached particles is thereby a useful physical quantity, since small particles, which are fully immersed within the viscous sublayer of the flow, will rather be removed due to diffusion than caught from the flow itself. The dimensionless particle diameter relates the particle size to the thickness of the viscous sublayer and has therefore been chosen to identify whether the particles were removed rather by diffusive or convective mass transport.This contribution presents the online measurement of particle size distributions during cleaning of starch and egg yolk soils in an automated laboratory test rig. To achieve accurate results for the particle sizes, measurements with Fraunhofer and Mie theory were compared. Furthermore, the influence of the cleaning temperature on the dimensionless particle diameter was examined for both soils.

Simulation of a stabilised control strategy for PEM fuel cell and supercapacitor hybrid propulsion system for a city bus

Fuel Cells (FC) are a clean energy source capable of powering a bus electrically with zero operating emissions. This research investigates the potential of FC and Supercapacitor (SC) hybrid buses for clean city transportation. To investigate the FC/SC hybridisation strategy, a scaled FC/SC hybrid drivetrain has been developed to provide the power system of a scaled bus model. The scaled model was developed as a MATLAB Simulink computer model and cross referenced against the constructed laboratory test rig for validation. A novel control strategy focusing on power balancing between the FC, the SC and the load has been developed and validated in the computer model. It has been demonstrated in both the test rig and computer simulation that the proposed control strategy is capable of maintaining a controlled and stable FC output while meeting different bus load regimes. The validated computer model can provide a reliably representative, convenient and low cost platform for further performance investigation and component optimisation of FC/SC hybrid drivetrains. The control strategy has also been demonstrated to be function as expected after scaling up the developed scaled model to a full scale model which can be used for simulation of practical bus performance.

Simultaneous identification of unbalance and shaft bow in a two-disk rotor based on correlation analysis and the SEREP model order reduction method

This paper focuses on a theoretical and experimental identification of two of the most common faults that occur in rotating machines, which exhibit similar problems: unbalance and residual shaft bow. Numerous studies deal with shaft bow, but only a few involve rotors containing many degrees of freedom and the simultaneous occurrence of these two faults. The identification procedure proposed here belongs to the techniques based on the mathematical model of rotors and faults. Finite elements were used to model the rotor, and the faults were identified using an approach based on correlation analysis, which involves only the rotor's responses in the time domain. The System Equivalent Reduction Expansion Process (SEREP) model reduction technique was employed in order to use only the disks' responses and avoid high computational costs. The identification equation derives from the Lyapunov matrix equation of the reduced system model and the fault parameters are identified by least-squares fitting, considering both magnitude and location. Since the shaft bow is considered constant, the faults were identified in two steps, which consider variations in the unbalance parameters: 1) theoretically, considering ten different cases of unbalance and subjected to the same shaft bow, and 2) experimentally, in which the same ten different cases are validated using experimental data from a laboratory test rig. The proposed procedure proved consistent in identifying two faults that occur simultaneously and exhibit similar symptoms.

Experimental analysis of stick-slip in drilling dynamics in a laboratory test-rig

A new test-rig to analyze drilling dynamics is presented in this article. Although simple, the test-rig can represent satisfactorily some phenomena observed in deep water drilling. The test-rig results are analyzed and stick-slip cycles are explained in detail. The explanations are in agreement with available field data found in the literature. One stick-slip cycle is extracted and analyzed thoroughly. Then, other cycles are presented to show the variability of the obtained experimental data. Finally, a model that might take into account hysteric effects is proposed for the bit-rock interaction. The parameters of the proposed model are identified using the experimental data. drill-string test-rig bit-rock interaction model drill-string dynamics experimental identification hysteresis model.

Development of a dynamically scaled wind turbine

Experimental analyses of modal parameters on operating wind turbines are associated with great technical expense, standstill times and therefore with high costs. This makes experimental research on operating wind turbines, for example testing innovative measurement strategies, uneconomical. Thus it is desirable to conduct portions of experimental research on laboratory test structures. In this paper the development of a scaled laboratory test rig is presented. It is designed in such a manner that the lower natural frequencies of a reference wind turbine are approximately reproduced. To find feasible physical parameters for the test rig, preliminary analyses based on an analytical model of a vertical cantilever beam with a top body were combined with experiments based on Operational Modal Analysis (OMA) and multibody simulations.

Optical measurement of high-temperature melt flow rate.

This paper presents an optical method and system for contactless measurement of the mass flow rate of melts by digital cameras. The proposed method is based on reconstruction of melt stream geometry and flow velocity calculation by cross correlation, and is very cost-effective due its modest hardware requirements. Using a laboratory test rig with a small inductive melting pot and reference mass flow rate measurement by weighing, the proposed method was demonstrated to have an excellent dynamic response (0.1s order of magnitude) while producing deviations from the reference of about 5% in the steady-state flow regime. Similar results were obtained in an industrial stone wool production line for two repeated measurements. Our method was tested in a wide range of melt flow rates (0.05-1.2kg/s) and did not require very fast cameras (120frames per second would be sufficient for most industrial applications).