Proposed Test Rig Research Articles

A test rig for the full characterization of the dynamics of shrouded turbine blades

Highly stressed forced vibrations experienced by Low Pressure Turbine (LPT) blades during their operation can result in high cycle fatigue (HCF) which can ultimately lead to failure. To avoid this occurrence, the vibration amplitudes must be anticipated and reduced. This is generally done by employing friction damping devices like under-platform dampers, shrouds and snubbers. In case of blades with shrouds at their tips, the adjacent shrouded blades are coupled to each other and three-dimensional periodic shroud contact forces acting on shrouds significantly influence the vibration amplitudes as energy is dissipated due to friction. Hence, for the experimental validation of the numerical contact models that are used for the prediction of nonlinear forced response of shrouded blades, it is equally necessary to measure the contact forces acting at the shrouds. Moreover, present-day requirement of more accurate and detailed models requires thorough and comprehensive experimental validation calling for the measurement of three-dimensional shroud contact forces from purposely designed test rigs.This study presents the design, development and operation of an experimental test rig that allows full characterization of the dynamics of shrouded turbine blade, i.e., simultaneous measurement of three-dimensional shroud contact forces and shrouded blade forced response. The starting point was the design of the test rig components based on the design requirements. This is followed by the description of the major components of the proposed test rig i.e., the three-dimensional contact force measurement system and the torque screw mechanism. In the subsequent section, the details of the experimental setup to measure the forced response and three-dimensional shroud contact forces simultaneously are highlighted as the test campaign is performed for different normal preloads and excitation force levels. Consequently, the effects of the variation in the normal preload and excitation force on the measured response and shroud contact forces are discussed. Finally, it is shown how the results establish the efficacy of the proposed test rig in providing a comprehensive depiction of the dynamic response of the shrouded blade and 3D shroud contact forces that will result in more accurate and reliable experimental validation of numerical tools.

A custom designed modular, scalable test system for an efficient performance evaluation of thermoelectric devices

• A modular, scalable test rig capable of evaluating unicouple, devices and modules. • Ability to handle most thermoelectric (TE) performance evaluation criterion’s including real-world endurance high temperature thermal cycling, thermal soaking and identifying defective devices is demonstrated. • Evaluated three different TE systems viz. Bismuth Telluride, Skutterudites and Half Heusler alloys across different temperature gradients. • Single software platform interacting with DAQ with special features like automatic temperature stability control, high vacuum control, inert gas purging to minimize high temperature oxidation/sublimation of TE device. Reliable and efficient performance evaluation of thermoelectric (TE) elements and devices is critical for developing high performance and robust thermoelectric generator. Due to the inherent thermomechanical coupling, testing thermometric devices is a challenge and requires design of customized test rigs for a thorough evaluation. This article discusses design and development of a modular, scalable customized test rig for performance evaluation of TE devices of different proportions. Various standard TE specifications like harvested power, specific power, instantaneous device resistance, power–current relationships, device efficiency/competence measured against time/temperature difference can be readily evaluated. Further, the test rig is also employed for mimicking real-world endurance thermal cycling tests, high temperature thermal soaking and using measured data to potentially identifying defective devices which have not been addressed in detail before. All these test results together can help determine the effectiveness of TE materials in an actual real world application setting. The scalability and robustness aspects of the proposed test rig is demonstrated by evaluating three different classes of TE systems viz. Bismuth Telluride, Skutterudites and Half Heusler alloys across different temperature gradients and various TE material/legs, devices or modules. The test is capable of handling other TE material systems, geometric configurations and temperature gradients that are not discussed in this work.

Biomass woodchip tracking by image analysis in a model of a fixed bed combustor

Energy sector sustainability is one of the main concerns in the recent years. Biomass, in form of woodchips, is interesting for direct combustion in external combustion cycles (e.g. supercritical CO2 Brayton cycles) due to the opportunity of using low quality and low environmental impact fuels. In this study, a direct combustion system working with biomass woodchips is investigated by means of an image analysis technique. The system is made up by a screw conveyor and a fixed bed, where the woodchips are processed. The analysed device operates in cold-condition, and woodchips are partially coloured according to their dimensional class to be traced once these reached the bed surface. A proper algorithm was developed to identify the particles size, define and detect macroparticles centres, and evaluate the main particles motion pattern by comparing the centre positions during time. The results were particularly useful to understand potential inefficiencies of the combustion system due to an uneven woodchips distribution. In addition, the results achieved with the proposed test rig and the adopted methodology can also be used to validate results from Discrete Element Modelling (DEM) simulations.

Lift distribution of washout twist morphing MAV wing

Micro Air Vehicle, or also commonly known as MAV, is a miniature aircraft that has been gaining interest in the industry. MAV is defined as a flying platform with 15cm wingspan and operates at a speed of around 10m/s. Recently, MAV has been exposed with the latest development and link towards the biologically-inspired designs such as morphing wing. Twist morphing wing is one of the latest MAV wing design developments. The application of Twist Morphing (TM) on MAV wing has been previously known to produce better aerodynamic performance. Previous study in washin TM wing has shown a promising possibility of generating higher lift force. Despite the benevolent performance exhibited by the washin TM wing, the lift distribution for the washout type of TM MAV is relatively unknown and still open to be explored. This is probably due to the lack of experimental test rig to produce the washout twist morphing motion on the MAV wing. Therefore, this research aims to produce a special test rig for washout TM wing that is compatible for wind tunnel experimental testing. By using the special test rig, the experimental investigation on the lift performance of washout TM MAV wing can be done. Based on the wing deformation results, it clearly shows that the proposed test rig is capable to produce up to 19.5mm tip deflection at the morphing point, which is also resulting in a significant morphing motion. Higher morphing force induces larger morphing motion. Based on the lift distribution results, they show that the morphing motion has significantly affected the overall lift distribution on the MAV wing. The morphing motion on TM wing has produced at least 17.6% and 5.33% lower CL and CLmax magnitude, respectively, with the membrane wing especially at the pre-stall region. However, the TM wing is still able to maintain the stall angle similar to the baseline wing at αstall= 31°. By maintaining high αstall value with lower CL and CLmax magnitude, TM wing produces more agility for the MAV maneuverability that will be useful for indoor mission or obstacle avoidance flight.

A novel test configuration designed for investigating mixed mode II/III fracture

In this paper, a novel test setup is introduced to investigate mixed mode II/III fracture (fracture under combined in-plane and out-of-plane shear loadings) in components weakened by crack. The designed loading fixture can exert the full range of mixed mode II/III loading conditions, from pure mode II to pure mode III, to a single edge cracked test specimen. The proposed test rig has a simple configuration as well as a low manufacturing cost and it is easy to be utilized and installed in conventional loading machines for performing fracture experiments. Three-dimensional finite element analysis has been employed for evaluating the performance and effectiveness of the test configuration in different mixed mode loading cases. The computational results demonstrate that the designed loading apparatus can appropriately create various mode mixities from pure mode II to pure mode III and is capable of assessing the mode II/III fracture behaviour of the materials experimentally.

Development of a test rig and a testing procedure for bicycle frame stiffness measurements

The stiffness measuring method for bicycle frames is not standardized, leading to a wide variety of test setups; they differ in many aspects such as applied load, support constraints and frame deflection measurement. The aim of this paper is to draw attention to this problem and to quantify the perturbing, unwanted side effects that influence the stiffness measurement of the bicycle frame. This is illustrated by developing a multi-purpose rating test method for bicycle frame stiffness. The proposed test rig design considers different aspects which should be taken into account when measuring the bicycle frame stiffness. In the experimental setup, it is observed that the contribution of the test bench compliance led to 21% difference in the frame stiffness results; the influence due to the head, the tube-bearing type the corresponding preload resulted in up to 19% difference in the stiffness results between the lowest and highest stiffness values measured; hysteresis effects caused by pulleys are estimated to introduce errors up to 11%; and the influence due to the operator variability and sensor accuracy is estimated to be less than 3%.

Catenary emulation for hardware-in-the-loop pantograph testing with a model predictive energy-conserving control algorithm

Pantograph current collectors, especially for high-speed trains, need to ensure safe contact with the catenary under stringent requirements on the dynamic contact force. A novel, high-dynamic pantograph test rig with accurate virtual catenary emulation is presented that allows for efficient, realistic, and reproducible testing. The complex dynamics of the pantograph/catenary interaction is modeled by a real-time-capable distributed-parameter description in moving coordinates. The proposed test rig controller incorporates model-predictive impedance control to match the desired catenary dynamics. Additionally, it keeps the exchange of the conserved quantities energy and momentum between the real pantograph and the virtual catenary consistent to increase physical trustworthiness of the results, even in high-dynamic test scenarios. The proposed methods are experimentally validated on the full-scale pantograph test rig.

Hardware-in-the-loop testing of bypass valve actuation system: Design and validation of a simplified real time model

During the start-up and shut-down phases of steam power plants many components are subjected to pressure and temperature transients that have to be carefully regulated both for safety and reliability reasons. For this reason, there is a growing interest in the optimization of turbine bypass controllers and actuators which are mainly used to regulate the plant during this kind of operations. In this work, a numerically efficient model for real-time simulation of a steam plant is presented. In particular, a modular Simulink™ library of components such as valves, turbines, and heaters has been developed. In this way, it is possible to easily assemble and customize models able to simulate different plants and operating scenarios. The code, which is implemented for a fixed, discrete step solver, can be easily compiled for a RT target (such as a Texas Instrument DSP) in order to be executed in real time on a low-cost industrial hardware. The proposed model has been used for quite innovative applications such as the development of a hardware-in-the-loop test rig of turbine bypass controllers and valve positioners. Preliminary experimental activities and results of the proposed test rig developed for Velan ABV are introduced and discussed.

Design and testing of a pulley and cable actuator for large ball valves

The objective of this work is the development of an innovative actuator for Velan ABV S.p.A., which is mainly used for control and special on/off applications where high efficiency and linear behaviors are desirable specifications. The main performances of the proposed actuator, which has been protected by a patent, have been compared with a conventional scotch yoke one, using both the simulation results and the experimental data. In order to measure the efficiency and the dynamical response of the actuators, the authors have designed a hydraulic test rig, configured to fulfill different testing procedures. In this way, it is possible to perform both static tests to identify actuator efficiency and dynamic hardware-in-the-loop tests in which an assigned load or valve impedance function is simulated to verify the response of the tested object in realistic operating conditions. Finally, the proposed test rig has been successfully used to perform reliability and fatigue tests in which the actuator is stressed with realistic and repetitive loads. Moreover, the integrated development of both innovative actuator and testing devices is explained introducing interesting concepts whose applications are normally limited to robotics (e.g. impedance and force control) or vehicular technology (e.g. smart suspensions and suppression of vibrations).

Design and Testing of an Innovative Wire Transmission for a Quarter-Turn Actuator

The object of this work is the development of an innovative wire actuator in collaboration with Velan ABV S.p.A., which will be mainly used in applications in which high efficiency and linear behavior are desirable specifications. In this work, the main features of the proposed actuator, which is protected by a patent, are evaluated and compared with respect to a conventional solution consisting of a scotch yoke (SY) transmission system. The comparison is performed using both the simulation results and the experimental data. In order to identify the efficiency and the dynamical response of the innovative actuator, the authors have designed a hydraulic test rig, which can be configured to perform different testing procedures. In this way, it is possible to perform both static tests to identify actuator efficiency, and dynamic ones, in which an assigned load or a valve impedance function is simulated to verify the response of the tested actuator in realistic conditions. Finally, the proposed test rig has been successfully employed to perform both reliability and fatigue tests in which the actuator is subjected to realistic and repetitive loads.

Close-to-Reality Sliding-Corrosion Test-Rig for Oilfield Application

Sliding-corrosion phenomena play a crucial role in reducing the lifetime of tubings in the oil production industry. The aim of the present work is to develop and apply a close-to-reality test rig to describe the tribological performance of low-alloyed Carbon-steel (C-steel) under sliding-corrosion conditions in O2-free environment. The proposed test rig is highly relevant for the oil production industry and has been designed at the Austrian Competence Center for Tribology (AC²T). The benefit of this equipment is that it allows the setting of the CO2 atmosphere at a certain partial pressure while simultaneously varying the pH-value, Cl− ion concentration, and temperature of the electrolyte solution. Pure corrosion phenomena are investigated within a designed coupon box where conditions of steam, electrolyte injection, static, and dynamic flow are controlled. In addition to the corrosive environment, a tribological reciprocating sliding contact is implemented between tubing segments and coupling samples. Within this study, a commercially available low-alloyed C-steel was selected as base material for the tubing, which was tribologically stressed under reciprocating sliding contact against spray metal coated couplings. The results show a high influence of the steel microstructure on the performance of low-alloyed C-steel tubings under sliding-corrosion. Additionally, the dominant damage mechanisms that are observed in real field applications could be successfully reproduced by experimental simulation using this newly designed close-to-reality test rig.

Preliminary design and validation of a Real Time model for hardware in the loop testing of bypass valve actuation system

During the start-up and shut-down phases of steam power plants many components are subjected to pressure and temperature transients that have to be carefully regulated both for safety and reliability reasons. For this reason, there is a growing interest in the optimization of turbine bypass controllers and actuators which are mainly used to regulate the plant during this kind of operations. In this work, a numerically efficient model for Real Time (RT) simulation of a steam plant is presented. In particular, a modular Simulink™ library of components such as valves, turbines and heaters has been developed. In this way it is possible to easily assemble and customize models able to simulate different plants and operating scenarios. The code, which is implemented for a fixed, discrete step solver, can be easily compiled for a RT target (such as a Texas Instrument DSP) in order to be executed in Real Time on a low cost industrial hardware. The proposed model has been used for quite innovative applications such as the development of a Hardware In the Loop (HIL) test rig of turbine bypass controllers and valve positioners. Preliminary experimental activities and results of the proposed test rig developed for Velan ABV are introduced and discussed.

Development of a multi-directional rating test method for bicycle frame stiffness

The methods for determining the bicycle frame stiffness exist in many forms. Because the stiffness measuring method is not standardized, each bicycle magazine or bicycle constructer uses his own test configuration. This leads to a wide variety of setups; they differ in many aspects such as applied load, boundary conditions and frame deflection measurement. To clarify some shortcomings in frame testing, a multi-directional rating test method for bicycle frame stiffness has been developed. The proposed test rig design considers different aspects that should be taken into account when measuring the bicycle frame stiffness.At first, it is important to eliminate perturbing side effects that influence the stiffness value of the bicycle frame. FE analysis revealed that using ‘very stiff’ boundary conditions to constrain certain degrees of freedom should be handled with the utmost caution. Using these non-rigid boundary conditions affects the bicycle frame deflection significantly. Therefore, prior to stiffness testing, the contribution of the test rig compliance should be estimated. It is advised to limit its estimated influence below 2 %. Hysteresis effects due to stick-slip and friction are avoided by omitting fixed boundary conditions and eliminating the friction force when using a pulley mechanism; if not errors up to 11 % are observed. It is recommended to use a rolling contact to constrain translation motion and to measure the force acting on the frame without other mechanisms between the force sensor and the bicycle frame. Another issue is the effect of the head tube bearing type and the preloading torque. The industrial bearings reduce the frame stiffness up to 19 % when comparing with steel bearing replicas. It is the operator’s decision to test bicycle frames with or without industrial bearings for stiffness measurements. Though, steel bearings are advised for mutual frame comparison since this avoids discussion about the differences among industrial bearings. The overall accuracy of the test result is expressed as percentage deviation on the 95 % confidence interval and includes both the influence of the operator and the sensors. To detect small changes between results from different frames, a percentage value of 2 % or less is desired.The selection of stiffness configurations is based on the major load components acting at the head tube, the bottom bracket and the rear-dropout. The bracket- and torsion stiffness are replaced with a specific classification of the test setup. The directional frame stiffness is as such assessed for individual load cases: (i) the in-plane vertical and horizontal stiffness of the bottom-bracket and rear-dropout, (ii) the transversal or out-of-plane stiffness of the bottom bracket and (iii) the torsion stiffness with or without the contribution of the rear-triangle of the bicycle frame. As such is detailed information available for the bicycle constructor to modify the design and for the cyclist when comparing the stiffness characteristics of different frame types.

On the Generated Heat at Advancing/Receding of Water on Surface Engineered Nanoporous Silica

In this work, ratio of the generated heat relative to the dissipated energy, during the cyclical advancing/receding of water on surface engineered nanoporous silica is evaluated based on a thermographical method. Proposed test rig is a compression-decompression cylinder divided into two chambers, one of constant volume and the other of variable volume. Silica particles are introduced inside the cavity of fixed volume, and a micro-filter is used to separate it by the chamber of variable volume, in which only water is supplied. Using an infrared-camera, the temperature distribution on the external surface of the cylinder is recorded versus the working time, and positions of the main heat sources are identified. Such tests allow evaluation of the dissipated energy and generated heat. One finds that the surface engineered nanoporous silica is able to dissipate large amounts of mechanical energy without significant heating, i.e., maximum 17 % of the dissipated energy is emitted in the infrared frequency range. Such result is surprising since the emissions recorded from traditional frictional dissipaters, such as hydro-pneumatic absorbers, rubber and foam absorbers, etc., are mainly (about 90%) in the infrared range, and only partially in the audio and visible frequency range.

A new approach to testing concrete coupling beams subjected to reversed cyclic loading

This paper presents an innovative experimental rig developed for tests of full-scale concrete coupling beams of tall shear wall buildings subjected to reversed cyclic loading. The coupling beams are generally subjected to very high bending moment and shearing force owing to rotations of the beam ends, which are forced by the deflection of shear walls under the action of lateral loading. Because no direct loads are generally applied to the beams, how to create the boundary conditions where two beam ends are forced to rotate equally and displace vertically is challenging in the laboratory tests. This can further be complicated by the requirement of applying reversed cyclic loading to the connected shear walls. The developed test rig allows for proper modelling of loading and boundary conditions in both monotonic and reversed cyclic load cases. Tests of the full-size specimens with different span-to-depth ratios can be conducted without changing the beam depth, which allows for direct comparisons of specimens and experimental results. The rig is capable of performing tests for investigating strength and ductility of the specimens with large rotational and vertical displacements. Available experimental methods to test coupled shear walls are reviewed to demonstrate the simplicity, accuracy and effectiveness of the proposed test rig and the method.

Research on the Hydraulic Coupling

A short account of the origins of the hydraulic coupling is followed by a description of a production model and its method of operation. Tests have been carried out both on a transparent plastic model and on the full-scale production coupling. From the author's experience of the design and application of hydraulic couplings a mathematical analysis is made which uses conventional design formulae and general roto-dynamic theory. Dimensionless parameters and empirical laws are established which are useful in the prediction of design performance, and an examination of fluid friction and shock losses is made. Sample calculations on production couplings using the derived theory show close agreement with actual practice. A short description of a proposed test rig and future lines of experiment is appended.