Test Rig Research Articles

Multi-Parametric Investigations on White Etching Crack Formation in Deep Grove Ball Bearings

Research on White Etching Cracks (WEC) in multiple bearing applications has identified various drivers that cause them. Lubricants and electricity combined with contact mechanics have been proven to catalyze WEC significantly. However, none of these factors solely cause WEC on its own; instead, combinations of factors discretize whether WEC appears or not. Hence, the WEC phenomenon appears to be multidimensional, making WEC still unpredictable. The current paper is about a systematic study using a Deep Grove Ball Bearing test rig to investigate how lubricant chemicals, combined with electricity and variations in oil flow and pressure, lead to WEC formation. It becomes evident that even under critical conditions for WEC formation, increasing oil flow and decreasing contact pressure can prevent WEC.

Development and Design Validation of an Inflow-Settling Chamber for Turbomachinery Test-Benches

At Leibniz University of Hannover, Germany, a new turbomachinery test facility has been built over the last few years. A major part of this facility is a new 6 MW compressor station, which is connected to a large piping system, both designed and built by AERZEN. This system provides air supply to several wind tunnel and turbomachinery test rigs, e.g., axial turbines and axial compressors. These test rigs are designed to conduct high-quality aerodynamic, aeroelastic, and aeroacoustic measurements to increase physical understanding of steady and unsteady effects in turbomachines. One primary purpose of these investigations is the validation of aerodynamic and aeroacoustic numerical methods. To provide precise boundary conditions for the validation process, extremely high homogeneity of the inflow to the investigated experimental setup is imminent. Thus, customized settling chambers have been developed using analytical and numerical design methods. The authors have chosen to follow basic aerodynamic design steps, using analytical assumptions for the inlet section, the “mixing” area of a settling chamber, and the outlet nozzle in combination with state-of-the-art numerical investigations. In early 2020, the first settling chamber was brought into operation for the acceptance tests. In order to collect high-resolution flow field data during the tests, Leibniz University and AERZEN have designed a unique measurement device for robust and fast in-line flow field measurements. For this measurement device, total pressure and total-temperature rake probes, as well as traversing multi-hole probes, have been used in combination to receive high-resolution flow field data at the outlet section of the settling chamber. The paper provides information about the design process of the settling chamber, the developed measurement device, and measurement data gained from the acceptance tests.

Full-size experimental investigations on planetary gear journal bearings in high-power wind turbines

Abstract To satisfy the large-scale and high-power demands of wind turbines, planetary gear journal bearings (PGJBs) have been applied in large wind turbine gearboxes (WTGs), as an alternative to traditional rolling bearings, due to their higher reliability and smaller size. To simulate the actual lubrication behaviors of PGJBs and investigate their hydrodynamic performance, a full-size test rig for PGJBs was built in this paper. A multi-parameter detection system coupled with the ultrasonic testing method was developed. Four ultrasonic piezoelectric elements, eight thermistors, two pressure transducers, and one torque sensor were used to obtain the film thickness, oil temperature, oil pressure, and friction torque data of the test PGJB. The rated condition experiment was conducted to investigate the variation of measured lubrication performance with the operating time. Three-dimensional predictions of oil film pressure, temperature, and thickness were presented to analyze the steady-state lubrication characteristic at the rated condition. Moreover, a series of steady-state experiments were also carried out to simulate the normal operations of the test PGJB at different conditions. And the measured results were verified by the numerical predictions. The influence of rotational speed, input load, oil supply temperature, and oil supply flow on the hydrodynamic performance of the test PGJB were explored.

Modular test rig for a rotor supported by gas foil bearings

AbstractFoil bearings for high speed turbomachinery are and have been studied in terms of load capacity and lift‐off speed, stability, thermal behaviour and manufacturing. This paper focuses on a modular rotor‐bearing test rig, with which design changes can easily be experimentally investigated. An exemplary design change is undertaken and its effects are studied. Furthermore, a simple procedure is introduced, with which rigid body modes of the rotor can be extracted from phase information derived from experimentally obtained time series data.

New evaluation method for defects propagation in toroidal roller bearings using dominant frequency of acoustic emission

ABSTRACT The increased use of roller bearings in recent years has made it vital to develop techniques for Condition Monitoring (CM) of these valuable assets. Toroidal Roller Bearings (TRB) are one of the recent inventions that has revolutionised some industries because of its unique design. In this study, newly produced TRBs were tested using Acoustic Emission (AE), vibration and temperature, on a specially designed test rig. The AE signal was recorded, processed, and analysed using FFT-based methods to transform from the time domain to the frequency domain, and to specify the Dominant Frequency (DF) of each hit in the signal. The result of the analysis was a layout on the time domain of the DFs of all AE hits along with RMSAE and other parameters, this layout was called DF map. The test was divided into three phases, and the DF bands were divided horizontally into three band groups. The aim is to establish a correlation between the phases and DF bands. Knowing the type of defects that are typical for each phase in the test provided insights to what are the DFs of that type. Promising results can be achieved using this measuring method on other types of bearings.

Investigation of the Sigma Approximation Technique for the Solution of the Time Spectral Equation System

Abstract The time spectral method is commonly utilized to analyze periodic unsteady flows within turbomachines. However, the time spectral solutions in regions with large temporal and spatial gradients, such as wakes, shocks, and boundary layers, can be plagued with unphysical oscillations, known as the Gibbs phenomenon. This paper presents an investigation into the sigma approximation technique, which is capable of significantly attenuating the Gibbs phenomenon by dampening high-frequency nonlinear components in the time spectral solutions. However, the optimal combination of the sigma factors remains to be ascertained considering the trade-off between the accuracy of solutions and the reduction of unphysical oscillations. In this study, a two-row compressor configuration is first selected, and numerical simulations are performed to evaluate the efficacy of this technique under near peak-efficiency and near-stall operating conditions. It is found that Gibbs-type unphysical oscillations can be effectively mitigated without notably compromising solution accuracy through an optimal combination of sigma factors. The NASA Stage 35 case study further verifies the effectiveness of the proposed optimal sigma factor combination in preserving the accuracy of time spectral solutions based on the data from test rig. Moreover, the von Neumann analysis reveals that the sigma approximation technique can enhance the numerical stability of the time spectral equation system, thereby allowing the use of aggressive numerical parameters to accelerate convergence. The stability analysis results are verified by a two-dimension bump under two different flow conditions and further assessed using the two-row compressor.

Complete Dynamics from Ignition to Stabilization of a Lean Hydrogen Flame with Thickened Flame Model

Abstract In recent years, attention has been paid to hydrogen thanks to its carbon-free nature and its interesting characteristics as an energy vector. Despite the large number of numerical analyses regarding hydrocarbon combustion in all the steady and unsteady processes, few papers that cover all those aspects are available in the literature for hydrogen flames. Therefore, a numerical methodology to explore the complete ignition sequence from the spark release to the flame stabilization is validated on a single-sector hydrogen burner. In this context, a preliminary DNS investigation of laminar spherical expanding flames is performed using different diffusive transport models to isolate their impact. The present work, carried out within the European project HESTIA, investigates the atmospheric test rig installed at the Norwegian University of Science and Technology operating with a lean, perfectly premixed, hydrogen-air flame stabilized on a conical bluff body. Four simulations are performed adopting the Thickened Flame Model with an energy deposition strategy to assess the impact of preferential and thermal diffusion, as well as grid resolution, on flame dynamics. 3D flame structure visualization coupled with detailed PIV/OH-PLIF measurements allows the investigation of the key mechanisms involved during the ignition. The dynamic response of the flame through axial fluctuations once the ignition transient is concluded, is reconstructed by the numerical strategy employed. Although the overall behavior is almost unchanged by including or not thermal diffusion effects, their local impact on the flame is evident leading to a better agreement with experimental data.

Comparison of simplex and duplex drum brakes linings with transverse slots in vehicles

In this paper, experimental comparison between Simplex and Duplex drum brake units performance for three different drum lining profile designs is carried out. The three linings profiles are normal (no slot), with one slot and with three slots. In this study, brake test rig has been designed to represent the actual braking process environment. Brake oil pressure and drum speed are the operational parameters that are varied during the experimental work. From the experimental work and mathematical models for brake force, brake factor, and final friction temperature, the comparisons were carried out. The final conclusions indicate that lining with one slot profile is the most suitable, since the percentage improvement of mean brake force and brake factor of duplex drum brake (D) linings versus simplex drum brake (S) linings reaching 84.09% and 82.73% higher than three slots lining profile but lower than lining with normal profile at low pressure 5 bar and low speed 50 rpm. Also, the percentage improvement of mean primary shoe final friction temperature reduction for the one slot profile reaches 30.00% higher than normal lining profile but lower than lining with three slots profile at high pressure 20 bar and drum speed 50 rpm.

Hydrocarbon Traps for the Air Intake System: Component Test Rig and SHED Test Procedure for Determining Their Efficiencies

Hydrocarbon traps in the air intake system (AIS) are a common method for controlling evaporative emissions from the air intake path. Several different systems are available, but there is no standard method for determining their efficiencies. Therefore, a component test rig for hydrocarbon traps was developed. Some optimizations were necessary to achieve emission characteristics observed in engine measurements. Using this setup, several measurements were performed on four different hydrocarbon traps. The results were in reasonable agreement with those from engine measurements. Two different hydrocarbon (HC) traps were selected for further studies. In these studies, the repeatability and the dependency of the emission mass level were investigated. Furthermore, the hydrocarbon concentration in the air filter box was determined using point source flame ionization detector (FID) sampling and a metal oxide semiconductor (MOS) sensor. The data showed a correlation with the emission mass determined in a sealed housing emission determination (SHED) test.

Design, Fabrication, and Commissioning of Transonic Linear Cascade for Micro-Shock Wave Analysis

Understanding shock wave behavior in supersonic flow environments is critical for optimizing the aerodynamic performance of turbomachinery components. This study introduces a novel transonic linear cascade design, focusing on advanced blade manufacturing and experimental validation. Blades were 3D-printed using Inconel 625, enabling tight control over the geometry and surface quality, which were verified through extensive dimensional accuracy assessments and surface finish quality checks using coordinate measuring machines (CMMs). Numerical simulations were performed using Ansys CFX with an implicit pressure-based solver and high-order numerical schemes to accurately model the shock wave phenomena. To validate the simulations, experimental tests were conducted using Schlieren visualization, ensuring high fidelity in capturing the shock wave dynamics. A custom-designed test rig was commissioned to replicate the specific requirements of the cascade, enabling stable and repeatable testing conditions. Experiments were conducted at three different inlet pressures (0.7-bar, 0.8-bar, and 0.9-bar gauges) at a constant temperature of 21 °C. Results indicated that the shock wave intensity and position are highly sensitive to the inlet pressure, with higher pressures producing more intense and extensive shock waves. While the numerical simulations aligned broadly with the experimental observations, discrepancies at finer flow scales suggest the need for the further refinement of the computational models to capture detailed flow phenomena accurately.

Efficiency of Bevel and Hypoid Gears—Test Rig Development and Experimental Investigations

The efficiency of bevel and hypoid gears is, alongside load capacity, one of their most important design criteria. To consider the efficiency of bevel and hypoid gears during the development and design process, validated calculation methods based on experimental investigations are necessary. However, the isolated experimental investigation of the load-dependent power losses of bevel and hypoid gears has not been adequately investigated, as most of the experimental investigations consider the complete gearbox. This paper presents a test rig that allows for the experimental investigation of the efficiency of bevel and hypoid gears with a measurement uncertainty of the efficiency of ∆η≤±0.08% according to the Guide to the Expression of Uncertainty in Measurement (GUM). Using the developed test rig, experimental investigations on the efficiency behavior of bevel and hypoid gears regarding the influence of the axial offset, driving direction, and microgeometry are carried out for different operating points varying in circumferential speed and load. This paper discusses the methodology and the first experimental results of a study on the efficiency of bevel and hypoid gears in detail.

Multi-sensor temporal-spatial graph network fusion empirical mode decomposition convolution for machine fault diagnosis

Multi-sensor time-series data at different locations contains not only temporal correlation information but also spatial correlation information which is treasure for machine fault diagnosis. Existing graph construction methods mainly apply different data analysis methods to connect nodes and edges. Few works, however, consider the location of the sensor itself and temporal correlation information of multi-sensor time-series data. To mine the relationship between spatial information and temporal information, the multi-sensor temporal-spatial graph is constructed in this paper. Hereinto, the different data points of multi-sensor are severed as different nodes which represents the spatial feature information. The temporal information is contained between different nodes of the same sensor. Moreover, an empirical mode decomposition graph convolution network (EGCN) is proposed to extract the feature. Specifically, the traditional graph convolution operator is changed to empirical mode decomposition which can decompose the input features into multiple intrinsic modal features to achieve adaptive feature extraction and improve the representation capability of the network. Finally, the different fault types can be classified by fully connected layers. Experiments from different test rigs demonstrate that the proposed method achieves a diagnostic accuracy exceeding 99 % under limited fault samples.

On the use of vibrations and temperatures for the monitoring of plastic chain conveyor systems

In industrial automation, the transportation of unit loads plays a crucial role. This paper addresses the under-explored area of plastic chain conveyors, a versatile and efficient means of transport within production processes. Despite their widespread use, these conveyors suffer from wear and tear due to continuous contact between the chain and guide rails, often leading to unscheduled shutdowns and increased costs. The literature on monitoring solutions for such systems is sparse, particularly for plastic chains. This paper aims to bridge this gap by surveying the most common wear mechanisms for these systems and presenting a physical model that describes the interaction between the chain links and guide rails, based on chain of masses, springs and dampers and the Archard wear model. This model allows to relate the variations due to wear with other physical quantities, such as passage frequencies of the links and heat generated due to friction. The comprehensive model provides analytical formulas to understand the vibrations induced by the chain on the platform and the guide-rail temperatures. To validate the model and evaluate how the measurements are affected by the degradation of the system, an extensive experimental campaign was conducted on a conveyor test rig, acquiring vibration and temperature data. The end goal is to identify and discuss methodologies suitable for estimating the wear mechanisms of conveyor systems, with a focus on the constraints of industrial environments. Hence, this study aims to lay the groundwork for defining monitoring solutions that enhance the maintenance efficiency of plastic chain conveyor systems. The results suggest that the power Spectral Densities (PSD) of the platform’s accelerations are sufficient to estimate the average links pitch, which in turn could be used to assess the chain elongation. Besides, the local temperatures confirmed the model observations, making them suitable for estimating the slide-rail thinning.

Numerical Analysis on Thermal Behavior of Composite Wall Combined Autoclaved Aerated Concrete With Thermal Insulting Material in Summer Day

Abstract Thermal insulation material (TIM) is commonly employed to enhance the thermal behavior of the lightweight walls. To further obtain the energy-saving effect of the walls, the composite wall (ATIM) combined autoclaved aerated concrete (AAC) block with TIM was present in this study. A testing rig with an ATIM wall was constructed and tested in summer design days, while the numerical modeling was developed and validated using the experimental data. Furthermore, reference walls of the brick and AAC with the same dimension as the ATIM wall were established to evaluate its thermal behavior. The thermal behavior and economic evaluation of the ATIM wall were then investigated by varying the thickness and position of the TIM using the numerical method. And the research results indicated that: (1) the average inner surface temperature of the ATIM wall is approximately 1.1 °C lower than that of the AAC wall, 1.3 °C lower than that of brick wall, the thickness of TIM is positively correlated with decreasing wall surface temperature, while TIM positions have minimal impact on reducing surface temperature; (2) heat gain reduction ratio for ATIM wall (δ = 20 mm) is approximately 52.7%, which is 8.1% higher than that of AAC wall, and variation in TIM position can decrease the heat gain, with inside or outside placement being more effective than positioning it in the middle part; (3) CO2 emission saving (CO2ES) and electricity cost saving (ECS) for room C (ATIM wall) is approximately 7.05 kg/100 m3/day and 5.23 RMB/100 m3/day, respectively, outperforming room A (brick wall) and room B (AAC wall) in terms of energy efficiency and economic benefits.

Horizontal Test Stand for Bone Screw Insertion

Screws are a versatile method of fixation and are often used in orthopaedic surgery. Various specialised geometries are often used for bone screws to optimise their fixation strengths in limited spaces at the expense of manufacturing costs. Additionally, ongoing research is looking to develop systems/models to automatically optimise bone screw tightening torques. For both applications, it is desirable to have a test rig for inserting screws in a regulated, instrumented, and repeatable manner. This work presents such a test rig primarily used for the validation of optimal torque models; however, other applications like the above are easily foreseeable. Key features include controllable insertion velocity profiles, and a high rate measurement of screw torque, angular displacement, and linear displacement. The test rig is constructed from mostly inexpensive components, with the primary costs being the rotational torque sensor (approx. 2000 €), and the remainder being approximately 1000 €. This is in comparison to a biaxial universal testing machine which may exceed 100,000 €. Additionally, the firmware and interface software are designed to be easily extendable. The angular velocity profiling and linear measurement repeatability of the test rig is tested and the torque readings are compared to an off-the-shelf static torque sensor.

Effects of Hydrogen on the Tribological Performance of Heavily Loaded Lubricated Contacts

The objectives of this investigation were to experimentally characterize the effect of hydrogen on the tribological performance of heavily loaded lubricated contacts. In order to achieve these objectives, a ball-on-disc film thickness and traction measurement test rig and a four-ball wear tester were modified to introduce gaseous hydrogen into the lubricated contact. Using the ball-on-disc test rig, lubricant film thickness, and traction were measured operating in air, nitrogen, and hydrogen environments. The results indicate that hydrogen environment has no effect on the lubricant film thickness and traction coefficient. The wear performance of the lubricant was evaluated in air, nitrogen, and hydrogen environments using the four-ball tester according to ASTM D4172 standard. Wear scar dimensions were determined through optical profilometry and compared for each condition. The results demonstrated that the wear scar diameter is slightly higher in a hydrogen environment. Additionally, the effects of hydrogen embrittlement on the wear performance were investigated using the four-ball tester. The balls used in the four-ball tester were precharged with hydrogen in Ammonium Thiocyanate. Wear scar profilometry results showed significantly larger wear scars and excessive pitting on the worn surface of precharged specimens. Results from this investigation shows that a gaseous hydrogen environment has a negligible effect on friction and wear as compared to diffused hydrogen in the material.

Comparison of acoustic, optical, and heat release rate based flame transfer functions for a lean-burn injector under engine-like conditions

Determining the flame transfer function plays a crucial role during the development phase of lean-burn injectors to predict the overall stability of the combustion system. This study develops an enhanced acoustic post-processing strategy using acoustic network modeling and compressible large-eddy simulation for a lean-burn aero-engine injector in a realistic test rig. Results show that optical flame transfer functions experimentally obtained align with those derived from large-eddy simulation based on heat release rate. However, discrepancies, especially in gain, are observed when using the standard acoustic post-processing method. By employing an acoustic network model, it is shown that comparable flame transfer functions can be achieved through refined post-processing strategies. This study highlights the limitations of conventional acoustic post-processing and underscores the necessity of explicit acoustic modeling in complex setups to accurately obtain the flame response. A generalized formulation applicable to a broader range of setups, extending beyond simple configurations, is presented as an alternative to the conventional acoustic post-processing method.

Fault diagnosis of planetary roller screw mechanism with a lightweight model based on federated learning

The fault data for Planetary Roller Screw Mechanisms (PRSM) is challenging to collect in real industrial settings due to the complex nature of practical operations and the lengthy accumulation period. Consequently, there has been little research on PRSM fault diagnosis. Additionally, the high processing cost of PRSM means that institutions are reluctant to make their fault data publicly available, creating a data barrier and further hindering research of the study on fault diagnosis of PRSM. To address these issues, Federated Learning (FL) is applied for PRSM fault diagnosis. In the FL framework, data remains in local storage, preserving data privacy. To reduce transmission costs, a lightweight model called SResNet18 is proposed. SResNet18 reduces parameters by 95.07 % and 61.93 % compared to ResNet18 and DSResNet18, respectively, which decreases the time needed for parameter uploading, model aggregation, and parameter returning. Additionally, SResNet18 has lower computational complexity, with 92.09 % and 36.66 % fewer FLOPs than ResNet18 and DSResNet18, respectively. Healthy and fault data of PRSM are collected on the PRSM testing rig, and the proposed method is evaluated. Results show that our method achieves the highest accuracy of 99.17 %, improving model performance while maintaining data privacy. The proposed SResNet18 also alleviates overfitting and reduces training time in the FL framework.

Assessment of hybrid machine learning models for non-linear system identification of fatigue test rigs

The prediction of system responses for a given fatigue test bench drive signal is a challenging problem, since highly dynamic loads from measurement campaigns must be reproduced accurately. Linear frequency response function models are commonly used for this system identification task, but energy intensive experimental iterations are required to account for system non-linearities. Two novel hybrid modeling strategies are suggested, which augment existing approaches using non-linear Long Short-Term Memory networks. These are trained and deployed on short subsequences of measurement data and recombined using a windowing technique, which enables their application to measurement data with high sampling rates. In addition to fatigue test bench commissioning, these hybrid models can also be employed in the field of virtual sensing. The approach is tested using non-linear experimental data from a servo-hydraulic test rig and this dataset is made publicly available. A variety of metrics in time and frequency domains, as well as fatigue strength under variable amplitudes, are employed in the evaluation. It is shown, that hybrid models can successfully use frequency response function models as a linear baseline estimate, which is further improved by Long Short-Term Memory networks to enable non-linear predictions.

Results in Engineering Experimental investigation of drag loss and plate separation behavior of wet clutches under external forces

Understanding the drag loss behavior of wet clutches is crucial for the development of low-loss clutch systems. For non-horizontal installation positions and non-stationary applications, external forces caused by the inclination or vehicle dynamics act on the plates. It has yet to be investigated how external forces influence the plate separation process and distribution and, subsequently, the drag loss behavior. Therefore, this study aimed to fundamentally investigate wet clutches' drag loss and plate separation behavior under the effect of external forces. The investigations were conducted in three steps. First, fundamental knowledge of the plate separation and drag loss behavior was gained. The effects of relevant design and operating parameters on the drag loss behavior were determined then. Separation springs were finally tested to avoid the influence of external forces. The drag loss and plate separation behavior were investigated on a drag torque test rig based on different clutch systems. The external forces were applied by inclining the test rig. The plate separation behavior was determined through image-based measurement of the plate movements. It was found that the plates separate under external forces and that the drag torque curve shows characteristics similar to wet clutches operated without external forces applied. The utilization of the set total clearance depends on the inclination angle. Hence, increasing the set total clearance does not generally imply lower drag losses, but increasing the inclination angle leads to higher drag losses. It was confirmed that the drag loss behavior is not influenced by external forces when using spacing elements. The findings of this study extend the existing body of literature and may support the development process of brake and clutch systems.