Small Test Rig Research Articles

Air Leakages at Microvalves: Pressure Decay Measurements and Extended Continuum Modelling of Knudsen Flows

To improve the performance of valves in relation to the leakage rate, a comprehensive evaluation of the valve characteristics and behavior during pressure exposure is important. Often, these low gas flow rates below 0.1 cm3/min cannot be accurately measured with conventional flow sensors. This paper presents a small and low-cost test rig for measuring gas leakage rates accurately, even far below 0.1 cm3/min, with the pressure decay method. These leakage flows are substantiated with a flow model, where we demonstrate the feasibility of modeling those gas flows with an extended Navier–Stokes framework to obtain more accurate theoretical predictions. As expected, the comparison to the experimental results proves that the classical Navier–Stokes system is unsuitable for modeling Knudsen flows. Hence, self-diffusion of gas, a wall-slip boundary condition, and an effective mean free path model were introduced in a physically evident manner. In terms of the calculated mass flow, while self-diffusion and slip boundary conditions explain deviations from the classical Navier–Stokes equation for Knudsen numbers already smaller than 1, the effective mean free path model has an effect, especially when Kn > 1. For simplified conditions, an analytical solution was presented and compared to the results of an OpenFOAM CFD-solver for flow rates through more complex gap-flow geometries of the flap valve. Hereby, acceptable deviations between 10% and 20% were observed. A comparison with measurement results was carried out. The reproducibility of the measurement method was verified by comparing multiple measurements of one silicon microvalve sample to a state-of-the-art flow sensor. Three geometrically similar passive silicon microvalves were measured with air overpressure decreasing from 15 kPa relative to atmospheric pressure. Maximum gas volume flowing in a blocking direction of 1–26 µL/min with high reproducibility and marginal noise were observed.

A novel electromechanical system for guide vane adjustment in a small turbine test rig

A novel electromechanical system for guide vane adjustment in a small turbine test rig

Dunaliella salina fuel blends as the secondary fuel for the microgas turbine engines: A combustion and emission study

With the increasing demand for fossil fuels causing a decline in oil resources, the development of bio-gasoline has the potential to reduce the dependence of the fuel market on fossil fuels. This paper presents the experimental results of performance and emission characteristics of biofuel in a micro gas turbine engine. The microalgae chosen for this study is Dunaliella salina and different blends includes DB0 (Jet A fuel 100% + Dunaliella salina 0%), DB25 (Jet A fuel 75% + Dunaliella salina 25%) and DB50 (Jet A fuel 50% + Dunaliella salina 50%).All experimental tests were conducted in a small test rig and at different engine speeds as 40000 rpm, 50000 rpm and 60000 rpm. The study analysed the performance metrics including thrust, thrust-specific fuel consumption, thermal efficiency, and emissions. Results showed that blends reduced static thrust and thrust-specific fuel consumption and enhanced thermal efficiency. At 55000 rpm, the DB25 and DB50 reported 3% and 15% reduction in the static thrust. However, 11% and 15% reduction in the TSFC has been noted respectively. The CO and NOx emissions were also reduced with the use of biofuels. There was no observed decrease in NOx production. As the concentration of the microalgae blends increases, the temperature in the combustion chamber also increased, leading to an increase in NOx production. The findings indicate that blending microalgae blends with Jet-A fuel can lower pollutant emissions while retaining the desired thrust level. This research suggests that an optimal blend of the two fuels can be found and that biofuels can be a viable alternative to petroleum-based energy.

RETRACTED: Repeatability in measurements and control settings of a small francis turbine test rig

A reduced scaled-down hydraulic turbine test setup has been designed. The test setup is made to investigate the mitigation of pressure pulsations like the rotating vortex rope (RVR) and its formation and problems related to prototype operation. The setup arrangements and instrumentations follow mostly the international electro-technical commission (IEC) standards. This paper presents the runner hub modification, calibration procedure, repeatability and systematic uncertainty estimation, and measurement methods as per the guidelines given in IEC 60193 and IEC 60041. The calibration and regression curves of all devices are presented. A LABVIEW program for open-loop operation at a constant head and closed-loop operation at constant discharge is also presented. Finally, the systematic and random uncertainty of hydraulic efficiency is discussed. • Design and development of small turbine test rig. • Design modification of runner cone profile. • Working of control feedback system using Partial Integral Differential (PID) controller. • Calibration of different instruments used in the small turbine test rig. • Random and systematic uncertainty of the small turbine test rig.

Highlights of aeroacoustic tests of a metal spacecraft cabin ventilation fan prototype

A metal spacecraft cabin ventilation fan suitable for aerodynamic and acoustic ground tests was designed and tested in the NASA Glenn Research Center Acoustical Testing Laboratory. The fan design featured a low-noise blade-vane count that was chosen to reduce the rotor-stator interaction tone noise. The fan was throttled through its operating range, and results indicated that the measured aerodynamic and acoustic performance was in good agreement with predictions. Recommendations for further research of quiet high-performance fans intended to support long duration human space exploration missions are offered. This small fan aerodynamic and acoustic test rig and the NASA Glenn Acoustical Testing Laboratory are valuable resources available for supporting NASA's aeronautics research and space exploration missions.

Influence of runner cone profile and axial water jet injection in a low head Francis turbine at part load

Development of rotating vortex rope (RVR) at part load (PL) operation is a source of pressure fluctuations in draft tube and power swings, which may lead to runner failure under extreme conditions. Fluid injection methodologies like air and water injection may be employed to mitigate the RVR and the pressure pulsations associated with it. A small turbine test rig is being developed at IIT Roorkee (India) to study the effect of the fluid injection measures (air/ water) in the Francis turbine. The present work summarizes a preliminary numerical investigation of the runner cone design and water jet injection to be used in the test rig. The runner cone is modified to incorporate provisions for axial water jet injection. Two different runner cone designs have been compared based on power output, efficiency, pressure recovery, and pressure pulsations in the draft tube for four different jet discharges. The water jet affects both the magnitude and the frequency of the pressure pulsations associated with RVR, and improves the overall efficiency. The results also indicate that the water jet injection may not always be effective and may increase pressure fluctuations in some cases.

Turbine Test Rig to Investigate Flow Instabilities in Draft Tube

Time-dependent phenomena in a reaction turbine such as rotor-stator interactions (RSI) and rotating vortex rope (RVR) contribute to pressure fluctuations, vibrations, and even failure of the machine. A small scale test rig is being developed to investigate RSI and RVR and to study RVR mitigation methods. The test rig is designed for a maximum available head and discharge of 8 meters and 0.05 m3/s, respectively. Provisions are made to operate the test rig in open and closed loops. The test rig is flexible to operate for the turbines of high specific speed (high head Kaplan turbine or very low head Francis) to low specific speed (high head Francis). The runner of the test rig is 200 mm in diameter at draft tube inlet. The turbine is connected with a variable speed generator to run up to 1000 rpm. This paper presents the design and arrangements of the test rig components according to the head and discharge conditions. Scale down design calculations for a model are performed using IEC 60193.

Influence of the runner cone design on the pressure fluctuations in the draft tube of a low head Francis turbine

This paper presents a preliminary numerical investigation on the design of the runner cone for a small turbine test rig under development at IIT Roorkee, India. The test rig is designed to study the formation and mitigation of rotating vortex rope (RVR) in the draft tube of a low head Francis turbine. The original runner cone design needs to be modified to include the provision for axial jet injection. Three different configurations, namely, a truncated cone and two original length cones with different nozzle positions, have been compared with the original cone to choose a suitable one for further investigations. The entire three-dimensional flow passage of the turbine unit has been simulated using the shear stress transport turbulence model after carrying out a mesh independence test on the original design. The proposed designs are compared at three different operating points. The amplitude and frequency of the pressure pulsations in the draft tube have been analyzed using the fast Fourier transform (FFT) method.

Deflagration-to-detonation transition in H2-CO-Air mixtures in a partially obstructed channel

In this study flame dynamics in homogeneous hydrogen-carbon monoxide-air (H2-CO-air) mixtures are investigated in an explosion channel. The small scale test rig is a 6 m long channel and has a rectangular cross section of 300 x 60 mm. Obstacles with a blockage ratio of 60% and a spacing of 300 mm are placed in the first section of the channel. A 2.05 m long unobstructed section in the rear of the channel allows for investigation of sustainable propagating flames and detonations. The fuel composition is varied from 100/0 to 50/50 vol.-% H2/CO mixtures. The overall fuel content ranges from 15 to 40 vol.-% in air aiming to obtain fast flames and deflagration-to-detonation transition (DDT). Flame speed and dynamic pressure data are evaluated. Results extend data obtained by Veser [1] and can be used for validation of numerical frameworks. Limits for fast flames and DDT in homogeneous H2-CO-air mixtures at the given geometry are presented.

Characterisation of deformation process and fracture mechanisms of P91 steel at 600 °C in small punch tensile testing

This paper investigates the microstructural evolution and fracture mechanism of the P91 steel during small punch tensile tests. Disc specimens, 8 mm in diameter and 0.5 mm in thickness, were tested in a small punch test rig at 600 °C using a constant displacement rate of 2 μm/s. Interrupted small punch tensile tests were performed to investigate the microstructural evolution in different deformation regimes. Deformed specimens were characterised by scanning electron microscopy and electron backscatter diffraction. Microstructure characterisation showed that block boundary alignment occurred in the plastic deformation direction, before achieving the maximum punch load. It was revealed that the martensitic structure was recovered when the tests progressed. The elongation of recovered grains occurred after achieving the maximum punch load. In addition, it was shown that the voids tended to nucleate along the recovered grain boundaries and became elongated to align with the plastic flow within the specimen.

Static characteristics of a simple rotor-bearing system: modelling and experiment

The dynamics of rotating machinery have been extensively investigated during the past century. To date, longer rotating shafts, higher rotating velocity, higher fluid pressure, and generally high performances are required. For this purpose, a deep understanding and a more accurate modelling of the rotating machinery dynamical behaviour is needed, especially in terms of the resultant vibrations and stability issues. In this paper, a mathematical model was developed for a simple rigid rotor-bearing system using finite element method. Several natural frequencies and corresponding mode shapes of the systems were presented. In order to validate the model, some experimental tests were performed using a small test rig. The response of the system in the frequency domain and the direct orbit of the shaft were plotted as well.

Measured and Simulated Forced Response of a Rotating Turbine Disk With Asymmetric and Cylindrical Underplatform Dampers

Abstract The dynamics of turbine blades with underplatform dampers (UPDs) is often experimentally explored by using small test rigs like two-blade models for cost and complexity reasons. In this paper, the dynamics of a large-scale academic turbine disk is measured on a special rotation test rig. Such measurements have rarely been published so far. The test rig supports speeds up to 3600 rpm and turbine disks up to a diameter of 1.2 m. The turbine disk is tested linearly as well as with asymmetric and cylindrical UPDs. The excitation forces and the excitation order are varied. The results prove the damper effectiveness by lowering resonance amplitudes. Additionally, the mistuning influence on the result depiction is discussed. The measurements are compared to simulations of the nonlinear frequency response functions (FRFs), showing good agreement.

Experimental and optical performances of a solar CPV device using a linear Fresnel reflector concentrator

A solar CPV device using a linear Fresnel reflector (LFR) concentrator is described. The design principle of the concentrator is provided. The solar concentrating processes are simulated by using the MCRT approach. A small scale test rig of the concentrator is constructed to investigate the actual optical and I–V performances of the CPV device. Both of the simulation and experimental results reveal that the proposed concentrator has a relatively high solar concentrating uniformity. The configuration and optical analyses of the concentrator are launched. The results show that the geometric concentrating ratio and ground utilization ratio both increase with the solar panel installing height increased. When the solar cell height is settled, the maximum value of ground utilization ratio exists with the mirror field width increased. The sun-tracking accuracy effect analysis is also carried out. The results indicate that the normalized optical efficiency of the CPV system using the LFR concentrator can be 0.62 or higher when the tracking error is less than 1°. A solar cell monomer and a cell module are used to carry out the I–V experiments. The test results of their energy conversion efficiencies are 14.7% and 13.6%, respectively.

Development of a Control System for a Small Size Seeding-performance Test Rig

Testing a seed drill indoors can save a great amount of time and labour force. Conventional seeding-performance test rigs usually need at least two people to operate it. Thus, a small size test rig with an automatic control system need to be developed. In this research, a control system was designed firstly. After that, rotation speed of seed-metering shaft were simulated by Simulink and the parameters of the control algorithm were obtained. Moreover, an experiment were conducted to calibrate the seed mass discharged in per cycle rotated by seed-metering shaft. According to the experimental results, the average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical seed mass subtracted the actual one and then divided the theoretical seed mass was seen as the error percentage of seed mass. Furthermore, 100% subtracted the error percentage was viewed as the accuracy of seed mass. The results showed that all accuracies of seed mass were higher than 82%, and the average accuracy of total experiments was 89.12%. Furthermore, t-test results showed that there was not significant difference between the actual seed masses and the theoretical ones. According to the statistical results, we can conclude that the control system can be applied on seeding-performance test rigs with an desirable performance.

Some considerations in using the small punch testing for thermally sprayed CoNiCrAlY coatings

Small punch testing exhibits great potential in mechanical characterisation of thin coatings. This testing method can be used to determine the mechanical performance of thermally sprayed coatings, especially to qualitatively characterise the effects of coating defects on the mechanical behaviour. In this work, some considerations in using the small punch testing for coatings are presented through a microstructure evolution analysis of a vacuum plasma sprayed CoNiCrAlY coating under small punch test. The CoNiCrAlY coating was characterised with a large number of un-melted particles as the coating defects. It is shown that the clamping in the small punch test rig can result in micro-cracking around the un-melted particles in the coating prior to testing. It is also found that the un-melted particles in the coating act as predominant cracking sites and fast failure occurred around the un-melted particles. Careful considerations need to be taken into account when using the small punch test for coatings to avoid any changes in the coating microstructure and plasticity during the clamping stage.

Investigating the reliability of wind anemometers on floating tension-leg platforms

This article investigates the reliability of two different first-class cup anemometers and a two-dimensional ultrasonic anemometer when subjected to surge motion as normally experienced on tension-leg platforms. The experimental study was carried out using two small land-based test rigs. One of the test rigs consisted of a short mast installed on an oscillating base designed to reproduce the surge motion of a tension-leg platform. The second rig involved an identical mast installed on a fixed base and used as a reference mast. Results indicated that the two different cup anemometer models overestimated the one-minute mean wind speed when compared to the ultrasonic sensor. The overestimation increased when the sensors were subjected to surge motions, especially those having high surge frequencies. It was highest at low wind speeds and became significantly less at higher ones.

Amine based CO2 capture – CFD simulation of absorber performance

The paper deals with the numerical modeling of CO2 removal from flue gases by amine solvent in an absorber column, i.e. the first stage of a post-combustion capture installation. The complex flow system including multi-phase gas-liquid countercurrent streams with chemical reaction and heat transfer is considered to resolve the CO2 absorption. A Computational Fluid Dynamics (CFD) model simulates a small laboratory test rig which has provided the reference data for model validation. A 30% aqueous monoethanolamine (MEA) solution was employed as a chemical solvent. A 2-fluid Eulerian model has been employed to resolve the flow in a random packed bed. The calculations were carried out for varying lean loading (0.375–0.425mol CO2/mol MEA), solvent to flue gases ratio (4.46–6.92kg/kg) and CO2 content (8–16%), with the results showing reasonable absorber behavior and satisfactory consistency with experimental data. It was found that the removal efficiency is weakly dependent on CO2 content in exhaust gases as long as the amine solution loading is kept at a sufficiently high level.

수직 원형관내 자연대류 열전달에서 기하구조의 영향

Natural convection heat transfer rates in vertical pipes were measured varying the diameter, length, and roughness of vertical cylinder. To achieve high Rayleigh number with relatively small test rig, mass transfer experiments instead of heat transfer were performed based on the analogy. Prandtl number was 2,014. The length of vertical cylinder was 0.1m, 0.3m, and 0.5m, which correspond to GrL , , and . To each length of vertical cylinder, the heat transfer rates were measured varying the iameter 0.005m, 0.01m, and 0.03m. The heat transfer rate for a short length pipe(0.1m) agreed with the prediction from Le Fevre correlation developed for a vertical plate for all diameter. The heat transfer rate decreases as the diameter and the length of the pipe increases. The heat transfer rate inside of vertical cylinder is affected by roughness only for a laminar flow regime.

Experimental verification of externally pressurized gas journal bearings with asymmetric gas supply (Supply gas pressure control operation using a small size test rig)

Experimental verification of externally pressurized gas journal bearings with asymmetric gas supply (Supply gas pressure control operation using a small size test rig)

Experimental Tests of Wind Turbine Main Shaft Motion on a Laboratory Test Rig


 
 
 This paper introduces research and discusses findings dealing with failure modes of gearboxes in wind turbines. These gearboxes fail in general after five years which is far below the expected design life of twenty years of a wind turbine. The research is taking a more holistic approach towards finding typical behaviour of the main shaft taking the transient nature of the wind into consideration. In this research, a small scale wind turbine test rig has been designed and manufactured with displacement sensors installed to observe the displacement of the main shaft at specific points, namely the main bearing locations of the forward framework of a wind turbine nacelle, where the main shaft is installed. The experimental data measured from the test rig is being analysed with common beam bending, statistical and fatigue theories to draw conclusions for long term loading in service. Aspects of the turbulent nature of the wind driving the wind turbine have been taken into consideration as being part of the aerodynamic loading onto the rotor and eventually the gearbox, transmitted through the main shaft. The purpose of the test rig at this stage is to obtain a quantitative insight into the motion of the main shaft. The deliberately chosen softer aluminum material and the more slender geometry for the components should provide exaggerated displacements which help to make motion and deformations more obvious. At this point, no resemblance to real size wind turbines has been established.