Prototype Test Data Research Articles

Research of the calculation formula for working clearance leakage flow of the hydrogen circulation pump

The hydrogen circulation pump (HCP), a device for recovering unconsumed hydrogen gas in fuel cell systems to improve efficiency, is an important equipment in fuel cell systems. Efficient calculation of the output flow rate of the HCP is crucial for accelerating the product development process, but there is a lack of an effective calculation formula for the working clearance leakage. In this paper, a series of HCP models with different working clearances are established and calculated using an overlapping grid simulation method, verifying that the traditional Roots blower leakage flow formula is feasible for HCP, although the maximum calculation error reaches 10.71%. Further study the pressure distribution law inside the HCP chamber, and revise the traditional calculation formula accordingly, so that the average calculation error of the series models is reduced from 5.75% to 3.82%, and the maximum error is also reduced to 7.73%. Compared with the prototype test data, though the flow values obtained from the two calculation formulas are slightly higher, the calculation error of the correction formula is relatively smaller. The research results indicate that the correction formula can more accurately predict the flow rate of HCP and has important application value.

Prediction of Thermionic Energy Conversion Performance and Parametric Effects Using Genetic Algorithms to Fit Physics-Inspired Model Equations to Prototype Test Data

Abstract Thermionic converters have potential as an energy conversion technology for high-temperature space and terrestrial applications using concentrated solar, nuclear reaction, and combustion processes as the heat source. Recent studies have generated experimental performance data for narrow-gap thermionic energy conversion devices. This investigation explores the use of genetic algorithms to fit existing data with physics-inspired model equations. The resulting model equations can be used for performance prediction for system design optimization or to explore parametric effects on performance. The model equations incorporate Richardson’s law for current density, including both the saturated and Boltzmann regimes, with appropriate relations for power delivered to the external load. The transition regime is characterized using two separate models, each accounting for nonuniformity in emission surfaces and irregularities in the manufacturing process. The trained models enable performance prediction of small-gap thermionic energy conversion devices. In this study, data were fitted for two different prototype designs. The prototype test data and postulated values for the work functions and a transition regime parameter are substituted into physics-inspired model equations, yielding performance models with three adjustable constants. Optimized values of these constants are determined using a genetic algorithm to best fit the experimentally determined performance data for prototype thermionic conversion devices tested in earlier studies. This approach is demonstrated to fit the performance data to within 9%. This methodology also allows the user to back-infer the effective work function values, which were found in this study to be consistent with independent measurement.

Study on the effectiveness of impact factor in underwater explosion model test

The dimensionless quantity is the invariant under the unit conversion, and the only choice to characterize the laws of physics. Aiming at the similarity law of underwater explosion model test, the deficiency of traditional impact factor and the similarity condition of single value of model test are analyzed by using dimensional analysis method and combining with domestic and foreign research. In view of the shortcomings of traditional impact factors, a new impact factor is derived from the perspective of single-value similarity based on the impact dynamic response characteristics of underwater explosion structures. Taking the midship cabin structure of a certain frigate as the prototype, the scale model tests are designed based on the traditional and new impact factors respectively. The effectiveness of the impact factors is evaluated from the aspects of structural damage characteristics, dimensionless deformation deflection, dimensionless velocity and dimensionless acceleration at the center of the structure. To account for the impact of structural characteristics, scale ratio, and proportional distance on the impact factor's effectiveness, various grillage, cabin, and hull girder model tests are conducted using ships of different tonnages as prototypes. The results of the model test, guided by the new impact factor, align well with the prototype test data. In contrast to the traditional impact factor, the model test exhibits greater precision for predicting structural responses, with a broad spectrum of potential applications.

Presentation and Verification of an Optimal Operating Scheme Aiming at Reducing the Ground Vibration Induced by High Dam Flood Discharge

Ground and environmental vibrations induced by high dam flood discharge from the Xiangjiaba hydropower station (XHS) has significant adverse effects on nearby building safety and the physical and mental health of surrounding residents. As an effective approach to simulate the flow-induced vibration of hydraulic structures, the hydro-elastic experiment approach has been extensively applied and researched by Chinese scholars, but the relevant systematic research is rarely reported in international journals. Firstly, the hydraulic and structural dynamic similarity conditions that should be satisfied by the hydro-elastic model are briefly reviewed and derived. A hydro-elastic model of the XHS was further constructed using self-developed high-density rubber, and the vibration isolation system (including open trenches and flexible connects) was applied to avoid the external disturbances of pump operation, vehicle vibration and other experiments in the laboratory. Based on the data of model and prototype dynamic tests, a back propagation (BP) neural network was established to map the acceleration of the physical model to the ground in the prototype. In order to reduce the ground vibration, experiments were carried out to meticulously evaluate the ground vibration intensity under more than 600 working conditions, and the optimal operation scheme under different discharge volumes is presented here in detail. According to the prototype test data in 2013, 2014, and 2015, ground vibrations were significantly reduced by applying the presented optimal operation principle which indicates that the presented hydro-elastic approach and the vibration attenuation operation scheme were effective and feasible.

Design and Prototype Test Data for a 300 kW Active Magnetic Bearings-Supported Turbine Generator for Natural Gas Pressure Letdown

Abstract A 300 kW integrated and fully sealed turboexpander-generator for natural gas pressure letdown (PLD) was developed by Baker Hughes, a GE company (BHGE), in conjunction with Calnetix Technologies. This paper describes the design and analysis of the generator, magnetic bearings, and touchdown bearings, with a focus on the dynamic performance and key characteristics of the machine. The permanent magnet (PM) synchronous generator is supported by PM-biased, homopolar magnetic bearings and has a maximum continuous operating speed (MCOS) of 31.5 krpm. A touchdown bearing system is implemented using rolling element bearings with soft mount supports. Also described is a thrust load balancing scheme that uses the thrust bearing coil current for reference. A time transient simulation showing the effect of process conditions on the AMB dynamics is shown. Preliminary data from the prototype mechanical run test are shown, including transfer functions measured using the magnetic bearings, Campbell diagram, and touchdown bearing drop test results.

Numerical Modeling and Experimental Characterization of Elastomeric Pads Bonded in a Conical Spring under Multiaxial Loads and Pre-Compression

Elastomeric components are widely used in the engineering field since their mechanical properties can vary according to a specific condition, enabling their applications under large deformations and multiaxial loading. In this context, the present study seeks to investigate the main challenges involved in the finite element hyperelasticity simulation of rubber-like material components under different cases of multiaxial loading and precompression. The complex geometry of a conical rubber spring was chosen to deal with several deformation modes; this component is in the suspension system placed between the frame and the axle for railway vehicles. The framework of this study provides the correlation between axial and radial stiffness under precompression obtained by experimental tests in prototypes and virtual modeling obtained through a curve fitting procedure. Since the material approaches incompressibility, different shape functions were adopted to describe the fields of pressure and displacements according to the finite element hybrid formulation. The material parameters were accurately adjusted through an optimization algorithm implemented in Python program language which calibrates the finite element model according to the prototype test data. However, as an initial guess, the proper constitutive model and its parameters were first defined based only on the uniaxial tensile test data, since this test is easy to perform and well understood. The validation of the simulation results in comparison with the experimental data demonstrated that care should be given when the same component is subjected to different multiaxial loading cases.

Open-source support toward validating and falsifying discrete mechanics models using synthetic granular materials—Part I: Experimental tests with particles manufactured by a 3D printer

This article presents a new test prototype that leverages the 3D printing technique to create artificial particle assembles to provide auxiliary evidences that supports the validation procedure. The prototype test first extracts particle shape features from micro-CT images of a real sand grain and replicates the geometrical features of sand grain using a 3D printer. The quantitative measurements of the particle shape descriptors reveal that the synthetic particles inherit some attributes such as aspect ratio and sparseness of the real materials while exhibiting marked differences for sphericity and convexity. While it is not sufficient to consider the printed particle assembles a replica of the real sand, the repeatable manufacture process provides convention tools to generate additional data that supports the validation procedure for particulate simulations. Oedometric compression tests are conducted on a specimen composed of the printed particles of identical size and shape to create benchmark cases for calibrating and validating discrete element models. Results from digital image correlation on the synthetic sand assemblies reveal that the fracture and fragmentation of the synthetic particles are minor, which in return makes particle position tracking possible. As our prototype test and research data are designed to be open source, the dataset and the prototype work will open doors for modelers to design further controlled experiments using synthetic granular materials such that the individual influence of each morphological feature of granular assemblies (e.g., shape and size distribution, void ratio, fabric orientation) can be individually tested without being simultaneously affected by other variables.

Design and Implementation of Effective Electrical Power System for Surya Satellite-1

Surya Satellite-1 is a nanosatellite developed by students of Surya University. The subject of this paper is the design and implementation of effective electrical power system for Surya Satellite 1. The electrical power system role is to supply other systems of the satellite with appropriate electrical power. First, the requirements of the electrical power system are defined. The architecture of the electrical power system is then designed to build the prototype. The orbit simulation is calculated to predict the power production. When prototype test and simulation data is gained, we make an operation scenario to keep the produced power and the consumed power in balance. The design of the modules of the electrical power system is carried out with triple junction solar cells, lithium ion batteries, maximum power point trackers, charging controllers, power distributions, and protection systems. Finally, the prototypes of the electrical power system are presented.

Design of Direct Embedment Foundations for Poles Under Moment Loads in Granular Soils

Introduction: The design of direct embedment pole foundations involves calculating the ultimate moment capacity and deflections/rotations of pole foundations at groundline. Methods: A theoretical model based on rigid piles is used as a basis for developing equations for the ultimate moment capacity of direct embedment pole foundation installed in granular soils. Results and Conclusion: The steps involved in the development are presented in this paper. Prototype test data are used to compare the predictions of the model and to validate the proposed method.

Characteristics of Process of Surmounting Obstacles by Downhole Tractors in Horizontal Shafts

A downhole tractor is a quick and efficient means of transporting logging devices and its obstacle performance directly influences the quality of the tractor’s work and is a critical element in studies of the tractor over-obstacle process. The construction of a faithful tractor over-obstacle model comprises (1) studies of the over-obstacle statics of the downhole tractor, including the relationship between the driving force of the motor, tractor resistance, and the height of the obstacle, along with the derivation of the static balance equation of the tractor over-obstacle process; (2) a dynamic analysis of the downhole tractor over-obstacle process, including compilation of the system of dynamic D’Alembert initial force equations and the system of D’Alembert inertial moment equations, and a more detailed description of the downhole tractor over-obstacle process, along with a more accurate calculation of the driving force required by the downhole tractor. It was found that matches downhole tractor prototype test data matches the data calculated by the analytic method. The use of the dynamic equations can increase the over-obstacle success rate of the downhole tractor in a horizontal well and solves the technical problems involved in overcoming obstacles.

Development and validation of a free-piston engine generator numerical model

This paper focuses on the numerical modelling of a spark ignited free-piston engine generator and the model validation with test results. Detailed sub-models for both starting process and steady operation were derived. The compression and expansion processes were not regarded as ideal gas isentropic processes; both heat transfer and air leakage were taken into consideration. The simulation results show good agreement with the prototype test data for both the starting process and steady operation. During the starting process, the difference of the in-cylinder gas pressure can be controlled within 1bar for every running cycle. For the steady operation process, the difference was less than 5% and the areas enclosed on the pressure–volume diagram were similar, indicating that the power produced by the engine and the engine efficiency could be predicted by this model. Based on this model, the starting process with different starting motor forces and the combustion process with various throttle openings were simulated. The engine performance during stable operation at 100% engine load was predicted, and the efficiency of the prototype was estimated to be 31.5% at power output of 4kW.

Equivalent pipe algorithm for metal spiral casing and its application in hydraulic transient computation based on equiangular spiral model

For the metal spiral casing of water turbines, a new equivalent pipe algorithm is developed based on the idea of equiangular spiral. Prototype tests and computations are carried out to investigate the hydraulic transient characteristics. The computation results by using the new model are in a good agreement with the prototype test data with respect to the maximum speed of the turbine-generator unit, the maximum water hammer pressure in the spiral casing and the maximum vacuum in the draft tube. The proposed method is a significant improvement over the conventional algorithm with the accuracy increased and the error reduced by about 3%.

Software Quality Control Based on Genetic Algorithm

Software evaluation has a crucial role in the life cycle of software production system. Producing suitable data for testing the behavior of the software is a subject of many researches in software engineering. In this paper software quality control with criteria of covering application paths is considered and a new method based on genetic algorithm for generating optimal test data is proposed. In this algorithm, the fitness function, population production mechanism and other parameters of genetic algorithm is determined. In addition, the population production stopping criteria is based on critical edges of control flow graph. Critical edges are those that their presence in a control flow graph path represents the presence of other edges and the edges test shows the adequacy of graph test paths. The simulation results on prototype test data show the effectiveness of the proposed method.

Penetration Resistance of Offshore Skirted Foundations and Anchors in Dense Sand

Penetration of skirts is an essential design issue for offshore skirted foundations and anchors in sand. Skirts may not penetrate far enough into dense sand by the available submerged weight alone. It may therefore be necessary to apply underpressure inside the skirt compartment to produce an increased driving force and to reduce the penetration resistance. This paper recommends procedures to calculate penetration resistance and required underpressure for skirts penetrated in dense sand with and without interbedded clay layers. The recommendations are based on interpretation of skirt penetration data from prototypes, field model tests, and laboratory model tests in dense sand. The paper first presents a model to calculate the penetration resistance of skirts penetrated by weight, or other external vertical load that does not cause flow of water in the sand. Two models are considered; one based on bearing capacity equations with friction angles from laboratory tests, and the other one based on empirical correlations with CPT tip resistance. The bearing capacity model gives more consistent correlations with the empirical data than the CPT model. Thereafter, a model to account for the effect of underpressure applied inside the skirt compartment is proposed. This model is developed based on interpretation of available prototype and model test data from skirts penetrated by underpressure. The results show that underpressure facilitates skirt penetration in sand considerably by providing both an additional penetration force and a reduced penetration resistance. It is also shown that interbedded clay layers can prevent flow of water through the sand and eliminate the beneficial reduction in penetration resistance.

Development of Numerical Dynamic Simulators for a Big Size Shaking Table (Verification of Numerical Simulators with the Prototype Test Data)

In this paper, we verified a numerical dynamics simulator for a big size shaking table that we proposed. We applied the numerical simulator to the prototype facilities for the largest 3-dimensional vibration test facilities, and compared the actually measured data and the numerical simulator outputs to verify the numerical simulator. As a result, we show that our new numerical simulator can realize frequency characteristics and acceleration time response exactly.

Vibration balanced miniature loudspeaker

The vibration that is generated by the receiver (loudspeaker) in a hearing aid can be a cause of feedback oscillation. Oscillation can occur if the microphone senses the receiver vibration at sufficient amplitude and appropriate phase. Feedback oscillation from this and other causes is a major problem for those who manufacture, prescribe, and use hearing aids. The receivers normally used in hearing aids are of the balanced armature-type that has a significant moving mass. The reaction force from this moving mass is the source of the vibration. A modification of the balanced armature transducer has been developed that balances the vibration of its internal parts in a way that significantly reduces the vibration force transmitted outside of the receiver case. This transducer design concept, and some of its early prototype test data will be shown. The data indicate that it should be possible to manufacture transducers that generate less vibration than equivalent present models by 15–30 dB.

Parameter correlation of impulse shapes using two-port synthesis

The authors derive equations for determining the time constants of the double exponential impulse from the commonly used parameters for several standard test impulses. They then proceed to synthesize a resistor-capacitor (RC) prototype circuit that will produce the desired impulse. The prototype network is realized through a computer-aided design (CAD) procedure using Cauer's RC ladder two-port synthesis method. Descriptions of prototype circuits and test data comparing the theoretical and experimental impulse shapes are also included. The results are a simplified method for determining time constants of a double exponential function from given impulse parameters and a method for deriving the component values for prototype circuits.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Model Study of Power Intake Gate of Mossyrock Dam

The action which catapulted one of the penstock service gates at Mossyrock Dam high in the gate shaft from where it fell, rebounded and inflicted severe damage to itself, its embedded steel beam sill and its operating mechanism, when it was used at a small opening to fill the penstock is described. Tests on a 1:26 scale model of the gate and penstock to ascertain how each of five separate forces contributed to the catapulting action and to develop corrective measures are analyzed. The model tests showed that the gate was catapulted up the shaft, perhaps as much as 50 ft., and that major alterations to the gate shaft base, not feasible for the Mossyrock installation, would be required to ensure against the action. Conditions that caused the model gate in early stages of the test program to stop at small openings while descending at slow speeds during simulated emergency closures are examined. Measures taken to assure model-prototype similarity and comparisons of model and prototype test data are presented.