Full Load Test Research Articles

Studies on semi-cylindrical solar tunnel dryer for drying wastewater sludge

Drying plays an important process for wastewater sludge management, as it can minimise the volume of wastewater sludge before disposal, and consequently the cost of storage, handling and transport. In this study, the wastewater sludge was dried by using a solar tunnel greenhouse drying system. The performance of the dryer for drying wastewater sludge has been analyzed through no load and full load test. The three full load drying tests recorded that the temperature inside the tunnel dryer fluctuated around 55±5°C; while the no load drying test, the temperature of the drying tunnel maintained within 60±5°C; as compared to the ambient temperature of 30±5°C. The average moisture content of solar dried sludge decreased from 88.69 - 90.84% to 7.78 – 13.30% in the mixing conditions and 14.78 – 19.52% in the non-mixing conditions, in 5 days. The study suggests that the semi-cylindrical solar tunnel dryer of wastewater sludge has given satisfactory results within five days.

Estimation of short-term settlements of MSW landfill materials using shear wave velocity

Limited availability of simple yet adequately validated tools for estimating the deformation potential of municipal solid waste (MSW) material poses difficulty in planning and managing landfill operations. Estimation of settlement of MSW landfills has remained a challenge because of heterogeneity and time-varying mechanical behavior of MSW materials and difficulty of extracting representative samples and reconstituting them for laboratory testing. An empirical correlation is proposed here for estimating the short-term settlement of landfill materials. The relationship was developed by calibrating laboratory data from axial (1D) compression and consolidated drained triaxial tests against field-measured shear wave velocities from five landfill sites with varied waste compositions. The correlation was validated against three full scale load tests; one obtained in this research and two reported by others, and a field compaction study from a fourth landfill. Although the proposed correlation was more accurate than an alternative developed earlier, overall it underestimated settlements by about 12%. The proposed relationship could therefore provide a conservative guidance in MSW landfill design and operation.

Research on Energy Metering System Based on Biomass Gasification Coupled Power Generation in a 600MW Power Plant

The biomass gasification coupled power generation project of a power plant is the first biomass gasification and coal-fired coupled power generation project using agricultural and forestry biomass residues as the main fuel in China, and has completed 72+24 hours of full load test run in September 2018. With the formulation of relevant standards, in order to further improve the overall operational capacity of the project, and give full play to the demonstration significance of the national coal-fired coupling power generation technology transformation pilot project, scientific and technological research has been carried out in such aspects as electricity metering. By upgrading the electricity metering system, on the one hand, it can meet the latest technical requirements of the electric power industry standard “Coal fired coupled biomass power generation biomass energy calculation Part 1: Agricultural and forestry waste gasification coupling”, on the other hand, it can solve the problems encountered in existing equipment such as short operation time, large maintenance volume, and low accuracy of gas composition detection, improving equipment stability, while reducing heat value loss, and reducing production costs, Improve production efficiency.At the same time, after the heat value analyzer is changed, the measured heat value loss is reduced by 20%. Based on the annual utilization hours of the gasifier, about 6400 tons of biomass fuel loss can be recovered in one year, and the annual fuel cost recovered is about 2.56 million yuan.

Assessment of experimental 1D and analytical 3D steady approaches of packed bed thermal conversion through the simulation of a 60-kW biomass boiler operating at half and full load

Among the different modelling strategies applied for the simulation of packed bed biomass combustion during the last two decades, the present paper detailed describes two models based on two of the most commonly used approaches and tests their performance through the simulation of a 60-kW wood pellet boiler. This contributes to analyze the behavior of both approaches working in different operating conditions and to determine what conditions are favorable for the models application. The first presented model is a 1D experimental method that introduces the products of the biomass thermal conversion through several sections of the bed top surface. The calculations are based on mass and energy balances and experimental determination of the reactive fluxes. The second model is an analytical 3D method that calculates the packed bed thermal conversion inside the CFD domain. This applies more complex calculations with a higher computational cost. For both models, the char oxidation reaction is calculated though four correlations that returns different CO/CO2 ratios. The bed conversion models and the char oxidation correlations are applied to two different tests with the boiler operating at half and full load with different fuels. The results show that both bed models have a similar overall behaviour. The 3D model has a reasonably good behaviour in all cases and is not significantly affected by the different char correlations. Both models give similar results when combustion conditions are favourable (full-load test). The 1D model is highly sensitive to the char oxidation correlations, especially in the half load test. In this case, it has a better behaviour with the correlations that produce lower CO/CO2 ratios. The analysis of the contours in the freeboard shows that, in the 3D bed model, an important part of the combustion process occurs in the bed volume, which is not meshed in the 1D model, and that advance in the combustion compensates the differences in the CO emitted by the bed.

Emulating Full-Load Testing of Air-Cooled Nanocrystalline IHT at Zero Power

High-power high-frequency air-cooled induction heating transformers, mostly used as current multiplier and isolation purposes, are custom designed. For their reliable performance and long life, the thermal evaluation at rated load is necessary. Creating an equivalent load as a test facility for reliability testing of such type of transformer is difficult. Characteristics of such loads drastically change after Curie temperature. Moreover, prolonged heating could increase the nearby ambient temperature and, more importantly, the traditional heat run test wastes large amount of energy. Whenever the coil is energized, windings of transformer draw respective rated current; even at no-load condition, the copper loss is at rated value. While both windings drawing rated current at a desired frequency, using the concept of localized eddy current loss as well as excess eddy current loss, this article proposes a novel method to inject requisite core loss to the magnetic circuit to emulate the characteristics of full-load condition but the power drawn from the transformer would be zero. The proposed idea would be validated where only a 200-W resonant inverter would be used to inject power loss equivalent to full-load condition of 30-kW transformer to emulate the heat run test.

Twin Inverter-Fed Induction Machines Artificial Loading Without Mechanical Coupling

This article presents an artificial loading method for induction machines using industrial static frequency converters (VFCs), low cost programmable logic controllers (PLCs) for command and control and standardized communication protocols. Different approaches of artificial loading method are presented in this paper. Induction machine full load testing is difficult, especially at high power and almost impossible for vertical axis machines. Mechanized IM start/stop procedure and closed-loop loading method, here presented, reduce overall testing time. The overall manpower cost is reduced thanks to the lack of IMs mechanical coupling. Moreover, thermal test at rated IM current and power losses equivalation are presented in this paper. Bidirectional VFC utilization for a single motor can't always be a solution for artificial loading because of high variations of grid power (voltage). Two identical IMs without mechanical coupling driven by two identical dc bus interconnected VFCs artificial loading method is presented in this paper. The power circulation between the machines is performed via the common dc link. This opens the possibility to test machines with rated power larger than the lab power source rating. The rated current artificial loading conditions are achieved without mechanical coupling, without VFC oversizing and using standard equipment.

Analytical model for laterally loaded pile groups in layered sloping soil

The historic canal wall structures in many Northern European cities have been built as masonry walls on a timber deck founded on timber piles. For analysis of the resistance of those structures and assessment of their remaining service life, suitable and accurate calculation models are needed. Thereto an analytical method was developed for modelling laterally loaded pile groups in layered sloping soil. In the proposed method, the bending of a pile, which is subjected to a lateral load and axial load, is described by a beam on a Winkler elastic foundation in which the soil behaviour is represented by a series of independent p-y springs, idealized with a bilinear elastic-perfect-plastic approximation. The plastic limit was computed with Brinch Hansen ultimate soil resistance and the elastic soil response by the Ménard stiffness. The plastic limit was corrected for each depth, based on the reduction of the passive soil wedge due to pile group effects and the presence of a sloping surface. The analytical model was calibrated and validated with three field experiments, one full-scale lateral load test of a 3 × 5 pile group in soft clays and silts (Snyder, 2004), one full scale lateral load test of a single pile located on a slope in layered soils (Mirzoyan, 2007) and one small scale lateral load test of a single pile located near a slope in sand (Abdelhalim et al., 2020). The proposed method can adequately predict bending moment distributions and pile deflections and in addition, a good consistency between the analytical model and experimental tests was observed. The method is very fast, making it suitable for probabilistic, Monte Carlo type, simulations and reliability updating to determine the probability of failure of quay walls or other structures with horizontally loaded piles.

Full and partial compression fatigue tests on welded specimens of steel St 52-3. Effects of the stress ratio on the probabilistic fatigue life estimation

The fatigue strength of structures subjected to cyclic loading depends strongly on the stress ratio. Particularly, in case of welded steel structures this fact is not considered in the corresponding standards nor in the guidelines. Experimentally, two approaches are used to study the effect of stress ratio on the fatigue life. On the one hand, based on the S-Ncurves obtained from tests performed at different stress ratios, the fatigue life under a particular stress range is estimated. On the other hand, the stress amplitude corresponding to a constant fatigue life is estimated by applying the failure criteria for fluctuating stress like the Goodman–Haigh relationship. This paper presents a general probabilistic model, which estimates the S-Nand Goodman–Haigh curves for any stress ratio. Afterwards, this model is applied on data obtained from full and partial cyclic compression loading tests performed on welded specimens made of steel St 52-3. The tested details correspond to the permissible notch condition limit occurred in highly stressed structures used to build ships.

3-D frame behaviour and load rating of truss bridges in railway infrastructure

Railway truss bridge load rating is studied herein using full scale diagnostic load test and 3-D finite element analysis. which has not been typically practiced. Forty-eight bridges of Canadian National Railway are included, with eight load tested. One of the focuses is the effect of a collision strut member (CS) to the behaviour of main truss members, especially the end post L0U1. For simplicity, CS was ignored in design and past load rating using 2-D truss analysis. Its effect is identified herein for increased live load stress by inducing bending, leading to unconservative rating. In addition, these spans are found to behave more closely to frames. Out-of-plane bending of main truss members is also studied as part of 3-D behaviour. A multiplicative adjusting factor (AF) is accordingly developed and recommended as the realistic solution to enhance load rating by addressing bending previously ignored in truss models, for a large number of bridges in the infrastructure network. The findings of this study have been implemented in practice and can be useful for design and evaluation of truss bridges in North America and other continents for stress calculation in both strength and fatigue limit states, while localised stress analysis with fine mesh for connections was out of this study’s scope.

Impact of default rate of antiretroviral use on viral load among HIV/AIDS patients in Tamale and Sunyani

Background: Highly Active Antiretroviral Therapy (HAART) for persons living with HIV/AIDS (PLWHA) is the gold standard for the management of HIV patients. Purportedly, patients who are not on HAART or defaulted from its use have adverse effects compared to those who adhere to the intake of HAART. Compliant individuals have improved quality of life and show healthy hematological parameters and HIV load as compared to HAART naïve individuals and defaulters. Supplementary and supportive treatment is crucial in HIV/AIDS patients on patients on antiretroviral therapy? Objective: This study was conducted to assess the consistency and default of HAART intake and other supportive treatments and its relationship with viral load on hematological parameters in two different geographical sites. Methods: Ethical clearance was obtained from Navrongo Health Research Centre. Questionnaires were administered to participants for their consent, demographic data, consistency of taking antiretrovirals, and types of antiretrovirals used. Full blood count and HIV load tests were carried out using Urit 5250 and Cobas Taqman / Cobas ampliprep fully automated analysers respectively. Results: Defaulters had a significant (p value=0.003) rise in their viral load (845334.38±409285.62) copies/mL in comparison to adherents in HAART intake 49571.69±30548.89) copies/mL. The hemoglobin level (10.51±0.60 g/dL) of defaulters was significantly (p-value = 0.007) lower than that of adherent (12.04±0.17 g/dL). The default rates in the two study sites were close (9.8% in Sunyani and 9.4% in Tamale). Conclusion: Antiretroviral default does not only lead to an increase in HIV load but also causes a reduction in hemoglobin levels. Hematinics supplementation therapy may help normalize hematological parameters in HIV infection

Design and Validation of an Unconventional 39-Slot PM Synchronous Motor With Asymmetric and Unbalanced AC Windings

One of the main issues in manufacturing rotors for integer slot surface-mounted permanent magnet (PM) synchronous motors is the rotor skew. Motor manufacturers typically prefer to avoid skewing due to the added complexity and the difficulty in controlling the accuracy of the skewing and achieving the required outcome. This article proposes a design that minimizes torque ripple without using any kind of skewing in the rotor using asymmetric ac windings with unconventional stator slot-pole combinations. First, feasible slot and pole combinations are reviewed for PM synchronous motors. Theory behind unconventional asymmetric and unbalanced ac winding PM motors is presented. A lumped-parameter magnetic equivalent circuit for such unconventional stator is provided for a 1.7-kW PM motor. Detailed 2-D finite element analysis (FEA) is performed and compared with the lumped parameter model. A prototype motor is manufactured, and open-circuit as well as full-load tests are performed. Good agreement between the analytical, FEA, and test results is obtained.

Applied methodology for temperature numerical evaluation on high current leads in power transformers

The majority of power transformer manufactures use their own proprietary design to build oil-immersed power transformers with high current busbar leads (HCBL) because there is no standardization or registered standard in the technical literature. Anyway, specialists certainly require a highly accurate temperature estimation regardless of the proprietary designs used to build these power transformers. It is well known that the temperature at the copper HCBL surface is mainly influenced by the Joule effect induced by the passing current, paper wrapping insulation characteristics, and temperature of the surrounding oil. In this context, we suggest a novel non-invasive technique for estimating the temperature of HCBL power transformers. Such methodology is simple and can be used to estimate the temperature for any power transformer despite designs strategies, becoming an algorithm that can be used in several commercial programs. The temperature is taken as a function of variables and measurements easily acquired from the transformer and, therefore, turns out to be an original and simple method. The methodology is based on the evaluation of the convection heat transfer coefficient h, which depends on the geometry factors and cooling fluid characteristics of the transformer. Since temperature levels are critically sensitive to h variations, Computer Fluid Dynamics (CFD)-based commercial software are a common-place tool for thermal analysis of power transformers as coefficient h must be calculated with very high precision and correctly evaluated. However, this solution have both high financial and computational burden. The skin and proximity effects are taken into account in the proposed methodology by using the Finite Element Method – FEM. Thus, we propose an efficient and simplified solution for temperature estimation. We will show that the solution is as accurate as the CFD programs, albeit, more economically and computationally viable. We validate the results by means of measurements made with Fiber Optic Temperature Sensors during a full-load test and show the estimation numerical accuracy for parameter h.

Research on anode power supply of low-power Hall thruster

Based on the small power, small size, and high-efficiency micro-thrust requirements of micro-satellites, this paper mainly studies the anode power supply topology suitable for micro-satellites. The flyback converter and the secondary volta ge doubler structure are used to achieve high gain. At the same time, in order to improve the efficiency, the resonant soft switching technology is used to achieve valley opening through the resonance of the transformer leakage inductance and the capacitor to realize the soft switching of the switch tube and the diode. This article developed a 250W experimental prototype, and conducted a series of no-load and full-load tests under closed-loop steady-state operation, which can realize the zero-voltage turn-on of the switch tube and the zero-current turn-off of the diode. The efficiency is up to 93.7% under full load conditions, while the output ripple is small and there is no oscillation, and the device stress is small, which proves to be suitable for use in the anode power supply of micro satellites.

Designing a test rig for ultimate load test of small horizontal axis wind turbine rotor blades

This paper presents a design of a test rig for structural static load testing of small horizontal wind turbine blades. It is a next step after the success of the DeVie project, a join-research project to boost the wind energy knowhow between Germany and Vietnam. According to the IEC-61400-23 standard for full scale ultimate load test of rotor blades, and based on existing facilities of HCMUT, especially the aerospace engineering lab. and the engineering mechanics lab., we propose a prototype of a test-rig for ultimate load test of rotor blades. And a rotor blade of 4 meters in length, manufactured by China, is used in case study of our structural static-load test-rig. The obtained results will be compared with the reverse engineering this rotor blade with QBlade/FAST in the same blade loading.

Intelligent optimization for bending moment in uniaxial fatigue loading test of wind turbine blades

Wind turbine mainly relies on blades to capture wind energy and complete energy conversion. Wind turbine blade is one of the key components of wind turbine. In the full scale load test of wind turbine blade, the moment matching is the key part of the test and the premise of wind turbine blade certification. In order to solve the matching problem of the bending moment and the arrangement of counterweight in the fatigue loading test, an improved intelligent optimization algorithm was proposed to achieve the purpose of moment matching. The relationship between the excitation frequency of the rotating mass and the natural frequency of the blade was determined through the identification of the modal test parameters, and the calculation model of the section bending moment was constructed. Based on the optimization algorithm, the joint optimization of moment distribution and amplitude control was carried out with the mean square error as the fitness function. The correctness and feasibility of the balance weight optimization scheme for moment matching in uniaxial fatigue test were verified through the blade test.

Edge-clamped two-way slabs containing low-ductility steel

This paper describes a series of full range load tests on two-way, edge-clamped reinforced concrete slab panels containing either Class L WWF or Class N deformed bars. Five rectangular slab panels were tested each with two adjacent fully restrained edges and two free edges. A point support was included under the corner of each panel at the intersection of the two free edges. Each slab specimen was loaded by four transverse loads applied symmetrically in the mid-panel region by a deformation-controlled actuator in a stiff testing frame. The continuous edge supports were provided by clamping two adjacent edges in a carefully designed and constructed testing frame. The slabs were instrumented with load cells to measure applied forces and reactions, strain gauges to measure strain in the steel reinforcement and on the concrete surfaces, linear variable displacement transducers and lasers to measure deflections at all stages of loading. The results of the tests are presented and evaluated, with particular emphasis on the strength, ductility and failure mode of the slabs.

Troubleshooting of a 330MW turbo generator unit during commissioning

During the commissioning stage of a 330MW turbo generator unit, several serious defects occurred, such as low vacuum of condenser, abnormal vibration of shafting and bearing damage. Through fault analysis and vibration test, the hidden danger in design, manufacture and installation were found out and solved, the unit successfully completed 168 hours full load test run and put into operation.

Helical Pile Capacity-to-Torque Correlation: A More Reliable Capacity-to-Torque Factor Based on Full Scale Load Tests

The capacity-to-torque ratio, Kt, has been used in the design of helical piles and anchors for over half a century. Numerous research efforts have been conducted to accurately predict this capaci-ty-to-torque ratio. However, almost of all these Kt factors are based on shaft geometry alone. The ca-pacity-to-torque ratio described herein was found to depend on the shaft diameter, shaft geometry, helix configuration, axial load direction, and installation torque. In this study, 799 full scale static load tests in compression and tension were conducted on helical piles of varying shaft diameters, shaft geometry, and helix configurations in different soil types (sand, clay, and weathered bedrock). The collected data were used to study the effect of these variables on the capacity-to-torque ratio and resulted in developing a more reliable capacity-to-torque ratio, Km, that considers the effect of the variables mentioned above. The study shows that the published Kt values in AC358 (ICC-ES Acceptance Criteria for Helical Piles Systems and Devices) underestimate the pile capacity at low torque and overestimate it at high torque. In addition, and based on probability analysis, the predicted capacity using the modified Km results in a higher degree of accuracy than the one based on the published Kt values in AC358.

Strength evaluation of deteriorated girder ends. I: Experimental study on naturally corroded I-beams

Corrosion is a common cause for steel bridge deterioration, primarily attributed to malfunctioning deck expansion joints. Aged joints fail to prevent water or deicing mixtures from penetrating into the bearing area triggering a corrosive process which locally damages the steel beams. Topologically non-uniform and highly uncertain, the appearance of corrosion makes the residual bearing capacity quite challenging to be accurately assessed by inspectors and engineers. The present study, the first part of a companion set of two papers, aims to evaluate and improve the efficiency of current strength assessment policies for un-stiffened rolled I-beams, based on field corroded girders tested in the laboratory. A total of six full scale loading tests are reported on naturally corroded girders, which were extracted from structurally deficient bridges in the state of Massachusetts. The test results indicate that provisions underestimate the capacities of five out of the six specimens, while the sixth test highlights the harmful effect of a web's deviation from plumbness. An alternative load path is also revealed for specimens with holes extending along the bottom at the girder web.

EXPERIMENTAL EVALUATION OF PERFORMANCE AND MECHANICAL RELIABILITY FOR HIGH PRESSURE CO2 INTEGRALLY GEARED COMPRESSOR

Energy saving has become a trend as well as a countermeasure for global environmental issues. It can be one of the efficient solutions for reducing energy consumptions by adopting integrally geared compressors instead of inline compressors for industrial plants. The development of key technologies for the design centrifugal compressor such as CFD, FEM, Rotor dynamic Analysis has enabled integrally geared centrifugal compressors for higher pressure applications than ever. A commercial size, 5 stages integrally geared CO2 centrifugal compressor of 20MPaG discharge pressure level was designed, manufactured and evaluated the fluid dynamic performances and rotor stability. It was installed in OEM’s factory and the full load and full pressure test was carried out using real CO2 gas. The actual compressor fluid dynamic performance has shown superior results even at high pressure supercritical gas conditions at the high pressure stages of the compressor. The mechanical performances such as rotor vibration and bearing temperature were also measured and observed that the vibration was substantially low and within safe limits even at high pressure operating conditions above 20MPaG. Also the authors established a novel on Direct Rotor Excitation Method to experimentally investigate the rotor stability even at a high operating pressure level of 20MPaG. With this technique the measurements of the actual rotor natural frequencies and the damping ratios (log decrement) during high pressure operating conditions provided more precise results rather than conventional casing excitation method. The open impeller blade vibration was measured during running condition by using a non-contact blade vibration measurement technique. This measurement results revealed that impeller blades stress against the centrifugal force and the external excitation force was very low compared to the allowable stress value of the impeller material. The fluid dynamic characteristics and mechanical reliability are assessed as acceptable including super critical gas condition of CO2 gas.