Small-scale Experimental Setup Research Articles

Digital single voltage loop control of a VSI with LC output filter

Abstract This paper deals with the output voltage control problem of a three-phase three-wire voltage source Inverter (VSI) with LC output filter. A novel discrete-time active damping technique is proposed in order to damp the filter resonance without the need of current feedback. The method is based on an inner voltage feedback with digital lead compensator on the feedback path. A modified digital resonant controller is also proposed to reject the current harmonic disturbance drawn by nonlinear loads. The resonant controllers are connected in series and the design is based on its zeros damping. Results from a small scale experimental setup are used to validate the proposed control strategy.

Emissions of toxic pollutants from co-combustion of demolition and construction wood and household waste fuel blends

Four different types of fuel blends containing demolition and construction wood and household waste were combusted in a small-scale experimental set-up to study the effect of fuel composition on the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs), chlorobenzenes (PCBzs), chlorophenols (PCPhs) and polycyclic aromatic hydrocarbons (PAHs). Two woody materials, commercial stemwood (ST) and demolition and construction wood (DC) were selected because of the differences in their persistent organic pollutants (POPs), ash and metals content. For household waste, we used a municipal solid waste (MSW) and a refuse-derived fuel (RDF) from MSW with 5–20 wt% and up to 5 wt% food waste content respectively. No clear effect on the formation of pollutants was observed with different food waste content in the fuel blends tested. Combustion of ST-based fuels was very inefficient which led to high PAH emissions (32 ± 3.8 mg/kgfuel). The use of DC clearly increased the total PCDD and PCDF emissions (71 ± 26 μg/kgfuel) and had a clear effect on the formation of toxic congeners (210 ± 87 ng WHO2005-TEQ/kgfuel). The high PCDD and PCDF emissions from DC-based fuels can be attributed to the presence of material contaminants such as small pieces of metals or plastics as well as timber treated with chromated copper arsenate preservatives and pentachlorophenol in the DC source.

Экспериментально-теоретический подход к расчету концентраций моноксида углерода и показателя токсичности при пожаре в условно герметичном помещении

Introduction. In previous works, the authors proposed a new approach to the calculation of the concentration of toxic products of combustion. The approach is based on determination the volume average density of toxic gases at any given time by using their experimental dependences on the mean volume temperature. The accuracy of this approach depends heavily on the error of determining the heat losses coefficients in small-scale experimental setup and real full scale room. In this paper, using experimental data obtained on small-scale pilot plant, it is proposed a different approach, that uses the theoretical and experimental dependences between average volume densities of toxic gases and the mean volume density of oxygen. It is not necessary to determine the heat losses coefficient and also solve differential equations of the conservation laws of toxic gases masses. Materials and methods. Coniferous wood building materials, transformer oil and PVC sheath cables are considered as combustible materials. Theoretical and experimental methods of gas dynamics and heat and mass transfer are used to determine the parameters of gases mixture during free convection. Theory and calculation. A physical and mathematical model for calculating the mean volume density of carbon monoxide and toxic index for the combined effects of CO and O 2 during the combustion of solid and liquid substances and materials in conventionally hermetic volume of arbitrary sizes is proposed. The model is based on the integral method for calculating thermal and gas dynamics of fire in the room. Formulas for calculating the mean volume density of CO and toxicity index for mutual effect of the action of CO and O 2 are obtained. Results. Experimental dependencies of mean volume density of carbon monoxide and toxicity index from mean volume density of oxygen are obtained in a small-scale pilot plant. A comparison of the theoretical values of mean volume density of CO and toxicity index derived using the proposed formulas with experimental values is made. Discussion. It is shown that the volume average density of carbon monoxide and the toxicity index for the combined effects of CO and O 2 during combustion of solid and liquid materials in conventionally hermetic volume of arbitrary sizes can be calculated by using only the average volume oxygen density and specific coefficients of separation of CO and deleting O 2 . The resulting formulas for calculating the mean density of CO and toxicity index of the mutual influence of CO and O 2 do not contain the geometric sizes of the room and combustible materials surfaces and, therefore, are fair in both small-scale and large-scale fire in the room. Conclusions. The proposed physical and mathematical model allows calculation of mean volume density of CO and toxicity index for combined effects of CO and O 2 during fire in a real full-scale room without solving the differential equation of conservation law of carbon monoxide mass and using the experimental dependence between the mean volume densities of CO and O 2 and the calculated average volume density of O 2 .

Field and Laboratory Tests and Analyses on Temperature and Relative Humidity in Underground Multi-tunnels

Dam tunnel ventilation has been widely used in underground hydropower station to save energy. In order to study the dam tunnel cooling (heating) effect, a 24 hours continuous field measurement is conducted in underground multi-tunnels; and heat transfer performance about the dam tunnel has been calculated and analyzed. Meanwhile, to figure out influencing factors to dam tunnel ventilation and heat transfer performance, based on similarity theory, a small-scale experimental set-up is made to simulate heat transfer process during air passing through the tunnel. The experimental results show that the velocity and temperature of the inlet air both have significant impacts on heat exchange. Taking the underground dam tunnel as a huge natural “air conditioner” to replace some mechanical heat/cold sources is an energy-saving method for Heating, Ventilation and Air Conditioning system in hydroelectric power plants.

A Small-Scale Experimental Extrusion Set-Up for Exploring Relationships Between Process-Induced Structures and Characteristics of Multiphase Polymer Systems

Taking immiscible polymer blends of polystyrene (PS)/poly(methyl methacrylate) (PMMA) as a case study, we present the capabilities of a small-scale experimental extrusion set-up for sightseeing the morphological evolution during processing and identify relationships between process-induced structure, blend rheology, and product (extruded sheet) properties. In-line rheo-optical data collected with an instrumented slit die coupled to the small-scale extrusion line are in agreement with the results reported elsewhere for model polymer blends studied with simpler and slower flow fields with less relevance to industrial application. Shear stress and first normal stress difference transients relate to the stretching, orientation, break up, and subsequent string arrangement of droplets probed in the die by in-line polarized optical microscopy and small-angle light scattering. The partially relaxed droplet morphology in extruded sheets has no impact on their mechanical properties which are essentially linked to those of PS and PMMA.

Experimental Investigation of Thermoelectric Power Generation Using Radiative Heat Exchange

This paper reports experimental investigation of a new concept of waste heat recovery for Thermoelectric Power Generation using Radiative heat exchange principle (TERX). To this end a small scale experimental setup was considered; it was composed of a heated plate, an absorber plate, thermoelectric modules and water cooled heat sink. The dimensions of absorber and heated plates were 0.2 m width and 0.3 m length. The air gap space between the two plates could be adjusted. Ten thermoelectric modules were connected in series parallel (5x2). Tests were made for different air gap spaces and fixed water flow rate (2L/min). A constant electric current (200W) was supplied to the heater of hot plate. Data collected included temperature at various positions and the electrical power generated. Experimental investigation confirmed that using radiative heat exchange principle could be considered for TE waste heat power generation. Increasing air gap decreased the electrical power generated as less radiative heat is absorbed by the thermoelectric modules. Under test conditions, the maximum measured electrical power is 0.3132 W at 0.5 cm of air gap, the corresponding temperature difference between the hot and cool sides of thermoelectric modules was about 35oC. Due to its simplicity of installation as no there is no need for direct contact between the thermoelectric generation set and the source of heat, the proposed concept offers a new alternative for waste heat recovery.

Optimized models for overload monitoring of power transformers in real time moisture migration model

In this paper a mathematical model, based on experimentation, to estimate the axial moisture distribution in power transformer windings was developed. The model considers the variables of moisture content in oil, top oil temperature, as well as the transformer's design parameters and ageing of the insulation system. The model was validated using a small-scale experimental setup, which represents a 75 MVA transformer. The developed model proved to be more accurate than existing models. It considers the axial moisture distribution in paper, in 4 thermal zones equidistantly distributed along the height of the winding. This paper compares the results of the proposed model with those provided by other authors.

Hybrid WSN and RFID indoor positioning and tracking system

Wireless sensor networks (WSNs), consisting of a large number of nodes to detect ambient environment, are widely deployed in a predefined area to provide more sophisticated sensing, communication, and processing capabilities, especially concerning the maintenance when hundreds or thousands of nodes are required to be deployed over wide areas at the same time. Radio frequency identification (RFID) technology, by reading the low-cost passive tags installed on objects or people, has been widely adopted in the tracing and tracking industry and can support an accurate positioning within a limited distance. Joint utilization of WSN and RFID technologies is attracting increasing attention within the Internet of Things (IoT) community, due to the potential of providing pervasive context-aware applications with advantages from both fields. WSN-RFID convergence is considered especially promising in context-aware systems with indoor positioning capabilities, where data from deployed WSN and RFID systems can be opportunistically exploited to refine and enhance the collected data with position information. In this papera, we design and evaluate a hybrid system which combines WSN and RFID technologies to provide an indoor positioning service with the capability of feeding position information into a general-purpose IoT environment. Performance of the proposed system is evaluated by means of simulations and a small-scale experimental set-up. The performed analysis demonstrates that the joint use of heterogeneous technologies can increase the robustness and the accuracy of the indoor positioning systems.

An experimental setup for autonomous operation of surface vessels in rough seas

SUMMARYA small-scale experimental setup for autonomous target tracking of a surface vessel in the presence of obstacles is presented. The experiments are performed in simulated rough seas through wave, current, and wind generation in a small indoor pool. Absolute position of the agent and the target as well as the obstacle size and position are provided through an overhead camera by detecting color light emitting diodes installed on all objects. Ordinary differential equations with stable limit-cycle solutions are used to define transitional trajectories around obstacles based on the camera data. A sliding mode control law is implemented for real-time tracking control which is capable of rejecting large disturbances from the generated waves and wind. The sliding mode control signals are sent to wireless receivers on the autonomous vessel where a proportional integral speed controller maintains the commanded speed. A special scaling method is presented to show that the environmental forces are similar to those of moderate through high sea states. Several experiments are presented where the autonomous vessel catches and follows a target boat moving in arbitrary trajectories in both the presence and absence of obstacles.

Freezing of geothermal borehole surroundings: A numerical and experimental assessment with applications

This study examines the thermal consequences of freezing the ground in the immediate vicinity of geothermal boreholes. First, a one-dimensional radial numerical heat transfer model is developed to evaluate heat transfer from the borehole wall to the ground. The model can account for multiple ground layers in the radial direction and phase change is handled using the effective capacity method. The results obtained from the model are in excellent agreement with the results given by analytical solutions for simple cases. A small-scale experimental set-up has also been built to validate the numerical model using temperature measurements. The apparatus mimics the behavior of a geothermal borehole and uses a homogeneous saturated laboratory-grade sand to reproduce unsaturated and saturated conditions. It is shown that the results of the numerical model are in good agreement with the experimental results.In the application section, the numerical ground model is combined with a borehole model to examine various scenarios involving typical heat pump operation. Results show that the borehole wall temperature remains around 0°C for several days when the ground freezes while it would drop to much lower values in non-freezing conditions. Freezing is restricted to a few centimetres around the borehole. If solar energy is available, and a 4-pipe borehole with two independent circuits is used, then it is possible to melt the ice and recharge the ground for the next freezing cycle. Using this approach, borehole depth can be reduced by as much as 38% in small thermal conductivity grounds.

On determination of the toxity index in stabilized liquid combustion in a room

An analysis is performed of thermal gasdynamic conditions for experiments to determine toxity of combustion products with a fire in a room. Consideration is given to mathematical models of calculating heat and mass transfer parameters in characteristic small- and large-scale rooms. Results of numerical experiments on determining the density of carbon oxide formed in combustion of benzene and turbine oil in stabilized combustion are presented. It is shown that the coefficient of heat loss is a necessary criterion of the equality of toxity indices in a small-scale experimental setup and in an actual room.

Optimal hybrid modeling approach for polymerization reactors using parameter estimation techniques

The dynamics of polymerization catalytic reactors have been investigated by many researchers during the past five decades; however, the emphasis of these studies was directed towards correlating process model parameters using empirical investigation based on small scale experimental setup and not on real process conditions. The resulting correlations are of limited practical use for industrial scale operations. A statistical study for the relative correlation of each of the effective process parameters revealed the best combination of parameters that could be used for optimizing the process model performance. Parameter estimation techniques are then utilized to find the values of these parameters that minimize a predefined objective function. Published real industrial scale data for the process was used as a basis for validating the process model. To generalize the model, an artificial neural network approach is used to capture the functional relationship of the selected parameters with the process operating conditions. The developed ANN-based correlation was used in a conventional fluidized catalytic bed reactor (FCR) model and simulated under industrial operating conditions. The new hybrid model predictions of the melt-flow index and the emulsion temperature were compared to industrial measurements as well as published models. The predictive quality of the hybrid model was superior to other models. The suggested parameter estimation and modeling approach can be used for process analysis and possible control system design and optimization investigations.

Dynamic modeling, simulation and control design of an advanced micro-hydro power plant for distributed generation applications

A small-scale hydropower station is usually a run-of-river plant that uses a fixed speed drive with mechanical regulation of the turbine water flow rate for controlling the active power generation. This design enables to reach high efficiency over a wide range of water flows but using a complex operating mechanism, which is in consequence expensive and tend to be more affordable for large systems. This paper proposes an advanced structure of a micro-hydro power plant (MHPP) based on a smaller, lighter, more robust and more efficient higher-speed turbine. The suggested design is much simpler and eliminates all mechanical adjustments through a novel electronic power conditioning system for connection to the electric grid. In this way, it allows obtaining higher reliability and lower cost of the power plant. A full detailed model of the MHPP is derived and a new three-level control scheme is designed. The dynamic performance of the proposed MHPP is validated through digital simulations and employing a small-scale experimental set-up.

Design of improved controller for thermoelectric generator used in distributed generation

This paper investigates the application of thermal generation based on solid-state devices such as thermoelectric generators (TEGs) as a novel technological alternative of distributed generation (DG). The full detailed modeling and the dynamic simulation of a three-phase grid-connected TEG used as a dispersed generator is studied. Moreover, a new control scheme of the TEG is proposed, which consists of a multi-level hierarchical structure and incorporates a maximum power point tracker (MPPT) for better use of the thermal resource. In addition, reactive power compensation of the electric grid is included, operating simultaneously and independently of the active power generation. Validation of models and control schemes is performed by using the MATLAB/Simulink environment. Moreover, a small-scale TEG experimental set-up was employed to demonstrate the accuracy of proposed models.

A simplified model of heat and moisture transfer for tailrace tunnel ventilating in hydropower station

Tailrace tunnel ventilating can be used as a highly efficient and energy saving air conditioning for factory buildings in hydropower stations. This paper describes a simplified model of heat and moisture transfer for tailrace tunnel ventilating system with the assumption of isothermal boundary for tunnel wall, and constructs a small-scale experimental set-up to simulate the heat and moisture transfer process during the air flowing through the tunnel. The model has been validated against the experimental and field-test data, and it shows a good agreement. This simplified model is intended for use in annual performances prediction of heat and moisture transfer or provides the design tools for tailrace tunnel ventilating system in hydropower stations.

Adsorption–Desorption Cycles for the Separation of Vapour-Phase Ethanol/Water Mixtures

A theoretical analysis and the results of the experimental verification of the adsorption-desorption process for ethanol dehydration are presented. This adsorption-desorption process is applied in industrial installations for the production of dehydrated ethanol as a fuel additive.In the present work, the experiments were performed using a small-scale experimental setup. The sequence of operations consisted of adsorption, vacuum desorption and purge. The adsorption column, filled with zeolite 3A pellets, was fed with a vapour-phase ethanol/water mixture containing 25 mol% water. The water vapour content at the column outlet was determined using gas chromatography. During the vacuum desorption step, the upper outlet of the column was connected to a vacuum pump. During the purge step, the lower outlet of the column was connected to a vessel containing pure ethanol while the upper outlet was connected to the vacuum pump.The process simulation results using the developed model have been compared with the expe...

Spectral Analysis of Pulsed Volume Breakdown in $ \hbox{SF}_{6}$ at High Pressures

The Z-machine, which is located at Sandia National Laboratories, is currently undergoing refurbishment to increase the output drive current. Due to increased switching voltage requirements, some switch failure modes have been identified with the laser-triggered gas switch design, including envelope surface flashover. In order to improve the performance and lifetime of these switches, a basic understanding of the underlying physics of the failure mechanisms is required. A small-scale experimental setup has been constructed to approximate conditions within the switch. The possible impact of the SF6 volume spark between the switch electrodes on the envelope surface flashover is investigated. Measured optical spectra of the SF6 volume spark over a wide pressure range, from rough vacuum to 40 psig overpressure, are analyzed regarding their potential to contribute to switch failure.

Effects of visual conditions and prey density on feeding kinetics of paralarvae of Octopus vulgaris from a laboratory spawning

Consumption rate and feeding success of newly hatched paralarvae of the cephalopod Octopus vulgaris preying on Artemia larvae were investigated in relation to visual conditions and prey density. Each paralarva was tested individually using a small-scale experimental setup; consumption over one day was measured at 208C. A factorial experiment was designed to investigate the effects on the consumption rate of two predictor variables: illumination/background (three levels: 7.5 W m 22 white light þ white background, 7.5 W m 22 white light þ blue background, darkness) and prey density (four levels: 2.35, 4.70, 9.40 and 14.10 Artemia metanauplii ml 21 ). Consumption rate varied significantly between different conditions of illumination and prey density. Light enhanced consumption rate, but different backgrounds yielded similar rates. The maximal consumption rate under illumination was close to 16 Artemia paralarva 21 day 21 , and it was around 5 Artemia paralarva 21 day 21 for assays in darkness. The predatory efficiency, measured as the proportion of prey consumed, was significantly affected by prey density, pointing to a type III functional response. The number of nonfeeding paralarvae was significantly higher in darkness and at low prey density.

Non-uniform granular pile–mat foundations: analysis and model tests

Granular piles are commonly used to improve bearing capacity and reduce settlements of soft soil in coastal and lowland areas. Due to various reasons, granular piles tend to acquire a non-uniform tapered-down cross-section in actual construction process. In this paper, a simple theoretical approach to predict deformation behaviour of soft ground reinforced with non-uniform granular pile–mat system is presented. A small-scale experimental set-up is fabricated in the laboratory and tests performed. Results predicted by the proposed approach compare well with the laboratory tests, and the field tests and other numerical test results available in literature. A parametric study has been carried out to evaluate the relative influence of granular mat thickness and relative stiffness on various responses of non-uniform granular piles.

Solar production of carbon nanotubes; structure evolution with experimental conditions

In this work we report the production of carbon nanotubes by direct vapourization of graphite targets containing different couples of catalysts using a 2 kW solar furnace. With this small-scale experimental set-up we observed the evolution of the structure of the produced nanotubes with experimental conditions, pressure and flow rate of the inert gas (argon) and target composition. High pressure favours the production of bundles of single-wall nanotubes (SWNTs) and the purity of the produced material depends on the target temperature and the cooling rate of the vapour. We also discuss the influence of the target composition.