Water Test Rig Research Articles

Leak detection and localization in water distribution systems using advanced feature analysis and an Artificial Neural Network

This study capitalizes on a dataset, originally including 280 sensory measurements from a laboratory-scale water distribution system, to advance the concept of leakage diagnosis and localization. The water distribution test rig are formulated in two configurations, namely looped and branched layouts. The paper processed time-domain data from accelerometers and dynamic pressure sensors into advanced statistical features of: Autocorrelation Coefficient (Au-C), and Signal Energy (Sig-E), to detect and localize the water leakage. By the Employment of these two features, the research developed an expert system of an Artificial Neural Network (ANN) model designed with optimal parameters, neurons, and hidden layers to classify the presence and pinpoint the location of leaks within the water test rig. The effectiveness of the current approach is quantitatively evaluated using F1-scores and accuracy metrics. A robust capability for both detecting and localizing leaks under varying conditions was established with a highest accuracy and F1-score of 86.5 % and 86.2 %, respectively. The findings underscore the potential of integrating advanced features with Artificial Intelligence (AI) in enhancing the reliability and dependability of water management expert systems. This approach contributes to the broader application of AI in managing water resources and infrastructure resilience with its support to improve leakage whereabouts.

Investigations on the performance of bottle blade overshot water wheel in very low head resources for pico hydropower

Abstract An overshot water wheel is considered as a low-cost and simple alternative for rural electrification. Hence, the aim of this study is to develop a noncomplex geometrical design of an overshot water wheel, namely, bottle blade overshot water wheel (BOWW), yet effectively operated for pico hydropower generation. The BOWW and hydro system were assessed at very low water head conditions, namely, 0.3, 0.4, and 0.5 m water head using a water test rig. According to the experimental results, the BOWW equipped with eight blades when operated at 0.5 m head produced significant mechanical power and electrical power up to 48.58 and 15.55 W. Analytically, the turbine with eight blades has 26.8–49.1% efficiency. Meanwhile, the effectiveness of four blades is between 5.66 and 28.96%. The results showed that eight blades performed well. Finally, it proves that, with a very low water head and low flow rate, the proposed system can perform and produce a significant power output for power generation.

An Experimental Investigation of Overshot Waterwheel in Very Low Head Water Resources for Pico Hydro

Waterwheels are considered a low-cost and simple alternative method for rural electrification and this paper aims to investigate the performance of a non-complex geometrical design of overshot waterwheel in a pico hydro system. The waterwheel and the hydro system have been assessed at very low water heads condition at 1.5 m water and 5 L/s flow rate using a water test rig. According to the experimental results, the proposed waterwheel manages to achieve significant rotational speed, mechanical torque, and efficiency. The rotational speed has produced more than 130 rpm with mechanical torque reaching up to 1.2 Nm. Analytically, the turbine with four bottles per blade has an efficiency of 32 %. This is higher than the efficiency of three bottles per blade at 24 %. The results have also indicated that the overall performance of overshot water wheels with four bottles blade is higher than the three bottles per blade. Furthermore, certain specific values of water head and flow rate have been found out to be able to obtain the optimum efficiency. At the same time, the values of water head and water flow rate have been also found to be proportional with the value of the mechanical torque produced. Finally, the ability of the proposed system to produce a considerable output for power generation has showed that it is potentially viable to be used at the actual field.

Experimental and Computational Analysis of the Swirling Flow Generated by an Axial Counter-Rotating Swirler in a Rectangular Model Chamber Using Water Test Rig

This paper reports the particle image velocimetry (PIV) measurement of swirling flow in a confined rectangular-shaped model combustion chamber. Water is used as the working fluid, and the average profiles of axial, radial, and magnitudes of velocity are given. Flow behavior is investigated and a rebound angle term is defined to investigate the direct effects of the noncircular chamber shape. Flow behavior near the walls is discussed in detail, as are other important swirling flow features such as the appearance of corner and central toroidal recirculation zones. Additionally, experimental data are compared with simulation results. Analyses were performed via commercial software STAR-CCM+ version 9.0. The large eddy simulation (LES) dynamic Smagorinsky subgrid scale, realizable k–ε model, and k–ω shear-stress transport (SST) detached eddy version were used as simulation tools. Three different test filters of 1.0, 2.2, and 3.0 were applied to the LES to identify improvements in accuracy. The overall best turbulence model is compared to the experimental result and reliability of such model is evaluated. The ability of such model was profound within the upstream and to some extent unreliable in downstream.

Impact of Cooling Air Injection on the Combustion Stability of a Premixed Swirl Burner Near Lean Blowout

In most dry, low-NOx combustor designs of stationary gas turbines, the front panel impingement cooling air is directly injected into the combustor primary zone. This air partially mixes with the swirling flow of premixed reactants from the burner and reduces the effective equivalence ratio in the flame. However, local unmixedness and the lean equivalence ratio are supposed to have a major impact on combustion performance. The overall goal of this investigation is to answer the question of whether the cooling air injection into the primary combustor zone has a beneficial effect on combustion stability and NOx emissions or not. The flame stabilization of a typical swirl burner with and without front panel cooling air injection is studied in detail under atmospheric conditions close to the lean blowout limit (LBO) in a full-scale, single-burner combustion test rig. Based on previous isothermal investigations, a typical injection configuration is implemented for the combustion tests. Isothermal results of experimental studies in a water test rig adopting high-speed planar laser-induced fluorescence (HSPLIF) reveal the spatial and temporal mixing characteristics for the experimental setup studied under atmospheric combustion. This paper focuses on the effects of cooling air injection on both flame dynamics and emissions in the reacting case. To reveal dependencies of cooling air injection on combustion stability and NOx emissions, the amount of injected cooling air is varied. OH*-chemiluminescence measurements are applied to characterize the impact of cooling air injection on the flame front. Emissions are collected for different cooling air concentrations, both global measurements at the chamber exit, and local measurements in the region of the flame front close to the burner exit. The effect of cooling air injection on pulsation level is investigated by evaluating the dynamic pressure in the combustor. The flame stabilization at the burner exit changes with an increasing degree of dilution with cooling air. Depending on the amount of cooling, only a specific share of the additional air participates in the combustion process.

Computational analysis of incompressible turbulent flow in an idealised swirl combustor

Isothermal turbulent swirling flow in a water test rig, representing an idealised swirl combustor, has been investigated experimentally and numerically. The Reynolds number based on combustor inlet diameter and mean axial velocity was 4600. Two cases were investigated at two different swirl intensities. Time-averaged velocities and RMS turbulence intensities were measured by Laser Doppler Anemometer (LDA), along radial traverses at different axial stations. In the three-dimensional, transient computations, Large Eddy Simulations (LES) and URANS Reynolds Stress Models (RSM) have basically been employed as modelling strategies for turbulence. To model subgrid-scale (SGS) turbulence for LES, the models owing to Smagorinsky and Voke were used. In one of the cases, Detached Eddy Simulations (DES) were also applied. The predictions have been compared with the measurements. It has been observed that LES provides the best overall accuracy, where no significant differences between the Smagorinsky and Voke models could be discerned.

Experimental and numerical investigation of isothermal flow in an idealized swirl combustor

PurposeThe main purpose of the paper is the validation of different modelling strategies for turbulent swirling flow of an incompressible fluid in an idealized swirl combustor.Design/methodology/approachExperiments have been performed and computations carried out for a water test rig, for a Reynolds number of 4,600 based on combustor inlet mean axial velocity and diameter. Two cases have been investigated, one low swirl and the other high swirl intensity. Measurements of time‐averaged velocity components and corresponding rms turbulence intensities were measured using laser Doppler anemometer, along radial traverses at different axial locations. In the three‐dimensional, unsteady computations, large eddy simulation (LES) and URANS (Unsteady Reynolds Averaged Navier‐Stokes Equations or Reynolds Averaged Numerical Simulations) RSMs (Reynolds‐stress models) are basically employed as modelling strategies for turbulence. To model subgrid‐scale turbulence for LES, the models due to Smagorinsky and Voke are used. No‐model LES and coarse‐grid direct numerical simulation computations are also performed for one of the cases.FindingsThe predictions are compared with the measurements and reveal that LES provided the best overall accuracy for all of the cases, whereas no significant difference between the Smagorinsky and Voke models are observed for the time‐averaged velocity components.Originality/valueThis paper provides additional valuable information on the performance of various modelling strategies for turbulent swirling flows.

Simulation of Turbulent Swirling Flows: Gas Turbine Combustor Application and Validation

In the first part of the paper, CFD analysis of the combusting flow within a high-swirl lean premixed gas turbine combustor and over the 1st row nozzle guide vanes is presented. In this analysis, the focus of the investigation is the fluid dynamics at the combustor/turbine interface and its impact on the turbine. The predictions show the existence of a highly-rotating vortex core in the combustor, which is in strong interaction with the turbine nozzle guide vanes. This has been observed to be in agreement with the temperature indicated by thermal paint observations. The results suggest that swirling flow vortex core transition phenomena play a very important role in gas turbine combustors with modern lean-premixed dry low emissions technology. As the predictability of vortex core transition phenomena has not yet sufficiently been investigated, a fundamental validation study has been initiated, with the aim of validating the predictive capability of currently-available modelling procedures for turbulent swirling flows near the sub/supercritical vortex core transition. In the second part of the paper, results are presented, which analyse such transitional turbulent swirling flows in a laboratory water test rig. It has been observed that turbulent swirling flows of interest are dominated by low-frequency transient motion of coherent structures, which can not be adequately simulated within the framework of steady-state RANS turbulence modelling approaches. It has been found that useful results can be obtained only by modelling strategies, which resolve the three-dimensional, transient motion of coherent structures, and do not assume a scalar turbulent viscosity at all scales. These models include RSM based URANS procedures as well as LES. To exploit the full potential of LES, however, additional attention needs to be paid to modelling issues such as achieving the necessary grid resolution as well as providing convenient inlet boundary conditions.

AN ANALYTICAL COMPARISON OF HYDRAULIC SYSTEMS BASED ON WATER AND ON OIL

Environmental protection regulations are becoming increasingly strict. By using water instead of a hydraulic mineral oil in power-control hydraulic systems we can make a very positive step in complying with these regulations. In this paper we present some preliminary results on twin-type hydraulic experiments, employing equal parts containing water and oil. Our initial findings suggest the need for modifications to the test rig, and a comparison of the behaviour between two similar hydraulic test rigs is shown. The main parameters measured during the investigation were the pressures, the spool displacements and the responses of the piston in the double-acting hydraulic cylinder. However, transient phenomena in the water and oil hydraulic test rig were also analysed and compared. Experiments were performed on systems with and without an applied load. The results reveal very different behaviours for the oil and the water hydraulics.

Flow Instability and Disk Vibration of Shrouded Corotating Disk System

This paper focuses on the interaction between the flow unsteadiness and disk vibration of shrouded corotating disk system to identify the nature of the flow-induced vibration of disks in the wide range of rotation speed below critical. Special attention is paid to the role of the vortical flow structure on the disk vibration and vice versa. The water test rig for optical measurement and the air test rig for hot-wire and vibration measurements are employed, both being axisymmetric models of 3.5in. hard disk drive. Before investigating fluid-solid interaction, the velocity and vorticity fields between disks are examined by employing a particle image velocimetry, in order to check the flow within our own apparatus to have the same characteristics as those commonly accepted. In the course of this preliminary experiment, it is found that “vortical structures” reported in the previous papers based on the flow visualization are actually “vortices” in the sense that it exhibits closed streamlines with concentrated vorticity at its center when seen from an observer rotating with the structure itself. The measurements of out-of-plane displacement of the disk employing different disk materials reveal that disk vibration begins to occur even in low subcritical speed range, and amplitude of nonrepeatable run out (NRRO) can be uniquely correlated by using the ratio between the rotating speed and the critical speed. The power spectral densities of disk vibration showed that the disk vibrates as a free vibration triggered by, but not forced by, the flow unsteadiness even in the high subcritical speed range. The disk vibration has negligible effect on the vortical flow structure suggesting the soundness of the rigid disk assumption employed in the existing CFD. However, RRO has significant influence on the flow unsteadiness even if the disks are carefully manufactured and assembled. Since the RRO is unavoidable in the real disk system, the flat disk assumption should be considered more carefully.

Error analysis based development of a bubble velocity measurement chain

In this paper a measurement chain for bubble velocity measurements has been designed, developed and tested. The sensing element used for testing is a double fiber optic probe. Error sources associated with the measurement techniques are illustrated by theoretical models. The conclusions are also valid for other sensing elements used to detect bubbles in two-phase flow. A special purpose data acquisition and processing system has been implemented to obtain velocity data from the sensor signals. The system can be used with other kinds of sensing elements. A test bench, suitable for generating horizontal air-water two-phase flows with well controllable bubble velocity, has been installed in a water test rig in order to test and calibrate the measurement chain using a double fiber optic sensing element.

An Investigation of the Flow Characteristics and of Losses in Radial Nozzle Cascades

A study was made of the flow in radial nozzle cascades using an air test rig and a water test rig. In the air test rig, three cobra probes were used in circumferential and spanwise traverses to determine the total pressure variations in the flow field at three radii downstream of the nozzles at which static pressure was also measured. The tests were made on two sets of nozzle blades having heights of 0.148 in. (0.376 cm) and 0.200 in. (0.508 cm), at trailing edge angles (measured from circumferential direction) of 15, 20, and 25 deg, and at two flow Mach numbers of approximately 0.2 and 0.35. The test results presented in this paper, in the form of loss coefficients and flow angles, were flow-weighted and averaged. Flow visualization in the air test rig was made on the walls bounding the nozzle blades using the graphite power-oil mixture technique. Additional tests were made on the water test rig using dye injection technique. Photographs were obtained showing clearly formation of secondary flow around each nozzle blade in the form of the leading edge vortex. The test results confirm the existence of the leading edge vortices reported peviously, and extend their study to the radial nozzle cascades.

A Study of the Cross Flow Fan

The cross flow fan has developed from the ideas of Mortier in the late 19th century and recently has been used with conspicuous success in small domestic appliances. No satisfactory theory is known, improvements having come from experimental development. The present work is also experimental. A closed-circuit fan test rig was constructed to obtain pressure, volume flow rate and efficiency for fans of various designs. Detailed measurements within the rotors were also obtained by hot-wire traverses. These tests were supplemented by visualization studies in a water test rig. It is found that improved pressure–flow characteristics are obtained by constructing the casing so that the vortex which forms in the fan is allowed to move circumferentially round the rotor as the output is throttled. This preserves a strong vortex and keeps the total pressure approximately constant as the flow is throttled. In many previous designs, which do not allow this kind of displacement, the vortex tends to move towards the centre of the rotor and to diminish in strength, leading sometimes to unstable operation.

Paper 10: Radial Forces in Centrifugal Pumps with Guide Vanes

At partial and overload conditions, radial decentralizing forces act upon the rotor of a centrifugal pump with guide vanes if the impeller is out of centre. The magnitude of these forces depends on load conditions, and the forces increase with growing eccentricity. At very small flow, these forces become non-stationary. They rotate at a considerably lower frequency than the velocity frequency and may lead to rotor vibrations. The paper discusses the effects of stationary and non-stationary radial forces, and resulting shaft deflections and vibrations, from measurements on two experimental test rigs. The paper also presents the results of research on the pressure distribution of guide vanes, carried out in air, and gives observations of flow patterns in a shallow water test rig.