Fluid Machines Research Articles

Measuring micro-sized leakage channel flow in macro-sized machines

In fluid machines, micro-sized clearances between a rotating shaft and a static casing give rise to leakage-flow losses. The moving boundary layer makes models non-trivial and complex to analyse. This study proposes a method to measure the leakage flow as a function of the channel width and rotational speed. The experimental setup consists of a rotating shaft enveloped by a cylindrical stator equipped with two micro-range actuators. Pressurised air, fed through the stator, induces a flow through two channels adjustable from 20 to 100 μm. At channel widths of 20 μm and 2 bar air pressure, the flow rate reduced by 25% at 9000 rpm compared to non-rotating, this speed-dependency was not measured above 4 bar. The actuators facilitated the assembly and enabled measurements of the speed and channel-size dependency of the leakage flow rate. The proposed methods and actuators can be extended to analyse more complex rotary-fluid machines.

CFD analysis of existing Mobile Disinfecting Units (MDUs)

The global economy, well-being, and public health are all gravely compromised by COVID-19. Thus, MDUs have been created to reduce such dilemmas. This document contains a study of a mobile disinfectant unit (MDU) that will mitigate the virus’ spread. By using simulation tools, a final design will be an overall improvement derived from the three models exhibited to generate simulations. Certain significant parameters were noted in doing the simulation, namely: (1) Contamination Removal Effectivity (CRE); (2) Air Distribution Performance Index (ADPI); and (3) Local Air Quality Index (LAQI). These are the coefficients that measure the units' effectiveness in lessening the contaminant present in ambient air and maintaining air comfortability. With the following parameters considered, an optimized design has been conceived having promising CRE, LAQI, and ADPI values by employing fluid machines such as fans, exhausters, and misting systems. Solidworks' CFD simulation concluded a better CRE and LAQI on the designed model than the existing ones having values close to 1, while its output ADPI is around 34%. Moreover, from the AnSys CFD simulation, the coverage area of the misting was around 95%, compared to its predecessors. These numbers prove that the designed model is indeed an enhancement of its predecessors.

Design and Construction of a Turbine Pump as Laboratory Scale Micro Hydro Electricity Learning Media

Lack of understanding of students about renewable energy can be produced from pumps, namely electrical energy. The energy produced by this pump is beneficial for rural areas that do not have electricity. The purpose of this research is to modify the pump as a turbine for a micro-hydro power plant which can be used by students of the Mechanical Engineering Department, the University of Muhammadiyah Pontianak as learning media in the field of fluid machines and laboratory-scale energy conversion machines. The research subjects were 15 students of mechanical engineering and pumps that were converted into turbines to generate electricity. The data collected first comes from the performance test of a pump that has been converted into a pump as a turbine. Further data was obtained from students through a pretest with a conceptual type of pump used as a power plant. Then after the pretest, students were treated by using and operating a pump as a turbine as a learning media. From this media, students must also explain the concept and how the pump as a turbine can produce electrical energy in writing. The student's written results obtained were analyzed to determine the effect of the pump as turbine model on students' understanding of conceptual analysis. The result of this research is a pump that has been converted into a pump as the turbine. In addition, as a simple practical tool to test the performance of the pump as a turbine. There was an increase in students' understanding in terms of the ability to describe the concept of power generation sources from pumps and analyze the process and workings of the pump as a turbine to produce electrical energy.

Special Issue on “CFD Based Researches and Applications for Fluid Machinery and Fluid Device, Volume II”

Computational fluid dynamics (CFD)-based advanced numerical optimization techniques are essential as practical tools used to enhance the performance of various fluid machines and fluid devices for realizing carbon neutrality [...]

Two-dimensional explainability method for fault diagnosis of fluid machine

The safe operation of the fluid machine is greatly affected by fault states. With the development of data collection technology in process industrial systems, data-based methods are widely applied in fault diagnosis. The observed data of the fluid machine belongs to typical multivariable time series, so the Euclidean features related to the observed timestamps and the non-Euclidean features related to the observed variables need to be extracted simultaneously by the fault diagnosis method. However, the existing diagnostic studies do not involve the explainability analysis of the diagnostic process, which makes it hard to evaluate the contribution of these features to the accurate diagnosis. An explainable diagnosis model based on temporal and graph convolutional neural network is proposed. The class activation map algorithm is improved to perform explainability analysis of the diagnosis process related to the observed variables and timestamps. Using the simulation data of the fluid machine, features related to observed variables and timestamps of six operating states are fully extracted. Through data experiments, this method can be utilized to achieve high-precision fault diagnosis, and can intuitively display the contribution of each observed variable and its each timestamp to network decision-making. This helps to trace system faults and has significant benefits for process safety assurance.

Comprehensive capacitance sensor calibration for high-speed fluid-machinery tip clearance characterization

This paper aims to lay a foundation for high-fidelity tip clearance measurements with capacitance sensors that can be adapted to any highspeed fluid machine, such as high-pressure turbines and compressors. A novel calibration procedure that does not involve rotating components is investigated and compared against established methods. First, a calibration bench is developed to demonstrate the static and dynamic performance of the sensors and perform quasi-static and dynamic calibrations in a controlled environment. Second, an in-situ methodology is developed to calibrate the sensors once installed in a turbine rig without complex positioning systems. A comprehensive uncertainty quantification analysis based on Markov Chain Monte Carlo sampling techniques shows that combined standard uncertainties as low as uc = 2.40 μm and uc = 4.69 μm could be achieved with the proposed bench and in-situ methodologies, respectively.

Acoustic signature analysis of a bladeless blower

There has always been a concern about acoustic emissions in traditional machinery. For example, in the transportation and power generation sectors, the market demands efficient, compact, lightweight, and low-cost devices with very low noise levels. In such a challenging context, as opposed to conventional turbomachinery, Tesla type bladeless fluid machine has the advantage of reducing the overall noise emissions level.The originality of this paper lies in its experimental acoustic signature characterization of a Tesla type bladeless blower, which has never been done before, nor is there any comparison to conventional blowers. A tailored experimental setup is described in order to evaluate the acoustic behavior of Tesla blower prototypes at different rotational speeds and distances. To achieve an accurate acoustic characterization, several measurement methods, as well as post-processing techniques, have been evaluated and compared.The results of this study have been compared with those obtained by conventional blowers, while considering the same tip speeds at different distances. A Tesla blower does not exhibit the blade passage phenomenon, as opposed to a conventional blower. A significant contribution of acoustic energy can thus be avoided which is due to its characteristic frequency and its harmonic components, which instead are significant in conventional turbomachinery overall acoustic noise.As a result of this innovative investigation, it has been determined that the air Tesla blower is significantly quieter than conventional dynamic machines, thus paving the way to novel applications for bladeless machinery, especially in those cases aimed at achieving a heightened level of acoustic comfort.

Facet Connectivity-Based Estimation Algorithm for Manufacturability of Supportless Parts Fabricated via LPBF.

Recent advances in additive manufacturing have provided more freedom in the design of metal parts; hence, the prototyping of fluid machines featuring extremely complex geometries has been investigated extensively. The fabrication of fluid machines via additive manufacturing requires significant attention to part stability; however, studies that predict regions with a high risk of collapse are few. Therefore, a novel algorithm that can detect collapse regions precisely is proposed herein. The algorithm reflects the support span over the faceted surface via propagation and invalidates overestimated collapse regions based on the overhang angle. A heat exchanger model with an extremely complex internal space is adopted to validate the algorithm. Three samples from the model are extracted and their prototypes are fabricated via laser powder bed fusion. The results yielded by the fabricated samples and algorithm with respect to the sample domain are compared. Regions of visible collapse identified on the surface of the fabricated samples are predicted precisely by the algorithm. Thus, the supporting span reflected by the algorithm provides an extremely precise prediction of collapse.

Numerical and Experimental Investigation of Streamlines for Tandem Impeller in a Centrifugal Pump

Abstract Radial fluid machines with conventional impeller often lead to flow separation in the blade passage in case of high flow deflection. Tandem blades can be used to counteract this problem. Due to their properties, a new thin boundary layer forms at the rear blade profile, which benefits the deflection of the flow. The present investigation focuses on a comparison between numerical and experimental streamline patterns on the impellers blades suction side. For this purpose, a conventional impeller is compared with a tandem impeller. Furthermore, a method for creating oil painting patterns in a rotating system is presented. The numerical investigations were performed using a full model (including inlet section, impeller, volute, outlet section and impeller side gaps). A total of four operating points were examined in the range from high partial load to overload. The same operating points were run in a pump loop during the experiment. The results of the present work show that the numerically and experimentally generated streamline patterns agree well with exceptions. It could be shown that a flow separation of the blades suction side can be prevented using tandem blades.

Energy parameters assessment, under scale effect calculation of centrifugal fans with radial blades

The centrifugal fans with radial blades are used in various industrial energy systems, associated with high dustiness, due to their self-cleaning ability and their reliable operation. Radial fans are used in cement, asphalt industries and various dust collection facilities. The uniqueness of the different working environment and the specifics of each system require the use of a fan, designed for the particular application. Due to the dimensions of the machines, before the fan is produced, it normally goes through model tests. In model studies of rotodynamic fluid machines, differences are sought between the expected parameters from the application of the similarity theory and the obtained energy parameters. These differences are commonly referred to as the scale effect. Estimating the scale effect in model tests leads to the use of energy efficient machines for a given system. These are the one, that give the desired system parameters when operating in the region of maximum efficiency. Thus, the purpose of modeling is to transfer the efficiency obtained for a given mode of operation of the model machine to the prototype. The operation in the optimal mode of the prototype fan leads to energy savings and a reduction in energy costs for a given technological system. In the presented paper are evaluated the differences between expected and obtained parameters that help to realize a model for a centrifugal fan with radial blades. The results of model tests, conducted on two geometrically similar centrifugal fans with radial blades, where the inlet and outlet angles of the impeller are the same (β1=β2=900 ), are given. The fan impellers are semi-open type with 12 blades. Each of the impellers is tested in a geometrically similar helical chamber. Model tests have been conducted on a laboratory test-bench, meeting the requirements of AMCA 210 or ISO5801. The test-bench is equipped with the complete measuring equipment, according to the standards used. During the model tests, both the energy parameters of the fans and the parameters of the surrounding environment are measured. The results of the energy tests of the fans are given in the paper, as well as the coefficients concerning the scale effect are determined and analyzed.

Performance Testing of Centrifugal Pump Type with 3 Hp Power

Pumps are fluid machines whose uses are very broad and important, ranging from industry to household needs. Selection of pump performance characteristics is very important and must be adjusted to the needs which include: discharge, head, power, and rotation. The performance characteristics of the pump are obtained through testing. In connection with the importance of information about pump performance characteristics, through this research activity efforts will be made to test centrifugal pumps using 3 hp of power. In this research, the data obtained from the direct test results will be entered, where the test is carried out at the Machine Performance Test Laboratory. In this test, the pump pressure data obtained from the gauge gradually with several valve openings, then the data is entered into the data table that has been prepared. The test was carried out to test the ability of the centrifugal pump test equipment using 3 HP power which was prepared as one of the laboratory pump test equipment for engine performance testing. In testing the centrifugal pump there are 3 variables that will be used to carry out the test, namely the first by using a tachometer which is useful for measuring shaft rotation, the second by using a Bordoun manometer which is useful for measuring fluid pressure, the third by using an orifice which functions to measure speed fluid.

ANALISIS UNJUK KERJA POMPA SENTRIFUGAL DENGAN PEMASANGAN INDUCER PADA LOCK NUT IMPELLER

Pompa sentrifugal merupakan mesin fluida yang paling banyak kita gunakan dalam kehidupan seharihari. Dalam pengoperasiannya terdapat banyak kerugian yang ditimbulkan oleh instalasi maupun konstruksi pompa itu sendiri. Telah banyak penelitian yang dilakukan untuk meminimalkan kerugiankerugian tersebut termasuk penelitian yang kami lakukan yaitu berupa modifikasi pada bagian inlet pompa sentrifugal. Penelitian ini bertujuan untuk mengetahui pengaruh pemasangan induser pada locknut impeller terhadap karakteristik pompa sentrifugal tipe aliran radial. Disini yang dimaksud dengan karakteristik pompa adalah head, debit, dan efisiensi pompa. Metode yang digunakan adalah eksperimen. Kegiatan yang dilaksanakan pada penelitian ini meliputi: perancangan dan perakitan alat pengujian pompa sederhana, pembuatan spesimen, pengambilan data, analisis dan pembahasan serta kesimpulan. Pada penelitian ini terdapat empat jenis pengujian, yakni: 1) Pompa sentrifugal tanpa modifikasi (normal); 2) Pompa modifikasi ke-1 dengan induser, panjang 25 mm; 3) Pompa modifikasi ke2 dengan induser, panjang 50 mm; dan 4) Pompa modifikasi ke-3 dengan induser, panjang 75 mm. Penelitian menunjukkan bahwa modifikasi dapat memperbaiki karakteristik pompa sentrifugal yang menjadi objek penelitian dimana terjadi peningkatan head total (Htot), debit (Q) dan efisiensi (ηp). Karakteristik terbaik yang diperoleh pada pompa modifikasi ke-2 dengan induser panjang 50 mm, disusuloleh pompa modifikasi ke-3 dengan induser panjang 75 mm, pompa modifikasi ke-1 dengan induser panjang 25 mm dan yang terendah adalah pompa tanpa modifikasi (normal). Karakteristik pompa sentrifugal Peningkatan tersebut disebabkan karena modifikasi dapat meminimalkan gejala pra-rotasi, turbulensi, serta pemisahan aliran. Atau dengan kata lain modifikasi menyebabkan terjadinya perbaikan pola aliran pada bagian inlet pompa sentrifugal.

Multi-Objective Optimization of Rear Guide Vane of Diagonal Flow Fan Based on Robustness Design Theory

As an essential fluid machine in national production, the optimal design of the performance of fans has long been a focus of research. In the format of small diagonal flow fans with rear guide vanes, there are too many design variables, and the design parameters interact with each other, resulting in a degradation of the fan’s performance under actual operating conditions. Under realistic conditions, many uncertainties exist in the object of study and fluctuations in variables and parameters lead to a specific deviation of the optimization target from the design target. A method is needed for the robust and optimal design of angular flow fans under stochastic operating conditions of the design variables. In this paper, a multi-objective aerodynamic performance powerful design method is proposed using Pearson correlation analysis, combined with CFD calculation method, Latin hypercube experimental design and the Kriging agent model, to optimize the rear guide vane structural parameters of the diagonal flow fan under uncertain aerodynamic performance conditions, analyze the flow field characteristics before and after the modification, and select the optimal design model for the release. The test results show that the total pressure of the optimized fan is increased by 86 Pa, and the noise is reduced by 2.4 dB. The proposed optimization method is effective and can also be used to optimize the performance of other types of fans.

Effect of clocking on entropy noise generation within an aeronautical high pressure turbine stage

This article reports a detailed experimental and numerical study of the clocking effect between entropy wave spots and stator leading edges on the evolution of the entropy wave and on indirect noise generation in a high pressure turbine stage. Experimental campaigns considering burner-representative temperature fluctuations injected upstream of an uncooled high-pressure gas turbine stage have been performed in the high-speed closed-loop test rig of the Fluid Machine Laboratory (LFM) of the Politecnico di Milano. Acoustic measurements focused on entropy noise generation have been carried out by the German Aerospace Center, DLR with two flush mounted in-duct microphone arrays. URANS CFD simulations with and without entropy fluctuations imposed at the stage inlet were performed with the TRAF code, developed by the Università degli Studi di Firenze. A numerical post-processing procedure, based on the time and space discrete Fourier transform (DFT) of the conservative variables, has been implemented to extract the low-frequency content connected to the entropy fluctuations and indirect noise emissions. Simulations show an overall good agreement with the experiments, especially at the stage outlet thus confirming the possibility to predict entropy noise by means of URANS simulations with time varying inlet conditions. By exploiting the combination of experiments and simulations, the evolution of the entropy wave, the identification of entropy noise generation areas, and the evaluation of indirect noise emissions, for the different clocking positions were properly assessed. This study also demonstrates that this type of simulations can be used for the geometric design optimization of combustor/turbine coupling performing detailed parametric studies concerning the clocking position of the perturbation source in order to reduce the turbine-combustor interactions and the indirect noise emissions.

Simulation of a Centrifugal Pump Based on a Lagrangian Particle Solver

Abstract A three-dimensional full-scale centrifugal pump is simulated using the moving particle semi-implicit (MPS) method. The generic smoothed wall (GSW) boundary is used and extended to three dimensions to address complicated wall shapes and thin-walled structures such as blades in turbomachines. The nonsurface detection technique (NSD) based on conceptual particles is introduced to avoid the loss of the particle-number-density near wall boundaries. A generic approach that can transfer arbitrary CAD models to wall-particle models is established by utilizing the nodal information of the shell mesh. An adaptative resolution technique is proposed by using fine and coarse particles to model the wall boundary with complex geometry. Fine and coarse particles are applied to curved and flat surfaces, respectively, to reduce the computational cost while maintaining high discretizing precision. A criterion based on the normal smooth angle (NSA) is defined to evaluate the local or global precision of established models and provide instructions for refinement. A fully-developed velocity inflow boundary based on 3D inlet rings and pressure outflow boundary based on the moving virtual wall is implemented. Three typical cases including hydrostatic cases with a typical geometry, flow over a two-dimensional backward-facing step, and flow over a three-dimensional tube are tested to verify the proposed models. A particle-based framework to simulate incompressible fluid machines, in which flow fields can be integrally discretized and solved within a single coordinate system, is established. The results are compared with those of the fine volume method and satisfactory agreements are observed.

Aircraft Icing Severity Evaluation

Aircraft icing refers to the ice buildup on the surface of an aircraft flying in icing conditions. The ice accretion on the aircraft alters the original aerodynamic configuration and degrades the aerodynamic performances and may lead to unsafe flight conditions. Evaluating the flow structure, icing mechanism and consequences is of great importance to the development of an anti/deicing technique. Studies have shown computational fluid dynamics (CFD) and machine learning (ML) to be effective in predicting the ice shape and icing severity under different flight conditions. CFD solves a set of partial differential equations to obtain the air flow fields, water droplets trajectories and ice shape. ML is a branch of artificial intelligence and, based on the data, the self-improved computer algorithms can be effective in finding the nonlinear mapping relationship between the input flight conditions and the output aircraft icing severity features.

Development of All Metal Multi-plate-type Capacitive Void Fraction Sensor for gas-liquid two-phase flow

In the aerospace field, liquid hydrogen and oxygen which are “cryogenic fluid” are used as the propellant for rockets and hypersonic engines. These fluids become easily a gas-liquid two-phase flow in pipes and fluid machines. We have developed small capacitive void fraction sensors which can measure in real time, which is used to control the flow rate of cryogenic fuel and to understand typical two-phase flow phenomena such as the cavitation. The conventional capacitive sensors have a structure in which two electrodes sandwich a pipe made of dielectric material. However, the dielectric material has problems such as insufficient strength under high pressure condition and decreasing measurement accuracy due to changes in dielectric constant with temperature change. We developed a new capacitive sensor which consists of only metal parts to solve these problems. On the other hand, it may cause a decrease in measurement accuracy due to the structural limitation. This paper presents the results of the electric field analysis and the static fluid experiment using silicon oil and air to verify the accuracy of the sensor. The mean errors obtained by the analysis and the experiment are 3.47 % and 5.32 %, respectively, which almost satisfy the required specification. However, it was found that the accuracy is poor in some void fraction ranges, and the sensor needs to be improved.

SAFER ON BOARD ENVIRONMENTS FOR INDONESIAN SEAFARERS AND FISHERS IN THE TIME OF COVID-19 AND BEYOND

The seafaring and fishing industries in Indonesia have been severely affected by the COVID-19 pandemic. There is an urgent need to research the best technical solutions to ensure the safety of seafarers and fishers so that they can keep working safely at sea. It is highly unlikely that the Indonesian fleet will be able to rapidly return to the pre-COVID-19 situation within the next few years. Therefore, long-term solutions are required. This research aims to provide guidance for owners, operators and masters to reconfigure their vessels and operations to ensure a safe working environment to counter the potential spread of the virus, as well as maintaining the integral safety of the vessels. The present paper reports several primary activities, including analysis of existing guidelines, questionnaire survey, computational fluid dynamics, remote monitoring and machine learning. These works are expected to provide indications on virus-hazardous areas for ships, inform guidelines on hygienic and reconfiguring means to counter COVID-19 and potentially the spread of similar viruses, and further establish a long-term monitoring and optimising system for ship safety and performance.

Effect of Rotational Speed Variation on the Flow Characteristics in the Rotor-Stator System Cavity

In this paper, to study the effect of dynamic and static interference of clearance flow in fluid machinery caused by changes in rotational speed, the model was simplified to a rotor-stator system cavity flow. Investigating the flow characteristics in the cavity by changing the rotor speed of the rotor-stator system is of considerable significance. ANSYS-CFX was applied to numerically simulate the test model and the results were compared with the experimental results of the windage torque of the rotor-stator system. The inlet flow rate and geometric model remained unchanged. With an increase in the rotating Reynolds number, the shear stress on the rotor wall gradually increased, and the maximum gradient was within l* < 0.15. In addition to the shear stress, the tangential Reynolds stress Rrθ contributed partly to the torque on the rotor wall. The swirling vortex formed by entrainment in the cavity of the rotor-stator system tended to separate at ReΦ= 3.53 × 106. As the rotating Reynolds number continued to increase, the secondary vortex finally separated completely. The strength of the vortex in the rotor turbulent boundary layer decreased with an increase in the rotating speed, but the number of vortex cores increased with the increase of speed. Depending on the application of the fluid machine, controlling the rotating speed within a reasonable range can effectively improve the characteristics of the clearance flow.

Enhanced slurry and cavitation erosion resistance of deep cryogenically treated thermal spray coatings for hydroturbine applications

The deterioration of fluid machines due to slurry and cavitation erosion significantly impairs their serviceability. In the present work, we investigated the influence of deep cryogenic treatment (DCT) on the slurry and cavitation erosion resistance of WC-10Co-4Cr coatings developed using the detonation spraying technique. For comparison, hydroturbine steels and other conventional (Alumina and Stellite 6) coatings were also investigated. All thermal spray coatings showed typical lamellar structure along with the presence of pores and splat boundaries. Among all the coatings, the WC-10Co-4Cr showed the highest slurry (up to 15 times) and cavitation (2 times) erosion resistance owing to high hardness and fracture toughness. Post DCT, the WC-10Co-4Cr coating showed further improvement due to reduced porosity and improved hardness without decrement in fracture toughness. As a result, the DCT coating showed 1.5 to 4.2 times improved slurry erosion resistance than the as-sprayed counterpart, along with 1.6 times higher cavitation erosion resistance. The improved tribological performance of the coating after DCT is associated with enhanced hardness due to the presence of nano precipitates and densification as analyzed using electrochemical techniques. The topological analysis of the eroded surfaces indicated micro-cutting, micro-cracking, and delamination as the primary mechanism controlling the erosion behavior of the coatings.