Research Paper
Dynamic Response
Zhinong Li; Fang Qiao; Yunlong Li; Shiyao Chen; Shijian Zhou; Fei Wang
Abstract
Currently, the existing study on rotor system with disk-shaft clearance primarily focuses on analyzing factors such as interference force and friction coefficient while neglecting the vibration characteristics during the rotational states. Therefore, a finite element model is established by taking rotor ...
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Currently, the existing study on rotor system with disk-shaft clearance primarily focuses on analyzing factors such as interference force and friction coefficient while neglecting the vibration characteristics during the rotational states. Therefore, a finite element model is established by taking rotor systems with disk-shaft clearance as the research object. The vibration characteristics of rotor systems under different clearances or rotation speeds are analyzed. Increasing clearance leads to gradual fluctuations in the speed difference of shaft to disk, accompanied by an increasing periodicity of these fluctuations. In the time domain diagram, beat vibration characteristic become evident, and its period undergoes noticeable changes. The amplitude of rotation frequency increases, while that of multiple frequency decreases gradually and tends to a constant value. The presence of clearance causes the orbit of the disk center to become an irregular circle, and the shape of 8 appears. Additionally, collision and friction of shaft to disk result in apparent serrations in the orbit. As the rotational speed increases, the speed difference initially increases but eventually reaches a stable value. The beat vibration characteristic disappears due to the small speed difference, leading to a small amplitude of the multiple frequency. The orbit of the disk center tends to become circular, and the serrated phenomenon weakens and disappears. Finally, the experiments of rotor systems with disk-shaft clearance are carried out. The results are in good agreement with the simulations, which verifies the correctness of the dynamic model. The research results can provide a theoretical basis for understanding rotor systems with disk-shaft clearance.
Research Paper
Computational Fluid Dynamics (CFD)
Aydin Zabihi; Nader Pourmahmoud
Abstract
3-fluid liquid-to-air membrane energy exchangers (LAMEEs) are economic dehumidification systems. Cooling tubes are put into dehumidifier liquid channels to regulate the internal temperature of the dehumidifier liquid. 3D computational fluid dynamics is used to simulate a 3-fluid LAMEE, and extra transfer ...
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3-fluid liquid-to-air membrane energy exchangers (LAMEEs) are economic dehumidification systems. Cooling tubes are put into dehumidifier liquid channels to regulate the internal temperature of the dehumidifier liquid. 3D computational fluid dynamics is used to simulate a 3-fluid LAMEE, and extra transfer of both heat and mass formulas, along with the essential equations that govern viscous fluid flow, are compiled using external computer programs known as UDS (User Defined Scalar). This study thoroughly investigates the impact of water inflow variables on system efficiency. The refrigeration fluid that runs inside the cooling tubes is water. The temperature distribution of the three fluids is investigated and the role of the refrigeration tubes based on their positions is evaluated on the desiccant solution cooling. Six tests are conducted to achieve the best arrangement of the inlet water conditions based on the tube’s geometrical location. At an intake water mass flow rate of 4.67 g/s, the latent and sensible effectiveness rise from 51% to 78% and 60% to 130%, respectively, when the input water temperature drops from 24.6 °C to 10.1 °C.
Research Paper
Internal Combustion Engine
R. Jyothu Naik; K. Thirupathi Reddy; S. Vishal Narayanrao
Abstract
This article describes an experimental study on fueling the port fuel injection homogeneous charge compression ignition (PFI-HCCI) combustion engine with plastic oil that is generated from waste plastics through the pyrolysis method. The study tested different exhaust gas recirculation (EGR) levels ...
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This article describes an experimental study on fueling the port fuel injection homogeneous charge compression ignition (PFI-HCCI) combustion engine with plastic oil that is generated from waste plastics through the pyrolysis method. The study tested different exhaust gas recirculation (EGR) levels of 0%, 5%, 10%, and 15% using a modified PFI-HCCI computerized 4-stroke, single-cylinder, water-cooled, direct injection Kirloskar diesel engine connected to an eddy current dynamometer. Furthermore, an engine running at 1500 rpm and a constant preheated air temperature (PHAT) of 140°C were assessed. In this experiment, fuel, 20% biodiesel waste plastic pyrolysis oil (WPPO), and continuous PHAT 140°C are used. The testing results show that the cylinder peak pressure and heat release rate for WPPO 20 with 15% EGR were attained at 39.70% and 15.09%, respectively. Additionally, port fuel injection with PHAT and WPPO 20% without EGR is reported to have a 45% higher brake thermal efficiency at full load in comparison to PFI-HCCI Diesel (D100). But when employed at full load with 15% EGR, the WPPO 20 blend also reduced smoke opacity by 30.74% and Oxides of Nitrogen (NOx) emission by 52.17%. On the other hand, compared to the PFI-HCCI (D100), there are higher emissions of carbon monoxide (CO) (22.07%) and unburnt hydrocarbon (UHC) (54.14%) with 15% EGR. Consequently, WPPO can be used for the PFI-HCCI engine.
Research Paper
Computational Fluid Mechanics (CFM)
S. Rasoolzadeh; M. Y. Hashemi
Abstract
The purpose of this paper is to numerically simulate unsteady, incompressible, and laminar flow with natural and mixed convection heat transfer in a square lid-driven cavity filled with Cu-Water nanofluid. Jameson method is used in conjunction with the Artificial compressibility method on the unstructured ...
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The purpose of this paper is to numerically simulate unsteady, incompressible, and laminar flow with natural and mixed convection heat transfer in a square lid-driven cavity filled with Cu-Water nanofluid. Jameson method is used in conjunction with the Artificial compressibility method on the unstructured grid in a viscous flow. Effects of Grashof number and nanoparticle volume fraction on the flow and heat transfer characteristics are investigated. Two-dimensional Navier-Stokes equations as the governing equations of the problem are discretized with the finite volume method. Spatial discretization is performed with a two-order central scheme; and Jameson artificial dissipation terms are added to equations to stabilize the solution. Unsteady terms are discretized with an implicit two-order scheme and are solved with fourth-order explicit Runge-Kutta method in pseudo-time. It is found that the Jameson method has good performance with a reasonable convergence rate. Results show that an increase in the volume fraction of nanoparticles improves heat transfer characteristics while the increase in the Grashof number, weakens the heat transfer due to the domination of natural convection.
Research Paper
Computational Fluid Dynamics (CFD)
Vikram A. Kolhe; Suyash Y. Pawar; Vishal D. Chaudhari; Ravindra L. Edlabadkar; Kailas V. Chandratre
Abstract
Measuring flow rate precisely in laminar flow has been a difficult task, especially when utilizing a Coriolis mass flow meter (CMFM) for low flow rate measurements. The meter often under-reads the mass flow rate, making it less useful in these conditions. The dominant factor affecting the CMFM's ...
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Measuring flow rate precisely in laminar flow has been a difficult task, especially when utilizing a Coriolis mass flow meter (CMFM) for low flow rate measurements. The meter often under-reads the mass flow rate, making it less useful in these conditions. The dominant factor affecting the CMFM's performance in laminar regions is secondary flow, which overshadows the generated Coriolis force, leading to an under-reading of the flow rate. Previous studies have indicated that tube curvature is the most significant parameter affecting secondary flow generation and the overall performance of the meter. An omega-shaped tube configuration featuring a continuous curvature has been identified as the optimal shape for maximizing the performance of a CMFM device in laminar flow. The purpose of the investigation is to study and compare the efficiency of various Omega tube designs that have undergone slight geometric alterations. Four different configurations were evaluated for maximum time lag by vibrating at their respective natural frequencies and keeping the sensor position along the centerline of the tube configuration.
Research Paper
Computational Fluid Dynamics (CFD)
Alireza Alinezhad; Ataallah Soltani Goharrizi; Ataallah Kamyabi
Abstract
In this paper, heat transfer and fluid flow around a solid cylinder wrapped with a porous layer in the channel were studied numerically by computational fluid dynamics. The homogeneous concentric and eccentric porous medium around a rigid and solid cylinder is supposed at local thermal equilibrium. The ...
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In this paper, heat transfer and fluid flow around a solid cylinder wrapped with a porous layer in the channel were studied numerically by computational fluid dynamics. The homogeneous concentric and eccentric porous medium around a rigid and solid cylinder is supposed at local thermal equilibrium. The transport phenomena within the porous layer and volume-averaged equations were employed; however, the conservation laws of mass, momentum and energy were applied in the channel. The main purpose of this study is to analyze and compare the heat flux of concentric and eccentric porous layer in the Reynolds number range of 1 to 40 and Darcy numbers of 10-2 to 10-6. It is found that with the decline of Darcy number, the vortex length is increased behind the solid cylinder surface. In addition, the heat flux rate of the cylinder is raised with the increase of Reynolds number. Finally, the results showed that the average Nusselt numbers in different Darcy and Reynolds numbers are higher in the eccentric porous layer than in the concentric porous layer. For example, our findings show that in , and , the average Nusselt number in the eccentric porous layer is higher than the concentric porous layer.
Research Paper
Fatigue
Mazuri Erasto Lutema; Awel Mohammedseid Momhur
Abstract
The most crucial parts that literally sustain the safety of railroad rolling stock from the subfloor are the wheels. However, during operation, several random parameters can impair their performance, resulting in the train's unsafety. These unpredictable characteristics can lead to fatigue failure, especially ...
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The most crucial parts that literally sustain the safety of railroad rolling stock from the subfloor are the wheels. However, during operation, several random parameters can impair their performance, resulting in the train's unsafety. These unpredictable characteristics can lead to fatigue failure, especially in a CHR2 high-speed train. This study aims to analyse the fatigue life of railway wheels for the CHR2 high-speed train due to different random parameters. Three scenarios with random parameters were considered: suspension system, passenger weight, and train speed. A 3D wheel model created by CAD and analyzed with finite element software ANSYS and nCode to validate the model by applying static force. A railway vehicle-track dynamics was modeled with a 30t axle load using the vehicle-track dynamics theory. Then Monte Carlo simulations were performed to produce random samples of sensitive parameters and analyze their effect distributions on wheel–rail contact under random wheel parameters. The findings demonstrate that the random parameters of the suspension system have more negative effects on fatigue life compared to random passengers’ weight and train speed; however, random passengers’ weight has a less negative impact compared to random suspension and passenger weight. The dynamic stress analysis results showed that the random suspension system parameters have a high maximum stress compared to that obtained from random passengers’ weight and train speed. Moreover, the random suspension system parameters have high maximum stress compared to that obtained from random passengers’ weight and train speed.
Research Paper
Meshless Numerical Methods
R. Shamsoddini; B. Abolpour
Abstract
One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the ...
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One of the main problems in liquid transfer tanks is the sloshing phenomenon. This phenomenon, which is associated with regular or irregular liquid waves inside the tank, can cause many risks. One of the most widely applied methods to control the fluctuations caused by the sloshing phenomenon is the use of baffles. Baffles are usually installed vertically or horizontally on the inner wall of the tank. In uniform samples (simple baffle), the hydrodynamic force on the baffle is significant. Therefore, in this research, mesh baffle from the category of permeable baffles is introduced and tested, which can significantly reduce the hydrodynamic forces on the baffle. Therefore, in the present work, the sloshing phenomenon in a rectangular tank is first modeled by smoothed particle hydrodynamics and validated. Then, the tank with a simple baffle and mesh baffle are modeled and examined. During the numerical solution (in each time interval), the hydrodynamic forces acting on the baffles are monitored and extracted. The comparison of the obtained results shows that in addition to reducing the fluctuations of the sloshing phenomenon, the mesh baffle also creates a lower hydrodynamic resistance force.
Research Paper
Dynamic Response
Y. H. Park
Abstract
A hydraulically driven mold oscillator challenges estimating the dynamic state variables precisely. Significantly, the additional stiffness effect of hydraulic oil is variable according to operating conditions, and it is hard to formulate it as a mathematical expression. This study investigates the dynamic ...
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A hydraulically driven mold oscillator challenges estimating the dynamic state variables precisely. Significantly, the additional stiffness effect of hydraulic oil is variable according to operating conditions, and it is hard to formulate it as a mathematical expression. This study investigates the dynamic characteristics of a mold oscillator operated by two hydraulic cylinders with other springs and dampers to determine the non-linear effect and estimate exact dynamic state variables to improve the accuracy control. The mold oscillator is excited in either step oscillation or sine-sweeping oscillation to measure its dynamic behaviors, including mold displacement and hydraulic cylinder pressure. Due to non-linear properties, the dynamic behavior change according to excitation conditions during sine-sweeping oscillation. Primarily, peak frequencies around 50 Hz are found from experimental pressure-displacement data in the frequency domain. To identify the oscillating mechanisms, equivalent 1-DOF and 2-DOF mass-damper-spring models for the mold oscillator are established. The fundamental system property is derived by experiment and a finite element multi-body dynamics model. In addition, inverse dynamics and numerical analysis are applied to derive the unknown force from the hydraulic servo system and structural characteristics. The unknown force is related to a friction problem and an elastic deflection by relative components near the mold. For high accuracy control, the unknown force model by an additional mass-spring model that causes high-frequency vibrations at 49, 48, 47, 46, or 45 Hz is suggested to formulate the equation of motion with the additional vibrations without any arbitrary modeling process.
Research Paper
Optimization
Ehsanolah Assareh; Iman Poultangari; Afshin Ghanbarzadeh
Abstract
With pitch angle control, wind turbines can retain power generated at high speeds of wind and avoid severe mechanical stress. By varying the angle of the blades of the wind turbines, they can keep the power generated up near the maximum amount. A controller based on PI is suggested due to control angle ...
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With pitch angle control, wind turbines can retain power generated at high speeds of wind and avoid severe mechanical stress. By varying the angle of the blades of the wind turbines, they can keep the power generated up near the maximum amount. A controller based on PI is suggested due to control angle of the pitch of the wind turbine blades in the present study. Therefore, PI controller gains are tuned via hybridization of firefly evolutionary algorithm and MLP artificial neural network so that the controller at its output sends a suitable control signal to the pitch actuator and thus varies the blades pitch angle appropriately to preserve power of the generator at a nominal amount even at high wind speeds. Simulating and analyzing the results was done by employing a five MW wind turbine made by National Renewable Energy Laboratory based on FAST software code. The simulation of the method showed that its performance is good.
