Search Results (14)

Rectangular aqueducts are critical building structures in large-scale water conveyance systems used worldwide. Liquid sloshing can produce hydrodynamic forces that threaten structural safety and long-term performance. This study analytically investigates the vibration characteristics of two-dimensional rectangular cantilever aqueduct systems while accounting for soil–structure interaction (SSI). To reduce sloshing and enhance the performance of the mechanical system, a bottom-mounted vertical baffle is proposed as a hydrodynamic damping solution. Through subdomain analysis, mathematical expressions for liquid potential fields are derived. The continuous liquid is represented through discrete mass–spring elements for dynamic analysis. Horizontal soil impedance is characterized by using Chebyshev orthogonal polynomial approximations with optimized least squares fitting techniques. A dynamic mechanical model for the soil–aqueduct–liquid–baffle coupling system is developed by using the substructure method. Convergence and comparative studies are conducted to validate the reliability of the proposed method. Between the current results and those reported previously, the variation in the first-order sloshing frequency is less than 1.10%. Parametric analyses evaluate how baffle size, baffle position, and soil properties influence sloshing behavior. The presentation of an equivalent analytical model is the novelty of this research. The results can provide the theoretical basis for optimizing anti-sloshing designs in hydraulic building structures, thereby supporting safer and more sustainable engineering practices. Full article

Ever-increasing demands to improve fuel burn efficiency of aero gas turbines lead to rises in fuel system pressures and temperatures, posing challenges for the structural integrity of the pump housing and creating internal deflections that can adversely affect volumetric efficiency. Non-invasive strain and vibration measurements could allow transient effects to be quantified and considered during the design process, leading to more robust fuel pumps. Fuel pumps used on a high bypass turbofan engine were instrumented with optical fibre Bragg grating (FBG) sensors, strain gauges and thermocouples. A hydraulic hand pump was used to facilitate measurements under static conditions, while dynamic measurements were performed on a dedicated fuel pump test rig. The experimental data were compared with the outputs from a finite element (FE) model and, in general, good agreement was observed. Where differences were observed, it was concluded that they arose from the sensitivity of the model to the selection of nodes that best matched the sensor location. Strain and vibration measurements were performed over the frequency range of 0 to 2.5 kHz and demonstrated the ability of surface-mounted FBGs to characterise vibrations originating within the internal sub-components of the pump, offering potential for condition monitoring. Full article

Determining the friction coefficients for uniform flows over very rough bottoms is a long-standing problem in open-channel hydraulics and river engineering. This experimental study presents measurements of the surface deformation as well as Darcy–Weisbach and Manning friction coefficients for steady, turbulent (6058 $\le \mathcal{R}e\le$ 28,502), and subcritical flows (0.14 $\le \mathcal{F}r\le$ 0.52) over large roughness elements, where $\mathcal{F}r$ and $\mathcal{R}e$ denote the Froude and Reynolds numbers, respectively. The experiments were conducted in a rectangular, inclined flume with a train of half-cylinders mounted on the bed, with radii in the range 20 mm $\le a\le$ 50 mm. These obstacles yield a relative submergence 1.45 $\le h_N/a\le$ 4.41 and a constant spacing ratio $e/a=12.8$ across all experimental runs, where $h_N$ and e denote the normal flow depth and the center-to-center spacing between cylinders, respectively. The relative amplitude of the surface profiles, ($\Delta h/a$), was analyzed and found to correlate strongly with $h_N/a$, $\mathcal{R}e$ and $\mathcal{F}r$. The results reveal very high values of the Darcy friction factor, f, which follows scaling laws of the form ${f\propto (h_N/a)}^{\widehat{n}}$, with $\widehat{n}<0$, independent of a, and ${f\propto \mathcal{R}e}^{\beta }$, where $\beta <0$ is closely linked to a. Scaling relationships for the Manning roughness coefficient, (n), were also investigated and are reported herein. Full article

The aim of this study is to propose a damper based on magnetorheological (MR) fluid and elastomer for application in vehicle engine mounting systems to dissipate the vibration energy transferred from the engine to the vehicle body. The magnetic circuit structure of the damper has been precisely designed, and its reasonableness has been verified by static magnetic field simulation. After the principle prototype’s completion, the damper’s mechanical properties are tested by an electro–hydraulic servo fatigue machine. The results show that with the current increase, the damper’s in-phase stiffness increases by 20.6%. The equivalent damping improves by 81.6%, which indicates that the damper has a good MR effect. A new phenomenological model is proposed, and a genetic algorithm is used to identify the parameters of the model. Finally, a 1/4 vehicle engine vibration damping system model is established and a dynamics simulation is carried out. The simulation results show that the damper effectively reduces the vibration transmitted from the engine to the body, and the vibration-damping effect is even more obvious through sky-hook control. This proves that the damper proposed in this study has good vibration-damping performance. Full article

For the vibration of automobile powertrain, this paper designs electro–hydraulic composite engine mounts. Subsequently, the dynamic characteristics of the hydraulic mount and the electromagnetic actuator were analyzed and experimentally studied separately. Due to the strong nonlinearity of the hybrid electromechanical engine mount, a Fractional-Order Least-Mean-Square (FGO-LMS) algorithm was proposed to model its secondary path identification. To validate the vibration reduction effect, a rapid control prototype test platform was established, and vibration active control experiments were conducted based on the Multiple–Input Multiple–Output Filter-x Least-Mean-Square (MIMO-FxLMS) algorithm. The results indicate that, under various operating conditions, the vibration transmitted to the chassis from the powertrain was significantly suppressed. Full article

Engine mounts serve three primary purposes: (1) to support the weight of the engine, (2) to lessen the transmitted engine disturbance forces to the vehicle structure/chassis or airplane fuselage, and (3) to limit the engine motion brought on by shock excitations. The engine mount’s stiffness must be high to control large engine motions and low to control chassis or vehicle body vibration. When hydraulic engine mounts are used, a device called a decoupler creates the dual stiffness requirement. However, numerous investigations have shown that the decoupler has the potential to rotate within its cage bound and become stuck or sink and obstruct fluid flow between the fluid chambers due to a density mismatch between the decoupler and the working fluid. In addition, most hydraulic engine mounts with a decoupler no longer act as vibration isolators but as hydraulic dampers. This study suggests a new amplitude-sensitive hydraulic engine mount design without a decoupler, where the vibration isolation of the engine mount is retained and there is a 75% reduction in the peak frequency, which further enhances the engine mount’s capabilities in comparison to the current hydraulic engine mounts with a decoupler. The new design concept and its mathematical model and simulation results will be presented. Full article

A hydraulic engine mount (HEM) is an advanced tuned mass damper (TMD) system used to isolate the noise and vibration from the engine to the chassis. This paper aims to design a semiactive HEM based on the TMD model, which only tunes damping without affecting the other lumped parameters of the TMD system. Firstly, the dynamic equations of an HEM modeled as a TMD system are derived based on the linear lumped parameter model (LPM). Each lumped parameter of the HEM is analyzed to identify the relevant parameters that affect damping. Secondly, a newly designed semiactive HEM design is proposed that utilizes a helical moving plate to simultaneously control both the inertia track area and length, resulting in precise damping tuning. To illustrate the dynamic performance of the newly designed HEM, calculations are presented based on various parameters for its tunable damping range and dynamic stiffness spectrum. Additionally, to demonstrate the performance of vibration isolation, this paper determines the optimal length and dynamic stiffness of the inertia track to minimize the transmissibility. Thirdly, to reveal the superiority of the newly designed HEM over the MR fluid mount, an example is presented where the MR fluid medium is used in place of conventional hydraulic fluid in the HEM while keeping all other parameters constant. Specifically, the novel semiactive HEM employs conventional hydraulic fluid and is spiral-driven by a moving plate while the MR fluid-based HEM is controlled by an additional tunable magnetic intensity controller. The nonlinear LPM of the newly designed HEM is verified by comparing the dynamic stiffness spectrum with the experimental results in the published literature. Then, the nonlinear LPM of the MR fluid mount is established, and its dynamic stiffness spectrum is calculated and compared with that of the newly designed HEM. The results indicate that the newly designed HEM and MR fluid mount have similar ranges of dynamic stiffness control, but the newly designed HEM does not require expensive MR/ER fluid or additional continuous external energy input to regulate the dynamic stiffness. Moreover, when using inexpensive low-viscosity hydraulic fluid, the newly designed HEM can provide a wider range of dynamic stiffness control. Full article

In most Asian countries, farmers have smallholdings ranging from one to two hectares. The tractor-mounted boom sprayers cannot practically be used in small size farms with divided plots and complex terrain. To cope with these issues, a prototype self-propelled crop sprayer was developed, including a 20-hp engine, 300 L liquid tank, and hydraulically-controlled spray boom with eight hollow cone nozzles. The spray symmetry of the hollow cone nozzle was evaluated under four pressures (2.5, 3, 3.5, and 4 bar) in the laboratory. The operating parameters of the sprayer, such as forward speed (4, 6, and 8 km h⁻¹), spray height (40, 55, and 70 cm), and pressure (3, 5, and 7 bar) were optimized by measuring three spray characteristics including droplet density, coverage percentage, and Volume Median Diameter (VMD) in the cotton field. The results revealed that the nozzle spray was symmetrical at 2.5 and 3 bar pressure as the R² value was higher than 0.96. The field test result showed that in all treatments, treatments T14 (6 km h⁻¹, 55 cm, 5 bar) and T22 (8 km h⁻¹, 55 cm, 3 bar) were suitable for spraying medium-to-low concentration solution (post-emergence herbicides and fungicides) and high concentration solution (insecticides and pre-emergence herbicides), respectively. The spray characteristics at treatments T14 and T22 were 64.7 droplets cm⁻², 26.7%, 230 µm, and 39 droplets cm⁻², 14.9%, and 219.8 µm respectively. The field efficiency of the sprayer was 61%. The spraying cost per unit area was 55–64% less compared to manual labor cost. In conclusion, a prototype self-propelled crop sprayer is an efficient and environment-friendly technology for small farms. Operating the sprayer at the optimal parameters also saves operational costs and time. Full article

This paper presents the results of studies on reducing the amount of vibrations in different frequency ranges generated by a combustion engine through the use of different types of engine mounts. Three different types of engine supports are experimentally and numerically analyzed, namely an elastomeric engine mount, an elastomeric engine mount with a hydraulic component and standard decoupling, and an elastomeric engine mount with a hydraulic component and a modified decoupler—with this engineering design being a novelty in the literature. Experimental tests that considered different excitation frequencies were performed for the three types of engine mounts. Experimental data for stiffness and damping were used to obtain nonlinear mathematical models of the two systems with hydraulic components through the use of an Artificial Neural Network (ANN). For the results, all of the mathematical models presented coefficients of determination, R², greater than 0.985 for both stiffness and damping, showing an excellent fit for the nonlinear experimental data. Numerical results using a quarter-car suspension model showed a large reduction in vibration amplitudes for the first vibration model when using the hydraulic systems, with values ranging between 48.58% and 66.47%, depending on the tests. The modified system presented smaller amplitudes and smoother behavior when compared to the standard hydraulic model. Full article

Active hydraulic mounts with an inertia track, decoupler membrane, and oscillating coil actuator (AHM-IT-DM-OCAs) have been studied extensively due their compact structure and large damping in the low-frequency band. This paper focuses on a comprehensive analysis of the active and passive dynamics and their fixed points in mid-low-frequency bands, which will be helpful for parameter identification. A unified lumped parameter mechanical model with two degrees-of-freedom is established. The inertia and damping forces of the decoupler/actuator mover may be neglected, and a nonlinear mathematical model can be obtained for mid-low-frequency bands. Theoretical analysis of active and passive dynamics for fluid-filled state reveals the amplitude dependence and a fixed point in passive dynamic stiffness in-phase or active real-frequency characteristics. The amplitude dependence of local loss at the fluid channel entrance and outlet induces the amplitude-dependent dynamics. The amplitude-dependent dynamics constitute a precondition for fixed points. A single fixed point in passive dynamics is experimentally validated, and a pair of fixed points in active dynamics for an AHM-IT-DM-OCA is newly revealed in an experiment, which presents a new issue for further analysis. Full article

In order to study the influence of the position of the bulb on the hydraulic performance of a submersible tubular pump device, based on a large-scale pumping station, two schemes—involving a front-mounted bulb and a rear-mounted bulb, respectively—were designed. The front-mounted scheme uses the GL-2008-03 hydraulic model and its conventional guide vane, while the rear-mounted scheme uses the optimized design of a diffuser vane. The method of combining numerical simulation and experimental testing was used to analyze the differences between the external and internal characteristics of the two schemes. The results show that, under the condition of reasonable diffusion guide vane design, the efficiency under the rear-mounted scheme is higher than that under the front-mounted scheme, where the highest efficiency difference is about 1%. Although the front-mounted bulb scheme reduces the hydraulic loss of the bulb section, the placement of the bulb on the water inlet side reduces the flow conditions of the impeller. Affected by the circulation of the guide vane outlet, the hydraulic loss of the outlet channel is greater than the rear-mounted scheme. The bulb plays a rectifying function when the bulb is placed behind, which greatly eliminates the annular volume of the guide vane outlet, and the water outlet channel has a smaller hydraulic loss. In the front-mounted scheme, the water flow inside the outlet channel squeezes to the outer wall, causing higher entropy production near the outer wall area. The entropy production of the rear-mounted scheme is mainly in the bulb section and the bulb support. This research can provide reference for the design and form selection of a submersible tubular pump device, which has great engineering significance. Full article

The aim of the research described in this paper is to analyse the synergistic effect of types of synthetic oil and their density on the value of the coefficient of friction (COF) of Ti-6Al-4V titanium alloy sheets. Lubrication performance of commercial synthetic oils (machine, gear, engine and hydraulic) was tested in a strip draw friction test. The friction tests consisted of pulling a strip specimen between two cylindrical fixed countersamples. The countersamples were placed in the simulator base mounted on a uniaxial tensile test machine. Due to the complex synergistic effect of different strip drawing test parameters on the COF, artificial neural networks were used to find this relationship. In the case of both dry and lubricated conditions, a clear trend was found of a reduction of the coefficient of friction with nominal pressure. Engine oil 10W-40 was found to be the least favourable lubricant in reducing the coefficient of friction of Grade 5 titanium sheets. The two main tribological mechanisms, i.e., galling and ploughing, played the most important role in the friction process on the test sheets. In the range of nominal pressures considered, and with the synthetic oils tested, the most favourable lubrication conditions can be obtained by using a type of oil with a low viscosity index and a high kinematic viscosity. Full article

Dynamic models of physical systems often contain parameters that must be estimated from experimental data. In this work, we consider the identification of parameters in nonlinear mechanical systems given noisy measurements of only some states. The resulting nonlinear optimization problem can be solved efficiently with a gradient-based optimizer, but convergence to a local optimum rather than the global optimum is common. We augment the dynamic equations with a morphing parameter and a proportional–integral–derivative (PID) controller to transform the objective function into a convex function; the global optimum can then be found using a gradient-based optimizer. The morphing parameter is used to gradually remove the PID controller in a sequence of steps, ultimately returning the model to its original form. An optimization problem is solved at each step, using the solution from the previous step as the initial guess. This strategy enables use of a gradient-based optimizer while avoiding convergence to a local optimum. The efficacy of the proposed approach is demonstrated by identifying parameters in the van der Pol–Duffing oscillator, a hydraulic engine mount system, and a magnetorheological damper system. Our method outperforms genetic algorithm and particle swarm optimization strategies, and demonstrates robustness to measurement noise. Full article

It is challenging for engineers to timely identify illegal ground intrusions in underground systems such as subways. In order to prevent the catastrophic collapse of subway tunnels from intrusion events, this paper investigated the capability of detecting the ground intrusion of underground structures based on dynamic measurement of distributed fiber optic sensing. For an actual subway tunnel monitored by the ultra-weak fiber optic Bragg grating (FBG) sensing fiber with a spatial resolution of five meters, a simulated experiment of the ground intrusion along the selected path was designed and implemented, in which a hydraulic excavator was chosen to exert intrusion perturbations with different strengths and modes at five selected intrusion sites. For each intrusion place, the distributed vibration responses of sensing fibers mounted on the tunnel wall and the track bed were detected to identify the occurrence and characteristics of the intrusion event simulated by the discrete and continuous pulses of the excavator under two loading postures. By checking the on-site records of critical moments in the intrusion process, the proposed detection approach based on distributed structural vibration responses for the ground intrusion can detect the occurrence of intrusion events, locate the intrusion ground area, and distinguish intrusion strength and typical perturbation modes. Full article