Academic literature on the topic 'Diaphragm power input'

AbstractThe synthetic jet actuators are one of the most investigated types of actuators used in heat transfer and active flow control. The energetic efficiency of actuators is a key parameter determining the possibility of device use. The actuators with two or more diaphragms have higher efficiency than the actuators with only one. The paper presents the investigations of the acoustic synthetic jet actuator with two opposite diaphragms. In the paper, synthetic jet velocity, Reynolds number and the energetic efficiency as a function of oscillating actuator frequency, for a different cavity, orifice configuration and one real input power P0 = 2 W were studied. The possibility of theoretical calculation of first and second resonance frequency were checked. The coupling ratio for actuators was calculated. The maximum energetic efficiency was η = 8.67% and Reynolds number Re = 8503. The possibility of using the same dependencies and rules during the design of actuators with two opposite diaphragms as in the case of actuators with one diaphragm was demonstrated. The results may be useful in the design of the actuators of the two membranes.

The paper presents the preliminary results of the experimental investigation of four various loudspeakers used for driving the synthetic jet actuator. The parameters, characteristic synthetic jet velocity, pressure inside the cavity, device sound pressure level (SPL), and the heat sink thermal resistance, were presented for various input power and driving frequency. The resonance frequency was determined based on electrical impedance. The highest synthetic jet momentum velocity was achieved at diaphragm resonance frequency. The maximum sound pressure level was observed, also at resonant frequency. For the same real power delivered to the actuator and for its resonance frequency, the heat sink thermal resistance had the lowest value for the specific loudspeaker. In turn, the synthetic jet velocity reached maximum for this actuator. For all actuators tested, the sound pressure level was dependent on momentum velocity.

We introduce a shape memory alloy (SMA) actuated micropump optimized for drug delivery applications. The proposed novel design integrates a built-in replaceable drug reservoir within the pump package forming a self-contained preloaded capsule pump with an overall pump volume of 424.7 μL. The new design results in a compact, simple, and inexpensive micropump and reduces the probability of contamination with attained almost zero dead volume values. The pump consists of NiTi-alloy SMA wires coiled on a flexible polymeric enclosure and actuated by joule heating. Unlike diaphragm and peristaltic SMA micropump designs that actuate transversely, our design is actuated longitudinally along the direction of the highest mechanical compliance resulting in large strokes in the order of 5.6 mm at 27% deflection ratio, actuation speed up to 11 mm/s, and static head pressures up to 14 kPa (105 mmHg) at 7.1 W input power; thus, high throughputs exceeding 2524 μL/min under free convention conditions could be achieved. A model was developed to optimize the pump’s geometrical parameters and the enclosure material. The model concluded that low stiffness enclosure material combined with thinner SMA wire diameter would result in the maximum deflection at the lowest power rating. To prove its viability for drug delivery applications, the pump was operated at a constant discharge volume at a relatively constant static head pressure. Furthermore, a design of bicuspid-inspired polymeric check-valves is presented and integrated onto the pump to regulate the flow. Since the built-in reservoir is replaceable, the pump capsule can be reused multiple times and for multiple drug types.

Summary A new technique for obtaining water-oil capillary pressure curves, based on nuclear magnetic resonance (NMR) imaging of the saturation distribution in flooded cores is presented. In this technique, a steady-state fluid saturation profile is developed by flooding the core at a constant flow rate. At the steady-state situation where the saturation distribution no longer changes, the local pressure difference between the wetting and nonwetting phases represents the capillary pressure. The saturation profile is measured using an NMR technique and for a drainage case, the pressure in the nonwetting phase is calculated numerically. This paper presents the NMR technique and the procedure for calculating the pressure distribution in the sample. Inhomogeneous samples produce irregular saturation profiles, which may be interpreted in terms of variation in permeability, porosity, and capillary pressure. Capillary pressure curves for North Sea chalk obtained by the new technique show good agreement with capillary pressure curves obtained by traditional techniques. Introduction Accurate petrophysical properties of reservoir rock such as capillary pressure, permeability, and relative permeability functions are essential as input for reliable oil in place estimations and for the prediction of the reservoir performance. Traditional methods for capillary pressure measurements are the mercury injection method, the diaphragm method, and the centrifuge method. In the mercury injection method,1 the nonwetting phase is mercury which displaces a gas. The samples are usually evacuated to a low pressure and Hg is then injected in steps allowing for pressure equilibrium at each step, or alternatively Hg is continuously injected. Corresponding data on injected volume of Hg and the injection pressure are recorded. This technique is widely used for measuring capillary pressure functions for low permeability rocks. This is primarily because it is generally believed that pressure equilibrium in each pressure step is readily obtained, while this is normally a problem for other methods where a liquid is the wetting phase. The disadvantage of this technique is the uncertainty in the scaling of the measured data to reservoir fluid data and conditions. In the diaphragm method or porous plate method, the problem concerning the scaling of the measured data is avoided, since this technique allows for the direct use of reservoir fluids. A water saturated sample is placed on a water-wet diaphragm to impose a boundary condition pc=0 to the wetting phase, i.e., the wetting phase is allowed to drain through the outlet end of the sample, at the same time as the nonwetting phase (oil or gas) is impeded. Pressure is added to the nonwetting phase and through a limited number of pressure steps, the capillary pressure curve is recorded. However, an important requirement is that equilibrium is obtained at each pressure step. This is the major problem when the diaphragm method is used on microporous materials. The drainage time may be considerable for each step, e.g., several weeks. In recent studies, thin micropore membranes have been used in an attempt to reduce the experimental time.2 Such a reduction will be less pronounced for low permeability rocks such as chalk since the flow resistance in the core is relatively more important. In the centrifuge method, the amount of liquid produced from the outlet end of the plug sample at a certain spin rate is read directly from a measuring tube during rotation. From the geometry of the centrifuge, the spin rate and the average fluid saturation in the plug, it is possible to calculate the capillary pressure relative to the inlet end of the sample.3 However, a number of assumptions must be made3,4: the sample must be homogeneous and have a well-defined outlet pressure boundary condition, i.e., condition pc=0, and drainage equilibrium must be established at each spin rate. Most of these conditions can only be approximated in practice. For the centrifuge method, the condition of drainage equilibrium may be questionable even for sandstone samples.5 Slobod6 reported that equilibrium had not been attained for a 2 mD sample after 20 hr of spinning. King7 concluded that low permeability rock samples may suffer from very long equilibrium times. After 10 days of spinning in the centrifuge, a Berea sandstone sample of 200 mD had just reached equilibrium. The objective of the development of the method presented here has been to avoid some of the disadvantages of the conventional methods described above. In this method a capillary pressure curve is obtained from a measured saturation profile after flooding the core. A similar experimental procedure was used by Richardson et al.8 to study end effects associated with flooding processes. The technique described here can be used with reservoir fluids. There is no porous plate to increase the flow resistance and the measurement of the capillary pressure function can be an integrated part of traditional flooding processes as performed with, e.g., unsteady-state relative permeability measurements. Only a very limited number of steps are needed, in principle only one step is required, therefore the time requirement for obtaining drainage equilibrium has not proved to be a problem. The technique utilizes the unavoidable end effect present in experiments with low permeability rocks. The capillary pressure function is obtained from the steady-state saturation profile in the core at drainage equilibrium.

pontomedullary respiratory network generates the respiratory pattern and relays it to bulbar and spinal respiratory motor outputs. The phrenic motor system controlling diaphragm contraction receives and processes descending commands to produce orderly, synchronous, and cycle-to-cycle-reproducible spatiotemporal firing. Multiple investigators have studied phrenic motoneurons (PhMNs) in an attempt to shed light on local mechanisms underlying phrenic pattern formation. I and colleagues (Marchenko V, Ghali MG, Rogers RF. Am J Physiol Regul Integr Comp Physiol 308: R916–R926, 2015.) recorded PhMNs in unanesthetized, decerebrate rats and related their activity to simultaneous phrenic nerve (PhN) activity by creating a time-frequency representation of PhMN-PhN power and coherence. On the basis of their temporal firing patterns and relationship to PhN activity, we categorized PhMNs into three classes, each of which emerges as a result of intrinsic biophysical and network properties and organizes the orderly contraction of diaphragm motor fibers. For example, early inspiratory diaphragmatic activation by the early coherent burst generated by high-frequency PhMNs may be necessary to prime it to overcome its initial inertia. We have also demonstrated the existence of a prominent role for local intraspinal inhibitory mechanisms in shaping phrenic pattern formation. The objective of this review is to relate and synthesize recent findings with those of previous studies with the aim of demonstrating that the phrenic nucleus is a region of active local processing, rather than a passive relay of descending inputs.

Abstract There is generally limited guidance available on the optimum clamping method for the diaphragms used in the synthetic jet actuators (SJAs). This paper describes the effects of clamping methods (O-rings, neoprene rubber washers and metal-to-metal clamping) on the actuator diaphragm displacement using Polytec scan vibrometer (PSV). Once the clamping type was implemented, an optimization study to examine the effect of geometrical parameters for three designs of synthetic jet actuators in quiescent conditions—in particular the number of orifices per cavity, the space between them, and their effects on the jet velocity—was performed. It has also been shown that with use the Helmholtz resonance of the cavity and amplitude modulation of the excitation signal, the actuator can exhibit a more significant “blowing” velocity at a reduced power input.

Analysis, design, fabrication, and experimental assessment of a symmetric three-phase free-piston Stirling engine system is discussed in this paper. The system is designed to operate with moderate-temperature heat input that is consistent with solar-thermal collectors. Diaphragm pistons and nylon flexures are considered for this prototype to eliminate surface friction and to provide appropriate seals. In addition, low loss diaphragm pistons, etched and woven-wire screen heat exchangers, and plastic flexures, as the main components of the system, are outlined. The experimental results are presented and compared with design analysis. Experiments successfully confirm the design models for heat exchanger flow friction losses and gas spring hysteresis dissipation. Furthermore, it is revealed that gas spring hysteresis loss is an important dissipation phenomenon for low-power Stirling engines and should be carefully addressed in design. Analysis shows that the gas hysteresis dissipation is reduced drastically by increasing the number of phases in a multiphase Stirling engine system. It is further shown that for an even number of phases, half of the engine chambers could be eliminated by utilizing a reversing mechanism within the multiphase system. The mathematical formulation and modal analysis of multiphase Stirling engine system are then extended to a system that incorporates a reverser. By introducing a reverser to the fabricated prototype, the system successfully operates in engine mode. The system proves its self-starting capability and validates the computed start-up temperature.

AbstractThe increasing use of polymer solutions as support fluids in pile drilling, diaphragm walling or tunnelling applications demands a more detailed discussion of their penetration behaviour and prediction thereof. In this context, the capillary bundle approach can be a useful tool. However, while it is widely discussed in the oil and gas application, the subject is currently addressed only scarcely with regard to support fluid penetration targeting stagnation, where small flow velocities and non-cohesive soil environments are of relevance. In these boundary conditions, the applicability of capillary bundle approaches is not yet sufficiently confirmed and substantiated. The current paper thus reviews current capillary bundle models based on Hagen–Poiseuille in combination with a power-law rheological model and discusses their applicability with respect to support fluid application in the context of experimental soil permeation tests for small gradients ($$i\le 10$$ i ≤ 10 ). Two granular materials of similar grain size, but different angularity (glass beads and sand), and four polymer solutions varying in polymer chain length and concentration are investigated, and the impact of model assumptions and bulk material input variables is systematically discussed. The experimental results show that the theoretical models are generally able to predict the filter velocity qualitatively for values above $${\bar{v}}=5\times 10^{-7}$$ v ¯ = 5 × 10 - 7 m/s and also quantitatively, when an empirical shift factor $$\alpha ^*$$ α ∗ is introduced and water permeability values are determined experimentally. With respect to the influence of soil parameters, it was found that the soil particle roughness decreases the flow velocity of the polymer solution despite similar hydraulic conductivity in water. Polymer chain length and concentration were observed to control the degree of possible dilution ($$\alpha ^*<1$$ α ∗ < 1 ) in the porous system compared to bulk rheological characteristics. It can therefore be concluded that capillary bundle models can indeed be applied in the targeted fields even though they are unable to predict a complete stagnation for $$i>0$$ i > 0 . However, rather than specific model assumptions for tortuosity, taking into account the specific soil-polymer interaction has shown to be of primary importance to ensure no under- or over-prediction of penetration velocities solely based on bulk rheology.

[Truncated abstract] The function of the diaphragm as a volume pump has not been adequately evaluated because there are no accurate methods to measure the volume displaced by diaphragm motion (ΔVdi). As a consequence, the work done, power output and efficiency of the diaphragm have not been measured. Efficiency of the diaphragm could be measured by relating the power output of the diaphragm to its neural activation. The aims of this thesis were to (a) develop a new biplanar radiographic method to measure ΔVdi and use this to evaluate the effect of costophrenic fibrosis and emphysema on ΔVdi, (b) develop a new fluoroscopic method to enable breath-by-breath measurements of ΔVdi, (c) evaluate a method for quantifying neural activation of the diaphragm, and (d) combine measurements of transdiaphragmatic pressure, ΔVdi, inspiratory duration and neural activation of the diaphragm to quantify the neuromechanical efficiency of the diaphragm

Hydraulic cylinders are the most common actuators for small, passive hydraulic systems. Friction and leakage of the actuators are the most crucial factors for force and volume efficiency. Development of a frictionless and leak-free cylinder would enable implementation of a passive human body controlled device. Due to the limitation of short stroke length in commercial rolling diaphragm (RD) cylinders, a novel fabric-elastomer long-stroke rolling diaphragm (LSRD) cylinder was developed, evaluated, and compared to the commercial rolling diaphragm, O-ring, and gap seal cylinders. The LSRD cylinder has low friction, zero leakage, and can operate at up to 700 kPa (100 psi). The performance of the LSRD cylinders was evaluated using an antagonist hydraulic transmission benchtop device. Axial motion of the LSRD cylinders was converted to a rotary motion on the input and output shafts using timing belts and pulleys. Two LSRD cylinders were engaged on each shaft and two lever arms were used to control the transmission device. A rotation of 90 degrees was achieved using LSRD cylinders with 1.5-inch stroke length. Friction, stiffness, tracking, impulse response, and step response tests were performed at 70, 170, and 275 kPa (10, 25, and 40 psi) preload pressures to evaluate the transmission device and LSRD cylinder dynamic performance. The results demonstrated that at least 275 kPa preload pressure is needed to have a satisfactory performance. The passive antagonist hydraulic transmission can be used in applications such as wearable robots and telepresence devices.

Common quarter-turn (QT) mechanisms used in nuclear plant air-operated valves (AOVs) include scotch yoke, lever, and link-and-lever mechanisms coupled to diaphragms and pistons. QT mechanism efficiency varies as a function of valve position and is a critical design input used to determine AOV margin. Because of the lack of publicly available data of a quality commensurate with “nuclear QA [quality assurance],” Kalsi Engineering, Inc. (KEI), initiated an independent QT-mechanism efficiency test program that includes a number of commonly used actuator manufacturers, models, and sizes based on a survey of U.S. nuclear power plants. The first test specimen was a diaphragm actuator with a lever QT mechanism. The diaphragm rod of the test specimen was instrumented with strain gauges so that a direct measurement of the net actuator force transmitted to the QT mechanism could be measured. In addition to the net thrust, the output torque, diaphragm pressure, and actuator position were measured. Measuring the net thrust, diaphragm pressure, and position allowed the spring rate, spring preload, and effective diaphragm area to be quantified. This test specimen was tested using two different types of bearings at the actuator shaft-to-lever connection. Needle bearings were used to provide torque results for a nearly frictionless QT mechanism, and bronze bearings were used to simulate a more realistic QT-mechanism configuration. Predictions made using the first-principles efficiency model are compared to efficiencies extracted from test. The predicted efficiency using a realistic range for the friction coefficient of the bronze bearings is in good agreement with the extracted efficiencies. Paper published with permission.

Most of the noise prediction methods, which has already been used, only applicable at low frequency range, below the first transverse duct mode. A developed method at this work, which suggested by Schram, avoided many simplification assumptions and is quite powerful for high Helmholtz numbers, i.e. when the turbulence/body interaction region is acoustically non-compact. By using numerical methods and an appropriate Green function, the method is applied to the prediction of sound in a duct obstructed by a diaphragm. The source fluctuations of the flow field are computed by a large-eddy simulation (LES) and are fed to the following acoustical computation as input data. The predicted power spectrum shows a fairly good agreement with a direct noise computation (DNC) results.

Kalsi Engineering, Inc. (KEI), initiated an independent test program that includes a number of actuator manufacturers, models, and sizes based on a survey of United States (U.S.) nuclear power plants. The test matrix includes evaluation of the effect of the key parameters on the effective diaphragm area (EDA) throughout the stroke. These parameters include stroke position, pressure, materials, measurement uncertainty, and manufacturing tolerances. Because of differences in the test data obtained by different sources for the same actuator type and size, systematic test procedures have been developed by KEI to address differences in the testing methods and test configurations, including testing of a balanced actuator (no spring in the actuator) vs. a spring-return actuator of the same diaphragm size. The effect of elevated temperature and aging may also be included later by testing a selected number of actuators based on industry input. The benefit of this program is to provide reliable data for air-operated valve (AOV) design-basis evaluations as required by U.S. Nuclear Regulatory Commission (NRC) Regulatory Issue Summary (RIS) 2000–03. This paper presents the results for the Masoneilan Model 38 Size 18 diaphragm actuator, which show that EDA is both position- and pressure-dependent. Paper published with permission.

In this paper the Active Vibration Control (AVC) of a three-story gantry type structure is designed. AVC is a viable solution to decrease drift (relative displacement between the slabs) in civil structures under seismic excitation. The structure under consideration is composed by six individual gantries. Dynamic models of these individual components are obtained using classical structural dynamic methods and include a reduction of its degree of freedom (DOF). The complete model of the three-story structure is obtained assuming a rigid diaphragm behavior of the slabs. This model is a multi-input, multi-output linear ordinary differential equation (ODE) including nine DOF. The obtained ODE equation is transformed to its equivalent multi-input MIMO state space realization. The state space format is the require representation to easily apply the proposed LQR, LQG and H∞ control techniques. In addition, this work considers the possible location of the PZT actuators within the structure. Real seismic data were used to test the system performance. The controlled system response shows a substantial improvement when compared to the non-controlled structure behavior.

Combined cycle units have become very popular in recent years as a source of power generation. Such units have a gas turbine as the topping cycle and a steam turbine as the bottoming cycle and can reach combined cycle efficiencies as high as 60%. The exhaust from the gas turbine is passed through a heat exchanger in which steam is generated for the steam turbine. This combined arrangement makes it less polluting as well. An important element of a combined cycle power plant is the steam turbine, which is the subject of this paper. Improvements to the design of advanced steam turbines require an improved understanding of the heat transfer within the various components of the unit. Physics-based ANSYS models for typical GE high pressure and intermediate pressure units have been developed. Components such as the rotor, diaphragm, and shells have been analyzed. The boundary conditions were derived from full-load, steady state flow analyses, steam turbine performance code outputs and computational fluid dynamics (CFD) analyses to develop normalized (non-dimensional) local flow conditions, with the normalizing parameters based on key cycle parameters. These normalized local flow conditions and cycle parameters were then used to define local transient boundary temperatures and heat transfer coefficients for input to the thermal ANSYS models. Transient analyses of components were performed. The results were compared with temperature measurements taken during the complete cycle of an operational steam turbine to validate and improve the methodology, and were applied to structural models of the components to predict their thermal growth and the net impact on the clearance between the rotor and diaphragms and other secondary flow paths in the steam turbine, including the packing seals. This paper will focus on the thermal modeling of a typical steam turbine. It will discuss the process used (summarized above) and the basic equations employed in the analyses. Results will be compared with shell temperature measurements obtained during the start up of a steam turbine in the field. Implications of the thermal results on power systems operation will be discussed. Plans for future improvements will be presented.

Conventional Thermoacoustic-Piezoelectric (TAP) energy harvesters convert thermal energy, such as solar or waste heat energy, directly into electrical energy without the need for any moving components. The input thermal energy generates a steep temperature gradient along a porous medium. At a critical threshold of the temperature gradient, self-sustained acoustic waves are developed inside an acoustic resonator. The associated pressure fluctuations impinge on a piezoelectric diaphragm, placed at the end of the resonator. The reverse phenomenon results in piezo-driven thermoacoustic refrigerators (PDTARs). A pressure wave driven by a piezo-speaker induces a temperature gradient across the porous body. In this study, the TAP harvester and the PDTAR are coupled with auxiliary elastic structures in the form of simple spring-mass systems to enhance their performance. The proposed addition is referred to as a dynamic magnifier and has been shown in different areas to amplify significantly the deflection of vibrating structures. A comprehensive model of the dynamically magnified thermoacoustic-piezoelectric (DMTAP) system has been developed earlier that includes equations of motions of the system’s mechanical components, the harvested voltage, the mechanical impedance of the coupled structure at the resonator end as well as the equations necessary to compute the self-excited frequencies of oscillations inside the acoustic resonator. Theoretical results confirmed significant amplification of the harvested power is feasible if the magnifier’s parameters are properly chosen. The performance of experimental prototypes of a DMTAP harvester and a PDTAR with a dynamic magnifier are examined here. The obtained experimental findings are validated against the theoretical results. Dynamic magnifiers serve as a novel approach to enhance the effectiveness of thermoacoustic energy harvesting and refrigeration.

Improvements to the design of advanced steam turbines require an improved understanding of the heat transfer within the various components of the unit. Physics-based ANSYS models for typical high pressure and intermediate pressure units have been developed. The boundary conditions were derived from full-load, steady state flow analyses, steam turbine performance code outputs and computational fluid dynamics (CFD) analyses to develop normalized (non-dimensional) local flow conditions, with the normalizing parameters based on key cycle parameters. These normalized local flow conditions and cycle parameters were then used to define local transient boundary temperatures and heat transfer coefficients for input to the thermal ANSYS model. Transient analyses of components were performed. The results were compared with temperature measurements taken during the operating cycle of an operational steam turbine to validate and improve the methodology and were applied to structural models of the components to predict their thermal growth and the net impact on the clearance between the rotor and diaphragms and other secondary flow paths in the steam turbine, including seals.

This paper presents power generation performance of unimorph PZT (lead zirconate titanate) cymbal harvesters optimally designed for the power requirements of a specific application. Proof-of-concept work has shown that the traditional cymbal design can be adapted to a new design that is capable of sustaining higher mechanical loads by replacing the piezoelectric plate with a unimorph circular piezoelectric diaphragm between the metal end caps. The unimorph circular diaphragm is constructed by bonding PZT to a steel substrate to provide increased strength. Additional work was performed to prepare the new cymbal design for large-scale implementation in a variety of applications. The parameters that affect energy harvesting performance for the cymbal structure are first optimized by parametric studies to produce optimum generated energy from a specific range of applied cyclic forces. Key parameters in the unimorph PZT cymbal design include the material properties and the dimensions of the end caps, the ratios of the diameters of the unimorph disc and the end cap cavity, and thickness ratio of the PZT layer and the substrate. Based on the optimized unimorph PZT cymbal structure, a specimen was then fabricated and tested on the load-frame to validate analytically predicted energy generating performance. The specimen was tested under a 1 Hz cyclic load of up to 2,100 N. The measured open circuit output voltages for two different load inputs were in accordance with the analytical prediction.