Silent Operation Research Articles

Advances in Electrochemical Hydrogen Compression and Purification

Electrochemical Hydrogen Compression (EHC) delivers pure gas at pressure on demand, with additional features such as single stage compression, no moving parts, silent operation and dynamic (reversible) flow control and low sensitivity to input pressure. Fast kinetics of hydrogen HOR/HER benefit the pump rate capability at the catalyst interface on the impermeable membrane. Here, we developed superior proton conductivity properties in combination with minimal hydrogen back-diffusion characteristics, to be able to compress to pressures as high as 100 MPa with competitive energy consumption. Results are shown at single cell and stack level pumping 2 kg hydrogen per day (also in the field), where relevant models indicate contributions from different processes and influence of operating conditions to the overall energy requirement (kWh/kg). This work will connect the inherent working principles behind this potentially disruptive technology, and its latest achievements, with the status quo of competing technologies, bringing forward near-future applications and energy scenarios.

Fuzzy Logic based Speed Control of BLDC Motor on Sensorless Technique for Space Applications

For space applications there is an increasing trend to move towards using Brushless Direct Current (BLDC) motors because of their high efficiency, silent operation, compact form, reliability, and low maintenance. Traditionally, BLDC motors are commutated in six-step pattern with commutation controlled by position sensors. BLDC motors do require rotor position information in order to select the appropriate commutation angle. To reduce cost and complexity of the drive system, sensorless drive is preferred. In this paper, circuits have been designed for sensorless control technique to be used in space application and carrying out its simulation in MATLAB using controller (FLC).The sensorless rotor position technique detects the zero crossing points of trapezoidal Back-EMF induced in the BLDC motor windings. Three phase Back-EMF Zero Crossing points are sensed while one of the three phase windings is not powered. The obtained information is processed in order to commutate the energized phase pair.

Hydrodynamic thrust generation and power consumption investigations for piezoelectric fins with different aspect ratios

Bio-inspired hydrodynamic thrust generation using piezoelectric transduction has recently been explored using Macro-Fiber Composite (MFC) actuators. The MFC technology strikes a balance between the actuation force and structural deformation levels for effective swimming performance, and additionally offers geometric scalability, silent operation, and ease of fabrication. Recently we have shown that mean thrust levels comparable to biological fish of similar size can be achieved using MFC fins. The present work investigates the effect of length-to-width (L/b) aspect ratio on the hydrodynamic thrust generation performance of MFC cantilever fins by accounting for the power consumption level. It is known that the hydrodynamic inertia and drag coefficients are controlled by the aspect ratio especially for L/b< 5. The three MFC bimorph fins explored in this work have the aspect ratios of 2.1, 3.9, and 5.4. A nonlinear electrohydroelastic model is employed to extract the inertia and drag coefficients from the vibration response to harmonic actuation for the first bending mode. Experiments are then conducted for various actuation voltage levels to quantify the mean thrust resultant and power consumption levels for different aspect ratios. Variation of the thrust coefficient of the MFC bimorph fins with changing aspect ratio is also semi-empirically modeled and presented.

Parametric Design of Gear Hob Cutter

The gears are some of the most used mechanical transmission due to the advantages its provide: constant transmission ratio, high power transmitted, high efficiency, small size, silent operation, precision kinematic, etc. This causes the wheel to be one of the most valuable machine elements both in terms of accuracy and processing technology as well. From the technological point of view due to high precision and productivity, one of the most methods used is processing with gear hob cutter. Although the tool profile does not depend on the number of teeth on the wheel, but only its module, large diversity of gear requires the design of gear hob cutters tailored to existing needs. As it is known the gear hob cutters are complicated and expensive gear cutting tools, both due to the manufacturing process and in terms of design, requiring a significant amount of calculations, high effort from the designer and consequently results in a large cycle of design. For this reason, the literature and in various websites, there are many studies and research information to optimize the design process and increase accuracy of gear hob cutters.

Permanent Magnet Motor Torsional Resonance Noise Reduction by Rotor Skew Phase Adjustment

SUMMARYHybrid Vehicles (HEVs) and Electric Vehicles (EVs) improve drive efficiency and reduce CO2 emissions by regenerative braking and operating the engine under optimum conditions. It is desirable to decrease the motor size and increase the maximum torque to minimize driving units. For these purposes, motors employing permanent magnets are now commonly used. The motor driving systems of HEVs and EVs must operate over variable speed ranges of up to 1:5. Over this large range, smooth, silent operation is desirable and important. The skew method is often adopted to ensure a smooth start and stop and silent operation by reducing torque ripple. However, this method possibly causes noise and motor vibration. This paper describes the mechanism of torsional resonance noise and vibrations arising from the skew method and a countermeasure to decrease them by optimizing the skew phase distribution on the rotating axis.

Miniature Piezoelectric Compressor for Joule-Thomson Cryocoolers

Joule-Thomson (JT) cryocoolers operate with a continuous flow of the working fluid that enters the cooler at a high pressure and leaves it at a lower pressure. Ideally, the temperature of the outgoing fluid equals the temperature of the entering fluid. JT cryocoolers that operate with pure refrigerants require high pressure of a few tens of MPa where the low pressure is usually around 0.1MPa. Circulation of the working fluid in such cases requires high pressure ratio compressors that evidently have large dimensions. JT cryocoolers can operate with much lower pressure ratios by using mixed-refrigerants. Cooling from 300K to about 80K in a single stage cryocooler normally requires a pressure ratio of about 1:25.In the present research a miniature compressor driven by piezoelectric elements is developed in collaboration between Rafael and the Technion. This type of compressor has the advantage of improved long life compared to other mechanical compressors, very low vibrations, and silent operation. In the current case, the design goal of the intake and discharge pressures has been 0.1 and 2.5MPa, respectively, with a flow rate of 0.06g/s. The compressor has two compression stages; 1:5 and 5:25.Several configurations have been considered, fabricated, and tested. The performance of the last configuration approaches the desired specification and is presented in the current paper together with the design concept.

Microfluidic Devices for Aerosol Speciation and Personal Exposure Assessment in Panel-Based Epidemiology

A need exists to develop simple, low-cost methods for aerosol speciation and air quality measurement to support both medium-to-large-scale epidemiology and citizen-based science. Our group has developed alternative approaches for aerosol speciation using microfluidic technologies designed to manipulate teardrop sample volumes. Traditional and paper-based microfluidics are poised to overcome many issues associated with chemical analysis of particulate matter (PM), namely: cost, ease-of-use, and sensitivity. Results can be read using either the naked eye or simple, low-cost instrumentation (i.e., a handheld or mobile device). Such assays cost only a few dollars and can be conducted by virtually anyone after simple training. We have developed microfluidic assays to measure reactive oxygen species and metals (Fe, Ni, Cu, Cr, Pb, Cd) in PM using a combination of colorimetric and electrochemical detection motifs. Detection limits of 0.1?g were achieved for colorimetric assays (appropriate for occupational exposures) while electrochemical assays provided detection limits of 0.1 ng (1 ppb solution levels; appropriate for ambient PM). We have also validated these techniques against standard reference methods with relatively good agreement. To complement these analytic techniques, our group has also developed a series of low-weight, low-burden personal air samplers. These air samplers feature micropumps that provide silent operation and a leap in energy efficiency that allows significant minimization. Initial prototypes weigh less than 150g, emit virtually no noise, and are about the size of a box of crayons. Production costs for these air sampling pumps are targeted for &lt; $100, about ten times less than current competing technologies.

Extraordinarily large swelling energy of iodine-treated poly(vinyl alcohol) demonstrated by jump of a film.

Organic material characteristics of volume change and stress generation have attracted the attention of many researchers aiming to develop chemomechanical systems such as artificial muscles and polymer engines having the advantages of high energy density and silent operation. Although polymer gels offer a relatively large actuator stroke, their mechanical properties are relatively poor and the working temperature is relatively low, often limited by the evaporation of liquid if contained. We have developed an iodine-treated poly(vinyl alcohol) having extraordinarily large vapor-induced deswelling stress reaching 59 MPa, which is one to two orders of magnitude greater than those of ordinary polymer gels. Furthermore, this material has extremely large volumetric and gravimetric energy densities reaching 1.3 × 106 J m−3 and 9.6 × 102 J kg−1, respectively, and an elastic modulus of a few GPa and is heat-resistant to at least 200 °C. The high performance of this material can be demonstrated by a jump of a film. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1357–1365

A Portable Oxygen Concentrator for Wound Healing Applications

Wound healing is a complex biological process that involves an organized cell assembly leading to tissue regeneration and repair, a process that requires oxygen. As has been reported in many studies, hypoxia delays wound healing; oxygen modulates the inflammatory response of the tissues and it serves as an infection control agent by enhancing the ability of leukocytes to kill bacteria when supplied in adequate amounts. In addition, it promotes collagen synthesis and stimulates angiogenesis. Most importantly, continuous oxygen application leads to wound closure, as has been shown in a number of clinical studies where closure rates as high as 80% have been observed for non-healing recalcitrant wounds. EPIFLO® (Ogenix, Beachwood, OH). (Figure 1) is a commercially available device that can deliver Transdermal Continuous Oxygen therapy and represents an inexpensive alternative to systemic hyperbaric oxygen therapy without the side effects of vasoconstriction, toxicity, and tissue destruction associated with the latter. EPIFLO is a light-weight (~100 g) electrochemical oxygen concentrator with no moving parts and silent operation. It generates continuously 3 mL/hour oxygen (98+% purity) and delivers to the wound site through a cannula tubing. It employs leading-edge oxygen ‘fuel cell’ concentration technology to stimulate tissue regenerative processes driving closure of delayed-healing acute or chronic wounds. This product is US FDA approved for a broad range of indications as a Class II Medical Device; prescribed on order of a physician. It is also CE, ISO 13485:2003 and CMDCAS (Canadian Medical Devices Conformity Assessment Scheme) Health Canada Certified The heart of the device is a Membrane Electrode Assembly (MEA) consisting of a perfluorosulfonic acid cation exchange membrane, such as NafionR, interposed between two high area electrodes made of finely divided Pt based metal catalysts (Figure 2). Atmospheric air composed mostly of ~ 21 % oxygen, 78 % nitrogen is exposed to the device through the slots in the seam formed between the lid and the bottom part of the enclosure, where when activated using a small battery, it promotes the reduction of dioxygen at the cathode and the oxidation of water at the anode to produce oxygen delivered through a suitable tubing to the wound. Since the cation exchange membrane has overall very low gas permeability, gases cannot permeate through the membrane, thus ensuring a higher than 98% purity of the product oxygen. This presentation will describe the critical steps involved in the bench-to-shelf process, invention to product, as well as the highly promising results found from its use in recalcitrant patients.

A multi-functional design approach and proposed figure of merits for solid state lighting systems

Energy has been identified as one of the most important problems during the last few years. One of energy efficient technologies may reduce consumed energy in buildings from 20 percent to less than 5 percent. A novel lighting technology has recently been evolved as light emitting diodes (LEDs) that can be over 7–10 times more efficient than conventional-old incandescent lamps. Therefore, LED lighting systems have been rapidly replacing conventional energy-hungry lighting products like incandescent lamps and more recently environmentally hazardous fluorescent lamps. While LEDs may produce large amounts of lumens, they are solid state based technologies similar to computer chips so they have to be kept cool at certain chip junction temperature. The demand for high light output LED systems lead to significant heat generation rates, so that higher heat fluxes result in elevated junction temperatures on LED chips in SSL lighting systems. Moreover, the changes on the junction temperature strongly impact the reliability, lifetime, light output and quality of the light. Because of their simplicity, reliability, low cost and silent operation, passive air-cooling systems are preferred in LED lamps. Passive metal based heat sinks are the main cooling components of typical LED lamps serves for both LEDs and driver electronics. Heat is dissipated generally from finned surfaces to ambient air with primarily convection mechanism and partially radiation. But it requires a large surface area and weight under the limitations of the standardized lamps. Thus, the optimization of the heat sink in an LED system is crucial. Developing figure of merits (FOM) is very important for designers and researchers to find the most optimal solution accounting for critical metrics such as size, weight, cost and performance. In the present study, thermal, electrical and optical experimental results of various commercial A-line LED lamps are investigated and a number of FOMs are proposed based on the performance, size and weight. Proposed FOMs aim to evaluate different aspects by combining a number of performance metrics. Results show that one can combine and analyze multi-purpose design parameters for thermal, electrical and optical performances and manufacturing for engineers and consumers.

Electric Vehicle Potential in Australia: Its Impact on Smartgrids

The availability of the technology and the promising acceptance of hybrid electric vehicles (HEVs) has encouraged car manufacturing companies to take solid steps toward the electric vehicle (EV) market. As it is spread over a vast surface area, Australia has high car usage and ownership rates, and the inefficiency of the public transportation system contributes to this. Therefore, Australia has a very large potential market for EVs. In addition to the well-known advantages, such as zero direct emissions, reduced dependency on oil, cheaper fuel, and more silent operation through smart grids, EVs also offer a unique benefit called vehicle-to-grid (V2G) technology. Through V2G technology, EVs can support better operation of the smart grids in terms of reliability and storage. Based on reliable statistics and social studies, this article studies the EV potential of Australia and envisages the impact of large EV utilization therein. The statistics indicate that the growing population will demand more cars, and acceptance of EVs could also benefit other areas, such as environmental conservation, finance, and energy production. Accordingly, a microgrid system with V2G technology has been modeled and simulated in three different conditions: islanded, IEEE-T14-bus system, and IEEE-34-bus system. The results are presented to forecast the necessary changes in the power networks for the large deployment of EVs.

Electrical Resistivity-Based Study of Self-Sensing Properties for Shape Memory Alloy-Actuated Artificial Muscle

Shape memory alloy (SMA) has great potential to develop light and compact artificial muscle (AM) due to its muscle-like high power-to-weight ratio, flexibility and silent operation properties. In this paper, SMA self-sensing properties are explored and modeled in depth to imitate the integrated muscle-like functions of actuating and self-sensing for SMA-AM based on the investigation of SMA electrical resistivity (ER). Firstly, an ER transformation kinetics model is proposed based on the simulation of SMA differential scanning calorimetry (DSC) curves. Then a series of thermal-electrical-mechanical experiments are carried out to verify the validity of the ER model, whereby the SMA-AM self-sensing function is well established under different stress conditions. Finally the self-sensing capability is further demonstrated by its application to a novel SMA-AM-actuated active ankle-foot orthosis (AAFO).

Influence of fuel properties on operational range and combustion characteristics of premixed diesel combustion with high volatility fuel

The effects of fuel properties including ignitability, volatility, and compositions on operational range and combustion characteristics of premixed diesel combustion with various high volatility model fuels and an ordinary diesel fuel were examined in a direct injection diesel engine. The indicated mean effective pressure was limited by knocking with high-intake oxygen concentrations and by unstable combustion or significant increases in CO and total hydrocarbon emissions with low-intake oxygen concentrations regardless of fuels. The fuel volatility has little effect on the combustion characteristics and the stable operational range in premixed diesel combustion. With increasing octane number, the combustion phasing is retarded, and higher intake oxygen concentrations can be employed within the tolerance limits of rapid combustion, expanding the stable premixed diesel combustion indicated mean effective pressure range. The operational range of premixed diesel combustion with normal heptane and toluene blend fuels shifts to higher intake oxygen concentrations when compared with primary reference fuels with the same research octane numbers, showing lower ignition characteristics than primary reference fuel. The silent, low-NOx, and smokeless operation with high thermal efficiency was possible with both primary reference fuel and normal heptane and toluene blend fuel when the intake oxygen concentration is optimized corresponding to indicated mean effective pressure.

Experimental characterization of self-sensing SMA actuators under controlled convective cooling

Shape memory alloy (SMA) wires are attractive for actuation systems due to their high energy density, light weight and silent operation. In addition, they feature self-sensing capabilities by relating electrical resistance measurements to strain changes. In real world applications SMAs typically operate in non-ambient air and it is imperative to understand an actuator’s behavior under varying convective cooling conditions, especially for smaller diameter wires, where convective effects are amplified. This paper shows that the multi-functionality of SMA actuators can be further extended by related heating power to convective air speed. It investigates the relationship between the normalized excess power needed and corresponding airspeed under controlled, laminar airflow patterns in a small-scale wind tunnel. For each experiment, airflow through the wind tunnel, strain in the SMA wire, and power supplied to the SMA wire were controlled, while the stress and resistance of the wire were measured. The ability to understand and predict an SMA wire’s behavior under various external airflows will aid in the design and understanding of future SMA actuated structures, such as micro-air vehicles, and shows that SMAs can function as self-sensing actuators and airspeed sensors.

Sigmoid-based hysteresis modeling and high-speed tracking control of SMA-artificial muscle

This paper presents a novel compact shape memory alloy (SMA) based artificial muscle (AM) with self-sensing, silent operation and high force-to-weight ratio functions. The AM has great potential to develop light and compact active ankle–foot orthosis (AAFO) for ankle–foot rehabilitation. However, its performance is severely limited by SMA's slow-speed response and hysteresis properties. Firstly, an effective forced vessel cooling method is introduced to improve the AM response speed without compromising its compactness. Then SMA hysteresis properties are deeply explored and modeled under different stress and driving frequency conditions, whereby the hysteresis is well compensated when the hysteresis model based feedforward controller is proposed to the AM. Finally, a newly AM actuated AAFO is proposed to demonstrate the actuating capability of the AM. Experimental results show that the AM response speed and accuracy are greatly improved with tracking frequency increased from 0.08 to 1Hz, RMS tracking errors reduced by up to 82%, which basically satisfies the initial ankle–foot rehabilitation application.

Implementing Vehicle-to-Grid (V2G) Technology With IEC 61850-7-420

Electric Vehicles (EVs) have become very popular due to climate change concerns and carbon emission reduction schemes. Accordingly, in recent years the awareness of people about EVs has increased significantly. In addition to the well-known advantages such as cleaner environment, less oil-dependency, cheaper fuel, more silent operation etc., through smartgrids, EVs offer a unique benefit called vehicle to grid (V2G) technology. In order to define the role of EVs as distributed storage devices, simulation works undertaken in Paladin Designbase 4.0 are presented in this paper. It is shown that through V2G, EVs can support better operation of smartgrids in terms of reliability and storage. In order to achieve these, the components of smartgrids shall communicate and share information via communication lines. Having a universal communication standard is vital for implementing the plug-and-play concept in smartgrids. IEC 61850, the substation automation standard, could be used for this purpose. However, it is insufficient and must be expanded to cover missing links. In this paper, authors propose an extension to the IEC 61850-7-420 standard by defining the information model for controlling the charging and discharging of EVs.

Towards Biomimetic Actuation in Prostheses Using Shape Memory Alloy

Shape Memory Alloy (SMA) has been identified as an ideal candidate to actuate the finger joints of hand prosthesis due to its silent operation, small size, high force to weight ratio and operational similarity with human muscles. When current is applied to a SMA wire, the material is heated up. A phase transformation from Martensite to Austenite takes place and the wire contracts. This work evaluates the displacement and force produced from the contraction of a type of SMA wire, i.e. Nitinol (Ni-Ti). The displacement is determined by a linear potentiometer while the force is determined by a load cell. Furthermore the impacts of varying the bias force exerted on the SMA wire and the input current passed through the wire are investigated. Such insight into the characteristics of SMA can be used to realize biomimetic actuation in order to improve the dexterity of hand prosthesis.

Flow Measurements in Metal Oxide-Nanoparticle Suspensions in a Rectangular Natural Circulation Loop

Natural circulation cooling systems, such as the thermosyphon loops are preferred as effective heat dissipation methods where a silent and vibration-free operation is desired in thermal control of devices and processes. Though anomalous enhancement in forced convection heat transfer coefficients have been reported for nanofluids, the effect of addition of nanoparticles to base fluids in natural convection circulation loops is not clearly understood. An experimental study is reported in this work, using aluminum oxide and copper oxide nanofluids with varying concentrations, in a thermosyphon loop. The flow velocity is arrived at from the measured pressure drop. At a nanoparticle concentration of 0.01% by volume Al2O3-water and CuO-water nanofluids shows 88.37% and 42.89% improvement in flow, respectively.

Research on Heat Transfer Regulation of Power-Split Hybrid Electric Vehicle under Silent Watch Operation

Silent watch operation is a typical driving condition of power-split hybrid electric vehicle (PSHEV) which has advantages of both series and parallel HEVs. Because of the complicated structure and operations of PSHEV, an advanced thermal management system with effective control strategy is needed urgently. Properly-adopted heat transfer regulations under different vehicle driving conditions are the basis of TMS control strategy establishment. In this study, we begin this work from the typical vehicle operation-silent watch operation. Then, the heat transfer regulation of PSHEV under silent watch operation is researched and analyzed with the present advanced TMS. The results can provide theory and data bases for the future research of TMS control strategy for PSHEV.

Permanent Magnet Motor Torsional Resonance Noise Reduction by Rotor Skew Phase Adjustment

Hybrid Vehicles (HEVs) and Electric Vehicles (EVs) improve the efficiency of a drive and reduce CO2 emissions by regenerative braking and operating the engine under optimum conditions. It is desirable to decrease the motor size and increase the maximum torque to minimize the driving units. For these purposes, motors employing permanent magnets have been commonly used recently. The motor driving systems of HEVs and EVs must operate over variable speed ranges of up to 1: 5. Over this large range, smooth, silent operations are desirable and important. The skew method is often adopted to ensure a smooth start and stop and silent operation by reducing the torque ripple. However, this method possibly causes noise and motor vibration. This paper describes the mechanism of torsional resonance noise and vibrations arising from the skew method and a countermeasure to decrease them by optimizing the skew phase distribution in the rotating axis.