Pneumatic Power Research Articles

Development of Non-Wearing Type Pneumatic Power Assist Device – Basic Concept and Performance Evaluation –

In Japan, where aging is faster than ever, the shortage of a young labor force is a serious problem, especially in the nursing field to support care recipients and in the primary industrial field to support heavy labor. Hence, the use of power assist devices that mechanically reduce the burden on the body is drawing increasing attention. This study focuses on the lifting motion, which can be performed by two methods, the squat method and the stoop method; the former involves bending the knee and the latter involves using the waist. The squat method is recommended because the burden on the waist is lower than that in the case of the stoop method. Currently, many types of wearable power assist devices to reduce the burden on the waist have been developed; however, they are based on the stoop method because of their assist mechanism. In this study, we developed a non-wearing type pneumatic power assist device that allows the squat method. After describing the basic concept and assist mechanism, the support effects are confirmed through experiments.

Hydrodynamics of onshore oscillating water column devices: A numerical study using smoothed particle hydrodynamics

Oscillating water column (OWC) device is possibly the most studied among various wave energy converters and many different realizations of the technology have been investigated. To study the complex hydrodynamic behaviour of an OWC, a two-dimensional numerical wave tank based on the weakly compressible smoothed particle hydrodynamics (SPH) method is developed in this paper. A simplified pneumatic model is proposed here to simulate the effect induced by a pneumatic power take-off system within the framework of a single-phase SPH model, and implemented to determine the air pressure imposed on the free surface inside the OWC chamber. Additionally, a regional ghost particle approach, as boundary condition in SPH, is proposed to better simulate fluid dynamics near a thin wall. The overall computation cost is reduced dramatically due to the employment of the regional ghost particle boundary condition method. First, the numerical model is validated under regular waves using published physical and numerical data. An extensive campaign of computational tests is then carried out, studying the performance of the OWC for various wall thicknesses and damping coefficient under various wave conditions. The results demonstrate that the present SPH model can be used as a practical tool for the development of high-performance OWCs.

Catalyst additive composition for reduction of sulfur in gasoline

Oscillating water column (OWC) device is possibly the most studied among various wave energy converters and many different realizations of the technology have been investigated. To study the complex hydrodynamic behaviour of an OWC, a two-dimensional numerical wave tank based on the weakly compressible smoothed particle hydrodynamics (SPH) method is developed in this paper. A simplified pneumatic model is proposed here to simulate the effect induced by a pneumatic power take-off system within the framework of a single-phase SPH model, and implemented to determine the air pressure imposed on the free surface inside the OWC chamber. Additionally, a regional ghost particle approach, as boundary condition in SPH, is proposed to better simulate fluid dynamics near a thin wall. The overall computation cost is reduced dramatically due to the employment of the regional ghost particle boundary condition method. First, the numerical model is validated under regular waves using published physical and numerical data. An extensive campaign of computational tests is then carried out, studying the performance of the OWC for various wall thicknesses and damping coefficient under various wave conditions. The results demonstrate that the present SPH model can be used as a practical tool for the development of high-performance OWCs.

Numerical Investigation of an Offshore Oscillating Water Column

In this study, a Numerical Wave Tank (NWT) was used to investigate the flowfield of an offshore Oscillating Water Column (OWC). An inviscid solution coupled to the Volume of Fluid method was carried out using ANSYSTM Fluent to simulate six different offshore OWC configurations. The waterside chamber angle, θ1, shoreside chamber angle, θ2, and immersion extension depth d, were varied to evaluate their effect on pneumatic power and efficiency. It was determined that configuration parameters with θ1 = 45o, θ2 = 90o and d = 0 m produced the highest power with an efficiency of 23.1%; results showed that this case had a higher static pressure inside the duct which was the predominant reason for a higher pneumatic power. The cases with an additional extension into the water, d, was found to reduce the pneumatic power when compared to a similar case without an extension.

Testing of High-Lift Common Research Model with Integrated Active Flow Control

A 10%-scale high-lift version of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested. The main objective of the test was to develop an AFC system that can provide the necessary lift recovery on a simple-hinged flap high-lift system while minimizing its pneumatic power requirement. The tests were performed in the 14- by 22-Foot Subsonic Tunnel at the NASA Langley Research Center. Three types of AFC devices were examined: the double-row sweeping jets (DRSWJ), the alternating pulsed jets (APJ), and the high-efficiency low-power (HELP) actuators. The DRSWJ and the APJ actuators used two rows of unsteady jets, whereas the HELP actuators used a combination of unsteady and steady jets, to overcome strong adverse pressure gradients while minimizing the mass flow usage. Nozzle pressure ratio, mass flow consumption, and the power coefficient were used for judging the performance efficiency of the AFC devices. The current data are presented with the Transonic Wall Interference Correction System method applied. The HELP actuation concept was effective in controlling flow separation in the linear region of the curves comparing lift coefficient to mass flow rate. The HELP actuation achieved a targeted lift coefficient increment of 0.5, thus meeting the lift performance goal of the NASA Advanced Air Transport Technology project.

Hydrodynamic optimisation of an axisymmetric floating Oscillating Water Column type wave energy converter with an enlarged inner tube

Wave Energy Converters (WECs) that are classified as Floating Oscillating Water Columns (FOWCs) of point absorber type are designed to achieve resonance, at frequencies that are favourable for wave energy extraction. The resonance frequency of a FOWC type WEC is highly dependent on the added mass of its OWC, which often requires a long spar tube to achieve well-performing hydrodynamics. A proposed measure for driving down the cost of the converter is to reduce its length, while finding another way of achieving the desired OWC added mass. Frequency-domain modelling and hydrodynamic optimisation of the Spar-buoy OWC was carried out for an enlarged spar tube segment inside the floater. Results are compared to those of buoys with equal spar and inner tube diameters. Frequency responses of optimised buoy geometries - with and without enlarged inner tubes - explore the differences in their hydrodynamics. Expanding the inner tube diameter of the Spar-buoy OWC may increase energy extraction by up to 6.7% and reduce the buoy mass by up to 11.4%, when operating in a Portuguese offshore location. A sensitivity analysis on mean annual pneumatic power to changes in inner tube diameter and spar tube length was performed.

Experimental Investigation and Simulation of a Boeing 747 Auxiliary Power Unit

Abstract Auxiliary power units (APUs) are a major driver of maintenance on civil aircraft. However, experimental data and performance simulations are rarely seen in public domain literature. While there is recourse to aircraft engine experience, this does not address the loading and the failure modes of an APU. This work aims to add to the literature, by experimentally investigating a Boeing 747 APU, collecting data under various power settings and ambient conditions, and using these data to calibrate a simple simulation model. This simulation model will subsequently be used to explore failure modes in the APU and hence what sensors may be needed for health monitoring purposes in future work. In this paper, a Boeing 747 APU rig development process and the testing strategy are presented. The rig is validated through a process that includes uncertainty analysis, repeatability tests, consistency tests, and comparison of the collected data with the calibrated simulation model. The results from the rig's validation indicate that the data collected from the APU is independent of its running time or the order of loading cycles imposed on it, i.e., the results are path independent. Changes in pneumatic and electrical power result in small changes in the rotational speed despite the fact that the rotational speed should remain constant. The rotational speed shows a slightly increasing trend when the extracted power rises, and this affects the APU thermodynamic characteristics. This work has resulted in a calibrated simulation model that will be further used in examining fault mode scenarios, as injecting these directly into the rig is seen as high risk.

System Designs and Experimental Assessment of a Seven-Mode Vehicle-Oriented Hybrid Powertrain Platform

This study developed a mechatronics platform for a seven-mode vehicle-oriented powertrain system. The innovative “all-in-one” concept was used for flexibly arranging various power or energy sources to be combined for various hybrid powertrains. Hence, it significantly reduces the cost and human resources for evaluating new-type power systems or developed vehicle control strategies on the same experimental platform. In this study, three power sources were chosen for providing hybrid power. The first source is a 125 c.c. spark ignition (SI) engine, where a controllable throttle valve governs the output torque, while a fuel meter measures the consumed fuel. The second one is a 1.5kW hub motor, where a motor control unit (MCU) and a 48V lithium battery pack properly provide the required electric power. The third source is an air engine, where a 220V air compressor and other components provide the pneumatic power. For the experimental platform, a developed Matlab/Simulink package receives the measured signals and sends the control commands to actuators. Through the on/off state control of three controllable e-clutches, three single-source modes, three dual-source modes, and one three-source mode (3+3+1) can be conducted. A 1.1kW/24V magnetic powder brake emulates the road load. The results show that three dual-source modes and a three-source mode were successfully operated. The efficiencies, torques and speeds, mass flow rates, etc. have been measured and calculated. This platform is aimed for the research fields of green energies, advanced powertrains, and power flow management.

Parametric Study for an Oscillating Water Column Wave Energy Conversion System Installed on a Breakwater

This study focuses on the analysis of the parameters of an oscillating water column (OWC) wave energy conversion system and wave conditions. Interactions between the dimensions of the OWC chambers and wave conditions are all taken into account to design an alternative OWC converter, called caisson-based OWC type wave energy converting system. A numerical method using an unsteady Navier-Stokes equations theorem in conservation form is used to analyze the proposed analytical model. The objective of this study is to try to apply an OWC wave energy converter to a caisson breakwater, which has been constructed in a harbor. The structure proposed in this study is a series of sets of independent systems, in which each set of converters is composed of three chambers to capture the wave energy, while better ensuring the safety of the caisson breakwater. Responses to be analyzed related to the conversion efficiency of the caisson-based OWC wave energy converting system include the airflow velocity from the air-chamber, the pneumatic power and the conversion efficiency in terms of a ratio between the pneumatic power and the energy of the incident waves. Parameters examined in this study include the dimensions of the OWC chamber features such as the orifice of the air-chamber allowing airflow in/output, the chamber length along the direction of incident waves, the size of the opening gate for incident waves and the submersion depth of the air-chamber. As found from the results, a best conversion efficiency from incident waves of 32% can be obtained for the extreme case where the orifice is very small, but for most other cases in the study, the best efficiency is about 15%.

Hybrid realizable [formula omitted]/laminar method in the application of 3D heaving OWCs

A hybrid realizable k−ε/laminar computational fluid dynamics method consisting of the realizable k−ε model, laminar model, volume of fluid Geo-reconstruct surface capturing method, and motion-based zonal mesh update method, is presented to study the hydrodynamics of floating oscillating water columns (OWCs). This method is capable of precisely capturing water elevations and motions of the OWC device structure. The simulations of the prototype model are established and dimensionless comparisons are performed with experiments. The results show that the movement of the OWC device structure shows little scale effect with or without the consideration of air compressibility and depends only on the Froude number. Test cases are conducted on the pneumatic power of a floating OWC at prototype scale, showing that pneumatic power increases with increasing incident wave height for a heaving OWC.

Experimental Assessment of a Fixed On-Shore Oscillating Water Column Device: Case Study on Oman Sea

Ocean wave is one of the renewable energy resources that these days various devices are used to extract its energy. Oscillating Water Column (OWC) installed on the shore is one of the wave energy absorption systems which has received attention due to its simple structure. Investigation of the pneumatic power is of great importance in such systems as the conversion of wave energy to pneumatic energy is the first step in OWCs’ energy conversion cycle. This study aims to assess the power available in a fixed onshore OWC plant according to the wave characteristics of the Oman Sea on the shores of Chabahar. For this purpose, a small-scale model of OWC was tested in the wave tank, and its pneumatic power was evaluated. In these experiments, the effects of various parameters including incident wave height and frequency, the front wall draft and the orifice diameter on the pneumatic power were investigated. The results show that increasing the wave height generally increases the pneumatic power; however, variations of power with the draft depends on the incident wave frequencies. The maximum achieved capture performance and maximum generated pneumatic power of the model are 18% and 0.7 watts, respectively.

Additive Manufacturing for VADs and TAHs - a Review

Heart disease or Advanced/Congestive Heart Failure (CHF) is one of the serious causes of death. Due to availability of low volumes of donor hearts, there has been an ongoing development of Mechanical Circulatory Support (MCS): Ventricular Assist Devices (VADs) and total heart replacement by Total Artificial Hearts (TAHs) for over 60 years. MCS systems had seen three phases of advancement. The first generation were largely mechanical devices and had pulsatility in their action, but were highly cumbersome, unreliable due to fatigue cracks and required an external pneumatic power and control. Smaller and continuous flow devices are the second generation MCS devices. Because of compact sizing they were suitable for implantations and were more durable than the first generation devices. Problems like pump thrombosis drove the development of motors with levitating or hydrodynamic rotors, leading to the development of third generation devices. Manufacturing of these electromagnetic devices for implantation has to adhere to the constraints of compatibility, space and weight. With the advent of new biomaterials, additive manufacturing is reportedly playing a significant role. Additive manufacturing reported for electromagnetic and electronic components had yielded considerably good performance. This paper reviews materials in electrical and electronics and also in bio medical sector suitable for Additive Manufacturing. An attempt is made to identify the materials that may be suitable for VADs and TAHs and the challenges to use AM techniques that complement each other to create next generation integrated-VADs and integrated-TAHs.

Performance Evaluation of an Electromagnetic Free Piston Compressor Without Permanent Magnets

The performance of a linear free piston gas compressor is investigated in this study. Two compressor pistons are mounted on a robust reciprocating cage mover, which is driven by a double-stator linear induction machine. Since the beginning of the 21st century, many permanent-magnet machines were investigated due to their high power density and efficiency. Less attention has been paid to linear induction machines (LIMs) that stand out through the fact that they do not require expensive rare-earth magnets, and moreover, they are insensitive to strong magnetic fields, high temperatures, and harsh working conditions. This enables them to be used with corrosive media, e.g., for a hydrogen compressor. Therefore, a prototype of a potentially more robust electromagnetic free piston gas compressor was built. It is evaluated on two test benches: First, the LIM is tested with a load motor that enables the measurement of the mechanical output power, and second, the free piston gas compressor is tested with ambient air and the discharge pressure and output flow rate are measured. The electrical power consumption, the mechanical output power of the linear motor, and the pneumatic output power of the free piston compressor are determined for various operating conditions. The measurement results are presented and the average cycle efficiencies are calculated. Moreover, the average cycle power losses of the LIM are analyzed.

Backdrivable and Fully-Portable Pneumatic Back Support Exoskeleton for Lifting Assistance

To reduce the possibility of lower back pain (LBP), which is the most frequent injury in manual labor, several back support exoskeletons have been developed and implemented for lifting motion assistance. Although pneumatic power transmission is attractive due to its inherent compliance and backdrivability, the portability of the pneumatic system is highly limited due to the bulky air compressors that provide compressed air to the system. Therefore, we aimed to develop a fully-portable pneumatic back support exoskeleton by integrating all pneumatic components in the system. The compressed air consumption and generation of pneumatic system were modeled to meet design requirements. The developed exoskeleton was completely stand-alone and provides 80 Nm of maximum extension torque for 6 liftings per minute (6 l/m). The upper limit of the resistance torque was estimated to be about 2 Nm, which implies high backdrivability. Finally, lifting experiments were performed and surface electromyography (sEMG) was measured to validate the physical assistance of the developed exoskeleton system for ten subjects. Compared to the case with no exoskeleton, the back muscle activation was significantly reduced with the assistances.

Design optimization of a purely radial turbine for operation in the inhalation mode of an oscillating water column

A vented Oscillating-Water-Column (OWC) simplifies the pneumatic energy conversion problem by rectifying air flow and enabling a unidirectional-air-turbine to be employed. It shifts power-extraction to the inhalation phase of the cycle and provides equivalent pneumatic power to a full-wave-cycle. Conventional Radial-air-turbines feature a low global-efficiency in OWC applications, however they offer simpler designs and lower thrust loads. The aim of this study is to modify the design of a centripetal-radial-turbine for optimum efficiency in steady-state using CFD methods for application with the pressure/flow profile experienced by the vented-OWC. Nine design variables were used to control the shape of the rotor and its adjustment to the inward-flow direction. The optimized rotor was found to achieve significant efficiency and output power by using asymmetric and non-zero-staggered blades. The downstream section was optimized for an efficient matching with the optimized-inflow-rotor and four parameters were used to control the shape of the downstream section. A diffuser with a 7-degree diffusion-angle was found to be the optimal connection between the turbine and the chamber. The inflow radial turbine obtained 81% peak efficiency in the steady-state, and its average efficiency over the expected flow coefficients is comparable to the axial-turbines used with OWCs.

The Wave-to-Wire Energy Conversion Process for a Fixed U-OWC Device

Oscillating water column (OWC) devices, either fixed or floating, are the most common wave energy converter (WEC) devices. In this work, the fluid dynamic interaction between waves and a U-shaped OWC breakwater embedding a Wells turbine has been investigated through unsteady Computational Fluid Dynamic (CFD) simulations. The full-scale plant installed in the harbor of Civitavecchia (Italy) was numerically modeled. A two-dimensional domain was adopted to simulate the unsteady flow, both outside and inside the U-OWC device, including the air chamber and the oscillating flow inside the conduit hosting the Wells turbine. For the numerical simulation of the damping effect induced by the Wells turbine connected to the air chamber, a porous medium was placed in the computational domain, representing the conduit hosting the turbine. Several simulations were carried out considering periodic waves with different periods and amplitudes, getting a deep insight into the energy conversion process from wave to the turbine power output. For this purpose, the three main steps of the overall energy conversion process have been examined. Firstly, from the wave power to the power of the water oscillating flow inside the U-duct. Secondly, from the power of the oscillating water flow to the air pneumatic power. Finally, from the air pneumatic power to the Wells turbine power output. Results show that the U-OWC can capture up to 66% of the incoming wave power, in the case of a wave period close to the eigenperiod of the plant. However, only two-thirds of the captured energy flux is available to the turbine, being partially dissipated due to the losses in the U-duct and the air chamber. Finally, the overall time-average turbine power output is evaluated showing that it is strongly influenced by a suitable choice of the turbine characteristics (mainly geometry and rotational speed).

GROUND-BASED EXPERIMENTAL TESTING OF ELEMENTS OF AUTOMATION OF PNEUMATIC-HYDRAULIC SYSTEMS OF ROCKET AND SPACE TECHNOLOGY

The design and production of sophisticated technical systems, which include modern rockets and other aircraft, requires their reliability and trouble-free operation. To achieve the required level of reliability of aerospace products, a wide variety of test methods are applied at all stages of the life cycle. One of the most important systems of the launch vehicle is the pneumatic hydraulic power system of the liquid rocket propulsion system. Development of new and improvement of existing methods of control and diagnostics is one way of increasing the design and technological reliability of products of aviation and space technology. The use of functional diagnostics systems for bench and flight tests significantly increases the reliability and efficiency of space rocket technology. Researches are directed on increase of a level of reliability of products of aerospace branch. Application of systems of functional diagnostics is described at bench tests. The results of experimental researches of elements of automatics of pneumatic hydraulic power supply systems of liquid rocket engines are considered. The technique of processing of experimental data of a pulsing-acoustic method of diagnostics with use of the mathematical technology of recognition of images is presented. Deciding rules of recognition of a technical condition of object of diagnosing by results of tests are resulted. The developed method with a high degree of accuracy allows to determine the technical condition of the object of diagnosis as defective or to detect the presence of characteristic defects. Experimental testing and the proposed method of processing the results showed the efficiency of the method.

Analysis of 6-Pulse and 12-Pulse in Conversion of the 115VAC/400Hz to 270 VDC for Application on Fighter

The development of aircraft secondary power technology is moving from mechanical power, pneumatic power and hydraulic power to electric power. The trend toward electric power is known as More Electric Aircraft (MEA). Modern military aircraft are designed using 270VDC for electric power system. Today, some military aircraft still use 115VAC/400Hz for their electrical power system. If this type of aircraft need provides 270VDC electrical power, then they require Multi-Pulse Transformer Rectifier Unit (TRU). The development of this type TRU has not been aimed to comply with aircraft military standards. This research investigates the variation of the number of pulses (p) and firing angle (α) to the amplitude ripple voltage, output voltage, and distortion factor in order to comply with the MIL-STD-704F standards. The multi-pulse transformer rectifier unit being analyzed consists of 6-Pulse and 12-Pulse. The research shows that the amplitude ripple voltage and distortion factor of the 6-Pulse TRU do not comply MIL-STD-704F. The amplitude ripple voltage and distortion factor of 12-Pulse comply MIL-STD-704F with firing angle (α) ≤4°.Keywords: Transformer Rectifier Unit, thyristor, ripple voltage, distortion factor, firing angle

Fluid-Solid Interaction Analysis for Improvement in the Dehumidification Characteristics of a Hollow Fiber Membrane Module for Use in a Pneumatic Power Unit

In this study, a flow analysis and a fluid-solid interaction analysis were performed on a hollow fiber membrane module used for dehumidification of a pneumatic system. To ensure the reliability of the flow analysis results, we performed the dehumidification experiment at a temperature of 30 °C and a relative humidity(RH) of 30% on a module with a similar to that of the analyses. shape only the part containing hollow fiber membranes was considered. Results of the dehumidification experiments were compared with the results of the flow analysis. The results of dehumidification experiments and the flow analysis had a difference of approximately 5%, and although the five models had different grid numbers, the results of flow analysis showed a difference of about 1% in the dehumidification efficiency ensuring the accuracy. A one-way fluid-solid interaction analysis with various materials was performed. From the result, we found that the baffle having the largest shape deformation was the one made of polyethylene material, which was then subjected to a 2-way fluid-solid interaction at 0.53 bar, 1 bar, 5 bar, and 10 bar. The fluid flow and the dehumidification characteristics were determined for different shapes of the deformed baffle. Finally, the effects of three types of flow paths based on the positions of the inlet and the outlet on the baffle deformation and the dehumidification efficiency were studied. We found that dehumidification efficiency was highest when inlet and outlet were positioned in a straight line.

Wave-to-Wire Model Development and Validation for Two OWC Type Wave Energy Converters

The Tupperwave device is a closed-circuit oscillating water column (OWC) wave energy converter that uses non-return valves and two large fixed-volume accumulator chambers to create a smooth unidirectional air flow, harnessed by a unidirectional turbine. In this paper, the relevance of the Tupperwave concept against the conventional OWC concept, that uses a self-rectifying turbine, is investigated. For this purpose, wave-to-wire numerical models of the Tupperwave device and a corresponding conventional OWC device are developed and validated against experimental tests. Both devices have the same floating spar buoy structure and a similar turbine technology. The models include wave-structure hydrodynamic interaction, air turbines and generators, along with their control laws in order to encompass all power conversion stages from wave to electrical power. Hardware-in-the-loop is used to physically emulate the last power conversion stage from mechanic to electrical power and hence validate the control law and the generator numerical model. The dimensioning methodology for turbines and generators for power optimisation is explained. Eventually, the validated wave-to-wire numerical models of the conventional OWC and the Tupperwave device are used to assess and compare the performances of these two OWC type wave energy device concepts in the same wave climate. The benefits of pneumatic power smoothing by the Tupperwave device are discussed and the required efficiency of the non-return valves is investigated.