Piston Type Research Articles

Analysis of the efficiency of balancing pistons of feed pumps

BACKGROUND: Thermo power industry demands the high level of reliability of pump equipment. Regarding that, improvement of reliability of feed pump structure and balancing device in particular is a relevant issue.
 AIMS: To perform numerical simulation of a balancing device in order to determine its optimal design and parameters. The study object is the balancing device of the PEN 290-115 feed pump
 METHODS: Two types of the balancing piston, two-stage and single-stage, were studied. The series of computational fluid dynamics simulations of the three-dimensional flow of a viscous liquid were performed using the ANSYS CFX software in order to study the efficiency of given designs.
 RESULTS: The calculated characteristics of the two designs of the unloading device were obtained. The influence of roughness and radial clearance on the efficiency of a cylindrical piston was studied. The simulation results showed that the radial clearance decrease leads to balancing device losses decrease. The roughness value increase may also lead to the leaks decrease, but its excessive increase leads to friction losses increase, so it is necessary to control both parameters when searching for the optimal roughness value.
 CONCLUSIONS: The optimal design of the balancing piston, which combines simplicity of manufacturing, reliability and energy efficiency, is proposed.

A high-order finite difference method with immersed-boundary treatment for fully-nonlinear wave–structure interaction

In order to predict nonlinear wave loading on marine structures, a fully nonlinear higher-order finite difference based potential flow solver with all boundary conditions treated by an immersed boundary method has been developed in this paper. The solver adopts high-order finite difference schemes for the spatial derivatives and a 4th order Runge–Kutta method for time stepping. Test cases of forced oscillation of a cylinder in an infinite fluid domain are first studied, which reveal the advantage of the acceleration potential method in terms of wave load computation. Then a wave generation problem using a piston type wave maker is tested. Special attention is paid to the intersection point between the free surface and the body surface, and a scheme which best meets the accuracy and stability requirements is suggested from several proposals. A novel hyperviscosity filter, which works for both uniform and non-uniform grids, is introduced to stabilize the time-domain solution of the wave maker problem. Finally, a forced heaving cylinder on the free surface is considered, and the nonlinear wave loads on the cylinder are analyzed and compared to benchmark results.

Research on unsteady flow measurement standard device based on active piston

In this paper, an unsteady flow measurement standard device is studied and designed. The device can be used to measure the flow rate of any liquid medium. First, through comparative analysis of the design scheme of the unsteady flow measurement standard device, the structure of the active piston type is determined, and the schematic diagram is designed. According to the schematic diagram, the mathematical model of the device based on the active piston is established, and the uncertainty of the device is evaluated. Second, the hardware control system is designed and built according to the uncertainty evaluation results. Then, the upper computer operating system of the device is constructed, and a highly integrated human-computer interaction data acquisition and control system is established. Finally, the measurement performance of the device is verified by comparing the set value with the measured value of flow rate, and the uncertainty of the device is analyzed. The combined standard uncertainty can meet the expected value of 0.5%.

Failure Analysis of the Aviation Piston Engine Lubricating Oil System

With the continuous development and progress of science and technology, aviation has also begun to become an important field related to public life. Aviation is no longer only related to national defense, but also has entered public life. Once an aircraft has a problem, it will bring devastating damage, so it is necessary to eliminate the danger as much as possible and reduce the potential accident. The aviation piston engine oil system has an important impact on the safety of piston type aircraft. Studying the fault problems of this system is very necessary for troubleshooting and improving aviation safety. This article introduces the aviation piston engine oil system, explains its common faults and causes, and explores the troubleshooting countermeasures for the aviation piston engine oil system.

IRREGULAR WAVEMAKER (PISTON TYPE) IN A NUMERICAL AND PHYSICAL WAVE TANK

This paper describes the design and execution of a wavemaker system (piston type) in the Dokuz Eylül University Hydraulic Laboratory flume to perform hydraulic model tests using regular and irregular waves. In this study, we will focus on generating the irregular waves from the target JONSWAP spectrum using an adjusted random phase method; also, the control software of the wavemaker is described. An identical numerical channel wave to the physical flume was modeled to compare and observe the irregular wave profile using Flow 3D, one of the advanced computational fluid dynamics (CFD) software. The paddle movement was validated by comparing the experimental converted irregular wave surface elevations to the wave spectrum to the numerical models of several waves.

Investigations on efficiency improvement of rolling piston type rotary compressor with a new-designed cylinder

Excellent cylinder thermal characteristics is important to improve the efficiency of rolling piston type rotary compressors, thus a new-designed cylinder was proposed to increase the heat transfer of the cylinder to the external ambient. The temperatures on the inner-wall of the original cylinder, the temperatures and heat fluxes on the outer-wall of the new-designed cylinder were measured. Then the influences of the cylinder thermal characteristics on the volumetric and electrical efficiencies of the original and new-designed compressors were analyzed. The experimental results show that the inner-wall temperatures of the new-designed cylinder were decreased by 7.0 °C at maximum compared to the original one, and the temperature drop was increased along with the rotation angle of the rolling piston in an approximately linear way. Consequently, the volumetric and electrical efficiencies of the new-designed compressor were increased by 3.52 % and 4.43 %, respectively. This study would be helpful to improve the efficiencies of rolling piston type rotary compressors.

Development of Piston Type Shape Memory Alloy Actuated Pump for Drug Delivery

Development of Piston Type Shape Memory Alloy Actuated Pump for Drug Delivery

THE USE OF ELEMENTS OF ART THERAPY IN CORRECTIVE-DEVELOPING WORK WITH CHILDREN

The article is devoted to the current problem of modern special pedagogy - the use of elements of art therapy in corrective and developmental work, because these elements are considered the most acceptable and effective in working with children with special educational needs. Rozkriti Zmіst is an individual Vikoristannye Elementiv art-therapy in the core-nitrum robot with a special dedication, the yak is able to be in the urahuvannya ditini, the type of jerk off piston. The directions of using elements of art therapy in correctional and developmental work are highlighted: psychophysiological (related to the correction of psychosomatic disorders), psychotherapeutic (related to the impact on the cognitive and emotional spheres), social-psychological (performs catharsis of aesthetic, regulatory, communicative functions ), socio-pedagogical (related to the development of aesthetic needs, the expansion of the general and artistic-aesthetic horizons, and the activation of the child's potential in practical artistic activity and creativity). Various aspects of the use of elements of art therapy are analyzed as one of the most interesting and creative methods of work, which helps to use the available opportunities of art to achieve positive changes in the emotional, intellectual and personal development of a child with special educational needs. It is noted that the use of elements of art therapy in corrective and developmental work with children with special educational needs allows for more effective influence on the formation of the emotional sphere, encourages the further development of compensatory properties of preserved functional systems, and improves the child's s it possible to carry out a simultaneous corrective effect on both primary, secondary and tertiary disorders, as well as to maximally mobilize the child's creative potential and find those ways of creative self-expression that best correspond to his capabilities and needs.

Experimental research on piston rings with different end face structures

In order to reduce the leakage and the temperature of the end face of the piston ring to prolong its service life, an experimental research of the piston ring with different types of end face structures is carried out. In this research, a high-pressure and high-speed rotary seal experiment bench is built, and the leakage and temperature experiment of piston rings such as traditional type, micro-pit type, circular arc groove type and V-groove type are carried out. The results show that when the pressure is 1–2 MPa and the speed is 1000–5000 rpm, the V-groove type piston ring has the best comprehensive performance among the four different structures of the piston rings, which can not only reduce the temperature of the piston ring to prolong the service life of the piston ring, but also reduce the leakage of the piston ring. The results of this research reveal the influence of different types of end face structures on the leakage and temperature of the piston ring, which can provide theoretical support for its optimal design.

Adaptability evaluation of piston type high pressure pump integrated with energy recovery device through the numerical simulation and one year's island desalination

Small-scale seawater desalination system with energy recovery devices is the mainstream technical solution to cope with fresh water issue and tight power supply in the exploitation of islands. Aiming at the complex working conditions, the adaptability of piston type high pressure pump integrated with energy recovery device (HPP-ERD) is investigated through the numerical simulation and all-year-round island desalination. The numerical results indicate that the consecutive flowrate regulation, broad pressure sustainability and uniform temperature distribution are realized in HPP-ERD within the flowrate of 5.30 m3/h, the pressure of 5.50 MPa, and the temperature of 25 °C. The experimental results prove that HPP-ERD exhibits excellent stability and adaptability at the starting stage and stopping stage, and achieves stable operation in the pressure range between 3.00 MPa and 5.50 MPa. The all-year-round operation demonstrates that HPP-ERD can adapt to the seawater temperature ranging from 0.85 °C to 25.69 °C and the humidity between 63% and 85%. The total internal leakage maintains nearly constant at 0.19 m3/h which contributes to the annual specific energy consumption (SEC) of 3.80 kWh/m3. This investigation provides researchers and engineers with the application references of HPP-ERD in island desalination system.

Long-term outcomes of stapes surgery

ObjectiveHearing improvement following stapes surgery is generally good; however, we sometimes encounter patients where hearing loss gradually progresses over the long term. In this study, we investigated the causes of hearing loss in these cases. MethodsA total of 30 ears from 23 patients, who underwent stapes surgery at Kitasato University Hospital from 2001 to 2021 and were followed up for ≥5 years, were included in the study. Changes in air conduction (AC) and bone conduction (BC) thresholds were measured, and hearing evaluation was performed by calculating the air–bone gap (ABG) at the mean of 4 frequencies. Cases with a postoperative ABG of ≤10 dB at 6 months after surgery were classified into the following groups according to their hearing changes at 5 years after surgery: Group A (no ABG increase of ≥10 dB and no AC threshold increase of ≥10 dB) and Group B (an ABG increase of ≥10 dB and an AC threshold increase of ≥10 dB). In groups A and B, we examined factors affecting long-term postoperative results. In addition, the patients who underwent reoperation were examined. ResultsThe AC thresholds 6 months and 5 years after surgery decreased significantly compared with those before surgery (p < 0.01); however, the BC thresholds 6 months and 5 years after surgery did not vary significantly from those before surgery (p > 0.05). Group A included 16 ears from 13 patients (53.3%), and Group B included 3 ears from 3 patients (10.0%). There were no significant differences in age, sex, surgical method, piston type, piston length, presence of incudostapedial joint subluxation, computed tomography findings, and preoperative ABGs between groups A and B (p > 0.05). A total of 6 reoperations were performed in 3 ears from 3 patients, and there were 5 operations with the platinotomy hole to be closed by bone regrowth and 3 operations with the narrowed long process of the incus. ConclusionIn 10.0% of the patients who underwent stapes surgery, the ABG improved 6 months after surgery; however, the AC threshold and ABG increased 5 years after surgery. Our findings suggested that piston displacement and the platinotomy hole to be closed by bone regrowth are possible causes of hearing loss in cases where hearing loss progresses in the long term after stapes surgery.

Theoretical analyses on a piston-based thermal engine for thermal underwater glider

• Heat transfer models on thermal engines for TUG are built and verified. • Performance of thermal engine are optimized based on the models. • A piston-type configuration is proposed for thermal engine. Thermal underwater glider (TUG) harvests the ocean thermal energy and glides for a few thousands of kilometers range in a self-propelled manner. Theoretical models on the ocean thermal energy conversion process have been well established for evaluating the conversion efficiency. However, the heat transfer process is rarely modeled for TUG, leading to an inadequate quantification on the output power. In this work, comprehensive theoretical models with both energy conversion and heat transfer processes are conducted on a piston type TUG. The models well predict the performance of the thermal engine as compared with the reported experimental data. The effects of the surface seawater temperature, nitrogen gas volume, nitrogen gas pressure, phase change material (PCM) volume, seawater velocity as well as the gliding angle on the performance of the thermal engine are discussed. The results show that the the effective output power of the nitrogen tank varies from 0.4 to 1.0 W when 4 L PCM is employed in the thermal engine. A lower initial nitrogen volume (1.0 to 0.6 L), larger initial nitrogen pressure (1.0 to 5.0 MPa), larger PCM volume (2.0 to 5.0 L), greater seawater velocity (0–3 m/s) and larger gliding angle (20° to 90°) is beneficial for the improvement of the energy conversion efficiency and output power of the thermal engine. This proposed theoretical models are essential for optimizing the design and operating parameters of thermal engine of a TUG.

A novel pneumatic actuator based on high-frequency longitudinal vibration friction reduction

Seals are an indispensable component of ordinary piston type pneumatic cylinders, but their presence inevitably introduces friction. Given that the friction is time-varying, uncertain and difficult to capture precisely, the output force of the pneumatic cylinder is difficult to obtain accurately. In addition, due to the serious negative damping effect in the low speed phase of the pneumatic cylinder friction characteristics, the motion servo control accuracy of pneumatic cylinders at low speeds is relatively poor. In this study, a novel longitudinal-vibration-mode pneumatic actuator with integrated piezoelectric stacks is developed with a resonant frequency of 5908 Hz for first-order longitudinal vibration. A new friction test system is set up and the test results show a maximum reduction of about 38.6 % in the static friction and 46.6 % in the dynamic friction of the pneumatic actuator for the high-frequency longitudinal resonance case. In the study of the effect of two-chamber pressure on friction reduction, it is found that the friction reduction rate decreases with the increase of two-chamber pressure. The preliminary motion trajectory tracking control results show that the high-frequency longitudinal resonance of the pneumatic actuator does help to reduce the maximum tracking error during the reverse process and improve the tracking accuracy of the motion trajectory.

Study on the propagation characteristics of pressure wave generated by mechanical shock in leaking pipelines

This paper focuses on the characteristics of pressure wave generated by an active mechanical shock in leaking pipelines. A piston type pressure wave generator was designed and applied to the pipeline experimental system and a three-dimensional (3D) numerical simulation model was developed based on the k-ε turbulence model and dynamic mesh. The experimental results showed that the maximum amplitude of pressure wave was about 104.71 kPa, and the leakage intensified the attenuation of pressure wave in space and time through quantitative analysis. Based on the 3D simulations, the processes of the pressure wave generation and propagation were revealed. The amplitude of pressure wave increased linearly with the increase of the maximum velocity of mechanical shock, and the effects of leakage on the waveforms of pressure wave were observed under the dimensionless analysis. In addition, a shorter duration of mechanical shock can increase the amplitude of the pressure wave generated. The results presented in this paper will contribute to the development and application of the transient leak detection method for pipeline systems.

Performance fluctuations and evaluation of a piston type integrated high pressure pump-energy recovery device

The development of energy recovery device (ERD) is a decisive factor for the recent prevalence of reverse osmosis (RO) technology in the seawater desalination field. Unlike broadly studied large scale ERDs, the investigations of small scale ERDs are scarcely reported, especially on the performance fluctuations under variable operating conditions. Based on an authors’ exploratory research on a piston type integrated high pressure pump-energy recovery device (HPP-ERD), further performance exploitation of the HPP-ERD is conducted. With a constructed experiment platform, the influences of inlet seawater temperature, inlet seawater salinity, as well as the operating frequency on the performance of the HPP-ERD coupled with seawater reverse osmosis (SWRO) desalination system are investigated. The temperature and salinity of the inlet seawater are numerically correlated with the specific energy consumption (SEC) of the HPP-ERD. With the correlated equation, the marine hydrological data of two observatories acquired from a national authoritative database, and the annualized life cycle cost approach incorporated, annual performance assessment is proposed for an SWRO desalination system equipped with the HPP-ERD in the light of energy and economic indices. The study results indicate that the proposed HPP-ERD is competent under various operating conditions for SWRO desalination systems.

Prediction and isolation of pyroshock in typical pyrotechnic device based on coupled modeling technique

In this paper, a typical piston pyrotechnic device was designed and the thin-walled circular tube was used as the energy absorber to isolate pyroshock. To provide accurate load and simulation results, a coupled numerical model linking propellant combustion and finite element analysis was established. A shock experiment for the typical pyrotechnic device was carried out to verify the correctness of the coupled model above. Further, the buffer performance of the thin-walled circular tube was investigated. The simulation results reveal that the maximum shock overload with the study case was reduced from 670,000 g to 20,000 g. The coupled model is capable of obtaining accurate dynamic load and accurately guiding the simulation in comparison with commonly utilized pyroshock prediction methods. For loads of varying precisions, the energy absorption rates of thin-walled circular tubes are similar with a maximum difference of 4.1%, while other buffer performance and stable appearance are drastically different. Furthermore, the influence of the thermal field is not taken into account in this paper, and the thermal-solid coupling based on the established coupled model is the next research topic.

Advancing in the decarbonized future of natural gas transmission networks through a CFD study

The injection of green hydrogen into the natural gas grid is a way to decarbonize the gas sector and build an economic transport route for the large-scale delivery of hydrogen. The suitability of the natural gas infrastructure for this purpose depends on the impact that hydrogen may have on the correct operation of its components and understanding the new flow conditions in the system is essential for this aim. Computational studies can anticipate the expected environment in the pipe system, assessing the readiness of the system. However, the experience on this topic is not extensive enough and deeper understanding is necessary. Here we show a CFD study to simulate the transport of H 2 /NG blends in a gas setup with the main characteristics of injection sites and gas pipelines representatives of the transmission gas network. This setup considers a blending station, the pumping and injection procedure, and different pipelines geometries to predict the behavior of various mixtures of H 2 /NG. It can be seen how (1) a good mixing is achieved in the blending station after a pipe length equivalent to 20–30 diameters is reached; (2) pumping gas by a piston type compressor shows pulsations in the flow regardless the composition of the blend that can be damped implementing mitigation measurements; and (3) asymmetries in the flow are found when the direction of the fluid changes after section reduction, but 20 diameters downstream of the reduction the flow is fully developed. • Modelling the injection of hydrogen in the natural gas transmission grid. • CFD studies to anticipate the behavior of the new fluid. • Mixing quality and possible segregation in blending stations considered. • Flow pattern when DN 80 pipes expands to a DN 150 or a DN 250 pipes. • Simulation of pumping of H 2 and CH 4 by a piston type compressor.

Dynamics of Submersion of a «Diving Buoy» with Account of Hull Compression and Depth-Wise Variation of Water Density

The paper employs a simplified approach to modeling of dynamics of submersion of a «diving buoy» subject to a depth-wise water density gradient and experiencing compression of the hull due to action of pressure. The latter effect is accounted for through use of well-known boiler formulae of structural mechanics allowing to analyze behavior of hulls made of different materials. Operation of a piston type buoyancy engine is modeled both for a hypothetical case of instantaneous change of buoyancy and for more practical case of finite buoyancy variation. As the analysis includes both acceleration/deceleration and constant speed modes of motion it enables to evaluate full time of submersion to a design depth. Calculated are the vertical position and speed of the vehicle versus time. Due to the fact that during submersion the growth of density results in deceleration and hull compression causes acceleration, the equilibrium condition is formulated which can be seen as hanging mode in which the buoy performs damped oscillations around a depth of hanging with a frequency depending on rates of density and compression. It is shown that to provide constant speed for a general case of density variation one has to secure a corresponding volume variation of the vehicle or a corresponding increment/decrement of differential buoyancy. At the end of the paper estimates are presented showing how much additional buoyancy should be carried on board to keep constant speed of submersion and how much power is needed for corresponding buoyancy control for a given density profile.

Thermal and Structural Analysis of Different Piston Geometries of Compression Ignition Engine

Improvement in performance of the diesel engines is carried out by focusing on several parameters. One among these is piston which undergoes higher thermal loads and thermal stresses during its entire working cycle and duration. Therefore, it is necessary to analyse the stresses that the piston can be able to withstand and give its contribution to maximize the engine performance. In this study, four different piston shapes were considered namely, flat, dome, cup and bowl type pistons. 3D models were developed for these pistons and simulations was carried out in the ANSYS at steady state conditions using finite element method (FEM). Based on the investigations, it was observed that the maximum temperature distributed was nearly same in all the types of pistons as 1133K which appeared near the combustion area. The thermal stress and total deformation values of the piston was found to be lesser for the flat and dome types of pistons. Based on the data obtained for thermal stress, temperature distribution, heat flux and total deformation, it can be suggested that flat or dome type pistons can be considered for use in the IC engine to maximize the performance of diesel engine.

다기능 조파기의 조파 운동과 발생 파형

Piston type wave makers or flap type wave makers are usually adopted as a wave maker which disturbing the fluid domain with sinusoidal motion. Recently hybrid wave maker which could be operated as not only piston type and/or flap type but also swing type wave maker have been devised by utilizing the link mechanism. The wave board of hybrid wave maker has been devised to be independently controlled by the horizontal actuators on upper and lower end of the wave board. The wave board could operate as a flap type wave board when the lower hinge is in a stationary condition and the upper hinge is operated with sinusoidal motion. On the contrary, the swing type wave board could be obtained by the lower hinge is activated and the upper hinge is in a stationary condition. When both end of the wave board is activated in a synchronized condition, the wave board motion become piston motion. In addition the hybrid wave maker could enhance the piston motion with flap motion or swing motion by selecting control parameters. Various wave board motion of hybrid wave maker and relevant wave form have measured on the wave board and departed location. It is appeared that the novel hybrid wave maker could be utilized for the improvement of wave qualities in experiments.