Piston Action Research Articles

DEVELOPMENT OF ENERGY-EFFICIENT AIR DEDUSTING

Among the sources of internal pollution one can point to dust, breath products of passengers, various emissions from finishing materials of trains and metro stations, etc. This problem is usually solved in two ways: wet cleaning of tunnels and stations and using powerful tunnel vacuum cleaners. Both of these methods have common disadvantages. Firstly, dust removal can only be carried out at night, when there are no trains on the line. Secondly, the dust removal installations themselves are expensive and are effective only at low speeds of dust movement through the tunnel. All metros in the world have a problem with dust removal. Research methods include analytical and computational studies of air distribution in the metro ventilation network using mathematical modeling methods using graph theory and flow algorithms, as well as experimental studies of air flow parameters in natural conditions of the Almaty metro.This article proposes an innovative method for dust removal of tunnel air based on the use of piston action of trains and labyrinth filters installed in station ventilation joints. The parameters of the calculation model of the metro line are substantiated on the basis of a decomposition approach to the mathematical modeling of aerodynamic processes by moving from a linear model of the metro line to a periodic open-loop model. Computational aerodynamics methods were used to determine the patterns of changes in air speed through the ventilation vent and the available pressure drop depending on the speed and mode of trains passing through the station.

Justification of an Energy-Efficient Air Purification System in Subways Based on Air Dust Content Studies

It is not uncommon that subways count as densely populated areas, so air quality standards, including fine dust concentration, have been established for them. As passengers and subway staff are exposed to potentially harmful airborne particles, addressing this issue is vital to ensuring a safe and healthy environment on the subway. To reduce the dust concentration in subway systems, the authors propose installing filters to capture dust in ventilation failures between subway tunnels near metro stations. A novel aspect of the proposed method is the fact that airflow will be moved through filters by using the piston action of trains passing through the tunnels. The result of this research provides empirical evidence regarding dust content and mass concentrations of PM2.5 and PM10 in subway environments. While some existing literature discusses air quality in subways, the inclusion of specific measurements and data from the experiment strengthens the understanding of the severity of dust-related air quality issues in such environments. The data for this study were collected in the Almaty subway (Republic of Kazakhstan) at four stations: Raiymbek Batyr, Almaty, Baikonur and Alatau. Measuring points were located on passenger platforms, in the halls and at the entrances to the station. The lab scale tests determined the percentage of particles by their diameters relative to the total volume of dust, the percentage of dust particles smaller than a certain diameter, the percentage of various metal oxides and the average dust density. A preliminary energy assessment has been done on the proposed method of air purification from dust. With a frequency of 24 pairs of trains per hour, the energy savings per ventilation failure will be 240.170 kWh.

Justification of the parameters of ring models in the decomposition of the ventilation network of an extended metro line for the calculation of air distribution

The piston effect of trains on air distribution and air exchange in tunnel and passenger structures of the metro with a single-track tunnel is in second place after the action of mechanical tunnel ventilation. When the tunnel fans are turned off (for example, during the cold season in an area with a sharply continental climate), almost the entire ventilation load is provided by the piston action. Since all elements of the metro ventilation network are connected by tunnels under the generally accepted scheme of longitudinal ventilation, the mutual influence of the ventilation modes of neighboring metro sections is very significant. Therefore, in order to obtain the correct result of air distribution modeling, at least 8 runs with stations should be included in the calculation scheme, which leads to increased requirements for computing power and calculation time. The article considers the decomposition of an extended metro line using ring models and justifies the number of calculated sections with stations for different train frequencies. A comparison of the calculation results for the ring and linear models is given. Calculations are performed using network methods for calculating air distribution.

Application of computational modeling to study the parameters of dusty air flows in subway

To date, the subway is the most promising type of urban public transport, which is used daily by thousands of passengers in the world. In modern subways, the problem is the content of suspended dust in the air, which exceeds the maximum permissible concentration. Especially dangerous is the dust fraction PM2.5 or less, capable of penetrating through the biological barriers of the human body. This article discusses the results of a number of studies aimed at determining the concentration, fractional and chemical composition of such dust in subway structures. One of the ways to combat dustiness of the air in subways is its filtration. The authors propose the use of filters installed in the jetty ventilation breakdowns, the air flow through which is provided by the piston action of trains. Determination of optimal design and operational parameters of such filters is carried out using computer modeling by the finite volume method. The article provides an overview of the existing computational mathematical models of the movement of dusty air as a multiphase flow, and considers the possibility of their application to the conditions of underground subway structures.

About the primary smoke of the subway tunnel when a burning train stops in it

The article is devoted to the study of aerodynamic processes occurring in a subway tunnel when a burning train stops in it. The dynamics of the deceleration of the air flow accelerated by the piston action of a moving train is investigated by computational modeling using the finite volume method. When gorenje trains in the tunnel, this flow carries toxic combustion products through the tunnel, thereby creating the primary smoke tunnel. The influence of the length of the tunnel section with a train and aerodynamic drag on the dynamics of air flow braking is considered. To accelerate the deceleration of the air flow, the use of smoke-retaining devices on the train is proposed, the effectiveness of their use is determined.

Numerical Studies for the Thermal Regime of a High-Speed Railway Tunnel Considering Piston Action on Seasonally Frozen Regions

Abstract Piston action describes the phenomenon that air at the train nose is pushed forward by the increased pressure and air at the train rear is drawn forward by the decreased pressure when a train passes through a tunnel. The variation of pressure changes the thermal environment inside the tunnel and promotes the frost damage generation in cold season. In this paper, a fluid-thermal-solid involving piston action is proposed. A high-speed railway tunnel that is located in the northeast of China is set in the background, and the influence of outside air temperature and train velocity on the thermal environment inside the tunnel are simulated and analyzed. The piston action can significantly change the temperature inside the tunnel, especially at the ends of tunnel. The temperature distribution is characterized by three zones, including disturbed zones at two sides of tunnel and undisturbed zone at tunnel middle. The freezing length is closely related to air temperature and train velocity. And also, the lengths are different at vault and rail of tunnel portal, which indicates that the anti-freezing measure should be different at these positions considering the cost. This paper can help us understand the temperature evolution process of tunnels under the action of piston wind and provide some guidelines for structural design of cold regional tunnels.

Numerical analysis of heat transfer between air inside and outside the tunnel caused by piston action

Piston action can affect the thermal environment inside the tunnel by changing the air pressure and velocity. This is extremely unfavorable for tunnels in cold regions because it causes frost damage in cold season. Understanding the influence of piston action on the air temperature distribution inside the tunnel can help us determine the length and location of frost damage. In this paper, a heat transfer numerical model considering piston action is developed. And then, a high-speed railway tunnel in the northeast of China is taken as an example to explore the temperature distribution laws via computational fluid dynamic (CFD). Afterwards, the effects of air temperature outside the tunnel and train velocity on temperature distribution are analyzed. The results show that the piston action can accelerate the heat transfer between cold air outside and inside the tunnel, the anti-freezing length near tunnel entrance and exit must be extended based on the calculation result of existed empirical formula. Before the train enters the tunnel, the freezing length near tunnel entrance is 1158 m. After the train passing through the tunnel, the freezing length near tunnel entrance is between 1495 m and 1497 m when the air temperature outside the tunnel decreases from −1 °C to −15 °C. Under different train velocities (80 km/h, 130 km/h, 160 km/h, 200 km/h and 250 km/h), the freezing lengths near tunnel entrance are 1458 m, 1469 m, 1472 m, 1497 m, 1498 m and its near tunnel exit are 330 m, 342 m, 349 m, 356 m, 357 m, respectively. In the section of 50 m away from tunnel entrance, the air temperature near the train changes suddenly, while the air temperature far away from the train changes gently. After the train passing through the tunnel, the air temperature inside the tunnel is consistent to that outside the tunnel within a specific distance from entrance. This study provides a guideline and references for the structure design and the construction of anti-freezing measurements for the tunnels in cold regions.

ГЕОМАГНІТНИЙ ЕФЕКТ ТУРЕЦЬКОГО ЗЕМЛЕТРУСУ 24 СІЧНЯ 2020 р.

Purpose:The main cause of geomagnetic disturbances are cosmic sources, processes acting in the solar wind and in the interplanetary medium, as well as large celestial bodies entering the terrestrial atmosphere. Earthquakes (EQs) also act to produce geomagnetic effects. In accordance with the systems paradigm, the Earth–atmosphere–ionosphere–magnetosphere system (EAIMS) constitute a unified system, where positive and negative couplings among the subsystems, as well as feedbacks and precondition among the system components take place. The mechanisms for the action of EQs and processes acting in the lithosphere on the geomagnetic field are poorly understood. It is considered that the EQ action is caused by cracking of rocks, fluctuating motion in the pore fluid, static electricity discharges, etc. In the course of EQs, the seismic, acoustic, atmospheric gravity waves (AGWs), and magnetohydrodynamic (MHD) waves are generated. The purpose of this paper is to describe the magnetic effects of the EQ, which took place in Turkey on 24 January 2020. Design/methodology/approach: The measurements are taken with the fluxmeter magnetometer delivering 0.5-500 pT sensitivity in the 1-1000 s period range, respectively, and in a wide enough studied frequency band within 0.001 to 1 Hz. The EM-II magnetometer with the embedded microcontroller digitizes the magnetometer signals and performs preliminary filtering over 0.5 s time intervals, while the external flash memory is used to store the filtered out magnetometer signals and the times of their acquisition. To investigate quasi-periodic processes in detail, the temporal variations in the level of the H and D components of the geomagnetic field were applied to the systems spectral analysis, which makes use of the short-time Fourier transform, the wavelet transform using the Morlet wavelet as a basis function, and the Fourier transform in a sliding window with a width adjusted to be equal to a fixed number of harmonic periods. Findings: The train of oscillations in the level of the D component observed 25.5 h before the EQ on 23 January 2020 is supposed to be associated with the magnetic precursor. The bidirectional pulse in the H component observed on 24 January 2020 could be due to the piston action of the EQ, which had generated an MHD pulse. The quasi-periodic variations in the level of the H and D components of the geomagnetic field, which followed 75 min after the EQ, were caused by a magnetic disturbance produced by the traveling ionospheric disturbances due to the AGWs launched by the EQ. The magnetic effect amplitude was estimated to be close to 0.3 nT, and the quasi-period to be 700-900 s. The amplitude of the disturbances in the electron density in the AGW field was estimated to be about 8 % and the period of 700-900 s. Damping oscillations in both components of the magnetic field were detected to occur with a period of approximately 120 s. This effect is supposed to be due to the shock wave generated in the atmosphere in the course of the EQ. Conclusions: The magnetic variations associated with the EQ and occurring before and during the EQ have been studied in the 1-1000 s period range. Key words: earthquake, fluxmeter magnetometer, quasi-periodic disturbance, seismic wave, acoustic-gravity wave, MHD pulse

Simulation of Gait Based Wearable Energy Harvesting using Human Movement

The portability of power for human health monitoring is considered a challenge for years to come and the recent development in wearable devices has encouraged this research area. This paper develops a composite energy harvesting paradigm that combines piezoelectricity and electromechanical energy production to energize the storage batteries powering wearable devices. A composite mathematical model that combines the piezoelectric process along with the electromechanical process comprising the piston action is developed using MatlabTM. The piezoelectric power is considered to be generated from the pressure created by human weight on it while walking and electromechanical power generated from the limb movement of the human being. The energy thus harvested from both these inputs are consolidated and fed to charge the batteries that feed the wearable sensors. The Lithium-Ion battery of 1.2V rated voltage is charged using the power generated from the mathematical models of both the piezoelectric and electromechanical power generation. The energy generated is found to be satisfactorily charging the battery.

Hydraulic fracturing effect on punching-induced cover-collapse sinkholes: a case study in Guangzhou, China

Punching-induced cover-collapse sinkholes occur rapidly, and multiple collapses occur simultaneously compared with those caused by other common factors, such as pumping, rainstorms and mining. Erosion cannot explain the formation of this type of collapse entirely. We studied the hydraulic fracturing effect from geological analysis, field groundwater monitoring, laboratory testing, and pressure calculation. Four stages can be established for the development of cover-collapse sinkhole based on a case study. Hydraulic fracturing and the suction effect cause sinkhole opening with the percussion bit falling and pulling repeatedly when the pile foundation is being built. The behavior can be likened figuratively to a piston action. The pressure of the calculated hydraulic fracturing effect is 6.05 × 104 Pa, which is equivalent to a 5.93-m-high water column and is much bigger than the critical pressure of 0.7 m at which hydraulic fracturing occurs in laboratory testing. The significance of this study from a practical perspective is to provide a preventative, early warning method for sinkhole opening by groundwater monitoring during pile foundation construction.

Improving the constant‐volume degree of combustion considering generatable range at low speed in a free‐piston engine linear generator system

Series hybrid vehicles using free‐piston engine coupled with linear generator are expected for high‐efficiency energy conversion systems. Such engines do not have a crank mechanism, which greatly reduces the friction loss. In addition, the piston action can be controlled freely by the generation braking thrust by using an inverter control. In a conventional crank engine, past research has shown that delaying the piston motion after the combustion increases the maximum combustion pressure, and this delay brings a constant‐volume degree close to the Otto cycle. In the free‐piston system, a high braking thrust is needed at a low piston speed immediately after combustion. However, the highest braking thrust was limited in the low‐speed range because the back electromotive force of a permanent magnet synchronous generator was too small. This article shows the range that can be theoretically attained for a low‐speed generator. The delaying piston movement with only the braking thrust improved the effective work by 25% near the top dead center. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

3D-CFD Simulation of Confined Cross-Flow Injection Process Using Single Piston Pump

Injection process into a confined cross flow is quite important for many applications including chemical engineering and water desalination technology. The aim of this study is to investigate the performance of the injection process into a confined cross-flow of a round pipe using a single piston injection pump. A computational fluid dynamics (CFD) analysis has been carried out to investigate the effect of the locations of the maximum velocity and minimum pressure on the confined cross-flow process. The jet trajectory is analyzed and related to the injection pump shaft angle of rotation during the injection duty cycle by focusing on the maximum instant injection flow of the piston action. Results indicate a low effect of the jet trajectory within the range related to the injection pump operational conditions. Constant cross-flow was used and injection flow is altered to vary the jet to line flow ratio (QR). The maximum jet trajectory exhibits low penetration inside the cross-flow. The results showed three regions of the flow ratio effect zones with different behaviors. Results also showed that getting closer to the injection port causes a significant decrease on the locations of the maximum velocity and minimum pressure.

A mechanical piston action may assist pelvic–pectoral fin antagonism in tree-climbing fish

In this research, we compared the anatomy and biomechanics of two species of mudskipper vs an aquatic sandgoby in view of terrestrial locomotion. Of particular interest was the relationship (if any) of pectoral fin movement with pelvic fin movement. We show that the pelvic fins of the terrestrial mudskippers studied herein, are retractable and move antagonistically with the pectoral fins. The pelvic fin of the sandgoby studied here is contrarily non-retractable and drags on any underlying substrate that the sandgoby tries to crawl across. We find that the pelvic and pectoral fin muscles of all fish are separated, but that the pectoral fins of the mudskipper species have bulkier radial muscles than the sandgoby. By coupling a detailed morphological investigation of pectoral-pelvic fins musculature with finite element simulations, we find that unlike sandgobies, the mudskipper species are able to mechanically push the pelvic fins downward as pectoral fins retract. This allows for an instant movement of pelvic fins during the pectoral fin backward stroke and as such the pelvic fins stabilize mudskippers through Stefan attachment of their pelvic fins. This mechanism seems to be efficient and energy saving and we hypothesize that the piston-like action might benefit pelvic–pectoral fin antagonism by facilitating a mechanical down-thrust. Our research on the biomechanics of tree-climbing fish provides ideas and greater potential for the development of energetically more efficient systems of ambulation in biomimetic robots.

Mechanically Automated Light Weight WAstage REmover [MALWWARE

This paper proposes an innovative, Eco-friendly, simply operated system for cleaning of light weight wastage materials on municipal roads, which is equipped with cylinders of a typical Internal Combustion engine with mechanical gear trains. With simple piston action, we can remove light weight wastes like dry leaves and thin plastic things. Our conventional and present vacuum cleaners use either Electric power or Gasoline, since it is a kind of polluting our environment in an indirect way. To overcome the disadvantages of conventional systems and to protect our environment, we use a pneumatic system here with the least number of moving parts which are cheaper than present vacuum cleaners. This system does not need either Electrical or Gasoline energy. It is as simple as pushing a wheelchair, so anyone can run this system. We can extend its application to any level. Our system has two operations. Both operations are simultaneous and give more power to the machine.

Accelerating piston action and plasma heating in high-energy density laser plasma interactions

In the field of high-energy density physics (HEDP), lasers in both the nanosecond and picosecond regimes can drive conditions in the laboratory relevant to a broad range of astrophysical phenomena, including gamma-ray burst afterglows and supernova remnants. In the short-pulse regime, the strong light pressure (>Gbar) associated ultraintense lasers of intensity I > 1018 W/cm2 plays a central role in many HEDP applications. Yet, the behavior of this nonlinear pressure mechanism is not well-understood at late time in the laser–plasma interaction. In this paper, a more realistic treatment of the laser pressure ‘hole boring’ process is developed through analytical modeling and particle-in-cell simulations. A simple Liouville code capturing the phase space evolution of ponderomotively-driven ions is employed to distill effects related to plasma heating and ion bulk acceleration. Taking into account these effects, our results show that the evolution of the laser-target system encompasses ponderomotive expansion, equipartition, and quasi-isothermal expansion epochs. These results have implications for light piston-driven ion acceleration scenarios, and astrophysical applications where the efficiencies of converting incident Poynting flux into bulk plasma flow and plasma heat are key unknown parameters.

Intraoperative ultrasonography used to determine the extent of surgery necessary during posterior fossa decompression in children with Chiari malformation Type I

In this retrospective analysis, the authors report a prospective study in which intraoperative ultrasonography was used to determine the extent of surgery necessary during posterior fossa decompression surgery for Chiari malformation Type I (CM-I) in children. Between 1995 and 2003, posterior fossa decompression was performed in 149 patients (mean 5.9 years of age, range 9 months-18 years of age) with CM-I. Of these, 130 underwent intraoperative ultrasonographic evaluation of the craniocervical junction (CCJ) and 15 did not. Four patients with craniosynostosis were excluded from the study. Duraplasty and tonsillar shrinkage were performed when ultrasonographic evidence showed significant decreases in cerebrospinal fluid (CSF) or abnormal tonsillar piston action. Surgical success was determined on the basis of clinical outcome and need for reoperation. One hundred and twenty-four (95.5%) of the children had successful outcomes following surgery and six (4.5%) experienced continued or worsening symptoms requiring reoperation. Forty patients did not undergo duraplasty because the ultrasonography evidence showed adequate decompression with bone removal alone. Of 90 patients with significant compression, decreased CSF dynamics, and/or abnormal tonsillar piston-like action at the CCJ, 85 underwent duraplasty and tonsillar shrinkage and five did not for various reasons. One patient in whom the dura mater was violated accidentally during bone decompression subsequently underwent duraplasty. Hospital stays lasted 6.4 +/- 3.9 days (mean +/- standard deviation) when duraplasty was performed compared with 4.3 +/- 1.1 days when it was not (p < 0.0003). After bone decompression alone, no patient experienced complications. After duraplasty, 12 patients experienced complications and had headaches, nausea, and pain more often than patients who underwent bone decompression alone. Mean tonsillar descent was 11 +/- 4 mm after bone decompression only and 13.9 +/- 4.9 mm after duraplasty, with tonsillar shrinkage (p < 0.0003) seen on magnetic resonance imaging. In patients who undergo decompressive surgery for CM-I, intraoperative ultrasonography may be a useful tool to aid the surgeon in deciding whether to opt for bone removal only or bone removal plus duraplasty and tonsillar shrinkage.

Calculation of Tunnel Ventilation in Shallow Subways

A procedure is proposed to determine the tunnel fan capacity taking into account the area of passenger spaces in stations, traffic flow, and traffic working intensity. The calculation results and experimental data are presented to substantiate possible use of air disturbances due to a piston action of trains moving in tunnels for ventilation of shallow subways.

交通換気力に関する研究(トンネル換気)

This section describes differences between usual and renewed parameters for the traffic piston action, used in the decision of the necessary ventilation volume, and methods to derive such new parameters are clarified.

Sound system coverage and intelligibility using AFR devices

AFR loudspeaker technology (audio full-range) combines the characteristics of distributed mode loudspeakers at mid and high frequencies with conventional loudspeaker piston action at low frequencies in a single driver. The combination retains the well-established advantages of the DML in respect of wide dispersion and improved interaction with reflective boundaries. A comparison study has been made using conventional 6-in. ceiling loudspeakers and AFR devices of comparable size in a typical open plan office situation. It is shown that the AFR devices exhibited noticeably improved coverage, clarity, and speech intelligibility. However, the use of traditional intelligibility measures, such as STI did not always reflect this subjectively observed trend. The use of STI or STIPa under high signal to noise conditions is questioned.

Analysis of a piston PSA process for air separation

The piston driven PSA process offers the potential for achieving productivity improvement by rapid piston action. In the present work, experiments were performed on a laboratory scale piston driven PSA test rig with provisions to vary all the important operating variables, namely, phase angle configuration, stroke length, cycling speed duration and angles of feed introduction and product withdrawal. Air separation on 13X zeolite was chosen as the model experimental system. Experiments with adsorbent particles of two different sizes confirmed that mass transfer resistance is important and may significantly affect the separation performance. A mathematical model was developed to simulate the process. The numerical solution was verified by simulating limiting conditions that had analytical solutions. Some basic model assumptions related to piston motion were verified by comparing with experiments conducted at well-defined limiting conditions like empty column and total recycle. Flow resistance in the connecting tubes seemed to explain the observed difference in both phase and amplitude of the pressure profiles measured at the two ends of the column. The model predictions were generally in good agreement with the experimental observations. The model was used to perform a parametric study in the operating regions that were not covered in the experiments. General inferences are made regarding the operating configurations that are expected to improve system performance.