Showing papers on "Piston published in 2015"

Banknote flattening device

Abstract: The utility model discloses a banknote flattening device, which comprises a pallet provided with a strip-shaped through-hole formed in the bottom thereof One end of the pallet sleeves one end of a banknote entering channel; the other end of the banknote entering channel is connected to a banknote entering slip-way; and an electric rolling shaft is arranged at the joint of the banknote entering slip-way and the banknote entering channel Two metal strips are arranged above the through-hole, and two electromagnetic strips are arranged below the through-hole, wherein two ends of each metal strip are connected to two ends of each electromagnetic strip through springs The lower parts of the electromagnetic strips are connected to two piston rods of a hydraulic cylinder through connecting rods Two annular conveyor belts are arranged in the pallet, the inner surfaces of the two annular conveyor belts are locked at two transmission shafts A single-chip microcomputer is arranged in the pallet; a sensing device is arranged on the inner wall of the banknote entering channel; and a collection box is arranged at one end, far away from a banknote entering device, of the pallet According to the utility model, the banknote flattening device is simple in principle and convenient to use, the rolled corners and winkles of banknotes can be automatically flattened, and surfaces of banknotes can be ironed to flat in a hot ironing way The banknote flattening device is high in working efficiency, good in flattening effect, and high in practical value

Non-equilibrium quantum heat machines

Abstract: Standard heat machines (engine, heat pump, refrigerator) are composed of a system ("working fluid") coupled to at least two equilibrium baths at different temperatures and periodically driven by an external device (piston or rotor) called sometimes work reservoir. The aim of this paper is to go beyond this scheme by considering environments which are stationary but cannot be decomposed into few baths at thermal equilibrium. Such situations are important, for example in solar cells, chemical machines in biology, various realizations of laser cooling or nanoscopic machines driven by laser radiation. We classify non-equilibrium baths depending on their thermodynamic behavior and show that the efficiency of heat machines operating under their influences is limited by a generalized Carnot bound.

On damping of two-dimensional piston-mode sloshing in a rectangular moonpool under forced heave motions

Abstract: Based on a similarity between piston-mode sloshing in a two-dimensional rectangular moonpool and a small-amplitude oscillatory flow through a slot in a slatted screen, a pressure discharge in the moonpool opening is theoretically quantified. This makes it possible, by changing the dynamic free-surface condition inside the moonpool, to account for the vortex-induced damping and thereby to modify the inviscid potential flow statement. The present paper is an important addition to Faltinsen et al. (J. Fluid Mech., vol. 575, 2007, pp. 359–397), where a discrepancy between the potential flow theory and model tests was reported. New calculations are supported by the earlier model tests of the authors as well as numerical data obtained by means of viscous solvers.

A Transient Thermoelastohydrodynamic Lubrication Model for the Slipper/Swashplate in Axial Piston Machines

Abstract: A transient lubrication model has been developed for the sliding interface between the slipper and swashplate in axial piston hydraulic pumps and motors. The model considers a nonisothermal fluid model, microdynamic motion of the slipper, as well as pressure and thermal deformations of the bounding solid bodies through a partitioned solution scheme. The separate contributions of elastohydrostatic and elastohydrodynamic lubrication are studied. Although hydrostatic deformation dominates, hydrodynamic effects are crucial for actual operation. Finally, the impact of transient deformation on lubricant pressure is explored, with its consideration necessary for accurate analysis.

Design and novel type of a magnetorheological damper featuring piston bypass hole

Abstract: This work proposes a novel type of magnetorheological (MR) damper configuration from which an excellent ride comfort can be achieved without using a sophisticated controller scheme. The proposed novel MR damper is featured by piston bypass holes to achieve low slope of the damping force in the pre-yield (low-piston-velocity) region and high magnitude of the damping force in the post-yield (high-piston-velocity) region. A mathematical model for the damping force of the proposed MR damper is formulated followed by the investigation on damping characteristics with respect to several geometrical design parameters such as the number of piston bypass hole, the diameter of the hole, the gap size of the orifice, the orifice length, the diameter of the bobbin, and the height of the coil. After selecting the main design parameters from the simulation results, numerical simulations for the damping force characteristics are conducted with eight design parameter sets to evaluate the significant effect on the damping force performance. The proposed MR dampers are then manufactured with the same design parameter sets and the damping force characteristics are experimentally obtained and compared with the analytical simulation results. It is identified from the parametric investigations that the size and the number of the piston bypass hole are very important on damping force characteristics of the proposed MR damper.

Acoustic non-diffracting Airy beam

Abstract: The acoustic non-diffracting Airy beam as its optical counterpart has unique features of self-bending and self-healing. The complexity of most current designs handicaps its applications. A simple design of an acoustic source capable of generating multi-frequency and broad-band acoustic Airy beam has been theoretically demonstrated by numerical simulations. In the design, a piston transducer is corrugated to induce spatial phase variation for transducing the Airy function. The piston's surface is grooved in a pattern that the width of each groove corresponds to the half wavelength of Airy function. The resulted frequency characteristics and its dependence on the size of the piston source are also discussed. This simple design may promote the wide applications of acoustic Airy beam particularly in the field of medical ultrasound.

Stable Operation and Electricity Generating Characteristics of a Single-Cylinder Free Piston Engine Linear Generator: Simulation and Experiments

Abstract: We present a novel design of a single-cylinder free piston engine linear generator (FPELG) incorporating a linear motor as a rebound device. A systematic simulation model of this FPELG system was built containing a kinematic and dynamic model of the piston and mover, a magneto-electric model of the linear generator, a thermodynamic model of the single-cylinder engine, and a friction model between the piston ring and cylinder liner. Simulations were performed to understand the relationships between pre-set motor parameters and the running performance of the FPELG. From the simulation results, it was found that a motor rebound force with a parabolic profile had clear advantages over a force with a triangular profile, such as a higher running frequency and peak cylinder pressure, faster piston motion, etc. The rebound position and the amplitude of rebound force were also determined by simulations. The energy conversion characteristics of the generator were obtained from our FPELG test rig. The parameters of intake pressure, motor frequency, and load resistance were varied over certain ranges, and relationships among these three parameters were obtained. The electricity-generating characteristic parameters include output power and system efficiency, which can measure the quality of matching the controllable parameters. The output power can reach 25.9 W and the system efficiency can reach 13.7%. The results in terms of matching parameters and electricity-generating characteristics should be useful to future research in adapting these engines to various operating modes.

Variable length connecting rod and variable compression ratio internal combustion engine

Abstract: A variable length connecting rod which can change the effective length comprises a connecting rod body, an eccentric member which is attached at the small end to the connecting rod body to be able to swivel and which changes the effective length of a variable length connecting rod when swiveled, one piston mechanism which has one hydraulic cylinder which is provided in the connecting rod body and one hydraulic piston which slides in the hydraulic cylinder, a direction switching mechanism which switches between supply and discharge of hydraulic fluid to the hydraulic cylinder, and a hydraulic fluid supply source which supplies the hydraulic cylinder with hydraulic fluid. The piston mechanism is configured so that the eccentric member swivels in one direction if hydraulic fluid is supplied to the hydraulic cylinder and so that the eccentric member swivels in the other direction if hydraulic fluid is discharged from the hydraulic cylinder.

Development of a sensitive experimental set-up for LIF fuel wall film measurements in a pressure vessel

Abstract: This paper focusses on fundamental investigations of fuel wall films, which are formed when the spray impinges on the piston or cylinder walls. To reproduce the wide range of operating conditions within homogeneously charged gasoline direct-injection engines, it is necessary to use a film thickness measurement method, which can be applied inside a high-pressure, high-temperature vessel. Hence, we developed a method based on laser-induced fluorescence that reaches: a precision better than 1 µm, a geometric resolution of 31 µm and a practical applicability for wall film thicknesses smaller 80 µm. To obtain accurate film thickness results, we provide a detailed description of the selection of the surrogate fuel isooctane with 3-pentanone as fluorescence tracer and the resulting assembly of the excitation source, beam expander, filters, camera and the essential image processing. Furthermore, advantages and disadvantages of other possible solutions are discussed. Earlier publications provide only little information about the accuracy of their calibration and measurement procedures. Therefore, we tested and compared three basic calibration methods to each other and provide an analysis of possible errors, such as the influence of the preferential evaporation of 3-pentanone. Finally, images of resulting wall films are presented, and practical considerations for the execution of the measurements like recording timings are discussed.

Common-rail fuel oil jet system controlled by double electromagnetic valves and applied to low-speed diesel engine for ship

Abstract: The invention provides a common-rail fuel oil jet system controlled by double electromagnetic valves and applied to a low-speed diesel engine for a ship. The common-rail fuel oil jet system comprises a fuel oil supply portion and a common-rail jet device. The fuel oil supply portion supplies fuel oil and servo oil to the common-rail jet device. In the common-rail jet device, an upper pressurizing piston cavity and a lower pressurizing piston cavity are formed between a pressurizing piston and a pressurizing piston body, and the pressurizing piston control valve controls the fuel oil supply portion to be communicated or not communicated with the upper pressurizing piston cavity, so that fuel oil pressurization or fuel oil suction is achieved; the electromagnetic fuel oil jet control valve conducts fuel oil-working-condition accurate flexible control over fuel oil jet timing and the circulation jet amount, a pressurized high-pressure fuel oil path in the lower pressurizing piston cavity is divided into two paths, one path reaches a control cavity, and the other path reaches a fuel oil containing groove. According to the common-rail fuel oil jet system, the two electromagnetic valves are used for control, fuel oil is used as fuel and servo oil at the same time, the structure is simplified, cost is reduced, mutual independence between fuel oil pressurization and jet and repeated jet are achieved, fuel oil jet timing, the fuel oil jet rule and the circulating fuel oil jet amount are more accurately controlled, the fuel oil economical efficiency and the emission performance of the diesel engine are improved.

Quantum optomechanical piston engines powered by heat

Abstract: We study two different models of optomechanical systems where a temperature gradient between two radiation baths is exploited for inducing self-sustained coherent oscillations of a mechanical resonator. From a thermodynamic perspective, such systems represent quantum instances of self-contained thermal machines converting heat into a periodic mechanical motion and thus they can be interpreted as nano-scale analogues of macroscopic piston engines. Our models are potentially suitable for testing fundamental aspects of quantum thermodynamics in the laboratory and for applications in energy efficient nanotechnology.

Double Compression Expansion Engine Concepts: A Path to High Efficiency

Abstract: Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)

Two-stroke engine with air leading type scavenging system

Abstract: The invention discloses a two-stroke engine with an air leading type scavenging system. The two-stroke engine comprises an air cylinder, wherein the air cylinder is connected with a crankcase, so as to form a cylinder body, a piston is arranged in the cylinder body, so as to divide the cylinder body into a combustion chamber and a crankcase chamber, and an exhaust passage, an inlet passage, a scavenging passage and an air inlet passage are formed in the cylinder body. The two-stroke engine is characterized in that the scavenging passage is communicated with the combustion chamber and the crankcase chamber, a scavenging outlet of the scavenging passage is formed in the inner wall of the air cylinder, the communication and blocking of the scavenging outlet and the combustion chamber are controlled through the piston, a scavenging inlet of the scavenging passage is formed in the inner wall of the crankcase, the communication and blocking of the scavenging inlet and the crankcase chamber are controlled through a crank valve, the air inlet passage is communicated with the scavenging passage, and air enters the scavenging passage in an inlet process and is firstly scavenged into the combustion chamber in a scavenging process. According to the two-stroke engine, the contact time of mixed gas with the air can be reduced, so that the purpose that clean air is scavenged into the combustion chamber of the air cylinder is realized, and the purposes of reducing escape of unburned mixed gas and stabilizing emission performance are achieved.

Direct numerical simulation of PRF70/air partially premixed combustion under IC engine conditions

Abstract: A three-dimensional direct numerical simulation (DNS) is performed to study the ignition and the combustion process of a primary reference fuel (PRF) under conditions relevant to partially premixed combustion (PPC) engines. Detailed transport properties together with a skeletal PRF chemical kinetic mechanism are employed in the simulations. The initial partially premixed charge is prescribed according to a two-injection of fuel strategy with a 50% exhaust gas recirculation (EGR). The motion of the piston, hence, the effect of compression of the charge due to the piston motion is considered. The simulations are performed with a fine mesh with a spatial resolution of 1.2 micrometers in a cubic domain of 614 micrometers on each side. The results show that there are three distinctive combustion regions in a domain under PPC conditions, a lean homogeneous mixture region, a fuel-rich region, and in between a region with stoichiometric mixture. Auto-ignition occurs first in the lean and stoichiometric mixture regions, followed by a partially premixed flame in the fuel-rich region and at last a CO oxidation phase in the fuel-rich region. In the lean mixture region, the fuel and the combustion intermediates such as CO are consumed almost completely due to the relatively fast combustion and the abundant oxygen. The CO formed in the regions with the stoichiometric and the fuel-rich mixture is consumed in a mixing controlled mode, which requires a high-level turbulence mixing or a sufficiently long residence time. NO is formed mainly due to the premixed combustion in the region with the stoichiometric mixture.

Pneumatic centering clamp used for cylindrical part

Abstract: The invention discloses a pneumatic centering clamp used for a cylindrical part. The pneumatic centering clamp comprises a base of a square-plate-shaped structure, a round groove is formed in the middle of the base and used for containing the work piece, a positioning pin is arranged in the center of the round groove, pneumatic clamping mechanisms are arranged at the middle points of the four sides of the base and comprise air cylinders, tile type clamping plates are arranged on piston rods of the air cylinders, and the clamping faces of the clamping plates right face the round groove. The work piece can be fixed from the side face and one end face of the cylindrical work piece, in this way, the problem that the end faces of the cylindrical work piece are difficult to machine is solved, the centering performance in the clamping process is high, deviation of the work piece in the machining process can be greatly reduced, and the machining precision is improved.