Piston-cylinder System Research Articles

Abstract 16610: A New Left Ventricle Vortex Formation Time for Clinical Assessment of Diastolic Filling Efficiency Based on Direct Mechanical Ventricular-Vascular Coupling: Evaluation in Heart-Failure and Healthy Cohort

Introduction: The mechanical coupling of the left ventricle (LV) and aorta creates the apical motion of the atrioventricular plane (AVP), resembling a piston-cylinder system, impacting early diastolic filling (J Am Heart Assoc. 2017;6:e004903). Furthermore, several clinical studies have suggested the vortex formation time (VFT) as an indicator of LV diastolic function (Eur. Heart J. Cardiovasc. Imaging. 2012;13(5):385-93). However, conflicting results exist in previous clinical studies, potentially due to deviations from the original fluid dynamics definition of VFT in a piston-in-cylinder setting. In this study, we propose a new VFT approach to assess LV diastolic filling performance based on direct mechanical ventricular-vascular coupling. Methods: Cardiac MRI was used on 69 healthy individuals and 19 heart failure (HF) patients. The clinical cohort (37% women) had a mean age of 46 [± 17.5] years and BMI of 24.8 [±4.5]. LV valvular diseases were excluded. VFT was assessed using the original L/D definition, where L represents ascending aortic recoil motion (piston displacement) and D represents the mitral valve orifice. Aortic displacement was measured on the three and four-chamber MRI scans by tracing the AVP. Mitral valve orifice was determined as the average of commissure distance (short-axis images) and the leaflet tip distance (three-chamber view). Results: The new VFT approach yielded a mean[± std.] of 4.73[±0.89] for the healthy group, and considerably lower values (3.24±0.83) for the patients with HF (figure 1). Conclusions: The proposed VFT based on the mechanical ventricular-vascular coupling and original fluid dynamic formulation, demonstrates a theoretical optimal value of approximately 4 in healthy individuals, while significantly lower in HF. This novel VFT has the potential to address existing discrepancies regarding the clinical significance of VFT and establish it as a promising indicator of left ventricular filling efficiency.

Direct measurement and calculation of rubber bulk modulus by piston-cylinder method using conventional mechanical testing equipment

This article describes a method to directly measure the bulk modulus of rubber using a piston-cylinder type apparatus. The function of the testing apparatus is to reliably transfer load to the water inside the vessel and allow for the accurate and continuous measurement of volumetric displacement as the contents are compressed. During the test, load is applied to a piston-cylinder containing the rubber test sample and water using a conventional mechanical testing load frame. Load and the travel of the piston are recorded by a load cell and extensometer, respectfully. A brass or stainless steel plug of the same dimensions as the test sample is tested as a control sample to isolate the compliance of the system, including the compressibility of water and compliance of the o-rings which seal the piston-cylinder system. The results from this control test are used to decouple the compliance of the system from the sample test results. Load-linear displacement data are mathematically converted to pressure-volumetric displacement data, from which bulk modulus is calculated. The test apparatus and method are validated using the known bulk modulus of water. Finally, the bulk moduli for two similar rubbers are evaluated. The validity of the results and limitations of the device are discussed.

A Feature-Extraction-Based Adaptive Refinement Method for Solving the Reynolds Equation in Piston–Cylinder System

A fast local refinement algorithm based on feature extraction is developed. In the mesh-based Reynolds equation solutions, two refinement features based on the physical parameters of fluid lubrication are firstly defined, namely, pressure value feature and pressure gradient feature. Then, a fast adaptive strategy different from the traditional methods based on residuals or recovery errors is constructed according to the features, which are expected to determine the element needed to be refined. Considering the update requirement of the feature parameters, an adaptive update strategy for feature parameters is also developed. Finally, the feasibility of the scheme is verified on a single-cylinder gasoline engine. Results show that the current algorithm can effectively reduce the computational scale while ensuring the computational accuracy of the mesh-based model, compared with the traditional global and local refinement strategy.

Research on Analysis of Friction and Lubrication Characteristics of Piston-Cylinder System in Internal Combustion Engines Using Improved Multi-Layer Thermal Resistance Model

Research on Analysis of Friction and Lubrication Characteristics of Piston-Cylinder System in Internal Combustion Engines Using Improved Multi-Layer Thermal Resistance Model

The Tribo-Dynamics Performance of the Lubricated Piston Skirt–Cylinder System Considering the Cylinder Liner Vibration

The tribo-dynamics performance of the piston–cylinder system is affected by multiple physical fields. The current work presents a novel multiphysics coupling method to model and analyze the lubricated piston skirt–cylinder interface considering the cylinder liner vibration. This method is implemented by coupling multibody dynamics of the crank-connecting rod–piston–cylinder system, the heat transfer of the cylinder and piston, hydrodynamics lubrication on the skirt–cylinder interface, vibration of the cylinder liner, and thermal as well as elastic deformation in the piston–cylinder system together with rheological characteristics of lubricating oil. The proposed method is adopted into a four-stroke gasoline engine to predict its dynamics and tribological characteristics, with the purpose of revealing the influence of cylinder liner vibration on the tribo-dynamics implementation of the piston–cylinder system. The results indicate that increasing the stiffness and damping coefficient of the cylinder is beneficial to suppress the vibration of the system, but it has little effect on the tribological characteristics of the piston skirt–cylinder interface.

Thermal conditioning of remoistened wheat straw to produce durable pellets

Agricultural biomass like wheat straw is known to be lacking natural binders to form durable pellets. Our previous research had shown that steam explosion of wood improved the durability of pellets. However, treated wood required drying prior to pelletization. Thermal conditioning is practiced in the animal feed industry to modify the ingredients of animal feed to produce high quality pellets. We hypothesized that thermal treatment of straw would result in biomass pellets with improved durability when compared to pellets made from untreated biomass. To test this hypothesis, the moisture content (mc) of the straw samples was adjusted to 5%, 10%, and 15% (wet basis). The moistened samples were subjected to dry heat in a sealed reactor set at 80, 100, and 120 °C for 5, 10, and 15 min. The treated straw samples were pelletized by using a single piston cylinder system. The highest durability 91.5% belonged to the treatment of 10% mc straw at 100 °C for 5 min. A response surface method confirmed that the initial mc 10%, treatment temperature 100 °C, and treatment time 5 min, produced the most durable pellets with the lowest unit energy input in forming pellets.

Experimental investigation on anti-wear coating design for a small aviation kerosene piston engine

The high temperature wear failure of piston-cylinder system is a severe threat to aviation kerosene piston engines. To design a suitable anti-wear coating for the cylinder wall of a small aviation kerosene piston engine, a face contact friction pair and a line contact friction pair were designed to model the friction between the piston and the cylinder wall and the friction between the piston ring and the cylinder wall, respectively, and the graphite coating, the hard anodized coating (HA coating) and the microarc oxidation coating (MAO coating) were prepared on the cylinder wall specimen. Wear tests under high temperature were conducted for both friction pairs, and the friction coefficients, wear mass loss and worn surface morphology were analyzed. The results show that under high temperature condition, the graphite coating shows the least improvement on the wear mass loss and the worn surface state, the MAO coating causes serious wear to the piston specimen of face contact friction pair, while the HA coating is recommended as a suitable anti-wear coating for the engine by effectively reducing the wear mass loss and improving the worn surface state in both line contact and face contact friction pairs.

A new approach for modeling and analysis of the lubricated piston skirt-cylinder system with multi-physics coupling

The lubrication of the piston skirt-cylinder interface involves multiple physical fields, and these physical fields are coupled. A new method is proposed in this study for modeling and analysis of the lubricated piston skirt-liner interface with multi-physics coupling. This method is implemented in COMSOL Multiphysics software by coupling the heat transfer of the cylinder and piston, multibody dynamics of the crank-connecting rod-piston-cylinder system, the hydrodynamics lubrication of the skirt-cylinder interface, the thermal and elastic deformation of the piston-cylinder system, as well as the rheological properties of lubricating oil. The proposed method is first validated with a previous method and then adopted to a four-stroke gasoline engine to predict its dynamics and tribological characteristics. Then, a case study of different skirt thicknesses is conducted to reveal the influence the stiffness of the piston skirt exerts on the tribo-dynamics performance of the piston-cylinder system. The results indicate that although a thinner skirt will affect the stability of piston motion and increase the slapping noise and wear, it will benefit hydrodynamic lubrication between skirt and cylinder and reduce friction power loss.

A New Approach for Modeling Mixed Lubricated Piston-Cylinder Pairs of Variable Lengths in Swash-Plate Axial Piston Pumps.

The swash-plate axial piston pump is one of the most widely used pumps due to its simplicity and compactness in structure. In such a pump, the piston-cylinder system plays a crucial role, with its lubrication characteristics greatly affecting the overall pumping performance. A new numerical approach is proposed in this study for modeling mixed lubricated piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps in the framework of multibody dynamics. The approach couples the hydrodynamic mixed lubrication model of the piston-cylinder interface with the multibody dynamics model of the piston pump. The lubrication model is established with a transient average Reynolds equation considering asperity contacts and is solved with the finite element method to derive the hydrodynamic forces of the lubricated pair, while the multibody dynamics model is established with Lagrangian formalism by considering hydrodynamic forces as external forces. Results for piston-cylinder interfaces of variable lengths in swash-plate axial piston pumps are presented, and the impacts of cylinder length and the tilt angle of the swash plate on the tribological performances of the interface are discussed. The results indicate that increasing the cylinder length can improve the stability and wear resistance of the piston, but it can exacerbate the frictional power loss. Moreover, although enlarging the tilt angle of the swash plate can effectively increase pump displacement, it can easily lead to serious friction, wear, and leakage problems. Consequently, the tilt angle of the swash plate should be carefully selected in practical applications.

Aspects Concerning the Use of Magnetoreological Fluids in Construction of Shock Absorbers

AbstractIn this paper, a review is made of the knowledge about magnetorheological fluids which are part of the class of intelligent materials. These are the fluids that do not comply with Newton’s law, their energization being realized through an external magnetic field. Essentially, magnetorheological fluid is a synthetic solution based on hydrocarbons, populated with soft magnetic particles (easy to magnetize and demagnetize). Shock absorbers that use magnetic fluids are found in the automotive industry for vibration pick-up. The shock absorber with elastic element and magnetorheological fluid presents the following advantages: the possibility of electric control of the stroke and the speed of response of the piston-cylinder system, by a contactless method; it has a simple and reliable construction; the proposed shock absorber is a watertight construction; no internal sealing elements compatible with the magnetorheological fluid are required; the shock absorber does not have components with relative movement at the level of the control element, reducing frictional forces.

Improved Procedures for Feature-Based Suppression of Surface Texture High-Frequency Measurement Errors in the Wear Analysis of Cylinder Liner Topographies

Studies on the effect of surface texture on cylinder liner wear is of great importance in many research areas due to the fact that a major part of the mechanical power losses in an engine are caused by friction in the piston-cylinder liner system. Interest from both manufacturers and customers in optimizing this mechanical system seems to be similar. The surface roughness of cylinder liners plays an important role in the control of tribological properties. Cylinder liner surface topography, which affects running-in duration, oil consumption, exhaust gas emissions and engine performance as well, was taken into detailed consideration in this paper. They were measured with a stylus (Talyscan 150) or non-contact—optical (Talysurf CCI Lite white light interferometer) equipment. Precise machining process and accurate measurement equipment may not provide relevant information about surface texture properties when the procedure of processing of received (raw) measured data is not selected appropriately. This work aims to compare various type of procedures for detection and reduction of some-frequency surface topography measurement errors (noise) and consider its influence on the results of wear analysis. It was found that assessments of some extracted areas (profiles) may be much more useful than the characterization of the whole of measured details when noise was defined. Moreover, applications of a commonly-used algorithm, available in the commercial software of the measuring equipment, for measurement errors suppression may be potentially decisive in the definition of measurement noise but, simultaneously, scrupulous attention should be paid if they are implemented adequately.

On trade-off relation between power and efficiency of piston-cylinder system

On trade-off relation between power and efficiency of piston-cylinder system

Modelling and analysis of slip conditions in hydrodynamic lubrication of a piston skirt-cylinder contact

Purpose After more than a century of agreement with the postulate of non-slip condition (adhesion to the wall), the study of fluid-solid boundary conditions has shown renewed interest over the past two decades. Although numerous studies have not yet been arrived to a complete description of slip phenomena, however, it appears that the influence of wetting and/or surface roughness results in a weak interaction between fluid and solid; thus, the presence of the slip phenomenon is observed at the fluid-solid interface. The purpose of this paper is to highlight the presence of the slip phenomenon at the lubricated piston skirt-cylinder contact. Design/methodology/approach For this proposal, a modified Reynolds equation and operating characteristics are determined by taking into account the slip conditions at the interface between oil-film and entire cylinder surface. Findings The findings indicate that the operating characteristics are strongly influenced when the slip conditions are taken into account at the interface between oil-film and cylinder surface. The friction force and dissipated power might be reduced to improve diesel engine performances. Originality/value Various research studies have been conducted to model the slip phenomenon in different lubricated contacts over the past two decades. However, there are no studies available concerning the piston-cylinder system. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0483/

Asperity level frictional interactions of cylinder bore materials and lubricant composition

Parasitic frictional losses in internal combustion engines of race vehicles adversely affect their performance. A significant proportion of these losses occur within the piston-cylinder system. This paper presents a study of the compatibility of cylinder bore surface materials with typical lubricant base constituent stock (poly alpha olefin and polyolester) as well as a fully formulated lubricant. Nanoscale boundary friction is measured using lateral force microscopy. The effect of material properties, nanoscale roughness and lubricant species upon underlying mechanisms of generated friction is presented. Advanced cylinder materials and coatings and lubricant molecular species used for high performance engines are investigated, and an integrated approach not hitherto reported in literature.

Low‐dimensional Magnetism and Antiferromagnetic Ordering in the Mixed‐valence Spin‐chain Cuprate TlCu2O2

TlCu2O2, a mixed‐valence spin‐chain cuprate, was synthesized in a piston cylinder system starting from thallium sesquioxide Tl2O3, cuprous oxide Cu2O and copper powder. The main structural characteristics are edge‐sharing (CuO2)n zigzag chains, which are linked in the perpendicular crystallographic direction by Cu+ to form a three‐dimensional network. Data from magnetic susceptibility and specific heat measurements show features typical for low‐dimensional magnetic exchange interactions. The long‐range antiferromagnetic ordering is observed at TN = 19.7 K. No weak ferromagnetic component can be detected, suggesting a plain Néel‐type spin‐ordered structure.

Primary gas-pressure standard from electrical measurements and thermophysical ab initio calculations

Mechanical standards for measuring gas pressure up to 7 MPa based on a piston–cylinder system are known with relative uncertainties on the order of 1 ppm (ref. 1). The challenges in an experimental realization lie in determining the effective area of special pressure balances and in accounting for the pressure distortion. Comparisons of the mechanical pressure standard with independent methods to exclude sources of systematic uncertainty are currently available only around 0.1 MPa at the required uncertainty levels. Here, such an independent cross-check is performed up to 7 MPa based on electrical measurements of helium gas. Enabled by recent progress in ab initio calculations, pressure can be accessed through measurement of the dielectric constant. By using theoretical values for the polarizability and the virial coefficients of helium, the change in capacitance and hence the pressure can be determined up to 7 MPa. The relative uncertainty of this method is below 5 ppm and can serve as a new primary pressure standard complementary to the mechanical pressure standard. This answers the long-standing question whether a pressure standard based on capacitance measurements could be devised2. The measurement of the dielectric constant combined with ab initio calculations of the polarizability and the virial coefficient of helium provides a new primary pressure standard, which is complementary to the mechanical standard.

Leakage Characteristic Identification of Labyrinth Seals on Reciprocating Piston through Transient Simulations

In the reciprocating labyrinth piston compressor, the characteristic of the internal leakage is crucial for the leakage management and performance improvement of the compressor. However, most of the published studies investigated the rotor-stator system, and those who study the reciprocating piston-cylinder system basically focus on the effects of the geometrical parameters. These conclusions could not directly be applied to predict the real-time leakage flow rate through the labyrinth seal because of the fast reciprocating motion of the piston, which will cause continually pressure change in two compression chambers, and then the pressure fluctuation will affect the flow through the labyrinth seal. A transient simulation model employing the multiscale dynamic mesh, which considers the effect of the reciprocating motion of the piston in the cylinder, is established to identify the characteristics of the internal leakage. This model was verified by a specially designed compressor, and the influence of various parameters was analyzed in detail. The sealing performance decreased linearly with the increase in the pressure ratio, and higher pressure inlet leads to higher leakage flow under the same pressure ratio. The labyrinth seal performance positively correlated to the increase of the rotational speed. Leakage characteristics of five working mediums were carried out, and the results indicated that the relative leakage decreased with an increase in the relative molecular mass. From this study, the realistic internal leakage flow rate under different operating parameters in the reciprocating labyrinth piston compressor could be predicated.

A remote position sensing method based on passive high magnetic permeability thin films

This article develops a fundamental new sensing principle for measuring the position of a moving object. The moving object is equipped with a thin film of high magnetic permeability. A stationary electromagnet and a magnetic sensor are located nearby. As the moving object’s position changes, the coupling between the electromagnet and the magnetic sensor changes, allowing highly accurate measurement of position of the moving object. This new sensing principle will allow remote non-contacting position measurement of moving objects without requiring any electronics or battery on the object. The feasibility of the new measurement system is verified using an experimental piston-cylinder system in which the position of the piston is accurately estimated with an accuracy of approximately 1% of the range of motion. The thin film is inexpensive and lightweight and could enable a new generation of position sensors superior to currently available position measurement technologies.

Numerical analysis of irreversible processes in a piston-cylinder system using LB1S turbulence model

A numerical analysis for the irreversible processes in an adiabatic piston-cylinder system was conducted using the Lam & Bremhorst low Reynolds number turbulence model (LB1) modified for compressible flows by Sarkar and Balakrishnan (LB1S model). Two-dimensional compressible momentum equation and energy equation which includes the substantial derivative of pressure and the viscous dissipation terms were solved numerically to obtain the state quantities of the system. The computations were performed for a single compression process with constant piston velocity, up=-10 m/s and for cyclic compression and expansion processes with sinusoidal velocity variation. The selected rotation speed ranges from 1000 to 50,000 rpm. The computations were performed for 10 cycles. It was found that the sinusoidal piston velocities have effects on the state quantities of the piston-cylinder system and it experienced an irreversible process when the piston moved with a finite velocity. For the case of single compression process, the flow was laminar when the piston velocity was below 10 m/s. In the cyclic processes, the flow was turbulent when the rotation speed is in the range from 2000 to 50,000 rpm. However, for the case of 2000 rpm, the flow was laminar only at the first cycle. This is due to the turbulent viscosity that is lower than dynamic viscosity (1.862×10-5 Pa s). It was found increasing the rotation speed will increase the value of the turbulent viscosity. In the cyclic processes for the cases N = 1000, 10,000 and 50,000 rpm, the internal energy increased by 0.003%, 0.028% and 0.289% of the compression work in each cycle, respectively.

Energy efficiency analysis of wet compression systems through thermo-fluid dynamic considerations

Wet compression systems are deployed in gas turbine power plants for energy savings in the compressor. The system works by injecting fine water droplets in the form of mist into the air stream ahead of the compressor. The water droplets evaporate both before entering the compressor and within the compressor and reduce the air temperature by absorbing latent heat of evaporation. In this study, an analysis is done on two-phase compression of air-water droplet mixture. The work is focused on understanding the fundamental concepts associated with two-phase compression. Hence, a simple piston-cylinder system is used as the domain to simulate the compression of air-water droplet mixture. During the processes, the pressure, temperature and relative humidity inside the cylinder have been monitored. Parametric studies are then performed for various values of starting relative humidity of the air, overspray percentage of water droplets, droplet diameter, and compression speed of the piston. In these studies, the deviation of PV and TV curves from the dry air compression curves, resulting from latent heat of vaporizing droplets are investigated. The studies show that smaller droplets, higher overspray and slower compression speeds significantly reduces the compressor work requirement, thereby increasing cost savings and environmental benefits of power generation. Interestingly, it is seen that the effect of initial relative humidity of the working fluid on energy savings is minimal. The corresponding efficiencies achieved through wet compression process are determined and tabulated.