Composite Piston Research Articles

Flow and heat transfer in multi-cavity pistons with oscillating cooling

Under high temperature and pressure conditions, pistons play a crucial role in managing thermal stress within combustion chambers. To analyze of the heat transfer characteristics of piston cooling systems in low-speed engines, this study developed and validated an oscillating cooling model featuring a composite piston with multiple cooling cavities. Using numerical simulation methods combined with dynamic mesh technology, the model replicates the long-stroke behavior of actual diesel engines and is validated against preliminary experimental data. The results demonstrates that during reciprocating motion, oil flowing through the telescopic sleeve interacts with gas from breather holes, forming a gas–liquid two-phase flow that significantly alters the liquid film coverage ratio (LFC) on wall surfaces, influencing heat transfer efficiency. As the filling rate increases from 28 % to 71 %, the average liquid film coverage (ALFC) rises by 0.27, and LFC fluctuation frequency decreases, with amplitude increasing by 0.08. Notably, the average Nusselt number (Nuavg) shows significant increases for top surface of inner cavity (TSIC) and side surface of inner cavity (SSIC) between filling rates of 52 % and 64 %, while the maximum increase for top surface of outer cavity (TSOC) and side surface of outer cavity (SSOC) occurs between 37 % and 52 %. Temperature drops at points A and B in the filling rate range of 28 % to 52 % were 1.37 K (4.09 K), which is notably higher than the 0.35 K (0.86 K) drop in the 52 % to 71 % range. Analyzing these changes indicates that the optimal filling rate for enhanced heat transfer performance is approximately 52 %. Furthermore, as engine speed increases from 135.2 to 202.8 rpm, the piston head filling rate decreases from 0.60 to 0.46, reducing both the contact area and the surface heat transfer coefficient. This study provides profound insights of the multiple cooling cavities under reciprocating motion and presents new strategies for optimizing piston cooling systems designed for low-speed engines.

Design, Static Structural and a Steady State Thermal Analysis of Aluminum Composite Piston

The aim of this project is to increase the life and to analyze the various characteristics of composite piston that is strength, weight, thermal conductivity, density, thermal stress and specific heat. Piston is the basic component of the automobile engine. The modified design of the composite piston in this project is compared with existing piston to analyze the Mean Time Between Maintenance. Now-a-days the pistons are made up of aluminium silicon alloy which expands enormously due to generation of heat in the piston. This will affect clearance volume and insufficient clearance can cause the piston to seize in the cylinder. Hence an alternative composite material (Al) which will reduce the expansion. These composite piston are mainly applicable in receprocating engines, pumps and marine ships. The temperature distribution of the piston will be analyzed with the help of ANSYS software. In this analysis, the rate of heat transfer and thermal stress are evaluated for different composition materials. Key Words: composite piston, aluminum silicon alloy, thermal stress, thermal distribution

Disturbance of sand samples obtained by piston samplers and ground freezing

High quality sampling of sand and silty sands is extremely challenging. Undisturbed samples of sand can be obtained by means of very expensive and time-consuming techniques such as ground freezing. Given the high costs and expertise required to obtain undisturbed sand samples through ground freezing, piston sampling techniques are usually used in engineering practice. This paper summarises the experiences, technical difficulties, disturbance analyses and issues encountered during sand sampling at the Norwegian Research Site at Øysand using piston sampling and ground freezing technology. Two state-of-the-art piston samplers were used (NGI-Geonor composite piston sampler and Geonor K-200 thin-wall push piston sampler) along with the state-of-the-art Japanese gel push piston sampler. Ground freezing was successfully achieved also both on sands and silty sands at Øysand. Sample disturbance was assessed qualitatively and quantitatively through analysis of micro-computed tomography images. Results from these analyses provide an overview of the strengths and weaknesses of the three piston samplers in comparison with ground freezing, together with recommendations for sampling of sands using piston techniques.

CAD/CAM versus 3D-printing/pressed lithium disilicate monolithic crowns: Adaptation and fatigue behavior

Objectivesthis study aimed to evaluate the adaptation and fatigue behavior of lithium disilicate glass-ceramic (LD) monolithic crowns produced by press (combined with 3D-printing) and CAD/CAM milling (control) techniques. Methodsthirty abutment preparations with a chamfer finish line were produced with a dentin analogue material and scanned with extraoral scanner. Captured images were processed using CAD software to design a premolar. Blocks of LD were milled using CAD/CAM system. For the press technique, crowns were first 3D-printed using a polymeric material and the heat-pressing protocol was performed. Crowns were adhesively cemented to the abutments and scanned using micro-CT. Files were processed and cross-sectional images were analysed in five measuring points: marginal, axial angle, axial, occlusal angle and occlusal. Fatigue test was performed in a MTS universal testing machine (2 Hz, 37°C distilled water) using an anatomic composite piston, following the step-stress method. Failures were detected with an acoustic system and confirmed by transillumination. A cumulative damage-Weibull distribution (95% CI) was used to analyze the fatigue data. Gap thickness data were analyzed using Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05). ResultsCAD/CAM milling resulted in larger gap thickness in the occlusal area and smaller gap thickness in the axial angle and axial area than press (p<0.05). The probability of failure was similar for crowns produced with CAD/CAM milling and press. The most frequent failure mode was radial crack. ConclusionsLD crowns produced using the combination of 3D-printing/press technique showed similar fatigue behavior than CAD/CAM milled control group, and resulted in smaller gap thickness at the occlusal region. Clinical significanceA more controlled process can be achieved by replacing conventional restoration waxing with 3D printing, which in combination with the press technique produces lithium disilicate glass-ceramic monolithic crowns with good adaptation and high fatigue survival.

Investigation on engine performance test on compression ignition engine with hybrid metal matrix composite piston

The increase in demand and introduction of stringent emission regulations resulted in the need to develop and implement innovative technologies towards improving the emission and performance characteristics of compression ignition engines. A hybrid metal matrix composite piston (HMMC) of Al7075 reinforced with 6% of 100 ?m silicon carbide (SiC) and 4% of 100 ?m Al2O3 was fabricated. The HMMC piston was mounted on a compression ignition four stroke single-cylinder constant speed engine and the test was carried out with eddy current dynamometer attached with computerized data acquisition system. This paper is focused on the study of performance of Al7075-SiC-Alumina composite piston for compression ignition engine application. Experimental investigations were performed at injection pressure of 200 and 220 bar on both standard piston and HMMC piston and analysed the performance, combustion and emission behaviour of compression ignition engine. From the results it was found that the HMMC piston exhibits an improved efficiency and thereby improving the lifetime of the engine. Though a little compromise in performance and emissions has been accepted, the implementation of HMMC pistons will reduce the carbon foot print of running an internal combustion engine.

Analiza hibridnog kompozita na bazi bronze kod klipa benzinskog motora

The development in automotive industry leads to economy and comfort of the vehicles and thus forces the designers to develop new materials for the improved performance. In this work, Bronze hybrid composite with Aluminium and Silicon reinforcement for spark ignition engine piston was fabricated through vacuum stir casting process. Conventional machining techniques such as turning, drilling and boring etc., were used to manufacture the piston. Thermal analysis on the composite piston was carried out using Finite Element Software ANSYS. The mechanical properties tensile and impact strength and hardness of the composite were measured. Wear analysis on the composite material was carried out and wear rate was calculated. The results were compared with the existing material and found enhanced with bronze hybrid composites. Emission test was also carried out and found improved. Microstructure examination was carried out to study the structure of the composites.

Finite element analysis of a composite piston for a diesel aircraft engine

The article presents calculations of thermal and mechanical loads of the piston, consisting of two parts: steel and aluminum. The calculations were made using FEM in the Abaqus software. The piston is characterized by a split construction and was equipped with a cooling oil channel. The piston will be used in an aircraft diesel engine characterized by opposite piston movement. The presented geometry of the piston is the next of the ones being developed earlier and contains preliminary assumptions as to the size and main geometrical dimensions. The thermal boundary conditions of the simulation tests assumed defined areas of heat reception surface and heating of the piston by defining a temperature map on its crown. The results of these studies were presented in the form of temperature distribution and heat flux on the surface of the tested element. The strength boundary conditions assumed a mechanical load in the form of pressure resulting from the pressure in the combustion chamber applied to the piston crown surface and the opposite pressure defined on the support at the surface of contact between the piston and the piston pin. The results of these tests were presented in the form of stress distribution on the surface of the tested element. As a result of the analyses carried out, the results constituting the basis for further modernization of the piston geometry were obtained.

Numerical Study on Fretting Wear of Mating Surface Between Piston Crown and Skirt in Heavy Duty Diesel Engine

Composite pistons are often used in heavy duty diesel engines due to its good reliability and durability. Owing to the alternating loads, fretting wear usually happens on the mating surfaces between piston crown and skirt. In this paper, a fretting wear finite element model is developed to analyze the mating surface wear of composite piston of heavy-duty diesel engine. The fretting wear model predicts the wear depth evolution for each working cycle based on Archard model and mesh updating technique, which is validated by previous pin and disk contact experiments. The wear evolution of the top contact surface of piston skirt is simulated according to engine operating condition, and fretting wear life is estimated by the decreasing process of crown-skirt connecting bolt preload. Effects of the shape of piston skirt top surface are also evaluated. In the end, the rationality of fretting wear model is validated by durability tests of diesel engine.

Characterization and engineering properties of the NGTS Onsøy soft clay site

In the 1960s, NGI investigated numerous potential research sites and established the first Onsoy soft clay site in 1968. In 2016, the NGTS project established five research sites, one of which is the NGTS Onsoy soft clay site. The purpose of this paper is to provide a reference for further in-situ and laboratory testing at the site and easy access to high-quality soil investigation data. The paper interprets the soil conditions providing engineering soil properties, comments on data reliability and quality, and correlations between different soil parameters where appropriate. The lightly overconsolidated soft clay site has been characterized based on extensive in-situ and laboratory testing. In-situ methods include electrical resistivity tomography, multichannel analysis of surface waves, total soundings, rotary pressure soundings, cone penetration testing with and without seismic and electrical resistivity measurements, dilatometer with seismic measurements, self-boring pressuremeter, electric piezometers, thermistor string, hydraulic fracture testing and earth pressure cells. Soil samples were obtained using Sherbrook block sampler, Geonor ϕ 72 mm piston sampler, Geonor ϕ 54 mm composite piston sampler and hydraulic piston and push samplers with liners. Laboratory tests include multi-sensor core logging, index testing, cyclic and monotonic, consolidated and unconsolidated triaxial tests, bender element tests, oedometer tests with constant rate of strain and incremental loading and direct simple shear tests.

Fretting fatigue optimization of piston skirt top surface of marine diesel engine

Composite pistons are often used in highly rated marine diesel engines. Fretting usually occurs on the mating surfaces of piston crown and skirt due to alternating loads. A finite element contact model is introduced to calculate the temperature and stress distribution in the composite piston of a marine diesel engine. The Archard model and Smith–Watson–Topper parameter (a prediction parameter of fretting fatigue, also called SWT parameter for short), which is used as fretting wear and fatigue criteria, are calculated according to the stress and strain variation and relative slip on the contact surface. The model has been validated by previous cylindrical–flat contact experiments. The effects of shape of contact face and pretension of bolts on fretting performance have been analyzed. To reduce the possibility of fretting failure of the composite piston, the expression of the generating line of the piston skirt contact surface has been designed by Theory of elasticity. The parameters of the generating line have been optimized with nonlinear sequential quadratic programming and finite element mesh updating method. The optimization results show that the fretting fatigue parameter SWT on the optimized contact surface can be reduced by more than 35.6%, which means the longer fatigue life of the pistons. Some suggestions for designing contact surfaces have also been proposed. In the end, the design was proved by durability tests of the engine.

Effect of sample disturbance on cyclic shear strength of normally to lightly OC clays

Tests on Onsøy clay (Ip = 24–27%) were performed to study the effect of sample disturbance on undrained static and cyclic shear strength. Samples with different degree of disturbance from sampling were used and parallel sets of monotonic and cyclic undrained laboratory tests were performed on block and 54 mm composite piston samples. A silty Drammen clay (Ip = 19%) which was studied earlier was included in the study. Test results indicated that there are significant effects of sample disturbance on both static and cyclic undrained shear strengths for both Onsøy and silty Drammen clays.

Mathematical modeling of dynamics of movement of the compound piston in the cylinder of the internal combustion engine

Cylinder piston group is the main part of friction in the engine, where usually mechanical losses appear, that is why its work and design should be considered from the point of view of tribology. The task of designing a cylinder - piston group as a friction unit is to select the basic geometric dimensions, the profile of the guide part in the longitudinal and transverse planes, the diametric gap, the coordinates of the piston pin arrangement and the center of mass. The solution of these problems is directly dependent on the possibility of studying the complex plane-parallel motion of the piston within the piston-cylinder liner clearance in the lubricant layer. At present, compound pistons are gaining traction from forced diesel engines with increased loads on the cylinder-piston group. The study of the movement of the compound pis-ton must include the solution of interrelated tasks: the investigation of the motion of the piston crown with a set of piston rings and the study of the motion of the piston skirt, taking into account the effect of the rocking motion of the connecting rod on it. The derivation of the equations of motion of all components of the piston and connecting rod is given in the article. Their combined solution and the resulting equations allow us to investigate the transverse motion of the crown of the composite piston and to evaluate the operation of the piston rings, and also taking into account the hydrodynamic lubrication of the skirt, to carry out a comprehensive study of the state of the skirt of the compound piston and, first and foremost, to investigate the influence of its basic design parameters on the conditions of the hydrodynamic grease. The developed mathematical model will allow on the basis of complex research the influence of the above parameters to develop a composite piston design that provides high technical and economic parameters of the engine.

DESIGN AND ANALYSIS OF COMPOSITE PISTON.

10Aug 2017 DESIGN AND ANALYSIS OF COMPOSITE PISTON. Raghunandan D , Gaddam Ramcharan and Dinesh Kumar. Saveetha School of Engineering, Chennai, India.

DEVELOPMENT OF STRUCTURES OF "LIGHT" PISTON FOR DIESEL ENGINES TYPE D100

The paper considers the option of replacing the composite piston serial type locomotive diesel 10D100 20 kg new - a mass of 13 kg. The results of optimization of the shape of the steel inside the top of the piston. It is shown that the calculated maximum temperature on the combustion chamber surface of the proposed design is somewhat lower than in batch, and safety factors in design strained areas not lower than serial. It is shown that the technical problems associated with the introduction of the proposed piston and its solutions.

An extension to the methodology for characterization of thermal properties of thin solid samples by photoacoustic techniques

The paper presents a study of possibilities to extend the present methodology for thermal characterization of thin solid samples by photoacoustic techniques. The present methodology consists of linear fitting of the experimental data to approximate the expressions derived from the composite piston model of photoacoustic response and it is mainly used for calculation of thermal diffusivity of thin samples. The study has shown that the methodology may be extended to calculation of thermal diffusivity, thermal conductivity and thermal expansion coefficients of thin samples by linear fitting in multiple frequency ranges and by analysis of the intersection frequency, which is the frequency where the magnitudes of two components of photoacoustic response in the composite piston model are equal. The analysis of numeric errors of the methodology has revealed the dominant sources and magnitude of the errors, leading to the conclusion that photoacoustic techniques should be carefully used as a tool for extensive thermal characterization of thin samples in the cases when other techniques are not applicable or have larger errors.

Note: Improved sensitivity of magnetic measurements under high pressure in miniature ceramic anvil cell for a commercial SQUID magnetometer

Two modifications have been made to a miniature ceramic anvil high pressure cell (mCAC) designed for magnetic measurements at pressures up to 12.6 GPa in a commercial superconducting quantum interference (SQUID) magnetometer [N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011); ibid. 83, 053906 (2012)]. Replacing the Cu-Be piston in the former mCAC with a composite piston composed of the Cu-Be and ceramic cylinders reduces the background magnetization significantly smaller at low temperatures, enabling more precise magnetic measurements at low temperatures. A second modification to the mCAC is the utilization of a ceramic anvil with a hollow in the center of the culet surface. High pressures up to 5 GPa were generated with the "cupped ceramic anvil" with the culet size of 1.0 mm.

樹脂複合化による焼結機能部品の開発

Sintered machinery parts have been widely used in automobiles, business machines and home appliances due to their priority of near net shaped parts can be inexpensively produced. On the other hand, with trend toward higher required functions for the parts, conventional sintered parts couldn’t have ensured the functions. Resin composite sintered parts are also one of the measures. So higher function parts that impart feature of sintered parts with feature of resin as hybrid parts that compensate lack of properties of the sintered parts have been developed. In this paper, resin composite piston for shock absorber and torque sensor for electric power steering which characteristically represent the developed parts are described.

Microstructure and Mechanical Behavior of in Situ Primary Si/Mg2Si Locally Reinforced Aluminum Matrix Composites Piston by Centrifugal Casting

Al-Si pistons are frequently damaged by burning piston top surface due to elevated combustion temperature, and by rubbing the first ring groove against the engine cylinder liner. To prevent piston from these damages, some technologies were invented, such as mounting high Ni cast iron ring around the first ring groove in Al alloy piston body and thermal resistant steel on piston top surface, and fabricating Al composite pistons by squeeze casting for enhancing the whole or local piston performance. In this paper, composite pistons locally reinforced with in situ primary Si and primary Mg2Si particles are fabricated by centrifugal casting. The microstructure characteristics, hardness and wear resistance of the composite piston are investigated and the motion characteristic of the in situ particles in centrifugal field is analyzed. The results of the experiments show that primary Si and Mg2Si particles mix up with each other in melt and segregate at the regions of piston top and piston ring grooves under the effect of centrifugal force. Particulate reinforced regions have a higher hardness and better wear resistance compared with the unreinforced regions and this performance increases after heat treatment. The analysis result of particle movement shows that, primary Si and primary Mg2Si particles move at approximately the same velocity in the centrifugal field, because of the growth of primary Si and fusion after colliding between primary Si particles, which compromised the velocity difference of primary Si and primary Mg2Si particles caused by the difference of their densities. Research results have some theory significance and applicative value of project in development of new aluminum matrix composites piston products.

박용 디젤엔진용 분리형 피스톤의 내구설계

A composite piston with a crown made of steel and a skirt made of NCI is used in a marine diesel engine, which has a maximum firing pressure of over 180 bar and a high thermal load. In the fatigue design of the composite piston, the fatigue is influenced by factors such as the load type, surface roughness, and temperature; further, the distribution ratio of the firing force from the crown to the skirt is important for optimizing the design of the crown and skirt. In this study, the stress gradient method was used to consider the effect of the load type. The temperature field on the piston was predicted by cocktail-shaking cooling analysis, and influence of high temperature on fatigue strength was investigated. The load transfer ratio and contact pressure were optimized by design of the surface shape and accurate tolerance analysis. Finally, the cooling performance and durability design of the composite piston were verified by performing a long-term prototype test.

Late Holocene forcing of the Asian winter and summer monsoon as evidenced by proxy records from the northern Qinghai–Tibetan Plateau

Little is known about decadal- to centennial-scale climate variability and its associated forcing mechanisms on the Qinghai–Tibetan Plateau. A decadal-resolution record of total organic carbon (TOC) and grainsize retrieved from a composite piston core from Kusai Lake, NW China, provides solid evidence for decadal- to centennial-scale Asian monsoon variability for the Northern Qinghai–Tibetan Plateau during the last 3770 yr. Intensified winter and summer monsoons are well correlated with respective reductions and increases in solar irradiance. A number of intensified Asian winter monsoon phases are potentially correlated with North Atlantic climatic variations including Bond events 0 to 2 and more recent subtle climate changes from the Medieval Warm Period to the Little Ice Age. Our findings indicate that Asian monsoon changes during the late Holocene are forced by changes in both solar output and oceanic–atmospheric circulation patterns. Our results demonstrate that these forcing mechanisms operate not only in low latitudes but also in mid-latitude regions (the Northern Qinghai–Tibetan Plateau).