Search

In swash plate type axial piston pumps, slipper/swash plate sliding surfaces is subject to high fluctuating load. Therefore, the slippers are required to provide stable operation and reduce losses due to sliding. The behavior of the slipper fluctuates in a complex manner due to changes in the hydraulic pressure in the cylinder and inertial forces caused by the reciprocating motion of the piston. However, the time variation of the oil film thickness distribution of the slipper has not been measured. Furthermore, there are no measurements of the movement of the spherical joint connecting the slipper and piston, which affects the slipper behavior. In this study, the visualized sliding test rig with a sapphire glass swash plate was developed. The oil film thickness distribution of the slipper and the rotation of the slipper and the piston were measured continuously during one rotation of the pump.

The purpose of this study was to determine the effect of variations in piston diameter and piston mass on the performance of a 4-stroke motorcycle. The method used is an experimental method with a quantitative approach. Data collection was carried out using the dynotest method, burret and stopwatch. The samples of this study are 3 types of pistons with different diameters where the piston mass varies to test the performance of a 4- stroke motorcycle including Torque, SFC (Specific Fuel Consumption) and BMEP (Break Mean Effective Pressure). The results of this study show that the p-value of the variation of piston diameter and mass is smaller than alpha p-value < alpha (0.05) which indicates that the variation of piston diameter and mass affects the performance of 4- stroke motorcycles. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The air permeability of a textile fabric belongs to the parameters which characterize its potential applications as garments, filters, airbags, etc. Calculating the air permeability is complicated due to its dependence on many other fabric parameters, such as porosity, thickness, weaving parameters and others, which is why the air permeability is usually measured. Standardized measurement instruments according to EN ISO 9237, however, are expensive and complex, prohibiting small companies or many universities from using them. This is why a simpler and inexpensive test instrument was suggested in a previous paper. Here, we show correlations between the results of the standardized and the custom-made instrument and verify this correlation using fluid dynamics calculations. [ABSTRACT FROM AUTHOR]

Control of large structures often involves the use of hydraulic equipment due to the large power requirements. In this study, a large telescope is taken as an example of a large structure. A large telescope is equipped with hydraulic support systems to adjust the deformation of the structure, as changes in its pointing direction and ambient temperature deform the structure and reduce the telescope's observational performance. In previous studies, hydraulic support system elements and piping paths have been discussed, but quantitative evaluations and design considerations for the overall system performance of multiple hydraulic support systems and telescope structures have not been discussed. In this paper, simple transfer function models are derived for a coupled system of multiple hydraulic support systems and telescope structures, which allow the static and dynamic transient response characteristics to be evaluated. A design example using these transfer function models is also proposed and it is shown that the selected design parameters enable the large telescope to meet the specifications.

In Compression ignition engines combustion occurs at higher temperatures that leads to a rapid rise in combustion pressure and amount of heat released. This may lead to lesser emissions during engine cycle. Moreover, occurrence of combustion takes place for a very small crank angles duration resulting in better thermal efficiency. On the other hand, the oil used for lubrication in IC engines is responsible for a significant amount of pollution and particles emitted into the environment. In order to comply with increasingly strict pollution standards, manufacturers make considerable efforts to minimize the impact of oil consumption on engine emissions. The purpose of this study is to develop a one-dimensional numerical simulation method using GT-Suite software to assess how the engine speed and load affect the oil film thickness, frictional force, and power losses during the operating engine cycle. The results obtained in this simulation were validated using experimental data, and there is good agreement between the numerical and experimental results. It was found in this paper that the maximum friction power losses were found to be 1.6 kW at middle of strokes and the minimum Oil film thickness was obtained in range of 9-38 μm. [ABSTRACT FROM AUTHOR]

As the importance of developing eco-friendly equipment getting increase, studying and developing compressor for ammonia that is one of the eco-friendly fuel are demanded. The type of the seal, called labyrinth seal, is used in this compressor. The labyrinth seal is a type of a mechanical seal that provides a winding path and prevent leakage of gases and fluid. In this study, analyzed flow characteristics of the labyrinth seal by its length and tried to find the efficient length for the labyrinth seal as the initial design stage. By considering geometry, allowable length, material properties and boundary conditions, calculated reduction rate of mass flow rate compared to the plain model. In the range of design criteria that is target mass flow rate, allowable length, reduction rate and volume of the model, selected an appropriate design length that is 150mm for the initial design.

DMP (Differences in Material Properties) often exists between temperature sensors and combustion chamber components of ICE (Internal Combustion Engine), resulting in IEs (Introduced Errors) in the temperature measuring process. In this paper, we present a comprehensive theoretical analysis of the correlation between introduced errors on chamber components and the DMP. The analysis process considers the characteristics of the chamber's heat transfer BC (Boundary Condition). Then, simulations are used to investigate the introduced error of hardness plug and thermocouple sensors on the top surface of an ICE aluminum alloy piston. The theoretical analysis results indicate that heat transfer BC can be segmented into the time-averaged and fluctuation parts, and IEs are linearly superimposed under these two parts of BCs. The heat conductivity impacts the time-averaged error and the product of heat conductivity, density, and heat capacity impacts the fluctuation error. The experimental and simulation results indicate that the max time-average error of the hardness plug on piston is 2.4 °C, with a fluctuation introduced error of 3.6 °C and a total introduced error of 6 °C; and the time-average introduced error of thermocouple sensor is 9.4 °C, with a fluctuation error of 5.8 °C and a total introduced error of 15.2 °C. Finally, a fluctuation error correction method is proposed to reduce error. After correction, the error is reduced by 71 % and 66 % for hardness plug and thermocouple, respectively.

Vortex rings can maintain their structure during motion and achieve longdistance transport with low energy consumption, which is a fluid transport method with great energy-saving potential. In this paper, a reciprocating vortex ring generator structure is designed, which can generate two vortex rings during the reciprocating motion of one piston, making full use of the thrust in the reciprocating motion period of the piston and improving the vortex ring generation frequency compared with traditional vortex ring generators. For the characteristics of long-distance transport of vortex rings, an experimental platform is designed and built, and 277 sets of experiments are carried out with different geometric parameters. The results show that the effect of generating two vortex rings could be achieved under other parameter conditions, except for some parameter conditions where the diameter ratio D1/D2 = 4. By analyzing the influence of baffle width ratio, length ratio, and diameter ratio on the moving distance of vortex rings, the performance of the vortex ring generator is preliminarily studied. In 277 sets of experiments, the maximum moving distance ratio x1 of vortex ring 1 is 13.7 when L1/L2 = 2.4, D1/D2 = 2, and w1 = 0.2. And the maximum moving distance ratio x2 of vortex ring 2 is 20 when L1/L2 = 2, D1/D2 = 2.5, and w2 = 0.2. [ABSTRACT FROM AUTHOR]

The Three-Piece Oil Control Ring (TPOCR) is becoming a viable option for heavy duty gas and hydrogen engines due to the low particle concentration in these engines. Although direct oil leakage from the gap is not likely to happen with the misalignment of the upper and lower rail gaps, there exist other less-apparent oil leaking mechanisms through the TPOCR. This work is targeted at understanding the oil leakage's source and destination through the rail and liner interfaces across the whole cycle. The 2D Laser Induced Fluorescence technique was applied on an optical engine to study the oil transport behavior. Combined with a TPOCR model for dynamics and lubrication, the mechanisms that cause rail twist and oil scraping by the upper rail were analyzed. It was found that the symmetrical rail can scrape the oil up in the up-strokes. The scraped oil first accumulates in the clearance between the upper rail and groove, as well as at the upper corner of the rail Outer Diameter before being transferred to both the third land and liner when the piston changes direction at Top Dead Center. Rails with an asymmetrical profile can reduce or enhance these effects depending the orientation of the rails. This study provides findings that could help design the engine to better control Lubricate Oil Consumption and properly lubricate the Top Dead Center's dry region at the same time. [ABSTRACT FROM AUTHOR]

This research is an experimental study conducted to determine the effect of variations in piston diameter on the performance of manual transmission motorbikes. The independent variables in this study are variations in the diameter of the piston with initial conditions 52.5 mm to 53 mm (modification 1) and 53.5 mm (modification 2). Then, the dependent variables in this study are torque, power, and fuel consumption. Torque and power tests were carried out using the dyno test equipment, and fuel consumption testing was done using a measuring cup and calculating the mass of fuel per unit of time; then, the research data was analyzed using quantitative descriptive techniques. In theory, changing the size of the piston affects the compression ratio, which in turn affects the vehicle's performance. After the research, it is known that there is an effect of variation in piston diameter on torque, power, and fuel consumption, where the highest torque is achieved in the use of a modified piston on 53.5 mm by 12.49%, then the highest power is achieved by 7.02%, and the highest fuel consumption is achieved by 17.15%.

Vortex rings can maintain their structure during motion and achieve long-distance transport with low energy consumption, which is a fluid transport method with great energy-saving potential. In this paper, a reciprocating vortex ring generator structure is designed, which can generate two vortex rings during the reciprocating motion of one piston, making full use of the thrust in the reciprocating motion period of the piston and improving the vortex ring generation frequency compared with traditional vortex ring generators. For the characteristics of long-distance transport of vortex rings, an experimental platform is designed and built, and 277 sets of experiments are carried out with different geometric parameters. The results show that the effect of generating two vortex rings could be achieved under other parameter conditions, except for some parameter conditions where the diameter ratio D1/D2 = 4. By analyzing the influence of baffle width ratio, length ratio, and diameter ratio on the moving distance of vortex rings, the performance of the vortex ring generator is preliminarily studied. In 277 sets of experiments, the maximum moving distance ratio x1 of vortex ring 1 is 13.7 when L1/L2 = 2.4, D1/D2 = 2, and w1 = 0.2. And the maximum moving distance ratio x2 of vortex ring 2 is 20 when L1/L2 = 2, D1/D2 = 2.5, and w2 = 0.2.

The air permeability of a textile fabric belongs to the parameters which characterize its potential applications as garments, filters, airbags, etc. Calculating the air permeability is complicated due to its dependence on many other fabric parameters, such as porosity, thickness, weaving parameters and others, which is why the air permeability is usually measured. Standardized measurement instruments according to EN ISO 9237, however, are expensive and complex, prohibiting small companies or many universities from using them. This is why a simpler and inexpensive test instrument was suggested in a previous paper. Here, we show correlations between the results of the standardized and the custom-made instrument and verify this correlation using fluid dynamics calculations.

To further improve the thermal state of the piston for better thermal design, a multi-objective optimisation algorithm was used in this paper to find the best combination of design variables. The results show that thermal barrier coating (TBC) can effectively prevent heat transfer to the piston, and the thicker the ceramic layer, the better the thermal insulation effect. The maximum temperature and maximum thermal stress of the optimised piston matrix can be reduced by a maximum of 55.54 °C and 43.94 MPa, with a reduction of 15.08 % and 25.43 %, respectively, compared with that of the aluminium alloy piston of 368.39 °C and 172.76 MPa. Moreover, the thermal stress at the bottom of the combustion chamber, a larger cross-sectional area of the cooling gallery can dissipate more heat, which can have a more significant impact compared to the thickness of the ceramic layer. The large temperature gradient causes the maximum thermal stresses of the TBC piston to occur on the surface where the metal bonding layer contacts the piston matrix. Such high thermal stress is the main cause of coating delamination. The findings of this study can provide a reference for improving the thermal state of the piston and enhancing the engine performance.

To improve the friction and wear performance of the piston-cylinder liner friction pair, inspired by earthworms and leeches, 27 kinds of pistons with cylindrical pit arrays are designed and processed. Through a friction test, four superior textured pistons are optimized, and wear, life and thermal imaging tests are performed. Finite element analysis of the friction pair model is performed, and the friction and wear mechanisms are discussed. The results show that the pistons with cylindrical pit arrays have excellent friction and wear performance, less heat generation by friction, longer lives and less scratches on the cylinder liner. The temperature of the optimized textured pistons was reduced by around 5–10 °C. The wear amount of some textured pistons was reduced by over 50%, resulting in an improvement in their lifespan of at least 30% or more. The results of the finite element analysis indicate that the textured piston exhibited reduced deformation and favorable stress–strain distribution and satisfied the required contact pressure. [ABSTRACT FROM AUTHOR]

Chemotaxis is a fundamental process whereby bacteria seek out nutrient sources and avoid harmful chemicals. For the symbiotic soil bacterium Sinorhizobium meliloti, the chemotaxis system also plays an essential role in the interaction with its legume host. The chemotactic signaling cascade is initiated through interactions of an attractant or repellent compound with chemoreceptors or methyl‐accepting chemotaxis proteins (MCPs). S. meliloti possesses eight chemoreceptors to mediate chemotaxis. Six of these receptors are transmembrane proteins with periplasmic ligand‐binding domains (LBDs). The specific functions of McpW and McpZ are still unknown. Here, we report the crystal structure of the periplasmic domain of McpZ (McpZPD) at 2.7 Å resolution. McpZPD assumes a novel fold consisting of three concatenated four‐helix bundle modules. Through phylogenetic analyses, we discovered that this helical tri‐modular domain fold arose within the Rhizobiaceae family and is still evolving rapidly. The structure, offering a rare view of a ligand‐free dimeric MCP‐LBD, reveals a novel dimerization interface. Molecular dynamics calculations suggest ligand binding will induce conformational changes that result in large horizontal helix movements within the membrane‐proximal domains of the McpZPD dimer that are accompanied by a 5 Å vertical shift of the terminal helix toward the inner cell membrane. These results suggest a mechanism of transmembrane signaling for this family of MCPs that entails both piston‐type and scissoring movements. The predicted movements terminate in a conformation that closely mirrors those observed in related ligand‐bound MCP‐LBDs. [ABSTRACT FROM AUTHOR]

This research presents an experimental and theoretical evaluation of the effect of poly-composition thermal barrier coatings on the performance and emission characteristics of the compression ignition engine. This work investigated the thermal and physical behavior of thermal barrier coating. The thermal barrier coating was coated into two layers, and the thermal plasma spray method was used to make the coating. The first layer is AT13, and the top layer is Yttria-stabilized zirconia. The coated and uncoated pistons were analyzed in the Ansys, and it has shown the temperature distribution of the pistons. The experimental report shows that the brake thermal and volumetric efficiency was increased by 7.52% and 1.06%, brake-specific fuel consumption was reduced up to 18.91%, emission of carbon monoxide was reduced by 50%, and hydrocarbon was reduced by 52.38%. [ABSTRACT FROM AUTHOR]

Piston damage is a frequent problem of engine durability and plays an important role in an engine's performance design. Recently, a large amount of piston erosion has occurred in a series of heavy-duty diesel engines. To investigate the reason for the piston erosion, a study of the computational fluid dynamics (CFD) of the combustion process in the cylinder and finite element analysis (FEA) of piston was carried out under different initial temperatures. The results show that when the initial temperature decreases from 380 K to 307 K, the mass of wall-wetting increases by 73%, and the maximum combustion pressure increases from 8.1 MPa to 11 MPa; when the initial temperature decreases from 350 K to 328 K, the highest temperature at the throat of the valve pocket increases by nearly 100 K, doubling the temperature fluctuation; and in the case of 328 K, areas exceeding 700 K are concentrated on the top surface of the piston, and the temperature gradient in the depth direction of the throat position decays rapidly. [ABSTRACT FROM AUTHOR]

Rejection analysis deals with the inspection of the quality of products and efficiency of the plant which are very important in the manufacturing process. It offers practical solutions to problems that arise during the piston manufacturing process. In this paper, a hybrid decision-making and quality control technique was applied to minimize the rejection rate of 90PS pistons. An observational technique was used to achieve the particular target involves the nature of the defect, a check sheet to gather data on the number of defects that occurred over the past three months, a Pareto chart was used to identify the main defect percentage, and a cause-and-effect diagram was used to find the causes. Results show that various defects were mitigated. As a result, the operation missing scrap in the manufacturing line was reduced from 1.52 to 0.50%, skirt size scrap from 0.64 to 0.20%, transportation scrap from 1.50 to 0.50%, and pinhole/compression height scrap from 2.33 to 1.00%. The results of this study helped improve the efficiency of the plant by minimizing the cost. [ABSTRACT FROM AUTHOR]

Piston is the main component of internal combustion engine. This transmits the thrust of burned gases to the connecting rod. In this paper, the design and analysis of piston is presented for the given specification engine. The design and modelling of the piston is done on Fusion 360 and analysis is done in the ANSYS software. The design file from Fusion 360 is imported in the ANSYS software and results are discussed. The piston of an internal combustion engine is subjected to thermal and thrust loads. Material of the piston is taken Aluminium alloy for the analysis purpose. Major complexity of thermal load variations is eliminated here, and critical values are analysed and structural and thermal analysis in the ANSYS is performed. [ABSTRACT FROM AUTHOR]

Nowadays, engine components are subjected to higher loads at elevated temperatures due to the increasing requirements regarding weight, performance, and exhaust gas emission. Thus, fatigue due to simultaneous thermal and mechanical loading became a determinant among the damage forms. The effect of a thermal barrier coating (TBC) on the thermal stress and fatigue life in a gasoline engine piston with considering stress gradient was studied. For this purpose, coupled thermo-mechanical analysis of a gasoline engine piston was performed. Then fatigue life of the component was predicted using a standard stress-life analysis and results were compared to the original piston. The results of finite element analysis (FEA) indicated that the stress and number of cycles to failure have the most critical values at the upper portion of piston pin and piston compression grooves. The obtained thermomechanical analysis results proved that the TBC system reduces the stress distribution in the piston by about 2.4 MPa and 8.5 MPa at engine speeds of 1000 rpm and 5000 rpm, respectively. The fatigue life results showed that the number of cycles of failure for the coated piston is approximately 12% and 31% higher than the original piston at engine speeds of 1000 rpm and 5000 rpm, respectively. To evaluate properly of results, stress analysis and fatigue life results is compared with experimental damaged piston and it has been shown that critical identified areas, match well with areas of failure in the experimental sample. [ABSTRACT FROM AUTHOR]

Fueling internal combustion engines with hydrogen is one of the most recommended alternative fuels today in order to combat the energy crisis, pollution problems, and climate change. Despite all the advantages of hydrogen fuel, it produces a higher combustion temperature than gasoline. In an internal combustion engine, the piston is among the numerous complex and highly loaded components. Piston surfaces are directly affected by combustion flames, making them critical components of engines. To examine the stress distribution and specify the critical fracture zones in the piston for hydrogen fuel engines, a three-dimensional CFD-solid-mechanics model of the internal combustion engine piston subjected to real thermomechanical loads was analyzed numerically to investigate the distribution of the temperature on the piston body, the interrelated thermomechanical deformations map, and the pattern of the stresses when fueling the engine with hydrogen fuel. With the aid of multiphysics COMSOL software, the CFD-solid-mechanics equations were solved with high accuracy. Despite the increase in pressure on the piston and its temperature when the engine is running on hydrogen fuel, the results show that the hydrogen fuel engine piston can withstand, safely, the thermomechanical loads. In comparison to gasoline fuel, hydrogen fuel caused a deformation of 0.34 mm, an increase of 17%. This deformation is within safe limits, with an average clearance of 0.867 mm between the cylinder liner and piston.

Motorcycle users in 2019 reached 133,617,012 units in Indonesia. The impact of a large number of motorcycle certainly attracts the interest of the industry to produce two-wheeled automotive vehicles. The piston is part of the engine that functions as a compression barrier in the combustion chamber, the piston material is aluminum alloy. Therefore, research was carried out on making pistons with investment casting methods, physical and mechanical patterns from 3D printers on pistons. This research starts from drawing the piston using CAD (computer-aided design), making a printed pattern from a 3D Printer machine with PLA (polylactide acid) material. The mold pattern is coated with a mixture of gypsum cement and silica powder. The casting process with a pouring temperature of 750ᵒC and a mold temperature of 200 ᵒC, 250 ᵒC, 300 ᵒC, 350 ᵒC, and 400 ᵒC. The results showed the largest grain size at a mold temperature of 400ᵒC. The highest hardness at 200 ᵒC mold temperature is 47.00 HRB and the lowest hardness at 400 ᵒC mold temperature is 40.56 HRB. The higher the temperature of the mold used, the level of porosity of a material will decrease. This is due to the temperature difference when pouring the molten metal and the lower mold temperature. This makes the metal solidification time longer. The higher the mold temperature, the slower the solidification time, the larger the grain structure, and the decreased hardness.

Introduction Stapes surgery for otosclerosis is a precise surgical procedure. To achieve excellent hearing results, a firm and stable attachment of the prosthesis to the long process of incus (LPI) is necessary. The present study provides details on the attachment site in two dimensions to choose an appropriate prosthesis and to ensure firm attachment for better surgical outcomes. Objective To study the diameter of the LPI and its relevance in determining the piston, used in stapes surgery by an in vivo method. Methods This study was conducted in 41 patients who underwent stapedotomy, where both Anteroposterior (AP) and Mediolateral (ML) diameters of the LPI were measured at the site of attachment of the piston using specially designed instruments, intraoperatively. Radiological data were obtained to measure the LPI diameter from the normal ears of 46 patients. It was measured from both the right and left side, hence 92 LPI diameters were obtained. Results The most commonly used site for prosthesis attachment is between 1–1.5 mm away from the tip of the LPI. We found great variability in the diameters of LPI in the attachment site, with the AP diameter ranging between 0.6 -1.5mm and the ML diameter ranging between 0.5mm-1.2 mm. Conclusion Pistons by design have characteristics of gripping incus that will vary between types. Based on LPI dimensions, ideal piston types with appropriate inner loop diameters are suggested in this study. HRCT before surgery should include measurements of the LPI as a guide to the choice of the prosthesis during surgery. [ABSTRACT FROM AUTHOR]

This study developed a friction measurement apparatus with a floating cylinder liner in a small motorcycle engine. In this measurement apparatus, joint plates were installed in the grooves on the outer periphery of the floating liner, and then the plates, as well as load washers of piezo type, were mounted in the cylinder block at both the thrust and the anti-thrust sides. A stepped ring, protruding inward, was mounted on the top of the floating liner so that cylinder pressure acting on the stepped portion was balanced in the vertical direction. Thus, it was possible to measure the friction in the sliding directions of the piston. Using this apparatus, the effect of the engine operating period on friction was investigated in a piston micro-dimpled with a fine particle bombarding process. Results indicated that, at low engine speeds, friction decreased with the operating period, but at high engine speeds, friction decreased after 10 hours of operation, and then increased after 20 hours of operation. [ABSTRACT FROM AUTHOR]

Reciprocating machines, compressors and engines are the most commonly used machines in our technical environment. It is impossible to create a perfect seal between moving parts, therefore the phenomenon of leakage occurs in all such machines, however as we will see, it mainly affects hot air engines, which operates without charge exchange. This article attempts to describe this phenomenon in a mathematical form, and assist helping to understand the difference between calculated and measured values. [ABSTRACT FROM AUTHOR]

Copyright of Automobile Technology & Material is the property of Automobile Technology & Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maritime transportation is the essence of the international economy. Today, about ninety percent of world trade is carried out by sea through 50,000 merchant ships. Most of these vessels are powered by mainline diesel engines due to their reliability and fuel efficiency. Reliability of system elements in general depends on random failures, significant wear during operation, additional wear during start-up. Accidental damage to diesel engine components is a major hazard during operation, as some parts (such as cylinder liners and pistons) are usually replaced during repairs. On the other hand, preventive service does not eliminate random malfunctions. Therefore, in the general problem of assessing the reliability of a diesel engine, there is a mathematical problem of assessing the reliability and durability, taking into account only the random failures of its elements, which are of the greatest practical importance. The purpose of the work is a mathematical study of the reliability of parts of the cylinder-piston group of the main engines of dry cargo ships. Using a systematic approach and a probabilistic statistical method, it was established that the most common and difficult case is the simultaneous action on a system element (for example, a cylinder sleeve) of factors that cause wear during the period of operation (including during the start-up period) and accidental failures. It was determined that the quality of the cylinder-piston system in ships of the "Ostriv Rosiyskiy" type is higher than in the ships of the "Simferopol" and "Murom" types. Empirical formulas for estimating the probability of emergency failure of main engine system elements during the period of operation between factory repairs were obtained, where the main danger during the period of operation was carried by accidental failures. Based on the results of the study, it is possible to establish a schedule for the periodicity of maintenance of the ship's main engine and the cost of losses due to ship downtime due to failures, and can also be used in the reliability study of other types of ship's main engines. The results make it possible to determine the reliability of the parts of the cylinder-piston group of the main engines of dry cargo ships. and, in particular, to establish the maintenance schedule of the ship's main engine and the cost of damages due to ship downtime due to failures, and can also be used in the study of the reliability of other types of main engines of other series of ships

The calculations of the thermal and stress-strain state of the two-stroke gasoline engine (CS5200) pistons are completed. The model of an original piston and a piston modified with catalytic materials is used in the calculations. The technique used in modeling static and thermal loads using the SolidWorks Simulation program is described. A comparative analysis of the results of modeling the original and modified pistons is given. The efficiency of the piston is estimated when the surface is modified with catalytic materials. The technique for estimating the boundary conditions is used to solve thermal and mechanical problems. It allows you to take into account the features of loading, as well as the available calculated and experimental data.

The article focuses on the problem of loading the combustion chamber of diesel engine pistons together with the method of its optimization using the DuralBowl technology. Along with the growing requirements of exhaust emission standards, the increasing competition in the efficiency of internal combustion engines, the load on the combustion pistons increases due to the increase in pressure and temperature of fuel combustion and the tendency to slim the structure. Numerical analyzes and analyzes of damaged pistons in diesel engines have shown that one of the places most exposed to piston damage are the combustion chambers. There is a concentration of thermomechanical stress at the edge of the combustion chamber, which may lead to the destruction of the piston and the necessity to carry out overhaul of the drive unit. One of the technologies that optimizes the strength of this zone is the DuralBowl local remelting process. This process allows for several timesimprovement in the fatigue strength of pistons in internal combustion engines. The article analyzes the thermomechanical load on the combustion chamber along with the impact of this load on the durability of pistons in diesel engines. An analysis of the DuralBowl process was also performed, aimed at eliminating the negative effects of loading the combustion chamber, extending the piston life. The analysis focused on the microstructure of the material before and after the DuralBowl process.

The cooling of engine piston is very important, and the fluid vibration characteristics of its internal cooling oil is the key to affect the heat transfer efficiency. In order to effectively ensure that the piston temperature will not be overloaded and avoid the reduction of sealing performance, a two-phase flow model in the piston cooling chamber is established in the paper. The flow field and heat transfer characteristics of the cooling oil are simulated by finite element method using FLUENT. In terms of model selection, VOF multiphase flow calculation and SST 1-model are selected as turbulence model. The setting of boundary conditions combines the piston stroke characteristics of the hydraulic cylinder, so as to obtain accurate inlet parameters, and obtain the oil liquid phase proportion distribution, oil velocity field and the change law of convective heat transfer coefficient under different piston positions. The results show that the instantaneous ratio of cooling oil is closely related to the speed, and increasing the oil speed is an important means to improve the heat transfer performance. The multiphase flow model has high reliability, and there is no obvious difference between the average convective heat transfer coefficient obtained by the near-wall model method and the wall function method. [ABSTRACT FROM AUTHOR]

Fueling internal combustion engines with hydrogen is one of the most recommended alternative fuels today in order to combat the energy crisis, pollution problems, and climate change. Despite all the advantages of hydrogen fuel, it produces a higher combustion temperature than gasoline. In an internal combustion engine, the piston is among the numerous complex and highly loaded components. Piston surfaces are directly affected by combustion flames, making them critical components of engines. To examine the stress distribution and specify the critical fracture zones in the piston for hydrogen fuel engines, a three-dimensional CFD-solid-mechanics model of the internal combustion engine piston subjected to real thermomechanical loads was analyzed numerically to investigate the distribution of the temperature on the piston body, the interrelated thermomechanical deformations map, and the pattern of the stresses when fueling the engine with hydrogen fuel. With the aid of multiphysics COMSOL software, the CFD-solid-mechanics equations were solved with high accuracy. Despite the increase in pressure on the piston and its temperature when the engine is running on hydrogen fuel, the results show that the hydrogen fuel engine piston can withstand, safely, the thermomechanical loads. In comparison to gasoline fuel, hydrogen fuel caused a deformation of 0.34 mm, an increase of 17%. This deformation is within safe limits, with an average clearance of 0.867 mm between the cylinder liner and piston. [ABSTRACT FROM AUTHOR]

A hermetic reciprocating compressor is one of the most critical parts for the energy efficiency of a household refrigerator. Piston-cylinder contact in the hermetic compressor accounts for most of the energy loss. The tribological performance of the piston-cylinder pair can be enhanced by introducing micro-texturing on the piston surface. In this research, an experimental study is presented to tribologically assess the effect of the micro-textured piston on the performance of the hermetically sealed reciprocating compressor. The micro-texture on the piston surface was prepared by the laser surface texturing method. Four different micro-textures were studied: radial micro-grooves, axial micro-grooves, mesh micro-grooves, and micro-dimples. The textures' size, shape, and depth were studied using scanning electron microscopy (SEM) and white light interferometry (WLI) techniques. The results were compared with the non-textured piston compressor. It was found that the radial, axial, and mesh micro-grooves pistons have a negative effect on the coefficient of performance of the hermetic reciprocating compressor. However, the piston with the micro-dimples texture increased the compressor's coefficient of performance by 1%. Refrigerant leakage from the piston-cylinder clearance was also investigated and it was observed that micro-dimples on the piston surface decrease the refrigerant leakage by 35% due to the presence of a continuous oil film between piston and cylinder. The compressor's cooling capacity (Qc) was observed to be increased by 1 W in the case of a micro-dimpled piston. [ABSTRACT FROM AUTHOR]

The following publication focuses on the design and manufacture of a grape press, by presenting the design and technological parameters of its main elements. Today, many innovative solutions are available that can be applied in the production of oenological machines. Designing and building such machines would make the work easier and save a lot of time for brewers. Therefore this machine is designed to help small grape producers to minimize the working processes. The manufacture and assembly of the juice extracting press was carried out in 2022 at the base of an agricultural holding in the Chirpan region in Bulgaria. For the construction of some of the parts of the machine, scrap materials were used, which can be recycled after reaching the end of their life cycle. This was done in order to reduce the financial costs of manufacturing the machine. The arrangement of the individual elements making up the machine is essential for the smooth running of the work process. The press consists of two main parts: a working chamber and a structural frame. The elements of the working chamber are made of stainless steel - handle (D = 20 x L = 640mm), tube with internal thread (D = 44 x L = 480 mm), pressure element (piston) (D = 480 mm), external cylinder (D = 540 x L = 400 mm), internal drum with holes (D =500 x L = 400 mm). The structural frame is composed of several elements: a cylindrical tray with dimensions (D = 600 x L = 80 mm), raised from the ground at a height of 460 mm. A screw rod (D = 38 x L = 340 mm) is mounted centrally on the tray. The working principle of the press is based on the transmission of the pressure force to squeeze out the grape must. The researcher plans to conduct a study with the newly created grape press by experimenting with extracting juice from other fruits. [ABSTRACT FROM AUTHOR]