Technology and equipment of vertical‑stack molding for the production of castings without pattern drafts

The article reports on the new technology and equipment of vertical‑stack molding (VSM), created by OJSC “BELNIILIT” for the manufacture of vertical‑stack molds. The development is intended for the production of molds and cast blanks of oil, which are later used for the manufacture of piston rings of internal combustion engines.The difference between the above‑mentioned technology and traditional methods of VSM is the use of models without drafts. The development is export‑oriented and has a great economic effect for ring manufacturers due to the absence of drafts on castings, since part of the mechanical operations for their processing is excluded, the metal consumption of blanks is reduced, the production spaces required in this regard are reduced, the necessary labor supply is reduced, etc.OJSC “BELNIILIT” has successfully carried out experimental design and technological work on the new scientific and technical products creation, which are of great interest to the world manufacturers of piston rings. An industrial sample of a molding machine and a mold manipulator were manufactured.

Research of surface layer properties of piston rings after gas thermal spraying

Today, one of the important problems of mechanical engineering is to increase the reliability and durability of machines. A special place in this matter is occupied by increasing the wear resistance of parts. As for diesel construction, the problem of increasing the hardness and wear resistance of piston rings is very important. Goal. The goal is study of the structure and nature of changes in the hardness of the surface layer obtained by gas-thermal combined spraying, after grinding, running-in and mileage of the diesel engine, i. e., at all stages of the production cycle. Methodology. The coating on the rings was applied by the method of two-wire metallization with independent supply of wires made of 11X18M steel and molybdenum. Metallographic analysis was used to study the structure of the obtained coating. The condition of the surface layer after coating, grinding, running-in and diesel run was studied by measuring the microhardness. Results. Metallographic analysis of the interface between steel and molybdenum coating – cast iron for many rings and different parts of one ring shows that the coating interacts closely with the substrate along the entire application profile. The structure of molybdenum particles demonstrates their fineness. This is due to the fact that the rapid crystallization under pressure contributes to the creation of a fine-grained structure. Comparison of the microhardness of molybdenum and steel wires with steel-molybdenum coating indicates a significant strengthening of molybdenum and steel particles during spraying, due to the processes of structure formation. Experimental data indicate the stability of the hardness of both molybdenum particles and steel particles, which is important for the coating in operation. Originality. Features of formation of a gas-thermal covering at a simultaneous electric arc spraying of molybdenum and 11Х18М steel on piston rings from pig-iron are established. It is shown that a layered structure is formed, which consists mainly of steel and molybdenum particles. The reasons for the wide range of properties of steel and molybdenum particles have been clarified. It is proved that the operational properties of steel-molybdenum coating are due to its antifriction properties, porosity, which provides self-lubrication of the friction surface, good adhesion to the substrate, which increases by 3–4 times compared to traditional methods. Practical value. The proposed technology of gas-thermal spraying significantly increases the service life of piston rings operating in wear conditions.

Study of the influence of vacuum-arc coating on the wear-resistance of piston rings

The effect of a multilayer vacuum-arc nanostructured Ti-Mo-N coating, its application parameters on the wear resistance of piston rings is studied. The effect of the parameters of vacuum-arc deposition on the nanohardness is established.

Investigation of piston ring wear engines by the mathematical statistics method

Improving the reliability and durability of internal combustion engines makes it possible to increase productivity and reduce the cost of operation. The study of nature and magnitude of piston rings wear is relevant and represents a scientific novelty. During the operation of internal combustion engines, it is almost impossible to determine the influence of various factors on the wear rate and the resource of piston rings. One of the most accurate ways to study the wear intensity and the service life values of internal combustion engines piston rings during operation is the statistical method. The method of mathematical statistics allows us to study the nature and magnitude of individual parts wear with a sufficient degree of accuracy, to determine the main causes of wear, to outline ways of increasing the parts wear resistance, to establish durability criteria, to reasonably assign standard service life of parts and plan the parts need for any period with a given probability, with climatic conditions being taking into account. The article presents the collected statistical material on the internal combustion engines piston rings wear of construction and road vehicles operated at construction sites of Rostov region. It has been processed according to the normal Gauss law and data on the wear and service life of piston rings are obtained. The obtained experimental data on the wear of piston rings in height are reliable to the distribution law and can be used to determine the intensity of engines piston rings wear at repair enterprises.

Study of the Kinematics and Dynamics of the Ring Pack of a Diesel Engine by Means of the Construction of CFD Model in Conjunction with Mathematical Models

The present research aims to analyze the kinematic and dynamic behavior of the piston ring package. The development of the research was carried out through the development of numerical simulation by means of CFD. The analysis involves the three piston rings for the development of simulations that are closer to the real conditions of the engine since most of the investigations tend to focus on the study of the compression ring only. The simulation was reinforced by the incorporation of mathematical models, which allow determining the piston kinematics, the lubrication properties as a function of temperature, contact friction, and gas leakage. For the simulation, the CAD of the piston and the connecting rod—crankshaft mechanism was carried out, taking as a reference the geometry of a diesel engine. From the results obtained, it was possible to show that the first ring exhibits considerably greater radial and axial movement compared to the second and third piston rings. Additionally, it was shown that the first and second rings tend to maintain a negative tilt angle throughout the combustion cycle, which facilitates the advancement of the combustion gases over the piston grooves. Therefore, it is necessary to use strategies so that these rings tend to maintain a positive inclination. The analysis of the pressure conditions in the second ring are 150% and 480% higher compared to the conditions present in the third ring. Due to the above, it is necessary to focus efforts on the design of the profile of this ring. The study of energy losses showed that the combination of leakage gases and friction are responsible for a mechanical loss between 6–16%. In general, the development of the proposed methodology is a novel tool for the joint analysis of the kinematic characteristics, pressure conditions, and energy losses. In this way, integrated analysis of changes caused by piston ring designs is possible.

Advanced Tribological Characterization of DLC Coatings Produced by Ne-HiPIMS for the Application on the Piston Rings of Internal Combustion Engines

Piston rings (PR) are known for almost a quarter of the friction losses in internal combustion engines. This research work aims to improve the tribological performance of PR by a recently developed variant of Diamond-like Carbon (DLC) coatings deposited in a mixture of Ar and Ne plasma atmosphere (Ne-DLC) by high-power impulse magnetron sputtering (HiPIMS). For the benchmark, the widely used Chromium Nitride (CrN) and DLCs deposited in pure Ar plasma atmosphere (Ar-DLC) were used. The tribological tests were performed on a block-on-ring configuration under different lubrication regimes by varying temperatures and sliding speeds. The analysis of the results was performed by Stribeck curves corresponding to each sample. An improvement of the tribological performance was observed for Ne-DLC films by up to 22.8% reduction in COF compared to CrN in the boundary lubrication regime, whereas, for the Ar-DLC film, this reduction was only 9.5%. Moreover, the Ne-DLC films achieved ultralow friction of less than 0.001 during the transition to a hydrodynamic lubrication regime due to better wettability (lower contact angle) and higher surface free energy. Increasing the Ne up to 50% in the discharge gas also leads to an increase of hardness of DLC films from 19 to 24 GPa.

On Blow-by Aerosol Sources in a Single-Cylinder Crankcase Environment

Crankcase aerosol contributes to the particulate matter (PM) emissions of combustion engines equipped with an open crankcase ventilation system. In case of closed crankcase ventilation, the aerosol forms deposits that diminish engine efficiency, performance, and reliability. Such issues are best avoided by highly efficient filters combined with in-engine reduction strategies based on a quantitative understanding of aerosol sources and formation mechanisms in a crankcase environment. This paper reports key findings from a study of aerosol spectra in the range of 0.01 μm to 10 μm obtained from a 1.3-L single-cylinder engine under well-defined conditions. Supermicron particles were formed mainly by cooling jet break-up when the piston was positioned in TDC, while at BDC aerosol generation decreased by about 90 % because the oil jet was short and thus stable. Motoring the engine yielded an additional peak around 0.7 μm. It is associated with oil atomization at the piston rings and increased strongly with cylinder peak pressure. No significant contribution of the bearings could be identified at peak pressures below 116 bar. Engine speed had only a minor effect on aerosol properties. Operating the engine in fired mode increased the submicron aerosol concentration substantially, presumably because high(er) peak pressures boost aerosol generation at the piston rings, and because additional particles may have formed from recondensing oil vapor generated at hotspots. Soot or ash aerosols could not be identified in the crankcase aerosol, because they may have been integrated into the bulk oil.

Insight into friction and lubrication performances of surface-textured cylinder liners and piston rings

The effects of surface-texture technology on the friction and lubrication mechanism of cylinder liner-piston rings (CLPR) were explored in this study. An inclined groove texture was machined on the CL of a S195 diesel engine and dimples designed on the gas ring. Friction and wear tests of nontextured (NT), CL textured (CLT), and PR textured (PRT) conditions were performed on a CLTR friction and wear tester under different temperatures. First, the characteristics of friction and lubrication at different temperatures were analyzed by examining friction and contact resistance. Then, the wear characteristics were analyzed by examining surface morphology parameters of the CL and the PR wear mass after testing. Finally, the friction and lubrication mechanisms of NT, CLT, and PRT were studied by analyses of real-time friction and contact resistance in one cycle. The results showed that, under the same temperature, CLT and PRT increased oil film thickness, improved the lubrication state, and reduced friction, with CLT better than PRT in these respects. With increased temperature, the wear degree of CL liners became larger. The existence of surface texture reduced CL wear, yielded CL surface morphology not excessively changed by temperature, and improved its supporting performance and oil storage capacity. The inlet suction effect, structural effect, micro-wedge action, balancing wedge action, squeezing effect, and cavitation effect should be taken into account together when exploring the mechanism of the influence of surface texture on friction pairs. This study provided a method for scholars to explore the friction and lubrication mechanism of different texture types and provided an experimental basis for improving the performance of CLPR friction pairs.