Piston Surface Research Articles

Dynamic characteristics analysis of shock absorber based on fluid simulation

Pneumatic spring dampers are extensively utilized within hydraulic systems, and the flow characteristics of the internal oil play a crucial role in determining noise and vibration levels. To validate the mechanical structure's reliability, the shock absorber was simplified and the fluid domain was extracted using a CFD method. The velocity field and pressure field under different conditions were then simulated and analyzed. A finite element model of the flow field was established, and its accuracy was verified by comparing simulation results of gas side pressure with experimental results. According to the working principle of the oil-gas spring, dynamic active surfaces in contact with the main piston and dynamic driven surfaces in contact with the floating piston were defined, determining moving conditions for dynamic grids. The results indicate that as the diameter of flow channels increases, there is a decrease in average pressure drop within the oil chamber (i.e., pressure loss within the flow field). Additionally, as bend angle increases, average pressure drop decreases. However, optimization effects become less significant beyond a certain bend angle.

Influence of swirl, tumble and squish flows on combustion characteristics and emissions in internal combustion engine- review

This study gives an overview of available literature on flow patterns such as swirl, tumble and squish in internal combustion engines and their impacts of turbulence enhancement, combustion efficiency and emission reduction. Characteristics of in-cylinder flows are summarized. Different design approaches to generate these flows such as directed ports, helical ports, valve shrouding and masking, modifying piston surface, flow blockages and vanes are described. How turbulence produced by swirl, tumble and squish flows are discussed. Effects of the organized flows on combustion parameters and exhaust emission are outlined. This review reveals that the recent investigations on the swirl, tumble and squish flows are generally related to improving in-cylinder turbulence. Thus, more experimental and numerical studies including the impacts of this organized flows on turbulence production, combustion behavior and pollutant formation inside the cylinder are needed.

Finite element analysis of thermal barrier properties under relevance vector machine in coated pistons and blades

Internal Combustion (IC) engines require Thermal Barrier Coatings (TBCs) to preserve their effectiveness and performance. By coating engine parts with TBCs, thermal fatigue and environmental heat loss may be minimised. To reduce heat loss in IC engines during the combustion stage, piston thermal barrier coating is extremely beneficial. Additionally, it is well known that power plants with higher energy efficiency tend to operate their gas turbines at higher operating temperatures. To produce TBCs for the thermal design of gas turbines and diesel engines with higher performance, an in-depth study on the thermophysical properties of TBCs is required. This article presents an experimental investigation into the combined effect of gas turbine blades and diesel engine pistons coated with a heat barrier, utilising two distinct Thermal Barrier Coatings. Initially, numerical calculations are used to assess the wall heat transfer model’s ability to control temperature and density. The piston and blade top surfaces received plasma-sprayed, Yttria-Stabilised Zirconia (YSZ) with different material combinations on the piston and blades are evaluated. The Finite Element Method is developed for the coating of the ideal thickness to analyse the failure mechanism of the TBC sample. To evaluate the fatigue residual lifespan of TBC pistons, as well as blades in high-power engines, the authors also created a relevant vector Machine-based lifetime prediction model. The CO, HC and NOx emissions, as well as the fuel depletion and braking thermal efficiency, are used to calculate the performance analysis of the coated piston and blades. The results demonstrated improved thermal process endurance and decreased thermal conductivity by 28% when compared to YSZ using the RVM method respectively.

Thermal analysis by numerical simulations of a multilayered coating applied on a heavy-duty diesel engine piston

A methodology to numerically study the impact of a thin, multi-layer coating applied on the piston crown surface of an internal combustion engine is proposed. It relies on a loose thermal coupling between 3D-RANS simulations of the combustion chamber and 3D conduction simulations of the piston. The approach allows to characterize the transient thermal behavior of the piston, which is crucial to capture the thermal swing effect of the coating, as well as its potential impact on the combustion, heat transfer and engine efficiency. This methodology is used to simulate the impact of a 200-µm, 3-layer coating, applied on the piston crown surface of a single-cylinder, heavy-duty Diesel engine, for one operating point. No gain in terms of efficiency is observed with the coated piston (the decrease in heat losses through the piston surface due to the coating is counter-balanced by an increase in heat losses through the non-coated cylinder head). However, the methodology proves capable of predicting a coherent thermal behavior of the coated piston (decrease in piston body temperature of 5 K, average bowl surface temperature swing amplitude of 60 K, <5 K temperature swing at the interface between the metallic substrate and the coating) and is able to provide insightful information regarding the impact of coating on volumetric efficiency, heat losses, combustion but also on the coating reliability itself, for a reduced computational cost compared to a fully coupled approach. It can then be employed to evaluate the effect of a coating applied not only on the piston but also on the cylinder head, which would certainly have a more significant impact on the engine efficiency.

Development And Application Of A New Visualization Technique Using Photochromism For Transport Process Of Lubricating Oil Around The Engine Piston

A new visualization technique using photochromism for the movement of oil film was developed and applied to an optical gasoline engine. A photochromic dye was dissolved in the oil and an arbitrary position of the oil film was illuminated by UV laser light, which makes a marker in the oil film via a photochromic reaction. The lifetime of color change by photochromism is relatively long and therefore, by tracking the movement of a marker makes it possible to visualize the movement of oil film directly. The color density was quantified based on the absorbance calculated from images taken before and after coloring in two wavelengths. Through the experimental and theoretical considerations, it was confirmed that the calculated absorbance is effective in reducing a noise originated by the color, the shape of the piston surface, the temporal variation of oil film thickness and the illuminating light intensity distribution. Furthermore, the value of the absorbance is in a very good linear relationship with the oil film thickness. This technique was applied to an optical gasoline engine and confirmed the availability of this technique. In the top land of piston surface, the oil film between the piston and cylinder liner was separated and the majority of the oil is at the piston surface and moved with the piston motion. The oil film thickness on the cylinder liner was very thin. On the contrary, at the piston skirt region, a wider region of the oil film is connected between the linear and the piston skirt. However, there are regions where the oil film between the liner and the skirt is separated by cavitation and the majority of the oil film is on the piston skirt. The change of the flow direction by the operating condition, i.e., the throttle condition, was able to clearly visualize, though the movement of oil film on the piston surface was very slow in normal case. The relatively fast complexed flow for opposite direction was also able to visualize by this technique.

Акустические характеристики пористого алюминия, применяемого для изготовления шумопоглощающих устройств промышленного оборудования

Noise-absorbing devices made of porous aluminum have been used as components of units and systems of modern industrial equipment (pressure regulators, compressors, exhaust systems, pneumatic tools, heat engines, etc.). The advantages of products made of the material are high mechanical strength, resistance to chemicals, vibrational and thermal loads, and recyclability. Noise absorption in the structure of porous aluminum is caused by the loss of energy as a result of viscous friction and heat exchange between oscillating air particles and the skeleton of the material. Structural parameters of porous metals significantly affect the efficiency of noise absorption. Experimental studies of sound-absorbing properties of porous aluminum samples of different thicknesses, porosity, and pore sizes have been carried out for the present paper. An acoustic impedance tube, in compliance with the requirements of ISO 10534 and ASTM E1050 on 5–20 mm thick samples, has been used for the study. The porosity of samples was 0.5–0.7, whereas the average pore size was equal to 0.6–2 mm. Two variants of sample installation have been investigated, i.e., without an air gap and with the formation of a 20 mm air gap relative to the surface of the rigid piston of the impedance tube. The impact of structural parameters and thickness of porous aluminum samples on their noise-absorption properties has been assessed based on the results of the study. It has been determined that the increase of average pore size within the range between 0.6 and 2 mm causes the reduction of the noise-absorption coefficient. The effect becomes more pronounced when a sample with the formation of an air gap relative to the piston surface is installed. With identical average pore sizes and thicknesses, the highest values of sound absorption coefficient by the porous aluminum samples have been registered for a porosity of 0.6. The study results can be used for the development and modernization of sound-absorbing devices for industrial equipment made of porous aluminum.

Theoretical and numerical investigation of introduced errors in surface temperature measurements of pistons applied in internal combustion engine

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.

Estimation of Piston Surface Temperature During Engine Transient Operation for Emissions Reduction

Abstract Piston surface temperature is an important factor in the reduction of harmful emissions in modern gasoline direct injection (GDI) engines. In transient operation, the piston surface temperature can change rapidly, increasing the risk of fuel puddling. The prediction of the piston surface temperature can provide the means to significantly improve multiple-pulse fuel injection control strategies through the avoidance of fuel puddling. It could also be used to intelligently control the piston cooling jet (PCJ), which is common in modern engines. Considerable research has been undertaken to identify generalized engine heat transfer correlations and to predict piston and cylinder wall surface temperatures during operation. Most of these correlations require in-cylinder combustion pressure as an input, as well as the identification of numerous model parameters. These requirements render such an approach impractical. In this study, the authors have developed a thermodynamic model of piston surface temperature based on the global energy balance (GEB) methodology, which includes the effect of PCJ activation. The advantages are a simple structure and no requirement for in-cylinder pressure data, and only limited experimental tests are needed for model parameter identification. Moreover, the proposed model works well during engine transient operation, with maximum average error of 6.68% during rapid transients. A detailed identification procedure is given. This and the model performance have been demonstrated using experimental piston crown surface temperature data from a prototype 1-liter 3-cylinder turbocharged GDI engine, operated in both engine steady-state and transient conditions with an oil jet used for piston cooling turned both on and off.

Plasma sprayed K2Ti6O13 as thermal barrier coatings with high thermal swing for diesel piston enabled by inter-splat bonding and porosity tailoring

Thermal swing coatings with high thermal diffusivity but low thermal conductivity could increase the efficiency of diesel engines by minimizing the piston surface thermal gradient. However, the thermal diffusivity is usually positively related to the thermal conductivity and thus it is generally difficult to deposit thermal barrier coating with a low thermal conductivity but high thermal diffusivity by plasma spraying. In the present work, K2Ti6O13 with intrinsic low thermal conductivity and low melting point (1350 °C) was used as the coating material to prepare a coating with a high ratio of thermal diffusivity to thermal conductivity. Results revealed that due to the low melting point feature of K2Ti6O13 all plasma sprayed coatings have high inter-splat bonding quality which resulted in a high thermal diffusivity close to the sintered counterpart. K2Ti6O13 coatings of high porosity were plasma sprayed by optimizing powder structure, which leads to a low thermal conductivity but influences little the thermal diffusivity. It is also found that the preferential evaporation of potassium oxide from the K2Ti6O13 molten droplets leads to the formation of the TiO2 phase and generates global pores in the coating. At optimized spray conditions by using sintered porous powder, the K2Ti6O13 coating with a porosity of 21 % and single K2Ti6O13 phase reveals the lowest thermal conductivity of 0.85 W/m·K and a high diffusivity of 0.43 mm2/s. The coating exhibits the highest thermal swing of about 91 °C, having much higher performance than the conventional thermal barrier coatings used for enhancing the thermal swing effect.

The efficiency of thermal protection of ICE pistons with the micro-arc oxidation

BACKGROUND: In order to protect pistons of internal combustion engines (ICE) from burnout and increase their durability, it is reasonable to use ceramic coatings formed on the piston head with micro-arc oxidation (MAO). Many scientific papers have been devoted to the study of the efficiency of these coatings. However, most of these studies were carried out at laboratory facilities simulating the engine operation, generally, not taking into account the real thermophysical parameters of the MAO coating. Therefore, the thermal protection efficiency of these coatings is difficult to assess. AIM: Study of efficiency of the thermal protection of pistons using a ceramic coating formed by micro-arc oxidation on the piston head with numerical simulation. METHODS: The study was conducted in the SolidWorks Simulation software. Two piston aluminum alloys were used as the piston material: AK12d (with a silicon content of 12%) and AK4-1 (with a silicon content of 0.35%). Temperature loads corresponding to the operation of a real engine were applied to the surfaces of the model piston. At the first stage of the study, the thermal state of pistons made of different uncoated alloys was simulated. At the second and third stages of the study, the effect of the coating thickness on the piston thermal state was simulated. The piston material of the second study stage was the AK4-1 alloy. The piston material of the third study stage was the AK12d alloy. Ceramics, which properties correspond to the coatings properties formed with the micro-arc oxidation method on these alloys, were used as the coating material. The coating thickness varied in the range from 50 to 350 µm in increments of 100 µm. The probing method was used to determine the temperature in various areas of the piston, such as at the piston head surface at the MAO coating and under it, in the area of piston grooves, at a piston skirt and the piston head from the side of a crankcase. RESULTS: With the simulation, it was found that: The micro-arc coating of the piston head reduces the thermal tension of the piston regardless of the aluminum alloy chemical composition. The efficiency of the piston’s thermal protection increases with an increase in the ceramic coating thickness and a decrease in its thermal conductivity coefficient. The greatest heat-protecting effect is achieved by the piston made of the AK12d eutectic alloy. CONCLUSIONS: It is found that the MAO coating at the piston head is an effective way to reduce the thermal tension of the ICE pistons. Increasing the ceramic coating thickness and a decrease in its thermal conductivity coefficient increases the efficiency of the pistons thermal protection. Reducing the thermal conductivity of the MAO coating and increasing the MAO coating thickness increases the temperature on the coating surface.

Synergistic effects of graphene additives and piston ring surface treatment on friction properties of engine oil

The use of nano-additives improves the performance of lubricants by minimizing energy loss due to friction and wear. In this study, tribological properties of cylinder liner-piston ring were improved by modifying monolayer graphene with surfactants. Additionally, surface chemical chromium coating and chemical heat treatment were conducted on the friction surfaces of specially made piston ring samples to further enhance the friction of piston ring. From the comparison of experimental results, the best lubrication performance was exhibited by the use of 0.05 wt% modified graphene nano-lubricant, which reduced the friction coefficient by approximately 31.1% and improved the anti-wear performance by approximately 59.6% compared to the base oil. In addition, the effect of the graphene nano-lubricant on the friction performance of chromium-coated samples was more substantial than that of the chemically heat-treated samples. Under high-temperature and heavy-load conditions, the corresponding friction coefficient was reduced by 15.5% and 34%, respectively, when compared to the base oils. This can be attributed to the porous surface of the chromium-coated sample, which promotes the storage of the graphene nano-lubricant. The results highlight the synergistic effect of graphene additives and piston ring surface treatment on the tribological performance.

Coupled models for propagation of explosive shock waves in cylindrical and spherical geometries

The propagation of shock waves in different geometries is crucial in engineering and scientific applications. A comprehensive model is developed to elucidate the hydrodynamic growth and decay of shock waves in cylindrical and spherical geometries by using the strong shock wave assumption. This model takes into consideration the conservation equations governing mass, momentum, and energy, thereby allowing for an accurate description of the coupled behavior between the piston and shock wave propagation. In contrast to the localized analysis employed in previous self-similar methods, this model incorporates the finite sound wave velocity to introduce the concept of retarded pressure on the piston surface. Consequently, the proposed model offers a multitude of advantages by providing a complete set of dynamic information concerning the trajectories, velocities, and accelerations of both the piston and shock wave. Furthermore, an asymptotic analytical solution is derived to describe the decay of shock waves in cylindrical and spherical geometries. To validate the theoretical analysis and illustrate the propagation characteristics of shock waves in these specific geometries, thorough comparisons are conducted. These findings contribute to the advancement of our understanding of shock wave dynamics in various physical systems, particularly in the field of plasma physics.

Particulate Matter Emission and Air Pollution Reduction by Applying Variable Systems in Tribologically Optimized Diesel Engines for Vehicles in Road Traffic

Regardless of the increasingly intensive application of vehicles with electric drives, internal combustion engines are still dominant as power units of mobile systems in various sectors of the economy. In order to reduce the emission of exhaust gases and satisfy legal regulations, as a temporary solution, hybrid drives with optimized internal combustion engines and their associated systems are increasingly being used. Application of the variable compression ratio and diesel fuel injection timing, as well as the tribological optimization of parts, contribute to the reduction in fuel consumption, partly due to the reduction in mechanical losses, which, according to test results, also results in the reduction in emissions. This manuscript presents the results of diesel engine testing on a test bench in laboratory conditions at different operating modes (compression ratio, fuel injection timing, engine speed, and load), which were processed using a zero-dimensional model of the combustion process. The test results should contribute to the optimization of the combustion process from the aspect of minimal particulate matter emission. As a special contribution, the results of tribological tests of materials for strengthening the sliding surface of the aluminum alloy piston and cylinder of the internal combustion engine and air compressors, which were obtained using a tribometer, are presented. In this way, tribological optimization should also contribute to the reduction in particulate matter emissions due to the reduction in fuel consumption, and thus emissions due to the reduction in friction, as well as the recorded reduction in the wear of materials that are in sliding contact. In this way, it contributes to the reduction in harmful gases in the air.

Study on Oil Supply Characteristics of Connecting Rod Small End Bearing With Splash Lubrication by Smooth Particle Hydrodynamics Method

Abstract The lubricating oil distribution significantly impacts the lubrication and cooling of the connecting rod small end bearing during the splash lubrication. This study investigates the oil supply for the small end bearing with splash lubrication utilizing the smoothed-particle hydrodynamics. The oil distribution and inlet volume are analyzed under various engine speeds. The results reveal that the oil moves close to the piston surface and hardly enters the oil bores, resulting in oil wastage. The oil entering the bores might be thrown out due to the inertia, causing the oil inlet volume to fluctuate. With increasing engine speeds, the total oil inlet volume under the quasi-steady-state gradually diminishes, exacerbating the lubrication conditions.

Assessment of piston quality using QFD-analysis

The article examines the state and prospects of agricultural machinery in the Russian Federation, studies of the parameters of accuracy and quality of ZMZ engine pistons using QFD analysis. As a result of the construction of the “House of Quality” for the use of the ZMZ engine piston at repair enterprises, it is necessary to carry out the following measures: enhanced control of piston markings; advanced training of workers who process the piston surface; improved control over the mass of manufactured pistons.

The testing and optimization of a bio-inspired textured piston for the BW-250 mud pump

To reduce the friction, wear, and temperature of the piston-cylinder liner friction pair, we designed and processed 27 kinds of bio-inspired textured pistons with cylindrical pits. Based on the experimental optimization design method, friction test, wear test, and thermal imaging test were carried out. Results show that the textured pistons can significantly reduce the friction. Various texture parameters have different effects on the mean friction force. The wear of the textured pistons is significantly less than that of the standard piston. The influence of the texture parameters on piston wear are analyzed through range analysis, regression equation, and 3D response surface method. The standard piston suffers from serious wear and tear. The cylindrical pit texture can supply lubrication and store abrasive particles, which can improve the wear condition of the textured piston surface to a certain extent. The friction heat of the textured pistons is small, which can reduce the average temperature of the friction pair.

Thermal Analysis of Different Piston Head Profiles by using FEM

The objective of this research work is to optimize the stress variations at the top of the piston in real engine conditions. During this pressure analysis on the examined surface of the piston, the thermal behavior is examined. The operating gas pressure, temperature and piston material functions are used as investigation functions. The analyzes carried out showed that the upper part of the piston could be damaged or broken due to the temperature caused by the working conditions, as the replacement of damaged or non-functioning parts is very expensive and usually difficult to obtain. Concave and convex piston profile designed in Solid Work 2023, used to design the piston geometry and for FEM analysis to optimize the thermal behavior of the used ANSYS R23.0 piston. Aluminum alloy and gray cast iron material for piston construction. Stress and displacement are analyzed for the piston by applying pressure to it in the structural analysis. By observing the results of the analysis, we can decide whether the piston we are designing is safe or not under the applied load conditions. Heat flow and thermal temperature distribution are analyzed using piston surface temperatures in thermal analysis.

Impact of thermal swing piston top land coatings on gasoline engine performance and raw emissions

Upcoming legislations aim to significantly reduce carbon dioxide and hydrocarbon emissions compared to current regulations. Accordingly, options have to be evaluated to not only convert the raw emissions in a catalytic converter, but also to reduce the raw emissions from the combustion process in the first place. Therefore, thermal piston top land coatings, which lead to an oscillating piston surface temperature were investigated on a single cylinder research engine using a gasoline RON95E10 fuel. Measurements were conducted at a compression ratio of 12.2 and a long Miller intake event. In this manuscript the results achieved with yttria stabilized zirconia in comparison to an uncoated piston are displayed. Significant effects of the coatings on the indicated efficiency could be observed mainly at low engine speeds and loads due to the high share of fuel energy in the wall heat losses and incomplete combustion. At these operating points, the reduction of wall heat losses can almost be fully transferred into indicated efficiency, leading to an increase in indicated efficiency of 6.3% by the yttria stabilized zirconia coating. At higher engine speeds and loads, the advantage in indicated efficiency vanishes and a decrease of 0.5% can be observed. Near full load operation the indicated efficiency slightly lower. However, the effects of a thermal swing coating on combustion efficiency and wall heat losses strongly depend on the operation conditions.

Thermo–Solid Coupling Analysis of Bionic Piston for a Mud Pump in Tunnel Engineering

With the development of mud shield tunnel construction technology, the demands on the working performance of a mud pump are becoming higher and higher. As one of the critical components of a mud pump that is easy to wear, the performance of the piston directly affects the operational efficiency and lifespan of the mud pump. The bionic shape of the piston was designed under the guidance of non-smooth surface characteristics of natural organisms to enhance friction and wear performance as well as longevity. The stress field and temperature field characteristics of the pistons with three bionic structures (pit, stripe, and prismatic) were analyzed based on finite element simulation. The stress field analysis results indicated that, for the prismatic shape and pit shape pistons, the maximum stress was concentrated in the lip regions, and both of them bore large stress at the root. For the stripe-shaped piston, the stress was dispersed on both sides of the stripe structure, the stress at the root was small, and the stress gradient along the axial direction was relatively gentle. The stripe-shaped bionic structure can significantly improve the stress distribution state on the piston surface, and the optimal stripe width was recommended to be between 1 and 1.5 mm. The temperature field analysis results indicated that, for the stripe-shaped piston, the surface temperature and heat flux were the smallest, and the temperature gradient was relatively smaller than that of pit-shaped and prismatic-shaped pistons, so it was easier to dissipate heat. When the stripe width was 1.5 mm, the temperature distribution was the most uniform, and the heat flux in localized areas was the smallest, so the heat generated by friction was relatively easy to discharge in the unit area.

Effect mechanism and quantitative analysis of injector faults on diesel engine performance

The nozzle deterioration, caused by carbon deposition, cavitation erosion, and other reasons, has a great influence on the power performance, emissions, and thermal load of the direct injection (DI) engine. To understand the manifold effects of nozzle fault on engines, a systematic explanation for the diverse fault phenomena and effect mechanism of nozzle abnormality on the engine performance is needed. The joint action of orifice diameter and fuel spread direction on the performance of a double-swirl diesel engine are numerically revealed and decoupled. The results show that the engine power performance is mainly affected by the change of orifice diameter, while the abnormal spray direction has a great influence on the emissions and the piston surface thermal load. Insufficient spray tilt angle leads to a more concentrated fuel distribution because the fuel of the faulty orifice is not effectively channeled and dispersed by the circular ridge, which causes a 15.29% increase in NOx and an 8.73% increase in soot emissions. Spray circumferential offset leads to increased soot, decreased NOx, and slightly decreased power due to asymmetric fuel distribution. Some fuel is directly injected and burned in the clearance between the piston crown and cylinder head due to the abnormal spray direction, which causes the maximum heat flux at the piston crown to be about 1.8 times that under normal state, greatly increasing the possibility of piston damage. In contrast, the spray circumferential offset mainly causes the position change of the thermal load, but not the magnitude change.