Piston Design Research Articles

Study on Friction and Wear Performance of Sliding Metal Seal Materials Under Reciprocating Motion.

During petroleum drilling, the reciprocating motion in the seal device leads to piston and sleeve wear, which may cause leakage of the sealing medium. Selecting appropriate materials for the piston and sleeve, along with surface modifications, can effectively prolong the seal service life of the seal. The friction and wear properties of piston and sleeve pairs of different materials in a metal sealing device were simulated by the laboratory "pin-on-block" reciprocating friction test. Pins made of 45# steel, 35CrMo, and 20Cr13 were used to simulate piston bulges, while 35CrMo samples were used to simulate sleeves. Additionally, the influence of DLC (diamond-like carbon) coating and QPQ (Quench-Polish-Quench) nitriding on the wear resistance of the materials was studied. Based on this, the friction and wear properties, along with the wear mechanism of different material pairs, were analyzed. The results show that the friction coefficient curves of the three piston base materials and the 35CrMo sleeve are similar, and the friction coefficient of 45# steel is lower than that of 35CrMo and 20Cr13 at the initial stage. The DLC surface coating exhibited the best anti-wear performance, with the lowest friction coefficient, minimal wear, and the most stable friction coefficient. Surface QPQ nitriding treatment can also improve the wear resistance of the base material. However, due to the oxide formed during nitriding being prone to flaking, the friction coefficient fluctuates significantly at the initial stage of testing, and its anti-wear performance was inferior to that of the DLC coating. This study on material pairing and surface modification provides theoretical support for material selection and surface modification design of pistons and sleeves in oil drilling sealing devices.

A Review on Cushioning Characteristics in High-Speed Hydraulic Actuators

Abstract High speed actuators are an integral part of the fluid power driven systems and cylinder cushioning requirement in these actuators is one of the important aspects. Cushioning is imperative in any high-speed actuator as it not only increases its life but also gives operating comfort to the operator. Fluid power driven systems are very common in many defence and industrial applications due to their high force/torque and power density. This review paper brings out the available literature in the field of hydraulic cylinder cushioning. Literature, consisting mainly of journal articles, research papers and other media contents is analysed for the key parameters of research in this field. The classification of cushioning methodology by different researchers is projected. The methodologies of modelling and simulation work carried out by various authors are analysed. Thereafter the optimization studies done for the cushion piston design in various literature are discussed. Lastly, experimental validation strategies as employed in certain papers are also brought out. Experimental study, and validation of non-conventional cushioning methodology is discussed, which is not much evidenced in the literature.

Liquid Piston Compression Heat Transfer Prediction via Thermal‐Resistance Network: Simulation, Experimental Validation, and Liquid Carryover Evaluation

Liquid piston compressors gain attention due to their potential for more efficient and isothermal compression compared to traditional solid piston compressors. Liquid piston compressors use a liquid column instead of a solid piston, allowing for innovative mechanisms to enhance heat transfer and achieve near‐isothermal compression. However, a validated analytical model for heat transfer in liquid piston compressors is still needed to understand the exhaust phase within a liquid piston. In this work, a thermal network model, able to predict the polytropic index to within 8% of the experimental results, is proposed. Moreover, thorough experimentation is conducted to measure the amount of liquid carried over to better understand the exhaust phase. In the results, it is revealed that the piston carries over 13–21 mL of liquid within the exhaust gas for 10–23 s of stroke. Notably, the difference in liquid carried over for the three‐stroke times is not statistically significant, indicating that the liquid carried over is a function of liquid piston design and not stroke time. Finally, most liquid piston applications consider only water; hence, for the first time, this research assesses the stability of a cycle using a nonflammable hydraulic fluid (Fuchs 46 M red) to enhance compressor longevity and material compatibility.

Research on Aircraft Engines and Advanced Power in Land, Sea and Air

This paper provides a comprehensive overview of advanced propulsion technologies in military applications across land, sea, and air domains. It examines the theoretical foundations of propulsion systems, tracing the evolution of aircraft engines from early piston designs to modern jet propulsion. The study explores current state-of-the-art technologies, including advanced turbofan engines, hybrid electric systems, and nuclear propulsion for naval vessels. Special attention is given to emerging fields such as unmanned aerial vehicle propulsion, hypersonic technologies, and stealth engine designs. The research also delves into futuristic concepts like magnetohydrodynamic propulsion and pulse detonation engines. Throughout the analysis, common themes of improved efficiency, enhanced power-to-weight ratios, and increased operational capabilities are highlighted. This paper aims to provide a holistic view of the current landscape and future trajectory of military propulsion technologies, underlining their critical role in shaping modern warfare capabilities.

THE PROBLEMAIICS OF ENSURING THE RELIABILITY OF THE SIDE SURFACE OF THE PISTONS OF BOOSTED ICES

Prospective directions and trends in the development of special-purpose engines are analyzed. An increase in swept volume power density of engines leads to a critical raise in thermal and mechanical stress in the engine structural elements and to a corresponding reduction in its resource. Pistons are among the elements of boosted engines that are most prone to failure. Among the characteristic critical zones of the piston design, in which losses of parametric and physical reliability were observed, a separate critical zone on the loaded and unloaded side of the piston skirt near the piston pin bores is singled out. An analysis of publications was carried out and it was shown that the occurrence of the phenomenon of wear or seizures of the side surface of the piston skirt, which is observed for the boosted designs in the specified zone, is not explained exhaustively in the existing system of scientific views. Understanding the causes of the described phenomenon of loss of reliability is necessary for diagnosing and developing measures to prevent it at the design stage. The paper puts forward a hypothesis that explains the occurrence or non-occurrence of the loss of reliability in the process of deformation of the local zone of the side surface of the piston skirt during uneven expansion of the material in presence of creep and simultaneous stress relaxation with possible strengthening of the material by the property of creep limit. The possible cases of deformation of a certain local zone of the side surface of the piston in an elastic setting and in the presence of creep and stress relaxation processes are considered. It is shown that the process of creep deformation in the studied zone can end before the occurrence of reliability loss even for the materials that are unable to be strengthened by the property of creep limit or could be strengthened only insignificantly. The general ways of increasing the reliability of the side surface of the piston are outlined, related to ensuring the level of local stresses being below the creep limit, ensuring the completion of the creep process before the clearance reaches the critical values, as well as achieving strengthening of the material by the property of creep limit, for materials capable of it, before the occurrence of creep in operation.

A new accelerated thermal fatigue experiment method of pistons and its application

This study proposed a new test method to take the piston instead of the internal combustion engine as the experimental object and use electromagnetic induction heating and auxiliary cooling to simulate the actual operating conditions of the piston during engine start-stop, to achieve accurate control of the temperature of the heating and cooling cycles. The experimental process can be accelerated by worsening the service conditions. In order to prove the feasibility of this scheme, the temperature field distribution, fatigue life, and failure mode of the piston are compared and analyzed using finite element simulation, theoretical calculation, and surface topography observation. The results show that the error between the simulated temperature value of the key point of the piston and the experimental value of the actual operating condition is less than 5%, the position and value of the maximum temperature of the piston under the thermal fatigue test condition are consistent with the actual engine operating condition, the error between the fatigue life test results and the theoretical calculation results is less than 10%, and the location and cracking mode of the main crack is consistent with the actual working condition. It is proved that the test method is reasonable and feasible, which can provide an important guarantee for the fast and efficient design of high-performance pistons.

Failure analysis and pin hole profile optimization design of combined piston for marine diesel engine based on Kriging model and NSGA-Ⅱ algorithm

Amidst the drive for enhanced performance and reliability in marine diesel engines, anti-fatigue design has emerged as a pivotal factor in ensuring safe operation. To investigate the cracking of a steel-topped aluminum-skirted combined piston in a marine diesel engine, thorough analyses were conducted on mechanical properties, chemical composition, and microscopic morphology. Subsequently, a piston thermo-mechanical coupling (TMC) model was established to simulate stress distribution and fatigue strength. Findings revealed that loose defects in the material and deformation mismatch in the pin hole bearing TMC were the primary factors contributing to cracking. Based on this, a multi-objective optimization (MOO) design method for piston pin hole profiles was proposed. Optimal pin hole profile design parameters were determined using the Kriging surrogate model and the second generation non-dominated sorting genetic algorithm (NSGA-II), and the nonlinear relationship between the design variables and the response objectives was obtained. Post-optimization, stress in the piston cracking source region decreased by 40.6%, peak contact pressure and stress in the pin hole decreased by 59.2% and 49.1%, respectively. Furthermore, the minimum fatigue safety coefficient improved from 0.86 to 1.18.

Design and Analysis of Piston by using Ansys Workbench

Abstract: In this study, structural analysis is investigated on conventional piston made of cast iron. Secondly analysis are performed on piston made of aluminum, titanium alloy , structural steel and fiber glass. The material used for the design of piston should have light weight, low cost, structurally and thermally withstand at very high pressure and temperature condition that will occur in combustion process. In this project, It has been decide to study a particular piston design And its capability for maximum gas pressure. In this work, initial planning is to make piston model using solid modeling software CATIA V5. It has been decided to mesh the geometry analyze using ANSYS. For the analysis of piston input conditions and process of analysis, a lot of literature survey has been done. High combustion gas pressure will act as a mechanical loads and causes major stresses in the critical region of the piston. Detailed static structural analysis is carried out for various loading conditions like maximum gas pressure load.

A theoretical framework for the analysis of an opposed piston linear engine design

Traditional crank-based engines face limitations due to mechanical, thermal, and combustion inefficiencies. In contrast, the opposed piston design of a linear engine generator mitigates frictional losses by eliminating rotational motion and crankshaft linkages. Instead, electrical power is generated through the oscillation of a translator within a linear stator. However, the lack of geometric constraints in the free piston design leads to uncertainties regarding dead center positions, resulting in challenges such as misfire, stall, over-fueling, and rapid load changes.This study aims to fill this gap by reviewing existing modeling literature and advancing the fundamental understanding of opposed piston linear engines (OPLE) with springs through the development of an idealized, nondimensional model. A combination of analytical and numerical models was developed to better understand the behavior of the OPLE. The model introduces a streamlined symmetric analytical solution, succeeded by a broader general analytical resolution, with careful attention to the significant influence of thermodynamic effects at each phase, offering insights into the engine's dynamic performance. Limitations inherent to the analytical solutions are addressed by a numerical scheme utilizing the Runge-Kutta technique. This approach guarantees swift and dependable computational outcomes, which captures cyclic variation. The alternator model amalgamates both linear and sinusoidal work profiles, adjusting the magnetic work output in response to fluctuations in the compression ratio relative to the Top Dead Center (TDC) clearance distance. This adjustment dictates the generator load for each translator.The proposed model integrates the dynamics of a damped spring-mass system with thermodynamic expressions representing in-cylinder processes. Simplifications are made assuming perfect springs, ideal gases, instantaneous heat transfer, and an average friction force dependent on stroke length for work output. Selected cases are analyzed to elucidate the system's fundamental behavior, both within and outside the context of the Otto cycle, showcasing natural and forced stability over multiple operation cycles. Notably, enhancing the baseline cylinder pressure, or input heat relative to spring stiffness can elevate the work-to-heat ratio values. The attained work-to-heat ratio within compression ratio window of 16 is approximately 28 %. While this percentage may fluctuate in the context of general FPLE designs, the model developed for OPLE in this work plays a crucial role in maintaining the engine within this narrowly defined efficiency range, without compromising the potential performance demonstrated in this study. Differences in compression ratios provided intriguing insights into the dynamics of the translator and the in-cylinder thermodynamics of the interconnected system. Lower TDC clearance resulted in high translator displacement, velocity, and enhanced thermal efficiency.

Optimisation of design parameters for a novel two-piston ionic compressor applied in hydrogen storage

The ionic compressor is an advanced and prospective compression technology for hydrogen storage. However, a complex wave phenomenon was observed inside the compression chamber due to the fluid flow vortex. This complex gas-fluid interaction can be intervened by a new mechanical design of the motion piston. In this paper, the thermodynamic performance of a novel homocentric two-piston ionic compressor was carried out by mathematical modelling of one compression cycle. The optimisation of the design parameters of the compressor proposed was conducted by the Taguchi method. This study found that the piston diameter ratio was the dominating factor accounting for more than 80 % of the contribution to the mass delivered, power consumption and specific energy consumption. The optimal design parameters were obtained as 0.7 for the piston diameter ratio, 0.5 for the stroke diameter ratio of Piston A and 0.1 for the trajectory parameter. Under the optimal design parameters, the specific energy consumption was obtained as 1563.38 kJ/kg.

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

Structural and Thermal Analysis of Diesel Engine Piston by Changing the Number of Ribs and Materials

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. The power produced by the engine & its efficiency depends on piston. In this paper both Structural & Thermal Analysis is carried out on Diesel engine piston considering three materials such as Aluminum Alloy (Al6061) & Forged Steel also by varying number of ribs. For this Analysis, Modeling of a piston is done using Catia V5 Software & then it is imported into Ansys Workbench. Stress, Strain & Deformation Values are decreased with the increase of Ribs in the Piston Design. The amount of heat flux is more for a piston provided with six ribs. Considering both Structural & Thermal Analysis it is observed that Aluminum Alloy with EIGHT Ribs has shown good results

A numerical procedure to obtain ideal piston trajectories and key design parameters for a hydrogen-fuelled resonating free piston generator

A new numerical procedure is presented to enable a hydrogen-fuelled two-stroke resonating free-piston generator target ideal Otto cycles to provide tracking paths for feedback control to maximise efficiency. Piston trajectories and design parameters are obtained for specified power, compression-ratio, and air-fuel-ratio. These parameters include scavenge port locations, heat release position, equivalent bottom-dead-centre position, and an electrical machine constant which is generally power-switched to take two values within a cycle. The main objectives of the paper are to develop the numerical procedure, and to demonstrate its use in finding a generator with maximum efficiency, and a generator with a single electrical machine constant, avoiding in-cycle power switching. To develop the procedure, a multi-physics generator model provides kinematics to an energy equation, culminating in a novel two-stage procedure. Stage-1 involves iteration and minimisation; Stage-2 just involves minimisation. Testing by simulation involves a 14-kW generator case study with compression ratio of 9, lean air-fuel equivalence ratio of 0.4, plus friction and electrical machine losses. An overall maximum generator efficiency of 54.9% is obtained using the procedure, compared to 51.3% without power switching. Computationally, the two-stage procedure proves highly efficient, typically taking around 11 min in total to complete on a desktop computer. The novelty of the procedure is its ability to optimally design and operate a hydrogen-fuelled resonating free-piston generator to meet a target specification, thereby offering a potentially inexpensive way to decarbonize transport, particularly in heavy duty applications.

Suppression of spurious responses near anti-resonance of TC-SAW resonators by selective thinning of SiO2

This paper discusses the generation mechanism and suppression of spurious resonances near the anti-resonance in temperature compensated surface acoustic wave devices using the SiO2/128°YX-LiNbO3 structure. Detailed field analysis is performed for the spurious resonances, and the result indicates that the spurious modes are caused by excitation and/or scattering near the electrode finger edges, and can be suppressed well by thinning of the SiO2 layer selectively in the gap region. It is also shown that most of spurious responses can be suppressed for the piston design using the Cu dots with the SiO2 selective thinning. In contrast, this selective SiO2 thinning does not work well for the piston design using the Cu stripes.

SAW velocity reduction and spurious modes suppression on the layer structure

This paper discusses the use of the layered structure for the SAW velocity reduction. First, it is shown that the insertion of SiO2 is crucial between the piezoelectric layer and the base substrate to keep a large electromechanical coupling factor even when the SAW velocity is reduced. It is also shown that the use of a high-velocity substrate such as Si is also crucial for bringing spurious resonances much higher than the main resonance. The impact of Si orientation is also discussed. Next, suppression of transverse mode resonances and lateral leakage is studied. It is shown that the double busbar structure offers Q enhancement through good lateral energy confinement, and its combination with the piston design also gives good transverse mode suppression. Furthermore, discussions are extended to a strong spurious resonance that appears near the anti-resonance.

S0-like SAW mode resonator on LiNbO3/SiO2/SiC structure

Abstract This paper discusses the basic properties of a surface acoustic wave (SAW) mode like the zeroth-order symmetric (S0) Lamb mode in the LiNbO3/SiO2/SiC configuration in detail. At first, the influence of the SiO2 insertion is discussed, and it is shown that SiO2 insertion offers significant enhancement of the electromechanical coupling coefficient K 2 for the S0-like SAW mode without significant reduction of the phase velocity. Then, the discussion is extended to spurious resonance characteristics. It is shown that the dummy electrodes are not necessary in this case. Then, two kinds of piston design are applied for the transverse suppression, and their effectiveness is discussed.

Ultra-wideband longitudinally coupled-resonator filters on lithium niobate using periodically slotted SiO2 as an acoustic coupler

This paper discusses the applicability of periodically slotted SiO2 as a coupler for ultra-wideband longitudinally coupled-resonator filters. It is shown that a −3 dB fractional bandwidth of more than 31% can be achieved by using lower-order three resonance modes. It is also shown that a periodically slotted SiO2 structure can also control the frequency dispersion of wave propagation along the surface, and transverse modes are suppressed well for one particular mode under a proper setting. Then the piston design is applied for the remaining two modes, and the spurious-free and flat-passband triple-mode filter is synthesized.

Computational fluid dynamics and Machine learning-based Piston-Bowl optimization for Energy-Assisted compression ignition of low cetane number sustainable aviation fuel blends

Hybrid-electric powertrains have been gaining tremendous interest to propel unmanned aerial vehicles (UAVs) for Advanced Air Mobility. Present UAV powertrains are designed with internal combustion engines capable of combusting single fuel types, which have significant restrictions on fuel ignition quality. However, sustainable aviation fuels (SAFs) can exhibit wide variance in ignitability with cetane numbers (CNs) ranging from 15 to greater than 50. Coupled with high-speed and high-altitude engine operating conditions, low CN jet fuels can pose a serious challenge to achieving reliable, clean, and fuel-flexible ignition. Energy-Assisted Compression Ignition (EACI) has demonstrated superior ignition-controlling capability with jet fuels due to the precise thermal energy deposition achieved from the continuously operating high-temperature Ignition-Assistant (IA). However, the current literature highlights enhancement needs in the operational capabilities of EACI strategy with low CN jet fuels. Therefore, this paper aims to demonstrate improved EACI characteristics of low and varying ignition-quality SAF blends used in high-altitude aerial conditions through a combined computational fluid dynamic (CFD) and machine learning (ML)-based piston-bowl optimization methodology. In this work, a CFD-enabled Design-of-experiments approach, covering nine piston-bowl and three operational parameters, is used to develop a Gaussian Process Regression (GPR)-based ML modeling routine. Further, a merit-function-driven piston-bowl optimization is performed using the GPR model for improved EACI operations with CN 30 SAF blend. The combined CFD and GPR methodology helped screen more than 20 million piston designs to find the optimum. The study found that the piston optimization allowed consistent improvements in EACI operability for CN 30 to CN 48 jet fuels with maximum reductions in ignition delays of 17% and CA50 (50% mass-burn fraction crank angle) of 22% for CN 30 SAF blend compared to the stock piston. The optimized piston-bowl also helped reduce IA input power requirements by 20–28%, thus improving the reliability and capabilities of EACI to achieve multi-jet fuel operation.

Study on the Physical Characteristics of Plasma and Its Relationship with Pore Formation during Laser-Metal Active Gas Arc Hybrid Welding of 42CrMo Steel

The automobile industry puts forward higher requirements for the design and manufacture of steel pistons. However, the welding of 42CrMo steel pistons still has unsolved technical problems, especially welding defects that cannot be directly detected, such as pores, which are easily generated inside the weld. A plasma experiment of laser-metal active gas arc (MAG) hybrid welding 42CrMo steel was conducted in this paper, and plasma signals inside and outside the keyhole were detected during the laser welding, leading laser laser-MAG hybrid welding, and leading arc laser-MAG hybrid welding of 42CrMo steel. The characteristic parameters such as electron temperature and electron density were calculated and analyzed to investigate the relationship between plasma behavior and the formation of weld porosity in the welding process of 42CrMo steel. Based on the fluctuations in plasma electron temperature and electron density, the prediction of pore formation in the weld of 42CrMo steel was made, aiming to provide guidance for achieving a stable and reliable laser-MAG hybrid welding process for 42CrMo steel.

ESTIMATION OF THE THERMALLY STRESSED STATE OF INTERNAL COMBUSTION ENGINE PISTONS, TAKING INTO ACCOUNT THE CREEP THRESHOLD OF THEIR SIDE SURFACE

When creating new engine designs, they are subject to ever more stringent requirements for specific power and reliability indicators while ensuring a combination of other performance indicators. The use of new design solutions or the transition to a different piston material can significantly increase the possible level of engine power. This requires a mandatory analysis of the thermal stress state of the structure. It is this analysis that can show whether one or another competing solution will be effective. This study shows the possible effectiveness of certain constructive measures. The diesel piston 4ChN12/14 was taken as the object of the research. Power levels corresponded to 20-30 kW/l. The analysis of the temperature and heat-stress states of the piston in two designs and for two materials - AL25 and AK4 alloys was carried out. The level of thermal stresses of the structure is set in an elastic setting. The obtained data allow to analyze the condition of the pistons and draw conclusions based on the concept of guaranteed reliability. In the analysis, we used the creep limits of materials that we previously determined. The analysis of the temperature state in the zone of the edge of the combustion chamber of the piston and in the zone of the groove for the first piston ring, where the reliability falling of the piston design is possible, has been analyzed. The creep threshold of materials by the side surface of the piston is estimated. The facts of the appearance of rubbing on pistons in the initial period of their loads are explained on the basis of exceeding the creep threshold of an unhardened material. It is shown that the creep threshold of the non-hardened piston material can be exceeded when, according to the criteria of the temperature state of the combustion chamber edge and the zone of the first compression ring, the design is operable. Based on the results of the analysis, conclusions were drawn about the performance of piston structures during power increasing using two options for oil cooling of the piston and during the transition from aluminum alloy AL25 to alloy AK4.