Ring Pack Research Articles

Theoretical analysis of the piston ring-pack for predicting friction and power loss in an internal combustion engine

The piston ring is considered an essential element in the operation of the internal combustion engine to improve its efficiency and reduce its emissions. It is resistant to high temperature and high-pressure gases in the combustion chamber. A one-dimensional analysis method of lubrication between piston rings and cylinder liner in mixed lubrication conditions is developed in this article by using the GT-Suite simulation software. We applied the finite difference numerical method to solve the Reynolds equation to obtain the variation during an engine cycle of the following parameters; film thickness, frictional force, and power loss. The solution results presented can be used to improve the design of the piston ring pack in internal combustion engines and is available for industry usage.

Examining a New Laboratory Method for Packing Soilless Substrate to Ensure Consistent, Appropriate Bulk Density When Measuring Static Physical Properties

Bulk density (Db) and subsequent physical properties are determined by the substrate and packing method. Packing method is the way one fills and compresses a substrate within a given volume. Bulk density produced in the laboratory may not align with “expected” published ranges due to variations in packing. Additionally, it is unknown if ranges identified as “typical” using a small volume sample ring reflect Db occurring in larger production size containers packed using commercial potting practices. Therefore, our objectives were to 1) emulate nursery practices and document the Db associated with a potted 2.8-L (#1) container, 2) develop and test the new “shim and compression” method to determine if it consistently packs sample rings to a Db commensurate with that of a 2.8-L nursery container, and 3) demonstrate how static physical properties are affected by the new “shim and compression” sample ring packing method compared with the traditional bench top tap method. When emulating nursery potting practices with 100% pine bark, coir, and peat, and blends of each, Db ranged from 0.08 g⋅cm−3 (coconut coir) to 0.17 g⋅cm−3 (pine bark). We used an espresso tamp and shims to pack the aforementioned substrates in sample rings. The Db achieved using a range in number of presses and discs was largely dependent on the substrate, but the desired Db was consistently achieved for each substrate. There was no effect of disc number on Db (P = 1.000) for any substrate. There was no effect of tamp number (P ≥ 0.0602) for all substrates except peat-amended, for which five tamps yielded a greater Db than one tamp (P = 0.0324). In an experiment in which a different technician who was accustomed to the conventional benchtop tap packing method performed both methods, method influenced Db (P < 0.0001), and the conventional method more closely attained the target Db. To our knowledge, this is the only report of Db observed in commercial container production facilities (i.e., “native”).

Simplified Wear Model for Power Cylinder under Engine Operating Conditions

A simple numerical approach is developed to predict the wear and friction of piston ring pack and cylinder liner during the break-in period and under transient speed conditions. In the model, a solution of mixed lubrications using the load-shearing concept is presented based on the selected elastic-plastic equations of asperity contacts in conjunction with well-established elastohydrodynamic equations. The model takes shear-thinning, thermal effects in elastohydrodynamic lubrication (EHL) and lubricant starvation effects into account. Modified Archard’s wear coefficient to describe the piston ring against cylinder liner wear is introduced. The approach is valid for the calculations of the asperity pressure at low values of the ratio of oil film thickness to combined roughness of the interacting surfaces, that is, less than 0.5. Applications are discussed, including association of piston side thrust force on wear and friction characteristics of piston ring/cylinder bore, gas blowby through the ring pack on the cylinder liner wear, a strong coating dependence for the piston ring wear, and wear distribution across the stroke under engine operating conditions. A good agreement between the experimental and analytical data indicates that the proposed model can be used to predict the wear and friction of the piston ring pack sliding against cylinder liner.

Tribo-dynamic modeling method and application to three-dimensional flexible PRL system

Research on the tribo-dynamics of the piston-cylinder liner (PCL) and piston ring-cylinder liner (PRCL) is vital due to their role in generating over 50 % of total engine friction loss and the impact on carbon emissions. Traditional studies, hindered by the structural and functional differences between pistons and rings, required separate simulation models, often overlooking crucial coupling characteristics. A unified tribo-dynamics modeling method for the piston-ring-liner (PRL) system is proposed in this paper, integrating the ring pack and piston into one multi-body system. This article models with global coordinates, unifying the form of governing, film thickness, and load equations of discontinuous lubrication domains for more efficient dynamics-lubrication coupling. The described method is applied to a marine engine, and the new tribology characteristics discovered after calculations are exhibited. It shows how piston deformation impacts ring tribology, indicating that increased profile height reduces the squeezing effect by allowing more ring movement. Additionally, ring assembly position significantly affects tribology parameters' circumferential distribution. Installing the ring with the end gap facing the piston pin side should be avoided, as it maximizes the negative impact of elastic force and secondary motion, deteriorating lubrication.

Chiral-structured heterointerfaces enable durable perovskite solar cells.

Mechanical failure and chemical degradation of device heterointerfaces can strongly influence the long-term stability of perovskite solar cells (PSCs) under thermal cycling and damp heat conditions. We report chirality-mediated interfaces based on R-/S-methylbenzyl-ammonium between the perovskite absorber and electron-transport layer to create an elastic yet strong heterointerface with increased mechanical reliability. This interface harnesses enantiomer-controlled entropy to enhance tolerance to thermal cycling-induced fatigue and material degradation, and a heterochiral arrangement of organic cations leads to closer packing of benzene rings, which enhances chemical stability and charge transfer. The encapsulated PSCs showed retentions of 92% of power-conversion efficiency under a thermal cycling test (-40°C to 85°C; 200 cycles over 1200 hours) and 92% under a damp heat test (85% relative humidity; 85°C; 600 hours).

Study of Hydrodynamics and Residence Time Distribution in a Trickle Bed Reactor

This study focuses on investigating the hydrodynamics using computational fluid dynamics (CFD) simulation and residence time distribution (RTD) within a trickle bed reactor (TBR). CFD simulation was performed on a packed column filled with structured packing of glass beads, while the experiments for RTD studies were conducted in a TBR filled with random packing of Raschig rings. The geometry of TBR and size of packing during CFD simulation was kept close to that of the experimental setup. CFD simulation results were obtained which predicted the flow of fluid through the TBR at different vertical planes along the column. The fluctuations of liquid velocity at various positions inside the reactor were predicted by the CFD model. RTD studies were performed for both pulse input and step input using a non-reactive tracer such as sodium hydroxide. The flowrate of water was varied from 0.6 LPH to 6 LPH for pulse input, while for step input the ratio of water to tracer flowrates was kept at 1:1, 1:2 and 2:1. This study allows us to understand how hydrodynamics and residence time distribution may have an effect on the performance of TBR.

Insights into reaction–diffusion behaviors of acetylene selective hydrogenation on pellet catalysts

AbstractIn this work, a particle‐resolved computational fluid dynamics model of the acetylene hydrogenation process is developed to investigate the effects of catalyst particle structures on the reaction–diffusion behaviors aiming to improve selectivity toward target ethylene. The effects of packing structures on mass and heat transfer are explored by employing particles with varying shapes, wall thicknesses, and external diameters. The simulation results reveal that decreasing diffusion paths and elevating reactor bed temperature will enhance ethylene selectivity, and cylinder and Raschig ring packing structures exhibit the lowest and highest ethylene selectivity of 35.6% and 48.9% at 70% of acetylene conversion, respectively. Reducing wall thicknesses of Raschig ring particles facilitates the diffusion of generated ethylene from the interior zone of catalysts but concurrently inhibits the conversion of acetylene to ethylene. The Raschig ring catalyst particle with 1.9 mm of wall thickness and 3.5 mm of external diameter is finally revealed to exhibit the highest ethylene selectivity.

Proline-Tyrosine Ring Interactions in Black Widow Dragline Silk Revealed by Solid-State Nuclear Magnetic Resonance and Molecular Dynamics Simulations.

Selective one-dimensional 13C-13C spin-diffusion solid-state nuclear magnetic resonance (SSNMR) provides evidence for CH/π ring packing interactions between Pro and Tyr residues in 13C-enriched Latrodectus hesperus dragline silk. The secondary structure of Pro-containing motifs in dragline spider silks consistently points to an elastin-like type II β-turn conformation based on 13C chemical shift analysis. 13C-13C spin diffusion measurements as a function of mixing times allow for the measurement of spatial proximity between the Pro and Tyr rings to be ∼0.5-1 nm, supporting strong Pro-Tyr ring interactions that likely occur through a CH/π mechanism. These results are supported by molecular dynamics (MD) simulations and analysis and reveals new insights into the secondary structure and Pro-Tyr ring stacking interactions for one of nature's toughest biomaterials.

Characterization of PPS Piston and Packing Ring Materials for High-Pressure Hydrogen Applications.

The widespread adoption of renewable energy hinges on the efficient transportation of hydrogen. Reciprocating piston compressor technology in non-lubricated operation will play a key role, ensuring high flow rates and compression ratios. These systems rely on advanced high-strength sealing solutions for piston and rod packing rings utilizing advanced fiber-reinforced polymers. Polyphenylene sulfide (PPS) polymer matrix composites have seen use in tribological applications and promise high mechanical strength and wear resistance. The presented work describes carbon and glass fiber-reinforced PPS matrix polymers in comparison, which are characterized by complementary methods to investigate their properties and potential for application in reciprocating compressor under non-lubricated operation. Thermo-mechanical and tribological testing was supported by microstructure analysis utilizing advanced X-ray and electron imaging techniques. New insights in micromechanical deformation behavior in regard to fiber materials, interface strength and orientation in fiber-reinforced polymers are given. Conclusions on the suitability of different PPS matrix composites for high-pressure hydrogen compression applications were obtained.

Frictional Losses of Ring Pack in SI and HCCI Engine

The vast majority of research dedicated to enhancing the homogenous charge compression ignition (HCCI) low-temperature combustion system is focused on improving controllability, efficiency and emissions. This article aims to assess the impact of HCCI combustion on the operation of the piston ring system. Utilizing the measured pressures in the combustion chamber of a single-cylinder research engine operating in spark ignition (SI) and HCCI modes at various loads, simulations were carried out using an advanced ring pack model. This model integrates the gas flow, ring dynamics and ring mixed lubrication models. Simulations revealed that differences in the pressure above the piston between the HCCI and SI combustion significantly influence ring pack performance. The predicted energy losses due to the friction of piston rings against the cylinder liner are up to 5% higher in the HCCI engine than in the SI engine. This identified drawback diminishes the advantages of the HCCI engine resulting from higher thermal efficiency, and efforts should be made to minimize this negative impact.

Development, verification and experimental validation of a 3D numerical model for tubular solar receivers equipped with Raschig Ring porous inserts

This study presents a numerical investigation of gaseous tubular absorbers used in a solar furnace and introduces a 3D model to simulate porous inserts with random packing of metallic Raschig Rings (RR) at pore-scale. A comprehensive verification and validation process was conducted based on the experimental data obtained at Plataforma Solar de Almeria (SF60). The evaluations were carried out on three samples, including a smooth pipe (SP) and two enhanced pipes (20RR and 40RR) with 20 mm and 40 mm RR inserts. The effects of several influential parameters, such as the fluid turbulence model, the effective thermal conductivity of the porous material, and the randomness of the RR in the porous structure, were studied to assess the accuracy and repeatability of the model in predicting thermal and fluidic characteristics of air inside the absorber pipes under different working conditions. A detailed thermo-hydraulic analysis revealed an irregular flow pattern inside the porous zone, while the air recirculation at the porous entrance and exit provides an uneven pressure drop distribution in the azimuthal direction. Moreover, fluid turbulence is enhanced downstream of the porous insert thanks to several stream jets formed by uneven flow discharge at the insert outlet face, which improves heat transfer in that area. The analyses demonstrated a significant improvement in heat transfer, with a maximum enhancement factor of 10–15 than the smooth tube. Additionally, in the evaluation of thermo-hydraulic performance, the enhanced absorbers exhibit Performance Evaluation Criteria up to 2, compared to the tube without RR inserts.

High-Strength PPS-Polymer Composites for Hydrogen High-Pressure Applications

Hydrogen technology can be one key for a transition to sustainable energy necessary to achieve climate targets and limit global warming to 1.5 °C since the beginning of the industrial revolution. Hydrogen as a CO2 neutral energy carrier must replace fossil fuels from the existing natural gas grid and infrastructure to enable an environmentally friendly and circular economy in future societies. Batteries and e-fuels are practicable technologies for short term and quantitatively limited energy provision, with disadvantages including raw material demands and technologically complex transformation cycles. Utilizing advanced power-to-gas concepts, hydrogen will not only be most efficient technology in energy storage, but also allows adaption and reuse of existing energy transportation infrastructure.To provide volatile hydrogen gas in the required flow and energy densities, advanced compression technology needs to be developed inspired by conventional gas compression systems. Reciprocating piston compressors are developed for high-pressure hydrogen applications, providing high pressure levels and flow rates. Compression equipment must be designed for non-lubricated dry-running conditions, as high gas purity standards of hydrogen do not allow for oil-based lubricants to be introduced into the process gas. High-strength carbon fiber reinforced composites are developed as piston and packing ring materials to withstand extreme pressure differences under harsh thermo-mechanically loaded operation conditions.Promising candidates with high strength and wear resistance in the form of PPS-polymers, are developed with PTFE solid lubricants and different carbon fiber fractions to combine high strength, with low friction and wear, improve pressure operation range, and limit down times of hydrogen piston compressors. The current work describes tribological testing of advanced PPS-polymers with 10 to 30 wt.% carbon fibers in a high-velocity tribometer under hydrogen gas atmosphere. Supporting thermo-mechanical tests give new insights in deformation mechanisms of fiber reinforced polymer composites and allow conclusions on their applicability for hydrogen compression.

High-Yield Synthesis of Colloidal Carbon Rings and Their Applications in Self-Standing Electrodes of Li-O2 Batteries.

The use of carbon materials in porous electrodes has impressive advantages. However, precisely tailoring the multilevel pore structure of carbon electrodes remains an unsolved challenge. Here, we report a highly efficient site-selective growth strategy to synthesize colloidal carbon rings by templating patchy droplets. Carbon rings are used for the direct fabrication of self-standing porous electrodes with hierarchical pores for lithium-oxygen batteries (LOBs). In situ atomic force microscopy reveals that during discharge the discharge products densely nucleate and grow on carbon rings, demonstrating that such rings are a very potential electrode material in LOBs. The hollow carbon ring electrode (HCRE) possesses micrometer-scale channels formed by random packing of rings and nanochannels consisting of ring-shaped hollow cavities connected by nanosized pores in the wall. Both channels contribute to ion transportation and gas diffusion, but the storage of the discharge products mainly lies in micrometer-scale channels, leading to a high discharge capacity of LOBs (20 658 mAh/g). Our work paves a new way to construct hierarchically porous electrodes for application in electrocatalysis and electrochemical energy storage.

Investigations on a solar humidification dehumidification desalination system equipped with various packing materials and multi-stage bubble column dehumidifier.

This work presents the theoretical and experimental investigation of a solar-powered humidification dehumidification desalination (HDD) system with different humidifier packing materials and a two-stage bubble column dehumidifier (BCD). Naturally available coconut shells (CS) and coconut shells with drilled holes (CSH) on the surface to improve water permeability were used as packing materials in the humidifier, and their performance was compared with that of commercial-type pall ring (PR) and raschig ring (RR) packings. An in-house developed numerical model of the HDD system in conjunction with a flat plate solar water collector was used in this study. Steady-state experimental results showed that CSH packing exhibited the highest volumetric mass transfer coefficient (0.00852kg/s), resulting in maximum humidifier efficiency (96%) and freshwater yield (2.16kg/hr), followed by PR (0.00841kg/s, 94%, and 2.137kg/hr), CS (0.00831kg/s, 90%, and 2.127kg/hr), and RR (0.0081kg/s, 81%, and 2.087kg/hr) at feedwater mass flow rate of 1.5kg/min and humidifier inlet temperature of 75 [Formula: see text]. Furthermore, transient outdoor test results showed that using a two-stage configuration in a BCD increased the daily average effectiveness to 0.93, as against 0.79 for a single-stage BCD. Employing CSH instead of PR and RR packings in the humidifier reduced freshwater costs by 6.2% and 7.6%, respectively.

Evaluating CO2 desorption performance of MEA solution with MnOx/HZ catalytic packings by visualization method

The high energy consumption in the CO2 desorption process is one of the main issues of the chemical absorption method. To address this issue, a MnOx modified HZSM-5 catalyst (MnOx/HZ) was prepared by impregnation method and used as catalytic packing to improve the CO2 desorption rate in the monoethanolamine (MEA) solution. Since the catalytic effects mainly work around the catalytic packing, a visualization method, which can measure the CO2 desorption rate per unit surface area (vCO2/area) of a single packing, is proposed to avoid some uncertain effects occurring as the conventional bubbling method is used. The results showed that the vCO2/area of the MnOx/HZ catalytic packing is 10.06 μmol·cm−2·s−1 at 80 °C, which is 1.78 times of that of HZSM-5 and 15 to 60 times of that of commercial packings. Actually, the MnOx/HZ has more Brønsted and Lewis acid sites than HZSM-5 according to the pyridine adsorption infrared spectroscopy (Py-IR) characterization. As a result, the apparent activation energy (Ea) of the CO2 desorption reaction with the addition of MnOx/HZ can be reduced by 58.6% and 18% compared with the addition of ceramic saddle ring packing and HZSM-5, respectively. However, the catalytic performance of MnOx/HZ packings degrades gradually due to the blockage of micropores by the reaction product, that needs to be settled in the future.

Thermo-mechanical properties and internal architecture of PI composites for high-pressure hydrogen applications

The efficient transport of Hydrogen is pivotal to the wide scale adaption of energy produced from renewable sources. Reciprocating piston compressors with high strength non-lubricated sealing solutions for piston and rod packing rings will be a key technology to fulfill gas purity and high-pressure gradients demands set by hydrogen applications. Polyimide polymer matrix composites have seen use in tribological applications and promise high mechanical strength and temperature resistance. The presented work describes carbon fiber reinforced Polyimide blends in comparison, characterized by complementary advanced methods to investigate their properties and potential for reciprocating compressor applications. Thermo-mechanical and tribological testing was supported by microstructure analysis utilizing synchrotron tomography and electron microscopy, pinpointing the necessity of dry lubricating additives such as PTFE. New insights in micromechanical deformation behavior of fiber reinforced polymers are given and promising fiber-reinforced polyimide compositions suitable for high-pressure hydrogen compression applications were identified.

Is monolithic configuration superior to random packing in a fixed bed reactor for CLC like processes?

In light of the geometric deficiencies and diffusion constraints of conventional packed-bed reactors, the potential application of monolithic configurations in fixed-bed reactors was explored using the structure-resolved CFD approach. This work delves into how geometric features of fixed beds influence flow patterns and related transport phenomena. To assess the performance of mass transfer and heterogeneous reactions in different configurations, we conducted simulations of fixed-bed chemical looping combustion (CLC) processes, in which a simplified model of non-catalytic gas-solid reactions is implemented to reduce the computational costs. Our findings highlight the importance of face contact between reaction tube and the monolithic structure, which effectively eliminates the inherent wall effects of random packing and enhances the radial heat conduction. More uniform geometry in the monolithic configuration naturally suppresses violent interstitial channeling flow in the random packing. Notably, the honeycomb configuration demonstrates an exceptionally low pressure drop, about two orders of magnitude smaller than that of the Raschig ring packing, and the designable monolithic configurations offers the potential to further reduce the pressure drop with enlarged voidage. Open-cell foams exhibit excellent convective and radial heat transport properties, promote homogeneous flow fields, and demonstrate superior performance in conjugate transport and heterogeneous reactions.

A Comparison of Hydrogen and Gasoline Piston Ring Simulations

This paper presents a transient mixed-lubrication hydrodynamic and gas flow simulation model for a piston ring pack for a four-stroke internal combustion engine. The analyses carried out compare two fuel types, hydrogen and gasoline, at a 2000 rpm low engine load (20%), as well as 3000 rpm low (20%) and high (100%) engine loads, to investigate the effects of the different fuels and loading conditions on the ring pack. In particular, the minimum oil film thickness at the top compression ring, the total ring friction of the ring pack, the friction power loss and the blow-by are studied. The simulation shows that, under the high load conditions at 3000 rpm, the hydrogen variant exhibits larger friction power losses, around a 200 W peak difference and larger blow-by throughout the expansion stroke of the engine cycle. A similar trend can be observed for the low loads, where larger friction power losses with peak differences of 30 W and 40 W for 2000 rpm and 3000 rpm, respectively, are observed. The blow-by results for the low load at 2000 rpm show a slight increase of approximately 22% more gas flow into the crankcase, while the 3000 rpm simulation shows a 50% increase in blow-by for the hydrogen variant at low load and a 40% increase at high load. The findings that are presented indicate that, although alternative fuel sources such as hydrogen are very attractive alternatives to fossil fuels such as gasoline, there can be unwanted side effects that could lead to the permanent damage of components through quicker wear or hydrogen embrittlement from the blow-by gas.

Tensile Characteristics of Rubber Material of Firefighting Supplies According to Test Piece Shape

Currently, rubber materials are widely utilized in firefighting supplies. They are utilized as rubber packing, such as air respirators, rubber bands, such as pipe windows, and rubber packing, such as fire extinguishers. EPDM initially utilized the rubber packing material, but because of aging and curing, it is difficult to maintain air tightness in the cracked gap; therefore, it has been replaced with NBR and utilized until now. In addition, among the material's physical properties, tensile properties are required, and the form usually adopted as a tensile test specimen is generally an aging form. However, rubber utilized in firefighting supplies employs rubber packing or rubber ring products. Currently, tensile tests are conducted by manufacturing a sample as a dumbbell from a separately manufactured sample without conducting a tensile test with a rubber ring-type specimen. Furthermore, questions often arise about the tensile properties of rubber rings. Therefore, this study tested the tensile properties with a ring-shaped specimen. In KS M ISO 37, it is generally known that an annular-type test piece is desirable for tensile strength measurement. An annular-type test piece has a lower value than an annular-type test piece, and an annular test piece with an elongation rate is almost the same value as an annular-type test piece. Therefore, the test was conducted to find the difference between the test piece as a dumbbell and the actual ring-shaped specimen. As a result of the tensile test, the tensile strength was found to be lower in the range of 11.8-15.5% in the ring-shaped test piece than in the age-shaped test piece, and the elongation rate was lower in the range of 4.1-40.1% than in the age-shaped test piece. This is thought to be because the stress of the stretched high-ring-shaped specimen is not equal to the cross-sectional area of the specimen. However, the tensile property value of the rubber material was satisfied with both types of test pieces with the reference value required for approval.

Optimization Study of CO2 Gas Absorption with NaOH Absorbent Continuous System in Raschig Ring Packing Column Using Box–Behnken Design

Increasing CO2 gas emissions results in climate change by increasing air temperature and worsening environmental problems. It is necessary to control CO2 gas in the air to overcome this. This research aims to optimize the absorption of CO2 gas in the air with 0.1 M NaOH absorbent in the column of the Raschig ring stuffing material using the response surface methodology (RSM). This research was conducted using a continuous system of three independent variables by varying the contact time (10–80 min), the flow rate of NaOH absorbent (2–5 L/min), and the flow rate of CO2 gas (1–5 L/min). The response variables in this study were the absorption rate (L/min) and mass transfer coefficient, while the air flow rate was constant at 20 L/min. Air and CO2 gas mix before absorption occurs and flow into the Raschig ring packing column so that contact occurs with the NaOH absorbent. Mass transfer of CO2 gas occurs into the NaOH absorbent, resulting in absorption. The results showed that the effect of contact time (min), the flow rate of NaOH absorbent (L/min), and CO2 gas flow rate individually and the interaction on CO2 absorption rate and mass transfer coefficient were very significant at a p-value of 0.05. Chemical absorption of CO2 also occurred due to the reaction between CO2 and OH- to form CO32− and HCO3−, so the pH decreased, and the reaction was a function of pH. Optimization using Design Expert 13 RSM Box–Behnken Design (BBD) yielded optimal conditions at an absorption time of 80 min, NaOH absorbent flow rate of 5 L/min, CO2 gas flow rate of 5 L/min, absorption rate of CO2 gas of 3.97 L/min, and CO2 gas mass transfer coefficient of 1.443 mol/min m2 atm, with the desirability of 0.999 (≈100%).