Reduce Friction Losses Research Articles

Numerical investigation of the performance and flow field of an annular jet pump with throat aeration

The method of throat aeration was used to improve the performance of the annular jet pump (AJP). In order to study the influence of throat aeration on the performance and flow field of the AJP, the CFD method was used. The results show that at a low flow rate ratio ( q) the appropriate aeration rate can narrow or even eliminate the recirculation region. Meanwhile, the efficiency of AJP is improved at a medium-to-high q. Notably, the maximum increase in efficiency is 7.32% at q = 0.7 and the optimal aeration rate should be between 1% and 2%. Since the dynamic viscosity of air is much lower than water, a small amount of air attached to the wall can reduce friction loss. The air flows along the wall after the air aerated into the throat, reducing the shear stress between the high-speed jet and the wall. At a low q, most of the area in the throat is the high efficiency drag reduction region which the drag reduction rate exceeds 80%. Moreover, the high efficiency drag reduction region extends toward the diffuser when the q is high. In addition, throat aeration can optimize the pressure distribution near the wall and axis.

Synergistic Effects of Surface Texture and Cryogenic Treatment on the Tribological Performance of Aluminum Alloy Surfaces

In order to improve the tribological properties of the 7075-T6 aluminum alloy used on the rotor surface, a combined method of cryogenic treatment and laser surface texture treatment was applied. Various tests, including metallographic microscopy, scanning electron microscopy, elemental analysis, microhardness measurements, were conducted to examine the wear morphology and modification mechanism of the treated 7075-T6 aluminum alloy surface. A numerical simulation model of surface texture was established using computational fluid dynamics to analyze the lubrication characteristics of V-shaped texture. The research finding that the 7075-T6 aluminum alloy experienced grain refinement during the cryogenic treatment process, enhancing the wear resistance of the V-shaped textures. This improvement delayed the progression of fatigue wear, abrasive wear, and oxidative wear, thereby reducing friction losses. The designed V-shaped texture contributes to reducing contact area, facilitating the capture and retention of abrasives, and enhancing oil film load-bearing capacity, thereby improving tribological performance. The synergistic effect of cryogenic treatment reduced the friction coefficient by 24.8% and the wear loss by 66.4%. Thus, the combination of surface texture and cryogenic treatment significantly improved the tribological properties of the 7075-T6 aluminum alloy.

Analysis of the Newest Design of Axial Piston Hydraulic Machines with Reduced Friction Losses and Leaks

Problem. Analysis of modern achievements in the field of volumetric hydraulic drives to improve the technical level of construction and road machines. Goal. Study of the design of the latest foreign development related to the improvement of the technical level of axial-piston volumetric hydraulic machines, in particular pumps and hydraulic motors according to the scheme of Innas floating cylinders. This design, according to the proposal of its inventors, is intended to work as pumps with a flow of up to 7400 l/min or hydraulic motors with a working volume of up to 5000 cm3 at a pressure of up to 50 MPa. Methodology. Analysis of the results of comparative bench tests of the Innas axial piston pump of the latest development and volumetric hydraulic machines of various designs, in particular axial and radial piston, as well as gear ones. Results. According to the results of comparative tests, the new design of the Innas axial-piston pump is significantly ahead of other serial hydraulic machines in terms of efficiency. The total efficiency value of 96 % achieved in the Innas pump shows the promise of such hydraulic machines. Originality. Analysis of the results of experimental studies with the determination of the features of the structures of hydraulic machines in terms of volumetric and hydromechanical power losses. It is concluded that Innas hydraulic motors can be used in trailing volumetric hydraulic drives with hydraulic power amplifiers, for which the characteristic of friction in the displacement mode is the main one from the point of view of the accuracy of the execution of the specified control signals. Practical value. The given materials are useful for specialists in the field of mechanical engineering, in particular, the design of volumetric hydraulic drives for construction and road machines

A research-inducing environment to technology using friction modifier for motor gasoline fuel

The share of gasoline with improved properties reaches up to 30 % of the total production of gasoline in the world. The main component of the additive packages for these fuels is a detergent additive. However, to ensure significant environmental, economic and power effects, additional substances that modify the surface of fuel system elements and reduce friction losses are required. These substances are known as friction modifiers. In recent years, there has been a notable increase in their importance due to the tightening requirements for the efficiency of internal combustion engines (ICEs) and the increased share of gasoline engines with direct fuel injection. The current research presents the results of a systematic analysis of existing materials in the field of development and functional properties of friction modifiers. The objective is to determine the magnitude of their real impact on fuel performance. This includes the ability to increase the efficiency of ICE and reduce its fuel consumption, thereby reducing the carbon footprint. Furthermore, the most common types of friction modifiers in commercial additives from various manufacturers are presented, and existing approaches to the mechanism of action of these components are studied in order to identify the most effective additive structure.

Reduction of Friction Loss by Arrangement of the Segment of the Polyimide Arms & Guides for Timing Chains in Automobile Engines

Reduction of Friction Loss by Arrangement of the Segment of the Polyimide Arms & Guides for Timing Chains in Automobile Engines

Does Engine Oil Type Affect Fuel Consumption in Passenger Vehicles? A Two-Year Investigation

Reducing fuel consumption to decrease CO2 emissions has become a key development factor in the automotive industry. An effective way to decrease fuel consumption is to reduce the influence of various sources of energy loss. One way to increase engine efficiency is to use low-viscosity engine oils to reduce friction losses in the engine’s tribological systems. The aim of the article was to analyze the relationship between the type of engine oil and fuel consumption in a group of 12 passenger cars. This was a homogenous group of identical cars, equipped with the same engine, operated under very similar conditions. Three groups of engine oils (Revline, Total, Orlen) were tested in vehicles and stressed with comparable workloads. The experiment was conducted over two years (two stages of research). The collected results were presented using graphs and compared using statistical tests, split into two stages of research, with four seasonal temperature groups. The study provides a detailed description of fuel consumption differences taking into account variations in ambient temperature. The analyses were focused on finding answers to two research questions: does the type of engine oil affect the variation in combustion levels, and what is the variability of fuel consumption in different seasons due to the ambient temperature variability? Briefly, in both stages of the study, vehicles using Revline oil attained the highest average fuel consumption throughout the study period. Vehicles using Total oil showed similar results to those using Revline oil, with the difference in fuel consumption not as noticeable during warmer months. Conversely, vehicles using Orlen oil demonstrated the lowest fuel consumption values during colder months, but higher levels during warmer months.

Analysis of exergy and heat transfer in a tube fitted with flapped V-baffles

Vortex generator is a device that shows promise in generating streamwise vortices that can be utilized for boosting the rate of heat transmission inside a cooling/heating system with a relatively smaller penalty in terms of friction loss. The primary goal of the current research is to maximize the comparative Nusselt number ratio (Nu/Nu0) to be as large as possible to lower the size of the system while keeping thermal performance as high as feasible to save more energy. Thus, in the current study, the impacts of inserting the flapped V-baffle vortex generator (FBVG) on the thermal effectiveness improvement of a round tube were experimentally investigated. At a fixed attack angle (α = 60°) and baffle blockage ratio (BR = b/D = 0.3), the geometrical behaviors of FBVGs placed periodically along two edges of a straight tape were six different flap angles (θ = 0°, 25°, 35°, 45°, 65° and 90°) and three ratios of baffle pitches (P/D = PR = 2.0, 1.5, and 1.0). The current V-baffles, which were positioned on both tape edges, were designed to reduce friction loss caused by interrupting the central core flow when placed on both tape sides. The measurement results focused on the friction loss and thermal behaviors, including exergy and entropy analyses for Reynolds number from 4750 to 29,270. In the findings, the Nusselt number and friction factor of FBVG at θ = 0° and PR = 1 are, respectively, up to 5.6 and 35.24 times larger than those of the smooth tube. The entropy generation (S˙gen′) seems to decline as θ and PR increase, with the smallest S˙gen′ found at θ = 0° and PR = 1 for lower Re. The FBVG has the greatest exergy efficiency (ηEx) at θ = 0° and PR = 1. To find the true benefits of FBVG, its thermal performance is estimated and seen to reach a maximum at about 2.44 with NuR = 4.65 at θ = 45° and PR = 1. The optimal scenario at θ = 25° and PR = 1 was preferred, however, since it yielded the largest NuR = 5.42 at TEF = 2.39.

Reduction of Disk Friction Loss by Applying a Fin to the Back of a Centrifugal Impeller

Abstract It is well known that the ratio of disk friction loss of low specific speed pumps is large. When the specific speed is 100 min−1, m3/min, m or less, the disk friction loss increases remarkably. In this study, focusing on the clearance flow from the diffuser outlet to the impeller outlet (This is called the outward flow) behind the centrifugal pump, a fin was installed on outer diameter side of the rotating wall on the back side of a centrifugal pump as a countermeasure, and the influence of changes in velocity distribution near the wall on disk friction loss was investigated by torque measurements, velocity measurement, and computational fluid dynamics (CFD) analysis. As a result, it was clarified that disk friction loss is decreasing by installing the fin in both torque measurements and CFD results, because the clearance flow is separated by fin and circumferential velocity is increased in the wake region of the fin in both measurements and CFD. In addition, it was clarified that disk friction coefficient (normalized torque) can be expressed as a function of the inlet swirl ratio and Reynolds number. Also, prediction equation is derived for each shape (with and without fin). According to the equation, it was found that disk friction loss reduction effect by installing a fin becomes larger when Reynolds number and the inlet swirl ratio are small.

Air-lift characteristics of rock core mass in gas–liquid–solid mixed flow

The air-lift reverse circulation drilling method enables efficient and continuous core extraction. However, the flow characteristics of gas–liquid–solid mixtures during core mass transport are complex, and developing a model to predict performance remains challenging. The flow characteristics of gas–liquid–solid mixtures inside the drill pipe are numerically analyzed by calculating the mixing transport of the core during the airlift process. By solving the momentum equations for multiphase flow, the distribution of physical quantities of three phases and pressure along the depth was calculated, and the laws of influence of the operating parameters on the transport characteristics of the core were analyzed. The results show that the drilling performance is related to the geometric parameters of the pipe and core, drilling speed, and depth. When the submergence ratio is increased to 0.9, the maximum liquid-phase superficial velocity is increased by 109% compared with that when the submergence ratio is 0.6. The size of the annular space gap 67 formed between the core and the pipe wall is the key to the core's mechanical properties, and the differential pressure gradient force increases with increasing core diameter. An increase in well depth reduces the fluid flow. In addition, increasing the pipe diameter improves drilling performance due to reduced friction losses, which elevates the air flow rate required for air-lift reverse circulation operation.

Optimization design and experimental research on cooling performance of U-shaped latticework cooling structure with perforations used for gas turbine blade

Latticework cooling structure provides great structural strength and well heat transfer enhancement commonly used for internal cooling of turbine blades. However, traditional rectangle latticework cooling structure raises friction loss badly and reduces cooling efficiency of turbine blades due to the increase of wetted surface area. A new latticework cooling structure with U-shaped sub-channel and perforations on raffles was proposed, aiming to promote heat transfer and reduce friction loss for latticework cooling structure. Numerical simulation, optimization method and experimental test are conducted to investigate heat transfer and fluid flow characteristics of this new latticework cooling structure. Optimization design based on response surface approximation model and non-dominated sorting genetic algorithms-Ⅱ was conducted and objectives were to maximize heat transfer and minimize friction loss. The optimal U-shaped latticework cooling structure with perforations was obtained and experimental research was conducted. Characteristics of heat transfer and friction loss between the optimal U-shaped latticework cooling structure with perforations and the rectangle latticework cooling structure were compared and analyzed. The experiment results showed that the overall heat transfer and thermal–hydraulic performances of the optimal U-shaped latticework cooling structure with perforations are 21.6–37.0% and 27.9–46.7% respectively higher than those of the rectangle latticework cooling structure while friction loss performance of the former is 16.3–29.2% lower than that of the latter as Reynolds number increases from 5000 to 50000. Moreover, empirical formulas for the optimal U-shaped latticework cooling structure with perforations and the rectangle latticework cooling structure are obtained. The present study indicates that the U-shaped latticework cooling structure with perforations not only maintains the superior heat transfer performance, but also reduces friction loss, which is mainly due to the perforation ribs reduce flow distance for part of coolant and also provide an impingement effect for the heated wall and enhance flow interactions and flow mixing.

Improvement of energy conversion efficiency in traveling wave rotary ultrasonic motor by increasing friction coefficient

This article introduces a method of enhancing the energy conversion efficiency of a traveling wave rotary ultrasonic motor with a flexible rotor by increasing the friction coefficient at the stator–rotor interface. The increased friction coefficient leads to improvements in energy conversion efficiency by increasing the output power and reducing friction loss power. Experimental verification showed that the friction coefficient in the interface increased from 0.21 to 0.32, the maximum energy conversion efficiency increased from 36.8% to 46.3%, and the interface friction loss was reduced.

Optimal Gear Shift Control of Two-Speed Dual-Clutch Transmission in Electric Vehicle for Smoothness and Friction Loss Reduction

Optimal Gear Shift Control of Two-Speed Dual-Clutch Transmission in Electric Vehicle for Smoothness and Friction Loss Reduction

Simulation methodology and numerical comparison of boxer and opposed free piston linear generator configuration in 0D/1D environment

Free Piston Linear Generators (FPLGs) are thermal machines suitable for both stationary power generation unit (PU) and vehicle propulsion. They convert chemical energy from the fuel into electric energy to charge a battery using a linear electric generator. Due to the reduction of friction losses and the ability to work with different compression ratios, FPLGs are potentially characterized by high overall global efficiency with respect to a conventional alternative internal combustion engine. Like conventional internal combustion engines, FPLGs have several configurations: single piston, dual piston, opposed piston and boxer are the configurations considered in this work. Two configurations are compared in this paper from a functional and energetic perspective: opposed piston (Opposed) and Boxer. This is done with the aim to highlights pro and cons of these configurations. They are modelled using the 0D/1D modelling coupling GT-Power® and Simulink®. The comparison between the two configurations was done modelling the architecture with the same size and in two-strokes operating mode. The comparison of the two configurations highlights differences between them in terms of scavenging process, thermodynamic efficiency and global energy efficiency, putting in evidence what aspects need to be improved for each configuration and what are their advantageous features. Boxer configuration can provide less power due to lower volumetric efficiency compared to the Opposed configuration. Boxer configuration can provide 102.2 kW while Opposed can provide 110.0 kW at full load with a frequency of 20 Hz (equivalent to 1200 rpm). The Opposed configuration results in lower heat loss but higher energy lost at the exhaust. The final balance shows that Boxer configuration has a slightly higher brake efficiency (equal to 28.9 %) compared to the value found for Opposed (27.6 %).

Deterministic Simulation of Surface Textures for the Piston Ring/Cylinder Liner System in a Free Piston Linear Engine

The use of synthesis gas (SYNGAS) from waste gasification has been pointed out as a key strategy to help the energy transition. However, SYNGAS’ low calorific power is considered a difficult obstacle to its technological use in internal combustion engines. To overcome this, a novel free-piston linear motor has been proposed to pave the way for the use of SYNGAS in the mobility sector. Surface texturing has vast potential to reduce friction losses in this system. This study utilizes a deterministic numerical model to investigate the mixed lubrication performance of a textured piston ring/cylinder liner conjunction in a free piston engine. The model considers the simultaneous solution of the lubrication and asperity contact problems at the roughness scale, including texturing features on the cylinder surface. The numerical model employs the Reynolds equation with mass-conserving cavitation to calculate the inter-asperity fluid pressure. The rough contact model utilizes the Hertz theory for elastic contact to calculate the contact pressure at each asperity between the piston liner surface and the admitted smooth and rigid ring surface. Surface texturing demonstrated remarkable effectiveness, particularly in the hydrodynamic lubrication regime, with a maximum friction reduction of 38.5% observed for an area coverage of 50%. This was accompanied by a notable shift in the transition from the boundary to the mixed lubrication regime. The textured surfaces exhibited consistent efficiency in reducing fluid pressure and shear stress as the coverage of the textured areas increased. The incorporation of dimples on these surfaces played a crucial role by augmenting the lubricant storage capacity while concurrently reducing the real shear and contact areas. This study offers valuable insights into the nuanced friction-reducing mechanisms of surface textures, illuminating their influence on the coefficient of friction and the formation of lubricant films across various lubrication regimes.

Повышение износостойкости и эффективности работы поршневого уплотнения двигателей внутреннего сгорания

The article examines the specific features of piston ring operation in internal combustion engines and proposes a new design to improve their wear resistance and efficiency. The piston ring, critical for sealing the combustion chamber, can create friction that affects the engine's durability and efficiency. Under conditions of high load and frequent wear, the importance of improved design solutions becomes evident. The proposed piston ring design includes the innovative use of graphite as a solid lubricant to reduce friction and enhance sealing. As a result of these design changes, based on a graphite coating and stepped joints, significant friction loss reduction and improved sealing were achieved. Tests on a prototype confirmed the effectiveness of the proposed design, showing reduced friction and energy loss, which positively impacted engine lifespan and overall performance. The results demonstrate the potential of the proposed solution for both traditional engines using motor oil and oil-free engines. Future plans include creating a test stand for more detailed testing and optimization of the piston ring segments, which will help ensure maximum engine performance and durability.

An inverse optimization of turbulent flow and heat transfer for a cooling passage with hierarchically arranged ribs in turbine blades

Owing to the limited cold-air amount and pressure in supply systems, high-efficient heat transfer with low-level friction loss is highly desired for cooling units of a turbine blade. To exploit the potential improvement of hierarchically arranged ribs in cooling passages proposed previously, multi-parameter optimizations for rib arrangements are implemented by integrating the simplified conjugate-gradient algorithm with the turbulent flow and heat transfer model. Rib heights as design variables are optimized with various performance indices as objective functions at a fixed Re. The optimizations confirm that using the wall temperature difference and Nu as the objective function, respectively, a limited heat transfer improvement is achieved with a greatly increased friction loss. Taking the overall performance factor as the objective function, different optimal designs at different constraint conditions possess hierarchical characteristics. A significant friction loss reduction of 52.1%, 54.7%, and 54.8%, is achieved with a moderate heat transfer loss of 10.9%, 7.0%, and 2.3%. Despite different thermal and friction performances, their overall performances are consistent with a remarkable increase of 13.9%, 21.2%, and 27.3%. Finally, the optimization strategy coupling the multi-parameter optimization and hierarchical scheme is confirmed as effective for enhancing the thermohydraulic performance of convective heat transfer systems with perturbation elements.

Enhancing solar air heater efficiency with 3D cylinder shaped roughness elements

Solar air heaters (SAHs) harness solar radiation to warm the air. This study investigates the efficacy of 3D cylindrical roughness features in enhancing heat transfer and reducing friction losses within SAHs. The configuration involves inline and staggered placement of 3D cylindrical roughness elements beneath the absorber surface. Through ASHRAE standard 93–77 testing, heat transfer and friction factors are examined across various cylinder roughness setups, with parameters such as relative roughness pitch (p/h) and gap (w/h) considered. The channel aspect ratio (W/B) is set at 5, and a relative roughness height (h/D) of 0.06 is maintained and flow Reynolds number (Re) is varied from 3000 to 8000. Regression analysis reveals a significant relationship between heat transfer and friction. Notably, at Re = 7910, p/h = 20, and w/h = 8 for staggered cylinder roughness, average friction factor (fav) increases by 171.3 %, and average nusselt number (Nuav) increases by 69.7 %. Similarly, the efficiency index (η) peaks at 0.8192 with inline roughness at Re = 2969, p/h = 20, and w/h = 8. The introduced 3D cylinder roughness elements disrupt the laminar sub-layer, amplifying convective heat transfer while curbing friction losses. This approach optimizes SAH performance within the studied parameter range, showcasing potential improvements for utilizing solar energy. Experimental results, along with expressions for average friction factor (fav) and average Nusselt number (Nuav), underscore the benefits of cylinder-shaped roughness geometries while maintaining h/D = 0.06. These findings introduce an innovative convective heat transfer method, enhancing SAH efficiency. Furthermore, the anticipated average friction factor (fav) and average Nusselt number (Nuav) values align within error limits of ±6.63 % and ±6.62 %, respectively, with improved regression coefficients indicating the stronger relationship and the influence of independent variables on dependent variables.

Effects of Reynolds Number and Tooth Front Angle on Leakage Loss and Heat Transfer Characteristics in a Rotating Labyrinth Seal

Abstract The labyrinth seal is effective in reducing leakage losses at the rotor blade top in the turbine. This study investigates the variation in labyrinth seal performance at different rotational speeds, different Reynolds numbers, and different tooth front angles. Three Reynolds numbers (Re = 6000, 10,000, 15,000), five rotational speeds (Ta/Re = 0, 0.01, 0.04, 0.08, and 0.1), and three tooth front angles(75 deg, 90 deg, and 102.4 deg) have been introduced. The variation of leakage losses and heat transfer under different conditions is compared and a detailed analysis of the flow field and energy losses is performed. The discharge coefficient is increased slightly with increased rotational speed for the same Reynolds number. This is caused by the high rotational speed reducing the throttling loss and vortex loss. The high rotational speed enhances the heat transfer at the tip wall of the passage, and also weakens the heat transfer at the tooth cavity bottom. Additionally, the sealing capacity of the labyrinth is better at large tooth front angles, which is caused by the reduction of frictional losses on the stator and eddy current losses in the tooth cavity. The change in local pressure loss also affects the velocity distribution along the channel, which is the reason for the change in the local Nusselt number.

Use of Functionalized Graphene-Based Materials on Grease

The growing awareness of reduced friction losses and new demands for electrical powertrains demand improved lubricants. Due to their unique properties, such as high thermal and electrical conductivity, graphene and its derivatives have been investigated for tribological applications, especially as lubricant additives. In this work, we investigated three commercially available graphene variants, one comprising a few layers and the other two comprising nanoplates, after functionalization as additives to lithium soap grease. The grease temperature dropping point increased by approximately 6 °C. Additionally, during the reciprocating friction test, friction increased with the test duration for the baseline grease, whereas it decreased for the ones containing graphene-based additives. On the test end, friction was reduced by 8% compared to the baseline grease. On a four-ball tribometer, the wear scar was reduced from 10 to 18% compared to the baseline grease. In general, no significant difference was seen between the three graphene-based variants. The promising results found with graphene nanoplates, a less expensive material than a few graphene layers, creates opportunities for a cost-competitive additive to commercial greases.

Numerical Investigations of Tribological Characteristics of Biomimetic-Textured Surfaces

Rail transportation has dramatically improved travel convenience, but it has also led to environmental pollution and energy consumption issues. These challenges can be partially addressed by reducing friction loss in the mechanical transmission of rail systems. This paper examines the tribological properties of bionic-textured surfaces inspired by snake- and sharkskin. This study focuses on generating bionic textured surfaces with randomly distributed peaks through numerical simulation and connecting them to a transient Reynolds equation and friction fatigue model. The bionic surface wear lubrication model considers the lubricating film’s thickness and contact pressure obtained from the GT model. The results reveal that the existence of a bionic texture can reduce the friction coefficient and wear amount on the contact surface. The findings of this study not only offer a potential solution for reducing energy consumption and emissions in intelligent rail transit systems but also hold promise for providing further insights into the numerical simulation of bionic weaving and the investigation of tribological characteristics.