Browse Topic: Lubricant viscosity
ABSTRACT The Department of Defense is a major consumer of petroleum products – over 700 million gallons per day. While the majority of fuel consumed is for aircraft, in terms of logistics and exposure of personnel to hazardous conditions, the amount of fuel consumed in ground vehicles is considerable, with the cost (in-theatre, delivered) ranging from $100 to $600/gallon. This paper addresses the impact that parasitic friction mechanisms (boundary lubrication and lubricant viscosity) have on engine friction and overall vehicle efficiency. A series of mechanistic models of friction losses in key engine components was applied to investigate the impact of low-friction technologies on the fuel consumption of heavy-duty, on-road vehicles. The results indicate that fuel savings in the range of 3 to 5% are feasible by reducing boundary friction and utilizing low-viscosity engine lubricants. The paper will discuss the implications of the studies (as performed for commercial heavy-duty trucks
Micro-dimple is one of the promising surface texturing technologies to reduce friction loss due to the generation of thicker oil film caused by the cavitation occurrence around the micro-dimples. In this study, the flow behavior of oil film around micro-dimples was directly observed by laser-induced fluorescence (LIF). LIF observation for the oil flow showed that micro- dimples induced the cavitation occurrence that contributed to increase the oil film thickness. This was in good agreement with the results of the friction test, and it was thus proved that the cavitation occurrence by micro-dimples is significantly effective for the friction reduction
The gear lubricants covered by this standard exceed American Petroleum Institute (API) Service Classification API GL-5 and are intended for hypoid-type, automotive gear units, operating under conditions of high-speed/shock load and low-speed/high-torque. These lubricants may be appropriate for other gear applications where the position of the shafts relative to each other and the type of gear flank contact involve a large percentage of sliding contact. Such applications typically require extreme pressure (EP) additives to prevent the adhesion and subsequent tearing away of material from the loaded gear flanks. These lubricants are not appropriate for the lubrication of worm gears. Appendix A is a mandatory part of this standard. The information contained in Appendix A is intended for the demonstration of compliance with the requirements of this standard and for listing on the Qualified Products List (QPL) administered by the Lubricant Review Institute (LRI). Appendix A contains a
This SAE Information Report was prepared by the SAE Fuels and Lubricants Technical Committee for two purposes: (a) to assist the users of automotive equipment in the selection of axle1 and manual transmission lubricants for field use, and (b) to promote a uniform practice for use by marketers of lubricants and by equipment builders in identifying and recommending these lubricants by a service designation
The engine power cylinder is comprised of the piston, piston rings, and cylinder. It accounts for a significant amount of total engine friction within reciprocating, internal combustion engines. Reducing power cylinder friction is key to the development of efficient internal combustion engines. However, isolating individual power cylinder tribocouples for detailed analysis can be challenging. In this work, a new reciprocating liner test rig is developed and introduced. The rig design is novel, using a stationary piston and a reciprocating cylinder liner. Friction is calculated from the force measured in the connecting rod which supports the piston. The rig allows for independent control of peak cylinder pressure, speed, and lubricant temperature. Using the newly developed test rig, several technologies for friction reduction are evaluated and compared. Friction reducing technologies include the use of a low-friction TiSiCN nanocomposite coating applied to the piston rings, a lubricant
On urban and emission homologation cycles, engines operate predominantly at low speeds and part loads where engine friction losses represent around 10% of the consumed fuel energy but would account for 25% of the fuel consumption once combustion efficiency is taken into account. Under such mild conditions, engine and engine oil temperatures are also lower than ideal. The influence of oil viscosity on friction losses are significant. By reducing lubricant viscosity, engine friction, fuel consumption and emissions are reduced. Tribological and machine learning models were investigated to predict the effect of oil viscosity on fuel consumption during the FTP75 emission cycle with the use of detailed actual emission test measurements. Oil viscosity was calculated with the measured oil temperature. As the same vehicle transient is followed in the cold and hot phases, the models were evaluated by comparing their prediction of fuel consumption in the hot phase versus the measured value. The
The piston assembly is the major source of tribological inefficiencies among the engine components and is responsible for about 50% of the total engine friction losses, making such a system the main target element for developing low-friction technologies. Being a reciprocating system, the piston assembly can operate in boundary, mixed and hydrodynamic lubrication regimes. Computer simulations were used to investigate the synergistic effect between low viscosity oils and cylinder bore finishes on friction reduction of passenger car internal combustion engines. First, the Reynolds equation and the Greenwood & Tripp model were used to investigating the hydrodynamic and asperity contact pressures in the top piston ring. The classical Reynolds works well for barrel-shaped profiles and relatively thick oil film thickness but has limitations for predicting the lubrication behavior of flat parallel surfaces, such as those of Oil Control Ring (OCR) outer lands. In these cases, a deterministic
One of the first tasks while designing pistons is to ensure the reliable engine operation with minimal friction losses. This is possible by ensuring the liquid friction in the piston-cylinder junction during the entire operating cycle. Therefore, it is important to assess the nature of friction in the piston-cylinder conjunction. This task can be broken down into a number of interrelated subtasks: determining the characteristics of the piston lateral movement, determining the piston deformations under thermal and mechanical loads, and calculating the hydrodynamic forces acting from the side of the oil layer in the conjunction. The use of software packages that solve these problems separately and their inclusion in the iterative process will lead to huge expenditures of computing time and is difficult to implement in carrying out design optimization problems. The authors have developed a mathematical model for the joint solution of the above problems, and carried out computational
This SAE Standard defines the limits for a classification of engine lubricating oils in rheological terms only. Other oil characteristics are not considered or included
The gear lubricants covered by this standard exceed American Petroleum Institute (API) Service Classification API GL-5 and are intended for hypoid-type, automotive gear units, operating under conditions of high-speed/shock load and low-speed/high-torque. These lubricants may be appropriate for other gear applications where the position of the shafts relative to each other and the type of gear flank contact involve a large percentage of sliding contact. Such applications typically require extreme pressure (EP) additives to prevent the adhesion and subsequent tearing away of material from the loaded gear flanks. These lubricants are not appropriate for the lubrication of worm gears. Appendix A is a mandatory part of this standard. The information contained in Appendix A is intended for the demonstration of compliance with the requirements of this standard and for listing on the Qualified Products List (QPL) administered by the Lubricant Review Institute (LRI). Appendix A contains a
More stringent Federal emission regulations and fuel economy requirements have driven the automotive industry towards more sophisticated vehicle thermal management systems to best utilize the waste heat and improve driveline efficiency. The final drive unit in light and heavy duty trucks usually consists of geared transmission and differential housed in a lubricated axle. The automotive rear axle is one of the major sources of power loss in the driveline due to gear friction, churning and bearing loss affecting vehicle fuel economy. These losses vary significantly with lubricant viscosity. Also the temperatures of the lubricant are critical to the overall axle performance in terms of power losses, fatigue life and wear. In this paper, a methodology for modeling thermal behavior of automotive rear axle with heat exchanger is presented. The proposed model can be used to predict the axle lubricant temperature rise. It also can be used to study the effect of coolant temperature on the axle
There is still a need in the industry for engine oils that have low viscosities to improve vehicle fuel efficiency but also protect engines from wear. Viscosity modifiers (VMs) are chief additives responsible for adjusting the viscometric characteristics of automotive lubricants. Most notably, VMs have a significant impact on a lubricant's viscosity-temperature relationship as indicated by viscosity index (VI), cold cranking simulator (CCS) viscosity, and high temperature high shear (HTHS) viscosity of engine oils. Functional copolymers bearing branched, linear, or anti-wear functionalities have been synthesized and evaluated for viscometric and wear protection performance. The resulting polymers improved tribofilm formation, shear stability and CCS viscosities. Indirect benefits including Noack improvement and trim oil reduction were observed
The aim of this study is to investigate how lubricants used for transaxles in hybrid electric vehicles (HEVs) and electric vehicles (EVs) give an impact on the cooling performance for electric motors. As a result, reducing lubricant viscosity improve heat transfer in both natural and forced convection conditions. Quantitative analysis could reveal that kinetic viscosity and heat conductivity of fluids are highly influential on the cooling performance. In addition, we investigated the effect of lubricant additive on fatigue life in bearing components by using a thrust needle roller bearing tester. Extreme pressure agent could control a morphology of the bearing raceway surface, playing a role in extending a fatigue life of the bearing
Applying friction modifier (FM) in low viscosity engine oil is one well known cost effective approach for improving a fuel economy of vehicles. At first, the characteristics and mechanisms of FMs on tribological phenomena were studied with surface analysis technics. The performance of FMs was also evaluated with engine component test and motored engine test to understand the friction property of FMs in engine application. Then the effect of driving cycle, lubricant viscosity and FMs in fuel economy performance under chassis dynamo were studied. Among tested FMs, molybdenum dialkyl dithiocarbamate (MoDTC) was the most effective at boundary lubrication, which is considered significantly important friction area for WLTP, latest procedure for fuel economy test, with low and ultra-low viscosity engine oil
Designing fuel economy lubricants is an art; finding the right balance between fuel economy and durability requirements is complex, with many trade-offs. To open new formulation spaces with ever increasing fuel economy, a deep understanding of how lubricating oils respond to different drive cycles, engine/transmission type and any coating properties, e.g. DLC, is required. In this paper, we describe how the implementation of WLTC requires lubricant optimization to deliver improved fuel economy under this test cycle and therefore, lubricant viscosity reduction becomes more important. We also illustrate optimization of the sludge system is key to reducing overall viscosity of lubricants for ultra low viscosity application, such as in SAE 0W- 8 viscosity grade oils. To meet the cleanliness challenges in an SAE 0W-8 environment, we describe a developmental sludge handling system with improved cleanliness at constant viscosity to conventional SAE 0W-8 lubricants. A SAE 0W-8 demonstration
This SAE Aerospace Information Report (AIR) establishes guidance for the specification of formulated lubricant properties which contribute to the lubricating function in bearings, gears, clutches, and seals of aviation propulsion and drive systems
This specification covers the requirements for a refined paraffinic petroleum-base lubricant
This SAE Standard defines the limits for a classification of automotive gear lubricants in rheological terms only. Other lubricant characteristics are not considered
The gear lubricants covered by this standard exceed American Petroleum Institute (API) Service Classification API GL-5 and are intended for hypoid-type, automotive gear units, operating under conditions of high-speed/shock load and low-speed/high-torque. These lubricants may be appropriate for other gear applications where the position of the shafts relative to each other and the type of gear flank contact involve a large percentage of sliding contact. Such applications typically require extreme pressure (EP) additives to prevent the adhesion and subsequent tearing away of material from the loaded gear flanks. These lubricants are not appropriate for the lubrication of worm gears. Appendix A is a mandatory part of this standard. The information contained in Appendix A is intended for the demonstration of compliance with the requirements of this standard and for listing on the Qualified Products List (QPL) administered by the Lubricant Review Institute (LRI). Appendix A contains a
See Table 1
It has been revealed by researches that lubricant properties have a great effect on the low-speed pre-ignition (LSPI) frequency in downsizing turbocharged direct-injection engines which are developed for better fuel economy. Droplets of lubricant or lubricant-gasoline mixture are considered to be the potential pre-ignition sources. Those droplets fly into the combustion chamber and ignite the gasoline-air mixture. To study lubricant droplets fundamentally, a novel set of droplet auto-ignition system is designed based on a Dibble Burner for this experiment. Influences of metallic additive contents, viscosities, lubricant diluted with gasoline and waste lubricant on the ignition delay of droplets are investigated by testing 12 groups of lubricants or lubricant-gasoline mixture. The equivalent diameter of each droplet generated by micro-syringes is around 2.1 mm. The co-flow temperature varies from 1123 K to 1223 K, and the experiments are carried out at atmospheric pressure. The auto
Legislation aimed at reducing carbon dioxide emissions is forcing significant changes in passenger car engine hardware and lubricants. Reduced viscosity lubricants can reduce friction levels and are therefore helpful to manufacturers seeking legislative compliance. MAHLE and Shell have worked together to determine the crankshaft, bearing and lubricant combination which minimizes friction with an acceptable level of durability. This paper describes the results of our joint simulation studies. MAHLE Engine Systems have developed in-house simulation packages to predict bearing lubrication performance. SABRE-M is a “routine” simulation tool based on the mobility method [1] curve fitting from the finite bearing theory to simulate the hydrodynamic lubrication in steady-state conditions. Whereas, SABRE-TEHL is a specialized simulation package used for performing Thermo-Elasto-Hydrodynamic Lubrication (TEHL) analysis of bearing systems. Predictions for bearing severity parameters allow more
An instantaneous piston ring/liner friction model has been presented to estimate the minimum oil film thickness and power loss contributed by piston rings under hydrodynamic lubrication. The model is based on lubrication theory considering lubricant viscosity variation with respect to temperature. A numerical scheme is developed to solve Reynolds and load equilibrium equations simultaneously to obtain the cyclic variation of oil film thickness and power loss. The model considers the ring profile geometry, the ring mechanical properties and their effects on the tribological performance of piston ring. The relevant trends and relations between parameters are considered with relatively simple approach to compute the minimum oil film thickness and mechanical power loss. Besides, Design of Experiment (DOE) technique and ANOVA analysis are employed to determine the effect of influential parameters such as ring width, ring crown height, ring elastic properties and ring end gap on the average
The gearbox is the main component for adjustment of speed and torque in automotive powertrain systems. In this work, numerical simulations were conducted to analyze the effect of the gear tooth geometry on the slide-to-roll ratio (SRR) and friction coefficient along the gear engagement, as well as on the overall transmission efficiency. Simulations were carried out using the AVL Excite Power Unit software. Elastohydrodynamic theory was applied to model the lubricated contact conditions. This model considers lubricant viscosity and the entraining velocity, curvature and roughness of the contacting surfaces. The simulated system is based on a manual transmission model coupled to a differential and a rigid wheel driver, which imposes rotation and torque profiles to the gears. The radius of curvature of tooth profile and angular velocity of the gear were varied, while maintaining the same characteristics of the lubricating oil. Results indicate a correlation between the increase in the
See Table 1
This index provides an overview of lubricants and symbols for the purpose of assisting the user in the identification of the appropriate product and relevant SAE specification. The aim is to better determine the best lubricant to be used for a particular application. If containers used for shipping lubricants are also to be marked, the same identification and symbols should be used. See also ISO 5169 Machine tools - Presentation of lubrication instructions
The greases have been classified according to the operating conditions under which they are used, because the versatile nature of greases makes it impractical to classify them according to end use. It will therefore be necessary to consult the supplier to be certain that the grease can be used in; for example, rolling bearings or pumped supply systems, and also concerning the compatibility of products (see Remarks in Table 1
See Table 1
This work develops a comprehensive thermohydrodynamic (THD) model for high-speed squeeze film dampers (SFDs) in the presence of lubricant inertia effects. Firstly, the generalized expression for Reynolds equation is developed. Additionally, in order to reduce the complexity of the hydrodynamic equations, an average radial viscosity is defined and integrated into the equations. Subsequently, an inertial correction to the pressure is incorporated by using a first-order perturbation technique to represent the effect of lubricant inertia on the hydrodynamic pressure distribution. Furthermore, a thermal model, including the energy equation, the Laplace heat conduction equations in the surrounding solids (i.e. the journal and the bush), and the thermal boundary conditions at the interfaces is constructed. Moreover, the system of partial differential hydrodynamic and thermal equations is simultaneously solved by using an iterative numerical algorithm. The proposed model is incorporated into a
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