Oil Supply Rate Research Articles

Impact of oil supply conditions on water lubrication assisted with minimal secondary lubricating medium

Abstract Previous research has revealed that introducing a secondary lubricating medium can temporarily enhance water-lubricated bearing performance, thereby reducing the risk of lubrication failure under challenging conditions. This study aims to identify the optimal injection point for the secondary lubricating medium and evaluates oil supply rate effects. Experiments are conducted using a block-on-ring test rig, complemented by CFD simulations to elucidate the underlying mechanisms. Three oil supply settings, upstream, inlet and outlet of the contact region, are compared. Results shows that upstream oil supply led to a lower critical speed at which the added oil loses any effect compared to the inlet oil supply and outlet oil supply. The effect of oil supply rates on friction reduction varies among the oil supply settings and ring rotational speeds. In conclusion, the most effective oil supply setting positions the injector at the outlet of the contact region, outperforming placement at the entrance of the contact region.

Research on vibration characteristics of silicon nitride 6206 full-ceramic bearing with different pre-tightening force and oil supply rate

Research on vibration characteristics of silicon nitride 6206 full-ceramic bearing with different pre-tightening force and oil supply rate

Hybrid digital twin for conditional lubricant oil transport simulation and oil consumption prediction in internal combustion engines

Reducing lubricant oil consumption (LOC) has long been an interest to engine manufacturers in an effort to reduce overall emissions from internal combustion (IC) engines. However, directly correlating engine operating conditions with LOC rates is a challenging task given its complex and multi-physics nature. Building on previous experimental observations and modeling efforts, a baseline hybrid model, which combines traditional physics-based numerical simulation with modern machine learning techniques, was developed. As the first step, the model is to compute the oil exiting the top ring gap with given oil supply rate and locations to the second land. Studies performed using the model reveal a strong dependency of LOC on engine speed, load as well as the relative locations of piston ring gaps. In particular, the close proximity of the oil source on second land to the top ring gap and the reverse gas flow at low load conditions can both induce high LOC. Piston ring gap rotations and the different oil supply mechanisms to the piston ring pack are also found to heavily influence the oil consumption behavior and oil film thickness distribution pattern. The present work is the first step to a more comprehensive model for predicting LOC for healthy systems of piston ring packs. The efficiency of the model made it possible to study the oil redistribution that takes many engine cycles to reach equilibrium and rotation of the ring gaps that could happen in reality at a time scale of minutes and even longer.

Reduction of lubricant life in lubrication systems for internal combustion engines due to high lubricant supply rates

The lubrication systems of internal combustion engines are not designed to avoid excessive oil consumption; therefore, the oil supply rate to the interior of the engine falls between two critical limits: ensuring the formation of a tribofilm that prevents engine wear and lowers high friction. However, it disregards the excessive depletion of the lubricating precursors that make up this protective tribofilm. In this work, the life of oil in lubrication systems for internal combustion engines is analyzed by means of simulations of the mass balances of the protective tribofilm formed inside the engine; results indicate that high lubricant supply rates cause early depletion of lubricant precursors, shortening the life of each batch of oil.

Leakage and friction characteristics at sliding surface of tip seal in scroll compressors

• Simultaneous measurement of leakage and friction at tip seal was conducted. • The influence of several parameters on seal effect and friction was clarified. • The influences of several parameters on seal effect and friction were generalized. • Lubrication condition at the tip seal based on the Stribeck curve was clarified. A tip seal is applied to prevent a radial leakage at a tip of scroll wrap in scroll compressors. When the tip seal is pressed hard against a base plate of the scroll, the radial leakage will decrease, while friction at the tip seal will increase. There is a trade-off between the leakage and the friction. It is needed to clarify the relationship between the leakage and the friction at the tip seal to optimize a scroll compressor design. In this study, a test apparatus which could evaluate the leakage and the friction at sliding surface of the tip seal simultaneously was developed. The influence of several parameters, such as upstream pressure, length and width of the tip seal, oil supply rate, rotational speed and oil viscosity, on the seal effect and the friction was examined with the test apparatus, and the influences of these parameters were generalized.

Which uncertainty is powerful to forecast crude oil market volatility? New evidence

AbstractThis paper focuses on distinguishing the predictive power of five newly developed uncertainty indices, that is, global and US economic policy uncertainty (GEPU and US EPU), global geopolitical risk (GPR), US monetary policy uncertainty (MPU) and equity market volatility (EMV), on crude oil market volatility. We construct the extended GARCH‐MIDAS models to assess the forecasting ability of these indices and then compare them with four commonly used oil volatility drivers: oil supply, oil demand, oil speculation and interest rate. Firstly, the in‐sample analysis suggests that all uncertainty indices and traditional determinants have significant impacts on oil volatility. Secondly, the out‐of‐sample evaluations suggest that US MPU, EMV and EPU indices are more powerful than other predictors to improve the forecasting accuracy of crude oil volatility, and US EMV exhibits the best prediction ability. Then, we find that EPU and MPU indices are more effective in forecasting high volatility in crude oil market, while traditional determinants together with US EMV index are more helpful in predicting low oil volatility. Finally, the forecasts of bad oil volatility can be improved by all predictors except for GEPU index, while the forecasts of good oil volatility can only be enhanced by US MPU, EMV and EPU.

Analysis and optimization of nonlinear carrying performance of hydrostatic ram based on finite difference method and Runge–Kutta method

Analyzing of nonlinear carrying performance of hydrostatic ram is among key research questions to improve heavy machine tools because the machining precision will be directly influenced by it. A dynamic model of nonlinear supporting characters for hydrostatic ram is developed in this work. Modified Reynolds equation is resolved by finite difference method numerically to determine the carrying capability. Dynamic equilibrium equation of hydrostatic ram under cutting force impact is solved by Runge–Kutta method to obtain the variation of tool tip position and evaluate the machining accuracy. An optimal oil supply rate allocation and oil pad size is proposed to improve the static and dynamic performance simultaneously based on method of bisection.

Effect of Inlet Structures on the Performance of Oil Supply System of a Variable Speed Rotary Compressor

Variable speed rotary compressors are now increasingly favored in the market of household air-conditioners in China due to its advantage of energy saving and system stability. Oil supply system plays a pivotal role in high efficiency and good reliability of a variable speed rotary compressor. This paper presents an investigation of the effect of inlet structures on the performance of oil supply system of a variable speed rotary compressor by means of numerical simulation and experiment. The method of volume of fluid (VOF) has been employed in the simulation model and a novel experimental test rig is designed to perform oil flow rate measurements in order to validate the simulated results. With the help of numerical simulation, oil flow patterns in oil pump can be visualized and oil supply rate under different working conditions can be predicted. Good agreement between the simulated oil flow rates and the experimental data has been achieved. The results indicate that oil supply rate increases with an increase in oil level height, oil viscosity as well as the rotating speed. Vertical oil suction pipe with a tapered port contributes to oil pumping in comparison with a straight suction pipe and no suction pipe. Additionally, the minimum rotational speed at which oil starts to flow out of the oil pump increases with the oil inlet diameter and the increment of oil inlet diameter allows the improvement oil pumping performance at a high rotating speed.

Techno‐economic performance of a bio‐refinery for the production of fuel‐grade biofuel using a green catalyst

AbstractThe main challenge to the wider use of biodiesel as a transport fuel has been its high cost of production. Studies have been performed to obtain the cheapest methods for biodiesel production. The calcium oxide catalyzed transesterification reaction has shown better performance for fuel‐grade biodiesel from cheaper feedstock. In this study, a calcium oxide catalyzed biodiesel production process is designed in four different scenarios based on different possible arrangements of the downstream processes.The process flow diagrams of the different scenarios were designed using Aspen Plus and Super Pro software. These process simulations were used to evaluate the techno‐economic performance of the process scenarios. Technical performance was been evaluated based on the quantity and quality of the biodiesel and glycerol produced, the amount of biodiesel produced per amount of feedstock consumed, and the amount of other valuable byproducts. Similarly, the economic performance of the process scenarios has also been assessed using parameters such as total investment cost, unit production cost, net present value, internal rate of return, payback time, and return on investment.Each of these four scenarios was divided into two production capacity levels to investigate the effect of change in production capacity on the economic feasibility of the process scenarios.The scenario with consecutive centrifugations for glycerol and soap separation, and distillation for biodiesel purification, evidenced poor technical performance, whereas the double reactor scenario provided more, and better quality, product, and the economic feasibility of this scenario was good when the oil supply rate was above 4600 kg h−1. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Effect of oil stirrer on the performance of oil supply system for a variable speed rotary compressor

This paper presents an investigation regarding the effect of oil stirrer on the performance of oil supply system for variable speed rotary compressors. Oil supply rate for oil pump with an oil stirrer is calculated by means of numerical simulation. To validate the simulation model, a novel test rig is built to perform oil flow rate measurements under different operating conditions. Good agreement between the simulation model and the experiment has been achieved. The results show that oil supply rate can be increased markedly with the help of oil stirrer whereas stirrer heights and geometric structures do not cause significant variations in oil pumping performance in the current situations of this research. Particularly, it is found that when the rotational speed is high enough, oil supply rate will stay stagnant or even depressed with an increase in rotational speed rather than simply increases with the speed.

Design of an intelligent monitoring system for hydrostatic turntable service performance evaluation

The accuracy maintenance and operation reliability of the hydrostatic turntable are associated with many factors whose influence on bearing load carrying capacity is the key question of researching the hydrostatic turntable. In this study, an intelligent hydrostatic turntable monitoring system is proposed based on multi-source data acquisition. Firstly, the timely main parameter variations are acquired through different kinds of sensors installed on the turntable to form an input data aggregation. Then, by analyzing the static, dynamic, and thermal characteristics of the turntable using Finite Difference Method (FDM) and Runge–Kutta method (RKM), a set of equations for the bearing performance evaluation is established. Computational results are converted to the motor signal for the pump for controlling oil supply rate. Finally, the load-carry supporting performance of each oil pad is controlled precisely and individually by a pump with multiple outputs driven by servo motors. An intelligent input, processing, and output (IPO) real-time system of the hydrostatic turntable is established to monitor its service performance. Finally, the accuracy compensation by data statistics and reliability evaluation by abnormal data detection are carried out to improve the working performance of hydrostatic turntable.

Performance evaluation of aluminium 6063 drilling under the influence of nanofluid minimum quantity lubrication

For environmental and economic reasons, recent research in industry and academia has sought ways to reduce the use of machining fluids. New cutting techniques are to be investigated to achieve this objective. Minimal quantity of lubrication (MQL) is a recent technique introduced in machining to obtain safe, environmental and economic benefits, reducing the use of coolant lubricant fluids in metal cutting. The objective of this work is to compare the performance of different lubrication conditions (dry, flooded, pure MQL and nanofluid MQL) with respect to the cutting forces (thrust force and torque), tool wear and surface roughness in the drilling of aluminium 6063 alloy by using HSS drill tools. In both MQL methods (pure MQL and MQL with nano-particles) oil supply rate is fixed at 200 ml/h and air pressure is fixed at 70 Psi. The nano-particles (Al2O3) of 20 nm in size are considered for the nanofluid with volumetric concentration of 1.5% in base oil (soya bean oil). The experimental results show that the nanofluid MQL (NFMQL) significantly increases the number of drilled holes and reduces the drilling torques and thrust forces as compare to other coolant-lubrication conditions. Superior results of NFMQL may be attributed to the reason that NFMQL produces low friction force at the tool/chip and tool/workpiece interfaces due to its rolling effect of nano-particles and superior cooling performance. In addition, the nanofluid MQL effectively eliminates chips and burrs to enhance the surface quality of holes and also increases the tool life by obtained lowest tool wear.

The influence of oil supply and cylinder liner temperature on friction, wear and scuffing behavior of piston ring cylinder liner contacts – A new model test

A reciprocating model test has been developed, which reproduces real load situation of the contact condition between the piston-ring and cylinder liner at fired top dead center (FTDC) of internal combustion engines. Friction, wear, and load carrying capacity (LCC) were studied as a function of temperature, oil supply rate, and normal force for a honed gray cast iron liner and a chromium plated piston ring. The results show similar liner wear to the ones in actual fired engine tests were obtained as long as normal forces that correspond to engine combustion pressures were applied. Also, a considerable dependency of the LCC on temperature and oil supply rate was found. However, oil supply rate did not influence coefficient of friction (COF) as much as expected.

Lubrication characteristics analysis of an air-oil lubrication system using an experimental design method

Air-oil lubrication has been widely used for high-speed spindle bearings because its oil delivery is positive and can be controlled very accurately. In this study, the effects of air-oil lubrication conditions, such as the oil discharge quantity, oil discharge interval, oil viscosity, air supply rate and tube length, were analyzed with respect to the variation of the oil supply rate. The analysis was carried out by using an air-oil lubrication characteristics evaluation system which was consisted of an air-oil lubrication unit, oil absorbent paper feeding unit and image processing unit. The variation of the oil supply rate discharged from the air-oil lubrication unit was gauged as the variation ratio of the oil band width on the oil absorbent paper measured by the image processing unit. A prediction model for the variation ratio of the oil band width was established based on a response surface method, and its reliability was proved by the fact that the predicted variation ratios of the oil band width agreed well with the measured variation ratios under the various air-oil lubrication conditions. In particular, the relationships between the variation of the oil band width and the air-oil lubrication conditions were examined by analyzing the interactions between the experimental factors.

An experimental investigation on effects of minimum quantity lubrication oil supply rate in high-speed end milling of Ti–6Al–4V

Minimum quantity lubrication is an alternative to realize machining titanium alloys both economically and ecologically. In order to apply minimum quantity lubrication more efficiently, an investigate of the effects of the operating parameters involving oil supply, compressed air supply, and nozzle orientation is required. This article focuses on the oil supply rate of minimum quantity lubrication and aims to identify the effects of the minimum quantity lubrication applications with different oil supply rates in high-speed end milling of Ti–6Al–4V. The experiments were conducted by adjusting the oil supply rate from 2 ml/h to 14 ml/h, and cutting force, surface roughness, tool wear and failure mode, and tool wear mechanism were discussed. The results indicate that the increase of the oil supply rate effectively reduces cutting force and surface roughness, but after 10 ml/h the reduction is no longer significant. Increasing oil supply has growing penetration depth along the cutting edge, and by increasing the oil supply rate the length of the chipping edge can be notably reduced. For an insufficient oil supply rate (2 ml/h∼10 ml/h) chipping on the cutting edge introduced by diffusion wear is the main tool rejection reason, but at 14 ml/h no diffusion wear is found and the uniform flank wear is dominant, owing to reduced cutting temperature.

Static Characteristics of Journal Bearings under Starved Lubricating Conditions

The static characteristics of journal bearings with an axial groove under starved lubrication are studied theoretically and a lubrication condition map is newly proposed. This map is represented using the contour map of the eccentricity ratio with the Sommerfeld number S in the horizontal axis and the dimensionless oil flow rate Qsup externally supplied in the vertical axis for the wide range of the operating conditions. It is found from the map that the eccentricity ratio increases with the decrease of Qsup. This tendency is more marked for a higher Sommerfeld number. Journal center loci show that the attitude angle decreases with Qsup. The degree of the starvation Λ and the oil supply rate Ψ are defined as the ratio of the dimensionless oil flow rate into the inlet of the oil film region to that obtained under the flooded lubrication condition and as the ratio of Qsup to Qsup* obtained under flooded lubrication conditions, respectively. The degree of starvation Λ varies with Ψ and the value of Λ can be determined by setting the value of Ψ. These facts suggest that the static characteristics and Λ are theoretically predicted once the value of Qsup or Ψ is determined.

Investigation on the oil supply system of a scroll compressor

A numerical model is developed for the complete oil supply system of a scroll compressor. The system includes oil sump, pickup tube, oil gallery, bearings, and associated oil feed holes, vent, and port. There are two fluids, oil and gas, inside the system. The flow is numerically simulated as a heterogeneous Eulerian-Eulerian turbulent multi-phase flow. The investigation covers the entire working process of the scroll compressor from dry-start to steady state. Two design parameters, initial oil sump depth and viscosity, are studied comparatively. The detailed oil-gas flow inside the oil supply system is characterized by the field quantities. The physical mechanisms controlling oil supply rate are defined. The oil supply rate and the bearing prime time (the time after which oil is flowing through a bearing) are obtained. The results can be used to design and optimize the oil supply system to improve the reliability and efficiency of scroll compressors.

Influence of Used Oil on Piston Ring Friction.

The influences of the used oil on the piston ring friction were evaluated by using a pin-on-disk type reciprocative sliding test equipment and an actual operating diesel engine in which the floating liner method was adopted. The major results are : (1) Because the used oil which contains highly concentrated soot is inferior in oil film spreading characteristics, the lubricating property is significantly lowered by reducing the oil supply rate ; (2) Even though the kinematic viscosity of the used oil is increased by the flocculation of soot, the effective viscosity on the sliding surface of the used oil is approximately equal to that of the fresh oil due to the de-flocculation of soot. The friction mean effective pressure obtained for the used oil is not different from that for the fresh oil ; and (3) Because the oil starved lubrication is dominant for the piston ring pack, the used oil raises the lubrication severity at the beginning of the power stroke, thereby causing the boundary friction to increase.

Effect of oil supply rate on temperature and contact of a con-rod big end bearing Shigeo Suzuki, Toshihiro Ozasa, Takashi Noda (Toyota Central R & D Labs., Inc.(, Toshiaki Konomi (Toyota Motor Corp.)

Effect of oil supply rate on temperature and contact of a con-rod big end bearing Shigeo Suzuki, Toshihiro Ozasa, Takashi Noda (Toyota Central R & D Labs., Inc.(, Toshiaki Konomi (Toyota Motor Corp.)

Initial Temperature Evaluation for Flash Temperature Index of Gear Tooth

In the AGMA standard for the scoring resistance evaluation of gears, flash temperature is used as an index indicating the risk of scoring. The flash temperature is expressed as the sum of flash rise of temperature and initial temperature. In this research, the initial temperatures are measured for various gear sets in running by thermocouples which are mounted just beneath the working surface of pinion. The effects of gear dimensions, rotating speed, and lubrication conditions on the initial temperature are clarified. An experimental formula is proposed for estimating the initial temperature, which depends on the temperature of oil inlet, the frictional power loss, and the running conditions such as rotating speed, contact position, and the oil supply rate. The estimated initial temperatures are in good agreement with the measured values. The proposed method is available for the scoring resistance evaluation of the vehicle transmissions.