Lubricant Flow Rate Research Articles

Dynamic characteristics of compensated hydrostatic thrust pad bearing subjected to external transverse magnetic field

This article presents finite element analysis to evaluate the performance of a compensated hydrostatic circular thrust pad bearing in the presence of a magnetic field. The influence of the magnetic field on the flow of an electrically conducting lubricant is expressed by incorporating the Lorentz force in the momentum equation, described by Maxwell equations and Ohm’s law. The modified Reynolds equation has been derived for a lubricant blended with long-chain polymer additives flowing in the presence of a transverse magnetic field. The Stokes couple stress theory has been used to describe effect of such additives on lubricant rheology. A source code has been developed in MATLAB to solve the modified Reynolds equation coupled with restrictor flow equations using the finite element method. The performance characteristics of the bearing system are evaluated in terms of pocket pressure, load-carrying capacity, lubricant flow rate, fluid film stiffness and damping coefficient. Comparative studies have been carried out for orifice and capillary compensated bearings. The limiting cases of the modified Reynolds equation yield performance characteristics of specific lubricants such as electrically conducting couple stress lubricant, couple stress lubricant, electrically conducting lubricant and Newtonian lubricant. It is noticed that the load-carrying capacity, fluid film stiffness and damping capabilities of the bearing get enhanced quite substantially in the presence of couple stress additives and a magnetic field.

Experimental Investigation on Unstable Vibration Characteristics of Plates and Drag Torque in Open Multiplate Wet Clutch at High Circumferential Speed

The drag torque caused by the viscous shear in open multiplate wet clutches has been studied in most available literature whose focus is placed on low circumferential speed. However, the drag torque increases drastically in the high circumferential speed range. The underlying physical principles and the influencing factors of the drag torque at high speed are still indeterminate. The present study aims to experimentally investigate the characteristics of the wobbling vibrations of plates and to characterize the effects of average clearance, flow rate of lubricant, shifting condition, and the number of friction interfaces on the drag torque at high circumferential speed. The result of the experiment reveals that the friction plate (FP) starts to wobble periodically at low circumferential speed, though the effect is insignificant. The dominant frequency of plate wobbling movements increases with the input speed. When wobbling vibrations of plates become unstable, the wobble gradually becomes nonlinear. The experiments confirm that the mechanical contacts between plates during the unstable wobbling vibration result in the drag torque rise at high circumferential speed. At high speed, the supplying flow rate of the lubricant influences the drag torque values. The rotation of separator plates (SPs) brings forward the torque rise and makes the drag torque rise smoother. By reducing the number of interfaces, the drag torque rise is delayed and the magnitude becomes smaller. Finally, a four-stage drag torque characteristic curve is illustrated to show the dominant factors of drag torque at different stages.

Influence of technological factors on characteristics of hybrid fluid-film bearings

The influence of the parameters of micro- and macrounevenness on the characteristics of a hybrid bearing with slotted throttling is considered in the present paper. The quantitative assumptions of calculation of pressure distribution, load capacity, lubricant flow rate and power loss due to friction in a radial hybrid bearing with slotted throttling are taken into account, considering the shape, dimensions and roughness of the support surfaces inaccuracies. Numerical simulation of processes in the lubricating layer is based on the finite-difference solution of the Reynolds equation using an uneven orthogonal computational grid with adaptive condensation. The results of computational and physical experiments are presented.

Lubricant flow analysis for effective lubrication of tractor forward/reverse clutch.

Owing to the high power requirements of tractors, their low-power transmission gears often experience durability problems such as burning of the clutch. The operation of tractors under high load conditions also causes clutch slip, with the consequent longer operation duration exacerbating the burning of the friction plate. Solving this problem requires effective lubricant distribution. This was achieved in the present study by the development of an analysis model for predicting the lubricant flow rate. The reliability of the model was verified by comparing its predictions for various operation conditions with experimental measurements. Using the model, it was determined that effective distribution of the lubricant could be achieved without significant modification of the system, by only adjusting the gaps between the clutch piston and the housing, and between the separation plates and the case.

Effective slip for flow through a channel bounded by lubricant-impregnated grooved surfaces

This study aims to investigate effective slip arising from pressure-driven flow through a slit channel bounded by lubricant-impregnated grooved surfaces. The problem for flow over longitudinal grooves is solved analytically using the methods of domain decomposition and eigenfunction expansion, while that for flow over transverse grooves is solved numerically using the front tracking method. It is found that the effective slip length and the lubricant flow rate can depend strongly on the geometry of the microstructure, the direction of flow, and the lubricant viscosity. In particular, the effective slip can be effectively enhanced by increasing the thickness of a lubricating film atop the ribs. Under the same conditions, a flow that is parallel to the lubricant-impregnated grooves will have a larger effective slip, but also a larger lubricant flow rate, when compared with the case of flow normal to the grooves. It is also shown that, in the case of transverse grooves, because of the downward displacement of the interface between the working/lubricating fluids, the effective slip length and lubricant flow rate may vary non-monotonically with the groove depth.

On the Predicted Effect of Angular Misalignment on the Performance of Oil Lubricated Thrust Collars in Integrally Geared Compressors

Multiple-stage integrally geared compressors (IGCs) offer improved thermal efficiency and easier access for maintenance and overhaul than single-shaft centrifugal compressors. In an IGC, a main bull shaft drives pinion shafts, each having an impeller at its ends. The compression of process gas in the compressor stages induces axial loads along the pinion shafts that are transmitted via thrust collars (TCs) to the main bull gear (BG) shaft and balanced by a single thrust bearing. Manufacturing inaccuracies and a poor assembly process can lead to static angular misalignments of the TC and BG surfaces that affect the operating film thickness as well as the force and reaction moments of the lubricated mechanical element. In a follow-up to San Andrés et al. (2015, “On the Predicted Performance of Oil Lubricated Thrust Collars in Integrally Geared Compressors,” ASME J. Eng. Gas Turbines Power, 137(5), pp. 1–9), this paper presents an investigation of the performance of a single thrust collar configuration operating with increasing static angular misalignment of either the TC or BG. The flow model solves the Reynolds equation of hydrodynamic lubrication coupled to a thermal energy transport equation to determine the film pressure and bulk temperature fields, respectively. The model predicts performance parameters such as power loss and lubricant flow rate, and force and moment stiffness and damping coefficients. Predictions show that misaligning of either the thrust collar or bull gear alters the load-carrying area in the lubricated zone, shifts the pressure field with peak magnitudes doubling or more depending on the degree and direction of TC or BG misalignment. Static angular misalignment does not significantly affect the power loss, temperature rise, etc., but does have an effect on the dynamic coefficients (both axial and angular). Finally, a reduced complex dynamic stiffness matrix for the lubricated TC shows that some cross-coupled stiffness and moment coefficients are nonzero, indicating hydrodynamic coupling between axial and angular motions for the pinion and bull gear shafts. The coupling could affect the placement of the system natural frequencies and associated mode shapes as well as the system stability.

A study on process parameters in end milling of AISI-304 stainless steel under electrostatic minimum quantity lubrication conditions

Effective lubrication and cooling are very critical to control friction and heat generation in metal-cutting processes. Conventionally, cutting fluids in flood form are employed during the processes; however, their usage is frequently seen to raise major environmental, economic, and employees’ health concerns. All these factors have urged researchers to search for alternatives to minimize or even eliminate cutting fluid usage. To serve that purpose, a new near-dry machining technique called “electrostatic minimum quantity lubrication” (EMQL) has been innovated and developed. EMQL is a technique using the synergetic effects between electrostatic spraying (ES) and minimum quantity lubrication (MQL), wherein a very small amount of lubricant, negatively charged by the electrostatically contact charged method, is directed into the machining area in the form of a fine, uniform, and highly penetrable and wettable oil mist. The focus of this study is to evaluate the performance of EMQL in end milling of AISI-304 stainless steel in terms of tool wear, cutting force, tool life, and surface roughness. The influence of EMQL process parameters such as charging voltage, air pressure, lubricant flow rate, and cutting speed is determined based on an experimental study. A comparison with the results obtained in completely dry, wet, and MQL machining is also provided. The experimental results show the effectiveness of EMQL as a viable alternative to conventional wet and MQL machining through the reduction in the friction at the tool–chip interface. It is found that the charging voltage is an important factor influencing the effective application of EMQL oil mist. EMQL with −5 kV voltage is recommended because it provides not only lower tool wear and cutting force but also higher tool life and better surface finish. In addition, it is found that there are the optimum lubricant flow rate and air pressure in end milling of AISI-304 stainless steel with EMQL. The proper selection of the above parameters can lead to a low-cost and eco-friendly machining.

The effect of minimum quantity lubrication in the intermittent turning of magnesium based on vibration signals

Abstract The present work shows an experimental investigation on intermittent turning based on vibration signals. The dependence of vibrations on the feed rate, minimum quantity lubrication (MQL) flow rate and the type of the interruption of the workpiece is evaluated. The results indicate that a part of the vibrations depends on the flow rate of the MQL system and its interaction with the feed rate, finding no dependency on the type of interruption. The influence of the MQL system is greater when machining at the lower feed rate. In addition, a strong relation between surface roughness and vibrations is identified. However, this relation is quite different depending on the environment used. In general, under dry conditions, the higher the vibrations the higher the surface roughness, while the opposite occurs when the MQL system is used.

Optimization of MQL flow rate for minimum cutting force and surface roughness in end milling of hardened steel (HRC 40)

The present work focuses on the performance modeling of hard milling to attain an optimum parameter setting for the minimum cutting force and surface roughness. Furthermore, it was attempted to compute the minimum quantity lubricant flow rate precisely, besides the cutting speed and table feed rate, by adopting Grey-based Taguchi method and composite desirability function. The experimental data was collected by end milling of hardened AISI 4140 steel using carbide cutter under dry and minimum quantity lubrication conditions according to Taguchi L 16 orthogonal array. The predictive model of the responses was formulated by using response surface methodology. The analysis of variance revealed that the table feed has the maximum influence on cutting force, and the flow rate of lubricant has the highest effect on surface roughness. The parameter setting at lower table feed, higher cutting speed, and 150-ml/h lubricant flow yield the minimum value of the responses. Finally, the results of confirmation test verified the adequacy and supremacy of the optimization models; however, Grey-based Taguchi method induced a better optimization.

Numerical Analysis of Turbocharger’s Bearing using Dynamic Mesh

Journal bearings are widely used in different machineries. Reynolds equation is the governing equation to predict pressure distribution and load bearing capacity in journal bearings. There are many analytical and numerical methods for solving this equation. The main disadvantage of these methods is their inability to analyze complex geometries. In this paper, a comprehensive method based on dynamic mesh method is developed to solve the conservation equations of mass, momentum and energy. This method has smaller error compared to other techniques. To verify the accuracy of this method, the bearings with different length to diameter ratios are analytically and numerically analyzed under different loads and compared with each other. In continue, the turbocharger’s bearing is numerically simulated and the effects of rotational speed change are studied. Finally, the turbocharger’s bearing with four axial grooves are simulated. The simulations results show that adding grooves to the turbocharger’s bearing causes the bearing eccentricity ratio and lubricant flow rate to increase and the attitude angle, rate of temperature rise and frictional torque to decrease.

Investigations on Surface Roughness Measurement in Minimum Quantity Lubrication Turning of Titanium Alloys Using Response Surface Methodology and Box–Cox Transformation

AbstractIn the present work, an attempt has been made to establish the accurate surface roughness (Ra, Rq and Rz) prediction model using response surface methodology with Box–Cox transformation in turning of Titanium (Grade-II) under minimum quantity lubrication (MQL) conditions. This surface roughness model has been developed in terms of machining parameters such as cutting speed, feed rate and approach angle. Firstly, some experiments are designed and conducted to determine the optimal MQL parameters of lubricant flow rate, input pressure and compressed air flow rate. After analyzing the MQL parameter, the final experiments are performed with cubic boron nitride (CBN) tool to optimize the machining parameters for surface roughness values i. e., Ra, Rq and Rz using desirability analysis. The outcomes demonstrate that the feed rate is the most influencing factor in the surface roughness values as compared to cutting speed and approach angle. The predicted results are fairly close to experimental values and hence, the developed models using Box-Cox transformation can be used for prediction satisfactorily.

ON THE STATIC ANALYSIS OF ANNULAR RINGH HYDROSTATIC THRUST BEARINGS LUBRICATED WITH COUPLE STRESS FLUIDS

In the present theoretical analysis, the static properties of the annular ring hydrostatic thrust bearings have been investigated. The lubricant in the system has been taken as non-Newtonian couple stress fluids. The effects of centrifugal inertia and couple stresses on the film pressure, load capacity and lubricant flow rate have been studied and a good agreement of the present results with the earlier established results has been observed. Analytic solution for pressure distribution has been obtained in the analysis taking into account, the influence of centrifugal inertia in the recess region. The effect of couple stress on pressure was found to be dependent on central recess radius but the decreasing load capacity and flow rate with the increase of couple stress parameter was observed in the analysis. Load capacity was also observed to be higher with the recess radius closer to the axis of the bearing.

Performance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application: An experimental comparison between R245fa and R1233zd

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial-inflow turbine is a small-scale prototype designed to convert the waste heat from the exhaust gases of a truck combustion engine and was developed mainly using components of truck turbochargers. It is directly connected to a high-speed synchronous generator. The bearings system of the turbine and the generator have the innovative particularity to be respectively lubricated and cooled down by the working fluid so no additional lubricant or coolant is needed. The experimental comparison is carried out over a test-rig equipped with the radial turbine. The heat wasted by the truck through the exhaust gases is simulated using an electric oil boiler coupled to the ORC loop. The electrical power supplied by the turbine, limited to a maximum of 3.5kWel by the generator, is then dissipated in a load bank composed of truck fans while the condenser is cooled by a water loop. Measurements in steady-state are performed in order to evaluate the performance of the turbine-generator set when varying the pressure ratio, the rotational speed, the inlet temperature and the mass flow rate of the turbine and the lubrication flow rate of the bearings for various oil temperatures and mass flow rates. In order to identify the most suitable fluid for the Waste Heat Recovery (WHR) application, three comparison methods are proposed and discussed based on the measurements. Finally, because the turbine-generator set is the first oil-free prototype developed by the manufacturer, potential sources of improvements are discovered and discussed.

Multi-objective optimization of minimum quantity lubrication in end milling of aluminum alloy AA6061T6

The purpose of this research is to optimize the process of minimum quantity lubrication (MQL) in the end milling of AA6061T6 using multi - objective genetic algorithm approach . R esponse surface methodology coupled with a central composite design of experiments is used for modeling. Data is collected from a vertical CNC milling cent e r and the input parameters are cutting speed, table feed rate , axial depth of cut and the minimum quantity lubrication flow rate . A nalysis of variance at a 95% confidence level is implemented to identify the most significant input variables on the CNC end milling process. Optimization of the responses is done using a multi - objective genetic algorithm. A m ulti - criteria decision making utility is used to find among the feasible range of optimum design s for the operating parameters and the responses. An iterative multi - criteria decision making algorithm is used to find the best design among those obtained from multi - objective optimization with respect to the given conditions. The best design obtained for the equal weightage case is the design at 5252 rpm, with a feed rate of 311 mm/min, a depth of cut of 3.47 mm and MQL flow rate at 0.44 ml/min.

Performance Analysis of a Nonrecessed Hybrid Conical Journal Bearing Compensated With Capillary Restrictors

The present paper deals with the performance analysis of a nonrecessed hole-entry hydrostatic/hybrid conical journal bearing with capillary restrictors. Finite element method has been used for solving the modified Reynolds equation governing the flow of lubricant in the clearance space of journal and bearing. The hole-entry hybrid conical journal bearing performance characteristics have been depicted for a wide range of radial load parameter (W¯r = 0.25–1.5) with uniform distribution of holes at an angle of 30 deg in the circumferential direction. The numerically simulated results have been presented in terms of maximum fluid film pressure, minimum fluid film thickness, lubricant flow rate, direct fluid film stiffness coefficients, direct fluid film damping coefficients, and stability threshold speed. However, the proposed investigation of nonrecess hole-entry hybrid conical journal bearing shows important performance for bearing stiffness and minimum fluid film thickness at variable radial load and at given operating speed.

Tribological performance evaluation and sensitivity analysis of piston ring lubricating film with deformed cylinder liner

The interface between piston ring and cylinder liner is lubricated with an oil film to improve wear resistance and operating life of the engine. The high combustion pressure, variable loadings, manufacturing errors, and thermal distortions in the engine cylinder deform the cylinder liner, thus making a significant effect on the lubricant performance. To investigate the effects of cylinder liner deformation on the piston ring lubrication, a 2D model of elastohydrodynamic lubrication under fully flooded conditions was considered. Various elliptically deformed profiles of the cylinder liner were tested to evaluate conformability, lubricating film thickness, friction, power loss, and lubrication flow rate for a complete four-stroke engine cycle. Comparative analysis of the simulation results was conducted to evaluate the dependency of engine performance on deformed bore shape. Results showed that the lubricating film thickness and engine performance parameters strongly depend on the cylinder liner shape and the degree of distortion.

Effect of Axial Groove on Steady State and Stability Characteristics of Finite Two-Lobe Hybrid Journal Bearing

The study of the steady state and stability characteristics including whirl instability of finite two-lobe hybrid journal bearing with an axial groove, located at the top from which oil is supplied at a constant pressure is obtained theoretically. The two lobes of 1600 arc each are separated by two axial oil groove of 20° circumferential extensions in the horizontal direction. A two-dimensional finite difference solution was used to predict the performance of finite length externally pressurized two-lobe hydrodynamic hybrid journal bearings.The Reynolds equation is solved numerically using finite difference method satisfying the appropriate boundary conditions to obtain the effect of speed parameter on bearing performance.The stability characteristics were found out using first-order perturbation method. With the change of speed Stiffness and damping coefficients behaviour was determined at various eccentricity ratios. The bearing load-carrying capacity, stiffness, lubricant flow rate, attitude angle and frictional torque due to bearing rotation increase with increase in eccentricity ratio and speed. A comparison is also made with plain cylindrical axial grooved journal bearing. It is found that externally pressurized two-lobe hybrid bearing is more superior to plain cylindrical axial-grooved oil journal bearing in terms of load capacity, improved end flow, friction losses and stability. The bearing is generally stable at high values of the eccentricity ratio and speed parameter.

A study on the effect of starvation in mixed elastohydrodynamic lubrication

The effect of starvation in mixed elastohydrodynamic lubrication (EHL) regime is studied. Numerical simulations are conducted for both line and point (elliptical) contacts with the consideration of the surface roughness. The degree of starvation is linked directly to the reduction in the lubricant mass flow rate. Results are presented to gain insight on the influence of starvation on the film thickness as well as the interaction between the surface asperities. Extensive sets of simulation results are used to quantify the effect of starvation in the EHL of rough surfaces. Expressions are developed to predict the percentage of the load carried by the surface asperities (asperity load ratio) as well as the reduction of the central and minimum film thickness in the starved mixed EHL.

The effects of minimum quantity lubrication (MQL) on machining force, temperature, and residual stress

Minimum quantity lubrication (MQL) machining has achieved noticeable attention in both academic and industry research areas due to its minimum costs and maximum environmental protection. This paper focuses on the analysis of the effects of MQL parameters such as the flow rate of lubricant and the air-oil mixture ratio on cutting performances in terms of cutting force, cutting temperature, and residual stress. Additionally, the cutting performances in MQL machining are also compared with the dry and flood cooling machining. The results show that the cutting fluid can considerably reduce the cutting force and cutting temperature in machining. For MQL machining, there is a maximum effective flow rate of lubricant and it is influenced by the cutting speed. When the flow rate of lubricant is beyond the maximum effective value, the air-oil mixture ratio will no longer affect the cutting performances in machining. This research can support the process planning in achieving the desired residual stress profile by strategically adjusting the MQL parameters.

Comparison between Nitrogen-Oil-Mist and Air-Oil-Mist Condition when Turning of Hardened Tool Stainless Steel

Minimum quantity lubrication (MQL) or as it’s called semi dry cutting is a technique which spray a small value of lubricant flow rate to the cutting zone area. MQL has been used in many machining process with different cutting tools and workpiece materials due to its green environments and economically advantageous. MQL has become an attractive option to dry and flood cutting in terms of reduce the temperature in the cutting zone and reduce the cost of the product. However, in MQL seems to be machining limited by cutting temperature, because at high speed the effect of oil mist becomes evaporated. Therefore another alternative cooling approach was used with oil mist in this research. This research presents study the performance of nitrogen gas as a coolant and oil mist as lubricant in turning of hardened stainless tool steel (STAVAX ESR) with hardness 48 HRC. Using a gas as coolant with oil mist is a new solution for enhancing machinability. Turning experiments are carried out on CNC turning machine. The cutting insert grade is KC5010 (PVD-TiAlN wiper coated carbide). The experimental results were: 1) nitrogen gas with oil mist prolongs tool life compare with air with oil mist. 2) better product surface finish by using nitrogen gas with oil mist.