Modeling Non-Newtonian Piston Skirts EHL in the Initial Engine Start Up

2010 ◽  
Author(s):  
Syed Adnan Qasim ◽  
Usman F. Chaudhri ◽  
M. Afzaal Malik ◽  
Riaz A. Mufti
Keyword(s):  
High Speed ◽  
Relaxation Times ◽  
Radial Clearance ◽  
Solution Technique ◽  
Engine Operation ◽  
Low Speed ◽  
Start Up ◽  
Piston Skirts ◽  
Engine Start ◽  
Speed Engine

In the normal high speed engine operation at small piston-to-bore radial clearance, elastohydrodynamic lubrication (EHL) of skirts and non-Newtonian lubricant behavior prevent adhesive wear, but in the initial engine start up, the large clearance, low speed and absence of EHL, cause start up wear. This study models 2-D upper convected Maxwell viscoelastic EHL of piston skirts at small radial clearance in a few initial low speed engine start up cycles by solving the Reynolds equation and using the inverse solution technique. The numerical analysis incorporate characteristic lubricant relaxation times and a perturbation method to predict and compare hydrodynamic and EHL pressures and film profiles. The effects of viscoelasticity on the lubricant characteristics, transverse eccentricities of piston, film thickness, and pressure fields in the hydrodynamic and EHL regimes are investigated. This study suggests that EHL film is formed at very small piston-to-bore radial clearance at low start up speed under assumed conditions to prevent start up wear as viscoelasticity produces a beneficial effect on piston skirts lubrication in the initial engine start up.

Modeling Viscous Isothermal Piston Skirts EHL in Very Low Initial Engine Start Up Speeds

2011 ◽  
Author(s):  
Syed Adnan Qasim ◽  
M. Afzaal Malik
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
High Viscosity ◽  
Solution Technique ◽  
Engine Operation ◽  
Low Speed ◽  
Start Up ◽  
Speed Optimization ◽  
Piston Skirts ◽  
Engine Start

In the normal low-speed engine operation, elastohydrodynamic lubrication (EHL) of piston skirts and lubricant rheology reduce friction and prevent wear. In a few initial start up cycles, a very low engine speed and absence of EHL cause adhesive wear. This study models hydrodynamic and EHL of piston skirts in the initial very low cold engine start up speed by using a high viscosity lubricant. The 2-D Reynolds equation is solved and inverse solution technique is used to calculate the pressures and film thickness profiles in the hydrodynamic and EHL regimes, respectively. The work is extended to investigate the effects of three very low initial engine start up speeds on the transverse eccentricities of piston skirts, film thickness profiles and pressure fields in the hydrodynamic and EHL regimes. Despite using a viscous lubricant, thin EHL film profiles are generated at low start up speeds. This study suggests very low speed optimization in the cold initial engine start up conditions to prevent piston wear under isothermal conditions.

Modeling Shear Heating in Piston Skirts EHL Considering Different Viscosity Oils in Initial Engine Start Up

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
S. Adnan Qasim ◽  
M. Afzaal Malik ◽  
M. Ali Khan ◽  
R. A. Mufti
Keyword(s):  
Thermal Loading ◽  
Energy Equation ◽  
Adhesive Wear ◽  
Solution Technique ◽  
Engine Operation ◽  
Start Up ◽  
Shear Heating ◽  
Viscosity Grade ◽  
Piston Skirts ◽  
Engine Start

A fully established elastohydrodynamic lubricating (EHL) film between the piston and the liner surfaces during normal engine operation minimizes piston slap and prevents adhesive wear. Wear cannot be prevented in the initial engine start up due to the absence of EHL film. During normal engine operation, thermal loading due to combustion dominates piston skirts lubrication. However, in a few initial cold engine start-up cycles, shear heating affects the lubricant viscosity and other characteristics considerably. This study models 2D piston skirts EHL by incorporating shear heating effects due to lubricant flow between the skirts and liner surfaces. The hydrodynamic and EHL film profiles are predicted by solving the 2D Reynolds equation and using the inverse solution technique, respectively. The temperature distribution within the oil film is given by using the 2D transient thermal energy equation with heat generated by viscous heating. The numerical analysis is based on an energy equation having adiabatic conduction and convective heat transfer with no source term effects. The study is extended to low and high viscosity grade engine oils to investigate the adverse effects of the rising temperatures on the load carrying capacity of such lubricants. Numerical simulations show that piston eccentricities, film thickness profiles, hydrodynamic and EHL pressures visibly change when using different viscosity grade engine lubricants. This study optimizes the viscosity-grade of an engine lubricant to minimize the adhesive wear of the piston skirts and cylinder liner at the time of initial engine start up.

Non-Newtonian Elastohydrodynamic Lubrication Fluid Flow Modeling of Piston Skirts Considering Low Speed Effects in Initial Engine Start Up

2010 ◽  
Author(s):  
Syed Adnan Qasim ◽  
M. Afzaal Malik ◽  
Usman F. Chaudhri ◽  
Riaz A. Mufti
Keyword(s):  
Fluid Flow ◽  
Film Thickness ◽  
Relaxation Times ◽  
Viscoelastic Model ◽  
Elastohydrodynamic Lubrication ◽  
Computational Method ◽  
Solution Technique ◽  
Start Up ◽  
Piston Skirts ◽  
Engine Start

Elastohydrodynamic lubrication (EHL) is critically essential to minimize engine wear at low engine start up speeds. During the normal engine operations at medium to high speeds, non-Newtonian characteristics of multigrade engine lubricants enhance engine life by preventing adhesive wear. By incorporating viscoelastic effects of a non-Newtonian lubricant and focusing on different low engine start up speeds, this study models EHL fluid flow in the initial engine start up conditions. A 2-D non-Newtonian piston skirts lubrication model and analysis at the time of engine start up is presented based on the upper convected Maxwell viscoelastic model. The analysis of a non-Newtonian lubricant between piston and cylinder liner by using characteristic lubricant relaxation times in all order of magnitude analysis is done by using a perturbation method. The EHL film profile is predicted by solving the two-dimensional Reynolds equation using the inverse solution technique and the finite difference computational method in the fully flooded lubrication conditions. At different low engine start up speeds, the effect of viscoelasticity on lubricant velocity and pressure fields is examined and the influence of film thickness on lubricant characteristics is investigated. Numerical simulations show that piston eccentricities, EHD pressures and film thickness profiles are functions of low range of engine start up speeds. This study suggests that the initial engine start up speed at low range can be optimized as viscoelasticity produces a beneficial effect on piston skirt lubrication in the initial engine start up.

Effects of High Initial Engine Start Up Speeds in Isothermal Fluid Flow and Piston Skirts EHL

2011 ◽  
Author(s):  
Syed Adnan Qasim ◽  
M. Afzaal Malik
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Adhesive Wear ◽  
Cooling System ◽  
Cylinder Liner ◽  
Operating Conditions ◽  
Solution Technique ◽  
Start Up ◽  
Piston Skirts ◽  
Engine Start

In the medium and high speed normal engine operating conditions a fully established elastohydrodynamic lubricating (EHL) film between the piston skirts and cylinder liner surfaces reduces friction and prevents adhesive wear. In the initial engine start up the absence of EHL film causes wear of piston skirts, especially at high speeds. In a few initial cold engine start up cycles, a highly efficient cooling system may not let the temperature to rise significantly and affect the viscosity and other characteristics of a lubricant. In view of the vulnerability of piston skirts to adhesive wear at high initial engine start up speeds, the hydrodynamic and EHL of piston skirts is modeled numerically. A 2-D Reynolds equation is solved by coupling the secondary piston motion and using a finite difference scheme. Transient hydrodynamic film thickness profiles are generated at a relatively high engine start up speed. In the EHL regime, the profiles of rising hydrodynamic pressures and film thicknesses are predicted by using the inverse solution technique in fully flooded conditions. The study is extended to a range of high engine start up speeds while using a fairly viscous engine lubricant. Numerical simulations show significant changes in the piston eccentricities and film thickness profiles in the hydrodynamic and EHL regimes at different start up speeds. Such variations alter the hydrodynamic and EHL pressures and visibly affect the load carrying capacity of the lubricant. This study suggests to optimize the high engine start up speed for the given viscosity grade engine lubricant when considering the vulnerability of skirts and liner surfaces to adhesive wear in the initial engine start up.

Modeling EHL of Rough Piston Skirts Using Different Viscosity-Grade Lubricants in Initial Engine Startup

2012 ◽  
Author(s):  
Syed Adnan Qasim ◽  
Mubashir Gulzar ◽  
Riaz A. Mufti ◽  
M. Afzaal Malik
Keyword(s):  
Cylinder Liner ◽  
High Viscosity ◽  
Solution Technique ◽  
Engine Operation ◽  
Start Up ◽  
Viscosity Grade ◽  
Piston Skirts ◽  
Interacting Surfaces ◽  
Engine Start ◽  
Lubrication Models

An engine lubricant plays a significant role in preventing adhesive wear of the rough interacting surfaces of the piston skirts and the cylinder liner. A fully established elastohydrodynamic lubricating (EHL) film, appropriate viscosity oil and the fairly rough interacting surfaces prevent wear during normal engine operation. The absence of an EHL film and inappropriate viscosity lubricant fail to minimize wear in the initial engine startup. This work considers a fairly viscous Newtonian engine lubricant to model the rough piston skirts hydrodynamic and EHL in the initial engine start up. The isotropic surfaces of the skirts and the cylinder liner having different roughness amplitudes are considered in the basic lubrication models. The flow factors are introduced in the 2-D average Reynolds equation, which is solved numerically to generate the hydrodynamic pressures. The inverse solution technique is used to develop the basic EHL model of the rough surfaces. The secondary piston dynamics and the contact geometry of interacting surfaces are incorporated in the basic lubrication models. The profiles of the piston eccentricities, secondary velocities, film thicknesses and pressures are generated as the function of 720 degrees crank rotation cycle. The study is extended to develop the lubrication models for the low and high viscosity grade engine lubricants separately. The simulation results are analyzed and compared with those of the basic lubrication model. The results show that the different lubricant viscosities alter the secondary displacements of the sliding piston and affect the lubrication of the rough interacting surfaces. The comparative analysis leads to optimize the use of appropriate viscosity-grade engine lubricant for a few low speed initial engine startup cycles.

Modeling Low-Viscosity 1st Compression Ring EHL at Large Radial Clearance in Initial Engine Start Up

2012 ◽  
Author(s):  
Syed Adnan Qasim ◽  
Rashid Naseer ◽  
Abdul Ghafoor ◽  
M. Afzaal Malik
Keyword(s):  
Thermal Loading ◽  
Radial Clearance ◽  
Solution Technique ◽  
Ic Engine ◽  
Engine Operation ◽  
Compression Ring ◽  
Low Viscosity ◽  
Start Up ◽  
Effective Seal ◽  
Engine Start

In normal IC engine operation 1st compression ring sustains thermal loads effectively. At large radial clearance in low-speed engine start up it has to act as effective seal against thermal loading. Absence of elastohydrodynamic lubricating (EHL) film and secondary displacements expose the ring to adhesive wear in initial engine start up. Isothermal hydrodynamic and EHL models of parabolic-faced ring are developed numerically after incorporating secondary dynamics of piston assembly at a low engine start up speed. Reynolds equation is solved to generate hydrodynamic pressures and film profiles in 4-stroke cycle. In EHL model inverse solution technique and elastic displacements of ring and liner are employed to generate pressures and film profiles. The simulation results suggest that a large ring-to-bore clearance increases eccentricity and affects EHL of 1st compression ring when a low-viscosity grade oil is used in initial engine start up.

Modeling of Shear Heating in Elastohydrodynamic Lubrication of Piston Skirts by Considering Different Viscosity Oils in Initial Engine Start Up

2010 ◽  
Author(s):  
M. Afzaal Malik ◽  
Syed Adnan Qasim ◽  
Mumtaz Ali Khan ◽  
Riaz A. Mufti
Keyword(s):  
Thermal Loading ◽  
Energy Equation ◽  
Adhesive Wear ◽  
Cylinder Liner ◽  
Solution Technique ◽  
Engine Operation ◽  
Start Up ◽  
Shear Heating ◽  
Piston Skirts ◽  
Engine Start

The presence of fully established elastohydrodynamic lubricating (EHL) film between piston skirt and cylinder liner during normal engine operation prevents adhesive wear, piston noise and slap. The absence of EHL in the initial engine start up fails to prevent the same. During normal engine operation, thermal loading due to combustion dominates piston skirts lubrication. However, in a few initial cold engine start up cycles, shear heating may be assumed to considerably affect the lubricant viscosity and other characteristics. This study undertakes a 2-D EHL modeling of piston lubrication by incorporating shear heating effects due to lubricant flow between skirts and liner surfaces. The EHL film profile is predicted by solving the 2-D Reynolds equation using inverse solution technique and the finite difference method in fully flooded lubrication conditions. The temperature distribution within oil film is given by using the 2-D transient thermal energy equation with heat generated by viscous heating. The numerical analysis is based on energy equation having adiabatic conduction and convective heat transfer with no source term effects. The study is extended to a number of engine lubricants having different viscosities to investigate the extent of adverse effects due to temperature rise on load carrying capacity of lubricants. Numerical simulations show that piston eccentricities, film thickness profiles, hydrodynamic and EHL pressures visibly change when using different viscosity grade engine lubricants. This study suggests that a lubricant of appropriate viscosity can be optimized keeping in view the vulnerability of piston skirts and cylinder liner to adhesive wear at the time of initial engine start up.

Numerical Study of Single Pad Externally Adjustable 120° Pad Bearing Using Fluid Structure Interaction

2021 ◽  
Author(s):  
Harishkumar Kamat ◽  
Chandrakant R. Kini ◽  
Satish B. Shenoy
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Film ◽  
Structural Deformation ◽  
Radial Clearance ◽  
Solution Technique ◽  
Eccentricity Ratio ◽  
Positive Direction ◽  
Film Pressure ◽  
Marine Propulsion

Abstract High-speed turbomachinery like turbine generators and marine propulsion systems uses special fluid film bearing called externally adjustable pad bearing due to their great advantages. The principal feature of this bearing is to alter the radial clearance and film thickness along the circumferential direction to improve the bearing performance parameters. In the present study, the effect of radial and tilt adjustment of 120° pad both in upward (or negative) and downward (or positive) direction on the bearing performance is predicted for various eccentricity ratios using the CFD technique. Later the influence of fluid film pressure on the bearing pad is examined using the FSI technique. Furthermore, the effect of eccentricity ratio on the bearing performance and also on pad structure is also analyzed using CFD coupled FSI analysis. The solution technique of the present numerical analysis is validated with the already published literature and the results are in good agreement. The numerical results suggest that for bearing with negative radial and negative tilt adjustment, bearing performance is superior compared to the other adjustments. However, the structural deformation is also significant for the negative radial and negative tilt adjustment. It is also observed that pad deformation increases with the increase in eccentricity ratio as there has been a rise in fluid film pressure.

Exhaust Emission Reduction from Compression Ignition Engine by Using Palm Biodiesel Blended with Nano Zinc Oxide Additive

2017 ◽  
Vol 909 ◽  
pp. 249-254
Author(s):  
Ponrawee Wanriko ◽  
Karoon Fangsuwannarak
Keyword(s):  
Palm Oil ◽  
Diesel Fuel ◽  
High Speed ◽  
Alternative Fuel ◽  
Exhaust Emission ◽  
Crude Palm Oil ◽  
Compression Ignition Engine ◽  
Engine Operation ◽  
High Speed Engine ◽  
Speed Engine

Biofuel modifications play a major role in a substitution for fossil fuel to be used in diesel engines and reducing exhaust emission. The most amounts of crude palm oil produced from Asian region can be an alternative fuel, sustainably. By the modifying crude palm oil into pure palm oil biodiesel (POB100), alkali trans-esterification procedure was operated. In the present, the high-quality POB products have been investigated considerably for alternative fuel in 4-cylinders high-speed diesel engine. The aim of this paper is to study in the improvement of POB quality by repeated-distillation and blending POB with nanoZnO additive. The high-speed engine combustion from consuming blended POB fuel were investigated the influences of exhaust emission under speed engine operation of 2,000 rpm and 3,000 rpm. The experimental results were shown that the POB fuel yielded at 84.54% from using 400 g. of raw materials. Both of redistilled POB and POB blended with nanoZnO additive showed the improvement of physical properties including viscosity, specific gravity and cetane number values being under ASTM standard values for high-speed engine. In addition, the results of exhaust emission from the engine showed the effective decrease of carbon monoxide (CO), carbon dioxide (CO2) around 13% due to using redistilled POB and POB blended nanoZnO additive compared with diesel fuel. Unburned hydrocarbon (HC) and nitric oxide (NOx) emissions of the diesel fuel condition. Therefore, this study suggests that nanoZnO blending POB in the small fraction about 0.005 wt% is able to provide the high potentiality for as a clean and alternative fuel.

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