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Technical Paper

The Optimum Design for Frictional Surface of Piston Ring of Engines

1999-05-03
1999-01-1526
Based on the principle of conjugate curve surface and the theory of hydrodynamic lubrication, the similar spherical spiral surface, which has the best lubrication effect, was obtained in the paper. Experiment show, this kind of frictional surface is lower 15% at power loss, and it is higher 13% at service life than the traditional frictional surface of piston ring, (such as barrel, stepped, cuneiform, rectangle and so on).
Technical Paper

Two-Dimensional In-Cylinder Flow Field in a Natural Gas Fueled Spark Ignition Engine Probed by Particle Tracking Velocimetry and Its Dependence on Engine Specifications

1999-05-03
1999-01-1534
An experimental study was made to investigate in-cylinder flow field in a natural gas fueled spark ignition engine and the effects of engine specifications on in-cylinder flow field. The instantaneous two-dimentional flow fields in a single-cylinder visualization engine, which has 75mm bore and 62mm stroke, were measured in various cross sections perpendicular to the cylinder axis by using the laser light sheet PTV method at various crank angles during intake, compression, and expansion strokes over the wide range of piston combustion chamber configuration, top clearance, and nominal swirl ratio. Flow fields during compression and expansion strokes were also calculated using KIVA2 simulation code for better understanding of the measured results. The results showed that induction-generated swirl is getting concentric to the cylinder center in compression stroke, and is shifted in the radial direction in expansion stroke.
Technical Paper

Gas Flows Through the Inter-Ring Crevice and Their Influence on UHC Emissions

1999-05-03
1999-01-1533
Influence of the inter-ring crevice, the volume between the top and second piston rings, on unburned hydrocarbon (UHC) emission was experimentally and numerically investigated. The ultimate goal of this study was to estimate the level of UHC emission induced by the blow-up of inter-ring mixture, i.e., unburned gases trapped in the inter-ring crevice. In the experiments, the inter-ring mixture was extracted to the crankcase during the late period of expansion and the early period of exhaust stroke through the engraved grooves on the lower part of cylinder wall. Extraction of the mixture resulted in the significant reductions of UHC emission in proportion to the increments of blowby flow rate, without any losses in efficiency and power. This experimental study has confirmed the importance of inter-ring crevice on UHC emission in an SI engine and established a relationship between the inter-ring mixture and UHC emission.
Technical Paper

The Adoption of SAE Aviation Piston Engine Oil Standards for Military Use

1999-04-20
1999-01-1566
This paper describes the final chapter of the military specifications for aviation piston engine lubricants. The adoption and evolution of the Society of Automotive Engineers (SAE) Standards J1966 and J1899 from their initial development in 1991 to the present is reviewed. It includes the fine-tuning and revisions of the technical requirements derived from experience gained in qualification programs conducted. Also included are notes regarding the overall commercial oil qualification process and the remaining role of the U.S. Navy for military use approvals
Technical Paper

Newton II Aircraft Powerplant Test Cell Mount

1999-04-20
1999-01-1580
The study of piston aircraft engines with the propeller mounted as the load has been restricted due to the equipment needed to measure the combination of instant engine torque and vibrational movements. This work details the development of an engine mount that has a torque sensitivity of less than 0.05 pound-feet for measuring horsepower, vibration forces, and torque. The hydraulic force measurement system used in the project is discussed and evaluated with the limitations encounter. A torque balance system that can be checked with primary weights for absolute accuracy was developed and described as well as the methods for determining instant vibrational forces and rotational stresses.
Technical Paper

Supercharged Homogeneous Charge Compression Ignition (HCCI) with Exhaust Gas Recirculation and Pilot Fuel

2000-06-19
2000-01-1835
In an attempt to extend the upper load limit for Homogeneous Charge Compression Ignition (HCCI), supercharging in combination with Exhaust Gas Recirculation (EGR) have been applied. Two different boost pressures were used, 1.1 bar and 1.5 bar. High EGR rates were used in order to reduce the combustion rate. The highest obtained IMEP was 16 bar. This was achieved with the higher boost pressure, at close to stoichiometric conditions and with approximately 50 % EGR. Natural gas was used as the main fuel. In the case with the higher boost pressure, iso-octane was used as pilot fuel, to improve the ignition properties of the mixture. This made it possible to use a lower compression ratio and thereby reducing the maximum cylinder pressure. The tests were performed on a single cylinder engine operated at low speed (1000 rpm). The test engine was equipped with a modified cylinder head, having a Variable Compression Ratio (VCR) mechanism.
Technical Paper

Performance and Emission Analysis of a Non-Conventional Gasoline Engine

2000-06-19
2000-01-1840
A new engine design concept, characterized by a single cylinder-double piston and a cycloid crank rotor instead of the conventional crankshaft has been developed recently by Gul & Co Development AB, Sweden. The rotor (crank disc) is equipped with an oval groove in the shape of a sinusoidal cycloid according to the expression varies from 0 to 1. Inside the oval groove a ball rolls/slides in order to transfer force from the piston to the rotor. Such a rotor contains groove surfaces for the valve movement control as well. Each turn of the rotor corresponds to four strokes for both the pistons. Thus, a full 4-stroke engine cycle is developed for a single non-conventional crankshaft revolution. Having the extra freedom to select an optimal piston movement, the new design is believed to have the potential to provide low emissions, low noise levels and lower fuel consumption. Therefore, it has been subjected to an engine thermodynamics simulation, to provide an insight to engine performance.
Technical Paper

In Search of the Perfect Ten - Piston Rating: The Complete Picture, the First Step to “Globalisation”

2000-06-19
2000-01-1816
Tasked by the Engine Lubricant Technical Committee (ELTC) of the Co-ordinating European Council (CEC), the Rating Steering Group (CEC SL071) and the Co-ordinating Research Council (CRC) Rating Advisory Panel have been working on the “Harmonisation” of rating methods within Europe. It has been recognised that during the last 40 years of product and technological advancements within the oil and additive industries the practical measurement of product performance has remained relatively unchanged. This paper reviews the current rating methods used within Europe and the benefits a single rating method could have on the future “Global” market place.
Technical Paper

Evaluation of Oil Performance Using the TU High Temperature Engine Test with a View to Extending Oil Drain Intervals

2000-06-19
2000-01-1822
The extension of engine oil drain intervals leads vehicle manufacturers to demand ever greater oil oxydation stability. These demands are evaluated by various tests, and particularly with the help of the ASTM III E and the CEC TU3 High Temperature engine test, which allow: the evolution of the viscosity during test to be observed the aptitude of the oil to avoid ring sticking to evaluated the merit rating of piston cleanliness to established (absence of deposits) This article aims to establish a correlation between the degradation of the engine oil in vehicle endurance and during theCEC TU3 High Temperature engine test on the test bench, and in high temperature laboratory tests. The results obtained on three types of oil (mineral, semi-synthetic and synthetic) while extending the oil drain intervals to 20 or 30000 km. As well as the oil thickening, the evolution of piston cleanliness during the vehicle endurance runs will be presented.
Technical Paper

Combustion Behavior Analysis in a Transparent Research Engine Equipped with a Common Rail Diesel Injection System

2000-06-19
2000-01-1825
This paper describes a preliminary characterization of in-cylinder spray and combustion behavior from a high-pressure common rail injection system. The engine used in the tests was a single-cylinder optical research diesel engine, adequately developed in a full-fired version, equipped with a common rail injection system. An elongated piston allows for the optical access to the combustion chamber for diagnostic applications. Characteristic of the optical engine is the availability to investigate different combustion system designs due to an interchangeable head-cylinder group. The system configuration tested in the present work corresponds to a four-cylinder engine of 1930 cc of displacement that is representative in the class of light duty d.i. diesel engine. Spray and combustion evolutions were visualized through a high-speed CCD camera synchronized with a copper vapor laser acting as light source.
Technical Paper

Dynamic EHL Film Thickness in Cam and Follower Contacts of Various Valve Lifts

2000-06-19
2000-01-1789
The resistance of driving forces in engine mainly comes from contact behaviors of many components such as piston skirt, piston rings, big-end or main bearings and other components of valve train system. The contact between cam and follower has one of the severest tribological behaviors in these components due to cyclic fluctuation of loads and sudden change of relative contacting speed. In order to verify the characteristics of frictional resistance and wear in these components, the investigation to find the minimum film thickness of these tribological components should be performed preferentially. This verification gives useful clue for better performance and endurance life of the whole engine system. In this investigation, the most important input parameters are the applied loads and the relative contacting velocities during the cycle. These parameters can be obtained from the simulation of kinematics and dynamics of valve train system.
Technical Paper

Prediction of Temperature, Viscosity and Thickness in Oil Film Between Ring and Liner of Internal Combustion Engine

2000-06-19
2000-01-1790
The temperature, the viscosity and the thickness in the oil film on the piston ring in internal combustion engines are predicted by using unsteady state two dimensional (2-D) thermohydrodynamics lubrication analysis, that is Reynolds equation and 2-D energy equation. The oil film temperature calculated using by unsteady state 2-D energy equation in which the heat generated from the viscous dissipation. The temperature distributions in the oil film are affected by the viscosity, the wall velocity and the oil film thickness and also the ring and liner surface temperatures, the convection and the conduction heat flow. The temperature of oil film increases with the increase of the engine speed for the viscous dissipation and there is an effect of unsteady term during near at the top dead center (TDC) and the bottom dead center (BDC). The viscosity by unsteady state analysis decreases with increase of the engine speed due to viscous dissipation.
Technical Paper

Oil Film Thickness Measurement and Analysis of a Three Ring Pack in an Operating Diesel Engine

2000-06-19
2000-01-1787
Oil film thicknesses of the piston top ring and the second ring of a truck diesel engine have been measured simultaneously by embedding capacitance type clearance sensors in the ring sliding surfaces. Owing to the above, several phenomena such as the variation in oil film thickness of each ring in one cycle, correlation between the rings, difference in oil film thickness between the thrust and counter thrust-sides, effects of engine operating conditions on oil film thickness, etc. have been determined. Efforts have been also made to analyze the causes of such phenomena according to the measured results of piston slap motion and ring motions, and the calculated results of oil film thickness.
Technical Paper

Development of a Piston Ring-Cylinder Bore Wear Model

2000-06-19
2000-01-1788
In an internal combustion engine, the wear in the piston ring/cylinder bore contact initially increases rapidly due to run-in and then attains a steady state during which the engine spends most of its useful life. This paper describes the development of an abrasive wear model for both cylinder bore and piston rings for the steady state period. The model took into account shear thinning of the lubricant, but it did not consider the effects of transient operations, geometry changes due to bore distortions, ring twist, ring motion, and corrosion. The model predicted the bore wear depth distribution from the top dead center (TDC) to the bottom dead center (BDC) and ring wear depth under different operating conditions. The maximum bore wear depth was predicted to occur at about 20 degrees after TDC where the combustion gas pressure reached its peak value. The model predicted an increase in bore and ring wear depth with increasing engine speed.
Technical Paper

An Investigation of Tribological Characteristics of Energy-Conserving Engine Oils Using a Reciprocating Bench Test

2000-06-19
2000-01-1781
Engine design and tribology engineers are constantly challenged to develop advanced products with reduced weight, reduced friction, longer life, and higher engine operating temperatures. The resulting engine systems must also meet more demanding emissions and fuel economy targets. Advanced energy-conserving lubricants and surface coatings are concurrently evolving to meet the needs of new engine materials. Because of the enormous cost and time associated with engine testing, much interest is being focused on the development of representative and repeatable bench tests for evaluation of engine materials and lubricants. The authors have developed a bench test employing reciprocating motion for evaluating friction and energy-conserving characteristics of lubricants.
Technical Paper

Piston Ring Cylinder Liner Scuffing Phenomenon Studies Using Acoustic Emission Technique

2000-06-19
2000-01-1782
In spite of being a popular topic in technical publications, scuffing between a piston ring face and the cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. The scuffing phenomenon described as the transfer of cylinder liner particles to piston ring surfaces due to inadequate lubrication and high temperature at top dead center could significantly decrease engine performance. The mechanism of scuffing origin and subsequent catastrophic seizure usually is evaluated by coefficient of friction measurements. The purpose of this paper is (1) to examine the usefulness of acoustic emission RMS measurements generated during testing that results from the friction between piston ring and cylinder liner segments and (2) to establish the relationship between such signals and different levels of the scuffing phenomenon.
Technical Paper

AVL SDIS Mk.II - Low Cost Automotive FI Applied to 2-Stroke Engines for Future CARB - Regulations

1999-09-28
1999-01-3285
The basic Semi-Direct-Injection System (SDIS) which is already in production for PWC and applied to small 2-wheeler engines features a low-pressure fuel injection system injecting through the rear scavenge port window in the cylinder symmetry plane onto the piston crown. The patented new SDIS Mk.II System [1] injects through an (additional) scavenge port window that is positioned above the scavenge ports and is controlled by a window in the piston skirt. This new arrangement allows longer injection duration and also other injector positions and directions. A CFD simulation by AVL's FIRE-CFD-code with moving piston and exhaust gas dynamics compares the different injector positions and directions for WOT and rated speed and for a part throttle low speed case. The SDIS Mk.II injection system consists of mass-produced automotive parts thus giving a low cost approach for present 2-stroke engines requiring only moderate engine modifications.
Technical Paper

Fuel Distribution and Mixture Formation Inside a Direct Injection SI Engine Investigated by 2D Mie and LIEF Techniques

1999-10-25
1999-01-3659
Two-dimensional Mie and LIEF techniques were applied to investigate the spray propagation, mixture formation and charge distribution at ignition time inside the combustion chamber of a direct injection SI engine. The results obtained provide the propagation of liquid fuel relative to the piston motion and visualize the charge distribution (liquid fuel and fuel vapor) throughout the engine process. Special emphasis was laid on the charge distribution at ignition time for stratified charge operation. By means of a LIEF technique it was possible to measure cyclic fluctuations in the fuel vapor distributions which explain the occurrence of misfiring.
Technical Paper

Further Experiments on the Effects of In-Cylinder Wall Wetting on HC Emissions from Direct Injection Gasoline Engines

1999-10-25
1999-01-3661
A recently developed in-cylinder fuel injection probe was used to deposit a small amount of liquid fuel on various surfaces within the combustion chamber of a 4-valve engine that was operating predominately on liquefied petroleum gas (LPG). A fast flame ionization detector (FFID) was used to examine the engine-out emissions of unburned and partially-burned hydrocarbons (HCs). Injector shut-off was used to examine the rate of liquid fuel evaporation. The purpose of these experiments was to provide insights into the HC formation mechanism due to in-cylinder wall wetting. The variables investigated were the effects of engine operating conditions, coolant temperature, in-cylinder wetting location, and the amount of liquid wall wetting. The results of the steady state tests show that in-cylinder wall wetting is an important source of HC emissions both at idle and at a part load, cruise-type condition. The effects of wetting location present the same trend for idle and part load conditions.
Technical Paper

Numerical Study of Fuel/Air Mixture Preparation in a GDI Engine

1999-10-25
1999-01-3657
Numerical simulations are performed to investigate the fuel/air mixing preparation in a gasoline direct injection (GDI) engine. A two-valve OHV engine with wedge combustion chamber is investigated since automobiles equipped with this type of engine are readily available in the U.S. market. Modifying and retrofitting these engines for GDI operation could become a viable scenario for some engine manufactures. A pressure-swirl injector and wide spacing injection layout are adapted to enhance mixture preparation. The primary interest is on preparing the mixture with adequate equivalence ratio at the spark plug under a wide range of engine operating conditions. Two different engine operating conditions are investigated with respect to engine speed and load. A modified version of the KIVA-3V multi-dimensional CFD code is used. The modified code includes the Linearized Instability Sheet Atomization (LISA) model to simulate the development of the hollow cone spray.
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