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An experimental technique termed the Instantaneous IMEP Method has been developed to measure piston and ring assembly friction. The technique requires very accurate measurements of cylinder pressure, connecting rod force and calculation of inertial forces. Friction force is the difference of these forces in consideration of the slider-crank geometry. A grasshopper linkage has been used to transmit the connecting rod force signal measured by a strain gage bridge. Inertial forces have been calculated with the assumption of distributed connecting rod mass. The test engine was a Chevrolet 5 litre V-8, modified for single cylinder operation. Piston and ring assembly friction has been determined under motoring conditions with and without compression as well as firing. Friction measurements have been made with SAE 30 and 50 grade oils at different temperatures. Boundary friction has been observed especially near top and bottom dead centers.

The Instantaneous IMEP method has been used to measure piston and ring assembly friction in a production Chevrolet 1.8 litre L-4 and a 5 litre V-8 engine modified for single-cylinder operation. Friction measurements are reported at different loads and speeds up to 1640 RPM under firing and motoring conditions with various oils and before and after break-in of the oil ring. Oils used were SAE viscosity grades 30, 50 and 30 with a friction modifier. Differences were found between motoring and firing friction, especially on the power and exhaust strokes. These differences diminished at higher speeds and lower loads where lubrication was more hydrodynamic. Differences in response to viscosity and friction modifier changes were noted between the two engines.

HEAT BALANCE STUDIES were conducted on a 1975 production 5.74ℓ V-8 and an experimental 3.69ℓ V-6 to determine sources of fuel economy differences when they were installed in a vehicle. Heat balance results, friction and fuel economy were explored during dynamometer tests simulating road load. Comparisons were made with and without certain emission control features. With comparable calibrations, the road load indicated efficiency was nearly the same for each engine as it would be installed in a vehicle with an appropriate axle ratio. The results suggest that engine friction and not combustion efficiency accounted for the major fuel economy difference.

This paper describes the friction characteristics of a 1.8 Litre J-car piston and ring assembly as influenced by oil rings of conventional design, but of varying tensions. In addition, the piston-ring assembly friction characteristics are reported for a set of oil viscosities ranging from 2 to 20 cSt with and without a molybdenum friction modifier. Multigrade oil results are shown also. Finally comparisons are presented between changes in friction measured by the Instantaneous IMEP Method and those measured by the dynamometer for the engine as a whole. Our results show large differences in piston-ring assembly friction as oil ring tension was varied. However, these differences became moderate after the oil ring broke-in. Both high and low oil viscosities increased piston and ring assembly friction. The friction modifier was most effective with a mid-range viscosity and provided virtually no benefit at viscosity extremes.

A two-dimensional finite element program has been developed to analyze the transient heat flow paths in low-heat-rejection engine combustion chambers. This analysis tool is used to study the transient heat transfer performance of a ceramic-coated piston with steel-alloy rings reciprocating within a ceramic-coated iiner at a speed of 1900 revolutions per minute. Throughout the cycle, the instantaneous boundaries of the combustion chamber are defined based on the position of the piston against the liner. Then, appropriate boundary conditions are applied to the component surfaces at every instant. Instantaneous piston and liner temperature distributions, heat transfer rates from the working fluid to these two components, as well as heat transfer rates between the two components are calculated by the program. The results are compared against the performance of a baseline cast-iron piston-liner assembly.

A new bench tester for laboratory simulation of piston ring and cylinder wear has been developed. Tests are made using liner segments which bear against a reciprocating piston ring. Temperatures up to 550°C, and loads and speeds representative of the most severe top ring conditions may be imposed. A precision oil spray system delivers the desired quantity and quality of oil to the wear interface. The computer controlled simulator duplicates the desired test cycle, and displays and stores data on friction forces and friction coefficients as the test proceeds. In this paper results are presented from the simulator for production and prototype ring and liner combinations, including ceramic coatings for potential use in advanced diesel engines. The importance of the method of oil delivery on test repeatability is emphasized. Some comparisons with Cameron Plint bench tests and firing engine results are presented.

The piston and ring assembly friction of a lightweight piston with lower compression height has been compared to that of a production assembly. Additional weight was added to the lightweight piston to study the effect of that variable alone. The lightweight piston reduced friction, especially in motoring tests. Within the speed range tested (up to 1640 rpm) the friction reduction of the lightweight piston could not be attributed to the lower mass itself.

Predicting the effects of transient heat conduction in low-heat-rejection engine components have been analyzed by applying instantaneous boundary conditions throughout a diesel engine thermodynamic cycle. This paper describes the advantages and disadvantages of one-dimensional finite difference and two-dimensional finite element methods by analyzing simple and complicated geometries like diesel bowl-in pistons. Also the performance characteristics of plasma sprayed zirconia, partially stabilized zirconia, and a monolithic reaction bonded silicon nitride ceramic materials are discussed and compared. Finite element studies have indicated that the steep temperature gradients associated with cyclic temperature swings in excess of 400 K may contribute to the failure of ceramic coatings near the corner joining the surface of the piston and the surface of the bowl for bowl-in pistons.

This study presents a systematic methodology for performing transient heat release analysis in a diesel engine. Novel techniques have been developed to infer the mass of air trapped in the cylinder and the mass of fuel injected on a cycle-by-cycle basis. The cyclic mass of air trapped in the cylinder is found accounting for pressure gradients, piston motion and short-circuiting during the valve overlap period. The cyclic mass of fuel injected is computed from the injection pressure history. These parameters are used in conjunction with cycle-resolved pressure data to accurately define the instantaneous thermodynamic state of the mixture. This information is used in the calculation and interpretation of transient heat release profiles.

This paper presents an overview of techniques for measuring friction using bench tests and fired engines. The test methods discussed have been developed to provide efficient, yet realistic, assessments of new component designs, materials, and lubricants for in-cylinder and overall engine applications. A Cameron-Plint Friction and Wear Tester was modified to permit ring-in-piston-groove movement by the test specimen, and used to evaluate a number of cylinder bore coatings for friction and wear performance. In a second study, it was used to evaluate the energy conserving characteristics of several engine lubricant formulations. Results were consistent with engine and vehicle testing, and were correlated with measured fuel economy performance. The Instantaneous IMEP Method for measuring in-cylinder frictional forces was extended to higher engine speeds and to modern, low-friction engine designs.

This work presents the development, validation and use of a SIMULINK integrated vehicle system simulation composed of engine, driveline and vehicle dynamics modules. The engine model links the appropriate number of single-cylinder modules, featuring thermodynamic models of the in-cylinder processes with transient capabilities to ensure high fidelity predictions. A detailed fuel injection control module is also included. The engine is coupled to the driveline, which consists of the torque converter, transmission, differential and prop shaft and drive shafts. An enhanced version of the point mass model is used to account for vehicle dynamics in the longitudinal and heave directions. A vehicle speed controller replaces the operator and allows the feed-forward simulation to follow a prescribed vehicle speed schedule.

An integrated vehicle system simulation has been developed to take advantage of advances in physical process and component models, flexibility of graphical programming environments (such as MATLAB-SIMULINK), and ever increasing capabilities of engineering workstations. A comprehensive, transient model of the multi-cylinder engine is linked with models of the torque converter, transmission, transfer case and differentials. The engine model is based on linking the appropriate number of single-cylinder modules, with the latter being thermodynamic models of the in-cylinder processes with built-in physical sub-models and transient capabilities to ensure high fidelity predictions. Either point mass or multi-body vehicle dynamics models can be coupled with the powertrain module to produce the ground vehicle simulation.

A key element to achieving vehicle emission certification for most light-duty vehicles using spark-ignition engine technology is prompt catalyst warming. Emission mitigation largely does not occur while the catalyst is below its “light-off temperature”, which takes a certain time to achieve when the engine starts from a cold condition. If the catalyst takes too long to light-off, the vehicle could fail its emission certification; it is necessary to minimize the catalyst warm up period to mitigate emissions as quickly as possible. One technique used to minimize catalyst warm up is to calibrate the engine in such a way that it delivers high temperature exhaust. At idle or low speed/low-load conditions, this can be done by retarding spark timing with a corresponding increase in fuel flow rate and / or leaning the mixture. Both approaches, however, encounter limits as combustion stability degrades and / or nitrogen oxide emissions rise excessively.

Exhaust gas recirculation (EGR) coolers are commonly used in diesel engines to reduce the temperature of recirculated exhaust gases in order to reduce NOX emissions. Engine coolant is used to cool EGR coolers. The presence of a cold surface in the cooler causes fouling due to particulate soot deposition, condensation of hydrocarbon, water and acid. Fouling experience results in cooler effectiveness loss and pressure drop. In this study, possible soot deposition mechanisms are discussed and their orders of magnitude are compared. Also, probable removal mechanisms of soot particles are studied by calculating the forces acting on a single particle attached to the wall or deposited layer. Our analysis shows that thermophoresis in the dominant mechanism for soot deposition in EGR coolers and high surface temperature and high kinetic energy of soot particles at the gas-deposit interface can be the critical factor in particles removal.

The often-observed differences in nitrogen oxides, or NOx, emissions between biodiesel and petroleum diesel fuels in diesel engines remain intense topics of research. In several instances, biodiesel-fuelled engines have higher NOx emissions than petroleum-fuelled engines; a situation often referred to as the "biodiesel NOx penalty." The literature is rich with investigations that reveal many fundamental mechanisms which contribute to (in varying and often inverse ways) the manifestation of differences in NOx emissions; these mechanisms include, for example, differences in ignition delay, changes to in-cylinder radiation heat transfer, and unequal heating values between the fuels. In addition to fundamental mechanisms, however, are the effects of "system-response" issues.

EGR coolers are mainly used on diesel engines to reduce intake charge temperature and thus reduce emissions of NOx and PM. Soot and hydrocarbon deposition in the EGR cooler reduces heat transfer efficiency of the cooler and increases emissions and pressure drop across the cooler. They may also be acidic and corrosive. Fouling has been always treated as an approximate factor in heat exchanger designs and it has not been modeled in detail. The aim of this paper is to look into fouling formation in an EGR cooler of a diesel engine. A 1-D model is developed to predict and calculate EGR cooler fouling amount and distribution across a concentric tube heat exchanger with a constant wall temperature. The model is compared to an experiment that is designed for correlation of the model. Effectiveness, mass deposition, and pressure drop are the parameters that have been compared. The results of the model are in a good agreement with the experimental data.