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Lowering lubricant viscosity to reduce friction generally carries a side-effect of increased metal-metal contact in mixed or boundary lubrication, for example near top ring reversal along the engine cylinder liner. A strategy to reduce viscosity without increased metal-metal contact involves controlling the local viscosity away from top-ring-reversal locations. This paper discusses the implementation of insulation or thermal barrier coating (TBC) as a means of reducing local oil viscosity and power cylinder friction in internal combustion engines with minimal side-effects of increased wear. TBC is selectively applied to the outside diameter of the cylinder liner to increase the local oil temperature along the liner. Due to the temperature dependence of oil viscosity, the increase in temperature from insulation results in a decrease in the local oil viscosity.

Signals indicative of in-cylinder combustion have been under investigation for the control of diesel engines to meet stringent emission standards and other production targets in performance and fuel economy. This paper presents the results of an investigation on the use of the ion current signal for the close loop control of a heavy duty four cylinder turbocharged diesel engine equipped with a common rail injection system. A correlation is developed between the start of ion current signal (SIC) and the location of the peak of premixed combustion (LPPC) in the rate of heat release trace. Based on this correlation, a PID closed loop controller is developed to adjust the injection timing for proper combustion phasing under steady and transient engine operating conditions.

A novel approach to condition the lubricant at a fixed station in the oil circuit is explored as a potential means to reduce additive requirements or increase oil drain interval. This study examines the performance of an innovative oil filter which releases no additives into the lubricant, yet enhances the acid control function typically performed by detergent and dispersant additives. The filter chemically conditions the crankcase oil during engine operation by sequestering acidic compounds derived from engine combustion and lubricant degradation. Long duration tests with a heavy-duty diesel engine show that the oil conditioning with the strong base filter reduces lubricant acidity (TAN), improves Total Base Number (TBN) retention, and slows the rate of viscosity increase and oxidation. The results also indicate that there may be a reduction in wear and corrosion.

The challenge posed by the long run times necessary to accurately quantify ash effects on diesel aftertreatment systems has led to numerous efforts to artificially accelerate ash loading, with varying degrees of success. In this study, a heavy-duty diesel engine was outfitted with a specially designed rapid lubricant degradation and aftertreatment ash loading system. Unlike previous attempts, the proposed methodology utilizes a series of thermal reactors and combustors to simulate all three major oil consumption mechanisms, namely combustion in the power cylinder, evaporative and volatile losses, and liquid losses through the valve and turbocharger seals. In order to simulate these processes, each thermal reactor allows for the precise control of the level of lubricant additive degradation, as well as the form and quantity of degradation products introduced into the exhaust upstream of the aftertreatment system.

EGR is a proven technology used to reduce NOx formation in both compression and spark ignition engines by reducing the combustion temperature. In order to further increase its efficiency the recirculated gases are subjected to cooling. However, this leads to a higher load on the cooling system of the engine, thus requiring a larger radiator. In the case of turbocharged engines the large variations of the pressures, especially in the exhaust manifold, produce a highly pulsating EGR flow leading to non-steady-state heat transfer in the cooler. The current research presents a method of determining the pulsating flow field and the instantaneous heat transfer in the EGR heat exchanger. The processes are simulated using the CFD code FIRE (AVL) and the results are subjected to validation by comparison with the experimental data obtained on a 2.5 liter, four cylinder, common rail and turbocharged diesel engine.

The focus of this study is to determine the effect of using B-20 (a blend of 20% soybean methyl ester biodiesel and 80% ultra low sulfur diesel fuel) on the combustion process, performance and exhaust emissions in a High Speed Direct Injection (HSDI) diesel engine equipped with a common rail injection system. The engine was operated under simulated turbocharged conditions with 3-bar indicated mean effective pressure and 1500 rpm engine speed. The experiments covered a wide range of injection pressures and EGR rates. The rate of heat release trace has been analyzed in details to determine the effect of the properties of biodiesel on auto ignition and combustion processes and their impact on engine out emissions. The results and the conclusions are supported by a statistical analysis of data that provides a quantitative significance of the effects of the two fuels on engine out emissions.

The objective of this work is to develop a strategy to reduce the penalties in the diesel engine performance, fuel economy and HC and CO emissions, associated with the operation in the low temperature combustion regime. Experiments were conducted on a research high speed, single cylinder, 4-valve, small-bore direct injection diesel engine equipped with a common rail injection system under simulated turbocharged conditions, at IMEP = 3 bar and engine speed = 1500 rpm. EGR rates were varied over a wide range to cover engine operation from the conventional to the LTC regime, up to the misfiring point. The injection pressure was varied from 600 bar to 1200 bar. Injection timing was adjusted to cover three different LPPCs (Location of the Peak rate of heat release due to the Premixed Combustion fraction) at 10.5° aTDC, 5 aTDC and 2 aTDC. The swirl ratio was varied from 1.44 to 7.12. Four steps are taken to move from LTC to ALTC.

In this study, changes in the composition of lubricant additives in the power cylinder oil are examined. Samples are extracted from a single cylinder heavy-duty diesel engine in two locations during engine operation; the crankcase and the top ring groove of the piston. Emissions of lubricant-derived ash-forming elements are lower than would be expected based on oil consumption and crankcase oil composition. This occurs partly because the inorganic additive compounds are less volatile than light-end hydrocarbons in the base oil. The tribology of the piston ring pack also affects the composition of the oil consumed in the power cylinder system. The elemental composition of oil extracted from the top ring groove is significantly different than the crankcase oil. Additive metals are concentrated in the top ring groove of the power cylinder. Detergent compounds (i.e. Ca and Mg) concentrate due to the volatility of the base oil. The metals associated with ZDDP (i.e.

One of the most challenging problems in diesel engines is to reduce unburned HC emissions that appear as (white smoke) during cold starting. In this paper the research is carried out on a 4-cylinder diesel engine with a common rail fuel injection system, which is able to deliver multiple injections during cold start. The causes of combustion failure at lower temperature limits are investigated theoretically by considering the rate of heat release. The results of this clearly indicate that in addition to low cranking engine speed, heat transfer and blow-by losses at lower ambient temperatures, fuel injection events would contribute to the failure of combustion. Also, combustion failure takes place when the compression temperature is lower than some critical value. Based on these results, split-main injection strategy was applied during engine cold starting and validated by experiments in a cold room at lower ambient temperatures.

This paper presents tribological modeling, experimental work, and validation of tribology parameters of a single cylinder turbocharged diesel engine run at various loads, speeds, intake boost pressures, and cylinder liner temperatures. Analysis were made on piston rings and liner materials, rings mechanical and thermal loads, contact pressure between rings and liner, and lubricant conditions. The engine tribology parameters were measured, and used to validate the engine tribology models. These tribology parameters are: oil film thickness, coefficient of friction between rings and liner, friction force, friction power, friction torque, shear rate, shear stress and wear of the sliding surfaces. In order to measure the oil film thickness between rings and liner, a single cylinder AVL turbocharged diesel engine was instrumented to accept the difference in voltage drop method between rings, oil film, and liner.

Thermal barrier coatings (TBC) are perceived as enabling technology to increase low heat rejection (LHR) diesel engine performance and improve its longevity. The state of the art of thermal barrier coating is the plasma spray zirconia. In addition, other material systems have been investigated for the next generation of thermal barrier coatings. The purpose of this TBC program is to focus on developing binder systems with low thermal conductivity materials to improve the coating durability under high load and temperature cyclical conditions encountered in the real engine. Research and development (R&D) and analysis were conducted on aluminum alloy piston for high output turbocharged diesel engine coated with TBC.

Adiabatics, Inc., with the support of the U.S. Army Tank Automotive Research & Development Engineering Center (TARDEC) has developed a low cost, durable ceramic composite cylinder bore coating for diesel engines operating under severe conditions. This bore coating is a ceramic composite consisting primarily of Iron Oxide, Iron Titanate and Partially Stabilized Zirconia. It is applied by unique chemical thermal bonding technology developed at Adiabatics, Inc. and is referred to as Low Temperature Iron Titanate (LTIT). This coating has been tested against a wide range of cylinder bore treatments ranging from hard chrome plate to hard Nickel Silicon Carbide (NikaSil) and found to provide a superior sliding wear surface. It is superior because it is compatible against most common piston ring materials and coatings.

The simulation of I.C. Engines operation, especially during transients, requires a fairly accurate estimation of the internal mechanical losses of the engine. The paper presents generic friction models for the main friction components of the engine (piston-ring-liner assembly, bearings and valve train), considering geometry of the engine parts and peculiarities of the corresponding lubrication processes. Separate models for the mechanical losses introduced by the injection system, oil and water pumps are also developed. All models are implemented as SIMULINK modules in a complex engine simulation code developed in SIMULINK and capable to simulate both steady state and transient operating conditions. Validation is achieved by comparison with measurements made on a four cylinder, common rail diesel engine, on a test bench capable to run controlled transients.

Frictional losses in the piston ring-pack of an engine account for approximately half of the total frictional losses within the power cylinder of an engine. Three-dimensional honing groove texture was modeled, and its effect on piston ring-pack friction and engine brake thermal efficiency was investigated. Adverse effects on engine oil consumption and durability were also considered. Although many non-conventional cylinder liner finishes are now being developed to reduce friction and oil consumption, the effects of surface finish on ring-pack performance is not well understood. A rough surface flow simulation program was developed to calculate flow and stress factors that adjust the solution of the Reynolds equation for the effects of surface roughness as has been done in the literature. Rough surface contact between the ring and liner was modeled using a previously published methodology for asperity contact pressure estimation between rough surfaces.

As a part of the effort to comply with increasingly stringent emission standards, engine manufacturers strive to minimize engine oil consumption. This requires the advancement of the understanding of the characteristics, sources, and driving mechanisms of oil consumption. This paper presents a combined theoretical and experimental approach to separate and quantify different oil consumption sources in a production spark ignition engine at different speed and load conditions. A sulfur tracer method was used to measure the dependence of oil consumption on engine operating speed and load. Liquid oil distribution on the piston was studied using a Laser-Induced-Fluorescence (LIF) technique. In addition, important in-cylinder parameters for oil transport and oil consumption, such as liner temperatures and land pressures, were measured.

The disturbances in the cylinder gas pressure trace caused by combustion in internal combustion engines have an impact on the shape of the rate of heat (energy) release (RHR). It is necessary to smooth the pressure trace before carrying out the RHR calculations and making any interpretations for the combustion process. Different smoothing methods are analyzed and their features compared. Furthermore, the selection of the smoothing starting point and its effect on the smoothing quality of pressure data are described. The Fast Fourier Transform (FFT) analysis is applied to determine the frequency of the disturbances in power spectrum and obtain the optimal specified smoothing parameter (SSP). The experimental data was obtained on a single-cylinder research diesel engine, running under simulated turbocharged steady state conditions. The experiments covered a wide range of engine operating parameters such as injection pressures, injection timing, and EGR ratios.

Adiabatics, Inc. with the support of the U.S. Army Tank Automotive & Armaments Command has examined the feasibility of using Diamond Like Carbon (DLC) films and Iron Titanate (Fe2TiO5 or IT) for sliding contact surfaces in Low Heat Rejection (LHR) diesel engines. DLCs have long been a popular candidate for use in sliding contact tribo-surfaces where a perceived reduction of friction losses will result in increased engine efficiency [1]. There exists a broad range of technologies for applying DLC films. This paper examines several types of these technologies and their future application to automotive internal combustion engines. Our work focuses upon DLC use for LHR military diesel engines where operating temperatures and pressures are higher than conventional diesel engines. However, a direct transfer of this technology to automotive diesel or gasoline engines exists for these thin films.

The paper analyses the particularities of the lubricating conditions at the contact between the cam and a flat tappet in the valve train of an internal combustion engine and develops a method for the calculation of the friction force. The existing lubrication models show the predominance of the entraining speed and oil viscosity on the thickness of the oil film entrapped between cam and tappet, predicting a very small value (less than 0.1 μm) of the oil film thickness (OFT). The oil viscosity increases exponentially with pressure in the Hertzian contact, determining non-Newtonian behavior of the oil in the contact zone. Using the model developed by Greenwood and Tripp [11] for the contact of two rough surfaces and the Eyring model [2] for the oil it is shown that non-Newtonian behavior of the oil prevails and that the OFT plays a secondary role on the friction force.

Diesel engine cold-start problems include long cranking periods, hesitation and white smoke emissions. A better understanding of these problems is essential to improve diesel engine cold-start. In this study computer simulation model is developed for the steady state and transient cold starting processes in a single-cylinder naturally aspirated direct injection diesel engine. The model is verified experimentally and utilized to determine the key parameters that affect the cranking period and combustion instability after the engine starts. The behavior of the fuel spray before and after it impinges on the combustion chamber walls was analyzed in each cycle during the cold-start operation. The analysis indicated that the accumulated fuel in combustion chamber has a major impact on engine cold starting through increasing engine compression pressure and temperature and increasing fuel vapor concentration in the combustion chamber during the ignition delay period.

Integrated control strategies for the O.P.E.R.A.S. (Optimization of injection Pressure, EGR ratio, injection Retard or Advance and Swirl ratio) are demonstrated. The strategies are based on an investigation of combustion and emissions in a small bore, high speed, direct injection diesel engine. The engine is equipped with a common rail injection system and is tested under simulated turbocharged engine conditions at two loads and speeds that represent two key operating points in a medium size HEV vehicle. A new phenomenological model is developed for the fuel distribution in the combustion chamber and the fractions that are injected prior to the development of the flame, injected in the flame or deposited on the walls. The investigation covered the effect of the different operating parameters on the fuel distribution, combustion and engine-out emissions.