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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.

The number of control actuators available on spark-ignition engines is rapidly increasing to meet demand for improved fuel economy and reduced exhaust emissions. The added complexity greatly complicates control strategy development because there can be a wide range of potential actuator settings at each engine operating condition, and map-based actuator calibration becomes challenging as the number of control degrees of freedom expand significantly. Many engine actuators, such as variable valve actuation and flow control valves, directly influence in-cylinder combustion through changes in gas exchange, mixture preparation, and charge motion. The addition of these types of actuators makes it difficult to predict the influences of individual actuator positioning on in-cylinder combustion without substantial experimental complexity.

The transient cone angle of pressure swirl sprays from injectors intended for use in gasoline direct injection engines was measured from 2D Mie scattering images. A variety of injectors with varying nominal cone angle and flow rate were investigated. The general cone angle behavior was found to correlate well qualitatively with the measured fuel line pressure and was affected by the different injector specifications. Experimentally measured modulations in cone angle and injection pressure were forced on a comprehensive spray simulation to understand the sensitivity of pulsating injector boundary conditions on general spray structure. Ignoring the nozzle fluctuations led to a computed spray shape that inadequately replicated the experimental images; hence, demonstrating the importance of quantifying the injector boundary conditions when characterizing a spray using high-fidelity simulation tools.

Contrary to the thick thermal barrier coating approach used in adiabatic diesel engines, the authors have investigated the merits of thin coatings. Transient heat transfer analysis indicates that the temperature swings experienced at combustion chamber surfaces depend primarily on material thermophysical properties, i.e., conductivity, density, and specific heat. Thus, cyclic temperature swings should be alike whether thick or thin (less than 0.25 mm) coatings are applied, Furthermore, thin coatings would lead to lower mean component temperatures and would be easier to apply than thick coatings. The thinly-coated engine concept offers several advantages including improved volumetric efficiency, lower cylinder liner wall temperatures, improved piston-liner tribological behavior, and improved erosion-corrosion resistance and thus greater component durability.

High thermal stresses in the cylinder heads of low heat rejection (LHR) engines can lead to low cycle fatigue failure in the head. In order to decrease these stresses to a more acceptable level, novel designs are introduced. One design utilizes scallops in the bridge area, and three others utilize a high-strength, low thermal conductivity titanium faceplate inserted into the firedeck (combustion face) of a low heat rejection engine cylinder head. The faceplates are 5mm thick disks that span the firedeck from the injector bore to approximately 10mm outside of the cylinder liner. Large-scale finite element models for these four different LHR cylinder head configurations were created, and used to evaluate their strength performance on a pass/fail basis. The complex geometry of this cylinder head required very detailed three-dimensional analysis techniques, especially in the valve bridge area. This area is finely meshed to allow for accurate determination of stress gradients.

The future of maintaining a superior mobile military ground vehicle fleet rests in high power density propulsion systems. As the U.S. Government desires to convert its powerplant base to heavy fuel operation, there arises the opportunity to incorporate new advanced materials into these heavy fuel engines. These newer materials serve the purpose of decreasing powerplant weight and develop new component designs to take advantage of improved strength and temperature capability of those materials. In addition, the military continues the effort for a non-watercooled Low Heat Rejection (LHR) diesel engine. This type of engine demands the use of ceramic and advanced ceramic composite material hardware. Furthermore, today's higher pressure fuel injection systems, coupled with reduced air/fuel ratio as a means of increasing horsepower to size and weight, will require thermal protection or change in material specification for many of the engine's components.

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.

When automobile hydrocarbons are exhausted into the atmosphere in the presence of NOx and sunlight, ground-level ozone is formed. While researchers have used Maximum Incremental Reactivity (MIR) factors to estimate ozone production, this procedure often overestimates Local Ozone Production (LOP) because it does not consider local atmospheric conditions. In this paper, an enhanced MIR methodology for estimating actual LOP attributable to a vehicle in a particular ozone problem area is presented. In addition to using tabulated MIR factors, the procedure also uses local hydrocarbon reaction terms and a relative mechanistic reactivity term that account for local atmospheric conditions. Through this approach, the effects of hydrocarbon reaction rates, hydrocarbon residence times, and prevailing HC/NOx ratio are accounted for. The procedure is intended to enable automotive engineers to more realistically estimate actual local ozone production resulting from hydrocarbon emissions.

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 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.

Adjusting the Residual Gas Fraction (RGF) by means of Variable Valve Actuation (VVA) is a strong candidate for controlling the ignition timing in Homogeneous Charge Compression Ignition (HCCI) engines. However, at high levels of residual gas fraction, insufficient mixing can lead to the presence of considerable temperature and composition variations. This paper extends previous modeling efforts to include the effect of RGF distribution on the onset of ignition and the rate of combustion using a multi-dimensional fluid mechanics code (KIVA-3V) sequentially with a multi-zone code with detailed chemical kinetics. KIVA-3V is used to simulate the gas exchange processes, while the multi-zone code computes the combustion event. It is shown that under certain conditions the effect of composition stratification is significant and cannot be captured by a single-zone model or a multi-zone model using only temperature zones.

A long-distance microscope with pulse-laser as optical shutter up to 25kHz was used to magnify the diesel spray at the nozzle hole vicinity onto 35-mm photographic film through a still or a high-speed drum camera. The injectors examined are high-pressure valve-covered-orifice (VCO) nozzles, from unit injector and common rail injection systems. For comparison, a mini-sac injector from a hydraulic unit injector is also investigated. A phase-Doppler particle analyzer (PDPA) system with an external digital clock was also used to measure the droplet size, velocity and time of arrival relative to the start of the injection event. The visualization results provide very interesting and dynamic information on spray structure, showing spray angle variations, primary breakup processes, and spray asymmetry not observed using conventional macroscopic visualization techniques.

A combined experimental and analytical approach was followed in this work to study stress distributions and causes of failure in diesel cylinder heads under steady-state and transient operation. Experimental studies were conducted first to measure temperatures, heat fluxes and stresses under a series of steady-state operating conditions. Furthermore, by placing high temperature strain gages within the thermal penetration depth of the cylinder head, the effect of thermal shock loading under rapid transients was studied. A comparison of our steady-state and transient measurements suggests that the steady-state temperature gradients and the level of temperatures are the primary causes of thermal fatigue in cast-iron cylinder heads. Subsequently, a finite element analysis was conducted to predict the detailed steady-state temperature and stress distributions within the cylinder head. A comparison of the predicted steady-state temperatures and stresses compared well with our measurements.

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.

This paper investigates theoretically the benefits of the Miller cycle diesel engine with and without low heat rejection on thermodynamic efficiency, brake power, and fuel consumption. It further illustrates the effectiveness of thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model which includes a friction model is used to estimate the overall improvement in engine performance. Miller cycle is accomplished by closing the intake valve late and the engine components are coated with PSZ for low heat rejection. A significant improvement in brake power and thermal efficiency are observed.

Experimental results focused towards developing tribological surface coatings coupled with liquid lubricant boundary layer effects, for advanced high temperature military diesel engine applications are presented. The primary focus of this work is in the area of advanced, low heat rejection (LHR) high output diesel engines, where high temperature boundary lubrication between the piston ring and the cylinder liner wall surface is critical for successful engine operation. The target temperature focused upon in our research is an operating top ring reversal (TRR) temperature of approximately 538°C. The technology advancement used for this application involves treating porous iron oxide/titanium oxide (Fe2O3/TiO2) and molybdenum (Mo) based composite thermal sprayed coatings with chemical binders to improve coating strength, integrity, and tribological properties. This process dramatically decreases open porosity to form an almost monolithic appearing coating at the surface1.

A naturally-aspirated, Miller cycle, Spark-Ignition (SI) engine that controls output with variable intake valve closure is compared to a conventionally-throttled engine using computer simulation. Based on First and Second Law analyses, the two load control strategies are compared in detail through one thermodynamic cycle at light load conditions and over a wide range of loads at 2000 rpm. The Miller Cycle engine can use late intake valve closure (LIVC) to control indicated output down to 35% of the maximum, but requires supplemental throttling at lighter loads. The First Law analysis shows that the Miller cycle increases indicated thermal efficiency at light loads by as much as 6.3%, primarily due to reductions in pumping and compression work while heat transfer losses are comparable.

The paper analyses the friction in the valve train of an internal combustion engine trying to separate the contribution of the different components to the total friction losses in the valve train. The measurements are performed on a running engine in order to avoid extraneous factors introduced by simulating rigs. The experimental engine is instrumented with strain gauge bridges on the rocker arm, the push rod and the camshaft to measure forces and moments acting on these components. Original techniques are developed to isolate and determine the friction forces between the valve stem and its guide, the friction force in the rocker arm bearing and the combined friction between cam/tappet and tappet/bore. It was found that the friction in the rocker arm bearing never reaches hydrodynamic conditions and that the friction coefficient between cam and tappet reduces with an increase in the engine speed.

Fuel wall impingement commonly occurs in small-bore diesel engines. Particularly during engine starting, when wall temperatures are low, the evaporation rate of fuel film remaining from previous cycles plays a significant role in the autoignition process that is not fully understood. Pre-injection chemiluminescence (PIC), resulting from low-temperature oxidation of evaporating fuel film and residual gases, was measured over 3200 μsec intervals at the end of the compression strokes, but prior to fuel injection during a series of starting sequences in an optical diesel engine. These experiments were conducted to determine the effect of this parameter on combustion phasing and were conducted at initial engine temperatures of 30, 40, 50 and 60°C, at swirl ratios of 2.0 and 4.5 at 1000 RPM. PIC was determined to increase and be highly correlated with combustion phasing during initial cycles of the starting sequence.

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.