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Spark-plug lifetime is limited by the ability of the ignition coil to generate a spark channel. Electrode erosion during operation causes the geometry to deform and the maximum voltage required to form a spark increases until the ignition coil is no longer able to form the spark channel. Numerical models that can analyze the breakdown of the plasma in a spark plug have typically been limited to vacuum electrical field simulations and full-fidelity plasma models. In the present work, we present a fast, predictive breakdown model that blends the speed and computational efficiency of electric field model and incorporates the essential physics of the breakdown event without having to pay the cost of solving the full set of plasma governing equations.

This paper discusses controller development for an active, off-road vehicle suspension system. A brief review of electronic filters and their characteristics is used to provide insight on the difficulties of designing a control algorithm for negotiating hilly and rough terrain at higher speeds. Two controller designs are presented. One was designed by pole placement and causes the suspension response to approximate a Type 1 Chebychev filter. The other was designed using constrained optimization. A comparison and discussion of simulation results leads to the conclusion that the suspension should be adaptively or predictively controlled for arbitrary terrain and velocity conditions.

Combustion chamber pressure measurement in engines via a passage is an old technique that is still widely used in engine research. This paper presents improved passage designs for an off-set electrode spark plug designed to accept a pressure transducer. The spark plug studied was the Champion model 304-063A. Two acoustic models were developed to compute the resonance characteristics. The new designs have a resonance frequency in a range higher than the fundamental frequency expected from knock so that the signal can be lowpass filtered to remove the resonance and not interfere with pressure signal components associated with combustion phenomena. Engine experiments verified the spark plug resonance behavior. For the baseline engine operating condition approximately 50 of 100 cycles had visible passage resonance in the measured pressure traces, at an average frequency of 8.03 kHz.

The arc breakdown phase in automotive spark-plugs is a sub-microsecond event that precedes the main spark event. This phase is typically characterized by strong non-equilibrium plasma phenomena with high voltage and currents. The nature of the initial breakdown phase has strong implications for the successful spark formation and the electrode erosion/lifetime. There are evidently very few studies that seek to characterize this phase in detail. The goal of this work is to investigate this non-equilibrium plasma arc breakdown phase, using high-fidelity computational modeling. We perform studies using the VizGlow non-equilibrium plasma modeling tool. During the early breakdown phase, the plasma forms thin filamentary streamers that provide the initial conductive channel across the gap. Once the streamers bridge the gap, the plasma begins to transition to a thermal arc.

While spark-ignition (SI) engine technology is aggressively moving towards challenging (dilute and boosted) combustion regimes, advanced ignition technologies generating non-equilibrium types of plasma are being considered by the automotive industry as a potential replacement for the conventional spark-plug technology. However, there are currently no models that can describe the low-temperature plasma (LTP) ignition process in computational fluid dynamics (CFD) codes that are typically used in the multi-dimensional engine modeling community. A key question for the engine modelers that are trying to describe the non-equilibrium ignition physics concerns the plasma characteristics. A key challenge is also represented by the plasma formation timescale (nanoseconds) that can hardly be resolved within a full engine cycle simulation.

Advanced Driver Assistance System (ADAS) has become a common standard feature assisting greater safety and fuel efficiency in the latest automobiles. Yet some ADAS systems fail to improve driving comfort for vehicle occupants who expect human-like driving. One of the more difficult situations in ADAS-assisted driving involves instances with cut-in vehicles. In vehicle control, determining the moment at which the system recognizes a cut-in vehicle as an active target is a challenging task. A well-designed comprehensive threat assessment developed for cut-in vehicle driving scenarios should eliminate abrupt and excessive deceleration of the vehicle and produce a smooth and safe driving experience. This paper proposes a novel methodology for threat assessment for driving instances involving a cut-in vehicle. The methodology takes into consideration kinematics, vehicle dynamics, vehicle stability, road condition, and driving comfort.

A third generation Gasoline Direct Injection Compression Ignition (GDCI) engine has been designed and built. The engine is intended to meet stringent US Tier 3 emissions standards with diesel-like fuel efficiency. While nearly every aspect of the engine design has been improved over the previous second generation engine, this paper is primarily concerned with two of the most critical subsystems - the thermal management and EGR systems. These are especially important because gasoline compression ignition combustion is sensitive to intake gas temperature and exhaust gas dilution. Both parameters may deviate from steady state targets during transients. The quality of combustion control during transient vehicle operation is limited by significant response delay in both the thermal management and EGR systems. The intake air coolers must be sized for sufficient heat transfer capacity under peak load operating conditions, which results in coolers having significant thermal inertia.

Predictions of the Fractal Engine Simulation code were compared with SI engine data in a previous paper. These comparisons were extremely good except for the single data set available at a low engine speed. Because of uncertainty regarding whether the lack of agreement for this case resulted from some difficulty with the experimental data or was due to lack of proper speed dependence in the model, additional comparisons are made for a range of speeds from 300-1500 rpm. The fractal burning model is a turbulence driven model (i.e., driven primarily by the turbulence intensity) that divides the combustion process into four sequential phases: 1) kernel formation, 2) early flame growth, 3) fully developed turbulent flame propagation, and 4) end of combustion. The kernel formation process was not included in the previous version of this model, but was found to be required to predict engine speed effects.

Lean mixture combustion might be an important feature in the next generation of SI engines, while diluents (internal and external EGR) have already played a key role in the reductions of emissions and fuel consumption. Lean burn modeling is even more important for engine modeling tools which are sometimes used for new engine development. The effect of flame strain on flame speed is believed to be significant, especially under lean mixture conditions. Current quasi-dimensional engine models usually do not include flame strain effects and tend to predict burn rate which is too high under lean burn conditions. An attempt was made to model flame strain effects in quasi-dimensional SI engine models. The Ford model GESIM (stands for General Engine SIMulation) was used as the platform. A new strain rate model was developed with the Lewis number effect included.

The use of electromechanical actuators for an active suspension on a main battle tank is investigated. A novel approach to the development of the active suspension control algorithms is presented along with simulation results to evaluate the electromechanical design requirements. The optimal electromechanical actuator design is described along with simulated performance results for a one roadwheel station electromechanical active suspension. Follow-up plans for the laboratory testing of a single wheel station system are also included.

This work examines the characteristics of a methanol fueled porous media burner, the principles of which may be used as a basis for a practical radiant heat source for an on-board catalytic methanol reformer. The burner uses a conventional engine port fuel injector designed for methanol use. The spray from the injector was impinged upon the bottom of a stack of two or three pieces of ceramic foam. The ceramics were 2.5 cm thick, 10 cm in diameter and were enclosed in a quartz cylinder for visualization. The upstream ceramic acted as a flame holder and the surface of the downstream ceramic was the radiation source. The range of air and fuel flow rates over which stable combustion was possible was investigated. Fuel flow rates between 0.12 and 0.48 gm/s were examined. Overall equivalence ratios between 0.65 and 0.2 resulted in stable combustion.

In premixed turbulent combustion models, two mechanisms have been used to explain the increase in the flame speed due to the turbulence. The newer explanation considers the full range of turbulence scales which wrinkle the flame front so as to increase the flame front area and, thus, the flame propagation speed. The fractal combustion model is an example of this concept. The older mechanism assumes that turbulence enables the penetration of unburned mixtures across the flame front via entrainment into the burned mixture zone. The entrainment combustion or eddy burning model is an example of this mechanism. The results of experimental studies of combustion regimes and the flame structures in SI engines has confirmed that most combustion takes place at the wrinkled flame front with additional combustion taking place in the form of flame fingers or peninsulas.

The Texas Project is a multi-year study of the emissions and fuel economy of aftermarket conversions of light-duty vehicles, including passenger cars, light light-duty trucks, and heavy light-duty trucks. The test fleet, consisting of 86 mostly 1994 model year vehicles, includes eight different types of light-duty vehicles that have been converted to dual fueled operation for either CNG or LPG and corresponding gasoline controls. Virtually every type of aftermarket conversion technology (referred to as a “kit” for convenience) is represented in the test matrix: eight different CNG kits and seven different LPG kits, all of which have closed loop control systems. One goal of The Texas Project is to evaluate the different kits for each of the applications. One method used for evaluating the different kits was by assessing their potential for attaining LEV certification for each of the vehicle applications.

The mixture preparation process was investigated in a direct-injected, 4-valve, SI engine under motored conditions. The engine had a transparent cylinder liner that allowed the fuel spray to be imaged using laser sheet Mie scattering. A fiber optic probe was used to measure the vapor phase fuel concentration history at the spark plug location between the two intake valves. The fuel injector was located on the cylinder axis. Two flow fields were examined; the stock configuration (tumble index 1.4) and a high tumble (tumble index 3.4) case created using shrouded intake valves. The fuel spray was visualized with the engine motored at 750 and 1500 RPM. Start of injection timings of 90°, 180° and 270° after TDC of intake were examined. The imaging showed that the fuel jet is greatly distorted for the high tumble condition, particularly at higher engine speeds. The tumble was large enough to cause significant cylinder wall wetting under the exhaust valves for some conditions.

Opposed-piston engines have been in production since before the 1930’s because of their inherent low heat losses and high thermal efficiency. Now, opposed-piston gasoline compression ignition (OP-GCI) engines are being developed for automotive transportation with stringent emissions targets. Due to the opposed-piston architecture and the absence of a cylinder head, fuel injection requirements and packaging are significantly different than conventional 4-stroke engines with central-mounted injectors. The injection process and spray characteristics are fundamental to achieving a successful combustion system with high efficiency, low emissions, and low combustion noise. In this paper, the fuel injection system for the Achates 2.7L, 3-cylinder OP-GCI engine is described. The fuel system was designed for 1800 bar maximum fuel pressure with two injectors mounted diametrically opposed in each cylinder.

Diesel engines have been the major power source for medium- to heavy-duty ground vehicles due to superior fuel efficiency and durability over gasoline engines. However, Diesel engines are the main contributors for non-renewable Diesel fuel consumption and NOx and particulate matter (PM) emissions. Biodiesel fuel has been considered as a promising alternative fuel and can be directly fed into Diesel engines without major modifications. In addition, biodiesel has demonstrated lower hydrocarbon (HC), carbon monoxide (CO), and PM emissions than Diesel fuel. Nevertheless, the NOx emissions of biodiesel are generally higher. To meet stringent NOx emission regulation, urea-based selective catalytic reduction (SCR) systems have been widely utilized in Diesel-powered vehicles. The application of biodiesel fuel to Diesel engines can significantly change the exhaust condition and thus increase the complexity of SCR design and controls.

A multi-dimensional model of the spark ignition process for SI engines was developed as a user defined function (UDF) integrated into the commercial engine simulation software CONVERGE™ CFD. For the present research, the model simulated spark plasma development in an inert flow environment without combustion. The UT model results were then compared with experiments. The UT CONVERGE CFD-based model includes an electrical circuit sub-model that couples the primary and secondary sides of an inductive ignition system to predict arc voltage and current, from which the transient delivered electrical energy to the gap can be determined. Experimentally measured values of the arc resistance and spark plug calorimeter measurements of the efficiency of electrical to thermal energy conversion in the gap were used to determine the thermal energy delivered to the gas in the spark gap for different pressures and gap distances.

Spark plug electrode heat transfer and its relationship with the thermal energy deposition from the spark plasma to the gas in the spark gap was studied under quiescent non-combusting conditions. The thermal energy deposition to the gas (N2) was measured with a spark plug calorimeter as a function of pressure, up to 30 bar. The measurements were carried out for two gap distances of 0.3 mm and 0.9 mm, for three nominally identical spark plugs having different electrode surface area and/or surface thermal conductivity. The unmodified baseline spark plug had a nickel center electrode (cathode) 2.0 mm in diameter, the first modified spark plug had both the ground and center electrodes shaved to a diameter of approximately 0.5 mm, and the second modified spark plug had copper inserts bonded to both electrodes. The experimental results were compared with multi-dimensional simulations of the conjugate heat transfer to the gas and to the metal electrodes, conducted using CONVERGE CFD.

Fuel stratification effects on the combustion and emissions behaviors for partially premixed compression ignition (PPCI) combustion of a high reactivity gasoline (research octane number of 80) was investigated using the third generation Gasoline Direct-Injection Compression Ignition (Gen3 GDCI) multi-cylinder engine. The PPCI combustion mode was achieved through a double injection strategy. The extent of in-cylinder fuel stratification was tailored by varying the start of second fuel injection timing (SOIsecond) while the first fuel injection event was held constant and occurred during the intake stroke. Based on the experimental results, three combustion characteristic zones were identified in terms of the SOIsecond - CA50 (crank angle at 50% cumulative heat release) relationship: (I) no response zone (HCCI-like combustion); (II) negative CA50 slope zone: (early PPCI mode); and (III) positive CA50 slope zone (late PPCI mode).

Continued improvement in the combustion process of internal combustion engines is necessary to reduce fuel consumption, CO2 emissions, and criteria emissions for automotive transportation around the world. In this paper, test results for the Gen3X Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2L, four-cylinder, double overhead cam engine with compression ratio ~17. It features a “wetless” combustion system with a high-pressure direct injection fuel system. At low load, exhaust rebreathing and increased intake air temperature were used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For medium-to-high loads, a new GDCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-end torque and power. Time-to-torque (TT) simulations indicated 90% load response in less than 1.5 seconds without a supercharger.