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An investigation of cyclic variability in a spark ignition engine is reported. Specifically, the predictions of an engine code have been compared with experimental data obtained using a well-characterized SI engine. The engine used for the experimental work and modeled in the code is the single cylinder research engine developed at Sandia National Laboratories and now operating at Drexel University. The data used for comparison were cylinder pressure histories for 110 engine cycles gathered during operation at a single engine operating condition. The code allows the various factors that could influence cyclic variability to be examined independently. Specifically, a model has been used to independently examine the effects of variations in equivalence ratio and of the turbulence intensity on cycle-to-cycle variations in the peak cylinder pressure, the crankangle of occurrence of peak pressure, the flame development angle, and the rapid burning angle.

Initial investigations of a new type of high energy ignitor for I.C. engines are described. The ignitor is a miniaturized railgun, or “railplug.” The railplug produces a relatively large mass of high velocity plasma. These characteristics may be advantageous for initiating combustion in a number of different applications. Unlike a plasma jet ignitor, the railplug plasma is driven not only by thermodynamic expansion, but by electromagnetic forces as well. Four experimental railplug designs were evaluated using schlieren and shadowgraphy visualization to examine plasma movement and shape. Railplug current and voltage were also measured. One railplug consisting of two unenclosed parallel rails was used to demonstrate the electromagnetically induced motion of the plasma at ambient conditions. Schlieren photos showed that the plasma plume moves strongly in the direction of the electromagnetic Lorentz forces.

A quasidimensional engine simulation which uses the concepts of fractal geometry to model the effects of turbulence on flame propagation in a homogeneous charge SI engine has been developed. Heat transfer and blowby/crevice flow submodels are included in this code and the submodels chosen are found to be reasonable. The model predictions of cylinder pressure histories are then compared with experimental data over a range of loads, equivalence ratios, and engine speeds. The model is not adjusted in any manner to yield better agreement with the data, other than by tuning the simple turbulence model used so as to yield agreement with data for the nonreacting flow. However, current information about the flame wrinkling scales in an engine is inadequate. Therefore, predictions are made for three different assumptions about the flame wrinkling scales which span the range of physically possible scales.

Improved submodels for use in a dynamic engine/vehicle model have been developed and the resulting code has been used to analyze the tip-in, tip-out behavior of a computer-controlled port fuel injected SI engine. This code consists of four submodels. The intake simulation submodel is similar to prior intake models, but some refinements have been made to the fuel flow model to more properly simulate a timed port injection system, and it is believed that these refinements may be of general interest. A general purpose engine simulation code has been used as a subroutine for the cycle simulation submodel. A conventional vehicle simulation submodel is also included in the model formulation. Perhaps most importantly, a submodel has been developed that explicitly simulates the response of the on-board computer (ECM) control system.

A team of student engineers at the University of Texas at Austin has designed and built “Texas Native Sun”, a solar powered vehicle for competition in GM Sunrayce U.S.A. The single-seat vehicle uses conventional photovoltaic solar cells to produce electricity for vehicle propulsion. The vehicle features graphite/epoxy composite monocoque construction, a high power-density permanent magnet electric motor, a mechanical/hydraulic continuously variable transmission, nickel-hydrogen satellite batteries, and a composite leaf spring suspension. The race strategies and tactics of energy management are optimized through use of a computer code which simulates the vehicle under race conditions. Much of the technology employed in the vehicle may one day become an ordinary part of future transportation systems which seek greater energy efficiency and less damage to the environment.

An experimental investigation of the use of an engine coolant exchange system for prewarming diesel engines before cold starting is discussed. This coolant exchange system involves connecting the coolant system of a fully warmed-up and running engine (e.g., a spark ignition engine) to that of the cold diesel to be started using hydraulic hoses with quick connect fittings and an auxiliary pump. The investigation was performed using a 4,3 liter V6 indirect injection diesel engine since this represents a difficult case for cold starting. The starting characteristics using the coolant exchange technique are compared to those using the production glow plug system, which includes a fuel heater and afterglow. It is shown that the coolant exchange system allows this engine to be started down to −26 °C, much colder than the −13°C limit for the production glow plug system.

A set of algebraic equations has been developed to replace the iterative thermochemical equilibrium subroutine in zero-dimensional and quasidimensional engine modeling codes. These equations allow calculation of the equilibrium composition given only the equivalence ratio and the fuel characteristics, thereby allowing the composition calculations to be performed external to the iterative main loop. This technique results in a decrease of the required computational time by up to a factor of 13, dependent upon the equivalence ratio and the fuel. The predictions of the equilibrium-equivalent code agree with those of a traditional equilibrium code within 2.5% for the four fuels examined (CH4, C3H8, C2H5OH, and i-C8H18) for compression ratios between 5 and 12:1, intake manifold pressures between 50 and 100 kPa, and equivalence ratios from 0.5 to 1.5. A technique for including constrained equilibrium to account for freezing of CO oxidation during the expansion stroke is also presented.