High efficiency detonation internal combustion engine (DICE) (1992)

Controlled detonation combustion could be used in future internal combustion engines to achieve high cycle eficiency and minimize NOx formation, if conventional design limitations are removed. Such an engine is herein proposed that uses a separate detonation combustion chamber which discharges tangentially into an expansion chamber formed by the piston and cylinder at top dead center. The expansion chamber is designed to efficiently store a portion of the detonation wave's kinetic energy in the form of a vortex, which is subsequently convened into static pressure. The rapid burning followed by leaning through mixing with air in the vortex chamber may reduce the formation of NOx and unburned hydrocarbons as compared to conventional combustion. The thermodynamic aspects of detonation combustion compared to either volume or pressure combustion yield a significant increase in combustion compression ratio for fuels such as natural gas. The shock wave propagation through the vonex chamber is described with a shock-capturing fmite element Euler flow code supporting the premise of vortex storage and rapid mixing characteristics. Potential problems and issues of such of the DICE are also addressed. *Assistant Professor, Aeronautical and Astronautical Engineering, University of Illinois at UrbanaChampaign, Urbana, IL ** Professor, Mechanical and Aerospace Engineering. West Virginia University, Morgantown, WV *** Graduate StudenL Mechanical Engineering, The Georgia Technical Institute. Atlanta, GA W This document, or portions of it, contains commercial information that is or may become the subject of a United States Patent application. W A. Natural Gas I C Engines Since the U.S. Clean Air Act was introduced [l], there has been strong interest in the cleaner burning and more thermally efficient operation of internal combustion (IC) engines. Alternate fuels, such as methane, are promising to reach such goals. However, current efforts to substitute alternate fuels for conventional liquid fuels in internal combustion engines face many obstacles. They include from problems with storage, distribution, ignition, low fuel efficiency, and emissions. The latter two problems are addressed in this new approach to the IC engine. The amount of work which can be produced inside an internal combustion engine by combustion products depends on their pressure relative to the surroundings. Consequently, the higher the initial stagnation pressure of the combustion products, the higher the power that can be produced during expansion, which increases the efficiency of the engine. The obtainable pressure is not only a function of supercharging and piston compression, but also of the process used to burn the fuel, which dictates the combustion compression ratio (CCR). One important aspect associated with the efficient use of alternative fuels in IC engines is maximizing the CCR. Slow burning fuels are combusted near pressure and usually produce a CCR of less than one. Such a process provides combustion products with a minimal potential for doing work. Note, most of our limited fossil fuels are currently burned inefficiently in the so called constant pressure burning mode including systems such as power plant furnaces, jet engines, and diesel engines. One such fuel, natural gas, is an abundant. inexpensive and desirable alternative fuel for IC engines as it is clean burning with high octane and cetane number and is thus capable of tolerating high piston compression ratio's without knock. Ignition is easy due to the wide ignition limits of natural gadair mixtures. In addition, Iwn-burning of methane produces low carbon monoxide and significantly reduces NOx formation (techniques are also being investigated which