An investigation of coal-water slurry as a compression ignition engine fuel.

摘要

This work investigated the viability of using a coal-water slurry fuel in a reciprocating single-cylinder prechamber type engine and included both numerical and experimental aspects. Analytically, a cycle simulation for a coal-fueled, internal combustion engine was modified to simulate the engine which would be used in the laboratory. The engine used in this work was a prechamber type diesel engine. The engine required several modifications before it could be operated successfully with coal-water slurry. These modifications included: (1) a diaphragm injection system for isolating the slurry fuel from the conventional fuel pump; (2) an inlet air heater to obtain a high temperature to improve the processes of evaporation of water, and devolatization and ignition of coal; (3) fuel cam and cam shaft alterations for changing static fuel injection timing; (4) a high speed data acquisition system for measuring time history of the cylinder gas pressure; and (5) a cooling system on the prechamber to prevent coal-water slurry from clogging in the injector.; In addition to engine tests, injection studies were performed using a Hycam, 16mm high speed motion picture camera, and a Bosch fuel pump test bench. The high speed cinematographic records provided limited quantitative data but did reveal some qualitative information on the ignition of slurry through a diesel injection nozzle. The ignition and combustion processes of coal-water slurry and diesel in the engine were studied using the modified engine discussed above. The major conclusions of these activities included: (1) the quality of atomization of coal-water slurry through the injection nozzle was not as good as that of diesel in terms of forming an atomized mist of droplets; (2) the coal-water slurry had lower combustion efficiencies and prolonged ignition delay periods as compared to diesel fuel; (3) higher needle lift pressures led to shorter ignition delay times for the coal-water slurry fuel; (4) increasing the inlet air temperature shortened ignition delay time and improved burning rate of the slurry; (5) dilution of the slurry with water did not significantly affect the combustion processes but did improve fuel handling in the delivery line; and (6) the viscosity index of slurry fuel was significantly decreased as the slurry fuel was diluted with water.