MONITORING EROSION IN COAL COMBUSTION ENGINES USING SURFACE LAYER ACTIVATION

A PROTOTYPE AUTOMATED SYSTEM HAS BEEN DEVELOPED FOR PRECISE IN SITU MEASUREMENT OF WEAR, CORROSION, OR EROSION BASED ON THE SURFACE LAYER ACTIVATION (SLA) TECHNIQUE. MEASUREMENTS ARE MADE BY DETECTING THE GAMMA RAY SIGNALS FROM TRACE AMOUNTS OF RADIONUCLIDES INCORPORATED IN THE SURFACE OF THE WEARING PARTS. AMOUNTS ARE SO SMALL THAT SAFETY AND DISPOSAL ARE NOT PROBLEMS. THE NUCLIDES ARE PRODUCED BY SHORT, CONTROLLED EXPOSURE TO PARTICLES FROM A VAN DE GRAAFF OR CYCLOTRON ACCELERATOR AND SERVE AS SURFACE MARKERS (AS OPPOSED TO TRACERS) FOR MEASUREMENT BY AN EXTERNALLY LOCATED DETECTOR SYSTEM. THE MEASURED DECREASE IN ACTIVITY IS DIRECTLY CORRELATED WITH LOSS OF SURFACE MATERIAL BY CALIBRATION MEASUREMENTS, ALLOWING AN EXTREMELY PRECISE, OFTEN SUBMICROMETER DETERMINATION OF WEAR. THIS METHOD HAS BEEN USED SUCCESSFULLY TO MEASURE MICROMETER-SCALE WEAR FROM DIESEL ENGINE CYLINDER LINERS, PISTON RINGS, BEARINGS, CAM SHAFTS, AND OTHER RECIPROCATING GASOLINE ENGINE COMPONENTS. THIS RESEARCH PROGRAM WILL INVESTIGATE THE FEASIBILITY OF ADAPTING THE SLAAPPROACH TO MEASURING THE RELATIVELY HIGH WEAR RATES PLAGUING BOTH TURBINE AND RECIPROCATING ENGINES OPERATING WITH COAL-BASED FUEL. THE ANTICIPATED EXTREME PRECISION OF THE TECHNIQUE SHOULD ALLOW THE ASSESSMENT OF PREVIOUSLY UNDETECTABLE DYNAMICS IN WEAR RATES OR DIFFERENCES IN DURABILITY OF TEST MATERIALS. ON-LINE CAPABILITY WILL ENABLE DETAILED MONITORING OF WEAR AS A FUNCTION OF OPERATING CONDITION OR FUEL COMPOSITION. BECAUSE OF THE SEVERITY OF THE EROSION PROBLEM IN SYSTEMS USING COAL SLURRIES OR MICRONIZED COAL AS FUEL, A PRECISION ON-LINE WEAR-MONITORING APPROACH WILL BE CRITICAL IN EVALUATING AND IMPROVING THE EFFECTIVENESS OF MEASURES TAKEN TO COUNTER WEAR.