MEASUREMENTS AT COMBUSTION TEMPERATURES

THE DEVELOPMENT OF A HIGH-TEMPERATURE DYNAMIC PRESSURE PROBE BASED ON A CAPACITIVE SENSOR IS PROPOSED. A THIN FLEXIBLE PLATE, ORIENTED PERPENDICULAR TO THE DIRECTION OF FLOW, AND A FIXED PLATE FORM A CAPACITOR. THE DYNAMIC PRESSURE GENERATED BY THE GAS FLOW (DENSITY TIMES VELOCITY SQUARED) DEFLECTS THE MEMBRANE, THUS VARYING THE CAPACITANCE AND CHANGING THE RESONANT FREQUENCY OF AN ELECTRIC CIRCUIT. THE FREQUENCY VARIATIONS ARE SAMPLED BY A MICROPROCESSOR. BY FITTING A NOSE CONE TO THE SENSOR, ALTERNATIVELY, IT MAY BE OPERATED IN THE PITOT-TUBE MODE. BECAUSE OF THE HIGH SENSOR RESOLUTION, THE SENSOR CAN OPERATE OVER A WIDE RANGE (TURNDOWN RATIO 140:1) WITH A FLOW RATE UNCERTAINTY OF LESS THAN 1%. AND, SINCE THE NATURAL FREQUENCY OF THE MEMBRANE IS ABOVE 20 KHZ, FAST FLOW TRANSIENTS AND PULSATIONS CAN BE MEASURED WITHOUT DISTORTIONS. DUE TO ITS SMALL OSCILLATING MASS, THE TRANSDUCER IS LARGELY INSENSITIVE TO EXTERNAL VIBRATIONS. THE PROPOSED PHASE I PROGRAM WILL INVOLVE THE INITIAL FEASIBILITY STUDY OF THE APPLICATION OF THE DYNAMIC PRESSURE TRANSDUCER CONCEPT FOR HIGH-TEMPERATURE FLOW MEASUREMENT, AND WILL INCLUDE THE DESIGN, MANUFACTURE, TESTING AND MODIFICATION OF A PROTOTYPE FLOWMETER.