New Sensor And Instrumentation For Relative Cylinder Power Measurements

The purpose of the previous project 1 was to design a sensor assembly, which could be used with a data acquisition system to measure the relative power of each cylinder on an internal combustion engine. A basic sensor assembly design and construction was completed as a laboratory requirement for the Mechanical Systems Design course. Pulses generated by the encoder pressed against engine crankshaft belt were acquired and stored in a file using a National Instruments 2 PCI 6023E, 200 kS/s (kilo-samples per second) throughput data acquision board and an application program developed using National Instruments LabVIEW 5.0 graphical programming software. The acquired data was processed using LabVIEW and the results were displayed. The change in the encoder signal frequency is proportional to the power generated by the individual cylinders of the engine. A plot is generated for two revolutions of the crankshaft. Tests showed that, due to the speed of the data acquisition board, only four-cylinder engines could be analyzed adequately. Recently a new data acquisition system was assembled with LabVIEW 7.0 software and a 400 kS/s data acquisition board. A more durable optical sensor was also purchased for the system. After assembling the system and designing a fixture to secure the sensor against engine crankshaft belt, test runs were run. A new LabVIEW program was written to acquire data using digital channels of the data acquisition board, instead of analog channels, to expand the range and the accuracy of measurements. Results indicate that the new optical-encoder/data acquisition/LabVIEW 7.0 system is capable of accurately measuring relative cylinder powers of 8-cylinder engines operating over 1000 rpm. For completeness of the theory, some sections of the previous work 1 were included.