Automotive turbocharger hot-gas test-stand data acquisition and control

Abstract

Turbochargers are an increasingly important module in modern vehicles. The calibration of a turbocharger unit requires the measurement of performance parameters namely pressure ratio, mass flow and efficiency as a function of rotational speed. A hot-gas-stand was built to provide a test-bench facility at the University of Malta. The mechanical design is briefly outlined in this paper but emphasis is on the data acquisition and control. Details of specifically designed electronic circuits and LabVIEW® are the main focus of this paper. The measurement of shaft speed with a non-contact hall effect sensor is described and the circuitry designed to extract the small signal from the measurement is detailed. The level of noise was significant mostly due to the 18 kW inverter used to power the 15 kW motor required to drive the supercharger which pushed air into the combustion chamber. Temperature control of the exhaust gases going out of the combustion chamber was controlled with a PID controller in LabVIEW® which regulated the fuel quantity that was admitted to the combustion chamber. Fuel used was Liquefied Petroleum Gas in the vapor state and fuel metering was achieved by Pulse Width Modulation of the metering valve. A small buffer tank was utilized downstream of the pulse-width-modulated valve to stabilize the pressure downstream of the valve which was then supplied to the burner.