Cascade temperature control of an automotive turbocharger hot-gas test-stand

Abstract

An experimental implementation of cascade control on the turbine inlet temperature of a turbocharger turbine is presented. The experimental setup used was a hot gas test stand developed for the determination of compressor and turbine characteristic maps of automotive turbochargers. The cascade control consisted of turbine inlet temperature as the outer loop (primary controller), while the propane buffer tank pressure feeding the burner as the inner loop (secondary controller). The propane buffer tank pressure was controlled through pulse width modulation of a solenoid valve connected to a propane cylinder. Temperature control between 500掳C and 800掳C (which is indicative of engine exhaust temperature) is presented along with the propane pressure control traces. The effect of the propane buffer tank size (which translates to the response time of the inner loop) is discussed. Also discussed is the inclusion of a propane orifice just upstream of the burner to match the increase/decrease rates of propane pressure in the buffer tank. This matching of pressure increase/decrease rates helped in simplifying the control scheme and removed the need for gain scheduling.