Experimental results of a low-pressure steam Rankine cycle with a novel water lubricated radial inflow turbine for the waste heat utilization of internal combustion engines

Abstract

A large proportion of the energy converted in internal combustion engines is lost via the exhaust gas at high temperature levels and via the coolant at low temperature levels of about 80 to 120 °C. Subsequent low-pressure steam Rankine cycles can be used to engage both heat sources in a single cycle for converting waste heat into mechanical or electrical energy. Experimental proof can show that steam Rankine cycles offer low system complexity, competitive efficiencies and favourable part load behaviour compared to other waste heat recovery cylces such as organic Rankine cycles. For this purpose, a low-pressure SRC test rig optimized for laboratory operation is developed which emulates different load conditions of an internal combustion engine for combined heat and power production. Test data is obtained and validated for part load operation at 60, 70 and 80 % load. A measured electrical efficiency of the steam Rankine cycle of 4 % and an exergetic efficiency of 14 % highlights its potential to compete with organic Rankine cycle applications and serves as proof of concept for the employed radial inflow turbine with water lubricated bearings.