As turbocharged diesel engines have evolved to higher brake mean effective pressure (BMEP) levels, with ultra-low levels of regulated emissions, it has become increasingly difficult to match the turbine and compressor in conventional turbocharger and achieve the desired level of performance and responsiveness. Emissions regulations result in the use of ultra-high levels of Exhaust Gas Recirculation (EGR) to control NOx and Diesel Particulate Filters (DPF) to control soot and particulate emissions. These technologies exacerbate the compressor/turbine matching issue by reducing the turbine corrected flow to as little as half the compressor corrected flow.
A new design concept is presented in this paper that significantly improves the performance of the turbine by changing the work/speed relationship of the compressor. This is accomplished by using a double-sided compressor and results in a secondary benefit of improved flow range of the compressor, achieved by stalling one of the compressor wheels. Due to the improved range of the compressor, the backward curvature can be reduced, which improves the pressure ratio capability.
When combined with a ball bearing cartridge, this concept results in a single turbo with a double-digit improvement of turbine efficiency, a high pressure, wide range compressor, in a small, compact package capable of providing performance unattainable in a conventional turbocharger configuration.
