In response to recent CO2 emissions regulations, the compatibility of acceleration performance and fuel efficiency improvement is indispensable as a product quality, and turbochargers are required to provide high boost pressures to generate high torques at low engine speed ranges. Double-scroll turbines, which have two flow passages and a valve, can achieve performance characteristics similar to single-scroll turbines by opening the valve at high engine speed ranges while realizing the performance characteristics of multi-entry turbines in low engine speed ranges. However, the two passages cause pressure distribution in the circumferential direction of the turbine, which results in problematic excessive aerodynamic noise. Mitsubishi Heavy Industries, Ltd. has achieved a significant reduction in the noise by utilizing analytical technology and testing verification, and this report describes the results of our initiatives.
