Session: 37-07 Radial - Performance 2

Submission Number: 177300

Effects of Degree of Reaction and Diffuser Inlet Flow Distribution on Turbocharger Radial Turbine Performance for Hydrogen Combustion Engines 

In recent years, the development of electric vehicles aiming for zero CO₂ emissions has been advancing. However, challenges such as insufficient battery energy density still remain. For this reason, the development of hydrogen engines that apply turbocharging technologies is also considered important. In hydrogen engines, lean combustion is employed to achieve high efficiency and reduced emissions. To ensure sufficient engine torque, turbochargers are required to provide higher boost pressure than conventional systems. For turbocharger radial turbines, it is necessary to apply a variable geometry system (VGS) that controls mass flow rate and output by adjusting the nozzle throat area according to various engine operating conditions. Furthermore, turbines are required to achieve both high pressure ratio and compactness, which results in operating under a lower velocity ratio condition. Therefore, achieving high efficiency under low velocity ratio conditions becomes a technical issue. In addition, to realize both high efficiency and compactness, it is important to generate a rotor exit flow that can suppress total pressure loss even when the diffuser passage expansion angle downstream of the rotor is large. In this study, to meet these requirements, an investigation was conducted on VGS turbines with varying degrees of reaction. CFD analysis and performance testing were carried out on turbines with different degree of reaction to examine the degree of reaction suitable for low velocity ratio conditions. Additionally, a study was conducted by varying the spanwise distribution of the rotor exit flow angle. Measurements of the spanwise distribution of the flow angle at the rotor exit were performed using a three-hole yaw meter, and together with pressure measurements at the diffuser inlet and outlet, the influence of the rotor exit flow angle distribution on the pressure loss in a rapidly expanding diffuser was investigated.

Presenting Author: Wataru Sato IHI Corporation

Presenting Author Biography: Wataru Sato is the team leader of the aerodynamics team at Turbomachinery & Machine Elements Department, Technology Platform Center, Corporate Research and Development Division, IHI. He specializes in aerodynamic development of turbomachinery.

Authors:

Wataru Sato IHI Corporation
Yuya Otaka IHI Corporation
Ryosuke Inomata IHI Corporation
Takuro Kiriaki IHI Corporation
Isao Morita IHI Corporation