Design for loss reduction in exhaust systems using thermal-hydraulic characteristics of high-frequency pulsating flow in engine curved pipes

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03931
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Hiroshima University
• Principal Investigator: OGATA Yoichi 広島大学, 先進理工系科学研究科(工), 准教授 (10323792)
• Co-Investigator(Kenkyū-buntansha): 西田 恵哉 広島大学, 先進理工系科学研究科(工), 特任教授 (90156076)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 脈動流 / 熱伝達

Outline of Final Research Achievements

The flow field and heat transfer characteristics of steady and pulsating flows at high frequencies corresponding to operating conditions of an actual engine are verified in straight and curved pipes simulating an actual engine. In curved pipes, flow field consists of the first mode of flow velocity along the pipe and the second mode with separation and reversed flow for both steady and pulsating flow. The decrease in boundary layer thickness due to the increase in flow velocity inside the bend and the impingement of the hot fluid on the outer wall side increases the one-period average local heat flux. While heat transfer is enhanced in phases with high maximum flow velocities, it is suppressed in phases where the minimum flow velocity is close to zero, and while there is no significant difference between straight and curved pipes in terms of overall heat transfer characteristics, suppressing the localised wall heat flux increase in curved geometries is an important factor.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

自動車レシプロエンジンの熱効率向上，およびエミッション低減に向けて，曲り管で構成されるエキゾーストマニホールドから排出される脈動乱流に伴う温度場・壁面熱伝達特性は，下流に設置されている三元触媒の性能に大きく影響することから，高周波で変動する流動場と局所壁面熱伝達の相関を明らかにすることで損失低減対策にも繋がる．