Stereoscopic Micro-PIV Measurement of Near-Wall Velocity Distribution in Strong Tumble Flow under Motored SI Engine Condition Tokyo Institute of Technology

Format:

Book

Conference/Event

Author/Creator:

Yamakita, Yoko, author.

Contributor:

Bae, Jaeok

Kosaka, Hidenori

Nagasawa, Tsuyoshi

Conference Name:

SAE Powertrains, Fuels & Lubricants Meeting (2020-09-22 : Krakow, Poland)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2020

Summary:

In order to reduce cooling loss of internal combustion engine, heat transfer mechanism near the wall should be clarified. For the prediction of heat transfer coefficient, various predictive formulas including Woschni model have been proposed. In the case of state-of-the-art lean burn SI engine, however, strong in-cylinder flow field with enhanced turbulence intensity compared to conventional engines is formed. Since wall heat transfer mechanism at such a complex flow field has not been clarified, development of accurate heat transfer model applicable for wide operation range including lean burn condition is desired.Flow velocity and temperature profiles inside wall boundary layer are strongly related to heat transfer mechanism. In this study, two dimensional-three components velocity distribution near piston top surface was measured at a compression stroke using a rapid compression and expansion machine (RCEM) and stereoscopic micro-PIV system. The bore, stroke, compression ratio, and compression time was 75mm, 128mm, 16, and 30ms (equivalent to 1000rpm), respectively. Double pulse Nd:YAG laser sheet was introduced from intake side, and PIV images near the piston surface around TDC were captured at motored condition with an image size of 16001200 pixel (4.3m/pixel) using two ICCD cameras.The obtained piston wall-tangential and laser sheet-normal (tumble axial direction) velocity components shows that the main flow is piston horizontal direction, while the direction is fluctuated to tumble axial direction in each experiment. In addition, power spectrum distribution, which was obtained by 2D-FFT analysis of wall-tangential and wall-normal velocity components, shows that for both components, gradient of the spectrum distribution approaches -5/3 (Kolmogorov's scaling law) with approaching TDC. This indicates that the flow field becomes inertial subrange around TDC. Moreover, separation of mean and turbulent velocity components using a spatial filter makes it possible to calculate turbulence energy, which decreases with approaching TDC during a compression stroke

Notes:

Vendor supplied data

Publisher Number:

2020-01-2019

Access Restriction:

Restricted for use by site license