The in-cylinder turbulent flow field of a small modern d.i. diesel engine motored over a wide speed range (from 1,000 to 3,000 rpm) has been studied with LDA. The engine has been modified with an optical access on the head, to allow measurements along horizontal planes. The experiments provide operational conditions similar to those of a real engine. Cycle-resolved LDA measurements were made in a reentrant combustion chamber. Data have been analyzed using the ensemble-averaging, low-pass filtering and spectral analysis techniques. Measurements during the intake and compression strokes highlight the jetlike character of the intake flow that generates large-scale rotating flow. This is characterized by high turbulence and unstable swirling flow, which becomes more stable during the compression stroke. The mean motion, as well as the rms turbulent velocity scale almost linearly with engine speed. The spectral analysis shows the turbulent flow field during the compression to be nonisotropic and nonstationary at all engine speeds.
Analysis of in-cylinder flow processes by LDA
Esposito Corcione F;Valentino G
1994
Abstract
The in-cylinder turbulent flow field of a small modern d.i. diesel engine motored over a wide speed range (from 1,000 to 3,000 rpm) has been studied with LDA. The engine has been modified with an optical access on the head, to allow measurements along horizontal planes. The experiments provide operational conditions similar to those of a real engine. Cycle-resolved LDA measurements were made in a reentrant combustion chamber. Data have been analyzed using the ensemble-averaging, low-pass filtering and spectral analysis techniques. Measurements during the intake and compression strokes highlight the jetlike character of the intake flow that generates large-scale rotating flow. This is characterized by high turbulence and unstable swirling flow, which becomes more stable during the compression stroke. The mean motion, as well as the rms turbulent velocity scale almost linearly with engine speed. The spectral analysis shows the turbulent flow field during the compression to be nonisotropic and nonstationary at all engine speeds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
