Flow effects due to valve and piston motion in an internal combustion engine exhaust port

Abstract

a b s t r a c tPerformance optimization regarding e.g. exhaust valve strategies in an internal combustion engine is often performed based on one-dimensional simulation investigation. Commonly, a discharge coefficient is used to describe the flow behavior in complex geometries, such as the exhaust port. This discharge coefficient for an exhaust port is obtained by laboratory experiments at fixed valve lifts, room temperatures, and low total pressure drops. The present study investigates the consequences of the valve and piston motion onto the energy losses and the discharge coefficient. Therefore, Large Eddy Simulations are performed in a realistic internal combustion geometry using three different modeling strategies, i.e. fixed valve lift and fixed piston, moving piston and fixed valve lift, and moving piston and moving valve, to estimate the energy losses. The differences in the flow field development with the different modeling approaches is delineated and the dynamic effects onto the primary quantities, e.g. discharge coefficient, are quantified. Considering the motion of piston and valves leads to negative total pressure losses during the exhaust cycle, which cannot be observed at fixed valve lifts. Additionally, the induced flow structures develop differently when valve motion is taken into consideration, which leads to a significant disparity of mass flow rates evolving through the two individual valve ports. However, accounting for piston motion and limited valve motion, leads to a minor discharge coefficient alteration of about one to two percent.

Investigation of the temporal evolution and spatial variation of in-cylinder engine fuel spray characteristics

“…The instantaneous spray fields at 4 different conditions at 3°a SOI from 3 individual injection cycles are decomposed into four parts and presented in Figs. [6][7][8][9]. Each spray field is reconstructed by using the modes listed in Table 2.…”

“…In addition, the advanced numerical simulation tools can also help the researchers to understand the in-cylinder phenomena [5][6][7][8][9][10][11]. Extensive research studies have been performed to study in-cylinder turbulent flow field CCV [12][13][14][15][16][17][18][19][20].…”

On discharge from poppet valves: effects of pressure and system dynamics

“…The expansion of the air in the cylinder during the exhaustion can, however, be viewed as an isentropic process Semlitsch et al 2015;Povey and Beard 2008). Thus, the temperature is related to the pressure as follows:…”

“…In another study Semlitsch et al (2015) investigated how valve and piston motion affects the exhaust process, again using LES. In this study, they performed simulations on a double exhaust-valve cylinder top.…”

Investigation of the Thermodynamic Process of the Refrigerator Compressor Based on the m-θ Diagram

“…The traditional method to obtain the flow coefficient of the valve is experiment blowing through the valve. Nowadays, with the development of CFD and FEA technology, the flow coefficient can be obtained with a numerical method [15].…”