Analysis of in-cylinder processes of an internal combustion engine with direct-injection using high-speed laser diagnostics

• Main Author: Müller, Sebastian H. R.
• Format: Others
• Language: English; en
• Published: 2012
• Online Access: https://tuprints.ulb.tu-darmstadt.de/2936/1/dissertation_sebastian_mueller.pdf; Müller, Sebastian H. R. <http://tuprints.ulb.tu-darmstadt.de/view/person/M=FCller=3ASebastian_H=2E_R=2E=3A=3A.html> (2012): Analysis of in-cylinder processes of an internal combustion engine with direct-injection using high-speed laser diagnostics.Darmstadt, Technische Universität, [Ph.D. Thesis]

This thesis describes and characterizes the in-cylinder processes of an internal combustion engine with direct-injection using high-speed laser diagnostics. The main goal is to further increase the understanding of the underlying physical and chemical processes within the cylinder, hence to increase the efficiency and reduce fuel consumption as well as exhaust gas emissions. A single cylinder research engine was equipped with a quartz glass ring mounted between the cylinder head and liner enabling a clear view of the in-cylinder processes. Planar imaging techniques were used to record the flow field, the fuel distribution as well as the flame propagation during the compression stroke inside the cylinder. All experiments were performed at a repetition rate of 6 kHz, allowing the recording of sequential crank angles (one image per crank angle at 1000 rpm) and multiple consecutive engine cycles. Each experiment focused on a single process (flow field, spray/flow field interaction, fuel distribution, and flame kernel development) as they were decoupled. In addition, statistical tools (e.g. the kinetic energy) were used to identify cycle-to-cycle variations and their individual distinctiveness. The individual error sources of the experiments were also addressed. The results are arranged according to their individual recording range. First, the flow field was recorded from 180° (bottom dead center) to 60° before top dead center using high-speed three-component stereoscopic particle image velocimetry. In contrast to conventional two-component particle image velocimetry, all three velocity components of the flow field were obtained within a single plane. Different parametric influences (charge motions tumble, swirl, and neutral as well as different engine speeds) were analyzed systematically by calculating the kinetic and turbulent kinetic energy. Additionally, the influence of the out-of-plane component with the different charge motions was investigated. Here, the assumption of an isotropic velocity distribution showed the directionality of the fluctuating velocities to be more uniform than expected. The interaction of the flow field with the fuel injection was investigated by imaging the flow field using high-speed two-component particle image velocimetry and the subsequent spray injection in a single recording. Analyzing this, the influence of the flow field to the deformation of the spray was investigated statistically. Secondly, the fuel distribution within the cylinder using the direct-injection system was analyzed with laser-induced fluorescence in order to identify inhomogeneities. A calibration procedure to determine fuel distribution anomalies was developed. Additionally, the fuel deposits on top of the piston crown and their cycle dependent evaporation process super positioned by the convective and diffusion processes was also recorded. Finally, the flame kernel development was investigated by recording the transient motion of the intermediate OH-radicals occurring in the flame front. Single cycle recordings of the flame kernel area were correlated to the simultaneously recorded pressure signal. The influence of synthetic exhaust gas recirculation on the flame kernel development was also analyzed.