Fuel Quality Evaluation by Changing the Compression Ratio in a Hydraulic Dynamic Combustion Rig 2003-01-3081
This paper presents results from experiments concerning diesel injection in a hydraulically actuated dynamic combustion rig.
One of the main aims of study was to investigate the effect of changes in the compression ratio of the dynamic combustion rig on the diesel spray development, ignition and early combustion phase.
Schlieren and shadowgraph images were taken of the injection and early combustion phase, together with recordings of the most important process parameters. The schlieren and the shadowgraph techniques for visualisation are powerful methods for studying spray development, ignition and combustion of the diesel process.
Tests carried out on the rig clearly demonstrate the value of the set up as a tool for investigations of changes in the compression ratio on the ignition and early flame development in general. The schlieren images presented from this study also contribute to the physical understanding of the ignition phase in diesel combustion as a function of compression ratio. In addition, the study also presents the dynamic Combustion Rig as a tool for basic HCCI research.
The rig gives the options to separate wide range of engine design- and operating parameters. During the experiments several test parameters were varied. The most important of these variables were the following:
Diesel Injection Pressure
Compression rate at the time of injection
The changes in the position of TDC are made possible by computer control of fast hydraulic servo valves controlling the piston movement.
The results show that the rapid compression machine used in these experiments is very well suited for tests on the effect of changes in the compression ratio on the ignition and early combustion phase. This result could be of special interest to the research field of Homogeneous Charge Compression Ignition (HCCI).
In this study it is shown that the reproducibility and repeatability of the compression ratio between each cycle is high.
Three out of five separate sprays from an automotive multi-hole diesel nozzle were studied by schlieren visualisation in one direction. The images show that it is possible to track the exact time and position of the start of ignition in each of the sprays for different compression ratios.