Performance enhancement of a diesel engine with a rotating injector – a numerical study

Improving engine performance is a constant challenge and various methodologies have been adopted by researcher’s world over. In this work, the dispersion characteristics of a rotating injector is studied by varying the umbrella angle (UA) followed by its combustion characteristics and comparing it to a static 3 – hole injector. The present numerical study is bench marked with the experimental data obtained from open literature for a 2 – hole injector with various umbrella angles. The volume fraction of the dispersed fuel along with its spray structure in relation to spray width is compared. This is done by processing the numerical contour plot using LabView image processing utility with appropriate calibration. From this study the 130 degree UA injector configuration was found to be effective when compared with 70. The combustion characteristics is now studied for this injector. It is found that the rotating injector has better dispersion and lowers NOx by 14 % when compared to a static injector with a very marginal loss in thermal efficiency. The rotary system has a lower heat release but a wider spread in comparison to a static case. This helps in marginally reducing the in-cylinder temperature and pressure lower NOx.

Experimental Validation of an Innovative Approach for GDI Spray Pattern Recognition

In the present automotive scenario, along with hybridization, GDI technology is progressively spreading in order to improve the powertrain thermal efficiency. In order to properly match the fuel spray development with the combustion chamber design, using robust and accurate diagnostics is required. In particular, for the evaluation of the injection quality in terms of spray shape, vision tests are crucial for GDI injection systems. By vision tests, parameters such as spray tip penetration and cone angles can be measured, as the operating conditions in terms of mainly injection pressure, injection strategy, and chamber counter-pressure are varied. Provided that a complete experimental spray characterization requires the acquisition of several thousand spray images, an automated methodology for analyzing spray images objectively and automatically is mandatory. A decisive step in a spray image analysis procedure is binarization, i.e., the extraction of the spray structure from the background. Binarization is particularly challenging for GDI sprays, given their lower compactness with respect to diesel sprays. In the present paper, two of the most diffused automated binarization algorithms, namely the Otsu and Yen methods, are comparatively validated with an innovative approach derived from the Triangle method—the Last Minimum Criterion—for the analysis of high-pressure GDI sprays. GDI spray images acquired with three injection pressure levels (up to 600 bar) and two different optical setups (backlight and front illumination) were used to validate the considered algorithms in challenging conditions, obtaining encouraging results in terms of accuracy and robustness for the proposed approach.

Effects of nozzle hole configuration of a multi-hole type gasoline direct injector on spray development under flash boiling conditions

The flash boiling phenomenon is critically affected by not only injection conditions such as fuel temperature, ambient pressure and physical properties of fuel but also the nozzle hole configurations of the injector. In this research, two kinds of injectors, having different nozzle hole configurations (a closed type and a opened type) were used to analyze the influence of flash boiling. Near-field and far-field spray visualization was performed using a high-speed camera based on the Mie-scattering imaging technique. Test parameters were injection pressure, ambient pressure, and fuel temperature. The spray length, spray width, length-to-width ratio, and axial velocity of spray development depending on time were measured using the MATLAB program for quantitative and objective analysis. Finally, the prediction equation for the spray length was derived using the least-squares method based on the experimental results. In the case of the closed type injector, the spray center contained a wide overlapped region because of the strong links between plumes. On the other hand, with the opened type injector, there was a relatively narrow overlapped region between plumes due to weak interaction between plumes. As a result, the closed type injector had a narrow and long spray structure and the opened type injector had a partially long and wide spray structure. According to the prediction equation, the spray develops depending on time more linearly under flash boiling conditions than under non-flash boiling conditions. The influence of flash boiling was smaller in the closed type injector because the closed type injector has less variation of the spray structure with varying injection conditions, ranging from non-flash boiling conditions to non-flash boiling conditions.