Phenomenological modeling of diesel spray with varying injection profile

Abstract

Accurate and quick prediction of spray characteristics such as spray penetration is paramount for the understanding and quantitative analysis of the combustion process in diesel engines, in order to perform parametric study on advanced combustion process in diesel engines, zero-dimensional diesel spray model is often used for the prediction of the spray evolution. In this study, a previous zero-dimensional diesel spray model applied for the spray penetration prediction including the part after the end of injection with a constant injection rate was extended to the cases with varying injection rate. The effective injection velocity was introduced into the previous spray model, which is defined as the ratio of the momentum flux and fuel mass flow rate over the spray tip cross-sectional area. Combined with this definition, the analysis of effective injection rate and its response time was performed during and after the end of injection. After that, the fuel mass flow rate and momentum flux over the spray tip cross-sectional area were derived for varying injection rate even after the end of injection based on the momentum and fuel mass conservation along the spray axis, and further the spray penetration. Finally, the developed model was validated by comparing with the experimental data.

Investigation on an Injection Strategy Optimization for Diesel Engines Using a One-Dimensional Spray Model

“…For model validation, the diesel spray tip penetration even after EOI with short injection duration was calculated and compared with the shadowgraph data of non-combusting diesel sprays in a constant volume chamber. The experimental setup and measuring equipment are the same as that in our previous study [11]. The constant volume chamber is in cylindrical shape with a volume of 150 cm 3 .…”

“…However, there is little relative research about this. Inversely, as the common used and typical injection rate shapes in diesel engines, scholars have devoted a great deal of effort to the triangle and rectangle as well as trapezoid shapes [9][10][11][12][13]. In order to compare the potential of varying injection rate shapes to lower the pollutant emissions of diesel engines more objectively and comprehensively and find the optimized injection strategy, five injection rate shapes (including triangle, ramping-up, ramping-down, rectangle and trapezoid) were selected in this paper, as shown in Figure 4.…”

“…In order to compare the potential of varying injection rate shapes to lower the pollutant emissions of diesel engines more objectively and comprehensively and find the optimized injection strategy, five injection rate shapes (including triangle, ramping-up, ramping-down, rectangle and trapezoid) were selected in this paper, as shown in Figure 4. To simulate the diesel spray propagation under the conditions extant in engines' cylinders, the ambient gas conditions are set as the actual in-cylinder pressure and temperature, so the calculation conditions are the same as given in Table 1, and the injection rates have been shown in a previous study [11].…”

“…Energies 2019, 12, x FOR PEER REVIEW 7 of 19 ramping-down, rectangle and trapezoid) were selected in this paper, as shown in Figure 4. To simulate the diesel spray propagation under the conditions extant in engines' cylinders, the ambient gas conditions are set as the actual in-cylinder pressure and temperature, so the calculation conditions are the same as given in Table 1, and the injection rates have been shown in a previous study [11]. Figure 5 shows the spray tip penetrations with the injection quantity of 0.417 mg and 0.833 mg for a single nozzle hole, respectively.…”

“…The shorter the injection duration, the higher the proportion of the ramping part. In the case of a small fuel injection quantity with a short injection duration, the injection rate shape always tends to be triangular [11,12], whose spray mixing characteristics are quite different from that of the commonly used injection rate shapes, like the square, boot or rectangle [9,10,13]. Besides, the advanced innovation of piezoelectric injectors makes a significant contribution to the extremely fast needle response time [14,15], meaning it is easer for diesel engines to adopt highly defined injection rate shapes to improve their performance.…”