Estimation of a suitable Schmidt number range in diesel sprays at high injection pressure

Proceedings of the Institution of Mechanical Engineers, Part D:

Carreres

et al. 2016

In this paper, a high-resolution visualization technique was used in combination with an extensively validated zero-dimensional model in order to relate the external structure of a diesel spray to the internal properties in the vicinity of the nozzle. For this purpose, three single-hole convergent nozzles with different diameters were tested for several pressure conditions. The analysis of the obtained images shows that the spray width significantly changes along the first few millimetres of the spray. From the high-resolution images obtained, two parameters were evaluated. The first is the external non-perturbed length, where droplet detachment was not observed. The second is a transitional length, which is defined as the axial position where the spray width increases linearly after transient behaviour, making it possible to establish a spray cone angle definition. Furthermore, the internal liquid core length was estimated for these nozzles using an extensively validated zero-dimensional model. The liquid core length proved to be correlated with both the transitional length and the non-perturbed length with a very high degree of reliability. In the case of the transitional length, a quadratic correlation was observed, whereas a linear relationship was confirmed between the liquid core length and the non-perturbed length. The results presented here may help to shed light on better understanding of such a complex process as atomization.

Section: Theoretical Derivationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the relation between the external structure and the internal characteristics in the near-nozzle field of diesel sprays

Benajes

Proceedings of the Institution of Mechanical Engineers, Part D:

Carreres

et al. 2016

“…A high resolution analysis of the first millimeters of the spray shows that in reality there is a transitional region until reaching the spray angle [21][22][23]. X-ray visualization techniques have allowed to obtained the mass fraction radial distribution inside the spray [24][25][26], characterized by similar Gaussian profiles to those typical of gas jets [24,27]. When the spray is injected into evaporative (high temperature)…”

Section: Uthmentioning

confidence: 99%

Experimental investigation of the effect of orifices inclination angle in multihole diesel injector nozzles. Part 2 – Spray characteristics

Payri

Morena

et al. 2018

Fuel

Self Cite

Diesel spray development is a key research topic due to its impact on the combustion characteristics. On the current paper, the effect of the orifices inclination angle on the spray penetration characteristics is evaluated. For this purpose, three nozzles with included angles of 90, 140 and 155 degrees are selected. Visualization tests are performed on a room-temperature constant-pressure vessel pressurized with a high-density gas (SF6), in order to reproduce the density conditions inside the combustion chamber at the start of the injection event. Both frontal and lateral Mie-scattering visualization are used, depending on the particular nozzle configuration. Results show how the spray penetration is slower as the inclination angle increases, which is linked to its lower nozzle outlet 2 velocity. A statistical correlation of the spray penetration as a function of the area and velocity coefficients is obtained and discussed.

“…Under this assumption, the impact force is equivalent to the momentum flux at the orifice outlet considering that the pressure in the chamber is uniform, the gravity effects are negligible and the direction of the fuel deflected is perpendicular to the sensor ([31] [32]). …”

Section: Spray Momentum Test Rigmentioning

confidence: 99%

Analysis of the combined effect of hydrogrinding process and inclination angle on hydraulic performance of diesel injection nozzles

Energy Conversion and Management

Carreres

Jaramillo

et al. 2015

Self Cite

ElsevierSalvador Rubio, FJ.; Carreres Talens, M.; Jaramillo Císcar, D.; Martínez López, J. (2015). Analysis of the combined effect of hydrogrinding process and inclination angle on hydraulic performance of diesel injection nozzles. Energy Conversion and Management. 105:1352-1365. doi:10.1016/j.enconman.2015. ANALYSIS OF THE COMBINED EFFECT OF HYDROGRIDING PROCESS AND ABSTRACTA computational study to investigate the influence of the orifices inclination and the rounding radius at the orifice inlet (consequence of the hydro-erosive grinding process applied after the orifices machining) over the internal nozzle flow is performed in this paper. The study starts with the analysis of experimental results where the mass flow and momentum flux of two nozzles with very different values of these two variables are compared. This analysis shows relatively small differences in terms of mass flow and momentum flux, since the higher losses associated to the higher deflection of the streamlines with a higher inclination of the orifices are counteracted by the higher rounding radius, which favors the flow entrance to the orifice.To explain this experimental outcome, an extensive computational study involving nine geometries that combine different inclination angles and rounding radius is conducted, in order to quantify the influence of both parameters on the flow separately, as well as to assess the potential of their combination. These geometries are compared in terms of discharge coefficient, critical cavitation conditions and effective injection velocity, among others. Results show differences up to 15% in terms of mass flow rate and 8% for the effective injection velocity among the two extreme cases (lowest inclination and highest hydro-erosion level versus the nozzle with the highest inclination and lowest hydro-erosion level). Given the importance of these phenomena on the subsequent mixing and combustion processes, the results hereby presented are of interest for Diesel engines injectors and combustion chambers designers.