Consequences of using biodiesel on the injection and air–fuel mixing processes in diesel engines

Energy Conversion and Management

Morena

Martinez-Lopez

et al. 2017

Diesel fuel injection systems are being used at higher injection pressure conditions over time because of more stringent emissions requirements. Thus, the importance to properly take into account the fluid compressibility on injection CFD simulations is also increasing. In this paper, an investigation of the compressibility effects in nozzle flow simulations has been carried out for injection pressures up to 250 MPa. To do so, the fluid properties (including density, viscosity and speed of sound) have been measured in a wide range of boundary conditions. These measurements have allowed to obtain correlations for the fluid properties as a function of pressure and temperature. Then, these equations have been incorporated to a CFD solver to take into account the variation of the fluid properties with the pressure changes along the computational domain. The results from

supporting

confidence: 73%

Assessment of compressibility effects on internal nozzle flow in diesel injectors at very high injection pressures

Energy Conversion and Management

Morena

Martinez-Lopez

et al. 2017

“…Significant effort has been also made in the modeling of diesel sprays [33][34][35][36]. Onedimensional phenomenological models, based on the gaseous jet analogy, have shown to be useful to evaluate the main spray features both in stationary and transient conditions [37,38]. Nevertheless, microscopic details of the spray such as the droplet velocity and diameter or the turbulence characteristics cannot be evaluated using these methodologies.…”

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

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.

“…This method has proved to be useful for images that clearly show two regions (liquid and gas) with different intensity levels. 1,6,18–21…”

Section: Experimental Toolsmentioning

confidence: 99%

“…It is well known that the spray characteristics are highly influenced by the flow features at the nozzle outlet. [18][19][20][21] However, study of these characteristics is very complicated owing to the small orifice diameters, the high velocities and the cavitation phenomenon that can take place inside the nozzle, especially in nonconvergent nozzles. [22][23][24][25][26] Additionally, many researchers have observed important increases in both the atomization level and the spray angle connected to the cavitation phenomenon.…”

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

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.