# Computational investigation of diesel nozzle internal flow during the complete injection event

• J. De la Morena
• G. Bracho
• D. Jaramillo
Technical Paper

## Abstract

Currently, diesel engines are calibrated using more and more complex multiple injection strategies. Under these conditions, the characteristics of the flow exiting the fuel injector are strongly affected by the transient interaction between the needle, the sac volume and the orifices, which are not yet clear. In the current paper, a methodology combining a 1D injector model and 3D-CFD simulations is proposed. First, the characteristics of the nozzle flow have been experimentally assessed in transient conditions by means of injection rate and momentum flux measurements. Later, the 3D-CFD modeling approach has been validated at steady-state fixed lift conditions. Finally, a previously developed 1D injector model has been used to extract the needle lift profiles and transient pressure boundary conditions used for the full-transient 3D-CFD simulations, using adaptive mesh refinement (AMR) strategies to be able to simulate the complete injection rate starting from 1 µm lift.

## Keywords

Nozzle Modeling Diesel Dynamic Moving-mesh

## Nomenclature

A

Constant for discharge coefficient vs. Reynolds equation

Aeff

Effective area

Ao

Geometrical area

Ca

Area coefficient

Cc

Contraction coefficient

Cd

Discharge coefficient

Cd,max

Maximum value of discharge coefficient vs. Reynolds

Cv

Velocity coefficient

Do

Geometrical nozzle diameter

$$\dot{m}$$

Mass flow

$$\dot{M}$$

Momentum flux

Pback

Discharge pressure

Pinj

Injection pressure

uo

Outlet nozzle orifice velocity

uth

Theoretical outlet orifice velocity, $$u_{\text{o}} = \sqrt {\frac{{2 \cdot (P_{\text{inj}} - P_{\text{back}} )}}{{\rho_{\text{f}} }}}$$

## Greek symbols

ΔP

Pressure drop, ΔP = Pinj − Pback

ρf

Fuel density

υf

Kinematic viscosity

λ

Flow coefficient or theoretical Reynolds number

## Notes

### Acknowledgements

This work was partly sponsored by “Ministerio de Economía y Competitividad”, of the Spanish Government, in the frame of the Project “Estudio de la interacción chorro-pared en condiciones realistas de motor”, Reference TRA2015-67679-c2-1-R. The authors would like also to thank the computer resources, technical expertise and assistance provided by Universidad de Valencia in the use of the supercomputer “Tirant”. Mr. Jaramillo’s Thesis is funded by “Conselleria d’Educació, Cultura i Esports” of Generalitat Valenciana in the frame of the program “Programa VALI + D para investigadores en formación, Reference ACIF/2015/040.

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© The Brazilian Society of Mechanical Sciences and Engineering 2018