Numerical simulation and extended validation of two-phase compressible flow in diesel injector nozzles

Abstract

In this paper, the ability of a computational fluid dynamics code to reproduce cavitation phenomena accurately is checked by comparing data acquired by numerical simulations against those obtained from different experiments involving the mass flow, the momentum flux, and the effective injection velocity. Cavitation is modelled using a single-phase cavitation model based on a barotropic equation of state together with a homogeneous equilibrium assumption. In the research reported in this paper, the ability to use the code for actual diesel injector nozzle geometries and conditions has been checked and validated. The main contribution of the present investigation and what makes it different from previous work in the literature is the consideration of extended experimental data for validation purposes: the mass flow, the momentum flux at the nozzle exit, and the effective injection velocity. These are unique features in contrast with other publications, which normally take into account at the most, if at all, the cavitation morphology or the mass flow. The results obtained and their comparison with available experimental data show how the model is able to predict the behaviour of the fluid in such conditions with a high level of confidence.

Near Nozzle Field Conditions in Diesel Fuel Injector Testing

“…Combining the above the state equation reads: (8) The model used for ψ due to the mixture fraction has the linear form that follows: (9) The solver includes the viscous effects of the fuel and models the total viscosity as a linear combination of the phase state viscosities in a similar way: (10) Equation (8) can then be solved in an iterative PISO loop for pressure in combination with the momentum equation: (11) The physical constants used for viscosity, density and saturation pressure, p sat are given in Table 1 below. The simulation was configured to use an LES approach for turbulence.…”

“…The selection of a transient solver can be justified since the timescales for injection processes are small and it is inherently a transient event with total time < 1ms. CavitatingFoam was originally developed by Karrholm [12] and has been successfully validated by Salvador et al [10,11] up to pressures of 110MPa.…”

“…The reader is directed to the extensive body of literature concerned with modelling of diesel injection nozzles such as [9,10,11,12]. However, as will be explained further, the pressure waves which also arise within the nozzle and injector are relevant and so have been included in the study.…”

“…The selection of a transient solver can be justified since the timescales for injection processes are small and it is inherently a transient event with total time < 1ms. CavitatingFoam was originally developed by Karrholm [12] and has been successfully validated by Salvador et al [10,11] up to pressures of 110MPa.The solver uses a linear barotropic compressibility model and the compressibility, ψ, is related to the acoustic function by the speed of sound, cThe solver uses the following barotropic equation of state: (4) and applies the following restrictions on the density and vapor fraction gamma (γ) using subscripts to denote vapour (v) or liquid (l):Combining the above the state equation reads:The model used for ψ due to the mixture fraction has the linear form that follows:The solver includes the viscous effects of the fuel and models the total viscosity as a linear combination of the phase state viscosities in a similar way:(10) Equation (8) can then be solved in an iterative PISO loop for pressure in combination with the momentum equation:The physical constants used for viscosity, density and saturation pressure, p sat are given in Table 1 below. Where B is the turbulent energy generation term, (13) Of which the Smagorinsky model is a subset where the energy balance between the dissipation term from 12 equals the generation term 13.…”

Estudio computacional de la influencia del levantamiento de aguja sobre el flujo interno y el fenómeno de la cavitación en toberas de inyección diésel

“…En este tipo de sistemas, el papel que desarrolla la presión de inyección y, por tanto, el sistema de inyección es marginal. Por ello, suelen emplearse inyectores de un único orificio con presiones relativamente bajas (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).…”