A new approach to compute temperature in a liquid-gas mixture. Application to study the effect of wall nozzle temperature on a Diesel injector

Abstract

Thermal effects on internal combustion engines have been always a hot topic. Concretely, temperature influence on the injection systems is still under research. In this work, a homogeneous model named Eulerian Spray Atomization (ESA) is used to simulate Engine Combustion Network (ECN) Diesel Spray A conditions. A new approach is considered for the thermodynamic model of the fuel and gas mixture. Experimentally obtained values of the liquid enthalpy are directly employed in the simulation to determine the temperature, without any need of knowing its heat capacity or expansion coefficient. This allows to accurately study heating and cooling phenomena inside the Diesel nozzle. Results show that two different boundary conditions could be applied at nozzle walls, either fixed temperature value or adiabatic walls, and still obtain good prediction of injection parameters. Also, the effect of fuel temperature has been investigated. For Spray A conditions, nozzle and spray parameters are the same regardless the fuel temperature. Nevertheless, fluid properties (density, velocity.. .) inside the nozzle significantly change; which means that these type of models could serve in future for cavitation erosion or coking studies.

Experimental and Computational Investigation of Subcritical Near-Nozzle Spray Structure and Primary Atomization in the Engine Combustion Network Spray D

“…To perform the simulations, an Eulerian homogeneous unsteady multiphase model has been implemented in OpenFOAM Foam-extend 3.2, similar to the one developed by Vallet et al [11]. The three main differences are: the pressure equation corrected by García-Oliver et al [12] is used instead of the equation of state of Vallet et al; the new model is compressible, so the energy equation is needed (in this case it is written in terms of static enthalpy) [13]; and liquid density and compressibility are computed through correlations to experimental data [13,40].…”

“…Even though the model has been thoroughly described in the literature and previous publications [12,13], a brief summary of the equations and sub-models is given. As previously mentioned, the liquid spreading into the ambient gas is modeled with a turbulent diffusion flux given by Fick's law.…”

“…However, the extremely fine droplets generated by the spray due to the high Re and We numbers result in a tremendous burden on the direct simulation of this type of two-phase flow, where the complexity of the interfacial area rapidly necessitates very high grid densities. Alternatively, the interface dynamics can be described by assuming that the interface is diffuse, as is done in the Eulerian Σ-Y approach [11][12][13], which assumes the liquid and gas phases are locally mixed. Relative to the sharp-interface capturing approaches, these methods provide a more computationally efficient means to model the spray.…”

Measurements of the mass allocation for multiple injection strategies using the rate of injection and momentum flux signals

“…Over the years, researchers have studied fuel sprays thoroughly to understand the fundamental processes and establish a reliable experimental set of data that enables the validation of more detailed numerical models. 11 In such sense, computational fluid dynamics (CFD) provides unmatched advantages that coherently complement experimental measurements, as they offer detailed spatial information of complex variables 12 with a high temporal resolution. Moreover, the predictive capabilities of validated CFD models can help to reduce testing times and production costs.…”

Engine combustion network special issue

“…There are many other examples where ''peloton-leading'' discoveries were made after identifying supposed problems. A partial list includes discoveries for internal nozzle flow, [7][8][9][10][11] plume interactions, 10,12,13 velocity, 10,13 mixing, 8,14,15 soot, [16][17][18] and supercritical mixing behavior. 19 Based upon the usual tracking metrics, the ECN has made remarkable progress since its founding 10 years ago.…”