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ABSTRACT
Wall film formation and evaporation were studied on a flat wall inside a constant-volume vessel using a three-dimensional numerical method. The computation was based on the discrete phase model (DPM) of spray dispersion, a spray–wall interaction model coupled with an enhanced wall film evaporation sub-model, in which the operating conditions of cold wall are considered for port fuel injection (PFI) engines. The influence of impacting parameters including injection pressure, the impingement distance from the injector and the impinged wall, injection duration, impingement angle, and wall temperature was discussed.
Nomenclature
| a | = | coefficient introduced in Eq. (15) |
| A | = | area |
| b | = | coefficient introduced in Eq. (15) |
| BM | = | Spalding number |
| Cf | = | skin friction coefficient |
| d | = | diameter |
| E | = | impact energy |
| F | = | force |
| h0 | = | film height |
| hf | = | convective coefficient |
| hfg | = | latent heat of vaporization |
| k | = | liquid thermal conductivity |
| = | evaporation rate | |
| M | = | molar mass |
| = | mass source | |
| = | unit normal | |
| p | = | pressure |
| q | = | heat flux |
| Re | = | Reynolds number |
| t | = | time |
| t′ | = | elapsed time from spray impinges on the wall |
| = | unit vector | |
| T | = | temperature |
| Vp | = | volume of the parcel |
| Yfs | = | mass fraction |
| δ | = | film thickness |
| μ | = | dynamic viscosity |
| ρ | = | density |
| σ | = | surface tension of the liquid |
| τ | = | shear stress |
| Subscripts | = | |
| a | = | air |
| b | = | boiling |
| bl | = | boundary layer |
| cond | = | conduction |
| conv | = | convection |
| f | = | fuel |
| g | = | gas |
| imp | = | impingement |
| inj | = | injection |
| l | = | liquid |
| p | = | particle |
| rent | = | re-entrainment |
| s | = | surface |
| vap | = | vaporization |
| w | = | wall |
Nomenclature
| a | = | coefficient introduced in Eq. (15) |
| A | = | area |
| b | = | coefficient introduced in Eq. (15) |
| BM | = | Spalding number |
| Cf | = | skin friction coefficient |
| d | = | diameter |
| E | = | impact energy |
| F | = | force |
| h0 | = | film height |
| hf | = | convective coefficient |
| hfg | = | latent heat of vaporization |
| k | = | liquid thermal conductivity |
| = | evaporation rate | |
| M | = | molar mass |
| = | mass source | |
| = | unit normal | |
| p | = | pressure |
| q | = | heat flux |
| Re | = | Reynolds number |
| t | = | time |
| t′ | = | elapsed time from spray impinges on the wall |
| = | unit vector | |
| T | = | temperature |
| Vp | = | volume of the parcel |
| Yfs | = | mass fraction |
| δ | = | film thickness |
| μ | = | dynamic viscosity |
| ρ | = | density |
| σ | = | surface tension of the liquid |
| τ | = | shear stress |
| Subscripts | = | |
| a | = | air |
| b | = | boiling |
| bl | = | boundary layer |
| cond | = | conduction |
| conv | = | convection |
| f | = | fuel |
| g | = | gas |
| imp | = | impingement |
| inj | = | injection |
| l | = | liquid |
| p | = | particle |
| rent | = | re-entrainment |
| s | = | surface |
| vap | = | vaporization |
| w | = | wall |