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Papers by kaushik saha

Springer proceedings in energy, 2024

Energy, Environment, and Sustainability, 2017

Detailed analysis of the internal and the near-nozzle flow of fuel injectors is a necessity for a... more Detailed analysis of the internal and the near-nozzle flow of fuel injectors is a necessity for a comprehensive understanding of any internal combustion engine performance. For gasoline direct injection engines, under part-load conditions, the in-cylinder pressure can be subatmospheric when the high-temperature fuel is injected, resulting in flash boiling. Detailed experimental characterization of such complex phenomena is extremely difficult. Three-dimensional computational fluid dynamics (CFD) simulations provide key insights into the flash boiling phenomena. The Spray G injector from Engine Combustion Network (ECN) has been considered for this study, which has eight counter-bored holes. Homogeneous relaxation model is used to capture the rate of phase change. Standard and RNG \(k-\epsilon \) turbulence models have been employed for modeling turbulence effects. Based on apriori thermodynamic estimates, three types of thermodynamic conditions have been explored: non-flashing, moderate flashing, and intense flashing. Numerical analyses showed that with more flashing the spray plumes grow wider due to the volume expansion of the rapidly forming fuel vapor. Mainly single-component fuel is studied in this work. Iso-octane is considered as the gasoline surrogate for this study. Binary component blends of isooctane and ethanol were also tested for blended fuel flashing predictions using the existing numerical setup. After careful estimation of blended fuel saturation properties, the simulations indicated that blended fuels can be more volatile than the individual components and thus exhibit more flashing compared to the cases with single-component fuels.

SAE Technical Paper Series, 2017

Frontiers in Mechanical Engineering

A numerical study has been carried out to understand the effects of Unsteady Reynolds Averaged Na... more A numerical study has been carried out to understand the effects of Unsteady Reynolds Averaged Navier-Stokes (standard k ― ε and RNG k ― ε model) and large eddy simulations (LES) on a multi-hole gasoline direct injection (GDI) system. The fuel injector considered in this study is the Spray G nozzle from the Engine Combustion Network (ECN). A blob injection model, based on empirical rate of injection (ROI) profile, is considered in this study. The latest data on spray penetrations from Engine Combustion Network is used for model validation along with experimental findings on suction velocity and local droplet diameter. The spray breakup is simulated by using the KH-RT breakup length model. The turbulence model constant Cε1, is tuned to match with the experimental data of liquid and vapor penetrations in simulations while using the standard k-ε turbulence model. On the other hand, the Kelvin-Helmholtz breakup model time constant (B1) and Rayleigh Taylor breakup length constant (Cbl) a...

Vibroengineering PROCEDIA, 2019

This study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 442... more This study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 4424 and MHKF-240 at 60 angle of attack under cavitation. The Schnerr and Sauer cavitation model along with Realizable k-ε turbulence model is used for numerical computation in commercial software ANSYS Fluent. The lift, drag and pressure coefficients for different cavitation numbers were studied. Among both the hydrofoils MHKF-240 gives a higher lift coefficient which is the parameter of better performance.

Cavitation-induced erosion is the result of repeated impacts from cavitation collapse events on a... more Cavitation-induced erosion is the result of repeated impacts from cavitation collapse events on a solid surface. To improve representation of the incubation period before material rupture within multiphase flow simulations, a new physics-based metric was derived based on cumulative energy absorbed by the solid material from repeated hydrodynamic impacts. Previous work by the authors validated the modeling framework through comparison of critical erosion sites and relative erosion severity with available experimental data. In this study, the predictive capabilities of the cavitation erosion metric are extended by relating the predicted stored energy with the solid material properties to estimate the incubation period. To extend the rigor of validation of the erosion predictions, the turbulent multiphase flow development was simulated over a range of Reynolds (Re = 1.5-2.0·10) and cavitation number (K = 1.60-1.78) conditions in an aluminum channel geometry featuring a sharp inlet corn...

Vibroengineering PROCEDIA, 2018

To get better understanding of vortex shedding mechanism, we conducted numerical simulation on NA... more To get better understanding of vortex shedding mechanism, we conducted numerical simulation on NACA 4418 hydrofoil at an angle of attack of 12° for 2D incompressible flow. The numerical method consists of transient, finite volume method using Transient SST turbulent model to capture the turbulent wake flows. At high Reynolds number the occurrence of 2D structures of shed vortices and the modulation of vortex-induced frequency are investigated. The lift, pressure and skin friction coefficients of hydrofoil were studied.

Proceedings of the 10th International Symposium on Cavitation (CAV2018), 2018

Extreme low pressure regions develop in the high pressure direct injection fuel flow inside the f... more Extreme low pressure regions develop in the high pressure direct injection fuel flow inside the fuel injector holes, compelling the liquid fuel to transform to vapour phase in the form of vapour cavities or bubbles, a phenomenon known as cavitation. The cavitation phenomenon determines the quality of primary atomization and hence affects the performance of direct injection diesel or gasoline engines. A cavitation model, coupled with the mixture multiphase approach and RNG k − turbulence model, has been developed and implemented in this study for analysing cavitation. The cavitation model has been implemented in ANSYS Fluent platform. The model predictions have been compared with results from experimental works available in the literature. A good agreement of the model predictions has been observed. Comparisons of the model with other cavitation models (Schnerr & Sauer and Zwart-Gerber-Belamri) available in ANSYS Fluent have been carried out with both mixture and Eulerian-Eulerian mu...

Transportation Engineering, 2020

Abstract This work presents the development of a cavitation-induced erosion risk assessment (CIER... more Abstract This work presents the development of a cavitation-induced erosion risk assessment (CIERA) tool that links multiphase flow simulation predictions with the progress towards material erosion. To develop a robust erosion modeling tool, the cavitation and erosion predictions for pressurized diesel fuel flow within a channel geometry were validated over a range of Reynolds and cavitation number conditions in two different aluminum channel geometries, one featuring a rounded inlet corner and the other with a sharp inlet corner. The multiphase flow development within the channel was modeled using a compressible mixture model, where phase change was represented with the homogeneous relaxation model and the turbulent flow evolution was modeled using a dynamic structure approach for Large Eddy Simulations. To improve representation of the incubation period before material rupture over existing approaches, a physics-based metric was derived based on the cumulative energy absorbed by the solid material from repeated hydrodynamic impacts. When the average peak pressure was related to the incubation period, the incubation period and its sensitivity to changes in flow conditions were found to be overpredicted. In contrast, predictions from CIERA provided a more accurate means to qualitatively and quantitatively predict the influence of flow conditions on the incubation period before material erosion. When the predicted stored energy was related to the solid material properties to estimate the incubation period, multiphase flow simulations demonstrated accurate representation of the sensitivity of erosion severity to changes in flow conditions. The use of CIERA led to quantitative agreement of the predicted incubation period within 5% of the experimentally measured incubation period.

SAE International Journal of Engines, 2016

Journal of Energy Resources Technology, 2016

A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a mult... more A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multihole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from the engine combustion network (ECN). Simulations have been carried out for a fixed needle lift. The effects of turbulence, compressibility, and noncondensable gases have been considered in this work. Standard k–ε turbulence model has been used to model the turbulence. Homogeneous relaxation model (HRM) coupled with volume of fluid (VOF) approach has been utilized to capture the phase-change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine nonflashing and evaporative, nonflashing and nonevaporative, and flashing conditions. Noticeable hole-to-hole variations have been observed in terms of mass flow rates for all the holes under...

SAE Technical Paper Series, 2012

SAE Technical Paper Series, 2011

... SCR Systems. Date Published: 2011-04-12. Paper Number: 2011-01-1317. DOI: 10.4271/2011-01-131... more ... SCR Systems. Date Published: 2011-04-12. Paper Number: 2011-01-1317. DOI: 10.4271/2011-01-1317. Author(s): Ehab Abu-Ramadan - Univ. of Waterloo KaushikSaha - Univ. of Waterloo Xianguo Li - Univ. of Waterloo. Abstract. ...

Journal of Thermal Spray Technology, 2012

A comprehensive computational model based on finite difference method was developed to study the ... more A comprehensive computational model based on finite difference method was developed to study the heat and mass transport within solution precursor droplets injected into a laminar microwave air plasma flow field. Plasma flow field was simulated as hot gas flowing in a quartz tube generated by volumetric heat addition in the microwave coupling region. The resulting air plasma had a maximum temperature of 6000 K. Droplets containing zirconium acetate precursor of different diameters and solute concentrations were injected into the axisymmetric laminar plasma flow along the centerline of the plasma. Variation of transport properties of the plasma surrounding spherical droplets and absorption of microwave radiation within these droplets were considered in the model. Model predictions suggest that solution droplets are not affected by the microwave radiation in the presence of high convective heat flux from microwave plasma. Smaller droplets and high solute concentrations result in formation of thicker precipitate shells around them based on the homogeneous precipitation hypothesis. Mass transport is found to be slower than heat transfer in the droplets. Microwave plasma allowing the possibility of injecting droplets axially into the high temperature plasma environment present the opportunity to produce more consistent precipitate states as compared to DC arc plasmas into which droplets are typically injected transversely in thermal spray applications.

Journal of Engineering for Gas Turbines and Power, 2013

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fue... more A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the single-fluid mixture approach with newly derived expressions for the phase change rate and local mean effective pressure—the two key components of the model. The effects of the turbulence, compressibility, and wall roughness are accounted for in the present model and model validation is carried out by comparing the model predictions of probable cavitation regions, velocity distribution, and fuel mass flow rate with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its higher viscosity. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. The renormalization group (RNG) k-ɛ model for turbulence modeling is reasonable by comparing its performanc...

Applied Energy, 2012

Biodiesel and more often its blends have been extensively used to mitigate the dependence on foss... more Biodiesel and more often its blends have been extensively used to mitigate the dependence on fossil fuel and the greenhouse gas emissions. However, a good understanding of the impact of the difference in the thermophysical properties of biodiesel and its blends from those of petroleum diesel is required to reap the benefits of biodiesel utilization. In this study a multicomponent evaporation model has been developed for pure and blended biodiesel droplets to investigate their evaporation characteristics in high temperature convective environment as encountered in practical combustion systems; and it is validated through a comparison with experimental results. The vaporization characteristics of pure diesel, pure biodiesel fuel droplets as well as the effect of mixing them in different proportions (B20 and B50) are presented. The results reveal that biodiesel droplets evaporate at a slower rate than the diesel droplets because of biodiesel's relatively low vapor pressure. Consequently, the blending of diesel fuel with small proportions of biodiesel results in an increase in the evaporation timescale of the blended fuel droplets. Diffusion in the liquid phase is observed to be the rate controlling factor for blended droplet vaporization. The possibility of internal gasification for blended droplets is also investigated. A droplet with higher quantity of diesel is more prone to undergo internal gasification but micro-explosion is not likely to occur at atmospheric pressure.

Flash boiling is known to be a common phenomenon for Gasoline Direct Injection (GDI) engine spray... more Flash boiling is known to be a common phenomenon for Gasoline Direct Injection (GDI) engine sprays. Homogeneous Relaxation Model has been adopted in many recent numerical studies for predicting cavitation and flash boiling. Assessment of the Homogeneous Relaxation Model has been presented in this study. Sensitivity analysis of the model parameters has been documented to infer the driving factors for the flash boiling predictions. The model parameters have been varied over a range and the differences in predictions for the extent of flashing have been studied. Apart from flashing in the near-nozzle regions, mild cavitation is also predicted inside the gasoline injectors. The variation in the predicted time-scales through the model parameters for predicting these two different thermodynamic phenomena (cavitation, flash) have been elaborated in this study. ∗Corresponding Author: ksaha@anl.gov

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fue... more A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the single-fluid mixture approach with newly derived expressions for the phase change rate and local mean effective pressure—the two key components of the model. The effects of the turbulence, compressibility, and wall roughness are accounted for in the present model and model validation is carried out by comparing the model predictions of probable cavitation regions, velocity distribution, and fuel mass flow rate with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its higher viscosity. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. The renormalization group (RNG) k  e model for turbulence modeling is reasonable by comparing its performa...

Springer proceedings in energy, 2024

Energy, Environment, and Sustainability, 2017

Detailed analysis of the internal and the near-nozzle flow of fuel injectors is a necessity for a... more Detailed analysis of the internal and the near-nozzle flow of fuel injectors is a necessity for a comprehensive understanding of any internal combustion engine performance. For gasoline direct injection engines, under part-load conditions, the in-cylinder pressure can be subatmospheric when the high-temperature fuel is injected, resulting in flash boiling. Detailed experimental characterization of such complex phenomena is extremely difficult. Three-dimensional computational fluid dynamics (CFD) simulations provide key insights into the flash boiling phenomena. The Spray G injector from Engine Combustion Network (ECN) has been considered for this study, which has eight counter-bored holes. Homogeneous relaxation model is used to capture the rate of phase change. Standard and RNG \(k-\epsilon \) turbulence models have been employed for modeling turbulence effects. Based on apriori thermodynamic estimates, three types of thermodynamic conditions have been explored: non-flashing, moderate flashing, and intense flashing. Numerical analyses showed that with more flashing the spray plumes grow wider due to the volume expansion of the rapidly forming fuel vapor. Mainly single-component fuel is studied in this work. Iso-octane is considered as the gasoline surrogate for this study. Binary component blends of isooctane and ethanol were also tested for blended fuel flashing predictions using the existing numerical setup. After careful estimation of blended fuel saturation properties, the simulations indicated that blended fuels can be more volatile than the individual components and thus exhibit more flashing compared to the cases with single-component fuels.

SAE Technical Paper Series, 2017

Frontiers in Mechanical Engineering

A numerical study has been carried out to understand the effects of Unsteady Reynolds Averaged Na... more A numerical study has been carried out to understand the effects of Unsteady Reynolds Averaged Navier-Stokes (standard k ― ε and RNG k ― ε model) and large eddy simulations (LES) on a multi-hole gasoline direct injection (GDI) system. The fuel injector considered in this study is the Spray G nozzle from the Engine Combustion Network (ECN). A blob injection model, based on empirical rate of injection (ROI) profile, is considered in this study. The latest data on spray penetrations from Engine Combustion Network is used for model validation along with experimental findings on suction velocity and local droplet diameter. The spray breakup is simulated by using the KH-RT breakup length model. The turbulence model constant Cε1, is tuned to match with the experimental data of liquid and vapor penetrations in simulations while using the standard k-ε turbulence model. On the other hand, the Kelvin-Helmholtz breakup model time constant (B1) and Rayleigh Taylor breakup length constant (Cbl) a...

Vibroengineering PROCEDIA, 2019

This study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 442... more This study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 4424 and MHKF-240 at 60 angle of attack under cavitation. The Schnerr and Sauer cavitation model along with Realizable k-ε turbulence model is used for numerical computation in commercial software ANSYS Fluent. The lift, drag and pressure coefficients for different cavitation numbers were studied. Among both the hydrofoils MHKF-240 gives a higher lift coefficient which is the parameter of better performance.

Cavitation-induced erosion is the result of repeated impacts from cavitation collapse events on a... more Cavitation-induced erosion is the result of repeated impacts from cavitation collapse events on a solid surface. To improve representation of the incubation period before material rupture within multiphase flow simulations, a new physics-based metric was derived based on cumulative energy absorbed by the solid material from repeated hydrodynamic impacts. Previous work by the authors validated the modeling framework through comparison of critical erosion sites and relative erosion severity with available experimental data. In this study, the predictive capabilities of the cavitation erosion metric are extended by relating the predicted stored energy with the solid material properties to estimate the incubation period. To extend the rigor of validation of the erosion predictions, the turbulent multiphase flow development was simulated over a range of Reynolds (Re = 1.5-2.0·10) and cavitation number (K = 1.60-1.78) conditions in an aluminum channel geometry featuring a sharp inlet corn...

Vibroengineering PROCEDIA, 2018

To get better understanding of vortex shedding mechanism, we conducted numerical simulation on NA... more To get better understanding of vortex shedding mechanism, we conducted numerical simulation on NACA 4418 hydrofoil at an angle of attack of 12° for 2D incompressible flow. The numerical method consists of transient, finite volume method using Transient SST turbulent model to capture the turbulent wake flows. At high Reynolds number the occurrence of 2D structures of shed vortices and the modulation of vortex-induced frequency are investigated. The lift, pressure and skin friction coefficients of hydrofoil were studied.

Proceedings of the 10th International Symposium on Cavitation (CAV2018), 2018

Extreme low pressure regions develop in the high pressure direct injection fuel flow inside the f... more Extreme low pressure regions develop in the high pressure direct injection fuel flow inside the fuel injector holes, compelling the liquid fuel to transform to vapour phase in the form of vapour cavities or bubbles, a phenomenon known as cavitation. The cavitation phenomenon determines the quality of primary atomization and hence affects the performance of direct injection diesel or gasoline engines. A cavitation model, coupled with the mixture multiphase approach and RNG k − turbulence model, has been developed and implemented in this study for analysing cavitation. The cavitation model has been implemented in ANSYS Fluent platform. The model predictions have been compared with results from experimental works available in the literature. A good agreement of the model predictions has been observed. Comparisons of the model with other cavitation models (Schnerr & Sauer and Zwart-Gerber-Belamri) available in ANSYS Fluent have been carried out with both mixture and Eulerian-Eulerian mu...

Transportation Engineering, 2020

Abstract This work presents the development of a cavitation-induced erosion risk assessment (CIER... more Abstract This work presents the development of a cavitation-induced erosion risk assessment (CIERA) tool that links multiphase flow simulation predictions with the progress towards material erosion. To develop a robust erosion modeling tool, the cavitation and erosion predictions for pressurized diesel fuel flow within a channel geometry were validated over a range of Reynolds and cavitation number conditions in two different aluminum channel geometries, one featuring a rounded inlet corner and the other with a sharp inlet corner. The multiphase flow development within the channel was modeled using a compressible mixture model, where phase change was represented with the homogeneous relaxation model and the turbulent flow evolution was modeled using a dynamic structure approach for Large Eddy Simulations. To improve representation of the incubation period before material rupture over existing approaches, a physics-based metric was derived based on the cumulative energy absorbed by the solid material from repeated hydrodynamic impacts. When the average peak pressure was related to the incubation period, the incubation period and its sensitivity to changes in flow conditions were found to be overpredicted. In contrast, predictions from CIERA provided a more accurate means to qualitatively and quantitatively predict the influence of flow conditions on the incubation period before material erosion. When the predicted stored energy was related to the solid material properties to estimate the incubation period, multiphase flow simulations demonstrated accurate representation of the sensitivity of erosion severity to changes in flow conditions. The use of CIERA led to quantitative agreement of the predicted incubation period within 5% of the experimentally measured incubation period.

SAE International Journal of Engines, 2016

Journal of Energy Resources Technology, 2016

A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a mult... more A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multihole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from the engine combustion network (ECN). Simulations have been carried out for a fixed needle lift. The effects of turbulence, compressibility, and noncondensable gases have been considered in this work. Standard k–ε turbulence model has been used to model the turbulence. Homogeneous relaxation model (HRM) coupled with volume of fluid (VOF) approach has been utilized to capture the phase-change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine nonflashing and evaporative, nonflashing and nonevaporative, and flashing conditions. Noticeable hole-to-hole variations have been observed in terms of mass flow rates for all the holes under...

SAE Technical Paper Series, 2012

SAE Technical Paper Series, 2011

... SCR Systems. Date Published: 2011-04-12. Paper Number: 2011-01-1317. DOI: 10.4271/2011-01-131... more ... SCR Systems. Date Published: 2011-04-12. Paper Number: 2011-01-1317. DOI: 10.4271/2011-01-1317. Author(s): Ehab Abu-Ramadan - Univ. of Waterloo KaushikSaha - Univ. of Waterloo Xianguo Li - Univ. of Waterloo. Abstract. ...

Journal of Thermal Spray Technology, 2012

A comprehensive computational model based on finite difference method was developed to study the ... more A comprehensive computational model based on finite difference method was developed to study the heat and mass transport within solution precursor droplets injected into a laminar microwave air plasma flow field. Plasma flow field was simulated as hot gas flowing in a quartz tube generated by volumetric heat addition in the microwave coupling region. The resulting air plasma had a maximum temperature of 6000 K. Droplets containing zirconium acetate precursor of different diameters and solute concentrations were injected into the axisymmetric laminar plasma flow along the centerline of the plasma. Variation of transport properties of the plasma surrounding spherical droplets and absorption of microwave radiation within these droplets were considered in the model. Model predictions suggest that solution droplets are not affected by the microwave radiation in the presence of high convective heat flux from microwave plasma. Smaller droplets and high solute concentrations result in formation of thicker precipitate shells around them based on the homogeneous precipitation hypothesis. Mass transport is found to be slower than heat transfer in the droplets. Microwave plasma allowing the possibility of injecting droplets axially into the high temperature plasma environment present the opportunity to produce more consistent precipitate states as compared to DC arc plasmas into which droplets are typically injected transversely in thermal spray applications.

Journal of Engineering for Gas Turbines and Power, 2013

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fue... more A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the single-fluid mixture approach with newly derived expressions for the phase change rate and local mean effective pressure—the two key components of the model. The effects of the turbulence, compressibility, and wall roughness are accounted for in the present model and model validation is carried out by comparing the model predictions of probable cavitation regions, velocity distribution, and fuel mass flow rate with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its higher viscosity. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. The renormalization group (RNG) k-ɛ model for turbulence modeling is reasonable by comparing its performanc...

Applied Energy, 2012

Biodiesel and more often its blends have been extensively used to mitigate the dependence on foss... more Biodiesel and more often its blends have been extensively used to mitigate the dependence on fossil fuel and the greenhouse gas emissions. However, a good understanding of the impact of the difference in the thermophysical properties of biodiesel and its blends from those of petroleum diesel is required to reap the benefits of biodiesel utilization. In this study a multicomponent evaporation model has been developed for pure and blended biodiesel droplets to investigate their evaporation characteristics in high temperature convective environment as encountered in practical combustion systems; and it is validated through a comparison with experimental results. The vaporization characteristics of pure diesel, pure biodiesel fuel droplets as well as the effect of mixing them in different proportions (B20 and B50) are presented. The results reveal that biodiesel droplets evaporate at a slower rate than the diesel droplets because of biodiesel's relatively low vapor pressure. Consequently, the blending of diesel fuel with small proportions of biodiesel results in an increase in the evaporation timescale of the blended fuel droplets. Diffusion in the liquid phase is observed to be the rate controlling factor for blended droplet vaporization. The possibility of internal gasification for blended droplets is also investigated. A droplet with higher quantity of diesel is more prone to undergo internal gasification but micro-explosion is not likely to occur at atmospheric pressure.

Flash boiling is known to be a common phenomenon for Gasoline Direct Injection (GDI) engine spray... more Flash boiling is known to be a common phenomenon for Gasoline Direct Injection (GDI) engine sprays. Homogeneous Relaxation Model has been adopted in many recent numerical studies for predicting cavitation and flash boiling. Assessment of the Homogeneous Relaxation Model has been presented in this study. Sensitivity analysis of the model parameters has been documented to infer the driving factors for the flash boiling predictions. The model parameters have been varied over a range and the differences in predictions for the extent of flashing have been studied. Apart from flashing in the near-nozzle regions, mild cavitation is also predicted inside the gasoline injectors. The variation in the predicted time-scales through the model parameters for predicting these two different thermodynamic phenomena (cavitation, flash) have been elaborated in this study. ∗Corresponding Author: ksaha@anl.gov

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fue... more A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the single-fluid mixture approach with newly derived expressions for the phase change rate and local mean effective pressure—the two key components of the model. The effects of the turbulence, compressibility, and wall roughness are accounted for in the present model and model validation is carried out by comparing the model predictions of probable cavitation regions, velocity distribution, and fuel mass flow rate with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its higher viscosity. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. The renormalization group (RNG) k  e model for turbulence modeling is reasonable by comparing its performa...