Antonis Dris - Academia.edu (original) (raw)

Papers by Antonis Dris

Research paper thumbnail of Moving Toward Establishing More Robust and Systematic Model Development for IC Engines Using Process Informatics

SAE technical paper series, Apr 12, 2010

Research paper thumbnail of Influence of Injection Timing and Piston Bowl Geometry on PCCI Combustion and Emissions

SAE International journal of engines, Apr 20, 2009

Research paper thumbnail of The Analysis of Heat Transfer in Automotive Turbochargers

Journal of engineering for gas turbines and power, Jan 25, 2010

Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely me... more Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely measured or accounted for in any turbocharger performance assessment. Existing measurements suggest that the difference in turbine efficiency calculated in the conventional way, by means of the fluid temperature change, under adiabatic conditions differs considerably from the usual diabatic test conditions, particularly at low turbine pressure ratio. In the work described in this paper, three commercial turbochargers were extensively instrumented with thermocouples on all accessible external and internal surfaces in order to make comprehensive temperature surveys. The turbochargers were run at ranges of turbine inlet temperature and external ventilation. Adiabatic tests were also carried out to serve as a reference condition. Based on the temperature measurements, the internal heat fluxes from the turbine gas to the turbocharger structure and from there to the lubricating oil and the compressor, and the external heat fluxes to the environment were calculated. A one-dimensional heat transfer network model of the turbocharger was demonstrated to be able to simulate the heat fluxes to good accuracy, and the heat transfer coefficients required were ultimately found to be mostly independent of the turbochargers tested.

Research paper thumbnail of Transition on Concave Surfaces

Research paper thumbnail of The Origin of Turbulent Spots

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, Jun 7, 1999

Research paper thumbnail of Boundary layer transition on a flat plate and concave surfaces

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Research paper thumbnail of W?rmerohrprinzip zur Erw?rmung von Motor- und/oder Getriebe?l

Research paper thumbnail of Moving Toward Establishing More Robust and Systematic Model Development for IC Engines Using Process Informatics

SAE Technical Paper Series, 2010

Research paper thumbnail of Influence of Injection Timing and Piston Bowl Geometry on PCCI Combustion and Emissions

SAE International Journal of Engines, 2009

Research paper thumbnail of The Origin of Turbulent Spots

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 1999

It has been suggested that a turbulent spot is formed when a transient separation occurs in the l... more It has been suggested that a turbulent spot is formed when a transient separation occurs in the laminar boundary layer and this criterion has been successfully used by Johnson and Ercan [1996,1997] to predict bypass transition for boundary layers subjected to a wide range of freestream turbulence levels and streamwise pressure gradients. In the current paper experimental results are presented which support the premise that the formation of turbulent spots is associated with transient separation. Near wall hot wire signals in laminar and transitional boundary layers are analysed statistically to produce probability distributions for signal level and trough frequency. In the laminar period the signal level is normally distributed, but during the inter-turbulent periods in the transitional boundary layer the distribution is truncated at the tower end, i.e. the lowest velocity periods in the signal disappear, suggesting that these are replaced during transition by the turbulent periods....

Research paper thumbnail of The Origin of Turbulent Spots

Journal of Turbomachinery, 2000

It has been suggested that a turbulent spot is formed when a transient separation occurs in the l... more It has been suggested that a turbulent spot is formed when a transient separation occurs in the laminar boundary layer and this criterion has been successfully used by Johnson and Ercan (1996, ASME Paper No. 96-GT-44; 1997, ASME Paper No. 97-GT-475) to predict bypass transition for boundary layers subjected to a wide range of free-stream turbulence levels and streamwise pressure gradients. In the current paper experimental results are presented that support the premise that the formation of turbulent spots is associated with transient separation. Near-wall hot-wire signals in laminar and transitional boundary layers are analyzed statistically to produce probability distributions for signal level and trough frequency. In the laminar period the signal level is normally distributed, but during the inter-turbulent periods in the transitional boundary layer, the distribution is truncated at the lower end, i.e., the lowest velocity periods in the signal disappear, suggesting that these ar...

Research paper thumbnail of The Analysis of Heat Transfer in Automotive Turbochargers

Journal of Engineering for Gas Turbines and Power, 2010

Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely me... more Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely measured or accounted for in any turbocharger performance assessment. Existing measurements suggest that the difference in turbine efficiency calculated in the conventional way, by means of the fluid temperature change, under adiabatic conditions differs considerably from the usual diabatic test conditions, particularly at low turbine pressure ratio. In the work described in this paper, three commercial turbochargers were extensively instrumented with thermocouples on all accessible external and internal surfaces in order to make comprehensive temperature surveys. The turbochargers were run at ranges of turbine inlet temperature and external ventilation. Adiabatic tests were also carried out to serve as a reference condition. Based on the temperature measurements, the internal heat fluxes from the turbine gas to the turbocharger structure and from there to the lubricating oil and the compr...

Research paper thumbnail of Transition on Concave Surfaces

Journal of Turbomachinery, 2005

Boundary layer measurements have been made on the concave surfaces of two constant curvature blad... more Boundary layer measurements have been made on the concave surfaces of two constant curvature blades using hot wire anemometry. All the current experiments were performed with negligible streamwise pressure gradient. Grids were used to produce a range of freestream turbulence levels between 1% and 4%. The freestream velocity increases with distance from a concave wall according to the free vortex condition making the determination of the boundary layer edge difficult. A flat plate equivalent boundary layer procedure was adopted, therefore, to overcome this problem. The Taylor–Goertler (TG) vortices resulting from the concave curvature were found to make the laminar and turbulent boundary layer profiles fuller and to increase the skin friction coeffiicent by up to 40% compared with flat plate values. This leads to a more rapid growth in boundary layer thickness. The evolution in the intermittency through transition is very similar to that for a flat plate, however, the shape factors a...

Research paper thumbnail of Moving Toward Establishing More Robust and Systematic Model Development for IC Engines Using Process Informatics

SAE technical paper series, Apr 12, 2010

Research paper thumbnail of Influence of Injection Timing and Piston Bowl Geometry on PCCI Combustion and Emissions

SAE International journal of engines, Apr 20, 2009

Research paper thumbnail of The Analysis of Heat Transfer in Automotive Turbochargers

Journal of engineering for gas turbines and power, Jan 25, 2010

Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely me... more Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely measured or accounted for in any turbocharger performance assessment. Existing measurements suggest that the difference in turbine efficiency calculated in the conventional way, by means of the fluid temperature change, under adiabatic conditions differs considerably from the usual diabatic test conditions, particularly at low turbine pressure ratio. In the work described in this paper, three commercial turbochargers were extensively instrumented with thermocouples on all accessible external and internal surfaces in order to make comprehensive temperature surveys. The turbochargers were run at ranges of turbine inlet temperature and external ventilation. Adiabatic tests were also carried out to serve as a reference condition. Based on the temperature measurements, the internal heat fluxes from the turbine gas to the turbocharger structure and from there to the lubricating oil and the compressor, and the external heat fluxes to the environment were calculated. A one-dimensional heat transfer network model of the turbocharger was demonstrated to be able to simulate the heat fluxes to good accuracy, and the heat transfer coefficients required were ultimately found to be mostly independent of the turbochargers tested.

Research paper thumbnail of Transition on Concave Surfaces

Research paper thumbnail of The Origin of Turbulent Spots

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, Jun 7, 1999

Research paper thumbnail of Boundary layer transition on a flat plate and concave surfaces

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Research paper thumbnail of W?rmerohrprinzip zur Erw?rmung von Motor- und/oder Getriebe?l

Research paper thumbnail of Moving Toward Establishing More Robust and Systematic Model Development for IC Engines Using Process Informatics

SAE Technical Paper Series, 2010

Research paper thumbnail of Influence of Injection Timing and Piston Bowl Geometry on PCCI Combustion and Emissions

SAE International Journal of Engines, 2009

Research paper thumbnail of The Origin of Turbulent Spots

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 1999

It has been suggested that a turbulent spot is formed when a transient separation occurs in the l... more It has been suggested that a turbulent spot is formed when a transient separation occurs in the laminar boundary layer and this criterion has been successfully used by Johnson and Ercan [1996,1997] to predict bypass transition for boundary layers subjected to a wide range of freestream turbulence levels and streamwise pressure gradients. In the current paper experimental results are presented which support the premise that the formation of turbulent spots is associated with transient separation. Near wall hot wire signals in laminar and transitional boundary layers are analysed statistically to produce probability distributions for signal level and trough frequency. In the laminar period the signal level is normally distributed, but during the inter-turbulent periods in the transitional boundary layer the distribution is truncated at the tower end, i.e. the lowest velocity periods in the signal disappear, suggesting that these are replaced during transition by the turbulent periods....

Research paper thumbnail of The Origin of Turbulent Spots

Journal of Turbomachinery, 2000

It has been suggested that a turbulent spot is formed when a transient separation occurs in the l... more It has been suggested that a turbulent spot is formed when a transient separation occurs in the laminar boundary layer and this criterion has been successfully used by Johnson and Ercan (1996, ASME Paper No. 96-GT-44; 1997, ASME Paper No. 97-GT-475) to predict bypass transition for boundary layers subjected to a wide range of free-stream turbulence levels and streamwise pressure gradients. In the current paper experimental results are presented that support the premise that the formation of turbulent spots is associated with transient separation. Near-wall hot-wire signals in laminar and transitional boundary layers are analyzed statistically to produce probability distributions for signal level and trough frequency. In the laminar period the signal level is normally distributed, but during the inter-turbulent periods in the transitional boundary layer, the distribution is truncated at the lower end, i.e., the lowest velocity periods in the signal disappear, suggesting that these ar...

Research paper thumbnail of The Analysis of Heat Transfer in Automotive Turbochargers

Journal of Engineering for Gas Turbines and Power, 2010

Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely me... more Heat transfers in an automotive turbocharger comprise significant energy flows, but are rarely measured or accounted for in any turbocharger performance assessment. Existing measurements suggest that the difference in turbine efficiency calculated in the conventional way, by means of the fluid temperature change, under adiabatic conditions differs considerably from the usual diabatic test conditions, particularly at low turbine pressure ratio. In the work described in this paper, three commercial turbochargers were extensively instrumented with thermocouples on all accessible external and internal surfaces in order to make comprehensive temperature surveys. The turbochargers were run at ranges of turbine inlet temperature and external ventilation. Adiabatic tests were also carried out to serve as a reference condition. Based on the temperature measurements, the internal heat fluxes from the turbine gas to the turbocharger structure and from there to the lubricating oil and the compr...

Research paper thumbnail of Transition on Concave Surfaces

Journal of Turbomachinery, 2005

Boundary layer measurements have been made on the concave surfaces of two constant curvature blad... more Boundary layer measurements have been made on the concave surfaces of two constant curvature blades using hot wire anemometry. All the current experiments were performed with negligible streamwise pressure gradient. Grids were used to produce a range of freestream turbulence levels between 1% and 4%. The freestream velocity increases with distance from a concave wall according to the free vortex condition making the determination of the boundary layer edge difficult. A flat plate equivalent boundary layer procedure was adopted, therefore, to overcome this problem. The Taylor–Goertler (TG) vortices resulting from the concave curvature were found to make the laminar and turbulent boundary layer profiles fuller and to increase the skin friction coeffiicent by up to 40% compared with flat plate values. This leads to a more rapid growth in boundary layer thickness. The evolution in the intermittency through transition is very similar to that for a flat plate, however, the shape factors a...