Dimitrios Kyritsis | Khalifa University (original) (raw)
Papers by Dimitrios Kyritsis
Energies, 2022
The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2... more The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2 flames was investigated numerically using a verified computational tool and validated mechanism. The results illustrate the dual role of the added H2O2 within the fuel jet. A small amount of H2O2 within the NH3 stream acted as a fuel additive that enhanced the reaction rate via reducing the kinetic time scale. However, a novel flame structure appeared when the H2O2 mole fraction within the fuel stream increased to χH2O2 > 16%. Unlike the pure NH3/O2 flame, a premixed reaction zone was discerned on the fuel side, in which H2O2 reacts with NH3 and played the role of an oxidizer. Then, the remaining NH3 that survived premixed combustion continues reacting with O2 and forms a non-premixed flame. As a result of this structure, it was shown that the well-established conclusion of “near-equilibrium” non-premixed flame analysis in which the strain on the flame is determined by the momentum f...
Journal of Thermal Science and Engineering Applications, 2017
The effect of the electric field on laminar nonpremixed counterflow propane flames was analyzed c... more The effect of the electric field on laminar nonpremixed counterflow propane flames was analyzed computationally. The computations were conducted using ANSYS fluent platform associated with a detailed kinetic mechanism. The mechanism was supplemented with a set of three reactions accounting for the consumption/production of three chemi-ions. It was established that the position of the flame could be only controlled through altering the intensity of the applied electric field. The effect of the applied electric field was included within the reactive flow equations via introducing two distinct terms: a body force term that accounts for the electric field effects on the momentum of the reactive mixture, and an extra diffusion term that accounts for the mobility charged species, namely ambipolar diffusion. This study clearly shows that electric force provides a potential for controlling the location of propane flames without affecting their structure.
Energies
Passive infrared optical gas imaging (IOGI) is sensitive to toxic or greenhouse gases of interest... more Passive infrared optical gas imaging (IOGI) is sensitive to toxic or greenhouse gases of interest, offers non-invasive remote sensing, and provides the capability for spatially resolved measurements. It has been broadly applied to emission detection, localization, and visualization; however, emission quantification is a long-standing challenge for passive IOGI. In order to facilitate the development of quantitative IOGI, in this review, we summarize theoretical findings suggesting that a single pixel value does not provide sufficient information for quantification and then we proceed to collect, organize, and summarize effective and potential methods that can support IOGI to quantify column density, concentration, and emission rate. Along the way, we highlight the potential of the strong coupling of artificial intelligence (AI) with quantitative IOGI in all aspects, which substantially enhances the feasibility, performance, and agility of quantitative IOGI, and alleviates its heavy ...
Energies, 2022
The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2... more The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2 flames was investigated numerically using a verified computational tool and validated mechanism. The results illustrate the dual role of the added H2O2 within the fuel jet. A small amount of H2O2 within the NH3 stream acted as a fuel additive that enhanced the reaction rate via reducing the kinetic time scale. However, a novel flame structure appeared when the H2O2 mole fraction within the fuel stream increased to χH2O2 > 16%. Unlike the pure NH3/O2 flame, a premixed reaction zone was discerned on the fuel side, in which H2O2 reacts with NH3 and played the role of an oxidizer. Then, the remaining NH3 that survived premixed combustion continues reacting with O2 and forms a non-premixed flame. As a result of this structure, it was shown that the well-established conclusion of “near-equilibrium” non-premixed flame analysis in which the strain on the flame is determined by the momentum f...
Water Resources Research, 2015
ABSTRACT
Journal of Energy Engineering, 2015
ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrain... more ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrained pulverized coal particles using Venturi effect. Particle Streak Velocimetry performed on coal-laden jets provided valuable insight into the relative velocity of entrained coal particles with respect to the fluid velocity. High-resolution still images and high-speed videos of laser-sheet light scattered by the coal particles were used in order to determine the mode of interaction of entrained coal particles with the flame front. The effect of combustion on the entrained coal particles was analyzed both in terms of macrostructure and microstructure using a combination of loose density measurement, Fraunhofer-diffraction-based particle size distribution measurements and Scanned Electron Microscopy. It was established that the combustion process did not have any significant effect on the macrostructure of the coal particles. At the same time, remarkable changes were observed in particle microstructure. Based on these findings, it was established that the coal particles underwent only partial devolatilization during their passage through the flame due to the small residence time. Hence it was concluded, that oxidation was basically a surface phenomenon. The effect of oxidizer composition on the combustion of coal particles was studied by comparing the measured particle size distributions for CH 4 /air, CH 4 /O 2 /CO 2 and CH 4 /O 2 flames.
Water Resources Research, 2015
ABSTRACT
Journal of Energy Engineering, 2015
ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrain... more ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrained pulverized coal particles using Venturi effect. Particle Streak Velocimetry performed on coal-laden jets provided valuable insight into the relative velocity of entrained coal particles with respect to the fluid velocity. High-resolution still images and high-speed videos of laser-sheet light scattered by the coal particles were used in order to determine the mode of interaction of entrained coal particles with the flame front. The effect of combustion on the entrained coal particles was analyzed both in terms of macrostructure and microstructure using a combination of loose density measurement, Fraunhofer-diffraction-based particle size distribution measurements and Scanned Electron Microscopy. It was established that the combustion process did not have any significant effect on the macrostructure of the coal particles. At the same time, remarkable changes were observed in particle microstructure. Based on these findings, it was established that the coal particles underwent only partial devolatilization during their passage through the flame due to the small residence time. Hence it was concluded, that oxidation was basically a surface phenomenon. The effect of oxidizer composition on the combustion of coal particles was studied by comparing the measured particle size distributions for CH 4 /air, CH 4 /O 2 /CO 2 and CH 4 /O 2 flames.
Proceedings of the Combustion Institute, 2002
Proceedings of the Combustion Institute, 2002
The development of a mesoscale catalytic combustor to be coupled with direct energy conversion mo... more The development of a mesoscale catalytic combustor to be coupled with direct energy conversion modules for power production is presented. The combustor has a volume on the order of few cm 3 and operates on JP8 jet fuel, which is electrosprayed at a flow rate on the order of 10 g/hr and equivalence ratios varying from 0.35-0.70. Temperatures in the range 900K-1300K are achieved with a ± 5% uniformity over the top circular surface of the burner. Using gas chromatographic analysis of the exhaust gases, a combustion efficiency on the order of 97% is estimated. Remarkably, no fouling, nor soot, nor NOx were detected in the exhaust gases, which resulted in clean and efficient combustion of even environmentally problematic liquid hydrocarbons.
Journal of the Mass Spectrometry Society of Japan, 2003
An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of ... more An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of coupling the combustor with direct energy conversion modules for power production. The combustor design relies on fuel dispersion by multiplexed electrosprays coupled with a series of catalytic meshes acting as ground electrode and initiators of the fuel oxidation. The combustor has a volume on the order of few cm 3 and operates on jet fuel (JP 8), which is electrosprayed at a flow rate on the order of 10 g/h with equivalence ratios varying from 0.35῍0.70. The behavior of the electrospray in high temperature environments is examined and the phenomenology of the electrospray in the combustion chamber is visualized using planar laser-induced fluorescence from a fluorescent tag doped into the fuel. Combustion e$ciencies on the order of 97῍ can be achieved with uniform temperatures at the catalyst in the range of 900῍1,300 K (within ῌ5῍) when the electrospray is operated in an unsteady mode, accompanied by a "hissing" sound characteristic of the onset of corona discharge. Remarkably, no fouling, soot, or NOx were detected in the exhaust gases, which resulted in clean and e$cient combustion of even environmentally problematic liquid hydrocarbons.
Journal of the Mass Spectrometry Society of Japan, 2003
An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of ... more An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of coupling the combustor with direct energy conversion modules for power production. The combustor design relies on fuel dispersion by multiplexed electrosprays coupled with a series of catalytic meshes acting as ground electrode and initiators of the fuel oxidation. The combustor has a volume on the order of few cm 3 and operates on jet fuel (JP 8), which is electrosprayed at a flow rate on the order of 10 g/h with equivalence ratios varying from 0.35῍0.70. The behavior of the electrospray in high temperature environments is examined and the phenomenology of the electrospray in the combustion chamber is visualized using planar laser-induced fluorescence from a fluorescent tag doped into the fuel. Combustion e$ciencies on the order of 97῍ can be achieved with uniform temperatures at the catalyst in the range of 900῍1,300 K (within ῌ5῍) when the electrospray is operated in an unsteady mode, accompanied by a "hissing" sound characteristic of the onset of corona discharge. Remarkably, no fouling, soot, or NOx were detected in the exhaust gases, which resulted in clean and e$cient combustion of even environmentally problematic liquid hydrocarbons.
International Journal of Vehicle Design, 2007
ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in... more ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in automotive technology. To this extent, a commercially available Gasoline Direct Injection (GDI) injector was modified in order to induce electrostatic charge in the non-conducting fuel spray. Spray morphology was characterised with visualisation experiments and spray structure was probed with Particle Image Velocimetry (PIV) and Fraunhofer light diffraction droplet size measurements. PIV data showed that electrostatically charged sprays presented pockets that were sparsely populated by droplets and areas of increased vortical motion at an injection pressure where the non-charged sprays were much more coherent. In this sense, electrostatic charging at relatively low pressures aided in the generation of flow patterns that are exhibited at higher pressures for non-charged sprays. Measurements of droplet diameter using a Fraunhofer light diffraction technique provided indications of increased resistance to droplet coalescence and a much smaller cyclic variation of droplet size for the electrostatically charged sprays.
International Journal of Vehicle Design, 2007
ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in... more ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in automotive technology. To this extent, a commercially available Gasoline Direct Injection (GDI) injector was modified in order to induce electrostatic charge in the non-conducting fuel spray. Spray morphology was characterised with visualisation experiments and spray structure was probed with Particle Image Velocimetry (PIV) and Fraunhofer light diffraction droplet size measurements. PIV data showed that electrostatically charged sprays presented pockets that were sparsely populated by droplets and areas of increased vortical motion at an injection pressure where the non-charged sprays were much more coherent. In this sense, electrostatic charging at relatively low pressures aided in the generation of flow patterns that are exhibited at higher pressures for non-charged sprays. Measurements of droplet diameter using a Fraunhofer light diffraction technique provided indications of increased resistance to droplet coalescence and a much smaller cyclic variation of droplet size for the electrostatically charged sprays.
Experimental Thermal and Fluid Science, 2014
Flow of CO 2 in the vicinity of its critical point was studied experimentally in two different fl... more Flow of CO 2 in the vicinity of its critical point was studied experimentally in two different flow configurations. First, a 60 cm long stainless steel pipe with 2.1 mm inner diameter was used to study near-critical CO 2 pipe flow. In terms of raw flow data, the results indicated high sensitivity of pressure drop to mass flow rate as well as to inlet conditions; i.e. pressure and temperature. Remarkably though, when friction factor and Reynolds number were defined in terms of the inlet conditions, it was established that the classical Moody chart described the flow with satisfactory accuracy. This was rationalized using shadowgraphs that visualized the process of transition from a supercritical state to a two-phase subcritical state. During the transition the two phases were separated due to density mismatch and an interface was established that traveled in the direction of the flow. This interface separated two regions of essentially single-phase flow, which explained the effective validity of the classical Moody chart. Second, Joule-Thomson throttling was studied using a 0.36-mm-diameter orifice. For conditions relevant to carbon capture and sequestration, the fluid underwent Joule-Thompson cooling of approximately 0.5°C/bar. The temperature difference during the cooling increased with increasing inlet enthalpy. Discrepancies with previous computed and experimentally measured values of Joule-Thompson throttling were discussed in detail.
Energy Conversion and Management, 2010
... engine of automotive type (with no modification on it), which possesses a high versatility an... more ... engine of automotive type (with no modification on it), which possesses a high versatility and ... purity) with normal diesel fuel, with 8%, 16% and 24% (by volume) n-butanol, on the ... Consideration of theoretical aspects of diesel engine combustion and of the differing physical and ...
Energy Conversion and Management, 2004
The present two zone model of a direct injection (DI) Diesel engine divides the cylinder contents... more The present two zone model of a direct injection (DI) Diesel engine divides the cylinder contents into a non-burning zone of air and another homogeneous zone in which fuel is continuously supplied from the injector and burned with entrained air from the air zone. The growth of the fuel spray zone, which comprises a number of fuel-air conical jets equal to the injector nozzle holes, is carefully modelled by incorporating jet mixing, thus determining the amount of oxygen available for combustion. The mass, energy and state equations are applied in each of the two zones to yield local temperatures and cylinder pressure histories. The concentration of the various constituents in the exhaust gases are calculated by adopting a chemical equilibrium scheme for the C-H-O system of the 11 species considered, together with chemical rate equations for the calculation of nitric oxide (NO). A model for evaluation of the soot formation and oxidation rates is included. The theoretical results from the relevant computer program are compared very favourably with the measurements from an experimental investigation conducted on a fully automated test bed, standard ''Hydra'', DI Diesel engine installed at the authorsÕ laboratory. In-cylinder pressure and temperature histories, nitric oxide concentration and soot density are among the interesting quantities tested for various loads and injection timings. As revealed, the model is sensitive to the selection of the constants of the fuel preparation and reaction sub-models, so that a relevant sensitivity analysis is undertaken. This leads to a better understanding of the physical mechanisms governed by these constants and also paves the way for construction of a reliable and relatively simple multi-zone model, which incorporates in each zone (packet) the philosophy of the present two zone model.
International Journal of Engine Research, 2013
The flame length characteristics of propane diffusion flame were investigated experimentally. Ele... more The flame length characteristics of propane diffusion flame were investigated experimentally. Electric fields produce ionic winds that act on ions in a flame, and the effect of ionic winds increases the diffusion coefficient of flame. For the diffusion flame, the longer the length, the more instability increases and affects the generation of NOx. With the influence of an electric field acting parallel to the flame, as the strength of the electric field acting on the flame grew stronger, the length of the flame shortened. The maximum reduction in flame length was 70% when a voltage of +5 kV was applied.
We report the construction of an optically accessible flow test section made of quartz to simulat... more We report the construction of an optically accessible flow test section made of quartz to simulate carbon dioxide flow through throttling devices in refrigeration systems. The existence of traces of lubricant oil (specifically Polyolester (POE)) in the working medium makes the flow amenable to Laser Induced Fluorescence (LIF) diagnostics. The molecular structure of these lubricants is rich in carbon – oxygen bonds which can cause fluorescence when excited by a laser in the near ultra-violet region of the spectrum. This technique was used to visualize the flow of CO2-oil mixtures through an optically accessible test section under various operating conditions. Upstream pressures as well as oil flow rates are the independent parameters of the experiment. The results of the measurements provide data on the concentration of the lubricant that is entrained by CO2 in the expansion device as well as information about the form with which the oil is transported through the ejector (liquid fil...
Energies, 2022
The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2... more The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2 flames was investigated numerically using a verified computational tool and validated mechanism. The results illustrate the dual role of the added H2O2 within the fuel jet. A small amount of H2O2 within the NH3 stream acted as a fuel additive that enhanced the reaction rate via reducing the kinetic time scale. However, a novel flame structure appeared when the H2O2 mole fraction within the fuel stream increased to χH2O2 > 16%. Unlike the pure NH3/O2 flame, a premixed reaction zone was discerned on the fuel side, in which H2O2 reacts with NH3 and played the role of an oxidizer. Then, the remaining NH3 that survived premixed combustion continues reacting with O2 and forms a non-premixed flame. As a result of this structure, it was shown that the well-established conclusion of “near-equilibrium” non-premixed flame analysis in which the strain on the flame is determined by the momentum f...
Journal of Thermal Science and Engineering Applications, 2017
The effect of the electric field on laminar nonpremixed counterflow propane flames was analyzed c... more The effect of the electric field on laminar nonpremixed counterflow propane flames was analyzed computationally. The computations were conducted using ANSYS fluent platform associated with a detailed kinetic mechanism. The mechanism was supplemented with a set of three reactions accounting for the consumption/production of three chemi-ions. It was established that the position of the flame could be only controlled through altering the intensity of the applied electric field. The effect of the applied electric field was included within the reactive flow equations via introducing two distinct terms: a body force term that accounts for the electric field effects on the momentum of the reactive mixture, and an extra diffusion term that accounts for the mobility charged species, namely ambipolar diffusion. This study clearly shows that electric force provides a potential for controlling the location of propane flames without affecting their structure.
Energies
Passive infrared optical gas imaging (IOGI) is sensitive to toxic or greenhouse gases of interest... more Passive infrared optical gas imaging (IOGI) is sensitive to toxic or greenhouse gases of interest, offers non-invasive remote sensing, and provides the capability for spatially resolved measurements. It has been broadly applied to emission detection, localization, and visualization; however, emission quantification is a long-standing challenge for passive IOGI. In order to facilitate the development of quantitative IOGI, in this review, we summarize theoretical findings suggesting that a single pixel value does not provide sufficient information for quantification and then we proceed to collect, organize, and summarize effective and potential methods that can support IOGI to quantify column density, concentration, and emission rate. Along the way, we highlight the potential of the strong coupling of artificial intelligence (AI) with quantitative IOGI in all aspects, which substantially enhances the feasibility, performance, and agility of quantitative IOGI, and alleviates its heavy ...
Energies, 2022
The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2... more The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2 flames was investigated numerically using a verified computational tool and validated mechanism. The results illustrate the dual role of the added H2O2 within the fuel jet. A small amount of H2O2 within the NH3 stream acted as a fuel additive that enhanced the reaction rate via reducing the kinetic time scale. However, a novel flame structure appeared when the H2O2 mole fraction within the fuel stream increased to χH2O2 > 16%. Unlike the pure NH3/O2 flame, a premixed reaction zone was discerned on the fuel side, in which H2O2 reacts with NH3 and played the role of an oxidizer. Then, the remaining NH3 that survived premixed combustion continues reacting with O2 and forms a non-premixed flame. As a result of this structure, it was shown that the well-established conclusion of “near-equilibrium” non-premixed flame analysis in which the strain on the flame is determined by the momentum f...
Water Resources Research, 2015
ABSTRACT
Journal of Energy Engineering, 2015
ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrain... more ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrained pulverized coal particles using Venturi effect. Particle Streak Velocimetry performed on coal-laden jets provided valuable insight into the relative velocity of entrained coal particles with respect to the fluid velocity. High-resolution still images and high-speed videos of laser-sheet light scattered by the coal particles were used in order to determine the mode of interaction of entrained coal particles with the flame front. The effect of combustion on the entrained coal particles was analyzed both in terms of macrostructure and microstructure using a combination of loose density measurement, Fraunhofer-diffraction-based particle size distribution measurements and Scanned Electron Microscopy. It was established that the combustion process did not have any significant effect on the macrostructure of the coal particles. At the same time, remarkable changes were observed in particle microstructure. Based on these findings, it was established that the coal particles underwent only partial devolatilization during their passage through the flame due to the small residence time. Hence it was concluded, that oxidation was basically a surface phenomenon. The effect of oxidizer composition on the combustion of coal particles was studied by comparing the measured particle size distributions for CH 4 /air, CH 4 /O 2 /CO 2 and CH 4 /O 2 flames.
Water Resources Research, 2015
ABSTRACT
Journal of Energy Engineering, 2015
ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrain... more ABSTRACT Combustion characteristics of pulverized coal were studied in a methane jet that entrained pulverized coal particles using Venturi effect. Particle Streak Velocimetry performed on coal-laden jets provided valuable insight into the relative velocity of entrained coal particles with respect to the fluid velocity. High-resolution still images and high-speed videos of laser-sheet light scattered by the coal particles were used in order to determine the mode of interaction of entrained coal particles with the flame front. The effect of combustion on the entrained coal particles was analyzed both in terms of macrostructure and microstructure using a combination of loose density measurement, Fraunhofer-diffraction-based particle size distribution measurements and Scanned Electron Microscopy. It was established that the combustion process did not have any significant effect on the macrostructure of the coal particles. At the same time, remarkable changes were observed in particle microstructure. Based on these findings, it was established that the coal particles underwent only partial devolatilization during their passage through the flame due to the small residence time. Hence it was concluded, that oxidation was basically a surface phenomenon. The effect of oxidizer composition on the combustion of coal particles was studied by comparing the measured particle size distributions for CH 4 /air, CH 4 /O 2 /CO 2 and CH 4 /O 2 flames.
Proceedings of the Combustion Institute, 2002
Proceedings of the Combustion Institute, 2002
The development of a mesoscale catalytic combustor to be coupled with direct energy conversion mo... more The development of a mesoscale catalytic combustor to be coupled with direct energy conversion modules for power production is presented. The combustor has a volume on the order of few cm 3 and operates on JP8 jet fuel, which is electrosprayed at a flow rate on the order of 10 g/hr and equivalence ratios varying from 0.35-0.70. Temperatures in the range 900K-1300K are achieved with a ± 5% uniformity over the top circular surface of the burner. Using gas chromatographic analysis of the exhaust gases, a combustion efficiency on the order of 97% is estimated. Remarkably, no fouling, nor soot, nor NOx were detected in the exhaust gases, which resulted in clean and efficient combustion of even environmentally problematic liquid hydrocarbons.
Journal of the Mass Spectrometry Society of Japan, 2003
An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of ... more An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of coupling the combustor with direct energy conversion modules for power production. The combustor design relies on fuel dispersion by multiplexed electrosprays coupled with a series of catalytic meshes acting as ground electrode and initiators of the fuel oxidation. The combustor has a volume on the order of few cm 3 and operates on jet fuel (JP 8), which is electrosprayed at a flow rate on the order of 10 g/h with equivalence ratios varying from 0.35῍0.70. The behavior of the electrospray in high temperature environments is examined and the phenomenology of the electrospray in the combustion chamber is visualized using planar laser-induced fluorescence from a fluorescent tag doped into the fuel. Combustion e$ciencies on the order of 97῍ can be achieved with uniform temperatures at the catalyst in the range of 900῍1,300 K (within ῌ5῍) when the electrospray is operated in an unsteady mode, accompanied by a "hissing" sound characteristic of the onset of corona discharge. Remarkably, no fouling, soot, or NOx were detected in the exhaust gases, which resulted in clean and e$cient combustion of even environmentally problematic liquid hydrocarbons.
Journal of the Mass Spectrometry Society of Japan, 2003
An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of ... more An application of the electrospray to mesoscale combustion is studied, with the ultimate goal of coupling the combustor with direct energy conversion modules for power production. The combustor design relies on fuel dispersion by multiplexed electrosprays coupled with a series of catalytic meshes acting as ground electrode and initiators of the fuel oxidation. The combustor has a volume on the order of few cm 3 and operates on jet fuel (JP 8), which is electrosprayed at a flow rate on the order of 10 g/h with equivalence ratios varying from 0.35῍0.70. The behavior of the electrospray in high temperature environments is examined and the phenomenology of the electrospray in the combustion chamber is visualized using planar laser-induced fluorescence from a fluorescent tag doped into the fuel. Combustion e$ciencies on the order of 97῍ can be achieved with uniform temperatures at the catalyst in the range of 900῍1,300 K (within ῌ5῍) when the electrospray is operated in an unsteady mode, accompanied by a "hissing" sound characteristic of the onset of corona discharge. Remarkably, no fouling, soot, or NOx were detected in the exhaust gases, which resulted in clean and e$cient combustion of even environmentally problematic liquid hydrocarbons.
International Journal of Vehicle Design, 2007
ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in... more ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in automotive technology. To this extent, a commercially available Gasoline Direct Injection (GDI) injector was modified in order to induce electrostatic charge in the non-conducting fuel spray. Spray morphology was characterised with visualisation experiments and spray structure was probed with Particle Image Velocimetry (PIV) and Fraunhofer light diffraction droplet size measurements. PIV data showed that electrostatically charged sprays presented pockets that were sparsely populated by droplets and areas of increased vortical motion at an injection pressure where the non-charged sprays were much more coherent. In this sense, electrostatic charging at relatively low pressures aided in the generation of flow patterns that are exhibited at higher pressures for non-charged sprays. Measurements of droplet diameter using a Fraunhofer light diffraction technique provided indications of increased resistance to droplet coalescence and a much smaller cyclic variation of droplet size for the electrostatically charged sprays.
International Journal of Vehicle Design, 2007
ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in... more ABSTRACT An experimental evaluation of the possibility of using 'electrospray' in automotive technology. To this extent, a commercially available Gasoline Direct Injection (GDI) injector was modified in order to induce electrostatic charge in the non-conducting fuel spray. Spray morphology was characterised with visualisation experiments and spray structure was probed with Particle Image Velocimetry (PIV) and Fraunhofer light diffraction droplet size measurements. PIV data showed that electrostatically charged sprays presented pockets that were sparsely populated by droplets and areas of increased vortical motion at an injection pressure where the non-charged sprays were much more coherent. In this sense, electrostatic charging at relatively low pressures aided in the generation of flow patterns that are exhibited at higher pressures for non-charged sprays. Measurements of droplet diameter using a Fraunhofer light diffraction technique provided indications of increased resistance to droplet coalescence and a much smaller cyclic variation of droplet size for the electrostatically charged sprays.
Experimental Thermal and Fluid Science, 2014
Flow of CO 2 in the vicinity of its critical point was studied experimentally in two different fl... more Flow of CO 2 in the vicinity of its critical point was studied experimentally in two different flow configurations. First, a 60 cm long stainless steel pipe with 2.1 mm inner diameter was used to study near-critical CO 2 pipe flow. In terms of raw flow data, the results indicated high sensitivity of pressure drop to mass flow rate as well as to inlet conditions; i.e. pressure and temperature. Remarkably though, when friction factor and Reynolds number were defined in terms of the inlet conditions, it was established that the classical Moody chart described the flow with satisfactory accuracy. This was rationalized using shadowgraphs that visualized the process of transition from a supercritical state to a two-phase subcritical state. During the transition the two phases were separated due to density mismatch and an interface was established that traveled in the direction of the flow. This interface separated two regions of essentially single-phase flow, which explained the effective validity of the classical Moody chart. Second, Joule-Thomson throttling was studied using a 0.36-mm-diameter orifice. For conditions relevant to carbon capture and sequestration, the fluid underwent Joule-Thompson cooling of approximately 0.5°C/bar. The temperature difference during the cooling increased with increasing inlet enthalpy. Discrepancies with previous computed and experimentally measured values of Joule-Thompson throttling were discussed in detail.
Energy Conversion and Management, 2010
... engine of automotive type (with no modification on it), which possesses a high versatility an... more ... engine of automotive type (with no modification on it), which possesses a high versatility and ... purity) with normal diesel fuel, with 8%, 16% and 24% (by volume) n-butanol, on the ... Consideration of theoretical aspects of diesel engine combustion and of the differing physical and ...
Energy Conversion and Management, 2004
The present two zone model of a direct injection (DI) Diesel engine divides the cylinder contents... more The present two zone model of a direct injection (DI) Diesel engine divides the cylinder contents into a non-burning zone of air and another homogeneous zone in which fuel is continuously supplied from the injector and burned with entrained air from the air zone. The growth of the fuel spray zone, which comprises a number of fuel-air conical jets equal to the injector nozzle holes, is carefully modelled by incorporating jet mixing, thus determining the amount of oxygen available for combustion. The mass, energy and state equations are applied in each of the two zones to yield local temperatures and cylinder pressure histories. The concentration of the various constituents in the exhaust gases are calculated by adopting a chemical equilibrium scheme for the C-H-O system of the 11 species considered, together with chemical rate equations for the calculation of nitric oxide (NO). A model for evaluation of the soot formation and oxidation rates is included. The theoretical results from the relevant computer program are compared very favourably with the measurements from an experimental investigation conducted on a fully automated test bed, standard ''Hydra'', DI Diesel engine installed at the authorsÕ laboratory. In-cylinder pressure and temperature histories, nitric oxide concentration and soot density are among the interesting quantities tested for various loads and injection timings. As revealed, the model is sensitive to the selection of the constants of the fuel preparation and reaction sub-models, so that a relevant sensitivity analysis is undertaken. This leads to a better understanding of the physical mechanisms governed by these constants and also paves the way for construction of a reliable and relatively simple multi-zone model, which incorporates in each zone (packet) the philosophy of the present two zone model.
International Journal of Engine Research, 2013
The flame length characteristics of propane diffusion flame were investigated experimentally. Ele... more The flame length characteristics of propane diffusion flame were investigated experimentally. Electric fields produce ionic winds that act on ions in a flame, and the effect of ionic winds increases the diffusion coefficient of flame. For the diffusion flame, the longer the length, the more instability increases and affects the generation of NOx. With the influence of an electric field acting parallel to the flame, as the strength of the electric field acting on the flame grew stronger, the length of the flame shortened. The maximum reduction in flame length was 70% when a voltage of +5 kV was applied.
We report the construction of an optically accessible flow test section made of quartz to simulat... more We report the construction of an optically accessible flow test section made of quartz to simulate carbon dioxide flow through throttling devices in refrigeration systems. The existence of traces of lubricant oil (specifically Polyolester (POE)) in the working medium makes the flow amenable to Laser Induced Fluorescence (LIF) diagnostics. The molecular structure of these lubricants is rich in carbon – oxygen bonds which can cause fluorescence when excited by a laser in the near ultra-violet region of the spectrum. This technique was used to visualize the flow of CO2-oil mixtures through an optically accessible test section under various operating conditions. Upstream pressures as well as oil flow rates are the independent parameters of the experiment. The results of the measurements provide data on the concentration of the lubricant that is entrained by CO2 in the expansion device as well as information about the form with which the oil is transported through the ejector (liquid fil...