Jose M. Desantes - Academia.edu (original) (raw)

Papers by Jose M. Desantes

Research paper thumbnail of Study on independent effects of diesel engine operating conditions on nitric oxide formation and emissions through schematical combustion simulation

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 1996

ABSTRACT

Research paper thumbnail of Multi-objective optimization of heavy duty diesel engines under stationary conditions

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2005

ABSTRACT New technological developments are helping to control contaminants in diesel engines but... more ABSTRACT New technological developments are helping to control contaminants in diesel engines but, as new degrees of freedom become available, the assessment of optimal values that combine to reduce different emissions has become a difficult task. This paper studies the feasibility of using artificial neural networks (ANNs) as models to be integrated in the optimization of diesel engine settings, with the objective of complying with the increasingly stringent emission regulations while also keeping, or even reducing, the fuel consumption. A large database of stationary engine tests covering a wide range of experimental conditions was used for the development of the ANN models. The optimization was developed within the frame of the European legislation for heavy duty diesel engines. Experimental validation of the optimized results was carried out and compared with the ANN predictions, showing a high level of accuracy, especially for fuel consumption and nitrogen oxides (NOx).

Research paper thumbnail of Intake pipes evaluation: comparison between paddlewheel and hot‐wire anemometry methods

Archive: Proceedings of The Institution of Mechanical Engineers, Part A: Journal of Power Engineering 1989 (vol 203), 1989

ABSTRACT

Research paper thumbnail of Combining Neural Networks and Genetic Algorithms to Predict and Reduce Diesel Engine Emissions

IEEE Transactions on Evolutionary Computation, 2007

Diesel engines are fuel efficient which benefits the reduction of CO 2 released to the atmosphere... more Diesel engines are fuel efficient which benefits the reduction of CO 2 released to the atmosphere compared with gasoline engines, but still result in negative environmental impact related to their emissions. As new degrees of freedom are created, due to advances in technology, the complicated processes of emission formation are difficult to assess. This paper studies the feasibility of using artificial neural networks (ANNs) in combination with genetic algorithms (GAs) to optimize the diesel engine settings. The objective of the optimization was to find settings that complied with the increasingly stringent emission regulations while also maintaining, or even reducing the fuel consumption. A large database of stationary engine tests, covering a wide range of experimental conditions was used for this analysis. The ANNs were used as a simulation tool, receiving as inputs the engine operating parameters, and producing as outputs the resulting emission levels and fuel consumption. The ANN outputs were then used to evaluate the objective function of the optimization process, which was performed with a GA approach. The combination of ANN and GA for the optimization of two different engine operating conditions was analyzed and important reductions in emissions and fuel consumption were reached, while also keeping the computational times low.

Research paper thumbnail of The development of a semi-empirical model for rapid NO x concentration evaluation using measured in-cylinder pressure in diesel engines

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2005

Research paper thumbnail of Modelling of the wall jet in a direct injection diesel engine

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 1992

ABSTRACT

Research paper thumbnail of CFD−Phenomenological Diesel Spray Analysis under Evaporative Conditions

Energy & Fuels, 2009

ABSTRACT A combined analysis of computational fluid dynamics (CFD) and phenomenological model is ... more ABSTRACT A combined analysis of computational fluid dynamics (CFD) and phenomenological model is proposed in this work to improve the liquid length predictions of diesel sprays under evaporative conditions. The stable diameter of droplets was evaluated using a trade-off mechanism between a standard CFD model and a phenomenological correlation, and this allowed a better prediction of the measured maximum liquid length than by using the collision models. The standard drop drag coefficient calculation was corrected with empirical correlations that introduce different effects, such as drop deformation, void fraction effects, and the influence of the mass transfer from liquid to vapor phase during the evaporation of droplets. Moreover, the heat and mass transfer between the droplets and gas were also corrected considering a larger surface area of the droplets caused by their deformation during the break-up process. Experimental data available in literature has been used to validate the model for single components and diesel fuels, and encouraging results have been obtained contributing to a better simulation of the atomization, breakup, and evaporative processes in sprays.

Research paper thumbnail of Study of the steady flow produced by direct injection diesel engine intake ports

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2001

n §tudy of the steady florv produced 5y direct injection diesel engine intake ports J N{ Dcsantcs... more n §tudy of the steady florv produced 5y direct injection diesel engine intake ports J N{ Dcsantcsl*, J V ltastorr ancl  lJoudou2 'cMT' Departalnento de Mâquirras y Motores Térniicos, univcrsidad politécnica clc valencia, spain 2LMI'TT, Faculté des sciences, université Ibn Tofair, Kenitra, Morocco Âbstrac(: Irr this 1.llt1lcr Illsct'I)«rltPlcr ancnr()nlctry is rrscrl t. elyrlrctcr.iz;c {5c s{crrrly llrrv licll irrside thc cylinder gcnçratcd -by thc trvo itttakc ports ol a lbur-valve cliesel heari over the wholc valve lilt range atlc{ to compare the pattcrns irI two <liflclcnt scc(ions ..,,,,,,.,r,,,1u rrscrl firr.globirl clrar]uctcrizlrtiorr in order to dccidc wlrich is nlore appropriatc lbr cylinder heacl evaluation. A more cletailecl investigation is perlormecl lbr two valve lifts where the change in the fiow patterns is nrore eviclent by applying a spectral analysis with tlie local norrnalized stoiting technique to study the turbule,t structures accorrpanying the in-cylincler swirl clevelopmcnt KeYrvortls: inlakc floiv, su'irl, turbrrlcncc, autocor.rclltion [unction, intcgral sc.lc NOTATION Au CD Cor'r

Research paper thumbnail of Computational study on the deposition of ultrafine particles from Diesel exhaust aerosol

Journal of Aerosol Science, 2006

Short-term in vitro assays are arising in order to determine the toxicity of native Diesel aeroso... more Short-term in vitro assays are arising in order to determine the toxicity of native Diesel aerosol particles, due to its association with adverse health effects. Estimation of the real quantity and characteristics of the particles deposition on the cells cultures in these assays becomes necessary to establish correlations between the particle deposition conditions and the biological indicators of toxicity of the exposed cells.

Research paper thumbnail of Methodology for measuring exhaust aerosol size distributions from heavy duty diesel engines by means of a scanning mobility particle sizer

Measurement Science & Technology, 2004

... mobility particle sizer JM Desantes, V Bermúdez, JV Pastor and E Fuentes CMT Motores Térmicos... more ... mobility particle sizer JM Desantes, V Bermúdez, JV Pastor and E Fuentes CMT Motores Térmicos, Universidad Politécnica de Valencia, Aptdo 22012, E-46071 Valencia, Spain E-mail: jmdesant@mot.upv.es ... Shop Air Inlet Dilution minitunnel Exhaust pipe Sample probe ...

Research paper thumbnail of Influence of nozzle geometry on ignition and combustion for high-speed direct injection diesel engines under cold start conditions

Fuel, 2011

Starting at low temperatures (below 0°C) is an important issue for current and near future diesel... more Starting at low temperatures (below 0°C) is an important issue for current and near future diesel engine technology. Low ambient temperature causes long cranking periods or complete misfiring in small diesel engines and, as a consequence, an increased amount of pollutant emissions. This paper is devoted to study the influence of nozzle geometry on ignition and combustion progression under glow-plug aided cold start conditions. This study has been carried out in an optically accessible engine adapted to reproduce in-cylinder conditions corresponding to those of a real engine during start at low ambient temperature. The cold start problem can be divided in two parts in which nozzle geometry has influence: ignition and main combustion progress. Ignition probability decreases if fuel injection velocity is increased or if the amount of injected mass per orifice is reduced, which is induced by nozzles with smaller hole diameter or higher orifice number, respectively. Combustion rates increase when using nozzles which induce a higher momentum, improving mixture conditions. For these reasons, the solution under these conditions necessarily involves a trade-off between ignition and combustion progress.

Research paper thumbnail of Study of mass and momentum transfer in diesel sprays based on X-ray mass distribution measurements and on a theoretical derivation

Experiments in Fluids, 2011

In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle fiel... more In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle field of diesel sprays injected into stagnant ambient air is reported. The study combines X-ray measurements for two different nozzles and axial positions, which provide mass distributions in the spray, with a theoretical model based on momentum flux conservation, which was previously validated. This investigation has allowed the validation of Gaussian profiles for local fuel concentration and velocity near the nozzle exit, as well as the determination of Schmidt number at realistic diesel spray conditions. This information could be very useful for those who are interested in spray modeling, especially at high-pressure injection conditions.

Research paper thumbnail of EVAPORATIVE DIESEL SPRAY MODELING

Atomization and Sprays, 2007

ABSTRACT A one-dimensional nonevaporative spray model has been extended to take into account the ... more ABSTRACT A one-dimensional nonevaporative spray model has been extended to take into account the effects of evaporation under direct-injection diesel engine conditions. The approach is based on the assumption that evaporation is limited by the mixing process between fuel and ambient gas, and makes use of nonideal gas state relationships for the description of the whole spray. Experimental results have been obtained by means of backlight illumination from a hot spray test rig. Comparisons between experimental and modeling results confirm the initial hypotheses. The model accurately predicts the influence of fuel type and both ambient and injection conditions on liquid spray penetration. An adequate prediction of the liquid penetration of a reference diesel fuel is achieved by considering the state relationships of a single-component surrogate fuel.

Research paper thumbnail of A 1D model for the description of mixing-controlled reacting diesel sprays

Combustion and Flame, 2009

The paper reports an investigation on the transient evolution of diesel flames in terms of fuelai... more The paper reports an investigation on the transient evolution of diesel flames in terms of fuelair mixing, spray penetration and combustion rate. A one-dimensional (1D) spray model, which was previously validated for inert diesel sprays, is extended to reacting conditions. The main assumptions of the model are the mixing-controlled hypothesis and the validity of self-similarity for conservative properties. Validation is achieved by comparing model predictions with both CFD gas jet simulations and experimental diesel spray measurements. The 1D model provides valuable insight into the evolution of the flow within the spray (momentum and mass fluxes, tip penetration, etc.) when shifting from inert to reacting conditions. Results show that the transient diesel flame evolution is mainly governed by two combustion-induced effects, namely the reduction in local density and the increase in flame radial width.

Research paper thumbnail of Microprocessor-Based Control of Engine Valve Timing

IEEE Industrial Electronics Magazine, 1983

The structure of the microcomputer controller and an outline of the software are presented in thi... more The structure of the microcomputer controller and an outline of the software are presented in this paper for both a premilinary and a fi'nal design.

Research paper thumbnail of Modified impulse method for the measurement of the frequency response of acoustic filters to weakly nonlinear transient excitations

Journal of The Acoustical Society of America, 2000

In this paper, a modified impulse method is proposed which allows the determination of the influe... more In this paper, a modified impulse method is proposed which allows the determination of the influence of the excitation characteristics on acoustic filter performance. Issues related to nonlinear propagation, namely wave steepening and wave interactions, have been addressed in an approximate way, validated against one-dimensional unsteady nonlinear flow calculations. The results obtained for expansion chambers and extended duct resonators indicate that the amplitude threshold for the onset of nonlinear phenomena is related to the geometry considered.

Research paper thumbnail of Study of mass and momentum transfer in diesel sprays based on X-ray mass distribution measurements and on a theoretical derivation

Experiments in Fluids, 2011

In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle fiel... more In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle field of diesel sprays injected into stagnant ambient air is reported. The study combines X-ray measurements for two different nozzles and axial positions, which provide mass distributions in the spray, with a theoretical model based on momentum flux conservation, which was previously validated. This investigation has allowed the validation of Gaussian profiles for local fuel concentration and velocity near the nozzle exit, as well as the determination of Schmidt number at realistic diesel spray conditions. This information could be very useful for those who are interested in spray modeling, especially at high-pressure injection conditions.

Research paper thumbnail of LDV measurements of the flow inside the combustion chamber of a 4-valve D.I. diesel engine with axisymmetric piston-bowls

Experiments in Fluids, 1996

LDV measurements of the tangential and radial velocity components have been performed to investi... more LDV measurements of the tangential and radial velocity components have been performed to investigate the flow patterns inside a 4-valve single cylinder diesel engine for various engine speeds, swirl numbers and piston-bowl geometries, under conditions similar to those of a production engine. The work focused on the near-wall region of the axisymmetric combustion chambers where the strong swirl-squish and spray-wall interactions take place. The different axial flow stratification observed in both velocity components has confirmed the influence of piston shape and intake configuration on the flow patterns and turbulence levels near compression TDC. Measured values are in reasonable agreement with those provided by a two-zone phenomenological model.

Research paper thumbnail of Limitations on the use of the planar laser induced exciplex fluorescence technique in diesel sprays

Fuel, 2005

The Planar Laser Induced Exciplex Fluorescence (PLIEF) technique is widely used to visualize and ... more The Planar Laser Induced Exciplex Fluorescence (PLIEF) technique is widely used to visualize and measure the fuel concentration fields in both liquid and vapor phases of DI Diesel sprays. However, the real limitations of the PLIEF technique in Diesel sprays and the accuracy of the results obtained are still a source of controversy. In this work, a complete methodology for

Research paper thumbnail of The modification of the fuel injection rate in heavy-duty diesel engines. Part 1: Effects on engine performance and emissions

Applied Thermal Engineering, 2004

An experimental study has been performed on the effects of injection rate shaping on the combusti... more An experimental study has been performed on the effects of injection rate shaping on the combustion process and exhaust emissions of a direct-injection diesel engine. Boot-type injections were generated by means of a modified pump-line-nozzle system, which is able to modulate the instantaneous fuel injection rate. The influence of different values of boot length and boot pressure has been evaluated by analysing the apparent rate of heat release and flame temperatures. Engine operating conditions at different rotating speed and injected fuel mass were considered in order to assess their effect on the injection rate shape.

Research paper thumbnail of Study on independent effects of diesel engine operating conditions on nitric oxide formation and emissions through schematical combustion simulation

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 1996

ABSTRACT

Research paper thumbnail of Multi-objective optimization of heavy duty diesel engines under stationary conditions

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2005

ABSTRACT New technological developments are helping to control contaminants in diesel engines but... more ABSTRACT New technological developments are helping to control contaminants in diesel engines but, as new degrees of freedom become available, the assessment of optimal values that combine to reduce different emissions has become a difficult task. This paper studies the feasibility of using artificial neural networks (ANNs) as models to be integrated in the optimization of diesel engine settings, with the objective of complying with the increasingly stringent emission regulations while also keeping, or even reducing, the fuel consumption. A large database of stationary engine tests covering a wide range of experimental conditions was used for the development of the ANN models. The optimization was developed within the frame of the European legislation for heavy duty diesel engines. Experimental validation of the optimized results was carried out and compared with the ANN predictions, showing a high level of accuracy, especially for fuel consumption and nitrogen oxides (NOx).

Research paper thumbnail of Intake pipes evaluation: comparison between paddlewheel and hot‐wire anemometry methods

Archive: Proceedings of The Institution of Mechanical Engineers, Part A: Journal of Power Engineering 1989 (vol 203), 1989

ABSTRACT

Research paper thumbnail of Combining Neural Networks and Genetic Algorithms to Predict and Reduce Diesel Engine Emissions

IEEE Transactions on Evolutionary Computation, 2007

Diesel engines are fuel efficient which benefits the reduction of CO 2 released to the atmosphere... more Diesel engines are fuel efficient which benefits the reduction of CO 2 released to the atmosphere compared with gasoline engines, but still result in negative environmental impact related to their emissions. As new degrees of freedom are created, due to advances in technology, the complicated processes of emission formation are difficult to assess. This paper studies the feasibility of using artificial neural networks (ANNs) in combination with genetic algorithms (GAs) to optimize the diesel engine settings. The objective of the optimization was to find settings that complied with the increasingly stringent emission regulations while also maintaining, or even reducing the fuel consumption. A large database of stationary engine tests, covering a wide range of experimental conditions was used for this analysis. The ANNs were used as a simulation tool, receiving as inputs the engine operating parameters, and producing as outputs the resulting emission levels and fuel consumption. The ANN outputs were then used to evaluate the objective function of the optimization process, which was performed with a GA approach. The combination of ANN and GA for the optimization of two different engine operating conditions was analyzed and important reductions in emissions and fuel consumption were reached, while also keeping the computational times low.

Research paper thumbnail of The development of a semi-empirical model for rapid NO x concentration evaluation using measured in-cylinder pressure in diesel engines

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2005

Research paper thumbnail of Modelling of the wall jet in a direct injection diesel engine

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 1992

ABSTRACT

Research paper thumbnail of CFD−Phenomenological Diesel Spray Analysis under Evaporative Conditions

Energy & Fuels, 2009

ABSTRACT A combined analysis of computational fluid dynamics (CFD) and phenomenological model is ... more ABSTRACT A combined analysis of computational fluid dynamics (CFD) and phenomenological model is proposed in this work to improve the liquid length predictions of diesel sprays under evaporative conditions. The stable diameter of droplets was evaluated using a trade-off mechanism between a standard CFD model and a phenomenological correlation, and this allowed a better prediction of the measured maximum liquid length than by using the collision models. The standard drop drag coefficient calculation was corrected with empirical correlations that introduce different effects, such as drop deformation, void fraction effects, and the influence of the mass transfer from liquid to vapor phase during the evaporation of droplets. Moreover, the heat and mass transfer between the droplets and gas were also corrected considering a larger surface area of the droplets caused by their deformation during the break-up process. Experimental data available in literature has been used to validate the model for single components and diesel fuels, and encouraging results have been obtained contributing to a better simulation of the atomization, breakup, and evaporative processes in sprays.

Research paper thumbnail of Study of the steady flow produced by direct injection diesel engine intake ports

Proceedings of The Institution of Mechanical Engineers Part D-journal of Automobile Engineering, 2001

n §tudy of the steady florv produced 5y direct injection diesel engine intake ports J N{ Dcsantcs... more n §tudy of the steady florv produced 5y direct injection diesel engine intake ports J N{ Dcsantcsl*, J V ltastorr ancl  lJoudou2 'cMT' Departalnento de Mâquirras y Motores Térniicos, univcrsidad politécnica clc valencia, spain 2LMI'TT, Faculté des sciences, université Ibn Tofair, Kenitra, Morocco Âbstrac(: Irr this 1.llt1lcr Illsct'I)«rltPlcr ancnr()nlctry is rrscrl t. elyrlrctcr.iz;c {5c s{crrrly llrrv licll irrside thc cylinder gcnçratcd -by thc trvo itttakc ports ol a lbur-valve cliesel heari over the wholc valve lilt range atlc{ to compare the pattcrns irI two <liflclcnt scc(ions ..,,,,,,.,r,,,1u rrscrl firr.globirl clrar]uctcrizlrtiorr in order to dccidc wlrich is nlore appropriatc lbr cylinder heacl evaluation. A more cletailecl investigation is perlormecl lbr two valve lifts where the change in the fiow patterns is nrore eviclent by applying a spectral analysis with tlie local norrnalized stoiting technique to study the turbule,t structures accorrpanying the in-cylincler swirl clevelopmcnt KeYrvortls: inlakc floiv, su'irl, turbrrlcncc, autocor.rclltion [unction, intcgral sc.lc NOTATION Au CD Cor'r

Research paper thumbnail of Computational study on the deposition of ultrafine particles from Diesel exhaust aerosol

Journal of Aerosol Science, 2006

Short-term in vitro assays are arising in order to determine the toxicity of native Diesel aeroso... more Short-term in vitro assays are arising in order to determine the toxicity of native Diesel aerosol particles, due to its association with adverse health effects. Estimation of the real quantity and characteristics of the particles deposition on the cells cultures in these assays becomes necessary to establish correlations between the particle deposition conditions and the biological indicators of toxicity of the exposed cells.

Research paper thumbnail of Methodology for measuring exhaust aerosol size distributions from heavy duty diesel engines by means of a scanning mobility particle sizer

Measurement Science & Technology, 2004

... mobility particle sizer JM Desantes, V Bermúdez, JV Pastor and E Fuentes CMT Motores Térmicos... more ... mobility particle sizer JM Desantes, V Bermúdez, JV Pastor and E Fuentes CMT Motores Térmicos, Universidad Politécnica de Valencia, Aptdo 22012, E-46071 Valencia, Spain E-mail: jmdesant@mot.upv.es ... Shop Air Inlet Dilution minitunnel Exhaust pipe Sample probe ...

Research paper thumbnail of Influence of nozzle geometry on ignition and combustion for high-speed direct injection diesel engines under cold start conditions

Fuel, 2011

Starting at low temperatures (below 0°C) is an important issue for current and near future diesel... more Starting at low temperatures (below 0°C) is an important issue for current and near future diesel engine technology. Low ambient temperature causes long cranking periods or complete misfiring in small diesel engines and, as a consequence, an increased amount of pollutant emissions. This paper is devoted to study the influence of nozzle geometry on ignition and combustion progression under glow-plug aided cold start conditions. This study has been carried out in an optically accessible engine adapted to reproduce in-cylinder conditions corresponding to those of a real engine during start at low ambient temperature. The cold start problem can be divided in two parts in which nozzle geometry has influence: ignition and main combustion progress. Ignition probability decreases if fuel injection velocity is increased or if the amount of injected mass per orifice is reduced, which is induced by nozzles with smaller hole diameter or higher orifice number, respectively. Combustion rates increase when using nozzles which induce a higher momentum, improving mixture conditions. For these reasons, the solution under these conditions necessarily involves a trade-off between ignition and combustion progress.

Research paper thumbnail of Study of mass and momentum transfer in diesel sprays based on X-ray mass distribution measurements and on a theoretical derivation

Experiments in Fluids, 2011

In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle fiel... more In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle field of diesel sprays injected into stagnant ambient air is reported. The study combines X-ray measurements for two different nozzles and axial positions, which provide mass distributions in the spray, with a theoretical model based on momentum flux conservation, which was previously validated. This investigation has allowed the validation of Gaussian profiles for local fuel concentration and velocity near the nozzle exit, as well as the determination of Schmidt number at realistic diesel spray conditions. This information could be very useful for those who are interested in spray modeling, especially at high-pressure injection conditions.

Research paper thumbnail of EVAPORATIVE DIESEL SPRAY MODELING

Atomization and Sprays, 2007

ABSTRACT A one-dimensional nonevaporative spray model has been extended to take into account the ... more ABSTRACT A one-dimensional nonevaporative spray model has been extended to take into account the effects of evaporation under direct-injection diesel engine conditions. The approach is based on the assumption that evaporation is limited by the mixing process between fuel and ambient gas, and makes use of nonideal gas state relationships for the description of the whole spray. Experimental results have been obtained by means of backlight illumination from a hot spray test rig. Comparisons between experimental and modeling results confirm the initial hypotheses. The model accurately predicts the influence of fuel type and both ambient and injection conditions on liquid spray penetration. An adequate prediction of the liquid penetration of a reference diesel fuel is achieved by considering the state relationships of a single-component surrogate fuel.

Research paper thumbnail of A 1D model for the description of mixing-controlled reacting diesel sprays

Combustion and Flame, 2009

The paper reports an investigation on the transient evolution of diesel flames in terms of fuelai... more The paper reports an investigation on the transient evolution of diesel flames in terms of fuelair mixing, spray penetration and combustion rate. A one-dimensional (1D) spray model, which was previously validated for inert diesel sprays, is extended to reacting conditions. The main assumptions of the model are the mixing-controlled hypothesis and the validity of self-similarity for conservative properties. Validation is achieved by comparing model predictions with both CFD gas jet simulations and experimental diesel spray measurements. The 1D model provides valuable insight into the evolution of the flow within the spray (momentum and mass fluxes, tip penetration, etc.) when shifting from inert to reacting conditions. Results show that the transient diesel flame evolution is mainly governed by two combustion-induced effects, namely the reduction in local density and the increase in flame radial width.

Research paper thumbnail of Microprocessor-Based Control of Engine Valve Timing

IEEE Industrial Electronics Magazine, 1983

The structure of the microcomputer controller and an outline of the software are presented in thi... more The structure of the microcomputer controller and an outline of the software are presented in this paper for both a premilinary and a fi'nal design.

Research paper thumbnail of Modified impulse method for the measurement of the frequency response of acoustic filters to weakly nonlinear transient excitations

Journal of The Acoustical Society of America, 2000

In this paper, a modified impulse method is proposed which allows the determination of the influe... more In this paper, a modified impulse method is proposed which allows the determination of the influence of the excitation characteristics on acoustic filter performance. Issues related to nonlinear propagation, namely wave steepening and wave interactions, have been addressed in an approximate way, validated against one-dimensional unsteady nonlinear flow calculations. The results obtained for expansion chambers and extended duct resonators indicate that the amplitude threshold for the onset of nonlinear phenomena is related to the geometry considered.

Research paper thumbnail of Study of mass and momentum transfer in diesel sprays based on X-ray mass distribution measurements and on a theoretical derivation

Experiments in Fluids, 2011

In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle fiel... more In this paper, a research aimed at quantifying mass and momentum transfer in the near-nozzle field of diesel sprays injected into stagnant ambient air is reported. The study combines X-ray measurements for two different nozzles and axial positions, which provide mass distributions in the spray, with a theoretical model based on momentum flux conservation, which was previously validated. This investigation has allowed the validation of Gaussian profiles for local fuel concentration and velocity near the nozzle exit, as well as the determination of Schmidt number at realistic diesel spray conditions. This information could be very useful for those who are interested in spray modeling, especially at high-pressure injection conditions.

Research paper thumbnail of LDV measurements of the flow inside the combustion chamber of a 4-valve D.I. diesel engine with axisymmetric piston-bowls

Experiments in Fluids, 1996

LDV measurements of the tangential and radial velocity components have been performed to investi... more LDV measurements of the tangential and radial velocity components have been performed to investigate the flow patterns inside a 4-valve single cylinder diesel engine for various engine speeds, swirl numbers and piston-bowl geometries, under conditions similar to those of a production engine. The work focused on the near-wall region of the axisymmetric combustion chambers where the strong swirl-squish and spray-wall interactions take place. The different axial flow stratification observed in both velocity components has confirmed the influence of piston shape and intake configuration on the flow patterns and turbulence levels near compression TDC. Measured values are in reasonable agreement with those provided by a two-zone phenomenological model.

Research paper thumbnail of Limitations on the use of the planar laser induced exciplex fluorescence technique in diesel sprays

Fuel, 2005

The Planar Laser Induced Exciplex Fluorescence (PLIEF) technique is widely used to visualize and ... more The Planar Laser Induced Exciplex Fluorescence (PLIEF) technique is widely used to visualize and measure the fuel concentration fields in both liquid and vapor phases of DI Diesel sprays. However, the real limitations of the PLIEF technique in Diesel sprays and the accuracy of the results obtained are still a source of controversy. In this work, a complete methodology for

Research paper thumbnail of The modification of the fuel injection rate in heavy-duty diesel engines. Part 1: Effects on engine performance and emissions

Applied Thermal Engineering, 2004

An experimental study has been performed on the effects of injection rate shaping on the combusti... more An experimental study has been performed on the effects of injection rate shaping on the combustion process and exhaust emissions of a direct-injection diesel engine. Boot-type injections were generated by means of a modified pump-line-nozzle system, which is able to modulate the instantaneous fuel injection rate. The influence of different values of boot length and boot pressure has been evaluated by analysing the apparent rate of heat release and flame temperatures. Engine operating conditions at different rotating speed and injected fuel mass were considered in order to assess their effect on the injection rate shape.