The effect of the amount of hydrogen addition on the fuel consumption and emission of a spark ign... more The effect of the amount of hydrogen addition on the fuel consumption and emission of a spark ignition engine has been studied. Dynamometer test results for a wide range of engine speeds, engine loads, equivalent ratio and hydrogen enrichment under steady state operation are presented, and the engine requirements for minimum b.s.f.c. are specified. A detailed model to simulate a four-stroke cycle of a spark ignition engine fuelled with hydrogen-enriched gasoline was used to predict the optimal amount of hydrogen supplement as well as the corresponding minimum best torque (MBT) optimal throttle position and emissions levels of CO and NOx. It has been shown that a significant reduction in the b.s.f.c, in the order of 20 per cent, is achieved with hydrogen-enriched gasoline for a hydrogen-fuel mass ratio of 6 per cent and equivalence ratio of 0.65. A very smooth operation has been observed under these conditions. The energy conversion gain is prominent at partial loads and depends only to a limited extent on the engine speed.
A simplified numerical code for thermal analysis of a helical heat exchanger for use in long-term... more A simplified numerical code for thermal analysis of a helical heat exchanger for use in long-term thermal energy storage in soil was developed. The model was verified for a particular case for which an analytical solution was available from the literature and was validated with experimental data obtained from field experiments. The differences between predicted and measured data were in the range of ±1°C, which is considered satisfactory for engineering design purposes. The model was prepared for use with an personal computer and thus provides a convenient and reliable design tool for such a system. The computer code may be easily modified for the study of the influence of incorporating phase-change material elements in the storage well.
A fairly detailed reaction scheme for the oxidation of n -butane and hydrogen mixture has been em... more A fairly detailed reaction scheme for the oxidation of n -butane and hydrogen mixture has been employed to study the effect of hydrogen addition on the time delay of n -butane/air mixture. The intricate paths and mechanism by which autoignition is developed have been investigated by using the time-dependent kinetic flow charts technique. It was concluded that the autoignition process of n -butane/air as well as of n -butane/hydrogen/air mixture may be divided into three main periods. In the first (50 μs), the fuel molecule is attacked by HO 2 radicals to produce H 2 O 2 molecules which, in turn, decompose into OH radicals. In the second (a few microseconds before ignition occurs), the OH radicals play the most important role in breaking down the hydrocarbon molecules. In the third, the CH 2 O is converted into HCO and an avalanche of a series of exothermic reactions takes place and accelerate the whole process. It was also concluded that the hydrogen enrichment has a retarding effect on the autoignition process. This is attributed to the reduction of the OH population in the second stage due to the reaction H 2 +OH→H+H 2 O.
An improved mathematical model is presented here to simulate the gas exchange of a two-stroke, cr... more An improved mathematical model is presented here to simulate the gas exchange of a two-stroke, cross or loop-scavenged engine. In this model, the geometry of the cylinder and port assemblies, as well as the physical conditions of operation are fully represented. The ...
The typical convex torque of a simple two-stroke engine having a port-controlled piston is attrib... more The typical convex torque of a simple two-stroke engine having a port-controlled piston is attributed to the backflow through the scavenge ports. It is proposed here to suppress the backflow by installing scroll diodes at the scavenge ports. Experimental observations on a fired engine ...
... Titre du document / Document title. VIBRATION SIGNATURE ANALYSIS AS A FAULT DETECTION METHOD ... more ... Titre du document / Document title. VIBRATION SIGNATURE ANALYSIS AS A FAULT DETECTION METHOD FOR SL ENGINES. Auteur(s) / Author(s). DEBOTTON G. ; BEN-ARI J. ; ITZHAKI R. ; SHER E. ; Revue / Journal Title. SAE transactions ISSN 0096-736X Source / Source. ...
ABSTRACT The voltage-current characteristics (VCC) of flame-assisted electrical coronas have been... more ABSTRACT The voltage-current characteristics (VCC) of flame-assisted electrical coronas have been measured in an inhomogeneous electric field. The electric field was created by applying a voltage less than 25 kV DC between a cylindrical metallic burner and a planar metallic grid, which was perpendicular to the axis of the burner. Both positive and negative polarities of the applied voltage were studied in the presence of a pre-mixed methane-air flame. The results were compared with the VCC measured for the same discharge gap in the absence of a flame. Simultaneously, with measuring a VCC the behavior of the flame was observed and its height was measured under a gradually increased voltage, which resulted in the flame shortening. For most cases complete extinction of the flame was achieved at a particular voltage. An exact spherically symmetric solution for a unipolar corona in the domain between two spherical electrodes, was used to model the discharge gap between the flame boundary and the grid and also to calculate the VCC for comparison with the experimental results. It is shown that in the presence of a flame, the experimental and theoretical VCCs can be matched if the radius of curvature of the flame tip increases with the total current. This agrees with the present experimental results, in which flattening of a flame was observed when the current was increased.
The effect of the amount of hydrogen addition on the fuel consumption and emission of a spark ign... more The effect of the amount of hydrogen addition on the fuel consumption and emission of a spark ignition engine has been studied. Dynamometer test results for a wide range of engine speeds, engine loads, equivalent ratio and hydrogen enrichment under steady state operation are presented, and the engine requirements for minimum b.s.f.c. are specified. A detailed model to simulate a four-stroke cycle of a spark ignition engine fuelled with hydrogen-enriched gasoline was used to predict the optimal amount of hydrogen supplement as well as the corresponding minimum best torque (MBT) optimal throttle position and emissions levels of CO and NOx. It has been shown that a significant reduction in the b.s.f.c, in the order of 20 per cent, is achieved with hydrogen-enriched gasoline for a hydrogen-fuel mass ratio of 6 per cent and equivalence ratio of 0.65. A very smooth operation has been observed under these conditions. The energy conversion gain is prominent at partial loads and depends only to a limited extent on the engine speed.
A simplified numerical code for thermal analysis of a helical heat exchanger for use in long-term... more A simplified numerical code for thermal analysis of a helical heat exchanger for use in long-term thermal energy storage in soil was developed. The model was verified for a particular case for which an analytical solution was available from the literature and was validated with experimental data obtained from field experiments. The differences between predicted and measured data were in the range of ±1°C, which is considered satisfactory for engineering design purposes. The model was prepared for use with an personal computer and thus provides a convenient and reliable design tool for such a system. The computer code may be easily modified for the study of the influence of incorporating phase-change material elements in the storage well.
A fairly detailed reaction scheme for the oxidation of n -butane and hydrogen mixture has been em... more A fairly detailed reaction scheme for the oxidation of n -butane and hydrogen mixture has been employed to study the effect of hydrogen addition on the time delay of n -butane/air mixture. The intricate paths and mechanism by which autoignition is developed have been investigated by using the time-dependent kinetic flow charts technique. It was concluded that the autoignition process of n -butane/air as well as of n -butane/hydrogen/air mixture may be divided into three main periods. In the first (50 μs), the fuel molecule is attacked by HO 2 radicals to produce H 2 O 2 molecules which, in turn, decompose into OH radicals. In the second (a few microseconds before ignition occurs), the OH radicals play the most important role in breaking down the hydrocarbon molecules. In the third, the CH 2 O is converted into HCO and an avalanche of a series of exothermic reactions takes place and accelerate the whole process. It was also concluded that the hydrogen enrichment has a retarding effect on the autoignition process. This is attributed to the reduction of the OH population in the second stage due to the reaction H 2 +OH→H+H 2 O.
An improved mathematical model is presented here to simulate the gas exchange of a two-stroke, cr... more An improved mathematical model is presented here to simulate the gas exchange of a two-stroke, cross or loop-scavenged engine. In this model, the geometry of the cylinder and port assemblies, as well as the physical conditions of operation are fully represented. The ...
The typical convex torque of a simple two-stroke engine having a port-controlled piston is attrib... more The typical convex torque of a simple two-stroke engine having a port-controlled piston is attributed to the backflow through the scavenge ports. It is proposed here to suppress the backflow by installing scroll diodes at the scavenge ports. Experimental observations on a fired engine ...
... Titre du document / Document title. VIBRATION SIGNATURE ANALYSIS AS A FAULT DETECTION METHOD ... more ... Titre du document / Document title. VIBRATION SIGNATURE ANALYSIS AS A FAULT DETECTION METHOD FOR SL ENGINES. Auteur(s) / Author(s). DEBOTTON G. ; BEN-ARI J. ; ITZHAKI R. ; SHER E. ; Revue / Journal Title. SAE transactions ISSN 0096-736X Source / Source. ...
ABSTRACT The voltage-current characteristics (VCC) of flame-assisted electrical coronas have been... more ABSTRACT The voltage-current characteristics (VCC) of flame-assisted electrical coronas have been measured in an inhomogeneous electric field. The electric field was created by applying a voltage less than 25 kV DC between a cylindrical metallic burner and a planar metallic grid, which was perpendicular to the axis of the burner. Both positive and negative polarities of the applied voltage were studied in the presence of a pre-mixed methane-air flame. The results were compared with the VCC measured for the same discharge gap in the absence of a flame. Simultaneously, with measuring a VCC the behavior of the flame was observed and its height was measured under a gradually increased voltage, which resulted in the flame shortening. For most cases complete extinction of the flame was achieved at a particular voltage. An exact spherically symmetric solution for a unipolar corona in the domain between two spherical electrodes, was used to model the discharge gap between the flame boundary and the grid and also to calculate the VCC for comparison with the experimental results. It is shown that in the presence of a flame, the experimental and theoretical VCCs can be matched if the radius of curvature of the flame tip increases with the total current. This agrees with the present experimental results, in which flattening of a flame was observed when the current was increased.
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