Papers by chokri boubahri
Journal of Energy Resources Technology, 2012
The main purpose of this research is to study the effect of various blends of an environmental fr... more The main purpose of this research is to study the effect of various blends of an environmental friendly alternative fuel “methyl ester” on the performance of a heavy diesel engine. The biodiesel was obtained from a chemical process: the transesterification of waste oils (frying oils). Tests were conducted on an engine test bench in accordance to DIN 2020 standards. Results obtained demonstrate that the biodiesel gives very interesting ecological advantages but engine performance was reduced slightly comparatively to those obtained with a pure diesel fuel. We have noted about 5% decrease in power and torque and about 2% in Nox emission for every 10% of biodiesel blend added comparatively to pure diesel. However, the use of biodiesel has slightly increased specific fuel consumption (about 6% for every 10% of biodiesel blend added).
Journal of Energy Resources Technology, 2012
The main purpose of this research is to study the effect of various blends of an environmental fr... more The main purpose of this research is to study the effect of various blends of an environmental friendly alternative fuel “methyl ester” on the performance of a heavy diesel engine. The biodiesel was obtained from a chemical process: the transesterification of waste oils (frying oils). Tests were conducted on an engine test bench in accordance to DIN 2020 standards. Results obtained demonstrate that the biodiesel gives very interesting ecological advantages but engine performance was reduced slightly comparatively to those obtained with a pure diesel fuel. We have noted about 5% decrease in power and torque and about 2% in Nox emission for every 10% of biodiesel blend added comparatively to pure diesel. However, the use of biodiesel has slightly increased specific fuel consumption (about 6% for every 10% of biodiesel blend added).
Journal of Energy Resources Technology, 2012
The main purpose of this research is to study the effect of various blends of an environmental fr... more The main purpose of this research is to study the effect of various blends of an environmental friendly alternative fuel “methyl ester” on the performance of a heavy diesel engine. The biodiesel was obtained from a chemical process: the transesterification of waste oils (frying oils). Tests were conducted on an engine test bench in accordance to DIN 2020 standards. Results obtained demonstrate that the biodiesel gives very interesting ecological advantages but engine performance was reduced slightly comparatively to those obtained with a pure diesel fuel. We have noted about 5% decrease in power and torque and about 2% in Nox emission for every 10% of biodiesel blend added comparatively to pure diesel. However, the use of biodiesel has slightly increased specific fuel consumption (about 6% for every 10% of biodiesel blend added).
Journal of Energy Resources Technology, 2012
The main purpose of this research is to study the effect of various blends of an environmental fr... more The main purpose of this research is to study the effect of various blends of an environmental friendly alternative fuel “methyl ester” on the performance of a heavy diesel engine. The biodiesel was obtained from a chemical process: the transesterification of waste oils (frying oils). Tests were conducted on an engine test bench in accordance to DIN 2020 standards. Results obtained demonstrate that the biodiesel gives very interesting ecological advantages but engine performance was reduced slightly comparatively to those obtained with a pure diesel fuel. We have noted about 5% decrease in power and torque and about 2% in Nox emission for every 10% of biodiesel blend added comparatively to pure diesel. However, the use of biodiesel has slightly increased specific fuel consumption (about 6% for every 10% of biodiesel blend added).
Effect of Fuel Injection Pressure on the Performance and Emission Analysis of Mahua Methyl Ester in a Single Cylinder Diesel Engine
International Journal of Ambient Energy
In the recent years, biodiesel has become a promising solution to the rapid depletion of the foss... more In the recent years, biodiesel has become a promising solution to the rapid depletion of the fossil fuel reserves as well as to the alarming amount of discharged pollutants. But inherent properties such as low volatility, high density and high viscosity have been pointed at for inducing most of its drawbacks. Many studies have been undertaken in order to inhibit these deficiencies. Hence, the aim of this study is to investigate the effect of varying injection pressure on performance and emission characteristics of a four-cylinder, four-stroke, compression ignition direct injection engine fuelled with mineral diesel fuel and 20%, 40% and 60% waste cooking oil biodiesel blends (B20, B40 and B60). To that end, five injection pressures were tested: the original 200 bar, 220 bar, 240 bar, 260 bar and 280 bar. Experiments were conducted in accordance with the procedure dictated by DIN 70020. This study revealed that implementing the injection pressure up to 240 bar induces significant improvement in the performance characteristics for all tested fuels to varying degrees. The B20, under this optimized injection pressure was found to offer the best performances characteristics. Increasing injection pressure has proven its worth within a restricted limit. Indeed, for 260 bar and 280 bar, for all tested fuels, performance and smoke level characteristics were found to be dwindling.
Evolution Mechanisms of T91 Steel in Subcritical Conditions and Role of an Internal Oxidation Zone
Oxidation of Metals
Analysis of changes in lattice parameter of a grade 91 steel during thermal ageing at 550 °C
Engineering Failure Analysis
Microstructural changes in the T91 steel (also known as the modified 9Cr1Mo steel), largely used ... more Microstructural changes in the T91 steel (also known as the modified 9Cr1Mo steel), largely used in thermal and nuclear power plants as well as petrochemical factories, have been studied, after isothermal ageing (at 550 °C) in laboratory, for different durations up to 7000 h (about 10 months of exposure). In-depth analysis about chemical and structural changes in the metallic substrate and secondary carbides (M23C6) were conducted using SEM, EDX and X-ray diffraction instrumentations. Results reveal a progressive restoration of the tempered martensitic matrix with holding time. Then, a continuous increase in size of secondary carbides was noticed until stabilization after >5000 h of ageing. Kinetic parameters of matrix lattice were determined using Johnson-Mehl-Avrami (JMA) model. Natural logarithm of the relative lattice parameter of the matrix varies linearly with that of ageing time. Thus, the Avrami exponent n and activation energy E were established. Diffusion of chromium and molybdenum from matrix into carbides lattice was proved which explains their continuous coarsening. That has a harmful effect on the long term stability of the microstructure. The time-temperature dependence of this transformation could be then a good indicator to assess the resistance of T91 steel to heat exposure.
Microstructure evolution and corrosion behaviour of an ASTM A213 T91 tube after long term creep exposure
Engineering Failure Analysis, 2017
This study deals with microstructural evolution, mechanical properties and oxidation/carburizatio... more This study deals with microstructural evolution, mechanical properties and oxidation/carburization behaviour of an ASTM A213 T91 super-heater tube after long term service in a power plant ; approximately 157.000 hours (about 18 years) in subcritical conditions (542 • C and 174 bar). This work provides good experience data to better evaluate the performances of this material, it can be referential for readers who are interested in martensitic heat-resistant steels, because the major previous studies were conducted in laboratories focusing on short creep experiences and oxidation behaviour. Our investigations suggest remarkable changes in the core and the walls of the tube. In the bulk material, the recovery of the tempered martensitic matrix and the coarsening of the M 23 C 6 carbides were observed, but the mechanical properties and the creep strength are still good. However, carburization/oxidation represents a major life time limiting factor by affecting about 20% of the tube thickness. The mechanisms of carburization, oxidation and microstructure evolution are here discussed.
Microstructure evolution and corrosion behaviour of an ASTM A213 T91 tube after long term creep exposure
Engineering Failure Analysis, 2017
This study deals with microstructural evolution, mechanical properties and oxidation/carburizatio... more This study deals with microstructural evolution, mechanical properties and oxidation/carburization behaviour of an ASTM A213 T91 super-heater tube after long term service in a power plant ; approximately 157.000 hours (about 18 years) in subcritical conditions (542 • C and 174 bar). This work provides good experience data to better evaluate the performances of this material, it can be referential for readers who are interested in martensitic heat-resistant steels, because the major previous studies were conducted in laboratories focusing on short creep experiences and oxidation behaviour. Our investigations suggest remarkable changes in the core and the walls of the tube. In the bulk material, the recovery of the tempered martensitic matrix and the coarsening of the M 23 C 6 carbides were observed, but the mechanical properties and the creep strength are still good. However, carburization/oxidation represents a major life time limiting factor by affecting about 20% of the tube thickness. The mechanisms of carburization, oxidation and microstructure evolution are here discussed.
Corrosion of a T91 steel tube, used in subcritical conditions in an oil power plant for 157,000 h... more Corrosion of a T91 steel tube, used in subcritical conditions in an oil power plant for 157,000 hours was characterized 7 mainly through SEM, TEM, EDX and DRX analyses. Severe oxidation and carburization took place in both the outer (boiler) 8 and inner (steam) wall sides. The nature and morphology of the oxide scale multi-layer structure (hematite, magnetite and spinel) 9 depended on the environment exposure. Specific attention was given to the internal oxidation zone (IOZ) at the oxide/metal 10 interface. Diffusion of chromium during the oxidation process was determined, and was proposed to be responsible for the 11 continuous advancement of oxidation to the core of material, which eventually gave rise to the spinel. Finally, in the bulk 12 material, coarsening of the secondary carbides (M 23 C 6) was the main form of microstructural evolution. 13
Uploads
Papers by chokri boubahri