Hesham M. El-Batsh

Effects of Alumina Nanoparticles Additives Into Jojoba Methyl Ester-Diesel Mixture on Diesel Engine Performance

Currently, using biofuels to operate diesel engines gets a great attention to the extent that it could replace the limited conventional fossil fuels. These fuels have a closed life cycle (renewable) and they have a remarkable effect on the global greenhouse phenomena. Moreover, the use of non-edible vegetable oils is considered a good choice after a suitable chemical and/or thermal treatment to convert them into esters. The use of jojoba oil shows a promising alternative fuel for conventional diesel fuel even there were unfavorable effects including power reduction. The wide spread usage of nano additives to improve the combustion quality may be a good solution for these problems. This study represents an experimental investigation to examine the effect of nano additives on diesel engine performance at variable operating conditions of load and speed. In this work, alumina nano-particles are added to a mixture of jojoba methyl ester (biodiesel) and conventional diesel fuel at the most recommended value (20% biodiesel and 80% diesel fuel) with different doses from 10 up to 50 mg/l. The received mixture is homogenized with an ultrasonicator mixer. It is found that, the appropriate nano-additives dose corresponding to optimal engine performance is about 30 mg/l. At this dose, the overall BSFC is reduced by about 6%, engine thermal efficiency is increased up to 7%, and all engine emissions have been reduced (NOx about 70%, CO about 75 %, smoke opacity about 5%, and UHC about 55 %) compared with the corresponding values obtained when only a blended fuel of 20% biodiesel is used.Copyright

Effect of the Radial Pressure Gradient on the Secondary Flow Generated in an Annular Turbine Cascade

This paper introduces an investigation of the effect of radial pressure gradient on the secondary flow generated in turbine cascades. Laboratory measurements were performed using an annular sector cascade which allowed the investigation using relatively small number of blades. The flow was measured upstream and downstream of the cascade using a calibrated five-hole pressure probe. The three-dimensional Reynolds Averaged Navier Stokes equations were solved to understand flow physics. Turbulence was modeled using eddy-viscosity assumption and the two-equation Shear Stress Transport (SST) k-ω model. The results obtained through this study showed that the secondary flow is significantly affected by the pressure gradient along blade span. The experimental measurements and the numerical calculations predicted passage vortex near blade hub which had larger and stronger values than that predicted near blade tip. The loss distribution revealed that secondary flow loss was concentrated near blade hub. It is recommended that attempts of reducing secondary flow in annular cascade should put emphasis on the passage vortex near the hub.

Effect of Secondary Flows on Heat Transfer of a Gas Turbine Blade

This study presents experimental and numerical investigation for three-dimensional heat transfer characteristics in a turbine blade. An experimental setup was installed with a turbine cascade of five-blade channels. Blade heat transfer measurements were performed for the middle channel under uniform heat flux boundary conditions. Heat was supplied to the blades using twenty-nine electric heating strips cemented vertically on the outer surface of the blades. Distributions of heat transfer coefficient were obtained at three levels through blade height by measuring surface temperature distribution using thermocouples. To understand heat transfer characteristics, surface static pressure distributions on blade surface were also measured. Numerical investigation was performed as well to extend the investigation to locations other than those measured experimentally. Three-dimensional nonisothermal, turbulent flow was obtained by solving Reynolds averaged Navier-Stokes equations and energy equation. The shear stress transport model was employed to represent turbulent flow. It was found through this study that secondary flow generated by flow deflection increases heat transfer coefficient on the blade suction surface. Separation lines with high heat transfer coefficients were predicted numerically with good agreement with the experimental measurements.

An Investigation on the Effect of Endwall Movement on the Tip Clearance Loss Using Annular Turbine Cascade

The aerodynamic losses in gas turbines are mainly caused by profile loss secondary flow, and tip leakage loss. This study focuses on tip leakage flow of high-pressure turbine stages. An annular turbine cascade was constructed with fixed blades on the casing, and the distance between blade tip and the hub was considered as tip clearance gap. The effect of endwall movement on loss mechanism was investigated by using experimental and numerical techniques. The measurements were obtained while the hub was fixed but the numerical calculations were carried out for both stationary and moving cascades. Upstream and downstream flows were measured by using a calibrated five-hole pressure probe. The steady incompressible turbulent flow was obtained by solving Reynolds averaged Navier-Stokes equations and by employing shear stress transport (SST) k-ω turbulence model. The total pressure loss coefficient obtained from the numerical technique was compared with the experimental measurements, and the comparison showed good agreement. Tip clearance vortices were observed in the tip clearance gap. It was found through this study that end-wall movement reduces tip leakage loss through the cascade.

Numerical study of the flow field through a transonic linear turbine cascade at design and off-design conditions

The flow field through a transonic linear turbine cascade is studied in this paper at design and off-design conditions. The compressible flow field is obtained by solving the equations governing the fluid flow and heat transfer. Two eddy-viscosity turbulence models are used to simulate the turbulence in turbine cascades: the standard k-ϵ model and the Spalart–Allmaras model. The standard k-ϵ model is the most universal and popular model for industrial flow and heat transfer simulations. It has the shortcoming of accurately predicting the profile loss in turbomachinery applications. The Spalart–Allmaras model is a relatively recent and simple one-equation model. In this paper, the model is tested for turbomachinery applications. The ability of the model to accurately predict the flow field in turbine cascade is tested. Blade loading, downstream wake distribution, total pressure loss coefficient, and exit flow angle are used in this study with comparisons to the standard k-ϵ model and experimental data. The design condition and the off-design conditions are considered.

Combustion Characteristics of Jojoba Methyl Ester as an Alternative Fuel for Gas Turbine

The strengthened requirements of new emission norms and the limited fuel resources are the major challenges for researchers over the world. The use of biofuels produced from vegetable oil will be a promising solution. In this case, Jojoba oil comes from very surprising plant as its seed contains 40–60% of its weight as raw oil and grows in desert. The trans-esterification process is used to convert jojoba oil into a Jojoba Methyl Ester (JME). This study aims to characterize the flame of JME as an alternative fuel in the gas turbines. Using of the premixed flame resulted in higher combustion efficiency and low emissions. The premixed flames for liquid fuels can be realized via use of lean premixed pre-vaporized (LPP) combustion method. In this work the jet fuel and blends of jet-JME fuel (with JME volume faction of 10, and 20%) are burned with LPP technique keeping the same equivalence ratio as it is used for burning the base jet fuel to determine the possibility to use the fuel mixture without any modifications in a specific LPP combustor. The main results indicate that, as volume content of JME increase the NOx emissions decrease to be lower than 10 ppm in case of B20. Moreover, the CO emission in case of B20 is higher than that of the jet fuel but at the end of the test section it does not exceed 0.15 %. In the same way, B20 produces higher UHC emissions than the jet fuel; however, at the end of the test section it does not exceed 80 ppm. So it can be concluded that blended Jojoba biodiesel can be used as an alternative fuel for jet fuel.Copyright