Ghassan Tashtoush

Combustion performance and emissions of ethyl ester of a waste vegetable oil in a water-cooled furnace

Food consumption around the world produces large amounts of waste vegetable oils and fats that, in many world regions, are disposed of in harmful ways. Consequently, this study intended to investigate the feasibility of utilizing this renewable and low cost fuel raw material as a diesel fuel replacement in small-scale applications such as in residential heating boilers. Specifically, the study examined the aspects of combustion performance and emissions of the ethyl ester of used palm oil (biodiesel) relative to the baseline diesel fuel in a water-cooled furnace. The combustion efficiency, ηc, and exhaust temperature, Texh, as well as the common pollutants and emissions were tested over a wide range of air/fuel ratio ranging from very lean to very rich (10:1–20:1). All tests were conducted at two different energy inputs for both fuels. The findings showed that, at the lower energy rate used, biodiesel burned more efficiently with higher combustion efficiency and exhaust temperature of, respectively, 66% and 600 °C compared to 56% and 560 °C for the diesel fuel. At the higher energy input, biodiesel combustion performance deteriorated and was inferior to diesel fuel due to its high viscosity, density and low volatility. As for emissions, biodiesel emitted less pollutants at both energy levels over the whole range of A/F ratio considered.

Effect of Graphite and/or Silicon Carbide Particles Addition on the Hardness and Surface Roughness of Al-4 wt% Mg Alloy

In this study, the fabrication of Al-4 wt% Mg-graphite and/or silicon carbide (SiC) particulate composites is described. Composites of Al-4 wt% Mg alloy with different volume percentage values of graphite and/or SiC particles are prepared using the compocasting technique. In this technique, graphite particles and/or SiC particles are added into a semi-solid slurry during the stirring of the melt. A pitched blade stirrer is used to stir the reinforcement particles in the slurry. The slurry is then poured in a metallic mold to obtain the cast composites. The effect of the addition of graphite and/or SiC particles and porosity content on the Rockwell hardness and machinability is studied in the present work. The results show that the porosities increase with increase in particles content while Rockwell hardness decreases with increase of graphite particles. But SiC particles are found to increase the hardness of composites. Surface roughness improves with graphite content in the cast composite, and poor surface finish is obtained when SiC particles are added.

The effect of a cold temperature valley on pulsating flame spread over propanol

The transient three-dimensional structures of velocity and temperature created by a pulsating flame spread over normal propanol were constructed from five independent transient measurements using five different techniques: laser sheet particle tracking (LSPT): smoke tracing (ST); dual wavelength holographic interferometry (DWHI): infrared thermography (IR): and high-speed photography (HSP). These measurements showed that the pulsating flame spread consists of five distinctly different steps. The first step is the onset of pulsation created by the stagnation of flame spread over the liquid, which is followed by the second step, formation of a cold liquid valley near the flames leading edge, and the third step, accumulation of liquid fuel vapor over the liquid surface. In the fourth step, the flame jumps through the formed premixed gas layer, leading to the final step, the cessation of spread. After the fifth step, the process returns to the first step, completing the entire pulsation cycle. Our experimental data confirm the formation of a small gas-phase circulation cell, as predicted by the University of California, Irvine, numerical model, and support the idea that the pulsating spread is triggered by the subsurface liquid convection that affects the gas-phase flow and the fuel vapor concentration. The second result is unique and suggests that a cold temperature valley formed on the liquid surface would play an important role in the mechanism of pulsating spread.

Study of Flame Spread Over JP8 Using 2-D Holographic Interferometry

Despite the widespread use of JP8 as a transportation fuel, and hence its importance to fire safety in the event of an accident, the characteristics of flame spread over JP8 are not well known. In order to better estimate fire growth rates, flame spread rates over JP8 and n-butanol were measured in this study as functions of initial liquid temperature. A Holographic Interferometry (HI) technique was employed in conjunction with a photographic recording sys tem to rapidly detect small temperature changes over an area including the liquid and gas phases. The laboratory-scale experiments were performed using the same apparatus employed in previous studies of flame spread over alcohol to al low comparison of the two sets of results. Flame spread data were obtained for JP8 fuel as a function of initial fuel temperatures between 15°C and 40°C. The four common spread patterns (pseudo-uniform, pulsating, uniform, and superflash) observed for alcohol by Akita [1] were also observed for flame spread over JP8. In order to estimate the heat flux carried by the subsurface convective flow, an energy balance in the liquid phase was performed by considering a con trol volume of the liquid ahead of the flame. From this analysis, the liquid-phase convection (Qcv) was found to be larger than both the gas-phase convection (Q g) and the heat loss (QL). This trend indicates that (Qcv) is the main mode of heat transfer for flame spread over liquid in the uniform regime of these experiments. It was also observed that JP8 requires a much higher ignition energy, in compari son with butanol, to initiate the flame spread, although both JP8 and butanol have approximately equal closed-cup flash point (Tf ~37°C). The difference is partly due to the low viscosity and relatively large surface-tension force of JP8 which generate a liquid convection flow more effectively than butanol.

Performance analysis of green engine-driven systems for space cooling

As fuel prices keep changing and energy reserves keep decreasing, efficient methods of energy utilisation and conversion should be used. Heat pumping is a good example where low-grade diluted thermal energy is abstracted from air outdoors and then transferred and concentrated at higher air temperature indoors. For space cooling, the thermal energy is abstracted from warm air indoors and then thrown outdoors. This work covers engine-assisted cooling systems both vapour compression and absorption, associated with gas turbine and internal combustion engines. Primary energy was found to be saved by about 50%, especially with gas turbines, relative to the basic electrical system operated by supplied electricity from the power plant.

Thermal design of parabolic solar concentrator adsorption refrigeration system

This study presents a thermal design of solar-powered adsorption refrigeration with the type of activated carbon-methanol pair. The designed module consists of an evacuated glass tube equipped with a parabolic solar concentrator as generator, sorption bed, evaporator, and condenser units. A thermodynamic design procedure and a mathematical model of a steady state system with activated carbon refrigerator have been developed. The adsorber is heated by solar energy collected by a parabolic solar concentrator. The temperature of the working pair in the adsorber, the amount of methanol leaving and reabsorb bed, and the refrigerated box was estimated. An optimize design of the system to achieve higher cycle COP was presented. Maximum cycle COP = 0.576 and COPnet = 0.375 with Tmax reached 157.8°C, TB = 57.5°C, Mac = 0.907 kg, and the concentration of methanoldesorped equal to 0.206 kg/kgac.

Experimental study of tracking 2-D Compound Parabolic Concentrator (CPC) with flat plate absorber

This paper presents an experimental investigation of tracking 2-D CPC collector with flat plate absorber under Jordan climate. A single axis solar tracking system was integrated with the collector in order to determine the quality of energy improvement gained due to tracking effect through comparing the maximum plate temperature of both tracking and stationary CPC collectors. The testing was conducted during the period from March to May 2013. Comparative results for the maximum plate temperature were presented. The results revealed that integrating tracking system with CPC collector increased the maximum temperature of the plate by 27.7%, 16.7% and 8.3% for March, April and May, respectively, in comparison with stationary CPC. The cost of the tracking system used in the testing represents 38.6 % of the total cost of the system. However, this percentage will be reduced when the collector is used for certain applications that require extra components.

Measurement Of A 3-D (Gas And Liquid) Flow Structures Generated By A Spreading Flame Over N-butanol

This paper discusses a new 3-D experimental data that were obtained by a laser-sheetparticle-tracking (LSFT) technique for a spreading flame over n-butanol. The major heattransfer process between the flames leading edge and the liquid is a highly transient phenomenon involving both liquid and gas phases. These interact with each other through exchanges of momentum, heat, and mass. We improved our original 2-D LSPT and made it applicable to study 3-D measurement. Using this new 3-D LSPT we measured a series of velocity profiles in a pulsating flame spread over n-butanol at different distances above or below the liquid surface and obtained 3-D flow visualization in both liquid and gas phases. The new LSPT confirmed the existence of twin vortex flow on the liquid surface and deep in the liquid a few mm below the surface. These vortices gradually disappear as the laser sheet moves down from the liquid surface. A similar twin-vortex structure in the gas phase was also observed for the first time. These results proved that the convective flow in both liquid and gas phases is 3-D in nature in the three trays we have used.

Effect of Acoustics on NoX Emission in Premixed Flame, Experimental Study

The effect of acoustic frequency on pollutants emissions from a premixed gas combustor has been investigated. A significant decrease (down to 61.5%) in nitrogen oxide (NO) emissions was observed in the presence of acoustic oscillation (two opposite square waves) in a premixed flame. Although the overall production of the pollutants is reduced, the reduction rate depends on the frequency and the direction of the acoustic field. It is shown that the acoustic effect can be considered as a possible alternative to flue gas reburn technology to achieve the same or even better effectiveness in NOx and CO pollutants reduction with much less cost.