Solution of Abel’s Integral Equation Using Tikhonov Regularization

This paper presents a method based on Tikhonov regularization for solving one-dimensional inverse tomography problems that arise in combustion applications. In this technique, Tikhonov regularization transforms the ill-conditioned set of equations generated by onion-peeling deconvolution into a well-conditioned set that is more stable to measurement errors that arise in experimental settings. The performance of this method is compared to that of onion-peeling and Abel three-point deconvolution by solving for a known field variable distribution from projected data contaminated with artificially-generated error. The results show that Tikhonov deconvolution provides a more accurate field distribution than onion-peeling and Abel three-point deconvolution, and is more stable than the other two methods as the distance between projected data points decreases.

A Thermal Model of a Fiber Optic Bundle for a Hybrid Solar Lighting System

Hybrid solar lighting (HSL) systems distribute natural sunlight to luminaires located in office or retail buildings in order to reduce energy consumption associated with conventional lighting systems. HSL systems reduce energy consumption directly by reducing the lighting energy and indirectly by reducing the associated cooling loads. A key component of the HSL system is the fiber optic bundle (FOB) that transmits the light from the collector to the luminaire. The observed thermal failure of the FOB when exposed to concentrated sunlight has motivated the development of a thermal model of this component. This paper describes the development of a predictive thermal model of the heat transfer in an FOB for an HSL system. The model is verified experimentally against temperature measurements obtained in the lab under controlled conditions and provides a powerful design tool that can be used to evaluate alternative thermal management strategies.

Experimental Evaluation of the Thermal Behavior of a Vertical Solar Tank Using Energy and Exergy Analysis

The thermal performance of a Thermosyphon Domestic Solar Water Heater (DSWH) with a vertical storage tank is investigated experimentally. The system is installed on a roof - top of a four person family house and its thermal characteristics is evaluated by means of carefully measuring the temperature distribution of water inside the storage tank, solar collector flow rate and its inlet and outlet temperatures as well as load/consumption outlet and inlet temperatures and the corresponding water flow rate under a realistic operating conditions. The measurements are conducted every hour starting from morning until late night on a daily basis and continued for about 120 days during August until November 2004. It is seen that thermal stratification is well established inside the tank from 11 AM until 10 PM especially during August to September enabling the tank to provide the necessary amount of hot water at an acceptable temperature. However, thermal stratification is observed to start degrading from mid-night until morning when there is no hot water supply from the collector and due to the diffusion of heat from the top hot water layers to the bottom cold region and conduction through tank’s wall. The thermal behavior of the storage tank is also assessed based on both energy and exergy analysis and its first and second law efficiencies are calculated. It is observed that the storage tank under study has an average first law efficiency of 47.8% and is able to supply the required amount of hot water at a proper temperature. The average second law efficiency of the storage tank is observed to be 28.7% and, although is less than its first low efficiency, but is high enough to ensure that the quality of the hot water supply is well preserved. The proper level of second law efficiency is due to the preservation of the thermal stratification inside the storage tank, leading to supply of hot water at highest possible temperature and hence highest possible energy potential. Experiments are also done for no-load conditions when the storage tank only interacts with the collector, without hot water withdrawal from the tank. It is seen that for no-load condition, thermal stratification continuously develops from morning until around 16 PM after which no noticeable changes in the temperature distribution inside the tank is observed.

Spray Penetration and Drop Size Studies of Diesel Fuels

Understanding the disintegration mechanism, spray penetration, and spray motion is of great importance in the design of a high quality diesel engine. The atomization process that a liquid would undergo as it is injected into a high-temperature, high-pressure air, is investigated in this work. The purpose of this study is to gain further insight into the atomization mechanism, the variation over time in droplet size distribution and spray penetration. This is done based on effect of chamber pressure, injection pressure, and type of fuel. A laser diffraction method is used to determine droplet mean diameters, single injection with synchronized time mechanism allowed the time dependent studies. Obscuration signals are obtained through a digital oscilloscope from which arrival time of spray can be measured. The spray penetration correlation obtained is compared to other correlation’s obtained from different other techniques used in the literature.

Numerical Simulations by Detailed Chemistry and Experimental Measurements of Diesel Combustion in a Light Duty Common Rail Direct Injection Engine

Present paper couples the use of a modified version of the KIVA-3V code including a model for detailed chemistry to an experimental investigation performed on an optically accessible diesel engine. The engine is equipped with a commercial four valves cylinder head and a Common Rail injection system. Digital images and UV-visible flame emission measurements are compared with the visualization of the numerical results. The diesel fuel surrogate is considered within the numerical code, namely a blend consisting of n-heptane and toluene, approximating the physical and ignition properties of the diesel oil. Products, soot and NOx formation is described by a chain of 283 reactions involving 69 species. The Partially Stirred Reactor (PaSR) assumption is adopted to maintain the computational cost within acceptable limits. The collections of digital images of the spray evolution, the mixture formation and the combustion processes are undertaken by running the engine at 1000 rpm. Commercial diesel fuel is injected by using a single injection.

Numerical Simulation of High-Temperature Air Direct-Ignition of Pulverized Coal

Numerical simulation method is employed in this article to investigate various high-temperature air direct-ignition processes of pulverized coal (PC). Several important factors are analyzed, which are the inlet velocity of primary air flow, PC concentration and the velocity and temperature of high temperature air. The flow, combustion and heat transfer in high temperature air oil-free ignition burner can also be obtained from the simulation results, which are in accordance with the experimental data. The research provides guidance for structure improvement and operation optimization of burner.

Electrical and Electronic Equipment Recovery and Recycling in Turkey

Discarded electrical and electronic equipment contains valuable materials, low value parts, and hazardous substances. There is a growing concern regarding the management of end-of-use equipment owing to the environmental concerns associated with discarding used devices. Electronic waste or scrap consumes valuable landfill space and may ultimately contaminate groundwater sources. In addition, replacing discarded components with new components typically consumes valuable virgin material resources. With the advent of the WEEE (Waste Electrical and Electronic Equipment) Directive, used electrical and electronic products are now being recovered in Turkey as a European Union (EU) candidate country, and several companies in Turkey have begun to recover latent value through disassembly and reuse/recycling of materials and components. To remain competitive, these companies must implement economical and environmentally responsible recovery processes. There are a number of research challenges associated with product recovery. This paper describes the current product recovery infrastructure in Turkey, and discusses future trends and drivers for successful product take-back.

Flue-Gas Versus Fuel-Injection Recirculation: Effects on Structure and Pollutant Emissions

In this study, a co-flow methane/air diffusion flame at Reynolds number of 6000 was numerically simulated. The co-flow air and fuel streams were diluted with Nitrogen in the range of 0% to 20%. The thermal and composition fields in the far-burner reaction zone (close to the exhaust) were computed, and the effects of diluent’s addition to the air stream (simulating FGR) and to the fuel stream (simulating FIR) were investigated. The results show that air-side dilution is very effective up to 5% diluent’s addition. For which, 95% and 65% drops in NO and CO emissions, respectively, along with a 16% increase in temperature, are predicted compared to the baseline case (0% dilution). However, beyond 5% dilution, no effect (reaction) has been predicted. On the other hand, the fuel-side dilution has shown an effect for all simulated diluent’s addition (i.e. 0%–20%). However, that effect is not systematic neither on temperature, CO or NO concentrations. For a similar 5% dilution to the fuel-side, a 14% increase in NO and a 97% decrease in CO are predicted, along with a 5.6% increase in temperature. The simulated results revealed that air-side dilution (simulating FGR) has a dramatic greater effectiveness in NO reduction, whereas, fuel-side dilution (simulating FIR) has a greater effectiveness in CO reduction. Besides, the results suggest an important role for Prompt-NO Fenimore mechanism.

Simplified Design of Combustion Chamber for Small Gas Turbine Applications

The combustion chamber of gas turbine unit is one of the most critical components to be designed. Scanning through literature reveals that the design methodologies for combustion chamber are available in a discrete manner and there exist a need to compile this information and evolve a systematic design procedure for combustion chamber. The present paper is an attempt towards presenting such a complete design methodology of combustion chamber for small gas turbine applications. The combustion chamber for the 20 kW gas turbine engine has been designed and fabricated as per these summarized design guidelines then checked for the axial and radial temperature profiles as well as liner wall temperatures, experimentally. The liner wall temperatures achieved is in the vicinity of 300°C when centerline temperature is of the order of 1300°C. This adequately validates the design methodologies proposed in this paper.

Performance Comparison of Flat Plate Collectors Fitted With Non Circular Risers With Integral Fins

The present study deals with comparison of experimentally determined performance characteristics of solar flat plate collectors fitted with novel designs of absorber plate involving non-circular risers with integral fins and operating under natural circulation mode. The main flow passages considered were square, triangular and semicircular in cross section. One standard solar flat plate collector with circular risers was also tested simultaneously for direct comparison. The test results indicate that the absorber fitted with the triangular sectioned risers yields the best performance in terms of the efficiency (63%), and the buoyancy induced flow per unit area (76 kg/hr-m2) from amongst the collectors investigated. It is followed by the absorbers fitted with the semicircular and square sectioned risers respectively. The standard solar flat plate collector is found to yield the lowest values i.e. 46 % and 40 kg/hr-m2 respectively.