Experimental and numerical study of MILD combustion in an open-end furnace with exhaust gas recirculation using methane and biogas

The world's energy demand by 2042 is estimated at about 18 billion tons of oil equivalent with 80% fulfilled by the combustion of fossil fuel. Combustion is predicted to be the most important way of generating energy to cater for these energy needs. The need to address energy sustainability (fuel depletion) and environmental pollution (emission) has led to an increased interest in energy efficiency improvement. Combustion technologies with higher thermal e�ciency and biogas (renewable) fuels are possible long-term solutions. The Moderate or Intense Low oxygen Dilution (MILD) combustion technology can play a significant role to produce higher thermal effi�ciency and reduce emissions. MILD combustion has achieved great success, however it needs further fundamental study due to the current limited research on open-end furnaces. In this study, an open-end furnace with an enclosure wall was used to capture the exhaust gas and utilised it as Exhaust Gas Recirculation (EGR). The EGR recirculates a portion of exhaust gas back to the combustion chamber to dilute the oxygen before the oxidant is mixed with the fuel and increases the reactant temperature. This setup is an open-end furnace because it allows a portion of the exhaust gas to flow out and be utilised as external EGR. In the case of a closed furnace, the exhaust gas is recirculated internally to dilute the reactants and increase their temperature. The wall thickness for the open-end furnace is very thin compared to the closed furnace which normally has a thick wall. The development and operating cost for the open-end furnace is cheaper than the closed furnace but the external EGR structure is an additional installation for the open-end furnace. The main objectives of this thesis are to conduct numerical modelling using Computational Fluid Dynamics (CFD) to design and develop the furnace, to develop and fabricate the new open-end furnace combustion chamber and to optimise the furnace performance to achieve MILD combustion. The numerical modelling for the MILD combustion using CFD has been extensively conducted on different burners and different scale furnaces. In this study, the three-dimensional CFD model was utilised to develop and optimise the furnace. The Reynolds-Averaged Navier-Stokes (RANS) equations were solved using realisable k–ε turbulent models which has been shown by others to be a reasonably accurate model to predict the combustion temperatures and combustion products. In this research, the results of the simulation slightly over-predict the flame temperatures by about 2 % compared to the experimental results. The non-premixed, partially premixed and premixed combustion with chemical equilibrium and non-adiabatic energy treatment for the thermo-chemical database were used. The Discrete Ordinates (DO) model was used to solve the radiative transfer equation for a finite number of discrete solid angles in the Cartesian co- ordinate system. The Weighted Sum of Gray Gas Model (WSGGM) was used for the absorption coefficient. The method of meshing was tetrahedrons patch conforming with advanced sizing function of proximity and curvature. The active assembly, fine span angle centre and fine relevance centre setting were used for all grids. All the governing equations were solved using the second order upwind discretisation scheme for higher accuracy of the calculation. The pressure-velocity coupling scheme with a least-squares cell-based gradient was used and presto was used as the pressure discretisation scheme. The early stage of the combustion chamber development started with a CFD simulation of a basic enclosed wall and top open combustion chamber. After analysing the results, two external EGR pipes were added. Then two more EGR pipes were added to make a total of four EGR pipes. The final model was improved with regard to the pipe size and the top part of the chamber design to ensure it collected an appropriate amount of the exhaust gas. This model was later used for the experimental and numerical modelling. The laboratory scale combustion chamber (total volume of 0.33 m3 and thermal ntensity of 18.8 kW/m3 atm) was developed and fabricated. In this study, the air and fuel supply system was also developed especially for this furnace operation. The parameters for the experimental study were the fuel compositions and the equivalence ratio. The experimental data was collected with 42 thermocouples (R-type and K-type), a gas analyser, an oxygen sensor and pressure transducers. The EGR flow rates were determined based on the pressures and temperatures in the EGR pipes. A National Instruments compact data acquisition system was used with analogue to digital converter modules and controlled by Labview software. Experimental tests were conducted where the secondary air supply was heated and non-heated while the reactants were varied to produce non-premixed, partially premixed and premixed flames. Methane fuel ignited more quickly than biogas due to its higher calorific value and lower self-ignition temperatures. The combination of heated secondary air with partially premixed fuel was the quickest to ignite. The combustion chamber, EGR and exhaust temperatures and the exhaust gas species were experimentally studied for the various equivalence ratios. The flame temperature for the biogas is lower than methane due to the lower calorific value of the fuel. Both methane and biogas flames produced very low NOx (2 ppm) for all flow rates whereas for carbon monoxide, biogas produced almost zero once the flame became steady. The numerical modelling for the partially-premixed methane and biogas using the same geometry and conditions as the experimental work is conducted and the flame temperatures are 1,499 K and 1,368 K respectively. These can be compared to the experimental flame temperatures for methane and biogas which are 1,483 K and 1,358 K respectively. The numerical modelling over-predicts by 1.13 % and 0.73 % respectively, which is good agreement. The exhaust gas species (CO2, H2O, O2 and NOx) were analysed at the exhaust pipe and the downstream of the EGR pipes. Both methane and biogas flames are lean. The combustion is completed with zero unburned hydrocarbons detected and excess oxygen was recorded for both the exhaust pipe and the downstream of the EGR pipes. At the downstream end of the EGR pipes, the excess oxygen is much higher due to the fresh supply of secondary air diluting the exhaust gas as expected. The NOx emissions for methane and biogas are very low (< 3 ppm) for both locations. The numerical sensitivity test was conducted to study the effect of the chamber wall temperature boundary condition on the flame temperature. The results show that the flame temperature is very sensitive to the combustion chamber wall boundary conditions. It concluded that biogas has advantages over methane due to lower peak temperature making the combustion chamber and burner last longer and be more economical to operate. More numerical modelling was conducted for the experimental furnace geometry; when appropriate oxygen dilution (3–13 %) and the preheated oxidant were applied, the model could achieve the MILD regime. The limitation of the developed experimental furnace was discussed where it required a minimum of 0.1 MW/m3 atm thermal density to achieve and sustain MILD combustion. Further simulations were conducted using the same furnace geometry except a luff-body air-fuel nozzle to successfully achieve MILD combustion. The oxygen mole fraction is diluted between 3 % and 13 % and the oxidant supply is preheated to achieve the overall reactant temperature above the fuel self-ignition temperature. The average and maximum chamber temperatures were almost identical at 3 % inlet oxygen mole fraction. The chamber temperature uniformity ratio was ≤ 20 % when the oxygen mole fractions were ≤ 13 %. The conventional flame was produced (the uniformity ratio of the chamber’s temperature was > 20 %) when the oxygen mole fraction reached > 14%. A new open-end furnace was designed, fabricated and tested experimentally as ell as numerically. The open-end furnace with the enclosed chamber numerically operated in the MILD combustion regime for both the industrial burner and the bluff-body burner. These results can be utilised by the heating industry and also for further studies by combustion researchers. It is recommended that future work to extend this study be carried out experimentally and numerically. The further studies can be undertaken using different fuel compositions, a new gas burner, higher secondary air preheating temperatures and a modified combustion chamber

Renewable Energy, A Tube Solar Collector using Nanofluids

In both power generation and other energy sectors, renewable energy is gradually becoming an alternative to fossil fuels

Konsep dan pihak yang bertanggungjawab dalam pengurusan zakat

Zakat merupakan satu daripada rukun Islam yang lima. Hukum menunaikan zakat adalah wajib ke atas semua orang Muslim. Nabi Muhammad SAW ialah pemimpin pemerintahan Islam sekali gus penanggung jawab tertinggi dalam pengurusan zakat, yang memerintahkan untuk mengutip harta zakat dari muzakki dan mengagihkan harta zakat kepada mustahiq. Permasalahan utama masa kini ialah kedapatan beberapa negara yang penduduknya majoriti Muslim tidak lagi memiliki hak dan kuasa dalam pengurusan zakat. Bahkan pengurusannya diserahkan kepada pihak perundangan yang berkuasa di negara tersebut atau dijalankan secara individu. Ini menyebabkan harta zakat tidak diurus oleh pihak pemerintah sekali gus menjejaskan pengurusan zakat itu sendiri seperti hak pelaksanaan zakat rakyat yang beragama Islam mulai terjejas, pengurusan zakat menjadi tidak efektif dan efisien serta menyebabkan ketidakadilan kepada mustahiq. Kajian ini membincangkan perihal pengurusan zakat dari sisi konsep dan pihak yang bertanggung jawab dalam melaksanakan pengurusan zakat berdasarkan syariat Islam, sama ada yang dilakukan oleh pemerintah Islam mahupun bukan Islam. Sebagai natijahnya, pihak pemerintah perlu mengambil alih tanggungjawab pengurusan zakat kerana ia melibatkan banyak pihak yang memerlukan peraturan dan pengaturan. Hanya pihak pemerintah yang memiliki kekuasaan dan alat yang sah untuk melakukan pengaturan dan mengambil tindakan atau hukuman kepada kalangan rakyat. Dalam pengurusan zakat di sesebuah negara, pihak pemerintah Islam perlu berpegang teguh dengan syariat Islam dan berlaku adil. Sementara itu, bagi pemerintah bukan Islam mereka perlu berlaku adil dalam pelaksanaan pengurusan zakatnya. Implikasi daripada hasil kajian ini mendapati negara-negara yang memiliki rakyat yang beragama Islam, perlu memberikan perhatian terhadap kepentingan rakyat dalam aspek pelaksanaan ibadah, terutama hal-ehwal pengurusan zakat. Antaranya ialah dengan membuat peraturan dan perundangan zakat yang khusus untuk rakyat yang beragama Islam agar hak mereka untuk menunaikan zakat dapat dituniakan, tanpa menjejaskan rakyat yang bukan beragama Islam

POSSIBLE IMPACT OF THE LATEST INTERNATIONAL STANDARD OF AUDITING 570 ON THE RATE OF GOING CONCERN OPINION ISSUANCE IN MALAYSIA

The problem that Malaysian auditors do not issue going concern opinion (GC opinion) to seriously financially distressed companies is still a pressing issue. The latest International Standards on Auditing 570 Going Concern (ISA 570) has been released and made effective in Malaysia starting from 15th December 2016. It is reasonable to expect that the new ISA 570 (2016) could at least reduce the incidence of Malaysian auditors do not want to issue GC opinion to financially distress companies. Overall, we are in the opinion that there is no strong ground to expect the new ISA (2016) can reduce the problem of Malaysian auditor do not issue GC opinion to a very large percentage of seriously financially distress companies. This is because there is no new stricter measure has been introduced in the latest ISA 570 (2016). However, Malaysian policy makers and standard setters still have at least four measures if they want to improve the rate and practice of GC opinion issuance in this country. Researchers on the other hand should examine the effectiveness of the new ISA 570 (2016), at least

A Brief Review on Thermal Behaviour of PANI as Additive in Heat Transfer Fluid

Since a decade ago, investigation on nanofluids has grown significantly owing to its enhanced thermal properties compared to conventional heat transfer fluids. This engineered nanofluid has been widely used in the thermal engineering system to improve their energy consumption by improving the thermal efficiency of the system. The addition of nano-size particles as additives dispersed in the base fluids proved to significantly either improve or diminish the behaviour of the base fluids. The behaviour of the base fluid highly depends on the properties of the additives material, such as morphology, size, and volume fraction. Among the variety of nanoparticles studied, the conducting polymers have been subject of high interest due to its high environmental stability, good electrical conductivity, antimicrobial, anti-corrosion property and significantly cheap compared to other nanoparticles. As such, the main objective of the present review is to provide an overview of the work performed on thermal properties performance of conducting polymers based nanofluids

Prediction of tool life by statistic method in end-milling operation

The aim of the this study is to develop the tool life prediction model for P20 tool steel with aid of statistical method, using coated carbide cutting tool under various cutting conditions. This prediction model was then compared with the results obtained experimentally. By using Response Surface Method (RSM) of experiment, first and second order models were developed with 95% confidence level. The tool life was developed in terms of cutting speed, feed rate, axial depth and radial depth, using RSM and design of experiment. In general, the results obtained from the mathematical model are in good agreement with that obtained from the experiment data’s. It was found that the feedrate, cutting speed, axial depth and radial depth played a major role in determining the tool life. On the other hand, the tool life increases with a reduction in cutting speed and feedrate. For end-milling of P20 tool steel, the optimum conditions that is required to maximize the coated carbide tool life are as follow: cutting speed of 140 m/s, federate of 0.1 mm/rev, axial depth of 1.5 mm and radial depth of 2 mm. Using these parameters, a tool life of 39.46 min was obtained

Green synthesis of lauryl palmitate via lipase-catalyzed reaction

Enzyme catalysis is most attractive for the synthesis of fine organic compounds, which are difficult to prepare and to handle by conventional means. In this work, green synthesis of lauryl palmitate, a wax ester was successfully carried out by lipase-catalyzed esterification of palmitic acid and lauryl alcohol. In this study, commercial immobilized lipase from Candida antartica (Novozym 435) was used as biocatalyst. The effect of various reaction parameters were optimized to obtain a high yield of wax esters. The optimum condition to produce lauryl palmitate was at reaction time (RT); 10 min, temperature (T); 40°C, amount of enzyme (E); 0.4 g, molar ratio of substrate (N); 2:1 and organic solvents of log P>3.5. The product was then subjected to characterize using Fourier-transform infrared spectroscopy (FT-IR) and Gas chromatography spectroscopy (GC) to ensure the purity of product obtained. Analysis of yield showed that at optimum condition, lauryl palmitate was produced in short time with high purity, >90%

The impact of management, family, and institution on the auditor's going concern opinion issuance decision

Incidents where external auditors do not issue a going concern audit opinion (GC opinion) to companies having severe financial problems have been reported globally. This issue motivated this study – (i) to investigate the effect of selected auditor characteristics in terms of specialization, tenure, and fee on GC opinion issuance and (ii) to examine the moderating effect of management’s, family’s, and institution’s influence on the relationship between auditor characteristics and GC opinion issuance. The study involves 644 Malaysian financially distressed listed companies in the period 2006 to 2012. The results of a panel logistic regression analysis show that auditor characteristics have no relationship with GC opinion issuance. Influential management - measured as the level of their ownership - can dampen the positive relationship between auditor specialization and auditor tenure with GC opinion issuance. The presence of an influential family, on the other hand, can strengthen the positive relationship between auditor tenure and GC opinion. No evidence about an influential institution’s impact on the GC opinion process could be found. In conclusion, while auditor characteristics do not affect the possibility of a GC opinion issuance, pressure imposed by influential management and family on the auditor during the audit opinion decision process does have an impact