Numerical investigation of the asymmetrical vortex combustor running on biogas

Biogas is an attractive renewable fuel to combat greenhouse gas (GHG) emissions. However, the low and variable quality of un-upgraded biogas present some challenges in terms of holding a stable flame and resulting emissions. Meanwhile, asymmetrical vortex combustor (AVC) has been shown to possess excellent flame stability even at very lean conditions. This work aims to study the suitability and potential of AVC to burn biogas by investigating its combustion characteristics and explaining its ultra-stable flame behavior. A numerical study was done where the flame stability was studied by looking at the flow field. Synthetic biogas of various compositions that reflect palm oil mill effluent (POME) biogas was used in this research. The combustion characteristics was studied for equivalence ratio ranging from very lean to very rich that explores the limit of the AVC. The results showed that this combustor is very capable of stably burning biogas of different compositions with correspondingly low emissions. This allows ready use of un-upgraded biogas which would have been cost prohibitive previously. The flame stability envelope is extended beyond that of pure methane with lean limit reaching down to 0.3 and the rich limit going beyond 2 compared to the published range of between 0.46 to 1.6. Flame stability was found to be due to two effects; the strong tangential vortex containing the flame region, and also the trapped vortex effect of the backward facing step which provides a secondary stable flame. Thus, it can be concluded that raw biogas can be utilized as fuel without costly upgrading by burning it in an AVC

Analysis of flow in pulse combustor tailpipe

Pulse combustion is known to have the higher combustion efficiency compared to conventional steady type burner in heating application (Putnam, 1971). However, there are many parameters need for scientific study in designing this kind of combustor. This study intends to model the pulse combustion in order to determine important characteristics that govern the performance of the pulse combustor. The important parameters identified in this study namely frequency, pressure oscillation and pulsating flow inside tailpipe. This study will be useful for predicting the capability of pulse combustor especially in heating application

Optimizing flame synthesis of carbon nanotubes: experimental and modelling perspectives

Synthesis of carbon nanotubes in flames has become highly attractive due to its rapid, inexpensive, and simple method of production. The study of flame synthesis of carbon nanotubes revolves around the control of flame and catalyst parameters to increase the synthesis efficiency and to produce high quality nanotubes. The control parameters include flame temperature, concentration of carbon source species, catalyst type, equivalence ratio, and fuel type. Carbon nanotubes which are produced with rapid growth rate and possess high degree of purity and alignment are often desired. The present study reviews various optimization techniques from the advanced studies of chemical vapour deposition which are applicable for the synthesis of nanotubes in flames. The water-assisted and catalyst free synthesis are seen as possible candidates to improve the growth rate, alignment, and purity of the synthesized nanotubes. The state-of-the-art of the flame synthesis modelling at particle and flame scales are reviewed. Based on the thorough review of the recent experimental findings related to the catalytic growth of nanotube, possible refinement of the existing particle scale model is discussed. The possibility of two-way coupling between the two scales in computational fluid dynamics may be a major contribution towards the optimization of the flame synthesis

Immuniregulatory response following fluranthene instillation in embryonated chicken eggs

The immunotoxic effect the air pollutant, floranthene in chicken has never been documented. This study was undertaken to determine the possible immunotoxicity of fluoranthene in embryonated chicken eggs. Fifty 9-day-ole embryonated chicken eggs were used in this study where 40 were each inoculated with fluoranthene at the dose of 15 mg/kg via the allantoic route. The remaining 10 eggs were inoculated with phosphate buffered saline (PBS) and acted as controls. All eggs were incubated at 37°C and candled every day for evidence of embryonic survival. Dead embryos (before 21 days old) were necropsied while the allantoic fluid and yolk collected for the determination of ND-HI titers. Chicks that hatched were sacrificed and blood was collected for ND-HI titer determination and lymphoid organs were procured for histopathology. Postmoetem findins fo fluoranthene inoculated embryos were stunted growth, generalized or localized harmorrahages especially at legs and head. Histopathologically, fluoranthene induced lymphoid hyperplasia in the thymus, spleen and bursa. Such change has led to an increase in antibody production compated to the controls. This study has provided evidence that fluoranthene may cross the egg barrier (in ovo) in avian species

UTILIZING ZUHD HADITHS FOR UPPER-CLASS CRIME PREVENTION

Crime is becoming more widespread, with varied motives and often involving influential elites. The consequences of crimes committed by these elites are enormous, affecting not only themselves but also their families, institutions, and others. Therefore, addressing the increasing crime committed by influential elites requires efforts focused on prevention rather than just heavy punishment. One potential solution is through a religious approach, particularly by referencing the hadiths of Prophet Muhammad (SAW). Several hadiths teach the concept of Zuhd, which emphasizes avoiding excessive wealth accumulation and enjoying giving and sharing blessings with others. This article aims to present the Prophet’s teachings on leading a humble life and not excessively valuing wealth. The study employed qualitative research methods, including a literature review of relevant library sources. As a result, this article emphasizes that the Prophet taught that the orientation of human life should not solely focus on fulfilling worldly demands but also on having faith in the afterlife. Prophet Muhammad (SAW) exemplified Zuhd in his life, and his example needs to be emulated in the modern world today. Elite individuals who embody Zuhd will be more capable of restraining themselves from committing crimes while fulfilling their duties. This is because the attribute of Zuhd encourages everyone capable of committing a crime to refrain from doing so

Interferometric synthetic aperture radar coherence constraints in heavily vegetated tropics

Success of Interferometry Synthetic Aperture Radar (InSAR) technique for deriving digital elevation model (DEM) in the heavily vegetated humid tropic using Sentinel-1 SAR has been controversial, owing to the difficulty in achieving good coherence. Yet achievable coherence with Sentinel-1 SAR over the heavily vegetated humid tropic has rarely been reported. Consequently, this paper evaluates coherence achievable with Sentinel-1 SAR over the heavily vegetated humid tropic. Twelve Sentinel-1 SAR over part of Johor selected based on perpendicular and temporal baselines considerations, were used as pairs of six reference and secondary images respectively and processed using Sentinel Application Platform (SNAP) to derive coherence maps and analysed accordingly. The result shows that regardless of image pairs baseline characteristics, coherence of above 0.6 over the heavily vegetated humid tropic with Sentinel-1 SAR can only be achieved in barely 10% of the study area. This result shall serve as eye-opener to geoscience community, especially SAR enthusiast looking forward to leveraging on SAR clouds penetrating ability, and Sentinel-1 SAR open access and short revisit circle to apply Sentinel-1 SAR in deriving DEM over heavily vegetated humid tropical environment. However, future studies shall focus on assessing consistency of good coherence patches and their usability in acquiring elevation

Flameless combustion of propane-air mixture in a laboratory scale burner

In this work, the operational and emission of the laboratory scale burner under the flameless combustion regime using propane is examined. The combustor is equipped with parallel jet burner systems with controlled gas fuel and oxidizer. The combustor consists of several ports that are used to measure temperature variation and analyze gas emission. The atmospheric air was heated by flowing it inside the chamber until the air temperature increased to approximately the auto ignition temperature of the fuel. The furnace under investigation has successfully produced temperature uniformity ratios that are one order of magnitude less than such of the visible flame mode. It is observed that, flameless combustion can be achieved by using propane as a fuel. The value of NOX emission during flameless combustion was reduced of about 70% in average compared to the conventional flame at certain range of equivalence ratio

Predictive numerical analysis on the mixing characteristics in a rotating detonation engine (RDE)

Detonation potential in rotating detonation engine (RDE) depends on well-mixed fuel and oxidizer in the annulus. A numerical study was carried out to analyze hydrogen (H2) – oxygen (O2) mixing in RDE prior to the detonation. A validation was effectively achieved by comparing the expected detonation criteria with the reported experimental results where less than 10 % error was observed. Non-reacting flow inside the annulus was examined with a new parameter describing the fuel uniformity, the amplitude of the maximum deviation from the H2 average mass fraction, |Smax |. The numerical results are generated at variable distance between the fuel injector and the oxidizer plenum, D to provide insights on the fuel uniformity and the mixing efficiency. Case A3 with D = 6 mm results in the worst mixing indicated by the highest |Smax | of 0.0156. This happened due to the impingement of fuel stream that separates the stream into two distinctive flows and formed two major vortices that separates the fuel streams. Case A1 with D = 2 mm results in the best mixing indicated by the lowest |Smax | of 0.0012 due to the cross flow collisions of fuel and oxidizer and large turbulent region created. The location of fuel inlet situated face to face with the 90° elbow wall has been predicted to generate the most significant fuel distribution imbalance within the annulus. In conclusion, prediction towards excessive fuel inhomogeneity in the annulus as one of the major factors affecting stability of detonation wave for RDE is achieved in this study

Storage optimization for digital Quran using sparse matrix with hexadecimal representation

Digital Quran is a common application today in smart devices such as hand phones and tablet. The verses are usually presented using images of verses on written in an Arabic font.This raise issues related to storage when representing the whole Quran text.This study proposed a hexadecimal digital representation technique for words in Arabic using UTF-8 for character encoding which is backward compatible with ASCII code.This paper will explain three approaches used in representing the digital Quran.They are the hexadecimal representation for each Quranic words, sparse matrix in representing verses of Al-Quran and double offset indexing for transforming the sparse matrix to efficiently use the space. This representation proof more than 50% reduction in the memory space for storage thus will increase the searching speed.The storage of words being optimized through the use of one memory space for that particular word rather than one memory space for each Arabic character in the words .This technique helps optimized memory management for the whole digital Quran.Due to the smaller size, the digital Quran can be conveniently installed in the future as standard applications in mobile devices