Investigation of Combustion Phenomena in a Single-Cylinder Spark-Ignited Natural Gas Engine with Optical Access

More demanding efficiency and emissions standards for internal combustion (IC) engines require novel combustion strategies, alternative fuels, and improved after-treatment systems. However, their development depends on improved understanding of in-cylinder processes. For example, the lower efficiency of conventional spark-ignited (SI) natural-gas (NG) engines reduces their utilization in the transportation sector. Single-cylinder optical-access research engines allow the use of non-intrusive visualization techniques that study in-cylinder flow, fuel-oxidizer mixing, and combustion and emissions phenomena under conditions representative of production engines. These visualization techniques can provide qualitative and quantitative answers to fundamental combustion-phenomena questions such as the effects of engine design, operating conditions, fuel composition, fuel delivery strategy, and ignition techniques.;The thesis is divided in two main parts. The first part focuses on the setup of a single-cylinder research engine with optical access including the design of its control system and the acquisition of in-cylinder pressure data and high-speed combustion images. The second part focuses on measurements of the turbulent flame speed using the high-speed combustion images. Crank-angle-resolved images of methane combustion were taken with a high-speed CMOS camera at a rate of 15,000 Hz. The optical engine was operated in a skip-firing mode (one fired cycle followed by 5 motored cycles) at 900 RPM and a load of 5.93 bar IMEP. The images show that flow turbulence and flame stretch resulted in flame velocities several order of magnitude higher compared to the laminar flame velocity. In addition, both in-cylinder pressure and optical data were used to determine the cycle-to cycle variability of the combustion phenomena

Neuroprotective effect of secretin in chronic hypoxia induced neurodegeneration in rats

Background: Hypoxia is a condition in any stage in the delivery of oxygen to cells which include decreased partial pressures of oxygen, less diffusion of oxygen in the lungs, insufficient hemoglobin, inefficient blood flow to the end tissue, and breathing rhythm. Secretin is an amino acid which plays proper functioning of gastro intestinal system.Methods: The current study was conducted to evaluvate the effect of exogenously administrated secretin on chronic hypoxic damage of brain in rat model. Experimental design consists of control animals, Control animals + secretin hypoxia exposed animals; hypoxia exposed animals +secretin (20ng/kg.bw).Results: The results of this study point to a possible role of Secretin as neuroprotectant.Conclusions: Further research on secretin needs to be conducted in order to confirm the deductions made by this study

Investigation of Pathways to Enhance SCR de-NOx Efficiency in Heavy-Duty Diesel Vehicle using an Optical Access Visualization Approach

With growing demands of adopting tighter control on tailpipe NOx regulations for heavy duty trucks, it is an active topic of discussion by regulators in the U.S. to further tighten the existing NOx standards from 0.2 g/bhp-hr to pursue a next phase of reduction as low as 0.02 g/bhp-hr for Class-8 application. High-levels of NOx conversion, in the order of ~98% may be required by SCR system in the future to provide an operating margin to increase fuel efficiency gains. To unleash this potential gain, the SCR technology employed should be capable of achieving high NOx conversion even during low exhaust temperature operating conditions, at the same time allow limited reductant (NH3) slip over transient drive cycle application. The present work will present findings from exploring areas of improvement in SCR system and in general the aspects of diesel engine aftertreatment system affecting SCR performance such as engine exhaust conditions including non-uniformity of flow, temperature and mal-distribution of NH3, urea mixing pipe design, etcetera in contribution towards meeting the projected regulations for NOx tailpipe limits of 0.05 g/bhp-hr in 2025 and 0.02 g/bhp-hr by 2035, for heavy duty vehicles. The central objective of this study is deemed that an optically accessible capability to visualize the SCR system and in specific urea spray injection process in detail would serve as a beneficial tool in investigating the specific conditions responsible for severity in factors contributing to reducing de-NOx performance The proposed work can be broadly outlined into the following two sections, To identify the factors contributing to deterioration of SCR de-NOx performance and thereby explore innovative solutions to abate them To develop a research capability for optical access visualization of SCR system, as a tool to aid in the assessment of factors contributing in affecting the NOx reduction performance, from the standpoint of after-treatment system design, thermal strategy and engine operating conditions Preliminary results indicate there exist a non-uniformity in the exhaust gas temperature at the inlet face of SCR catalyst brick. The resulting effect is likely to cause a non-uniformity in the NH3-NOx distribution. Uniformity of NH3/NOx species concentration, a.k.a., ammonia to NOx ratio (ANR) plays a very critical in affecting SCR conversion performance. The non-uniformity effect was studied over surrogate HD-FTP, and selective steady state points comprising of a test matrix with a combination of 3 levels of space velocities, 3 levels of SCR inlet temperature, to represent light, medium and high: engine load and engine speed activity regimes. Results indicate that at a high load condition, even though the NO2/NOx ratio were close to 1:1 molar ratio, the ANR was very poor suggesting that an alternative pathway in SCR reduction could have taken place and at high temperature, owing to the storage buffer depleting at a fast rate, with a NH3 slip average of 77ppm. The study suggests it is necessary to obtain a more accurate map of temperature mal distribution across the different monolith channels of the SCR under transient conditions to better understand the factors responsible for localized undesirable ANR. Another principal factor affecting the SCR performance is the inlet NO2/NOx ratio. Controlling the NO2/NOx ratio close to 0.5 is conducive for fast-SCR reaction kinetics. Preliminary studies were conducted to understand the effect of this parameter on SCR NOx reduction, NH3 slip and NH3 storage buffer on different engine operating conditions. Further, this work would present results from study the benefit of utilizing low grade heat rejected from the engine, such as coolant thermal energy, in raising the temperature of NOx reductant being dosed. Furthermore, detailed characterization studies of particle size distribution and particle number (PN) concentration from the standpoint of different urea injection strategies would be presented. Results from this study would provide insights into the effect of adopting different dosing strategies, on the compliance of tailpipe PN limits. The research work is significant because, there is limited availability of systemic experimental work and in-fact presence of very few platforms that has included the modern heavy-duty stock engine set-up without significant design modifications, after-treatment conditions replicating real world challenges and related in-vehicle equipment configuration for the studies involving SCR performance using optical access setup. The work will contribute to building fundamental knowledge in understanding urea-based deposits formation process from advanced diesel engine after-treatment system configuration; the interaction between engine operating conditions, DEF injection rate and after-treatment system design that influence the urea formation & decomposition process under investigation

Phylogenetic identification and metabolic potential of bacteria isolated from deep sea sediments of Bay of Bengal and Andaman Sea

561-572Deep sea is an extreme environment which harbours diverse microbial communities. The deep sea ecosystem of the northeastern part of Indian Ocean is poorly studied. In this study, to explore the bacterial diversity of the unexplored environment, we designed culture independent (denaturant gradient gel electrophoresis DGGE) and culture dependent (16S rDNA) methods. The samples for this study were taken from the depths of 1850 m off Barren Island of the Andaman Sea, and 2000 and 1400 m off Chennai and Cudallore of the Bay of Bengal. The phylogenetic analysis, based on 16S rDNA sequence data, has suggests their affiliation to three major phyla viz. Firmicutes (48%), Proteobacteria (30%, alpha and gamma-class) and Actinobacteria (22%). Bacillus was the most frequently isolated genus. This is the first report on the isolation of Brucella, Fictibacillus, Mesorhizobium and Cobetia spp. from deep sea sediments. Eleven of the 34 operational taxonomic units probably represents new species. To investigate the metabolic potential, the isolates were screened for production of the extracellular hydrolytic enzyme and antibacterial compound. Almost 91% of isolates showed production of at least one of the extracellular hydrolytic enzymes, such as caesinase, alpha-amylase, urease, gelatinase, lipase and DNase. Streptomyces was the only genus which showed antibacterial activity. This study highlights that the examined deep sea environment could be a hot spot for microbial derived natural products