A Development of a New Image Analysis Technique for Detecting the Flame Front Evolution in Spark Ignition Engine under Lean Condition

The aim of herein work is to develop an automatized algorithm for detecting, as objectively as possible, the flame front evolution of lean/ultra-lean mixtures ignited by low temperature plasma-based ignition systems. The low luminosity characterizing the latter conditions makes both kernel formation and combustion development difficult to detect accurately. Therefore, to estimate the igniter capability to efficiently ignite the mixture, ever more performing tools are required. The present work proposes a new image analysis technique, based on a dual-exposure fusion algorithm and on Convolutional Neural Networks (CNNs), to process low brightness images captured via high-speed camera on an optical engine. The performance of the proposed algorithm (PA) is compared to the one of a base reference (BR) algorithm used by the same research group for the imaging analysis. The comparison shows the capability of PA to quantify the flame radius of consecutive combustion cycles with lower dispersion if compared to BR and to correctly detect some events considered as misfires or anomalies by BR. Moreover, the proposed method shows greater capability to detect, in advance, the kernel formation with respect to BR, thus allowing a more detailed analysis of the performance of the igniters. A metric quantitative analysis is carried out, as well, to confirm the above-mentioned results. Therefore, PA results to be more suitable for analyzing ultra-lean combustions, heavily investigated to meet the increasingly stringent legislation on the internal combustion engines. Finally, the proposed algorithm allows us to automatically estimate the flame front evolution, regardless of the user’s interpretation of the phenomenon

Investigation of the Lean Stable Limit of a Barrier Discharge Igniter and of a Streamer-Type Corona Igniter at Different Engine Loads in a Single-Cylinder Research Engine

Currently, the Radio-Frequency Corona Ignition systems represent an important solution for reducing pollutant emissions and fuel consumption related to Internal Combustion Engines while at the same time ensuring high performance. These igniters are able to extend the lean stable limit by increasing the early flame growth speed. Kinetic, thermal and ionic effects, together with the peculiar configuration of the devices, allow to start the combustion process in a wider region than the one involved by the traditional spark. In this work two corona igniters, namely a Barrier Discharge Igniter and a Corona Streamer Igniter, were tested in a single-cylinder research engine fueled with gasoline at different engine loads in order to investigate the igniters performance through indicated analysis and pollutant emissions analysis. For each operating point, the devices control parameters have been set to ensure maximum energy releasement into the medium with the aim of investigating, at the extreme operating conditions, the capability of the devices to extend the lean stable limit of the engine. The Corona igniters have been tested on a constant volume calorimeter as well, reproducing the engine pressure conditions at the corresponding ignition timing. The target is to give an estimation of the thermal energy released during the discharge and then to compare their capability to provide high-stability energy

Off-design operation of coal power plant integrated with natural gas fueled molten carbonate fuel cell as CO2 reducer

The paper presents an experimental investigation of a Molten Carbonate Fuel Cell (MCFC) fueled by methane in order to predict how to reduce CO2 emissions from the flue gas of a real power plant. MCFCs can be placed in the flue gas stream of a fossil fired power plant to separate CO2 by transferring it from the cathode side to the anode side. As a result, a mixture of CO2 and H2O is separated from which pure CO2 can be obtained through condensation of water. The main advantages of this solution are: additional power generation, reduced CO2 emissions and higher system efficiency. Furthermore, coal plants seem to be the ideal candidate to retrofit with MCFC plant due to their high exhaust CO2 content and to the low cost of the fuel that encourages its application despite the narrower emission requirement. The experimental results show that use of an MCFC could reduce CO2 emissions by 90% with over 30% efficiency in additional power generation and by demonstrating a broad range of different operative conditions

Modeling the performance of MCFC for various fuel and oxidant compositions

100 cm2 molten carbonate fuel cells (MCFC) was used for testing the fuel and oxidant composition influence on MCFC performance as a temperature function. The fuel composition varies over the cell surface, and throughout the stack, because inlet fuel is rich in H2 (and CO2), while the exhaust stream is depleted. The cell performance is usually not uniform over the entire surface. It is thus necessary to examine the cell performance as a function of fuel utilization. In a laboratory-sized cell, this is usually difficult to do. An alternative approach is to investigate performance as a fuel composition function. Based on the obtained experimental data for different compositions, the MCFC mathematical model was calibrated. The new approach for modeling the voltage was used. Electrochemical, thermal, electrical and flow parameters are collected in the 0-D mathematical model. A validation process for various experimental data was made and adequate results are shown

SOFC operating with ammonia: Stack test and system analysis

Ammonia has been studied as a potential energy vector and suitable fuel for Solid Oxide Fuel Cells (SOFCs). The use of ammonia could guarantee high electrical efficiency, with a carbon free and high energy density fuel. This study analyzes the potential of a power generation system based on a SOFC fueled by NH3. Experimental tests on a SOFC short stack were developed using both pure and diluted ammonia. The tests demonstrated the operation of the concept and highlighted possible advantages in terms of thermal equilibrium. Decomposition of ammonia introduces an endothermic reaction that permits heat absorbance in the anode and a better control of stack temperature. Based on tests results, a thermodynamic model of a complete system was designed and studied. The results demonstrate that the ammonia fueled SOFC is more efficient than an equivalent hydrogen fueled one, due to the cooling effect of internal reactions that reduces ancillaries energy consumptions related to cathode air flow

Theoretical study and performance evaluation of hydrogen production by 200 W solid oxide electrolyzer stack

High temperature steam electrolyzers, taking advantage of high temperature heat, can produce more hydrogen by using less electrical energy than low temperature electrolyzers. This paper presents an experimental study on hydrogen production by using a 200 W solid oxide stack working in reverse mode. A thermodynamic study of the process was performed by measuring the heat and mass balance of stack at different operating conditions. Different definitions of efficiency were used to highlight the limit and potential of the process. The I–V curve, the flow rate measurements and the GC analysis on outlet flows were used to calculate the hydrogen and oxygen productions. In addition, the influence of steam dilution, water utilization and operating temperature on conversion efficiency and stack's thermal balance was evaluated. With this aim, the tests were performed at three operating temperature (700 °C, 750 °C and 800 °C) over a range of steam inlet concentration from 50% to 90% and water utilization up to 70%. The hydrogen and oxygen flows produced by electrolysis, at different loads, were directly measured after water condensation: net flows up to 2.4 ml/(min cm2) of hydrogen and 1.2 ml/(min cm2) of oxygen were measured and compared to the theoretical ones, showing a good agreement

Experimental Analysis of SOFC Fuelled by Ammonia

In this study, ammonia is presented as a feasible fuel for solid oxide fuel cells (SOFCs). Ammonia has several interesting features as fuel due to low-production cost, high-energy density and, focusing on fuel cells and hydrogen application, ammonia is an excellent H2 carrier thanks to high value of volumetric and gravimetric densities. The paper reports experimental test performed to evaluate the feasibility of NH3 directly fed to a 50 cm2 single cell SOFC. A test plan was developed to compare pure ammonia with an equivalent mix of ammonia, nitrogen, and hydrogen and the study of temperature and voltage values strongly indicates that a two stage oxidation of ammonia can be predicted and a previous cracking reaction occurs in the cell due to the nickel catalytic contribution. The study of temperatures and of heat flows show how the cell is cooled down to lower temperature because of heat adsorbed by the reaction and by flow mix entering the anode. The study shows also how for operative temperatures below 800 °C the cracking reaction takes place in the cell active area. Efficiency test demonstrates that the cell can operate at 300 mW cm–2 and 30% efficiency based on ammonia LHV

Sulphur compounds removal from natural gas using porous materials for high temprature fuel cell applications

Sulfur compounds present as odorants in natural gas like thiophenes,mercaptans,and sulifdes, cuase severe poisoning on high tempreature fuel cell catalysts evev at very low concentration, below 1 ppm. Therefore a deep sulpfur removal from inlet gas mixture is strongly needed and it has to be coupled with an accurate determination of sulfur concentration in the gas stream. Among the different developed filtering solutions, adsorption using porous materials represents a very attractive option, mainly in view of systems simplicity and costs. In this work, adsorptive removal of organic and inorganic sulfur compounds was carried out ina fixed bed floew reactor, using different types of porous materials, such as virgin and impgregnated activated carbons and zeolites. The purpose was to evaluate sorbet capacity of singulkra adsorbents varying process paramaters such as space velocity. The sorbents display differences in adsorpitve capacity among the individual sulfur compounds in natural gas: a comparison among odorants and H2S adsorption is in particular shown. A composite sorbent was realized and tested in order to exploit the selectivity of singular adsorbent materials

EXPERIMENTAL ANALYSIS OF SOFC FUELLED BY AMMONIA

Ammonia (NH3) has very interesting features as fuel for solid oxide fuel cell (SOFC). This study presents preliminary experimental results on a single cell SOFC fueled by ammonia. The study focuses on the cracking reaction that permits to transform ammonia into N2 and H2. This reaction offers to the fuel cell a perfect mix for the operation in safety and efficient conditions. The study compares several polarization curves realized with pure H2, a mix of H2/N2 and a mix of H2/NH3 and pure NH3 at high operation temperature (800°C). The results show how a complete reaction of NH3 can be predicted and an equivalent performance can be obtained substituting the H2/N2 mix with equivalent amount of ammonia

Dimethyl sulfide adsorption from natural gas for solid oxide fuel cell applications

The use of solid oxide fuel cell (SOFC) systems in micro-CHP applications is of great interest because of high efficiency, low emissions and absence of noise. However, SOFCs are sensitive to degradation caused by organic sulfur compounds present in natural gas or added as odorants. Among them, dimethyl sulfide (DMS) is one of the sulfur species most resistant to purification treatments and, relative to DMS removal, a lack in literature is highlighted for the investigated application. Regarding adsorption technology, the present work deals with an organic sensitivity performance analysis of different commercial sorbents. Virgin and impregnated activated carbons and a natural zeolite were tested, varying gas hourly space velocity, reactor geometry and filter assembly. Because of differences in activity towards DMS exhibited by the investigatedmaterials, to exploit their selectivity, also layered sorbentswere realized and tested. Starting from resulting data, for the yearly operation of 1 kWel SOFC-based micro-CHP system, an optimization of filter assembly (also considering multi-layered configurations) and operative conditions was performed, leading to a strong reduction in filter volume (up to five times) and cost (more than three times), with overall pressure drops compatible with pipeline gas distribution pressure