Sharif Digital Repository

Flameless Combustion was experimentally studied. In this combustion mode, inlet air is preheated and products are recirculated inside the chamber. Therefore, the reaction zone is spread from a limited front to a wider area with that of a lower peak temperature and very lower Nitrogen Oxides (NOx) production. Controllable parameters are preheating temperature, equivalence ratio, and fuel and air mass flow rates. Applying similar conditions, the flameless combustion was compared to the diffusion flame. Measurable parameters are exhaust temperature and composition, including NOx. Reaction zone homogeneity is observed by photographing inside the combustion chamber through its visual access... 

Mobile Sources are the main source of air pollutant emission in Tehran, the capital city of Iran. Everyday thousands of vehicles commute in roads and highways. Unfortunately, People are exposed to high level of particulate matter and gaseous contaminants in automobile cabins. Even though this environment is exposed to high pollutant concentration emitted by on-road vehicle, In comparison with other built environment, in-cabin commuter exposure and its key parameters has never been quantified. In general, this work entails measurement of in-cabin air quality, predicting mathematical models for calculating Air-Exchange-Rate (AER) in vehicles and on-road vehicle emission measurement. Our... 

Today, the importance of transportation and motor vehicles is crystal clear for everyone. On the other hand, energy crisis and the emissions of these vehicles are two fundamental problems of internal combustion motors. On account of this, the diesel vehicles have absorbed researchers’ attentions due to their higher efficiency and low fuel consumption.Due to high diesel vehicle efficiency, it is tried to substitute gasoline vehicles with these vehicles. In addition, the unrecyclable nature of fossil fuels has led to more attention to renewable energies such as biofuels. A lot of kinds of herbal oils have identical characteristics with diesel fuel.In this research, the combustion of Rapeseed... 

Heavy fuel oil (HFO) is usually consumed in large scale furnaces, e.g., those of power plants. Experience shows that its combustion produces large amount of NOx emission. In present study, a large scale heavy fuel oil fired furnace is numerically simulated to investigate different possible solutions for NOx reduction. In this regard, a computational framework is firstly designed benefiting from the researches reported previously in literature. The results of this framework are then compared with available measurements to evaluate the accuracy of current designed computational framework. Second, the influences of a number of different controlling parameters are studied carefully to improve... 

In recent decade, pollution reduction is one of challenges in front of engineers. Nowadays accurate prediction of temperature and harmful Pollutants is vital, this leads to various models for turbulent combustion to predict combustion-generated pollutants. One of the most widely used models for simulating turbulent combustion is Flamelet because of separating the chemical reactions and the turbulent flow field. The unsteady state assumption of Flamelet model is capable of reasonably predict complicated phenomenon such as slow chemical reaction and radiation. The purpose of this study is to calculate combustion-generated emissions by Flamelet model and reduce these emissions by engineering... 

High Swirl Combustors can provide stable flames in wide range of operating conditions. Double swirl combustors, as one of the newest designs in this field, have particular effects on improving the efficiency of combustion chambers in terms of flame stability, mixing process quality and reducing combustion pollutants. In this study, a double swirl gas turbine combustor, SGTMC, which is redesigned version of a German combustor (GTMC), has been investigated. According to experimental section of this study, lean stability limits, UHCs, CO and NOx has been measured and analyzed. Results show that this burner can provide a stable flame even in very low equivalence ratios. Also in some specific... 

In the present study, a 3D combustion chamber was simulated using FLUENT6.32. The objectives were to obtain detailed information on the combustion characteristics and NO formation in the furnace, and also to examine the effect of Oxygen enrichment on the combustion process. The combustion chamber has internal dimensions of 60 cm wide, 90 cm high and 190 cm long. The fuel pipe diameter is 1.25 cm and the air pipe diameter is 3.5 cm. The 3-D Reynolds Averaged Navier Stokes (RANS) equations together with standard k-ε turbulence model are solved by Fluent 6.3. Air/fuel flow rate ratio is varied as 1.3, 3.2 and 5.1 and the oxygen enriched flow rates are 28, 54, 68 lit/min. NO emission was... 

In present study, two bioreactors for biological and chemical removal of nitrogen oxides are modeled. Nitrogen oxides are of the most important pollutants in flue gas stream. These components are hazardous materials and could lead to acid rain, ground-level ozone, smog and the depletion of ozone layer. There are several methods for removing these pollutants which are categorized to two main groups: non-biological and biological methods. Biological removal has the advantage of removing the pollutants by an acceptable efficiency. In present study, two packed-bed bioreactors are modeled by the means of considering two kinds of biological removal mechanism in defined operating conditions. The... 

Combustion and NOx emissions were simulated by quasi-dimensional and ratereaction methods respectively in a turbocharged CNG engine. Mean-value turbulence modeling was carried out during compression and combustion processes to simulate combustion process better. The most appropriate NG flame speed for the CNG turbocharged engine was applied and ignition delay was ended when flame radius became more than turbulence integral length scale. Hemispherical flame propagated from spark gap center and its intersection with reciprocating Mexican-hat piston bowl was calculated analytically. Thermal boundary layer, as a novel approach, was considered in the simulation and a better agreement of predicted... 

Every year, air pollution is causing immense harm to humans and the environment. To cause Air pollution, several factors are involved. Among these are the sources of emissions such as factories, power plants and Cars, meteorological factors such as temperature and wind speed and geographical conditions such as altitude, postal and looming around the area, land slope and soil type region. The aim of this study is to identify factors that affect the ozone concentration in Tehran, which could help identifying other secondary pollutants. For this purpose, a combination tailored to the geography of Tehran using CMAQ-WRF-SMOKE-made programs. This model includes four intervals each of which lasting... 

Environmental regulations with respect to the marine diesel emissions have become stricter during recent years, thereby imposing traffic limitations on Iranian ships preventing them to enter emission control areas. Nitrogen oxides (NOx), as one of most important air pollutants, have adverse impacts on public health and ecosystem, so as the ships are the primary source of NOx internationally, the after-treatment system finds more urge to be developed. In this study, a NOx reduction system using non-thermal plasma technology is studied in order to determine its application and efficiency for NOx removal from the exhaust gas of Iranian marine diesel engines. Meanwhile, important factors were...