Sharif Digital Repository

Iran’s big cities air pollution is one of the major challenges to authorities in view of public health. Tehran City has been facing more and more air quality problems over the last decade. The criteria pollutants in Tehran are PM2.5, PM10. Particulates and especially ultrafine particles have been identified as the most toxic component of the polluting mixture. Considering diesel engine operation concepts, these types of engines are one of the main source emission of ultrafine particles, with more than 58%, in Tehran. So controlling particulates emitted from these sources, is one of the first steps to improve air quality. Diesel Particulate Filters (DPFs) are well-known and effective way to... 

Reducing air pollutant emissions from vehicles is a difficult and time consuming procedure which needs utilizing of modern emission control equipment and setting strict regulations for car factories and drivers as well. How efficient these policies are and proposing operative solutions for air quality improvement depend on developing a sustainable model which is used in vehicle emission predictions and their share in total emissions. Emission factors are not constant values as they can be affected by various operational and ambient parameters. Development of Emission inventories calls for a huge number of measurements using different vehicles in diverse conditions. Thus, recognition of... 

According to limitation of fossil fuel consumption and cost, reduction of fuel consumption is very important in internal combustion engine. This requirement becomes twofold in light of the greenhouse effect of CO2 on global warming. Therefore, the use of engines with less fuel consumption is a global success. Diesel engines are among the most productive internal combustion engines. They have a lower fuel economy and carbon monoxide. But unfortunately, these engines respectively in rich and dilute blend have highly soot and nitrogen oxides. One of the methods in the development of the combustion process is the low temperature combustion method, which reduces the production of Knox due to low... 

As elevation increase, environmental impacts will change, and this will affect on vehicle performance. The pressure drop and consequently the drop in air density at high altitude affect the volumetric efficiency of the engine. This exacerbates engine combustion, since the engine displacement volume is constant, with the drop in air density, the intake air mass flow rate decreases. In this situation, the engine does not have enough air to burn the fuel, and as a result the engine ignition will getting into the defect. ECU only changes the amount of injecting fuel and has no control on the entering air flow to the engine. In such circumstances, emissions from the vehicle are expected to... 

Diesel particulate filters (DPFs) are used in active and passive regeneration exhaust systems in order to reduce the soot emission of diesel engines. Soot regeneration process initiates at a certain minimum temperature. In Compression Ignition (CI) engines, the intake is not throttled usually, and load control is carried out by adjusting the amount of fuel injected into the cylinders. Consequently in low load working condition, as the fuel mass decreases, the air to fuel ratio increases that results in lowered exhaust gas temperature. On the other hand, passive regeneration strategies alone are not enough and it should be backed up by an active regeneration system in order to guarantee... 

Increasing greenhouse gases in the atmosphere has many unpleasant consequences. Transportation sector has 23 percent allocation in emitting those gases. Alternative fuels can be considered as a solution in order to decreasing greenhouse gases and less dependency on the fossil fuels. It is noteworthy that between biofuels, bioethanol has the maximum share (based on International Energy Agency, IEA, bioethanol will hold 27 percent share in supplying energy in transportation sector). In this thesis, assessment of exhaust emissions and fuel consumption of a light- duty vehicle with the gasoline and E85 fuels is performed. Note that, engine calibration was not altered. The implemented method is... 

Homogeneous Charge Compression Ignition (HCCI) engines are the new generation of internal combustion engines which have diesel-like thermal efficiency, while they have low nitrogen oxide and soot emission. One of the major problems of HCCI engines is combustion timing control due to its dependence on reactivity of the charge and chemical kinetics. Moreover, limiting operation range between knock and misfiring is the other drawback of using these kind of engines. In the present work, partially homogeneous HCCI combustion in a single cylinder diesel engine is modeled using Computational Fluid Dynamics (CFD) coupled with chemical kinetics. Simulation includes the engine cycle from exhaust valve... 

Real fuels contain hundreds of hydrocarbons such as linear and chain paraffins, naphthenes, olefins and aromatics.Behavior of this real fuels are represented by mixtures with simple compounds. Since engine with homogeneous charge compression ignition (HCCI) is a promising combustion concept able to provide very low NOx and PM diesel engine emissions while keeping good fuel economy, for use in vehicles requires kinetic reaction mechanism to simulate the hydrocarbons oxidation and it’s rules.combustion control is facing with basic problem in this engine.unlike conventional methods, . HCCI combustion is a kinetically controlled process and start of combustion will be controlled and dominanted... 

Tehran is the most populated area in Iran and is one of the most densely populated cities in the world where almost 40 percent of all days have been classified as unhealthy for sensitive groups. According to emission inventory of Tehran over than 85 percent of emission are due to different types of vehicles. And light duty vehicles share more than 80 percent all vehicles and are responsible for most of carbon monoxide and nitrogen oxides emitted in Tehran atmosphere. In this study real emission factor of Hybrid Synergy vehicles which just have been introduced to Tehran fleet were tested under real conditions of streets. Data produced in this research have been combined with previous... 

In recent years, the idea of Homogenous charge compression ignition (HCCI) engines has been in the center of attention as a new generation of internal combustion engines. Intense decrease in pollutant emission rate like NOx, low fuel consumption and high thermal efficiency are the main reasons of why these engines are in center of attention, however, some drawbacks, which the main one combustion control which happens in limited operation range between knock and misfiring has limited the use of these engines. Hence approaches like adding synthesis gas, using exhaust gas recirculation, controling effective comperession ratio by using variable valve timing, changing the input conditions... 

Today air pollution has become one of the major urban management concerns. Air pollution could have dangerous effects on human health in short time or long time in many situations. Numerical modelling is one of the most applicable among different ways for predicting pollutant concentration like field measurement, physical model in wind tunnel, and simulation. Modelling of pollutant dispersion is a way for estimating concentration and aggregation of the pollutant near the surface and with different distances from pollution source. In different dispersion models, one of simplest is the Gaussian model. In this approach it is supposed that emission plume obeys from Gaussian distribution and is... 

The city of Tehran is dealing with air pollution problems for years. Providing a solution for this problem requires information about different pollutants emission sources. In this subjects, emission factors and emission models are essential tools for decision makers. Among different mobile emission sources in Tehran, motorcycles are of high importance. In this project, for the first time in Iran, exhaust gas pollutants emission of 66 motorcycles with different ages and engine displacement volumes were measured according to Euro-3 standard certification procedure. Measurement results showed that none of the tested motorcycles passed the Euro-3 certification limit on CO emission. Calculations... 

Ethanol is a promising alternative fuel in terms of addressing future energy and environmental problems, so we can use ethanol as a fuel in passenger cars to eliminate enviremental problems. in this study, the CEV13-038 injector from ACRUS company is modeled. the research purpose is focused on the effect of ethanol , geometrical parameters, and the fuel type on the injected mass quantity and on turning the fuel supply system from a gasoline based system to ethanol based one.
In the first step of this study, The effect of ethanol, fuel temperature, needle lift, nozzle diameter and number of nozzles... 

Tehran, with approximately 750 km2 of land area, a population of more than 8 million people with about 4 million active on-road vehicles, is dealing with serious air pollution problems. To model the environmental phenomenon precisely, this study aims to develop on-road air pollutant emission factor matrices based on existing traffic in Tehran routes and to run air quality modelling within Tehran geographic boundaries. We developed emission factor matrices using SMOKES-MOVES emission modeling system. To do so, we calculated on-road emission factors from actual traffic-related data and run MOVES emission model. And use use them for different pollutants considered in air quality models. Then,... 

Combustion sources such as diesel vehicles are the most of the particular matter sources in ambient air. Near the tailpipe, exhaust is very hot, condense and have high velocity. This properties cause to need special methods and instrument to collect them. Numerously of combustion sources will emitted the VOCs, IVOCs, and SVOCs. This component mixed with ambient air and changing to particle phase from gas phase. Reaction between nitrogen oxides with sunlight cause to damage ozone layer and tissue in long time. Furthermore, breathe of VOCs gases cause to eye irritation, gastrointestinal effects, Damage to the nervous system, headache, dizziness, fatigue, vibration and loss of organ... 

Air pollution modeling is a powerful and low-cost tool for taking appropriate strategies to control air pollution. In this research, the effects of vegetation on air pollutant dispersion were studied using computational fluid dynamics models. At the beginning, aerodynamics and thermal effects of vegetation on reactive pollutant dispersion including NO, NO2 and O3 under photochemistry cycle were investigated in two different geometries. In the first geometry, tree planting in an urban environment involving several canyons was simulated. Results show that tree planting causes flow reversal, temperature decrease, and concentration field change. Concentration change of each pollutant not only... 

With the road transportation vehicles being widely used, concerns have been increased regarding their unwanted effects. Air pollution, climate change, and oil supply security are among these effects. Many alternative fuels and propulsion systems have been proposed to be used instead of conventional ICE vehicles in recent decades. This project intends to conduct a Techno-Economic comparison between different vehicle powertrains so as to select the suitable choice to substitute conventional ICE vehicles. The vehicle options are ICE vehicles using both gasoline and CNG as fuels, Hybrid Electric Vehicles (HEVs), Plug-in Hybrid Electric Vehicles (PHEVs), and Electric Vehicles (EVs). The amount of... 

By expansion of urban areas and increasing in number of vehicles commuting, tunnels are one of the most inevitable part for developing urban areas. Nevertheless, one of the important topics about tunnels is exhaustion of polluted air into its surroundings. Tohid Tunnel, stretching about 2136 meter, is currently the longest urban tunnel in Iran, connecting Chamran and Navvab Highway from north of Fatemi street, to the Shokufeh street. Now, exhausting pollutants is done only by north and south portals beside a middle shaft. The purpose of this project is to analyze pollutant dispersion from south portal of Tohid tunnel which is located in Navvab residential region. This is done by considering... 

In this study, in the base case using a modeling system WRF=CAMx Distribution concentration of all pollutants from mobile sources in an episode of 60 days (November and December 2015) is calculated in Tehran. In this context, the emissions inventory related to mobile sources outputs the code in Fortran and WRF meteorological model to model air quality prepared and then using the CAMx, Tehran’s air quality is simulated. In order to verification in this case, the results of pollutant concentration NO2, CO, PM2٫5, with concentrations of air pollution monitoring stations compared. Given that in this study the concentration of pollutants from mobile sources is modeled, predicted by the model,... 

Alternative fuels are considered as a solution to increase energy security, reduce dependence on conventional fossil fuels (gasoline and diesel), and reduce greenhouse gas emissions. In this context, bioethanol has been very much considered in recent years. This fuel is combined with gasoline and used by cars. Flexible fuel vehicles are cars that can be used in various blend of gasoline and ethanol. Ethanol has a higher octane number than gasoline, and its mixture with gasoline increases the number of octane fuels. However, this fuel has a lower thermal energy than gasoline, which increases the fuel consumption of ethanol and gasoline relative to pure gasoline. The purpose of this study is...