Sharif Digital Repository

Direct injection spark ignition lean burn engine with stratified mixture is concerned recently and research and development are in its initial stage. In this thesis, at first a thermodynamic simulation of these engines was done for investigating of stratified mixture effects on combustion characterization and compare it with homogeneous one. In this modeling we use from turbulent flame speed model for mass burning rate analysis, multizone model for exact measuring of temperature distribution, full chemical kinetic model for emission concentrations and some proposed mixture formation for predicting of stratified mixture. The results shown that stratification is caused to improve combustion... 

The growing use of fossil fuels and their impacts on the environmental pollution, mostly originating from internal combustion engines, is one of the important issues in environmentally friendly energy management. One of the key solutions to improve engine performance and reduce exhaust emissions of internal combustion engines is direct injection of bio-fuels. In this regard, in the present study some new biofuels such as Bio-Norouzak, Modified Bio-Ethanol (MBE), and Modified Bio-Diesel (MBF) have been introduced and effects of different parameters on their sprays have been investigated experimentally and analytically. The literature survey shows there is not any comprehensive study on the... 

Due to increasing of internal combustion engine applications in metropolitan, reduction of emission is one of the challenging issues for engine companies. Natural gas is a promising fuel for the strict legislation of emission in many countries. Vast variety of natural gas sources in Iran and also lower carbon to hydrogen content of natural gas motivates us to use this fuel for engine application. Using natural gas also helps to increase the variety of fuel basket in Iran. Present research has focused on mixture formation and injection characteristics of natural gas direct injection engine. Injection and mixture formation in direct injection engines is very important for good combustion and... 

Energy crisis is one of the crises which human beings face these days. Optimizing the operation of energy consuming machines is one of the most effective methods in decreasing energy consumption. Gasoline direct injection engines as new achievements in automobile and propulsion industry, reduce fuel consumption by increasing the engine efficiency. In these types of engines, a high pressure injector injects fuel directly into the combustion chamber instead of injecting fuel in intake ports. Thus, because of evaporation cooling, the mixture cools down, so the possibility of achieving higher compression ratios in higher engine speeds and loads, without occurrence of knock is provided. Increase... 

Energy crisis is one of the crises which human beings face these days. Optimizing the operation of energy consuming machines is one of the most effective methods in decreasing energy consumption. Gasoline direct injection engines as new achievements in automobile and propulsion industry, reduce fuel consumption by increasing the engine efficiency. In these types of engines, a high pressure injector injects fuel directly into the combustion chamber instead of injecting fuel in intake ports. Thus, because of evaporation cooling, the mixture cools down, so the possibility of achieving higher compression ratios in higher engine speeds and loads, without occurrence of knock is provided. Increase... 

The design of inlet ports for spark ignition internal combustion engines has a direct and well-known influence on performance and emissions as a result of changes in volumetric efficiency and fuel burn rate.The design of ports is becoming more critical as SI engines are developed further to meet increasingly stringent exhaust emissions legislations. Lately further emphasis has been placed on port design by the re-emergence of the direct injection gasoline engine.
Due to lean burning, combustion instability and increasing the cycle to cycle variations, in the direct injection engine, combustion charactersitics will be improved by increasing the tumble in-cylinder flow and the turbulence... 

The application of internal combustion engine is vast in different context, such as transportation and power generation. Therefore to investigation of these objects and the importance of flame front development, a combustion chamber with constant volume is designed and manufactured. The chamber designing is based on the experimental knowledge and numerical simulation of chamber and glasses. The combustion chamber made of stainless steel and contained transparent quartz glasses in both side of it to provide the ability of using schlieren photography method and investigation of flame. The great advantage of present chamber is the capability of different type of combustion, including fuel and... 

First studies in internal combustion engines have focused on increasing engine power and efficiency, reducing engine volume and improving fuel quality. However, nowadays most studies are concentrated on decreasing exhaust emissions and usage of regenerative fuels while maintaining engine size, efficiency and power. Surveying fuel type in direct injection engines, requires investigation of microscopic and macroscopic spray characteristics including spray tip penetration, spray cone angle, spray area and sauter mean diameter, since these parameters determine air-fuel mixture quality. In this study, spray of ethanol as a regenerative fuel that reduces emissions such as NOx and CO is...