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combustion-stability
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Combustor`s Operational Limit Enhancement for a Small Turbojet Engine
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Turbine engines performance is notably dependent on environmental conditions, i.e. pressure and temperature and also on flight speed. Every engine has a specific flight ceiling, i.e. altitude above which engine shuts down. Engine shut down during altitude increase, is because of combustor performance loss and its efficiency and stability decrease. Combustor stability limit can be extended by performing modifications such as replacing fuel injectors and/or improving fuel characteristics, and the combustor can be used for higher altitude whitout any required change in design. In this thesis, influence of combustor various parameters like air flow rate, fuel equivalence ratio, inlet pressure...
Numerical Analysis of an Afterburner Combustion Stability
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Inlet flow of afterburners comes from the burnt products of the primary combustion chamber. The fuel is injected and the mixture is ignited to form a flame which is stabilized behind a flameholder in the afterburner. Flame stability stems from wake (recirculation zone) of flameholder. With the aid of high residence time of flow behind the flameholder reactants get the time to catch activation energy. Some parameters like oxygen content, mass flow rate, inlet temperature, and nozzle area ratio play an important role in afterburner combustion efficiency and flame stability. In this study we focused on afterburner combustion stability in GE J85-21 engine. This engine will be in service through...
Experimental and Numerical Investigations of Reactivity Controlled Compression Ignition (RCCI)Combustion Fueled by Diesel and Natural Gas
, Ph.D. Dissertation Sharif University of Technology ; Hosseini, Vahid (Supervisor) ; Shamloo, Amir (Supervisor)
Abstract
In this thesis, reactivity controlled compression ignition (RCCI) combustion fueled by diesel and natural gas is experimentally and numerically investigated. Natural gas as a fuel with low reactivity is injected into the intake manifold, and diesel as a fuel with high reactivity is injected directly into the combustion chamber. One of the main goals of this thesis is to experimentally examine the effect of important parameters on combustion phasing control, operational range extension, and pollutants. Natural gas is one of the important sources of energy in Iran and the world. Using natural gas in internal combustion engines can cause methane to slip into the atmosphere and intensify the...
Development of mechanistic engineering code for combustion instability prediction in LRE
, Article 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Hartford, CT, 21 July 2008 through 23 July 2008 ; June , 2008 ; 9781563479434 (ISBN) ; Fatehi, H ; Amanpour, H ; Sharif University of Technology
2008
Abstract
The prevention of combustion instability is unquestionably the greatest technical challenge and can be a significant cost driver in new engine development programs. In order to meet challenge, a predictive stability code is required. The main objective of this work is to develop a mechanistic engineering code for analysis of high frequency combustion instability in LRE. The developed MEchanistic Combustion Stability COmputer Program (MECSCOP), evaluates combustion stability using the transfer function approach, whereby the ability of the chamber to dissipate acoustic oscillations is compared to the oscillatory combustion driving mechanisms. The driving mechanisms are classified by the source...
Detailed analysis of the effects of biodiesel fraction increase on the combustion stability and characteristics of a reactivity‐ controlled compression ignition diesel‐biodiesel/natural gas engine
, Article Energies ; Volume 15, Issue 3 , 2022 ; 19961073 (ISSN) ; Hosseini, V ; Sharif University of Technology
MDPI
2022
Abstract
A single‐cylinder marine diesel engine was modified to be operated in reactivity controlled compression ignition (RCCI) combustion mode. The engine fueling system was upgraded to a common rail fuel injection system. Natural gas (NG) was used as port fuel injection, and a die-sel/sunflower methyl ester biodiesel mixture was used for direct fuel injection. The fraction of bio-diesel in the direct fuel injection was changed from 0% (B0; 0% biodiesel and 100% diesel) to 5% (B5) and 20% (B20) while keeping the total energy input into the engine constant. The objective was to understand the impacts of the increased biodiesel fraction on the combustion characteristics and stability, emissions, and...
An experimental study on the effect of hydrogen enrichment on diesel fueled HCCI combustion
, Article International Journal of Hydrogen Energy ; Volume 36, Issue 21 , 2011 , Pages 13820-13830 ; 03603199 (ISSN) ; Hosseini, V ; Neill, W. S ; Chippior, W. L ; Dumitrescu, C. E ; Sharif University of Technology
Abstract
This paper experimentally investigates the influence of hydrogen enrichment on the combustion and emission characteristics of a diesel HCCI engine using a modified Cooperative Fuel Research (CFR) engine. Three fuels, n-heptane and two middle distillates with cetane numbers of 46.6 and 36.6, are studied. The results show that hydrogen enrichment retards the combustion phasing and reduces the combustion duration of a diesel HCCI engine. Besides, hydrogen enrichment increases the power output and fuel conversion efficiency, and improves the combustion stability. However, hydrogen enrichment may narrow the operational compression ratio range and increase the knocking tendency. Both the overall...