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Homogeneous Charge Compression Ignition (HCCI) Combustion Simulation using a Multi-Zone Chemical kinetics Model

Voshtani, Sina | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45710 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hosseini, Vahid
  7. Abstract:
  8. 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 directly, compound fuels, layering fuel in combustion chamber and so on are mentioned as some solutions. In this study, a kinetic-thermodynamic model for HCCI engines is simulated which specifically studies self-ignition. Modeling is done through a zero dimensional single zone and a semi-dimensional multi zone model which modeling algorithm is obtained completely stands alone. Natural gas is chosen as the fuel to be studied, though the use of natural gas in HCCI engines is difficult due to its low tendency to self-ignition. However, due to highly rich resources of this fuel in our country, this fuel is chosen in this study. The aim of this study is to investigate the start of combustion of natural gas by use of complete chemical kinetics from the view of thermodynamics and kinetics, and also finding some ways to control the combustion in different functional conditions. Results show that single zone model can predict functional behavior of HCCI engine truly to some degree. However, start of combustion with the determination of initial conditions from experimental data, is predicted precisely. Multi zone model, after investigating the effect of number of zones, predicts pressure change behavior and start of combustion precisely and even obtains combustion period like in real. Besides, adding synthesis gas (changing the percent and combination of species) and also adding reformer gas, with the study of change in thermodynamic and kinetic properties of combustion, change combustion timing and are appropriate methods for controlling self-ignition. This capability has remarkable influences on broadening engine functional area (combustion stability), increasing efficiency and reducing fuel consumption
  9. Keywords:
  10. Homogeneous Charge Compression Ignition (HCCI) ; Single-Zone Model ; Combustion Start ; Combustion Control ; Reformer Gas ; Multi-Zone Method

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