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Experimental and Numerical Investigations of Reactivity Controlled Compression Ignition (RCCI)Combustion Fueled by Diesel and Natural Gas

Zarrinkolah, Mohammad Taghi | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55570 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hosseini, Vahid; Shamloo, Amir
  7. Abstract:
  8. 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 greenhouse effect. Few studies have been done on combustion stability and methane slip of RCCI engines, therefore parts of the thesis have been dedicated to these topics. This thesis is defined in two numerical and experimental sections. The experimental section is also divided into two subsections: equipping the engine laboratory and conducting experimental tests. The experiments are performed at a constant engine speed and to examine the effect of each parameter, the start of direct fuel injection is swept from misfiring to knock limits. All the thermodynamic and combustion data have been recorded with Motorazma and AVL Indicom soft wares.In the numerical section, with the help of the AVL-FIRE CFD tool three combustion regimes were simulated; a conventional diesel methane dual-fuel combustion and two modes of reactivity-controlled compression ignition with early and late injections. The results indicate that with the increase in the energy fraction of natural gas, the maximum pressure inside the cylinder and the maximum rate of heat release decrease, the amount of unburned hydrocarbons increases, the maximum temperature inside the cylinder and NOx decreases, the IMEP variation coefficient increases and the combustion become more unstable. Combustion instability is characterized by the coefficient of variation (COV) of indicated mean effective pressure (IMEP), measured 4.2% for B5 (95% diesel-5% biodiesel) and 4.8% for B20 (80% diesel-20% biodiesel) compared to 1.8% for B0 (pure diesel). The experimental results show that by splitting direct fuel injection and injecting less fuel mass in the first stage, more methane burns inside the combustion chamber. The results of the numerical simulation indicate that by switching the combustion regime from conventional dual fuel to RCCI combustion with late and early injection, 12% and 33% less methane slip occurs, and decreasing diesel fuel spray angle from 120o to 90o and 60o results in a 45% and 74% increase of methane slip
  9. Keywords:
  10. Reactivity Controlled Combustion Ignition Engines (RCCI) ; Low Temperature Combustion ; Combustion Stability ; Chemical Kinetic ; Soot ; Nitrogen Oxides ; Methane Slip ; Unburned Hydrocarbons ; Diesel Fuel ; Gaseous Fuels

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