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Numerical and Experimental Study of the Partially Premixed Combustion Used in a Compressed Natural Gas Spark-Ignition Direct-Injection Engine

Askari, Omid | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43314 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Kazemzadeh Hannani, Siamak; Ebrahimi, Reza; Metghalchi, Hamid
  7. Abstract:
  8. 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 characterization and reduce NOx emission especially in low equivalence ratio. For fundamental study of flammable mixture formation and partially premixed combustion, injection and combustion will be investigated inside a transparent constant volume combustion chamber. Experimental tests are done in two distinct sections. First, spray development and characterization including spray tip penetration, spray cone angle and overall equivalence ratio were investigated under 30-90 bar fuel pressures and 1-5 bar chamber pressure. Then, Flame propagation images and combustion characteristics were determined via pressure-derived parameters and analyzed at a fuel pressure of 90 bar and a chamber pressure of 1 bar at different stratification ratios (from 0% to 100%) at overallequivalence ratios of 0.6, 0.8 and 1.0. Shorter combustion duration and higher combustion pressure were observed in direct injection-type combustion at all fuel air equivalence ratios compared to those of homogenous combustion. For finding more results and completing experimental section, flow field, shock cells, heat transfer rate, temporal and spatial distribution of of pressure, temperature, equivalence ratio and emission concentration were modeled using AVL-FIRE code based on constant volume combustion chamber geometry. This numerical model was validated with experimental
    data.
  9. Keywords:
  10. Methane ; Numerical Simulation ; Experimental Studies ; Thermodynamic Modeling ; Emission Reduction ; Direct Injection Spark Ignition (DISI)Engine ; Schileren Optical Method

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