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Theoretical and Experimental Investigation of NOx Reduction in a CNG Turbocharged Internal Combustion Engines

Kharazmi, Shahaboddin | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47589 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Mozaffari, Ali Asghar; Hajilouy Benisi, Ali
  7. Abstract:
  8. Combustion and NOx emissions were simulated by quasi-dimensional and ratereaction methods respectively in a turbocharged CNG engine. Mean-value turbulence modeling was carried out during compression and combustion processes to simulate combustion process better. The most appropriate NG flame speed for the CNG turbocharged engine was applied and ignition delay was ended when flame radius became more than turbulence integral length scale. Hemispherical flame propagated from spark gap center and its intersection with reciprocating Mexican-hat piston bowl was calculated analytically. Thermal boundary layer, as a novel approach, was considered in the simulation and a better agreement of predicted mass fraction burned was achieved especially at end part of combustion process as compared with corresponding experimental results. Cylinder pressure and mass fraction burned are validated with the experimental result of Sharif Turbocharging Lab and the simulation studies followed by the validated code. Simulation revealed that higher excess air ratio at a rate of 20% decreased maximum indicated power 9% and improved minimum ISFC 7%. The last rate reaction coefficients of extended Zeldovich Mechanism published by Berkeley University Gas Research Institute were employed for the NOx simulation. NOx emissions simulation results were validated with the corresponding experimental data and the max deviation was 5%. The effects of excess air ratio and spark retard on WOT NOx emissions were investigated by the validated code. NOx emissions augmented with the increase of excess air ratio until it reached to its peak value at about 1.1 from
  9. Keywords:
  10. Combustion Simulation ; Nitrogen Oxide Emission ; Natural Gas Spark Ignition Engine ; Turbocharged Natural Gas Spark Ignition ; Turbulence Simulation ; Nitrogen Oxide Emission Simulation ; Spark Timing ; Excess Airration ; Thermal Boundary Layer

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