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Experimental & Numerical Investigations of the effects of the Intake Port Geometry on the In-Cylinder Flow of Direct Injection Spark Ignition Engine

Mohammadebrahim, Abolfazl | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45622 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Behshad; Kazemzadeh Hannani, Siamak
  7. Abstract:
  8. The design of inlet ports for spark ignition internal combustion engines has a direct and well-known influence on performance and emissions as a result of changes in volumetric efficiency and fuel burn rate.The design of ports is becoming more critical as SI engines are developed further to meet increasingly stringent exhaust emissions legislations. Lately further emphasis has been placed on port design by the re-emergence of the direct injection gasoline engine.
    Due to lean burning, combustion instability and increasing the cycle to cycle variations, in the direct injection engine, combustion charactersitics will be improved by increasing the tumble in-cylinder flow and the turbulence intensity.Therefore, a deep understanding of how the fluid motion inside the cylinder in the engine design is required.
    Computational fluid dynamics (CFD) method is employed to gain further insight into the characteristics of the in-cylinder flow field. The comparison between measured and predicted results of the in-cylinder tumble flow and flow coefficient generated by a port-valve-liner assembly on a steady-flow test bench is presented. A reasonably good level of agreement is achieved. A CAD parametric model of port geometry is created to enable variations practically and quickly. Employing CFD analysis, the relationship between design parameters and port flow characteristics is established. The influence of new blockage patterns on in-cylinder flow is also studied. The study is aimed at determining the influences of the intake adaptor, test pressure, adaptor length and diameter, adaptor roughness, paddle wheel diameter, and asymmetric valves lifting on the flow coefficient and the swirl intensity measurements. In studies of this kind, researchers generally tend to adopt different test parameters to arrive at a nonuniform base to compare results from several investigations. This work is aimed at verifying the quantitative differences detected using these test parameters.The findings revealed that the swirl intensity depends on the pressure test, adaptor length, and the entry type to a significant degree. Moreover, it was observed that the intake adaptor is the most effective test parameter on the flow coefficient.
    Finally, the sensitivity analysis has been performed in order to investigate the experimental results and to correlate them with the test parameters.

  9. Keywords:
  10. Fluent Software ; Computational Fluid Dynamics (CFD) ; Direct Injection Spark Ignition (DISI)Engine ; Intake Port ; Swirling Flow

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