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Experimental and Analytical Investigation of Bio-fuels Blends in the Direct Injection Engine

Ghahremani, Amir Reza | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49270 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Hassan; Mozaffari, Ali Asghar; Hajinezhad, Ahmad
  7. Abstract:
  8. The growing use of fossil fuels and their impacts on the environmental pollution, mostly originating from internal combustion engines, is one of the important issues in environmentally friendly energy management. One of the key solutions to improve engine performance and reduce exhaust emissions of internal combustion engines is direct injection of bio-fuels. In this regard, in the present study some new biofuels such as Bio-Norouzak, Modified Bio-Ethanol (MBE), and Modified Bio-Diesel (MBF) have been introduced and effects of different parameters on their sprays have been investigated experimentally and analytically. The literature survey shows there is not any comprehensive study on the spray characteristics of Bio-Noruzak, MBE, and MBF fuels. Due to this point in the first part, the effects of ambient and injection conditions on spray properties of several biofuels such as Bio-Ethanol, Bio-Noruzak, MBE and MBF fuels and their different blends with conventional fossil fuels (gasoline and diesel) in a direct injection system, have been thoroughly studied. Macroscopic characteristics of spray such as tip penetration length, cone angle, projected area and volume are investigated applying high-speed Schlieren method. A graphical user interface software namely "Image Analyzer Pro. (IAP)" is developed to analyze images and export the results. Applying quasi-steady jet theory, microscopic characteristics of spray such as equivalence ratio, Ohnesorge number and Sauter Mean Diameter are surveyed. Based on atomization physics of droplets, dimensional analysis has been performed to develop a new non-dimensional number namely Atomization Index (AI). AI number which is the ratio of square of inertial forces to the product of viscouse and surface tension forces, determines the atomization level of the spray. Results show that increasing AI number decreases SMD and improves atomization behavior of the spray as well. Since outcomes of Ohnesorge and AI numbers verify each other, and AI number can clarify the relative atomization level of different cases without drawing a diagram, AI as a proper number can be applied in further studies. To have a reasonable estimation of the calculated parameters, uncertainty analysis has been performed, as well. Beside, theoretical correlations predicting experimental results have been extracted applying least squares method and curve fitting. Furethermore, the transient under-expanded jet flow has been investigated analytically employing two-step separation of variables method, and the results have been validated well with the experimental data. The effects of eddy viscosity and pressure ratio on steady state flow are studied. Results show that increasing the eddy viscosity decreases the velocity magnitude and required time to reach fully developed jet as well. Increasing the pressure ratio increases the required time to reach steady state almost linearly. Moreover, behavior of velocity in radial coordinate at different times is studied and graphically demonstrated. In the transient region, tip penetration is obtained and validated with the experimental results in the literature and velocity profile at different times has been sketched. The present physical approach helps researchers to understand the behavior of under-expanded jet flow from transient to steady conditions
  9. Keywords:
  10. Fuel Spray ; Analytical Solution ; Direct Injection Spark Ignition (DISI)Engine ; Internal Combustion Engines ; Biofuel ; High Speed Visualization

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