Sharif Digital Repository

The effects of hydrogen addition, diluent addition, injection pressure, chamber pressure, chamber temperature and turbulence intensity on methane-air partially premixed turbulent combustion have been studied experimentally using a constant volume combustion chamber (CVCC). The fuel-air mixture was ignited by centrally located electrodes at given spark delay times of 1, 5, 40, 75, and 110 ms. Experiments were performed for a wide range of hydrogen volumetric fractions (0% to 40%), simulated diluent volumetric fractions (0% to 25% as a diluent), injection pressures (30-90 bar), chamber pressures (1-3 bar), chamber temperatures (298-432 K) and overall equivalence ratios of 0.6, 0.8, and 1.0.... 

Natural gas has widely been used as a fuel in conventional Diesel and spark ignition engines. The better understanding of injector parameters on the jet structure is helpful for the combustion optimization. This paper presents an experimental and numerical study on the jet structure of gaseous fuel injector in spark ignition direct injection engine by Schlieren technique and numerical procedure. Helium was injected through a gaseous injector at the different pressure ratios and nozzle diameters to understand the effects of nozzle geometry and pressure ratio for a dedicated correlation of CNG-SIDI injector. It was found that higher pressure ratio and exit nozzle diameter led to more tip... 

Constant volume transparent test combustion chambers are extensively used for investigating injection and fuel burning properties of various combustion engines. Their configuration depends on the engine type and the research purpose. Material of components, shape and dimensions of the chamber and its parts, ease of use, accessibility, sealing and safety of the assembly are the parameters needed to be considered in designing the test cell. This paper explains, structural design of a test combustion chamber and its optical windows using finite element analysis of ANSYS 12.0 software for bearing high pressure variations and thermal shocks of combustion. It was designed for conducting CNG direct... 

This study presents fundamentals of spray and partially premixed combustion characteristics of directly injected methane inside a constant volume combustion chamber (CVCC). The constant volume vessel is a cylinder with inside diameter of 135 mm and inside height of 135 mm. Two end of the vessel are equipped with optical windows. A high speed complementary metal oxide semiconductor (CMOS) camera capable of capturing pictures up to 40, 000 frames per second is used to observe flow conditions inside the chamber. The injected fuel jet generates turbulence in the vessel and forms a turbulent heterogeneous fuel-air mixture in the vessel, similar to that in a compressed natural gas (CNG) direct... 

The combination of direct torque control and permanent magnet synchronous motors (PMSMs) provides a highly dynamic drive. In this paper direct torque control method of PMSM is merged with a sensorless control algorithm and a robust flux observer is proposed which results in a high performance highly reliable drive. First a high frequency signal injection method within DTC algorithm is introduced to estimate the rotor position of PMSM. Then the method is modified in order to estimate stator dynamic inductances. The stator inductances are then used in a current model flux observer  

Fetal stem cells, which can be isolated from the organs of fetuses, differentiate along multiple lineages. Their advantages over their adult counterparts include better intrinsic homing and engraftment and lower immunogenicity, and they are less ethically contentious. It is noteworthy that Mesenchymal Stem Cells (MSC) can be activated and mobilized at the site of damaged tissue. Since vascular delivery suffers from a pulmonary first pass effect, direct or systemic injection of MSCs into the damaged tissue is preferred, particularly in the case of versatile tissue ischemia. Ultrasound applies acoustic energy with a frequency above human hearing (20 kHz). Ultrasound imaging or sonography...