Collapsars may be a source for the “long” Gamma Ray Bursts (GRBs) in the BATSE catalog. Collapsars may radiate gamma rays anisotropically by beamed jet emission close to the observer’s line of sight. These jets must penetrate the radiation-dominated medium of their collapsar progenitor and break through its atmosphere in order to produce a GRB. We present a study of previously published, axisym...

Long-duration gamma-ray bursts (GRBs) require an engine capable of driving a jet of plasma to ultrarelativistic bulk Lorentz factors of up to several hundred and into narrow opening angles of a few degrees. We use global axisymmetric stationary solutions of magnetically dominated (force-free) ultrarelativistic jets to test whether the popular magnetic-driving paradigm can generate the required ...

We consider the time-dependent evolution of a relativistic jet following its breakout through the surface of a massive compact star, as envisaged in the collapsar model of gamma-ray bursts. At breakout, the jet is tightly collimated by the pressure of its hot cocoon, which is created as the jet traverses the star. After breakout, the cocoon pressure drops and the jet expands toward its natural ...

The rapid growth of the aviation sector around the globe has witnessed an overwhelming impact on fossil fuel resources. With the implementation of stricter environmental laws over emissions by conventional jet fuels, growing demand for research on alternative fuels has become imperative. One-hundred percent Synthetic Paraffinic Kerosene (SPK) and Fully Formulated Synthetic Jet Fuel have surface...

The use of alternative fuels to traditional kerosene-based ones in turbo-jet engines is currently being widely explored and researched. However, the application area small turbojet with thrust ratings up 2 kilo-newtons, which are used as auxiliary power units or propel aircraft drones, not well This paper explores ethanol a sustainable fuel its effects on operation engine under laboratory condi...

In this paper it is attempted to predict the off-design performance of a jet engine. After a review of the governing equations, the off-design performance is investigated by two methods. In the first method, the component characteristic curves of the Gas Turbines are used. In the second method some design point parameters and the reference state conditions are employed. The results obtained by ...

SUMMARY Further experiments, to investigate the interference of the Jet stream issuing from a high bypass ratio engine mounted below a wing, are described. Tests have been made with a two-dimensional wing, and two nozzle shapes representing engues with different fan cowl lengths. A Jet blonng from these nozzles produced negligible interference on the wing upper surface. However, a change in th8...

The study of core noise from turbofan engines has becomemore important as noise from other sources such as the fan and jet were reduced. A multiple-microphone and acoustic-source modeling method to separate correlated and uncorrelated sources is discussed. The autoand cross spectra in the frequency range below 1000Hz are fitted with a noise propagation model based on a source couplet consisting...

A spark plug fuel injector (SPFI), which is a combination of a fuel injector and a spark plug was developed with the aim to convert any gasoline port injection spark ignition engine to gaseous fuel direct injection (Mohamad in Development of a spark plug fuel injector for direct injection of methane in spark ignition engine. PhD thesis, Cranfield University, 2006). A direct fuel injector is com...

A torus of reduced differential rotation can form in the inner <∼ 10pc core of active galactic nuclei incurring a density enhancement that can account for obscuration of X-rays in Seyferts when the initial inner core to black hole mass ratio ∼ > 50. The same density enhancement and reduction in differential rotation can also lead to dynamo growth of poloidal fields which attain a magnitude ∼ 10...