Spray combustion is numerically simulated, using the Euler equations for the droplet phase assuming a continuous fluid, and the full Navier-Stokes equations for the gas phase. Both phases are connected through mass, momentum and energy exchange equations. Further more, the droplet phase has an initial radius distribution, and it is divided into nine groups of different initial radius, and they are treated as individual phases. Vaporization and combustion of fuel droplets are included in the calculation. Two types of sprays; full corn and hollow corn are simulated. Results of profiles of velocity of the full corn type show good agreements with the spray theory, and results of velocity fields of the hollow corn type show behaviors of induced vortexes. And droplet groups of different radius show individual trajectories.
In Part 1 and Part 2, the authors presented a new finite element formulation for the analysis of large deformations of spatial beams, and demonstrated the accuracy and the efficiency of the proposed method by the numerical examples. In this paper, we analyze the post-buckling behavior of clamped circular arches subjected to a central concentrated load, and conduct experiments to verify the numerical results. The experimental data agree well with the numerical results, confirming the efficiency of the proposed method.
Pilot-Induced Oscillation (PIO) was encountered in the company flight test of the T-2CCV research vehicle. The main cause of the roll PIO was due to unexpected large pilot input and to increased delay of the aircraft response by its large pilot input. The delay of roll response has much difference between with large input and with small input. That is why the flight control system falls into nonlinear system by actuator rate limit in case of controlling the aircraft with large pilot input. This paper shows analysis of the characteristics of the PIO and its improvement.
Ignition of a parallel hydrogen injection into a supersonic hot air stream and ignition of a cold premixed combustible hydrogen/air stream heated by a hot air jet were investigated by a high-resolution TVD LU-SGS numerical algorithm. The present two-dimensional simulation included detailed chemistry in terms of elementary reactions, as well as a multispecies molecular transport model and the Baldwin Lomax algebraic turbulent model. In the case of a cold hydrogen injection into a hot air stream, numerical simulation showed that, with a decrease of the width of fuel jet, ignition point moves upstream quickly. The present results also showed that ignition distance was linearly dependent on the logarithmic function of the width of the fuel jet. Furthermore, the phenomenon could be still observed even for a very low concentration of hydrogen in the fuel jet. In the case of a premixed hydrogen/air stream ignited by a hot air jet, with a decrease of the width of air jet, ignition point moved very slightly downstream. However, there existed an ignition limit for the width of air jet, that is, if the width of the air jet was less than this limit, ignition became impossible. Furthermore, this ignition limit depended strongly on the initial temperatures of air stream and premixed hydrogen/air stream.
Scramjet engine performances were evaluated by several simple analyses employing single efficiency or assuming constant pressure combustion cycle (Brayton cycle). A new specific impulse formula was derived from the Brayton cycle analysis which suitably included effects of mass, momentum and energy addition by fuel injection as well as combustor drag. Ideal values of specific impulse were calculated by the analyses and compared to find suitable one to represent that of the ramjet/scramjet. Analytical equations for fuel mass ratio of a spaceplane utilizing air breathing engines were derived from some of single efficiency analyses and compared with that of the rocket. A performance index for the scramjet combustors was proposed to evaluate relative importance of combustion and drag in the combustors.
The performances of a shockless-in-rotor supersonic axial flow compressor are discussed on the basis of one dimensional flow analysis. Some characteristics are derived as follows in comparison with an ordinary shock-in-rotor supersonic axial flow compressor having the same inlet Mach number. 1) Normal shock loss can be avoidable in the entire passage including both rotor and stator. 2) The exit flow from rotor is turned in the opposite direction to the rotational one of rotor. 3) The absolute total pressure ratio per stage is small. 4) The starting problem is relieved. 5) The supersonic multistages may be easily put into practical use.