A system dynamics simulation model for evaluating the effect of the moon resource exploitation on the earth ecological and economics system is improved to be more conformable to the expected capital investment and discard conditions. The relation between the parameters and the simulation result is analyzed for this improved model and the effective range of the conditions in the moon resource exploitation is roughly estimated.
In this paper the dynamics of cavitation vapor bubble in cryogenic liquid nitrogen are investigated experimentally and analytically. The bubbles are produced by focusing a giant pulse of Q-switched ruby laser into the liquid nitrogen in a cryostat, and the dynamics of the laser-induced bubble are studied by means of high-speed photography by using an image converter camera with the framing rates of 105 frames/s. A numerical analysis is also performed on the behavior of a bubble in cryogenic liquid. The mathematical formulation takes account the effect of liquid inertia (incompressible liquid), non-equilibrium condensation of the vapor in the bubble, and the heat transfer at the bubble wall. The experimental data on the bubble motion in liquid nitrogen under the near-equilibrium initial conditions with an atmospheric pressure are compared to the numerical solutions. Among the results obtained, the bubble motion observed indicates more violent and decaying behavior than the estimated tendency. The heat and mass transfer effects including the evaporation and condensation phenomena have the strong influence on the vapor bubble motion in cryogenic liquid. Qualitatively the numerical analysis can simulate the experimental results.
A quick automatic method is presented for evaluating a propeller performance combined to an engine. The formulation is obtained through drastic simplification by retaining the essential parts only. A scheme —“thrust-consistent scheme”— is constructed for the part of propeller analysis. Accuracy-examination has been made both for static and forward moving conditions, and confirmed to be within ten% errors. One example of application to an engine-propeller combination is presented, which shows that the present method is much convenient to select the best set of several parameters such as diameter, solidity, and pitch etc.
This paper shows an improved performance of a five stages axial flow compressor and a two stages fan applying a wide chord blade in some of their rotor stages. The estimation procedure of maximum loading capability on the wide chord rotor blade is also described in this paper based on the analogy between a compressor rotor blade and a diffuser passage. A procedure for estimating the maximum pressure rise potential and minimum flow rate boundary was formulated on the basis of meanline parameters, such that it can be used during the preliminary design early phase in the planning. A good agreement is demonstrated between the predicted and tested stall pressure and stall flow rate limits for the wide chord compressor and fan.
Six-component measurements of a model of a wing-in-ground effect craft (WIG) “Marine Slider: μ sky” were conducted in a low speed wind tunnel using a running belt as the ground plane. The “μ sky-1” was an experimental marine craft with a simple ram wing. Its wing section was a high cambered thin section to improve its performance in the ground effect. The wing of the test model was a square wing of the aspect ratio 0.625 with tip plates extending downward from both tips. Results obtained show that the ground effect is remarkable for this wing. The drag was reduced not enough. The reason was that there was a strong shear flow in a narrow clearance between the hull bottom and the ground surface. The shear flow increased the drag.
In order to improve normal maneuverability of airship, hybridization is conceived in which a part of the gross weight is supported by dynamic lift. The simplest way is to utilize the dynamic lift of the gas envelope itself. Someone suspect that excessive induced drag happens due to the low aspect ratio. This problem is investigated here, being compared with the case where an additional fixed wing is adopted. Conclusively use of the dynamic lift due to the gas envelope itself is not necessarily inefficient, because of no additional structural weight.