With the development of the increasing demand for cooling air in cabin and electronic components on aircraft, it urges to present an energy-efficient optimum method for the ram air inlet system. A ram air performance evaluation method is proposed, and the main structural parameters can be extended to a certain type of aircraft. The influence of structural parameters on the ram air performance is studied, and a database for the performance is generated. A new method of integrating the BP neural networks and genetic algorithm is used for structure optimization and is proven effective. Moreover, the optimum result of the structure of the NACA ram air inlet system is deduced. Results show that (1) the optimization algorithm is efficient with less prediction error of the mass flow rate and fuel penalty. The average relative error of the mass flow rate is 1.37%, and the average relative error of the fuel penalty is 1.41% in the full samples. (2) Predicted deviation analysis shows very little difference between optimized and unoptimized design. The relative error of the mass flow rate is 0.080% while that of the fuel penalty is 0.083%. The accuracy of the proposed optimization method is proven. (3) The mass flow rate after optimization is increased to 2.506 kg/s, and the fuel penalty is decreased by 74.595 Et kg. The BP neural networks and genetic algorithms are studied to optimize the design of the ram air inlet system. It is proven to be a novel approach, and the efficiency can be highly improved.

Forced convection heat transfer is a significant factor for the thermal control of a stratospheric airship. However, most of researches were conducted without considering the influence of flight state causing serious errors. In order to accurately predict the forced convection heat transfer of the stratospheric airship at an angle of attack, firstly, an empirical correlation of Nusselt number (Nu) as function of Reynolds number (Re) andlength to diameter ratio (e) is developedunder horizontal state based on a validated computational fluid dynamic (CFD) method. Then, a correction factor K, considering its angle of attack (α), is proposed to modify this correlation. The results show that: (1) Nusselt number increases with the increase of Reynolds number, decreases as the length to diameter ratio changes from 2~6, and increases as the angle of attack changes from 0 •~2 0 • . (2) At higher Reynolds number, the calculated results are 30 percent higher than those of previous studies with α = 20 • . (3) Compared with α and e, the effect of Re on correction factor K can be ignored, and K is a strong equation of α and e. The efficiency of heat transfer is increased by 6 percent with α = 20 • . The findings of this paper provide a technical reference for the thermal control of a stratospheric airship.

Structural parameters optimization of submerged inlet using least squares support vector machines and improved genetic algorithm-particle swarm optimization approach, Engineering Applications of

A variable geometry auxiliary inlet for a wide-body aircraft environmental control system with moveable deflectors operating in a large mass flow rate range is studied through numerical simulation and wind tunnel tests, which yields a design method for the variable geometry auxiliary inlet with high performance. The characteristics of the flow field are studied by numerical simulation. The results show that the favorable pressure gradient and the roll-up vortices are the major impetus that inhales the incoming flow into the inlet. The law of regulation and the performance variation under different conditions are obtained by wind tunnel test. The flow coefficient increases first but then decreases with the increase in the inlet opening, and the pressure rise ratio and total pressure recovery coefficient increase first and then decrease with the increase in the mass flow rate. In general, under the condition of a high Mach number (Ma > 0.4), the inlet opening of this test configuration should not exceed 50%. The deflectors can maintain the normal work of the environmental control system by moving properly to control the mass flow rate of the auxiliary inlet.