Characteristics, in particular synchronous reactance, of the aircraft AC generator have important effects not only on the dynamic stability of the aircraft AC generating system, but on the weight of the generator. This paper gives the relation of the synchronous reactance to the weight of the generator First, the electrical magnetic weight (EMW), i.e. sum weight of the electrical winding and the magnetic iron core is discussed as a function of the synchronous reactance. Second, theoretical formula is obtained for the synchronous reactance to minimize the EMW. Last, the total weight (TW) of the generator is examined upon the data of several present-use generators and the empirical formula expressing the TW is obtained as a function of cooling constant, speed, output capacity and the synchronous reactance. The purpose of this paper is to assist system engineers or users of the aircraft AC generating system in finding the best generator for their particular application.
An experimental study was made to investigate the mixing and NOx formation in a swirlstabilized, diffusion-type flame in a model combustor operating at lean fuel/air ratios. The city gas was injected from a fuel injector into an air flow passed through a swirler. The temperature, stable species and NOx concentration profiles in the combustor were measured over a range of air flow velocities through the swirler from 5 to 20m/s, fuel injection velocities from 36.4 to 145.4m/s, overall equivalence ratios Φ from 0.2 to 0.8 and nominal fuel injection angles from 60° to 180°. The effects of these parameters on NOx concentration in the flame zone and the emission level of NOx from the combustor were discussed. The effects of mixing rates were also estimated by examination of the local equivalence ratio profiles across the flame zone. In general, the flame clearly showed the characteristics of a fuel jet flame near the fuel injector. The temperature and the concentration profiles across the main flame zone and the recirculation zone change considerably with change in Φ. In the case of comparatively low value of Φ, it was shown that the high mixing rate had the effect of lowering the local equivalence ratio in the flame zone and the combustion gas temperature early in the post-flame zone. Then, the emission levels of NOx can be reduced by achieving high mixing rate due to the increase of air flow velocity and the variation of the fuel injection angle, at the expense of slight increase of the emission levels of CO. The minimum emission level of NOx obtained is 0.23g NO2/kg fuel at Φ of 0.2. Although the emission levels of NOx from the present combustor are still higher than those from lean premixed system, they were found to be much lower than those from conventional diffusion flame combustor.
The transien tresponse of beams subjected to transverse impact loading is investigated. The constitutive equations describing elastic/viscoplastic properties of materials are used in the analysis. The interaction between bending moment and shear force, and rates of strain in the plastic range are included in the constitutive equations. Rotatory inertia and shear deformation are considered in the equations governing the motion of the beam. Numerical solutions are obtained by the method of characteristics for the impact problem of beams and compared with experimental results. The following conclusions were derived: 1) The present analysis based on the methods of characteristics provides a reasonably good description of the process of the high velocity deformation on beams. 2) The shape of the yield surface does not critically affect the dynamic response of beams subjected to transverse impact loading.
The constitutive equations are formulated from the rate dependent mechanical models which express the elastic-viscoplastic and the elasticviscoplastic-plastic materials. Wave propagations are analyzed for the one dimensional stress bar experiment by using the constitutive equations. Comparisons are made for the stress as well as the strain with the experimental data. It may be concluded that annealed copper possesses both noninstantaneous and instantaneous plastic properties.
The present paper concerns itself with a numerical approach to a linear optimal control problem with a quadratic performance index. In the present technique, the augmented performance index is discretized within each time element through the ordinary finite element technique and all of the necessary conditions for the performance index to be stationary are obtained in the form of algebraic equations. The main advantages of the present method are: 1) the problem is treated throughout without loss of linearity, 2) the state variables are eliminated from the performance index and the problem is reduced to the simple one of finding the sequence of the control variables alone, 3) the matrices which appear in the formulation are sparsely populated, so the computing time to obtain the solution is reduced. A general formulation is given and some numerical examples are shown to demonstrate the effectiveness of the present approach.