Akira Nishizawa

Modeling of propeller electric airplane and thrust control using advantage of electric motor

Electrical airplanes (EAs) have become practical in the recent years. Considering the increase of demand on smaller aircraft and the attention to environmental issues, the demand on small EAs is expected to grow in the coming decade. However, the accident rate of small aircrafts is higher than that of larger aircrafts, so ensuring higher safety of EA is very urgent. In this paper, the new thrust control method based on new EA propeller plant is proposed. This method can be applied to new advanced flight control systems of EA, which can be expected to improve the safety of EA. The effectiveness of the proposed method is verified through simulations and experiments.

Range extension control system for electric airplane with multiple motors by optimization of thrust distribution considering propellers efficiency

In the recent years, attention has been gathered in the research field of electric airplanes (EAs), which have electric motors as a power source. EAs have many advantages including low environmental impact and safety. The flight range per charge, however, is shorter than that of conventional airplanes. This paper proposes a range extention control system (RECS) which extends the flight range of EAs by control. It is shown that the power consumption can be minimized by optimizing thrust distribution on multiple propellers with different properties. The effectiveness of the proposed method is verified by simulations and experiments.

Experimental investigation of the flow instability near the attachment-line boundary layer on a yawed cylinder

The behavior of small disturbances in a 3-D laminar boundary layer on a yawed cylinder was experimentally investigated. This setup simulates the flow around the leading edge of swept wings. Since multiple instability modes appear near the attachment-line region, a point-source disturbance was artificially introduced to separate these modes. Amplitude and phase distributions of the disturbances originating from the point source were measured using a hotwire probe near the attachment-line flow to test existing theoretical predictions. Hotwire measurements show that two instability modes definitely coexist and overlap in the middle portion of the wedge-shaped region developing downstream of the point source. Decomposition by 2-D fast Fourier transform (FFT) analysis enables us to separate one oblique wave from the other. One of the oblique waves belongs to the cross-flow instability mode, which travels to the attachment line and grows even at Reynolds numbers that are slightly lower than the critical Reynolds number for the attachment-line instability. The origin of the other mode is not identifiable, because it has peculiar characteristics different from both the streamline-curvature instability mode and the cross-flow instability mode. This mode decays in the downstream direction for all frequencies examined. By investigating the spatial characteristics of the small disturbance, the critical Reynolds number for cross-flow instability was successfully determined in the off-attachment-line region. The value, Rc = 543, was lower than the critical Reynolds number of Rc = 583 for the attachment-line flow. Furthermore, the critical frequency and wavenumber were in good agreement with existing predictions based on linear stability theory.

Dispersive Disturbances due to Cross-Flow and Streamline- Curvature Instabilities in 3-D Boundary Layers

Three-dimensional laminar boundary layers are susceptible to cross-flow instability and streamline-curvature instability, both of which lead to growth of longitudinal vortices. It is practically difficult to distinguish one instability mode from the other in the natural process of laminar-turbulent transition. Unlike plane-wave disturbances, however, the point-source disturbances evolve into dispersive development of their different components, which will result in separate appearance of two instability modes downstream of a point source. Continuous excitation from a small hole is applied to the boundary layer on a yawed circular cylinder evolving into a wedge-shaped pattern downstream of the hole, while a pulsed jet through a tiny hole is used to generate disturbances of a wave-packet type in the flow on a rotating-disk. Spatial development of localized disturbances corresponding to these experimental configurations can be described by linear stability analysis based on the complex ray theory. Comparison between experimental results and theoretical calculations shows qualitative and even quantitative agreement for either case.

Numerical Simulation on Active Separation Control of MEL001 Airfoil by MJVG

In order to obtain fundamental performances of the newly developed micro-jet vortex generator, MJVG, installed on MEL001 airfoil, a series of numerical simulation was carried out. MJVG is an array of continuous small jets and can generate single longitudinal vortex with arbitrary size and intensity. Main results in this study is summarized as follows: 1) Based on the experimental observation, gain in the work done by the lift due to MJVG seems to be promising, even including mechanical losses. 2) There were cases where MJVG actually brought appreciable increase in the lift / drag ratio. 3) At a certain condition, MJVG was found to be effective to suppress the fluctuation of the aerodynamic force acting on the body.