Papers by Keyword: Stall

Abstract: This computational study is aimed at studying the effects of flap deflection angle on aerodynamic coefficients of NACA 2412 airfoil and thus predicting the suitability of using the airfoil with flap at various phases of flight. The change in airflow over the airfoil at different angles of attack (0, 4, 8 and 12 degrees) and at different flap deflections give a clear understanding for the use of right combination of these two parameters. A full package of pictorial description for visualizing the changes in flow with and without the flap is provided through pressure and velocity contours.

Abstract: As a result of incorrect operation causing the stall of primary fan, the pressure of primary air continuously decreased. Therefore, the combustion stability in boiler has been disturbanced greatly, and the generation unit trips due to water-coal ratio imbalance. In this paper, the stall accident resulted from incorrect operation have been analyzed, and correct operation for the fan have been put forward. Namely, the precursory phenomena of stall can be found and eliminated. Correct operations can keep the pressure of primary air stable. It is concluded that adopting the suitable water-coal ratio and air-coal ratio are helpful to keep the unit on safe.

Abstract: To accurately depict the dynamic characteristics for aircraft stall by aerodynamic model, a Wavelet Neural Network (WNN) stall aerodynamic modeling method based on Particle Swarm Optimization (PSO) algorithm and Artificial Fish Swarm (AFS) algorithm is proposed. Numerical examples show that the proposed method has a good prediction precision, and it is also effective and feasible to build the aerodynamic model from flight data for aircraft stall.

Abstract: The simulations of a low-speed axial compressor rotor with two tip clearance sizes, 0.5% chord and 1.5% chord, were performed in the study. Overall performance and detailed flow fields at near stall condition are analyzed. The results show that the rotor stall occurs at higher mass flow condition with large tip clearance. For the small tip clearance the tip leakage vortex and the corner vortex both contribute significantly to the rotor stall, and the interaction between the vortices promotes the stall generation. While for the large tip clearance the tip leakage vortex plays a primary role, and the vortices interaction is ignorable.

Abstract: Static force measurement aerodynamic wind tunnel test data provided by the aircraft normally used to predict the stall characteristics, predicted aircraft deviated,spin Sensitivities, numerical simulation of aircraft stall, spin dynamics and so on. Based on practical flight, the paper analyzed the harm of limit state flight-spin to the flight safe, emphasized the static force test techniques at high angles of attack, and obtained a series of aerodynamic test date, managed them to spin prediction analysis.

Abstract: Every compressor has a stall line. In the vicinity of the stall line, the flow field is inherently unsteady due to the interactions between adjacent rows of blades, formation of small stall cells, flow separation and the viscous effects including shock-boundary layer interactions. These factors may aggravate to a state of local breakdown of flow or a total breakdown of flow or with a disastrous flow reversal. This paper starts with an overview on the previous researches about compressor stall and surge. Subsequently, it describes the effects of these instabilities in overall engine performance and design with/ without any control. The main objectives of this paper are to review the phenomenon of instability and methodology to suppress the rotating stall and surge by enlarging the stable operating range of compressor with the application of various control systems. This paper surveys research developments in this field and also tries to find an improved solution to increase the engine performance by applying various surge control strategies. Finally, the paper focuses on some recommendations towards a better design of compressor especially for aircraft power plant.

Abstract: The paper obtains motor pressure, flow and speed and the engine speed curves with time by theoretically analyzing closed hydraulic system of wheel walk engineering machinery and establishes a mathematical model of the system and AMESim simulation model. The simulation curves show that in some cases the external loads react against motor and drive motor speeding and then motor outlet flow increase that leads to the pressure of low-pressure side increasing and the pressure of high-pressure side reducing. The mutation of system pressure drives bump and engine speeding that equates to the engine speed is lower than the speed corresponding to the motor flow, which is engine stall problem. The simulation results show that the basic reason of engine stall is walking condition mutation leads to motor speeding and system pressure mutation and then motor reacts against bump and engine.

Abstract: Numerical method using HI and HOH meshing combined B - L turbulent model and S - A turbulent model separately based on the Rotor 37 compressor Rotor was applied to the steady flow. results on pressure characteristic curve, stall point forecast etc were compared with related experimental data. This paper discussed calculation precision influenced by the turbulence model and numerical computation grid. This numerical investigation was basis for subsequent compressor internal flow field study.