Instantaneous secondary flows

The outline of this paper is as follows. First, a theoretical model of unsteady motions in a combustion chamber with feedback control is constructed. The formulation is based on a generalized wave equation which accommodates all influences of acoustic wave motions and combustion responses. Control actions are achieved by injecting secondary fuel into the chamber, with its instantaneous mass flow rate determined by a robust controller. Physically, the reaction of the injected fuel with the primary combustion flow produces a modulated distribution of external forcing to the oscillatory flowfield, and it can be modeled conveniently by an assembly of point actuators. After a procedure equivalent to the Galerkin method, the governing wave equation reduces to a system of ordinary differential equations with time-delayed inputs for the amplitude of each acoustic mode, serving as the basis for the controller design. 

In most of the early PUT attempts, the streaming velocities did not evolve continuously over time instead, they were instantaneous quantities that were freshly reassigned at each time step of the simulation. Such PUT procedures, however, might introduce other problems. At one extreme, PBTs interpret all secondary flows as thermal fluctuations and therefore weaken them. In the other extreme, if the u j s in a PUT scheme are heavily influenced by the... 

The instantaneous velocity field measurements indicate that a secondary stream, travelling in the direction opposite to the primary flow, is established within the collar to create the countercurrent shear layer. The dynamics of the countercurrent shear layer is conducive to the stabilization of the premixed jet flame up to... 

Be capable of providing post-tranalent shutdown flow requirements Indefinitely> assuming Instantaneous loss of power to the primary cooling system and concurrent loss of flow In the secondary cooling system. 

The laser Doppler technique samples the flow velocity at discrete times corresponding to the passage of a particle through the intersection volume. The velocity sampled at these times can be considered as a primary measurement quantity or raw data. The derivation of flow parameters or secondary measurement quantities, such as mean flow velocity, turbulence level or turbulence spectra, requires further data processing. The statistical quantities most frequently computed from the measured instantaneous velocity data are the mean (number or time average) particle velocity components (vi), the standard deviation (a ) and the turbulent intensity (/ ). The index i denotes the axis direction, thus i = 1,2,3. 

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