This paper describes a class of nonlinear phenomena existing in the hypersonic flow and supersonic combustion process of scramjet engines:catastrophe,hysteresis and bifurcation,and further finds out the general rules(topological invariance)for the stability boundaries of mode transition in scramjet engines.With this topological invariance,a topological approach is put forward to model the stability boundaries,which may contribute to a complexity reduction of high-dimensional modeling when con-sidering more perturbation parameters,and help to explore the physical laws of the nonlinear phe-nomena.Accordingly,this paper interprets the characteristic of combustion mode transition based on the cusp topological model in singular theories,and observes the bifurcation characteristic in com-bustion mode transition.Moreover,a modeling approach is proposed to mathematically describe the stability boundaries of combustion mode transition in scramjet engines,and the model has high ac-curacy comparing to the simulation data,which proves the validation of the basic ideas proposed in this paper.Finally,future research directions are proposed.
A newly designed strut is proposed in this paper for fuel injection and flame holding in a liquid-kerosene-fueled supersonic combustor.The thickness of the strut is 8mm and the front blockage is about 8%.The characteristic of this strut is that extra oxygen can be injected through a set of orifices at the back of the strut,which can change the local flow field structure and ER(Equivalence Ratio).Based on the above mentioned strut,a stable local flame is generated at the back of the strut and the main combustion can be organized around this local fire.Numerical simulation is conducted to compare the local flow field distribution at the back of the strut with/without extra oxygen injection.Experiments are conducted to test the combustion characteristics based on this fuel injection and flame holding strategy.The temperature distribution which can reflect the local flame characteristic has been measured in the experiments conducted under cold incoming supersonic air flow condition.In addition,the overall combustion performance in a full-scale supersonic combustor has been evaluated in the experiments conducted under hot incoming supersonic air flow condition.Results show that this strut strategy is very promising since it can organize stable supersonic combustion at the center of the combustor without any cavity or rearward facing step.Besides that,even with the 8mm thick strut,the combustion can be stable in a wide range of ER from 0.25-1 by using liquid room-temperature kerosene.
Jichao HuJiang QinJuntao ChangWen BaoYouhai ZongQingchun Yang
In this paper, we investigate the approximation of completely resonant nonlinear wave systems via deterministic learning. The plants are distributed parameter systems (DPS) describing homogeneous and isotropic elastic vibrating strings with fixed endpoints. The purpose of the paper is to approximate the infinite-dimensional dynamics, rather than the parameters of the wave systems. To solve the problem, the wave systems are first transformed into finite-dimensional dynamical systems described by ordinary differential equation (ODE). The properties of the finite-dimensional systems, including the convergence of the solution, as well as the dominance of partial system dynamics according to point-wise measurements, are analyzed. Based on the properties, second, by using the deterministic learning algorithm, an approximately accurate neural network (NN) approximation of the the finite-dimensional system dynamics is achieved in a local region along the recurrent trajectories. Simulation studies are included to demonstrate the effectiveness of the proposed approach.
The problem of transient stability for a single machine infinite bus system with turbine main steam valve control is addressed by means of a novel adaptive backstepping method in this paper.The recursive design procedure of the proposed controller is much simpler than that of the existing controller based on conventional adaptive backstepping method.In the system,the damping coefficient is measured inaccurately,and the reactance of transmission line also contains a few uncertainties.A nonlinear robust controller and parameter updating laws are obtained simultaneously.The system does not need to be linearized,and the closed-loop error system is guaranteed to be asymptotically stable.The design procedure and simulation results demonstrate the effectiveness of the proposed design.
Liying SUN,Jun ZHAO (Key Laboratory of Integrated Automation of Process Industry,Ministry of Education,and School of Information Science and Engineering,Northeastern University,Shenyang Liaoning 110004,China)
In this paper,we investigate the identification of system dynamics of a completely resonant nonlinear wave sys...
Tao Peng is with the College of Automation Science & Engineering,South China University of Technology,Guangzhou 510640,China.Cong Wang is with the College of Automation Science & Engineering,South China University of Technology,Guangzhou 510640,China.
