Calculation of Wall Temperature for Aircraft Exhaust System with Considering Gas Radiation Heat Transfer

The coupled numerical simulation of flow field, solid temperature field, species concentration field and gas radiation transfer/ energy field based on statistical narrow-band correlated-k （SNBCK） model, is employed to accurately predict aerothermodynamic characteristic of aircraft exhaust system. A series of methods to increase computational efficiency and descend computational resources make it possible to finish the calculation in PC. The parameters of narrow-band model are evaluated by HITEMP line-by-line database. Three examples have proved the accuracy of using these methods to solve flow heat transfer coupled problem and radiation transfer/energy equation, which are the calculation of temperature distribution of water-cooling nozzle in rocket engine, the calculation of carbon dioxide absorptivity at 4.3 micron band, and the gas radiation heat transfer evaluation of the cylindrical furnace. Finally, the inner flaps temperature distribution of ejecting nozzle with floating outer flaps is computed, under high-altitude, high-speed and afterburning conditions. Two completely different air-inlet schemes of ejecting channel almost achieve the same effect in cooling inner flaps.

Vector deflection stability control of aero-engine based on linear active disturbance rejection

Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle(AVEN),a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control(LADRC)is proposed.Firstly,based on CFD numerical simulation,aerodynamic performance model of AVEN is established,and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed.Subsequently,the integrated model of AVEN/-turbofan engine is established by Simulink/AMESim co-simulation.Finally,the nozzle throat area control loop based on LADRC is designed.The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system.The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%,indicating a high degree of confidence.Compared with the conventional PID control,the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%,which effectively improves the control stability of the vector deflection.Meanwhile,the fuel flow ratechange during the vector deflection process is smaller and more economical,which provides an important reference for engineering applications.

High Efficient Numerical Simulation of Infrared Radiation from a Hot Exhaust Nozzle

A coupled model,capable of simulating transonic flow,solid heat conduction,species transport,and gas radiation,is developed that provides better computational treatment of infrared radiation from hot exhaust nozzles.The modeling of gas radiation is based on a statistical narrow-band correlated-k analysis,whose parameters are deduced from the HITEMP line-by-line database.To improve computational efficiency,several methods are employed.A mixed analytical-numerical algorithm is described for the stiffness of the two-equation turbulence model and an alternating direction implicit pretreatment for the ill-conditioned matrix appearing in the coupled problem of flow and solid heat conduction.Moreover,an improved multigrid method and a symmetry plane treatment of the radiation transfer-energy equations are also introduced.Four numerical simulations are given to confirm the efficiency and accuracy of the numerical method.Finally,an account of the aerothermodynamics and infrared characteristics for two types of nozzles are presented.The infrared radiation intensity of the Chevron ejecting nozzle is clearly smaller than that of the common axisymmetric ejecting nozzle.All computations can be performed on a personal computer.

Estimation of Exhaust Gas Temperature of the Rocket Nozzle using Hybrid Approach

In this paper the theoretical model is built for ZEpHyR(ZARM Experimental Hybrid Rocket) main engine which is being developed at ZARM institute,Bremen,Germany.The theoretical model is used to estimate the temperature of exhaust gas.The Conjugate Gradient Method(CGM) with Adjoint Problem for Function Estimation iterative technique is used to solve the Inverse Heat Conduction Problem(IHCP) to estimate the heat flux and internal wall temperature at the throat section of the nozzle.Bartz equation is used to calculate the convective heat transfer coefficient.The exhaust gas temperature is determined using the estimated heat flux,the wall temperature at internal surface of nozzle and the heat transfer coefficient.The accuracy of CGM iterative scheme to solve the IHCP is also investigated and its results are presented.