Fuzzy logic controller design with unevenly-distributed membership function for high performance chamber cooling system

Fuzzy logic controller adopting unevenly-distributed membership function was presented with the purpose of enhancing performance of the temperature control precision and robustness for the chamber cooling system.Histogram equalization and noise detection were performed to modify the evenly-distributed membership functions of error and error change rate into unevenly-distributed membership functions.Then,the experimental results with evenly and unevenly distributed membership functions were compared under the same outside environment conditions.The experimental results show that the steady-state error is reduced around 40% and the noise disturbance is rejected successfully even though noise range is 60% of the control precision range.The control precision is improved by reducing the steady-state error and the robustness is enhanced by rejecting noise disturbance through the fuzzy logic controller with unevenly-distributed membership function.Moreover,the system energy efficiency and lifetime of electronic expansion valve(EEV) installed in chamber cooling system are improved by adopting the unevenly-distributed membership function.

Thermal-structural analysis of regeneratively-cooled thrust chamber wall in reusable LOX/Methane rocket engines

To predict the thermal and structural responses of the thrust chamber wall under cyclic work,a 3-D fluid-structural coupling computational methodology is developed.The thermal and mechanical loads are determined by a validated 3-D finite volume fluid-thermal coupling computational method.With the specified loads,the nonlinear thermal-structural finite element analysis is applied to obtaining the 3-D thermal and structural responses.The Chaboche nonlinear kinematic hardening model calibrated by experimental data is adopted to predict the cyclic plastic behavior of the inner wall.The methodology is further applied to the thrust chamber of LOX/Methane rocket engines.The results show that both the maximum temperature at hot run phase and the maximum circumferential residual strain of the inner wall appear at the convergent part of the chamber.Structural analysis for multiple work cycles reveals that the failure of the inner wall may be controlled by the low-cycle fatigue when the Chaboche model parameter c3= 0,and the damage caused by the thermal-mechanical ratcheting of the inner wall cannot be ignored when c3〉 0.The results of sensitivity analysis indicate that mechanical loads have a strong influence on the strains in the inner wall.

Numerical simulation of temperature and relative humidity in zero energy cool chamber

Temperature and relative humidity are important parameters that can affect the storage of food in a zero energy cool chamber(ZECC).The distributions of average temperature and relative humidity are influenced by factors such as chamber size,water temperature,load weight and filler thickness.In this research,thermal environment analysis using numerical simulation of biological respiration was conducted for tomatoes stored in a ZECC.The ZECC was composed of inner and outer brick walls,filler(a mixture of sand and zeolite),water between the walls and a shading curtain.The results obtained from the numerical model were compared by setting different values for each factor.The following conclusions are drawn after comparison and analysis of results:(1)the distributions of average temperature and relative humidity are strongly related to the thickness of the filler–a thicker filler causes a lower temperature;(2)the water temperature in the filler exerts little influence on the average temperature and relative humidity;and(3)the lowest temperature and the highest relative humidity can be achieved with a chamber size of 0.6 m and a load weight of 30 kg.In addition,to validate the results of the numerical model,the simulation results are compared with experimental data,which show good agreement.It is confirmed that numerical simulation can be satisfactorily applied to predict the distribution of environmental parameters such as temperature and relative humidity in a cool chamber.