Optimization of combined endoreversible Carnot heat engines with different objectives

Taking the output power, thermal efficiency, and thermo-economic performance as the optimization objectives, we optimize the operation parameters of a thermodynamic system with combined endoreversible Carnot heat engines in this paper. The applicabilities of the entropy generation minimization and entransy theory to the optimizations are discussed. For the discussed cases, only the entransy loss coefficient is always agreeable to the optimization of thermal efficiency. The applicabilities of the other discussed concepts to the optimizations are conditional. Different concepts and principles are needed for different optimization objectives, and the optimization principles have their application preconditions. When the preconditions are not satisfied, the principles may be not applicable.

Goal Programming for Stable Mode Transition in Tandem Turbo-ramjet Engines

This article, in order to guarantee the stable mode transition in tandem turbo-ramjet engines, investigates the multi-objective and multi-variable goal programming algorithm. First, it introduces the structural features of the variable cycle turbo-ramjet engines, the principles of selecting the mode transition operation point and the design parameters, and the characteristics of the turbofan mode and the ramjet mode. Second, a component-based variable cycle turbo-ramjet engine model is developed to simulate the mode transition process. Third, the Newton-Raphson algorithm is used to solve the multi-variable and multi-objective optimization problem. The results show that with the maximum residua of only 0.06%, this algorithm has an acceptable convergence that meets the predetermined goals. Finally, the simulation shows that the stable turbo-ramjet mode transition could be realized with the mode transition control law developed by the algorithm.

Recent research progress on airbreathing aero-engine control algorithm

Airbreathing aero-engines are regarded as excellent propulsion devices from ground takeoff to hypersonic flight,and require control systems to ensure their efficient and safe operation.Therefore,the present paper aims to provide a summary report of recent research progress on airbreathing aero-engine control to help researchers working on this topic.First,five control problems of airbreathing aero-engines are classified:uncertainty problem,multiobjective and multivariable control,fault-tolerant control,distributed control system,and airframe/propulsion integrated control system.Subsequently,the research progress of aircraft gas turbine engine modelling,linear control,nonlinear control,and intelligent control is reviewed,and the advantages and disadvantages of various advanced control algorithms in aircraft gas turbine engines is discussed.Third,several typical hypersonic flight tests are investigated,and the modelling and control issues of dual-mode scramjet are examined.Fourth,modelling,mode transition control and thrust pinch control for turbine-based combined cycle engines are introduced.Followed,significant hypersonic airframe/propulsion integrated system control is analysed.Finally,the study provides specific control research topics that require attention on airbreathing aero-engines.

Enhancing tylosin production by combinatorial overexpression of efflux,SAM biosynthesis,and regulatory genes in hyperproducing Streptomyces xinghaiensis strain

Tylosin is a 16-membered macrolide antibiotic widely used in veterinary medicine to control infections caused by Gram-positive pathogens and mycoplasmas.To improve the fermentation titer of tylosin in the hyperproducing Streptomyces xinghaiensis strain TL01,we sequenced its whole genome and identified the biosynthetic gene cluster therein.Overexpression of the tylosin efflux gene tlrC,the cluster-situated S-adenosyl methionine(SAM)synthetase gene metK_(cs),the SAM biosynthetic genes adoK_(cs)-metFcs,or the pathway-specific activator gene tylR enhanced tylosin production by 18%,12%,11%,and 11%in the respective engineered strains TLPH08-2,TLPH09,TLPH10,and TLPH12.Co-overexpression of metK_(cs)and adoK_(cs)-metFcs as two transcripts increased tylosin production by 22%in the resultant strain TLPH11 compared to that in TL01.Furthermore,combinational overexpression of tlrC,metK_(cs),adoK_(cs)-metFcs,and tylR as four transcripts increased tylosin production by 23%(10.93g/L)in the resultant strain TLPH17 compared to that in TL01.However,a negligible additive effect was displayed upon combinational overexpression in TLPH17 as suggested by the limited increment of fermentation titer compared to that in TLPH08-2.Transcription analyses indicated that the expression of tlrC and three SAM biosynthetic genes in TLPH17 was considerably lower than that of TLPH08-2 and TLPH11.Based on this observation,the five genes were rearranged into one or two operons to coordinate their overexpression,yielding two engineered strains TLPH23 and TLPH24,and leading to further enhancement of tylosin production over TLPH17.In particular,the production of TLPH23 reached 11.35 g/L.These findings indicated that the combinatorial strategy is a promising approach for enhancing tylosin production in high-yielding industrial strains.