The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detona...The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detonation engines,and rotating detonation engines.The RRDE organizes the processes of reactant compression,detonation combustion,and burned gas expansion in a single rotor,allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers,thus significantly improving the total pressure gain of the propulsion system.The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations.The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity,the rotor rim velocity,and the equivalence ratio of reactant.Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE.Once the inlet velocity exceeds the critical value,the engine cannot achieve positive total pressure gain.Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE.Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities.While at higher inlet velocities,increasing the equivalence ratio may reduce the total pressure gain.Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters.The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range.This study provides the preliminary theoretical basis and design reference for the RRDE.展开更多
DEA(data envelopment analysis) models can be divided into two groups: Radial DEA and non-radial DEA, and the latter has higher discriminatory power than the former. The range adjusted measure(RAM) is an effective and ...DEA(data envelopment analysis) models can be divided into two groups: Radial DEA and non-radial DEA, and the latter has higher discriminatory power than the former. The range adjusted measure(RAM) is an effective and widely used non-radial DEA approach. However, to the best of our knowledge, there is no literature on the integer-valued super-efficiency RAM-DEA model,especially when undesirable outputs are included. We first propose an integer-valued RAM-DEA mode with undesirable outputs and then extend this model to an integer-valued super-efficiency RAM-DEA model with undesirable outputs. Compared with other DEA models, the two novel models have many advantages: 1) They are non-oriented and non-radial DEA models, which enable decision makers to simultaneously and non-proportionally improve inputs and outputs;2) They can handle integer-valued variables and undesirable outputs, so the results obtained are more reliable;3) The results can be easily obtained as it is based on linear programming;4) The integer-valued super-efficiency RAM-DEA model with undesirable outputs can be used to accurately rank efficient DMUs. The proposed models are applied to evaluate the efficiency of China’s regional transportation systems(RTSs) considering the number of transport accidents(an undesirable output). The results help decision makers improve the performance of inefficient RTSs and analyze the strengths of efficient RTSs.展开更多
基金support from the National Natural Science Foundation of China(No.52306152)the China Postdoctoral Science Foundation(No.2023M731912)。
文摘The study presents a new type of detonation engine called the Ram-Rotor Detonation Engine(RRDE),which overcomes some of the drawbacks of conventional detonation engines such as pulsed detonation engines,oblique detonation engines,and rotating detonation engines.The RRDE organizes the processes of reactant compression,detonation combustion,and burned gas expansion in a single rotor,allowing it to achieve an ideal detonation cycle under a wide range of inlet Mach numbers,thus significantly improving the total pressure gain of the propulsion system.The feasibility and performance of RRDE are discussed through theoretical analysis and numerical simulations.The theoretical analysis indicates that the performance of the RRDE is mainly related to the inlet velocity,the rotor rim velocity,and the equivalence ratio of reactant.Increasing the inlet velocity leads to a decrease in the total pressure gain of the RRDE.Once the inlet velocity exceeds the critical value,the engine cannot achieve positive total pressure gain.Increasing the rim velocity can improve the total pressure gain and the thermodynamic cycle efficiency of RRDE.Increasing the equivalence ratio can also improve the thermodynamic cycle efficiency and enhance the total pressure gain at lower inlet velocities.While at higher inlet velocities,increasing the equivalence ratio may reduce the total pressure gain.Numerical simulations are also performed to analyze the detailed flow field structure in RRDE and its variations with the inlet parameters.The simulation results demonstrate that the detonation wave can stably stand in the RRDE and can adapt to the change of the inlet equivalence ratio within a certain range.This study provides the preliminary theoretical basis and design reference for the RRDE.
基金Supported by the National Natural Science Foundation of China(71862026)the China Postdoctoral Science Foundation(2018T110209)+2 种基金the Natural Science Foundation of Inner Mongolia(2018MS07006)the“13th Five Year”Plan of Educational Science Research in Inner Mongolia(NGJGH2018016)the State Scholarship Fund of China Scholarship Council(20180815502)。
文摘DEA(data envelopment analysis) models can be divided into two groups: Radial DEA and non-radial DEA, and the latter has higher discriminatory power than the former. The range adjusted measure(RAM) is an effective and widely used non-radial DEA approach. However, to the best of our knowledge, there is no literature on the integer-valued super-efficiency RAM-DEA model,especially when undesirable outputs are included. We first propose an integer-valued RAM-DEA mode with undesirable outputs and then extend this model to an integer-valued super-efficiency RAM-DEA model with undesirable outputs. Compared with other DEA models, the two novel models have many advantages: 1) They are non-oriented and non-radial DEA models, which enable decision makers to simultaneously and non-proportionally improve inputs and outputs;2) They can handle integer-valued variables and undesirable outputs, so the results obtained are more reliable;3) The results can be easily obtained as it is based on linear programming;4) The integer-valued super-efficiency RAM-DEA model with undesirable outputs can be used to accurately rank efficient DMUs. The proposed models are applied to evaluate the efficiency of China’s regional transportation systems(RTSs) considering the number of transport accidents(an undesirable output). The results help decision makers improve the performance of inefficient RTSs and analyze the strengths of efficient RTSs.
