| Improving gas turbine cycle thermal efficiency has become a research hotspot in the field of energy and power nowadays.The traditional gas turbine based on the Brayton cycle has a large entropy change in combustion process,which greatly limits the further improvement of cycle thermal efficiency.Rotating detonation combustion has the advantages of constant volume combustion,such as self-pressurization,low entropy change and low pollutant generation.The gas turbine with rotating detonation combustion technology may achieve the high cycle thermal efficiency of constant volume combustion cycle,and the inherent advantages of small volume,light weight,high unit-power,small vibration and low noise.However,the research on rotating detonation combustion technology of gas turbine is still in the initial stage.Systematic research on the characteristic parameters of rotating detonation combustor and theoretical research of rotating detonation gas turbine cycle are still insufficient.Therefore,further research on the basic characteristic and construction of overall performance prediction model of rotating detonation combustor are of great theoretical significance and academic value for improving the thermodynamic cycle model of rotating detonation gas turbine and promoting technological revolution of gas turbine cycle.In this paper,the numerical study on hydrogen-air and methane-air rotating detonation combustion field and the experimental study on hydrogen-air rotating detonation combustor were carried out to analyze the influence of the controllable boundary conditions including inlet air conditions and structure size on basic characteristic of rotating detonation combustion field,establish mathematical model of rotating detonation combustor,and systematically investigate the cycle characteristics of rotating detonation gas turbine.The main research is as follows:(1)A series of experimental study on hydrogen-air rotating detonation combustion and numerical study on hydrogen-air and methane-air rotating detonation combustion was carried out to explore the development process and pressurized characteristic of rotating detonation combustion field.In the experiment,the maximum velocity of hydrogen-air rotating detonation wave was 1456.1m/s at air inlet total pressure of 430 k Pa,and there was an unstable development stage after ignition in rotating detonation combustor.In the further numerical study,it was found that: There were three types of collisions in unstable stage of hydrogen-air rotating detonation combustor,including detonation waves collision,shock waves collision,collision between detonation wave and shock wave.The relatively stable field gradually formed after collision between detonation wave and shock wave,while quenching happened after detonation waves collision.Direction turning ramdomly of reinitiation detonation wave was ascribed to the emergence and development of local high pressure area after quenching.In the methane-air rotating detonation combustor,there existed two types of collision in unstable stage,including collisions between detonation wave and shock wave/flame surface.But there was no quenching phenomenon,and oblique shock wave appeared after collision between detonation wave and flame surface.(2)The pressurized characteristic of rotating detonation combustor was directly related to entropy change and Gibbs free energy change.The complex wave system in the rotating detonation combustion field(oblique shock wave,transmist shock,deflagration zone,etc.)led to an obvious entropy increase after the pressurization process of detonation combustion.In the calculated condition,the pressurization ratio of the rotating detonation combustor was 2.0664,which was significantly different from that of constant volume combustion(5.6278).(3)To further explore the change rule of detonation combustion characteristics,systematic research on the characteristic parameters of methane-air rotating detonation combustor in different inlet total pressures,inlet total temperatures,inlet equivalence ratios and axial sizes was carried out by numerical simulation based on two-dimensional Euler equations.It was found that: Pressurized ratio had positive relationship with inlet equivalence ratio,negative relationships with inlet total temperature and axial size,and almost no relationship with inlet total pressure.Specific mass flow rate had positive relationship with inlet total pressure,negative relationships with inlet total temperature and inlet equivalence ratio.Combustion thermal efficiency had a little change in all calculated conditions,all more than 99.5%.(4)Based on the research on generation mechanism and influencing factors of methane-air rotating detonation combustion pressurized characteristic,directly mixing rotating detonation gas turbine cycle scheme and interstage bleeding rotating detonation gas turbine cycle scheme were proposed.Combined with numerical calculation of rotating detonation combustor and simulation calculation of gas turbine cycle simulation,the influences of the six factors including compressor pressure ratio,compressor efficiency,turbine efficiency,turbine inlet total temperature,combustor inlet equivalence ratio and interstage bleeding position on cycle characteristics of rotating detonation gas turbine were researched using control variate method in different limited conditions(constant methane mass flow rate,constant turbine inlet total temperature and constant combustor flow area).Moreover,the sensitivity analysis work of the six influencing factors was also carried out.The results showed that both the two schemes had significantly improvement on cycle thermal efficiency and cycle net power compared with those of traditional gas turbine,and the former scheme had better effect.With the same variational range of each factor,turbine efficiency and interstage bleeding position had the greatest influence on increments of cycle thermal efficiency and cycle net power,while combustor inlet equivalence ratio had the least influence.(5)Mathematical model of rotating detonation combustor was established based on variation of pressurized characteristics of rotating detonation combustor,and cycle computing model of methane-air rotating detonation gas turbine finally established in this paper.It was found that: At turbine initial temperature of 1450 K,cycle thermal efficiency and cycle net work of rotating detonation gas turbine reached 0.3859 and 10966.0k W,respectively increased by 0.0248(6.87%)and 1304.4k W(13.50%)compared with those of traditional gas turbine.Meanwhile,compressor pressure ratio decreased by 2.2324(15.95%).With decrease of the load,the increments of cycle thermal efficiency and cycle net work gradually increased while the decrement of compressor pressure ratio reduced.At turbine initial temperature of 1279 K,increments of cycle thermal efficiency and cycle net work respectively reached 0.0539(17.92%)and 1603.2k W(25.76%).In addition,the influences of combustor flow area and ambient temperature on cycle characteristic parameters of the rotating detonation gas turbine was investigated.Furthermore,cycle characteristic parameter increment variation qualitative computational method was summited to qualitatively analyze the change trend of cycle characteristic parameter increments in different working conditions.Overall,all results showed that cycle characteristic parameters of rotating detonation gas turbine had significant advantages over those of traditional gas turbine in different working conditions. |
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