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Abstract To explore an effective way for the nozzle design of a pulse detonation rocket engine (PDRE), theoretical and experimental researches have been carried out. The exhaust process and optimal converging/diverging area ratios of a nozzle were theoretically analyzed. Pressure and velocity fluctuations of the exhaust flow were considered to be the major issues. A fluidic solution which employs nitrogen flows in the nozzle throat and divergent section has been tested. The fluidic nozzle is able to adjust the effective area ratios according to the incoming flow. The effective convergent area ratio varied from 2.0 to 2.2, and the divergent one varied from 5.0 to 1.8. It is proved that the fluidic nozzle effectively improved the propulsive performance of the engine. A maximum average thrust increase of 137.8% was obtained in proper conditions. Highlights • A key-points nozzle design method for the PDRE was carried out. • Effect of a fluidic nozzle on the propulsive performance of a PDRE was validated. • Thrust and specific impulses were discussed in details. [ABSTRACT FROM AUTHOR]

To provide preferable operating conditions for biomass carbonization, the carbonization properties of maize straw, cotton stalk and poplar wood were investigated in nitrogen atmosphere by segmented heating process at different final temperatures of 300–800 °C for 1 h. Segmented heating carbonization contributes to higher ratio of mass and energy yields than a constant temperature/linear heating process with final temperature of around 300 °C. The fuel properties and characteristics of raw and carbonized biomass were analysed systematically. Increasing carbonization temperature, the fuel ratios of the obtained chars rise exponentially, and the profile of atomic H/C ratio versus atomic O/C ratio approximately decreases linearly. There are small changes of sulphur and nitrogen content in the chars. To provide an estimation method for higher heating value for torrefied/carbonized biomass, a new correlation is proposed based on ultimate analysis. The correlation is H H V = 19.9579 + 0.1284 C + 0.3355 H − 0.1209 O − 1.3836 N − 5.4680 S , which is validated through experimental data. The correlation has a low level of errors, that the correlation efficient, mean absolute error, average absolute error and average bias error are 0.971, − 6.75 × 10 − 6 MJ, 1.2% and 0.02% respectively. This work will make a contribution to the biomass pretreatment process. [ABSTRACT FROM AUTHOR]