The classifications and characteristics of deep-sea underwater vehicles are introduced， then the way in which the propulsive force of each deep-sea underwater vehicle is generated is analyzed respectively， and the main types and characteristics of the thrusters of deep-sea underwater vehicles are summarized. Altogether， the configuration and structural characteristics of 5 typical types of deep-sea underwater vehicle thrusters are introduced. And according to the characteristics of failure mode of the thruster’s failure， six types of common failure modes， incentives and common diagnostic methods of deep-sea underwater vehicle thrusters are presented. Qualitative analysis of diagnostic methods， analytical model diagnosis methods and signal processing diagnosis methods are used to summarize current research progress of fault diagnosis technology for deep-sea underwater vehicle thrusters， and the suggestions for the development of deep-sea underwater vehicles and their failure diagnosis technologies are put forward.

Gearbox is one of the main vibration sources of the ship's power transmission system. In order to study the vibration performance and optimization measures of the ship gearbox， and then realize the low noise of the ship， taking a ship gearbox as an example， through combining bench test and vibration spectrum analysis， the main factors affecting the vibration of the gearbox are analyzed， and the relevant key factors are optimized and improved. According to the results of vibration analysis， the gearbox is optimized from two aspects： gear modification design and improvement of hydraulic oil supply system. And after taking optimization measures the gearbox is verified by vibration test and vibration spectrum analysis. The results show that the vibration performance of gearbox has been effectively improved by gear modification and hydraulic oil supply system improvement. In the case of this paper， after gear modification， the vibration peak value at gear meshing frequency is reduced by 40.2% and the total vibration level is reduced by 1.85dB. After further measures of hydraulic oil supply system improvement， the total vibration level of gearbox is reduced by 9.99dB. Gear modification and hydraulic oil supply system improvement have engineering application value for improving vibration performance of ship gearbox.

The design and development process of YF-77， a 50-ton LOX/LH ₂ rocket engine for Long March 5 launch vehicle is introduced systematically in this paper. Firstly， by analysing the characteristics of LOX/LH ₂ rocket engine and the development status of LOX/LH ₂ rocket engine at home and abroad， the technical route of the new generation launch vehicle and the development background of the 50-ton LOX/LH ₂ rocket engine are described. Then， the overall technical scheme and characteristics of the 50-ton LOX/LH ₂ rocket engine are analysed and summarized， and on this basis， the technical specifications of the main components of the engine are analysed. Then， the test run of the engine， reliability verification and troubleshooting of the engine are analysed. Finally， the development and technical characteristics of the 50-ton LOX/LH ₂ rocket engine are summarized， and the development of LOX/LH ₂ rocket engine and LOX/LNG engine in China is prospected.

In this paper,the energy and the combustion characteristics of ammonium pe-rchlorate/nitramine composite propellants were theoretically analysed and experimentally examined.A range of composition was provided for studyingthe formulation of high energy,low ablation,minimum smoke,low pressure exponent propellants as well as low burning rate gas producer.It was also pointed out that problem of DDT does not exist for the nitramine composite propellants.

In order to acquire a better understanding of atomization characteristics under oscillating backpressure conditions, as to gas liquid shear coaxial injector, impinging jet injector and swirl injector that are widely used in liquid rocket engines, the present study reviews recent advances of atomization characteristics of a single liquid jet, gas liquid shear jet, impinging jets, and swirling flow under oscillating backpressure conditions. The main action mechanism of backpressure oscillations on atomization is summarized. Also some problems that existed in previous studies and the key technology that needs breaking through are interpreted. By the review it is concluded that oscillating backpressure affects the atomization field mainly by two ways. One way is to change pressure drop to influence injection thus to affect the atomization process. The other way is to affect atomization directly by oscillating gas field. Plenty of work still needs to be done to study atomization characteristics under oscillating backpressure conditions while some technical difficulties below should be overcome. As for the experiments, backpressure capsule that can generate high-amplitude and high-frequency oscillating backpressure is demanded. At the same time, the disturbance to the atomization field should be at the least. Advanced optical diagnostic apparatus is demanded to acquire atomization field information in the backpressure capsule. As for the simulation, high-fidelity numerical simulation of atomization should be carried out. Also the generation, development, and propagation of pressure wave should be studied. The interaction between oscillating backpressure and atomization field should be investigated based on the two points mentioned above.

To investigate the pressure pulsation characteristics of underwater supersonic jet flow field and the force characteristics on the floating mine， based on the VOF （Volume of fluid） multiphase flow model， a numerical model of supersonic gas jet under different working conditions（under-expansion， full-expansion， over-expansion） was established to study force characteristics on the floating mine. The results show that under the under-expansion condition， the thrust of the engine is gentle and the average thrust is about 12.2kN， and the force on the floating mine has never been negative. Under the full-expansion condition， the positon where necking and bulging of the gas jet occur is far away from the mine body， which weakens violently thrust oscillation of the engine and the vibration of the force on the shell of the floating mine. Under the over-expansion condition， the positon where necking and bulging of the gas jet occur is close to the nozzle， and the thrust of engine pulsates violently， generating 21.7% of the oscillation amplitude. When bulging occurs， the pressure in the flow field significantly reduces， which reduces the force on the rear body of the floating mine， and increases the resistance of the shell. The maximum negative thrust of the floating mine is 27kN.

To study the effects of oxygen concentration on the ignition performance of zirconium powder, the combustion process of zirconium powder was observed by CO ₂ laser ignition bench, high-speed camera, two-color infrared thermometer and fiber optic spectrometer. The ignition delay time, combustion time, combustion intensity and combustion temperature parameters during the combustion of zirconium powder were obtained. Subsequently, the phase characteristics of the combustion products were analyzed by XRD. It is known from the experimental results that the combustion process of zirconium powder can be divided into four stages: lighting, intense combustion, stable combustion and flame extinction according to the flame shape. The oxygen concentration has an important influence on the ignition and combustion performance of zirconium powder. The ignition delay times of zirconium powder in the four working conditions of C1~C4 are 15ms, 17.5ms, 22.5ms and 25ms, respectively. The combustion temperatures are 1542℃, 1520℃, 1425℃ and 1405℃, respectively. Therefore, increasing the oxygen concentration is beneficial to shorten the ignition delay time and combustion time, increase the combustion temperature and combustion intensity, and improve the ignition and combustion performance of the zirconium powder. As the oxygen concentration increases, the flame size, flame brightness and combustion intensity show an increasing trend. At the same time, it was found that the main phase of the combustion product of zirconium powder at four different oxygen concentrations is ZrO ₂, and no phase such as ZrN and ZrC is produced.

In order to understand the internal ballistic performance of the hot water rocket engine, the experiment was performed in different initial pressure, different spray pipe diameter and different water added. Through the experiment, the working data of the engine under different conditions were obtained. Through the analysis of the data, four working stages of the engine were put forward,which were initial segment, transition segment, approximately linear segment and a trailing segment,respectively.The influence law of the initial pressure, nozzle diameter, the amount of water added on the internal ballistic performance of the engine were obtained. Meanwhile,it has been found that in the engine working process, the pressure curves experience a sharp decline first and then slow drop, but when the initial pressure is lower, the pressure curve in the transition period would experience a short rise first then decrease fluctuation. And it is observed that the specific impulse of the hot water rocket engine is greatly influenced by initial pressure, but has nothing to do with spray pipe diameter or water added and the thrust calculation formula of the conventional rocket engine is not suitable for hot water rocket engine. 

On the basis of comparison with experimental data verifying the reliability of model， two-dimensional axisymmetric numerical model with secondary combustion and trail cover movement was established for double pressure peaks shock of missile low-temperature gas-ejection. The flow field mechanism of the ring cavity smoothing missile bottom pressure curve was studied， and the influence of structural parameters on the pressure impact smoothing effect was analyzed by decoupling， and the idea of ordinal optimization was put forward. The numerical results show that the ring cavity with the function of storage of oxygen can effectively prevent gas from diffusing upward， making the secondary combustion expand along the time dimension， thereby smoothing the impact of missile bottom. After the arrangement height and annular radius of ring cavity are established by geometric constraints of initial chamber space， the length can be taken as the main structural parameters to control the curve of missile bottom pressure， and expansion or contraction of angle as the structure parameter to fine tune， then the pressure curve can approximate the ideal design curve. After arranging the optimal ring cavity， the peak acceleration is reduced by 9.26%， and out of the cylinder speed is reduced by 4.13%， and out of the cylinder time is extended by 2.5%.

High power nuclear electric propulsion (NEP) highly integrates space nuclear reactor and high power electric propulsion technologies, with the advantages of high power density, very high specific impulse and high thrust, which can be applied for large interplanetary missions, such as orbital transfer task of super large spacecraft, robotic interplanetary missions and manned Mars exploration, greatly enhancing human ability in deep space exploration. This paper presents the principle and system configuration of high power NEP system, and summarizes the progress of several critical techniques. Moreover, both research process and recent development in worldwide are also outlined.

Experimental and numerical investigations were conducted in order to obtain the characteristics of kerosene mist in supersonic/subsonic mixing layer. The spatial distribution and droplet diameter of mist were recorded by pulse exposure photography of particle image velocimetry system while the motion and droplet diameter distribution of mist were obtained by a commercial software Fluent. Results show that the spatial distribution of the mist along streamwise direction is comprised of cross jet region including cross jet breakup stage and entraining diverting stage， and mixing layer region which covers shear breakup stage and droplet tracing stage. The shape of spatial distribution in streamwise cross sections changes from circle to ellipse. The Sauter mean diameter （ SMD） of droplets decreases from 400μm to 65μm. The cross-jet breakup stage and shear breakup stage are the two main stages reducing the SMD. The large velocity gradient of the supersonic/subsonic mixing layer is beneficial to the droplet breakup， especially for larger diameter droplets.

Numerical simulations and experiments of a Ma 9 oblique detonation engine were conducted to study the combustion mechanism of oblique detonation engines. Firstly， a full-scale engine model with a length of 2.8m was designed. The engine inlet is a two-stage compression inlet composed of two 15°-inclined ramps. The hydrogen is pre-injected into the main flow at the leading front of the inlet by three strut-injectors. Secondly， the mixing process at the inlet and the combustion process in the combustor were numerically simulated. In the numerical simulations， the governing equations are Reynolds average Navier-Stokes equations with SST k- ω turbulence model and 9-species and 19-recations detailed chemical reaction kinetics. The numerical results show that the mixing process of hydrogen along the inlet is good. The stable oblique detonation waves and normal detonation waves are obtained in the combustor. Finally， the experiments under Ma 9 flight conditions were conducted in the shock tunnel. The stable flow fields of oblique detonation engine were established in the duration of 50ms test time of the shock tunnel. The experimental results are in good agreements with numerical results which means that stable oblique detonation waves were successfully obtained in the shock tunnel experiments. This research results demonstrate the technical feasibility of oblique detonation engines.

In order to investigate the effects of fuel/oxidizer injection and blending on detonation and the rapid initiation and steady propagation of detonation in non-premixed environment in the rotating detonation engine （RDE）， a linear model detonation engine （LMDE） is used to simplify the physics problem of interaction between real fuel injection and detonation wave. The RNG k-ε turbulence model combined with the three-dimensional unsteady reaction flow simulation method of 7 steps， 7 species hydrogen/air mechanism are used to investigate the interaction between detonation wave and mixed gas， attenuation of detonation and self-holding characteristics in real inject conditions. The results show that the mixing evenness of hydrogen/air should be at least 0.6 to make the detonation wave propagate in the non-premix environment. The inlet pressure ratio between hydrogen holes and air slot needs to meet the requirement that when the detonation enters the combustion chamber， the region of non-premixed gas is just near the hydrogen holes， and the energy is completely released to maintain the propagation of the detonation.

The intelligent control technology of marine diesel engine is to introduce artificial intelligence algorithms into the field of marine diesel engine control to improve the control performance of complex， time-varying and nonlinear system. Focusing on the research of diesel engine subsystem controller designed based on intelligent control algorithms and the research of diesel engine online performance optimization based on nonlinear model prediction framework， the research status and progress of marine diesel engine intelligent control technology are reviewed， and the main theories and methods involved in this research field are analyzed. According to the different application requirements of intelligent control of marine diesel engine， the application of intelligent control methods of marine propulsion diesel engine in new combustion modes， complex gas systems， speed tracking and other control problems is mainly introduced. The advantages and disadvantages of intelligent control methods are analyzed， and the future research directions and challenges of intelligent control technology in the field of marine diesel engine control are discussed.

The one-dimensional coupled stream tube model is presented and used for analysis of combustion and flow processes in liquid rocket engine at apogee. The effects of various factors on combustion efficiency are also analyzed.

Variable cycle engine (VCE) has several variable geometry parameters. In this paper，a new method called ‘Reverse Method’ was developed to design the multiple variable steady state control law for VCEs. Based on the sensitivity matrix，the variables of the component based performance model were replaced with variable geometric parameters. Thus the state factors and components parameters were given while the variable geometric parameters were iterated during the procedure of engine off-design balancing which allows the optimal design of VCE steady state control law. Results showed that the ‘Reverse Method’ has the same accuracy and rate of convergence as the conventional component based model，while its astringency is better. The subsonic cruise control law for a dual-bypass VCE is optimized employing the ‘Reverse Method’ to minimize the installed specific fuel consumption (SFC). Optimization results showed 7.8% and 16.4% reduction in installed SFC compared to the fixed geometry dual-bypass mode and the single-bypass mode respectively. By using this optimized control law，the sea level installed SFC was decreased by 3.4%. It can be concluded that the ‘Reverse Method’ is a practical way to design the optimal steady state control law for VCEs.

The demand for improving the performance of turbine engines is constantly increasing， and so higher temperature resistance and more lightweight become extremely demanding for turbine rotors. At present， the performance of superalloy turbine rotor approaches its limit， and superalloy is difficult to meet the requirements of substantially reducing weight and rising temperature of turbine rotors in the future. Therefore， fabricating turbine rotors by ceramic matrix composite （CMCs） becomes an inevitable trend. This paper introduces the design， preparation， machining and testing of CMCs turbine rotors， as well as the progresses of CMCs turbine rotors in various countries. Those researches show that CMCs turbine rotors have great advantages and potentials in application of liquid rocket engines and aero engines. The performance of heat and thermal impact resistant of turbine rotors made by the continuous fiber reinforced CMCs is preliminary verified， but the weak strength and low toughness is shortage of CMCs for aeroengine application. Improving the strength and toughness of CMCs has becomes a hot topic and inevitable trend in the future.

To explore internal flow field on the inlet cover separation process， based on overset method to solve N-S equation， the evolution process of internal flow field and characteristic flow field structure were analyzed in detail during inlet cover separation. Numerical simulations show that a V- swept shock wave is formed at the front of the inlet cover， and a backward facing step that induces a pair of streamwise vortexes with the opposite vectors is formed at the rear of inlet cover when the inlet is blocked. On the separation process， the V-swept shock wave and the backward facing step both affect the internal flow. The mass flow rate at throat reaches its peak at intermediate moment then drops to a stable value. If the flow is quasi-steady and no large separation zone exists in the inner inlet during the separation process， inlet starts when the V-swept shock wave meets the lip line， and the motion of inlet cover no longer affects the internal flow field afterwards. The assumed constant acceleration rotation was consistent with the real rotation， and a more accurate motion simulation suggests the cubic angular velocity function.

Combustion chamber of cryogenic liquid rocket engine and air heater has characteristics of high pressure， heavy flow of cryogenic fuels and demands repeated starts， for which the safety and reliable ignition is difficult. A high back pressure plasma ignitor meeting with these requirements was designed and studied. The voltage-current characteristics of Ar and N ₂ working at high inlet pressures were studied by experiments and results showed that N ₂ worked well within a wide pressure range. Emission spectrum diagnose showed that the electron density of Ar，N ₂ plasma jets reached the local thermodynamic equilibrium（LTE） criterion and showed concentrated ignition power under inlet pressures of several MPa. The average temperature of N ₂ plasma was lower than that of Ar， while just the reverse at the anode outlet. N ₂ plasma jet lasted longer in atmosphere， sucking and mixing the air， which resulted in the temperature drop but would accelerate the evaporation， mixture and ignition of cryogenic liquid fuels. The plasma caused the formation of active particles like ozone and oxynitride， which would also promote the ignition and chemical reactions. Higher back pressure caused higher output voltage， and raising inlet pressure and current helped to stabilize the output voltage under high back pressure. Ignition experiments in the combustion chamber of combustion-type air heater showed that N ₂ plasma could ignite the alcohol-air and alcohol-LOX-air within a short period when placed in the center of the injection surface. The ignitor worked stably even the back pressure reached 5MPa， and repeated operations caused slightly electrode erosion， showing prospects in reliable and repeated ignition of liquid rocket engine.