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.

Marine gas turbines dominate the power of large and medium-sized surface warships， which is an important symbol of naval modernization. This paper reviewed the development history of marine gas turbines in the world， and introduced the development of marine gas turbines from Aero-Derivative and independent development. The technical characteristics and performance of typical marine gas turbines LM2500 series， MT30 and UGT25000 were analyzed. Then， the development direction of marine gas turbines in terms of improving power and thermal efficiency， improving reliability and maintainability， developing product serialization and pedigree， etc. are prospected. And， the key technologies that need to be developed in the aspects of materials and manufacturing processes， metal additive manufacturing， aerodynamic design， low emissions， cooling and thermal barrier coatings， dual-fuel， intelligent and hybrid power， etc. are put forward.

The advantages of underwater fuel cell propulsion are high energy conversion efficiency and energy density， low noise and no gas emissions， thereby improving the performance of unmanned undersea vehicles （UUVs） in terms of range， depth and stealth. As such， underwater fuel cell propulsion is a very promising candidate for future UUVs. This paper introduces the system components and working principle of the underwater fuel cell propulsion system. The recent progress on key technologies is reviewed， including fuel cell-powered UUVs， hydrogen-oxygen fuel cell and energy-dense reactant storage. Future research work in this field is also discussed. In terms of hydrogen-oxygen fuel cells， pure oxygen supply and closed-cycle operation would bring water removal and corrosive issues， which should be carefully dealt with. In terms of hydrogen and oxygen sources， high energy density formats include water-reactive aluminum and diesel reforming for hydrogen acquisition， lithium perchlorate for oxygen acquisition， which deserve increasing research.

Due to the complex vortex structure in Jet in cross-flow (JICF)，turbulence model has significant influence on the CFD simulations of JICF. Four turbulence models including S-A，Realizable k-ε，k-ω and SST k-ω are compared in the simulations of JICF under the blowing ratios of 0.5 and 1.5，respectively. The simulation results are validated by comparing with experimental data. The effects of vorticity tensor and strain tensor on turbulence production are analyzed. The simulation results show that four turbulence models can give satisfing prediction for the flow structure downstream of jets. Under the low blowing ratio，the S-A model performs best in general. Under the high blowing ratio，the k-ω model results are among the most accurate.

Regulations on emission and fuel economy of marine power system are becoming stricter， which drives the rapid development of marine diesel engine turbocharging technologies towards high turbocharging， high efficiency， and electrification. From the perspective of turbocharging systems and turbocharger components， basic principles， main characteristics and application models of domestic and foreign marine diesel engine turbocharging technologies are elaborated on. Turbocharging systems including two-stage turbocharging， sequential turbocharging， variable geometry turbocharging and electric turbocharging technologies are focused on followed by the overview of development of turbocharging components including high-efficiency， wide-range compressor and high-efficiency turbine. At last， the development trend of marine diesel turbocharging technologies is prospected.

Low-frequency auto oscillation occurs in the pipeline system of flow regulator under the condition of small flow and large pressure drop. In order to deeply understand the mechanism of auto oscillation， a numerical simulation study was carried out based on the dynamic model of spring oscillator of flow regulator in combination with a certain output-flow-stabilized regulator and pipeline system. The numerical simulation results show that the auto oscillation frequency is 94 Hz， which is consistent with the engine test results. The influence of flow regulator structure parameters on the stability of the system was analyzed. The triangular slide valve throttle can suppress the auto oscillation of the pipeline system. The mechanism of auto oscillation is hydrodynamic oscillation with the throttling interface of the slide valve， and it forms a positive feedback effect on the pipeline system. When the comprehensive stiffness coefficient of the flow regulator is less than zero， the pipeline system will be unstable and oscillate. The load characteristic test of a certain flow regulator shows that the stability of pipeline system becomes worse as the pressure drop of flow regulator increases. The amplitude-frequency characteristic and stability boundary obtained by simulation are consistent with the test results.

Marine low speed engine is the first choice for sea-going ship propulsion power， due to economy and reliability. The technology feature and development process of low speed engine were reviewed. According to current low speed engine technology development status， the principle and feature of several emission and green house gas reduction solutions are analysed. Selective catalytic reduction（SCR） for diesel engine is the most popular solution to reduce NO _x. Dual fuel technology is current best choice for the integrated solution for NO _x， SO _x， black carbon and green house gas reduction. Neutral carbon and smart will be the future development directions of low speed engine.

The development history of CZ-5 launch vehicle has been briefly reviewed. Combining with the development situation of the launch vehicle propulsion system abroad， the design criteria and overall scheme of the propulsion system of CZ-5 launch vehicle have been summarized. Details of a series of new technologies of propulsion system with independent intellectual property rights during the development led by CZ-5 have been deeply included， including new generation powerful rocket engines， circulation precooling， cryogenic rocket POGO（the longitudinal instability and low frequency vibration caused by the coupling of the dynamic characteristics of the liquid launch vehicle structure system and propulsion system） restriction， high reliability of pressurization transportation system， test run of 5m diameter LOX/LH ₂ propulsion system and unattended on-site operation during test and launch stage. At the same time， the new expectations for the future requirements of CZ-5 propulsion technology and maintenance improvement have been suggested， such as continuous improvement of cryogenic rocket engines， whole process automatic test and launch，propulsion system fault diagnosis，advanced POGO restriction and long-termed on standby and on orbit.

In order to study the effects of the pintle injector structure on combustion performance of the thrust chamber of LOX/CH ₄ engine， a non-adiabatic stable diffusion flamelet model considering real-fluid properties was adopted in the numerical simulation of the transcritical combustion and flow in the thrust chamber of LOX/CH ₄ engine with pintle injector. The results reveal that two recirculation zones can be formed near the thrust chamber head of engine with pintle injector. When the width of the radial injection channel and the diameter of the needle decrease within a certain range， the chamber pressure and the gas temperature can be increased， and the combustion performance of the thrust chamber can be improved. In addition， for the value of the ‘skip distance’， in order to improve the combustion performance of the thrust chamber and consider the cooling of the thrust chamber head， the value of the non-dimensional ‘skip distance’ should be around 1.

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.

Long March 5 is China’s new generation of large-scale launch vehicle （code-named CZ-5）. The core stage is bundled with four boosters， and each booster uses a dual-unit parallel liquid oxygen kerosene high-pressure staged combustion engine. Considering the real situation of the first launch of the Long March 5， this paper analyzes the failure modes of launch vehicles at home and abroad， and puts forward the measures that should be taken to avoid the risk of the booster system. Combined with the starting characteristics of booster stage and the first-stage engines， the ignition matching characteristics of the different engines in the first launch of the Long March 5 are discussed. The development history， technical characteristics， and adaptability of thermal environment for YF-100 series liquid oxygen kerosene engine are briefly described， and the engine’s potential of reusability and wide-range thrust adjustment is analyzed with emphasis. The thrust-to-weight ratio of liquid oxygen kerosene staged engines is compared， the impact of engines with different thrust-to-weight ratios on the carrying capacity of rocket is studied， and the methods to improve engine’s performance are summarized （such as using pump back swing technology， high-strength and light-weight Materials， etc.）. It is pointed out that the new generation of liquid oxygen kerosene engine must pursue high performance， high thrust-to-weight ratio， lower cost and enhance adaptability under the premise of high reliability.

In order to simplify the calculation of random vibration fatigue of welded pipe， this paper proves that the structural stress referred to by structural stress method in welding fatigue analysis is consistent with the nominal stress calculated by material mechanics， and a simplified method for rapid design and fatigue analysis is proposed， which is not only independent of FE-Safe software，but also takes advantage of the efficiency of beam element model. In addition， based on the random vibration calculation results of the beam element model， the effects of the multi-scheme arrangement of damping clamps on the welding fatigue life of the structure are discussed. It is considered that the scattered clamps and the increased number can effectively avoid the resonance frequency of the structure， but it does not necessarily improve the fatigue life of the welding， and may even accelerate the failure of the welding position. The specific layout design needs to combine the fatigue calculation results.

Based on concentrated combustion time-lag model，the effects of system damping on combustion stability were studied here. Firstly，flow induced shear stress was introduced into the governing equation as resistance term，and by using the match boundary layer at combustion front，new concentrated time-lag model considering the damping effect was established. Secondly，through band-pass filtering and correlation analysis，Tim Liuwen’s method was adopted to indirectly extract damping coefficients for each acoustic model from the test data of unstable combustor. At last，the newly derived damping coefficients were added into the new model as resistance term，and the stability curve for this test was recomputed. It is indicated that the damping coefficient of each mode is not larger than 0.1，and the damping coefficient will be reduced as the model number improved. On the other hand，compared with the original model and contemporary model，system gain was reduced by about 48% when considering the damping effect，which means that introducing the system damping has some influence on the model precision for prediction. Furthermore，it is proved that increasing system damping will reduce the system gain and improve its stability simultaneously.

A series of direct connected tests of the multi-cavity dual-mode scramjet operated in a simulated flight number range of 4.5 ~ 5.0 and a total temperature range of 1048 ~ 1231K were carried out for a further understanding of how the fuel injection strategy affected the flow field structure and the performance of the engine. Steady wall static pressure and outlet total pressure were obtained during the experiments with different fuel injection equivalence ratio，injection position or injection stages. The experimental data was particularly processed and analyzed with the one-dimensional impulse analysis program. According to the results，the thrust of the engine effectively increased as the equivalence ratio is enhanced，but both the combustion efficiency and the specific impulse of the engine are synchronously decreased. The combustion efficiency and the thrust increared 5.6% and 4.4%，respectively，by moving the fuel injection position forward. The flow field structure is obviously influenced by the fuel injection distribution. The more fuel is injected from the downstream cavity，the farther downstream the thermal throat is located. And much more heat is required to form the thermal throat. When the fuel is injected from the upstream cavity and downstream cavity，a wide subsonic region which is to the benefit of the combustion and heat releasing of the fuel is formed. The combustion efficiency and the thrust of the engine increased by 10.4% and 10.8%，respectively，with this strategy.

The droplet evaporation and combustion processes are very sensitive to temperature. In order to obtain the response characteristics of heat release to temperature oscillation while fuel droplet combustion，the two-phase reaction of fuel droplet of heptane has been numerically investigated. The variations of amplitude and phase angle of heat release rate are mainly studied at the flow temperature oscillation frequency of 2kHz，5kHz and 10kHz and oscillation amplitude of 5%，10% and 15%，and the effects of droplet diameters are also considered at the same time. The simulation results indicate that，the amplitude of oscillation of heat release rate increases greatly with the increases of the frequency and amplitude of flow temperature oscillation. The phase difference of temperature oscillation and heat release rate oscillation appears to be mainly influenced by the frequency of temperature oscillation. The change of droplet diameter could effectively influence the dynamic heat release response characteristics，and at the same condition，the amplitude of heat release rate oscillation decreases while the droplet diameter becomes smaller. With the interaction within temperature oscillation，evaporation and heat release processes，droplet combustion heat release appeared significant non-linear characteristics in some conditions.

In order to obtain the change law of the physical and chemical properties of high-energy synthetic kerosene （GN-1 kerosene） with temperature and pressure， and to grasp the difference in application characteristics between GN-1 kerosene and rocket kerosene in service， theoretical calculations and experimental methods were used to investigate the physical and chemical properties （density， viscosity， constant pressure specific heat capacity， thermal conductivity， surface tension） change law， safety characteristics （flash point， spontaneous combustion temperature， ignition point， explosion limit， toxicity）， flow heat transfer and coking characteristics， and ignition delay characteristics， which were compared with rocket kerosene. The experimental data of density， viscosity， specific heat capacity， thermal conductivity and surface tension of GN-1 kerosene at the highest temperature not exceeding 200℃ and the highest pressure not exceeding 25MPa were obtained through experimental research. The physical and chemical properties change laws in the range of -40~350℃， 0.1~60MPa of GN-1 kerosene were obtained by theoretical calculations， which were compared with rocket kerosene. In addition， the research results also show that the flash point of GN-1 kerosene is 40℃ （lower than that of rocket kerosene 74℃）， the spontaneous combustion temperature is 305℃ （higher than that of rocket kerosene 225℃ ）， and the ignition point is 47℃ （lower than that of rocket kerosene 82℃）， the explosion limit range of GN-1 kerosene is 0.44%~2.9% （40℃）， the acute oral toxicity LD ₅₀ values of GN-1 kerosene and rocket kerosene are both over 5000mg/kg. At an inlet pressure of 10MPa， a flow rate of 10m/s， and the inner wall temperature of 480°C， the heat transfer coefficient of GN-1 kerosene is 14.4% higher than that of rocket kerosene. Under the condition of using GH3128 high temperature alloy pipe， the test section average coking rate at the outlet oil temperature of GN-1 kerosene at 220℃ is 4.43 times that of the outlet oil temperature at 150℃. The test section average coking rate of GN-1 kerosene in the 316L stainless steel pipeline is 22.3% that in the GH3128 high temperature alloy pipeline. In the temperature range of 970～1105K， the ignition delay time of GN-1 kerosene is 55.6%～69.3% that of rocket kerosene.

In order to accurately predict the central propellant deflection angle of pintle injector， the theoretical model of central propellant deflection angle was established based on flow field analysis. A central propellant deflection angle formula was deduced from the momentum conservation equation， which was verified by numerical simulation and experimental results. Moreover， the effects of structure parameters and working parameters on the central propellant deflection angle were analyzed. The results show that the predicted values of the theoretical model are in good agreement with the numerical and experimental results. The injection area of sleeve shielding has the greatest influence on the deflection angle of the central propellant. In the case of variable thrust， the central deflection angle decreases as the injection area of sleeve shielding increases. Injection pressure drop， wall thickness and cavity depth at the bottom of central cylinder have little effect on central deflection angle. When the injection area of sleeve shielding is constant， the deflection angle with a cavity at bottom of the central cylinder is about 6° larger than that without a cavity. This model can provide an important reference for the engineering design and the further accurate calculation of spray angle at variable thrust of pintle injector.

In order to study the simulation accuracy and applicability of the numerical modeling method for filtration device in marine gas turbine intake system， for a marine gas turbine double-channel intake system， the Fan boundary condition and porous media model are used to model the complex structure of filtration device （shutter and filter）， and the detailed numerical calculation of the flow field characteristics in the intake system is carried out. Research shows that most of total pressure loss of the intake system results from the total pressure loss in primary air filter and the flow loss in the shaft.Compared with Fan boundary condition， the porous media model can obtain more practical flow field inside the intake system and more reliable prediction of total pressure loss. The difference in the flow loss of the intake system calculated by the two methods does not exceed 10%. When using Fan boundary condition， it is necessary to ensure that the filtration device does not play an obvious role in rectifying， and the experimental data of pressure loss is complete， while porous media model can be selected under the given physical parameters of filtration device， such as resistance coefficient and porosity.

Aiming at the applications for space launch vehicle main engines， a half open oxygen-rich staged combustion mixture cycle engine scheme，with which an open fuel supply subsystem and an closed oxygen supply subsystem are applied， is proposed in this paper. The specific impulse performances of this kind of mixture cycle are calculated， and comparing with open cycle， convention closed cycle and full flow closed cycle， its advantages and shortcomings are discussed from the viewpoint of being used as reusable space launch vehicle engines. The detail system parameters for a 1000kN thrust level liquid oxygen kerosene mixture cycle engine are calculated. The results show that for the new mixture cycle engine， sea level specific impulse can attain 303s under the main combustion chamber pressure of 26.5 MPa. Meanwhile， its high critical design margin， along with the compatibility of turbo-pump mediums， can be obtained at the cost of a small loss of specific impulse.