Abstract: A method for optimizing a layer-stacking sequence of a composite material pressure vessel. includes determining design variables of a to-be-optimized composite material pressure vessel based on design objectives thereof, the design objectives including a liner size and a working pressure of the composite material pressure vessel, and the design variables including filament winding angles, winding layer thicknesses, and winding layer quantities; establishing a finite element model based on layer-stacking information and boundary conditions of the to-be-optimized composite material pressure vessel, the layer-stacking information being the design variables; modeling the liner of the pressure vessel by solid elements, and modeling composite material layers of the pressure vessel by continuum shell elements.

Abstract: Transformerless stacked active bridge (TSAB) direct current (DC)-to-DC power converters designed based on parent switched capacitor (SC) converter topologies. The TSAB DC-to-DC power converter includes the SC converter. The SC converter includes a plurality of switches and a plurality of capacitors. Each capacitor of the plurality of capacitors is electrically coupled to at least one of the plurality of switches. The plurality of capacitors includes tree capacitors, and link capacitors forming a loop with at least one of the tree capacitors. The TSAB DC-to-DC power converter includes at least one inductor electrically coupled in series to at least one of the link capacitors. The TSAB DC-to-DC power converters provide high efficiency bi-directional operation without requiring isolation transformers.

Abstract: An elasticator and a preparation method thereof and a casing expansion loss prevention elastic spacer fluid for cementing are provided. The preparation method of the elasticator includes the following steps of: (1) taking polycaprolactone and an inorganic porous material for fully mixing under a heating condition to obtain a mixture; and (2) mixing the mixture with a high-elastic modulus rubber powder to obtain an elasticator.

Abstract: The present invention relates to a combined crushing super-variable-diameter drill bit for natural gas hydrate exploitation, including a joint, an outer cylinder connected to the joint by thread, a nozzle I mounted in the outer cylinder, a mechanical locking mechanism, a blade telescoping mechanism, an end cap connected to the outer cylinder by thread, a seal ring IV mounted to the end cap, and a nozzle II mounted in the end cap by threaded connection. The present invention achieves integrated operation of conventional drilling and draw-back expanding, which can effectively solve the problems that the existing hydrate drill bit cannot drill a large borehole, cannot mechanically lock an extending position of the blade to stabilize the size of the borehole, and a single crushing method is inefficient.

Abstract: The present invention provides an automatic jet breaking tool for solid fluidization exploitation of natural gas hydrate, which mainly includes an upper joint, an outer cylinder, an inner sliding sleeve, a lockup sliding sleeve, a thrust bearing, a spring, a jet joint, a telescopic jet sprinkler, a plug block and an extrusion seal ring. The present invention mainly adopts the principle of throttling control pressure to control the position of the inner sliding sleeve by controlling a flow rate of a drilling fluid, so as to turn on and turn off the jet breaking tool. The application of the present invention can realize automatic jet breaking of solid fluidization exploitation of the natural gas hydrate, reduce procedures of a round trip operation, and effectively improve the efficiency and safety of the exploitation operation of the natural gas hydrate.

Abstract: Transformerless stacked active bridge (TSAB) direct current (DC)-to-DC power converters designed based on parent switched capacitor (SC) converter topologies. The TSAB DC-to-DC power converter includes the SC converter. The SC converter includes a plurality of switches and a plurality of capacitors. Each capacitor of the plurality of capacitors is electrically coupled to at least one of the plurality of switches. The plurality of capacitors includes tree capacitors, and link capacitors forming a loop with at least one of the tree capacitors. The TSAB DC-to-DC power converter includes at least one inductor electrically coupled in series to at least one of the link capacitors. The TSAB DC-to-DC power converters provide high efficiency bi-directional operation without requiring isolation transformers.

Abstract: The present invention provides an automatic jet breaking tool for solid fluidization exploitation of natural gas hydrate, which mainly includes an upper joint, an outer cylinder, an inner sliding sleeve, a lockup sliding sleeve, a thrust bearing, a spring, a jet joint, a telescopic jet sprinkler, a plug block and an extrusion seal ring. The present invention mainly adopts the principle of throttling control pressure to control the position of the inner sliding sleeve by controlling a flow rate of a drilling fluid, so as to turn on and turn off the jet breaking tool. The application of the present invention can realize automatic jet breaking of solid fluidization exploitation of the natural gas hydrate, reduce procedures of a round trip operation, and effectively improve the efficiency and safety of the exploitation operation of the natural gas hydrate.

Abstract: The present invention relates to a combined crushing super-variable-diameter drill bit for natural gas hydrate exploitation, including a joint, an outer cylinder connected to the joint by thread, a nozzle I mounted in the outer cylinder, a mechanical locking mechanism, a blade telescoping mechanism, an end cap connected to the outer cylinder by thread, a seal ring IV mounted to the end cap, and a nozzle II mounted in the end cap by threaded connection. The present invention achieves integrated operation of conventional drilling and draw-back expanding, which can effectively solve the problems that the existing hydrate drill bit cannot drill a large borehole, cannot mechanically lock an extending position of the blade to stabilize the size of the borehole, and a single crushing method is inefficient.