A hermetic compressor includes a closed vessel for storing lubricating oil, an electric-driving element, and a compressing element driven by the electric-driving element. The compressing element includes a cylinder block forming a compression chamber, a piton that reciprocates inside the compression chamber, and an oiling device for supplying the lubricating oil to an outer circumference of the piston. A first oil groove is concavely formed on the outer circumference of the piston, and a second oil groove is concavely formed on a side opposite to the compression chamber relative to the first oil groove. The second oil groove has a spatial volume same or greater than that of the first oil groove. An expanded clearance portion is provided such that a clearance between the piston and the cylindrical hole portion broadens from a top dead point to a bottom dead point.

A lubricating oil supply apparatus may include a rotational portion that rotates together with a rotational shaft and a fixed portion that maintains a fixed location thereof and supplies oil through a space that circles with respect to a rotational center of the rotational portion, thereby supplying oil regardless of a rotational direction of the rotational shaft.

A compressor and a refrigeration system having the same are provided. The compressor includes a crankcase, a thrust bearing and a crankshaft. The crankcase is formed with a crankshaft hole therein and provided with a mounting protrusion at an upper end thereof. The crankshaft hole runs upward through the mounting protrusion. The thrust bearing is fitted over the mounting protrusion. The crankshaft is rotatably disposed within the crankshaft hole, has a thrust part, and is formed with an oil supply passage therein. A lower end face of the thrust part is abutted against an upper end face of the thrust bearing. A cavity is defined by the mounting protrusion, the thrust bearing and the thrust part. A through hole is formed in a peripheral wall of the crankshaft for communicating the oil supply passage with the cavity.

A compressor and a refrigeration system having the same are provided. The compressor includes a crankcase, a thrust bearing and a crankshaft. The crankcase is formed with a crankshaft hole therein and provided with a mounting protrusion at an upper end thereof. The crankshaft hole runs upward through the mounting protrusion. The thrust bearing is fitted over the mounting protrusion. The crankshaft is rotatably disposed within the crankshaft hole, has a thrust part, and is formed with an oil supply passage therein. A lower end face of the thrust part is abutted against an upper end face of the thrust bearing. A cavity is defined by the mounting protrusion, the thrust bearing and the thrust part. A through hole is formed in a peripheral wall of the crankshaft for communicating the oil supply passage with the cavity.

A vacuum generation system, in particular for applications to hybrid-drive motor vehicles, comprises a vacuum pump (10) arranged to be independently driven by either an internal combustion engine (1 1) or an electric motor (12) depending on the vacuum conditions in utilizing devices (15) and the operating conditions of the internal combustion engine. A pump for use in such a system and a method of vacuum generation by using the system are also provided.

A control method and a control device applied to an electric fracturing apparatus are provided. The electric fracturing apparatus includes a plunger pump and a first motor configured to drive the plunger pump, and the method includes: acquiring a preset displacement of the plunger pump; acquiring a rotation speed of the first motor and a discharge pressure of the plunger pump; determining a real-time displacement of the plunger pump based on the rotation speed of the first motor and the discharge pressure of the plunger pump and adjusting the real-time displacement; and upon the real-time displacement reaching the preset displacement, allowing the first motor to be kept in a stable operation state.

A control method and a control device applied to an electric fracturing apparatus are provided. The electric fracturing apparatus includes a plunger pump and a first motor configured to drive the plunger pump, and the method includes: acquiring a preset displacement of the plunger pump; acquiring a rotation speed of the first motor and a discharge pressure of the plunger pump; determining a real-time displacement of the plunger pump based on the rotation speed of the first motor and the discharge pressure of the plunger pump and adjusting the real-time displacement; and upon the real-time displacement reaching the preset displacement, allowing the first motor to be kept in a stable operation state.

A multistage compression system uses refrigerant and oil. The multistage compression system includes a low-stage compressor that compresses the refrigerant, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, an oil return pipe that returns the oil discharged by the high-stage compressor to the low-stage compressor, and an oil discharge pipe that discharges the oil in the low-stage compressor. The low-stage compressor includes a compression part that compresses the refrigerant, a motor that drives the compression part, and a container that houses the compression part and the motor. The container forms a high-pressure space storing compressed refrigerant. Inside of the oil return pipe and inside of the oil discharge pipe are connected to the high-pressure space.

An air compression system includes an air compression device and a cooling structure. The air compression device includes a liquid-cooled motor and a compressor. The cooling includes a radiator, a cooler, a first liquid conveying tube, a second liquid conveying tube, a third liquid conveying tube, a fourth liquid conveying tube and a cooling liquid. The radiator interconnects the compressor for cooling a lubricating liquid in the compressor; the first liquid conveying tube interconnects the radiator and the cooler; the second liquid conveying tube interconnects the radiator and the cooler; the third liquid conveying tube interconnects the liquid-cooled motor and the cooler; the fourth liquid conveying tube interconnects the liquid-cooled motor and the cooler; and the cooling liquid is filled into the cooler, so as to reduce the space occupied by the cooling structure.

An air compression system includes an air compression device and a cooling structure. The air compression device includes a liquid-cooled motor and a compressor. The cooling includes a radiator, a cooler, a first liquid conveying tube, a second liquid conveying tube, a third liquid conveying tube, a fourth liquid conveying tube and a cooling liquid. The radiator interconnects the compressor for cooling a lubricating liquid in the compressor; the first liquid conveying tube interconnects the radiator and the cooler; the second liquid conveying tube interconnects the radiator and the cooler; the third liquid conveying tube interconnects the liquid-cooled motor and the cooler; the fourth liquid conveying tube interconnects the liquid-cooled motor and the cooler; and the cooling liquid is filled into the cooler, so as to reduce the space occupied by the cooling structure.