The Different of Jet Pumps and Centrifugal Pumps- Taizhou Haipai Import & Export Co., Ltd.

I. Overview

Jet pumps and centrifugal pumps are two different types of pumps, which differ in working principles and application fields.

The working principle of a jet pump is to use the jet effect of a high-pressure working fluid to transport fluid. It consists of a nozzle, a mixing chamber, and an expansion tube. The working fluid is ejected from the nozzle at high speed, forming a low pressure in the vacuum chamber, sucking in the transported liquid, and then entering the mixing chamber for energy exchange and speed uniformity. Finally, the speed is slowed down through the diffusion chamber, and the pressure is recovered to achieve the purpose of transporting the liquid. Jet pumps are suitable for high temperature, high pressure, and high vacuum fields, such as vacuum evaporation, vacuum drying, etc.

Centrifugal pumps increase the kinetic energy of the fluid through a rotating impeller to achieve fluid transportation. The fluid enters from the central axis of the impeller, and then is accelerated and thrown outward along the blades of the impeller, collected by the pump casing and guided to the outlet. The working principle of a centrifugal pump is to convert mechanical energy into kinetic energy and pressure energy of the fluid. Centrifugal pumps are widely used in industrial and civil fields, such as water supply, irrigation, drainage, etc.

In general, jet pumps mainly rely on the jet effect of working fluid to transport fluid, and are suitable for special environments and high vacuum fields; while centrifugal pumps increase the kinetic energy and pressure of the fluid through the rotating impeller, and are suitable for a wide range of fluid transportation needs.

II. Jet Pumps

(1) Advantages and limitations of jet pumps.

1) Compared with centrifugal pumps, jet pumps have the following advantages in industrial applications:
·Safety: Jet pumps have no mechanical transmission and mechanical working components, and use the energy of another working fluid as a power source to transport low-energy liquids. They have good safety when pumping flammable and explosive materials.

·Simple structure: Jet pumps have a simple structure, reliable operation, no leakage, and do not require special personnel to supervise. They are suitable for use in special underwater and dangerous occasions.

·Energy saving and environmental protection: Jet pumps can use pressurized wastewater and waste steam (gas) as working fluids, thereby saving energy.

·Strong adaptability: Jet pumps are suitable for high temperature, high pressure, and high vacuum fields, such as vacuum evaporation, vacuum drying, vacuum refrigeration, vacuum distillation, etc.

·High cleaning efficiency: Water jet pumps use the impact force of high-pressure water flow to clean equipment, with high cleaning efficiency and strong destructiveness.
·No secondary pollution: No chemicals are used in the cleaning process, so there will be no secondary pollution to the environment.

2) However, jet pumps also have some limitations:

·Low efficiency: The efficiency of jet pumps is usually low, generally not exceeding 30%, although new multi-stream jet pumps, multi-stage jet pumps and pulse jet pumps have improved the efficiency of energy transfer.

·High civil engineering investment: Especially water vapor jet pumps, a higher installation height may be required, resulting in a large civil engineering investment.

·Compression ratio limitation: The compression ratio of a single-stage water vapor jet pump is generally not more than 10, which may limit its use in some applications.

·Medium limitation: The working medium consumption of the jet pump is large, especially the air jet pump, which must have a large-capacity air compressor.

In summary, jet pumps are widely used in industrial applications for their safety, simple structure, energy saving and environmental protection, but at the same time, it is also necessary to pay attention to their limitations in efficiency, civil engineering investment, and medium supply.

(2) How to improve the efficiency of the jet pump to overcome its low efficiency limitation?

· Optimization design: By optimizing the nozzle design, the geometry of the mixing chamber and the diffuser chamber, the flow loss can be reduced and the efficiency can be improved. For example, the basic theory of the gas dynamics function method is used to analyze and design the performance indicators and structural dimensions of the ejector.

· Use of drag reducing polymer: Introducing drag reducing polymer (DRP) into the suction flow of the jet pump can significantly reduce the resistance in the pump and improve efficiency. According to research, this method can increase the efficiency from 13.8% to 26.7% and reduce the resistance by 46%.

· Steam pressure matching: Reasonable matching of the pressures of high and low pressure steam can improve the efficiency of the jet pump. By using high pressure steam to inject low pressure steam, the quality of high pressure steam can be reduced while the quality of low pressure steam can be improved, and steam with various pressures between high and low pressure steam pressures can be generated.

· Condensate recovery: The flash steam generated by condensate can be recovered by using a jet pump condensate recovery device, and the steam quality can be improved and reused, thereby saving energy.

· Jet pump type desuperheater and pressure reducer: Using a jet pump type desuperheater and pressure reducer instead of a conventional pressure reducer can simultaneously adjust the steam pressure and temperature and recover waste heat steam. It is an efficient and energy-saving device.

· Combined with a liquid ring vacuum pump: The combination of an ejector and a liquid ring vacuum pump can form a composite system that can produce a high vacuum. This composite system has low energy consumption and can improve the stability and efficiency of the system.

· Optimize operating conditions: By optimizing the operating conditions of the jet pump, such as adjusting the pressure and flow of the working fluid, the working efficiency of the jet pump can be improved.

· Use advanced calculation models and programs: Developing and applying calculation programs to solve the mathematical model of steam jet pump design can help designers to accurately design and select steam jet pumps, thereby improving the working performance of the jet pump.

III. Centrifugal pump

(1) Advantages and limitations of centrifugal pumps

1) Advantages

·Simple structure: Centrifugal pumps are usually composed of a pump body, an impeller, a shaft and a motor. They have a simple structure and are easy to maintain and operate.

·Wide range of applications: Centrifugal pumps can be used for various types of fluids, including clean water, sewage, chemicals, oils, etc., and have a wide range of applications.

·High efficiency and energy saving: In the design and manufacturing process, centrifugal pumps are usually more efficient, and can efficiently convert electrical energy into mechanical energy, reducing energy consumption.

·Easy to control: By adjusting the valve or using frequency conversion technology, the flow and head can be easily controlled to adapt to different process requirements.

·High reliability: The design and manufacturing process of centrifugal pumps are mature, the operation is reliable, and the failure rate is low.

·Cost-effectiveness: Compared with other types of pumps, centrifugal pumps have lower initial investment and operating costs and are more economical.

·Easy to expand: The processing capacity of the system can be expanded by increasing the number of pumps or changing the model of the pump.

2) Limitations

·Sensitive to fluid properties: Centrifugal pumps are sensitive to the viscosity and solid content of the fluid. Fluids with high viscosity or containing a large amount of solid particles may affect the efficiency and life of the pump.

·Head limitation: The head (i.e. the height of the fluid) of the centrifugal pump is limited, and it is not suitable for applications that require extremely high heads.

·Starting shock: Centrifugal pumps will produce a large water hammer effect when starting, which may cause impact on the pipeline system and the pump itself.

·Required auxiliary equipment: Centrifugal pumps usually require motor drive, so they require additional power systems and control systems.

·Installation requirements: Centrifugal pumps have high requirements for installation accuracy and alignment. Improper installation may affect the performance and life of the pump.

·Maintenance requirements: Although the structure is simple, the impeller and seals of the centrifugal pump need to be inspected and replaced regularly, and the maintenance workload is large.

·Noise problem: Centrifugal pumps may produce a lot of noise during operation, especially at high speed or large flow.

(2) How to improve and overcome the limitations of centrifugal pumps?

· Fluid property adaptability: Choose a centrifugal pump model suitable for high viscosity or solid particle fluids, or use a cutter to pre-treat the fluid to reduce the particle size. Use a self-cleaning or open impeller design to reduce the risk of clogging.

· Reduce starting shock: Use a soft starter or variable frequency starting technology to reduce the water hammer effect during startup. Consider the strength of the pipeline system during design to withstand the transient pressure during startup.

·Maintenance and reliability: Implement regular preventive maintenance programs, including inspection and replacement of wearing parts. Use high-quality materials and sealing technology to improve the corrosion resistance and sealing performance of the pump.

·Precise installation: Ensure accurate alignment of the pump and drive equipment to reduce mechanical wear during operation. Provide detailed installation guidelines and training to ensure installation quality.

·Reduced noise: Design low-noise pump models, use sound insulation materials and soundproof rooms. Use noise reduction technologies in pump design, such as optimizing the shape of impellers and guide vanes.

·Improve efficiency and head: Use efficient impeller and guide vane designs, optimize flow channels to reduce energy losses. Use variable frequency drive technology to adjust the operating speed of the pump according to actual needs.

·Adapt to different working conditions: Provide a variety of pump models to adapt to different working conditions, such as different temperatures, pressures and media characteristics. Use adjustable designs, such as adjustable impeller outlet width or blade angle.

·Adopt advanced technology: Use CFD simulation and intelligent optimization algorithms for design to improve pump performance and efficiency. Use advanced materials and manufacturing technology to improve the durability and reliability of the pump.

·User training and support: Provide user training to ensure the proper use and maintenance of the pump. Establish a fast-response customer support system to solve operation and maintenance problems.