Background
With the increasing problems of environmental pollution and energy shortage, the development and utilization of low-temperature heat sources such as solar energy, geothermal energy, biomass energy and industrial waste heat are widely concerned, and organic working media have the physical property of low-boiling-point evaporation, so that organic Rankine cycle (ORC for short) is commonly adopted in the process of converting waste heat recovery and heat power. The organic working medium centripetal turbine is used as a driving device in an organic Rankine cycle power generation system, and the safety and reliability of the operation of the organic working medium centripetal turbine are widely regarded;
in a solar photo-thermal power generation system, the load of a boiler is limited by the area of a solar heat collecting plate, and if a high initial steam parameter is ensured, the steam flow is very small. Compared with an axial flow turbine, the radial inflow steam turbine has the characteristics of small volume, high rotating speed and compact structure, and is more suitable for occasions with small volume flow and high specific enthalpy drop. Particularly, with the development of materials and manufacturing processes, people pay more and more attention to the development of the centripetal steam turbine;
also with the wide application of natural gas and coal gas, the gas consumption is continuously rising. The natural gas pressure energy is recycled and utilized to generate electricity, which becomes a research and development hotspot in the field, the upstream pressure of the fuel gas is higher, the pressure required by a user side is basically stable, the pressure difference adjustment in the middle needs a centripetal turbo expander with a high pressure ratio to bear, and the expander needs to have a larger flow variation range due to the unstable gas consumption of the user.
The reversing turbine is usually solved by adopting a speed-level axial flow turbine or a high-expansion-ratio centripetal turbine, and is widely applied to rocket engines.
The centripetal turbine has the characteristics of simple and compact structure, simple manufacturing process, low manufacturing cost, convenient installation, high efficiency (the current single-stage centripetal turbine isentropic efficiency can reach more than 90 percent), high single-stage expansion ratio (the single-stage centripetal turbine can replace two or more axial flow turbines) and the like. The method is widely applied to the expansion turbine of small and medium-sized gas turbines, turbochargers, refrigerating devices, liquefying devices and the like.
Centripetal turbines are mostly single stage with a maximum single stage expansion ratio of 15. Because of the particularity of the centripetal turbine structure, the difficulty in realizing the multistage centripetal turbine is very high, and along with the higher and higher requirement of the inlet pressure, the expansion ratio required by the system is continuously increased, and the traditional single-stage centripetal turbine can not meet the requirement.
Therefore, in order to solve the above-mentioned technical problems, the search for a supersonic radial turbine is an important subject of research by those skilled in the art.
SUMMERY OF THE UTILITY MODEL
The embodiment of the utility model discloses supersonic speed centripetal turbine for solve traditional single-stage centripetal turbine and can not satisfy the requirement of inlet pressure more and more high, the technical problem that the expansion ratio of system requirement constantly increases.
The embodiment of the utility model provides a supersonic centripetal turbine, which comprises a Laval nozzle, a centripetal impeller and a circular ring shell which is arranged around the centripetal impeller;
the outer side wall of the circular ring shell is uniformly provided with a plurality of gas inlets, the Laval nozzle is arranged in the circular ring shell, the inlet end of the Laval nozzle is communicated with the gas inlets, and the outlet end of the Laval nozzle faces to the center of the centripetal impeller.
Optionally, the laval nozzle includes an integrally formed convergent section, a throat section, and a divergent section;
the inlet end is arranged on the contraction section, the outlet end is arranged on the expansion section, and the contraction section, the throat part and the expansion section are sequentially connected.
Optionally, the pipe diameter of the constriction section gradually constricts from the inlet end to the throat;
the pipe diameter of the expanding section is gradually enlarged from one end close to the throat part to the outlet end.
Optionally, the axis of the laval nozzle and a tangent to a contact surface of the laval nozzle with the outer sidewall of the annular housing are at an angle of 15 ° to each other.
Optionally, a rotating shaft is connected to the centripetal impeller.
Optionally, the centripetal impeller comprises a disk and blades;
the blades comprise a plurality of blades which are uniformly arranged on the wheel disc, and a flow channel for air to flow in is formed between the blades.
Optionally, the laval nozzle is welded to the interior of the annular housing.
Optionally, the laval nozzle is threadedly attached to the interior of the annular housing.
Optionally, the laval nozzle and the annular housing are of an integrally formed structure.
Optionally, the rotating shaft further comprises a bearing which is arranged outside the annular shell and is connected with the rotating shaft.
According to the technical solution provided by the utility model, the embodiment of the utility model has the following advantage:
in the embodiment, the Laval nozzle is utilized to convert the pressure energy of high-pressure gas into high-speed kinetic energy, the Mach number of the outlet of the nozzle can usually reach more than 2, the radial entering high-speed airflow pushes the centripetal impeller to rotate to the rated rotating speed, the gas in the centripetal impeller is continuously expanded, and the single-stage pressure ratio can reach more than 20 for the air-separation expander; for a steam centripetal turbine, the single-stage isentropic enthalpy drop can exceed 900KJ/Kg, and the occupied space is only about half of the double-row adjusting stage; in the application of ORC, when the working medium is R245fa or R123, the inlet pressure is further increased under the condition of constant temperature of the heat source, even the inlet gas is allowed to enter a two-phase area, and the work capacity of the turbine is increased to the maximum extent; the structural design ensures that the expansion work is done and the occupied space is small, the Laval nozzle is arranged in the annular shell, so that the uniform introduction of gas and centripetal impeller are facilitated, and the outer diameter of the nozzle is ensured not to exceed the limit.
Example one
Referring to fig. 1 to 3, the present embodiment provides a supersonic radial turbine comprising:
the centrifugal impeller comprises a centripetal impeller 2, a circular ring shell 1 and a plurality of Laval nozzles 5, wherein the circular ring shell 1 surrounds the centripetal impeller 2, a plurality of gas inlets 4 for gas to enter are uniformly distributed on the outer side wall of the circular ring shell 1, the Laval nozzles 5 are arranged in the circular ring shell 1, an inlet end 54 of each Laval nozzle 5 is communicated with the gas inlets 4, an outlet end 55 of each Laval nozzle 5 faces the center of the centripetal impeller 2, and airflow enters the centripetal impeller 2 through the Laval nozzles 5 along the radial direction of the centripetal impeller 2.
In the embodiment, the Laval nozzle 5 is utilized to convert the pressure energy of high-pressure gas into high-speed kinetic energy, the Mach number of the outlet of the nozzle can usually reach more than 2, the radial entering high-speed gas flow can push the centripetal impeller 2 to rotate to the rated rotating speed, the gas in the centripetal impeller 2 is continuously expanded, and the single-stage pressure ratio can reach more than 20 for the air-separation expander; for a steam centripetal turbine, the single-stage isentropic enthalpy drop can exceed 900KJ/Kg, and the occupied space is only about half of the double-row adjusting stage; in the application of ORC, when the working medium is R245fa or R123, the inlet pressure is further increased under the condition of constant temperature of the heat source, even the inlet gas is allowed to enter a two-phase area, and the work capacity of the turbine is increased to the maximum extent; the structural design ensures that the expansion work is done and the occupied space is small, the Laval nozzle 5 is arranged in the annular shell 1, so that the uniform introduction of gas and the centripetal impeller 2 are facilitated, and the outer diameter of the nozzle is ensured not to exceed the limit.
Further, referring to fig. 3, the laval nozzle 5 of the present embodiment includes a contracting section 51, a throat portion 52 and an expanding section 53, wherein the inlet end 54 is disposed on the contracting section 51, the outlet end 55 is disposed on the expanding section 53, and the contracting section 51, the throat portion 52 and the expanding section 53 are sequentially connected.
Further, the laval nozzle 5 is of an integrally formed structure.
Further, the pipe diameter of the contraction section 51 gradually contracts from the inlet end 54 to the throat 52, and the pipe diameter of the expansion section 53 gradually enlarges from the end near the throat 52 to the outlet end 55.
It should be noted that the convergent section 51 of the laval nozzle 5 converges from a large size to a medium size to a narrow throat. The narrow throat is then gradually dilated from small to large. The gas in the nozzle is forced under high pressure into the convergent section 51 of the nozzle and exits through the throat 52 and divergent section 53. The structure can change the speed of the airflow due to the change of the spray cross section area, so that the airflow is accelerated from subsonic speed to sonic speed to supersonic speed.
Further, referring to fig. 2, the axis of the laval nozzle 5 and the tangent of the contact surface of the laval nozzle 5 with the outer sidewall of the annular housing 1 in the present embodiment form an angle of 15 ° with each other.
It should be noted that in order to obtain a larger gas flow, more laval nozzles 5 are arranged in a limited space, and the laval nozzles 5 can be tilted in the axial direction, for example, by 30% of the number of laval nozzles 5 when arranged at the above-mentioned angle of 15 °.
Further, the centripetal impeller 2 in the present embodiment includes a disk and blades 3 disposed on the disk;
wherein, a flow channel for air to flow in is formed among the plurality of blades 3, and the number of the blades 3 is reasonably matched to obtain the optimal number of the blades according to the flow channel.
Further, the centripetal impeller 2 in this embodiment is further connected with a rotating shaft, and the centripetal impeller 2 mainly functions to efficiently convert kinetic energy of gas into kinetic energy of shaft rotation outwards through rotation. The rotating shaft in this embodiment is further connected with a bearing, and the bearing is located outside the annular shell 1.
Further, referring to fig. 2, the laval nozzle 5 of the present embodiment is disposed inside the circular housing 1, and the installation manner thereof includes welding, screwing through bolts, or directly casting together with the circular housing 1.
It should be noted that the fixing manner of the laval nozzle 5 is not limited in this embodiment.
Application example
Referring to fig. 1 to 3, the present application provides a supersonic radial turbine comprising:
at a suitable pressure ratio P3/P1At this time, the gas flow is accelerated in the contraction section 51 until mach number Ma of the throat 52 becomes 1, and then decelerated in the expansion section 53 until the outlet Ma becomes less than 1 and the outlet pressure becomes equal to the critical pressure, i.e., P3=PeThis flow regime is referred to as the critical regime of the laval nozzle.
When in a critical state, no shock wave exists in the spray pipe, and the whole flow in the pipe can be regarded as isentropic flow. When P is present3>PeDuring the process, the airflow still accelerates in the nozzle contraction section 51 until the throat 52Ma is less than 1, decelerates in the expansion section 53 until the outlet, the outlet Mach number Ma is less than 1, and the process belongs to a subcritical flow channel state: when P is present3<PeAt the moment, a flow passage in the spray pipe is called as a supercritical state, the gas is accelerated to a throat part 52Ma which is 1 in a contraction section 51, the gas is continuously accelerated to an outlet Mach number Ma which is more than 1 in an expansion section 53, and the gas flow generates compression waves at the outlet of the spray pipe; the Laval nozzle 5 works in a supercritical state, high-speed airflow reaches the supercritical state at the nozzle outlet, the high-speed airflow enters the centripetal impeller 2, the moving blade can bear partial enthalpy drop due to certain circumferential speed difference of the static blade and the moving blade of the centripetal impeller 2, the airflow continuously expands in the centripetal impeller 2 and converts the speed into the rotational kinetic energy of the centripetal impeller 2, the gas is axially discharged, and the airflow is still in a supersonic state at the part of the impeller.
The enthalpy drop distribution of the Laval nozzle 5 and the centripetal impeller 2 is realized by adjusting the degree of reaction, the degree of reaction of a common axial flow speed stage is lower and is between 0.02 and 0.05, supersonic airflow passes through a flow channel formed between the blades 3, and fluid is compressed, so that the outlet pressure of the movable blade is higher than the inlet pressure of the movable blade, and the turbine stage inevitably has the design characteristic of negative degree of reaction, the scheme selects larger degree of reaction by utilizing the circumferential speed difference between the centripetal impeller 2 and the nozzle, and the reasonable range is between 0.3 and 0.5;
the centripetal impeller 2 mainly has the main effects that the kinetic energy of gas is efficiently converted outwards into axial rotation kinetic energy through rotation, in a runner of the centripetal impeller 2, the action of shock waves and a boundary layer has great influence on the pneumatic performance, and the shock waves and the action point positions of adjacent blades 3 are moved upstream to reasonable positions, so that the phenomenon of flow deterioration caused by superposition of two separation trends (separation caused by the action of the shock waves and the boundary layer and separation caused by the large-curvature wall surface of airflow circumfluence) is avoided, the flow separation after the action of the shock waves at the suction side and the boundary layer is delayed or restrained, the pneumatic performance of a cascade is improved, and the working capacity of a turbine is increased.
Taking a certain air expander as an example, the inlet is air with the pressure of 2.2Mpa and the normal temperature, the outlet pressure is atmospheric pressure, the design is designed according to the idea described in the above embodiment, the spray pipes bear large enthalpy drop, the number of the laval spray pipes 5 is 15, the number of the centripetal impeller 2 channels is 19, the mach number of the outlet of the laval spray pipe 5 reaches Ma 3-1.7, the speed of the high-speed airflow entering the movable vanes reaches 500m/s, the airflow continuously expands in the impeller to do work, and the temperature of the gas at the outlet of the impeller is reduced to-150 ℃; the average mach number Ma of the outlet of the moving blade 3 is 0.76, and the efficiency of the turbine shaft reaches more than 70 percent; the design can also be applied to a micro gas turbine for combined cooling, heating and power generation.
Taking a steam reversing impeller of a certain ship as an example, when a unit reverses in a forward reversing mode, the flow rate of upstream airflow is slightly reduced, the pressure is increased to saturated steam of 4.5Mpa, the exhaust back pressure is unchanged, the ratio of inlet pressure to outlet pressure exceeds 100, a single-stage supersonic turbine matched with a Laval nozzle 5 and a centripetal impeller 2 is selected because the turbine space is small, the average value of the Mach number of the airflow at the outlet of the nozzle reaches about 2.5, and the nozzle is of a convergent-divergent nozzle structure. The gas flow passes through the nozzle, and the internal energy and the pressure energy of the fluid are converted into the high-speed kinetic energy of the fluid. The circumferential component of the speed of the fluid sprayed by the spray pipe pushes the movable impeller to rotate, in order to obtain a larger circumferential component of the outlet speed of the nozzle, the geometric gas outlet degree of the spray pipe is relatively smaller, the size of the angle not only influences the circumferential component of the speed of the gas flow, but also increases the flow loss of the spray pipe to a certain extent by an excessively small geometric gas outlet angle, and increases the nonuniformity of the gas flow along the circumferential direction; however, in order to allow a larger flow, more nozzle channels are required in a limited space, and the channels can be inclined in the axial direction, for example, by 15 ° to the circumferential plane, which can increase the number of channels by 30%. The steam turbine technology can also be applied to the field of solar photo-thermal power generation.
Taking a waste heat recycling ORC unit of a certain plant as an example, the temperature of industrial waste heat is about 300 ℃, the organic working medium is heated to 160 ℃ after heat exchange with a R245fa working medium, the working medium is pressurized by a working medium pump at a turbine inlet of 3.27Mpa, the outlet backpressure of 0.14Mpa, the expansion pressure ratio reaches 23.39, the designed rotating speed of a centripetal turbine is 26500RPM, the density of the organic working medium is high, the sound velocity is low, and the supersonic speed state is easily reached, so the design is carried out according to the method, the outlet speed of a Laval nozzle 5 is 283m/s, the actual Mach number reaches 2, the relative Mach number of the outlet of the centripetal impeller 2 is 1.1, and partial kinetic energy is. The turbine exhaust temperature after work is about 77 ℃.
It introduces to have gone on in detail the utility model provides a supersonic speed centripetal turbine, to the general technical personnel in this field, the foundation the utility model discloses the thought of embodiment all has the change part on concrete implementation and application scope, to sum up, this description content should not be understood as right the utility model discloses a restriction.