Design and selection method of the first and last blades of organic fluid expander

Abstract

The invention relates to the technical field of waste heat utilization of bulk energy, and in particular to a method for designing and selecting the first and last blades of an organic working fluid expander, which includes calculating and adjusting the inlet parameters of the first blade group under the inlet parameters corresponding to the low back pressure outlet working condition of the expander, calculating and adjusting the outlet parameters of the last blade group under the low back pressure outlet working condition parameters of the expander, calculating the inlet parameters of the first blade group under the inlet parameters corresponding to the high back pressure outlet working condition of the expander, calculating the outlet parameters of the last blade group under the high back pressure outlet working condition parameters of the expander, calculating the expansion ratio and selecting the number of stages, calculating and determining the throat area, limiting the nozzle outlet angles in the first and last blade groups, and providing a method for designing and selecting the last stage and the last blades of an R245fa organic working fluid expander with high efficiency and good variable working condition performance through the above steps.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat utilization of distributed energy, and in particular to a method for designing and selecting a first set and a last set of blades for an organic working fluid expander. Background Art

[0002] The organic working fluid Rankine cycle system can convert low-temperature waste heat, low-temperature industrial waste heat, and low-pressure or no-pressure geothermal steam that are difficult to utilize in the water vapor Rankine cycle system into electrical energy or mechanical energy. The widespread application of this cycle system has important practical significance for implementing energy conservation and emission reduction and geothermal energy utilization. The organic working fluid turboexpander is the core equipment of the organic Rankine cycle system. Its efficiency and adaptability to changes in system operating conditions are mainly affected by the first and last sets of blades of the expander. Therefore, the design and selection of the first and last sets of blades have become an important part of the design and selection of the cycle system.

[0003] At present, organic working fluid expanders, especially those widely used in the field of low-temperature heat recovery, use R245fa as the circulating medium. Compared with conventional condensing axial flow turbines, the absolute value of the outlet pressure of the last set of blades varies widely, and the outlet medium density is usually more than 100 times that of conventional steam turbines. Due to the similarities and differences between the physical properties of organic working fluids and water vapor, the enthalpy of the first set of blades of organic working fluid expanders is lower than that of water vapor turbines, and high efficiency is required. However, the design and selection method of conventional condensing axial flow turbine turbines is not suitable for the first and last sets of blades of R245fa organic working fluid axial flow turbine expanders. Summary of the invention

[0004] The purpose of the present invention is to provide a method for designing and selecting the first and last groups of blades for an organic working fluid expander, aiming to solve the technical problem that the traditional condensing axial flow turbine steam turbine design and selection method in the prior art is not suitable for the first and last groups of blades for an R245fa organic working fluid axial flow turbine expander.

[0005] To achieve the above object, the present invention adopts a method for designing and selecting the first and last blades of an organic working fluid expander, comprising the following steps:

[0006] Calculate and adjust the first set of blade inlet parameters under the inlet parameters corresponding to the low back pressure outlet condition of the expander;

[0007] Calculate and adjust the parameters of the last blade port of the expander under low back pressure outlet operating parameters;

[0008] Calculate the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander;

[0009] Calculate the outlet parameters of the last blade group under the high back pressure outlet operating parameters of the expander;

[0010] Calculate expansion ratio and select series;

[0011] Calculate and determine throat area;

[0012] Defines the nozzle exit angle in the first and last sets of blades.

[0013] Among them, in the step of calculating and adjusting the parameters of the last blade port under the low back pressure outlet operating parameters of the expander:

[0014] According to the known expander outlet low back pressure parameters, the expander outlet static pressure P out1 and mass flow rate G 1 , first estimate the turbine outlet temperature T out1 , combined with the initially determined exhaust shell, the expander exhaust shell pressure loss △P is calculated out1 , the static pressure at the outlet of the last blade P l1 And the volume flow rate G at the outlet of the last blade l1 .

[0015] Among them, the method for estimating Tout1 is:

[0016] P in1 ,T in1 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in1 ;

[0017] S in1 and P out1 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl1 ;

[0018] Assuming the isentropic efficiency of the expander η to be a value between 82% and 86%, the turbine outlet enthalpy H ssl1 =H f1 -η*(H f1 -H sl1 );H ssl1 and P out1 , using the basic equation of physical properties to calculate T out1 ;

[0019] If △P out1 / (P in1 -P out1 )>0.02, increase the exhaust casing flow capacity, repeat the calculation and adjust the parameters of the last blade port until △P out1 / (P in1 -P out1 )≤0.02.

[0020] Among them, in the step of calculating the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander:

[0021] According to the known inlet parameters corresponding to the high back pressure outlet working condition of the expander, the inlet static pressure P of the expander in2 And static temperature T in2 , mass flow rate G 2 , combined with the shell obtained in step 1, calculate the expander intake shell pressure loss △P in2 , Total pressure P at the inlet of the first set of turbine rotor blades f2 , enthalpy H f2 , volume flow rate G f2 .

[0022] Among them, in the step of calculating the outlet parameters of the last set of blades under the high back pressure outlet operating parameters of the expander:

[0023] According to the known expander outlet high back pressure outlet operating parameters, the expander outlet static pressure P out2 and mass flow rate G 2 , first calculate the turbine outlet temperature T out2 , combined with the exhaust shell obtained in step 2, the pressure loss of the expander exhaust shell △P is calculated out2 , the static pressure at the outlet of the last blade P l2 And the volume flow rate G at the outlet of the last blade l2 .

[0024] Among them, in the steps of calculating the expansion ratio and selecting the series:

[0025] By P f1 , P l1 Find the total expansion ratio π 1 , through P f2 , P l2 Find the total expansion ratio π 2 , the proposed aerodynamic series is 2≤n≤5, so that n satisfies 1.53<π 2 ^(1 / n)<π 1 ^(1 / n)<1.88. When multiple n satisfy the condition at the same time, take the smaller value.

[0026] Among them, in the step of calculating and determining the throat area, the calculation process is:

[0027] π 11 =1.1*π 1 ^(1 / n) as the first-stage blade expansion ratio, combined with G f1 Calculate the throat area A of the first stage impeller under high back pressure state parameters inCR1 , π 21 =0.9*π 1 ^(1 / n) as the expansion ratio of the last blade;

[0028] Using π 11 , G f1 , P f1, the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in1 ;

[0029] Using π 21 , G l1 , P l1 , the throat area A of the last stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out1 ;

[0030] Using π 11 , G f2 , P f2 , the throat area A of the first stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in2 ;

[0031] Using π 21 , G l2 , P l2 , the throat area A of the first stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out2 .

[0032] The beneficial effects of the present invention are as follows: by first calculating and adjusting the inlet parameters of the first group of blades under the inlet parameters corresponding to the low back pressure outlet working condition of the expander, then calculating and adjusting the port parameters of the last group of blades under the low back pressure outlet working condition parameters of the expander, then calculating the inlet parameters of the first group of blades under the inlet parameters corresponding to the high back pressure outlet working condition of the expander, then calculating the outlet parameters of the last group of blades under the high back pressure outlet working condition parameters of the expander, then calculating the expansion ratio and selecting the number of stages, then calculating and determining the throat area, and finally limiting the nozzle outlet angles in the first group and the last group of blades, a high-efficiency R245fa organic working fluid expander terminal with good variable working condition performance is provided. The design and selection method of the first and last stage blades. The pressure, volume flow, mass flow and other operating conditions of the organic working fluid expander have a wide range of variation. Its working medium is organic working fluid, which ensures the inlet pressure of the first group of blades, the outlet pressure of the last group of blades and the expansion ratio of the turbine, and at the same time obtains more accurate turbine inlet and outlet design input parameters; through reasonable stage value selection, the basic and blade shape losses caused by large expansion ratio or the negative impact of the impeller and blade shape caused by too small expansion ratio are avoided; the throat area under each operating condition is calculated, and reasonable throat parameters are selected according to the operating condition characteristics, so that the organic expander can adapt to a wide range of operating conditions and organic working fluid properties, and maintain high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 It is a flow chart of the steps of the method for designing and selecting the first and last blade groups of the organic working fluid expander of the present invention.

[0035] Figure 2 is the estimated T of the present invention out1 Flowchart of the steps.

[0036] Figure 3 is the estimated T of the present invention out2 Flowchart of the steps.

[0037] Figure 4 It is a flow chart of the steps of calculating and determining the throat area of ​​the present invention. DETAILED DESCRIPTION

[0038] See also Figures 1 to 4 The present invention provides a method for designing and selecting the first and last blades of an organic working fluid expander, comprising the following steps:

[0039] S1: Calculate and adjust the first set of blade inlet parameters under the inlet parameters corresponding to the low back pressure outlet condition of the expander;

[0040] S2: Calculate and adjust the parameters of the last blade port under the low back pressure outlet operating parameters of the expander;

[0041] S3: Calculate the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander;

[0042] S4: Calculate the outlet parameters of the last blade group under the high back pressure outlet operating parameters of the expander;

[0043] S5: Calculate the expansion ratio and select the number of stages;

[0044] S6: Calculate and determine the throat area;

[0045] S7: Define the nozzle outlet angles in the first and last groups of blades.

[0046] First, calculate and adjust the inlet parameters of the first group of blades under the inlet parameters corresponding to the low back pressure outlet working condition of the expander, then calculate and adjust the port parameters of the last group of blades under the low back pressure outlet working condition parameters of the expander, then calculate the inlet parameters of the first group of blades under the inlet parameters corresponding to the high back pressure outlet working condition of the expander, then calculate the outlet parameters of the last group of blades under the high back pressure outlet working condition parameters of the expander, then calculate the expansion ratio and select the number of stages, then calculate and determine the throat area, and finally limit the nozzle outlet angles in the first and last groups of blades, so as to provide a high-efficiency R245fa organic working fluid expander with good variable working condition performance and the last stage and last stage blade design. The selection method is used. The pressure, volume flow rate, mass flow rate and other operating conditions of the organic working fluid expander have a wide range of variation. Its working medium is organic working fluid, which ensures the inlet pressure of the first group of blades, the outlet pressure of the last group of blades and the expansion ratio of the turbine, and at the same time obtains more accurate turbine inlet and outlet design input parameters; through reasonable stage values, the basic and blade shape losses caused by large expansion ratios or the negative impact of impeller and blade shape caused by too small expansion ratios are avoided; the throat area under each operating condition is calculated, and reasonable throat parameters are selected according to the operating characteristics, so that the organic expander can adapt to a wide range of operating conditions and organic working fluid properties and maintain high efficiency.

[0047] Among them, in the step of calculating and adjusting the parameters of the last blade port under the low back pressure outlet operating parameters of the expander:

[0048] According to the known expander outlet low back pressure parameters, the expander outlet static pressure P out1 and mass flow rate G 1 , first estimate the turbine outlet temperature T out1 , combined with the initially determined exhaust shell, the expander exhaust shell pressure loss △P is calculated out1 , the static pressure at the outlet of the last blade P l1 And the volume flow rate G at the outlet of the last blade l1 .

[0049] Among them, the estimated T out1 The method is:

[0050] S21: P in1 ,T in1 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in1 ;

[0051] S22: S in1 and P out1 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl1 ;

[0052] S23: Assuming the isentropic efficiency of the expander η to be a value between 82% and 86%, the turbine outlet enthalpy H ssl1 =H f1-η*(H f1 -H sl1 );H ssl1 and P out1 , using the basic equation of physical properties to calculate T out1 ;

[0053] S24: If △P out1 / (P in1 -P out1 )>0.02, increase the exhaust casing flow capacity, repeat the calculation and adjust the parameters of the last blade port until △P out1 / (P in1 -P out1 )≤0.02.

[0054] First, P in1 ,T in1 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in1 , then S in1 and P out1 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl1 , and the isentropic efficiency of the expander η is assumed to be a value between 82% and 86%, and the turbine outlet enthalpy H ssl1 =H f1 -η*(H f1 -H sl1 );H ssl1 and P out1 , using the basic equation of physical properties to calculate T out1 , if △P out1 / (P in1 -P out1 )>0.02, increase the exhaust casing flow capacity, repeat the calculation and adjust the parameters of the last blade port until △P out1 / (P in1 -P out1 )≤0.02.

[0055] Among them, in the step of calculating the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander:

[0056] According to the known inlet parameters corresponding to the high back pressure outlet working condition of the expander, the inlet static pressure P of the expander in2 And static temperature T in2 , mass flow rate G 2 , combined with the shell obtained in step 1, calculate the expander intake shell pressure loss △P in2 , Total pressure P at the inlet of the first set of turbine rotor blades f2 , enthalpy H f2 , volume flow rate G f2 .

[0057] Among them, in the step of calculating the outlet parameters of the last set of blades under the high back pressure outlet operating parameters of the expander:

[0058] According to the known expander outlet high back pressure outlet operating parameters, the expander outlet static pressure P out2 and mass flow rate G 2 , first calculate the turbine outlet temperature T out2 , combined with the exhaust shell obtained in step 2, the pressure loss of the expander exhaust shell △P is calculated out2 , the static pressure at the outlet of the last blade P l2 And the volume flow rate G at the outlet of the last blade l2 .

[0059] Among them, the estimated T out2 The method is:

[0060] S31: P in2 ,T in21 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in2 ;

[0061] S32: S in2 and P out2 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl2 ;

[0062] S33: Combined with the η determined in the improved step 2, the turbine outlet enthalpy H ssl2 =H f2 -η*(H f2 -H sl2 );

[0063] S34: With H ssl2 and P out2 , using the basic equation of physical properties to calculate T out2 .

[0064] First, P in2 ,T in21 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in2 , then S in2 and P out2 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl2 , combined with the η determined in the improved step 2, the turbine outlet enthalpy H ssl2 =H f2 -η*(H f2 -H sl2 ), and finally H ssl2 and P out2 , using the basic equation of physical properties to calculate T out2 .

[0065] Among them, in the steps of calculating the expansion ratio and selecting the series:

[0066] By P f1 , P l1 Find the total expansion ratio π 1 , through P f2 , P l2 Find the total expansion ratio π 2 , the proposed aerodynamic series is 2≤n≤5, so that n satisfies 1.53<π 2 ^(1 / n)<π 1 ^(1 / n)<1.88. When multiple n satisfy the condition at the same time, take the smaller value.

[0067] The inlet pressure of the first set of blades, the outlet pressure of the last set of blades and the expansion ratio of the turbine are guaranteed, and more accurate turbine inlet and outlet design input parameters are obtained.

[0068] Among them, in the step of calculating and determining the throat area, the calculation process is:

[0069] S61: π 11 =1.1*π 1 ^(1 / n) as the first-stage blade expansion ratio, combined with G f1 Calculate the throat area A of the first stage impeller under high back pressure state parameters inCR1 , π 21 =0.9*π 1 ^(1 / n) as the expansion ratio of the last blade;

[0070] S62: Using π 11 , G f1 , P f1 , the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in1 ;

[0071] S63: Using π 21 , G l1 , P l1 , the throat area A of the last stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out1 ;

[0072] S64: Using π 11 , G f2 , P f2 , the throat area A of the first stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in2 ;

[0073] S65: Using π 21 , G l2, P l2 , the throat area A of the last stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out2 .

[0074] First, π 11 =1.1*π 1 ^(1 / n) as the first-stage blade expansion ratio, combined with G f1 Calculate the throat area A of the first stage impeller under high back pressure state parameters inCR1 , π 21 =0.9*π 1 ^(1 / n) as the expansion ratio of the last blade, and then use π 11 , G f1 , P f1 , the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in1 , and then use π 11 , G l1 , P l1 , the throat area A of the last stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out1 , and then use π 21 , G f2 , P f2 , the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in2 , and then use π 21 , G l2 , P l2 , the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out2 , when A in1 / A in2 >1.25 or A in2 / A in1 >1.25, the first-stage blades use partial air intake, in other cases, the first-stage blades use full-circle air intake, and A in1 , A in2 The larger value is taken as the throat area A of the first blade inC , when A in1 / A in2 >1.25 or A in2 / A in1 >1.25, the first-stage blades use partial air intake, in other cases, the first-stage blades use full-circle air intake, and A in1 , A in2 The larger value is taken as the throat area A of the first blade inCR Due to the large difference between the gas density at low back pressure and the gas density at high back pressure, A out1 >Aout2 ,This scheme sets the reaction degree of the last blade group in the range of 0.2 to 0.35 to improve the flow characteristics of the nozzle ring and the moving blades. out1 / A out2 When using A out1 As the final exit throat area A out , when 1.56 ≥ A out1 / A out2 >1.25, let A out =0.9*A out1 , when A out1 / A out2 When >1.56, the first set of blades uses part of the intake air.

[0075] Among them, in the process of defining the nozzle outlet angles in the first and last groups of blades:

[0076] When performing blade profile control, the angle between the airflow at the outlet of the last stage nozzle ring and the axis of the turbine rotor is between 62° and 67°; the angle between the airflow at the outlet of the first stage nozzle ring and the axis of the turbine rotor is between 64° and 70°.

[0077] When performing blade profile control, the angle between the airflow at the outlet of the last-stage nozzle ring and the axis of the turbine rotor is set between 62° and 67°; the angle between the airflow at the outlet of the first-stage nozzle ring and the axis of the turbine rotor is set between 64° and 70°, so that the organic expander can adapt to a wide range of operating conditions and physical properties of organic working fluids and maintain high efficiency.

[0078] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for designing and selecting the first and last blades of an organic fluid expander. It is characterized in that The steps include: Calculate and adjust the first set of blade inlet parameters under the inlet parameters corresponding to the low back pressure outlet condition of the expander; Calculate and adjust the outlet parameters of the last blade group under the low back pressure outlet operating parameters of the expander; Calculate the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander; Calculate the outlet parameters of the last blade group under the high back pressure outlet operating parameters of the expander; Calculate expansion ratio and select series; Calculate and determine throat area; limiting the nozzle exit angles in the first and last groups of blades; In the steps of calculating the expansion ratio and selecting the number of series: By P f1 , P l1 Find the total expansion ratio π 1 , through P f2 , P l2 Find the total expansion ratio π 2 , the proposed aerodynamic series is 2≤n≤5, so that n satisfies 1.53<π 2 ^(1 / n)<π 1 ^(1 / n)<1.

88. When multiple n satisfy the condition at the same time, take the smaller value. In the steps of calculating and determining the throat area, the calculation process is: π 11 =1.1*π 1 ^(1 / n) as the first-stage blade expansion ratio, combined with G f1 Calculate the throat area A of the first stage impeller under high back pressure state parameters inCR1 , π 21 =0.9*π 2 ^(1 / n) as the expansion ratio of the last blade; Using π 11 , G f1 , P f1 , the throat area A of the first stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in1 ; Using π 21 , G l1 , P l1 , the throat area A of the last stage impeller under low back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out1 ; Using π 11 , G f2 , P f2 , the throat area A of the first stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation in2 ; Using π 21 , G l2 , P l2 , the throat area A of the last stage impeller under high back pressure conditions is calculated by combining the throat area calculation equation with the basic physical equation out2 ; When A in1 / A in2 >1.25 or A in2 / A in1 >1.25, the first-stage blades use partial air intake, in other cases, the first-stage blades use full-circle air intake, and A in1 , A in2 The larger value is taken as the throat area A of the first blade inCR ; When 1.25 ≥ A out1 / A out2 When using A out1 As the final exit throat area A out , when 1.56 ≥ A out1 / A out2 >1.25, let A out =0.9*A out1 , when A out1 / A out2 When >1.56, the first set of blades uses part of the intake air.

2. The method for designing and selecting the first and last blades of the organic working fluid expander according to claim 1, It is characterized in that In the steps of calculating and adjusting the outlet parameters of the last blade group under the low back pressure outlet operating parameters of the expander: According to the known expander outlet low back pressure parameters, the expander outlet static pressure P out1 and mass flow rate G 1 , first estimate the turbine outlet temperature T out1 , combined with the initially determined exhaust shell, the expander exhaust shell pressure loss △P is calculated out1 , the static pressure at the outlet of the last blade P l1 And the volume flow rate G at the outlet of the last blade l1 .

3. The method for designing and selecting the first and last blades of the organic working fluid expander according to claim 2, It is characterized in that The method to estimate Tout1 is: P in1 ,T in1 As the independent variable, the entropy S at the turbine inlet is calculated using the basic physical property equation. in1 ; S in1 and P out1 As the independent variable, the isentropic enthalpy H at the turbine outlet is calculated using the basic physical property equation. sl1 ; Assuming the isentropic efficiency of the expander η to be a value between 82% and 86%, the turbine outlet enthalpy H ssl1 =H f1 -η*(H f1 -H sl1 );H ssl1 and P out1 , using the basic equation of physical properties to calculate T out1 ; If △P out1 / (P in1 -P out1 )>0.02, increase the flow capacity of the exhaust casing, repeat the calculation and adjust the parameters of the last blade outlet until △P out1 / (P in1 -P out1 )≤0.

02.

4. The method for designing and selecting the first and last blades of the organic working fluid expander according to claim 3, It is characterized in that In the step of calculating the first set of blade inlet parameters under the inlet parameters corresponding to the high back pressure outlet condition of the expander: According to the known inlet parameters corresponding to the high back pressure outlet working condition of the expander, the inlet static pressure P of the expander in2 And static temperature T in2 , mass flow rate G 2 , combined with the shell obtained in step 1, calculate the expander intake shell pressure loss △P in2 , Total pressure P at the inlet of the first set of turbine rotor blades f2 , enthalpy H f2 , volume flow rate G f2 .

5. The method for designing and selecting the first and last blades of the organic working fluid expander according to claim 4, It is characterized in that In the steps of calculating the outlet parameters of the last set of blades under the high back pressure outlet operating parameters of the expander: According to the known expander outlet high back pressure outlet operating parameters, the expander outlet static pressure P out2 and mass flow rate G 2 , first calculate the turbine outlet temperature T out2 , combined with the exhaust shell obtained in step 2, the pressure loss of the expander exhaust shell △P is calculated out2 , the static pressure at the outlet of the last blade P l2 And the volume flow rate G at the outlet of the last blade l2 .

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