A variable nozzle turbine design method under geometric and aerodynamic constraints

Abstract

The present invention discloses a variable nozzle turbine design method under geometric and aerodynamic constraints. The method is: based on the aerodynamic performance and working fluid conditions of the prototype ordinary turbine under the maximum speed working condition, the design requirements of the variable nozzle turbine and the characteristic constants of the flowing working fluid are determined; the key parameters of the variable nozzle turbine are determined by combining the empirical formula and the volute and impeller dimensions of the prototype ordinary turbine; the overall thermal parameters of the variable nozzle turbine stage are calculated; the variable nozzle turbine wheel diameter ratio and the reaction degree value range are set; the main structural parameters of the nozzle ring are determined according to the structural dimensions of the prototype ordinary turbine volute and the inlet diameter of the variable nozzle turbine impeller; the main structural parameters of the variable nozzle turbine are obtained according to the above calculation results and given parameters. The method improves the low-speed torque characteristics and dynamic responsiveness of ordinary turbocharging technology.

Description

Technical Field

[0001] The present invention relates to the technical field of turbocharger flow-through component design, and more specifically, to a variable nozzle turbine design method under geometric and aerodynamic constraints. Background Art

[0002] As an important component of diesel engines, turbochargers can effectively increase diesel engine power and reduce exhaust emissions. Due to limiting factors such as manufacturing cost and flow capacity, conventional turbocharging technology is usually used in the design of traditional diesel engine turbochargers. However, under extreme environmental conditions such as plateaus, atmospheric pressure, air density and oxygen content decrease, resulting in a sharp drop in the medium and low speed external characteristic torque of conventional turbochargers. At the same time, under transient conditions, the boost pressure response lags, resulting in poor dynamic responsiveness of the diesel engine and other problems.

[0003] The use of variable nozzle turbocharging technology is one of the most effective ways to improve the torque characteristics and dynamic responsiveness of diesel engines under low-speed operating conditions. Variable nozzle turbocharging technology continuously adjusts the effective flow area of ​​the turbine inlet according to the changes in the diesel engine operating conditions, thereby achieving a good match between the supercharger and the diesel engine, and effectively improving the torque characteristics and dynamic responsiveness of the diesel engine. Zhuge Weilin proposed a design method for a variable nozzle turbine by expanding the size of the volute without changing the prototype ordinary turbine impeller. This method effectively improves the torque characteristics and dynamic responsiveness of the diesel engine under low-speed conditions, but leads to problems such as reduced efficiency and increased supercharger size. Summary of the invention

[0004] The purpose of the present invention is to provide a variable nozzle turbine design method under geometric and aerodynamic constraints to improve the low-speed torque characteristics and dynamic responsiveness of the turbocharger in order to address the technical defects existing in the prior art.

[0005] The technical solution adopted to achieve the purpose of the present invention is:

[0006] A variable nozzle turbine design method under geometric and aerodynamic constraints comprises the following steps:

[0007] (1) Based on the aerodynamic performance and working conditions of the prototype ordinary turbine under the maximum speed condition, determine the design requirements of the variable nozzle turbine, including: inlet flow G, inlet total pressure Outlet static pressure P2, inlet total temperature The wheel efficiency η0 and the turbine speed n T ; Determine the characteristic constants of the flowing fluid, including: gas constant R, isobaric specific heat capacity c p and specific heat ratio k;

[0008] (2) Combined with the scope of experience ( 0.75≤ψ≤0.85, 14°≤α1≤25°, etc.) and the volute and impeller dimensions of the prototype ordinary turbine to determine the key parameters of the variable nozzle turbine, including: impeller inlet diameter D1, nozzle ring speed coefficient Impeller speed coefficient ψ, nozzle ring outlet blade airflow angle α1, impeller outlet relative airflow angle β2, impeller inlet and outlet blockage coefficients τ1, τ2;

[0009] (3) Calculate the overall thermal parameters of the variable nozzle turbine stage. The calculation formula is as follows:

[0010]

[0011] In the formula, π T is the turbine stage expansion ratio, is the isentropic expansion work of the turbine stage, c a is the turbine imaginary expansion velocity, k is the specific heat ratio;

[0012] (4) Setting the variable nozzle turbine wheel diameter ratio The range of the reaction degree Ω [Ω0,Ω n ] and iteration step length h;

[0013] (5) Setting the variable nozzle turbine wheel diameter ratio

[0014] (6) Set the variable nozzle turbine reaction degree Ω = Ω0;

[0015] (7) Calculate the variable nozzle turbine impeller inlet parameters. The calculation formula is as follows:

[0016]

[0017] In the formula, is the isentropic expansion work in the nozzle ring, c1 is the absolute velocity at the impeller inlet, P1 is the working fluid pressure at the impeller inlet, T1 is the working fluid temperature at the impeller inlet, ρ1 is the working fluid density at the impeller inlet, Z is the number of blades at the impeller inlet, and l1 is the blade height at the impeller inlet;

[0018] (8) Calculate the variable nozzle turbine impeller outlet parameters. The calculation formula is as follows:

[0019]

[0020] Where u1 is the impeller circumferential speed, u2 is the circumferential speed at the impeller outlet mid-diameter, D2 is the geometric mid-diameter of the impeller outlet section, β1 is the relative airflow angle of the impeller inlet, ω1 is the relative velocity of the impeller inlet, ω2 is the relative velocity of the impeller outlet, T2 is the working fluid temperature at the impeller outlet, ρ2 is the working fluid density at the impeller outlet, and A is 2p is the geometric area of ​​the impeller outlet cross section, D2s is the impeller outlet outer diameter, D 2h is the inner diameter of the impeller outlet;

[0021] (9) Calculate the variable nozzle turbine stage circumferential efficiency. The calculation formula is as follows:

[0022]

[0023] Where η is the variable nozzle turbine stage circumferential efficiency obtained by one-dimensional thermodynamic calculation;

[0024] (10) Determine the variable nozzle turbine impeller outlet inner diameter D 2h The diameter of the shaft connected to the prototype ordinary turbocharger is D shaft , the relationship between the variable nozzle turbine stage circumferential efficiency η and the prototype ordinary turbine stage circumferential efficiency η0 and the variable nozzle turbine impeller inlet relative speed ω1 and outlet relative speed ω2. If D 2h ≤D shaft ||η≤η0||ω2<ω1, then execute step (11); otherwise, execute step (12);

[0025] (11) Let Ω = Ω + h, and judge whether Ω and Ω n If Ω≤Ω n , then return to step (7); otherwise, let Return to step (6);

[0026] (12) According to the prototype common turbine volute base circle diameter D0, the volute outlet section height b and the variable nozzle turbine impeller inlet diameter D1, the nozzle ring inlet and outlet diameters D are determined. n0 , D n1 And the nozzle blade height l n , the calculation formula is as follows:

[0027]

[0028] So far, the main structural parameters of the variable nozzle turbine have been calculated, including: impeller inlet diameter D1, impeller outlet inner and outer diameters D 2h , D 2s , impeller inlet blade height l1, impeller inlet blade number Z, nozzle ring outlet blade flow angle α1, nozzle ring inlet and outlet diameter D n0 , D n1 , nozzle blade height l n The variable nozzle turbine design method under the above geometric and aerodynamic constraints can be applied to the design of existing common turbine modifications or to the design of variable nozzle turbines.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The variable nozzle turbine design method under geometric and aerodynamic constraints of the present invention uses an iterative solution method to perform variable nozzle turbine thermal calculations, which can quickly calculate the main structural parameters of the variable nozzle turbine under the premise of meeting the design requirements. The variable nozzle turbine design based on the method of the present invention can effectively solve the technical problems of insufficient torque and dynamic response hysteresis when ordinary turbocharging technology runs at low speed in extreme environments such as plateaus.

[0031] 2. The present invention provides a variable nozzle turbine design method under geometric and aerodynamic constraints, which can be used for the retrofit design of existing common turbines. Based on the method of the present invention, the design of a variable nozzle turbine can be achieved by reducing the size of the prototype turbine impeller while ensuring that the overall aerodynamic performance of the prototype common turbine remains unchanged. At the same time, since the size of the prototype common turbine volute is not changed, the overall structural size of the variable nozzle turbocharger after the retrofit design does not change, which has better practical application significance for improving the torque characteristics and dynamic responsiveness of common turbocharging technology. DETAILED DESCRIPTION

[0032] The variable nozzle turbine design method under geometric and aerodynamic constraints of the present invention is described in detail below with reference to examples. It should be noted that this embodiment is narrative and does not limit the scope of protection of the present invention.

[0033] The variable nozzle turbine design method under geometric and aerodynamic constraints of the present invention constrains the size and aerodynamic performance of the variable nozzle turbine according to the size and aerodynamic performance of the prototype ordinary turbine volute, and provides specific steps for one-dimensional thermal calculation of the variable nozzle turbine.

[0034] The variable nozzle turbine design method under geometric and aerodynamic constraints of the present invention specifically comprises the following steps:

[0035] (1) Based on the aerodynamic performance and working conditions of the prototype ordinary turbine under the maximum speed condition, the design requirements of the variable nozzle turbine are determined, including: inlet flow rate G, inlet total pressure Outlet static pressure P2, inlet total temperature The wheel efficiency η0 and the turbine speed n T ; Determine the characteristic constants of the flowing fluid, including: gas constant R, isobaric specific heat capacity c p and specific heat ratio k;

[0036] (2) Combined with the scope of experience ( 0.75≤ψ≤0.85, 14°≤α1≤25°, etc.) and the volute and impeller dimensions of the prototype ordinary turbine to determine the key parameters of the variable nozzle turbine, including: impeller inlet diameter D1, nozzle ring speed coefficient Impeller speed coefficient ψ, nozzle ring outlet blade airflow angle α1, impeller outlet relative airflow angle β2, impeller inlet and outlet blockage coefficients τ1, τ2;

[0037] (3) Calculate the overall thermal parameters of the variable nozzle turbine stage. The calculation formula is as follows:

[0038]

[0039] In the formula, π T is the turbine stage expansion ratio, is the isentropic expansion work of the turbine stage, c a is the turbine imaginary expansion velocity, k is the specific heat ratio;

[0040] (4) Setting the variable nozzle turbine wheel diameter ratio The range of the reaction degree Ω [Ω0,Ω n ] and iteration step length h;

[0041] (5) Setting the variable nozzle turbine wheel diameter ratio

[0042] (6) Set the variable nozzle turbine reaction degree Ω = Ω0;

[0043] (7) Calculate the variable nozzle turbine impeller inlet parameters. The calculation formula is as follows:

[0044]

[0045] In the formula, is the isentropic expansion work in the nozzle ring, c1 is the absolute velocity at the impeller inlet, P1 is the working fluid pressure at the impeller inlet, T1 is the working fluid temperature at the impeller inlet, ρ1 is the working fluid density at the impeller inlet, Z is the number of blades at the impeller inlet, and l1 is the blade height at the impeller inlet;

[0046] (8) Calculate the variable nozzle turbine impeller outlet parameters. The calculation formula is as follows:

[0047]

[0048] Where u1 is the impeller circumferential speed, u2 is the circumferential speed at the impeller outlet mid-diameter, D2 is the geometric mid-diameter of the impeller outlet section, β1 is the relative airflow angle of the impeller inlet, ω1 is the relative velocity of the impeller inlet, ω2 is the relative velocity of the impeller outlet, T2 is the working fluid temperature at the impeller outlet, ρ2 is the working fluid density at the impeller outlet, and A is 2p is the geometric area of ​​the impeller outlet cross section, D 2s is the impeller outlet outer diameter, D 2h is the inner diameter of the impeller outlet;

[0049] (9) Calculate the variable nozzle turbine stage circumferential efficiency. The calculation formula is as follows:

[0050]

[0051] Where η is the variable nozzle turbine stage circumferential efficiency obtained by one-dimensional thermodynamic calculation;

[0052] (10) Determine the variable nozzle turbine impeller outlet inner diameter D 2h The diameter of the shaft connected to the prototype ordinary turbocharger is D shaft , the relationship between the variable nozzle turbine stage circumferential efficiency η and the prototype ordinary turbine stage circumferential efficiency η0 and the variable nozzle turbine impeller inlet relative speed ω1 and outlet relative speed ω2. If D 2h ≤D shaft ||η≤η0||ω2<ω1, then execute step (11); otherwise, execute step (12);

[0053] (11) Let Ω = Ω + h, and judge whether Ω and Ω n If Ω≤Ω n , then return to step (7); otherwise, let Return to step (6);

[0054] (12) According to the prototype common turbine volute base circle diameter D0, the volute outlet section height b and the variable nozzle turbine impeller inlet diameter D1, the nozzle ring inlet and outlet diameters D are determined. n0 , D n1 And the nozzle blade height l n , the calculation formula is as follows:

[0055]

[0056] So far, the main structural parameters of the variable nozzle turbine have been calculated, including: impeller inlet diameter D1, impeller outlet inner and outer diameters D 2h , D 2s , impeller inlet blade height l1, impeller inlet blade number Z, nozzle ring outlet blade flow angle α1, nozzle ring inlet and outlet diameter D n0 , D n1 , nozzle blade height l n .

[0057] Example: The specific process of designing a modification from a common industrial turbine to a variable nozzle turbine is as follows:

[0058] 1) Determine the design requirements of the variable nozzle turbine and the characteristic constants of the flow medium: inlet flow rate G = 0.9292 kg / s, inlet total pressure P0 * =278622Pa, outlet static pressure P2 = 90000Pa, inlet total temperature T0 *=903.15K, wheel efficiency η0 = 0.70, turbine speed n T =72000rpm, gas constant R = 287, isobaric specific heat capacity c p =1131 J / (kg·K), specific heat ratio k=1.34;

[0059] 2) Determine the key parameters of the variable nozzle turbine: impeller inlet diameter D1 = 110 mm, nozzle ring velocity coefficient Impeller speed coefficient ψ = 0.95, nozzle ring outlet blade airflow angle α1 = 27 degrees, impeller outlet relative airflow angle β2 = 40 degrees, impeller inlet and outlet blocking coefficients τ1 = 0.965, τ2 = 0.85;

[0060] 3) According to formula (1), the overall thermal parameters of the variable nozzle turbine stage are calculated. The result is the turbine stage expansion ratio π T =3.0958, turbine stage isentropic expansion work Turbine imaginary expansion speed c a =713.63m / s;

[0061] 4) Setting the variable nozzle turbine wheel diameter ratio Reaction degree Ω∈[0.4, 0.6], iteration step h=0.01;

[0062] 5) Setting the variable nozzle turbine wheel diameter ratio Final Result

[0063] 6) Set the variable nozzle turbine reaction degree Ω = 0.4, and the final result Ω = 0.56;

[0064] 7) According to formula (2), the main structural parameters of the variable nozzle turbine impeller inlet are calculated. The final result is that the number of impeller inlet blades Z = 12, and the impeller inlet blade height l1 = 17.6 mm;

[0065] 8) According to formula (3), the main structural parameters of the variable nozzle turbine impeller outlet are calculated, and the final result is the impeller outlet outer diameter D 2s =103mm, impeller outlet inner diameter D 2h =20.1mm;

[0066] 9) The variable nozzle turbine stage circumferential efficiency is calculated according to formula (4), and the final result is that the variable nozzle turbine stage circumferential efficiency η = 0.74;

[0067] 10) Judge D 2h ≤D shaft ||η≤η0||ω2<ω1(D shaft =20mm), if it is satisfied, go to step 11), otherwise go to step 12);

[0068] 11) Let Ω=Ω+0.01, and determine the relationship between Ω and Ω n =0.6. If Ω≤Ω n , then return to step 7); otherwise, let Return to step 6);

[0069] 12) According to the prototype common turbine volute base circle diameter D0 = 130 mm, volute outlet section height b = 17 mm, variable nozzle turbine impeller inlet diameter D1 = 110 mm and formula (5), determine the nozzle ring inlet diameter D n0 =130mm, nozzle ring outlet diameter D n1 =114mm, nozzle blade height l n =17mm;

[0070] The variable nozzle turbine design method under geometric and aerodynamic constraints of the present invention iteratively calculates the one-dimensional thermal calculation method of the variable nozzle turbine under the constraints of the volute size and aerodynamic performance of the prototype ordinary turbine, thereby realizing the rapid design of the main structural parameters of the variable nozzle turbine, while ensuring that the overall size and aerodynamic performance of the turbine do not change, thereby solving the difficult problems of insufficient low-speed torque and dynamic response hysteresis of ordinary turbocharging technology, and realizing the retrofit design of the ordinary turbine to the variable nozzle turbine.

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A variable nozzle turbine design method under geometric and aerodynamic constraints, characterized in that: The steps include: (1) Based on the aerodynamic performance and working conditions of the prototype ordinary turbine under the maximum speed condition, the design requirements of the variable nozzle turbine are determined, including: inlet flow rate G, inlet total pressure Outlet static pressure P2, inlet total temperature The wheel efficiency η0 and the turbine speed n T ; Determine the characteristic constants of the flowing fluid, including: gas constant R, isobaric specific heat capacity c p and specific heat ratio k; (2) Combined with the empirical range: 0.92≤φ≤0.97, 0.75≤Ψ≤0.85, 14°≤α1≤25°, and the volute and impeller dimensions of the prototype ordinary turbine, the key parameters of the variable nozzle turbine are determined, including: impeller inlet diameter D1, nozzle ring velocity coefficient Impeller speed coefficient ψ, nozzle ring outlet blade airflow angle α1, impeller outlet relative airflow angle β2, impeller inlet and outlet blockage coefficients τ1, τ2; (3) Calculate the overall thermal parameters of the variable nozzle turbine stage. The calculation formula is as follows: In the formula, π T is the turbine stage expansion ratio, is the isentropic expansion work of the turbine stage, c a is the turbine imaginary expansion velocity, k is the specific heat ratio; (4) Setting the variable nozzle turbine wheel diameter ratio The range of the reaction degree Ω [Ω0,Ω n ] and iteration step length h; (5) Setting the variable nozzle turbine wheel diameter ratio (6) Set the variable nozzle turbine reaction degree Ω = Ω0; (7) Calculate the variable nozzle turbine impeller inlet parameters. The calculation formula is as follows: In the formula, is the isentropic expansion work in the nozzle ring, c1 is the absolute velocity at the impeller inlet, P1 is the working fluid pressure at the impeller inlet, T1 is the working fluid temperature at the impeller inlet, ρ1 is the working fluid density at the impeller inlet, Z is the number of blades at the impeller inlet, and l1 is the blade height at the impeller inlet; (8) Calculate the variable nozzle turbine impeller outlet parameters. The calculation formula is as follows: Where u1 is the impeller circumferential speed, u2 is the circumferential speed at the impeller outlet mid-diameter, D2 is the geometric mid-diameter of the impeller outlet section, β1 is the relative airflow angle of the impeller inlet, ω1 is the relative velocity of the impeller inlet, ω2 is the relative velocity of the impeller outlet, T2 is the working fluid temperature at the impeller outlet, ρ2 is the working fluid density at the impeller outlet, and A is 2p is the geometric area of ​​the impeller outlet cross section, D 2s is the impeller outlet outer diameter, D 2h is the inner diameter of the impeller outlet; (9) Calculate the variable nozzle turbine stage circumferential efficiency. The calculation formula is as follows: Where η is the variable nozzle turbine stage circumferential efficiency obtained by one-dimensional thermodynamic calculation; (10) Determine the variable nozzle turbine impeller outlet inner diameter D 2h The diameter of the shaft connected to the prototype ordinary turbocharger is D shaft , the relationship between the variable nozzle turbine stage circumferential efficiency η and the prototype ordinary turbine stage circumferential efficiency η0 and the variable nozzle turbine impeller inlet relative speed ω1 and outlet relative speed ω2; if D 2h ≤D shaft ‖η≤η0||ω2<ω1, then execute step (11); otherwise, execute step (12); (11) Let Ω = Ω + h, and judge whether Ω and Ω n The size relationship; if Ω≤Ω n , then return to step (7); otherwise, let Return to step (6); (12) According to the prototype common turbine volute base circle diameter D0, the volute outlet section height b and the variable nozzle turbine impeller inlet diameter D1, the nozzle ring inlet and outlet diameters D are determined. n0 , D n1 And the nozzle blade height l n , the calculation formula is as follows:

2. An application of the variable nozzle turbine design method under geometric and aerodynamic constraints as described in claim 1 in the design of existing ordinary turbine modifications; or in the design of variable nozzle turbines.

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