JP2012177355A - Twin scroll type radial flow turbine and supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase turbine efficiency of a twin scroll type radial flow turbine by suppressing pressure loss in a turbine impeller.SOLUTION: A relation between a circumferential angle θ and an axial position z of a turbine impeller 7 at an arbitrary point of a turbine rotor blade 11 is determined by a prescribed curved line CL. The axial position of the curved line CL at a curved point F is set so as to be the same as the axial position of an intersection N between an extension line EL of a distal end edge 23T of a partition wall 23 and a front edge of the turbine rotor blade 11.

Description

  The present invention relates to a twin scroll type mixed flow turbine that generates a rotational force using pressure energy of exhaust gas exhausted from an engine.

  In recent years, various developments have been made on twin-scroll turbines that can increase the rotational efficiency by the pulse effect of engine exhaust. The configuration of a typical twin-scroll turbine is briefly described as follows. (See Patent Document 1 and Patent Document 2).

  A typical twin scroll type turbine includes a turbine housing, and a turbine impeller is rotatably provided in the turbine housing. The turbine impeller includes a wheel that can rotate around an axis (the axis of the turbine impeller), and a plurality of turbine blades that are provided on the outer peripheral surface of the wheel at intervals in the circumferential direction.

  The turbine housing is formed with a gas intake port for taking in exhaust gas from the engine, and a gas exhaust port for discharging the exhaust gas is formed at the outlet side of the turbine impeller in the turbine housing. An annular (spiral) twin scroll flow path is formed inside the turbine housing so as to surround the turbine impeller, and the twin scroll flow path communicates with the gas inlet. An annular (spiral) partition wall is formed in the twin scroll flow path, and the twin scroll flow path is separated from the hub side portion (wheel side) of the front edge of a plurality of turbine rotor blades by the partition wall. An annular first scroll passage for supplying exhaust gas toward the portion) and an annular second scroll for supplying exhaust gas toward the shroud side portion (tip side portion) of the leading edge of the plurality of turbine rotor blades It is divided into a flow path.

  Therefore, the exhaust gas taken in from the gas inlet is circulated from the inlet side to the outlet side of the turbine impeller via the twin scroll flow path (first scroll flow path and second scroll flow path). Thereby, a rotational force (rotational torque) can be generated using the pressure energy of the exhaust gas. Here, by rotating the exhaust gas having different exhaust timing from the engine through the first scroll flow path and the second scroll flow path, the rotational efficiency of the turbine impeller can be increased by the pulse effect of the exhaust of the engine.

JP 2006-348894 A JP 2009-281197 A

  By the way, in the twin scroll type turbine, the front edge of the turbine blade is parallel to the axis of the turbine impeller, and the front edge of the turbine blade is directed from the shroud side (tip side) to the hub side (wheel side). Accordingly, it can be divided into a mixed flow turbine inclined with respect to the axis so as to gradually approach the axis. In addition, the latter twin scroll type mixed flow turbine can improve the acceleration response of the turbine impeller by reducing the wheel thickness compared to the former twin scroll type radial turbine. Attention has been paid.

  However, in the twin scroll type mixed flow turbine, the first scroll inflow of the exhaust gas flowing into the hub side portion of the front edge of the turbine rotor blade from the first scroll flow path in the direction parallel to the axial direction. Although the angle is acute, the second scroll inflow angle of the exhaust gas flowing from the second scroll flow path into the tip side portion of the leading edge of the turbine rotor blade becomes an obtuse angle. The sign of the metal angle (blade angle of the leading edge) is reversed from positive to negative on the way from the hub side to the shroud side, increasing the incidence, which is the difference between the exhaust gas flow angle and the turbine blade inlet metal angle (See paragraph). Therefore, there is a problem that the pressure loss (energy loss) in the turbine impeller (between adjacent turbine blades) increases, and the turbine efficiency of the twin scroll type mixed flow turbine decreases.

  Therefore, an object of the present invention is to provide a twin scroll type mixed flow turbine having a novel configuration capable of solving the above-described problems.

  The inventor of the present application has repeated trial and error in order to solve the above-mentioned problems, and has found new knowledge, and has completed the present invention based on this new knowledge. Before explaining the features of the present invention, the process until finding new knowledge will be described.

  According to the literature (Srithar Rajoo, Ricardo Martinez-Botas, 2008, "Mixed Flow Turbine Research: A Review" ASME Journal of Turbomachinery, vol. 130) investigated by the inventors of the present invention, a single scroll type mixed flow turbine In the following, the following equation (between the inlet metal angle (blade angle of the leading edge) βb of the turbine blade, the cone angle λ of the turbine blade (see FIG. 4), and the chamber angle φ of the turbine blade: The relationship 1) is established.

tanβb = cosλ · tanφ Equation (1)
Further, in the turbine rotor blade configured based on the radial elements, it extends radially outward (radially) from the axis of the turbine impeller in an arbitrary cross section along the radial direction of the turbine impeller. In other words, the relationship between the axial position (turbine impeller axial position) z and the circumferential angle (circumferential angle about the turbine impeller axis SC) θ at an arbitrary point of the turbine rotor blade is shown in FIG. As shown in FIG. 2, the curve is determined by a prescribed curve (θ = f (z)). When the radial position (radial position) r at an arbitrary point of the turbine rotor blade is set, the relationship of tan φ = r (dθ / dz) is established. Therefore, equation (1) can be replaced with equation (2) described later.

tan βb = cos λ · r (dθ / dz) Equation (2)
When applying the formula (2) to a twin scroll type mixed flow turbine, when flowing from the first scroll flow path to the hub side portion of the front edge of the turbine rotor blade (when flowing from the first scroll flow), It is necessary to divide the flow into the shroud side portion (tip side portion) of the leading edge of the turbine rotor blade from the second scroll flow path (when flowing from the second scroll flow path).

  As shown in FIG. 5, when flowing from the first scroll flow path, the cone angle λ in the equation (2) is an angle (hereinafter referred to as the flow angle from the first scroll flow path with respect to a direction parallel to the axial direction). It can be regarded as synonymous with λa (referred to as first scroll inflow angle as appropriate), and equation (2) can be replaced by equation (3) described later. Here, the first scroll inflow angle λa is an acute angle (λa <90 °).

tan βb = cos λa · r (dθ / dz) (3)
Similarly, when flowing from the second scroll flow path, the cone angle λ in the equation (2) is an angle flowing from the second scroll flow path with respect to a direction parallel to the axial direction (hereinafter referred to as “ It can be considered that it is synonymous with λb (referred to as a two-scroll inflow angle), and equation (2) can be replaced by equation (4) below. Here, the second scroll inflow angle λb is an obtuse angle (λb> 90 °).

tan βb = cos λa · r (dθ / dz) (4)
In the conventional twin scroll type mixed flow turbine, cos λa> 0 in the equation (3) and r (dθ / dz)> 0 in the equation (3), so that tan βb> 0 when flowing from the first scroll flow path. Thus, the inlet metal angle βb> 0 of the hub side portion of the turbine rotor blade is satisfied. On the other hand, since cos λa <0 in equation (4) and r (dθ / dz)> 0 in equation (4), tan βb <0 when flowing from the second scroll flow path, and the turbine blade shroud The side entry metal angle βb <0. In other words, the sign of the inlet metal angle of the turbine blade is reversed from positive to negative on the way from the hub side (shroud side) to the shroud side (tip side), and as shown in FIG. Incidence i, which is the difference between β and the inlet metal angle βb of the turbine blade, increases. The flow angle β of the exhaust gas increases in inverse proportion to the radial length of the leading edge of the turbine rotor blade.

  As a result of examining the above-mentioned points, the inventor of the present application has determined that the sign of the inlet metal angle βb of the turbine rotor blade is not reversed from positive to negative in the middle from the hub side to the shroud side (tip side) It has been found that it is necessary to satisfy r (dθ / dz) <0 in equation (4). That is, the axial position at the inflection point F of the curve CL (the axial position where dθ / dz = 0) is the axial position at the intersection N between the extension line EL of the leading edge of the partition wall and the leading edge of the turbine blade. The sign of the inlet metal angle of the turbine blade is not reversed from positive to negative on the way from the hub side to the shroud side, and the exhaust gas flow angle β It was possible to find a new finding that the incidence i, which is the difference in the blade inlet metal angle βb, can be reduced.

  Next, features of the present invention will be described.

  A first feature of the present invention is a twin scroll type that is used in a supercharger that supercharges air supplied to an engine side, and that generates a rotational force using pressure energy of exhaust gas exhausted from the engine. A turbine turbine having a shroud (inner wall) inside, a wheel rotatably provided in the turbine housing and rotatable about an axis (axis of a turbine impeller), and the wheel As the front edge extends from the shroud side (tip side) to the hub side (the wheel side or the root side), the tip edge extends along the shroud of the turbine housing. A turbine impeller comprising a plurality of turbine rotor blades inclined with respect to the axis so as to gradually approach the axis. A gas intake port for taking in exhaust gas exhausted from the engine is formed in the engine housing, and a gas exhaust port for discharging exhaust gas is formed on the outlet side of the turbine impeller in the turbine housing. An annular (spiral) twin scroll flow path communicating with the gas inlet is formed so as to surround the turbine impeller, an annular partition wall is formed in the twin scroll flow path, and the twin scroll flow path is An annular first scroll passage for supplying exhaust gas toward the hub side portion of the front edge of the plurality of turbine blades by the partition wall, and the shroud side of the front edge of the plurality of turbine blades The turbine rotor blade, which is partitioned by an annular second scroll flow path for supplying exhaust gas toward the portion (tip side portion) The relationship between the axial position at an arbitrary point (axial position of the turbine impeller) and the circumferential angle (circumferential angle around the axis of the turbine impeller) is determined by a prescribed curve. And the axial position of the inflection point of the curve is the same as the axial position at the intersection of the extension line of the leading edge (center of the leading edge) of the partition wall and the leading edge of the turbine blade. It is set as the gist.

  According to the first aspect of the present invention, the exhaust gas taken in from the gas intake port passes through the twin scroll flow path (the first scroll flow path and the second scroll flow path), and the inlet side of the turbine impeller From the outlet to the outlet side. Thereby, a rotational force (rotational torque) can be generated using the pressure energy of the exhaust gas. Here, exhaust gas having different exhaust timing from the engine is alternately circulated through the first scroll flow path and the second scroll flow path, thereby increasing the rotation efficiency of the turbine impeller by the pulse effect of the engine exhaust. be able to.

  The relationship between the axial position and the circumferential angle at an arbitrary point of the turbine blade is determined by the curve, and the axial position at the inflection point of the curve is determined by the extension line of the leading edge of the partition wall and the turbine motion. Since it is set to be the same as the axial position at the intersection with the leading edge of the blade, the sign of the inlet metal angle of the turbine blade is directed from the hub side to the shroud side when the above-described novel knowledge is applied. There is no inversion on the way from positive to negative, and the incidence, which is the difference between the flow angle of the exhaust gas and the inlet metal angle of the turbine rotor blade, can be reduced.

  The gist of a second feature of the present invention is that the supercharger for supercharging the air supplied to the engine side includes the twin scroll type mixed flow turbine having the first feature.

  According to the 2nd characteristic, there exists an effect | action similar to the effect | action by a 1st characteristic.

  According to the present invention, the sign of the inlet metal angle of the turbine blade is not reversed from positive to negative in the middle from the hub side to the tip side, and the incidence can be reduced, so that the inside of the turbine impeller (in the adjacent relationship) It is possible to increase the turbine efficiency of the twin scroll type mixed flow turbine by suppressing the pressure loss between the turbine blades.

FIG. 1 is a view showing a main part of a twin scroll type mixed flow turbine according to an embodiment of the present invention, and is a partial view showing a relationship between an axial position and a circumferential angle at an arbitrary point of a turbine rotor blade. Contains. FIG. 2 is a diagram showing the flow angle of exhaust gas and the inlet metal angle of the turbine blade from the hub side to the shroud side of the turbine blade in the twin scroll type mixed flow turbine according to the embodiment of the present invention. FIG. 3 is a side sectional view of a twin scroll type mixed flow turbine according to an embodiment of the present invention. FIG. 4 is a diagram for explaining the process up to finding new knowledge, and is a part showing the relationship between the axial position and the circumferential angle at an arbitrary point of the turbine rotor blade in a single scroll type mixed flow turbine. Includes figures. FIG. 5 is a diagram for explaining the process until finding new knowledge. Specifically, the first scroll passage angle and the second scroll passage angle of the twin scroll type mixed flow turbine are explained. Yes. FIG. 6 is a diagram for explaining the process up to finding new knowledge. In a conventional twin scroll type mixed flow turbine, the flow angle of exhaust gas and the inlet metal angle of the turbine blade are set as the hub of the turbine blade. Shown from side to shroud.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the drawings, “FF” indicates the forward direction, and “FR” indicates the backward direction.

  As shown in FIG. 3, the twin scroll type mixed flow turbine according to the embodiment of the present invention is used in a supercharger for a vehicle that supercharges air supplied to the engine side, and exhaust gas exhausted from the engine. The rotational energy is generated using the pressure energy. The specific configuration of the twin scroll type mixed flow turbine 1 is as follows.

  The twin scroll type mixed flow turbine 1 includes a turbine housing 3, and the turbine housing 3 has a shroud (inner wall) 3S on the inner side. Moreover, the turbine housing 3 is being fixed to the rear side of the bearing housing 5 in the supercharger for vehicles.

  A turbine impeller 7 is rotatably provided in the turbine housing 3. The components of the turbine impeller 7 will be described. A wheel 9 is provided in the turbine housing 3, and the wheel 9 can rotate around the axis SC of the turbine impeller 7. The outer peripheral surface (hub surface) extends radially outward from the axial direction (front-rear direction) of the turbine impeller 7. A plurality of turbine blades 11 are provided on the outer peripheral surface of the wheel 9 at intervals in the circumferential direction, and a tip edge (outer edge) 11T of each turbine blade 11 is a shroud 3S of the turbine housing 3. It extends so that. Furthermore, the front edge 11L of each turbine blade 11 is gradually moved closer to the axis SC of the turbine impeller 7 from the shroud side (tip side) toward the hub side (wheel 9 side or root side). It is inclined with respect to the axis SC. The wheel 9 is integrally connected to one end (rear end) of a turbine shaft (rotor shaft) 15 that is rotatably supported by the bearing housing 5 via a bearing 13 or the like.

  A gas intake port 17 for taking in exhaust gas exhausted from the engine is formed at an appropriate position of the turbine housing 3, and this gas intake port 17 can be connected to an exhaust manifold (not shown) of the engine. Further, a gas discharge port 19 for discharging exhaust gas is formed on the outlet side of the turbine impeller 7 in the turbine housing 3 (the rear side of the turbine housing 3). The gas discharge port 19 is directed rearward. The diameter is increased.

  An annular (spiral) twin scroll passage 21 is formed in the turbine housing 3 so as to surround the turbine impeller 7, and the twin scroll passage 21 communicates with the gas inlet 17. An annular (spiral) partition wall 23 is formed in the twin scroll flow path, and an extension line EL of the leading edge 23T (center of the leading edge 23T) of the partition wall 23 is the turbine blade 11. It intersects with the front edge 11L. The twin scroll flow path 21 is an annular (spiral) first scroll flow path 25 that supplies exhaust gas toward the hub side portion 11Lh of the front edge 11L of the plurality of turbine rotor blades 11 by the partition wall 23. And an annular (spiral) second scroll passage 27 that supplies exhaust gas toward the shroud side portion (tip side portion) 11Ls of the leading edge 11L of the plurality of turbine blades 11. ing. In addition, the flow path areas of the first scroll flow path 25 and the second scroll flow path 27 are gradually reduced along the rotation direction of the turbine impeller 7.

  Then, the characteristic part of the twin scroll type mixed flow turbine 1 which concerns on embodiment of this invention is demonstrated.

  As shown in FIG. 1, the plurality of turbine blades 11 are configured based on radial elements as shown in Japanese Patent Application Laid-Open No. 2008-133765, and specifically, in the radial direction of the turbine impeller 7. It is configured to extend radially from the axial center SC of the turbine impeller 7 (in the radial direction outside of the turbine impeller 7) in an arbitrary cross section along. In other words, the axial position of the turbine impeller 7 at an arbitrary point of the turbine rotor blade 11 (the axial position of the turbine impeller 7) z and the circumferential angle (the circumferential angle around the axis SC of the turbine impeller 7) θ. 1 is determined by a prescribed curve CL (θ = f (z)) as shown in FIG. The axial position at the inflection point F of the curve CL is set to be the same as the axial position of the intersection N between the extension line EL of the leading edge 23T of the partition wall 23 and the front edge of the turbine blade 11. ing.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  Exhaust gas taken in from the gas inlet 17 is circulated from the inlet side to the outlet side of the turbine impeller 7 via the twin scroll passage 21 (the first scroll passage 25 and the second scroll passage 27). Thereby, the turbine shaft 15 can be rotated by generating a rotational force (rotational torque) using the pressure energy of the exhaust gas. Here, by rotating the exhaust gas having different exhaust timing from the engine through the first scroll passage 25 and the second scroll passage 27 alternately, the rotational efficiency of the turbine impeller 7 is enhanced by the pulse effect of the exhaust of the engine. Can do.

  The relationship between the axial position z and the circumferential angle θ at an arbitrary point of the turbine rotor blade 11 is determined by the defined curve CL, and the axial position at the inflection point F of the curve CL is the tip edge 23T of the partition wall 23. 2 and the front edge 11L of the turbine rotor blade 11 are set to be the same as the axial position at the intersection N. Therefore, when the above-described novel knowledge is applied, as shown in FIG. The sign of the inlet metal angle βb of the rotor blade 11 does not reverse from positive to negative on the way from the hub side to the shroud side, and the flow angle of the exhaust gas compared to the twin scroll type mixed flow turbine according to the conventional example Incidence i, which is the difference between β and the inlet metal angle βb of the turbine rotor blade 11, can be sufficiently reduced. In FIG. 2, the inlet metal angle βb of the turbine rotor blade in the twin scroll type mixed flow turbine according to the conventional example is shown by a two-dot chain line.

  Therefore, according to the twin scroll type mixed flow turbine 1 according to the embodiment of the present invention, the incidence i can be sufficiently reduced as compared with the twin scroll type mixed flow turbine according to the conventional example. The pressure loss in the adjacent turbine blades 11) can be suppressed, and the turbine efficiency of the twin scroll type mixed flow turbine 1 can be increased.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, It can implement in a various aspect. Further, the scope of rights encompassed by the present invention extends not only to the twin scroll type mixed flow turbine 1 but also to a supercharger for a vehicle equipped with the twin scroll type mixed flow turbine 1.

β Flow angle βb Inlet metal angle β Inlet metal angle θ Circumferential angle λa First scroll inflow angle λb Second scroll inflow angle λ Cone angle φ Chamber angle CL Defined curve F Specified curve inflection point i Incident 1 Mixed flow turbine 3 Turbine housing 3S shroud 5 Bearing housing 7 Turbine impeller SC Turbine impeller shaft 9 Wheel 11 Turbine blade 11L Turbine blade leading edge 11Lh Turbine blade front edge hub side portion 15 Turbine shaft 17 Gas intake Inlet 19 Gas outlet 21 Twin scroll flow path 23 Partition wall 23T End edge of partition wall EL Extension line of tip edge of partition wall N Intersection 25 of extension line of tip edge of partition wall and front edge of turbine blade Scroll channel 27 Second scroll channel

Claims (2)

A twin scroll type mixed flow turbine that is used in a supercharger that supercharges air supplied to an engine side and generates a rotational force by using pressure energy of exhaust gas exhausted from the engine,
A turbine housing having an inner shroud;
A wheel rotatably provided in the turbine housing and rotatable about an axis, and provided at a distance from an outer peripheral surface of the wheel and having a leading edge extending along the shroud of the turbine housing A turbine impeller having a plurality of turbine blades inclined with respect to the axis so that the edge gradually approaches the axis as the edge moves from the shroud side to the hub side, and
A gas intake port for taking in exhaust gas exhausted from the engine is formed in the turbine housing, and a gas exhaust port for discharging exhaust gas is formed on the outlet side of the turbine impeller in the turbine housing,
An annular twin scroll passage communicating with the gas inlet is formed inside the turbine housing so as to surround the turbine impeller, and an annular partition wall is formed in the twin scroll passage, and the twin scroll passage is formed. Is an annular first scroll passage for supplying exhaust gas toward the hub side portion of the front edge of the plurality of turbine blades by the partition wall, and the front edge of the plurality of turbine blades. Partitioned into an annular second scroll flow path for supplying exhaust gas toward the shroud side portion,
The relationship between the axial position and the circumferential angle at an arbitrary point of the turbine blade is determined by a prescribed curve, and the axial position at the inflection point of the curve is an extension line of the leading edge of the partition wall. The mixed flow turbine is set to be the same as the axial position of the intersection of the turbine blade and the leading edge of the turbine blade. In the supercharger that supercharges the air supplied to the engine side,
A supercharger comprising the twin scroll type mixed flow turbine according to claim 1.

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