JPS5932680B2 - Suction channel of axial flow type fluid machine - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvement of a suction flow path for an axial flow type fluid machine.

The gas suction port of an axial flow type fluid machine such as an axial flow fan or an axial flow pump is installed on the upstream side of the inlet guide vane of the fan or the fan rotor blade, and slowly flows the relatively slow gas in the upstream duct. The purpose is to accelerate the fan blades to create a uniform axial flow at the required level just in front of the fan rotor blades.

For this reason, a typical axial fan has a simple suction port shape as shown in FIG. 1 or 2.

That is, in the example shown in FIG. 1, a suction port inner cylinder 14 is disposed on the upstream side of the suction port casing 12 connected to the upstream duct 11 and the fan rotor blades 15 so that its axis coincides with the fan axis as shown in the figure. In the example of FIG. 2, the fan casing 22 connected to the upstream duct 21
A suction flow path is formed as shown in the figure on the upstream side of the fan rotor blades 24, and includes a suction port inner cylinder 23.

In FIG. 1, 13 indicates a fan casing, and 16 indicates an inner tube of a dispensing diffuser. In FIG. 2, 25 indicates an inner tube of a dispensing diffuser.

In the shape of the suction passage of the conventional axial fan as shown above,
In the case of an axial fan that handles gas containing a duct, the dust contained in the gas collides directly with the fan rotor blades and tends to cause erosion of the fan rotor blades, thus shortening the life of the fan rotor blades. There was a drawback.

This phenomenon also applies to axial flow pumps.

This is true even when the diameter of the upstream duct 11 is large as in the example shown in FIG. 1, or when the upstream duct 21 and fan casing 22 have the same diameter as in the example shown in FIG.
The suction flow path formed by the suction port inner cylinder 14 or the fan casing 22 and the suction port inner cylinder 23 gradually decreases in cross-sectional area from the upstream side to just before the fan rotor blade, accelerating the airflow.

In these normal suction channels, if dust is included in the airflow, the fan rotor blades will undergo significant erosion at the tips, shortening the life of the blades. This is because the pulsation of the average flow is small, as shown by the arrow line in FIG. 2, and therefore, centrifugal force does not act much on the duct particles riding on the flow, and they directly enter the fan rotor blades along with the airflow.

Wear of the fan rotor blades is proportional to the dust concentration and proportional to the third to fourth power of the relative velocity of the dust particles.

Therefore, when a uniform concentration of dust flows from the tip to the root of the fan rotor blade, the tip of the rotor blade is significantly worn, and this determines the life of the rotor blade of the axial fan.

The present invention eliminates the drawbacks of the suction flow paths of conventional axial fans and axial pumps, and moreover, the pressure loss at the suction port of the axial fan is small, and the suction flow path does not disturb the uniformity of airflow. This was proposed for the purpose of realizing a flow path, and the suction casing has an opening at one end connected to an upstream duct and an opening at the other end connected to the fan casing, and an axis centered at the upstream axis of the fan rotor blade. In the suction flow path of an axial flow fluid machine consisting of a suction port inner cylinder arranged to have a suction port, the flow path diameter of a certain cross section of the suction casing is formed to be smaller than the tip diameter of the fan rotor blade, and the cross section The section and the upstream duct and the vicinity of the connection section with the fan casing are connected by a flow path whose diameter gradually increases, and the size of the cross-sectional area of the suction flow path of the above-mentioned cross section is set to the size of the cross-sectional area of the passage of the fan rotor blade. The present invention relates to a suction flow path of an axial flow type fluid machine, which is characterized in that the suction flow path is set to be more than 1.

The present invention will be specifically explained below with reference to FIGS. 3 to 6.

Note that the illustrated example shows an example in which the present invention is applied to an axial fan.

In FIG. 3, 31 is an upstream duct, 32 is a suction casing whose one end opening is connected to the downstream side of the upstream duct 31, and the other end opening of the suction casing 32 is connected to a fan casing 35; 32, the inner diameter gradually decreases as it goes from the upstream side to the downstream side, and reaches its minimum at a certain cross-sectional point A, which is the diameter of the suction flow path.

The suction flow path diameter gradually increases from point A toward the downstream side, so that the diameter at the downstream end is slightly larger than the fan rotor blade diameter Dt. It is formed like this.

That is, the flow path diameter Do at point A in the cross section of the suction casing 32
is set smaller than the diameter Di of the fan moving blade 35.

Further, the cross-sectional area of the suction flow path at the cross-sectional point A is set so as not to be smaller than the passage area of the fan rotor blades 350.

That is, the suction flow path at the cross-sectional point A is formed such that Do×Dt, π π , Do2≧−;(Dt2−D, “).

Here, Dr indicates the root diameter of the fan moving blade 35.

Reference numeral 33 denotes a suction port inner cylinder, and the inner cylinder 33 is formed into a rounded, almost conical shape so that its tip is located on the downstream side near the cross-sectional point A of the suction casing 32, as shown in the figure. The cross-sectional area of the suction flow path is the fan rotor blade 35
It is formed into the shape shown in the figure so that the airflow is gradually and smoothly narrowed toward the center of the fan, and at the same time promotes the pulsation of the airflow toward the center of the fan.

Reference numeral 34 indicates the inner cylinder support blade, 36 indicates a fan disk, 37 indicates a main shaft, 38 indicates a fan casing, and 39 indicates a fan stationary blade.

One embodiment of the suction channel of the axial fan of the present invention is constructed as described above, and as the fan rotor blades rotate 350 times, the gas flows once into the axial fan as shown by arrow B in FIG. The flow pulsates as it approaches and then moves away from the center line C, and then enters the fan rotor blade 35 as a flow that recovers in the axial direction over a relatively short distance.

As a result, as shown in Fig. 4, particles (dust) in the gas 4
1 receives a viscous force Fv in the gas flow direction and a centrifugal force Fc acting in the pulsating direction, and moves in the direction of the dashed arrow, which is the direction of the resultant force.

In other words, the dust as a whole tends toward the root of the fan rotor blade 35.

Therefore, as shown in FIG. 5, the dust concentration distribution E immediately before the fan rotor blade 35 is significantly higher at the root than at the tip of the fan rotor blade 35, and the gas flow velocity distribution F recovers uniformly.

Since the suction flow path of the axial flow type fluid machine such as the axial flow fan and the axial flow pump of the present invention has the above-described configuration and function, according to the present invention, the tip of the fan rotor blade 35 The circumferential speed is high but the dust concentration is low, while the dust concentration is high at the root of the fan rotor blade but the circumferential speed is low. The life of the blades of the fan rotor blades is significantly increased, as there is no longer a risk that the blades will be rapidly worn out.

Further, there is a practical effect that there is no risk of impairing the aerodynamic performance of the fan.

In the above embodiment, the shape of the suction port inner cylinder 33 is formed into a rounded, almost conical shape, but the inner cylinder promotes pulsation of the substantial flow of gas and may impede aerodynamic performance. If not, a normal cannonball-shaped one as shown in FIG. 6, for example, may be used.

[Brief explanation of drawings]

1 and 2 are schematic vertical cross-sectional views of a conventional example, FIG. 3 is a schematic vertical cross-sectional view of an embodiment of the present invention (however, only the upper half is shown), and FIG. 4 is a schematic vertical cross-sectional view of an embodiment of the present invention. An explanatory diagram of the direction of dust flow in the case of
FIG. 5 is a diagram showing the dust concentration distribution and gas flow velocity distribution state in the height direction of the fan rotor blade, and FIG. 6 is a longitudinal cross-sectional view of a modified example of the suction port inner cylinder. In Figs. 3 to 6, 31: upstream duct, 32 suction casing, 33 2 suction inner cylinder, 35 Nifuan rotor blade, Do: minimum inner diameter of suction casing, Dt = fan rotor blade tip diameter, Dr = fan Rotor blade root diameter.

Claims (1)

[Claims] 1. An axial flow fluid machine consisting of a suction casing whose opening at one end is connected to an upstream duct and the opening at the other end is connected to a fan casing, and an inner cylinder of the suction port arranged to have the axis on the upstream side of the fan rotor blades. In the suction flow path of the machine, the diameter of the cross section of the suction casing is smaller than the tip diameter of the fan rotor blade, and the diameter of the cross section and the vicinity of the connection between the upstream duct and the fan casing is gradually reduced. An axial flow type fluid machine, characterized in that the cross-sectional area of the suction flow path of the cross-sectional portion is set to be larger than the cross-sectional area of the passage of the fan rotor blade. Machine suction flow path.