Booster compressor with tandem blading

Abstract: To provide a booster structure capable of obtaining a desired pressure ratio with fewer stages. The moving blade of a booster 2 is a boundary layer control tandem moving blade 11.

Description: The present invention relates to the booster structure of a jet engine. More specifically, the present invention relates to a jet engine booster structure having a pressure ratio in a single stage improved. In the prior art, cf. the article Jörg Sieber : "Technologieentwicklung für zukünftige ummantelte Propfantriebwerke, MTU Focus, no 1, 1994, pages 5, 6, there has been provided a booster 2' in the downstream of a fan 1 in order to enhance the performance of a high bypass engine, as shown in FIG. 11. As shown in FIG. 11, however, the booster 2' is provided at the same shaft 3' as the fan 1 and the number of revolution of the booster 2' is the same as that of the fan 1, whereby the circumferential speed of the moving blade 4 of the booster 2' is, therefore, limited by that of the fan 1. Due to this, the circumferential speed of the moving blade 4 is considerably lower than a desired speed, so that a pressure ratio in a single stage becomes quite low. This results in a problem that the booster 2' must consist of many stages so as to ensure a desired pressure ratio. Also, if the number of stages of the booster 2' increases, the entire length of a compressor increases, resulting in a problem that the weight of an engine E' increases. Furthermore, an increase in weight causes various problems. The present invention has been made in view of the problems according to the prior art and has an object to provide a booster structure capable of obtaining a desired pressure ratio with fewer stages. The present invention provides a jet engine booster structure comprising a boundary layer control tandem moving blade, characterised in that an inflow angle with a tandem moving blade lattice is within a range from 50 degrees to 70 degrees, and an efflux angle from a tandem moving blade lattice is within a range from 0 degree to 45 degrees. Preferably, a deflection angle by a stator blade is within a range from 0 degree to 45 degrees. The present invention also provides a jet engine comprising such a booster structure. It will be appreciated from the embodiments described hereinafter that since the moving blade of the booster is a tandem moving blade, a pressure increase in a single stage is large and, therefore a desired pressure increase can be attained with fewer stages. In order that the present invention may be well understood, various embodiments thereof, which are given by way of example only will now be described with reference to the accompanying drawings, in which: FIG. 1 is a schematic view of a turbo fan engine provided with a booster structure of embodiment according to the present invention; FIG. 2 is a schematic view of the important parts of the booster structure in the embodiment according to the present invention; FIG. 3 is a typical view of a flow of the tandem moving blade used in the embodiment; FIG. 4 is an explanatory view showing velocity triangles in a tandem moving blade lattice and a stator blade lattice used in the embodiment; FIG. 5 is a side view of one example of the tandem moving blade lattice; FIG. 6 is a cross-sectional view showing a HUB section of the tandem moving blade lattice in FIG. 5; FIG. 7 is a cross-sectional view showing a MEAN section of the tandem moving blade lattice in FIG. 5; FIG. 8 is a cross-sectional view showing a TIP section of the tandem moving blade lattice shown in FIG. 5; FIG. 9 is a schematic view of a testing device used for a performance test of the embodiment and a comparative example; FIG. 10 is an explanatory view showing a measurement method in the testing device shown in FIG. 9; and FIG. 11 is a schematic view of a turbo fan engine provided with a conventional booster structure. A turbo fan engine E having a jet engine booster structure in mode 1 of working the present invention is shown in FIG. 1 and the important parts thereof are shown in FIG. 2 schematically. In the booster structure, the moving blade of a booster 2 is a tandem moving blade 11. The tandem moving blade 11 is specifically a boundary layer control tandem moving blade 11. In other words, the moving blade lattice of this booster 2 is a tandem moving blade lattice 10. The shapes of the front blade 11 and rear blade 12 of the tandem moving blade 11 in this tandem moving lattice 10, the positional relationship between the front blade 12 and the rear blade 13, the positional relationship between the tandem moving blade lattice 10 and a stator blade lattice 20, pitches of the tandem moving blade lattice 10 and stator blade lattice 20 and the like are determined by performing three-dimensional calculation fluid dynamics using a computer. As for the tandem moving blade lattice 10, for instance, as typically shown in FIG. 3, the speed, momentum and the like of a jet spouted from the trailing edge of the lower surface of the front blade 12 onto the upper surface of the rear blade 13 are regulated, thereby causing the jet to flow along the upper surface of the rear blade 13. As a result, separation of a boundary layer on the upper surface of the rear blade 13 is set to be restricted to the vicinity of the trailing edge of the rear blade 13. In other words, the boundary layer of the rear blade 13 is controlled by the front blade 12. Reference symbol 3 in the figure denotes a shaft which drives the fan 1 and the booster 2, reference symbol 14 denotes a disk and reference symbol 21 denotes a stator blade. Any program for three-dimensionally analyzing a flow around the blade lattice and the distribution of a shock wave can be used, and an application program thereof is not particularly restricted. In addition, the shape of the stator blade lattice 20 is preferably set such that the inflow angle ( with the tandem moving blade lattice 10 shown in FIG. 4 is within a range of 50 to 70 degrees. Also, the shapes of the front blade 12 and rear blade 13 of the tandem moving blade lattice 10 are preferably set such that the efflux angle ( from the tandem moving blade lattice 10 in this case is within a range of 0 to 45 degrees. Further, the deflection angle by the stator blade 21 is preferably within a range of 0 to 45 degrees. Thus, the tandem moving blade lattice 10 having the above characteristics can be obtained by setting the positional relationship between the front blade 12 and the rear blade 13 of the tandem moving blade 11 and that of the tandems 11 and 11 or, for instance, the dimensional relationship between the front blade 12 and the rear blade 13 as shown in FIGS. 5 through 8, by changing the mutual relationship between the front blade 12 and the rear blade 13 from a state in which the front blade 12 and the rear blade 13 are laid down together from an HUB section to a TIP section to a state in which they rise together, and by gradually increasing the gap between the front blade and the rear blade 13. In other words, if the front blade 12 and the rear blade 13 are twisted together, the tandem moving blade lattice 10 having the above characteristics can be obtained. As stated above, in this embodiment, the tandem moving blade lattice 10 is used for the moving blade of the booster 2 and a pressure ratio in a single stage is, therefore, high. Thus, the number of stages of the booster 2 can be reduced, with the result that the dimensions of a compression mechanism structure can be decreased and the weight thereof can be reduced, as well. It is noted that the tandem moving blade 11 having such characteristics that the boundary layer of the rear blade 13 is controlled by the front blade 12 is defined as "boundary layer control tandem moving blade" in the present specification. Now, the present invention will be described more specifically based on a more specific embodiment. Embodiment and Comparative Example: A boundary layer control tandem moving blade lattice (embodiment) having principal items shown in Table 1 was fabricated with a shape of and a dimension shown in FIGS. 5 through 8, which tandem moving blade lattice served as a booster. The performance of this booster was measured by a testing device shown in FIG. 9. In addition, a conventional blade lattice (comparative example) having principal items shown in Table 2 was fabricated with the same width as that of the tandem moving blade according to the embodiment, and the performance thereof was measured by the same testing device in the embodiment. As typically shown in FIG. 10, measurement was performed by disposing a total pressure measuring probe and a total temperature measuring probe in front and rear portions of the blade (points A and B in FIG. 10) respectively, and radially traversing the probes every millimeter between TIP and HUB section. An flow rate was measured by an orifice provided in the upstream of an inlet duct section. The number of revolutions of the blade lattice was measured by a revolution measuring pick-up provided on a rotation shaft of a disk to which the blade lattice is attached. Each data obtained by the measurement was processed in the following manner. (1) Each of average measured values of a total pressure and a total temperature between the TIP and HUB sections on the portions A and B is calculated. (2) A pressure ratio is calculated based on a ratio PB/PA of an average value PB of the total pressure on the point B to an average value PA of the total pressure on the point A. (3) An average value TB of the total temperature on the point B and an average value TA of the total temperature on the point A are also calculated, and the average value PB of the total pressure on the point B and the average value PA of the total pressure on the point A which have been calculated are also used to obtain an efficiency by the following equation. η = TA {(PB/PA) (k-1)k -1}/(TB-TA) where η is Adiabatic efficiency and k is Adiabatic exponent. Table 1 shows the result of measurement in the embodiment, and the pressure ratio, pressure increase and the adiabatic efficiency thus calculated together with principal items of the embodiment. Table 2 shows a result of measurement, the pressure ratio, the pressure increase and the efficiency in the comparative example. Embodiment Principal Item Measured value Number of blades Front blade 24 - - - - Rear blade 24 Diameter of blade tip (mm) 265 ------- Number of revolutions (rpm) 16023 16000 Flow rate (kg/s) ----- 3.25 Pressure ratio ----- 1.3 Pressure increase ----- 0.3 Adiabatic Efficiency (%) ----- 87 Comparative Example Principal Item Measured value Number of blades 24 ------ Diameter of blade tip (mm) 265 ------ Number of revolutions (rpm) 16023 16000 Flow rate (kg/s) ----- 3.25 Pressure ratio ----- 1.15 Pressure increase ----- 0.15 Adiabatic efficiency (%) ----- 86.5 It is apparent from a comparison between Table 1 and Table 2 that a high pressure ratio of 0.3 which is about 2.0 times as high as that of the comparative example can be obtained in the embodiment while keeping the same efficiency as in the comparative example. Although the present invention has fully been described based on the mode of working the invention and embodiment, it is to be understood that the present invention should not be limited thereto and various changes and modifications are possible. For instance, while the tandem moving blade lattice has a single stage, the number of stages can be two or three in accordance with a required pressure ratio. As disclosed so far in detail, in the booster structure of the embodiment, the booster moving blade is a tandem moving blade. Due to this, the structure has excellent advantage in that a pressure increase in a single stage is larger and that a desired pressure increase can be attained with fewer stages. Besides, since the booster is allowed to have fewer stages, the embodiments exhibit excellent advantage in that the entire length of the compressor can become smaller and the weight thereof can be reduced.

Claims: A jet engine booster structure (2) characterised in that it comprises a boundary layer control tandem moving blade, whereby an inflow angle with a tandem moving blade lattice (10) is within a range from 50 degrees to 70 degrees, and an efflux angle from a tandem moving blade lattice (10) is within a range from 0 degree to 45 degrees. A jet engine booster structure (2) according to claim 1, wherein a deflection angle by a stator blade (21) is within a range from 0 degree to 45 degrees. A jet engine (E) comprising a booster structure according to claims 1 or 2.

Inventors: HASHIMOTO KEISUKE, SAKAI YUSUKE, SUGA SHINYA, HASHIMOTO, KEISUKE, SAKAI, YUSUKE, SUGA, SHINYA
Applicants: KAWASAKI HEAVY IND LTD, KAWASAKI JUKOGYO KABUSHIKI KAISHA
Application year: 1999
Main classification: F01D5
IPC codes: F02C7, F02K3, F04D29, F01D5