GB2036185A

GB2036185A - Turbosupercharger

Info

Publication number: GB2036185A
Application number: GB7940297A
Authority: GB
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1978-11-22
Filing date: 1979-11-21
Publication date: 1980-06-25
Also published as: GB2036185B; JPS5576828U; JPS5856337Y2

Abstract

A turbosupercharger for an internal combustion engine comprises a turbine 2, an air compressor 1 driven by the turbine, and a bypass duct 7 for introducing compressed air into the turbine inlet nozzle. A control valve 8 is disposed in the bypass duct for opening and closing the duct, the control valve being operated by detecting the output pressure of the compressor in such a manner that the bypass duct is completely closed at the rated point of the engine and is gradually opened in response to the increase of the output pressure of the compressor and the decrease of the dynamic pressure therein when a partial load is imposed on the engine. The air inlet into the turbine is formed by a pair of plates or ribs 14a, 14b extending within the inlet scroll. <IMAGE>

Description

SPECIFICATION Turbosupercharger This invention relates to turbosuperchargers particularly but not exclusively for use in supercharged diesel engines.

In general, the high efficiency region is located in the viz nit of a surge line in the compressor map. Therefore, if the rated point and maximum point are located within such high efficiency region, the fuel consumption rate of the engine can be reduced. However, high-torque-rise engines which have been required lately are disadvantageous in that because of the gradient of the working line thereof being lower than that of the surge line, if the engine is driven with its maximum torque located near the high efficiency region of the compressor, then the fuel comsumption rate at a rated point or load will increase, and reversely, if the rated point draws near the high efficiency point of the compressor, then the maximum torque point will enter the surge line so that the engine cannot be driven.

In a majority of current engines, the torque can be increased sacrificing the performance at the rated point but if the performance at the rated point is regarded as important, the following methods can be employed.

(1) To limit the fuel supply rate at the maximum torque point outside the surge line; (2) To discharge the compressor outlet air towards the turbine outlet at the maximum torque point.

(3) To bleed the gas in the turbine inlet at the maximum torque point and discharge it towards the turbine outlet.

The above-mentioned methods are, however, disadvantageous in that the torque rise is reduced.

It is therefore an object of the present invention to provide a turbosupercharger for an internal combustion engine which is capable of being operated in a maximum efficiency range of a compresssor.

Another object of the present invention is to provide a turbosupercharger for an internal combustion engine which is capable of attaining a high torque rise without sacrificing fuel consumption rate at the rated point of the engine.

In accordance with an aspect of the present invention, there is provided a turbosupercharger for an internal combustion engine, comprising a turbine driven by the exhaust gas from the internal combustion engine, the turbine having a turbine nozzle formed therein, an air compressor driven by the turbine and adapted to supply compressed air to the internal combustion engine, and bypass means for directly introducing compressed air from the air compressor into an outlet portion of the turbine nozzle.

Preferably a control valve means is disposed in the bypass means for opening and closing the bypass means, the control valve means being operated by detecting the output pressure of the air compressor in such a manner that the bypass means is completely closed at the rated point of the engine and is gradually opened in response to the increase of the output pressure of the air compressor and the decrease of the dynamic pressure therein when partial loadds are imposed on the engine.

The above and other objects, features and advantages of the present invention will be readily apparent from the following description of certain specific embodiments given by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a turbosupercharger according to the present invention; Figure 2 is a sectional view of an air compressor showing the compressed air being bypassed from the diffuser portion of the compressor; Figure 3 is a schematic illustration of a vaneless nozzle type turbine showing how the compressed air is introduced into the turbine from the compressor through the bypass means; Figure 4 is a sectional view of a compressor and a vane-less nozzle type turbine combination showing another arrangement for compressed air intake into the turbine from the compressor through the bypass means;; Figure 5 is a sectional view taken along the line V-V of Fig. 4; Figure 6 is a schematic illustration of vaned nozzle type turbine showing how the compressed air is introduced into the turbine.

Figure 7 is a sectional view of a vaned nozzle type turbine showing another arrangement of the compressed air intake into the output side of a turbine nozzle via the bypass means; Figure 8 is a schematic illustration of a control valve disposed in the bypass means; and Figure 9 is a graph showing the relationship between the rate of air flow and the pressure ratio of an air compressor according to the present invention.

In the drawings; reference numeral 1 denotes an air compressor, 2, a turbine connected to the compressor 1 and 3 a power turbine.

The outlet side of the compressor 1 communicates through an air inlet pipe 5 with the air inlet side of the engine 4. The exhaust exit side of the engine 4 is connected through an exhaust pipe 6 to the inlet side of the turbine 2. Further, extending from the outlet side of the compressor 1 to the inlet side of the turbine 2 is a bypass circuit or extraction passage 7 which is provided with a control valve 8.

The delivery of the compressed air from the compressor 1 into the bypass circuit 7 is made, as shown in Fig. 2, by connecting a chamber 10 formed in the diffuser portion 9 of the compressor 1 to the bypass circuit 7.

However, this invention is not to be limited thereto as the bypass circuit 7 may be connected to the air inlet pipe 5 so as to allow the compressed airr to be introduced into the turbine 2. A boundary layer is liable to be generated on the side of the shroud of the impeller 1 a of the compressor thereby lowering the efficiency of the compressor but if the compressed air is bled from the diffuser portion 9 of the compressor 1 as shown in Fig. 2 the stagnant air in the vicinity of the boundary layer can be bled so as to improve the efficiency of the compressor.

Regarding the introduction of the compressed air from the bypass circuit 7 into the turbine, in case of vaneless nozzle type turbines as shown in Fig. 3, the position at which the bled compressed air is introduced into the turbine should preferaly be the area between a turbine nozzle 11 and a rotor 26 in which area a low static pressure prevails. In this area, because the gas flows at a high speed, a part of the heat energy is converted into the kinetic energy and the static pressure is lowered so that a sufficient pressure differential is obtained between the said area and the outlet of the compressor 1 to enabls bleeding of the compressed air.

In the arrangement of Figs. 4 and 5, there is formed in the inner face of a housing 1 3 of the turbine a compressed air passage 14 which may be connected to the bypass circuit 7. As can be seen from Figs. 4 ind 5, the compressed air passage 14 is formed between a pair of plates or ribs 14a and 14b located in a scroll of the turbine to supply the bled compressed air into the air passage 14 so that because of the reduced static pressure within the scroll the bleeding of compressed air is possible even in the event of reverse boosting in which the turbine inlet pressure is higher than the compressor outlet pressure.

Moreover, because of the bled compressed air flowing in the direction of the main current, the drop in thhe efficiency of the trubine can be reduced.

In case of vaned nozzle turbines as shown in Fig. 6, the bypass circuit 7 may be connected to the space between the turbine nozzle 11 and a rotor 26.

Further, as shown in Fig. 7, an air nozzle 1 2 may be located parallel to the turbine nozzle 11 of the turbine 2, the air nozzle 1 2 being connected to the bypass circuit.

As shown in Fig. 8, the aforementioned control valve 8 is disposed in the bypass circuit 7, is connected to a ventury tube including a reduced diameter portion 1 5 which is forrned in the rir inlet pipe 5 A valve stem 1 6 having lands 1 7 and 1 8 is slidably disposed in a valve bore 1 9.

A sleeve 20 is movably mounted on the valve stem 1 6 within the valve bore 1 9 and controls communication between the inlet pipe 5 and the bypass passage 7. Valve chambers 21, 22 and 23 and 24 are defined in the valve bore 19. The chambers 21 and 23 are connected to a pipe 27 disposed in the air suction pipe 5 for detecting the total output pressure comprising the static pressure and the dynamic pressure inside the air suction pipe 5. The chamber 22 is connected to a pipe 28 which is connected to the air inlet pipe at the reduced diameter portion 15, so that the static pressure is introduced into the chamber 22. The chamber 24 is open to the atmosphere. Compression springs 29 and 30 are accommodated within the chambers 22 and 24 respectively. Mounted within the chamber 22 is a stop 31.

Thus, when the venturi's differential pressure is high the sleeve 20 is moved to the left and abuts against the stop 31 as shown in Fig. 8 to close the bypass circuit 7. When the differential pressure is low, the sleeve 20 is moved to the right by the action of the spring 29 thereby opening the inlet of the bypass passage 7. When the compressor's outlet pressure in the inlet pipe 5 is high, the sleeve 20 is moved to the right so as to open the bypass passage 7., whilst when the compres sor's outlet pressure is low, the sleeve 20 is moved to the left by the action of the spring 30 to close the bypass passage 7.

Therefore, at a rated point, the control valve 8 for controlling the bled compressed air flowing through the bypass circuit 7 is completely shut off, and at partial loads the control valve 8 will be gradually opened in response to the decrease of the dynamic pressure and the increase of the total pressure in the outlet of the compressor or in the air inlet pipe 5.

Thus, by directly bleeding the compressed air from the compressor 1 to the turbine 2 through the bypass circuit 7, the working point of the compressor 1 in the graph of Fig.

9 is shifted from a point A' when no bypassing is made to a point B' where the flow rate is increased when bypassing is made.

At the rated point or load, the working point of the compressor is sufficiently spaced from the surge curve, and the bypass circuit 7 is shut off by the control valve 8.

As described in detail above, according to the present invention, the outlet side of the compressor 1 is connected through the bypass circuit 7 to the inlet side of the turbine 2. The bypass circuit 7 is provided with the control valve 8 which is actuated by the delivery pressure of the compressor 1 so as to ccompletely shut off the bypass circuit 7 at the rated point or load, and to open the bypass circuit gradually in response to the decrease of tiie dynamic pressure and in crease of the total pressure in the outlet of the compressor 1. Therefore, the compressor can be operated in a high efficiency region so that low fuel consumption and high torque rise an be achieved.

Further, in the preferred embodiment of the present invention, the arrangement is such that the bled compressed air can be introduced into the turbine at the turbine nozzle outlet having a low static pressure. Therefore, a sufficient amount of bleeding air can be obtained, and the torque of the engine can be increased tc a high level, without sacrificing the fuel consumption rate at the rated point of load.

Claims

1. A turbosupercharger for an internal combustion engine, comprising a turbine driven by the exhaust gas from the internal combustion engine, the turbine having a turbine nozzle formed therein, an air compressor driven by the turbine, and adapted to supply compresssed air to the internal combustion engine, and bypass means for directly introducing compressed air from the air compressor into an outlet portion of the turbine nozzle.

2. A turbosupercharger as claimed in Claim 1 further comprising control valve means disposed in the bypass means for opening and closing the bypass means, the control valve means being operated by detecting the output pressure of the air compressor in such a manner that the bypass means is completely closed at the rated point of the engine and is gradually opened in response to the increase of the output pressure of the air compressor and the decrease of the dynamic pressure therein when partial loads are imposed on the engine.

3. An turbosupercharger as claimed in Claim 1 or Claim 2 wherein the bypass means is connected with the air compressor at a position located in or adjacent to a diffuser portion of the air compressor.

4. A turbosupercharger as claimed in any one of the preceding claims wherein an air passage is formed by a pair of plates or ribs along and inside of a turbine scloll and the bypass means is connected with the said air passage.

5. A turbosupercharger as claimed in any one of Claims 1-3 wherein the turbine is a vaned nozzle turbine and the bypass means is connected with a portion positioned between a turbine nozzle and a rotor.

6. A turbosupercharger as recited in any one of the preceding claims wherein the bypass means is connected with the turbine at a portion having the lowest static pressure.

7. A turbosupercharger as specifically described herein with reference to Figs. 1 and 9 and Fig. 2 or Fig. 3 or Figs. 4 and 5 or any one of Figs. 6-8 of the accompanying drawings.