WO2019239010A1

WO2019239010A1 - Turbocharger

Info

Publication number: WO2019239010A1
Application number: PCT/FI2019/050450
Authority: WO
Inventors: Kimmo VIINIKANGAS; Toni FINGERROOS
Original assignee: Finger Motors Oy
Current assignee: Finger Motors Oy
Priority date: 2018-06-12
Filing date: 2019-06-11
Publication date: 2019-12-19
Anticipated expiration: 2020-12-12
Also published as: FI20185535A1; FI128190B

Abstract

The invention relates to a turbocharger, which comprises a compressor housing (10), a compressor wheel (12) inside the compressor housing, a first turbine housing (14), a first turbine wheel (16) inside the first turbine housing, which has a radius r1, a second turbine housing (18), a second turbine wheel (20) inside the second tur- bine housing, which has a radius (r2), and an axis (22), on which the compressor wheel, first turbine wheel and second turbine wheel are arranged. The first turbine wheel and the second turbine wheel are substantially of different size.

Description

Turbocharger

The invention relates to a turbocharger, which comprises a compressor housing, a compressor wheel inside the compressor housing, a first turbine housing, a first tur- bine wheel inside the first turbine housing, which first turbine wheel has a radius, a second turbine housing, a second turbine wheel inside the second turbine housing, which second turbine wheel has a radius, and an axis, on which axis the compressor wheel, first turbine wheel and second turbine wheel are arranged.

The power and efficiency of combustion engines, especially diesel engines, can be improved with the aid of the supercharger. An exhaust gas supercharger obtaining its power from engine exhaust gas, a so-called turbocharger, comprises a compres- sor housing, inside which there is a compressor wheel, and a turbine housing, inside which there is a turbine wheel, and an axis connecting the compressor wheel and turbine wheel. Exhaust gas expelled from the engine rotates the turbine wheel, whereby the compressor wheel packs air via the engine’s intake pipes and intake manifold into the cylinders. Due to the turbocharger, more air and fuel can be led into the cylinders, whereby the power and efficiency of the engine grows.

A disadvantage of the turbocharger is that it starts to produce sufficient boost pres- sure only when the RPM of the engine has risen high enough. This phenomenon is known as the turbo lag. The turbocharger’s lag can be influenced by means of de- signing of the turbine and compressor housings and the wings of the impellers in them, i.e. the turbine wheel and compressor wheel. If the turbocharger is designed to function well at low engine RPMs, it cannot reach maximal power at high engine RPMs. Correspondingly, if the charger is dimensioned to function optimally at high engine RPMs, the turbo lag grows. In the designing of turbochargers, it is generally necessary to make a compromise between the functionality of high and low RPMs.

The functionality of the turbocharger at different RPMs can be improved also by using variable wing impellers as turbine wheels. Such chargers are however tech- nically complicated, and their manufacturing and maintenance costs are expensive.

Publication US 4339922 shows a turbocharger, where the turbo part includes two turbine housings, both of which have their own turbine wheel. Both turbine wheels are connected to the same axis as the compressor wheel. The flow of exhaust gas from the engine to the turbines is controlled with valves, so that at low engine RPMs exhaust gas is led only into one of the turbine housings, and as the exhaust gas pressure grows, exhaust gas is led into both turbine housings to rotate both turbine wheels. With the solution shown in publication US 4339922 the functionality of the turbocharger can be extended to different engine RPM ranges, but still the turbo- charger functions optimally within a relatively narrow engine RPM range.

An object of the invention is to provide a turbocharger, by which the problems relat- ing to known turbochargers can be reduced. The objects of the invention are ob- tained with a turbocharger, which is characterized by what is presented in the inde- pendent claim. Some advantageous embodiments of the invention are presented in the dependent claims.

The invention relates to a turbocharger, which comprises a compressor housing, a compressor wheel inside the compressor housing, a first turbine housing, a first tur- bine wheel inside the first turbine housing, which has a radius, a second turbine housing, a second turbine wheel inside the second turbine housing, which has a radius, and an axis, on which the compressor wheel, first turbine wheel and second turbine wheel are arranged. In the turbocharger according to the invention, the first turbine wheel and the second turbine wheel are substantially of different size.

In an advantageous embodiment of the turbocharger according to the invention, the radius of the second turbine wheel is at least 20 % larger than the radius of the first turbine wheel, advantageously at least 35 % larger than the radius of the first turbine wheel, most advantageously at least 50 % larger than the radius of the first turbine wheel. The turbine wheel radius has two different lengths; the Inducer length and the Exducer length. The turbine wheel radius in this description specifically means the Exducer radius length of the turbine wheel.

Another advantageous embodiment of the turbocharger according to the invention additionally comprises a first inlet throat in the first turbine housing, a second inlet throat in the second turbine housing, a first exhaust gas channel leading to the first inlet throat, a second exhaust gas channel leading to the second inlet throat, and a valve, with which the second exhaust gas channel can be closed. By closing the valve leading to the second exhaust gas channel, all the exhaust gas coming from the engine can be steered to flow to the first turbine housing to rotate the smaller first turbine wheel.

In still another advantageous embodiment of the turbocharger according to the in- vention the first turbine housing has an exit opening for the outflow of exhaust gas and the turbocharger further has a circulation channel leading from the exit opening to the second exhaust gas channel, to the section between the valve and the second inlet throat. Along the circulation channel, the exhaust gas leaving the first turbine housing can be led onwards to the second turbine housing.

An advantage of the invention is that it makes possible an increase in boost pressure at lower engine RPMs without having the engine power reduced at high RPMs. The invention thus improves the engine’s efficiency and increases the engine’s power.

It is further an advantage of the invention that it makes possible a more efficient recirculation of exhaust gas especially in diesel engines, by increasing the pressure on the exhaust manifold side at low RPMs, whereby the flow of exhaust gas from the exhaust manifold to the intake manifold is made possible.

In the following, the invention will be described in detail. In the description, reference is made to the enclosed drawings, in which figure 1 shows as an example a principal view of a turbocharger according to the invention.

Figure 1 shows as an example a principal view of a turbocharger according to the invention. In the figure a turbocharger means a device aggregate, which is placed inside a rectangle drawn with dotted lines. The engine 48 left outside the area de- limited by the rectangle and the parts belonging thereto are not part of the turbo- charger according to the invention.

The turbocharger comprises a compressor housing 10 and two turbine housings; a first turbine housing 14 and a second turbine housing 18. Inside the compressor housing there is a compressor wheel 12, inside the first turbine housing there is a first turbine wheel 16 and inside the second turbine housing there is a second tur- bine wheel 20. The compressor wheel and the turbine wheels are attached on the same axis 22, so that all the wheels on the axis rotate at the same RPMs as the axis. The compressor wheel and turbine wheels are prior art impellers used in tur- bochargers, the structure of which is not described further in this presentation.

The compressor housing 10 has an intake opening 40, through which the compres- sor wheel 12 rotating in the compressor housing takes air into the intake housing. In the wall of the compressor housing there is an outlet opening 42, which continues as an intake channel 44, through which air can flow into the intake manifold 46 and onward to the engine 48 cylinders. In the wall of the first turbine housing 14 there is a first inlet throat 24, and in the wall of the second turbine housing 18 there is a second inlet throat 26. The first turbine wheel has a radius n , and the second turbine wheel has a radius r₂. The turbine wheel radius in this description means the Exducer radius length of the turbine wheel. In the turbocharger according to the invention the first turbine wheel is substantially smaller than the second turbine wheel, i.e. the radius of the first turbine wheel is substantially smaller than the radius of the second turbine wheel. The radius of the second turbine wheel is thus at least 20 % larger than the radius of the first turbine wheel. Advantageously, the radius of the second turbine wheel is at least 35 % larger than the radius of the first turbine wheel. It can even be thought that the radius of the second turbine wheel can be at least 50 % larger than the radius of the first turbine wheel. The radius of the first turbine wheel can be in the range of 20-35 mm and the radius of the second turbine wheel can be in the range of 25-50 mm.

As a continuation of the inlet throat of the first turbine housing 14 there is a first exhaust gas channel 34 and as a continuation of the inlet throat of the second tur- bine housing 18 there is a second exhaust gas channel 36. The first and second exhaust gas channel join into one channel, which connects to the engine exhaust manifold 50. Exhaust gas generated in the combustion of fuel and air can thus easily exit the engine cylinders via the exhaust manifold and exhaust gas channels to the first turbine housing and second turbine housing. In the branching point of the first and second exhaust gas channel there is a valve 28, with which the second exhaust gas channel can be closed completely. The opening and closing of the valve is ad- justed with an actuator 29. The first turbine housing further has an exit opening 52, through which the exhaust gas can exit the turbine housing. A circulation channel 32 is attached to the exit opening, so that the first end of the circulation channel is connected to the exit opening and the second end is connected to the second ex- haust gas channel 36 in the section between the valve 28 and the second inlet throat 26. The exhaust gas can thus flow from the first turbine housing along the circulation channel and second exhaust gas channel to the second turbine housing 18, from where it exits through the exit opening 52 to an exhaust pipe not shown in the figure.

Figure 1 shows the turbocharger according to the invention in a situation, where the engine 50 connected to the turbocharger is used at a low RPM. Thus, the actuator 29 is used to control the valve 28 to close the second exhaust gas channel 36, whereby all the exhaust gas generated in the engine cylinders is steered into the first turbine housing 14 to rotate the first turbine wheel 16. The rotation of the first turbine wheel makes the compressor wheel 12 rotate, whereby the boost pressure and engine power increases. The small first turbine wheel is dimensioned to rotate already at low engine RPMs, whereby the turbocharger“wakes” to produce boost pressure quickly, i.e. the turbo lag is small. The exhaust gas exits the first turbine housing via the circulation channel 32 and the second exhaust gas channel 36 to the second turbine housing and onwards via the exit opening to the exhaust pipe system. When the engine RPM rises sufficiently high, the size of the first turbine housing or turbine wheel starts to restrict the exhaust gas flow and the exhaust manifold pres- sure rises in relation to the pressure of the intake manifold. Thus, the actuator 29 opens the valve 28 into the position drawn in the figure with a dotted line, whereby exhaust gas can flow from the exhaust manifold 50 directly also into the second turbine housing 18 to rotate the second turbine wheel 20. In order to determine the right time for the valve to open, there is a pressure sensor 54 in the channel section between the exhaust manifold and valve, with which pressure sensor the exhaust gas pressure is measured in the channel. As the exhaust gas pressure rises above a set threshold value, the actuator 29 opens the valve leading into the second ex- haust gas channel. The large second turbine wheel rotating in the second turbine housing produces boost power well at high engine RPMs, whereby the engine power is improved also at high RPMs.

Some advantageous embodiments of the turbo charger according to the invention have been described above. The invention is not limited to the solutions described above, but the inventive idea can be applied in different ways within the scope of the claims.

Claims

1. A turbocharger, which comprises a compressor housing (10), a compressor wheel (12) inside the compressor housing (10), a first turbine housing (14), a first turbine wheel (16) inside the first turbine housing (14), which first turbine wheel (16) has a radius (n), a second turbine housing (18), a second turbine wheel (20) inside the second turbine housing (18), which second turbine wheel (20) has a radius (r₂), and an axis (22), on which same axis (22) the compressor wheel (12), first turbine wheel (16) and second turbine wheel (20) are arranged, characterized in that the first turbine wheel (16) and second turbine wheel (20) are substantially of different size.

2. The turbocharger according to claim 1 , characterized in that the radius (r₂) of the second turbine wheel (20) is at least 20 % larger than the radius (r-i) of the first turbine wheel (16), advantageously at least 35 % larger than the radius (n) of the first turbine wheel (16), most advantageously at least 50 % larger than the radius (n) of the first turbine wheel (16).

3. The turbocharger according to claim 1 or 2, characterized in that it further comprises a first inlet throat (24) in the first turbine housing (14), a second inlet throat (26) on the second turbine housing (18), a first exhaust gas channel (34) leading to the first inlet throat (24), a second exhaust gas channel (36) leading to the second inlet throat (26), and a valve (28), with which the second exhaust gas channel (36) can be closed.

4. The turbocharger according to claim 3, characterized in that the first turbine housing (14) has an exit opening (52) for outflow of exhaust gas and the turbo- charger additionally has a circulation channel (32) leading from the exit opening (52) to the second exhaust gas channel (36), to the section between the valve (28) and second inlet throat (26).