GB2504096A

GB2504096A - Turbocharger compressor housing with EGR inlet and mixer

Info

Publication number: GB2504096A
Application number: GB1212675.1A
Authority: GB
Inventors: Anthony Demots; Steve Johnson
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2012-07-17
Filing date: 2012-07-17
Publication date: 2014-01-22
Anticipated expiration: 2032-07-17
Also published as: DE102013106748A1; GB2504096B; GB201212675D0; CN203515789U

Abstract

A turbocharger 130 for an i.c. engine, eg a diesel engine, has a compressor housing with an air inlet preferably comprising a chamber 137 immediately upstream of the compressor blades 38. A transverse EGR inlet 139 allows exhaust gas 100 to flow into the chamber 137. A barrier 160 within the compressor inlet provides a barrier between inlet air 102 and EGR gas 100. The barrier 160 has at least one opening, eg perforations 162 and/or longitudinal slots (262, fig.6), to allow exhaust gas to pass the barrier and mix with inlet air. The barrier 160 may taper toward its end 164 nearer the compressor blades 38 and the apertures 162 may be arranged in ring-like patterns and may be more numerous and/or larger towards that end. The downstream end of the barrier (360, fig.7) may not extend so far into the inlet to leave a gap (362) allowing EGR gas to pass the barrier and mix with air.

Description

Improved Mixing for Exhaust Gas Recirculation The present invention relates to turbochargers and exhaust gas recirculation (EGR) systems in vehicles. In particular, but not exclusively, the invention relates to modified turbochargers which allow the mixing of fresh intake air and exhaust gas.

Exhaust gas recirculation (EGR) is used to reduce the amount of nitrogen oxide (NOx) emissions in petrol and diesel engines. In an EGR system, a portion of an to engine's exhaust gas is recirculated back to the engine cylinders. For diesel engines, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. NOx forms primarily when a mixture of nitrogen and oxygen is subjected to a high temperature, and so the lower combustion chamber temperatures caused by EGR reduces the amount of NOx that the combustion IS generates.

In a vehicle engine, a turbocharger includes a compressor that increases the mass of air entering the engine, resulting in greater performance in terms of one or both of power and efficiency. The compressor is powered by a high speed turbine that is driven by the engine's exhaust gases.

There are two types of EGR systems: low and high pressure EGR. In a conventional low pressure EGR system, exhaust gas is fed into the compressor inlet, to be boosted back into the engine. A low pressure EGR system is typically combined with a diesel particulate filter (DPF). The DPF collects particulate material from the exhaust, and the exhaust gas is typically filtered and cooled before being recirculated to the compressor. This is shown in Figure 1.

The pressure of the exhaust gas is low and the filtering and cooling of the gas cause the pressure to drop further. It is therefore necessary to provide means to assist the flow of EGR gas to the compressor. For instance, as shown in Figure 1, a throttle may be provided to increase back pressure in order to drive exhaust gas through the low pressure EGR loop. However, it is known that the use of a throttle or the like is detrimental to engine performance.

It is desirable to provide an improved system which assists the flow of EGR gas to the compressor with less effect on engine performance.

The hot EGR gas is mixed with cool fresh air from the air intake before being drawn into the compressor. Good mixing produces an even distribution of to temperatures and air densities at the compressor inlet face, and hence more efficient use of the compressor. Poorly mixed flows (such as hot on one side of the circular inlet, and cold on the other) results in the compressor being less efficient due to the density differences.

IS The recirculated exhaust gas contains water vapour. When the gas is cooled, which occurs when the gas is mixed with cold air, condensate can form. If the condensate forms too far upstream of the compressor, the condensate will impact the compressor blades. Because of the extreme speeds achieved by compressor blades (between Mach 1 and Mach 2), water droplets can cause substantial damage.

Typically, a mixing unit comprising an annular ring is provided upstream of the compressor for this and this is shown in Figure 2. The annular ring may be integrated into the joint between the compressor inlet and intake duct as shown in Figure 3.

It is desirable to provide an improved system which provides efficient mixing close to the compressor blades.

The conventional mixing unit can also create a noise issue due to whistling produced by air or gas flowing over a large cavity in the annular ring.

It is desirable to provide an improved system which is at least one of: simpler, comprising fewer components, and allowing adjustment or easy optimisation of the mixing of air and EGR gas.

According to the present invention there is provided a turbocharger for an engine comprising: a compressor housing defining a compressor inlet fluidly connectable to an air intake of the engine, wherein the compressor inlet has a transverse inlet to which is fluidly connectable to an EGR system of the engine; and a barrier device provided within the compressor inlet to provide a barrier between air and exhaust gas entering the compressor inlet, wherein the barrier device includes at least one opening to allow exhaust gas to pass the barrier and mix with air flowing to the compressor inlet. I5

The compressor inlet may define a chamber upstream of the compressor blades.

The transverse inlet may be provided at the chamber. The barrier device may be provided at the chamber.

The barrier device may include a plurality of apertures, each aperture providing an opening. The barrier device may be perforated. Alternatively or in addition, the barrier device may include a mesh portion.

The apertures may be arranged in one or more patterns. The apertures may be arranged such that they are more numerous towards a first end which is adjacent to the compressor blades. The apertures may be arranged such that they are larger towards the first end.

Alternatively or in addition, the barrier device may be mounted within the compressor inlet such as to form a gap, the gap providing an opening. The gap may be provided at a region of low pressure. The gap may be formed adjacent to the compressor blades.

Alternatively or in addition, the barrier device may include one or more slots which provide an opening. The slots may be longitudinal with respect to the direction of the flow of air from the air intake to the compressor blades. The slots may extend from a first end of the barrier device which is adjacent to the compressor blades.

to The barrier device may define a bore which decreases in cross sectional area in a direction towards the first end. The barrier device may be substantially conical.

The barrier device may be formed by stamping. Alternatively, the barrier device may be formed by swaging a pipe or the like. Alternatively, the barrier device is may be a machined casting. The openings may be formed by stamping. The barrier device may be formed from steel.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of a prior art engine system; Figure 2 is a sectional end view of a prior art mixing unit; Figure 3 is a sectional side view of a prior art compressor and attached mixing unit; Figure 4 is a sectional side view of a compressor in accordance with a first embodiment of the invention; Figure 5 is a plan view of the compressor of Figure 4; Figure 6 is a sectional side view of a compressor in accordance with a second embodiment of the invention; and Figure 7 is a sectional side view of a compressor in accordance with a third embodiment of the invention.

Figure 1 shows a prior art engine system 10. Exhaust gas 100 from the engine drives a turbine 32 of a turbocharger 30 and then flows through a diesel to particulate filter (DPF) 40. A portion of the exhaust gas 100 is vented to atmosphere, while another portion is recirculated back to the engine 20 via the compressor 34 of the turbocharger 30. A throttle 46 is provided to increase back pressure to drive the recirculated exhaust gas 100. The recirculated exhaust gas passes through a filter 42 and cooler 44 before reaching a mixing unit 50 which mixes the exhaust gas 100 with air from an air intake 22 of the engine 20.

The mixing unit 50 is attached to an inlet 36 of the compressor 34 and this is best seen in Figures 2 and 3. The mixing unit 50 fits over the compressor inlet 36 and an 0 ring 58 seals the connection. The conventional compressor inlet 36 includes a tapered portion 37 to accelerate and straighten the flow of air 102 and exhaust gas 100 towards the compressor blades 38.

The mixing unit 50 includes an annular ring 52 arranged concentrically within a pipe 54 which connects the air intake 22 to the compressor 34. Air 102 flows within the bore of the annular ring 52. The pipe 54 includes a T piece and a second pipe 48 is transversely connected to the cooler 44 and the pipe 54.

Recirculated exhaust gas 100 flows into the annulus 56 defined by the pipe 54 and annular ring 52. The annular ring 52 includes perforations to allow exhaust gas 100 to mix with the air 102.

Figure 4 shows a first embodiment of the invention. Like features are given like reference numerals.

As before, the turbocharger 130 includes a compressor housing which defines a compressor inlet 136 and the inlet 136 is fluidly connected to the air intake 22.

However, the tapered portion 37 has been removed (by machining or a new profile is cast) and this defines a chamber 137 immediately upstream of the compressor blades 38. Also, a transverse inlet 139 connected to the EGR system is provided at the inlet 136, specifically at the chamber 137 to allow to exhaust gas 100 to flow into the chamber 137.

The turbocharger 130 also includes a barrier device 160. This is located within the chamber 137 and provides a barrier between air 102 and exhaust gas 100 entering the chamber 137. Specifically, air 102 flows within a bore defined by the barrier device 160 and exhaust gas 100 flows externally to the barrier device 160.

However, the barrier device 160 is perforated and so includes a number of apertures 162. Each aperture 162 provides an opening which allows exhaust gas 100 to pass the barrier and mix with air 102.

The barrier device 160 has a first end 164 adjacent to the compressor blades 38.

The barrier device 160 is conical and has a bore which decreases in cross sectional area in a direction towards the first end 164. Therefore, the barrier device 160 provides a substitute for the tapered portion 37 of the conventional turbocharger 30. However, the apertures 162 of the barrier device 160 allow the mixing of exhaust gas 100 and air 102 closer to the compressor blades 38.

Because of this, the formation of any condensate is likely to occur after the mix has passed the compressor blades, and so damage is reduced.

Also, exhaust gas 100 is mixing with air 102 within the tapered portion defined by the conical barrier device 160 and therefore at a local region characterised by low fluid static pressure and high velocity. This helps to effectively suck exhaust gas into the compressor 134. This assists the flow of exhaust gas 100 in the low pressure EGR system.

The apertures can be arranged in one or more ring-like patterns. The patterns can be arranged such that the apertures are more numerous and/or larger towards the first end.

The apertures can be adjusted in various ways to aid mixing. For example smaller holes can be provided near the inlet 100, and larger holes at the far side to of the chamber 137, so as to encourage exhaust gas to flow evenly around the circumference of barrier device 160.

As shown in Figure 5. the exhaust gas and air conduits can simply be bolted to the turbocharger 130.

Figure 6 shows a second embodiment of the invention. Like features are given like reference numerals.

In this embodiment, the barrier device 260 includes a number of slots 262 and these provide the openings which allow exhaust gas 100 to pass the barrier and mix with air 102. The barrier device 260 may or may not also include perforations similar to the first embodiment.

The slots 262 are longitudinal with respect to the main direction of fluid flow. The slots extend from the first end 264 of the barrier device 260. Therefore, even when the first end 264 extends into the inlet 136 past the chamber 137, exhaust gas 100 can pass through the slots 262 to mix with air 102.

Figure 7 shows a third embodiment of the invention. Like features are given like reference numerals.

In this embodiment, the barrier device 360 is configured and/or mounted within the compressor inlet 136 in such a way that the first end 364 does not extend so far into the inlet 136. This forms a gap 362, and the gap 362 provides the opening to allow exhaust gas 100 to pass the barrier and mix with air 102. The barrier device 360 may or may not also include perforations or slots similar to previous embodiments.

Since the gap 362 is provided adjacent to the first end 364, the opening is located at a region of low pressure and close to the compressor blades 38.

to Therefore, as in previous embodiments, exhaust gas 100 is mixing with air 102 in a legion of low pressure and high velocity.

The effect this produces has been investigated and Table I below shows the difference in static pressure at this region compared with the pressure more is remote from the compressor blades 38. In the table, the properties labelled 2' relate to the first end of the barrier device, while the properties labelled 1' relate to the opposite end of the device. These latter properties also relate to a conventional arrangement since mixing of exhaust gas 100 and air 102 occurs further upstream (and at the widest portion of the compressor inlet).

Air Mass Flow 300 kg/hr Density of Air 1.2041 kg/mA3 Diameter 1 50 mm Diameter 2 38 mm Area 1 0.00196 mA2 Area 2 0.00113 mA2 Velocity 1 35.2474 rn/s Velocity 2 61.0238 m/s Dynamic Pressure 1 0.74797 kPa Dynamic Pressure 2 2.24198 kPa Static Pressure 1 99.252 kPa Static Pressure 2 97.758 kPa Delta (difference in static pressure) 1.494 kPa

Table I

There was therefore a 1.5 kPa improvement in suction over the conventional setup for the application investigated. The difference in pressure from the DPF to the compressor inlet was approximately 3 kPa, therefore the obtained improvement is of a substantial magnitude. Exhaust gas 100 will be more effectively drawn through the EGR system, thus reducing the need to use the choke 46. Therefore, fuel economy is improved.

The barrier device is a simple and inexpensive device, easily formed by stamping or by swaging a pipe or the like. It can be formed from mild steel or the like. The device can be easily modified, with the apertures/slots/gap adjusted to provide optimum mixing for the particular application.

An important advantage of the invention is that there is no need for an additional mixer component. This simplifies the arrangement and reduces cost.

Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.

Claims

Claims 1. A turbocharger for an engine comprising: a compressor housing defining a compressor inlet fluidly connectable to an air intake of the engine, wherein the compressor inlet has a transverse inlet which is fluidly connectable to an EGR system of the engine; and a barrier device provided within the compressor inlet to provide a barrier between air and exhaust gas entering the compressor inlet, wherein the barrier device includes at least one opening to allow exhaust gas to pass the barrier and mix with air flowing to the compressor inlet.
2. A turbocharger as claimed in claim 1, wherein the compressor inlet defines a chamber upstream of the compressor blades.
3. A turbocharger as claimed in claim 2, wherein the transverse inlet is provided at the chamber.
4. A turbocharger as claimed in claim 2 or 3, wherein the barrier device is provided at the chamber.
5. A turbocharger as claimed in any preceding claim, wherein the barrier device includes a plurality of apertures, each aperture providing an opening.
6. A turbocharger as claimed in claim 5, wherein the barrier device is perforated.
7. A turbocharger as claimed in claim 5 or 6, wherein the apertures are arranged in one or more patterns. l0
8. A turbocharger as claimed in any of claims 5 to 7, wherein the apertures are arranged such that they are more numerous towards a first end which is adjacent to the compressor blades.
9. A turbocharger as claimed in any of claims 5 to 8, wherein the apertures are arranged such that they are larger towards the first end.
10. A turbocharger as claimed in any preceding claim, wherein the barrier device is mounted within the compressor inlet such as to form a gap, the gap to providing an opening.
11. A turbocharger as claimed in claim 10, wherein the gap is provided at a region of low pressure.is
12. A turbocharger as claimed in claim 10 or 11, wherein the gap is formed adjacent to the compressor blades.
13. A turbocharger as claimed in any preceding claim, wherein the barrier device includes one or more slots which provide an opening.
14. A turbocharger as claimed in claim 13, wherein the slots are longitudinal with respect to the direction of the flow of air from the air intake to the compressor blades.
15. A turbocharger as claimed in claim 13 or 14, wherein the slots extend from a first end of the barrier device which is adjacent to the compressor blades.
16. A turbocharger as claimed in any preceding claim, wherein the barrier device defines a bore which decreases in cross sectional area in a direction towards the first end. Ii17. A turbocharger as claimed in claim 16, wherein the barrier device is substantially conical.18. A turbocharger as claimed in any preceding claim, wherein the barrier device is formed by stamping.19. A turbocharger as claimed in any of claims 1 to 17, wherein the barrier device is formed by swaging a pipe.to 20. A turbocharger as claimed in any of claims I to 17, wherein the barrier device is a machined casting.