DE202015002208U1 - internal combustion engine - Google Patents

Abstract

An internal combustion engine (110) comprising an air inlet duct (205) provided with a compressor (240), wherein a portion of the air inlet duct (205) downstream of the compressor (240) comprises a local restriction (500).

Description

TECHNICAL AREA

The present disclosure relates to an internal combustion engine, in particular an internal combustion engine of a motor vehicle.

More particularly, the present disclosure relates to a damping system for improving the charging system of an internal combustion engine, which is particularly applied to a low-cylinder vehicle.

BACKGROUND

Most internal combustion engines are known to be turbocharged. A turbocharger is an engine charging device that is used to allow an engine of a given size to produce more power. The advantage of a turbocharger is that it compresses a larger mass of air that is drawn into the combustion chamber of the engine, resulting in increased performance and / or efficiency.

Modern internal combustion engines are increasingly requiring so-called "low-end torque," which is essentially the torque under full load conditions that the engine provides at low speed (i.e., at the lower end of the torque curve at full load). This low speed torque is usually achieved by improving the engine's boost capacity.

It is known that turbocharged engines can experience some problems with stalling the compressor when operating at low speed. A stall is a phenomenon that occurs at a low mass air flow into the compressor causing the flow to break, resulting in instability and noise. When a compressor reaches the surge line, it is no longer able to compress the air, and under extreme conditions, the air flow can be reversed by the compressor.

The surge limit of the compressor is usually represented as a specific curve in the compressor map, i. H. in an empirically determined map that relates the compression ratio and mass flow rate through the compressor.

The stall phenomenon may be promoted by air pulsations occurring in the intake line of the engine connecting the compressor to the intake manifold. The movements of the opening and closing of the intake valves create pressure waves in the fluid domain in the intake manifold which propagate from the intake valves to the compressor and back again. The pressure waves can lead to fluctuations in the mass flow rate. At low engine speeds, the phenomenon is compounded by the lower frequency of valve movements. This results in oscillations of the mass flow rate around a cycle average operating point in the compressor map, which affects the occurrence of the surge line. Generally, with a fixed average mass flow rate in the compressor, the maximum pressure ratio achieved is reduced by an increase in the amplitude of the mass flow rate oscillations, which degrades the performance of the compressor.

Because of the pressure waves propagating in the inlet ducts, therefore, the compressor stall occurs earlier (i.e., at lower pressure ratios) than predicted by the compressor map.

These negative effects of propagating pressure waves are much more severe in a two-cylinder engine than in a standard four-cylinder engine where the air mass flow in the intake manifold is more constant.

To mitigate this effect and dampen the pressure waves, it might be helpful to expand the diameter of at least a portion of the inlet duct. However, this solution would result in poor transient performance due to the inertia of the larger amount of air in the inlet conduit.

SUMMARY

An object of the present invention is to provide a compact apparatus capable of damping the amplitude of the pressure waves to values similar to those of a four-cylinder engine, thereby delaying the occurrence of stall without affecting the transient behavior.

These and other objects are achieved by the embodiments of the invention having the features described in the independent claims. The dependent claims describe secondary aspects of the invention.

In particular, an embodiment of the invention provides an internal combustion engine comprising an air inlet duct provided with a compressor, a portion of which Air inlet duct downstream of the compressor comprises a local constriction.

This improves low speed performance because the surge line occurs at higher pressure ratios. It also achieves a reduction in CO ₂ emissions, as the engine can run at low speed and thereby generate higher torques. The rated power is also increased due to a higher volumetric efficiency of the internal combustion engine.

According to one aspect of the present invention, the local restriction has a constant cross-section.

This embodiment of the invention achieves the same effects as described above in combination with a very low cost embodiment of the invention.

According to one aspect of the present invention, the motor includes an actuator to change a cross section of the local restriction.

This embodiment of the invention achieves the same effects as already described, but in addition to this, it is also possible to adapt the local constriction to different engine operating points to minimize pressure drops at higher engine speeds.

According to another aspect of the present invention, the local constriction is defined by a convergent section and a divergent section located downstream of the convergent section.

This aspect of the invention minimizes pressure drops.

According to another aspect of the invention, the convergent portion and the divergent portion have an identical shape and length.

This aspect of the invention has the effect of dampening pressure waves propagating from the compressor to the intake valve and pressure waves propagating from the intake valve to the compressor with the same efficiency.

According to a further aspect of the invention, the convergent section and / or the divergent section have a rounded profile in an axial cross-section.

This aspect of the invention has the effect of further minimizing the pressure drops.

According to another aspect of the present invention, the local restriction has a minimum cross-sectional diameter that is between 40% and 70% of a diameter of the inlet conduit.

This aspect of the invention has the effect of optimizing the performance of the local constriction.

According to a further aspect of the invention, the internal combustion engine is a two-cylinder engine.

This aspect of the invention has the effect of improving the performance of two-cylinder engines, which are particularly prone to stalling at the compressor at low engine speeds.

In accordance with another aspect of the invention, an intercooler is disposed between the compressor and the local constriction.

This aspect of the invention causes the local constriction to operate with a higher density fluid, which improves the local constriction efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

Now, the present invention will be described by way of example with reference to the accompanying drawings.

1 schematically shows an internal combustion engine according to an embodiment of the invention.

2 schematically shows a detail of the air inlet pipe of the motor vehicle system of 1 ,

3 is an alternative embodiment of the present invention.

4 is another alternative embodiment of the present invention.

5 FIG. 12 is a graph showing the mass flow rate in the intake pipe at a certain crank angle.

6 is a simplified cross-sectional view of the internal combustion engine of 1 ,

PRECISE DESCRIPTION

Some embodiments may be a motor vehicle system 100 include that in the 1 and 6 is shown and that an internal combustion engine (ICE) 110 with an engine block 120 owns, the at least one cylinder 125 with a piston 140 defined, which has a coupling with which the crankshaft 145 is turned. A cylinder head 130 works with the piston 140 together to a combustion chamber 150 define. An air-fuel mixture (not shown) enters the combustion chamber 150 introduced and ignited, resulting in hot expanding combustion gases, leading to a reciprocation of the piston 140 to lead. Each of the cylinders 125 Has at least two valves by a camshaft 135 operated at the same time as the crankshaft 145 rotates. intake valves 215 selectively release air from the inlet 210 in the combustion chamber 150 , exhaust 216 allow the outlet of the exhaust gases through an outlet 220 , In some examples, a camshaft phasing system 155 used to selectively the timing between the camshaft 135 and the crankshaft 145 to change.

The air can be the cylinders 125 via an intake manifold 200 be supplied. An air inlet pipe 205 leads the intake manifold 200 Ambient air too. It can be a throttle 330 be provided to the air flow to the intake manifold 200 to regulate. In addition, a system for compressed air such as a turbocharger 230 with a compressor 240 that is together with a turbine 250 turns, be used. The rotation of the compressor 240 increases the pressure and the temperature of the air in the inlet pipe 205 and in the intake manifold 200 , One in the lead 205 containing intercooler 260 can reduce the temperature of the air. The turbine 250 turns when flowing from an exhaust manifold 225 coming exhaust gases. The turbine 250 may be a variable geometry turbine (VGT) or fixed geometry and / or have a wastegate.

The motor vehicle system 100 can still use an electronic control unit (ECM) 450 configured to receive signals from or to various, with the ICE 110 connected sensors and / or devices to send or receive to operate it. The internal combustion engine can be a diesel engine.

1 shows in particular a high pressure side 208 the air inlet duct 205 , in particular in the part downstream of a compressor 240 ,

The internal combustion engine 110 includes an engine block 120 , the at least one cylinder 125 defined, the at least one air inlet 210 associated with an inlet valve 215 is coupled. An air inlet pipe 205 is with a compressor 240 provided to the inlet 210 To supply air. A section of the air inlet duct between the compressor 240 and the inlet valve 215 includes a local narrowing 500 ,

In other words, the local narrowing 500 in the inlet pipe 205 located downstream of the compressor. In the present specification, the term "local" is used to mean a constriction 500 to define only a small section of the length of the inlet pipe 205 for example less than 5% of it.

The local narrowing 500 can through an annular part 510 be formed directly in the inlet pipe 205 is arranged, whereby it can have a fixed, constant cross-section.

Like this in 2 can be seen, the local narrowing 500 through a convergent section 505 and through a divergent section 506 formed directly downstream of the convergent section 505 is arranged. In the present specification, the term "downstream" is used for the main flow direction in the inlet conduit 205 (ie from the compressor 240 to the inlet valve 215 ) used.

According to the present embodiment, the annular part 510 be symmetric with respect to a transverse plane A. In this case, the convergent section 505 and the divergent section 506 identical in shape and length. Therefore, the local narrowing dampens 505 extending from the compressor 240 to the intake valves 215 spreading pressure waves and extending from the intake valves 215 to the compressor 240 spreading pressure waves with the same efficiency.

Another embodiment may provide that the convergent section 505 and the divergent section 506 are different in shape and length.

The profiles of the convergent 505 and / or the divergent section 506 have a rounded axial profile that results in a flow separation with the formation of a free vortex V that dampens the peaks of the pressure waves that are in the inlet duct 205 spread.

That through the local narrowing 500 caused behavior is better understood by the following explanations.

In the upstream pipes (right side of 2 ) the mean flow velocity is indicated by u (where u is lower than the speed of sound); if the flow is the local narrowing 500 happens, its velocity u 'increases as a function of the ratio d / D. The higher speed and the profile curvature in the divergent section 506 cause a flow separation with the formation of the free vortex V.

The higher the peak-to-peak amplitude of the movements of the intake valves 215 in the inlet pipe 205 caused by pressure waves, the more effective is the local constriction 500 caused dispersion, which transfers energy into the vortex flow. The turbulence therefore reduces the peak-to-peak amplitude of the propagating pressure waves. The reduction in peak-to-peak amplitude is particularly good in the graph of 5 where the dashed line shows the mass flow rate in a standard inlet line while the solid line shows the mass flow rate under the same conditions, but with the local constriction 500 a cross-sectional extension follows.

Since the variations in mass flow rate caused by the pressure waves are greatly reduced in the lower speed range, the pumping limit shifts to the left side of the compressor map (lower mass flow rates), resulting in better compressor performance and therefore better lower engine speed performance.

According to another embodiment of the invention, the local constriction 500 , followed by a cross-sectional extension 502 , through a calibrated orifice 550 be formed in the inlet pipe 205 downstream from the compressor 240 is arranged. 4 shows this embodiment. The same reference numerals as used above denote the corresponding parts here.

In both embodiments described above, the local restriction may have a circular cross section, and the smallest diameter "d" of the passage may be between 40% and 70% of the inlet conduit "D" diameter measured in a section upstream and downstream near the local narrowing 500 located. The ratio d / D is preferably 50-60% and especially 55%. The diameter of the inlet pipe 205 in the section between the compressor 240 and the throttle 330 apart from the local constriction described here 500 be constant.

In another embodiment, in 3 is shown, the local constriction has a variable passage cross-section, wherein an actuator 600 by the ECM 450 is controlled, the cross section of the local narrowing 560 changed with variable passage cross section (arrows F).

In any of the embodiments described above, the local constriction 500 downstream from the intercooler 260 be arranged.

The local narrowing 500 can also be directly in the inlet line 205 be formed, or it may be a separate part of the inlet pipe 205 being "in line" with her.

It has been proven that the local narrowing 500 is particularly effective in two-cylinder engines and at least in engines with less than 4 cylinders.

In the foregoing summary and detailed description, at least one exemplary embodiment has been presented; however, it should be noted that there are a large number of modification options. It should also be noted that the exemplary embodiment or exemplary embodiments are only examples and are not intended to limit the scope, applicability, or construction in any way whatsoever. Rather, the foregoing summary and detailed description will provide those skilled in the art with a practical guide to implementing at least one example embodiment, it being understood that various changes may be made in the functions and arrangements of the elements described with reference to an exemplary embodiment without departing from the spirit of the invention Scope of protection as defined in the appended claims and their legal equivalents.

LIST OF REFERENCE NUMBERS

100

Automotive system

110

internal combustion engine

120

block

125

cylinder

200

intake manifold

205

Air inlet line

208

High pressure side

210

inlet

215

intake valves

216

exhaust

225

exhaust manifold

230

turbocharger

240

compressor

250

turbine

260

Intercooler

320

EGR valve

330

throttle

450

electronic control unit (ECM)

500

local narrowing

502

Cross-sectional widening

505

convergent section

506

divergent section

510

annular part

550

calibrated orifice

560

local constriction with variable passage cross-section

Claims (9)

Internal combustion engine ( 110 ), comprising an air inlet line ( 205 ) with a compressor ( 240 ), wherein a portion of the air inlet duct ( 205 ) downstream of the compressor ( 240 ) a local narrowing ( 500 ). Internal combustion engine according to the preceding claim, wherein the local constriction ( 500 ) has a constant cross-section. Internal combustion engine ( 110 ) according to claim 1, comprising an actuator ( 600 ) for changing a cross section of the local constriction ( 500 ). Internal combustion engine ( 110 ) according to one or more of the preceding claims, wherein the local constriction ( 500 ) through a convergent section ( 505 ) and through a downstream of the convergent section (FIG. 505 ) arranged divergent section ( 506 ) is defined. Internal combustion engine ( 110 ) according to claim 4, wherein said convergent section ( 505 ) and the divergent section ( 506 ) have an identical shape and length. Internal combustion engine ( 110 ) according to claim 4, wherein said convergent section ( 505 ) and the divergent section ( 506 ) have a rounded axial profile. Internal combustion engine ( 110 ) according to one or more of the preceding claims, wherein the local constriction ( 500 ) has a minimum cross-sectional diameter (d) that is between 40% and 70% of a diameter (D) of the inlet conduit. Internal combustion engine ( 110 ) according to one or more of the preceding claims, wherein the internal combustion engine is a two-cylinder engine. Internal combustion engine ( 110 ) according to the preceding claim, wherein an intercooler ( 260 ) between the compressor ( 240 ) and the local narrowing ( 500 ) is arranged.

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