Patent Publication Number: US-2021189979-A1

Title: Method for operating an internal combustion engine

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates to a method for operating an internal combustion engine. 
     Description of Related Art 
     In order to raise the nitrogen oxide conversion rates of an SCR catalytic converter, especially under low load of an internal combustion engine, it may be necessary, for example, to increase an exhaust gas temperature. 
     In conventional practice, the residual gas rate at low load can be influenced by way of the valve overlap. However, this results in an increase in the depth of the valve pockets in the piston, which, in turn, is relevant for consumption. 
     To carry out internal exhaust gas recirculation into the combustion chamber of a diesel internal combustion engine, AT 005 783 U1 discloses that the inlet valve is opened briefly during the exhaust stroke. In order to achieve an improvement in emissions in the low engine speed range, on the one hand, and in the medium and high engine speed range, on the other, it is envisaged that the start of the preliminary lift of the inlet valve occurs in the region of 180° to 210° of crank angle after the TDC position of the ignition. 
     US 2009/0194080 A1 relates to a method for scavenging residual combustion gas of an internal combustion engine with direct injection, in particular a diesel engine. When the engine is running at low speeds and under high load conditions, at least one sequence of opening/closing of inlet valves is performed during a sequence of opening/closing of exhaust valves in the exhaust phase of the engine in order to achieve scavenging of the residual burnt gas. 
     SUMMARY 
     It is the underlying object of the present disclosure to provide a method in which the exhaust gas temperature can be raised under low load. 
     The object is achieved by the features of independent claim  1 . Advantageous developments are indicated in the dependent claims and the description. 
     The present disclosure relates to a method for operating an internal combustion engine (e.g. a four-stroke internal combustion engine and/or multi-cylinder internal combustion engine). 
     The method comprises producing a pressure pulse (e.g. a significant and/or sudden and/or time-limited and/or one-time pressure increase, e.g. a pressure pulsation, e.g. a cyclical pressure pulsation) in an exhaust line of the internal combustion engine. The method comprises feeding exhaust gas (e.g. residual exhaust gas) from a combustion chamber of a cylinder into an inlet passage of the cylinder during an exhaust stroke of the cylinder by means of propagation of the pressure pulse from the exhaust line into the combustion chamber of the cylinder. The method comprises feeding the exhaust gas from the inlet passage of the cylinder into the combustion chamber of the cylinder during an inlet stroke of the cylinder. 
     The method makes it possible to raise the exhaust gas temperature at low load by means of internal residual gas control (residual exhaust gas control) without negatively affecting the full-load performance of the internal combustion engine. The possible nitrogen oxide conversion rates of an SCR catalytic converter increase as a result. The method uses the pressure pulsations in the exhaust line to deliver residual gas from the combustion chamber into an inlet tract of the internal combustion engine. The residual gas is then flushed back into the combustion chamber of the cylinder in the inlet stroke, thereby reducing the fresh air mass in the combustion chamber of the cylinder by the mass of the residual gas. Owing to the reduced air and thus also exhaust gas mass flow, the exhaust gas temperature rises while the engine torque remains constant without negatively affecting the charge exchange work of the engine. 
     In one exemplary embodiment, the pressure pulse in the exhaust line is produced by opening an exhaust valve of another cylinder of the internal combustion engine during an exhaust stroke of the other cylinder. 
     In another exemplary embodiment, the other cylinder is operated with a phase offset with respect to the cylinder, preferably with a phase offset of approximately −120° of crank angle (e.g. in the case of a six-cylinder internal combustion engine) and/or of −720° of crank angle/number of cylinders of the internal combustion engine. 
     The pressure pulse can expediently be passed via an exhaust turbine, for example, e.g. from an exhaust manifold, via the exhaust turbine to another exhaust manifold. 
     For example, the exhaust line can be of single-flow configuration, i.e. with one exhaust manifold, or of multi-flow configuration, i.e. with a plurality of exhaust manifolds. 
     In one embodiment, the feeding of exhaust gas from the combustion chamber of the cylinder is brought about only by an increase in a cylinder pressure in the combustion chamber of the cylinder by means of the pressure pulse. The cylinder pressure can preferably be increased by means of a charging pressure in the inlet passage of the cylinder and/or of the internal combustion engine. 
     In another embodiment, the pressure pulse propagates from the exhaust line into the combustion chamber of the cylinder through an (e.g. already) opened exhaust valve of the cylinder, preferably during an exhaust stroke of the cylinder. 
     In one variant embodiment, the feeding of exhaust gas from the combustion chamber of the cylinder into the inlet passage of the cylinder by means of the pressure pulse is accomplished by opening an inlet valve of the cylinder preferably during an exhaust stroke of the cylinder and/or during the pressure pulse. 
     In another variant embodiment, the feeding of the exhaust gas from the inlet passage of the cylinder into the combustion chamber of the cylinder is carried out during an inlet stroke of the cylinder by opening an inlet valve of the cylinder. 
     In one exemplary embodiment, the inlet valve of the cylinder opens only when the pressure pulse propagates into the combustion chamber of the cylinder. Alternatively or in addition, the inlet valve of the cylinder opens only when the cylinder pressure in the combustion chamber of the cylinder is increased by the pressure pulse above a charging pressure in the inlet passage of the cylinder and/or of the internal combustion engine. 
     In another exemplary embodiment, the inlet valve of the cylinder closes when or before the cylinder pressure in the combustion chamber of the cylinder once again falls below a charging pressure in the inlet passage of the cylinder and/or of the internal combustion engine. 
     In one embodiment, the inlet valve of the cylinder opens at the beginning of the exhaust stroke of the other cylinder, and/or the inlet valve of the cylinder opens when the exhaust valve of the other cylinder opens. Alternatively or in addition, the inlet valve of the cylinder opens in the exhaust stroke of the cylinder and/or closes before the end of the exhaust stroke of the cylinder. 
     In another embodiment, the inlet valve of the cylinder is open in a range of between 100° of crank angle after BDC (bottom dead center of a piston movement of a piston associated with the cylinder) in the power stroke of the cylinder and 150° of crank angle after BDC (bottom dead center of the piston movement of the piston associated with the cylinder) in the exhaust stroke of the cylinder. 
     In one variant embodiment, the inlet valve of the cylinder opens at approximately or after 100° of crank angle after BDC (bottom dead center of a piston movement of a piston associated with the cylinder) in the exhaust stroke of the cylinder and/or the inlet valve of the cylinder closes at approximately or before 150° of crank angle after BDC (bottom dead center of a piston movement of a piston associated with the cylinder) in the exhaust stroke of the cylinder. 
     In another variant embodiment, the inlet valve of the cylinder is open for approximately or less than 50° of crank angle in the exhaust stroke of the cylinder. 
     In one exemplary embodiment, a maximum lift of the inlet valve of the cylinder during the exhaust stroke of the cylinder is less than a maximum lift of the inlet valve of the cylinder during an inlet stroke of the cylinder. 
     In another exemplary embodiment, a maximum lift of the inlet valve of the cylinder during the exhaust stroke of the cylinder is less than ⅓ or less than ¼ of a maximum lift of the inlet valve of the cylinder during an inlet stroke of the cylinder. 
     In another exemplary embodiment, a maximum lift of the inlet valve of the cylinder during the exhaust stroke of the cylinder is less than 3 mm, preferably between 1 mm and 2 mm. For example, a maximum lift of the inlet valve of the cylinder during the inlet stroke of the cylinder can be around 10 mm. 
     In one embodiment, a valve timing curve of the inlet valve of the cylinder is invariable, and/or a valve timing curve of the inlet valve of the cylinder is implemented by a non-switchable and/or rigid cam of a camshaft of the internal combustion engine. 
     In another embodiment, an actuating device, preferably a valve gear, for actuating the inlet valve of the cylinder is rigid and/or non-switchable. Alternatively or in addition, a valve timing curve of the inlet valve of the cylinder is under low load of the internal combustion engine and under medium load and/or under full load of the internal combustion engine. 
     In one variant embodiment, the method furthermore comprises operating the internal combustion engine under low load while the pressure pulse is being produced, exhaust gas is being fed from the combustion chamber, and/or the exhaust gas is being fed from the inlet passage. 
     In another variant embodiment, the method furthermore comprises operating the internal combustion engine in a range of up to 30% to 35% and/or up to 40% of load (partial load or % of a rated load of the internal combustion engine) and/or in a low-speed range, preferably between 800 rpm and 1400 rpm, while the pressure pulse is being produced, exhaust gas is being fed from the combustion chamber, and/or the exhaust gas is being fed from the inlet passage. 
     In one exemplary embodiment, the method is carried out to increase an exhaust gas temperature in the exhaust line, preferably under low load of the internal combustion engine, preferably to increase a conversion rate of an SCR catalytic converter in the exhaust line. 
     In another exemplary embodiment, the internal combustion engine comprises a plurality of cylinders (e.g. 4, 6, 8, 10, 12 or more) and the method is used for each cylinder of the internal combustion engine. 
     The present disclosure also relates to an internal combustion engine or to a commercial vehicle (e.g. a bus or heavy goods vehicle) having an internal combustion engine designed to carry out a method as herein. 
     It is also possible to use the method as disclosed herein for passenger vehicles, large engines, off-road vehicles, stationary engines, marine engines etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments and features of the present disclosure which are described above can be combined in any desired way. Further details and advantages of the present disclosure are described below with reference to the appended drawings, in which: 
         FIG. 1  shows a schematic internal combustion engine suitable for carrying out a method in accordance with the present disclosure; 
         FIG. 2  shows a diagram which shows various pressure values against a crank angle of an internal combustion engine; 
         FIG. 3  shows a diagram which shows various pressure values and valve timing curves against a crank angle of an internal combustion engine in accordance with the present disclosure; and 
         FIG. 4  shows a schematic flow diagram of an illustrative method in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments shown in the figures partially coincide, and therefore similar or identical parts are provided with the same reference signs and attention is also drawn, for the explanation thereof, to the description of the other embodiments or figures in order to avoid repetition. 
       FIG. 1  shows an internal combustion engine  10 . The internal combustion engine  10  is embodied as a multi-cylinder internal combustion engine, preferably as a six-cylinder in-line engine. However, it is also possible for the internal combustion engine to have more or fewer cylinders and/or a different arrangement of cylinders. The internal combustion engine  10  is preferably designed as a four-stroke internal combustion engine. The internal combustion engine  10  can preferably be designed as a diesel internal combustion engine. The internal combustion engine  10  can expediently be included in a motor vehicle, preferably a commercial vehicle (e.g. a heavy goods vehicle or bus). 
     The illustrative internal combustion engine  10  has a first to sixth cylinder  12 . The cylinders  12  are operated with a phase offset of 120° of crank angle relative to one another. The fifth cylinder of the plurality of cylinders  12  can have a phase offset of −120° of crank angle with respect to the first cylinder of the plurality of cylinders  12 , for example, etc. While the exhaust stroke is beginning in the fifth cylinder of the cylinders  12 , for example, the first cylinder of the plurality of cylinders  12  is already in the middle of the exhaust stroke. If the internal combustion engine  10  has a different number of cylinders, the cylinders accordingly have different phase offsets relative to one another, e.g. −720° of crank angle/number of cylinders. 
     The cylinders  12  each have at least one inlet passage  14 , a combustion chamber  16  and at least one exhaust passage  18 . The inlet passages  14  and the exhaust passages  16  can be arranged in a cylinder head of the internal combustion engine  10 , for example. Via the inlet passages  16 , charge air, for example, can be fed to the combustion chambers  16 . Via the exhaust passages  18 , exhaust gas can be discharged from the combustion chambers  16 . 
     The cylinders  12  furthermore each have at least one inlet valve  20  and at least one exhaust valve  22 , preferably each having two inlet valves  20  and two exhaust valves  22  per cylinder  12 . By means of the inlet valves  20 , a fluid connection can be established between the inlet passages  14  and the respective combustion chambers  16  of the cylinders  12 . By means of the exhaust valves  22 , a fluid connection can be established between the combustion chambers  16  and the respective exhaust passages. The inlet valves  20  and exhaust valves  22  can be arranged in a cylinder head of the internal combustion engine  10 . The inlet valves  20  and the exhaust valves  22  can be designed as poppet valves, for example. 
     The internal combustion engine  10  has an exhaust line  24 . The exhaust line  24  is of double-flow design, for example, as illustrated, with a first exhaust manifold  26  and a second exhaust manifold  28 . The first exhaust manifold  26  connects the exhaust passages  18  of the first three cylinders of the plurality of cylinders  12  to an exhaust turbine  30  of an exhaust turbocharger. The first exhaust manifold  26  carries exhaust gas out of the first three cylinders of the plurality of cylinders  12  to the exhaust turbine  30 . The second exhaust manifold  28  connects the other three cylinders of the plurality of cylinders  12  to the exhaust turbine  30  in order to feed exhaust gas to the exhaust turbine  30 . The exhaust line  24  can also have more or fewer exhaust gas flows or exhaust manifolds. 
     It is possible, in particular, for each of those cylinders of the plurality of cylinders  12 , the exhaust passages  18  of which are connected directly to a common exhaust manifold  26  or  28 , to be operated with a phase offset of 240° of crank angle. 
     An exhaust gas aftertreatment device  32  can be arranged downstream of the exhaust turbine  30 . In particular, the exhaust gas aftertreatment device  32  can have a device for selective catalytic reduction of nitrogen oxides in the exhaust gas or an SCR catalytic converter device (SCR=selective catalytic reduction)  34 . A nitrogen oxide conversion rate of the SCR catalytic converter device  34  may be temperature-dependent. Particularly at low exhaust gas temperatures, e.g. when starting the engine or during low-load operation of the internal combustion engine  10 , an exhaust gas temperature may be too low for a desired nitrogen oxide conversion rate. 
     The method disclosed herein and an internal combustion engine which carries out the method disclosed herein are capable of raising an exhaust gas temperature during low-load operation by using a pressure pulse in the exhaust line and by means of a double inlet valve lift. 
       FIG. 2  shows different pressure characteristics during a power stroke of the internal combustion engine  10  with reference to one of the plurality of cylinders  12  (the “cylinder  12  under consideration”) for a low-load operating point. 
     The chain-dotted curve A corresponds to an illustrative pressure characteristic in the inlet passage  14  of the cylinder  12  under consideration. The dotted curve B corresponds to an illustrative pressure characteristic in the respective exhaust passage  18  of the cylinder  12  under consideration. The solid curve C corresponds to an illustrative pressure characteristic of a cylinder pressure in the combustion chamber  16  of the cylinder  12  under consideration. 
     Curve A shows that the pressure in the inlet passage  14  of the cylinder  12  under consideration is substantially constant. The pressure falls slightly when the inlet valve  20  of the cylinder  12  under consideration is open in the intake stroke or the inlet stroke. In the intake stroke, charge air flows into the combustion chamber  16  of the cylinder  12  under consideration. During the other strokes, the pressure in the inlet passage  14  is substantially constant, with slight fluctuations, which are caused, for example, by the opening and closing of other inlet valves  20  of other cylinders  12 . For example, the pressure in the inlet passage  14  may be between 1.3 bar and 1.4 bar when the internal combustion engine  10  is operated under low load, as illustrated by way of example. 
     Curve B shows that a pressure in the exhaust passage  18  of the cylinder  12  under consideration fluctuates quite severely during a cycle. When the exhaust valve  22  of the cylinder  12  under consideration is opened at the end of the expansion stroke, the pressure rises sharply and is gradually dissipated in accordance with a cylinder pressure characteristic C in this region. In addition, there are further pressure pulsations in the exhaust passage  18  of the cylinder  12  under consideration, to be specific every 120° of crank angle. The pressure positions are caused by the opening of the exhaust valves  22  of the other cylinders  12 . In the example illustrated, the high pressure pulses during the compression stroke and the intake stroke are caused by those cylinders  12  which are connected to the same exhaust manifold  26  or  28  as the cylinder  12  under consideration. The lower pressure pulses during the expansion stroke, the expulsion stroke and at the end of the intake stroke and into the compression stroke are caused by those cylinders  12  which are connected to the other exhaust manifold  26  or  28  from the cylinder  12  under consideration. The transmission of the lower pressure pulses takes place by way of a connection of the exhaust manifolds  26  and  28  by the exhaust turbine  30 . This connection is indicated in a purely schematic way by a dotted line in  FIG. 1  and is provided with the reference sign  36 . 
     Curve C shows that a cylinder pressure during the expansion stroke is greatly increased. In addition, it is illustrated in region D that the cylinder pressure in the second half of the expulsion stroke (exhaust stroke) is even higher. The reason for the increase lies in the effect of the pressure pulse in the exhaust passage  18  of the cylinder  12  under consideration (see curve B). This pressure pulse is caused by the opening of the exhaust valve  22  of a cylinder of the plurality of cylinders  12  which is being operated with a phase offset of −120° of crank angle. During this period of time, this cylinder operated with a phase offset of −120° of crank angle begins its exhaust stroke at the beginning of the period of time, the exhaust gas being expelled through the opened exhaust valve  22  during this stroke. 
     It has been recognized that the cylinder pressure increase caused in the cylinder  12  under consideration by the pressure pulse in the exhaust line  24  can have an effect such that, owing to the pressure pulse (curve B), the cylinder pressure (curve C) rises higher than the charge air pressure (curve A). In the exemplary embodiment with the six-cylinder internal combustion engine, the cylinder pressure of the cylinder  12  under consideration during the expulsion stroke is higher than the charging pressure in a region of about 280° of crank angle and 330° of crank angle. 
     This insight can be used, exploiting the effect of the pressure pulse, to deliver residual gas from the combustion chamber  16  of the cylinder  12  under consideration into the inlet passage  14  of the cylinder  12  under consideration. It is proposed to open the inlet valve  20  of the cylinder  12  under consideration during this phase, in the exhaust stroke, in addition to the standard inlet lift during the intake stroke, as additionally illustrated in  FIG. 3 . 
     In addition to the curves of  FIG. 2 ,  FIG. 3  additionally shows a valve timing curve of the exhaust valve  22  of the cylinder  12  under consideration as a dotted curve E and a valve timing curve of the inlet valve  20  of the cylinder  12  under consideration as a chain-dotted curve F. 
     Curve E shows that the exhaust valve  22  of the cylinder  12  under consideration is opened during the exhaust stroke. 
     Curve  11  shows that the inlet valve  20  of the cylinder  12  under consideration performs a double lift. The inlet valve  20  opens a first time in the exhaust stroke, more specifically precisely while the pressure pulse is increasing the cylinder pressure in the combustion chamber  16  of the cylinder  12  under consideration by way of the charging pressure in the inlet passage  14 . Residual gas then flows through the opened inlet valve  20  into the inlet passage  14  of the cylinder  12  under consideration. The inlet valve  20  of the cylinder  12  under consideration then closes before the cylinder pressure in the combustion chamber  16  of the cylinder under consideration falls back below the charging pressure. The inlet valve  20  of the cylinder  12  under consideration then opens again normally in the intake stroke. In the intake stroke, residual gas is flushed back out of the inlet passage  14  into the combustion chamber  16  of the cylinder  21  under consideration. At the same time, the fresh air mass in the combustion chamber  16  of the cylinder  12  under consideration is reduced by the mass of the residual gas. Owing to the reduced air and thus also exhaust gas mass flow, the exhaust gas temperature rises while the engine torque remains constant without negatively affecting the charge exchange work of the engine. The scavenging of the residual gas can be used to bring about an exhaust gas temperature increase in the exhaust line  24  under a low load of the internal combustion engine  10  in order to increase a nitrogen oxide conversion rate of the SCR catalytic converter device  34 . 
     The residual gas quantity in the low-load range can be preset by way of the lift length and lift height of the inlet valve  20  during the exhaust stroke. It is possible that the additional lift of the inlet valve  20  will have an effect on the maximum possible rated power of the internal combustion engine. Standard engines generally have a significantly negative scavenging gradient at rated power, i.e. the exhaust gas backpressure is significantly higher than the charging pressure. This leads to increased residual gas rates even at rated power. The lift size and lift length of the additional lift of the inlet valve  20  must therefore be correctly designed in order to avoid reducing the rated power. 
     In respect of the lift length, the proposal for the illustrative six-cylinder internal combustion engine  10  is that the inlet valve  20  of the cylinder  12  under consideration is open in a range between 100° of crank angle after BDC in the exhaust stroke of the cylinder  12  under consideration and 150° of crank angle after BDC in the exhaust stroke of the cylinder  12  under consideration. 
     In respect of a maximum lift of the inlet valve  20  of the cylinder  12  under consideration, it is proposed that this lift should be less than ⅓ during the exhaust stroke of the cylinder  12  under consideration or less than ¼ of a maximum lift of the inlet valve  20  of the cylinder  12  under consideration during an inlet stroke of the cylinder  12  under consideration, e.g. around 1 mm to 2 mm, as illustrated. 
     The orientation, length and height of the additional lift has thus been configured in such a way that as much residual gas as possible is scavenged into the inlet passage  14  in the low-load range, and there is only a small change toward “normal” timings at higher engine loads in the main driving range. 
     The advantageous configuration of the additional lift at the inlet valve  20  in the exhaust stroke ensures that the additional lift can be carried out both under partial load and under full load without having a significantly negative effect under full load. Thus, there is no need to provide a switchable system for selective activation of the additional lift of the inlet valve  20 . Instead, it is sufficient if the inlet valve  20  is actuated by a robust, rigid, non-switchable cam of a camshaft or, more generally, by way of a rigid, non-switchable valve gear which brings about the same valve timing curve for all the load ranges. Thus, the valve timing curve of the inlet valve  20  under low load of the internal combustion engine  10  is identical to that under medium load and under full load of the internal combustion engine  10 . 
     A method for operating an internal combustion engine for increasing an exhaust gas temperature has been derived from the above principle of exploiting the pressure pulsations in the exhaust line  24  of the internal combustion engine  10 , said method being described below in a greatly simplified way with reference to  FIG. 4  in conjunction with  FIGS. 1 to 3 . 
     In a method step S 10 , a pressure pulse is produced in the exhaust line  24  of the internal combustion engine  10 . For example, the pressure pulse can be brought about in the exhaust line  24  by opening the exhaust valve  22  of one of the plurality of cylinders  12  during an exhaust stroke of said cylinder, as is described with reference to  FIGS. 2 and 3 . In the context of the teaching of the present disclosure, however, it is possible to exploit any other pressure pulse in the exhaust line  24  and/or to produce a pressure pulse in some other way. 
     In a method step S 12 , the pressure pulse propagates in the exhaust line  24 . The pressure pulse penetrates through an exhaust valve  22 , already opened in the exhaust stroke, of one of the plurality of cylinders  12 , into the combustion chamber  16  thereof, and increases the cylinder pressure there. The cylinder pressure is increased by way of the charging pressure in the inlet passage  14  of the same cylinder  12  (see region Din  FIGS. 2 and 3 ). 
     In a method step S 14 , exhaust gas or residual gas is fed from the combustion chamber  16  into the inlet passage  14 . The feeding is made possible by the additional lift of the inlet valve  20  of the cylinder during the exhaust stroke (see  FIG. 3 ). The inlet valve  20  is opened only after the cylinder pressure has been increased by way of the charging pressure. The inlet valve  20  is closed before the cylinder pressure falls below the charging pressure. 
     In a method step S 16 , the exhaust gas is flushed back out of the inlet passage  14  into the combustion chamber of the cylinder  12  during the inlet stroke. As explained above, an exhaust gas temperature can thereby be increased under low load in order to increase a nitrogen oxide conversion rate of the SCR catalytic converter device. 
     Even if the method has been described only for one of the cylinders  12 , it can in principle be used for any of the plurality of cylinders  12 . A different cylinder, which is operated with a phase offset, then brings about the pressure pulse in the exhaust line  24 , for example. 
     The present disclosure is not restricted to the preferred exemplary embodiments described above. On the contrary, a large number of variants and modifications that likewise make use of the inventive concept and therefore fall within the scope of protection is possible. In particular, the present disclosure also claims protection for the subject matter and the features of the dependent claims independently of the claims to which reference is made. In particular, the features of independent claim  1  are disclosed independently of one another. In addition, the features of the dependent claims are also disclosed independently of all the features of independent claim  1 . All range data herein should be interpreted as disclosed in such a way that, as it were, all the values which fall within the respective range are disclosed individually, e.g. also as respective preferred outer limits of the respective range. 
     LIST OF REFERENCE SIGNS 
     
         
           10  internal combustion engine 
           12  cylinder 
           14  inlet passages 
           16  combustion chambers 
           18  exhaust passages 
           20  inlet valves 
           22  exhaust valves 
           24  exhaust line 
           26  first exhaust manifold 
           28  second exhaust manifold 
           30  exhaust turbine 
           32  exhaust gas aftertreatment device 
           34  SCR catalytic converter device 
           36  connection 
         A-C pressure characteristics 
         D pressure pulse 
         E-F valve timing curves