Abstract:
Chaotic air flow structures in internal combustion engine manifolds may lead to poor combustion performance and hence undesirable emissions such as visible smoke. Manifolds with flow characteristics compromised by other design requirements are especially prone to these poor characteristics. To overcome these, an engine air induction arrangement includes a feed passage having an end portion in a manifold with cylinder ports. The end portion is formed in such a manner that air exiting the end portion via an opening is hindered from travelling away from the cylinder ports. This improves the flow structure and evens air distribution to the cylinder ports, hence improving the combustion process and reducing emission levels.

Description:
TECHNICAL FIELD 
     The present disclosure relates to improving airflow within a structure. In particular, but not exclusively, the disclosure relates to improving the airflow in a manifold of an internal combustion engine. 
     BACKGROUND 
     Incomplete combustion in internal combustion engines may cause visible smoke exiting the exhaust system. This may contravene emission regulations and may also be perceived as negative by users and other members of the public with regards to health and environment issues. 
     A multi-cylinder internal combustion engine can produce excessive smoke during low engine speeds if the air feed passage terminates at the manifold. Combustion airflow fed into the manifold from a feed passage can have an unstructured characteristic and can become chaotic once in the manifold. The chaotic airflow motion in the manifold continues into the inlet port to the combustion chamber and causes the in-cylinder swirl motion to become unstable resulting in incomplete combustion. Smoke issues are limited at higher speeds due to the airflow structure changing with the airflow speed. One solution is to adapt the port shape design, but this will result in high development costs and may have a negative impact on the performance at higher engine speeds where emission levels are critical. Further challenges may arise due to restrictions to the design of the manifold itself, as the availability of multiple customer options may depend on particular manifold configurations. The present disclosure is directed at overcoming one or more of the above identified problems. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present disclosure there is provided an air induction arrangement for an internal combustion engine with an inlet manifold having a first cylinder port and at least a second cylinder port. It further has a feed passage having an opening within the inlet manifold, the opening having a periphery. A first portion of the periphery is distal to the first of the cylinder ports, a second portion of the periphery is proximal to the first of the cylinder ports. The first portion protrudes further into the inlet manifold than the second portion. 
     According to another aspect of the disclosure there is provided an air induction arrangement for an internal combustion engine, comprising an inlet manifold having a plurality of cylinder ports and a feed passage having an opening within the inlet manifold. The opening is formed such as to hinder air departing from the opening from travelling away from the cylinder ports. 
     A further aspect of the disclosure provides an air induction arrangement for an internal combustion engine, comprising an inlet manifold having a plurality of cylinder ports and a feed passage having an end within the inlet manifold. The end includes means for hindering air departing from the feed passage from travelling away from the cylinder ports. 
     Yet another aspect of the disclosure provides a method of operating an internal combustion engine comprising supplying air to a combustion site, supplying fuel to a combustion site and combusting the fuel and air. The particle emissions from the combustion step is reduced by supplying air to the combustion site via an air induction arrangement as disclosed. 
     Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic frontal view of an internal combustion engine showing feed passage and intake manifold. 
         FIG. 2  is a fragmentary schematic representation of a first embodiment of an engine air induction arrangement according to the present disclosure. 
         FIG. 3  is a schematic representation of a possible detail of the first embodiment looking in the direction of arrows  3 — 3  in  FIG. 2 . 
         FIG. 4  is a fragmentary schematic representation of a second embodiment of an engine air induction arrangement according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , internal combustion engine  10  is shown as a turbocharged engine, but the principle of this disclosure may also be applied to engines with other induction arrangements such as supercharged engines or naturally aspirated engines. 
     Exhaust gas produced by the combustion process in internal combustion engine  10  flows from cylinder head  12  through passage  14  to turbocharger  16 . Turbocharger  16  draws in induction air via an air filter (not shown) and forces the air through a feed passage  18  into manifold  20 . Feed passage  18  is connected via flange  24  to the top side of manifold  20 , but a different arrangement may be achieved by removing manifold cover plate  23 . Removing manifold cover plate  23  reveals an alternative mounting position for a feed passage similar to feed passage  18 , but adapted to correspond to this alternative position. The ability to vary the position of the connection between the feed passage and the manifold enables a set of different engine envelopes to suit different installation environments. 
       FIG. 2  shows a first embodiment of the present invention. Manifold  120  is shown as having cylinder ports  122   a ,  122   b  and  122   c , but the principle is applicable to manifolds with any number of cylinder ports. Manifold  120  may have a plurality of openings adapted to receive a feed passage such as feed passage  118 . In  FIG. 2  a possible arrangement is shown having two openings. However, more openings could be present to offer a larger degree of flexibility in installation options. The arrangement shown has feed passage  118  connected to manifold  120  via opening  119  in surface  125  of manifold  120 . Feed passage  118  is connected via flange  124  to the top side of manifold  120 , but a different arrangement may be achieved by removing manifold cover plate  123  to reveal opening  121 . 
     Air is fed into manifold  120  via feed passage  118 . Feed passage  118  has an end portion  126  within manifold  120 . End portion  126  has a longitudinal axis  130  which in this example coincides with longitudinal axis  131  of a part of feed passage  118  that is external of manifold  120 . Axes  130  and  131  are shown as being perpendicular to surface  125 , but perpendicularity is not essential therefore axes  130  and  131  may intersect surface  125  at other angles. 
     End portion  126  further has an opening  128  with periphery  132  through which the air flows into manifold  120 . In this example, all portions of periphery  132  lie in a same plane, but periphery  132  may be formed of portions lying in different planes or following different curvatures. 
     Periphery  132  has a first portion  134  and a second portion  136 , portion  134  being distal and portion  136  being proximal to cylinder ports  122 . Reference point  138  is the intersection of axis  130  and a point lying in the same plane as surface  125 . As seen from reference point  138 , portion  134  protrudes further into manifold  120  than portion  136 . This has the effect that any air exiting opening  128  is hindered from travelling away from cylinder ports  122  and is at least partially prevented from forming chaotic air flows having directions other than generally towards cylinder ports  122 . Therefore most air will follow concurrent flow paths, resulting in a substantially even distribution to cylinder ports  122 . If end portion  126  is a cylindrical member cut at an angle across longitudinal axis  130 , periphery  132  will have a substantially elliptical shape as shown in  FIG. 3 . 
       FIG. 4  shows a second embodiment of the present disclosure. Manifold  220  is shown as having cylinder ports  222   a ,  222   b  and  222   c , but the principle is applicable to manifolds with any number of cylinder ports. Manifold  220  further has a plurality of openings adapted to receive a feed passage such as feed passage  218 . In  FIG. 4  a possible arrangement is given as example showing two openings. However, more openings could be present to offer a larger degree of flexibility in installation options. The arrangement shown has feed passage  218  connected to manifold  220  via opening  219  in surface  225  of manifold  220 . Feed passage  218  is connected via flange  224  to the top side of manifold  220 , but a different arrangement may be achieved by removing manifold cover plate  223  to reveal opening  221 . 
     Air is fed into manifold  220  via feed passage  218 . Feed passage  218  has an end portion  226  within manifold  220 . End portion  226  has an opening  228  with periphery  232  through which the air flows into manifold  220 . In this example, all portions of periphery  232  lie in a same plane, but periphery  232  may be formed of portions lying in different planes or following different curvatures. End portion  226  comprises a substantially elbow shaped portion. The elbow is shown as extending less than 90 degrees, however the angle of the elbow can be different if preferred. This has the effect that any air exiting opening  228  is hindered from travelling away from cylinder ports  222  and is at least partially prevented from forming chaotic air flows having directions other than towards cylinder ports  222 . Therefore most air will follow concurrent flow paths, resulting in a substantially even distribution to cylinder ports  222 . Alternatively the elbow shaped portion may be replaced by two or more portions of tube connected together in such a way that their longitudinal axes do not coincide or run parallel to each other. 
     INDUSTRIAL APPLICABILITY 
     This disclosure provides a solution for overcoming a chaotic air flow structure in an engine manifold. Conflicting practical requirements for manifolds may lead to compromises in the design. For example, the manifold may have to be designed in such a way that multiple entry points for a feed passage are available. However, this may result in less than optimal flow characteristics within the manifold due to the shape of the manifold. To improve these flow characteristics, the disclosure reveals a feed pipe design that hinders air from travelling in undesired directions in a manifold and hence improves airflow structures. 
     To achieve this, the illustrated embodiments of the present disclosure shows feed pipe  118  having an end section  126 ,  226  located within manifold  120 ,  220 . End section  126 ,  226  is formed in such a way that it hinders air exiting end section  126 ,  226  through opening  128 ,  228  in a direction away from cylinder ports  122 ,  222 , creating a much improved airflow structure in the manifold, encouraging a substantially even air distribution to cylinder ports  122 ,  222 . This has a direct and positive impact on the combustion process, as the structured air flow and even air distribution improve the in-cylinder swirl, which is critical for achieving optimum combustion. In use, combustion air is supplied to a combustion chamber or other combustion site (not shown) via an engine air induction system as described above. Fuel is also supplied to the combustion site via suitable, well known mechanisms such as fuel injectors for example. The fuel and air are combusted, for example by compression ignition or spark ignition. Particle emissions are reduced compared to prior designs by supplying the combustion air to the combustion site via an engine air induction system as described above. These reduced emissions can be achieved especially at relatively low engine speeds. Although the various embodiments are described above, those skilled in the art will appreciate that modifications may be made without departing from the scope of the following claims.