GB2140503A - Ejectors in I.C. engine exhaust systems - Google Patents

Abstract

Exhaust gases from one engine cylinder are passed through an exhaust duct 1 into a chamber 5 defined by a casing 6 of essentially frusto-conical shape. The accelerated exhaust gases emerging from the exit end 7 of the chamber 5 suck exhaust gases from another cylinder through exhaust duct 2 and chamber 8, the combined exhaust gases being expelled through the trumpet shaped outlet section 12. Pairs of cylinders (23,24,25,26, Fig. 2 and 3) may be connected to respective outlet sections 12 with balance pipes (27,30) connecting the respective chambers 8 and the respective carburettors (28,29). <IMAGE>

Description

SPECIFICATION A method and apparatus for improving the power output of a multi-cylinder automobile engine and exhaust systems therefor This invention relates to a method and apparatus for improving the power output of a multi-cylinder automobile engine and to exhaust systems therefor.

Conventionally the exhaust gases expelled from each cylinder of a multi-cylinder automobile engine are fed through individual exhaust ducts forming part of a branch manifold system having a common outlet leading to a silencer box and thence to an exhaust outlet section.

It is an object of the present invention to provide an improved exhaust system which increases the power output of the automobile engine.

In accordance with the present invention the power output of a multi-cylinder automobile is improved by enhancing the exit velocity of the exhaust gases from at least some of the cylinders of the automobile engine.

According to the present invention there is provided a method of operating a multi-cylinder automobile engine in which the exhaust gases expelled from one cylinder are utilised to assist in the propulsion through an exhaust system of gases expelled from another cylinder fired subsequently to the said one cylinder, thereby improving the power output of the engine.

More specifically, there is provided in accordance with the present invention a method of operating a multi-cylinder automobile engine in which exhaust gases expelled from one cylinder are accelerated into a volume which receives exhaust gases from another cylinder fired subsequently to the said one cylinder thereby accelerating the exhaust gases withdrawn from the said other cylinder and improving the power output of the engine.

Advantageously the power output of the automobile engine is improved by utilising the exhaust gases from half the number of cylinders in the engine to accelerate the withdrawal, or scavenging, of exhaust gases from the remaining cylinders of the engine. This may be achieved by employing a single system in which the exhaust from half the cylinders is fed through a compression or acceleration chamber and the exhaust gases from the remaining cylinders are all fed to the region of the outlet from the compression or acceleraton chamber in order that these exhaust gases from the remaining cylinders are propelled at a higher velocity from the exhaust system to the atmosphere.

Alternatively, there may be provided a plurality of compression or acceleration chambers through each of which the exhaust gases from one cylinder are passed in order to exert the accelerating effect on the exhaust gases from another cylinder to assist in the propulsion of the exhaust gases from that other cylinder through the exhaust system.

In all cases the cylinders are selected so that a cylinder from which exhaust gases are passed through the compression or acceleration chamber is a cylinder which is fired before another cylinder from which exhaust gases are accelerated or scavenged by the exhaust gases from the first-mentioned cylinder. Preferably the first-mentioned cylinder im mediately precedes the other cylinder in the firing order.In the case where a common compression or acceleration chamber is used the cylinders may be regarded as being made up of two sets of cylinders, the cylinders of one set being fired alternately with the cylinders of the other set, and all the cylinders of the one set having their exhausts connected to the compression or acceleration chamber and all the cylinders of the other set having the withdrawal of the exhaust gases from them assisted by being connected to a region near the outlet from the compression or acceleration chamber.

The present invention further provides, in com bination, an automobile engine comprising piston and cylinder devices to be fired in a predetermined sequence, and an exhaust system for discharging exhaust gases from the cylinders to atmosphere, the exhaust system including an exhaust duct from at least one cylinder leading to a compression chamber which has an outlet of cross-sectional area substantially less than the cross-sectional area of a surrounding member into which the exhaust gases pass from the compression chamber, and the surrounding member being connected to receive exhaust gases directly from an exhaust duct leading from another cylinder which is fired subsequently to the said one cylinder in the predetermined sequence.

Preferably the compression chamber is a chamber of frusto-conical shape. In the preferred embodiment which will be described, the compression chamber is generally of frusto-conical shape and is formed from two members each of frusto-conical shape with different cone angles, the two members being joined so that the frusto-conical member with the smaller cone angle defines the outlet from the compression chamber.

A pair of exhaust systems may be employed with a suitable four cylinder automobile engine. When such a pair of exhaust systems is used the pressures within the chambers defined by the surrounding members are preferably equalised by a balance pipe interconnecting these chambers.

The present invention will be further understood from the following detailed description of preferred embodiments thereof which is made, by way of example, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional side view of one embodiment of an exhaust system in accordance with the present invention for improving the power output of an automobile engine, Figure 2 shows schematically an arrangement employing a pair of exhaust systems as illustrated in Figure 1 to improve the power output of a four cylinder engine, and Figure 3 is a perspective view of a construction embodying the arrangement of Figure 2.

In the drawings the same or similar parts are designated by like reference numerals.

Referring to Figure 1 there are shown exhaust ducts 1 and 2 having, at ends 3 and 4, ports adapted for connection to exhaust outlets of different cylin ders of a multi-cylinder automobile engine. Exhaust duct 1 passes exhaust gases into a compression chamber 5 which is formed from a metal casing 6 of essentially frusto-conical shape. Exhaust gases are delivered into the frusto-conical compression cham ber 5 atthe end of the chamber 5 where the cross-sectional area of the chamber 5 is at a maximum and is substantially greater than the cross-sectional area of the exhaust duct 1 so that the exhaust gases expand into the entry portion of the chamber 5 with increase of velocity.However, as the gases pass down the chamber 5, from left to right as seen in Figure 1,they are compressed by the decreasing cross-sectional area of the frusto-conical section until they are discharged from an exit end 7 of the chamber 5 which is within an outer chamber 8 to which exhaust gases are supplied from exhaust duct 2.

Although it is within the scope of the present invention for the compression chamber 5 to be made from a single frusto-conical member, in the preferred embodiment of the invention illustrated in Figure 1 the compression chamber 5 is made from two frusto-conical sections 9 and 10. The first frustoconical section 9 at the inlet end of compression chamber 5 has a slightly greater cone angle than the second frusto-conical section 10, the narrower end of which forms the exit aperture at the end 7 of the compression chamber 5. The length of the compression chamber 5 is therefore extended as compared with the case when the compression chamber 5 is formed from a single frusto-conical section similar to the frusto-conical section 9.

As the exhaust gases are expelled with increased velocity from the exit 7 of the compression chamber 5 so these exhaust gases suck from the chamber 8, which is defined bythe metal casing 11, exhaust gases which reach the chamber 8 from exhaust duct 2. Propulsion of exhaust gases through the duct 2 from the cylinder connected to the port at the end 4 of the duct 2 is thus assisted, and a scavenging effect is applied to the cylinder connected to the end 4 of the exhaust duct 2.

The combined exhaust gases from exhaust ducts 1 and 2 are expelled from the exhaust system through a trumpet shaped exhaust outlet section 12.

Instead of exhaust ducts 1 and 2 having ends 3 and 4 with ports which are connected directly to the cylinder heads, the exhaust ducts 1 and 2 may be the outlets from separate branch manifold systems each of which passes the exhaust gases from half the cylinders of the engine. In such a use of the exhaust system of Figure 1 to improve the power output of a six cylinder in-line engine, exhaust duct 1 is connected to the exhaust outlets of the first, second and third cylinders while exhaust duct 2 is connected to the exhaust outlets of the fourth, fifth and sixth cylinders.The conventional firing sequence (1,5,3, 6, 2, 4) of the six cylinder in-line engine thus provides that the feeding of exhaust gases from one cylinder of the engine through exhaust duct 1 is immediately followed by the feeding of exhaust gases from the next cylinder to be fired through exhaust duct 2, the propulsion of the gases from exhaust duct 2 being assisted by the accelerated gases from exhaust duct 1.

The exhaust system of Figure 1 can be applied directly to any automobile engine, for example when used with a four cylinder Ford engine exhaust duct 1 is connected to the first and third cylinders and exhaust duct 2 to the second and fourth cylinders.

In order to obtain the greatest benefit from the use of an exhaust system in accordance with this invention, the distance travelled by the exhaust gases before reaching the junction of exhaust duct 1 and compression chamber 5 or the junction of exhaust duct 2 and chamber 8 should be kept as short as is practicable. In this way the velocity of the exhaust gases passed into the chambers 5 and 8 falls by as little as possible from the velocity at which these gases are emitted from their respective cylinders of the automobile engine. Preferably the distances travelled by the exhaust gases before reaching the chambers 5 and 8 are less than one foot (30 centimetres), and in an exhaust system constructed as illustrated in Figure 1 the lengths of the exhaust ducts 1 and 2 may be, for example, nine to ten inches (22 to 25 centimetres).

Figure 2 of the accompanying drawings is a schematic diagram of an arrangement in which a pair of exhaust systems in accordance with Figure 1 are used to improve the power output of a horizontally opposed (flat) four cylinder VW engine.

Figure 2 shows diagrammatically exhaust systems 21 and 22 which are both essentially similarto the exhaust system illustrated in Figure 1. Each of the exhaust systems 21 and 22 includes exhaust ducts 1 and 2, a compression chamber 5 formed by a frusto-conical member 6 which accelerates exhaust gases from duct 1 into a chamber 8 which receives exhaust gases from exhaust duct 2. The combined gases are then directed to atmosphere through the trumpet shaped exhaust outlet section 12 of the respective exhaust system.

The exhaust ducts 1,1 are connected respectively to the second and fourth cylinders 24 and 26 of the four stroke engine, while exhaust ducts 2,2 are connected respectively to the first and third cylinders 23 and 25 of the four stroke VW engine. The firing order for the four stroke VW engine is 1,4,3,2, i.e.

cylinders 23, 26, 25, 24. The pressures in the respective exhaust systems 21 and 22 of Figure 2 are equalised by a balance pipe 27 which interconnects the chambers 8,8.

Figure 3 of the accompanying drawings is a perspective view of an actual construction of an exhaust system according to the invention for use with a four cylinder engine in the manner discussed with reference to Figure 2. The ends 3 and 4 of the pairs of exhaust ducts 1 and 2 are bolted on to the two cylinder blocks containing, respectively, the cylinders 23, 24 and the cylinders 25, 26 so that the exhaust gases from these cylinders are fed to the exhaust ducts 1 and 2 as described with reference to Figure 2.

When a pair of exhaust systems is employed as in Figures 2 and 3, and the automobile engine whose power output is being enhanced has twin carburettors 28 and 29 (as shown in Figure 3), a further balance pipe 30 is advantageously provided to equalise the pressures of the fuel components in the carburettors.

It has been found that the use of an exhaust system in accordance with the present invention can provide an increase of as much as 18% to 20% in the power output (brake horsepower) of an automobile engine with which the exhaust system of the present invention is used.

Desirably the frusto-conical member or members defining the compression chamber 5 and the metal casing 11 defining the chamber 8 are made from thicker metal section than the exhaust outlet section 12.

Claims (15)

1. A method of operating a multi-cylinder automobile engine in which the exhaust gases expelled from one cylinder are utilised to assist in the propulsion through an exhaust system of gases expelled from another cylinder fired subsequently to the said one cylinder, thereby improving the power output of the engine.

2. A method of operating a multi-cylinder automobile engine in which gases expelled from one cylinder are accelerated into a volume which receives exhaust gases from another cylinder fired subsequently to the said one cylinder thereby accelerating the exhaust gases withdrawn from the said other cylinder and improving the power output of the engine.

3. A method according to Claim 2 in which the engine has at least four cylinders which comprise two sets of cylinders, the cylinders of one set being fired alternately with the cylinders of the other set, and in which the exhaust gases expelled from one set of cylinders are accelerated to assist in the propulsion through the exhaust system of gases expelled from the other set of cylinders.

4. A method according to Claim 2 in which the engine has four cylinders and in which the exhaust gases from separate pairs of cylinders are directed through separate exhaust systems in each of which the exhaust gases from one cylinder of a pair assist in the propulsion through that exhaust system of gases expelled from the other cylinder of the same pair, and in which the gas pressures in the respective exhaust systems are balanced by interconnecting the respective exhaust systems.

5. A method according to Claim 4 in which the four cylinder engine is fed by two carburettors and in which a balance in the fuel supply between the pairs of cylinders fed by respective carburettors is effected by providing an interconnection between the two carburettors.

6. In combination, an automobile engine comprising piston and cylinder devices to be fired in a predetermined sequence, and an exhaust system for discharging exhaust gases from the cylinders to atmosphere, the exhaust system including an exhaust duct from at least one cylinder leading to a compression chamber which has an outlet of crosssectional area substantially less than the crosssectional area of a surrounding member into which the exhaust gases pass from the compression chamber, and the surrounding member being connected to receive exhaust gases directly from an exhaust duct leading from another cylinder which fired subsequently to the said one cylinder in the predetermined sequence.

7. The combination according to Claim 6 wherein the compression chamber of the exhaust system is a chamber of frusto-conical shape.

8. The combination according to Claim 7 wherein the frusto-conical compression chamber is formed from two members each of frusto-conical shape with different cone angles and joined so that the frustoconical member with the smaller cone angle defines the outlet from the compression chamber.

9. The combination according to Claim 6 in which a second exhaust system similar to the said exhaust system is provided and in which a balance pipe interconnects the volumes within the surrounding members of the two exhaust systems to equalise the pressures therein.

10. An exhaust system for discharging to atmosphere exhaust gases emitted from the cylinders of piston and cylinder devices in an automobile engine, the exhaust system including a first exhaust duct for connection at one end to a cylinder of an automobile engine, a compression chamber connected to the other end of the first exhaust duct, the compression chamber having a cross-sectional area substantially greater than the cross-sectional area of the exhaust duct at the end where the compression chamber is connected to the first exhaust duct and the compression chamber tapering to an outlet of substantially smaller cross-sectional area, a surrounding member defining an outer chamber around at least part of the compression chamber and downstream from the outlet of the compression chamber, a second exhaust duct for connection at one end to another cylinder of the automobile engine and having the other end connected to the outer chamber, and an exhaust outlet section for conveying exhaust gases from the outer chamber to atmosphere.

11. An exhaust system according to Claim 10 wherein the compression chamber is frusto-conical in shape.

12. An exhaust system according to Claim 10 or Claim 11 wherein the compression chamber is formed from two members of frusto-conical shape with different cone angles joined so that the frustoconical member with the smaller cone angle defines the outlet from the compression chamber.

13. An exhaust system according to anyone of Claims lotto 12 wherein the surrounding member defining the outer chamber includes an aperture for connection through a balance pipe to the outer chamber of a similar exhaust system, the exhaust ducts of which are connected to other cylinders of the automobile engine.

14. An exhaust system constructed and arranged substantially as described with reference to Figure 1 of the accompanying drawings.

15. The combination of an automobile engine and an exhaust constructed substantially as de scribed with reference to the accompnying draw ings.