GB2084647A

GB2084647A - An exhaust manifold for an internal combustion engine

Info

Publication number: GB2084647A
Application number: GB8031673A
Authority: GB
Original assignee: SOC D'ETUDES DE MACHINES THERMIQUES SEMT
Current assignee: SOC D'ETUDES DE MACHINES THERMIQUES SEMT
Priority date: 1980-10-01
Filing date: 1980-10-01
Publication date: 1982-04-15

Abstract

An exhaust manifold for an internal combustion engine with a plurality of working cylinders comprises a connecting duct between each of the cylinders and the manifold, the manifold being integrally formed with the head. The connecting ducts are shaped as a nozzle with a gas flow passageway of cross-sectional area in a range from 0.6 to 1.7 times the surface area of the theoretical effective passageway cross-section as calculated by the following equation:- <IMAGE> The surface area of the passageway cross-section of the manifold is in a range from 0.6 to 1.7 times the surface area of the theoretical passageway cross-section of the manifold as calculated by the following equation:- <IMAGE> <IMAGE>

Description

SPECIFICATION An exhaust manifold for an internal combustion engine The present invention relates generally to improvements in a method of and in a device for promoting the gas flow through an internal combustion engine exhaust manifold, such as disclosed in the British patent application No. 2731/78 of January 24, 1978.

The process described in the main patent relates to a method for damping out pressure oscillations in an exhaust manifold of several, and preferably from four to ten, working cylinders, per bank or row of power cylinders, of an internal combustion engine, e.g. of the supercharged type, with gas ejection effect at the inlet of the exhaust manifold.This method consists, upon opening of the exhaust valve until the piston reaches a point in the vicinity of its bottom dead center, in keeping at a maximum the residual potential energy of the cylinder gases during their passage through the connecting pipe between cylinder head and exhaust manifold, towards the end of the expansion stroke, thus reducing the increase in entropy of the gases by throttling the gas flow in maximum proximity to or close vicinity of the cylinder outlet, and then in increasing the ejection effect through acceleration of the gas flow within the exhaust manifold by converting the pressure energy into speed energy imparted to the gases present in the exhaust manifold, by reducing the uniform passage-way cross-section of flow in the manifold to a value substantially lower than that of the cylinder bore, so as to maintain therein a flow velocity with attendant decrease in the static pressure in order to facilitate the emptying of the cylinder, so as to obtain the highest possible gas flow velocity through recovery of the potential energy which is normally lost at each gas puff at a time at which the expansion work supplied to the piston is made maximum and the discharge work provided by the piston is reduced to a minimum, respectively.

The said previous patent application relates also to an exhaust manifold for carrying out said method, wherein each connecting pipe between cylinder head and exhaust manifold is shaped as a nozzle whose cross-sectional areas at its outlet (on the manifold side) and at its inlet (on the cylinder side) are in a a ratio ranging between 0.3 and 0.8, preferably bet- ween 0.4 and 0.5. It is also stated in said previous patent application that the ratio of the inner diameter of the exhaust manifold to the cylinder bore is ranging from 0.30 to 0.75 whereby the exhaust manifold may in particular be made with a diameter substantially smaller than that of the exhaust manifolds generally used in the known state of prior art.

A main object of the present invention is to provide other definitions of the sizes of each connecting nozzle and of the exhaust manifold, respectively.

Such new definitions are now depending on the cross-sectional surface area of the piston and on its rated speed.

The invention accordingly provides an exhaust manifold for performing the process of damping out the pressure oscillations within such an exhaust manifold of several and preferably from 4to 10 working cylinders per bank or row of cylinders of a for instance supercharged internal combustion engine, with a gas ejection effect at their ingress into the exhaust manifold, and such as defined in the said previous patent application.The exhaust manifold according to the present invention is characterized in that the connecting pipe between each cylinder head and the exhaust manifold, shaped as a nozzle, has an effective or actual gas flow cross-section at the throat of the nozzle stream, the surface area of which is in a range extending from 0.6 to 1.7 times the surface area of the theoretical effective cross-section of the nozzle given by the general equation: rated piston Effective cross- Cross-sectional speed (m/s) sectional surface = surface area of x area the piston 100 (m/s) According to another characterizing feature of the invention, the surface area of the effective gas flow cross-section at the throat of the nozzle stream is in a range preferably of from 0.9 to 1.1 times the surface are of the effective cross-section yielded by the previous equation.

According to a further characterizing feature of the invention, the surface area of the cross-sectional passageway of the exhaust manifold is in a range of from 0.6 to 1.7 times the surface area ofthetheoreti- cal passage-way cross-section of the exhaust manifold as given by the following equation: rated piston Theoretical cross- Cross-section speed (m/s) section area of = area of piston x manifold 31 (mls) According to still another characterizing feature of the invention, the surface area of the cross-sectional passage-way of the exhaust manifold is preferably in a range of from 0.9 to 1.1 times the surface area of said theoretical passage-way cross-section of the exhaust manifold.

According to a preferred embodiment of the invention, the pipe or duct connecting each working cylinder to the exhaust manifold is integrated into the cylinder head of the engine.

According to another characterizing feature of the preferred embodiment of the invention, the exhaust manifold has a modular construction consisting of several like intermediate sections.

The present invention will be better understood and further objects, characterizing features, details and advantages thereof will appear more clearly as the following explanatory description proceeds with reference to the accompanying diagrammatic drawings given by way of non-limiting example only and wherein: - Figure lisa diagrammatic view showing a longitudinal section of a portion of an exhaust manifold according to the invention; and - Figure 2 is a view in cross-section taken upon the line Il-Il of Figure 1.

Referring to the drawings and before defining the structure of the exhaust manifold according to the invention, it should be pointed out that the cylinder head 1 of the for instance supercharged internal combustion engine involved, comprising an exhaust manifold per bank of row of working cylinders, is actually divided into several separated cylinder heads 2 the number of which corresponds to that of the working cylinders. Each cylinder head 2 comprises a conventional part 2a adapted to receive the intake and exhaust valves etc, i.e. all the component elements associated with the operation of the valves, and a part 2b which extends the part 2a and is shaped so asto incorporate the duct 13 connecting the working cylinder to the exhaust manifold 4.

The exhaust manifold 4 has a modular construction and consists of a plurality of like intermediate sections 5. Each sleeve-like manifold section 5 comprises, at one end thereof, a circular flange 6 and a circularshoulder7 positioned near thins end. The other end of said sleeve-like section has its peripheral outer surface merging into a tapered or conical end portion 8.

In the part 2b of the cylinder head associated with a working cylinder of the engine are provided two inlet and outlet ports 9, 10, respectively, aligned in coaxial registering relationship and communicating with the inside of the cylinder head.

One manifold section 5 is inserted, with its free end or with that end which is opposite from that fitted with the flange 6, into the inlet port 9 of the associated cylinder head until the shoulder 7 of the manifold section 5 is caused to come into engagement in abutting relationship with the cylinder head surface surrounding the inlet port 9. The inside of the cylinder head 2 within its part 2b is shaped so as to define, together with the manifold section 5, an annular space 11 having a ring-shaped passage-way cross-section gradually decreasing in the direction of the gas flow so as to provide for an ejection effect of the gases at their entrance or incoming flow into the exhaust manifold.This annular space 11, thus defined between the part 2b of the cylinder head and the manifold section 5, freely communicates with the space 12 of the part 2a of the cylinder head at the outlet of the exhaust valves 13 (Figure 2) and accordingly forms the connecting duct 3 between the working cylinder and the exhaust manifold. The annular space 11, at the outlet of the manifold section 5 in the direction of gas flow, assumes again a cylindrical shape with a diameter corresponding to the inner diameter of the manifold section 5 and which communicates with the outlet port 10 of the cylinder head. In order to establish the continuity of gas flow between any two manifold sections 5, there is provided a connecting system 15 arranged between the outlet port 10 of the cylinder head and the adjacent manifold section 5 in the direction of gas flow.This connecting system, provided at the outside between two cylinder heads 2, consists for instance of a ringshaped member partially inserted, owing to the provision of a shoulder 17, into the outlet port 10 of the cylinder head whereas the other end of the ringshaped member 16 terminates into a circular flange 18 adapted to be connected to the circular mating flange 6 of the adjacent manifold section 5 in the direction of gas flow, with the possible interposition of an expansion bellows 19 provided at each end of a circular flange 20. The connections between flanges are carried out through the agency of clamping rings or like fastening or tightening bands 21 known per se.

Each connecting system 15 between any two successive manifold sections 5 is covered with a heatinsulating lining or lagging 22. Each cylinder head 2 is cooled by means of a liquid flowing in particular within a space 23 of the part 2b of the cylinder head located between the connecting duct 3 and the outer wall of the cylinder head.

In this embodiment of the invention, each connecting duct 3 shaped as a nozzle exhibits an effective or actual gas flow passage-way cross-section at the throat of the stream, having a surface area lying in a range of from 0.6 to 1.7 times the surface area of the theoretical effective passage-way cross-section of the nozzle yielded by the following general equation: rated piston speed (m/s) Effective cross- = Cross-section x section area area of piston 100 (m/s) According to a preferred embodiment of the invention, the surface area of the effective passage-way cross-section of each connecting duct 3 or nozzle is in the range of from 0.9 to 1.1 times the surface area of said theoretical effective passageway cross-section.

The exhaust manifold 4 has a passage-way crosssectional surface area which is in the range of from 0.6 to 1.7 times the surface area of the theoretical passage-way cross-section of the manifold given by the following general equation: rated piston Theoretical cross- Cross sectional speed (m/s) sectional surface = area of piston x area of manifold 31 (mls) According to a preferred embodiment of the invention, the surface area of the passage-way cross-section of the exhaust manifold 4 is in the range of from 0.9 to 1.1 times the surface area of the theoretical passage-way cross-section of the exhaust manifold.

The angle of incidence a of the gases flowing out of each connecting duct 3, i.e. the angle of the main gas flow direction with respect to the longitudinal center line axis of the exhaust manifold, should advantageously remain small.

Such a structure of the exhaust manifold offers many advantages: its construction is substantially simplified owing to the provision of connecting units or assemblies which are as compact as possible due to their integration into the cylinder head; -the structures of the cylinder head 2, of each manifold section 5 and of each connecting member 15 may be arranged in such a way as to provide for the gas flow in one direction as well as in the other or opposite one, i.e. the inlet and outlet ports 9, 10, respectively, of the cylinder head may be considered in the reverse order as outlet and inlet ports, respectively; such a symmetrical relationship is particularly advantageous with V-type engines; -the clearance or dead volume is the least one, i.e. the connecting distances between the cylinders and the exhaust manifold are reduced to a minimum, thereby promoting the operation of the modular exhaust systems of the pulse-converter kind such as defined in the said previous patent application.

- There are no or only a little additional losses of energy in the exhaust gases with respect to an exhaust manifold such as disclosed in the said previous patent application, i.e., in relation to conventional exhaust manifolds provided outside of the cylinder head and therefore lined with an heatinsulating lining or lagging which would act upon the exhaust gases by decreasing their temperature and which is not likely to avoid the presence of hot spots. This eventually will make the shapes of such exhaust manifolds complicated.In contrast thereto, with the exhaust manifold according to the invention, each manifold section is inserted into the cylinder head and therefore need not be heat-insulated and furthermore the cylinder head cooling system is sufficiently far away from the associated manifold section so as to not exert any influence on the gas temperature.

-The adjustments of the gas flow passage-way cross-sections at the throat of the stream, at the outlet of each connecting duct or nozzle, are facilitated to a large extent and may be carried out without altering the cylinder head. It indeed suffices for instance to modify through a simple machining step the tapered or conical shape 8 of the ends of the manifold sections 5 in order to modify the annular gas flow passage-way cross-section.

- Each connecting duct, exhibiting an annular passage-way cross-section decreasing in the direction of gas flow, also performs the function of a trap for retaining or stopping parts such as valves, likely to come from the combustion chamber.

It should be understood that the invention is not at all limited to the embodiment described and shown which has been given by way of illustrative example only and the invention comprises all the technical equivalents of the means described as well as their combinations if same are carried out according to its gist and used within the scope of the appended

Claims

claims. CLAIMS

1. An exhaust manifold for carrying out the method of damping out the pressure oscillations within such a manifold of several and preferably of from 4 to 10 working cylinders per bank of working cylinders of a for instance supercharged internal combustion engine, with gas ejection effect at their inlet into said manifold, characterized in that the connecting duct between each working cylinder and the exhaust manifold, shaped as a nozzle, has an effective or actual gas flow passage-way crosssection at the throat of the stream the surface area of which is in a range of from 0.6 to 1.7 times the surface area of the theoretical effective passage-way cross-section of said nozzle as yielded by the following general equation:: rated piston Surface area of Surface area of speed (m/s) effective passageway = piston cross- x cross-section section 100 (m/s) and in that the surface area of the passage-way cross-section of said manifold is in a range of from 0.6 to 1.7 times the surface area of the theoretical passage-way cross-section of said manifold as given by the following equation: rated piston Surface area of Surface area of speed (m/s) theoretical manifold = piston cross- x passage-way section 31 (mls) cross-section

2. An exhaust manifold according to claim 1, characterized in that said range of nozzle passageway cross-sections is between 0.9 and 1.1 times the surface area of said effective passage-way crosssection.

3. An exhaust manifold according to claim 1 or 2, wherein said range of manifold passage-way crosssections is between 0.9 and 1.1 times the surface area of said theoretical passageway cross-section of the manifold.

4. An exhaust manifold according to at least any one of the foregoing claims, wherein each nozzle is integrated into the cylinder head of said engine.

5. An exhaust manifold according to at least any one of the foregoing claims, comprising a modular construction consisting of like intermediate sections.

6. An exhaust manifold according to claim 5, for an internal combustion engine with separate cylinder heads, wherein each manifold section of for instance sleeve-like shape is inserted into an inlet port of the associated cylinder head, said connecting duct or nozzle consisting of an annular space having a passage-way cross-section which gradually decreases in the direction of gas flow and is defined between said manifold section and said cylinder head and connects the cylinder outlet to the exhaust manifold with attendant ejection effect of the gases at their entrance into the latter.

7. An exhaust manifold according to claim 6, wherein said annular space communicates in the gas flow direction with a cylindrical space of same diameter as the inner diameter of the exhaust manifold and which itself communicates with an outlet port of the cylinder head.

8. An exaust manifold according to claim 6, or 7, wherein each manifold section associated with one cylinder head is connected to the outlet port of the cylinder head.

8. An exhaust manifold according to claim 6 or 7, wherein each manifold section associated with one cylinder head is connected to the outlet port of the cylinder head located upstream in the gas flow direction by a cylindrical flanged connecting device.

9. An exhaust manifold according to any one of claims 5 to 8, wherein each manifold section may be inserted indifferently into said inlet port or into said outlet port of said cylinder head, said cylinder head ports indifferently performing the function of an inlet or of an outlet

10. An exhaust manifold according to claim 6, wherein the gas passage-way cross-section at the outlet of each connecting duct is altered through simple machining of the outer peripheral surface of the associated manifold section.

11. An exhaust manifold substantially as described herein with reference to and as shown in the accompanying drawings.