WO1979000707A1

WO1979000707A1 - Multi-inlet air flow passage arrangement for diesel engines

Info

Publication number: WO1979000707A1
Application number: PCT/US1979/000049
Authority: WO
Inventors: A Goloff; M Stratton
Original assignee: Caterpillar Tractor Co
Priority date: 1978-03-03
Filing date: 1979-01-31
Publication date: 1979-09-20
Also published as: GB2036172A; DE2938823T5; JPS55500106A; HK73483A; GB2036172B

Abstract

An inlet air passage (14) introduces air into a cylinder bore (12) of a diesel engine (10) in a direction along a flow path substantially tangent to the cylinder bore to provide a swirling of the air within the bore. A second inlet air passage (14) introduces air into the same cylinder bore in a direction along a flow path toward the centerline of the cylinder bore axis which minimizes swirl within the cylinder bore. The non-swirling air flow path is utilized during start up and cold idle and the swirling air flow path is individually used when the engine operates through its intermediate speed range with both air flow paths being simultaneously directed into the cylinder bore during high speed operation of the engine for optimum volumetric efficiency.

Description

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Description

Multi-Inlet Air Flow Passage Arrangement for Diesel Engines

Technical Field The invention relates to diesel engines, and more particularly to the introduction of air into the cylinder bores through a plurality of inlet air pas¬ sages formed in the cylinder heads thereof.

Background Art It is known to use a plurality of air inlet valves with corresponding air inlet ports corαmunicating with the inlet air passages for each cylinder bore of diesel engines. In the past, such air inlet passages have been helically configured to produce a swirling flow path of air into the cylinder bores. Swirling flow^' paths are shown in U.S. Patent 3,898,966 issued to List on August 12, 1975 and in U.S. Patent 3,884,209 issued to List et al on May 20, 1975. It has been found, however, that excessive swirl in such air flow path is detrimental during start up and cold idle be¬ cause it prolongs the time of "white smoke" operation of the engine and thus prolongs the period of objection¬ able hydrocarbon emissions. Further, it has been found that excessive amounts of swirl inevitably are produced at the expense of volumetric efficiency of the engine. Throttled inlet air' passages are known to be used for stratified charge versions of some engines such as the rotary piston engines, as shown in U.S. Patents 3,905,337 issued to Shimoji et al on September 16, 1975 and 3,901,198 issued to Yamamoto on August 26, 1975. At low engine speeds or low loads the air enters through a restricted tangential passage located in the cylinder housing. This gives high entry velocity and makes stratified charge operation possible. At high engine speeds unrestricted passages in. the end housing are opened in order to get the needed volu¬ metric efficiency. Such operation would, however, be detrimental in a direct injection diesel engine since it is advantageous at low speeds and light loads to operate with a minimum of turbulence in the air being directed into the cylinder bores.

Disclosure of Invention The present invention is directed to over¬ coming one or more of the problems as set forth above. According to the present invention there is provided an improved multi-inlet air flow passage arrangement for engines having cylinder bores covered by cylinder heads. The arrangement comprises a swirϊ type entry passage introducing air flow to a first valve port which opens to. the cylinder bore in the engine block for directing such air flow through a path substantially tangent to the cylinder bore. A second non-swirl type entry duct passage serves to introduce air flow to a second valve port which opens to the same cylinder bore through an axially extending path.

In another aspect the invention comprises a method of controlling inlet air flow to the cylinder bore of a diesel engine to minimize emission on start up and cold idle operation while retaining high volu¬ metric engine efficiency throughout the full range of engine speeds. The method comprises introducing air into the cylinder bore through a non-swirling path generally toward or parallel to the axis of the cylinder bore during start up and cold idle engine operation and introducing air through a second path substantially tangent to the cylinder bore to cause

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OMPI swirling of- the air within the cylinder bore only when. t e_u engine is operating at other than start up and cold idle.

Other features and advantages will become apparent from the following specification taken in connection with the accompanying drawings.

Brief Description of Drawings

Figure 1 is a partial perspective view of a direct injection diesel engine with inlet air passages;

Figure 2 is a partially sectioned plan view of an air flow entry arrangement with a control and sensors shown schematically;

Figure 3 is a sectional view taken along line III-III of Figure 2;

Figure 4 is a sectional view taken along line IV-IV of Figure 2;

Figure 5 is a sectional view illustrating an alternate embodiment of the structure shown in Figure 4; and

Figure 6 is a fragmentary view illustrating an alternate embodiment for the entry passage shown in Figure 2.

Best Modes for Carrying out the Invention Figures 1 and 2 illustrate a diesel engine

10 which has one or more cylinder bores 12. An im¬ proved air flow entry arrangement 14, best seen in Figure 2, includes a swirl type entry passage 16 for introducing air flow to a first generally circular valve 18. The first valve 18 opens from a head 20 to the cylinder bore 12 and has its periphery 22 sub¬ stantially tangent to the cylinder bore 12 and its axis 24 substantially parallel to an axis 26 of the cylinder bore 12.. The^* air flow is introduced from the first valve 18 into the cylinder bore 12 sub¬ stantially tangent to the outer wall thereof.

A non-swirl type entry passage 28 introduces air flow to a second generally circular valve 30 which opens to the head 20 of the cylinder bore 12. The air flow from the second valve 30 is introduced to the cylinder bore 12 with substantially only axial and possibly radial velocity components, i.e., sub¬ stantially-parallel to or aimed at the axis 26. Thus, the air flow from the second valve 30 has primarily an axial as opposed to a tangential flow vector.

First throttle valve means, including a first butterfly valve 32 is provided for controlling the amount of air flow through the swirl type entry passage 16. Further, means are provided for closing the first butterfly valve 32 during start up and cold idle of the engine 10. In the embodiment illustrated in Figures 1 and 2 the first throttle valve closing means comprises a control 34 which senses engine tem- perature via a temperature sensor 36 and motivates the movement of a lever 38 which opens or closes the butterfly valve 32. The swirl type entry passage 16 does not provide air flow to the cylinder bore 12 on start up or during cold idle operation under the direction of the control 34. The control 34 can also sense engine speed as via an engine speed sensor 40 for a purpose which will later be apparent.

Second throttle valve means including a second butterfly valve 42 is preferably provided in the non-swirl type entry passage 28 for controlling the amount of air flow therethrough. Further, means are generally provided for closing the second butter¬ fly valve 42 at intermediate speeds of the engine 10. In the embodiment illustrated, the control 34 also includes means for closing the second butterfly valve 42. Said means can include a lever 44 motivated by the control 34. Movement of the lever 44 is controlled by the control 34 responsive to engine speed as sensed by the engine speed sensor 40 whereby the second butterfly valve 42 is closed at intermediate speeds of the engine 10. Thus, the non-swirl type entry passage 28 is generally open at start up and cold idle operation and at high engine speed operation, while being closed at intermediate engine speeds. In Figures 2 and 3, there is illustrated one preferred configuration of the swirl type entry passage 16. In this configuration a straight tube 46 has a generally circular or oval cross-section, and is angularly oriented relative to the first valve 18 so that a center line 48 of said tube 46 forms an an- gle A, in the range of about 30° to 50° with said valve axis 24. An inner wall 50 comprises that portion of the tube 46 nearest to the cylinder bore 12 and forms an angle, B, of at least about 40° with said valve axis 24. An outer wall 52 comprises that portion of said tube 46 farthest from the cylinder bore 12 and forms an angle, C, in the range of about 30° to 50° with said valve axis 24. The outer wall 52, if ex¬ tended in the direction of air flow, clears a seat 54 of said first valve 18. Preferably, the clearance of the valve seat 54 is related to the diameter, D, of the cylinder bore 12 whereby said clearance falls within a range from about 0.005D to about.0.015D. Preferably, the tube 46 has a length, L, from its intersection 56 with a plane defined by said valve seat 54 to an air entry end 58 thereof which falls within a range from about 0.5 to about 2.5 times a mean diameter, d, of said tube 46.

In the embodiment illustrated in Figure 6 the swirl type entry passage 16' has a first portion 60 extending away from the first valve 18" generally parallel to the valve axis 24' and a second portion 62 generally perpendicular to the first portion 60 and extending away from the cylinder bore 12' . The pas¬ sage 16' has an outer generally lineraly extending wall 64 generally tangent to the cylinder bore 12* adjacent the first valve 18" and an inner wall 66 op¬ posite the outer wall 64. A section 68 of the inner wall 66 adjacent the first valve 18' has a concave surface 70 which faces the outer wall 64. In the embodiment illustrated, the concave surface 70 is formed by a vane 72 in a recess 74 in the section 68 of the inner wall 66. The vane 72 extends from a first end 76 adjacent the first valve 18' to a second end 78 spaced from the first valve 18'. A pin 80 pivotally mounts the second end 78 of the vane 72 in the recess 74. Preferably, the concave surface 70 corresponds to a surface of a cylinder which has an axis parallel to the axis of the cylinder bore 12' and has a radius of curvature which falls within a range from about 65% to about 35% of the radius of curvature of the cylinder bore.12'. A chord 82 drawn across the con¬ cave surface 70 aims substantially at the axis 24' of the first valve 18' so that a distance from said axis 24' to a nearest extension of the chord 82 is preferably no more than about 10% of the length of the diameter, D, of the cylinder bore 12'.

Figure 4 shows one embodiment of the non- swirl type entry passage 28. This passage has a curved tube 84 which bends the air path entering via the second valve 30 so that this air path enters gen¬ erally directly axially of the cylinder bore 12.

Figure 5 illustrates an alternate embodi¬ ment of the non-swirl type entry passage. In this embodiment, the non-swirl type entry passage 28' is similar to the structure illustrated in Figure 3 and as has been discussed above for the swirl type

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OMPI entry passage 16. To remain non-swirl, the entry duct 28' introduces the air through the straight tube 46' in a nontangential direction relative to the cyl¬ inder bore 12' and more particularly generally axially and somewhat radially into the cylinder bore 12*, e.g., in the position shown in Figure 5.

Method

In accordance with the method of the present invention air flow is controlled to a cylinder bore 12 of a direct injection diesel type engine 10 to minimize undesirable emission on start up and cold idle while retaining high volumetric engine efficiency at all operating speeds. A non-swirl air flow is introduced substantially parallel to or coplanar with the axis 26 of the cylinder bore 12 during start up and cold idle operation as via the second valve 30. A swirl air flow is introduced tangentially to the cyl¬ inder bore 12 as via the first valve 18 only when the engine 10 operates at other than start up and cold idle. In one embodiment introduction of the non-swirl air flow is stopped during intermediate speed operation of the engine 10 as by controlled operation of the second butterfly valve 42. In this embodiment intro¬ duction of the non-swirl air flow is preferably re- started during high speed operation of the engine 10 so that air is permitted to flow through both passages to provide optimum volumetric efficiency. This can be controlled by a control 34 operating responsive to engine speed as sensed by an engine speed sensor 40. Generally, the introducing, stopping and restarting of the non-swirl air flow comprises opening, closing and reopening of a non-swirl flow throttle valve, in the embodiment illustrated the second butterfly valve 42. The introducing of the swirl air flow generally com¬ prises opening a swirl flow throttle valve, in the embodiment illustrated the first butterfly valve 32. The opening of the first butterfly valve 32 can be controlled, for example, through use of the control 34 operating responsive to a signal from the engine temperature sensor 36.

Through operating as just described above, engine efficiency is substantially improved and the previously mentioned problems of the prior art are substantially eliminated.

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Claims

Clai s

1. A multi-inlet air-flow passage (14) arrangement for an engine having a cylinder bore (12) and a head (20) covering said bore, comprising: first air flow directing means (16) for introducing air past a first valve (18) into the cylin¬ der bore along a first flow path substantially tangent to the bore and causing swirling of the air within the bore; and second air flow directing means (28) for in- troducing air past a second valve (30) into the bore along an axially extending second flow path while causing minimal swirling of the air within the bore.

2. An arrangement as in claim 1, including: control means (34) for selectively utilizing said first and second flow paths either individually or in combination during various phases of engine operation.

3. An arrangement as in claim 1, including: first throttle valve means (32) in said first air flow directing means for controlling the amount of air flow therethrough; and means (38) for closing said first throttle valve means during engine start up and cold idle.

4. An arrangement as in claim 3, including: second throttle valve (42) means in said second air flow directing means for controlling the amount of air therethrough; and means (44) for closing said second throttle valve means at intermediate engine speeds.

5. An arrangement as in claim 4, wherein said first air flow directing means comprises: a straight tube (46) angularly oriented relative to said first valve such that a centerline (48) of said tube forms an angle, A, of about 30° to 50° with an axis (24) of said first valve; an inner wall (50) of said tube which comprises that portion of said tube nearest to the cylinder bore forms an angle, B, of at least about 40° with said valve axis; and an outer wall (52) of said tube which comprises that portion of said tube farthest from the cylinder bore forms an angle, C, in the range of about 30° to 50° with said valve axis, said tube having a generally circular or oval cross-section, said outer wall, if extended in the direction of air flow clearing a seat (54) of said first valve.

6. An arrangement as in claim 4, wherein said first air flow directing means comprises: a first portion (60) extending away from said first valve generally parallel to an axis (24) thereof and a second portion (62) generally perpendi¬ cular to said first portion and extending away from said cylinder bore, said first air flow directing means having an outer generally linearly extending wall (64) generally tangent to said cylinder bore adjacent said first valve and an inner wall (66) opposite said outer wall, a concave surface (70) forming a section (68) of said inner wall, adjacent said first valve and facing towards said outer wall.

7. An arrangement as in claim 4, wherein said second air flow directing means comprises: a straight tube (46) leaving said second valve (30) at such an angle that a centerline of said tube forms an angle, A, in the range of about

OM Claim 7 - continued

30° to 50° with an axis (24) of said second valve, an inner wall (50) of said tube which comprises that portion of said tube nearest to the cylinder bore forms an angle, B, of at least about 40° with said valve axis and an outer wall (52) of said tube which comprises that portion of said tube farthest from the cylinder bore forms an angle, C, in the range of about 30° to 50° with said valve axis, said tube having a generally circular or oval cross-section, said outer wall if extended in the direction of air flow clearing a seat (50) of said valve.

8. An arrangement as in claim 2, wherein said first air flow directing means comprises: a straight tube (46) leaving said first valve. (18) at such an angle that a centerline of said tube forms an angle, A, in the range of about 30° to 50° with an axis (24) of said first valve, an inner wall (50) of said tube which comprises that portion of said tube nearest to the cylinder bore forms an angle, B, of at least about 40° with said valve axis and an outer wall (52) of said tube which comprises that portion of said tube farthest from the cylinder bore forms an angle, C, in the range of about 30° to 50° with said valve axis, said tube having a generally circular or oval cross-section, said outer wall if extended in the direction of air flow clearing a seat (54) of said valve.

9. An arrangement as in claim 2, wherein said first air flow directing means comprises: a first portion (60) extending away from said first valve (18) generally parallel to an axis (24) thereof and a second portion generally (62) perpendicular to said first portion and extending Claim 9 - continued away from said cylinder bore, said first air flow directing means having an outer generally linearly extending wall (64) generally tangent to said cylin¬ der bore adjacent said first valve and an inner wall (66) opposite said outer wall, a concave surface (70) forming a section (68) of said inner wall adjacent said first valve and facing towards said outer wall.

10. An arrangement as in claim 2, wherein said non-swirl type duct comprises: a straight tube. (46') leaving said valve at such an angle that a centerline (48) of said tube forms an angle, A, in the range of about 30° to 50° with said valve axis, an inner wall (66) of said tube which comprises that portion of said tube nearest to the cylinder forms an angle-, B, of at least about 40° with said valve axis and an outer wall (64) of said tube which comprises that portion of said tube farthest from the cylinder forms an angle, C, in the range of about 30° to 50° with said valve axis, said tube having a generally circular or oval cross-section, said outer wall if extended in the direction of air flow clearing a seat of said valve.

11. An arrangement as in claim 5, wherein said second air flow directing means comprises: a straight tube (46') leaving said second valve at such an angle that a centerline of said tube forms an angle. A, in the range of about 30° to 50° with an axis of said second valve, an inner wall of said tube which comprises that portion of said tube nearest to the cylinder bore forms an angle, B, of at least about 40° with said valve axis and an outer wall of said tube which comprises that portion of said tube farthest from the cylinder bore forms an Claim 11 - continued angle, C, in the range of about 30° to 5Q° with said valve axis, said tube having a generally circular or oval cross-section, said outer wall if extended in the direction of air flow clearing a seat of said valve.

12. A method of controlling (34) air flow to a cylinder bore (12) of a direct injection diesel type engine to minimize emission on start up and cold idle while retaining high volumetric engine efficiency at all engine operating speeds, comprising: introducing a non-swirl axial air flow to said cylinder bore during start up and cold idle engine operation; and introducing a swirl air flow tangentially to said cylinder bore only when said engine operates at other than start up and cold idle.

13. A method as in claim 12,. including: stopping introduction of said non-swirl air flow during intermediate speed engine operation.

14. A method as in claim 13, including: restarting introduction of said non-swirl air flow during high speed engine operation.

15. A method as in claim 14, wherein said introducing, stopping and restarting of said non- swirl air flow comprises opening, closing and re¬ opening of a non-swirl flow throttle valve.

16. A method as in claim 12, wherein said introducing of said swirl air flow comprises opening a swirl flow throttle valve.

17. A method as in claim 16, including: stopping introduction of said non-swirl air flow during intermediate speed engine operation.

18. A method as in claim 17, including: restarting introduction of said non-swirl air flow during high speed engine operation.

19. A method as in claim 18, wherein said introducing, stopping and restarting of said non-swirl air flow comprises opening, closing and reopening of a non-swirl flow throttle valve.