Cylinder head

Abstract

Claims

Jan. 20, 1953 M. W. GARLAND 2,626,102 CYLINDER HEAD Filed April 6, 1949 INVEN TOR. M. W. GARLAND Patented Jan. 20, 1953 CYLINDER HEAD Milton W. Garland, Waynesboro, Pa., assignor to Frick Company, Waynesboro, Pa., a corporation of, Pennsylvania Application April 6, 1949, Serial No. 85,810 13 Claims. 1 This invention relates to the flow of fluids and more particularly to a cylinder head designed to permit the fluids compressed in a cylinder to escape through the discharge ports in the head with a minimum of turbulence and in such a way that the volumetric efficiency of the cylinder is improved over that obtained with conventional structure. The problem of improving the efliciency of power plants, compressors, and the like, has received a great deal of attention. This invention is particularly concerned with the improvement of volumetric efiiciency of a reciprocating compressor of the type having a discharge valve containing head. It is not limited however to a compressor, but has obvious application to other devices including internal combustion engines and the like. Heretofore, in order to obtain the maximum useful work output from a compressor, the clearance volume has usually been designed to be as small a percentage of the total cylinder volume as physically possible. Various attempts have been made to improve the volumetric efficiency by tapering and streamlining the valve ports which has usually consisted in the use of rounded corners and tapered approaches to the valve openings. These attempts have only met with limited success and usually the increase in the clearance volume occasioned by the change in form has substantially or completely offset any gain otherwise obtain-able through the use of these expedients. Accordingly, it is an object of the present invention to provide a reciprocating compressor discharge valve containing cylinder head of improved construction resulting in substantially higher volumetric efliciency of the compressor. A further object of the invention is the pro vision of a discharge valve containing cylinder head of improved construction permitting the compressed fluids to be discharged through the valve opening with minimum turbulence resulting in improved volumetric efliciency. A still further object of the invention is the provision of a method of constructing a discharge valve containing cylinder head applicable to various sizes of units which is simple and easy to perform and which results in substantial improvement in the performance of the unit. These and other objects of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a section through a cylinder showing the improved construction applied to the discharge valve containing head; and, Fig. 2, a bottom plan view of the cylinder head. Referring to the drawings, the cylinder shown includes a wall Hi having a thickened upper rim II for the reception of the cylinder head l2, 9. piston I3 of conventional construction being shown within the cylinder. The cylinder head includes a plurality of discharge openings l6 and I7 and a plurality of intake openings (not shown) the latter of which are positioned between the outer discharge openings and the periphery of the cylinder head. In conventional cylinder construction the surface H of the head which is in contact with the fluids in the cylinder is flat or plane in order that the clearance volume between it and the face I5 of the piston be as small as physically possible to insure efficient operation of the cylinder, the volumetric efficiency generally indicating the efficiency of the design of the construcion. The application of tapering or streamlining adjacent to the port openings to improve volumetric efficiency has been practiced but has not eliminated the turbulence in. the compressed fluid seeking to escape through the. ports and as a result the success achieved by conventional streamlining has been limited due to the losses caused by the turbulence. The turbulence occurs as a result of various increments of the compressed fluid arriving at a discharge opening at a given instant and having widely differing velocities, the impact of one on the other producing turbulence. The reason for the diflerences in the velocity of various increments of the compressed-fluid is apparent from a consideration of the construction and operation ofv a conventional cylinder and cylinder head. When the piston is at or near the top of its stroke, and the volume which the compressed fluid occupie within the cylinder is approximately the clearance volume thereof, the discharge valves open for a very brief duration of time during which the compressed fluid escapes therethrough. Considering the construction shown in the drawings the cylinder has two series of discharge openings or ports I6 and I1. The radial width of the opening of each series is substantially equal and the distance from the axis I8 of the openings in each series is the same. Although two series of ports are shown, obviously a diiierent number may be employed in accordance with the requirements of a particular construction. 3 The ports are provided with conventional valves During the time that the discharge valves are open the compressed fluid within that portion of the cylinder at a radius equal to or greater than that of the center line 20 of the ports l6 discharges through the ports Hi. The portion of the cylinder head overlying this volume is shown by the dimension arrows 23. Similarly that between center line 20 and a median line 24 equidistant between the center line 25 of the ports l1 and the center line 20 of the ports l6 discharges through the ports It, the portion of the cylinder head overlying this volume being shown by the dimension arrows 26. The volume between the line 24 and the center line 25 of the ports l1, shown by dimension arrows 26, is adapted to move inwardly toward the axis [8 to be discharged through the ports I1, and the volume between the center line 25 and the axis l8, shown by the dimension arrows 21, moves radially outwardly to be discharged through the ports II. If the surface of the head is flat, as in conventional structure, it is apparent that the volume shown by the dimension arrows 23 is substantially greater than that between the dimension arrows 26, and that the velocity of the compressed fluids within the former space must be substantially greater than that of the compressed fluids within the latter space in order for them to escape through the ports within the time permitted. Furthermore, it is apparent that the compressed fluid which is initially near the cylinder wall must have a higher velocity to escape through the ports than that which is nearer the axis of the cylinder. The effect is substantially the same as that which occurs when a fluid flows through a converging pipe, its velocity increasing as the cross-sectional area decreases. In order to have a condition of smooth flow which insures conversion of pressure into velocity with minimum losses, the present invention provides for the tapering of the face of the valve containing head such that substantially the same velocity of approach of the discharge fluids into the ports from all directions of flow is achieved. In order. to accomplish this it is necessary to design the cylinder head so that when the piston is spaced therefrom the distance at which the discharge valves open, that the volume of the compressed fluid which flows radially inwardly to a discharge port is not decreased as a result of thejflow. obtained. The value of in may be taken adjacent to the periphery of the cylinder head within the space, hi for this radius substantially equalling the normal clearance of the piston within the cylinder. The annular machined groove 2! may be ignored so far as the design of the surface is concerned. The required slope for the surface 29 of the head between the median line 24 and the center line 25 of the ports ll may be found in similar manner. It will be understood that surfaces 28 and 29 are frusto-conical, although the invention is not limited to this particular configuration. It will also be apparent that the peripheral and central portions of the inner surface of the head lie in substantially the same 1 plane, since in the illustrated embodiment, no discharge port is located at the axis, and that the tapering toward ports I6 is inwardly from the cylinder wall, or closely adjacent thereto. It will be found that the slope of the wall will be the same for all increments of fluid that move toward the axis of the cylinder for discharge. The portions of the compressed fluid within the space defined by the dimension arrows 26 and 21 which move toward the cylinder wall and away from the axis of the cylinder to reach the discharge ports are not accelerated to increased velocity as they move radially if the surface of r the cylinder head is flat overlying these portions. In order for the velocity of the compressed fluid in various portions of the space to be the same, it is necessary that the areathrough which they flow be proportional to the volume of the fluid flowing through the area in order that the effect of a converging pipe will be obviated. Consider that the volume of fluid within the cylinder at the time that the discharge valves open consists of an infinite number of ring shaped increments about the axis l8 of the cylinder. At a distance 1'1 from the axis the height of the increments is h]. and at a distance T2, the height is hz. In order for the velocity of the ring increments at T1 to be the same as that of the ring increments at 12 it is necessary that the volume of each of the rings be the same. For this condition to be present it is necessary that ha .equal h]. times the proportion that n is to 12. By finding any two values of h at corresponding values of r, the slope of the taper of the surface and the center line 20 of the ports I6 may be Although theoretical considerations of velocity would indicate that these portions of the cylinder wall should be tapered outwardly from the face to form a ledge, this obstructs the flow and is therefore impractical. A slight inward taper has beenfound best to assure smooth flow and is regarded as a practical limitation on the theoretical approach. a With a conventional compressor the discharge valves are usually set to open at a pressure corresponding to that. within the cylinder when the piston is at or near the top of its stroke. In other words the volume within the cylinder at the instant that the discharge valves open is of the order of the clearance volume of the compressor. For the compressor head illustrated the normal clearance is -020 inch. Before grooving the compressor head, that is with the face of the head flat, the clearance volume was about 2.9%, and the volumetric efiiciency was approximately By providing a uniform streamlining or taper around each opening as in conventional practice, the clearance volume was 3.84% and the volumetric efficiency 82%. After applying the tapering in accordance with the present invention the clearance volumebecame 5.34% and the actual volumetric efficiency under the same pressure conditions was increased to 85%. Although the invention is primarily concerned with the design of a compressor head of the type shown in the drawings it has obvious applications to other types of structure and to other power plants. 7 1 It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown in the drawings and described in the specification but only as indicated in the appended claims. What is claimed is: 1. A cylinder head for use with a flat ended piston comprising a circular end member .hav-.- ing a first and a second series of uniformlyspaced ing positioned an equal distance from the axis of the member'and being of 'substantially the, same radial width, that portion of the surface; of the member defined by a point at its axis, a. circle equidistantly spaced from the series of ports whose axis is that of the end member, and a circle adjacent to the periphery of the cylinder head whose axis is that of the end member lying in the same plane, the surface of the head being high at the portions defined, the surface sloping inwardly from the axis as far as the radial center of the first series of ports, the surface sloping uniformly inwardly from the circle between the series of ports toward the first series of ports and forming an apex with the surface sloping inwardly from the axis to the radial center of the ports, the surface sloping inwardly from the circle between the series of ports toward the second series of ports, and the surface sloping uniformly inwardly from the circle adjacentto the periphery of the cylinder head toward the second series of ports. 2. A cylinder head for use with a flat ended piston comprising a circular end member having a first and a second series of ports, each of the ports in a series being equidistant from the axis of the cylinder and of equal radial width, the surface of the cylinder head sloping uniformly inwardly from a line adjacent to the periphery as far as a line defining the center of the second series of ports, the surface sloping outwardly from said line as far as a line equidistant the series of ports, the surface sloping uniformly inwardly from said line to a line defining the center of 'the first series of ports, and the surface sloping outwardly from the line defining the center of the first series of ports to a point coincident with the axis of the cylinder, said point, said line equidistant the series of ports, and said line adjacent to the periphery all lying in the same plane. 3. A cylinder head for use with a fiat ended piston comprising a circular end member having a first and a second series of ports, each of the ports in a series being equidistant from the axis of the cylinder and of equal radial width, the surface of the cylinder head sloping uniformly inwardly from a line adjacent to the periphery as far as the second series of ports, the surface sloping outwardly from said ports as far as a line equidistant the series of ports, the surface sloping uniformly inwardly from said line to the first series of ports, and the surface sloping outwardly from the first series of ports to a point 00- incident with the axis of the cylinder, said point, said line equidistant the series of ports, and said line adjacent to the periphery all lying in the same plane. 4. The structure defined in claim 3 in which the slope of the surface of the cylinder head sloping uniformly inwardly from adjacent to the periphery as far as the second series of ports, and the slope of the surface sloping inwardly from a line equidistant the series of ports to the first series of ports is the same. 5. The structure defined in claim 3 in which the slope of the surface sloping out-wardly as far as a line equidistant the series of ports and the slope of the surface sloping outwardly to a point coincident with the axis of the cylinder is zero. 6. A cylinder head for use with a fiat ended piston comprising a circular end member having one or more discharge openings of substantially equal radial width arranged in a circle whose axis is the axis of the cylinder, the surface of the cylinder head from the peripheral portion to the circle of" discharge openings being wardly toward the axis. 7. Ina compressor, a cylinder,.a cylinder head, and a piston adapted to reciprocate within the cylinder, the cylinder head including a plurality of discharge openings, valves controlling the flow thru said openings, the discharge valves opening to permit discharge through the discharge openings when the clearance volume between the piston and cylinder head is a predetermined value corresponding to a predetermined normal clearance, the discharge openings being spaced from the periphery of the cylinder head and arranged in a circle whose axis is that of the cylinder and each having substantially the same radial width as the other, the surface of the cyl-' inder head from adjacent the periphery thereof to the openings being uniformly tapered inwardly such that the clearance of the head at the openings is to the normal clearancea-djacent to the periphery as the radius of the cylinder head adjacent to the periphery is to the radius of the circle of the discharge openings, whereby the compressed fluids moving towards the axis to the discharge openings are not compressed as a result of moving in such direction. 8. In a compressor, a cylinder, a cylinder head, and a piston adapted to reciprocate within the cylinder, the cylinder head including a plurality of discharge openings, valves controlling the flow thru said openings, the discharge valves opening to permit discharge through the discharge openings when the clearance volume between the piston and cylinder head is a predetermined value corresponding to a predetermined normal clearance, the discharge openings being spaced from the periphery of the cylinder head and arranged in a circle whose axis is that of the cylinder, the surface of the cylinder head from adjacent to the periphery thereof to the openings being umformly tapered inwardly such that the clearance of the head at the openings is to the normal clearance as the radius of the cylinder head is to the radius of the circle of the discharge openings, whereby the compressed fluids moving towards the axis to the discharge openings are not compressed as a result of moving in such direction. 9. In a compressor, a cylinder, a cylinder head, and a piston adapted to reciprocate within the cylinder, the cylinder head having a :plurality of series of discharge openings, all the openings in each series being the same distance from the axis, the surface of the cylinder head being radially tapered inwardly toward the axis and to the openings so that the volume of all radial increment of compressed fluid approaching said each series of openings toward the axis remains constant. 10. In a reciprocating compressor a cylinder, a cylinder head, and a piston adapted to reciprocate within the cylinder, the cylinder head having a plurality of radially spaced discharge openings, the surface of the head being tapered inwardly toward the axis and to the openings such that the velocity of approach of fluid compressed within the cylinder at the moment of discharge is the same for all increments of fluid approaching a given opening. 11. In a compressor, a cylinder having an internal wall, a cylinder head, and a piston, the cylinder head having an interior face and including discharge openings spaced from the axis of the cylinder head and from the wall, the piston having a face in communication with said intapered 'in-" 7 terior face, said interior face bein'g taperedinawardly from the periphery of the cylinder head to the discharge openings, such that opposite portions of the faces diverge between the cylinder and the discharge openings. 12. In a compressor, a cylinder having an interna1 wall, a cylinder head, and a flat ended piston adapted to reciprocate within the compressor, the cylinder head including discharge openings spaced from the axis of the cylinder 10 head and from the wall, the cylinder head having an interior face opposite the flat ended piston, said face being tapered inwardly from the wall to the discharge openings. 13. For use with a cylinder having an internal wall and a pistonhaving a face, a cylinderhead having an internal surface for communication with the face comprising an end member having discharge openings spaced from the wall and from the'axis of the cylinder, the peripheral and central portions of the internal surface of the cylinder head lying in substantially the same plane, the surface of the" cylinder head being tapered inwardly from the peripheral portion to the openings. I MILTON W. GARLAND. REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number Name Date 400,668 Hambay Apr. 2, 1889 457,243 Bartliif Aug. 4, 1891 1,870,139 Pierotte Aug. 2, 1932 15 2,260,113 Frost Oct. 21, 1941 2,312,883 Demann Mar. 2, 1943 2,339,048 Bixler Jan. 11, 1,944 FOREIGN PATENTS 20 Number Country 7 Date, 596,925 Germany May 12, 1934

Description

Topics

Download Full PDF Version (Non-Commercial Use)

Patent Citations (7)

NO-Patent Citations (0)

    Title

Cited By (3)

    Publication numberPublication dateAssigneeTitle
    US-3131856-AMay 05, 1964Vilter Manufacturing CorpReciprocating piston type gas compressor
    US-5149254-ASeptember 22, 1992White Consolidated Industries, Inc.Refrigeration compressor having a contoured piston
    US-5980223-ANovember 09, 1999Danfoss Computers GmbhRefrigerant compressor having an asymmetrically contoured piston