MULTI STAGE COMPRESSOR

Description

FIELD OF THE INVENTION

The present disclosure relates to a multi stage compressor for compressing fluid.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 11,156,231 discloses a multistage compressor for compressing fluid. US application publication 20090044548 discloses a two-stage vapor cycle compressor.

OBJECT OF THE INVENTION

Objects of the invention are to provide a more efficient and compact multistage compressor.

SUMMARY OF THE INVENTION

In one aspect, the disclosure provides a compressor device for compressing fluid, comprising: a motor-compressor housing side portion; a fixed group; a rotatable group; wherein all elements of the fixed group are fixed relative to the motor-compressor housing side portion so that they do not move relative to the motor-compressor housing side portion; wherein all elements of the rotatable group are fixed to one another so that they do not move relative to one another; wherein the motor-compressor housing side portion, the fixed group, and the rotatable group are configured, so that the rotatable group is rotatable about to an axis of rotation relative to the motor-compressor housing side portion and the fixed group, and so that the rotatable group is constrained from moving along the axis of rotation, constrained from rotating perpendicular to the axis of rotation, and constrained from translating perpendicular to the axis of rotation relative to the motor-compressor housing side portion and the fixed group; wherein the fixed group comprises a motor stator section, a first stage compressor wheel housing, a diffuser structure, and a second stage compressor wheel housing; wherein the rotatable group comprises a permanent magnet, a first stage compressor wheel; and a second stage compressor wheel; wherein the motor-compressor housing side portion extends from a motor-compressor housing side portion rear end to a motor-compressor housing side portion front end; wherein the motor-compressor housing side portion has interior surfaces that define a motor chamber; wherein the motor stator section and the permanent magnet reside in the motor chamber; wherein the motor-compressor housing side portion, the fixed group, and the rotatable group are configured to provide a fluid flow path for fluid to flow to a first stage compression passage and then to a second stage compression passage; wherein the second stage compressor wheel housing comprises a rear disk portion, a front disk portion, and an axially extending neck portion; wherein the axially extending neck portion comprises a rear region that extends from the rear disk portion and a front region that extends from the front disk portion; wherein the axially extending neck portion extends from the rear region to the front region; wherein the rear disk portion has a substantially radially extending rear surface region and a substantially radially extending first portion of a front surface region; wherein the front disk portion has a substantially radially extending rear surface region and a substantially radially extending front surface portion; wherein the first stage compression passage includes a first stage initial region and a first stage final region; wherein the first stage initial region comprises space between a generally cylindrically shaped outer surface region of the first stage compressor wheel and an opposing surface of the first stage compressor wheel housing; whereby rotation of the rotatable group in a first direction of rotation about the axis of rotation urges fluid in the first stage initial region to move along the fluid flow path towards the first stage final region; wherein the first stage final region comprises space between opposing surfaces of the diffuser structure and a rear surface region of the rear disk portion; wherein fluid flowing from the first stage initial region through the first stage final region enters the second stage compression passage; wherein the second stage compression passage comprises a second stage first region and a second stage second region; wherein the second stage first region is formed by opposing surfaces of the axially extending neck portion and a generally cylindrically shaped outer surface region of the second stage compressor wheel; whereby rotation of the rotatable group in the first direction about the axis of rotation urges fluid in the second stage first region to move along the fluid flow path towards the second stage second region; wherein the second stage second region has one surface formed by the substantially radially extending front surface portion of front disk portion; and wherein the substantially radially extending first portion of the front surface region of the rear disk portion opposes, and is spaced, along a direction of the axis of rotation, from the substantially radially extending rear surface region of the front disk portion, defining a gap there between.

In addition, dependent aspects include: wherein an aspect ratio of the gap is between 0.3 and 1000; between 1 and 100; between 2 and 100; and between 3 and 20; wherein an aspect ratio of the gap is between 3 and 10; wherein a thermal ratio is between 0 and 0.8; wherein a thermal ratio is between 0 and 0.5; wherein a front disk periphery thickness to gap length ratio is between 0.5 and 10; wherein a front disk center thickness to gap length ratio is between 0.3 and 10; wherein the second stage compressor wheel housing further comprises an axially and radially extending support wall extending radially out from the axially extending neck portion and extending axially from the rear disk portion to the front disk portion.

In addition, dependent aspects include: wherein the substantially radially extending rear surface region extends at an angle of within plus or minus thirty degrees from a plane perpendicular to the axis of rotation; the substantially radially extending first portion extends at an angle of within plus or minus thirty degrees from a plane perpendicular to the axis of rotation; and the substantially radially extending front surface portion extends at an angle of within plus or minus thirty degrees from a plane perpendicular to the axis of rotation; wherein the substantially radially extending rear surface region extends at an angle of within plus or minus ten degrees from a plane perpendicular to the axis of rotation;

• • the substantially radially extending first portion extends at an angle of within plus or minus ten degrees from a plane perpendicular to the axis of rotation; and the substantially radially extending front surface portion extends at an angle of within plus or minus ten degrees from a plane perpendicular to the axis of rotation.

In addition, dependent aspects include: wherein the diffuser structure comprises a diffuser cover and a diffuser back plate, and wherein the diffuser cover is press fit onto the diffuser back plate; further comprising a motor-compressor housing end cap and wherein a first rear surface region of the motor-compressor housing end cap opposes the substantially radially extending front surface portion of front disk portion and forms a surface of the second stage second region.

In addition, dependent aspects include wherein the second stage second region opens to a volute defined by a recessed region of the motor-compressor housing end cap extending azimuthally around axis of rotation, and an opposing front surface portion of the front disk portion; and wherein the volute has an opening to a compressor fluid outlet conduit which terminates at a compressor fluid outlet port to space outside the compressor device.

In addition, dependent aspects include wherein the interior surfaces of the motor-compressor housing side portion defines a motor-compressor housing outlet port; and wherein the motor-compressor housing side portion, the fixed group, and the rotatable group are configured to provide a fluid flow path for fluid to flow from the motor-compressor housing outlet port to the first stage compression passage.

Each of these dependent aspects is useable with any of the other dependent aspects in a compressor device.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure is described in conjunction with the following drawing figures, wherein like reference numerals denote the same or like elements.

FIG. 1 is a perspective view showing the front, top, and right sides of novel compressor device 1, axis of rotation 2, and direction of rotation 3.

FIG. 2 is a front view of novel compressor device 1 showing section view indicator I.

FIG. 3 is left side view of novel compressor device 1.

FIG. 4 is a right-side view of novel compressor device 1.

FIG. 5 is a top view of novel compressor device 1 oriented with the front side at the bottom of the page.

FIG. 6 is a back view of novel compressor device 1.

FIG. 7 is a bottom view of novel compressor device 1.

FIG. 8 is a perspective view of separator housing portion 8 in which axis of rotation 2 is canted towards the right side.

FIG. 9 is a perspective view of motor-compressor housing side portion 7 showing regions of motor chamber 93.

FIG. 10 is a perspective view of first stage compressor wheel housing 100.

FIG. 11 is a section view identified by section indicator I in FIG. 2, and showing section view indicator II.

FIG. 12 is magnified view section II identified in FIG. 11.

FIG. 13 is also a magnified view section II identified in FIG. 11 identifying additional elements.

FIG. 14 left side view of second stage compressor wheel housing 128, showing section view indicator III.

FIG. 15 the section view of second stage compressor wheel housing 128 indicated by section view indicator Ill in FIG. 14.

DETAILED DESCRIPTION OF THE FIGURES

FIGS. 1-15 are taken from a solid model for a specific disclosed embodiment, and therefore fine detail is significant. However, horizontal and vertical scale between figures varies somewhat since the 2-dimensional images were magnified by slightly different amounts in the horizontally and vertically directions. Variations that are believed to be feasible and operable are mentioned after describing the relevant features of the disclosed embodiment.

FIG. 1 shows compressor housing front side 4 and compressor housing right side 5 of novel compressor device 1, axis of rotation 2, and direction of rotation 3. Arrowhead on axis of rotation 2 defines a positive direction.

FIG. 1 shows novel compressor device 1 comprises housing 300 comprising, from front to back relative to the positive direction defined by axis of rotation 2, motor-compressor housing end cap 6, motor-compressor housing side portion 7, separator housing portion 8, converter housing side portion 10, and converter housing end cap 11.

FIG. 1 shows exterior surfaces of motor-compressor housing end cap 6, motor-compressor housing side portion 7, separator housing portion 8, converter housing side portion 10, and converter housing end cap 11 comprise: compressor fluid outlet conduit 9; converter housing side portion 10; converter housing end cap 11; bolt 12; bolt 13; compressor fluid outlet port 14; instrumentation ports 15; projected portion 16 of motor-compressor housing side portion 7; right rear AC phase cable gland 17; compressor fluid inlet port 18; bosses of motor-compressor housing side portion 7 including boss 19, boss 20, boss 21, and boss 22, and compressor fluid inlet conduit 23, and bolt 200.

FIG. 1 shows bolt 12, and another bolt identical to bolt 12, each extending through apertures in upper portions of separator housing portion 8, converter housing side portion 10, and converter housing end cap 11.

FIG. 1 shows bolt 200 on the right side of compressor device 1, extending through apertures in boss 21 of motor-compressor housing side portion 7, separator housing portion 8, converter housing side portion 10, and converter housing end cap 11 FIG. 1 shows two more bolts on the right side of compressor device 1 extending through apertures in motor-compressor housing side portion 7, separator housing portion 8, converter housing side portion 10, and converter housing end cap 11. FIG. 1 shows bolt 13 extending through an aperture in motor-compressor housing end cap 6 and into an aperture in motor-compressor housing side portion 7. Bolts 12, 13, 200 and the other bolts mentioned rigidly constrain housing elements of compressor device 1 to one another.

FIG. 1 shows motor-compressor housing side portion 7 comprises boss 19, boss 20 boss 21, boss 22. The term “boss” refers to additional material of a physical structure, generally having a form that can be used for mechanical structural connection to other elements. FIG. 1 shows motor-compressor housing side portion 7 also comprises instrumentation ports 15 and projected portion 16. FIG. 1 shows right rear AC phase cable gland 17, partially visible, projects from the rear side of compressor device 1. FIG. 1 shows motor-compressor housing end cap 6 comprising compressor fluid outlet conduit 9, which terminates at compressor fluid outlet port 14.

FIG. 2 is a front view of compressor device 1 in which lower center electrical feedthrough connector 25 is visible.

FIG. 3 is a left side view of compressor device 1 in which appear measurement port 30, measurement conduit 31, boss 32, and casting datum 33, all as portions of motor-compressor housing side portion 7.

FIG. 4 is a right-side view of compressor device 1 in which more fully appears right rear AC phase cable gland 17.

FIG. 5 is a top view of compressor device 1 showing tops views of left rear AC phase cable gland 50, center rear AC phase cable gland 51, as well as right rear AC phase cable gland 17.

FIG. 6 s a back view of compressor device 1 showing the back surface of converter housing end cap 11.

FIG. 7 is a bottom view of compressor device 1.

FIG. 8 is a perspective view of the rear of separator housing portion 8 showing O-ring groove 80, axially aligned cylindrical aperture 81, tubular inner surface 82, and fluid flow aperture 83.

O-ring groove 80 provides a seat for an elastomeric loop to provide a fluid seal. Fluid flow aperture 83 provides a path for fluid to flow therethrough to motor chamber 93 (see FIG. 9). FIG. 8 shows 3 additional apertures similar in shape and function to fluid flow aperture 83 which are spaced azimuthally around axis of rotation 2. Axially aligned cylindrical aperture 81 provides a constraint to retain rotatable group 120 (see FIG. 11) substantially colinear with axis of rotation 2.

FIG. 9 is a substantially rear perspective view, having axis of rotation 2 canted slightly towards the left of motor-compressor housing side portion 7. FIG. 9 shows O-ring groove 90, motor-compressor housing outlet port 91, inner surface 92 of motor-compressor housing side portion 7, motor chamber 93, axially aligned cylindrical aperture 94, tubular inner surface 95 of motor-compressor housing side portion 7, rear end 96 of motor-compressor housing side portion 7, and identifies hidden front end 97 of motor-compressor housing side portion 7.

FIG. 9 shows rear end 96 includes O-ring groove 90. O-ring groove 90 provides a seat for an elastomeric loop to provide a fluid seal.

FIG. 9 shows inner surface 92 substantially defines motor chamber 93 which substantially encloses motor stator section 123 (see FIG. 11).

FIG. 9 shows that inner surface 92 substantially defines compressor housing outlet port 91 which provides a path for fluid to flow therethrough, from motor chamber 93 out of a front end of motor-compressor housing side portion 7, to conduit 103 of first stage compressor wheel housing 100 (see FIG. 10).

FIG. 9 shows that motor-compressor housing outlet port 91 is one of six such ports substantially equally spaced in the azimuthal direction around axis of rotation 2.

FIG. 9 shows axially aligned cylindrical aperture 94 which provides a constraint to retain rotatable group 120 (see FIG. 11) substantially colinear with axis of rotation 2. Axially aligned cylindrical aperture 94 extends to a front end (not shown) of motor-compressor housing side portion 7.

FIG. 10 is a substantially rear perspective view having axis of rotation 2 canted slightly towards the left, of first stage compressor wheel housing 100.

FIG. 10 shows O-ring groove 101, conduit surface 102, conduit 103, axially aligned cylindrical aperture 104, and generally cylindrical inner surface 105 of first stage compressor wheel housing 100.

FIG. 10 shows O-ring groove 101 which provides a seat for an elastomeric loop to provide a fluid seal. Conduit surface 102 defines conduit 103 for fluid to flow there through. Conduit 103 is canted toward axis of rotation 2 so that the port of conduit 103 on the front side of first stage compressor wheel housing 100 is closer to axis of rotation 2 than the port of first stage compressor wheel housing 100 on the rear side of first stage compressor wheel housing 100. Conduit 103 provides for fluid flow therethrough to inlet 125 to first stage compressor wheel 118 (see FIG. 12). Axially aligned cylindrical aperture 104 and generally cylindrical inner surface 105 provide a constraint to retain rotatable group 120 (see FIG. 11) substantially colinear with axis of rotation 2.

FIG. 10 shows that conduit 103 is one of six such conduits equally spaced in the azimuthal direction around axis of rotation 2.

FIG. 11 is the “I” side section view of FIG. 1. FIG. 11 shows power converter chamber 110, power converter 111, bolt 112, thrust bearing plate 113, rear stub 114, permanent magnet 115, front stub 116, securing bolt 117, first stage compressor wheel 118, second stage compressor wheel 119, rotatable group 120, rear fluid foil bearing slot 121, secondary fluid flow conduit 122, motor stator section 123, front fluid foil bearing slot 124, and fixed group 301.

FIG. 11 shows that power converter chamber 110 contains power converter 111. Power converter 111 is shown schematically, and represents a power converter for converting electrical power received in compressor device into a form useful for driving rotatable section 120 by applying the converted power to motor stator section 123. Power conversion is well known in the art.

FIG. 11 shows motor stator section 123 resides in motor chamber 93.

FIG. 11 identifies rotatable group 120 which consists of elements that are constrained to rotate together. Rotatable group 120 includes bolt 112, thrust bearing plate 113, rear stub 114, permanent magnet 115, front stub 116, securing bolt 117, first stage compressor wheel 118, second stage compressor wheel 119. Securing bolt 112 secures in a recess in rear stub 114. Thrust bearing plate 113 has surfaces that oppose surfaces constrained to housing elements, thereby constraining axial movement of rotatable group 120 relative to housing elements. Rear stub 114 and front stub 116 are formed from Inconel. Securing bolt 117 secures in a recess in front stub 116. Securing bolt 117 passes through apertures in first stage compressor wheel 118 and second stage compressor wheel 119. Securing bolt 117 has a head defining a rim that opposes a forward annular surface of second stage compressor wheel 119.

FIG. 11 shows that permanent magnet 115 resides in the motor chamber 93.

FIG. 11 also identifies fixed group 301. Fixed group 301 comprises all elements that are fixed relative to motor-compressor housing side portion 7 so that they do not move relative to motor-compressor housing side portion 7. Fixed group 301 includes elements identified in FIGS. 11 and 12 including motor stator section 123; first stage compressor wheel housing 100; a diffuser structure consisting of diffuser cover 126 and diffuser back plate 127; and second stage compressor wheel housing 128. These fixed elements either contain peripheral structure that mate to interior surfaces of the housing that fix them relative to the housing or blanks or threaded bores for pins or bolts to secure them to other fixed elements within the housing in manners well known in the art.

Motor-compressor housing side portion 7 and fixed group 301 constrain rotatable group 120 from translating and rotating perpendicular to the axis of rotation.

FIG. 11 shows rear fluid foil bearing slot 121 and front fluid foil bearing slot 124 provide for relatively low friction bearing surfaces that facilitate rotation of rotatable group 120. Secondary fluid flow conduit 122 provides a path defined within motor-compressor housing side portion 7 that communicated with thrust bearing plate 113.

FIG. 12 is a magnified view of the “II” section of FIG. 11, showing first stage compressor wheel housing 100, first stage compressor wheel 118, second stage compressor wheel 119, inlet 125 to first stage compressor wheel 118, diffuser cover 126, diffuser back plate 127, second stage compressor wheel housing 128, bolt 129, O-ring 130, inlet 131 to second stage compressor wheel 119, volute 132, opposing surface region 133, rear disk portion 134, axially extending neck portion 135, front disk portion 136, front surface region 137 of rear disk portion 134, substantially radially extending rear surface region 138 of front disk portion 136, gap 139, axially extending support wall 140, O-ring 141, peripheral generally cylindrical surface 151 of front disk portion 136, rear region 220 of annular outer surface 150 of axially extending neck portion 135, front region 221 of annular outer surface 150 of axially extending neck portion 135, inside surface portion of motor-compressor housing side portion 7, cylindrical inner surface 223 of motor-compressor housing end cap 6, substantially radially extending first portion 224 of front surface region 137, second portion 225 of front surface region 137, and third portion 226 of front surface region 137.

FIG. 12 shows inlet 125 to first stage compressor wheel 118 communicating with first stage compression passage 201, for fluid flow. Diffuser cover 126 is press fit onto diffuser back plate 127. Bolt 129 helps secure diffuser back plate 127 to second stage compressor wheel housing 128. Additional bolts like bolt 129 may be present, but are not shown by the cross-section of FIG. 12. O-ring 130 is an elastomeric seal disposed in a groove in a rear surface of motor-compressor housing end cap 6. O-ring 130 forms a seal between the rear surface of motor-compressor housing end cap 6 and a front surface of motor-compressor housing side portion 7. Volute 132 extends azimuthally around axis of rotation 2 and communicates with compressor fluid outlet conduit 9 (see FIG. 1) to provide fluid out of compressor device 1 at a higher pressure than fluid entering compressor device 1 through compressor fluid inlet conduit 23.

FIG. 12 shows volute 132 is a space between a region of front surface region 152 (see FIG. 14) of front disk portion 134 of second stage compressor wheel housing 128 and a rear surface region of motor-compressor housing end cap 6.

FIG. 12 shows opposing surfaces contact region 133 to be where a front surface region of first stage compressor wheel housing 100 opposes and contacts a rear surface region of rear disk portion 134 of second stage compressor wheel housing 128. Opposing surfaces contact region 133 extends from the first stage compression passage 201 (see FIG. 13) radially outward to inside surface region 222 of motor-compressor housing side portion 7.

FIG. 12 shows front surface region 137 of rear disk portion 134 includes substantially radially extending first portion 224, second portion 225, and third portion 226. Substantially radially extending first portion 224 extends, from rear region 220 of annular outer surface 150 (see FIG. 15) of axially extending neck portion 135 of second stage compressor wheel housing 128, substantially radially outward. Second portion 225 extends from substantially radially extending first portion 224 and curves towards the negative direction of axis of rotation 2. Third portion 226 extends from second portion 225 radially away from axis of rotation 2, and terminates at inside surface region 222 of motor-compressor housing side portion 7.

FIG. 12 shows substantially radially extending rear surface region 138 of front disk portion 136 of second stage compressor wheel housing 128 extends from front region 221 of annular outer surface 150 (see FIG. 15) of axially extending neck portion 135 of second stage compressor wheel housing 128, substantially radially outward to generally cylindrical surface 151 of front disk portion 136 (see FIG. 14).

FIG. 12 shows gap 139 defined by the space between substantially radially extending first portion 224 of front surface region 137 of rear disk portion 134 of second stage compressor wheel housing 128 and substantially radially extending rear surface region 138 of front disk portion 136 of second stage compressor wheel housing 128 (see FIG. 14).

FIG. 12 shows axially and radially extending support wall 140 extending radially away from axially extending neck portion 135, and extending axially from front surface region 137 to substantially radially extending rear surface region 138.

FIG. 12 shows peripheral generally cylindrical surface 151 of front disk portion 136 contacts cylindrical inner surface 223 of motor-compressor housing end cap 6. Peripheral generally cylindrical surface 151 includes an O-ring groove (unnumbered) containing an elastomeric seal to prevent fluid flow from volute 132 to gap 139. Peripheral generally cylindrical surface 151 of front disk portion 136 extends axially forward to front surface region 152 of front disk portion 134 (see FIG. 14).

FIG. 13 is the same magnified “II” section view of FIG. 11, shown in FIG. 12. FIG. 13 identifies additional elements, including:

FIG. 13 shows first stage compression passage 201 includes first region 202, second region 203, third region 204, and fourth region 205, generally cylindrically shaped outer surface region 206 of first stage compressor wheel 118, generally rear surface region 207 of diffuser cover 126, diffuser cover facing surface region 208 of first stage compressor wheel housing 100, curved outer surface region 209 of diffuser cover 126, curved rear surface region 210 of rear disk portion 134, front surface region 211 of diffuser cover 126, substantially radially extending rear surface region 212 of rear disk portion 134 of second stage compressor wheel housing 128, second stage compression passage 213, first region 214 and second region 215 of second stage compression passage 213, generally cylindrically shaped outer surface region 216 of second stage compressor wheel 119, generally cylindrically shaped inner surface region 217 of axially extending neck portion 135 of second stage compressor wheel housing 128, radially extending front surface portion 218 of front disk portion 136 of second stage compressor wheel housing 128, and rear surface portion 219 of motor-compressor housing end cap 6.

FIG. 13 shows first region 202 to be the space between generally cylindrically shaped outer surface region 206 of first stage compressor wheel 118 and generally cylindrical inner surface 105 of first stage compressor wheel housing 100. First region 202 extends axially towards the front and then curves to extends radially away from axis of rotation 2.

When the rotatable group 120 rotates in direction of rotation 3, vanes of the first stage compressor wheel 118 in first region 202 urge fluid in first stage compression passage 201 to flow generally axially in the positive direction of axis of rotation 2, that is towards the front end of compressor device 1, and then flow radially away from axis of rotation 2.

FIG. 13 shows second region 203 to be the space between generally rear surface region 207 of diffuser cover 126 and diffuser cover facing surface region 208 of first stage compressor wheel housing 100. Second region 203 extends from first region 202 radially away from axis of rotation 2 and then curves to extend in the positive direction of axis of rotation 2.

First region 202 and second region 203 form an initial region of first stage compression passage 201 where fluid in first stage compression passage 201 passes first stage compressor wheel 118 and attains its maximum radial distance from axis of rotation 3.

FIG. 13 shows third region 204 to be the space between curved outer surface region 209 of diffuser cover 126 and curved rear surface region 210 of rear disk portion 134. Third region 204 extends from second region 203 in the positive direction of axis of rotation 2 and curves inward to end where it extends generally radially inward.

FIG. 13 shows fourth region 205 to be the space between front surface region 211 of diffuser cover 126 and substantially radially extending rear surface region 212 of rear disk portion 134 of second stage compressor wheel housing 128. Fourth region 205 extends from third region 204 radially inward and then curves towards the positive direction of axis of rotation 2 where it connects with inlet 131 to second stage compressor wheel 119.

Third region 204 and fourth region 205 form a final region of first stage compression passage 201 where fluid in first stage compression passage 201 passes from its maximum radial distance from axis of rotation 3 a smaller distance from axis of rotation 2. Vanes on diffuser backplate in the final region urge circulating fluid to flow towards inlet 131 to second stage compressor wheel 119.

FIG. 13 shows second stage compression passage 213 including first region 214 and second region 215.

FIG. 13 shows first region 214 to be the space between generally cylindrically shaped outer surface region 216 of second stage compressor wheel 119 and generally cylindrically shaped inner surface region 217 of axially extending neck portion 135 of second stage compressor wheel housing 128. First region 214 extends axially forward from inlet 131 and then curves away from axis of rotation 2 to extend generally radially away from axis of rotation 2. When the rotatable group 120 rotates in direction of rotation 3, vanes of the second stage compressor wheel 119 in first region 214 urge fluid in second stage compression passage 213 to flow generally axially in the positive direction of axis of rotation 2 and then radially away from axis of rotation 2 toward volute 132.

FIG. 13 shows second region 215 to be the space radially extending front surface portion 218 of front disk portion 136 of second stage compressor wheel housing 128 and rear surface portion 219 of motor-compressor housing end cap 6. Second region 215 extends from first region 214 radially away from axis of rotation 2 to volute 132.

FIG. 14 is a left side view of second stage compressor wheel housing 128 and FIG. 15 is the Ill section identified in FIG. 14. FIGS. 14 and 15 show peripheral generally cylindrical surface 151, annular outer surface 150 of axially extending neck 135, front surface region 152 of front disk portion 134, base 153 of axially extending support wall at annular outer surface 150, neck portion radius 154 of annular outer surface 150 of axially extending neck portion 135, axial extent 155 of gap 139, axial extent 156 of a peripheral region of front disk portion 136 from substantially radially extending rear surface region 138 to front surface region 152, support wall radial extent 157 of axially and radially extending support wall 140, inner radius 158 of axially extending neck portion 135, outer radius 159 of front disk portion 136, thickness 160 of base of axially extending support wall at annular outer surface 150, axially extending support wall 161, axially extending support wall 162, and substantially radially extending first portion 224 of front surface region 137.

FIG. 14 shows axial extent 156 from substantially radially extending rear surface region 138 to front surface region 152 of front disk portion 134 of peripheral generally cylindrical surface 151.

FIGS. 13 and 14 shows axial extent 163 from substantially radially extending rear surface region 138 to radially extending front surface portion 218, of front disk portion 136, at a distance halfway between axis of rotation 2 and outer radius 159 of front disk portion 136. Radially extending front surface portion 218 of front disk portion 136 exists along second region 215 of the second stage compression passage 213 (see FIG. 13).

FIG. 14 shows axial extent 155 of gap 139 is from substantially radially extending first portion 224 of front surface region 137 of rear disk portion 134 to substantially radially extending rear surface region 138 of front disk portion 136.

FIGS. 14 and 15 show gap 139 extends radially from annular outer surface 150 to peripheral generally cylindrical surface 151 of front disk portion 136.

FIG. 15 shows axially and radially extending support wall 140 extending radially from base 153 to outer radius 159 of front disk portion 136. Base 153 has thickness 160.

FIG. 15 shows axially extending neck portion 135 has inner radius 158 and an outer radius being portion radius 154, relative to axis of rotation 2.

FIG. 15 shows axially and radially extending support wall 161 and axially and radially extending support wall 162 having the same shape as axially and radially extending support wall 140, and being equally spaced azimuthally around axis of rotation 2. FIG. 15 shows support wall 162 having support wall radial extent 157 from axis of rotation 2.

Relative lengths of elements 154-160 and 163 are:

The aspect ratio is defined to be the ratio of the depth to the width of gap 139.

The aspect ratio formula for gap 139 of compressor device 1 is the values of:

• • (element 159−element 154)/element 155=

The aspect ratio of compressor device 1 is (432−210)/45=222/45=4.9.

The material-filled area is defined to be the area in a plane perpendicular to axis of rotation passing through gap 139, within the annulus from neck portion radius 154 to outer radius 159, of the area of the walls 140, 161, and 162, and the area of the annulus from inner radius 158 to neck portion radius 154.

The total area is defined to be the area in a plane perpendicular to axis of rotation passing through gap 139, that is within the annulus from neck portion radius 154 to outer radius 159.

The thermal ratio is defined to be the material-filled area divided by the total area.

The formula for the thermal ratio of compressor device 1 (which assumes the areas of walls 140, 161, 162 are rectangular), is:

• • material filled area divided by total area, which equals the values of:
  • {3*(element 160)*(element 157−element 154)
  • +Pi*(element 154**2−element 158**2)}
  • divided by
  • (Pi*(element 159**2−element 158**2)

The value of the thermal ratio for compressor device 1 is:

• • ={3*111*(425−210)+3.14*(210**2−142**2)} divided by (3.14*(432**2−142**2)=
  • {333*215+3.14*(44100−20164)}/3.14*(186624−20164)=
  • {71595+75159)/522684
  • =0.28

The front disk periphery thickness to gap length ratio is defined to be the ratio of the thickness of the periphery of front disk portion 136 to thickness of gap 139.

The front disk periphery thickness to gap length ratio for compressor device 1 is given by axial extent 156 of front disk portion 136 divided by axial extent 155 of gap 139.

The front disk periphery thickness to gap length ratio for compressor device 1 is 105/45=2.3

The front disk center thickness to gap length ratio is the axial extent of front disk portion 136 at a distance halfway between axis of rotation 2 and outer radius 159 of front disk portion 136 divided by thickness of gap 139.

The front disk center thickness to gap length ratio for compressor device 1 is given by the formula axial extent 163 divided by gap width 155

The front disk center thickness to gap length ratio for compressor device 1 is 67/45=1.5.

VARIATIONS FROM THE DISCLOSED EMBODIMENT

The converter housing, power converter, bosses, and other structure unrelated to the function of compressing fluid, are not necessary.

Components can be formed from any material providing sufficient structural strength and rigidity, such as hard plastics, metals, and ceramics.

In the preferred embodiment, second stage compressor wheel 119 and second stage compressor wheel housing 128 are formed from an aluminum allow.

While two compression stages are shown, any number greater than two compression stages may be present. Specifically, 3-5 compressor stages are contemplated. Each of the compression stages, after the first stage, may incorporate a second stage compressor wheel housing like second stage compressor wheel housing 128 including the disclosed gap between two disk-like portions.

Fluid flow through the motor chamber, for example, for the purpose of cooling the electric motor elements is not required. That is, the fluid at relatively low pressure may enter the compressor device at a compressor device inlet port close to the first stage compressor wheel housing 100.

The number of apertures similar to fluid flow aperture 83 is not critical and may vary from the 4 shown, for example, between 1 and 20. If present, the number of motor-compressor housing outlet port 91 are not critical and may vary from the 6 shown, for example between 1 and 20.

The number of conduits similar to conduit 103 is not critical and may vary from the 6 shown, for example between 2 and 20.

Various mechanical constraining techniques, including bolts, nuts, press-fits, and pins may be used to mechanically secure elements of the rotatable group to one another, and elements of the fixed group to one another and to housing elements.

The first stage compressor wheel housing 100 may have more than one gap disposed axially instead of the single gap 139.

Motor-compressor housing end cap 6 is separate from motor-compressor housing side portion 7 to facilitate assembly. However, both elements may be integrated into a single element.

The aspect ratio of the gap in the second stage compressor wheel housing may be between 0.3 and 1000; 1 and 100; 2 and 100; 3 and 20; and 3 and 10.

The thermal ratio of the second stage compressor wheel housing may be between 0 and 0.8, and 0 and 0.5.

The front disk periphery thickness to gap length ratio of the second stage compressor wheel housing may be between 0.5 and 10.

The front disk center thickness to gap length ratio of the second stage compressor wheel housing may be between 0.3 and 10.

The term substantially radially extending, for the substantially radially extending rear surface region; the substantially radially extending first portion; and the substantially radially extending front surface portion, means extending within an angle within plus or minus 45 degrees from a plane perpendicular to the axis of rotation.

Preferably, the substantially radially extending rear surface region; the substantially radially extending first portion; and the substantially radially extending front surface portion, each extend at an angle within plus or minus 30 degrees from a plane perpendicular to the axis of rotation, and more preferably at an angle within plus or minus 10 degrees from a plane perpendicular to the axis of rotation, and most preferably, at nominally zero degrees from a plane perpendicular to the axis of rotation.