Abstract:
A hydrogen blower is provided and includes a housing having a drive unit and a compressor unit disposed therein. The drive unit is separated from the compressor unit by a neutral chamber, whereby the neutral chamber effectively seals the drive unit from the compressor unit. The drive unit includes a drive shaft, whereby the drive shaft extends generally between the drive unit and the compressor unit to selectively drive the compressor. In addition, the drive shaft fixedly supports a series of fan blades such that rotation of the drive shaft imparts a pressure on the neutral chamber to effectively seal the drive unit from the compressor unit. In this manner, the drive motor, compressor, and drive shaft may be packaged in a single housing while effectively sealing the drive unit from the compressor unit through cooperation between the fan blades and the neutral chamber.

Description:
FIELD OF THE INVENTION 
     The present invention relates to hydrogen blowers, and more particularly, to an improved hydrogen blower for use in a fuel cell system. 
     BACKGROUND OF THE INVENTION 
     In hydrogen blower applications, it is desirable to package a drive unit and a compressor unit within a single housing. Further, it is desirable that the drive unit be capable of selectively driving the compressor unit in response to system load. Further yet, it is desirable that the drive unit and compressor unit are disposed in separate chambers within the housing to effectively seal the drive unit from the compressor unit. To that end, a sealing system disposed between the drive unit chamber and the compressor unit chamber plays a significant role. 
     Typically, a hydrogen blower is used within a fuel cell system or in a hydrogen storage application such as at a hydrogen station or the like to supply a stream of compressed hydrogen to a fuel cell stack. In a typical fuel cell system, a hydrocarbon fuel is processed in a fuel processor, for example, by reformation and partial oxidation processes, to produce a reformate gas which has a relatively high hydrogen content on a volume or molar basis. This hydrogen gas is fed through an anode chamber of a fuel cell stack. At the same time, oxygen in the form of an air stream is fed into a cathode chamber of the fuel cell stack. The hydrogen from the reformate stream and the oxygen react in the fuel cell stack to produce electricity. To maintain a constant and consistent stream of hydrogen supply to the fuel cell stack, a hydrogen blower is typically provided between the reformation process and the fuel cell stack. 
     Conventional hydrogen blower systems, compress and store hydrogen within a housing due to the interaction of a drive unit and a compressor unit. Specifically, a conventional drive unit such as an electric motor is disposed within the housing and includes a drive shaft fixedly attached to the compressor unit to selectively drive the compressor unit in response to a system load. Typically, the compressor unit includes a series of impellers, whereby the impellers compress the hydrogen due to the rotation of the drive shaft and the interaction of the air flow therein. In this manner, the compressed hydrogen is typically stored within the housing and may be selectively released when needed. Releasing of the compressed hydrogen governs the system load as more hydrogen will need to be compressed as the housing is drained, thus regulating the rate and frequency at which the drive unit rotates the impellers. 
     To ensure that the hydrogen blower maintains a high efficiency, a seal is commonly disposed between the drive unit and the compressor unit. The seal serves to keep the compressed hydrogen separate from the drive unit in an effort to maintain the efficiency of the compressor. As can be appreciated, any loss of hydrogen between the compression unit and the drive unit results in an overall loss in blower efficiency. Conventional sealing systems commonly include a flexible member or ring such as a rubber gasket, or the like, disposed between the drive unit and the compressor unit. The gasket is commonly fixedly attached to the drive shaft for rotation therewith and forms a barrier between the drive and compression units. 
     While adequately preventing the hydrogen from passing from the compression unit to the drive unit, the conventional sealing systems can be complex, expensive to manufacture, and create a relatively large amount of frictional resistance. 
     Therefore a hydrogen blower that provides a drive unit operable to drive a compressor unit disposed within a common housing, while maintaining a seal between the drive unit and the compressor unit, is desirable in the industry. Additionally, providing a seal between the drive unit and a compressor unit that improves and maintains high efficiency is also desirable. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a hydrogen blower including a housing having a drive unit and a compressor unit disposed therein. The drive unit is separated from the compressor unit by a neutral chamber, whereby the neutral chamber effectively seals the drive unit from the compressor unit. The drive unit includes a drive shaft, whereby the drive shaft extends generally between the drive unit and the compressor unit to selectively drive the compressor. In addition, the drive shaft fixedly supports a series of fan blades such that rotation of the drive shaft imparts a pressure on the neutral chamber to effectively seal the drive unit from the compressor unit. In this manner, the drive motor, compressor, and drive shaft may be packaged in a single housing while effectively sealing the drive unit from the compressor unit through cooperation between the fan blades and the neutral chamber. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a cross-sectional view of a hydrogen blower in accordance with the principles of the present invention; 
         FIG. 2  is a cross-sectional view of a seal of the hydrogen blower shown in  FIG. 1 ; and 
         FIG. 3  is a cross-sectional view of a second embodiment of a hydrogen blower in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG. 1 , a hydrogen blower  10  is provided and includes a drive unit  12 , a compressor unit  14 , and a neutral chamber  16 , each disposed within a common housing  18 . The drive unit  12  includes a motor  20  disposed in a motor chamber  22  of the housing  18 . A first fan  24  is connected to a first end of a motor driven shaft  26 . A second fan  28  is drivingly connected to the motor shaft  26  and is disposed in the neutral chamber  16 . The neutral chamber  16  is disposed between the drive unit  12  and a compressor unit  14  to seal or isolate the compressor unit  14  from the drive unit  16 . 
     The compressor  14  is disclosed as a two-stage impeller-type compressor including a first impeller  30  and a second impeller  32  which are each disposed in a compressor chamber  34  of the housing  18  and are rotatably driven by the shaft  26  connected to the motor  20 . The compressor chamber  34  includes an inlet passage  36  and an outlet passage  38 . The inlet passage  36  is concentrically disposed about the end of the shaft  26  while the outlet passage  38  is provided in a side surface of the housing  18 . According to a preferred embodiment of the present invention, hydrogen gas is drawn into the compressor chamber  34  through the inlet passage  36  and is initially compressed by the first impeller section  30  of the dual stage compressor unit and is then compressed further by the second impeller  32  prior to exiting the compressor chamber  34  through outlet passage  38 . 
     According to one aspect of the present invention, a first bearing and seal assembly  40  is disposed between the compressor chamber  34  and neutral chamber  16 . The bearing and seal assembly  40  is designed to inhibit or limit the flow of the compressed hydrogen from the compressor chamber  34  into the neutral chamber  16 . 
     A second seal assembly  42  is provided between the motor chamber  22  and the neutral chamber  16 . As best shown in  FIG. 1 , the seal  42  includes a first cylindrical member  44  which is mounted to the shaft  26  for rotation therewith. A second cylindrical member  46  is supported by a partition plate  48 . The first cylindrical member includes radially outwardly extending fins  50  which cooperate with radially inwardly extending fins  52  of the second cylindrical member  46  to form a labyrinth flowpath between the first and second cylindrical members  44 ,  46 . 
     The housing  18  includes air passages  56  provided in an upper surface of the motor chamber  22 . Air is drawn through air passage  56  into the motor chamber  22  by the fan  24 . The air entering the motor chamber  22  passes over the controller  32 , in the form of a circuit board, to provide cooling for the controller  32 . The air then passes through the motor chamber  22  for cooling the motor  20 . The fan  24  pressurizes the motor chamber  22  such that a pressure is applied on the motor chamber side of the seal  42  in order to inhibit the flow of gases from the neutral chamber  16  into the motor chamber  22 . 
     While the bearing seal assembly  40  is designed to preferably completely inhibit the flow of hydrogen from the compressor chamber  34  into the neutral chamber  16 , any hydrogen that may escape from the compressor chamber  34  through the seal  40  into the neutral chamber  16  will be mixed with air that passes through the second seal  42  into the neutral chamber  16  and is exhausted through exhaust passage  60  provided in the side of the neutral chamber  16  due to the rotation of the fan  28  within the neutral chamber  16 . A catalyzer  62  is provided in the outlet passage  60  of the neutral chamber  16 , to react the fluid mixture disposed within the neutral chamber prior to the fluid mixture being dissipated from the housing  18 . 
     The housing  18  is preferably comprised of three or more sections, including an upper section  18   a  which primarily encloses the motor chamber  22 , an intermediate section  18   b  which primarily encloses the neutral chamber  16 , and a lower section  18   c  which primarily encloses the compressor chamber  34 . The intermediate housing section  18   b  includes a pair of radially inwardly extending partition plates  64 ,  48  which support portions of the first and second seal assemblies  40 ,  42 , respectively. The housing  18  includes a recessed portion  68  disposed around the motor  20  for providing support thereof. The motor  20  is a standard motor design that allows air passage through the motor coils to enhance cooling thereof. The upper end of the shaft  26  is supported by a bearing  70  which is supported by a bearing support plate  72  provided with openings therein to allow air passage therethrough. The controller unit  58  is supported by a second support plate  74  provided with openings  76  provided therein to allow cooling air to flow therethrough. 
     Now with reference to  FIG. 2 , the seal  40  disposed between the neutral chamber  16  and compressor chamber  34  will now be described. The seal  40  includes a slide ring  80 , a collar  82 , a slide head  84 , and a shield  86 . The slide ring  80  includes a central bore  88  and a first and second surface  90 ,  92 . The central bore  88  fixedly receives the main body of the drive shaft  26  and is fixed for rotation therewith. The collar  82  includes a central bore  94  and a first and second surface  96 ,  98 , whereby the first surface  96  of the slide head  82  opposes and is attached to the second surface  92  of the slide ring  80 . The central bore  94  rotatably receives the drive shaft  26  such that the drive shaft  26  is not permitted to rotate relative thereto. The slide head  84  is disposed adjacent to the collar  82  and includes a reaction surface  100 , an engagement surface  102 , and a recess  104 . The reaction surface  100  is disposed adjacent the second surface  92  of the slide ring  80  whereby the reaction surface  100  is spaced from the second surface  92  of the slide ring  80  to define an air stream therebetween, as will be discussed further below. The slide head  84  is non-rotatably supported by a bracket  106 , whereby the bracket  106  includes a reaction surface  108 , a channel  110 , and a flange  112 , extending from the channel  110 . The slide head  84  is supported generally between the flange  112  and the reaction surface  108 , and is permitted to translate therein. The slide head  84  is supported by a spring  114  disposed in the channel  110  such that the spring  114  imparts a bias on the slide head  84  such that the slide head  84  is biased toward, but does not contacts the second surface  92  of the slide ring  80 . Spring  114  limits the axial movement of the slide head due to pressure variations. The bracket  106  further supports the slide head  84  through the interaction of an O-ring  116 , whereby the O-ring  116  is disposed between the reaction surface  108  and the recess  104  of the slide head  84 , as best shown in  FIG. 2 . In this manner, the slide head  84  is permitted to translate relative to the bracket  106  through the bias imparted thereon by the spring  114 . The O-ring  116  serves to maintain a seal between the reaction surface  108  and the slide head  84  as the slide head  84  translates relative to the bracket  106 . In this regard, the recess  104  provides a clearance  118  generally between the bracket  106  and the slide head  84  to provide the slide head  84  with the ability to move relative to the bracket  106  while still maintaining contact with the O-ring  116 . The bracket  106  is fixedly supported by the partition wall  64  at the central aperture  120  by the shield  86  in an effort to provide the bracket  106  with the requisite strength required to support the seal  40  and further to prevent fluids from entering the seal  40 . The shield  86  extends from the flange  112  and includes a flange  122  which serves to block an area generally between the slide head  84  and the slide ring  80 . Specifically, as the fluid is caused to flow over the second seal  40 , the flange  122  blocks the flow from entering the second seal  40  and directs the flow to an area generally between the slide head  84  and the slide ring  80 . In this manner, the fluid enters the seal  40  generally between the slide head  84  and the slide ring  80  in a controlled manner, and may be controlled through the interaction of the slide ring  80 , the slide head  84 , and collar  82 . Specifically, because of the rotation of slide ring  80  relative to slide head  84 , an airstream is created flowing into the compressor chamber  34  sealing it against loss of hydrogen coming out of it. 
     To regulate the flow of fluid through the seal  40 , the spring  114  is adjusted to fit the particular application. Because the slide ring  80  is rotating relative to the slide head  84 , precise adjustment of the spring  114 , such that the slide head  84  is maintained in close proximity to the slide ring  80  is required. Maintaining the slide head  84  in close proximity to the second surface  92  of the slide ring  80  is important as this will restrict fluid flow through the seal  40  and will thereby improve the overall effectiveness of the seal. Adjustment of the spring constant, or type of spring used, will vary depending on the application and desired fluid flow through the seal  40 . Specifically, if a small amount of fluid flow is desirable, spring  114  can be utilized so as to get as close to the second surface  92  of the slide ring  80  as possible, while to allow for more fluid to pass through the seal  40 , the spring  114  will be relaxed, thereby increasing the distance between the slide head  84  and slide ring  80 . In the present case, it is desirable to inhibit most, if not all, of the fluid from passing through the seal  40  to ensure that the compressor chamber  34  is sealed from the neutral chamber  16 . However, a slight flow of hydrogen through this seal  40  is properly channeled out of the neutral chamber  16  due to the positive pressure on the back side of seal  42  and the operation of the fan  28  within the neutral chamber  16 . Thus, no hydrogen leakage through the seal  40  is allowed to enter the motor chamber  42 . 
     The seal  40 , as just described, is defined as a gas seal as opposed to a mechanical friction seal, as there is no friction between the slide head  84  and slide ring  80 . It is estimated that as compared to a standard friction-type mechanical seal, the friction work is reduced to less than six percent for the gas sealed seal construction as compared to the standard friction-type seal. Thus, the system of the present invention, while allowing slight flow of hydrogen through the seal  40  greatly reduces the amount of friction work required as compared to a friction-type seal. A hydrogen gas that passes through the seal  40  is properly discharged from the neutral chamber  60  so that it cannot enter the motor chamber  22 . 
     With reference to  FIG. 3 , the construction of the hydrogen blower  10   a  is the same as described above with reference to  FIG. 1  with the exception that the seal  42   a  has been changed to a gas-type seal as described above with respect to the seal  40 . In addition, an additional air outlet  192  is provided in the motor chamber  22  to exhaust a majority of the air that is blown through the motor chamber  22 , while still maintaining a predetermined air pressure on the seal  42   a  to allow a small amount of air leakage through the seal  42   a , as described above with reference to gas seal  40 . With this arrangement, small amounts of air are allowed to leak through seal  42   a  and small amounts of hydrogen are allowed to leak through seal  40 . These small amounts of air and hydrogen are mixed in the neutral chamber  16  and discharged through the outlet passage  60  due to the rotation of the fan  28 . 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scone of the invention.