Abstract:
A rotor 20 having several impellers 21 interleaved with a multi-stage stator 30 pumps ambient air through each stage in a path that flows radially outward through impeller vanes 27 against a stator wall 32 where the air is retroverted and directed radially inward through a stator passageway 36 to the next rotor impeller 21. Flow through each stage increases air temperature so that the output air, in addition to being blown forcibly enough to pass through ductwork, is warmed enough to afford space heating.

Description:
BACKGROUND 
     Several air heaters have exploited the fact that air is warmed as it flows turbulently through the blades of a blower or pump. The temperature increase in a single pass of the air through blower blades is usually tiny, however, so that practically useful increases in air temperature have required that the air pass many times through the blower blades. Although this gradually heats the air, it greatly diminishes the ability of the blower to move the air elsewhere. 
     We have found a way of heating air effectively in a multi-stage blower that can also pump air at a flow rate adequate to serve as a space heater. Each stage of our heater is especially effective in heating air and can achieve at least a 10° temperature rise--to require only a few stages for a practically usable temperature increase. Since the air passes only once through each stage, our heater is also effective as a through-flow pump that can distribute heated air through ducts in a building. Our heater heats return air without changing moisture content or causing any odor; and since it has no high temperature region, it is safe and practical in explosive or flammable environments. 
     SUMMARY OF THE INVENTION 
     Our air heater and pump uses a multi-stage rotor and stator in which a series of rotor impellers are interleaved with series of stator passageways. Through-flowing air, pumped radially outward by each rotor impeller, is directed against a stator wall and then retroverted back on a radially inward path. Each stator stage, besides retroverting the discharge air from each rotor impeller, provides a radially walled passageway for guiding inflowing air back to an inlet of the next rotor impeller. The air thus flows in a zigzag path radially outward and inward, increasing the air temperature at each stage, as the air is pumped through the heater. Our invention includes the way the stator stages are stacked and structured relative to rotor impellers and the way these are spaced and interleaved with stator stages. Our heater&#39;s objectives include simplicity, economy, safety, efficiency, and capability of serving both as an air-pumping blower and as a heater that can increase the temperature of the through-flowing air by several tens of degrees. 
    
    
     DRAWINGS 
     FIG. 1 is a partially cross-sectioned, partically schematic, elevational view of a preferred embodiment of our heater; 
     FIG. 2 is a fragmentary and partially cross-sectioned view of preferred rotor and stator stages for the heater of FIG. 1; 
     FIG. 3 is a partially cutaway view of a rotor impeller used in the heater of FIGS. 1 and 2 and taken along the line 3--3 of FIG. 2; 
     FIG. 4 is a diagonal cross-sectional view of the rotor impeller of FIG. 3; 
     FIG. 5 is a partially cutaway view of a stator used in FIGS. 1 and 2 and taken along the line 5--5 of FIG. 2; and 
     FIG. 6 is a partially cutaway side elevational view of the stator of FIG. 5. 
    
    
     DETAILED DESCRIPTION 
     Heater 10, as shown in FIGS. 1 and 2, includes a motor 15 turning a rotor 20 within a stator 30 arranged in a box 11 that is preferably lined with insulation 12 to reduce noise and heat loss. An air inlet 13 admits ambient or return air into box 11, and an outlet duct 14 directs the heated, outflowing air--usually to conventional ductwork. A stand 16 supports stator 30 and motor 15 in the path of inflowing air that keeps motor 15 cool and slightly warms the air as it proceeds to intake 18 around shaft 17 in the initial stator stage 31. 
     Inside of stator stage 31, as shown in FIG. 2, inflowing air encounters the first rotor impeller 21, which pumps the air radially outward. Impeller 21 drives the air at a high velocity from peripheral discharge 22 against wall 32 of stator stage 31, where the air is retroverted radially inward. The considerable turbulent energy involved in forcing air at a high velocity against stator wall 32 and turning the air back for a radially inward flow raises the air temperature at least several degrees. 
     The radially inward flow of the air toward the inlet of the next impeller 21 occurs through passageways 36 between a pair of axially spaced and radially extending stator walls 33 and 34, connected by generally radial vanes 35. These radial passageways 36 through each stator stage 31 lead from the peripheral discharge region 22 of each rotor impeller 21, radially inward to an inlet 23 of a succeeding impeller 21. Stator passageways 36 separate inward-flowing air from the rapidly rotating surfaces of impellers 21, which tend to pump air radially outward. The alternating outward and inward flow of air through each rotor and stator stage repeats as the air passes from inlet 18 to outlet 19. We have found that each stage can increase air temperature by at least 10° so that the six stages shown in FIG. 2 can increase return air temperature by 60° to 80° in a single pass through heater 10. 
     We prefer that each rotor impeller 21 and each stator stage 31 be identical, except for stator inlet 18 and outlet 19. We also prefer that stator stages 31 be stacked together as shown in FIG. 2 for interleaving stator passageways 36 with rotor impellers 21. This allows identical rotor and stator stages to be manufactured economically and stacked together as illustrated for each heater 10. Lack of any high temperature hot spot within the heater allows resin material to be used in its working parts, so that both impellers 21 and stator stages 31 can be injection molded or resin material for low cost fabrication and quiet operation. 
     Air inflow through inlet 18 into the first stator stage 31 can be controlled in various ways, and a simple expedient shown in FIG. 2 is to arrange an air inlet control flange 26a around a lower spacer 26 on shaft 17 to determine the size of the air opening through inlet 18 into the first stator stage 31. Other arrangements, such as aperture plates and cowled inlets, are also possible. 
     We prefer that each rotor 21 be formed of a disk 24 keyed to shaft 17 on which a collar 25 supports a lower spacer 26 and a series of upper spacers 29 positioning each rotor disk 24 axially on shaft 17. Rotor vanes 27 extend generally radially outward between disk 24 and an annular plate 28. There are many other ways that air-pumping vanes 27 can be arranged on an impeller disk 24, and annular plate 28 may not be necessary. Most of the air-pumping work is done by the outer regions of the vanes 27, and these are what drive the pumped air rapidly outward against stator wall 32. 
     Stator stages 31 nest and stack together, as shown in FIG. 2, by providing each stage 31 with a peripheral wall 37 having a diameter large enough to receive the smaller diameter wall 32 of a stacked stator stage 31. Each stator stage 31 also includes a barrier wall 33 extending radially inward from peripheral wall 32 to at least the inlet region 23 of each rotor impeller 21. Annular wall 34 on the opposite side of stator passageway 36 is spaced radially inward from peripheral wall 32 to admit retroverted air into passageway 36. 
     Air discharged from the final rotor impeller 21 impinges on wall 32 of the final stator stage 31 and from there is guided through a preferably convolute outlet 19 leading to output duct 14. Outlet 19 can also be tangential or have other suitable shapes. 
     Experience with different models of our kinetic heater has shown that the size and shape of the inlet and outlet openings affect performance, both in temperature rise and pounds per minute of air throughput. Constricting inflow or outflow tends to increase the temperature rise and decrease the through-flow rate, and opening up the inlet or outlet has the opposite effect. We prefer that outlet 19 be kept open and efficient for effectively delivering heated air, and we prefer adjusting inlet opening 18 to control the air inlet rate for different circumstances, depending on the need for temperature rise or through-flow rate. 
     Performance of our heater can also be varied by changing the number of rotor and stator stages; changing the diameters of the rotor impellers; changing the shape, number, or axial extent of the vanes 27 on the rotor impellers; and changing the axial width of stator passageways 36, which we prefer to keep adequately wide. Different dimensions of rotor impellers can be mixed in a single heater to adjust temperature rise or air through-flow rate. The rotor can also be powered by different sizes of motors or even by different prime movers turning at different speeds to vary performance. Guiding principles are that the energy input is divided between temperature rise and air through-flow rate, opening or easing the air flow path increases the flow rate and reduces the temperature rise, and constricting or impeding the air flow path increases the temperature rise. 
     A space heater according to our invention, using a five horse motor 15 turning at 3400 rpm, maintains a through-flow rate in a range of 10 to 14 pounds per minute with a temperature increase from inlet to outlet of 60° to 80° F. This heater can operate continuously without overheating motor 15 and can produce 12,000 BTU per hour at a thermal efficiency of about 95%. We have attained the same temperature increase and thermal efficiency with a three horse power model producing a smaller flow rate; and of course, larger and smaller models are also possible. Box 11 keeps our noise level reasonably low; and our heater has the advantages of no change in moisture content of the air being heated, no odor production, and lack of any high temperature hot spot.