Very High Speed Hydraulic Turbine Drive

High speed rotating apparatuses are often driven by electric motors or internal combustion engines. In such cases a speed increasing gear box is needed. There is a great need in the engine industry for compact, light weight superchargers utilizing high efficiency drive systems which transmits the power the power from the engine shaft to the supercharger. According to an article at page 27 of the August 1993 issue of Popular Science, Miller cycle engines, developed by Mazda "requires a compact, high-efficiency air compressor-conventional turbochargers and superchargers just can't generate the volume of air required". The article further states, "Mazda teamed with heavy equipment manufacturer Ishikawajima-Harima Heavy Industries Co. to develop a belt driven, screw-type compressor supercharger. The new supercharger is expensive, which is one reason Mazda doesn't plan to use the Miller-cycle engine in small cars. Lean-burn technology makes more sense there . . . "

Turbochargers of many designs are driven by engine exhaust. One such model is Model To 4B 3S supplied by Turbonetics Inc. This unit produces a compressor ratio (output pressure/atmospheric pressure) of 1.52. The various parts of this unit can be purchased separately from Turbonetics as listed in its catalog.

Gear driven and belt driven oil pumps are commercially available in the 10 to 20 HP range for producing oil pressures in the range of 1,000 to 2,500 PSIG at flows of 20 to 40 GPM.

The Applicant has been issued a U.S. patent (U.S. Pat. No.: 5,013,214) for a high speed water driven fan. Disclosed in the specification was a turbine which produced 4 horsepower at 10,000 RPM. The specification referred to and provided guidance for increased horsepower designs and higher RPM's. The hydraulic design of the present invention is based of extensive tests of the Applicant's high speed water turbine driven high velocity fan with water pressure differentials of up to 450 psi and generating 19.6 HP at 14,250 RPM. Relatively low stress levels and low operating temperature of the reference fan turbine wheel has allowed for the 2.07 inch diameter wheel to be made entirely of Delrin type plastic.

It is known that plastic turbines are generally less expensive to produce than metal turbines, but at very high rotating speeds and high temperatures plastic turbines do not have sufficient strength to provide reliable performance. For very small steel turbine wheels, standard milling procedures are not feasible and electro discharge machining is typically utilized which is very expensive. Typical production costs of making a 0.80 inch diameter turbine wheel with 34 blades is on the order of $300. Sintering is another possibility, but its tooling costs and development risks would be very high.

Utilization of high temperature thermoplastics to make very high speed turbine wheels would lower the cost significantly since the blades could be milled with conventional techniques, but the combined effects of high centrifugal stresses and high oil temperatures would cause the plastic to deform and creep with time, especially in the hub area where precision fit between the shaft and the wheel bore is required at all times.

It is known that a significant advantage of superchargers over turbochargers is that the superchargers respond immediately to increased engine power whereas turbochargers tend to lag on acceleration. Superchargers driven by an oversized oil pump can actually anticipate increased demand for engine power by controlling the oil pressure to react with the accelerator. For motor vehicle superchargers high turbine efficiencies, low cost and long life expectancies are all of paramount importance.

The present invention provides a small, compact, relatively low cost, long life and very high speed hydraulic turbine drive. Typical power of this turbine is in the range of 5 to 20 horsepower with operating speeds of 50,000 to 200,000 RPM. The turbine blades are produced at low cost as a part of a thermoplastic turbine wheel and the strength needed for very high centrifugal forces is provided by compressing substantially all of the plastic turbine wheel, except for the blades, within a metal sleeve. A preferred embodiment is driven by a hydraulic pump geared mechanically to a motor vehicle engine and drives a compressor for supercharging the engine.

FIG. 1 is a cross sectional drawing showing a preferred embodiment of the present invention.

FIG. 2 is a drawing showing an exploded view of a prior art turbocharger.

FIGS. 3 and 4 are drawings showing views of the nozzle arrangement of a preferred embodiment of the present invention.

The turbine described in detail herein is designed for use with the compressor and bearing assembly portion of the TO4B turbocharger, sold by Turbonetics Incorporated, 650 Flinn Avenue, Unit 6, Moorpark, Calif. A drawing of this model is shown in FIG. 2. The dashed line in FIG. 2 encircles the parts not used in a preferred embodiment of the present invention. The parts I use are individually available from the Turbonetics catalogs.

The preferred embodiment of the present invention provides a very high speed hydraulic turbine driven supercharger. The supercharger comprises a turbine wheel which achieves the low cost advantage of small plastic turbines with the strength, higher temperature and durability advantages of steel by combining the two materials in a novel fashion. The blades of the turbine wheel are made of high strength thermoplastic material, Polysulfone and it is shrunk fitted within a wheel hub of steel.

Described herein by reference to FIG. 1 is a turbine with a wheel of only 0.665 inch diameter with the capability of generating 9.6 HP at 69,750 RPM, with pressure differentials of 930 psi and having the capability of operating at the fluid temperatures of 150 to 170 degrees Fahrenheit. These fluid temperatures are achievable by cooling the hydraulic fluid with ambient air.

Turbine drive 8 includes plastic turbine wheel 11 on which are machined 28 turbine blades 31 which are an integral part of turbine wheel 11. Except for the protruding turbine blades 31, the plastic turbine wheel 11 is almost entirely contained within the cylindrical bore formed by steel shaft 14 and steel end cap 13. Tubular steel spacer 12 functions to dimensionally limit the amount of squeeze exerted by steel turbine shaft 14, steel end cap 13 and self locking steel fastener 17 which is screwed into turbine shaft 14. The volume contained between the tubular steel spacer 12, the cylindrical bore of the steel turbine shaft 14 and the cylindrical bore of the steel end cap 13 is calculated to provide a relatively low amount of compressive stress within the plastic turbine wheel 11 when assembled and a moderate amount of compressive stress within the plastic turbine wheel 11 when the turbine temperature rises to its operating temperature of approximately 170 degrees F. The torque from the plastic turbine wheel 11 is transmitted into the steel turbine shaft 14 due to friction caused by the compressive loads generated by the plastic turbine wheel 11. As shown in FIG. 1, steel turbine shaft 14 is shrink fitted into compressor shaft 15 so as to form a continuoous supercharger drive shaft. Alternatively, a single solid shaft could also be utilized. At operating speeds of about 70,000 RPM, the plastic wheel is subjected to centrifugal stresses which produce hoop tension. When these tension stresses are combined with the prestressed compressive stresses the overall net stress level is still compressive. Persons skilled in the art can adjust for various levels of net stress by adjusting the length of steel spacer 12 and/or the dimensions of plastic wheel relative to the dimensions of spacer 12 and the inside diameters of the cylindrical spaces in cap 13 and shaft 14. In this preferred embodiment, to OD of the base of the plastic wheel is nominally 8.00 mm and the ID of the shaft and the end cap is nominally 8.00 mm. The length of the spacer 12 is 12.0 mm compared to a 12.02 mm length for the plastic wheel. In this configuration the plastic wheel is precooled by about 50 degrees F. for easy assembly.

Inlet fitting 22 is threaded into turbine housing 21 holding the turbine nozzle body 18 firmly within the turbine housing 21 and providing together with rubber O-Rings 23 and 24 sealed conditions for cavity 32 which is subject to the high oil pressure. O-Ring 26 seals the turbine housing 21 against commercially supplied turbocharger housing 41. Commercially supplied sliding seal ring 16 provides the oil seal between the commercially supplied turbocharger housing 41 and the turbocharger shaft 15. A peripheral clamp 42 provides firm connection between the turbine housing 21 and the commercially supplied turbocharger housing 41.

As indicated in FIGS. 3 and 4, in this embodiment 12 turbine nozzles are drilled at an angle of 15 degrees with the plane of the face of the nozzle body outlet surface. FIG. 3 shows the plan view of the exit portion of the turbine nozzles 50 as viewed in the plane 3--3 in FIG. 4. FIG. 4 shows a section through the nozzle body 18 along the plane 4--4 in FIG. 3 and combines such view with the plane view of turbine blades 19 and turbine wheel 11. High hydrodynamics efficiency of nozzle 50 in attributed to the particular combination of round cross sectioned nozzles 50 and the gradual change in the cross section of the flow area along the centerline axis of the individual nozzles 50. The turbine nozzles 50 are positioned close to each other within the nozzle body 18 so as to produce minimum wakes of low velocity fluid in between the passage areas of nozzles 50 and turbine blades 19. Such wakes are considered to be generally harmful to the turbine hydraulic efficiency. Such nozzle positioning as shown in FIG. 3 and 4 maximizes the percentage of the turbine blades frontal flow area occupied by the high velocity fluid relatively to the frontal flow area occupied by the wakes.

During operation high pressure oil (preferably at about 930 psi) enters the turbine via inlet channel 27. It flows through inlet passages 28 into cavity 32 which supplies the oil flow to the 12 nozzle passages 50 which are contained within turbine nozzle body 18. The oil flow accelerates through nozzle passages 50 converting pressure energy into kinetic energy which is then utilized to provide a driving force to the plastic turbine blades 31. Oil exits from the plastic turbine blades 31 into exit cavity 34 and is discharged at low pressure through exit channel 33.

The hydraulic turbine drive described herein will provide very substantial advantages in cost and performance as compared to prior art turbine drives, especially for high speed turbine drives in the 5 to 25 horsepower range. I provide in the following table design details applicable to three preferred embodiments recommended for use as drives for motor vehicle superchargers.

It should be understood that the specific form of the invention illustrated and described herein is intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. There are many other uses for this turbine drive other than to drive a supercharger. Compressor units other than that of Turbonetics could be used for superchargers. Turbine wheels with diameters as low as 0.350 inch and as large as 1.25 inch could be utilized effectively under the teachings of this invention. The number of turbine blades could be increased or decreased within the range of about 18 to 40. With changes obvious to persons skilled in the art, the unit described above could be driven with other fluids such as water. Nozzle angles as small as 10 degrees and as large as 30 degrees could be used. The base of the plastic wheel could be confined and compressed within a metal containment in many other arrangements other than the one specifically described. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.