Single Stage Radial Inflow Turbine Research Articles

Experimental investigation of a Thermally Driven Heat Pump based on a double Organic Rankine Cycle and an oil-free Compressor-Turbine Unit

This paper presents the experimental investigation of a concept of Thermally Driven Heat Pump (TDHP), based on the coupling of a vapor compression heat pump cycle and an Organic Rankine Cycle (ORC). The studied concept uses a single stage centrifugal compressor directly coupled to a single stage radial inflow turbine. The shaft is rotating on gas bearings, which allows the system to be oil-free. Like most of the other TDHP's, this system has the advantage to work with a variety of fuels or heat sources like wood pellets, natural gas, solar heat, geothermal heat or waste heat. A prototype using R134a as working fluid and with a heating capacity of about 40 kW has been developed. The results of the first tests are presented.

High-speed microfabricated silicon turbomachinery and fluid film bearings

A single-crystal silicon micromachined air turbine supported on gas-lubricated bearings has been operated in a controlled and sustained manner at rotational speeds greater than 1 million revolutions per minute, with mechanical power levels approaching 5 W. The device is formed from a fusion bonded stack of five silicon wafers individually patterned on both sides using deep reactive ion etching (DRIE). It consists of a single stage radial inflow turbine on a 4.2-mm diameter rotor that is supported on externally pressurized hydrostatic journal and thrust bearings. This work presents the design, fabrication, and testing of the first microfabricated rotors to operate at circumferential tip speeds up to 300 m/s, on the order of conventional high performance turbomachinery. Successful operation of this device motivates the use of silicon micromachined high-speed rotating machinery for power microelectromechanical systems (MEMS) applications such as portable energy conversion, micropropulsion, and microfluidic pumping and cooling.

Gas Turbines for Missile Ground Support

HANDLING, testing, and launching of guided missiles require a multitude of services which are external to the missile proper. Specific requirements for such ground support equipment are dictated by the operational concept of the missile system and the detail design of the missile. In general, hydraulic, electric, mechanical, and pneumatic power are needed at the site of operation for erecting and aligning, fueling, calibration, checkout, and launching. The proper selection of the prime movers for such services is of great importance, considering the safety, reliability, quality, and control requirements. In addition, depending on the operational concepts, emphasis may be placed on such items as versatility, transportability, self-sufficiency, and logistics. Considering these, the advantage of using gas turbine prime movers is definitely indicated. The lightweight, compact engines are capable of using a wide variety of fuels and are easy to integrate with the driven components, such as pumps, compressors, and generators. Solar Aircraft Company has designed and is manufacturing a variety of gas turbine driven power units for diverse applications. Solar combines them in complete packages for ground, shipboard, and airborne electric generator sets, space heaters, smoke generators, air bleed power supplies, and pumps. The present production units use as the prime movers the 50-hp Mars and the 500-hp Jupiter engines. The Mars engine weighs approximately 100 lb, which includes the gearbox and the accessories, and its dimensions are 23 in. in height, 17 in. in width, and 23 in. in length. I t develops 50 bhp at a speed of 40,000 rpm, or 42 ppm bleed air with a bleed air pressure of 18.3 psig. Air mass flow, pressure ratio, and fuel consumption are 2.7 pps, 2.5:1, and 2.2 lb/bhp X hr, respectively. The Jupiter engine weighs approximately 990 lb, including gearbox and accessories; its dimensions are 42 in. by 32 in. by 91 in. I t develops up to 520 bhp at 20,000 rpm, or 150 ppm bleed air with a pressure of 45 psig. Air mass flow, pressure ratio, and fuel consumption are 9 pps, 4.6:1, and 0.92 lb/bhp X hr, respectively. Both engines are designed for operation over a temperature range from — 65 F to + 130 F. They operate on all commonly used fuels, such as gasoline, jet engine fuel, diesel fuel, and kerosene. Complete protection against overspeed, overtemperature, and loss of oil pressure is provided. Construction of both engines is simple and compact. The Mars engine employs a single-stage centrifugal compressor, single elbow combustor, and a singlestage radial inflow turbine. Turbine and compressor are mounted back-to-back on the same shaft. The Jupiter engine employs a ten-stage axial compressor, single combustor, and a three-stage axial turbine. For constant speed application, the three stages are coupled together, whereas for variable speed application the third stage of the turbine is not connected to the gas producer section but mounted on a separate power take-off shaft. Both engines have completely automatic electrical start systems, and power is available in less than one minute even at extreme low temperatures. Preheating is not required. The Mars engine is also available with a hand-crank starting system; the Jupiter engine is adaptable for pneumatic or fuel-air starting systems. Standard speed control systems for both engines incorporate a droop-type governor with 5 per cent droop from no load to full load and steady-state speed variation of ± 0 . 5 per cent. The system is adaptable for isochronous governing and parallel operation w^hen used for generator set applications. Other types and sizes of gas turbine prime movers are presently in development to satisfy power requirements different from those of the described units. I t is important that proper and timely consideration be given to the ground support requirements for guided missiles systerns so that optimization of the system be achieved, and an effective research tool or weapon be developed. The gas turbine prime mover should play a more important role in this concept in the future, due to its inherent characteristics and flexibility for integration into such a complex system.