Full admission baseline performance was obtained for a 0.4 linear scale of the LF460 lift fan turbine over a range of speeds and pressure ratios without leakage air. These cold-air tests covered a range of speeds from 40 to 140 percent of design equivalent speed and a range of scroll inlet to diffuser exit static pressure ratios from 2.0 to 4.2. Results are presented in terms of specific work, torque, mass flow, efficiency, and total pressure drop.

https://ntrs.nasa.gov/api/citations/19770005057/downloads/19770005057.pdf

Cold-air performance of a tip turbine designed to drive a lift fan. 1: Baseline performance

High thrust and low specific fuel consumption (SFC) are important for vertical takeoff and landing (VTOL) vehicles. An effective way to decrease the SFC is to increase the bypass ratio (BPR) of the propulsion system. The air-driven fan (or fan-in-wing) has a very high bypass ratio and has proved to be successful in VTOL aircrafts. However, the tip turbine that extracts energy for the air-driven fan faces the low-solidity problem and performs inadequately. In this study, we developed a high-reaction method for the aerodynamic design of a tip turbine to solve the low-solidity problem. A typical tip turbine was selected and designed by both conventional and high-reaction methods. Three-dimensional flow fields were numerically simulated through a Reynolds-averaged Navier-Stokes (RANS)-based computational fluid dynamics (CFD) method. The energy extraction rate was proposed to evaluate and display the energy extraction capability of the turbine. The results showed that the high-reaction turbine could solve the low-solidity problem and significantly increase the isentropic efficiency from approximately 80.0% to 85.6% and improve the isentropic work by 71.9% compared with the conventional method (from 10.28 kW/kg to 17.67 kW/kg).

https://www.mdpi.com/1996-1073/12/15/3003/pdf

Numerical Investigations of a Tip Turbine Aerodynamic Design in a Propulsion System for VTOL Vehicles

Partial admission performance was obtained for a 0.4 linear scale version of the LF460 lift fan turbine over a range of speed from 40 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratio from 2.2 to 5.0. The investigation was conducted in two parts, with each part using a different side of the turbine scroll to simulate loss of a gas generator. Each side had an arc of admission of 180. Results are presented in terms of specific work, torque, mass flow, and efficiency.

/pdf/cold-air-performance-of-a-tip-turbine-designed-to-drive-a-1vtaw8121r.pdf

Cold air performance of a tip turbine designed to drive a lift fan. 2: Partial admission

Performance data were obtained experimentally for a 0.4 linear scale version of the LF460 lift fan turbine for a range of scroll inlet total to diffuser exit static pressure ratios at design equivalent speed with simulated fan leakage air. Tests were conducted for full and partial admission operation with three separate combinations of rotor inlet and rotor exit leakage air. Data were compared to the results obtained from previous investigations in which no leakage air was present. Results are presented in terms of mass flow, torque, and efficiency.

/pdf/cold-air-performance-of-a-tip-turbine-designed-to-drive-a-4pwtotz68a.pdf

Cold-air performance of a tip turbine designed to drive a lift fan. 3: Effect of simulated fan leakage on turbine performance

Performance was obtained over a range of speeds and pressure ratios for a 0.4 linear scale version of the LF460 lift fan turbine with the rotor radial tip clearance reduced to about 2.5 percent of the rotor blade height. These tests covered a range of speeds from 60 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratios from 2.6 to 4.2. Results are presented in terms of equivalent mass flow, equivalent torque, equivalent specific work, and efficiency.

/pdf/cold-air-performance-of-a-tip-turbine-designed-to-drive-a-3ysjvbe1af.pdf

G. M. Hotz

Papers

Cold-air performance of a tip turbine designed to drive a lift fan

Cold-air performance of a tip turbine designed to drive a lift fan. 1: Baseline performance

Cold air performance of a tip turbine designed to drive a lift fan. 2: Partial admission

Cold-air performance of a tip turbine designed to drive a lift fan. 3: Effect of simulated fan leakage on turbine performance