Influence of Alternative Engine Concepts on LCTR2 Sizing and Mission Profile

Abstract

The Large Civil Tiltrotor (LCTR) was developed as part of the NASA Heavy Lift Rotorcraft Systems Investigation in order to establish a consistent basis for evaluating the benefits of advanced technology for large tiltrotors. The concept has since evolved into the second-generation LCTR2, designed to carry 90 passengers for 1,000 nm at 300 knots, with vertical takeoff and landing. This paper examines the impact of advanced propulsion system concepts on LCTR2 sizing. Two concepts were studied: an advanced, single-speed engine with a conventional power turbine layout (Advanced Conventional Engine, or ACE), and a variable-speed power turbine engine (VSPT). The ACE is the lighter engine, but requires a multi-speed (shifting) gearbox, whereas the VSPT uses a lighter, fixed-ratio gearbox. The NASA Design and Analysis of Rotorcraft (NDARC) design code was used to study the trades between rotor and engine efficiency and weight. Rotor performance was determined by Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II), and engine performance was estimated with the Numerical Propulsion System Simulation (NPSS). Design trades for the ACE vs. VSPT are presented in terms of vehicle weight empty for variations in mission altitude and range; the effect of different One Engine Inoperative (OEI) criteria are also examined. Because of its strong effect on gearbox weight and on both rotor and engine efficiency, rotor speed was chosen as the reference design variable for comparing design trades. The two propulsion concepts had nearly identical vehicle weights and mission fuel consumption, and their relative advantages varied little with cruise altitude, mission range, or OEI criteria; high cruise altitude and low cruise tip speed were beneficial for both concepts.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 2012
Accession Number
ADA563393

Entities

People

  • C. W. Acree Jr.
  • Christopher A. Snyder

Organizations

  • National Aeronautics and Space Administration

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Aerodynamics
  • Aircraft Equipment
  • Aircrafts
  • Airframes
  • Altitude
  • Efficiency
  • Fuel Consumption
  • Gas Turbines
  • Propulsion Systems
  • Rotary Wing Aircraft
  • Tilt Rotor Aircraft
  • Tilt Wing Aircraft
  • Turbine Components
  • Turbines
  • Turbomachinery
  • Vehicles
  • Vertical Takeoff Aircraft

Readers

  • Aerospace Engineering
  • Aerospace Propulsion Engineering.
  • Maritime Combat Support and Expeditionary Logistics.