Concept description and assessment of the main features of a geared intercooled reversed flow core engine

Intercooled turbofan cycles allow higher overall pressure ratios to be reached which gives rise to improved thermal efficiency. Intercooling also allows core mass flow rate to be reduced which facilitates higher bypass ratios. A new intercooled core concept is proposed in this paper which promises to alleviate limitations identified with previous intercooled turbofan designs. Specifically, these limitations are related to core losses at high overall pressure ratios as well as difficulties with the installation of the intercooler. The main features of the geared intercooled reversed flow core engine are described. These include an intercooled core, a rear-mounted high-pressure spool fitted rearwards of the low-pressure spool as opposed to concentrically as well as a mixed exhaust. In these studies, the geared intercooled reversed flow core engine has been compared with a geared intercooled straight flow core engine with a more conventional core layout. This paper compares the mechanical design of the high-pressure spools and shows how different high-pressure compressor and high-pressure turbine blade heights can affect over-tip leakage losses. In the reversed configuration, the reduction in high-pressure spool mean diameter allows for taller high-pressure compressor and turbine blades to be adopted which reduces over-tip leakage losses. The implication of intercooler sizing and configuration, including the impact of different matrix dimensions, is assessed for the reversed configuration. It was found that a 1-pass intercooler would be more compact although a 2-pass would be less challenging to manufacture. The mixer performance of the reversed configuration was evaluated at different levels of mixing effectiveness. This paper shows that the optimum ratio of total pressure in the mixing plane for the reversed flow core configuration is about 1.02 for a mixing effectiveness of 80%. Lower mixing effectiveness would result in a higher optimum ratio of total pressure in the mixing plane and fan pressure ratio.

[1]  Arthur J. Glassman.  Users manual for updated computer code for axial-flow compressor conceptual design , 1992 .

[2]  Martin Nilsson,et al.  The Lightweight Integration of Intercoolers to the Turbofan Engine , 2011 .

[3]  Konstantinos Kyprianidis,et al.  Assessment of Future Aero-engine Designs With Intercooled and Intercooled Recuperated Cores , 2011 .

[4]  Konstantinos Kyprianidis,et al.  Assessment of the performance potential for a two-pass cross flow intercooler for aero engine applications , 2013 .

[5]  Andrew Rolt,et al.  Assessment of New Aero Engine Core Concepts and Technologies in the EU Framework 6 NEWAC Programme , 2010 .

[6]  T. H. Frost.  Practical Bypass Mixing Systems for Fan Jet Aero Engines , 1966 .

[7]  B. Lakshminarayana.  Methods of Predicting the Tip Clearance Effects in Axial Flow Turbomachinery , 1970 .

[8]  W. N. Barack,et al.  An improved turbine disk design to increase reliability of aircraft jet engines , 1976 .

[9]  Abhijit Guha,et al.  Optimum fan pressure ratio for bypass engines with separate or mixed exhaust streams , 2001 .

[10]  Andrew Rolt,et al.  Minimising Loss in a Heat Exchanger Installation for an Intercooled Turbofan Engine , 2011 .

[11]  B. V. S. S. S. Prasad,et al.  Computational Investigation of Effect of Axial Spacing on Blade Row Interaction in a 1½ Stage Axial Flow Turbine , 2009 .

[12]  Duncan Walker,et al.  Aerodynamic Design of the Core Duct System for an Intercooled Aero Engine , 2011 .

[13]  Dr.-Ing. Ch. Mundt,et al.  Performance improvement of propulsion systems by optimization of the mixing efficiency and pressure loss of forced mixers , 2002 .

[14]  Robert R. Van Nimwegen.  DESIGN FEATURES OF THE GARRETT ATF3 TURBOFAN ENGINE , 1971 .

[15]  Tomas Grönstedt,et al.  Design and Analysis of an Intercooled Turbofan Engine , 2010 .

[16]  V. Sundararajan,et al.  Preliminary Estimation of Engine Gas-Flow-Path Size and Weight , 1998 .

[17]  H. Pearson.  Mixing of Exhaust and By-pass Flow in a By-pass Engine , 1962, The Journal of the Royal Aeronautical Society.

[18]  Andrew Rolt,et al.  Multidisciplinary Analysis of a Geared Fan Intercooled Core Aero-Engine , 2013 .

[19]  Andrew Rolt,et al.  Duct Aerodynamics for Intercooled Aero Gas Turbines: Constraints, Concepts and Design Methodology , 2009 .

[20]  David M. Mathis.  Fundamentals of Turbine Design , 2003 .

[21]  Vishal Sethi,et al.  PROOSIS - A Collaborative Venture for Gas Turbine Performance Simulation using an Object Oriented Programming Schema , 2007 .