Session: 28-04 Structural/System Design and Dynamics

Paper Number: 102297

102297 - Finite Element Analysis of Apu Mounting (3-2-1) in Aircraft/helicopter Application Using Lumped Mass Modal Analysis 

Introduction

An aircraft and/or helicopter typically includes an auxiliary power unit (APU). The APU is used to supply electrical power to systems and components while the aircraft is parked on the ground, in flight, and during aircraft taxiing or landing. In some applications, the APU also provides the bleed air to the main engine. The APU is generally comprised of a compressor, which is operatively connected to a generator to drive it. The generator produces the electrical power required to drive the systems and components.  The APU is located where it can easily be accessible for maintenance.   In this paper, Mounting of APU is discussed.

In the literature, HVAC compressors are mounted using isolators [1,2,3], whose main purpose is to isolate vibration from compressor to the other components and results in either a reduction of noise or vibration. In addition, APUs are also used on commercial vehicles such as semi-trucks, with the main issues related to the vibration response and acoustic noise emission of a new liquid fueled fuel cell APU (auxiliary power unit) system are discussed and analyzed in the literature [4,5]. In this paper, the vibration concern deals with the design of a two-stage isolation mount system to shield these critical parts from the shock and steady-state dynamics coming through the truck frame during on-road traveling conditions only.

Paper Summary

The finite element method is used to analyze the mounting of the APU. The proposed approach can also account for a rigid support structure.  The following loads are considered:

a)       Vibration Environment [6]

b)       Shock Environment [6]

c)       Operating vibration of APU

d)       Temperature Environment

e)       APU Self-weight load distribution

 

The choice of analysis method depends on the location of the support at gear box and the APU, mounted either three point supports, or four point supports at both component locations using 3-2-1 concept.

The final goal of this paper is to provide the frequencies map based on the different frequencies of excitation which compromise of the above loads in each direction.

References

1.       Fu, W. and Mathuria, P.H., “Vibration Isolator for Single Piston Hermetic Compressors – A Case Study”, NOISE-CON 2008, Dearborn, Michigan, July 28-31.

Mathuria, P.H. and Mezache, M., “Mounting Design of a Compressor for Improving Sound Rating of an Out-door unit”, IMAC-XXVI, Orlando, FL, Feb 4-7, 2008.

Mathuria, P.H. and Mezache, M., “Transmission Experimental Investigation of Sound Pressure Levels Variation during Modulation of a Compressor in a Unit - Case Study”, 18^th International Compressor Engineering Conference and 11^th International Refrigeration and Air-conditioning conference at Purdue, Lafayette, IN, 2006.

4.       Mathuria, P.H., T.C. Lim, W.S. Shepard Jr., S.R. Bell, M. Venturi, H.H. Dobbs and E. Kallio, “Vibration and Shock Considerations in the Design of a Truck-mounted Fuel Cell APU System,” Journal of Commercial Vehicles, 111(2), pp. 579–588, 2002.

5.       Mathuria, P.H., Lim, T.C, Shepard, W.S., Bell, S., and Venturi, M., Vibration and Shock Considerations in the Design of a Truck-mounted Fuel Cell APU System, 2002 SAE International Truck & Bus Meeting & Exhibition, Detroit, November 18-20, 2002.

MIL-STD-810H, DEPARTMENT OF DEFENSE TEST METHOD STANDARD: ENVIRONMENTAL ENGINEERING CONSIDERATIONS AND LABORATORY TESTS, Jan 31 2019.

Presenting Author: Parag H. Mathuria Pratt and Whitney

Presenting Author Biography: Parag Mathuria is Rotodynamics Practitioner at Pratt and Whitney since 2016. He has accumulated extensive experience in 23+ years in the field of Mechanical engineering specialized in vibration. He earned Bachelor and Master degree in Mechanical engineering from Shivaji University, India and PHD in Mechanical Engineering from IIT Bombay. He has published 15+ Journal and conference papers in the area of sound and vibration and two patents. His most recent endeavors have been to perform the rotodynamic analysis in APU, Aero-engine and Rigs using experimental and analytical tools.

Authors:

Gregory Savela Pratt and Whitney
Parag H. Mathuria Pratt and Whitney
James Taubler Pratt and Whitney
Daniel Belotto Pratt and Whitney
James Masloski Pratt and Whitney