2003/2004

AIAA Foundation

Undergraduate Team Engine Design Competition

I. RULES

1. All groups of 3 to 10 undergraduate AIAA branch or at-large Student Members are eligible and encouraged to participate.

2. Six copies of the design will be submitted; each must bear the signatures, names, and student numbers of the project leader and the AIAA Student Members who are participating. Designs that are submitted must be the work of the students, but guidance may come from the Faculty Advisor and should be accurately referenced and acknowledged.

3. Design projects that are used as part of organized classroom requirement are eligible and encouraged for competition.

4. The prizes shall be: First place-$2,500; Second place-$1,500; Third place-$1,000. Certificates will be presented to members of the winning design team for display at their university and a certificate will also be presented to each team member and the faculty project advisor. One representative from the first place design team will be expected to present a summary design paper at an AIAA Conference in 2004. The AIAA Foundation will defray reasonable airfare and lodging for the team representative.

5. More than one design may be submitted from students at any one school. Projects should be no more than 100 double-spaced typewritten pages and typeset should be no smaller than 10pt Times (including graphs, drawings, photographs, and appendix) on 8.5” x 11.0” paper. Up to five of the 100 pages may be foldouts (11” x 22” max).

6. If a design group withdraws its project from the competition, the team chairman must notify the AIAA National Office immediately!

II. SCHEDULE AND ACTIVITY SEQUENCES

Significant activities, dates, and addresses for submission of proposal and related materials are as follows:

A. Letter of Intent — 15 March 2004

B. Receipt of Proposal — 4 June 2004

C. Announcement of Winners — August 2004

Groups intending to submit a proposal must submit a Letter of Intent (Item A), with a maximum length of one page to be received with the attached form on or before the date specified above, at the following address:

Mr. Stephen Brock

AIAA Student Programs

1801 Alexander Bell Drive, Suite 500

Reston, VA 20191-4344

The finished proposal must be submitted (postmarked) to the same address on or before the date specified for the Receipt of Proposal (Item B).

III. PROPOSAL REQUIREMENTS

The technical proposal is the most important factor in the award of a contract. It should be specific and complete. While it is understood that all of the technical factors cannot be included in advance, the following should be included and keyed accordingly:

1. Demonstrate a thorough understanding of the Request for Proposal (RFP) requirements.

2. Describe the proposed technical approaches to comply with each of the requirements specified in the RFP, including phasing of tasks. Legibility, clarity, and completeness of the technical approach are primary factors in evaluation of the proposals.

3. Particular emphasis should be directed at identification of critical, technical problem areas. Descriptions, sketches, drawings, systems analysis, method of attack, and discussions of new techniques should be presented in sufficient detail to permit engineering evaluation of the proposal. Exceptions to proposed technical requirements should be identified and explained.

4. Include tradeoff studies performed to arrive at the proposed design concept.

5. Provide a description of automated design tools used to develop the design.

IV. BASIS FOR JUDGING

1. Technical Content (35 points)

This concerns the correctness of theory, validity of reasoning used, apparent understanding and grasp of the subject, etc. Are all major factors considered and a reasonably accurate evaluation of these factors presented?

2. Organization and Presentation (20 points)

The description of the design as an instrument of communication is a strong factor on judging. Organization of written design, clarity, and inclusion of pertinent information are major factors.

3. Originality (20 points)

The design proposal should avoid standard textbook information, and should show the independence of thinking or a fresh approach to the project. Does the method and treatment of the problem show imagination? Does the method show an adaptation or creation of automated design tools?

4. Practical Application and Feasibility (25 points)

The proposal should present conclusions or recommendations that are feasible and practical, and not merely lead the evaluators into further difficult or non-solvable problems. Is the project realistic from a cost standpoint? Does the presentation include environmental impact studies (where applicable) and analysis of the function of the design in or for society?

AIAA Foundation Student Design Competition 2004

Undergraduate Team – Engine

Propulsion System for a Supersonic Business Jet

- Request for Proposal -

Air-Breathing Propulsion Technical Committee

July 2003

Abstract

Proposals are requested for design of the propulsion system for a Supersonic Business Jet for entry into service in 2010. The aircraft will carry a total of 8 passengers & crew. It will be powered by two engines and will have an overall range of 4,000 nautical miles. It will cruise at a Mach number of 2.0 and an altitude of 50,000 feet. Thrust requirements have been established from an initial mission analysis and are included in the RFP. It may be assumed that these will not change. The primary selection criteria for the engines are specific fuel consumption, acquisition & maintenance costs and weight, although noise at take-off and emissions are also of concern. A set of design guidelines consistent with anticipated levels of engine technology is provided. Component performance maps are also provided but their use is optional.

Dr. Ian Halliwell - AIAA Air Breathing Propulsion Technical Committee

Modern Technologies Corporation

Tel: 440 243 8488

e-mail: ihalliwell_mtc@crusolutions.com

Contents

1. Introduction

2. SBJ Specification

3. The Mission

4. The Airplane

5. Engine Design

6. Design Constraints & Guidelines

7. Competition Rules & Expectations

References

Attachments

A. Gross Thrust Requirements over the Aircraft Mission

B. Component Performance Maps

C. Engine Design Limits

D. Fans & Compressors: Tip Speed – Pressure Ratio Correlation

E. Sideline Noise vs. Jet Velocity for an Untreated Conical Nozzle

1. Introduction

The high end of commercial travel is eroding from the large commercial carriers and is being transferred to the business jet market. Consequently this market segment has seen dramatic growth in recent years (Reference 1). The projected cost of a Supersonic Business Jet is no longer very different from the acquisition cost of today’s high-end subsonic equivalent. The commercial argument for the design of the SBJ is quite convincing in itself, but additional incentive is supplied by other potential military applications and the delivery of special time-critical payloads.

Figure 1. The Range of the Supersonic Business Jet

The objective of this competition is to generate conceptual designs of a propulsion system that would power a supersonic business jet with minimum impact on the environment. Reduced noise and emissions pose important challenges, driven by environmental legislation, but these are not the only criteria used in the selection of a final engine design. A level of technology commensurate with entry-into-service in 2010 should be used to design a feasible system.

The selection criteria for a supersonic business jet are:

Ø Specific fuel consumption

Ø Acquisition & maintenance costs

Ø Weight

2. SBJ Specification

Proposals are requested for design of the propulsion system for a Supersonic Business Jet. The engine requirements and relevant background are as follows.

• The aircraft will carry a total of 8 passengers & crew.

• It will be powered by two engines.

• It will have an overall range of 4,000 nautical miles.

• It will cruise at a Mach number of 2.0 at an altitude of 50,000 feet.

• The mission profile is shown in Figure 2.

Figure 2. The Supersonic Business Jet Mission

3. The Mission

The SBJ mission profile is shown in Figure 2 and consists of

• standard sea level takeoff

• climb to cruise altitude

• cruise at constant speed at the optimum altitude for the best altitude/Mach number combination

• descent

• landing.

The minimum cruise altitude is 50,000 ft with a 70,000 ft maximum limit. Typically the airplane begins its cruise phase at an altitude slightly higher than the minimum and climbs 6,000 feet or more in order to seek an optimal altitude as fuel is consumed and weight is reduced.

4. The Airplane

Figure 3. Conceptual Supersonic Business Jet used in Mission Analysis

The initial mission analysis has already been completed on a baseline engine/airframe combination using the NASA Glenn Flight Optimization System (FLOPS) code with the Numerical Propulsion System Simulation (NPSS) program generating the engine cycle & performance data. The aircraft used for the analysis is a conceptual design of a supersonic business jet with a total of 8 occupants (passengers & crew), powered by two engines. The aircraft length is fixed at 132.5 feet; the wingspan is 55feet with a wing area of 1560 sq feet; the maximum cabin width is 6.7 feet; the wing aspect ratio is 1.94 with 68° sweep and a thickness-to-chord ratio of 0.0288. The mission analysis code iterated on the fuel load to achieve minimum gross take off weight while meeting the mission goals, namely - an overall range of 4,000 nautical miles, a cruise Mach number of 2.0 at an altitude of 50,000 feet, with the mission profile as is shown in Figure 2. The engines were scaled to meet the aircraft requirements within the following additional constraints.

• Maximum field length of 7,000 ft. for both takeoff and landing

• Maximum approach velocity of 140 knots

• Minimum potential rate of climb of 100 ft/min

• Minimum thrust margin of 0.1. (This is accounted for in Attachment A along with installation effects. It may be assumed that installation effects do not change within the current engine study)

5. Engine Design

A mission analysis has already been carried out, based on data given in the previous three sections. As a result, Attachment A contains a table of values of gross thrust that each of the two engines must generate at each segment of the mission. The corresponding Mach numbers and altitudes are also listed. The mission profile begins at brake release (Mach number = 0.0, altitude = 0.0 feet) and continues through the sideline noise measurement point at take-off (Mach number = 0.32, altitude = 689 feet). Altitude and Mach number continue to increase until the cruise conditions (Mach number = 2.0, altitude = 50,000 feet) are reached. Note that this data has been selected from a much more extensive mission matrix as being reasonably representative of actual flight conditions. This information has been generated using the NASA Glenn NPSS cycle code, based on a “datum” engine configuration together with the airframe characteristics alluded to above. The total weight of the 2 datum engines is 18,288 lbm and this figure is consistent with the data shown in the table superimposed on the mission profile Figure 2. Clearly the aircraft thrust requirements remain the same regardless of the engine type, if it is assumed there are no significant changes in engine size, weight and installation effects – and this assumption should be made for the purposes of this engine design exercise!

Each design team should select critical mission point(s) at which to design their candidate engines and justify their selection(s) of design point(s). Not all mission segments are critical but it is necessary, nevertheless, that the engines are capable of completing the mission.

No additional analysis of the airframe characteristics is required – this is an engine design study. However, should a relevant issue arise as a result of the engine design exercise, it should be recognized and addressed qualitatively.

Different engine types should be considered and appropriate thermodynamic cycle models should be generated. For each configuration a design matrix should be determined, based on a limited number of combinations of the major design variables. Trade studies should then be carried out in order to select an optimum solution within each engine type. Each design team should apply the Figures of Merit, to determine their final design selection for the SBJ engines.

6. Design Constraints & Guidelines

Attachment B contains component performance maps. These will enable initial values of component efficiencies to be estimated at the chosen design points and along the subsequent operating lines. Use of these is optional. As the component designs evolve, performance changes may well occur and simple scaling of the maps should reflect such changes. The scaling methods should be described.

• Inlet. A half-round, external compression inlet is recommended. Its general features are shown in the sketch below.

A map of pressure recovery characteristics for this type of inlet is given in Figure B1 as a function of freestream Mach number and the area ratio A₀/A_c, where

A₀ = A_0I – A_0BLD – A0_bp

A_0I = area of free streamtube of air entering the inlet

A_0BLD = area of free streamtube of bleed air entering the inlet

A₁ = inlet capture area.

Assume 3% spillage and 3% bleed. For simplicity, it may also be assumed that installation losses are accounted for in the thrust values in Attachment A. Further details and possible alternatives may be found in Reference 3.

• Fan & HP Compressor. The fan and compressor performance maps in Figures B2 & B3 are presented in standard format. It may be worth noting, however, that the “R-lines” are merely a convenient means of locating points on the map in conjunction with the speed lines.

• Nozzle. It is recommended that an axisymmetric, convergent-divergent nozzle be used. The internal performance is represented by the gross thrust coefficient, C_FG. This is shown in Figure B8 as a function of the nozzle pressure ratio (P_t8/P₀) and nozzle throat-to-exit area ratio (A₈/A₉). While it is acknowledged that the nozzle boat-tail angle will affect the installation losses, it may be assumed for simplicity that the effects are negligible and are accommodated within the thrust values quoted in Attachment A. Further details and alternatives may be found in Reference 3.

The new engines should be designed to a consistent set of limits and guidelines that correspond to an entry into service of 2010. A number of these are listed in Attachment C. It should be noted that the use of these extremes is not mandatory! Attachment D is a correlation that indicates an empirical relationship between blade tip speeds in fans & compressors and the pressure ratio generated in a corresponding first stage. This may be used to assist with some initial design choices.

Environmental legislation (FAR36 Stage 3 et seq.) dictates that sideline noise at take-off should not exceed 92 EPNdB. Attachment E, from Reference 2, indicates estimates of sideline noise at take-off for a typical supersonic business jet as a function of the jet velocity from an untreated circular nozzle. It should be noted that sideline noise is measured with the aircraft at an altitude of 689 feet and a Mach number of 0.32. (This condition is included in the thrust table in Attachment A.) The 92 EPNdB limit is superimposed on the chart. In the event that an engine design fails to meet this criterion, appropriate modifications must be made to the nozzle so that it produces the necessary noise suppression.

There are also legislative issues to be addressed for emissions. NO_x at both cruise and take-off & landing is to be minimized in addition to CO₂ and unburned hydrocarbons. In addition to the application of sophisticated advanced combustor technology, not expected to be available to student design teams, this general problem can be addressed simply by minimizing the fuel burn.

The final engine features should include the following:

· Customer bleed air = 0.5 lbm/s from compressor delivery

· Power off-take from HP spool = 75 hp

· Maximum tip diameter = 36 inches

7. Competition Rules & Expectations

The existing rules and guidelines for the AIAA Foundation Student Design Competition should be observed. In addition, the following specific suggestions are offered for the Engine Design Competition.

It is not expected that student teams produce design solutions of industrial quality, however it is hoped that attention will be paid to the practical difficulties encountered in a real-world design situation and that these will be recognized and acknowledged. If such difficulties can be resolved quantitatively, appropriate credit will be given. If suitable design tools and/or knowledge are not available, then a qualitative description of an approach to address the issues is quite acceptable.

In a preliminary engine design the following features must be provided:

· An engine configuration with a plot of the flowpath that shows how the major components fit together, with emphasis on operability at different mission points.

· A clear demonstration of design feasibility, with attention having been paid to technology limits.

· Stage counts.

· Blade and vane counts.

· Spanwise distributions of flow properties with appropriate consideration to radial equilibrium.

· Estimates of component performance and overall engine performance.

· In preliminary design, trends are more important than absolute values. This is particularly relevant when it comes to engine weight and costs. We are looking for an optimum solution selected from a matrix of possible candidates.

It is intended that a volunteer team of experienced engine designers will provide technical assistance. These will be from the AIAA Air Breathing Technical Committee, the NASA Glenn Research Center and industry. E-mail addresses and/or telephone numbers will be provided to student teams who officially enter the competition.

References

1. “The Business Case for Higher Speed”

Richard Aboulafia.

Aerospace America. AIAA. July 2001.

2. “Noise Suppression Nozzles for a Supersonic Business Jet”

James R. Stone, Eugene A. Krejsa, Ian Halliwell & Bruce J. Clark.

AIAA-2000-3194.

36^th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Huntsville, AL. 2000.

3. “A Computer Code for Estimating Installed Performance of Aircraft Gas Turbine

Engines. Vol. III – Library of Inlet/Nozzle Configurations & Performance Maps”

NASA CR 159693.

Edward J. Kowalski & Robert A. Atkins Jr. The Boeing Company. December 1979.

Suggested Reading

1. “Gas Turbine Theory”

H. Cohen, G.F.C Rogers & H.I.H Saravanamuttoo.

John Wiley & Sons. 3^rd Edition 1987 et seq.

2. “Aircraft Engine Design”

J.D. Mattingly, W. Heiser & D.H. Daley.

AIAA Education Series. 2^nd Edition 2002.

3. “Civil Jet Aircraft Design”

L.R. Jenkinson, P. Simpkin & D. Rhodes.

AIAA Education Series. !999.

4. “Jet Propulsion”

N. Cumpsty.

Cambridge University Press. 2000.

Attachment A. Gross Thrust Requirements over the Aircraft Mission

Case No.	Mach Number	Altitude (ft)	Gross Thrust (lbf)
1.	0.0	0.0	22,380
2.	0.32	689	20,120
3.	0.4	12,400	12,970
4.	0.6	18,600	10,760
5.	0.8	24,800	9,338
6.	1.0	31,000	8,495
7.	1.2	37,200	7,890
8.	1.4	43,400	7,333
9.	1.6	49,600	6,390
10.	2.0	50,000	8,498

Attachment B. Component Performance Maps

Attachment C. Engine Design Limits

Parameter	Design Limit
Fan
Minimum inlet radius ratio (rhub/rtip)	0.37
Maximum specific flow	42.0 lbm/ft^2
Maximum tip speed	1800 ft/s
Minimum stall margin	20 %
HP Compressor
Maximum compressor delivery temperature ,T3	1250 °F
Maximum tip speed	1600 ft/s
Maximum exit radius ratio (rhub/rtip)	0.935
Minimum stall margin	15 %
HP Turbine
Maximum temperature at first rotor leading edge,T41	2900 °F
Maximum stage loading coefficient (y)1	1.2
Maximum blade hub turning angle (Db)	134 °
Maximum relative exit Mach number	1.2
Minimum stage reaction at hub	15 %
Maximum AN^2 at exit	50 ´ 10^9
LP Turbine
Maximum stage loading coefficient (y)1	0.9
Maximum absolute exit Mach number	0.6
Maximum relative exit Mach number	1.0
Maximum mean exit swirl angle	30 °
Maximum AN^2 at exit	40 ´ 10^9
Minimum stage reaction at hub	15 %
Minimum exit radius ratio (rhub/rtip)	0.6

Attachment D. Fans & Compressors: Tip Speed – Pressure Ratio Correlation

Attachment E. Sideline Noise vs. Jet Velocity for an Untreated Conical Nozzle

92 EPNdB limit

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1 y = Dh/2U_m²

1 y = Dh/2U_m²