Some Future Trends in Aero Engine Design for Subsonic Transport Aircraft

Jackson, Anthony

doi:10.1115/1.3446164

Cited by 10 publications

(10 citation statements)

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“…In the present methodology, once the optimum specific thrust is determined from DEC analysis (Section 8), and OPR and isentropic efficiencies (at affordable technology level) are chosen, Fig. 7, Equation (11) and Equation (22) quickly give the optimum values of B, FPR and T M that would minimise sfc. This analytical procedure, therefore, gives hand calculations almost the same power and accuracy as sophisticated computer programs at the initial phase of design.…”

Section: Overall Optimisation Methodologymentioning

confidence: 99%

“…All quantities in Equation 11are non-dimensional numbers. Figure 3 shows graphically the prediction of Equation (11). One interesting feature of Equation 11is that if r\ KE = 1 (ie in the case of ideal energy transfer from the core stream to the bypass stream) the bypass ratio B drops out of the equation.…”

Section: Determination Of the Optimum Fan Pressure Ratio (Fpr) 0pmentioning

confidence: 99%

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Optimisation of aero gas turbine engines

Guha

2001

Aeronaut. j.

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A systematic methodology for the thermodynamic optimisation of civil bypass engines (turbofan or advanced propulsors) is presented, which would be useful for designing air-breathing engines based on “clean-sheet analysis”. The process starts with establishing an optimum specific thrust for the engine based on an economic analysis (installation constraints, noise regulations etc. also need to be considered). The task of the optimisation process is then to find the combination of optimum values of fan pressure ratio, overall pressure ratio, bypass ratio and turbine entry temperature concurrently that maximises overall efficiency at the fixed specific thrust. This procedure is quite different from the usual single-variable parametric performance studies which do not give proper optimum values and may involve large excursion in the value of the specific thrust unacceptable for a particular mission. Additionally, several, simple and explicit, analytical relations are derived here from fundamental principles, which perform well against numerical optimisation performed by a specialist computer program employing iterative and advanced search techniques. The analytical relations accelerate the optimisation process and offer physical insight. Present numerical computations with real gas properties have established new concepts in turbofan optimisation (for example, the existence of an optimum bypass ratio and optimum turbine entry temperature). The question of optimum jet velocity has been addressed. An analytical expression for the optimum jet velocity at a given bypass ratio has been derived which performs well against numerical optimisation results.

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Section: Overall Optimisation Methodologymentioning

confidence: 99%

Section: Determination Of the Optimum Fan Pressure Ratio (Fpr) 0pmentioning

confidence: 99%

Optimisation of aero gas turbine engines

Guha

2001

Aeronaut. j.

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“…While evaluatingthe partial derivativesin Eqs. (5) and (6), B and P m h are assumed constant.Together they specify a constant inlet air ow. Because the speci c thrust is the ratio of net thrust and mass ow rate of air at the inlet, Eq.…”

Section: Separate-stream Bypass Enginesmentioning

confidence: 99%

“…Improvementsin propulsive ef ciency,componentef ciency and cycle ef ciency contribute approximately one-third each to this gain in performance. The publications made by experts from industry (e.g., Jackson, 6 Bennett, 7 Wilde, 8 and Birch 9 ) contain a wealth of experience, information, and calculation results. However, the details of calculation method are not known to the readers.…”

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confidence: 99%

Optimum Fan Pressure Ratio for Bypass Engines with Separate or Mixed Exhaust Streams

Guha

2001

Journal of Propulsion and Power

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The optimum fan pressure ratio is determined both numerically and analytically for separate-stream as well as mixed-stream bypass engines. The results are applicable to civil and military engines. The optimum fan pressure ratio is shown to be predominantly a function of the speci c thrust and a weak function of the bypass ratio. Two simple, explicit equations, one for each type of engine, have been derived that specify the optimum fan pressure ratio. The predictions compare very well against numerical optimization performed by a specialist computer package employing iterative and advanced search techniques and real gas properties. The analytical relations accelerate the optimization process and offer physical insight. It has been shown that the optimum fan pressure ratio achieves the condition V jc /V jh =´K E in a separate-stream engine and the condition V 163 /V 63 ¼´K E in a mixedstream engine. The condition V 163 /V 63 ¼´K E applies even under situations when signi cant departures from the normally assumed condition p 016 /p 06 ¼ 1 can occur. LPT = isentropic ef ciency of the low pressure turbiné NB = isentropic ef ciency of the bypass nozzle Subscript op = optimum value

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“…A similar study focusing on geared and open rotor arrangements as well as heat exchanged cycles is presented by Hirschkron & Neitzel (1976). An interesting discussion on how specific thrust levels were expected to evolve in the mid-70's based on the economic and technological projections of that time period is given by Jackson (1976); the author has also provided an update to that discussion based on current economical and technological projections (Jackson, 2009). Wilde (1978), Young (1979), and Pope (1979) provide a good reference on how the future for civil turbofan engines for medium and long range applications was envisaged in the late 70's.…”

Section: An Evolving Visionmentioning

confidence: 99%