Identifying Optimal Fan Compressor Pressure Ratios for the Mixed-Stream Turbofan Engine

Millhouse, Paul T.; Kramer, Stuart; King, Paul I.; Mykytka, Edward F.

doi:10.2514/2.5534

Cited by 12 publications

(4 citation statements)

References 4 publications

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“…P16/ P6 was selected as unity since the study found it to be optimum. 3,4 In the mixer, conservation of mass, momentum and energy is performed to obtain the mixed properties and hence the thrust. The mixer calculation should be similar to the one in the isolated MATLAB model 2 described later.…”

Section: Mixed Exhaust Configurationmentioning

confidence: 99%

Aerothermodynamic Benefits of Mixed Exhaust Turbofans

Khalid¹

2017

FMRIJ

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Section: Mixed Exhaust Configurationmentioning

confidence: 99%

Aerothermodynamic Benefits of Mixed Exhaust Turbofans

Khalid¹

2017

FMRIJ

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“…Low bypass ratio mixed flow turbofan engines used for military applications differ considerably compared to high bypass ratio turbofan engines with respect to engine performance, control constraints, the more complex mission definition and the use of afterburner. Recent research on low bypass ratio mixed flow turbofan engines has focused on areas such as cycle parameter optimization [20][21][22] and use of bypass air for cooling purposes [23]. It is remarkable that despite the continuously growing power demand from advanced radars, electrical actuation and mission systems [2], up until now very little work has been devoted to the field of power extraction and its relation to the performance of the propulsion system.…”

Section: Introductionmentioning

confidence: 99%

Design Considerations of Low Bypass Ratio Mixed Flow Turbofan Engines with Large Power Extraction

Rosell¹,

Grönstedt

2022

Fluids

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The possibility of extracting large amounts of electrical power from turbofan engines is becoming increasingly desirable from an aircraft perspective. The power consumption of a future fighter aircraft is expected to be much higher than today’s fighter aircraft. Previous work in this area has concentrated on the study of power extraction for high bypass ratio engines. This motivates a thorough investigation of the potential and limitations with regards to performance of a low bypass ratio mixed flow turbofan engine. A low bypass ratio mixed flow turbofan engine was modeled, and key parts of a fighter mission were simulated. The investigation shows how power extraction from the high-pressure turbine affects performance of a military engine in different parts of a mission within the flight envelope. An important conclusion from the analysis is that large amounts of power can be extracted from the turbofan engine at high power settings without causing too much penalty on thrust and specific fuel consumption, if specific operating conditions are fulfilled. If the engine is operating (i) at, or near its maximum overall pressure ratio but (ii) further away from its maximum turbine inlet temperature limit, the detrimental effect of power extraction on engine thrust and thrust specific fuel consumption will be limited. On the other hand, if the engine is already operating at its maximum turbine inlet temperature, power extraction from the high-pressure shaft will result in a considerable thrust reduction. The results presented will support the analysis and interpretation of fighter mission optimization and cycle design for future fighter engines aimed for large power extraction. The results are also important with regards to aircraft design, or more specifically, in deciding on the best energy source for power consumers of the aircraft.

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“…For civil engines, particularlyfor medium to long range aircrafts, the FPR op can be calculated under cruise conditions. For military engines, optimization may be mission speci c. However, Millhouse et al 1 have shown that, although the most fuel-ef cient values of such parameters as bypass ratio and OPR depend on the integrated effects of the various ight altitudes, Mach numbers, and thrust required throughout the mission, it is possible to locate heuristically the most ef cient FPR to complement other engine parameters independent of the mission. Thus, the relations derived in this paper can be used in the design of both civil and military engines.…”

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confidence: 99%

“…However, the value of the ratio p 016 =p 06 rises under off-designconditions:If the value of this ratio used at the design point is greater than one, serious mixing losses may result at off-design operations.Therefore, it is prudent to choose the value of p 016 =p 06 between 0.95 and 1 at the design point even if it is slightly suboptimalat that particularoperatingpoint. Numerical calculations of Millhouse et al1 show that if the condition p 016 =p 06 ¼ 1 is used…”

mentioning

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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Identifying Optimal Fan Compressor Pressure Ratios for the Mixed-Stream Turbofan Engine

Cited by 12 publications

References 4 publications

Aerothermodynamic Benefits of Mixed Exhaust Turbofans

Aerothermodynamic Benefits of Mixed Exhaust Turbofans

Design Considerations of Low Bypass Ratio Mixed Flow Turbofan Engines with Large Power Extraction

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

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