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Research Papers: Gas Turbines: Turbomachinery

Multidisciplinary Assessment of the Control of the Propellers of a Pusher Geared Open Rotor—Part II: Impact on Fuel Consumption, Engine Weight, Certification Noise, and NOx Emissions

[+] Author and Article Information
Pablo Bellocq

Rotating Machinery Department,
TOTAL S.A.,
Pau Cedex 64018, France
e-mail: pablo.bellocq@total.com

Inaki Garmendia

Mechanical Engineering Department,
University of the Basque Country UPV/EHU,
Plaza de Europa, 1,
San Sebastian 20018, Spain
e-mail: inaki.garmendia@ehu.es

Vishal Sethi

School of Engineering,
Cranfield University,
Bedford MK430AL, UK
e-mail: v.sethi@cranfield.ac.uk

Alexis Patin

Advanced Projects Department,
Turbomeca,
Bordes Cedex 64511, France
e-mail: alexis.patin@turbomeca.fr

Stefano Capodanno

School of Engineering,
Cranfield University,
Bedford MK430AL, UK
e-mail: stefano.capodanno@gmail.com

Fernando Rodriguez Lucas

EA International,
Magallanes 3,
Madrid 28015, Spain
e-mail: frl@empre.es

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 30, 2014; final manuscript received November 7, 2015; published online January 12, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(7), 072603 (Jan 12, 2016) (8 pages) Paper No: GTP-14-1597; doi: 10.1115/1.4032009 History: Received October 30, 2014; Revised November 07, 2015

Due to their high propulsive efficiency, counter-rotating open rotors (CRORs) have the potential to significantly reduce fuel consumption and emissions relative to conventional high bypass ratio turbofans. However, this novel engine architecture presents many design and operational challenges both at engine and aircraft level. The assessment of the impact of the main low-pressure preliminary design and control parameters of CRORs on mission fuel burn, certification noise, and emissions is necessary at preliminary design stages in order to identify optimum design regions. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational, or regulatory constraints. Part I of this two-part publication presents a novel 0D performance model for counter-rotating propellers (CRPs) allowing an independent definition of the design and operation of each of the propellers. In Part II, the novel CRP model is used to create an engine performance model of a geared open rotor (GOR). This engine model is integrated in a multidisciplinary simulation platform which was used to assess the impact of the control of the propellers, on specific fuel consumption (SFC), engine weight, certification noise, and NOx emission, for a GOR with a 10% clipped rear propeller designed for a 160 PAX and 5700 NM aircraft. The main conclusions of the study are: (1) Minimum SFC control schedules were identified for climb, cruise, and descent (high-rotational speeds for high thrust and low-rotational speeds for low thrust), (2) SFC reductions up to 2% in cruise and 23% in descent can be achieved by using the minimum SFC control. However, the relatively high SFC reductions in descent SFC result in ∼3.5% fuel saving for a 500 NM and ∼0.7% fuel saving for a full range mission, (3) at least 2–3 dB noise reductions for both sideline and flyover can be achieved by reducing the rotational speeds of the propellers at a cost of ∼6% increase of landing and takeoff cycle (LTO) NOx and 10 K increase in turbine entry temperature, (4) approach noise can be reduced by at least 2 dB by reducing CRP rotational speeds with an associated reduction of ∼0.6% in LTO NOx, and (5) the control of the CRP at takeoff has a large impact on differential planetary gearbox (DPGB) weight, but it is almost identical in magnitude and opposite to the change in low-pressure turbine (LPT) and CRP weight. Consequently, the control of the CRP at takeoff has a negligible impact in overall engine weight.

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References

Figures

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Fig. 1

CROR architectures [2]

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Fig. 2

GOR engine performance model schematic in PROOSIS

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Fig. 3

Engine noise sources contribution (ENPL)

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Fig. 4

SFC versus Fn and N1 (ISA, 35,000 ft, M0 = 0.75, N1 = −N2)

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Fig. 5

SFC versus N1 and nR (ISA, 35,000 ft, M0 = 0.75, Fn = 17 kN)

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Fig. 6

Sideline and flyover noise versus N1 and nR

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Fig. 7

Takeoff NOx emissions versus N1 and nR

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Fig. 8

DPGB weight versus takeoff N1 and nR

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