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

Abstract

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.

Gradient-like minimization methods for aeroengines diagnosis and control

“…PROOSIS V R is a well-known stateof-the-art tool for advanced simulation of gas turbine engine performances, 33 and provides the TURBO V R library, which includes a complete catalogue of gas turbine components that facilitates the modeling and simulation of virtually any sort of imaginable gas turbine cycle. 34 Both the PROOSIS V R simulation platform and the TURBO V R toolkit have been widely used and extensively validated in studies related to the performances of gas turbine cycles -ranging from the typical current civil turbofan configurations to the most innovative cycle arrangements or even counterrotating open-rotor configurations (see, for instance, Camilleri 35 and Bellocq et al, 36,37 among many others)-which makes the aforementioned tools very suitable for the intended purpose of this research. The complete diagram of the engine being considered for this study is depicted in Figure 1.…”

Preliminary Design Framework for the Power Gearbox in a Contra-Rotating Open Rotor

“…In the early 2000s, the dramatic rise in fuel prices and the urge for cleaner engine technologies rejuvenated the industry's interest in open rotor technology as one potential solution to those problems [38]. In DREAM (valiDation of Radical Engine Architecture systeMs) the performance and mechanical aspects of a DPGB were incorporated to the engine design setup for a geared CROR [4]. The unavailability of a mechanical preliminary design methodology for the transmission system was highlighted and a methodology was proposed to estimate its dimensions and weight based on the preliminary design of the gearset.…”

“…A schematic representation of the resultant differences in the available design space for the transmission system can be seen in Figure 3, based on the design approaches followed in DREAM, as per [4], and DEMOS. The development of a gearbox pre-design tool for aero-engines is reported in [40].…”

“…The need for compact engines has led the designers to introduce speed-reducing transmission systems to avoid excessively-long multistage turbines [4]. Some key challenges of geared engine arrangements are the weight, efficiency, physical size and mechanical integrity of the transmission systems.…”

Analytical Model for the Performance Estimation of Pre-Cooled Pulse Detonation Turbofan Engines

“…To address loss source iii), high bypass ratio geared turbofans are being investigated [3] as well as counter-rotating open rotors [4]. With regards to loss source ii), introducing cooling within the compression system has been a widely adopted approach to enable higher overall pressure ratios (OPRs) for a given turbine entry temperature (TET) [5,6].…”