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

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Vishal Sethi ◽  
Alexis Patin ◽  
Stefano Capodanno ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Full Range ◽  
Low Pressure ◽  
Performance Model ◽  
Preliminary Design ◽  
Fuel Saving ◽  
Low Thrust ◽  
Regulatory Constraints ◽  
Open Rotor ◽  
The Impact

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.

Advanced 0-D Performance Modelling of Counter Rotating Propellers for Multi-Disciplinary Preliminary Design Assessments of Open Rotors

2014 ◽  
Author(s):  
Pablo Bellocq ◽  
Vishal Sethi ◽  
Stefano Capodanno ◽  
Alexis Patin ◽  
Fernando Rodriguez Lucas
Keyword(s):  
Fuel Consumption ◽  
Low Pressure ◽  
Performance Model ◽  
Preliminary Design ◽  
Performance Modelling ◽  
Performance Point ◽  
Regulatory Constraints ◽  
And Control ◽  
The Impact ◽  
A Performance

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. The required preliminary design simulation tools should ideally be 0-D or 1-D (for computational purposes) and should capture the impact of the independent variation of the main low pressure system design and control variables such as: the number of blades, diameter and rotational speed of each propeller, the spacing between the propellers and the torque ratio of the gearbox or the counter rotating turbine amongst others. From a performance point of view, counter rotating propellers have historically been modelled as single propellers. Such a performance model does not provide the required flexibility for a detailed design and control study. This paper presents a novel 0-D performance model for Counter Rotating Propellers (CRPs) based on the classical low speed performance model for individual propellers and the interactions between them. This model also incorporates a compressibility correction which is applied to both propellers. The proposed model is verified with publicly available wind tunnel test data from NASA. The novel 0-D counter rotating propeller performance model is used to produce a performance model of a geared Open Rotor engine with a 10% clipped propeller. This engine model is first used to study the impact of the control of the propellers on the cruise fuel consumption. Subsequently, the engine performance model is integrated in a multi-disciplinary simulation platform to study the impact of the control of the propellers on the certification noise. The results of this case study show that 1–2% SFC savings at cruise are possible and an optimal control schedule is identified. It is also concluded that significant certification noise reductions are possible through an adequate control of the rotational speeds of the propellers.

Multidisciplinary Assessment of the Control of the Propellers of a Pusher Geared Open Rotor—Part I: Zero-Dimensional Performance Model for Counter-Rotating Propellers

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Vishal Sethi ◽  
Alexis Patin ◽  
Stefano Capodanno ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Fuel Consumption ◽  
Test Data ◽  
Wind Tunnel Test ◽  
Performance Model ◽  
Preliminary Design ◽  
Open Rotor ◽  
And Control ◽  
The Impact ◽  
A Performance

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. The required preliminary design simulation tools should ideally be 0D or 1D (for computational purposes) and should capture the impact of the independent variation of the main low-pressure system design and control variables, such as the number of blades, diameter and rotational speed of each propeller, the spacing between the propellers, and the torque ratio (TR) of the gearbox or the counter-rotating turbine (CRT), among others. From a performance point of view, counter-rotating propellers (CRPs) have historically been modeled as single propellers. Such a performance model does not provide the required flexibility for a detailed design and control study. Part I of this two-part publication presents a novel 0D performance model for CRPs allowing an independent definition of the design and operation of each of the propellers. It is based on the classical low-speed performance model for individual propellers, the interactions between them, and a compressibility correction which is applied to both propellers. The proposed model was verified with publicly available wind tunnel test data from NASA and was judged to be suitable for preliminary design studies of geared and direct drive open rotors. The model has to be further verified with high-speed wind tunnel test data of highly loaded propellers, which was not found in the public domain. In Part II, the novel CRP model is used to produce a performance model of a geared open rotor (GOR) engine with a 10% clipped propeller designed for a 160 PAX and 5700 NM aircraft. This engine model is first used to study the impact of the control of the propellers on the engine specific fuel consumption (SFC). Subsequently, it was integrated in a multidisciplinary simulation platform to study the impact of the control of the propellers on engine weight, certification noise, and NOx emission.

Preliminary Design Assessments of Pusher Geared Counter-Rotating Open Rotors: Part II — Impact of Low Pressure System Design on Mission Fuel Burn, Certification Noise and Emissions

2015 ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Vishal Sethi
Keyword(s):  
System Design ◽  
Rotational Speed ◽  
Low Pressure ◽  
Design Parameters ◽  
Preliminary Design ◽  
Pressure System ◽  
Regulatory Constraints ◽  
Fuel Burn ◽  
Low Pressure System ◽  
The Impact

In this 2-part publication, the impact of the main low pressure system parameters of a counter rotating Geared Open Rotor (GOR) on mission fuel burn, certification noise and emissions is presented for a 160 PAX medium haul class aircraft. Due to their high propulsive efficiency, GORs 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 parameters of GORs 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 describes the main low pressure (LP) system design choices for a GOR as well as the preliminary design philosophy and simulation framework developed for the assessments. Part II presents the assessment studies. A fixed reference aircraft and mission were used to evaluate the different GOR engine designs. The results are presented in the form of 1-D or 2-D plots in which one or two design parameters are varied at the same time. The changes in mission fuel burn, certification noise and emissions are expressed as differences relative to a baseline design, due to the fact that preliminary design tools were used for the assessments. The main conclusions of the study are: • Increasing spacing between the propellers (from 0.65 to 1.3m) reduces noise significantly (∼6 EPNdB for each certification point) with a relatively small fuel burn penalty (∼0.3–0.5%) • Relative to unclipped designs, 20% clipped CRPs reduce flyover noise by at least 2.5 EPNdB and approach noise by at least 4.5 EPNdB. The corresponding fuel burn penalty is ∼2%. • Sideline and flyover noise can be reduced by increasing the diameter of the CRP and appropriately controlling CRP rotational speeds. Approach noise can be reduced by either reducing the diameters or the rotational speeds of the propellers. • Regardless of clipping, reducing the rotational speed of the rear propeller relative to the forward propeller reduces noise and, to a certain limit, also mission fuel burn. Further reductions in rotational speed would have an adverse effect on fuel burn. • For given rotational speeds of the propellers, the torque ratio of the gearbox is fixed within ±3%.

Preliminary Design and Performance of Counter Rotating Turbines for Open Rotors: Part II — 0-D Methodology and Case Study for a 160 PAX Aircraft

2016 ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Jordane Legrand ◽  
Vishal Sethi
Keyword(s):  
Design Methodology ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Preliminary Design ◽  
Regulatory Constraints ◽  
Trade Offs ◽  
And Performance ◽  
The Impact

Direct Drive Open Rotors (DDORs) have the potential to significantly reduce fuel consumption and emissions relative to conventional turbofans. However, this engine architecture presents many design and operational challenges both at engine and aircraft level. At preliminary design stages, a broad design space exploration is required to identify potential optimum design regions and to understand the main trade offs of this novel engine architecture. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. Design space exploration assessments are done with 0-D or 1-D models for computational purposes. These simplified 0-D and 1-D models have to capture the impact of the independent variation of the main design and control variables of the engine. Historically, it appears that for preliminary design studies of DDORs, Counter Rotating Turbines (CRTs) have been modelled as conventional turbines and therefore it was not possible to assess the impact of the variation of the number of stages (Nb) of the CRT and rotational speed of the propellers. Additionally, no preliminary design methodology for CRTs was found in the public domain. Part I of this two-part publication proposes a 1-D preliminary design methodology for DDOR CRTs which allows an independent definition of both parts of the CRT. A method for calculating the off-design performance of a known CRT design is also described. In Part II, a 0-D design point efficiency calculation for CRTs is proposed and verified with the 1-D methods. The 1-D and 0-D CRT models were used in an engine control and design space exploration case study of a DDOR with a 4.26m diameter an 10% clipped propeller for a 160 PAX aircraft. For this application: • the design and performance of a 20 stage CRT rotating at 860 rpm (both drums) obtained with the 1-D methods is presented. • differently from geared open rotors, negligible cruise fuel savings can be achieved by an advanced propeller control. • for rotational speeds between 750 and 880 rpm (relatively low speeds for reduced noise), 22 and 20 stages CRTs are required. • engine weight can be kept constant for different design rotational speeds by using the minimum required Nb. • for any target engine weight, TOC and cruise SFC are reduced by reducing the rotational speeds and increasing Nb (also favourable for reducing CRP noise). However additional CRT stages increase engine drag, mechanical complexity and cost.

Preliminary Design and Performance of Counter Rotating Turbines for Open Rotors: Part I — 1-D Methodology

2016 ◽  
Author(s):  
Pablo Bellocq ◽  
Inaki Garmendia ◽  
Jordane Legrand ◽  
Vishal Sethi
Keyword(s):  
Fuel Consumption ◽  
Design Methodology ◽  
Design Space Exploration ◽  
Design Space ◽  
Preliminary Design ◽  
Flow Conditions ◽  
Power Extraction ◽  
And Performance ◽  
The Impact

Direct Drive Open Rotors (DDORs) have the potential to significantly reduce fuel consumption and emissions relative to conventional turbofans. However, this engine architecture presents many design and operational challenges both at engine and aircraft level. At preliminary design stages, a broad design space exploration is required to identify potential optimum design regions and to understand the main trade offs of this novel engine architecture. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints. Design space exploration assessments are done with 0-D or 1-D models for computational purposes. These simplified 0-D and 1-D models have to capture the impact of the independent variation of the main design and control variables of the engine. Historically, it appears that for preliminary design studies of DDORS, Counter Rotating Turbines (CRTs) have been modeled as conventional turbines and therefore it was not possible to assess the impact of the variation of the number of stages (Nb) and rotational speed of the propellers. Additionally, no preliminary design methodology for CRTs was found in the public domain. Part I of this two-part publication proposes a 1-D preliminary design methodology for DDOR CRTs. It allows an independent definition of the Nb, rotational speeds of both parts of the CRT, inlet flow conditions, inlet and outlet annulus geometry as well as power extraction. It includes criteria and procedures to calculate: power extraction in each stage, gas path geometry, blade metal angles, flow conditions at each turbine plane and overall CRT efficiency. The feasible torque ratios of a CRT are discussed in this paper. A form factor for the CRT velocity triangles is defined (similar to stage reaction on conventional turbines) and its impact on performance and blade design is discussed. A method for calculating the off-design performance of a CRT is also described in Part I. In Part II, a 0-D design point (DP) efficiency calculation for CRTs is proposed as well as a case study of a DDOR for a 160 PAX aircraft. In the case study, three main aspects are investigated: A) the design and performance of a 20 stage CRT for the DDOR application; B) the impact of the control of the propellers on cruise specific fuel consumption, C) the impact of the design rotational speeds and Nb of the CRT on its DP efficiency, engine fuel consumption and engine weight.

Aircraft Engine Performance Improvement by Active Clearance Control in Low Pressure Turbines

2009 ◽  
Author(s):  
Christian Knipser ◽  
Wolfgang Horn ◽  
Stephan Staudacher
Keyword(s):  
Fuel Consumption ◽  
Performance Improvement ◽  
Engine Performance ◽  
Aircraft Engine ◽  
Low Pressure ◽  
Performance Model ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Cooling Air ◽  
Clearance Control

In order to minimize fuel consumption, resulting in reduced operating costs and lower environmental impact, turbofan engines must be of high overall efficiency. The design of the low pressure turbine (LPT) plays a significant role in the development of such engines. During a flight mission changing operating conditions (spool speeds, temperatures, pressures, etc.) cause altering magnitudes of the LPT tip clearance, leading to a decrease in LPT performance. As minimum clearances usually do not occur in steady state cruise condition — the major flight condition concerning fuel consumption — active measures to minimize radial tip clearance (ACC – active clearance control) must be incorporated to achieve a considerable reduction in fuel consumption over the whole flight mission. Actively minimizing radial tip clearance by manipulating the turbine casing requires energy in terms of cooling air (thermal ACC), electrical or hydraulical power (mechanical ACC). The cooling air or the power respectively must be provided by the engine itself, thus partly compensating the benefit gained through the improved LPT behavior. This paper investigates the potential of ACC systems from a whole engine perspective. The approach uses a performance model of a state-of-the-art high bypass turbofan engine with a thermal LPT-ACC system to assess the different benefits and detriments of an enhanced ACC. The overall benefit in TSFC for the simulated engine is compared to measured data of other engines indicating an increase of ACC effectiveness with increasing bypass ratios. To compensate deterioration losses due to single rub-in events, closed-loop controls are required. A tip clearance sensor allows the ACC to adapt to an individual engine. As thermal ACC systems show an optimum benefit with a corresponding optimum ACC cooling air flow, the additional TSFC benefit by compensating deterioration is limited. The achievable overall performance improvement is evaluated for different control loops. Mechanical ACC systems bear the highest potential of eliminating clearance losses, while only minor improvements can be made for thermal ACC systems.

Impact of an Optimized Power Turbine Disks Cavity on Geared Open Rotor Performance: A Multidisciplinary Approach in the Preliminary Design

2013 ◽  
Author(s):  
Paolo N. Peraudo ◽  
Claudio Abbondanza ◽  
Dario G. Pastrone ◽  
Paolo Maggiore ◽  
Gian Paolo De Poli
Keyword(s):  
Fuel Consumption ◽  
High Speed ◽  
Short Range ◽  
Specific Fuel Consumption ◽  
Preliminary Design ◽  
Cooling Flows ◽  
Research Activities ◽  
Power Turbine ◽  
Open Rotor ◽  
Turbine Disks

A constantly growing number of studies have been oriented to Green Aircraft and Green Engine concepts during last several years in order to reduce pollutants and carbon-dioxide production by 2020. Ultra high by-pass engines are recently getting the highest interest by academia, research centers and industries. Among the most recent research activities, many studies are focused on geared architectures, the Geared Turbofan (GTF) and the Geared Open Rotor (GOR). The GOR architecture seems to be the most promising radical architecture for short-range aircraft as climbing and landing phases interest the major part of the whole mission. Our work refers to the most recent research activities and is focused on the preliminary design of a GOR-like engine. A multidisciplinary modular simulation environment was developed to allow researchers the chance to directly relate the considered disciplines. Introductory trade-off studies were carried on to effectively show GOR capabilities amongst the most innovative engines. A reference low-bypass turbofan was used as the core of the considered GOR engine, as previously done by General Electric for its original Open Rotor engine. GOR performance were predicted on-design and off-design, by relating to a reference short-range mission. Optimization studies of the GOR high-speed power turbine disks cavity were performed to reduce disk weight and cooling flows, complying with several engineering constraints, such as aerodynamics, structural and manufacturing constraints. Finally the optimization outcomes were linked to the performance code to capture their impact on the overall engine efficiency and specific fuel consumption. Preliminary results show that it is possible to get a remarkable improvement in the specific fuel consumption by minimizing the required cooling flows of the GOR power turbine. Moreover, for a required thrust level, engine weight may be reduced.

Preliminary Design Assessments of Pusher Geared Counter-Rotating Open Rotors: Part I — Low Pressure System Design Choices, Engine Preliminary Design Philosophy and Modelling Methodology

2015 ◽  
Author(s):  
Pablo Bellocq ◽  
Iñaki Garmendia ◽  
Vishal Sethi
Keyword(s):  
System Design ◽  
Low Pressure ◽  
Design Parameters ◽  
Preliminary Design ◽  
Simulation Framework ◽  
Pressure System ◽  
Design Philosophy ◽  
Fuel Burn ◽  
Low Pressure System ◽  
The Impact

In this 2-part publication, the impact of the main low pressure system parameters of a pusher counter rotating Geared Open Rotor (GOR) on mission fuel burn, certification noise and emissions is presented for a 160 PAX medium haul class aircraft. Due to their high propulsive efficiency, GORs 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 parameters of GORs 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 describes the main low pressure (LP) system design choices for a GOR as well as the preliminary design philosophy and simulation framework developed for the assessments. Part II presents the assessment studies. The simulation framework described in this paper comprises the following models: engine and aircraft performance, engine mechanical design and weight, engine certification noise and emissions. A novel aspect of the presented simulation framework is that the design point efficiency and the design feasibility of the low pressure components are calculated for each engine design.

Performance Evaluation of the CVC With Open Rotor Engine Technologies as Propulsion Systems for Subsonic Aircraft

2010 ◽  
Author(s):  
Nqobile Khani ◽  
Georgios Doulgeris ◽  
Riti Singh
Keyword(s):  
Fuel Consumption ◽  
Long Range ◽  
Constant Volume ◽  
The Novel ◽  
Propulsion Systems ◽  
Technology Investment ◽  
Fuel Burn ◽  
Constant Volume Combustion ◽  
Open Rotor ◽  
The Impact

This paper evaluates the constant volume combustion (CVC), the open rotor (OR) and constant volume combustion with open rotor (CVCOR) engine technologies as propulsion systems in subsonic aircraft. Available simulation codes are used to compare different engine technologies assuming the same level of technology investment, to identify the cycle optimum, to calculate the thrust specific fuel consumption (SFC) and to determine flight mission fuel burn for a short range and a long range aircraft. Compared to turbofans of current and of equal technology, it is concluded the novel cycles give better uninstalled SFC performance and better fuel burn performance installed for short and long range missions. Within the constraints of this study, it is concluded the novel cycles offer better thermal efficiencies, increasingly higher overall pressure ratios and yield a lower fuel burn compared to turbofans of current and of equal technology. The novel cycles would be viable as future propulsion systems if the primary design target is fuel consumption. The CVCOR and OR would be comparable based on SFC alone. However installation losses make the CVCOR a better prospect considering the effects of OPR and BPR. Against the impact of increasing fuel costs, it would be beneficial to use the novel cycles.

Conceptual design study of a geared turbofan and an open rotor aero engine with intercooled recuperated core

2018 ◽  
Vol 232 (14) ◽  
pp. 2713-2720 ◽  
Author(s):  
C Salpingidou ◽  
D Misirlis ◽  
Z Vlahostergios ◽  
M Flouros ◽  
F Donus ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Specific Fuel Consumption ◽  
Pollutant Emissions ◽  
Low Thrust ◽  
Tubular Heat Exchanger ◽  
Work Demand ◽  
High Pressure Compressor ◽  
Aero Engine ◽  
Open Rotor ◽  
Aero Engines

The development of more efficient aero engines is becoming a matter of great importance due to the need for pollutant emissions reduction (e.g. CO2, NOx). Toward this direction, two of the most promising aero engine architectures that have been proposed are the ultrahigh by-pass geared turbofan and the open rotor configurations, both of which are targeting the low thrust-specific fuel consumption and reduced NOx production. In the current study, investigations are performed in order to determine the improvements in thrust-specific fuel consumption for these configurations. More specifically, on the basic geared turbofan and open rotor configurations an intercooler and a recuperator are implemented between the compressors and the exhaust nozzle, respectively. The intercooler is installed in order to reduce the high pressure compressor work demand, while the recuperator is used in order to preheat the compressor discharge air by exploiting the otherwise wasted increased enthalpy content of the exhaust hot gas. The recuperator consists of elliptically profiled tubes and its design is based on the innovative tubular heat exchanger core arrangement that has been invented and developed by MTU Aero engines AG. The intercooled recuperative geared turbofan is evaluated against a nonintercooled recuperative geared turbofan, while the intercooled recuperative open rotor is evaluated against a nonintercooled recuperative open rotor. The results showed that the implementation of intercoolers and recuperators can further improve specific fuel consumption and can also lead to NOx emission reduction.

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