Jeff Schutte

Technology Assessment of NASA Environmentally Responsible Aviation Advanced Vehicle Concepts

The National Aeronautics and Space Administration’s (NASA) Environmentally Responsible Aviation (ERA) project is conducting research at an integrated system level on promising concepts and technologies expected to mature in the N+2 time frame. ERA has a need to perform a systems level analysis of these concepts and technologies to estimate and track performance towards ERA’s goal of simultaneously achieving improvement in metrics for fuel burn reduction, noise margin, and LTO NOx emissions reduction. This paper describes work done for the system level comparison of tube and wing versus hybrid wing body airframe configurations using both advance ultra high bypass ratio direct drive and geared turbofan engines. The results focus on the interdependencies between the ERA fuel burn and noise metrics.

Updates and Modeling Enhancements to the Assessment of NASA Environmentally Responsible Aviation Technologies and Vehicle Concepts

The National Aeronautics and Space Administration’s (NASA) Environmentally Responsible Aviation (ERA) project is conducting research at an integrated system level on promising concepts and technologies expected to mature in the N+2 time frame. It is essential for ERA to perform a systems level analysis of these concepts and technologies in order to estimate and track performance towards ERA’s goal of simultaneously achieving improvement in metrics for fuel burn reduction, noise margin, and LTO NOx emissions reduction. Previous vehicle modeling and technology assessment work conducted for the ERA project illustrated system level comparison of tube and wing versus hybrid wing body airframe configurations, as well as between ultra high bypass ratio direct drive and geared turbofan engines. Guidance drawn from these results has led to an updated list of ERA technologies of interest. Additionally, development of improved modeling capabilities and a better understanding of key technology impacts have been accordingly incorporated into an updated technology assessment. This assessment evaluates changes to the technology portfolio, incorporates updated technology assumptions, augmented vehicle and technology models, and includes for the first time LTO NOx estimates for advanced combustors. These new set of results allow for an understanding of the interdependencies between each of the ERA metrics and provide an update on ERA’s capability of achieving its goals.

Ultra High Bypass Ratio Engine Sizing and Cycle Selection Study for a Subsonic Commercial Aircraft in the N+2 Timeframe

This paper presents an engine sizing and cycle selection study of ultra high bypass ratio engines applied to a subsonic commercial aircraft in the N+2 (2020) timeframe. NASA has created the Environmentally Responsible Aviation (ERA) project to serve as a technology transition bridge between fundamental research (TRL 1–4) and potential users (TRL 7). Specifically, ERA is focused on subsonic transport technologies that could reach TRL 6 by 2020 and are capable of integration into an advanced vehicle concept that simultaneously meets the ERA project metrics for noise, emissions, and fuel burn. An important variable in exploring the trade space is the selection of the optimal engine cycle for use on the advanced aircraft. In this paper, two specific ultra high bypass engine cycle options will be explored: advanced direct drive and geared turbofan. The advanced direct drive turbofan is an improved version of conventional turbofans. In terms of both bypass ratio and overall pressure ratio, the advanced direct turbofan benefits from improvements in aerodynamic design of its components, as well as material stress and temperature properties. By putting a gear between the fan and the low pressure turbine, a geared turbo fan allows both components to operate at optimal speeds, thus further improving overall cycle efficiency relative to a conventional turbofan. In this study, sensitivity of cycle design with level of technology will be explored, in terms of both cycle parameters (such as specific thrust consumption (TSFC) and bypass ratio) and aircraft mission parameters (such as fuel burn and noise). To demonstrate this sensitivity, engines will be sized for optimal performance on a 300 passenger class aircraft for a 2010 level technology tube and wing airframe, a N+2 level technology tube and wing air-frame, and finally on a N+2 level technology blended wing body airframe with and without boundary layer ingestion (BLI) engines.© 2011 ASME

Multi-Design Point Cycle Design Incorporation into the Environmental Design Space

A multi-point design cycle analysis methodology has been developed and implemented into the Environmental Design Space to ensure the proper matching of engine and aircraft. The method ensures the feasibility of the engine designs throughout the cycle design space by adjusting the design to simultaneously meet performance requirements and constraints at different operating conditions. EDS incorporates NPSS for the cycle analysis and utilizes its solver to find the solution of a system of nonlinear equations established by the user and the NPSS auto solver to that meets all requirements and constraints.

Probabilistic Technology Assessment for NASA Environmentally Responsible Aviation (ERA) Vehicle Concepts

We present and demonstrate different approaches of subjective probability encoding pertinent to technology impact modeling for probabilistic assessment of advanced vehicle concepts. Results are generated and discussed using NASA Environmentally Responsible Aviation as a relevant technology development and integration effort. We show that different techniques are suitable and can be selected on the basis of available technology impact information, and that significant differences are observed on the results across alternative methods. Uncertainty on percent fuel burn reduction and cumulative noise margin below Stage 4 is observed to be within 5% and 3 dB respectively. The impact and variability of technologies on noise margin for the hybrid wing body concept is also notably dominated by the inherent noise shielding benefits of this configuration.

Surrogate Modeling for Simultaneous Engine Cycle and Technology Optimization for Next Generation Subsonic Aircraft

This paper presents an engine sizing and cycle selection study of ultra high bypass ratio engines applied to a subsonic commercial aircraft in the N+2 (2025) timeframe. NASA has created the Environmentally Responsible Aviation (ERA) project to serve as a technology transition bridge between fundamental research (TRL 1–4) and potential commercial application (TRL 7). Specifically, ERA is focused on subsonic transport technologies that could reach TRL 6 by 2020 and can be integrated into an advanced vehicle concept to simultaneously meet the ERA project metrics for noise, emissions, and fuel burn. An important variable in exploring the technology trade space is the selection of the optimal engine cycle for use on the advanced aircraft. Previous literature demonstrated the cycle optimization using a design of experiments (DOE) to explore the engine cycle design space for a pre-defined technology package. However, since the optimal engine cycle is dependent upon the specific technology package, this process would have to be repeated to ensure optimal performance for each technology package. With more than 80 technologies to be analyzed, the combinatorial space of technology packages is enormous. As a result, executing a DOE to find the optimum engine cycle for each technology package is infeasible. To address this issue, it is proposed to use surrogate models that encompass the engine cycle and technology design space to enable fast and accurate optimization of the engine cycle for any given technology package.This paper describes the generation and analysis of surrogate models used for technology assessment and cycle optimization of an ultra high bypass geared turbofan engine architecture. The first study in the paper shows that a single surrogate model can be used to accurately simulate both a technology and cycle design space. To demonstrate the proposed surrogate modeling approach, the cycle design space for three different technology packages was analyzed. This study demonstrated that when an optimal cycle is found within the constrained interior of a design space, the surrogate modeling approach is quite accurate. The study also established that the surrogate models can also be used to assess potential cycles at the boundaries or even outside of the region for which they were trained.© 2012 ASME

Evaluation of N+2 Technologies and Advanced Vehicle Concepts

The National Aeronautics and Space Administration’s (NASA) Environmentally Responsible Aviation (ERA) project is conducting research at an integrated system level on promising concepts and technologies expected to mature in the N+2 time frame. ERA has a need to perform a systems level analysis of these concepts and technologies to estimate and track performance towards ERA’s goal of simultaneously achieving improvement in metrics for fuel burn reduction, noise margin, and LTO NOx emissions reduction. This paper describes work done for the system level comparison of tube and wing plus various unconventional airframe configurations using both advance ultra high bypass ratio direct drive and geared turbofan engines. The results focus on the interdependencies between the ERA fuel burn and noise and NOx emission metrics.

Engine Design Strategy for Boundary Layer Ingesting Propulsion Systems With Multiple Non-Symmetric Engine Inlet Conditions

Boundary layer ingesting inlets for hybrid wing body aircraft have been investigated at some depth in recent years due to the theoretical potential for fuel burn savings. Such savings derive from the ingestion of a portion of the low momentum wake into the propulsor to reenergize the flow, thus yielding total power savings and reducing required block fuel burn.A potential concern for BLI is that traditional concepts such as “thrust” and “drag” become less clearly defined due to the interaction between the vehicle aerodynamics and the propulsive thrust achieved. One such interaction for the HWB concept is the lateral location of the inlet on the upper surface which determines the effective Reynolds number at the point of ingestion. This is an important factor in determining the amount of power savings achieved by the system, since the boundary layer, displacement, and momentum thicknesses are functions of the local chord length and airfoil shape which are all functions of the lateral location of the engine. This poses a design challenge for engine layouts with more than two engines as at least one or more of the total engines will be operating at a different set of changing inlet conditions throughout the flight envelope.As a result, the engine operating point and propulsive performance will be different between outboard and inboard engines at flight conditions with appreciable boundary layer influence including key flight conditions for engine design: takeoff, top of climb, and cruise. The optimal engine design strategy in terms of performance to address this issue is to design separate engines with similar thrust performance. This strategy has significant challenges such as requiring the manufacturing and certification of two different engines for one vehicle. A more practical strategy is to design a single engine that performs adequately at the different inlet conditions but may not achieve the full benefits of BLI.This paper presents a technique for cycle analysis which can account for the disparity between inlet conditions. This technique was used for two principal purposes: first to determine the effect of the inlet disparity on the performance of the system; second, to analyze the various design strategies that might mitigate the impact of this effect. It is shown that a single engine can be sized when considering both inboard and outboard engines simultaneously. Additionally, it is shown that there is a benefit to ingesting larger mass flows in the inboard engine for the case with large disparity between the engine inlets.Copyright

Comparison of Advanced Vehicle Concepts through Pareto-Optimal Technology Sets

In previous work a technology portfolio composition problem was formulated from a multi-objective optimization perspective in order to find favorable combinations of technologies for a given vehicle configuration to satisfy prescribed environmental goals. The work implemented the Non-Sorted Genetic Algorithm II (NSGA-II) on a pool of 91 technologies applied to a Large Twin Aisle tube-and-wing aircraft and optimized for: percent fuel burn reduction relative to a 2005 reference vehicle, LTO NOX percent reduction relative to CAEP/6 limits, and cumulative noise margin relative to Stage IV limits. This work expands upon the previous work by studying six vehicles including: Large Single Aisle Tube and Wing (LSA), Large Single Aisle Over the Wing Nacelle (LSA OWN), LTA, Large Twin Aisle Mid Fuselage Nacelle (LTA MFN), Large Twin Aisle Hybrid Wing Body (LTA HWB), and Large Twin Aisle Box Wing (LTA BW). Pareto frontiers for each vehicle are generated and are thoroughly examined by evaluating which technologies govern clustering and patterns on the Pareto surface, the corners of the performance trade space, and comprise the region surrounding the compromise point. The Pareto surface is also assessed in terms of emerging patterns in the number of technologies of non-dominated solutions as well as the overall location and span of the Pareto surface in the objective space. Based on the characterization of the Pareto set of solutions for each aircraft concept a comparative analysis is drawn across concepts to identify overarching technology trends, outline technology scalability phenomena, and isolate the performance impact of aircraft concepts in the objective space. Altogether this work provides greater insight into trends, interactions, and tradeoffs of next generation technologies and aircraft concepts, and in parallel it demonstrates a new approach to systems analysis where single solutions are replaced by the entire locus of Pareto optimal solutions.

Framework Development for Performance Evaluation of the Future National Airspace System

Sustainability of the National Airspace System (NAS) continues to be a major concern to its governing body, the Federal Aviation Administration (FAA). Several research efforts are addressing the sustainability needs of the future NAS, including the Continuous Lower Emissions, Energy and Noise (CLEEN) program under the FAA, and the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) projects of the National Aeronautics and Space Administration (NASA). These initiatives are focused on developing and maturing technologies that would mitigate the environmental impacts of aviation. Alternatively, the Next Generation air transportation system (NextGen) is to provide substantial efficiency improvements from an operational perspective. Also, bio-fuels continue to be an attractive alternative to conventional jet fuels given their reduced life cycle emissions. This paper proposes an integrated framework that would evaluate the performance of the future NAS under different scenarios that consider varying technology, operation, and biofuel contributions. The objective is to assess whether or not the system level goals laid out by the International Air Transport Association (IATA) will be met.