Zhibo Chen
Title: Aft Fuselage Boundary Layer Ingesting Propulsion System Design.
Abstract: New aircraft concepts based on distributed propulsion (DP) and boundary layer ingestion (BLI) have the potential to reduce aircraft fuel burn and emissions compared to same-year conventional aircraft. These concepts can be enabled by high-power density motors supplied with power from batteries and/or a generator driven by a gas turbine. This presentation describes the conceptual design of a turbo-electric, single-aisle, mid-range aircraft with tail-integrated distributed propulsors for BLI. Six tail-BLI propulsors, driven by 0.5 MW electric motors, are installed on the aircraft, with a non-axisymmetric aft fuselage and a T-tail, in addition to two next-generation underwing turbofan engines. The estimated fuel burn benefit is 8.5% in Payload Range Fuel Consumption at a cruise Mach number of 0.8, compared to a baseline next-generation conventional aircraft. The non-axisymmetric aft fuselage creates swirl into the tail-BLI propulsors, with the fan rotational direction chosen for co-swirl to reduce incidence. The number and size of the tail propulsors are set by the fuel burn trade, between maximizing ingested boundary layer kinetic energy defect and minimizing propulsion system weight. The propulsor fan pressure ratio is set by the trade between propulsor weight and propulsive efficiency. This research study presents a rigorous assessment of the potential for fuel burn reduction with tail-integrated, BLI, distributed propulsors and gives guidelines concerning the design features that enable this improvement in fuel burn.
Dr Hiromitsu Kakudo
Title: On the Mechanism for Rotating Cavitation Onset in a Four-Bladed Rocket Engine Turbopump Inducer
Abstract: Cavitation instability in turbopump inducers is one of the major risks for launch vehicles. Unsteady loads on inducer blades and the turbopump rotor system can be caused by cavitation dynamics and lead to instability. For example, the cavitation dynamics can couple with the propellant feed system and result in POGO instability. Despite a large number of studies aimed at mitigating these risks, the fundamental understanding of the underlying mechanisms responsible for cavitation instability is still limited. The present study characterizes the different cavitation regimes of a four-bladed inducer using unsteady pressure and optical measurements, specifically the transition from tip vortex cavitation to alternate blade cavitation and rotating cavitation, depending on cavitation number. Cavitation compliance and mass flow gain factor, the two key parameters characterizing inducer dynamics and pumping system stability, are inferred from the measurements using a previously developed dynamic inducer model. The criterion for rotating cavitation onset, governed by the position of the blade tip vortex, is validated via optical measurements. A first-principles-based model for the trajectory angle of the tip vortex cavitation is established and yields good agreement with experimental results. The paper demonstrates that the criterion for rotating cavitation onset is independent of inducer geometry and sets the stage for more generalized inducer design guidelines to address cavitation instability.
Joseph Chiapperi
Title: “An Integrative Course in Turbomachine Design, Manufacturing, and Measurement”
Abstract: A new course entitled Advanced Manufacturing for Aerospace Engineers was developed for junior- and senior-level students in the Department of Aeronautics and Astronautics at MIT. It is a one-semester project-based course in which students, in small teams of two or three, design, manufacture, assemble, and test an electric turbopump for a notional rocket engine. The project applies several different disciplines, including fluid dynamics, turbomachinery, rotordynamics, additive manufacturing, material science, economics, instrumentation, measurement, and technical communication. The course is divided into three phases – (i) fluid-mechanical design of the radial pumps, (ii) rotordynamic design of the rotor-casing structural system, and (iii) final integration, assembly, and testing. In the first two phases, the students assess baseline systems, design and fabricate their own systems to meet the overall project requirements, and then test their new components in a laboratory setting. The assessment is carried out using hand-calculations based on first principles, commercial software, and experiments. In the third phase, the students assemble their components from the first two phases into the final pump to be tested. Each phase includes lectures, laboratory sessions, and problem sets, and is concluded with a technical report and presentation. The pumps are designed according to functional requirements, including pressure rise and mixture ratio.
The novelty of this course is its integrative, multi-disciplinary, open-ended structure. The project modules take students through an entire research and development cycle, including design, fabrication, assembly, testing, and reporting. These steps are fulfilled in a hands-on setting, giving the students real-world experience with simulation, modeling, fabrication, and measurement, as well as the limitations of these methods. The integrative structure allows the students to develop an understanding of the connection between their design work and the manufacturing steps, and ultimately to the performance of their final products. The open-ended nature of the project encourages students to choose designs different from those of their peers, giving them a personal connection to their project. This seminar discusses the structure and content of the course, lists the intended learning objectives, and evaluates the effectiveness of the course components at enabling students to achieve the learning objectives. Student achievement is primarily assessed with the three presentations. Two anonymous surveys were used to obtain student feedback on the efficacy of the course components as well as their primary takeaways from the course. The presentation scores and the performance in the lab activities show that the students achieved the learning objectives. The survey feedback shows that the course achieved the department goals of providing greater access to hands-on manufacturing work for undergraduate students, and that this hands-on work enabled a deep connection to the project and the course concepts.