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Mavris,
Dimitri N.
Mavris,
Dimitri N.
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ItemPerformance Assessment of a Distributed Electric Propulsion System for a Medium Altitude Long Endurance Unmanned Aerial Vehicle(Georgia Institute of Technology, 2021-08) Markov, Alexander A. ; Cinar, Gokcin ; Gladin, Jonathan C. ; Garcia, Elena ; Denney, Russell K. ; Mavris, Dimitri N. ; Patnaik, Sounya S.Distributed propulsion systems are enabled by electrified aircraft and can provide aero-propulsive benefits. The magnitude and impact of these benefits rely on the location of propulsors on the vehicle, the amount of propulsive force generated by those propulsors, vehicle geometry, and the extent of hybridization of the propulsion system. With an increased number of degrees of freedom over conventionally electrified aircraft, the full extent of the impacts of this technology have not yet been explored, especially for military applications. This study builds on a previous one that implemented a series hybrid and turboeletric propulsion architecture on a turboprop UAV, by introducing a distributed electric propulsion system on the same vehicle. The previous study showed that with a hybrid architecture, the same performance, in terms of range and endurance, could not be achieved for a fixed gross take-off weight. This study investigates the impact of the distributed propulsion system with the goal of identifying the benefits over the previous vehicle and determining the level of technology required to break even with the conventional propulsion UAV. In incorporating the new propulsion system, the engine and main motor are resized, leading edge wing mounted propellers and motors are added to the configuration, and a new battery sizing strategy is implemented. Preliminary results show that, although this new system shows increased range and endurance over the series hybrid vehicle, it still falls short compared to the conventional vehicle with current levels of technology. Although improvements are needed to the electrical system technology to reduce the weight enough to break even with the conventional system, the new vehicle shows increased performance during climb, and has the capability to store energy during the mission. With the proper power management and battery utilization strategies, this system can provide reduction in fuel burn and improved performance during certain phases of the mission which could be beneficial for military applications.
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ItemFeasibility Assessments of a Hybrid Turboelectric Medium Altitude Long Endurance Unmanned Aerial Vehicle(Georgia Institute of Technology, 2020-08) Cinar, Gokcin ; Markov, Alexander A. ; Gladin, Jonathan C. ; Garcia, Elena ; Mavris, Dimitri N. ; Patnaik, Soumya S.Electrified propulsion systems can provide potential environmental and performance benefits for future aircraft. The choice of the right propulsion architecture and the power management strategy depends on a number of factors, the airframe, electrification objectives and metrics of interest being the most critical ones. Therefore, the generic advantages and disadvantages of various electrified propulsion architectures must be quantified to assess feasibility and any possible benefits. Moreover, the objectives and the metrics of interest can be different for military applications than commercial ones. This research investigates the feasibility of turboelectric and hybrid turboelectric propulsion architectures integrated within a medium altitude long endurance surveillance unmanned aerial vehicle. The electrified propulsion system is desired to provide the same endurance and takeoff and landing field length characteristics of the baseline aircraft. This paper presents the results of the first phase of this research where only the electrified propulsion system is sized while the airframe is kept fixed. Physics-based models and a generic mission analysis methodology are used to evaluate the performance of the major subsystems of the propulsion system and to provide a full flight mission history. A state of the art rechargeable battery is employed for the hybrid case. Various power management strategies where the battery is discharged and charged in different flight segments are explored for varying sizes of battery packs. Results indicate that, while none of the architectures can offset the added weight and the efficiency factors of the electrical components as expected, the hybrid turboelectric propulsion architecture can provide fuel burn and performance benefits when sized for, and operated under, a specific set of power management strategies.
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ItemTransient Surrogate Modeling for Thermal Management Systems(Georgia Institute of Technology, 2020-01) Van Zwieten, Andrew ; Cinar, Gokcin ; Garcia, Elena ; Gladin, Jonathan ; Mavris, Dimitri N.In typical multidisciplinary design optimization problems, with varying missions, aerodynamic data, engine data, Thermal Management Systems (TMS), and other parameters it can take upwards of millions of runs to cover the full design space which result in extremely large computational burden, reducing the effectiveness of the design process. The objective of this work is to create a technical approach, leveraging existing concepts in surrogate modeling and other relevant fields, for the creation of a Transient TMS surrogate model. This work utilizes Design of Experiments to intelligently sample a model’s design space, surrogate modeling to enable instantaneous predictions, and state space modeling to allows surrogates to carry predictions forward. By leveraging these three components, a six step methodology was developed. This paper explains the developed methodology with an application on a notional Transient TMS. We first pre-process the time dependent data and possible correlations between input variables, then break down a set of input variables into a series of step functions which represent input schedules in a fraction of the time. We create Artificial Neural Network models to predict the future response of a metric of interest using the current response of both the input step functions and the corresponding output. We finally test whether the surrogates which were created with step functions could be used to predict the future response of the metric of interest for a full time trace of a sample aircraft mission. We show that this methodology yields acceptable predictions for both the partial and full time trace, with a maximum error of 5% and 10%, respectively.