Browsing by Author "Liu, Chengyuan"

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    Methodology for the assessment of distributed propulsion configurations with boundary layer ingestion using the discretized miller approach
    (Praise Worthy Prize, 2017-06-30) Valencia, Esteban; Liu, Chengyuan; Nalianda, Devaiah; Panagiotis, Laskaridis; Gray, Iain; Singh, Riti
    The growing global environmental awareness has motivated the search for more fuel-efficient aircraft propulsion systems. In this context, a configuration based on distributed propulsion with Boundary Layer Ingestion (BLI) has been found to present potential performance benefits. The concept has been documented and explored extensively during the last few years and various aerodynamic integration issues, such as: high levels of distortion and low intake pressure recovery; have been identified as factors that may be detrimental in realizing the technology full potential. Parametric and parallel compressor (PC) approaches have been used to assess the effect of these aerodynamic issues on propulsors fan performance. However, in the context of BLI, these tools are unable to assess the effects of combined radial and circumferential distortion that are present. In order to assess the combined distortion patterns and the effects of distortion at component and system levels, this study uses a novel method based on semi-empirical correlations denominated the Discretized Miller (DM) approach. This method was developed for BLI systems previously by the author, and it is now incorporated into the propulsor performance method to assess the effects of the combined radial and circumferential distortion patterns. The performance analysis, undertaken at a component and system level, aims to assess several propulsion architectures, using Thrust Specific Fuel Consumption (TSFC) as figure of merit. To define the suitability of the distributed propulsor array in this study, an airframe layout based on the N3-X aircraft concept and High Temperature Superconducting (HTS) electric motor capabilities were assumed. The key contribution of this study is to enable the introduction of the concept of thrust split between energy source and propulsion system in the system analysis, and thereby, allows the assessment of its effects on different propulsion system layouts, while considering the BLI induced distortion. The results obtained with this alternative performance method showed that BLI reduces the fan efficiency of a conventional fan by approximately 2%, whilst corroborating the TSFC trends observed in previous studies. The study also indicates that when sizing effects of propulsors and core-engines were neglected, a propulsion system configuration with 75% thrust split was found optimum.
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    Turboelectric Distributed Propulsion System Modelling
    (Cranfield University, 2013-12) Liu, Chengyuan; Singh, R.; Laskaridis, Panagiotis; Doulgeris, Georgios
    The Blended-Wing-Body is a conceptual aircraft design with rear-mounted, over wing engines. Turboelectric distributed propulsion system with boundary layer ingestion has been considered for this aircraft. It uses electricity to transmit power from the core turbine to the fans, therefore dramatically increases bypass ratio to reduce fuel consumption and noise. This dissertation presents methods on designing the TeDP system, evaluating effects of boundary layer ingestion, modelling engine performances, and estimating weights of the electric components. The method is first applied to model a turboshaft-driven TeDP system, which produces thrust only by the propulsors array. Results show that by distributing an array of propulsors that ingest a relatively large mass flow directly produces an 8% fuel burn saving relative to the commercial N+2 aircraft (such as the SAX-40 airplane). Ingesting boundary layer achieves a 7-8% fuel saving with a well-designed intake duct and the improved inlet flow control technologies. However, the value is sensitive to the duct losses and fan inlet distortion. Poor inlet performance can offset or even overwhelm this potential advantage. The total weight of the electric system would be around 5,000-7,000 kg. The large mass penalties further diminish benefits of the superconducting distributed propulsion system. The method is then applied to model a turbofan-driven TeDP system, which produces thrust by both the propulsors array and the core-engines. Results show that splitting the thrust between propulsors and core-engines could have a beneficial effect in fuel savings, when installation effects are neglected. The optimised thrust splitting ratio is between 60-90%, the final value depends on the propulsor intake pressure losses and the TeDP system bypass ratio. Moreover, splitting the thrust can reduce the weight of the electric system with the penalty of the increased core-engine weight. In short, if the power density of the superconducting system were high enough, turboshaft-driven TeDP would be preferable to power the N3-X aircraft