Integrated mission performance analysis of novel propulsion systems: analysis of a fuel cell regional aircraft retrofit

This paper presents the development and application of an integrated, higher-fidelity framework developed within CHARM (the Cranfield Hybrid electric Aircraft Model) for the design, performance analysis and overall evaluation of novel electrified propulsion systems. The developed framework is used to model and analyze the performance characteristics of a Fuel Cell (FC) regional aircraft system in comparison with a conventional regional aircraft and a hydrogen gas turbine regional aircraft retrofit. The FC propulsion system and the hydrogen gas turbine are retrofitted to the same conventional aircraft platform. Physics-based aircraft performance calculations, propeller maps, gas turbine component maps, off-design cycle analysis, electric component maps, calculations for the electric power management and distribution, and a Proton-Exchange Membrane FC (PEMFC) configuration sized to cover the power requirements of a regional aircraft, are integrated within this framework to capture the performance and interaction of components, sub-systems and aircraft during any flight mission and conditions. The aircraft performance, the propulsion system performance characteristics and the emissions of the three technologies are calculated and discussed to understand the challenges and opportunities of using hydrogen-electric propulsion (FC). The effect of capturing the variable mission parameters and flight phases on the performance of the electric power system and FC is presented and compared against a lower fidelity modeling approach for the electric powertrain. The sensitivity of the FC propulsion system and its attributes to varying mission requirements (island-hopping, range, cruise altitude, ambient conditions), as well as the change in the consumed fuel, are demonstrated. This framework can be used to inform the decision-making for the design of electric components and thermal management systems (TMS), and the importance of capturing the trade-off between mass, efficiency and operational constraints in the design process is highlighted. Also, the off-design performance of the electric power system designs and FC is modeled to decide if the design is within acceptable limits under various conditions, and capture the effect of mission requirements and flight conditions on the energy consumption of the overall aircraft system. Finally, a parametric analysis addresses the effect of power density improvement with future technology on the energy per passenger and feasibility of the FC regional aircraft

The impact of multi-stack fuel cell configurations on electrical architecture for a zero emission regional aircraft

All-electric aircraft can eliminate greenhouse gas emissions during aircraft mission, but the low predicted energy storage density of batteries (=0.5 kWh/kg), and their life cycle, limits aircraft payload and range for regional aircraft. Proton Exchange Membrane Fuel Cells (PEMFCs) using hydrogen are explored as an alternative power source. As the effort on designing high power density and highly efficient fuel cell systems continues, a trade off study on the effect of fuel cell configurations and the electrical conversion strategy on system efficiency, total weight, failure cases, and reduction of power due to failures, will inform future designs. Introducing viable fuel cell stacks and electrical configurations motivates such a trade off study, as well as concentrated design effort into these components. Currently available fuel cell stacks are designed at lower power (in the range of 150kW) to what is required for regional aircraft propulsion (in the range of 4MW). Hence to achieve the total required power, the fuel cell stacks are connected in parallel and series to create multi-stack configurations and provide higher power. In this study, multi-stack fuel cell configurations and the selected DC/DC converters are assessed. Each configuration is evaluated based on power converter design and redundancy, design for high voltage, degradation of fuel cell stacks, total system efficiency, and controllability of fuel cell stacks

An enhancer variant at 16q22.1 predisposes to hepatocellular carcinoma via regulating PRMT7 expression

Abstract Most cancer causal variants are found in gene regulatory elements, e.g., enhancers. However, enhancer variants predisposing to hepatocellular carcinoma (HCC) remain unreported. Here we conduct a genome-wide survey of HCC-susceptible enhancer variants through a three-stage association study in 11,958 individuals and identify rs73613962 (T > G) within the intronic region of PRMT7 at 16q22.1 as a susceptibility locus of HCC (OR = 1.41, P = 6.02 × 10⁻¹⁰). An enhancer dual-luciferase assay indicates that the rs73613962-harboring region has allele-specific enhancer activity. CRISPR-Cas9/dCas9 experiments further support the enhancer activity of this region to regulate PRMT7 expression. Mechanistically, transcription factor HNF4A binds to this enhancer region, with preference to the risk allele G, to promote PRMT7 expression. PRMT7 upregulation contributes to in vitro, in vivo, and clinical HCC-associated phenotypes, possibly by affecting the p53 signaling pathway. This concept of HCC pathogenesis may open a promising window for HCC prevention/treatment