Opportunities of cryogenic system for hybrid electric propulsion aircraft/solar airship with LH2 and high temperature superconductor

A comprehensive analysis for research and development (R&D) of the technical appearance and calculation of the technical characteristics of a new hybrid electric propulsion aircraft/solar airship (HEPA) with LH2 and cryocooling system with high temperature superconductivity (HTS) can be used at any stage of the design process of a hybrid electric passenger aircraft in the implementation of the EU FUTPRINT50 international program. A new conceptual synthesis for the creation of an optimal cryogenic cooling system based on the Brayton reverse cycle using turbomachines with basic design schemes for the use of significant cryogenic power with low temperature values has been created for computational mat. models using test thermodynamic models of individual circuit elements, taking into account the efficiency of each element, their hydraulic losses in the lines of all elements of the system: calculation of hydraulic losses in the channel element, thermal control in regenerative heat exchangers with a turbocharger and calculation of a turbo expander. The real-time use of a low-capacity wireless sensor-detector or additional charging components from solar energy based on the Seebeck-Peltier effect will be more effective due to the introduction of graphene structures in the design. Experimental development of a two-stage electric compressor and a turbo expander for demonstration tests of a cryogenic cooling system in the MAI laboratory has been carried out.


Introduction
The prospects for the development of new and highly efficient hybrid electric aircraft (HEA) concepts with hybrid electric propulsion (HEP) for regional and long routes airlines are basing on the analysis of the main 'story' of the any famous Cryo Aeroprojects and directly related to the use of more profitable cryogenic cooling systems for onboard electrical components and the placement of volumetric tanks of liquid hydrogen (LH2) for Cryoplane  The most advantageous is the use of liquid nitrogen (LN) cooling systems and calculations for liquid hydrogen (LH2) or helium (LHe) and the creation of test demo stands complex for optimizing their operating modes, profitable introduction of electric units based on the use of the effect of hightemperature superconductivity (HTS), which confirmed the importance in the development of the international project FUTPRINT50 in EC and cooperation with CIAM. TsAGI, GosNIIAS and NIC name N. Zhukovsky on the creation of future hybrid electric passenger regional aircraft [6].

Development and creation of cryogenic cooling systems for aircraft electrical components
When performing optimization tasks during design analysis, modeling and creation of optimal cryogenic cooling systems (CCS) for on-board electric drives, turbo coolers, energy storage (batteries) and electrical wiring of a hybrid electric propulsion of Cryoplane aircraft [1,3] based on liquid refrigerants (LN, LHe, LH2) to ensure high efficiency thermal management process of their implementation requires rational approaches and experimental solutions to achieve the best level of transfer-recuperate energy -and the weight return and ensuring the compactness and technological profitability of the equipment based on the high-temperature superconductivity (HTS) effect for minimize 3D sizes and weight HEP aircraft components and solar airship parts.
Various studies at MAI on the design appearance and simulate calculation of the technical characteristics of the cooling component system with HTS for the hybrid electric propulsion of a new aircraft or disk airship can be used for new research with well-known aviation industrial leaders -TsAGI and CIAM. For a mathematical model created using thermodynamic models of individual elements of structural schemes that take into account the efficiency of each element, hydraulic losses in the paths of all elements of the system, and a new version of the architectural scheme of an optimal cryogenic cooling system based on the reverse Brayton cycle using turbomachines was considered, and also with the basic scheme of designing and using cryogenic systems for a given level of cooling performance and the level of temperature difference with a model calculation of hydraulic losses in the channel (pipelines) of a contour element with a heat-protective coating, taking into account the thermal regulation of regenerative heat exchangers with the calculation of turbo charger and turbo expander data. This includes experience in the development of a two-stage neon electric compressor and a turbo expander with a promising high-speed suspension system on gas-dynamic bearings and their testing on the effectiveness of a cryogenic cooling system on the MAI laboratory schematic architecture and test stand-demonstrator picture, as shown on Fig.3 [7]. The selection and analysis of a possible cryogenic system according to the criterion of energy-weight efficiency K kc ' max will be determined by a decrease in the mass of the m ep electric drive structure due to the use of graphene technologies, which is represented by the mass reduction coefficient k graf , a decrease in the mass of the cryo cooling system of the m kri batteries through the coefficient k b and onboard power cables through the coefficient k k , a decrease in the mass of thermal protection of hydrogen tanks m tk through the coefficient k tk relative to the take-off weight of the aircraft m to , which can be imagined: K kc 'max = min (k graf m ep + k b m kri + k k m kri + k tk m tk )/m to , (1) where K kc 'max for any versions of calculation simulation aircraft/ airship model of mass (weight) analysis consist about 0,70-0,75 as perspective graphene technology high efficiency as may special fixing in our conclusion. It's the main progress point may be confirm the more detail results inside as two previously publications: one from the University of Columbia 'Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene' (Science Paper, 2008) [ 8 ] and second paper by our joint research with the MAI HTS Electric Lab 'Superconducting Propulsion System with LH2 Cooling for All-Electric Aircraft' (J. Phys.: Conf. Ser.,1559, 2020) in the IOP publication [ 9 ].

The possibilities of local cooling systems using the Seebeck-Peltier effect and highly conductive composite multilayer graphene nano structures
On board the passenger aircraft, various low-power and autonomous electrical systems of sensors, detectors and controllers are provided, spaced over long distances from the main power sources -from engines, batteries and generators -at the ends of the wing, fuselage and tail. At the same time, their power supply can be discrete, but requires electrical wiring. In order to avoid additional costs of weight and weighting of these components, it is possible to use real-time cooling of low-capacity wireless sensors-detectors based on the Seebeck-Peltier effect, which improves the weight return of components for an airplane/ airship. This effect consists in the fact that if a constant voltage is applied to two terminals of an electrical circuit consisting of two conductors made of different materials, then one of the contact surfaces will heat up, and the second will cool, i.e. the Seebeck effect gives the recovery of thermal energy into electrical energy and the release of heat.
The Peltier effect is most strongly observed in the case of the use of p-and n-type semiconductors of conductivity. Depending on the direction of the electric current through the contact of semiconductors of different typesp-n-and n-p-junctions due to the interaction of charges represented by electrons (n) and holes (p), and their recombination, energy is either absorbed or released. As a result of the passage of an electric current of a certain polarity, a temperature difference is formed between the radiators of the Peltier module: one radiator works as a refrigerator, the other radiator heats up and serves to remove heat. If you need to get the maximum delta T up to 150C, then assemble a cascade of several Peltier batteries. 5 Devices based on the Peltier effect are extremely reliable, as they have no moving parts and practically do not need maintenance. At the same time, it is possible that their use in combination with additional filmsurface cooled charging components from solar energy will be effective due to the introduction of superconducting nano-thin graphene structures in flexible electrical elements and in reinforcementhardening to obtain lighter composite structures and aircraft assemblies.

Application of Peltier cooling system and graphene unique data
a. Thermoelectric cooling is used in various types of detectors, electronic equipment, portable refrigerators and mini-coolers using highly efficient graphene technologies.
b. If cooling devices with high reliability are required, which are placed in small spaces inside the aircraft, for powerful integrated circuits in local thermoelectric coolers of small volumes.
c. Solid-state heat pumps using the Peltier effect are advantageous in thermoelectric cooling devices with elements of graphene structures.
It is necessary to analyze the most advantageous properties and facility of graphene and borophene: -graphene has a higher electrical conductivity and practically has no resistance, and graphene has 70 times higher electron mobility than silicon. Thus, the mobility of graphene charges is more than 1,000,000 cm 2 / V *s. The electron velocity in graphene is 10,000 km/s, although in a conventional conductor the electron velocity is about 100 m/s, it has a high electrical capacity, the specific energy consumption of graphene is approaching 65 kWh/kg. This indicator is 47 times higher than that of lithium-ion batteries, which are so common today; it has a high thermal conductivity, it is 10 times more thermally conductive than copper. Its thermal conductivity is about 5000 W / m * K, full optical transparency is characteristic, which is advantageous for thin films of solar cells, it absorbs only 2.3% of light and is optically transparent in a wide range from UV to far-IR, graphene is capable of producing electrical energy, in particular, when the flow of salt water on the graphene sheet, it is able to generate electrical energy by converting the kinetic energy; real slim 2D structure of graphene is very flexible and significantly more durable than steel, to lightweight composite mesh and synthetic ropes inside and on top of the aircraft and airships, graphene is the lightest material, it is 6 times lighter than a pen, and under certain conditions graphene activates another ability that allows it to "heal" "holes" in its crystal structure in case of damage, which increases survivability and reliability.

Design and development of integrated circuits of aircraft and airship disks
Comprehensive design analysis and synthesis, modeling and creation of possible variants of cryoplane concepts of various layout schemes (classical and integrated with the Integral Bodyplane MAI and Wing Bodyplane AIRBUS fuselage), taking into account certain difficulties of volumetric placement of heatshielding tanks for LH2 inside an aircraft as Ecranoplane MAI (in 1980 years) as analogy to the ECIP BLC project (in 1990 years) / solar disk airship (as type Thermoplane MAI) and the addition of energy from film coatings with solar panels similar to the SOLARSTRATOS high altitude flight test project from Switzerland [ 4,10 ] . To choose the layout solutions of a hybrid electric aircraft, it is necessary to take into account the typical conditions and volume-weight differences between liquid hydrogen LH2 and Kerosene in Tab. 1: As part of the research work at MAI, a digital structural and parametric analysis of alternative layouts of any concept of an aircraft of various layout alternatives with the required small or large passenger capacity was carried out, the architecture of which is shown in Fig.6 [11,12].   Since lightweight thin-walled composite wing structures of a modern passenger aircraft have relatively large aero elastic end deformations and wing oscillation frequencies in flight, as well as during run-up on the runway, the presence of electric piezo-damper systems (EPDS) can give an additional increase in recuperated electricity up to 10-12%, which reduces the level of initial electricity reserve in Li-ion-Graphen batteries of the aircraft and improves the weight return of the aircraft as a whole.

Conclusion
The desire to implement new high-performance conceptual solutions in design research when creating hybrid electric aircraft/solar airships and their power plants will be directly interfaced: -with the implementation of optimal and integrated low-cost cryogenic cooling systems for highpower on-board electric power components (electric motors, electric generators, recuperators and energy storage) with high electrical conductivity and/or superconductivity (power cables, controllers and on-board buses, rechargeable Li-ion batteries and surface nano film solar cells) with new unique materials, including graphene and borophene technologies, which significantly improve specific performance in terms of weight return, strength and compactness; -with research and experimental verification-testing of new components of cryosystem and verification of complex computational methods of mathematical modeling for the maximum efficiency of these systems when switching from one to another cryosystem -from liquid nitrogen to liquid helium and hydrogen, where hydrogen is also an environmentally friendly fuel, but requires large structural tank spaces and high-quality thermal protection using thin and light-strength highly conductive graphene nanotubes, reducing the mass of structures as K kc 'max up to 25-30%.