Fan as a means of transportation

Air-conditioning and life-support systems, shafts and tunnels ventilation, cooling of propulsion units of land and air transport vehicles, power engineering and petrochemistry — this is only an incomplete list of applications of fans. And within lifting and propulsion systems of drones, hovercraft and wing-in-ground effect aircraft, they can provide cargo transportation, monitoring of weather conditions, and rescue operations. Concepts of such vehicles are designed by TsAGI scientists.

The Head of the Department of Subsonic Internal Aerodynamics of Aviation and Industrial Systems of the Division of Hydrodynamics and Industrial Aerodynamics of TsAGI Viktor Mitrofovich speaks about the work in the field of fan-type vertical take-off and landing drones.

In fact, since the beginning of its almost century-long history, TsAGI used to research aerodynamics of propellers, fans, and air flow ducts. A huge scientific process stock was created in this field, the methods of aerodynamic designing and experimental study of various air movement devices were developed. The fan and air duct aerodynamics school leading in our country and having authority abroad was created in TsAGI. For the works of 1930–1940 in designing cooling systems of combat aircraft engines, the group of researchers of the Moscow Complex of TsAGI headed by K.A. Ushakov was granted the Stalin award. In 1977 for creation of shaft fans for the Norilsk mining complex, the Head of the Axial Fans Sector I. V. Brusilovskiy became the winner of the State Prize. It’s known that the tunnel fans developed in the Institute were installed in the Moscow Metro. “The workers of the underground railway still remember them with appreciation,” noted Viktor Mitrofovich.

According to the expert, about 80% of fans produced in our country are made as per TsAGI’s research results. One of the prospective applications of years-long achievements of the Institute in the aerodynamics of fans and elements of air flow ducts of air-moving systems today are lifting and propulsive systems of various aircraft and in particular unmanned vertical take-off and landing aircraft.

Remember the International Aviation and Space Shows MAKS-2013 and MAKS-2015. The TsAGI booth demonstrated models of vertical take-off and landing drones of single-fan and multi-fan designs. They caused increased interest among the visitors, and not least because of its unconventional appearance. Viktor Mitrofovich himself, slightly ironically but kindly, calls single-fan aircraft “pepelatsa” — recalling the famous domestic comedy “Kin-Dza-Dza.” Actually, the above mentioned vehicles deserve special attention among the vertical take-off and landing unmanned aircraft developed and researched by the specialists of TsAGI since the 1960s.

In 2006 the Institute’s scientists presented its development which constitutes a flying fan. The blade system (i.e., fan. — Editor’s comment) of this drone is surrounded by a casing being an annular wing and creates lifting force both in hovering and in horizontal flight, as well as protects the fan’s impeller against external impacts. The propulsive device is equipped with a straightener that prevents the swirl of air flow at the outlet, which means that it provides an absence of reaction torque typical for single-screw helicopters. The “flying fan” is fitted with audio and video cameras and a telemetry system. It can serve as an excellent aid, for example, in ice patrol. “Ice-breakers travelling on the Northern Sea Route should monitor the situation on the course. There are quite severe conditions, very strong wind, therefore serious restrictions exist for the application of helicopters. In such situations, the ‘flying fan’ can become an alternative, which screw is protected with annular casing,” states Viktor Mitrofovich.

“Initially, we focused on the single-fan scheme. Why? Because such kind of aircraft is able to fly both on its own and be a basis for more complicated assemblies,” he commented. That’s how the concept of transport drones presented at MAKS-2015 emerged. The lifting and propulsive system is formed by six fans, and supports are used for landing. According to the scientists, a drone of similar design can overcome a distance up to 300 km and transport up to 400 kg of cargo in a special container.

What are the advantages of such aircraft? What distinguishes them in the realm of drones? First of all — unpretentiousness to take-off and landing conditions. According to Viktor Mitrofovich, a ‘flying fan’ can even take off from a window sill and land in bush — it doesn’t need special grounds as for other aircraft. Protection of the blade system with a casing protects the drone from external damages. "Imagine a situation: you need to deliver rescue equipment to a burning building, e.g., a skyscraper. A helicopter needs to land on a specially prepared surface, whereas a transport drone doesn’t need such a “ceremonial reception,” explains the scientist. The compactness of the design has no less role: according to Viktor Mitrofovich, a six-fan aircraft will be no larger in size than an off-road vehicle. Finally, TsAGI specialists note that the annular casing enclosing each fan allows the application of aerodynamically highly loaded blade systems realizing the preset parameters at minimum circumferential speeds and correspondingly, at minimum noise levels. This is also an advantage before aircraft with free blades.

The field of application of such drones can be very wide. Fire extinguishing, participation in rescue operations, delivery of cargo to hard-to-reach areas — an incomplete list of variants of their operation. For instance, in the conditions of the extreme North, where the problem of logistics is especially critical due to severe climatic conditions, the TsAGI development has a chances to become one of the optimum solutions for the development of transport infrastructure. “Some time ago we visited the conference in Naryan-Mar. Local specialists took interest in our fan transport systems. You must agree that if there is a problem of delivery of a comparatively small cargo on a target route, it’s advisable to send a drone that prevents the risk of crew life, is economical and less sensitive to weather conditions due to its design,” says Viktor Mitrofovich.

“Flying fans” are controlled by radio channels. They are able to fly in both automatic mode by preset coordinates and under the control of an operator. According to the scientist, propulsion units of such drones can be anything: from an internal combustion engine, gas-turbine engine to electric drive and accumulator batteries. “Their combinations are permissible as well. For instance, combination of electric drive and gas-turbine engine — solutions may be very diversified,” notes the expert. As regards to the materials, the key requirement here is strength and low weight, because take-off from unprepared grounds and landing have the danger of damages of the structure. Therefore, composite materials acquire special importance for the creation of such aircraft.

“Fan-type drones are a special class of vehicle. It has been less studied and requires great scientific and experimental work. Special manuals and guidelines exist for designing airplanes, but sufficiently full recommendations for such drone projects don’t exist. But TsAGI possesses its own software created through many-years of experience of fan research. And our Institute is strong in its ability of comprehensive approaches to the development of such types of drones. Many enterprises, including those in other countries, dealt with such aircraft, but, perhaps, only TsAGI possess the whole set of methods and experimental abilities in Russia,” summarizes Viktor Mitrofovich.

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