Russian drones with a pulsating rocket engine
Now the topic of unmanned aviation does not leave the pages of popular science and military-technical publications, which is associated with a revolutionary technical breakthrough in this area, but the topic is far from new. And especially for Kazan. Here, in the late 1950s, the Sokol Design Bureau was created, which developed, in particular, flying targets for training air defense firing. In an updated form, the enterprise continues to work to this day, releasing targets on turbojet engines. However, in the late 1980s, in a difficult time for the defense industry, the former employees of the liquidated Sokol promising development department created their own production cooperative, which, surprisingly for those times, continued to create unmanned aerial vehicles. Nowadays, the company "Enix" produces several models of unmanned reconnaissance drones, as well as targets for air defense, but unlike the former colleagues from the "Falcon" Eniks chip - PuVRD.
“I became interested in PuVRD as far back as 1961, ” says Valery Pobezhimov, General Director and Chief Designer of Enix JSC, “and since then I have mainly been engaged in it. The problem is that when the global rocket and aviation industry switched to turbojet engines, interest in a pulsating jet engine faded away. Over the past decades, turbojet engines have been brought up to outstanding efficiency and fuel efficiency indicators, and nobody, with rare exceptions, has been involved in the development of PuVRD. This was partly due to the fact that the turbojet engine is very complicated from an engineering point of view, but simple from the point of view of the knowledge of the gas-dynamic processes occurring in it. With PuVRD everything is exactly the opposite. ”
PuVRD is an engine with no moving parts (valveless version) and almost no moving parts (valve version). The valveless PuVRD is a U-shaped design consisting of a combustion chamber and an input (shorter) and output (longer) pipe connected to it. Both pipes face one way. When launched, fuel (gas, gasoline, kerosene, coal dust) enters the combustion chamber and air is pumped. The mixture is ignited by an electric discharge, a flash occurs. The fuel mixture, expanding, expands, exhaust gases rush into both pipes, creating a jet draft. Fuel is supplied continuously. But when part of the exhaust already leaves the short inlet pipe, the other part still continues to move along the long outlet pipe. A rarefaction occurs in the combustion chamber, air is sucked in from the inlet pipe. Part of the exhaust also enters the combustion chamber, in which unburned fragments of fuel still remain. They ignite and the next cycle begins. That is, to ignite a mixture of electric discharge is no longer required. The pulsation of the expansion - rarefaction cycles occurs rather slowly - with a frequency of up to 160 Hz, and therefore the operation of the air-propulsion system is accompanied by an incredibly loud low-frequency buzz. (We spoke in detail about the design and operating principles of the engine in the August issue of the PM for 2013).
Originally from Russia
PuVRD, the simplest internal combustion engine, was born in the mid 60-ies of the XIX century. One of his fathers was the Russian engineer Nikolai Teleshov. At the same time, similar designs were presented by the Frenchman de Louvier and the Swede Wiberg. In the XX century, the famous Soviet rocket engineer Vladimir Chelomei, who even before the Great Patriotic War actively studied gas-dynamic processes in the engine and created his own designs, became a true enthusiast of this power plant. At the end of the war, Chelomei got acquainted with the captured samples of the German V-1 cruise missile (V-1), developed by Robert Lusser and Fritz Gosslau. On the basis of his own development and German experience, Chelomei designed the first Soviet cruise missiles 10X, 14X, 16X. The latter accelerated to 900 km / h, which was an enormous speed for the PuVRD, but Chelomei’s hopes that his beloved brainchild would be able to work effectively on supersonic sound did not materialize. I had to switch to a turbojet engine.
“In those days, the problem was that the study of complex non-linear processes that took place inside the engine was at an early stage, there was no reliable mathematical model for calculating more efficient air-propelled air-propelled air propulsion systems, ” says Valery Pobezhimov. - Our company is the only one in the country that not only produces flying targets on this type of engine, but also carries out research work to improve technologies. Here is an example: the French company Snecma produced its PURP with a thrust of 60 kg, in which the length of the outlet pipe is slightly less than 3 m. This is a lot for an aircraft that could push such an engine forward. Our M135 engines with similar thrust are three times shorter and fit perfectly into the size of the E95 target. Today, there is already a reliable mathematical model, new materials have appeared, for example, heat-resistant ceramics, and all this could seriously improve the characteristics of the PuVRD, but we are a small company, we are doing everything at our own expense and we cannot conduct broader research. ”
Fire on the ears!
PuVRD does not have to be an engine. It can be, for example, an effective heat generator - Enix had to build a plant for heating water pumped into an oil well by order of oil industry workers. More exotic applications may be found. “For example, an engine operating at a frequency of 7 Hz, ” argues Valery Pobeyzhimov, “at a certain power of the generated sound wave, it could act as a kind of acoustic weapon: such infrasound is fatal to humans. On the other hand, there were suggestions to build a PuVRD with an ultrahigh pulsation frequency (using electric ignition) - for example, 20, 000 Hz. For human hearing, it would work silently, but could in theory develop a much more powerful craving. However, the practical implementation of such ideas requires serious additional investments. "
Now, the use of PuVRD seems to be the most appropriate for flying targets. The main factor is the low cost of the power plant compared to the turbojet engine. The target is designed for a maximum of 10 launches, but, of course, its eyelid may be shorter if it is shot down. For such an essentially consumable, an expensive engine is a big luxury. The E95 targets and the recently introduced E08M (on a dual air-propulsion system) are launched from the catapult, reach speeds of up to 500 km / h, operate at altitudes from 100 to 2000 m. During the flight (both in manual control mode and offline) they are capable of twists and turns, dive with an angle of inclination of the trajectory to 30 degrees, perform figures "slide" and "snake".
Today, the territory occupied by the company "Enix", concentrated both design and manufacturing units. Here engines are made and final assembly of targets is carried out. Here in a small building, tests of promising models and finished serial engines are being tested. The engine starts in a special room, separated from the room with control equipment by a wall with a window made of thick glass. And still you have to wear headphones. Launched PuVRD quickly heats up and publishes its signature low and very loud rumble. The sound easily penetrates the headphones, and without them you can listen to this roar for a very short time!The article “Fiery pulse” was published in the journal Popular Mechanics (No. 11, November 2017).