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European Journal of Applied Sciences – Vol. 9, No. 5

Publication Date: October 25, 2021

DOI:10.14738/aivp.95.11057. Lokotko, A. V. (2021). Gas Turbine Jet Engine. European Journal of Applied Sciences, 9(5). 472-489.

Services for Science and Education – United Kingdom

Gas Turbine Jet Engine

Lokotko, A. V.

Doctor of Technical Sciences

ABSTRACT

The concept of a gas turbine jet engine is proposed. The purpose of the development

is to increase the thermal efficiency of the engine by increasing the temperature of

the working fluid. The engine is a Segner wheel type device with a rotating

combustion chamber and tangentially mounted nozzles. The torque is generated by

the reaction force of the jets emanating from the nozzles. Full expansion of the

working fluid takes place in a system of rotors installed coaxially with the

combustion chamber and also equipped with jet nozzles. Cooling of the combustion

chamber and chamber nozzles is carried out by a liquid metal coolant circulating

due to centrifugal forces in combination with the thermosiphon effect. Calculated

estimates show that at a working fluid temperature corresponding to the

combustion temperature of a stoichiometric mixture of hydrocarbon fuel with air,

the thermal efficiency in the design mode is 0.47, the specific fuel consumption is

0.25 kg / kWh, which is comparable with the corresponding indicators for diesel

engines. The device received: a patent of the Russian Federation for an invention

and a German patent for a utility model.

Key words: gas turbine jet engine (GTJE), nozzle, design mode, reaction force of outflow

jets, centrifugal compressor, multistage expansion, liquid metal coolant.

Gas turbine engines (GTE) have a number of advantages over piston engines. They have a higher

power density, a change in torque that is favorable for transport vehicles, i.e. better adaptability

coefficient, full expansion of the working fluid, 2-3 times longer resource due to balance and

minimization of rubbing surfaces, lower consumption of lubricating fluids, low requirements

for fuel quality regardless of the octane number, shorter preparation time for start-up,

especially at low temperatures. Meanwhile, GTJE are inferior to piston engines in terms of

efficiency. This is determined by the insufficiently high thermal efficiency (efficiency) - the ratio

of the useful work to the consumed heat - due to the limitation of the temperature at the turbine

inlet due to insufficient heat resistance ofthe turbine blades. Lowering the temperature of gases

to permissible limits in the known GTJE is achieved by supplying a large amount of air,

significantly exceeding that required for fuel combustion at a stoichiometric ratio [1].

Additional power is expended on pumping excess air. An increase in the permissible operating

temperature in certain cases is achieved by increasing the heat resistance of turbine blades, for

example, the use of thermal barrier coatings based on cermets and (or) internal cooling of the

blades. The best foreign gas turbine engines have a gas temperature at the turbine inlet of

1500C, with the prospect of increasing it to 1700C [2], but these values are significantly lower

than the combustion temperature of stoichiometric mixtures of hydrocarbon fuels with air,

equal to ~ 2100C [3]. That is, there are potentially opportunities to increase the temperature

of the working fluid and, consequently, to increase the efficiency of the engine. It is known [1]

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Lokotko, A. V. (2021). Gas Turbine Jet Engine. European Journal of Applied Sciences, 9(5). 472-489.

URL: http://dx.doi.org/10.14738/aivp.95.11057

that an increase in the temperature of the working fluid by every 50 degrees increases the

efficiency by 2%.

GTE installed on ground vehicles have relatively low power and, therefore, low air

consumption. In this case, the diameter of the turbine impeller turns out to be small, and in the

presence of rotor blades, the negative effect of the relative increase in the clearances between

the rotor and stator increases, and the efficiency of the turbine decreases.

With the aim of increasing the efficiency, it seems promising to create a jet gas turbine engine

with a rotating combustion chamber and the outflow of a working fluid from jet nozzles similar

to the Segner wheel known from the physics course. In this case, the turbine blades are

eliminated, which makes it possible to increase the temperature, and the gaps between the

rotor and the stator of the turbine are eliminated.

In essence, a device with rotating rocket engines is implemented, the thermodynamic efficiency

of which, as is known [4-6], is comparable to the efficiency of piston engines. The available rich

experience in cooling rocket engine nozzles operating at very high temperatures allows us to

hope for the possibility of implementing the combustion process of hydrocarbon fuels at a

stoichiometric ratio.

Jet devices that create a torque on the shaft and a gas turbine engine with a rotating combustion

chamber and jet nozzles are known [7 - 9].

The closest to the proposed device is the engine described in [9]. The power unit is made in the

form of a jet turbine, on the outer surface of the rotating combustion chamber (CC) of which

blades of a two-stage centrifugal compressor are installed, simultaneously playing the role of

cooling elements of the combustion chamber. Heat recovery is carried out by heating the air

entering the combustion chamber before the second stage of the compressor in a rotating

recuperator heated by exhaust gases.

The disadvantages of this technical solution are: additional heat supply to the air in the process

of increasing pressure, which reduces the compression ratio of the compressor and the

efficiency of the power unit as a whole, the difficulty of providing sufficient heat removal from

the combustion chamber due to the small coefficient of heat transfer to air. In addition, a single- stage turbine does not allow full expansion of the working fluid in the event of a further increase

in the compressor compression ratio.

In the proposed jet GTJE [10], these disadvantages are eliminated. The engine has a rotating

combustion chamber with gas outflow from tangentially located non-expanding nozzles. The

outflow occurs at the speed of sound at a critical pressure drop. When the pressure in the jet

and the surrounding space is equal (design mode), the wave pressure losses arising in the case

of supersonic outflow are eliminated. However, the use of nozzles with sonic outflow does not

allow the working fluid to be fully expanded in one stage; multi-stage expansion is required.

Subsequent expansion of the working fluid on turbine stages with traditional airfoil blades

would lead to a small degree of wheel partiality and large ventilation losses. Therefore, in the

engine under consideration, the expansion of the working fluid occurs in several rotating

chambers (rotors), sequentially covering the combustion chamber, the number of which