Gas-dynamic Stability Research Articles

Influence of space–chord ratio of the airfoil cascade on the flow «choking» regimes in the blade channel

Gas turbine engines are a major part of propulsion systems of different aircrafts. Gas-dynamic stability of compressors of aircraft GTE is achieved by using various compressor regulation methods to ensure unstalled flow of blade rows in all operation modes of the engine. The loss of gas-dynamic stability of the compressor is caused by flow separation in blade rows and critical flow regimes (flow “choking” regime) in the blade channels of separate stages. So far, flow “choking” regimes in the blade channels are not fully investigated. The effect of the cascade space–chord ratio on flow “choking” regimes in the blade channels of the airfoil cascade was studied in the paper. The authors have proposed a theoretical relationship, allowing to calculate flow “choking” regimes with different space–chord ratio of the airfoil cascade. The authors have performed a series of calculations of flow in airfoil cascades in “choking” regimes using numerical simulation. To close the averaged Navier-Stokes equations, the Menter’s SST model was used. Adaptive irregular computational grid was selected to solve this problem. For the calculation, second-order design scheme with the local use of the first-order design scheme was used. Results of studying the flow in airfoil cascades have shown a significant effect of the stall zone behind the front edge of the blades at negative angles of attack on the flow in the blade channels. Decrease in the actual minimum flow area of the blade channel leads to a reduction in the value of the Mach number Ммах, at which flow “choking” regime in the blade channels by the air consumption occurs. The results have shown that the greater the space–chord ratio of airfoil cascades, the larger the relative influence of the boundary layer thickness on the critical flow regime. Generalized characteristics of “choking” regimes of compressor cascades can be used for calculating “choking” regimes of the axial-flow compressor stages in determining the boundaries of gas-dynamic stability and “choking” boundaries of multi-stage axial-flow compressors.

RAISING GAS-DYNAMIC STABILITY MARGIN OF AXIAL AND CENTRIFUGAL COMPRESSOR STAGES BY MEANS OF VANED DIFFUSER BOUNDARY LAYER CONTROL / DUJŲ DINAMINIO STABILUMO RIBOS AŠINIO IR IŠCENTRINIO KOMPRESORIAUS PAKOPOSE DIDINIMAS ATLIEKANT STABILIZUOTO DIFUZORIAUS PARIBIO SLUOKSNIO KONTROLĘ

Generalised research results that consider the upgradability of axial and centrifugal gas turbine engine compressors by means of gas-dynamic boundary layer control on bladed disks are demonstrated. Active and passive methods are used. Comparative analysis of the results has been carried out. The analysis is purposed to determine the influence of the flow circulation around the aerofoils on the performance of compressor single-row bladed disks with smooth blades and rough blades and under the condition that vortex generators are installed. An increase in the efficiency of aviation gas-turbine engines and in their gas-dynamic stability margin support leads to the enhancement of the parameters and performance of compressors: increase in loading of aerodynamic bladed disks, improvement of their economical efficiency, improvement of margin of the continuous flow around the compressor grids, etc. Airflow in the compressor grid is characterised by the flow region in the flow core and also by the flow regions in the wall boundary layers on the grid blades where shock waves, vortices, air swirls, and flow separation phenomena take place. The principle objective of the work is to research the possibilities of influence on the parameters of the elements of compressors and overall performance of gas-turbine engines via the methods of active and passive flow regulation. Active flow regulation is realised either by rendering the auxiliary gas mass to the blades boundary layer, or by suction (withdrawal) of the boundary layer (its part) from the surfaces of blades. Passive flow around regulation is characterised by influence on the boundary layer by means of energy redistribution in the flow itself. Santrauka Šiuo tyrimu siekiama nustatyti sparno profilio aptekejimo įtaką vienos eiles menčių kompresoriaus su lygiomis ir šiurkščiomis mentemis darbui, esant įdiegtiems sūkurio generatoriams. Pagrindinis darbo tikslas – ištirti kompresoriaus elementų ir bendro dujų turbininių variklių darbo įtaką parametrams, taikant pasyvų ir aktyvų srauto reguliavimo metodus. Padidinus dujų turbininių variklių našumą ir jų dujų dinamikos stabilumo ribas, pagereja kompresorių darbas ir parametrai: padideja aerodinaminių diskų su mentemis apkrova, jie tampa ekonomiškai našesni, padideja nepertraukiamo srauto riba aplink kompresoriaus plokšteles.

DYNAMICS OF LOSS OF GASDYNAMIC STABILITY OF TURBO-ENGINE

Dynamic of rotating stall and surge development in axial compressor after loss of gasdynamic stability is considered in the article. The Moore—Greitzer model is used for research. The model takes into account non-linear features of compressor characteristics and property of the compressor system. A bifurcation analysis was carried out to determine the system stability.

USE BIFURCATION THEORY TO ASSESS THE STABILITY OF CURRENTS IN THE AXIAL COMPRESSOR

In the paper surge is considered as self-oscillation phenomenon. Possibility of surge prediction and effect on its development with the help of feedback controllers is investigated. Solving of a problem of non-linear control using the bifurcation theory is considered in the article. The Moore—Greitzer model (MG86) is used for research of processes in the compressor after loss gasdynamic stability. The model takes into account non-linear features of compressor characteristics and property of the compressor system. The model allows to determine what type of phenomena (rotating stall or surge) can appear, to establish distinctions in character surge oscillations and to estimate influence of various factors on area surge modes, to determine area of steady modes.

Метод визначення температури газу перед турбіною газотурбінних двигунів

Calculating method of definition of gas temperature before turbine is represented. This method is based on using of compressors characteristics and gasdynamic stability of GTE

Features of performing stall tests and adjusting antistall systems for protecting centrifugal compressors with electromagnetic bearings

Stall tests are performed for superchargers NTs-16/76-1.44 and NTs-12/56-1.44 under operating conditions with a reduction in flow rate by 15–20% below the calculated stall limit (confirmed by tests on model gas, and here stall is not recorded). It is established that the position of the line for the safe operating limit of gas dynamic stability depends markedly both on the electrodynamic properties of the magnetic suspension control system and on the magnetic properties of the supercharger rotor (weight, moment of inertia, natural bending vibration frequencies, etc.).

Dynamic of gas turbine engine gasdynamic stability loss

Dynamic of rotating stall and surge development in axial compressor after loss of gasdynamic stability is considered in the article. The Moore – Greitzer model is used for research. The model takes into account non-linear features of compressor characteristics and property of the compressor system. To determine system stabile state bifurcation analyze is carried out.

Incorporating the gas-dynamic stability margin in determining the working range for an axial compressor

Experience has shown that the failures that lead to breakages and shutdowns in turbine compressors are substantially related to the loss of gas-dynamic stability or prolonged operation near the stability limit, i.e., under conditions where there are prominent detached flows characteristic of that zone. The main reason for such failures is the inadequate gas-dynamic stability margin adopted for the steady-state and transient modes.

Estimation of gasdynamic compressor stability characteristics of turbojet engine in operation

Considered is the method of evaluation of gas dynamic stability of compressors in operation. The method is based on the determination of position of operating rating curve on curves of compressors taking into consideration conditions of joint work units of gas turbine engine. Given are results of numeric experiment for three-shaft two-flow turbojet engine D-36 on PC

Spectrum of gas-dynamic perturbations and stability of a supersonic plasma flow in the presence of joule heating

Spectrum of gas-dynamic perturbations and stability of a supersonic plasma flow in the presence of joule heating

Intense Beam Heating of an Orifice Flow

Experimental results are reported for the first time on orifice flows in which deposited electron-beam energy exceeds flow stagnation enthalpy. The experiment simulates the ion-beam-gas-flow interaction of the gas-target neutron generators planned for fusion engineering research. While gas-dynamic stability is observed, plasma-dynamic-gas-dynamic interactions are found to be important at high power and ionization densities.

Experimental simulation of a free jet gas target neutron generator

The interaction of a tritium ion beam and a deuterium free jet gas target reproduces the true fusion neutron spectrum, and the large heat removal capacity of the deuterium flow makes this system a possible high flux (≳ 10 14 neutron/cm 2 s) source for CTR materials research. Experimental simulation of the Free Jet Gas Target Neutron Generator concept was carried out with the use of a powerful electron beam impacting on a nitrogen free jet target in order to investigate the gas flow charateristics, including gas dynamic stability, as well as the radiative and plasma properties of the target. These experiments, the first in which beam energy greater than gas stagnation enthalpy has been deposited in a high speed flow, indicate gas dynamic stability of the targets tested.

Investigation of the gasdynamic stability of a detonation wave in a gas mixture

Investigation of the gasdynamic stability of a detonation wave in a gas mixture

Allowance for gas-dynamic factors in the design of electric-arc heaters with vortex gas stabilization

The gas-dynamic stability limits of electric-arc heaters have been experimentally investigated and the effect of the principal electrical, gas-dynamic and geometrical factors on arc stabilization is established. A design equation for calculating anode diameter is obtained such that steady vortex stabilization is ensured within the operating range of the heater.