Test device for low-endurance thermal fatigue of structural materials in gas flows

FIELD: test equipment.

SUBSTANCE: device includes gas generator and operation part with structural material sample, connected in series. Gas generator features removable mixing head. Cylindrical combustion chamber of the gas generator features ignition device and orifice plate. Operation part includes interconnected clamping flange with central hole and flange holding a sample. Central longitudinal axes of flange and sample are coincident. Internal cylindrical surface of clamping flange forms an annular slot with the sample surface, the slot joins a cavity ending with output nozzle through end outlet holes in the flange around sample.

EFFECT: possible maintenance of required pressure-heat loading modes for samples, modelling natural thermal stress state of structural materials of various aggregates operating in alternate heat modes.

1 dwg

 

The invention relates to test equipment, namely to devices for the study of thermal fatigue of structural materials, and can be used for experimental verification of the calculated prediction of low-cycle strength of structural materials (heat-resistant steels and alloys) under the cyclic action of an inhomogeneous temperature fields and thermal stresses occurring in the material at a flow sample of high-velocity gas with different temperatures, simulating in situ conditions of temperature and force loading of structural materials (km), for example units of liquid rocket engines (LRE).

When working LRE structural elements subjected to impact loads (mechanical and thermal) associated in time with the startup processes that work mode on and off. LRE reusable (when debugging and certification tests) exposed to these types of loads repeatedly.

With repeated (cyclic) loading manifest in the material processes, typical of fatigue when loading and after removal of the load are the residual stress and the residual (plastic) deformation.

Uncooled design elements LRE, warmed on the stationary modes of operation to temperatures of the order of 600÷650°C, under�alauda at the output of the motor effects of non-stationary temperature fields with a high level of temperature gradients in the material together with the influence of internal pressure and when you turn off the engine - the effect of cooling the internal surfaces of the already-heated material (during the purging of the internal cavities), leading to the emergence of high gradients of temperatures.

High level of temperature gradients (at the start and during the engine operation) is carried out by wrapping the inner surface of the combustion products with a high convective heat transfer coefficients, and this leads to the compression strength of the material near the surface and, consequently, to the emergence of compressive deformation, transition with increasing temperature and increasing compressive stress in the plastic. Further heating of the structure with the alignment of the temperatures under the action of internal pressure results in stretching of the material at the inner surface and with increasing tensile stress to repeated plastic deformation when the engine is in a stationary mode. Cooling down with a lower convective heat transfer coefficients and temperature equalization structure during the cooling, ending the cycle of thermal loading causes compression of the material near the inner surface, usually in the elastic region of deformation.

On the outer side of uncooled lead structural members LRE under unsteady heating and the influence of� internal pressure tensile stresses occur and deformation, but plastic deformation can occur in the zones of stress concentration (change in thickness, the edge effects on the joints of structural members). When aligning fields of temperatures, the freezing and cooling are implemented compressive stress and strain.

Thus, cyclic thermal loads lead to accumulation of plastic deformation and further to a gradual destruction of the material (formation of fatigue cracks), the so-called thermal fatigue.

Similar processes of cyclic thermal impact on the material can occur in the machine elements working under conditions of variable thermal regimes, for example, in aircraft engines, power plant turbines, the devices of chemical technology, nuclear reactors, etc.

The known device for testing samples of materials in low-cycle thermostast in which the heating of samples of material in the loop is given by a direct electric current. For example, such a device is described in the article [1]. Also known devices in which the heating of the tubular samples is performed by a heater inside the sample. An example of such a device may be the device described in [2], where the sample is heated tungsten heater to a high temperature (1500°C).

Installations using t�Chia heating methods, do not allow across the sample uneven heating and cooling of material that occurs in the flow of the material gas flow with high rates of convective heat transfer, i.e. does not allow to simulate in-situ stress-strain state of the material under consideration of machine elements.

Known stand for testing properties of materials in the gas stream, protected by the patent [3]. Stand, described in the patent, is a complex structure that allows you to load samples of both mechanical and thermal load on a given cycle. In the study samples only thermostast the design of the stand can be easier. From the description of stand structure implies that the samples are gas tract across the gas stream. With this arrangement, heating of the samples will be uneven in height because of the "flow" of heat in places of fastening of samples, the so-called edge effect. In the presence of edge effects of the sample height should be such that there is some kind of working part of the sample, that is, the region where edge effects will be minimal. This can be attributed to shortcomings of the device.

Known apparatus described in the author's evidence [4] and developed on the basis of GOST 9.910-88 [5]. The unit is designed for ISS�of adowania thermal structural materials in gas flows and contains the working part (purge the chamber of rectangular cross section with grips for test specimens), connected to the combustion chamber, which serves the air and fuel. Installation is also provided with a supply system to purge the chamber of aggressive gases and blocks of management of heating of the samples and record the sample temperature and gas flow. This setting is closest in technical essence to the proposed invention and is selected as a prototype.

The disadvantages of such a facility may include, as in the above analogy, the presence of edge effects that occur when the selected form of samples and the method of installation. To completely eliminate the influence of the edge effects is almost impossible, even if the great height of the sample. This leads to the fact that the Central portion and the end portions of the sample heat flow varies. Furthermore, according to the prior art, the samples are installed in the blowdown chamber of rectangular cross section in several rows at equal distance from each other. With this arrangement, to ensure uniform flow of samples, and hence the same heating of the samples impossible. Samples located at the rectangular wall of the purge chamber, blown by a stream varies from two sides, as the channels formed by these samples on one side with the wall of the purge chamber, and on the other side with neighboring samples differ. All samples�tanglevine in the second row, must be at a distance from the first row of samples that the ow has time to recover, otherwise the flow of images of the second row will be different from the flow of images of the first row. Also the disadvantages include the prismatic specimens with a sharp edge parallel to the slit, as such samples are difficult to produce. In the described setup, the combustor operates in air and fuel. From the context it is clear that under the fuel refers to a kind of liquid fuel (kerosene, gasoline, etc.), this means that the composition of the combustion products is limited, and cannot model the impact on the samples of the natural gas stream of a different composition.

The technical task of the invention is to provide a simple design of the device, allowing to carry out intensive cyclic thermal loading of km by wrapping the surface of a sample gas flow of different temperature with high speeds, providing heating with high levels of temperature gradients in the material during the cycle. The device creates such conditions of test sample in which the sample material is implemented stress-strain state of near full-scale.

The thickness of the heated (cooled) of the sample material and, therefore, its characteristic size of sismer�we with thicknesses of real structures thermostast material which is investigated.

The technical result is that the design of the device allows to provide the necessary modes of thermal power loading samples with the full-scale simulation of thermal stress state of the investigated structural materials of various units operating under variable thermal conditions.

For solving the task and the technical result is proposed a device for experimental study of low-cycle thermal structural materials in gas flows, which consists of series-connected gas generator and the working part of the sample, the gas generator has a removable mixing head, a cylindrical combustion chamber of the gasifier is equipped with igniter and throttle washer, the working part consists of interconnected clamping flange with a Central opening and the flange is mounted with a sample, wherein the Central longitudinal axis of the flange and the sample are the same, the inner cylindrical surface of the clamping flange forms with the sample surface an annular gap, through which the end of the outlet holes, made in the flange around the sample, is connected with the cavity ending in an outlet nozzle.

Technical results� is achieved by the following features of the device:

1. In the study of thermal fatigue of the material used in a particular thermal stress unit, it is important to model variables the conditions in which the working parts of this material, as they determine appear in the material variables are the temperature gradients, leading reusable unit to the hysteresis of elastic-plastic deformations in the material and eventually to fatigue failure of the material, which at the initial stage manifests itself in the form of the generated surface cracks. Such conditions include the composition of the gas stream, its temperature, pressure and speed in the vicinity of the considered structural member at different points in time depending on the operating modes of the unit. These conditions define the process of heat exchange between the gas stream and the material. For heating the sample material in the proposed device uses a gas generator with temperature and composition similar to natural gas to flow over the parts in the Assembly. To obtain a gas stream of desired composition and temperature of the gasifier is used with interchangeable mixing heads, different type of mixing element (elements) constructed to provide optimal mixing of the components used fuel. For Oh�of ardania sample lines feeding fuel components is nitrogen (or air);

2. The characteristic size of the sample (diameter of the cylindrical part) is selected depending on the thickness of the material elements of real structures subjected to cyclic thermal and force effects. The design of the working part allows you to change the size of the annular gap formed by the cylindrical surface of the Central hole of the clamping flange and the cylindrical surface of the sample, by changing the size of the Central hole of the clamping flange. Changing the size of the annular gap and the selection of the appropriate gas flow allows to choose the desired speed of gas flow along the sample surface to provide the desired rate of heating (cooling) of the sample material, i.e. to simulate the desired cycle thermal power loading of the material. The rate of heating (cooling) of the sample material to the rate of heating (cooling) of the material under consideration of the sub-Assembly is checked by conducting unsteady calculation of the change of thermal state of the sample at a selected change of parameters of the gas flow over the cycle thermal power loading. The proposed design of the working part of the sample allows cyclic thermal loading of km by wrapping the surface of a sample gas with high velocities, providing a high insulation level�ü temperature gradients in the material per cycle.

To ensure uniform composition of the gas stream to the working part of the installation length of the combustion chamber of the gasifier should be at least 7-10 its diameters, in addition, in the Central part of the combustion chamber is installed a throttle washer, the diameter of which is selected such that the pressure drop across it amounted to several atmospheres. For uniform flow initial segment sample projecting into the combustion chamber, has a conical shape with a rounded end.

Since the sample is in the form of a body of rotation, it is possible to make it easy.

The essence of the invention is illustrated by the figure, which shows a diagram of the device for the study of low-cycle thermal structural materials in gas flows.

The proposed device includes a gas generator 1 and connected in series with him working part 2. The gas generator 1 has a removable mixing head 3. The cylindrical combustion chamber 4 of the gas generator 1 is equipped with a throttle washer 5 and the ignition device 6. The working part consists of interconnected clamping flange 7 with a Central opening and a flange 8 is mounted with a sample 9. The Central longitudinal axis of the flange 8 and sample 9 coincide. The inner cylindrical surface of the clamping flange 7 forms with the outer cylindrical surface�the surface of the sample 9 the annular gap 11, which end of the outlet holes 10 formed in the flange 8 around the sample 9, is connected with the cavity 12, ending in an outlet nozzle 13.

A study of low-cycle thermal km (heat-resistant steels and alloys) in gas flows using the proposed device in the following way.

In the study of thermal fatigue of machine elements working under conditions of variable thermal regimes, determined by the conditions in which the working parts of the investigated material. These conditions include thermophysical parameters (temperature, pressure, composition, speed) of the gas flow around the considered structural elements of the unit. Thermophysical parameters of the gas flow vary in time in accordance with the modes of the plant, the change of which in a single unit is one cycle of thermal power loading of the material. The totality of these parameters and their change in time define appear in the material, the temperature gradient, that is, determine the change of thermal stress state of the material during operation of the unit under consideration.

Depending on the thickness of the material under consideration, the elements of real structures subjected to cyclic thermal forces�the PTO effects, select the diameter of the cylindrical part of the sample. Then taking into account the working conditions of parts of the test material is determined by the size of the annular gap, which is at a selected gas flow rate will provide a desired rate of heating (cooling) of the sample material. To check the implementation of the required rate of heating (cooling) of the sample material at the selected geometric dimensions of the working part and the sample and changing the parameters of the gas flow during the loading cycle (heating and cooling), carried out a calculation of transient heat flow of the sample gas flow with temperature and composition, varying according to a given cycle. Next, the sample is made of the investigated material and is installed with an interference fit in a blind hole (nest), made in the flange 8. Surface treatment and heat treatment technology of the sample material should correspond to the surface treatment and heat treatment of the material of the considered structural element.

The sample construction material installed in a blind hole (socket) flange of the working part, so that the Central longitudinal axis of the flange and the sample coincided. The said flange is connected to the clamping flange of the working part and the flange of the cylindrical combustion chamber of the gasifier.

Modeling cycle thermal power loading mater�Ala of the structural elements of the unit under consideration is provided by the alternation of modes of operation of the gasifier of the proposed device. To heat the sample 9 material in the combustion chamber of the gasifier is the burning of the fuel components in the ratio required for generating gas of desired composition and temperature. The ignition of the fuel components is carried out igniter. In this case the mixing head of the gas generator is selected proceeding from the condition to ensure optimal mixing of the components used fuel. In the flow of the sample received the gas generator at a rate determined by the selected flow parameters (flow rate, composition and temperature of the gas), and the preferred size of the annular gap, in the sample material occurs, the temperature gradient of the near-field, that is, provide the desired heating rate of the material. The cooling of the sample used nitrogen (or air), which is served by lines feeding fuel components in the gas generator, with stops supply of the fuel components in the gas generator. Nitrogen is commonly used in rocket engines with blow-by highways from residual fuel components. Range of flow rate of nitrogen (or air) for the selected size of the annular gap is provided by the desired rate of cooling of the sample material. Fed on lines of the oxidant and fuel nitrogen (or air) also provides purge highways fuel components and cavities is open�your head from residual fuel components.

The pressure in the system is ensured by selection of the size of the outlet nozzle 13.

Manage change modes of heating and cooling in the device is realized by automation of the test bench in a predetermined sequence diagram corresponding to a single cycle thermal power loading of the sample material.

The device operates as follows. On the mode of heating of the sample material components fuel ratio required for generating gas of desired composition and temperature, are served in the mixing head 3 of the gasifier 1, where they are ignited using the ignition device 6. The products of combustion of the propellants entering the combustion chamber 4 in the working part 2, flow around the sample 9, which guarantees the desired heating rate of the sample material. If in a loop of loading provides the transition to the heating mode with a different temperature (higher or lower), the automation of the test bench changes the flow rate of one of the components of the fuel, which in turn changes the ratio of fuel components and, respectively, temperature of the combustion products. Appropriately changing the heating rate of the sample material. When switching from the heating mode to the cooling mode turns off the supply of fuel components in the mixing head of the gas generator, and the lines flow components Topley�and served the nitrogen (or air), with the flow providing the desired cooling rate of the sample material. At the same time nitrogen is blown through the supply line and the cavity of the mixing head from the remnants of the fuel components. The temperature and pressure of the gas flow at different modes of operation are controlled by temperature sensors (thermocouples) and pressure mounted on the combustion chamber of the gas generator before working parts.

Periodically after a certain number of loading cycles with the help of modern diagnostic tools are inspecting the surface of a sample for the presence of surface cracks. Upon detection of surface cracks is compared experimentally obtained number of load cycles until fatigue cracks with the calculated values obtained for this sample. The frequency of inspection of the sample surfaces for cracks is selected based on the computational prediction of low-cycle strength.

Method of calculation to determine thermal stress state and prediction of low-cycle strength include:

1. The formation of the array of source data, including mechanical (elastic modulus E, coefficient of thermal linear expansion α, the tensile strength σin, proof strength σ0,2the coefficient of transverse contraction ψ) and thermophysical (heat coefficient�rovagnati - λ, specific heat - CP, density ρ) characteristics of the investigated materials depending on the temperature, composition, pressure, temperature and thermophysical characteristics of the gas flow (molecular weight M, the coefficient of thermal conductivity λ, specific heat - CP and the dynamic viscosity µ) depending on the mode of operation of the unit under consideration;

2. The choice of the computational domain of the test sample or host unit. The computational domain depends on the geometry of the sample or host unit and is chosen according to the symmetry of boundary conditions;

3. The formation of the boundary conditions that determine the change in heat and thermal stress state of the investigated sample or sub-Assembly in accordance with the modes of operation of the gas generator or of the unit under consideration, the components of the cycle thermal power loading of the material.

To the boundary conditions for thermal calculation are the conditions of convective heat transfer (α - coefficient of heat transfer, T is the temperature of the gas flow along the streamlined surface of the sample or sub-Assembly, variable in time according to the modes of operation of the gasifier or the air handling unit.

To the boundary conditions for the calculation of thermal stress state are the pressure distribution and its change in time and three-dimensional temperature field of nestacionarnog� thermal calculation (see (4));

4. Using the finite element method is non-stationary thermal calculation for determining the change in thermal state of the sample and (or) node unit for cycle thermal power loading.

The results of calculations of thermal state of the sample is verified that the rate of heating (cooling) of the sample material to the rate of heating (cooling) of the material of the reality of the host unit when the selected geometric dimensions of the working part of the sample in combination with changing the parameters of the gas flow over the cycle thermal power loading. Received, the time varying cycle of loading three-dimensional temperature field is a boundary condition for the calculation of thermal stress state of the sample or host unit;

5. Using the finite element method calculation of thermal stress state of the investigated sample or host unit and the estimate of the number of loading cycles before the formation of fatigue cracks (cracks).

According to the results of the calculations determined the most dangerous in the amplitude of plastic deformationΔεaiplace. Build settlement and deformation diagram in the coordinates σθθ- εθθand σXX- εXXand graphs of εi, εθθcycles of loading NC.

By the calculation diag�the AMM define the parameters to calculate the number of cycles [6]:

- the amplitude of the intensity of deformationΔεai;

the ratio η=(σXXrrΘΘ)/σitaking into account the three-dimensionality of the stress state.

The number of cycles NCbefore the formation of the crack is calculated from the relation

Δεai=εpp(η,T)(4NCm+1+re1-re)-1+σ-1E(T)(1+σ-1σin1+re1-re)-1

where reiminimaxthe ratios of the intensity of deformation;

εPR(η,T) is the maximum deformation as a function of depth of the stress state and temperature;

σ-1=k-1·σB- the limit qi�chip metallic strength k-1=0.4-0.002·(σB-70), determined by the tensile strength σB(kg/mm2), as a function of temperature;

m=0.5-0.002·(σB-70).

Experimental verification of the calculated prediction of low-cycle strength of structural materials under cyclic action of an inhomogeneous temperature fields and thermal stresses occurring in the material when the flow around the surface high-velocity gas with different temperatures, simulating in situ conditions of temperature and force loading of structural materials of various units operating under variable thermal regimes, allows to verify the computational method. Further this calculation method allows to receive and consider the forecasts of low-cycle strength already at the design stage of similar units operating in conditions of multiple variable thermal regimes.

The design of the proposed device allows you to quickly and correctly carry out studies of low-cycle thermal structural materials of various units operating under variable thermal regimes, with full-scale simulation of thermal stress state (TNDS) structural members to define the limits of low-cycle strength.

LIST of CITED DOCUMENTS

1. Golubovsky E. R., Bychkov N. G., Khamidullin S. A., �azlea O. A. Experimental evaluation of crystallographic anisotropy of thermal fatigue of single crystals of the alloy based on NI3AL for high temperature parts of aircraft gas turbine engines. FSUE TsIAM them. P. I. Baranova and FSUE VIAM. Bulletin of engine No. 2/2011.

2. Romanov A. N. The fracture under low-cycle loading. M.: Nauka, 1988. 282 PP.

3. Stand for testing the mechanical properties of materials in the gas stream. Patent RU 2377529 C1, 08.12.2008.

4. Method of testing samples of materials to thermal fatigue. Author's certificate SU 1173256 And, 25.01.1984.

5. GOST 9.910-88 unified system of protection from corrosion and ageing. Metals, alloys, heat-resistant coating. Test method thermostast gas flow in a wedge-shaped samples. M.: Gosstandart, 1988.

6. Makhutov N. And. Deformation fracture criteria and calculation of structural members for strength. M.: Mashinostroenie, 1981. 272.

A device for investigation of low-cycle thermal structural materials in gas flows, consisting of series-connected gas generator and a working part with the sample construction material, characterized in that the gas generator has a removable mixing head, a cylindrical combustion chamber of the gasifier is equipped with igniter and throttle washer, the working part consists of interconnected Saginov� flange with a Central opening and the flange is mounted with a sample, the Central longitudinal axis of the flange and the sample are the same, the inner cylindrical surface of the clamping flange forms with the sample surface an annular gap, through which end output holes formed in the flange around the sample, is connected with the cavity ending in an outlet nozzle.



 

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5 cl, 1 tbl, 4 dwg

FIELD: power engineering.

SUBSTANCE: reactor vessel steel samples are heated to temperature from 300°C, their further ageing is carried out at this temperature within certain time, subsequent tests of samples are carried out for impact bending, and test results are analysed to determine the value of the shift of critical brittleness temperature, at the same time samples of reactor vessel steel in process of ageing at the temperature of reactor vessel operation of 300-320°C are additionally exposed to neutron radiation with flux of 1011-1013 n/cm2·sec for 103 hours, after that they perform baking at the temperature of 400-450°C with duration of at least 30 hours, and assessment of extent of steel embrittlement is determined using the value of shift of critical brittleness temperature ΔTk(t) as a result of thermal ageing for the time making more than 5·105 hours, in accordance with a certain mathematical expression.

EFFECT: increased accuracy of assessment of extent of embrittlement of VVER-1000 reactor vessel embrittlement as a result of thermal ageing.

3 tbl

FIELD: process engineering.

SUBSTANCE: invention relates to monitoring the flue gas composition. This method is suitable for monitoring of steam boiler operation at burning the chlorine-containing fuel. It can also be used at pyrolysis, gasification and the like processes. Composition of flue gases resulted from thermal processes, particularly, at combustion of biological fuel or fuel produced from wastes is monitored by measurement of quantity of particles of definite sizes at, at least, one point in flue gas path. Measured are particles of sizes that are known to be composed of alkaline metal chlorides.

EFFECT: monitoring of alkaline metal chloride compositions in flue gases.

9 cl, 6 dwg

FIELD: physics; control.

SUBSTANCE: invention relates to space, aviation, radio engineering, instrument-making and mechanical engineering and can be used in all industries for automatic control of the thermal state and functional parameters of technical devices. The method for automatic control of the thermal state and functional parameters of technical devices involves setting and determining the type and parameters of thermal functions of technical devices, from which values of thermal functions during operation of the devices and downtime thereof are calculated, and making adjustments in actuating devices through a numerical control computer system upon reaching the calculated values of set acceptable values. The method involves determining the type, the time variation characteristics of standard laws of thermal functions of the position, movement and state of technical devices, heat-loaded parts thereof, assemblies and components during heating and cooling thereof for each controlled functional parameter during operation of a technical device and during downtime thereof. Statistical characteristics of the time variation of thermal functions of heating and cooling for each controlled functional parameter during operation of the device and during downtime thereof are established during multiple tests. The obtained characteristics of the time variation of thermal functions in the working volume of the technical device during operation and downtime thereof are then used to calculate the value and/or position and/or movement and/or state of the controlled functional parameter in accordance with the operating time or downtime, for the current range of positions, movements and states of heat-loaded parts, assemblies and components of technical devices, and when values and/or positions and/or movements and/or states reach, with given probability, set acceptable values, the controlled functional parameter of the technical device is adjusted through a numerical control computer system by changing and acting on current parameters and functioning characteristics which define the level of the thermal conditions or state of heat-loaded devices.

EFFECT: high accuracy of functioning of technical devices, high reliability thereof, stability of maintaining the level or range of values of functional output parameters of the position, movement and state of technical devices during operation thereof, carried out without using additional mechanisms, devices and systems for measuring temperature and/or thermal deformations and/or the position and/or movement and/or state of heat-loaded parts of devices.

6 dwg

FIELD: measurement equipment.

SUBSTANCE: device comprises: a sensor comprising a sensitive element and a heating element configured for heating of the sensitive element to the previously set operating temperature, besides, the sensitive element is perceptive to the specified gas so that at least one electric property of the sensitive element varies depending on presence of the specified gas, besides, the electric property of the sensitive element is measured by a gas metering device; and a control circuit comprising a heating element controller connected to the heating element and measuring its electric property, besides, the control circuit has a source of heating energy supplying energy to heating element. The controller of the heating element is connected with a source of heating energy and controls its operation depending on measurement of the electric property of the heating element; a facility of pulse modulation connected with the controller of the heating element, the source of heating energy for control of the energy value supplied to the heating element. At the same time the facility of pulse modulation is made as capable of generation of the first set of energy pulses, having certain duration, and the second set of energy pulses, having another, shorter duration for maintenance of temperature of the heating element substantially at the permanent level. Also the invention relates to the method for manufacturing and method of operation of the gas metering device.

EFFECT: device is manufactured and operated in a profitable and reliable manner.

8 cl, 5 dwg

FIELD: physics.

SUBSTANCE: method of determining dryness of wet steam involves measuring pressure in a controlled stream of steam. A steam sample is then collected from the controlled stream, the collected sample is throttled into a flow chamber and calculations are carried out based on the measured parameters. The collected steam sample flows from the first flow chamber into a second flow chamber. Both chambers are placed in the controlled stream of steam or other heating medium. Pressure and temperature is measured in each chamber. After the second chamber, flow rate, pressure and temperature of the collected sample is measured. The value of flow rate is then established based on parameters measured in the first chamber.

EFFECT: determining dryness of a stream of wet steam without condensing the collected sample.

1 dwg

FIELD: measurement technology; material quality control.

SUBSTANCE: method involves testing lubricant material sample in presence of air with stirring constant volume under optimum temperature selected with its dependence on lubricant base and a group of operational properties during a time interval characterizing equal oxidation degree taken into account. Acting in equal time intervals, absorption coefficient is measured for luminous flow absorbed by oxidized lubricant material by applying photometry methods. Viscosity and thermal oxidative stability coefficient Ktos are calculated by using relationship like Ktos = Ka μ0in, where Ka is the luminous flow absorption coefficient of oxidized lubricant material; μ0 and μin are the viscosities of oxidized and initial state lubricant, respectively. Graphic dependence of thermal oxidative stability coefficient against luminous flow absorption coefficient of oxidized lubricant material is plotted. Rate of oxidation end products release and their influence upon tested lubricant viscosity growth is determined from plot slope angle tangent with respect to abscissa axis after inflection point. The inflection point coordinates are used for determining the starting point the oxidation end products release begins.

EFFECT: high reliability of estimation method.

4 dwg

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