RU2312379C9 - Method of predicting quantitative parameters of condensation trails emitted by aircraft engines for estimation of their compliance with permisible ecological level of emissions - Google Patents

Abstract

FIELD: aviation and ecology; environmental control.

SUBSTANCE: proposed method consists in measurement of altitude H in cruising flights, pressure P, temperature t_HB, partial pressure steam contained in atmospheric air e_HB, turbine exhaust gas temperature t_t and rotational speed of engine, calculation of temperature gradient of moisture mixed with exhaust jet B₀. Besides that, magnitude of quantitative parameter of steam super-saturation in mixed exhaust jet of engine is calculated by definite formula.

EFFECT: possibility of normalizing of quantitative characteristics of condensation trails depending on their effect on radiation balance of atmosphere and ground surface for reduction of content of carbon dioxide in exhaust jet of aircraft engine.

1 dwg

Description

The invention relates to the field of aviation and ecology in terms of air pollution and their impact on climate change and ways to reduce the impact.

Modern assessments of anthropogenic environmental impacts confirm the importance of a better understanding of the role of atmospheric pollution (particles, aerosols and gases) in the direct and indirect impact on climate change. The climate on earth is highly dependent on the process of radiant heat exchange between the atmospheric and terrestrial surfaces. As a result of this process, a balance of radiant energy is established - the radiation balance, which is the difference between the radiation absorbed by the earth's surface and its own radiation. The heat transfer process is as follows. At every moment of time, the earth's surface absorbs relatively short-wavelength solar radiation, heats up and emits already longer-wavelength (infrared) radiation In _ir . A significant part of this terrestrial radiation is absorbed by the atmosphere, which also emits long-wave radiation as a result. Part of this radiation is directed toward the earth and is called the oncoming radiation of the atmosphere, B _a . The flow of this oncoming radiation reaches the earth's surface, but it is not a completely black body, therefore only part of this radiation is absorbed δB _a . The difference between the intrinsic radiation B _o earth surface and part of the absorbed radiation δV _a counter called the effective radiation of the earth's surface B ^* = B _ik -δV _a.

If the effective radiation is positive, i.e. B ^* > 0, then the earth's surface cools and vice versa, if B ^* <0, i.e. δB _a > B _ir , then heats up.

Thus, the radiation balance of the atmosphere and the earth’s surface is established as a result of the interaction of the short-wave radiation coming from the sun, R ', and the long-wave (infrared) effective radiation of the earth’s surface. Quantitatively, this is expressed by the equation:

R = R'-R ^* = (1-r) F '+ (1-r) iB ^* = (1-r) (F' + i ) -B _uk + δB _a,

here r is the albedo; (1-r) F '- direct solar radiation; (1-r) i is the radiation scattered in the atmosphere.

Effective radiation depends on climatic conditions, season, time of day, and on the presence of gas pollution and aerosols in the atmosphere, especially water vapor, and even more so on drops of water and ice crystals, i.e. cloud cover.

Cirrus clouds play a very significant role in establishing the radiation balance, which, according to experts, can cover up to 30% of the earth’s surface on average, therefore an increase in their density and area as a result of anthropogenic influences may cause significant warming on Earth in the future.

A significant contribution to the pollution of the upper troposphere and lower stratosphere is made by aviation. The combustion products emitted by aircraft engines increase the concentration of carbon dioxide, water vapor, methane, nitrogen oxides, etc. and contain aerosols and particles, which in turn initiate the formation and development of cirrus clouds. As a result, all these factors increase the “greenhouse” effect of the atmosphere. In this context, the expected increase in air traffic may have a significant impact on the development, extent and frequency of cirrus cloud formation.

One of the most significant factors in the influence of aviation on the formation and development of cirrus clouds is the condensation trails (traces) of aircraft, which are formed as a result of condensation and freezing of water vapor contained in the exhaust jet of aircraft engines. Condleds are formed at the same heights as cirrus clouds, in structure they are close to them and they are even called artificial cirrus clouds (Cirrus tractus). According to estimates from the beginning of the 1990s, the area covered by the trail can be on average about 0.1% of the earth's surface, but varies greatly by region, and by 2050 it can be expected to increase to 0.5%. The expected increase will occur as a result of both an increase in air traffic and an increase in the efficiency of aircraft engines. But much more significant is that under appropriate meteorological conditions (increased humidity at low temperatures, usually below -40 ° C), in the upper layers of the troposphere and lower layers of the stratosphere, conduces can serve as a triggering mechanism (“trigger” effect) for formation and especially for intensive development of cirrus clouds existing near the route of the airway.

As you know, the environmental impact of aviation is divided into three categories: local pollution affecting the airport itself and its environs, regional impacts covering more extensive areas, and global impacts affecting the global climate as a whole due to an increase in the greenhouse effect. The influence of aviation on the formation and development of cirrus clouds is a global impact and may in the future cause a significant impact on the radiation situation on the planet.

In order to reduce pollution levels (noise and emission of gaseous substances and particles), ICAO recommends promoting the implementation of additional, including operational means and methods (rules, restrictions) to reduce the harmful effects on the environment. In connection with the foregoing, it is advisable to establish a quantitative criterion characterizing the trail, depending on the degree of their influence on the radiation balance of the atmosphere and the earth's surface. This, in turn, requires the establishment of a certain boundary value of such a criterion, a norm, the excess of which is considered unacceptable, and measures must be taken to reduce the harmful effects of the issue of conductor tracks.

For a quantitative assessment of the effect of traces on the change in the radiation balance, one should compare their influence with the influence of other polluting factors of aircraft engine emissions.

A report by the Intergovernmental Panel on Climate Change (A Special Report of IPCC Workning Groups of the Intergovermental Panel of Climate Change. Cembridge University Press, 1999) summarizes the Earth’s atmosphere on the effects of various components of aircraft engine emissions on the radiation balance of the atmosphere with an estimate of the level components at the beginning of the 1990s and projected by the 2050s. This is illustrated by the diagram in figure 1.

The main "greenhouse" or "greenhouse" (greenhouse) gas is currently considered carbon dioxide (CO ₂ ). The UN Kyoto Protocol (Kyoto Protocol to the UN Framework Convention on Climate Change dated May 9, 1992) states that other anthropogenic emissions of greenhouse gases should be estimated in the "carbon dioxide equivalent" and should not exceed the amounts established for them. The application for the invention proposes to compare the impact on the radiation balance of the conductor with the effects of carbon dioxide based on the IPCC Report. For this, it is necessary to determine the quantitative criteria characterizing the properties of the traces and establish a correlation dependence of these criteria with the intensity of the effect of the traces on the radiation balance. As such criteria, the “supersaturation indicator” of steam can be taken, which is the value of the maximum supersaturation of steam above water during cooling and mixing of the exhaust stream with the surrounding air.

When assessing the impact of conductor traces, stable, dense conductor traces should be taken into account, as they have a significant effect on the radiation balance. The conditions for the formation of the trail are characterized by the level of steam supersaturation in the mixed stream above water, and the conditions of existence (duration) of the already formed trail are characterized by the level of atmospheric humidity, and if the humidity of the ambient air is higher than saturation above the ice, then the trails will exist for a long time, if the humidity is It will be below saturation due to ice, the conductor will begin to evaporate and its lifetime will be limited.

With increased concentration in the atmosphere of nuclei (nuclei) of crystallization, traces can also form at humidity below saturation above water, but above saturation it is necessary to use ice. But the intensity of the formation of such traces is usually low and they are unstable.

Thus, the quantitative signs of a dense, stable conductor are the value of the supersaturation index above a certain positive value above water and the partial pressure of steam in the ambient air is not lower than the saturation pressure above the ice.

Methods for determining the conformity of polluting components of aircraft engine emissions to the maximum permissible standard concentrations are contained in the ICAO International Standard "Environmental Protection", Appendix 16 to the Convention on International Civil Aviation, Volume II "Emission of Aircraft Engines", 1993, and in those developed on the basis of this Standard Domestic Aviation Rules AP-34 "Environmental Protection. Emission of Pollutants by Aircraft Engines. Standards and Tests", 2003

In these documents, the following emission components are standardized and subject to compliance with standards: smoke (soot and other solid particles) and gases: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NO _x ). Compliance check is performed by sampling from the engine exhaust jet in bench conditions at engine operating modes corresponding to the stages of a standard take-off and landing cycle (take-off, climb, approach, taxiing, small earth gas).

The method of checking compliance of the concentration of gaseous substances with the standards is as follows:

- install the engine on a test bench;

- install the sampler in the center of the exhaust stream at a distance within 18 ... 25 diameters of the exhaust nozzle;

- start the engine and maintain to a steady state temperature in each test mode;

- a sample is taken for each component to be tested and fed to the appropriate gas analyzer;

- the obtained measurement data lead to standard atmospheric conditions;

- determine the quantitative value of the sample according to the formula D _p / F ₀₀ , g / kN, where D _p - the mass of the tested component in grams; F ₀₀ - take-off thrust set for a given engine in kilotons. The obtained value shall not exceed the standard value established for this emission component.

The method for checking the conformity of smoke is carried out in the same sequence, but the differences are as follows: the sampler is installed at a distance from the nozzle exit no more than 0.5 nozzle diameter, the selected sample is pumped using a vacuum pump through a filter device in which smoke particles are deposited on the filter element, remove the filter element, using a reflectometer determine the reflectivity of the contaminated filter R _s , compare it with the reflectivity of a clean reference filter R _w , SN = 100 (1 -R _s / R _w ), which shall not exceed the established normative value.

Closest to the proposed method is the method of the authors W. Schumann, R. Busen and M. Ploor (see Journal of Aircraft, V.37, No. 6. Nov.2000 and Aerosp, Sci. Technol, 4.2000), which measure the height , flight speed, pressure, temperature, atmospheric humidity, fuel consumption, calculate the temperature gradient of the partial vapor pressure (Δе _page ) in the mixed stream (which is the tangent of the angle of inclination of the mixing line) by the formula:

- индекс паровыделения (масса водяного пара, выделяющегося при сгорании 1 кг топлива), р - атмосферное давление, С_р - удельная теплоемкость воздуха, Q - теплотворная способность топлива, η - КПД тяги силовой установки самолета, ε=0,622 - отношение газовых постоянных воздуха и пара, строят график зависимости линии смешения от температуры е_стр=f(T) и накладывают его на график температурной зависимости парциального давления насыщенного пара над водой E_в и надо льдом Е_л, качественно сравнивают полученные графики и делают вывод: если линия смешения проходит высоко над кривой E_в и при этом величина парциального давления пара в окружающем воздухе e_нв не ниже давления насыщенного пара надо льдом е_нв≥Е_л, то образуется устойчивый, долго сохраняющийся кондслед, если линия смешения проходит близко к кривой E_в и парциальное давление пара в окружающем воздухе e_нв<Е_л, то образуется слабый, быстро исчезающий кондслед, если линия смешения проходит ниже кривой E_в, то кондслед не образуется.Where

is the steam evolution index (mass of water vapor released during combustion of 1 kg of fuel), p is atmospheric pressure, C _p is specific heat of air, Q is the calorific value of fuel, η is the thrust efficiency of the aircraft power plant, ε = 0.622 is the ratio of gas gas constants of air and steam, build a graph of the temperature dependence of the mixing line e _pp = f (T) and overlay it on the temperature dependence of the partial pressure of saturated steam above water E _in and over ice E _l , qualitatively compare the obtained graphs and conclude: if the mixing line p rohodit high above the curve E _in magnitude and thus the partial vapor pressure in the surrounding air e _nv not lower than the saturated vapor pressure over ice _HB e ≥E _L, then a stable, long-lasting kondsled if mixing line passes close to the curve E and _a partial the vapor pressure in the ambient air is e _nv <E _l , then a weak, rapidly disappearing trail forms, if the mixing line passes below the curve E _in , then the trail does not form.

The disadvantages of the method are as follows: there are no quantitative criteria characterizing the properties of the conductors, therefore they can only be assessed qualitatively and rather roughly, the method does not provide for the possibility of evaluating the conductors in relation to their effect on the radiation balance of the atmosphere and the earth.

The aim of the invention is to establish the principle of normalizing quantitative indicators of the characteristics of the conductors depending on their influence on the radiation balance of the atmosphere and the earth's surface so that the influence of the conductors does not exceed the effect of carbon dioxide in the exhaust jet of aircraft engines.

The technical result from the use of the invention is quantitative control over the effect of cruising flights of aircraft on the radiation balance of the atmosphere and the earth’s surface and, in the future, issuing recommendations on the development of measures to reduce the negative impact of conduction on changes in the radiation balance of the atmosphere and the earth’s surface.

(см. фиг.1), вычисляют величину показателя пересыщения пара (h_ΣДВ) в смешанной струе двигателя по формуле: h_ΣДВ=(t_М-t_НВ)·B₀-E_В(t_М)+e_НВ, где t_M - температуру, соответствующую максимальному пересыщению, определяют по формуле t_М=9,142 ln B₀-45,57°С; E_В(t_М) - парциальное давление насыщенного пара над водой при температуре t_M, сравнивают полученную величину показателя пересыщения h_ΣДВ с зачетным значением показателя пересыщения h_ΣЭД, соответствующим экологически допустимому уровню эмиссии кондследов (в эквиваленте воздействия двуокиси углерода), который заранее устанавливают следующим образом: анализируют результаты наблюдений полетов самолетов с различными типами двигателей, выделяют случаи начала образования устойчивых кондследов, в которых значения количественных показателей пересыщения не менее 10...12 Па соответствуют граничным значениям показателя пересыщения h_ΣГР, статистически осредняют полученные значения по всем выделенным случаям наблюдений h_ΣГР.СР и устанавливают экологически допустимое значение показателя пересыщения h_ΣЭД в эквиваленте двуокиси углерода (т.е. из условия, чтобы радиационные воздействия кондследов не превышали радиационного воздействия СО₂) с помощью соотношения:

To achieve this goal and obtain the expected technical result in the proposed method, which includes cruising flights, measuring the height H and the corresponding atmospheric pressure (P), temperature (t _HB ), partial vapor pressure (e _HB ) in atmospheric air, exhaust gas temperature behind the turbine (t _T ), rotational speeds and second fuel consumption of the estimated type of aircraft engine, calculation based on the above data of the temperature gradient of humidity of the mixed exhaust stream (mixing line gradient) (V ₀ ), st Atistic data from the results of studies of the intensity of radiation exposure to the atmosphere of various emission components of aircraft engines, in particular condoms (W _KC ) and carbon dioxide

(see figure 1), calculate the value of the index of steam supersaturation (h _ΣDV ) in the mixed jet of the engine according to the formula: h _ΣDV = (t _M -t _HB ) · B ₀ -E _B (t _M ) + e _HB , where t _M is the temperature corresponding to the maximum supersaturation, is determined by the formula t _M = 9.142 ln B ₀ -45.57 ° C; E _B (t _M ) is the partial pressure of saturated steam above water at a temperature of t _M , the obtained value of the supersaturation index h _{ΣДВ is compared} with the set value of the supersaturation index h _ΣED corresponding to the environmentally acceptable level of conductor emission (equivalent to carbon dioxide exposure), which is set in advance as follows: analyze the results of observations of flights of aircraft with various types of engines, identify cases of the beginning of the formation of stable condoms, in which the values of quantitative indicators supersaturations of at least 10 ... 12 Pa correspond to the boundary values of the supersaturation index h _ΣGR , statistically average the obtained values for all selected cases of observation h _ΣGR.СР and establish an environmentally acceptable value of the supersaturation index h _ΣED in the equivalent of carbon dioxide (i.e., from the conditions that the radiation exposure of the conductors do not exceed the radiation exposure of CO ₂ ) using the ratio:

и W_KC - интенсивности радиационного воздействия соответственно двуокиси углерода и кондследов. По данным Отчета IPCC 1999 года

и W_KC=0,026 Вт/м².Where

and W _KC are the intensities of radiation exposure, respectively, of carbon dioxide and traces. According to 1999 IPCC Report

and W _KC = 0.026 W / m ² .

By comparing the results of h _ΣDV with the value of h _ΣED , a conclusion is made on the conformity of the conductors emitted by the checked engine type to the environmentally acceptable level of emission: if h _ΣDV ≤h _ΣED , then the emission of the conductors is within acceptable limits, otherwise measures should be taken to reduce the emission intensity Conductors of this type of engine.

Example

The expected conditions for the formation of condleds and their quantitative indicators are predicted for flights at levels of 9, 10 and 11 km to assess their compliance with an environmentally acceptable level of emission.

At the indicated heights, measurements were made of pressure (P) and temperature (t _nv ) of atmospheric air, gas temperature behind the turbine (t _t ), engine speed (revolutions) and fuel consumption. Based on these data and the known flow characteristics of the engine type being evaluated, (α _cm ) and temperature (T _cm ) of the mixed jet at the nozzle exit of the engine are determined and then reduced to standard atmosphere conditions; the relative humidity for the calculations is taken to be 60%, which corresponds to the partial pressure of the vapor in the ambient air (e _nv ), equal to saturation above the ice at the appropriate temperature.

The data obtained are shown in the table:

N, km 9 10 eleven R, kPa 30.8 26.5 22.7 t _nv , ° С -43 -fifty -56 e _nv , Pa 9 3.8 1.8 α _cm 11.7 11.8 11.9 T _cm , K 376 370 367

We calculate the index of supersaturation of the vapor in the mixed stream h _Σdv :

h _Σdv = (t _m -t _nv ) B ₀ -E _in (t _m ) + e _nv , Pa,

where the gradient of the partial vapor pressure in the mixed stream (the tangent of the angle of inclination of the mixing line) is calculated by the formula:

where M _p is the relative mass of steam, for currently used jet fuel is equal to M _p = 0,084 kg / kg, E _in (t _m ) is the partial pressure of saturated steam above water at a temperature of t _m ; and the temperature t _m corresponding to the maximum supersaturation, determined by the formula: t _m = 9.142 ln B ₀ -45.57 ° C. The dependence of E _in on temperature is available in the reference and specialized literature, and is also approximated with satisfactory accuracy by the Magnus formula:

where a = 7.63 and b = 241.9.

The calculation results are summarized in the table:

N, km 9 10 eleven B ₀ , Pa / K 2.43 2.06 1.72 t _m , ° С -37.45 -38.95 -40.61 h _Σdv , Pa -2.1 5,4 10.8

и кондследов W_кс, которые по данным отчета IPCC 1999 года равны

и W_кс=0,026. Следовательно,

To determine the value of the supersaturation index, which corresponds to an environmentally acceptable level of conduction emissions, we will use the data from observations of consecrated traces, the analysis of which has established that the boundary value of the supersaturation index, corresponding to the beginning of the formation of stable conduces, is approximately hΣ _gr.avg = 10 ... 12 Pa, the environmentally acceptable value of the indicator h _Σed is determined taking into account the ratio of intensities of radiation exposure to the atmosphere of carbon dioxide

and kondsledov W _COP, which according to the IPCC 1999 report, the equal

and W _cc = 0.026. Hence,

We take the average value of h _Σed = 7.6 Pa.

From a comparison of the values of the indicator h _Σdv obtained above with the value of h _Σed, it can be seen that, at the level of 11 km, the effect of conductor tracks exceeds the permissible level. We interpolate the obtained data within the range of 9 ... 11 km and we find that the impact of the conductors does not exceed the permissible limit to an altitude of about 10.3 km, and at altitudes of 9.2 km and below, the formation of conductors in the considered operating mode of this engine is not expected.

Claims (1)

A method for predicting the quantitative indicators of condensation trails emitted by aircraft engines to assess their compliance with an environmentally acceptable level (EDU) of emissions, including measuring cruise altitude H, pressure P, temperature t _nv , partial pressure of atmospheric water vapor e _nv , gas temperatures the turbine t _t and the rotational speed of the engine type being checked, the calculation of the temperature gradient of humidity of the mixed exhaust stream B _o , characterized in that the quantity a significant indicator of steam supersaturation in the mixed exhaust stream of the engine under test h _Σdv = (t _m -t _nv ) In _o -E _in (t _m ) + е _нв , where h _Σdv is a quantitative indicator of steam supersaturation in the mixed exhaust stream of the engine under test; t _m is the temperature corresponding to the maximum supersaturation of steam in the mixed exhaust stream; In ₀ - temperature gradient of humidity of the mixed exhaust stream; t _nv - air temperature; E _in (t _m ) is the partial pressure of saturated steam above water at a temperature corresponding to the maximum supersaturation of steam; е _нв - partial pressure of water vapor in atmospheric air; and comparing the obtained value of the quantitative indicator h _Σdv with a predetermined value of the quantitative indicator h _Σed corresponding to the environmentally acceptable level of radiation exposure of airplane tracks, for this, according to the results of monitoring cruising flights of civil aviation within the conditions of formation of the tracks, there are cases of the beginning of the formation of stable tracks in which the values of quantitative supersaturation h _Σdv installed at least 10 ... 12 Pa statistical Ki values obtained are averaged for a plurality of parameter measurements _Σgr.sr h, a environmentally allowable value score is set _Σed supersaturation h of carbon dioxide equivalent, based on the condition that the radiation exposure kondsledov emission of radiation exposure does not exceed the carbon dioxide emissions into the atmosphere, according to the following the ratio

Where

and W _cc are the intensities of the radiation exposure of carbon dioxide and traces, respectively, of 0.018 W / m ² and 0.026 W / m ² according to the generalized data of the Intergovernmental Group of Experts (A Special Report of IPCC, Cembridge University, 1999), then, based on the results of the comparison, Conclusion on the conformity of the impact of the traces of the tested engine type to an environmentally acceptable level of emission.