RU2532074C2 - Method to assess serviceability of catalytic neutraliser of spent gases of internal combustion engine with forced ignition - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to devices for treatment of spent gases of gasoline internal combustion engines with forced ignition (ICE). The method to assess serviceability of a catalytic neutraliser of spent gases of a gasoline ICE consists in determination of the ratio of quantity of carbon dioxide (CO₂), contained in spent gases arriving to the catalytic neutraliser and also leaving it, and making a decision on serviceability of the catalytic neutraliser by the value of the specified ratio. Detection of CO₂ quantity is carried out by measurement with ICE in service.

EFFECT: provision of valid detection of serviceability of a catalytic neutraliser by minimum number of parameters.

7 cl, 1 dwg

Description

The invention relates to the field of engine manufacturing, in particular to exhaust gas purification devices for internal combustion engines (ICE) with positive ignition.

BACKGROUND

Air pollution by harmful exhaust emissions from internal combustion engines in the 21st century has become one of the global environmental problems. There is only one way to solve it - the car should become environmentally friendly. An important place here belongs to neutralization systems that can several times reduce the toxicity of exhaust gases.

According to their chemical properties, the substances contained in the exhaust gases are divided into several main groups: oxygen, water vapor, carbon oxides (CO), nitrogen oxides (NOx), sulfur dioxide, hydrocarbons (CH), aldehydes and soot.

There are EUROPEAN (Euro 3, Euro 4, Euro 5) and CALIFORNIAN (LEV, ULEV, SULEV) standards that establish standards for the toxicity of exhaust gases by the content of CO, CH and NOx in them.

During the existence of the problem of exhaust emissions, many methods and methods have been developed to reduce their amount or reduce toxicity, for example:

- improving the design of ICE and improving the quality of their manufacture;

- the search for new types of fuel and the use of various fuel additives;

- the creation of power plants for cars that emit less harmful substances;

- the development of devices that reduce the content of harmful components in the exhaust gases.

Practice has shown that at the same time it is impossible to achieve the level of toxicity of exhaust gases (FG) required by the legislation of developed countries in the first three ways. Therefore, neutralization of exhaust gases in the exhaust system has become widespread. In this case, the gases released from the engine cylinders are treated with special neutralizing devices until they are released into the atmosphere.

The main type of catalyst used is the exhaust gas catalytic converter located on the exhaust manifold of the internal combustion engine or immediately after it.

Unburned residues (CO, CH, NO _x ), interacting with the surface of the catalytic layer, are oxidized by oxygen, which is also present in the exhaust gases. As a result of the reaction, heat is generated that warms up the catalyst and, thereby, the oxidation reaction is activated. Ultimately, at the exit from a working exhaust catalytic converter (hereinafter referred to as the catalyst), the exhaust gases contain mainly N ₂ and CO ₂ .

During operation, the oxidizing ability of the converter is reduced, in connection with this, constant monitoring of its performance is necessary.

, где C_CO,2 - измеренная концентрация монооксида углерода в ОГ за каталитическим нейтрализатором, C_CO.1 - измеренная концентрация. Данное изобретение может быть использовано только для контроля работоспособности каталитического нейтрализатора ОГ дизельного ДВС и не подходит для бензинового. Ограничением для указанного способа также может служить установка перед нейтрализатором фильтров для улавливания твердых частиц дизелей, что приводит к повышению минимальной температуры начала каталитических реакций в нейтрализаторе, в то время как она жестко связана с определением степени превращения СО.A known method of monitoring the operability of a catalytic converter (exhaust patent RU 2267619 C2, class IPC F01N 9/00, published April 20, 2003), in which the operability of a catalytic converter of a diesel engine exhaust gas during its operation is characterized by a certain minimum operating temperature of the onset of carbon monoxide conversion (CO) and a certain degree of _CO conversion of CO by directly measuring the CO concentration in combination with a temperature measurement. To estimate the residual catalytic activity of the catalytic converter, the difference ΔT between the actual temperature T _{A of the exhaust gas} at the outlet of the catalytic converter and stored in memory as a function of speed and load with a minimum operating temperature T _{CO of 50% is fresh.} the beginning of the conversion of carbon monoxide on a fresh catalyst: ΔT = T _A - T _{CO, 50%, fresh.} and determine the degree of r _CO conversion of carbon monoxide. Moreover, r _CO is determined by the following formula

where C _{CO, 2} is the measured concentration of carbon monoxide in the exhaust gas behind the catalytic converter, C _CO.1 is the measured concentration. This invention can only be used to monitor the performance of the exhaust gas catalytic converter of a diesel engine and is not suitable for gasoline. A limitation for this method can also be the installation of filters in front of the catalyst to capture solid particles of diesel engines, which leads to an increase in the minimum temperature for the onset of catalytic reactions in the catalyst, while it is tightly connected with determining the degree of CO conversion.

The isothermal process of oxidation of products of incomplete combustion in a diesel engine further reduces the difference between the actual exhaust gas temperature at the converter output and stored as a function of speed and load. Also, the loss of effectiveness of the converter very often occurs unevenly: CO, CH, NOx. Catalysis by CO can pass successfully, but by the sum of CH, NOx is no longer there.

Closest to the claimed invention is a method for on-board diagnostics of a catalytic converter of an exhaust gas of a transport internal combustion engine (see patent RU 2059080, class IPC F01N 3/20, publ. 04/27/1996) in which the converter is diagnosed when the fuel supply regulator is operated with time delays when switching fuel supply relative to the moments of reaching the threshold values of the signal of the first λ probe. A parameter characterizing the ratio of the sensitivities of the 1 probes to the change in the oxygen concentration in the exhaust gases at a given value of the time delays is taken as a criterion for the efficiency of the converter. Since the assessment of the operability of the converter is carried out by comparing the sensitivity of the l-probes to the oxygen concentration in the exhaust gases depending on the concentration of products of incomplete combustion in them, and the ratio of their concentrations at the inlet and outlet of the converter directly characterizes its oxidizing ability.

This method requires a fairly sophisticated algorithm for controlling the laws of fuel supply. In addition, several λ-probes operating in different temperature and gas environments have different service life and may introduce errors in the diagnosis of operability and reliability of the results.

SUMMARY OF THE INVENTION

The technical task in the development of the claimed invention was to create a method that provides a reliable assessment of the effectiveness of the exhaust gas converter of internal combustion engines with positive ignition during its operation.

The problem is solved by a method characterized by the following set of features:

a method for evaluating the operability of a catalytic converter of an exhaust gas of a gasoline internal combustion engine (ICE), which consists in the fact that when the internal combustion engine is measured, the ratio of the amount of carbon dioxide ( CO ₂ ) contained in the exhaust gas entering and leaving the catalytic converter, and the magnitude of the specified ratio decide on the health of the catalytic converter.

Wherein:

- the measurement of the ratio of the amount of CO ₂ can be made in accordance with the test cycles indicated in the regulatory documents;

- the measurement of the ratio of the amount of CO ₂ can be carried out in accordance with the cycles determined in accordance with the test procedure adopted by the tester for a specific type of engine and / or a specific type of converter, or for a specific type of engine equipped with a specific converter;

- the measurement of the amount of CO ₂ can be made by sensors that are installed during the installation of the catalytic converter (permanently present sensors);

- measurement of the amount of CO ₂ can be carried out by sensors that are installed during the diagnostic tests (sensors are installed only during the determination of health);

- when deciding on the performance of the catalytic converter based on the magnitude of the ratio of CO ₂ contained in the exhaust gases entering and emerging from it, may take into account the change in exhaust gas temperature before and after the catalytic converter.

The technical result in the implementation of this method is to reliably determine the operability of the catalytic converter by the minimum number of parameters.

DETAILED DESCRIPTION OF THE INVENTION

The claimed invention is as follows. On a working internal combustion engine with positive ignition, for example, running on gasoline and / or liquefied natural gas and / or compressed associated gas equipped with a catalytic converter, the ratio of carbon dioxide CO ₂ contained in the exhaust gases discharged from the internal combustion engine and entering the catalytic converter is measured - СО ₂ (1) and coming out of it - CO ₂ (2). The value of the specified ratio of CO ₂ (1) / CO ₂ (2) decide on the health of the converter.

The measurement of the ratio of CO ₂ (1) / CO ₂ (2) can be carried out in accordance with the test cycles specified in regulatory documents, for example, in accordance with GOST RF 51832-2001 "Internal combustion engines with positive ignition, powered by gasoline, and vehicles gross weight more than 3.5 tons equipped with these engines. Emissions of harmful substances. Technical requirements and test methods "or ESC (European Stationary Cycle) or in accordance with the test procedure adopted by the tester, for a specific type of engine, and / or certain type converter, or a particular type of engine, equipped with a specific converter.

Obtaining the claimed technical result - a reliable determination of the health of the catalytic converter by the minimum number of parameters during the implementation of the method is confirmed by the following.

Carbon dioxide ( CO ₂ ) is a non-toxic compound. At the same time, this component qualitatively characterizes the main redox reactions taking place in the catalytic blocks of the converter:

1) CmHn + (m + n / 4) * O ₂ -> m * CO ₂ + n / 2 * H ₂ O;

2) CO + ½ * O ₂ -> CO ₂

3) CO + NO-> ½ * N ₂ + CO ₂ ;

4) CmHn + 2 * (m + n / 4) * NO -> (m + n / 4) * N ₂ + n / 2 * H ₂ O + mCO ₂ ;

5) CHn + 2H ₂ O = CO ₂ + (2 + n / 2) * H ₂ .

(Chemische Industrie. Sonderdruck aus Heft 8/85 / Katalysatoren fur den Umweltschutz (Bernd Engler, Reinhold Brand, p. 31).

The better the catalyst (the presence in the catalytic layer of the active layers of platinum, palladium, rhodium, cerium, ruthenium - rare-earth elements), the higher (with the same amount of CO, CH, NOx in the exhaust gas (OG), the concentration of CO ₂ (2) in the OG ICE after the converter.

With the aging of the converter, this value is constantly decreasing, and with a complete loss of the converter’s operability, the amounts of CO ₂ before and after the converter are practically equal to CO ₂ (1) = CO ₂ (2)

Therefore, analyzing the ratio of CO ₂ (1) / CO ₂ (2), you can decide on the health of the converter.

If the specified ratio is greater than the maximum allowable required ratio ( CO ₂ (1) / CO ₂ (2) -> max) corresponding to a working neutralizer, i.e. the amount of CO ₂ (2) is less than established, they decide on an unacceptable decrease in the operability of the converter.

The maximum allowable required ratio of CO ₂ (1) / CO ₂ (2) is determined experimentally and / or calculated by the formulas of the redox reactions that must occur in the converter, taking into account the required exhaust gas emission standards for a specific (specific) type engine, and / or a specific type of converter, or a specific type of engine equipped with a specific converter.

For example, it is known that for a specific type of ICE a specific converter is used (such as Deguss on VW, Nissan Murana Infinity cars. Type Bazal on Opel Astra, Mazda 3, BMW cars.

Company Engelhard on a car General Motors. (N.M. Popova. Catalysts for the purification of exhaust gases from motor transport, Alma-Ata: Nauka, pp. 38-40).

The required ratio of CO ₂ (1) / CO ₂ (2), depending on the diagnostic modes, is documented in the form of calibration tables and / or can be stored in the on-board electronics memory as a function of the crankshaft speed and load to ensure continuous diagnostics.

In order to ensure constant monitoring and diagnostics of the neutralizer operability, CO ₂ sensors must be present in the ICE-converter unit constantly, i.e., they are installed during the installation (connected to the exhaust manifold of the internal combustion engine) of the neutralizer.

The claimed method is illustrated in the drawing, on which the ratios of CO ₂ (1) to CO ₂ (2) are given along the abscissa axis, and the operability of the converter along the ordinate axis:

point 1 corresponds to a new 100% operational converter;

point 2 - neutralizer, the performance of which does not correspond to the required;

point 3 - a fully inoperative converter.

According to the present invention, it is proposed to control the ratio of CO ₂ before (CO ₂ (1)) and after ( CO ₂ (2)) the exhaust gas catalyst, in combination with measuring the temperature of the exhaust gas, as an additional factor characterizing the aging of the catalyst. As the exhaust gas temperature should rise when the converter is working. (Reducing the toxicity of automobile engines (O. I. Zhegalin, P. D. Lupachev) p. 73, Moscow, "Transport" 1985).

The range of the required temperature change for a properly working converter depending on the CO ₂ ratio is determined on the basis of exothermic redox reactions? which can occur on the catalytic bed of the catalyst with various combinations of CO, CH, NOx or experimentally.

If, at a value of the ratio of CO ₂ (1) / CO ₂ (2) corresponding to a working converter, the temperature change of the exhaust gases before and after the catalytic converter is less than a certain one, a decision is made about the unreliability of the test results and the need to verify the CO ₂ sensors and / or temperature sensors .

After verification, the performance tests are repeated.

All possible temperature values are critical for a workable converter in all its operating points of the internal combustion engine, can also be stored in the on-board electronics memory as a multi-parameter characteristic as a function of load and speed.

This method is applicable only to internal combustion engines with positive ignition, since in internal combustion engines with compression ignition (diesel internal combustion engines) the oxidation reactions of products of incomplete combustion are predominantly isothermal. The concentrations of CO ₂ before and after the converter are almost identical.

The method for determining the operability of the neutralizer using the CO ₂ content in the exhaust gas (OG) of the internal combustion engine requires the tightness of the exhaust system, because air entering them can lead to unreliable results.

The rate of decrease in the efficiency of the converter depends on the type of converter, its design, the health of the internal combustion engine, the quality of the fuel, oil, and operating conditions. If the initial efficiency of the neutralizer for CO, CH, NOx is 99.9%, then the maximum efficiency is not lower than 80%.

To meet modern Euro 5 standards, the drop in the efficiency of the converter should be no more than 15-20%.

Claims (6)

1. The method of evaluating the health of the catalytic converter of the exhaust gases of an internal combustion engine with forced ignition (ICE), characterized in that when the internal combustion engine is measured, the ratio of the amount of carbon dioxide (CO ₂ ) contained in the exhaust gas entering the catalytic converter, as well as leaving him, and the magnitude of the specified ratio decide on the health of the catalytic converter. 2. The method according to claim 1, in which the measurement of the ratio of the amount of CO ₂ produced in accordance with the test cycles specified in the regulatory documents. 3. The method according to claim 1, in which the measurement of the ratio of the amount of CO _{2 is} carried out in accordance with the cycles in accordance with the test procedure adopted by the tester for a specific type of engine, and / or a specific type of converter, or a specific type of engine equipped with a specific catalytic converter. 4. The method according to any one of claims 1 to 3, in which the measurement of the amount of CO ₂ produced by sensors installed during installation of the catalytic converter. 6. The method according to any one of claims 1 to 3, in which the measurement of the amount of CO _{2 is} carried out by sensors installed during the diagnostic tests. 7. The method according to any one of claims 1 to 3, in which a decision is made on the operability of the catalytic converter based on the ratio of the amount of CO ₂ contained in the exhaust gas entering and leaving it, taking into account the change in temperature of the exhaust gas before and after the catalytic converter .