MXPA97001993A - A system for recirculating the exhaust gases for a compression starting method and a method for controlling the recirculation of the exhaust gases in a compression engine engine - Google Patents

Abstract

The present invention relates to a system for the recirculation of the exhaust gases in a compression ignition engine, which includes a first pressure sensor for perceiving an absolute pressure of the gas in an intake manifold of the engine, a sensor of the engine speed to detect a rotary speed of the engine crankshaft, a fuel supply rate sensor to detect a rate, fuel supply to the engine, a conduit to provide a passage for fluid between the exhaust manifold and the inlet manifold, and an exhaust gas recirculation valve arranged in the duct to regulate a flow of the exhaust gas the exhaust manifold to the inlet manifold, and an element to control the recirculation valve for the exhaust gases of such so that the flow of exhaust gases through the duct that passes from the exhaust manifold to the intake manifold that regulated, characterized by e the exhaust gas recirculation system further comprises a second pressure presensor for sensing an absolute gas pressure in an exhaust manifold of the engine, an air charge temperature sensor for detecting an intake air temperature in the manifold input the motor, and an electronic controller to receive signals from the first and second pressure sensors, engine speed sensor, fuel supply rate sensor and the air charge temperature sensor, calculate an optimal proportion of the gas exhaust that must be recirculated to the incoming air based on the received signals and calculate a position of the valve that allows an optimal proportion of the exhaust gas with respect to the inlet air to pass through the conduit to the inlet manifold, and operates the element intended to control the exhaust gas recycling valve in order to place the valve in the calculated position. valve to allow an optimum proportion of the exhaust gas to the inlet air so that it passes through the conduit from the exhaust manifold to the intake manifold.

Description

A SYSTEM FOR THE RECIRCULATION OF EXHAUST GASES FOR A COMPRESSION IGNITION ENGINE AND A METHOD TO CONTROL THE RECIRCULATION OF EXHAUST GASES IN AN ENGINE FIELD OF COMPRESSION IGNITION 5 TECHNICAL FIELD The present invention relates to the recirculation of exhaust gases in internal combustion engines as a strategy to control pollution and in particular refers to an exhaust gas recirculation system for ignition engines by compression. PREVIOUS TECHNIQUE At the end of the 1950s it was established that the exhaust emissions of internal combustion engines 15 constituted elements that contributed significantly to the photochemical smoke and the mixture of smoke and haze ("smog"), which covered the industrialized cities in all the world. The damage caused to human health, animal life and the environment in general has been studied thoroughly and at the same time meticulously documented because of the effects of such exhaust emissions. To reduce the levels of haze / smoke, or "smog", governments have created laws tending to control emissions of pollutants at their sources, including those emissions of exhaust gases that come from the engines of ,? internal combustion. Beginning in the early 1960s, the manufacturers of gasoline-powered engines and through 5 spark ignition (Otto cycle), began to install the first rudimentary devices to abate pollution, of which they are still being used today. . Over the years, as the use of automobiles has become popular, legislation The government has become stricter with respect to the emission levels of engine exhaust with Otto cycle and the vehicle manufacturers have responded with more complicated equipment applied to their engines in order to comply with the stricter regulations. While emission emissions from engines with otto cycle have been strictly regulated, governments have largely neglected compression ignition engines (diesel engines) since these engines are more fuel efficient and have relatively lower levels of the 20 emissions than engines with otto cycle, without pollution control equipment. Another contributing factor has probably been the much smaller number of diesel engines in use compared to the number of engines with otto cycle, which are currently used. 25 As you learned more and more through Research conducted on the effects of emissions from leaks that caused pollution, governments have legislated increasingly stringent controls of a wider range of such emissions. In the early 1980s, emissions from vehicles powered by diesel fuel began to be examined and manufacturers of diesel engines were forced to follow the path taken by the manufacturers of vehicles operated with the Otto cycle and they applied a variety of increasingly complex strategies and very sophisticated devices as very varied responses to government legislation regulating acceptable levels of exhaust emissions. In the mid-1970s, manufacturers of otto-cycle engines developed a strategy to recycle a portion of the exhaust gases back into the intake manifold to subject that portion of the recirculated exhaust to combustion conditions in order to control nitrogen oxides (NOx), carbon monoxide (CO), and total hydrocarbon emissions (international abbreviation THC). The recirculation of exhaust gases (RGE), by introducing gases from the exhaust inside the combustion cycle, causes lower temperatures in the combustion chamber and thus inhibits the formation of Ox while promoting the oxidation of some of the previously burned hydrocarbons. The control of exhaust gas recirculation is performed by RGE type valves that are popular in 5 cycle engines and much less in diesel engines. Until the early 1990s, RGE valves were operated and controlled pneumatically and therefore they were not able to accurately monitor or respond quickly to different speeds and loads of the engine. The method of pneumatic actuation and control also induces inaccuracies in the correct placements of the valves as well as delays in the response times due to changing barometric pressures in the surrounding atmosphere. In the early 1990s, the RGE valves controlled by motor controllers based on microprocessors using electric actuator motors, for motors that worked in the otto cycle. A system for controlling the amount of recirculated exhaust gas for a diesel engine is also known and This procedure has been described by Ikeda in U.S. Patent No. 4,562,821, which was granted on January 7, 1986. In this system, an electronic controller perceives or explores the speed of the motor, the pressure in the inlet manifold, the rate Supplying fuel, the temperature of the engine coolant well as the brightness of the combustion flame in order to control the recirculation of the exhaust gases in a diesel engine. The system has two main flaws. First, an expensive combustion flame brightness detector system is needed by this strategy. The sensors do not back up without problems in the existing motors since a special adaptation of the motor is needed. In addition it can be said that the system is based on a vacuum-operated RGE valve, which, as noted above, is slow to respond to rapidly changing engine operating conditions. Another approach to reducing emissions from diesel engines has been the development of dual fuel and multi-fuel systems in order to replace a portion of the normally burned diesel fuel in compression ignition engines with a gaseous fuel that burns Cleaner and lighter, such as a natural gas. Extensive research has shown that the compatibility of the GOR with the double or multiple fuel type engines is quite different from the system applied in the otto cycle engines. In double or multiple fuel type engines, the optimum RGE can vary between 0% and more than 50%, and the manifold pressure differentials are quite low. Therefore it has been shown that a GOR system in a engine with otto cycle and the corresponding strategy are not suitable for use in compression ignition engines in general terms and in combustion engines with double or multiple fuel type in particular. ESSENCE OF THE INVENTION It is an object of the present invention to provide an RGE system for compression ignition engines that allows precise control in real time of the amount of exhaust gas recirculated to the engine. It is another object of the invention to provide an RGE system which is adapted to be then fitted to an existing compression ignition engine. It is still another object of the invention to provide an RGE system that is adapted to be included as original equipment in a compression ignition engine without having to redesign the architecture of the engine. These and other objects are implemented in an exhaust gas recirculation system for a compression ignition engine, comprising: a first pressure sensor for perceiving an absolute gas pressure in an intake manifold of the engine; a second pressure sensor for perceiving an absolute pressure of the gas in an exhaust manifold of the engine; a motor speed sensor to determine a rotational speed of the motor; a sensor of the fuel supply rate to detect a fuel supply rate for the engine; a temperature sensor for charging with air to detect a temperature of the inlet air in the intake manifold of the engine; a conduit for providing a passage for the fluid between the exhaust manifold and the inlet manifold, and a valve for the recirculation of the exhaust gases disposed in the conduit for regulating an exhaust gas flow from the exhaust manifold to the manifold of entry; an element for controlling the exhaust gas recirculation valve so as to regulate the flow of exhaust gas passing through the conduit from the exhaust manifold to the intake manifold; and an electronic controller to receive signals from the first and from the second pressure sensor, from the engine speed sensor, from the fuel supply rate sensor as well as from the temperature sensor for the air charge, in order to compute an optimum rate of exhaust gas in relation to the inlet air, based on the received signals, deriving therefrom a position of the valve that allows the optimum proportion of the exhaust gas to the air of Inlet passes through the conduit to the inlet manifold, and thus acts on the medium intended to control the recirculation valve of the exhaust gases in order to position the valve in the derived valve position for the purpose of allowing a Optimal proportion of the exhaust gas to the inlet air passes through the conduit from the exhaust manifold to the inlet manifold.

According to another aspect of the invention there is provided a method to control the recirculation of the exhaust gases in a compression ignition engine in which instead of directly controlling the percentage of RGE, the method takes advantage of the flow rate of the mass of air as a function of the speed of the engine and the rate of fuel supply as its variable of basic control and here it is assumed that the air mass flow rate in general terms must remain constant for a certain combination between speed of the motor and load of the motor, with application of the value of the RGE to maintain that flow rate of the air mass at different temperatures and inlet and exhaust pressures. Specifically, a method is provided to control the recirculation of the exhaust gases in a compression ignition engine comprising: a) scanning, that is, perceiving a fuel supply rate for the engine; b) perceive a rotary speed of the motor; c) to perceive an absolute pressure in the exhaust manifold and an absolute pressure in the intake manifold, of the engine to calculate a pressure drop between the exhaust manifold and the inlet manifold; d) determining a volumetric efficiency of the gas flow through the motor as a function of the rotational speed and the pressure drop; e) determine a percentage of the GOR as a function of the rotational speed and the fuel supply rate for the engine; f) determining a temperature of the gases in the exhaust manifold as a function of the rotational speed and the fuel supply rate for the engine; g) perceiving a temperature of the inlet air, namely the air in which it is introduced into the inlet manifold; h) calculating a density of the exhaust gas fluid based on the absolute pressure inside the exhaust manifold, or a molecular weight of the exhaust gases and the exhaust gas temperature; i) calculating a volumetric flow of the exhaust gas through the RGE valve; j) derive a variable based on the volumetric flow of the exhaust gas passing through the valve RGE, the density of the exhaust gas fluid and the pressure drop in order to define a required position for the RGE valve; k) move the RGE valve to the required position. Accordingly, the present invention provides an electronically controlled recirculation system, relatively simple for compression ignition engines that makes use of components usually available on the market in order to provide a device that lowers pollution in an inexpensive manner and that can be adjusted later on an existing compression ignition engine or that can be provided as original equipment on new engines. The system includes an electronic motor controller, a pressure sensor absolute in the intake manifold of the engine, an absolute pressure sensor in the engine exhaust manifold, a fuel supply rate sensor, a rotary engine speed sensor as well as a temperature sensor the air charge. The recirculation of gas from The exhaust is controlled by an electronically operated RGE valve which is preferably a butterfly valve which has a valve position sensor. The position of the valve is preferably controlled by an electronic stepper motor, in order to ensure a fast and accurate response to changing engine and load operating conditions. As noted above, the invention also provides a novel method for controlling the recirculation of exhaust gases in compression ignition engines whereby an optimum percentage of the RGE is derived empirically under controlled test conditions so that it is reached a balance between efficiency ends maximum and minimum emissions of pollutants. The flow rate of the mass passing through the engine is then calculated using the definition of the GOR percentage and an air density that compensates for variations in ambient air temperature and barometric pressure. The flow rate of the mass is used to calculate the flow of the RGE that passes through the RGE valve so that the position of the valve can be adjusted to achieve the optimum percentage of the GOR. The proper position of the valve is derived by taking advantage of a function that yields a number without dimensions from the volumetric flow of the exhaust gas passing through the RGE valve, the density of the exhaust gas and the pressure drop from the exhaust manifold to the inlet manifold. The number without dimensions is then used to locate the correct position of the valve in a two-dimensional table. The method of controlling the recirculation of exhaust gases is based on the following assumptions, namely that: 1) both the air and the exhaust gas behave like an ideal gas in the intervals of temperatures and pressures encountered in the operation of the engine; 2) that the temperature of the exhaust gases for a specific condition of speed and load of the engine is changing negligibly without changing the temperature of the inlet air or the barometric pressure; 3) that the volumetric efficiency is only a function of the differential between engine speed and pressure between the intake and exhaust manifolds; 4) that the composition of the exhaust gas is adequately represented by 02, N2, C02 and H20 to calculate the properties of the exhaust gas, since the concentrations of all other components of the exhaust gas are insignificant; and 5) for multi-fuel engines, the influence of the gaseous fuel on the molar mass of the air mixed with the exhaust gas within the intake manifold is insignificant. BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of the invention will now be explained by way of example only and with reference to the following drawings, in which: Figure 1 is a schematic diagram of an engine of compression ignition equipped with an exhaust gas recirculation system according to the invention; Figure 2 is a partially fragmented side view of a preferred embodiment of an RGE type valve (Exhaust Gas Recirculation) for use in the exhaust gas recirculation system for a compression ignition engine shown in FIG. Figure 1; Figure 3 is a logic diagram of the method for controlling the recirculation of the exhaust gases in a compression ignition engine according to the present invention; Figure 4 shows a table used to determine the volumetric efficiency as a function of the engine speed and the pressure drop between the exhaust manifold and the intake manifold of a compression ignition engine; Figure 5 shows a table that serves to determine the percentage of RGE as a function of the engine speed and the fuel supply rate for a compression ignition engine; Figure 6 shows a table that serves to determine the temperature of the exhaust gases as a function of engine speed and engine speed. fuel supply in a compression ignition engine; Figure 7 shows a table for determining a valve position of the RGE type as a function of the exhaust gas flow, exhaust gas density and low pressure between the exhaust manifold and the intake manifold of an ignition engine by compression; and Figure 8 shows a table used to determine the position of an RGE type valve as a function of the counts in the electronic motor controller clock, based on the output of a potentiometer to monitor the position of the RGE valve. BEST METHOD FOR CARRYING OUT THE INVENTION The apparatus and method according to the invention can be described in terms of a physical arrangement and of equipment components, control logic and calculation procedures. In order to facilitate a complete understanding of the invention, it has been arranged according to the detailed description of the preferred embodiment. Physical Disposition and Components of the Equipment Figure 1 shows a schematic diagram of a compression ignition engine 20, equipped with an exhaust gas recirculation system, according to the invention. The compression ignition engine 20 may be a diesel engine or a multi-fuel engine, such as for example a diesel engine and natural gas, whose construction is known in the art and therefore is not explained in this document. The compression ignition engine 20 is equipped with an inlet manifold 22 for supplying combustion air to the engine cylinders (not shown) and an exhaust manifold 24 for letting the combustion gases escape from the ignition engine cylinders by compression 20. The system for exhaust gas recirculation (hereinafter referred to as the RGE system) is controlled by an electronic controller 26. The electronic controller 26 may be an electronic motor controller for controlling other operations of the compression ignition engine 20 as well as controlling the RGE system, may also be an electronic controller dedicated to the function of controlling the RGE system according to the invention. The electronic controller 26 may be any of a number of dedicated processors that are commercially available for motor control systems. A primary function of the electronic controller of an engine is to control the position of an RGE valve 28 which is located within a conduit for the recirculation of the exhaust 30, which interconnects the exhaust manifold 24 with the intake manifold 22. The RGE valve 28 will be explained in more detail with reference to Figure 2. The RGE valve 28 includes a control link 36 which is connected to a motor link 34 which is pivotally connected to an electrical stepper motor 32 which controls the rotary position of the RGE valve 28. In order to provide effective and optimum control of the RGE valve 28, a number of sensors are required to monitor the operating conditions of the compression ignition engine 20. Those sensors include an absolute pressure sensor in the intake manifold, 38, which is located in the intake manifold 22, as well as an absolute pressure sensor in the exhaust manifold 40, which is located in the exhaust manifold 24. When the compression ignition engine 20 is an engine for multiple fuel, the system may include a fuel mode selector switch 42 to change the diesel engine only to a multiple fuel mode, for example, c omo as a fuel combination consisting of diesel and natural gas. The system also includes a fuel delivery rate sensor 44, typically a high resolution potentiometer that monitors the position of a fuel pedal or some equivalent element such as a throttle position sensor. The engine is also equipped with a sensor for the rotation speed of the engine 46 (hereinafter referred to as an RPM sensor). 46) to determine the rotational speed of the engine crankshaft. The RPM sensor 46 is preferably a Hall Effect sensor, which can be attached to the diesel fuel injection pump of the compression ignition engine 20, a flywheel, or an output end of the crankshaft as desired. The location of the RPM sensor 46 is not important as long as it provides a reliable indication of the rotational speed of the engine crankshaft. The system also includes an air charge temperature sensor 48 which measures the temperature of the combustion air brought into the intake manifold 22. The exhaust system of the compression ignition engine 20 is also typically equipped with a catalytic converter 52 , however, this catalytic converter is an auxiliary element to the exhaust gas recirculation system according to the present invention. Figure 2 shows a side elevation view of a partial cross section passing through a preferred construction for the RGE valve 28 for use in the exhaust gas recirculation system according to the invention. The RGE valve 28 includes a central passage 54 having a diameter preferably equal to or greater than the diameter of the exhaust recirculation duct 30 (see Figure 1). The central passage 54 can be closed by a butterfly valve 56 which is located rotatably by a valve arrow 58, which is connected at its lower end to the valve link RGE 34 and at its upper end to a high resolution potentiometer 60 of a type that is well known in the automotive industry. The high resolution potentiometer 60 is used to determine a rotary position of the butterfly valve 56 in a manner that will be explained in more detail below. The RGE valve 28 is preferably an electronically controlled butterfly valve since that construction provides a rapid and accurate control response to the changing combustion conditions within the compression ignition engine 20, as will be explained later, in greater detail. The Control Logic Figure 3 shows a flow chart of the general control logic executed by the electronic motor controller 26 in order to control the position of the RGE valve 28 and thereby control the amount of exhaust gas recirculated from the exhaust manifold 24 to the input manifold 22. The controller executes a loop or program circuit that starts by determining a controlled fuel supply rate, that is, ordered, from the fuel supply rate sensor 44 and ending with Orient butterfly valve 56 of the RGE 28 valve to a orientation required to provide an optimum exhaust gas recirculation to the inlet manifold 22. The control logic will now be explained in more detail. As shown in Figure 3, the process begins with a step 62 in which an ordered fuel supply rate for the compression ignition engine 20 is determined by an analysis of the input signals from the supply rate sensor. 44. In step 64, the electronic controller 26 calculates the rotational speed of a motor by analyzing the output signals from an RPM sensor 46, preferably a Hall Effect sensor (not shown), attached to a pump. diesel fuel injection engine (also not illustrated) that runs at half the speed of the engine for a 4-speed engine. In step 66 the electronic motor controller 26 reads the input signals from the absolute pressure sensor in the exhaust manifold 40 and the absolute pressure sensor in the inlet manifold 38 and calculates a low pressure (? P ) according to the following formula: P = Absolute Pressure - Abolute Pressure Exhaust Manifold (kPa) Inlet Manifold (kPa) In step 68, the results of steps 62 to 66 are used to determine the volumetric efficiency, or be the percentage of RGE, and the temperature of the exhaust gases from the tables of the data that are empirically derived from tests made with the engine using a compression ignition engine monitored with a dynamometer in a way well known in the art. Figure 4 shows the structure of a table used to extract the volumetric efficiency of the motor as a function of the motor speed and the pressure drop (? P). The table according to the preferred embodiment is arranged in rows of values assigned respectively to? P and the columns of the values assigned respectively to RPM. The values assigned respectively to each row and to each column of Figure 4 may be incremental, but are not necessarily expressed in equal increments. The assigned value will depend on the particular engine model that must be equipped with RGE and can be assembled around certain engine speeds in particular to obtain a finer resolution and better control at a particular operating speed range in order to arrive to a certain emission standard. It is also to be understood that the size of the table in Figure 4, as shown, is only illustrative since the size of the required table is dictated by the performance characteristics or performance that you want to achieve. The data in Figure 4 are derived empirically based on a mathematical definition of the volumetric efficiency of the motor, provided by the formula: in what? vo? is the volumetric efficiency of the engine, Qtot is the total volumetric flow that passes through the intake manifold in liters per second, RPM is the rotational speed of the engine crankshaft and Vd? sp is the displacement volume of the engine in liters. In view of the fact that there is only one entry stroke for every two revolutions of the crankshaft in a compression ignition engine consisting of four cycles, the number of entry strokes is divided by 2. Given this definition and the fact that the temperature mixed air, exhaust gas and gaseous fuel in a multi-fuel engine can not be measured accurately, the data used to complete the table shown in Figure 4, are preferably obtained from a motor operating in the mode of diesel, only without GER. When the engine is operating in diesel mode only at the test stand and Qaire is measured with a gas flow meter. The RPM is measured and the equation solve for to obtain the volumetric efficiency for; each cell in Figure 4. The percentage of RGE is derived from the table shown in Figure 5 in which the percentage of RGE is expressed as a function of the rotational speed of the engine and the rate of fuel supply. The data contained in this table are also preferably derived empirically from a test with a specific engine dynamometer for tests, based on the mathematical definition of the **% RGE expressed by the formula: % RGE = = 100% in which Qaire is the volumetric flow of air entering the engine at a certain air temperature and a certain pressure in the inlet manifold, Qqas is the flow volumetric of the gaseous fuel entering the engine if the compression ignition engine 20 is a multi-fuel engine and Gtot is the total volumetric flow through the intake manifold. With the engine running at a test stand, it places the RGE 28 valve in such a way that a balance between maximum thermal efficiency and minimum pollutant emissions is achieved. Qgas can be determined from the ordered fuel rate, Qtot is known and can be derived from Figure 4 and air can be measured with employment of a gas flow meter. The percentage of GOR is then calculated for complete the data in Figure 5. The temperature of the exhaust gases is derived from the table shown in Figure 6 in which the temperature of the exhaust gases is expressed as a function of the rotational speed of the engine and the fuel supply rate. The temperatures are expressed in ° C and the test engines are empirically derived from actual temperature measurements after a desired value of the RGE percentage has been established with a given RPM level and fuel supply rate. The temperatures derived from the tables shown in Figure 6 must be converted to Kelvin before they can be used in the calculations to calculate the exhaust gas fluid density and the exhaust gas volume flow as explained below. All the incremental intervals in the tables shown in Figures 4 to 6 and all the data in the tables are specific to the engine model and are derived empirically during the passes of the dynamometer tests in each specific model. In addition, the electronic controller 26 is programmed to execute a linear two-dimensional interpolation in which the sensor values fall between the individual values loaded in the tables. This allows a precise response to the operating conditions in so much that the amount of memory required to store the tables is limited. In step 70 of Figure 3, the electronic controller 26 reads the temperature of the air inlet using the sensor 48 for the temperature of the air charge. In step 74, the density of the exhaust gas fluid is calculated based on the absolute pressure prevailing in the exhaust manifold, the molecular weight of the exhaust gas, the gas law constant as well as the gas temperature of the exhaust gas. escape, starting from the table shown in Figure 6 with the use of the formula: in which pexh represents the fluid density of the exhaust gas, Pexh represents the absolute pressure that prevails in the exhaust manifold, MWexh represents the molecular weight of the exhaust gas, R is the gas law constant (8.3144 kmol / kg'K) and Texh is the exhaust gas temperature derived from the table shown in Figure 6. In step 76, the electronic controller uses the fluid density (peXh) and the pressure drop (? P) to calculate the volumetric flow (Qrge) of the exhaust gas passing through the RGE valve 28 using the formula: _ («& t -« fcire - «% as) * R * re) -h rge = in which Qrge represents the volumetric flow of the exhaust gas passing through the RGE valve, nStót is the total mass flow of the gases passing through the inflow manifold nfeire is the flow of the mass of air that passes to through the inlet manifold, «fe * is the flow of the mass of the gaseous fuel passing through the inlet manifold of a multi-fuel engine, R is the gas law constant, Texh is the temperature of the gas of exhaust derived from the table shown in Figure 6, PeXh is the absolute pressure in the exhaust manifold 24 and MWexh is the molecular weight in g / mol of the exhaust gas inside the exhaust manifold 24. All variables found on the right side of this equation are known with the exception of / &ire, "Stot and iTexh- For a detailed explanation of how" Stbt and? 7exh are calculated, see the section on calculation procedures that are presents below. The volumetric air flow (Qa ± re) is calculated using the following formula: _. (.% RGE?, ""., "," Min. Entry stroke "8.3144 Teas < 2a? Re = 1 \ *? Vol * RPM * Vdisp * * / JJ6 * 100%; 60sec 2 rev 16.04 enda The resulting value of Qa-.re also makes reference to the temperature of the air (Taire) ca? and the pressure from the input (input) collector I dropped with which the RGE percentage was specified. Therefore, the flow of the required air mass is derived by multiplying the volumetric air flow from this equation by the air density calculated using the law constant on the gases (with MWairß = 28.97), in which (Pent? ada) lime 0. 287 * '((7Tair-ee)) ccal With the flow of the air mass calculated in this way, the air mass flow does not vary with fluctuations in barometric pressure or inlet air temperature. In view of the fact that the flow of the mass of the fuel towards the engine is not affected by fluctuations in the ambient temperature and in the pressure, the optimum quantity of air will always be supplied to achieve the complete combustion of all the injected fuel. In step 78 of Figure 3, a variable is derived to determine the required position of the RGE valve using the function: Qrger the volumetric flow of RGE is known from the calculation executed above, pexh is also known from the calculation executed above and? P is calculated by deducting the absolute pressure of the input manifold from the Absolute pressure of the exhaust manifold, as described above. The dimensionless number derived from this function is used to place a valve position (valve ß) in Figure 7. In step 80, the current position of the RGE 28 valve is determined by measuring the clock counts accumulated by the electronic motor controller in response to the potentiometer signal from the high resolution potentiometer 60 associated with the valve arrow 58 of the RGE 28 valve. The table shown in Figure 8 illustrates the relationship between the counts of the clock and the position of the arrow in degrees from a totally closed position with respect to the central passage 54 of the RGE 28 valve. After the current position of the RGE valve has been determined, the required position of the RGE valve determined in step 78 is compared with reference to the table shown in Figure 8, with the current position of the RGE valve and a correction factor is calculated. In step 84, the electronic controller 26 commands the electric stepper motor 32 to move the valve RGE28 from its current position to the required position, when the current position is not equal to the required position determined in step 78. Then the program returns to step 62 and the procedure is repeated. The frequency of executing this procedure depends on a number of factors, including other tasks executed by the electronic controller 26. Typically the process is repeated every 4 to 12 milliseconds, ensuring that the RGE 28 valve is always positioned optimally and in tune with the changing operating conditions. Calculation Procedures The calculations required to determine the flow of the total mass of the gases through the engine, the molecular weight of the exhaust gas and the specific heating of the components of the exhaust gases are explained below.

To facilitate an understanding of the calculations, the variables used are presented here: «fei-e = is the flow of the mass of air that passes into the engine r &gc = mass flow of the exhaust gas passing through the RGE valve (g / s) «Seas = flow of the mass of gaseous fuel entering the engine« fesi = flow of the mass of diesel fuel into the engine r & ot) = total mass flow passing through of the intake manifold Taire- air temperature in the inlet manifold, just upstream of the mixing point Texh = exhaust gas temperature Tgas = temperature of the gaseous fuel when it enters the intake manifold Tmix = mixed temperature of air, exhaust gas and gaseous fuel Pentrada = absolute pressure in the inlet manifold Pexh = exhaust manifold absolute pressure R = constant of the law of gases, 8.33144 kmol / kg »K Caire = volumetric flow of air entering the engine with Taire and Pentrada (1 / s) Qgas = volumetric flow of the gaseous fuel entering the engine in Taire and Pentrada (1 / s) Qtot = total volumetric flow that passes through the intake manifold in Taire and Pentr da (1 / s) VdesP = motor displacement volume (1 / s) MW = Molecular weight (g / mol) h = enthalpy (kJ / kg »K) Cp = specific heating (kJ / kg K) Calculation of Total Mass Flow: The total mass flow ("fet) is derived as a result of multiplying the total volumetric flow (Otot) by the density (pentrated) of the mixture of the air, exhaust gas and gaseous fuel (in the case of a fuel engine) multiple) with the mixed temperature and the pressure of the inlet manifold, in which the input density can be calculated using the gas law constant, as follows: Pentrada * MW? x Centered = R * Tr ?. in which MWmíx is approximated by 28.5 kg / kmol. To calculate the mixed temperature, Tmix, the first law of thermodynamics is required. The first law of thermodynamics for the mixing process is: «fei-e * Aa-re +« S% e *? Rge + «ugly *« gas = / -fcrt *? Tot however, for an ideal gas h = Cp * T in such a way that this equation becomes: flfcire * (Cp) air * Taire + / ≥ (Cp) ex-- * Texh + «ugly * (Cp) gas * Tgas =« ftbt * (Cp) p-ix * Tmix Specific heating of air and gaseous fuels is assumed to be constant at 1.0035 kJ / kg »K for air and 2.2537kJ / kg» K for gas (eg methane for multi-fuel engines) . However, the specific heat of the exhaust gas will vary with the composition and temperature of the exhaust gases. The calculation of the specific heat of the exhaust gas and its molecular weight based on the stoichiometry of combustion is explained below. The specific heat of the mixture is an average mass of the specific heats of air, exhaust gas and natural gas, derived from: Combining the five equations presented below and rearranging the yields we have: ((Cp) ej-h * 7lfe? Re + "ugly) - (Cp) a? Re *" feíre - (Cp) gas * "ugly) * T mix + («Ft-re * (Cp) a-re * Ta-re + gas * (Cp) gas * Tgas - (« feíre + «ugly) * (Cp) exl- * Texh) * Tm-x This equation is quadratic expressed in Tpu.x of the form: with a solution for the quadratic formula of: -b ± V¿ > 2 - ac mix - the Once you know the mixed temperature, Tmlx, then you can calculate the mixed density Pentrada, from the equation: Pentrada * MW xs. .entry = and the equation is used: «& t = Qtot * / > input in order to calculate the flow of the total mass «fet, Calculation of Molecular Weights and Specific Heat: The optimum proportions of the recirculated exhaust gas to the inlet air, exhaust gas compositions, molecular weight and specific heat required to determine the volumetric flow, the Qrge of the exhaust gas passing through the RGE valve, are determined by representing the diesel fuel CHi.g, in which the stoichiometric combustion of diesel fuel and air is written in the following manner: Cff? .9 +7.024 (0.2102 + 0.79N2)? COt + 0.95H2O + 5.549N2 Based on the mass, this combustion reaction is written as: tgCflr? .9 + 3.39 ^ g? 2 + 11.16 ^ g-V2? 316kgC? 2 + 1.23kgH2? + lU6kgN2 For multiple fuel engines that burn natural gas, for example, like diesel, natural gas can be represented as 100% methane (CH4), and the stoichiometric combustion of natural gas in air is written as: CZ- 4 + 9,524 (0.21? 2 + 0.79N2)? C02 + 2ÍT2O + 7.52N2 Based on the mass, this combustion reaction is written as: lkgCH + 339kg? 2 + 13.14¡tgN2? l.lAkgCOi + 2.25kg? + U.UkgNi Based on the previous stoichiometry, the optimum ratio of the recirculated exhaust gas to the inlet air f, is provided by: Let xx and y ± be the fractions of mass and molars respectively of the constituent i. Based on the previous stoichiometry, the mass fractions of each constituent in the exhaust are then provided by: 7 &-re + flfesl + i 0233A »- 3.39? & yes - 3.99 / & a * «Síire + 7 &S1 + / ugly The molar fraction of each constituent is given by: The molecular weight of the exhaust gas is given by: The specific heat of the exhaust gas is given by: (Cp) exh = y ^) i in which (Cp) ± is the specific heat of the pressure-constant in units of kj / kmol.K for each exhaust constituent, in the following way: (CP) 82 = -3.7357 + 30.529T05 - 4.1034T + 0.024198T2 (P) H20 = 143.05 - 183.54T025 + 82.75 l? 05 + 3.6989T (CP) N2 = 39.060- 512.79T "16 + 1072.7T-2 - 820.40T" 3 (CP)? 2 = -37.432 + 0.020102T15 - 178.57T "15 + 236.88T" in which with TeXh in Kelvin degrees. These calculation procedures allow the electronic controller 26 to accurately compensate the changes »At ambient temperature and barometric pressure to ensure that there is an optimum ratio of the recirculated exhaust gas to the inlet air, and that this proportion is maintained under all operating conditions. Industrial Applicability The RGE system according to the invention remarkably reduces the level of the main contaminants in compression ignition engines, i.e. nitrogen oxides (N0X) and carbon monoxide (CO). When these oxides combine with water present in the atmosphere, they form different acids that are extremely corrosive to organic and inorganic matter. These acids contribute to the problem of acid rain and NOx also it is an important factor in the formation of fog with photochemical smoke and ozone at ground level. The RGE system, according to the present invention, also improves the combustion of hydrocarbons and therefore promotes greater fuel efficiency. Under low engine load conditions, the RGE system helps maintain the air and fuel ratio in a more efficient range without resorting to a choke of the motor's air intake that steals energy. Likewise, the "sowing", that is, the bombardment of the mixture of air and fuel with the hot exhaust gas containing active chemical radicals, promotes a faster and more complete combustion to lower the levels of the unburned total of the hydrocarbons in the exhaust gas. Furthermore, it can be said that the RGE system according to the invention raises the exhaust temperature of the engine to a certain degree due to the displacement of the cold inlet air with the hot exhaust gas, which results in a faster activation and a more efficient operation. of any noble metal exhaust catalyst attached to the engine exhaust system. A better catalyst operation promotes a more efficient removal of contaminants from the exhaust stream, such as carbon monoxide and hydrocarbons in their entirety.

In view of the fact that the RGE 28 valve is operated electronically instead of being controlled by the pneumatic way, the system provides a precise response at high speed to the different loads of the motor. The electronic controller 26 provides both an accurate determination of the optimum recirculation rates of the exhaust gas and a highly accurate positioning of the RGE valve 28. Inasmuch as the system provides accurate variable positioning of the RGE valve 28, the The motor responds with an approved energy or is efficient under all operating conditions and eliminates the undesirable effects of black smoke and poor motor running due to the introduction of too much recirculated exhaust gas, the phenomenon that was a common problem in the RGE control systems of the prior art. Those skilled in the art will realize that it is possible to introduce changes and modifications in the preferred embodiment, described above, without departing from the spirit of the invention. Therefore, the intention is expressed that the scope of this invention is limited only by the scope expressed in the appended claims.

Claims (23)

1. Claims 1. A system for the recirculation of the exhaust gases in a compression ignition engine, including a first pressure sensor for perceiving an absolute pressure of the gas in an intake manifold of the engine, a sensor for the velocity of the engine for detecting a rotational speed of the engine crankshaft, a fuel supply rate sensor for detecting a fuel supply rate for the engine, a conduit for providing a passage for fluid between the exhaust manifold and the engine. inlet manifold, and an exhaust gas recirculation valve arranged in the duct to regulate an exhaust gas flow from the exhaust manifold to the inlet manifold, and an element to control 15 the recirculation valve for the exhaust gases in such a way that the flow of the exhaust gases through the duct that passes from the exhaust manifold to the exhaust manifold "" ^ entrance is regulated, CHARACTERIZED BECAUSE the exhaust gas recirculation system also includes a second 20 pressure sensor for detecting an absolute pressure of the gas in an exhaust manifold of the engine, an air charge temperature sensor for detecting an inlet air temperature in the engine inlet manifold, and an electronic controller for receiving signals of the first and 25 second pressure sensors, engine speed sensor, fuel supply rate sensor and the air charge temperature sensor, calculate an optimal proportion of the exhaust gas that must be recirculated to the incoming air based on the received signals and calculate a valve position that allows that there is an optimum proportion of the exhaust gas with respect to the inlet air to pass through the conduit to the inlet manifold, and operate the element intended to control the recirculation valve of the exhaust gas in order to place the valve in the position calculated from the valve to allow an optimum ratio of the exhaust gas to the inlet air so that it passes through the conduit from the exhaust manifold to the inlet manifold.
2. 2. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 1, wherein the engine speed sensor is a sensor with a Hall Effect that is attached to an output arrow of the engine. a pump for fuel of the engine.
3. 3. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 1 or 2, wherein the fuel supply rate sensor is a high resolution potentiometer that measures a position of a pedal for fuel for the engine.
4. 4. An exhaust gas recirculation system for a compression ignition engine as claimed in claims 1, 2 or 3, wherein the exhaust gas recirculation valve is a mechanically controlled throttle valve having a mechanical link to move the throttle valve from a fully closed position to a throttle valve. completely open position. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 4, wherein the element for controlling the exhaust gas recirculation valve is an electric stepper motor that is operatively connected to the link mechanic. 6. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 5, wherein the throttle valve is associated with a high resolution potentiometer to indicate a current position of the throttle valve with respect to to the totally closed position. 7. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 6, wherein the electronic controller accumulates a count based on a high resolution potentiometer output signal and the count is used to Determine the current position of the throttle valve with respect to the fully closed position. 8. An exhaust gas recirculation system for a compression ignition engine as claimed in any of the preceding claims, wherein the compression ignition engine is a diesel engine. 9. An exhaust gas recirculation system for a compression ignition engine as claimed in any of the preceding claims, wherein the compression ignition engine is a dual fuel engine. 10. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 9, wherein the compression ignition engine is a dual fuel engine equipped to operate with diesel and natural gas as fuels. 11. An exhaust gas recirculation system for a compression ignition engine as claimed in claims 1, 2, 3, 4, 5, 6 or 7, in which the compression ignition engine is a fuel engine multiple 12. An exhaust gas recirculation system for a compression ignition engine as claimed in claim 11, wherein the compression ignition engine is a multiple fuel engine equipped to operate with diesel, natural gas and hydrogen as fuels. 13. A method to control the recirculation of gas from exhaust in a compression ignition engine, which includes the step of perceiving a fuel supply rate for the engine, perceiving a rotary speed of the engine and perceiving an absolute pressure in the intake manifold of the engine. CHARACTERIZED BECAUSE the method additionally comprises the steps to perceive an absolute pressure in the exhaust manifold and to calculate a low pressure between the exhaust manifold and the inlet manifold; determine a volumetric efficiency of the gas flow through the motor as a function of the rotational speed and the low pressure; to determine a percentage of RGE, that is to say recirculation of the exhaust gases, as a function of the rotational speed and the fuel supply rate for the engine; determining a gas temperature in the exhaust manifold as a function of the rotational speed and the fuel supply rate for the engine; to perceive a temperature of the air of entrance of that air that is attracted in the collector of entrance; calculating a fluid density of the exhaust gas based on an absolute pressure prevailing in the exhaust manifold, a molar mass of the exhaust gas and the temperature of the exhaust gas; calculate a volumetric flow of the exhaust gas passing through the RGE valve; derive a variable based on the volumetric flow, the fluid density of the exhaust gas and the pressure drop in order to place a required position of the RGE valve and move the RGE valve to the required position. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claim 13, in which the volumetric efficiency of the gas flow through the engine is determined by a data query in the table, which are derived empirically from tests with compression ignition engine dynamometer. 15. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13 or 14, in which the percentage of RGE is determined by a query in the table of the data that are derived empirically from operational tests of the compression ignition engine. 16. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13, 14 or 15, in which the temperature of the gas in the exhaust manifold is determined by a query in the data table empirically derived from operational tests of the compression ignition engine. 17. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13, 14, 15 or 16, wherein the The required position of the RGE valve is derived from a query in the table of valve positions as a function of the variable. 18. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claim 13, wherein the method further includes the steps of determining a current position of the RGE valve; compare the current position of the RGE valve with the required position of the RGE valve; derive a difference between the current position and the required position; and actuating an element that serves to control a position of the RGE valve in order to move the RGE valve by an equivalent of the difference derived between the current position and the required position. 19. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13, 14, 15, 16, 17 or 18, in which the compression ignition engine is a diesel engine . 20. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13, 14, 15, 16, 17 or 18, in which the compression ignition engine is a dual fuel engine . 21. A method for controlling the recirculation of exhaust gas in a compression ignition engine, as claims in claim 20, in which the compression ignition engine is a dual fuel engine adapted to use diesel and natural gas as fuels. 22. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claims 13, 14, 15, 16, 17 or 18, in which the compression ignition engine is an engine of multiple fuel. 23. A method for controlling the recirculation of the exhaust gas in a compression ignition engine, as claimed in claim 22, in which the compression ignition engine is a multi-fuel engine adapted to use diesel, natural gas and hydrogen as fuels. SUMMARY OF THE INVENTION A system for exhaust gas recirculation for a compression ignition engine and a method for controlling the recirculation of exhaust gases in compression ignition engines are disclosed. The method and apparatus are adapted to control the recirculation of exhaust gases in diesel engines and / or multiple fuels (such as diesel and natural gas). The apparatus includes a first pressure sensor (38) for perceiving an absolute gas pressure in the intake manifold (22) of the engine (20), a second pressure sensor (40) to scan an absolute pressure of the gas inside the exhaust manifold (24) of the engine (20), a sensor for the engine speed (46) to detect the number of revolutions per minute of the engine, a sensor of the rate of refueling (44) to perceive the combustion rate commanded for the engine (20), a temperature sensor (38) for detecting the inlet air temperature found in the inlet manifold (22), a duct (30) ) to direct the exhaust gases from the exhaust manifold (24) to the inlet manifold (22). An electronically operated mechanical valve (28) present in the conduit to control the flow of the exhaust gas as well as an electronic controller (26) to analyze the signals from the sensors and produce control signals to the electric stepper motor (32) that controls the position of the valve (28). Advantages include precise control of exhaust gas recirculation in real time, a rapid response to changing combustion conditions resulting in lower pollutant emissions and higher fuel efficiency. Another advantage lies in a system that can be adjusted without problem to an existing compression ignition engine or that can be included as part of the original equipment in new engines without having to redesign the engine.