KR100291803B1 - Large two stroke and grade internal combustion engine control method and engine for use in the method - Google Patents

Abstract

The large two-stroke supercharged internal combustion engine E is connected to an upstream side of the turbocharger T / C and has a reactor R for reducing the NO _X component in the exhaust gas. At least one sensor S1, S2, S3 measures at least one engine parameter, and it is determined by the control unit CU whether the reactor R is heated by exhaust gas, and by such heating the supercharger The amount of energy supplied to (T / C) is reduced. When it is determined that it is heated, the control unit CU is opened to supply supplemental air or gas to the engine. This supply is done by starting the auxiliary blower AB and / or by activating the control means V of the bypass conduit to supply a larger amount of exhaust gas to the turbine T of the supercharger in order to increase power. .

Description

Large 2-stroke supercharged internal combustion engine control method and engine for use in the method

The invention relates to a reactor for reducing the composition of NO _x (nitrogen oxide) in exhaust gas connected to an upstream side of a turbocharger and at least one engine parameter for determining whether the reactor cools the exhaust gas. A method for controlling a large two-stroke supercharged internal combustion engine with means for measuring engine parameters.

Taking into account environmental protection, and the country to adopt a law determining the limits of the NO _X released into a lower value increases every year. Therefore, it is desirable to install an exhaust gas purification device in a large marine engine to operate continuously. Catalysts known in the automotive industry cannot be used in marine engines. The reason is that marine engines operate using a large amount of air and must burn heavy oil, a fuel containing a significant amount of heavy metals and sulfur. In automobiles having a supercharger, a catalyst device is provided upstream of the turbine, and CO (carbon monoxide) and HC (hydrocarbon) in the exhaust gas are reacted with O ₂ and generate heat, thereby generating exhaust gas passing through the reactor. Can be heated. Thus, the operating conditions of such an engine are different from those of an engine having a reactor for reducing the NO _x component in the exhaust gas.

EP 0,492,989 discloses a diesel engine having a reactor connected downstream of the supercharger to reduce the NO _x component of the exhaust gas. A temperature sensor is arranged at the gas outlet of the reactor. When the gas temperature of the reactor becomes higher than the upper limit for the catalytic reaction, more air is supplied to the engine, for example by closing a waste gate valve in the turbocharger's turbine. In this method, the exhaust gas can be well purified, but the operating conditions of the engine are ignored.

Since the temperature of the exhaust gas when the exhaust gas is supplied to the reactor needs to be at least 300 ° C, when the engine is a large two-stroke engine used as a ship propulsion engine, the reactor is connected to the exhaust device in front of the supercharger. Should be. Recently, ships with a reactor that removes NO _x components in the exhaust gas of an engine at a larger rate have been experimentally developed. Such a known engine is known as MAN B & W Diesel A / S, published in December 1991, in the literature "Emission Control of Two-Stroke Diesel Engine." Low Speed Engines ". The engine includes an exhaust gas receiver connected to the exhaust side of the reactor for reducing the NO _x component of the exhaust gas, a supercharger, an exhaust gas receiver having a turbine and a gas inlet connected to the gas outlet of the reactor. A reactor bypass conduit connectable to the turbocharger turbine, cutting-off means installed in the bypass conduit, and an auxiliary blower for supplying scavenging and filling air. The reactor uses a so-called "selective catalytic reduction process" (SCR) which mixes the exhaust gas with ammonia and passes the mixture into a special catalyst at a temperature of 300 to 400 ° C. The catalyst reduces NO _x to N ₂ and water. In order to fully consume ammonia and reduce the NO _x component in the exhaust gas to a sufficient degree, the volume of the catalyst should be made large enough.

The minimum limit value of the NO _X from the vessel outlet (threshold values) have been applied only to the water body of water. Known engine devices are provided by bypass conduits with blocking means, whereby the reactor is completely disconnected during the main voyage of the vessel, and the reactor is fully connected when the vessel navigates offshore, as long as engine operating conditions permit, there are upper limits on the minimum outflow of NO _X is designed to be applied. Thus, the blocking means of the bypass conduit is usually fully open or completely closed.

As a result of the applicant's experiment of the above engine, when the engine load suddenly increases (for example, when the vessel is accelerated or in an emergency berth), the power corresponding to the instantaneous engine load in which the supercharger is increased is increased. Since it could not be received, it was found that the reactor needs to be completely separated. It has also been found that other drawbacks arise when the reactor must be connected by closing the valve in the bypass conduit and opening the valve just upstream and downstream of the reactor. In other words, the relatively cold reactor drastically lowers the temperature of the exhaust gas upstream of the supercharger, as a result of which the supercharger engine device vibrates and, in the worst case, stops the operation of the engine. To avoid this undesirable condition, a small amount of exhaust gas is passed through a separate reactor to keep the reactor slightly warm. In addition, by installing means for measuring the temperature difference between the two sides of the reactor, the valve of the bypass conduit in a two-step process to delay final closure and complete separation of the reactor until the temperature drop as it passes through the reactor is sufficiently small. To close it.

It is an object of the present invention to provide a method for controlling a large two-stroke supercharged engine that ensures the normal continuous operating state of the engine and also purifies exhaust gas.

In order to achieve the above object, the method according to the present invention bypasses a part of the exhaust gas downstream of the reactor with respect to the supercharger when the measured engine parameter falls below a predetermined minimum limit, and the measured engine parameter is When the minimum limit indicating that the exhaust gas is being cooled by the reactor is exceeded, the partial exhaust gas is partially or partially passed through the turbine of the supercharger so as to supply a larger amount of air or gas upstream of the turbine. It is characterized by that.

This is an environmentally optimal configuration in that all exhaust gases pass through the reactor even when the engine load is increased.

As the engine load increases, the temperature of the exhaust gas rises, heating the reactor. Since the reactor has a large heat capacity, it takes a long time to heat the reactor to a high temperature, and during this heating time, the exhaust gas temperature behind the reactor is somewhat lower than the exhaust gas temperature in front of the reactor, It means that the energy of the exhaust gas in the rear is not large enough to accommodate the power corresponding to the instantaneous engine load by the compressor of the supercharger. In other words, the large heat capacity of the reactor and the connection of the reactor upstream of the supercharger cause some time delay in the effect of increasing engine load on the supercharger, which delay increases with changes in engine load.

The time for which the exhaust gas is cooled at the same time as the reactor is heated is determined according to the present invention, and during this time, by supplying more air or gas to the supercharger, even when the engine load is changed even in the period immediately after the engine load is changed. It can be guaranteed to accommodate exactly adapted scavenging and filling air.

The supplementary air can be suitably supplied as charging air by an auxiliary blower supplying air at 55% and higher engine load. Known auxiliary blowers are shut down at about 50% engine load. By setting the blower for a larger load, the auxiliary blower has sufficient capacity to compensate for the reactor's heating at engine start-up, so that the auxiliary blower remains operational when the engine load exceeds 50% during acceleration. You can get the effect.

Determination of the operating point at which more air / gas should be supplied is empirically obtained with regard to the instantaneous memory of the engine and the rapid degree of load change without supplying more air / gas. Can be done by comparison with a value.

Alternatively, the operating point may be a point in time at which the temperature difference of the exhaust gas throughout the reactor exceeds a predetermined minimum limit.

The invention also relates to a turbocharged internal combustion engine for use in the method described above, the engine having an exhaust gas receiver, a turbine connected at the output side to a reactor for reducing the NO _x component of the exhaust gas, and at the gas outlet of the reactor. A supercharger having a connected gas inlet, at least one sensor for measuring engine parameters, and an auxiliary blower for supplying scavenging and charging air. According to the invention, the engine comprises a bypass conduit capable of connecting the exhaust passage between the reactor and the turbine of the supercharger to an exhaust passage downstream of the turbine, control means capable of blocking the bypass conduit in whole or in part, and a sensor. On the basis of the signal received from the controller, it is determined whether the reactor cools the exhaust gas, and when the exhaust gas is cooled by the reactor, the control unit adjusts the control means toward the closed position.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Figure is a schematic structural diagram of one embodiment of an engine according to the present invention.

The figure shows, for example, a large two-stroke internal combustion engine capable of generating 40 MW of power. Air is supplied to the engine through a compressor (C) of the supercharger and an auxiliary blower (AB) for supplying air to a charging air cooler (not shown) for introducing air into the combustion chamber, and exhaust gas is supplied through an exhaust valve. It is discharged to the exhaust gas receiver (ER), the receiver is connected to the reactor (R) through the exhaust passage (1), the reactor can remove more than 90% of the NO _x component of the exhaust gas. The exhaust passage 2 extending from the outlet of the reactor leads to the inlet of the turbine T of the supercharger, and the outlet of the turbine portion communicates to the outside through the exhaust passage 3.

The bypass conduit 4 extends from the exhaust passage 2 on the upstream side of the turbine T to the exhaust passage 3 on the downstream side of the turbine. The bypass conduit has a control means (V) which is continuously adjustable from the fully open position to the fully closed position.

In the case of stationary operation of the engine, the supercharger (T / C) has a high efficiency to supply excess power. Therefore, since the supercharger does not need the entire exhaust gas to supply the required amount of scavenging and filling air to the engine E, the control means V is adjusted to a partially open position, so that the compressor C of the supercharger is ) Supplies the desired volume of air correctly. The exhaust gas flowing through the bypass conduit 4 can be used, for example, in a power turbine (not shown), but it is of course also possible to pass the exhaust gas directly into the exhaust passage 3. Regarding the efficiency of the supercharger, an efficiency η of about 64% is required for the operation of the engine without a reactor. At present, a supercharger having an efficiency of η = 73% can be obtained.

Reactor (R) is a so-called SCR (selective catalytic reduction) reactor manufactured by Danish company Haldor Topsoe A / S. With respect to the reactor already known per se, an engine with 40 MW of power requires a reactor comprising about 13.5 tonnes of catalytic material. It is also possible to use a smaller amount of catalyst material, but in this case a larger amount of ammonia flows out along with the purified exhaust gas.

Since the reactor R has a large heat capacity, as the load of the engine increases, as described above, the gas is cooled during the passage of the reactor, and only after a certain time, the increased load reaches the turbine T of the supercharger. Will provide increased energy.

The control unit CU is connected to three sensors S1, S2, S3 via respective wires 5, 6, 7. These sensors measure engine parameters (operation, ie performance parameters), and on the basis of these engine parameters, the control unit is powered by the exhaust gas to the extent that the reactor supplies supplementary energy to the supercharger to supply the desired amount of air. Determine whether it is heated.

With regard to the appropriate engine parameters, the sensor S1 can measure the instantaneous engine load based on the amount of fuel supplied to the cylinder in operation. The sensor S2 can measure the temperature of the exhaust gas in the exhaust passage upstream of the reactor R, and the sensor S3 can measure the temperature of the exhaust gas just upstream of the inlet of the turbine T. have. Optionally, the engine parameters measured by the sensor can be the pressure in the air / gas unit of the engine at the measuring points located downstream of the compressor C and upstream of the turbine T.

The control unit CU can determine the need for supplemental air based on only one measured engine parameter that is continuously measured over time, and then the change over time of the engine parameter is determined by Compared with the minimum limit, it is possible to determine whether the reactor R will absorb energy from the exhaust gas by the amount it has to supply make-up air / gas. The change over time of the engine load is compared with a predetermined minimum limit for the change of the load, for example in the control unit. The comparison corresponding to this can be made based on the temperature T1 of the exhaust gas upstream of the reactor R measured by the sensor S2. Alternatively, the control unit may receive a temperature signal from both the sensor S2 and the sensor S3 and, based thereon, calculate a temperature difference between the temperature T1 on the upstream side of the reactor and the temperature T2 on the downstream side. have.

If the measured engine parameter exceeds a predetermined minimum limit, the control unit CU transmits a signal to the engine E for supplying a larger amount of air / gas. This signal is transmitted through the wire 9 to the motor control unit of the auxiliary blower AB to start the auxiliary blower or to increase the output of the auxiliary blower. Optionally, the control unit transmits a signal to the control means V via the wire 8, adjusts the control means toward the closed position, introduces a small amount of exhaust gas into the bypass conduit 4, and the turbine. It is possible to introduce a large amount of exhaust gas into (T).

The control unit CU can also be designed to start the auxiliary blower when the first minimum limit is exceeded and to reduce the gas flow through the bypass conduit 4 when the second minimum limit is exceeded. have. In the embodiment shown in the figure, it is preferable that the second minimum limit is made smaller than the first minimum limit so that the control unit closes the bypass conduit 4 before starting the auxiliary blower. However, when the power turbine is connected to the bypass conduit 4, it is preferable to start the auxiliary blower first. For example, the first minimum threshold may be set to T2 / T1 = 0.5 and the second minimum threshold may be set to T2 / T1 = 0.25.

At the end of the heating of the reactor R, the amount of energy absorption is reduced, so that the control unit CU can reduce the supply amount of supplemental air / gas as the engine returns to its stable operating state.

The bypass conduit can also be connected, for example, downstream of the compressor of the supercharger, to communicate with the atmosphere to discharge excess air, or to the inlet of the turbine of the supercharger. In both cases, the excess air of the supercharger does not pass through the engine, thereby reducing the flow of air through the bypass conduit, thereby making it possible to supply a larger amount of air to the engine.

Claims (6)

Connected to an upstream side of the turbocharger (T / C) to determine the reactor R for reducing the component of NO _x (nitrogen oxide) in the exhaust gas and to determine whether the reactor R cools the exhaust gas. 12. A method for controlling a large two-stroke supercharged internal combustion engine E having means for measuring at least one engine parameter for the purpose of: when the measured engine parameter falls below a predetermined minimum limit, the downstream side of the reactor R Part of the exhaust gas is bypassed to the supercharger T / C, and when the measured engine parameter exceeds the minimum limit indicating the state in which the exhaust gas is being cooled by the reactor, Within the large two-stroke supercharger, characterized in that the partial exhaust gas is partially or partially passed through the turbine T of the supercharger T / C to be supplied upstream of the turbine. How to engine control. The method of controlling a large two-stroke supercharged internal combustion engine according to claim 1, wherein supplemental air is supplied as charging air by an auxiliary blower (AB) which supplies air at an engine load of 55% or more. The method of claim 1, wherein the control unit CU measures and stores the instantaneous load of the engine, compares the change over time of the engine load with a predetermined minimum limit for load change, and compares the result with the result of the comparison. And based on said control unit, a supply of a larger amount of air / gas is controlled by said control unit. The control unit CU measures and stores the temperature T1 of the exhaust gas in the exhaust receiver and the temperature T2 of the exhaust gas at the inlet of the supercharger T / C. The difference between the two temperatures is determined by the control unit, and when the temperature difference exceeds a predetermined minimum limit, the control unit starts supplying a larger amount of air / gas. How to control large two-stroke supercharged internal combustion engines. The auxiliary blower AB according to any one of claims 2 and 4, wherein the auxiliary blower AB is operated by the control unit CU when the temperature difference exceeds a first minimum limit. When exceeding the second minimum threshold, which is greater than the minimum threshold of?, The control unit CU passes more exhaust gas to the supercharger T / C. . A supercharger (T / C) having an exhaust gas receiver (ER) connected at the output side to the reactor (R) for reducing the NO _x component of the exhaust gas, a turbine (T), and having a gas inlet connected to the gas outlet of the reactor; In a large two-stroke supercharged internal combustion engine, comprising at least one sensor (S1; S2; S3) for measuring engine parameters, and an auxiliary blower (AB) for supplying scavenging and charging air, the reactor A bypass conduit (4) capable of connecting an exhaust passage (2) between (R) and a turbine (T) of the supercharger to an exhaust passage (3) downstream of the turbine, the bypass conduit in whole or in part On the basis of the control means V which can be cut off and the signal received from the sensor, it is determined whether the reactor R cools the exhaust gas, and when the exhaust gas is cooled by the reactor, the closed position is determined. Towards above Large two-stroke supercharged internal combustion engine being configured as a control unit (CU) for adjusting the control means according to claim.