JP3115894B2 - Control method for large two-stroke turbocharged engine and engine used for this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactor connected to the upstream side of a turbocharger for reducing the NOx (nitrogen oxide) component of exhaust gas, and whether or not the reactor cools the exhaust gas. Means for measuring at least one engine parameter to determine whether the engine is a large two-stroke turbocharged engine.

More and more countries are adopting laws that set lower NOx emission thresholds in consideration of environmental protection. Therefore, it is desirable to provide an exhaust gas purifying device in a large marine engine so as to operate continuously. Catalysts known in the automotive industry cannot be used in marine engines. This is because marine engines operate with large amounts of air and burn fuel heavy oils containing significant amounts of heavy metals and sulfur. In a car having a turbocharger, a catalyst device is provided upstream of the turbine,
CO (carbon monoxide) and HC (hydrocarbon) in exhaust gas are converted to O ₂
(Oxygen), and at the same time, generate heat to heat the exhaust gas passing through the reactor. Therefore, the operating conditions of such an engine are different from those of an engine having a reactor for reducing the NOx component of the exhaust gas.

When the exhaust gas is supplied to the reactor, the temperature of the exhaust gas must be at least 300 ° C. Therefore, if the engine is a large two-stroke engine used as a ship propulsion engine, the reactor should be turbocharged. Must be connected to the exhaust system before. The reactor utilizes a so-called "selective catalytic reduction method" (SCR) in which the exhaust gas is mixed with ammonium and the mixture is passed through a special catalyst at a temperature of 300 ° C to 400 ° C. The catalyst converts NOx to N ₂
(Nitrogen) and water. The volume of the catalyst must be large enough to ensure that ammonium is completely consumed and the NOx content in the exhaust gas is reduced to a sufficient extent.

The thresholds for NOx emissions from ships apply only to some types of inshore waters. Known engine systems include a bypass conduit with cut-off means that completely disconnects the reactor during the main voyage of the vessel and, when the engine operating conditions permit, reacts when the vessel is meandering in the inshore waters. The device is designed to be fully connected and an upper threshold for NOx outflow applied. Thus, the cutoff means of the bypass conduit is usually completely open or completely closed.

As a result of tests by the applicant of the above-described engine, when the engine load increases rapidly (for example, when the ship is accelerating or emergency stopping (braking)), the turbocharger responds to the increased instantaneous engine load. Since it was not possible to receive power, it turned out that the reactor had to be completely disconnected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for controlling a large two-stroke turbocharged engine to also purify exhaust gases while guaranteeing normal continuous operation of the engine.

In order to achieve the above object, the method according to the present invention is characterized in that a part of the exhaust gas downstream of the reactor is turbocharged when the measured engine parameter falls below a predetermined threshold value. Bypass the charger,
When the engine parameters exceed a threshold value indicating that the exhaust gas is being cooled by the reactor, the partial exhaust gas is supplied to the turbocharger so as to supply more air or gas to the upstream side of the turbine. That is, it is sent to the turbine in whole or in part.

This is an environmentally optimal configuration in that all exhaust gases pass through the reactor, even at increased engine loads.

When the engine load increases, the temperature of the exhaust gas increases and heats the reactor. Since the reactor has a large heat capacity, it takes a long time to heat the reactor to a high temperature, during which time the exhaust gas temperature behind the reactor becomes somewhat lower than the temperature in front of the reactor. This means that the energy of the exhaust gas behind the reactor is not large enough for the turbocharger compressor to receive power corresponding to the instantaneous engine load. In other words, the large heat capacity of the reactor and the connection of the reactor upstream of the turbocharger
There is a time delay in the effect of increasing engine load on the turbocharger, which delay increases with changes in engine load.

The time during which the reactor is cooled and at the same time the exhaust gas is cooled is determined in accordance with the present invention, during which time more air or gas is supplied to the turbocharger so that during the period immediately following the charging of the engine load, Also,
It can be ensured that the engine receives scavenging and charging air precisely adapted to the engine load.

Make-up air can be suitably supplied as charging air by an auxiliary blower that delivers air at 55% and above engine load. Known auxiliary blowers were shut down at about 50% engine load. By sizing the blower for a larger load, the auxiliary blower has sufficient capacity to compensate for the heating of the reactor at engine start,
When the engine load exceeds 50% during acceleration, an effect that the auxiliary blower is activated can be obtained.

Determining the operating point where more air / gas should be supplied
Memory of the instantaneous load of the engine and more air /
The determination is made based on a comparison with an empirically known value regarding the speed of change of the load when the gas is not supplied.

Alternatively, the operating point may be when the temperature difference across the reactor exceeds a predetermined threshold.

The present invention further relates to an engine used in the above method, the engine comprising an exhaust gas receiver connected on the output side to a reactor for reducing the NOx content of the exhaust gas, a turbine, the turbine of the reactor. It comprises a turbocharger having a gas inlet connected to a gas outlet, at least one sensor for measuring engine parameters, and an auxiliary blower for supplying scavenging and charging air. According to the invention, this engine is characterized by a bypass conduit which can connect the exhaust passage between the reactor and the turbocharger turbine to an exhaust passage downstream of the turbine, and the bypass conduit being entirely or partially Based on the control means that can cut off the gas and the signal received from the sensor, determine whether the reactor has cooled the exhaust gas, and when the exhaust gas is cooled by the reactor, control toward the closed position It consists of a control unit that regulates the means.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an engine according to one embodiment of the present invention.

The figure shows a large two-stroke engine capable of producing, for example, 40 MW of power. Air is supplied to the engine via a compressor C of the turbocharger and an auxiliary blower AB which supplies air to an air cooler (not shown) for flowing air into the engine, and the exhaust gas passes through an exhaust valve to exhaust gas. After being discharged to the receiver ER, the receiver is connected to the reactor R via the exhaust passage 1, and the reactor can remove 90% or more of the NOx component of the exhaust gas. The exhaust passage 2 extending from the outlet of the reactor communicates with the inlet of the turbine portion T of the turbocharger, and the outlet of the turbine portion communicates with the outside via the exhaust passage 3.

The bypass conduit 4 extends from the exhaust passage 2 upstream of the turbine T to an exhaust passage downstream of the turbine T. The bypass conduit has control means V which can be continuously adjusted from a fully open position to a fully closed position.

Turbocharger T / C for stationary engine operation
Has a high efficiency so that it can supply excess power.
Thus, since the turbocharger does not require all the exhaust gas to deliver the required amount of scavenging and charging air to the engine E, the control means V is adjusted to a partially open position and the turbocharger is adjusted. Compressor C accurately delivers the desired amount of air. The exhaust gas flowing through the bypass conduit 4 is, for example, a power turbine (not shown).
However, it is of course possible to directly send exhaust gas into the exhaust passage 3. Regarding the efficiency of the turbocharger, it is such that for an operation of the engine without a reactor, an efficiency η of about 64% is required. Today, it is possible to obtain a turbocharger with an efficiency η of 73%.

The reactor is Danish company Hardor Topse A / S
This is a so-called SCR (selective catalytic reduction) reactor manufactured by S). For this reactor known per se, 40
An engine with MW power requires a reactor containing about 13.5 tonnes of catalytic material. It is possible to use a smaller amount of catalyst material, but in this case a larger amount of ammonia will flow out together with the purified exhaust gas.

Since the reactor R has a large heat capacity, when the engine load increases, as described above, the gas is cooled while passing through the reactor, and if a certain time does not elapse, the increased load is applied to the turbine T of the turbocharger. Inability to supply increased energy.

The control unit CU has the wires (electric wires) 5, 6,
7 are connected to three sensors S1, S2, S3. These sensors measure engine parameters (operating or performance parameters) and, based on these engine parameters, the control unit uses the exhaust gas to the extent that it supplies supplemental energy to the turbocharger to deliver the desired amount of air. Determine if the reactor has been heated.

For the appropriate engine parameters, sensor S1 can measure the instantaneous engine load based on the amount of fuel supplied to the operating cylinder. The sensor S2 can measure the temperature of the exhaust gas in the exhaust passage on the upstream side of the reactor R, and the sensor S3
Can measure the temperature of the exhaust gas immediately upstream of the inlet to the turbine T. Instead, the engine parameters measured by the sensors are downstream of the compressor C and the turbine T
Engine air at a measurement point located upstream of
The pressure in the gas device may be used.

The control unit CU can determine the need for make-up air based on only one measured engine parameter measured as a function of time, and then determine the change in engine parameter as a function of time for each parameter change over time. Compared to the threshold value, it can be determined whether the reactor has absorbed energy from the exhaust gas by the amount to supply make-up air / gas. The change in engine load as a function of time is compared in the control unit, for example, with a predetermined threshold value for the change in load. The corresponding comparison is the sensor
The measurement may be performed based on the temperature T1 of the exhaust gas on the upstream side of the reactor R measured by S2. Instead, the control unit receives temperature signals from both sensors S2 and S3,
Based on this, the temperature difference between the upstream temperature T1 and the downstream temperature T2 of the reactor may be calculated.

If the measured engine parameter exceeds a predetermined threshold, the control unit CU sends a signal to the engine E to supply more air / gas. This signal is transmitted to the motor controller of the auxiliary blower AB via the wire 9 to start the auxiliary blower or increase the output of the auxiliary blower. Alternatively, the control unit transmits a signal via wire 8 to the control means to adjust the control means towards the closed position, to allow a small amount of exhaust gas to flow into the bypass conduit and to provide a large amount of exhaust gas to the turbine T. You may make it flow in.

The control unit can also be configured to start the auxiliary blower when a first threshold is exceeded and to reduce the gas flow through the bypass conduit 4 when a second threshold is exceeded. . In the embodiment of FIG. 1, preferably, the second threshold value is smaller than the first threshold value, and the control unit closes the bypass line 4 before starting the auxiliary blower. However, when a power turbine is connected to the conduit 4, it is desirable to start the auxiliary blower first. For example, the first threshold is set to T2 / T1 = 0.5, and the second threshold is set to T2 / T1 = 0.25.

When the heating of the reactor R approaches the end, the energy absorption amount decreases. Thus, the control unit can reduce the make-up air / gas supply when the engine returns to its stable operating state.

Also, a bypass conduit can be connected, for example, downstream of the compressor of the turbocharger to communicate with the atmosphere to exhaust excess air, or connected to the inlet of a turbine of the turbocharger. In these cases, the excess air of the turbocharger does not pass through the engine, thus reducing the airflow through the bypass conduit, thereby allowing more air to be supplied to the engine.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 37/02 F02B 37/12 F02B 37/04

Claims (6)

(57) [Claims] A reactor (R) connected upstream of a turbocharger (T / C) for reducing the NOx component of exhaust gas.
A method for controlling a large two-stroke turbocharged engine (E), comprising: means for measuring at least one engine parameter to determine whether the reactor (R) is cooling exhaust gas. In the above, when the measured engine parameter becomes smaller than a predetermined threshold value, a part of the exhaust gas on the downstream side of the reactor (R) is bypassed to the turbocharger (T / C). When the engine parameters exceed the threshold value indicating that the exhaust gas is being cooled by the reactor, the partial exhaust gas is totally or partially removed from the turbine of the turbocharger (T / C). (T)
An engine control method comprising: supplying a larger amount of air or gas to an upstream side of the turbine. 2. The method according to claim 1, wherein
An engine control method characterized in that auxiliary air is supplied as charging air by an auxiliary blower (AB) that supplies air at an engine load of 55% or more. 3. The method according to claim 1, wherein the instantaneous load of the engine is measured and stored by a control unit (CU) and the change of the engine load as a function of time. A predetermined threshold value for changing the load, and controlling the supply of a larger amount of air / gas by the control unit based on a result of the comparison. 4. The method according to claim 1, wherein a temperature of exhaust gas at an exhaust receiver (T1) and the turbocharger (T / C) are controlled by a control unit (CU). Exhaust gas temperature at the inlet of the
2) is measured and stored, and the temperature difference between these two temperatures is determined by the control unit, and when the temperature difference exceeds a predetermined threshold value, a larger amount of air / gas is An engine control method characterized by starting supply. 5. A method according to claim 4, wherein said auxiliary blower (A) is controlled by said control unit (CU) when said temperature difference exceeds a first threshold value.
B), and when the temperature difference exceeds a second threshold value that is larger than the first threshold value, the control unit sends more exhaust gas to the turbocharger (T / T).
C) An engine control method characterized by flowing into the engine. 6. A large-sized two-stroke turbocharged engine for use in the method according to any one of claims 1 to 5, wherein the reaction device (R) reduces an NOx component of exhaust gas. An exhaust gas receiver (ER) connected on the output side to a turbocharger (T / C) comprising a turbine (T) and having a gas inlet connected to the gas outlet of the reactor, and measuring engine parameters An engine comprising at least one sensor (S1; S2; S3) and an auxiliary blower (AB) for supplying scavenging and charging air, the reaction device and the turbocharger turbine (T).
And a control means (V) that can cut off the bypass conduit in whole or in part. Determining whether the reactor (R) has cooled the exhaust gas based on the signal received from the sensor, and when the exhaust gas has been cooled by the reactor, the control means moves toward the closed position; An engine, comprising: a control unit (CU) for adjusting the pressure;