FI106882B - A method for controlling a large turbocharged internal combustion engine and the engine used in this method - Google Patents

Description

106882

FIELD OF THE INVENTION The invention relates to a method for controlling a large turbocharged internal combustion engine powered by a turbocharged and equipped with means for measuring at least one engine parameter to determine if the reactor cools the exhaust gases.

From an environmental point of view, it is expected that a growing number of countries will introduce rules setting even lower limits on NOx emissions. Therefore, it is expected that large marine engines will have to be continuously equipped with exhaust gas cleaning equipment. Marine engines cannot use catalysts known in the automotive industry because marine engines run on large amounts of air and burn heavy fuel oil containing some heavy metals and sulfur. Upstream of the Tur-15 silicon, turbocharged automotive engines can be equipped with a catalyst that causes the CO and HC in the exhaust gases to react with the CO 2 while generating heat so that the exhaust gases are heated as they pass through the reactor. Thus, the operating conditions of these engines differ substantially from those of an engine equipped with a reactor to reduce the NOx content of the exhaust gases.

EP-A-0 492 989 discloses a diesel engine having a reactor coupled downstream of the turbocharger to reduce the NOx content of the exhaust gases. A temperature sensor is located at the outlet of the gas from the reactor. When: the temperature of the gas in the reactor is higher than the upper limit of the catalytic reaction, more air is supplied to the engine, for example by closing the exhaust valve of the turbocharged engine. In this way, good exhaust gas cleaning can be achieved, but the operating conditions of the internal combustion engine are not taken into account.

Since the exhaust gas temperature must be at least 300 ° when fed to the reactor, 4; · 1 must necessarily be connected to the exhaust gas system prior to turbocharging, when the engine is a large type typically used as a marine propulsion engine. In recent years, some ships have been experimentally equipped with a reactor that removes most of the engine's NOx content. This known engine is described in "Emission Control of Two-Stroke Low Speed Diesel Engines", December 1991, by MAN B&W Diesel A / S. It has an exhaust outlet receiver coupled to the reactor outlet side to reduce the NOx content of the exhaust gases, a turbocharger with turbines having a gas inlet coupled to the reactor gas outlet, a reactor bypass tube that can connect the exhaust receiver to the turbocharger turbine and an auxiliary fan to supply cleaning and supercharging air. The reactor uses a so-called Selective Catalytic Reduction Process (SCR), in which the exhaust gases are mixed with ammonia and the exhaust gases are passed through a special catalyst at a temperature in the range of 300-400 ° C. The catalyst reduces the NOx content to N2 and water. The catalyst must have 10 relatively large volumes in order to ensure full utilization of the ammonia and to achieve a sufficient reduction of the NOx content of the exhaust gases.

The limit values for NOx emissions from ships currently apply only to a limited number of coastal waters. By means of a bypass pipe with a closing means, the known engine system is designed so that the reactor is completely separated during most of the ship's voyage and - if engine conditions permit - fully engaged when the vessel sails in near-coastal waters where NOx emission ceilings are in effect. The closing means in the bypass pipe is thus normally either completely open or fully closed.

The applicant's experience with the aforementioned engine showed that the reactor had to be shut down completely if the engine load had to be suddenly increased, for example when steering a ship or during emergency braking, since the turbocharger did not receive the power corresponding to the instantaneous engine load. Another flaw was found when the reactor had to be turned on by closing the bypass valve and immediately opening the 25-liters upstream and downstream reactor. The relatively cold reactor caused a sudden drop in exhaust temperature upstream of the turbocharger, causing the turbocharger system to start vibrating, which in severe cases stopped the engine. This situation is unacceptable and, to avoid this, a small amount of the exhaust gas was passed through a shut down reactor to keep it slightly warm, and means were provided to measure the temperature difference over the reactor so that the bypass valve could be closed in two steps, · Complete switch-on was delayed until there was a small enough temperature difference across the reactor.

It is an object of the present invention to provide a method for controlling a Greater 35 turbocharged internal combustion engine to ensure continuous normal engine operation, including exhaust gas cleaning.

To achieve this object, the method according to the invention is characterized in that, downstream of the reactor, some of the exhaust gas bypasses the turbocharger when the measured parameter of the engine is below a predetermined threshold and passes wholly or partially through the turbine turbine upstream more air or gas is injected when the measured parameter of the engine exceeds a threshold indicating that the reactor cools the exhaust gases.

This is an environmentally optimal arrangement where all the exhaust gases are passed through the reactor, even with increasing engine loads.

As the engine load increases, the temperature of the exhaust gases increases, resulting in a warming of the reaction 10. Because of the high heat capacity of the reactor, heating the reactor to a higher temperature can take time and during this period the temperature of the exhaust gases after the reactor is somewhat lower than before the reactor, which means that the energy content of the exhaust gases after the reactor is not high enough for the turbocharger -15 power corresponding to this load. In other words, the high heat capacity of the reactor and its connection to the upstream side of the turbocharger have the effect of increasing the engine load with a certain delay and increasing the delay as the load changes.

By determining when the reactor is heated in accordance with the invention while the exhaust gases are cooling, and by supplying more air or gas to the turbocharger during these cycles, it can be ensured that the engine receives a sufficient amount of purifying and supercharging air properly fitted to the engine load cycle.

Suitably, additional air can be supplied as charge air by means of an auxiliary fan which supplies 25 air at engine load up to 55% and above. Previously known auxiliary fans switch off when the motor load is about 50%. Dimensioning the fans at high loads can result in the auxiliary fan having sufficient capacity at start-up to compensate for reactor heating, and the auxiliary fan operating during ship steering: 30 when the engine load often exceeds 50%.

Determining the operating point where more air / gas needs to be supplied can be accomplished by recording the instantaneous engine load and comparing it to known values of how quickly the load can be changed without feeding more air / gas.

4, 106882

Alternatively, said operating point can be determined when the temperature difference of the exhaust gases over the reactor exceeds a predetermined threshold.

The invention further relates to a turbocharged internal combustion engine for use in the above process, comprising an exhaust receiving chamber having a reactor at its outlet coupled to reducing the NOx content of the exhaust, a turbocharger with turbines having a gas inlet coupled to at least one reactor gas outlet engine. for measurement, and an auxiliary fan to supply cleaning and charging air. According to the invention, this engine is characterized by a bypass tube which can connect the reactor and turbocharger turbine turbine 10 exhaust channel to an exhaust channel downstream of said turbine, a control means that can completely or partially block the bypass tube, and a control unit exhaust gases and adjusting the control means toward the closed position as the reactor cools the exhaust gases.

In the following, examples of the invention will be explained in more detail with reference to the rather reduced drawing, which shows a circuit diagram of an embodiment of an internal combustion engine according to the invention.

The drawing shows an internal combustion engine which can produce, for example, 40 MW. Air is supplied to the engine via a turbocharger compressor C and possibly also through auxiliary blower AB, which supplies air to the charge air cooler (not shown), from which air flows further to the combustion spaces and further through exhaust valves to the exhaust gas receiving compartment ER more than 90% of the NOx content of the exhaust gases. From the reactor outlet, the exhaust duct 2 leads to the turbine turbine turbine part T si-25, which outlet is connected to the ambient air via the exhaust duct 3.

The bypass pipe 4 leads from the exhaust duct 2 upstream of the turbine T to the exhaust duct 3 downstream of said turbine. The bypass pipe has a control means V which is continuously adjustable from the fully open position to the fully closed position 30.

The efficiency of the turbocharger T / C is so high that, with the engine running steadily, the supercharger provided extra power. Since the turbocharger thus does not need all the exhaust gas to produce the required amount of cleaning and charging air for the engine E, the control means V is adjusted to such a partially open position that the compressor C of the turbocharger 35 delivers exactly the desired amount of air. Exhaust gases flowing through bypass 4 can be used in the unpowered turbine, although naturally the exhaust gases can also be led directly out to exhaust duct 3. From the point of view of turbocharger efficiency, it can be mentioned that if the engine runs without a reactor, an efficiency of about η = 64% is required. Today, turbo-superchargers with an efficiency of η = 73% are available.

5 The reactor is a so-called SCR reactor manufactured by the Danish company Haldor Topsoe A / S. In connection with this known reactor, it should be noted that a 40 MW engine requires a reactor containing about 13.5 tonnes of catalytic material. A proportionately lower amount of catalyst may be used, but this would involve higher ammonia emissions among the purified exhaust gases.

Because reactor R has a high thermal capacity, increasing engine load will result in cooling of the gases as they pass through the reactor, as mentioned above, and only after some time will the load increase lead to more energy to turbine turbine T.

15 Three sensors SI, S2 and S3 are connected to the control unit CU by means of the respective wires 5, 6 and 7. The sensors measure engine parameters (in-use or performance parameters) and based on these engine parameters, the control unit determines whether the reactor R has been heated enough by the exhaust gas to supply the required amount of air to the turbocharger.

20 As examples of suitable engine parameters, it can be mentioned that the sensor SI can measure the instantaneous engine load based on the amount of fuel supplied to the working cylinders. The sensor S2 can measure the exhaust gas temperature in the exhaust duct upstream of the reactor R, and the sensor S3 can measure the exhaust gas temperature immediately upstream of the turbine T inlet. Alternatively, the engine parameter provided by the sensor mi-25 may be the engine air / gas system pressure at the measuring point placed downstream of the compressor C and upstream of the turbine T.

The control unit CU can determine the amount of auxiliary or auxiliary air required based on a single riveted motor parameter, continuously measured as a function of time 30, and the change in motor parameter over time can then be compared to predetermined thresholds of parameter time variations to determine whether reactor R that additional air / gas must be supplied. For example, the temporal change in the load on the motor can be compared to predetermined thresholds for the change in load on the control unit. Equivalent ver. . The flare may also be made by the sensor S2 upstream of the reactor R, measured for the background of the exhaust gas temperature T1. Alternatively, the control unit may receive 610,6882 temperature signals from both sensor S2 and sensor S3, and calculate the differences based on this.

If the measured (measured) motor parameters) exceed a predetermined threshold, the control unit CU will send a signal to supply more air / gas to the motor E. Via line 9, this signal may be transmitted to the motor control of the auxiliary fan AB, which either starts the auxiliary fan. or increase it. Alternatively, the control unit may, via line 8, send a signal to the control means V, which is then adjusted towards the closed position so that a smaller portion of the exhaust gas flows through the bypass pipe 4 and a larger portion through the turbine T10.

The control unit CU may also be designed to start the auxiliary fan when the first threshold is exceeded, and then reduce the flow of gases through the bypass pipe 4 when the second threshold is exceeded. In the embodiment of Fig. 1, the second threshold is often preferably lower than the first, so that the control 15 closes the bypass pipe 4 before starting the auxiliary fan. However, if a power turbine is connected to pipe 4, it may be convenient to start the auxiliary fan first. For example, the first threshold is set to T2 / T1 = 0.5, while the second threshold is set to T2 / T1 = 0.25.

When the heating of the reactor R is nearly complete, its energy absorption decreases, 20 and thus the control unit CU can reduce the supply of additional air / gas while the engine remains in a steady state.

The bypass can also be located elsewhere, for example, by connecting it from the downstream side of the turbocharger compressor to the ambient air too out. for blowing, or by connecting it to a turbocharger turbine inlet. In either case, the excess air in the turbocharger is not conducted through the engine, and thus more air can be supplied to the engine by reducing the air flow through the bypass.

i ·· I · «·

Claims (6)

7 106882 A method for controlling a large turbocharged internal combustion engine (E) equipped with a reactor (R) upstream of the turbocharger (T / C) to reduce the NOx content of the exhaust gases, and provided with means for measuring at least one of the engine parameters. to determine whether the reactor (R) cools the exhaust gases, characterized in that, downstream of the reactor (R), some of the exhaust gases bypass the turbocharger (T / C) when the measured parameter of the engine is below a predetermined threshold and ) through the turbine (R) so that more air or gas is supplied upstream of the turbine when the measured parameter of the engine exceeds a threshold indicating that the reactor cools the exhaust gases. 2. Förfarande enligt patentkrav 1, kännetecknat av att tillaggsluft inmatas med 20 tillhjälp av en hjälpfläkt (AB), som matar luit dä motorbelastningen är t.o.m. och 55%. Method according to Claim 1, characterized in that the auxiliary fan (AB), which supplies air with a load of up to 55% of the motor, supplies additional air. 3. Förfarande enligt patentkrav 1 eller 2, kännetecknat av att motoms momen-tana belastning och registreras i en styrenhet (CU), som Jämför belastningens'! tidsmässiga förändring med fömtbestämda tröskelvärden for förändringar i belastingen, och att utgäende frän jämförelsen styrs tillförseln av tillaggsluft / gas. Method according to Claim 1 or 2, characterized in that the instantaneous load of the motor is measured and recorded in a control unit (CU) which compares the time change of the load with predetermined thresholds of the load changes and that the control unit controls the supply of additional air / gas. 4. Förfarande enligt face av föregäende patentkrav 1-3, kännetecknat av att i styrenheten (CU) mott och registreras at low temperature temperature mottagningsutrym-met (Tl) for avgaser og avgasemas temperature at ingängen (T2) account turboladden (T2) att skillnaden mellan dessa tva tempurer bestäms i styrenheten; och att 30 styrenheten aktiverar tillförseln av tillaggsluft / gas ifall skillnaden mellan dessa tvä temperatureurer överskrider et fömtbestämt tröskelvärde. Method according to one of the preceding claims 1 to 3, characterized in that the control unit (CU) measures and records the exhaust gas temperature at the exhaust gas receiving space (T1) and the exhaust gas temperature at the inlet (T2) of the turbocharger (T / C); that the difference between the two temperatures is determined by the · ·; you; and that the control unit initiates the supply of additional air / gas if the difference between the two temperatures exceeds a predetermined threshold. 5. Förfarande enligt patentkrav 4 och 2, tiltecknat av att styrenheten (CU) activator hjälpfläkten (AB) dä temperatureurskillnaden ørkrider that förkel treskkelvärd, och att styrenheten (CU) styr ytterligare avboler tur turer account. andra tröskelvärd, som företrädesvis är högre än det första tröskelvärdet. Method according to claims 4 and 2, characterized in that the control unit (CU) starts the auxiliary fan (AB) when the temperature difference exceeds the first threshold value, and that the control unit (CU) delivers additional exhaust gases to the turbocharger (T / C) when the temperature exceeds a second threshold value, which is preferably higher than the first threshold. A large turbocharged internal combustion engine for use in a method according to any one of claims 1 to 5, comprising an exhaust gas receiving space (ER) having a reactor (R) coupled to its outlet to reduce the NOx content of the exhaust gas; a turbocharger (T / C) with turbines (R) having a gas * * 35 inlet coupled to the reactor gas outlet; at least one sensor (S1; S2; s 106882 S3) for measuring a motor parameter; and an auxiliary fan (AB) for supplying flushing and charge air, characterized in that it has a bypass tube (4) which can connect the exhaust channel (2) between the reactor (R) and the turbocharger to the turbine (T) to the exhaust channel (3) downstream of said turbine. ); a control means 5 (V) which may completely or partially block the bypass pipe; and a control unit (CU) for determining, on the basis of signals received from the sensor, whether the reactor (R) cools the exhaust gases and controls the control means toward the closed position when the reactor cools the exhaust gases. 10 1. Förfarande för att styra en stor turboladdad förbränningsmotor (E) som upp- Ströms frän en turboladdare (T / C) försedd med en Reactor (R) för att minska halien av Nox i avgasema, och som försedd med organ för att runt ätminstone en parameter hos motom för att fastställa huruvida react (R) kyler avgaser, turn-tecknat av att nedströms frän reactom (R) passerar en del av avgasema turboladda-15 ren (T / C) d fast en häl motom underskrider that the tres-kelvärde, och leds helt eller delvis genom turboladdarens (T / C) turbine (R), sav att uppströms frän turbine inmatas luer eller gas dä motoms fastställda parameter överskrider et tröskelvärde som anger att reactom kyler. 6. Stor turboladdad förbräimingsmotor att använ avg vid förfarandet enligt face av föregäende patent krav 1-5, innefattande et mottagningsutrymme (ER) för avga-5 ser, on utgängssida kopplats en Reactor (R), med vilken halien av Nox i avga ; en turboladdare (T / C) coarse turbine (R), stem gasingäng kopplats account reactor gasutgang; ätminstone en givare (SI; S2; S3) för att put en parameter hos motom; och en hjälpfläkt (AB), med vilken spol- och laddningsluft inmatas, kanknetecknad av att den innefattar et förbiledningsrör (4) som kan förena avgas-10 kanalen (2) mellan reactom (R) och turboladdaren (T) med en avgaskan ) belä-gen nedströms frän nämnda turbin; ett styrorgan (V) som kanel helt eller delvis sluta förbiledningsröret; och en styrenhet (CU) som utgäende frän signaler mottagna frän givaren fastställer huruvida Reactor (R) kyler avgaser och som reglerar et styrorgan mot dess slutna Leave Reactor kyler avgaser. 1 · • «