JPH03164526A - Compound internal combustion engine - Google Patents

Abstract

PURPOSE:To attain the low generation of NOx in a compound internal combustion engine obtaining output from the output of an internal combustion engine and that of an exhaust recovery turbine with the exhaust of the internal combustion engine as a drive source by controlling the variable capacity mechanisms of an exhaust turbocharger and the exhaust recovery turbine according to the O2 density of the exhaust. CONSTITUTION:A generator 11 is driven by the power of an internal combustion engine 10, the exhaust turbine 25 of a turbosupercharger 20 is driven by exhaust from the internal combustion engine 10, and exhaust from the exhaust turbine 25 is led into a reducing combustion furnace 30. A part of the exhaust from the internal combustion engine 10 is sent into an exhaust recovery turbine 18 for driving a generator 17, and the exhaust finished with work is led into the reducing combustion furnace 30. The exhaust is then cleaned by burning fuel 31 in the reducing combustion furnace 30 and fed into an exhaust gas boiler 40 to generate steam, thus driving a steam turbine 41 for driving the generator with this steam. In this case, the turbines 25, 18 are respectively provided with variable capacity mechanism, and the variable capacity mechanism is controlled to keep the O2 density of engine exhaust to the specific value.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a compound internal combustion engine.

[Prior Art] Fig. 2 shows a conventional compound internal combustion engine. The internal combustion engine 10 is supplied with fuel, and a generator 11 generates electrical output.

Exhaust gas from the internal combustion engine 1o passes through an exhaust pipe 13, drives an exhaust turbine 21 of an exhaust turbocharger 20, and is then led to a reduction combustion furnace 3o.

At this time, a branch pipe 15 is provided in the exhaust pipe 13, and a part of the exhaust gas is guided to the exhaust gas recovery turbine 16 that drives the generator 17 to output electricity, and then merges with the exhaust gas that drove the turbocharger mentioned above. It is guided to a reduction combustion furnace 30.

Hydrocarbon fuel 31 is added to the reduction combustion furnace 3o, and NOx in the exhaust gas is reduced by its reducing atmosphere, and the exhaust gas is discharged into the atmosphere through the exhaust gas boiler 40 as clean exhaust gas.

The exhaust gas boiler 40 recovers exhaust heat, generates steam, rotates a steam turbine 41, and obtains electrical output from a generator 43 driven by the steam turbine. Note that the steam that has driven the steam turbine 41 is turned into water by the condenser 42 and is supplied to the exhaust gas boiler 40 to operate the steam cycle.

Furthermore, the exhaust turbine 21 is connected to a coaxial compressor 22.
The air is compressed into high-pressure air supply, which is supplied to the internal combustion engine 10 via the air supply pipe 2.

[Problems to be Solved by the Invention] In order to prevent pollution, it is necessary to reduce NOx in the exhaust gas discharged from an internal combustion engine and make the exhaust gas clean. Therefore, the exhaust gas from the internal combustion engine needs to be brought into a reducing combustion furnace 3o to make the entire gas a reducing atmosphere. However, as shown in FIG. 3, when the amount of fuel supplied to the internal combustion engine 10 is small, that is, when the engine is under partial load, the 02a degree of the exhaust gas becomes large as shown by 'IIAQ' in the figure.

Furthermore, when the temperature of the air sucked into the compressor 22 of the turbocharger 20 is low, the suction efficiency improves, and a large amount of intake air is sent to the internal combustion engine 1o.
As shown by the dotted chain line m, the 02 concentration in the exhaust gas increases even with the same amount of fuel supplied to the internal combustion engine 10. As the 02 concentration in the exhaust gas increases, the amount of hydrocarbon fuel 31 required to make the exhaust gas a reducing atmosphere in the reducing combustion furnace 30 increases.
The twisting efficiency of the entire internal combustion engine decreases.

Therefore, even if the load on the internal combustion engine 1o, that is, the amount of fuel supplied, or the atmospheric temperature changes, it is necessary to keep the 0□ concentration of the exhaust gas almost constant as shown by the dotted line n in FIG. 3.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional apparatus and to provide a composite internal combustion engine with low overall fuel consumption, which is controlled so that the O2 concentration in the exhaust gas remains approximately constant even when operating conditions change.

[Means for Solving the Problems] The composite internal combustion engine of the present invention includes a variable displacement mechanism disposed in the exhaust turbine and/or the exhaust gas recovery turbine of the exhaust turbo supercharger 2o; (load) signal, a detection signal for 07 concentration in the exhaust gas discharged from the internal combustion engine, and a signal for the flow rate of air flowing into the compressor of the exhaust turbo supercharger, and the 02 concentration in the exhaust gas from the internal combustion engine is set to a specified value. and control means for controlling the variable capacitance mechanism so as to maintain the variable capacity mechanism.

[Operation] The variable capacity mechanism of at least one of the exhaust turbine and the exhaust gas recovery turbine is controlled by three signals from the internal combustion engine to change the work ratio between the exhaust turbine and the exhaust gas recovery turbine, thereby controlling the supply to the internal combustion engine 10. By controlling the amount of air, the 02 concentration of the exhaust gas can be brought to a specified value.

[Embodiment] An embodiment of a composite internal combustion engine according to the present invention will be described below with reference to FIGS. 1 and 3.

FIG. 1 is a block diagram of the first embodiment, and FIG. 3 is a performance curve diagram of the same embodiment.

The present invention maintains the 02 excess rate in the exhaust gas of an internal combustion engine at a constant state regardless of the engine load conditions, minimizes the NOx content in the exhaust gas, and discharges it as clean exhaust gas, and improves the overall fuel efficiency as a combined internal combustion engine. The aim is to maintain it in good condition.

First, the exhaust turbine of the exhaust turbo supercharger 20 is assumed to be the exhaust turbine 25 with a variable displacement mechanism. Further, an 8M exhaust gas recovery turbine 18 with a variable capacity mechanism is also installed in the branch pipe 15. Note that the variable capacity mechanism is a mechanism that controls the amount of exhaust gas flowing into the exhaust turbine by adjusting the turbine nozzle area.

An air flow meter 50 is attached to the air intake system of the compressor 22 of the turbocharger 20, and its output signal 51 is sent to the controller 60.
Enter. Further, a fuel flow meter 52 is attached to the fuel system 14 of the internal combustion engine 10, and its output signal 53 is inputted to the controller 60. Further, an exhaust O2 concentration detector 54 is attached to the exhaust pipe 13, and its output signal 55 is inputted to the controller 6o.

Next, the output signals 61 and 62 from the controller 60 are used to control the capacities of the variable displacement exhaust turbine 25 and the variable displacement exhaust recovery turbine 18, respectively.

Next, the operation of the first embodiment will be explained.

At a partial load where the amount of fuel supplied to the internal combustion engine 10 is small, the controller 60 detects the output signal 53 of the amount of fuel supplied and uses the output signal from the controller 60 to control the variable capacity exhaust turbine 25 of the turbocharger. The capacity of the recovery turbine 18 with variable capacity mechanism is increased accordingly.

As a result, the amount of exhaust gas flowing through the variable displacement exhaust turbine 25 is reduced, and the amount of work required to drive the compressor 22 is reduced, so the amount of air supplied to the internal combustion engine 10 is reduced, and the 02 concentration in the exhaust gas is reduced to maintain a specified value. .

In addition, since the intake efficiency is improved even when the atmospheric temperature is low, the controller 60 detects an increase in the amount of air supplied to the internal combustion engine based on the 8-force signal 51 of the air flow meter 50, and outputs the output signal 61. 62 allows the concentration of 02 in the exhaust gas to be set to a specified value by the same effect as described above.

Note that the recovery turbine 18 with a variable capacity mechanism whose capacity has been increased by the output signal 62 of the controller 60 has a larger flow rate of exhaust gas, and the electric output 17 has become larger, so that the thermal efficiency can be improved accordingly.

The second embodiment is a case in which only the exhaust gas recovery turbine is provided with a variable displacement mechanism (not shown). At a partial load where the amount of fuel supplied to the internal combustion engine 10 is small, the controller 60 increases the capacity of the variable displacement exhaust gas recovery turbine 18 using the output signal 62.

As a result, the total exhaust capacity flowing through the side turbine is increased.

Therefore, the exhaust pressure at the turbine inlet of the turbocharger 20 decreases, and the effective energy that can be released when the exhaust gas expands to atmospheric power becomes smaller. Therefore, the amount of work required to drive the compressor 22 of the exhaust turbine 21 is reduced, so the amount of air supply is reduced, and the 02 concentration of the exhaust gas is reduced to a specified value.

At this time, the amount of exhaust gas flowing through the variable displacement recovery turbine 18 increases relatively, but as described above, the effective energy of the exhaust gas decreases, so the electric output 17 does not increase, and the first embodiment Thermal efficiency becomes worse.

Although not shown, the third embodiment is a case where only the exhaust turbine 25 of the exhaust turbo supercharger 20 is provided with a variable displacement mechanism. At a partial load where the amount of fuel supplied to the internal combustion engine 10 is small, the variable capacity mechanism increases the capacity of the exhaust turbine 25 in response to the output signal 61 of the controller 60.

As a result, as in the second embodiment, the effective energy of the exhaust gas becomes smaller, the amount of air supply decreases, and the 02 concentration of the exhaust gas becomes smaller and reaches the specified value.

[Effects of the Invention] The present invention is configured as described above, and controls the turbo supercharger and the exhaust gas recovery turbine through a controller into which detection signals of the fuel flow rate of the internal combustion engine, the 02 concentration in the exhaust gas, and the intake air amount are input. By controlling at least one variable capacitance mechanism, the 02 concentration in the exhaust gas can be minimized, and NOx
It is possible to achieve a reduction in energy consumption and an improvement in overall thermal efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the first embodiment, FIG. 2 is a diagram corresponding to FIG. 1 of the conventional example, and FIG. 3 is a performance curve diagram of the conventional example and the embodiment. 10... Internal combustion engine, 11.17... Generator, 18.
... Recovery exhaust turbine, 20... Exhaust turbo supercharger. 22...Compressor, 25...Exhaust turbine, 5
0... Air flow meter, 52... Fuel flow meter, 54...
・02 Concentration detector, 60...Controller 6 Fig. 2 Fig. Maximum amount of fuel supplied to the internal combustion engine Fig. 3

Claims (1)

[Claims] In a compound internal combustion engine that obtains more output from the output of an internal combustion engine having an exhaust turbo supercharger and the output obtained by driving an exhaust recovery turbine with the exhaust gas of the internal combustion engine; the exhaust turbine or/and exhaust of the exhaust turbo supercharger; A variable capacity mechanism provided in the recovery turbine; a signal for the fuel flow rate supplied to the internal combustion engine, a detection signal for O_2 concentration in the exhaust gas discharged from the internal combustion engine, and air flowing into the compressor of the exhaust turbo supercharger. a control means to which a flow rate signal is input and which controls the variable displacement mechanism so as to maintain the O_2 concentration of the internal combustion engine exhaust gas at a specified value.