JPS59165852A - Fuel supply device for gas engine - Google Patents

Abstract

PURPOSE:To reduce exhaust emission by forming a lean fuel mixture with a gas mixer during running within a rated load, while to avoid lack of output and reduce exhaust emission by correcting percentage of excess air during running under overload. CONSTITUTION:A main jet needle 11 is provided in a main gas passage 9 of a gas mixer 1, and is reciprocated by a step motor 8. The step motor 8 is reciprocatably operated by a dual system signal comprising a signal X to be generated by an electronic governor 31 for detecting load fluctuation of an engine and a signal Y to be generated by a device 21 for detecting percentage of excess air during running under overload. The device 21 is provided on the upstream side of a catalyst device 20, and functions in such a manner as to converge the percentage of excess air within a suitable range where the catalyst device 20 is maintained normally active.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel supply system for a gas engine, which is equipped with a catalyst device for purifying exhaust gas, and which burns a lean air-fuel mixture when operating at a rated load or lower.

In the engine, a lean mixture with a predetermined excess air ratio or higher (
For example, when a mixture with an excess air ratio of 7.3 is combusted, exhaust emission concentrations such as N% and HClC0 can be reduced as shown in the first factor, and the thermal efficiency can be reduced as shown in Figure 2. On the other hand, during overload operation, the output will be insufficient.In contrast, high output can be obtained by burning a rich mixture (for example, a mixture with an excess air ratio of /,0) (see Figure 2). ) On the other hand, as shown in FIG. 1, there is a characteristic that as exhaust emissions (NOX, HClCO) increase, thermal efficiency also decreases.

In addition, in order to simultaneously reduce NOx and oxidize HC and CO using a catalyst device for exhaust gas purification, such as a three-way catalyst, the air-fuel ratio of the intake system should be theoretically adjusted as shown in Figure 3. A very narrow range near the air-fuel ratio (air ratio /,
0-1:0.00! It is known that it is necessary to converge within the range of ;

In view of the combustion and exhaust characteristics of an engine as described above, the present invention aims to achieve low exhaust emission and high thermal efficiency in a gas engine equipped with a catalytic device without causing a lack of output in the entire load range of the engine. In order to achieve this, it is now possible to automatically correct the air transitivity in the appropriate direction in response to changes in engine load.4! The fuel supply device for a gas engine according to the present invention forms a lean air-fuel mixture in a gas mixer when operating at a rated load or below. Combustion reduces exhaust emissions and improves thermal efficiency, and during overload operation, the excess air ratio of the intake mixture is corrected to an appropriate range where the catalyst reacts actively, eliminating power shortages and reducing exhaust emissions. In order to reduce the amount of excess air, the main jet needle of the gas mixer is directly connected to a step motor that is operated forward and backward in response to a signal emitted from an empty % excess ratio detection device for detecting the excess air ratio. This is characterized in that the main jet needle can be automatically operated in an appropriate direction in response to changes in the excess air ratio.

Hereinafter, the fuel supply system for a gas engine of the present invention will be explained based on the embodiment shown in FIG. 1. In the fuel supply system of the embodiment shown in FIG. 3 is an air cleaner, t is a zero governor for adjusting the gas fuel supply pressure appropriately according to the intake air pressure of the engine, and 3 is a constant pressure for the gas fuel supplied from the gas fuel supply source. The instrument governor is shown for setting.

The gas fuel G supplied from the gas vibe 7 to the main gas passage 9 of the gas mixer l through the instrument governor 3 and the zero governor is fed into the intake passage /≠ from the nozzle /B attached to the venturi I/j of the intake passage /g. is injected into the intake passage l.
In Il, the air is mixed with intake air A taken in from the air cleaner 3 side at an appropriate ratio and is taken into the intake cylinder 2 side of the engine.

A catalyst device 2 for purifying exhaust gas is installed in the exhaust pipe 6 of the engine.
0 is set. This catalyst device 20 is N0X91
A three-way catalyst is used that simultaneously reacts with exhaust emissions such as 1C and CO to reduce and oxidize.

A main jet needle // is provided in the main gas passageway of the gas mixer/, and by adjusting the amount of advance and retreat of the main jet needle //, the 'fM amount of gas fuel G supplied to the nozzle/O side is controlled. It is now possible to do so.

This main jet needle/l is directly connected to a step motor r that moves forward and backward in a linear direction.
When the valve is operated in the backward direction (downward), the needle l/ is operated in the direction of opening the valve port IO (in the direction of arrow N).

This step motor r is operated by two systems of signals: a signal X emitted from the Kameko governor 31 that detects the square cylinder fluctuation of the engine, and a signal Y emitted from the excess air ratio detection device 2/ to be described later during overload operation. Each one is in turn in order to be operated forward and backward. Note that these signals are transmitted to the step motor via a controller (microcomputer) 30.

The signal During overload operation, the step motor is operated so that the main jet needle // moves in the valve opening direction (arrow 8, N direction). Therefore, when the engine is operated at a rated load or below, a lean mixture (e.g. excess air ratio /, tI~/, 6) is formed in the gas mixer /.
Also, during overload operation, the gas mixer 1 is turned on to form a rich air-fuel mixture within the excess air ratio range described below.

Said exhaust! 6, an air excess ratio detection wave B2/ for detecting the air excess ratio of the intake air-fuel mixture is provided upstream of the installation position of the catalyst device 20. In this embodiment, oJ1 in the exhaust gas g is used as the excess air ratio detection device 2/.
A sensor is installed in the line to detect the excess air ratio of the intake air-fuel mixture by detecting the air flow rate.

Tonora sensor 2/ has catalyst unit A (three-way catalyst) 20 set to N.
Each exhaust emission, such as ' That is, the 0:L sensor value is 0 in the exhaust gas g when the excess air ratio of the intake mixture is higher than the upper v3a positive range (/, 0 ± 0.00 evening) (when the mixture is thin). ．． In terms of concentration, the output is maintained at L level, but the excess air ratio decreases to /. When the voltage drops to 0.0, the sensor 2/ detects this as well, and becomes an H level output state. The ■level signal is emitted from sensor 2/.

The controller 30 operates the step motor in response to the signal Y sent from the O sensor 27, and when the level signal ■ is emitted from the O sensor 27, the step motor R throttles the main jet needle L/. direction (in the direction of arrow M), and restricts the flow rate of the gas fuel G flowing through the main gas passage to prevent air overflow! It acts to increase the I ratio (make the mixture leaner). Also, the excess air ratio is within the above appropriate range (/,
0±o, oos), the output sensor 2/ becomes L level, but when the engine is overloaded, the signal X issued from the electronic governor 3/ immediately switches the step motor K to the main jet needle// During overload operation, the step motor is moved back and forth in small increments to keep the excess air ratio of the intake air-fuel mixture constant so that the catalytic converter is activated. It acts to converge to an appropriate range circle that responds to.

In FIG. 1I, group number /7 is a slow fuel passage, /l is a flow control valve, and lde is a throttle valve.

Reference numeral 2 is a surge tank for reducing pressure pulsations in the intake air, and the surge tank 22 is part of the venturi of the intake passage/≠! It is interposed in the middle of the loading pressure cover 2 which connects the intake pressure extraction boat 23, which opens at the upstream position from the bottom, and the negative pressure plan 2'l of the zero governor.

Sasa No. 21. , 27.

Each of these valves is a solenoid valve.

Next, the present invention will be explained in detail. The gas engine fuel supply device of the present invention has the following effects.

(1) When the engine is operating under rated load, a lean mixture is combusted, and during overload operation, the excess air ratio of the intake mixture is corrected to an appropriate range where the catalyst reacts actively. , exhaust emissions (NOx * HCv CO
), it is possible to improve thermal efficiency when operating at a rated load or below, and there is no shortage of output even during overload operation.

(2) The main jet needle of the gas mixer is directly connected to a step motor that moves forward and backward in response to a signal emitted from the excess air ratio detection device for detecting the excess air ratio. To automatically operate the main jet needle in an appropriate direction according to fluctuations, and to simplify the arrangement for operating the main jet needle even in a fuel supply device configured to automatically operate the main jet needle. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the characteristics of excess air ratio and exhaust emissimine concentration, Fig. 2 is a graph showing the characteristics of excess air ratio, output, and thermal efficiency, and Fig. 3 is a graph showing the characteristics of excess air ratio and purification of exhaust emissimin. FIG. 4 is a system diagram of a gas engine fuel supply device according to an embodiment of the present invention. l...Gas mixer...Step motor tower...Main gas passage//...Main jet needle 20...Catalyst loading 2/...Excess air ratio detection device

Claims (1)

[Claims] /・ Catalyst device for exhaust gas purification in the exhaust path (20)
On the other hand, when operating under rated load, the gas mixer (1) forms a lean mixture and burns the lean mixture, and during overload operation, the gas mixer (1)
The main jet needle (/l) of 1) is adjusted so that the excess air ratio of the intake mixture can be corrected to an appropriate range in which the catalyst device (20) actively reacts, and the main jet needle (/l) of , a fuel supply device for a gas engine, characterized in that it is directly connected to a step motor (su) which is operated to move forward or backward in response to a signal emitted from an excess air ratio device (fa<2/) for detecting an excess air ratio. .