JPS6132115Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an operation control device for a dual fuel engine that uses both liquid fuel and gaseous fuel, which maintains the air-fuel ratio at an appropriate value during gaseous fuel operation and automatically when an abnormality occurs in the air-fuel ratio. The system is designed to switch to liquid fuel operation.

By the way, this type of dual-fuel engine is primarily a land-based engine that is normally operated using gaseous fuel supplied from the outside, and in the event of an emergency or the like when the supply of fuel is stopped, it can continue to operate using liquid fuel. However, if the ratio of the fuel and combustion air, that is, the air-fuel ratio, is not maintained at an appropriate value during gas fuel operation, the combustion condition will become unstable, resulting in increased fuel consumption and the emission of unburned fuel. In addition, if the air-fuel ratio becomes abnormal due to a failure in the control device such as a gaseous fuel pump that controls the air-fuel ratio or its drive system, not only will the above-mentioned negative effects become significant, but it may also cause abnormalities in the exhaust system. This can lead to situations such as explosions.

The present invention addresses these problems with dual fuel engines, and is equipped with a sensor that detects the air-fuel ratio based on exhaust temperature, etc., and also uses a signal from the sensor to indicate that the air-fuel ratio is within a predetermined normal range. When detected, the air-fuel ratio control device is operated to maintain the air-fuel ratio at an appropriate value while maintaining the operating mode in the gaseous fuel operation mode, and when an abnormality due to a failure of the control device is detected, The operation mode is switched from the gas fuel operation mode to the liquid fuel operation mode. By using just one sensor, this normally prevents harmful effects such as increased fuel consumption and the discharge of unburned fuel, and also prevents situations such as abnormal explosions due to gaseous fuel operation in abnormal situations. , it was possible to continue operating the engine by switching to liquid fuel operation.

This will be explained below using an example shown in the figure.
In FIG. 1, 1 is a dual fuel engine, 2 is a supercharger installed in the engine, and an exhaust pipe 3 is connected to the turbine side of the supercharger.
An air supply manifold 5 is connected to the air delivery path 2a on the blower side via an intercooler 4, and a bypass 2c is provided between the air delivery path 2a and the air suction path 2b. ,
A bypass valve 6 for shutting off is provided. Here, the exhaust pipe 3 has a sensor 7 for detecting the exhaust temperature.
However, since the exhaust temperature corresponds to the air-fuel ratio, the sensor 7 indirectly detects the air-fuel ratio. Reference numeral 8 indicates a gaseous fuel supply pipe led to the engine from the outside, 9 indicates a shutoff valve provided on the pipe, and 10 indicates a branch portion 8a of the pipe and the air supply manifold 5.
The gaseous fuel supply valve is installed at each confluence part of the branching part 5a, and the valve is opened by the hydraulic oil discharged from the gaseous fuel pump 11 for a time corresponding to the discharge amount, and the gaseous fuel is supplied together with the combustion air. Supplies the combustion chamber. Reference numeral 12 denotes a liquid fuel pump, and the liquid fuel discharged from the pump is injected into the combustion chamber through a nozzle 13 installed in each cylinder, and the gaseous fuel and liquid fuel pumps 11 and 12 are equipped with discharge amount control devices 14 and 15 such as solenoids.

In addition to the above configuration, as shown in FIG. 2, the engine 1 includes an operation mode setting device 25 which receives the exhaust gas temperature signal a from the sensor 7 and adjusts the exhaust temperature indicated by the signal a, that is, the air-fuel ratio. A control circuit is provided to operate the Here, the operation mode setting device 25 includes a bypass valve 6 in the supercharger 2 shown in FIG. 1, a cutoff valve 9 on the gaseous fuel supply pipe 8,
This is a general term for the discharge amount control device 14 of the gaseous fuel pump 11 and the discharge amount control device 15 of the liquid fuel pump 12, and depending on these conditions, the operation mode of the engine 1 is set to liquid fuel operation mode or gaseous fuel operation mode. mode. Of these, the bypass valve 6 that controls the amount of air supplied to the combustion chamber and the discharge amount control device 14 of the gaseous fuel pump 11 that controls the amount of gaseous fuel supplied are used to control the air-fuel ratio during gaseous fuel operation. It also acts as a device.

Next, the configuration and operation of the control circuit shown in FIG. a normal state control unit comprising a first comparator 23 that compares the range set by the above signal a with the exhaust temperature indicated by the signal a; and an abnormal temperature range setting that sets an abnormal range of the exhaust temperature corresponding to an abnormal air-fuel ratio. An abnormality control unit is provided, which includes a second comparator 24 that compares the range set by the setting device 22 and the exhaust temperature indicated by the signal a.

When the exhaust temperature, that is, the air-fuel ratio is within the normal range, a normal signal a' is generated from the first comparator 23 of the normal control section. A gas fuel operation continuation signal A' is sent to the operation mode setting device 25 in response to the signal b. As a result, when the air-fuel ratio is normal, the bypass valve 6 shown in FIG.
The cutoff valve 9 opens the gas fuel supply pipe 8 to supply gas fuel to the engine, and the discharge amount control device 14 of the gas fuel pump 11 The opening time of the gaseous fuel supply valve 10 by canceling the restriction on the discharge amount of the hydraulic oil,
That is, the supply amount of gaseous fuel is controlled, and the discharge amount control device 15 of the liquid fuel pump 12 limits the amount of liquid fuel discharged from the pump 12 to only the amount necessary for ignition during gaseous fuel operation. In this way, gaseous fuel operation is carried out continuously. In this case, when the air-fuel ratio indicated by the signal a from the sensor 7 fluctuates within the above normal range, the continuation signal
A′ returns the air-fuel ratio to a proper value, so that the air-fuel ratio control device, that is, the bypass valve 6 that controls the amount of air supplied to the combustion chamber and the discharge of the gaseous fuel pump 11 that controls the amount of gaseous fuel supplied, At least one of the quantity control devices 14 is activated, thereby converging and maintaining the air-fuel ratio at an appropriate value.

On the other hand, if the exhaust temperature, that is, the air-fuel ratio, indicated by the signal a from the sensor 7 is within the abnormal range above or below the predetermined limit value, the second comparator 24 of the control circuit
An abnormality signal a'' is output from , and a switching signal to liquid fuel operation is sent to the operation mode setting device 25 based on the signal a'' and the gaseous fuel operation signal b.
As a result, if the air-fuel ratio (exhaust temperature) becomes abnormal due to a failure of the air-fuel ratio control device, the bypass valve 6 in the supercharger 2 closes and the A sufficient amount of air necessary for fuel operation is supplied to the combustion chamber, the shutoff valve 9 on the gaseous fuel supply pipe 8 is closed, and the discharge amount control device 14 of the gaseous fuel pump 11 is turned off from the gaseous fuel pump 11. Gaseous fuel supply valve 1 by stopping the discharge of hydraulic oil
0 is closed, the supply of gaseous fuel is stopped, and the discharge amount control device 15 of the liquid fuel pump 12 releases the restriction on the discharge amount of the pump 12, so that the required amount of liquid fuel is combusted from the nozzle 13. In this way, the engine 1 is switched to liquid fuel operation. At the same time, the switching signal A'' causes the display device 26 to display a message such as "exhaust temperature abnormality" or "gaseous fuel operation not possible", and the alarm device 27 such as a buzzer to issue an alarm.

As described above, according to the present invention, in a dual fuel engine that selectively performs liquid fuel operation and gas fuel operation, one sensor can maintain the air-fuel ratio at an appropriate value while continuing gas fuel operation. Control is performed to switch from gas fuel operation to liquid fuel operation when the air fuel ratio is abnormal due to a failure of the air fuel ratio control device or the like. As a result, the air-fuel ratio is maintained at an appropriate value during normal gas fuel operation, preventing harmful effects such as fuel consumption and unburned fuel emissions, and when an abnormality occurs, the exhaust system is shifted to liquid fuel operation. In addition to preventing abnormal explosions inside the engine, the engine continues to operate using liquid fuel, and for example, in the case of power generation engines, it is possible to cope with emergencies such as power outages. It is. Particularly, according to the present invention, since the normal control and the abnormal control are performed based on the output of one sensor as described above, there is an advantage that the structure is simple and can be implemented at low cost.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of various parts of an engine showing an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a control circuit in the embodiment. 1 is an engine, 7 is a sensor, 21 to 24 are control circuits, 25 is an operation mode setting device (6 is a bypass valve, 9 is a cutoff valve, 14 and 15 are discharge amount control devices for gaseous fuel and liquid fuel pumps) .

Claims (1)

[Scope of utility model registration request] In a dual-fuel engine equipped with an operation mode setting device that sets the operation mode to either a liquid fuel operation mode or a gaseous fuel operation mode, an air-fuel ratio sensor that detects an air-fuel ratio and an output signal from the sensor are received. , when the air-fuel ratio is within a predetermined normal range during gas fuel operation, the air-fuel ratio control device is operated to maintain the air-fuel ratio at an appropriate value while maintaining the operation mode setting device in the gas fuel operation mode; An operation control device for a dual-fuel engine, comprising: a control circuit that switches the operation mode setting device from a gaseous fuel operation mode to a liquid fuel operation mode when the air-fuel ratio is in an abnormal range.