JPS5867938A - Abnormal combustion preventing device in alcohol- reformed gas engine - Google Patents

Abstract

PURPOSE:To make it possible to improve the performance and fuel-milage of an alcohol-reformed gas engine and as well to prevent abnormal combustion, by lowering a gas/fuel ratio upon the generation of abnormal combustion so that the temperature is lowered under the evaporation of alcohol and as well the concentration of hydrogen is lowered. CONSTITUTION:A load arithmetic unit 47 calculates a load factor L in dependence upon an accelerator actuating amount S and a rotational speed Ne, and a gas/fuel ratio arithmetic unit 48 calculates a ratio alphago in accordance with the load factor L, and a setting unit 50 sets the ratio alphago or a limited gas/fuel ratio alphaglim given by the supply pressure Pg of reformed gas, whichever is smaller. The gas/fuel ratio alphag is promptly lowered by a predetermined amount DELTAalphag when the gas fuel ratio setting unit 50 receives a detecting signal from an abnormal combustion sensor 43, and then, is gradually recovered. Thus, the flow rate of alcohol increases so that the intake temperature is lowered due to the evaporation heat of alcohol, thereby the combustion temperature is also lowered to its normal value and therefore abnormal combustion is prevented without the lowering of output power being accompanied therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION Seriki 1jl relates to measures to avoid abnormal combustion in alcohol reformed gas engines.

As a conventional device of this kind, for example,
There is one such as that described in Publication No. 04542. This has a 51/c configuration as shown in FIG. 1, and the reformed gas introduced from the gas inlet 1 is supplied to the engine 4 through a gas flow meter 2 and the flow rate controlled by a gas valve 3. The air introduced from the air cleaner 5 flows into a primary air supply path 6 and a secondary air supply path T which are parallel to each other. After the flow rate is controlled by the primary air supply path 6 and the secondary air supply path 3 provided at Tk, the air is merged and supplied to the engine 4. When engine output is required, such as during high speed and high load, liquid alcohol is supplied to the engine 4 with the flow rate controlled by the alcohol injector 10.

The gas pulp 3 and the primary air supply path 6 are linked via a link 11, and the amount of operation of the accelerator operated by the driver is transmitted to both pulps 3.8 via an accelerator wire 12. , the secondary air valve 9 is the gas flow meter 2
The air current detected by k is proportional to the engine 4
The required fuel flow rate is set as follows. Then, when the flow rate of reformed gas is sufficient, the required flow rate is changed.

At the same time, the secondary air valve 9 is opened wide to dilute the air-fuel mixture. Conversely, when the supply of reformed gas is insufficient, the shortage of reformed gas is replaced by the fluid alcohol supply mode. At the same time as the supplement, the secondary air valve 9 is closed to reduce the excess air ratio of the mixture. or,
For calculating the alcohol supply amount as described above, the choletronilla 13 is used, into which the intake air amount E and the reformed gas supply amount are input.

The reformed gas obtained by thermally decomposing alcohol in Tonoori has hydrogen and carbon monoxide as its main components, and since the hydrogen concentration is high, the weight flow rate of the reformed gas in the total fuel is small. ratio (below)
/fuel ratio) is high, abnormal combustion such as backfire, premature ignition, and knocking is likely to occur. The occurrence of such abnormal combustion is affected by the outside temperature, humidity, composition of reformed gas, etc.* Therefore, in conventional engines as described above, in order to prevent the occurrence of abnormal combustion, the excess air ratio and the 2/fuel ratio had to be set with a margin of 4 for each of the above-mentioned fluctuation factors, and therefore fuel efficiency had to be sacrificed to some extent.

The present invention has been made in view of the above, and is a means to detect abnormal combustion when it occurs and quickly avoid abnormal combustion by reducing the /fuel ratio, thereby preventing various troubles associated with abnormal combustion. The alcohol reformer improves engine performance and fuel efficiency by setting the excess air ratio and ')':Z'7 fuel ratio to optimal values during normal operation when normal combustion occurs. The purpose of the present invention is to provide a device for avoiding abnormal combustion in high quality gas engines.

The present invention will be explained in detail below based on an embodiment shown in FIGS. 2 to 4.

FIG. 2 is a system diagram showing an embodiment of the present invention, in which a reformer 22 containing a reforming catalyst is installed in a reforming vessel 21 installed in the exhaust system of an engine 20. The liquid aluminum sent out from a fuel tank (not shown) via a pump passes through a Narconil passage 25 equipped with a cutoff valve 23 and a check valve 2'4, and is preheated via a double-pipe gas cooler 26. , is fed into the reformer 22. The alcohol supplied to the reformer 22 is thermally decomposed by the reforming catalyst, which is heated and maintained by the exhaust gas of the engine 20, and flows into the passage 30 into reformed gas. 31 is a gas manifold, and 32 is a flow of exhaust gas supplied to the reformer 22.
This is an exhaust bypass valve that controls the heating capacity of the reformer 22. Further, upstream of the gas valve 28, there is a gas pressure sensor 33 that detects the supply pressure of reformed gas, which is a parameter of the state of the reforming reaction in the reformer 22, and a safety valve that opens when the gas pressure rises abnormally. A 4° dove is provided.

Air is supplied from an air cleaner (not shown) to an air flow sensor 3.
The flow rate is controlled by the air valve 36 through the intake passage 3 through S.
0, mixes with the reformed gas discharged and supplied from the nozzle 21-, and is supplied to the engine 20. However, the unreformed liquid alcohol is flow-controlled by the alcohol injector 37 and sent to each of the engine 20. Suction and air are injected and supplied to the boat section. Reference numeral 38 is a glacial regulator for controlling the supply pressure of alcohol, and reference numeral 39 is a return passage for returning excess alcohol to the tank.

The controller 40 that controls the gas valve 28, the air valve 36, and the alcohol injector 31 includes an operation amount sensor 41 that detects the operation amount of the accelerator pedal operated by the driver, that is, the accelerator operation amount, and a gas pressure sensor 33. , a rotational speed sensor 42 and 1 that detects the rotational speed of the engine, the air flow sensor 35, and the engine 2.
The outputs of an abnormal combustion sensor 43, which detects abnormal combustion through the vibration of the zero cylinder brake, are supplied, and the optimum supply of reformed gas, alcohol, and air is calculated according to the output information of these sensors. 4445 is a servo valve.

FIG. 3 is a four-wheel diagram showing an example of the controller 40, in which the air valve calculation unit 46 outputs the reformed gas supply pressure Pg output from the gas pressure sensor f33.
and the accelerator operation amount B output from the operation amount sensor 41.
is input to calculate the air valve opening degree Va, and the air valve 36 is operated to realize this opening degree. At this time,
When the supply pressure Pg of the reformed gas is sufficiently high, the ratio of the air valve opening Va to the accelerator operation amount Inc is increased (on the contrary, when the gas supply pressure pg is low, the air valve opening Va is increased). In addition, the reformed gas supply pressure P
When g is zero, the ratio between the accelerator operation amount 8 and the air pulp opening degree Va is set to the same value as the alcohol engine.

The load calculation unit 41 is 71. Based on the accelerator operation amount 8 detected by the operation amount sensor +41 and the engine rotational speed N· detected by the rotational speed sensor 42, the required load of the engine, that is, the load factor is calculated.

``3/Fuel ratio calculation unit 48 calculates the load factor''
The /ffi ratio αgo is calculated, the reformed gas supply pressure Pg is input, and the limit is selected. The actual "3/fuel ratio αg" is set from the "S/fuel ratio setting unit) 5G," but when the abnormal combustion detection signal is supplied from the abnormal combustion sensor 43 to this fuel ratio setting unit) 50, this /Fuel ratio αg is instantaneously reduced by a predetermined amount Δαg, and then gradually restored by so-called proportional/integral control, which is repeated to reduce the value to a value that avoids abnormal combustion.

The fuel calculation unit 51 calculates the intake air flow rate Ga output from the air flow sensor 3s and the fuel ratio setting unit 50.
tj) C7 fuel ratio αg outputted from tj) and C7 fuel ratio αg are input to calculate the fuel required flow rate Gf of the engine. Furthermore, this required flow rate O
f is the stoichiometric air-fuel ratio no.

Assuming that C is a constant, when the reformed gas supply pressure pg is high and the load factor is small, it is possible to increase the 77/fuel ratio αg and also increase the excess air ratio to increase thermal efficiency. desired.

Further, the "3/fuel ratio αg and the required fuel flow rate Gf obtained as described above are supplied to the gas flow rate calculation unit 52 and the alcohol flow rate calculation unit 53, and each unit 52.5
3, the reformed gas supply amount G1 and the alcohol supply amount at are calculated, and the gas valve 28 and the alcohol injector 37 are controlled to realize these flow rates.

In addition, the output signals G and Gt of each Enin) 52.58 are as follows: Gg-αg-Gf at error (l-4g)・Gf There is no need to explain in detail what is given by.

That is, in order to optimize the fuel consumption rate of the engine 20, the gas/fuel ratio α should be set to 0.7 as shown in the upper half of FIG.
It is desirable to set the knock margin in the range of ~0.9, but in this range, the knock margin is as small as 5, as shown in the lower half of the figure.

Therefore, with emphasis on fuel efficiency, the fuel ratio αg is set to 0.
．． If it is set in the range of 7 to 0.9, there is a disadvantage that even slight fluctuations in outside temperature, humidity, and reformed gas composition easily cause pack fire, premature ignition, and abnormal combustion with knocking tendency. Additionally, in order to prevent abnormal combustion due to knocking, it is sufficient to control the excess air ratio, but since abnormal combustion is likely to occur in the tipping range, that is, when the amount of air-fuel mixture charged is close to the maximum, It is virtually impossible to prevent abnormal combustion by increasing the excess air ratio. Furthermore, although some abnormal combustion can be suppressed by changing the ignition timing, it has not been possible to completely prevent premature ignition.

However, in the present invention, when the occurrence of abnormal combustion is detected, the 7''/fuel ratio αg decreases and the flow rate ratio of alcohol in the total fuel increases, so the intake air temperature decreases due to the heat of vaporization of the alcohol.

As a result, the temperature inside the combustion chamber also decreases, so the overall
The combustion temperature can be lowered to a normal value without changing the fuel supply amount, that is, the overall heat generation and amount related to output, and abnormal combustion can be prevented without a decrease in output. It is.

Therefore, even if the fuel ratio αg is set within the best fuel efficiency range, abnormal combustion such as knocking, packfire, and premature ignition is prevented, and various troubles associated with this type of abnormal combustion can be avoided as much as possible. can.

In the embodiment, the occurrence of knocking is detected from the vibration of the cylinder block, but it is also possible to detect knocking, packfire, etc. by detecting the vibration of the intake manifold and also the fluctuation of the angular velocity of the engine flywheel. In particular, when it is necessary to detect only backfires that pose a safety problem, a flame sensor such as a flame sensor may be provided in the intake system.

Furthermore, in the embodiment, the accelerator operation amount and the intake air flow rate are detected by separate sensors, but at least during steady operation, a relational expression holds between the two, so either one can be used as an index of the other. You can also use it.

As explained above, according to the present invention, when abnormal combustion occurs, the gas/fuel ratio is reduced, the temperature of the intake air-fuel mixture is lowered by the vaporization effect of alcohol, and the hydrogen concentration is lowered to promptly avoid abnormal combustion. Therefore, it is possible to avoid abnormal combustion while setting the gas/fuel ratio and excess air ratio to conditions that provide the best fuel efficiency. Therefore, the performance and fuel efficiency of this type of alcohol reformed gas engine can be further improved, and at the same time, damage to the engine due to abnormal combustion can be prevented, and engine safety can also be improved.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a conventional example, Fig. 2 is a system diagram of an embodiment of the present invention, Fig. 3 is a block diagram of the controller, and Fig. 4 is a fuel efficiency and optimum ignition timing for the fuel ratio. FIG. 20... Engine 22... Reformer 28...
・Gas valve 3F...Alcohol injector 4
0...Controller 43...Abnormal combustion sensor patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima

Claims (2)

[Claims] (1) In an alcohol reformed gas engine configured to supply reformed gas obtained by reforming alcohol and unreformed liquid alcohol as fuel, an abnormal combustion sensor for detecting abnormal combustion in the engine; Abnormal combustion avoidance in an alcohol reformed gas engine, comprising: control means for controlling the proportion of reformed gas in fuel to be reduced to a value that avoids abnormal combustion when abnormal combustion occurs based on a detection signal from a senna. Device. (2) The abnormal combustion avoidance device for an alcohol reformed gas engine according to claim 1, wherein the abnormal combustion sensor detects abnormal combustion through vibrations of the cylinder block or intake manifold of the engine. .