JPS6053766B2 - catalytic combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine having a reciprocating piston with a catalyst disposed in the combustion chamber to initiate and drive combustion at compression temperatures within the combustion chamber.

Hereinafter, in this specification, this internal combustion engine will be referred to as a catalytic combustion engine. It is an object of the present invention to provide compression ignition of the injected fuel used in diesel engines, albeit at a higher compression ratio than is normally practiced with commercially available high octane gasoline spark ignition gasoline engines. The object is to provide an internal combustion engine that can operate at a much lower compression ratio than is required. For example, the maximum compression ratio of the internal combustion engine to the braking force output is about 12:1, and this is based on the fact that the ideal thermal efficiency of the internal combustion engine is expressed by the following equation.

That is, in the above equation, R represents the compression ratio, and γ represents the ratio of the specific heat at constant pressure to the specific heat at constant volume of air.

．． The thermal efficiency η of the engine when plotted against the compression ratio R gradually flattens out as the compression ratio increases, but shows a rapid rise at the beginning. As the compression ratio increases, the operating losses of the internal combustion engine increase, i.e. the ideal average effective pressure is reduced to a larger average based on the friction subtracted to arrive at the net average effective pressure representing the actual power output. It comes to have pressure. The optimum value for the compression ratio with respect to braking force output is approximately 12:1. The above is
In particular, reference is made to spark-ignition gasoline engines with a compression ratio of 12:1, including uncontrolled self-ignition or "pre-ignition" before the moment of spark ignition of the charge, and charging performed by firing a spark at an appropriate time. The use of special gasolines with high resistance to "knock" due to self-ignition of the charge far from the combustion chamber after normal ignition of the combustion chamber is required.

Such fuels are not widely available commercially, and construction of gasoline engines with such compression ratios is not feasible. On the other hand, a typical diesel engine uses a high compression ratio to raise the temperature inside the combustion chamber to a value that allows self-ignition of the diesel fuel injected into the combustion chamber just a little before top dead center at the end of compression. It is required to have the following.

As the swept volume of individual cylinders decreases, higher compression ratios are required to compensate for the loss of charge heat during compression. For example, cards, comments, marks (
In small compression single-ignition engines, such as those with a pre-combustion chamber (see British Patent No. 78632), a sufficient cold start (using a heating plug) and diesel distillate as the injected fuel are used. A compression ratio of approximately 21:1 is required for high speed, low load operation without misfires.Such diesel engines should not be operated at compression ratios lower than 12:1. is impossible.Furthermore, 91R
Even if gasoline of 0N (Research Octane Number) or methanol (methyl alcohol) of RON of 100 or more is used as the injected fuel, the compression ignition engine as described above can be operated even if the compression ratio is increased to 12:1 or 21:1. It is impossible to do so.

The reason for this is that high-octane high-quality gasoline, which is the main characteristic of high-quality gasoline normally used in spark-ignition engines, has a high self-ignition temperature and the subsequent ignition delay time is long, or diesel fuel easily This is because once it is injected into an engine cylinder under compression pressures and temperatures that will cause it to ignite, it will fail to ignite. Various proposals have been made to provide a catalytic combustion engine having a pre-combustion chamber in which a catalytic combustion element is installed; for example, a catalytic combustion engine proposed in British Patent No. The combustion engine has a partially cylindrical pre-combustion chamber, with which a transmission passage communicates, and compressed air is charged directly from the cylinder tangentially into the core combustion chamber during each combustion stroke. The combustion engine is designed to create a vortex flow in the chamber around its axial direction, and the combustion engine is further equipped with a liquid fuel injection device, and a nozzle of this device injects fuel into the pre-combustion chamber through the mouth of the transmission passage. is arranged within the transmission passage so as to inject.

Further, the catalytic ignition element is mounted inside the pre-combustion chamber on the inner wall thereof or at a distance from the inner wall. however,
The catalytic combustion engine using liquid fuel provided by the present invention has at least one cylinder head, a pre-combustion chamber formed in the head and cooperating with each cylinder, and an upper part of the piston to separate the combustion space and the pre-combustion chamber in the cylinder. A portion of the total air charge is pre-combusted via the transmission passage in a tangential direction during each compression stroke of the piston under pressure, so that a portion of the total air charge creates a vortex within the pre-combustion chamber. It is designed to be sent into the room.

Furthermore, the combustion engine includes an injector for injecting liquid fuel into the precombustion chamber slightly before top dead center of each compression stroke;
A combustion engine having a catalytic element disposed within the pre-combustion chamber to initiate and enhance combustion of an air-fuel mixture in the pre-combustion chamber, the catalytic element arranged to facilitate gas flow from one side to the other. It consists of a screen having a number of openings or passages through its thickness, which are transversely divided so as to completely divide the pre-combustion chamber into two volumes. That is, the injector injects the fuel spray at a position spaced apart from the screen, and the transmission passage is connected to the first volume part and the pre-combustion chamber at a space spaced apart from the screen, so that the extension of the center line thereof does not intersect with the screen. A second volume exists. The catalyst element is preferably in the form of a sheet, grid or mesh with perforations;
For example, it is preferable to use a gauze supported on a support frame and made of or coated with a catalytically active material.

If the above-mentioned transmission passage is formed in a "hot plug", which is formed by a recess in the refractory material inserted into the cylinder head, forming the lower side of the so-called pre-combustion chamber, the catalyst screen is The recess in the plug forms the aforementioned second volume, with the periphery interposed between the hot plug and the adjacent surface of the cylinder head. become.

(In this case, the engine is considered to have a vertical piston axis with the cylinder head at the top, and the axis of the vortex in the pre-combustion chamber is horizontal). When a "hot plug" is inserted into a well formed in a cylinder head, the periphery of the catalyst screen will be surrounded by the periphery of the plug and squeezed between the plug and the peripheral wall of the well. As mentioned above, the feature of the present invention is that the injection device
It is arranged so that the fuel spray is injected from a position above the catalyst screen along a center line such that the extension of the injection does not intersect the screen, and when using a screen with a flat top surface, the injection Preferably, the devices are arranged so as to be spaced upwardly along the aforementioned centerline and approximately parallel to the screen, or at least to spray downwardly and non-inclined towards the screen; , a combustible mixture of air and injected fuel is formed on the catalyst screen, eliminating any mechanical interference during injection through the screen.

Usually, a heating plug is provided to assist in cold starting, and its tip protrudes into the pre-combustion chamber at a position downstream of the fuel injection point and upstream of the mouth of the communication passage. The downstream and upstream sides here are defined with respect to the flow direction of the vortex created in the compression stroke core combustion chamber, respectively. Even if the heating plug becomes active during a cold start, it is surprisingly effective to position the heating plug so that at least a portion of the injected fuel spray falls directly onto the plug during normal operation. I realized something.
The use of a catalytic screen in the engine of the present invention, as specified in the foregoing description, facilitates ignition of the fuel injected into the pre-combustion chamber to achieve a low compression ratio, e.g.
In the range between 1 and 15:1. It becomes possible to ignite even if
It became possible to use fuel with a compression ratio that would normally not be available. Thus, in the embodiment of the present invention,
An l-piston engine is provided that operates on 91R0N gasoline and (100+ RON) methanol at a compression ratio of 12:1 without spark ignition.

The invention will be explained in more detail below on the basis of embodiments of the accompanying drawings. The engine in the illustrated embodiment is a single cylinder experimental diesel engine with bores and strokes each having a length (depth) of 85 m, and FIG. 11 is shown.

The cylinder head 10 has a card, comet, mark type (Ricard OCOmetMark type).
A pre-combustion chamber 13 similar to that described in British Patent No. 78632 Wani is provided, and this pre-combustion chamber 13 has a semicircular upper part 14 connected to a short cylinder intermediate part 15 and a cylinder block 20. Front part 1 of the cylinder head provided at the top
9 and a lower part formed by a shallow recess 16 of a refractory hot plug 17 inserted into a well 18 of a refractory hot plug 17. A transmission passage 21 inclined with respect to the longitudinal axis of the reciprocating movement of the piston is formed in the hot plug 17 and is connected to the pre-combustion chamber 13.
and the combustion cavity 22 above the piston 11 in the cylinder 12. 1 of the combustion air introduced into the cylinder during one combustion stroke of the piston 11
The part passes through the transmission passage 21 and enters the pre-combustion chamber 13 in a pressurized state from a tangential direction. In this way, the pre-combustion chamber 13
This creates a vortex flow in the direction indicated by arrow 31 within the piston and around a horizontal axis transverse to the reciprocating axis of the piston. A catalyst element 25 is provided in the pre-combustion chamber 13, and this element 2
5 is a gauze screen of catalytic material, for example of platinum, supported on a wide mesh support grid 26 of large diameter, high heat resistant wire. The catalytic element is also arranged in a recess 16 of the plug 17 such that its peripheral edge coincides with the periphery of the plug 17 and is located between the adjacent surfaces of the plug and the well 18.
It is provided across the top of the pre-combustion chamber 13 and only within the pre-combustion chamber 13. It is firmly fixed. Further, in this embodiment, the catalyst element 25 is fixed to the grid 26 by metal stitching and has a diameter of approximately 2.5 mm.
Gauze with Ming mesh per cm was used;
The choice of gauze of this size is a matter of convenience, and does not mean that it is the best choice. (An example of a catalyst screen is shown in Figures 2-3)
. In this way, the catalyst element 25 completely traverses the pre-combustion chamber 13 and connects it to the upper space 14A where the sprayed fuel is injected.
and a lower space defined by the recess of the plug 17.

A fuel injector 28 is installed in the hole of the cylinder head 10, and is inserted into the upper space 14 of the pre-combustion chamber 13 along a horizontal center line 28A parallel to and above the upper surface plane of the catalyst screen 25.
Liquid fuel is injected into A.

The center line 28A of the injection by the injector 28 is located above the catalyst screen 25 at about half the total height of the upper space 14A of the pre-combustion chamber and intersects with the tubular heating plug 29. This plug 29 is provided in the head 10, and its tip is provided so as to protrude into the upper space 14A of the pre-combustion chamber in the downstream region of the nozzle of the injector 28 with respect to the direction 31 of the vortex flow in the pre-combustion chamber. ing. Further, the spray angle of the injector nozzle is arranged to be narrow so that the fuel spray injected into the upper space 14A directly hits the heating plug 29. With the above-described configuration, the heating plug 29 is energized by simply passing a heating current for a short period of time before starting from a cold state, and even if it is switched after starting, it is effective for combustion for normal operation. It turns out that there is. Furthermore, by using the catalytic gauze screen 25 arranged as described above, the pre-combustion chamber 13 can be placed just before top dead center of combustion, as shown in experiments conducted by the applicant.
The ignition conditions for the fuel injected into the tank are considerably improved.

In fact, even in experiments using a compression ratio of 12:1, which is close to the ideal value for an internal combustion engine but would not work in a normal diesel engine, raw gasoline (91R0M
) and about 1% lubricating oil to lubricate the fuel injection pump as the injected fuel, and the engine started well and operated satisfactorily when the heating plug was utilized only during starting.

Also, fully satisfactory operating conditions were obtained in subsequent experiments using methanol containing 1% lubricating oil. As a result, it was found that diesel oil can also be used satisfactorily as a fuel. When the gauze screen 25 was not provided in the pre-combustion chamber 13, compression ignition and combustion were not successful for any of these fuels at this compression ratio. In these experiments, the shape of the combustion chamber (aside from injector location), the use of a high-pressure fuel injection system, and the actual injection timing were all compared to those used in conventional Glue-card, Komet, and Mark type compression ignition chambers. It was practically the same as the one given. According to experimental results, it is possible to use substances that are difficult to normally use as fuel in a combustion chamber that uses a catalyst, but I believe that this is because an oxidation reaction occurs due to the catalyst, and the atomized fuel is ignited at a much lower compression temperature than usual. This seems to be because it can be done. By performing combustion using a catalyst in this way, it is expected that the amount of unburned hydrocarbons will be reduced and the amount of carbon monoxide in the exhaust gas will also be reduced.

In the first experiments described above, a platinum gauze catalytic screen 25 was used, but catalytic elements 25 made of other materials, such as other platinum-coated non-catalytic materials or other catalytic Gauze made of certain materials can also be used.

Furthermore, in the above-mentioned experiments, cylinder heads with modified card, comment, or mark type precombustion chambers were used; The present invention can also be applied to a cylinder head having a type such as a comet type or a mark type type in which a cylinder space above a piston and a vortex-enhanced precombustion chamber are connected through a transmission passage.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a portion of the cylinder head of the engine and a portion of the cylinder itself, and FIGS. FIG. 2 is a plan view and a vertical cross-sectional view. 10... Cylinder head, 13... Pre-combustion chamber, 14A... First volume part, 16... Second volume part (recessed part), 17... ...hot plug, 1
8...well, 21...transmission passage, 2
5... Catalyst element (screen), 26...
... Catalyst element support frame, 28 ... Fuel injection device, 28A ... Center line of fuel injection spray, 29
... Heating plug, 31 ... Vortex flow path (direction) in the pre-combustion chamber.

Claims (1)

[Scope of Claims] 1. A preheating chamber is provided in the cylinder head of one or each cylinder and communicates with the preheating chamber through a gas transmission passage leading to a narrow space provided above the piston in the cylinder. catalytic combustion without spark ignition, wherein the gas transmission passage is oriented substantially tangentially to the inner wall surface of the preheating chamber so that a gas flow vortex is generated during the compression stroke of the piston; In a liquid-fuel operated reciprocating piston internal combustion engine of the type, the preheating chamber 13 extends completely across the interior of the preheating chamber 13 and traverses the flow path of the gas flow vortex and divides the interior of the preheating chamber into two separate spaces. 14A
, a gas permeable catalyst screen 25 installed at a position dividing the space 16, an opening of the gas transmission passage 21 opening to the space 16, and a liquid fuel directly injected at predetermined time intervals toward the space 14A. A catalytic combustion engine characterized in that the preheating chamber 13 has an engine having a fuel injection means 28. 2. The catalyst screen 25 is planar, and the injection center line 28A of the injection means 28 is aligned with the catalyst screen 25.
2. The catalytic combustion engine according to claim 1, wherein the fuel is injected from the injection means 28 at a position apart from the plane and parallel to the plane. 3 A hemispherical recess is formed in the inner surface portion 14 that forms the internal space of the preheating chamber 13 on the side away from the cylinder 12, and a transmission passage 21 is formed in the portion 15 opposite to the recess.
a concave recess guided toward the opening of the cylinder, the longitudinal direction of the transmission passage 21 is inclined with respect to the axial direction of the cylinder, and the longitudinal axis of the transmission passage 21 is inclined with respect to the axial direction of the cylinder; The planar part of the catalyst screen 25 extends perpendicularly to the cylinder axis so that a gas flow vortex is generated around it, and the flat part of the catalyst screen 25 extends in a direction perpendicular to the cylinder axis, and is located midway between the parts 14 and 15, which is the inner surface of the preheating chamber 13. The catalyst screen 2
5. The catalytic combustion engine according to claim 1 or 2, wherein a catalytic combustion engine is provided with a catalytic combustion engine. 4. The transmission passage 21 is formed in a so-called hot plug 17 made of a refractory material inserted into the cylinder head 10, and the hot plug 17 has an opening above which the opening of the transmission passage 21 in the preheating chamber 13 opens. forming a recessed space 16 with the catalyst screen 25 extending across the top of the hot plug 17 with a peripheral edge of the catalyst screen between adjacent peripheral surfaces of the hot plug 17 and the cylinder head 10; 4. The catalytic combustion engine according to claim 1, wherein the recessed space 16 is covered with the catalyst screen 25 by being inserted therein. 5. Insert the hot plug 17 into the well 18 formed in the cylinder head 10, so that the peripheral edge of the catalyst screen 25 wraps around the hot plug 17, and the hot plug 17 and the well 18 are separated. The catalytic combustion engine according to claim 4, wherein the catalytic combustion engine is held between the catalytic combustion engine and the surrounding wall surface.