Diesel engine and method for improving the performance thereof

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efficiency, and thus reformed fuel is introduced into

DIESEL ENGINE AND METHOD FOR IMPROVING said sylinders during the suction stroke of the engine. ... THE PERFORMANCETHEREOF 'According to this invention, the combustion effi ciency of a diesel engine is improved as follows;

BACKGROUND OF THE INVENTION . It has been well known that a pilot injection, auxiliary injection and fumigation are very effective in improv 1. Field of the invention

This invention relates to a method for improving the ing the combustion efficiency of a diesel engine. P. H. combustion efficiency of a diesel engine and the diesel Schweitzer stated that diesel knock is reduced by the engine. . . . . . fumigation improving the engine efficiency in his Re 2. Description of the Prior Art :10 port published in SAE Transactions Volume 66, 1958. In a diesel engine, heretofore, fuel is ignited by inject Diesel knock is generally attributed to an undue in ing the fuel into the compressed air taken in the cylin crease of the ratio of dp/de where P denotes an explo ders under a high pressure. According to this method, sion pressure and 6 a crank travel angle, said ratio of the diesel engine unfavourably tends to cause a diesel dp/de having an interrelationship with an ignition de engine knock. The diesel engine according to this in 15 lay. Although the factors for the ignition delay can not vention improves the combustion efficiency of the en unconditionally be judged with the physical and chemi gine by reducing the diesel engine knock and increas cal factors being entangled complicatedly, it is clear ing the performance thereof. that a preflame reaction plays an important role in the delay. In the process of a preflame reaction, intermedi

SUMMARY OF THE INVENTION 20 ates such as lower hydrocarbons and oxygen-contain The primary object of this invention is to provide a ing compounds such as aldehydes, ketones and perox method for improving the combustion efficiency of a ides as well as chain carriers taking part in the combus diesel engine characterized in that, in the type of a tion are generated by a thermal decomposition or slow diesel engine wherein fuel is ignited by injecting itself oxidation reaction of fuel. Accordingly, the ignition into the compressed air introduced in the cylinders 25 delay can be shortened by supplying a sufficient under a high pressure, another quantity of the fuel is amount of the intermediates of these hydrocarbons and reformed and introduced into the cylinders during the chain carriers in advance right before the injection of a suction stroke of the engine in a system separate from main fuel or by generating a sufficient amount of these a fuel injection system. compounds in the combustion chamber at the time of Another object of this invention is to provide a diesel 30 injection. In short, the presence of an active preflame engine characterized in that, in the type of a diesel reaction occuring during the compression stroke be engine wherein fuel is ignited by injecting itself into the fore the main fuel injection can not only shorten the compressed air introduced into the cylinders under, a ignition delay but also improves the combustion there high pressure, an auxiliary air intake pipe is connected 35 after. Further, there is recognized a great difference in to a part of a main air intake pipe, a reformer is pro the kind of fuel to be used of the preflame reaction vided in said auxiliary air intake pipe, which reforms a when it is observed in the compression stroke after a separately introduced auxiliary fuel from a main fuel to fumigation is carried out with various kinds of fuel. be supplied by the fuel injection system, and this re This invention aims at carrying out, what is called, a formed auxiliary fuel is then introduced into the cylin 40 fumigation in a diesel engine where a part of supplied ders during the suction stroke of the engine. fuel is reformed into a mixture comprising decomposi Other objects will become apparent from the De tion and oxidation products and the mixture of fuel scription of Preferred Embodiment. hydrocarbons, the mixture being introduced into the BRIEF DESCRIPTION OF THE DRAWINGS cylinder thereafter.

45 When this reformed fuel is introduced into the cylin

FIG. 1 shows the relationship between the rate con ders, an active preflame reaction takes place in the process of the compression stroke, thereby supplying stant of decomposition reaction and the reaction tem sperature of various hydrocarbons and petroleum distil sufficient intermediates of hydrocarbons and chain lates. carriers before the injection of main fuel. FIG. 2 shows the spontaneous ignition temperature 50 Consequently, the injection delay is shortened re of the various hydrocarbons, and markably. Moreover, apart from the above, the im FIG. 3 is a schematic view illustrating an embodiment provement of air utilization rate and burning velocity of the present invention. improve the performance. As mentioned above, this

DESCRIPTION OF THE PREFERRED

invention is to introduce into the cylinders a reformed 55 fuel containing a relatively large amount of intermedi

EMBODIMENT: ates through the reformation of a part of fuel and this This invention is to provide a diesel engine with a reformed fuel spreads comparatively uniformly all over reduced diesel engine knock and an improved perform the internal space of the cylinders in the suction and ance thereof by improving the combustion efficiency of compression strokes causing an active preflame reac the engine. in the type of the diesel engine wherein 60 tion in the meantime. In this invention, an active pre ignition is carried out by injecting a fuel into the com flame reaction takes place all over the space increasing pressed air taken into the cylinders under a high pres the burning velocity after the ignition by a main fuel sure, characterized in that an auxiliary fuel in an injection remarkably and reducing afterburning as amount proportional to that of a main fuel is separately compared with the type of a conventional diesel engine reformed into a mixture comprising decomposition and 65. in which air is present only in the vicinity of a main oxidation products and the mixture of fuel hydrocar injection fuel source, thereby enhancing the combus bons from the main fuel supply system to be ignited by tion all over the internal space of the cylinders and a fuel injection in order to improve the combustion improving the air utilization rate. Consequently, the

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amount of smoke generated in the cylinder is reduced the burning velocity higher than hydrocarbons. The improving the performance remarkably. increase of the burning velocity of the hydrocarbons is The combustion efficiency of a diesel engine is im attained by the reformation reaction through decompo proved from a chemical point of view. sition and oxidation in which the opening of rings by In the process of a combustion by compression igni 5 breaking C-C bonds thereby producing small oxida tion, the composition of hydrocarbons constituting a tion compounds and the increase of the degree of us fuel and the combustion efficiency of hydrocarbons saturation with the compounds by spliting hydrogen off greatly influence the ignition of the injected fuel and C-H bonds of the compounds are effected. the spreading of flame. This is because the liquid parti It has been known that, when a fuel with a low cetane cle of fuel injected into the combustion space of the O number which is of poor ignition is used, a normal cylinders maintained under a high temperature and combustion is difficult to be effected because of the high pressure evaporizes and the evaporized hydrocar longer time of ignition delay, however, if the fuel is bons influence the ignition mechanism in its processes added with an oxidizing agent such as organic peroxide up to the ignition, which is subjected to a slow oxida or nitrate and then introduced into the cylinder, the tion reaction accompanied by cool flame. Further 15 combustion in the cylinder can be improved. This fact more, the composition of hydrocarbons constituting is explained by the result that upon burning hydrocar the fuel and the combustion efficiency thereof. also bons, a promotor of the generation of the reaction influence flame propagation speed affecting the travel products is separately supplied which is to be accumu ling reaction Zone surrounding the ignition nuclei pre lated during the induction period of oxidation reaction sent in a combustible jet mixture and the burning veloc that is a preflame reaction, thereby facilitating the start ity at the interface between the flame and the combus of combustion and increasing the burning velocity of tible mixture.

The composition of hydrocarbons constituting a fuel gaseous The mixture in flame propagation.

reforming of fuel is carried out under the follow for a diesel engine is not uniform and according to the ing reforming conditions. For instance, if a part of the analysis made by such a method as Fluorescent Indica supplied diesel light oil having

a boiling-point range of tor Adsorption method, a diesel fuel is composed of 10% at a distillation temperature of 230 C and 95% at alkanes consisting of n- and isoparaffines, naphthenes consisting mainly of monocyclo- and bicycloparaffines a330°C low is burnt at a comparatively low temperature and oxygen concentration, that is, at 400 - 800C and the balance being olefins having one, two or more under atmospheric pressure within the range of an aromatic rings and none of the aromatic ring. 30

Generally, it is recognized that the ignition efficiency catalyst on condition of air-fuel weight ratio 1 to 5, using a-alumina as a of a liquid hourly space velocity of diesel fuel has the relation with the phenomenon of of 0.5-5.0 and it is reformed in vapor phase with thus an ignition delay in the cylinders, and from the view generated point of the hydrocarbons constituting the fuel, n 0.1 - 0.5 bysteam within a range of steam-fuel ratio of weight, a gaseous product of oxygen-con paraffins of the fuel displays the best ignition property 35 followed in a decreasing order by olefins, naphthenes, taining compounds is obtained which is the oxidation iso-paraffines and aromatic hydrocarbons. This is evi product monoxide of non-hydrocarbons such as hydrogen, carbon and carbon dioxide, and hydrocarbons hav dent from the fact as shown in FIG. 1 showing the rate constant of decomposition reaction of various hydro ing 1 - 6 carbon atoms generated at a conversion rate carbons and petroleum distillates, that usually heavier 40 of 30 - 80%, together with a liquid unreacted, decom petroleum distillates are easy of decomposition at low position and oxidation products and a mixture of hy temperatures and that in the spontaneous ignition tem drocarbons.

perature indicating a minimum temperature of com In other words, a mixture comprising decomposition bustion in which a fuel burns itself in flame when hy and oxidation products and the mixture of fuel hydro drocarbon fuel is heated in the air, as shown in FIG. 2, 45 carbons is obtained.

it goes down accordingly as the boiling point rises in According to an analysis of liquid unreacted and homologues and in ones with the same molecular decomposition and oxidation products and the mixture weight, it goes down in the following order, aromatice of hydrocarbons carried out by a fluorescent indicator hydrocarbons, naphthenes and paraffines. adsorption method, hydrocarbon components consti In FIGS. 1 and 2, a shows an asphalt, b an atmo 50 tuting material diesel light oil is remarkably reformed spheric distillation-residual oil, c a light oil, d naphtha, through the decomposition in vapor phase as men e hexane, fpentane, g butane, h propane, i ethane, j tioned above wherein the contents of alkanes such as n mononuclear aromatic hydrocarbons, k iso-paraffins, l and iso-paraffins and naphthenes composed mainly of cycloparaffins, mn-paraffins, in monoolefins. mono-and bi-cycloparaffines markedly decrease while Further, the burning velocity of a premixture related 55 the content of olefins hydrocarbons composed mainly to flame propagation after the ignition of a combustible of mono- and di-olefins increases. mixture in the cylinders affects the completion of com In other words, the hydrocarbon component of a bustion processes. In other words, the burning velocity diesel fuel is reformed by dehydrogenation through a changes according to the composition of hydrocarbons treatment under the presence of a small amount of air constituting the premixture. In the hydrocarbons hav 60 and moisture of the hydrocarbon component constitut ing the same number of carbon atoms, the burning ing the diesel fuel, generation of lower hydrocarbons velocity increases as the degree of unsaturation in through the chemical bond rupture of hydrocarbons, a creases and in homologues, it decreases as the number process of decomposition and oxidation reaction such of carbon atoms increases except paraffins. as production of olefins hydrocarbons by opening rings. The burning velocity of paraffins is about the same as 65 The composition of said products contained in the ones with more carbon atoms, while aromatic hydro mixture comprising decomposition and oxidation prod carbons show the same burning velocity as other hydro ucts and the mixture of fuel hydrocarbons can be carbons. However, oxygen-containing compound has changed by allowing for such reforming conditions as

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temperature, air to fuel weight ratio, use of a catalyst tion to the flow rate of the main fuel measure a fixed and the selection thereof. .." . . .. . .. weight ratio of air in proportion to the flow rate and The said mixture comprising decomposition and oxi introduce it with said fuel into the reforming means 6. dation products and the mixture of fuel hydrocarbons The reforming means 6 reforms the fuel and air from itself contributes to the improvement of combustion the air meter 5 in said means and flow the reformed consisting of intermediates serving to improve the com gaseous mixture into the main air intake pipe 2. It com bustion after being introduced into the cylinders, or a prises inside a housing 20 from its upstream an air inlet mixture easily producing chain carriers. . . . . .. tube 58, auxiliary fuel injection tube 59, combustion FIG.3 shows one embodiment of the diesel engine of cylinder 21, ignition means 22, reaction beds or cata this invention, where 1 indicates a cylinder, 2a main air 10 lyst beds 23 and 24.

intake pipe. , The combustion cylinder 21 has openings at both An auxiliary air intake pipe 3 is connected to a part ends forming an inner path 25 inside the combustion of the main air intake pipe 2 and an air pump 4, air cylinder and an outer path 26 between the combustion meter 5 and reforming means 6 are connected in that cylinder 21 and the housing 20, said inner path 25 and order to said air intake pipe 3 from upstream of the 15 outer path 26 communicating with each other at both pipe. The air pump 4 is driven by the engine, the inlet ends of the combustion cylinder 21. Further, the com of which is connected to an air cleaner 14 while the bustion cylinder 21 has numerous perforations 27 outlet to the air meter 5. At the same time, a pressure through which the said inner path 25 and the outer path regulator 7 is provided downstream of the air pump 4 26 communicate with each other. . .. for maintaining the pressure of the air supplied from 20 The portion where a plug is mounted at the top of a the air pump relatively low and constant, the excess air ignition means 22 opens. Said air inlet tube 58 opens of the pressure regulator. 7 flowing into the main air into the outer path 26 in the vicinity of said auxiliary Numeral 9 indicates a fuel injection means (an injec 25 fuel injection tube 59 and the air flowing from the air

inlet tube 58 goes partly into the inner path 25 directly, tion pump) having a pneumatic governor for use in an another part of which going into the inner path 25 ordinary diesel engine. Numeral 10 is an auxiliary ven through the perforations 27 of the combustion cylinder turi-tube provided at the outlet for a venturi negative 21, and the remaining part joining in the one flowing pressure of a main throttle valve 8 in the main air in through the inner path at the down stream of the com take pipe 2, which is connected to a vacuum chamber of said fuel injection means 9 via the negative pressure 30 bustion

cylinder 21 through the outer path 26. The fuel injected into the inner path 25 directly from the outlet pipe 11. The vacuum chamber is connected to a control rack via a disphragm, and through the change auxiliary fuel injection tube 59. The ignition means 22 is of an ordinary ignition system for use in a conven of position of the control rack, the amount of a main tional spark-ignition type internal combustion engine fuel injection is changed. Numeral 9a is a fuelinjection only without a distributor kit. The first reaction bed 23 nozzle, each being provided on each cylinder head, 35 is composed of such a refractory as alumina and the which is connected to an injection pipe 12 and the said fuel injection pump 9 respectively. It acts to inject into like in the form of a honeycomb having a function as heat-storage as well as that of preventing the flame the cylinders a required amount of a main fuel for the from flowing downstream. It is followed by the reaction engine, which amount is measured and sent into by a bed 24 holding a catalyst material as necessary. plunger pump.9b is an injection nozzle connected to an 40 auxiliary, fuel plunger pump (not shown) provided sep valve, 17 an intake port, 18 an exhaust 16 In the figure, 15 is an intake valve, an exhaust port and 19 a arately from the one for each cylinder in the fuel injec piston. ..

tion means 9 and to an injection pipe 13, and is driven simultaneously by a cum axis for driving the plunger for Next, in the embodiment of this invention constituted each cylinder. . . . as the above, the fuel introduced into the cylinder 1 is

The structure of the plunger pump for an auxiliary supplied as main fuel from the fuel injection means 9 and the injection nozzle 9a. As mentioned above, the fuel is entirely the same as that for a plunger pump for measured each cylinder. The diameter of a plunger is so set that and fixed rate of the flow rate of fuel of 8 the amount of fuel to be injected per stroke of a the 25% of the main fuel is supplied as auxiliary fuel into plunger pump for auxiliary fuel is within a range of 50 auxiliary fuel injection tube 59 of the reforming from 8 to 25% of the total main fuel. means 6 via the injection nozzle 9b and the air meter 5. The air meter 5 comprises a fuel pool 51, control The air meter 5 detects and measures the flow rate of valve 52, spring 55, air inlet 56, variable orifice 57, air fuel, controlls the flow rate of air such that the air-fuel injection tube 58 and auxiliary fuel delivery tube 59 weight ratio becomes constant (selecting one from 1 - and said control valve 52 is provided with a groove 53 55 5) and introduces it into the air inlet tube 58. In the and a needle valve 54 at one end. Since control valve reforming means 6, the auxiliary fuel injected into the 52 is pushed back against the spring 55 accordingly as inner path 25 becomes liquid particles and in the pro the path area of the groove 53 increases in proportion cess of passing through the air supplied into the com to the flow rate of auxiliary fuel injected into the fuel bustion cylinder 21 from the air inlet tube 58, an ignit pool 51 by the injection nozzle 9b, the needle valve 54 60 able and combustible mixture is formed on the surface moves such that the path area of the variable orifice 57 of the particles, causing them easy to ignite and burn in between the air inlet 56 and the air injection tube 58 is flame by an ignition through electric spark generated in increased. - the plug at the top of the ignition means 22. Although Thus the adaption of the path area and the like to the heat generation in the burning enhances the evapora constancy of a weight ratio of the flow rate of air in 65 tion of the liquid particles since the air is not supplied jected into the reforming means 6 and that of the flow in a sufficient amount as mentioned above to effect a rate of the auxiliary fuel can be attained easily. The-air perfect combustion, a part of the auxiliary fuel burns meter 5 acts to flow an auxiliary fuel in a fixed propor and the remaining part either gasifies or decomposes

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into a fuel gas of high temperatute and the flame begins 3. A method according to claim 1, wherein said first to vanish. quantity is within a range of 8-25% of said fourth quan Since the gas flowing from the combustion cylinder tity.

21 into the reaction bed 23 downstream turns out to be 4. A method according to claim 1, wherein said re a gaseous mixture of high temperature consisting of a forming is carried out at 400-800° c under atomos residual flame, burnt gas containing water generated by pheric pressure.

5. A method according to claim 1, wherein an air-fuel a partial combustion of the fuel, a small amount of air ratio of said first mixture is 1-5. supplied from the outer path and fuel gas, it heats the reaction bed 23 in passing through the bed and at the 6. A method according to claim 1, wherein said sec same time, the flame vanishes making the temperature O ond mixture contains hydrogen and carbon monoxide. of the gaseous mixture uniform, the mixture in turn 7. A method according to claim I, wherein said sec ond mixture contains hydrocarbons which have 1-6 causing a decomposition and oxidation reaction. If the carbon mixture is passed through the reaction bed 24 holding atom.

8. A method according to claim 1, further comprising a catalyst material which is provided following the bed 15 a step 23 as necessary, this reaction of the gaseous mixture is of comprising mixing said second mixture with further pronounced. In other words, the composition of said third quantity of air before feeding them to said hydrocarbons is reformed. The reformed gaseous mix combustion9. A chamber.

method according to claim 1, wherein said re ture passing through the reaction beds 23 and 24 joins forming step comprises igniting said first mixture by a in and is mixed with a main air in the main air intake 20 ignition spark plug disposed in said reformer. pipe 2 and is introduced into the cylinder 1 during the 10. A method according to claim 1, wherein said suction stroke of the engine. As mentioned above, a reformer comprising a catalyst bed through which said mixture comprising decomposition and oxidation prod first mixture passes.

ucts and the mixture of fuel hydrocarbons as being a 11. A diesel engine for improving the performance reformed fuel introduced into the cylinder 1 improves 25 thereof comprising:

the combustion efficiency of diesel engine remarkably. a combustion chamber;

In this embodiment, a favorable result is obtained when a piston disposed in said combustion chamber; the flow rate of auxiliary fuel is 8 - 20% of that of the a power take-off mechanism operatively connected main fuel. If it is set at less than 8%, a sufficient effect to said piston and cooperating therewith for pro of fumigation is not obtained due to insufficient fumi 30 ducing and transmitting power produced in said gation. If over 25%, an unfavorable ignition takes place combustion chamber; a main fuel injection system before the main fuel injection to be effected at the connected to said combustion chamber for inject completion of the compression stroke. ing main fuel into said combustion chamber; Furthermore, the said reforming conditions can be an air supply system connected to said combustion mitigated by selecting the catalyst material to be used 35 chamber for supplying an air into said combustion in the reaction beds 23 and 24 with a view to promoting chamber;

a decomposition and oxidation reaction on contact a means for reforming fuel into a mixture containing which is a part of the main reaction. When a catalyst is decomposition and oxidation products and supply used by allowing for the essential conditions of catalyst 40 ing said mixture into said combustion chamber; and the like such as temperature, air to be supplied an anxiliary fuel supply system connected to said (oxygen concentration), liquid hourly space velocity of reforming means for supplying anxiliary fuel into fuel hydrocarbons with regard to the amount of cata said reforming means;

lyst, the mixture comprising decomposition and oxida an anxiliary air supply system connected to said re tion products and the mixture of fuel hydrocarbons is 45 forming means for supplying an auxiliary air into selectively obtained which takes part in the combustion said reforming means; and an exhaust system con mechanism giving a favorable effect. nected to said combustion chamber for discharging What is claimed is: exhaust produced gases in said combustion cham 1. A method for improving the performance of a ber.

diesel engine comprising the steps of 12. A diesel engine according to claim 11, wherein introducing a first mixture of a first quantity of fuel said reforming means comprises:

and a second quantity of air into a reformer; a reforming chamber connected to said air supply reforming said first quantity of fuel in the presence of system means connected to said reforming cham said second quantity of air into a second mixture ber and said auxiliary fuel supply system and said containing decomposition and oxidation products; 55 auxiliary air supply system for metering the amount feeding said second mixture to a combustion cham of said auxiliary fuel supplied through said auxiliary ber of said engine; fuel supply system and controlling amount of auxil feeding a third quantity of air to said combustion iary air to be fuel into said reforming chamber and chamber, wherein said third quantity of air has not an ignition spark plug disposed in said reforming passed through said reformer; 60 chamber, said auxiliary fuel being ignited by said injecting a fourth quantity of fuel into said combus ignition spark plug and reformed in the presence of tion chamber, wherein said fourth quantity of fuel said auxiliary air.

has not passed through said reformer; 13. A diesel engine according to claim 12, wherein burning said second mixture and said fourth quantity said reforming means further comprises of fuel in said combustion chamber. 65 a catalyst bed disposed downstream of said ignition 2. A method according to claim 1, wherein said sec spark plug in said reforming chamber. ond mixture and said third quantity of air are fed during 14. A diesel engine according to claim 12, wherein the suction stroke of said engine. said reforming means further comprising

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a cylinder disposed is said reforming chamber, said said controlling means is adapted to permit the flow cylinder having a perforated wall thereof, said igni rate of said auxiliary air in proportion to the flow rate tion spark plug being disposed is said cylinder. of said auxiliary fuel. 15. A diesel engine according to claim 12, wherein 17. A diesel engine according to claim 16, wherein an air fuel ratio of a mixture of said auxiliary fuel and air catalyst bedded in said catalyst bed is a-alumina. is 1-5.

16. A diesel engine according to claim 12, wherein