US2822789A - Injection of heavy fuel into diesel engines and valve means therefor - Google Patents

Description

Feb. 11, 1958 J. L. PHILIPS ETAL 2,822,789

INJECTION OF HEAVY FUEL INTO DIESEL ENGINES AND VALVE MEANS THEREFOR Filed June 15, 1956 FIG.-/

Fla-2 FIG-2 Judson L Philips Thomas J. Bov

y 124w." aw m i a Inventors INJECTION OF HEAVY FUEL- INTO DIESEL ENGINES AND VALVE MEANS THEREFOR JudsonL.Philips,UpperMontclair, N..J., and Thomas J.

Bov, Hamilton, Ohio,.assignrs to Esso Research and- Engineering Company, a corporation of Delaware Application June 15, 1956, Serial No. 591,712 Claims. (Ql. 123-32) The'present invention relates to improvements in the injection of heavy fuels into diesel engines and valve means therefor; More particularly, the" invention relates to improvements by means of which diesel engines, and particularly large engines such as'those used' on marine vessels and the like, may be operatedon fuel'which is considerably heavier than that for which they were originally designed.

In the operation of large diesel engines, the volume of fuel consumption amounts to a very substantial item of cost. Moreover, due to increased demand over the world for middle and lighter distill'ates frompetroleum, there has been a tendency towards the production of excessive surpluses of heavy residual oils. In some parts of the world these oils can be converted economically to more valuable products by coking and other'upgradi'ng operations. In other portions, however, his much more desirable to increase the economic consumption ofthe-se heavy re'sidual'oils directly rather than to attempt to convert them to other products.

In recent years, serious attempts have been made to feed'heavier and heavier oils of residual type directly to large internal combustion engines, particularly large diesel engines. When suitably preheated, these fuels burn satisfactorily to supply power. However, the heavy residual oils are prone to form large quantities? of deposits rapidly so as to interfere seriously with continuing and satisfactory engine operation.

According to the present invention, by relatively minor and inexpensive re-design of certain critical parts in the fuel injection system, it has been found possible to switch over to full time operation of large engines on the heaviest grades of residual oil, such as Bunker C. The injection of these fuels in such a manner as to avoid the serious deposit problems hitherto encountered is a primary object of the invention.

A further object of the invention is to eliminate substantially the need for frequent dismantling and cleaning of valves and other operating parts of the fuel supply systems for large diesel engines operating on heavy fuels.

A still further object of the invention is to control more accurately the operating temperature as well as other characteristics of the critical parts of fuel injection systems for large diesel engines.

The foregoing and other objects which will appear as this description proceeds will become more readily apparent on consideration of a detailed description of the invention. Hence, reference will next be made to the accompanying drawing which forms a part of this specification.

In the drawing, Fig. 1 shows a typical vertical cross section through the operating tip and valve seat portions of a conventional prior art fuel injection valve which is of a type commonly used on large marine diesel engines.

Fig. 2 is a view similar to Fig. 1, showing certain modifications made in the course of experimentation, with a view to improving the standard prior art inject-ion nozzle of Fig. 1.

Fig. 3 is another view, similar to Fig. 1, showing further features of the present invention applied to the same type of valve. I

Referring now to Figs. 1, 2, and 3, in'eachfigure, the numeral 25 designates the forward or outlet end' portion of a fuel injection nozzle assembly. In each figure, the" nozzle end portion isshown greatly enlarged in order to illustrate the features of the conventional nozzle, and also the improvements thereto which characterize the present invention. The general nozzle structure, represented by Fig. 1', is of typical design and wellknown' in the" art, as are the means for supplying both fuel andcooling liquid, thereto, and also the means for operating thevalve, and the manner in which such a valve is operatively associated with anengine, such as a diesel engine. To simplify the present'disclosure, the showing and description of all such parts are omitted.

Referring now to Fig. 1, it will be noted that thenoz zle' body 25 is provided with an internal bore which i's'enlarged at 29, tapered at 31 to converge the bore walls towards theseat portion 33, and terminating in the outlet bore 35. The nozzle end element comprises" a water jacketed member or portion 37 containing the spray'tip member 39.

The valve seat 33 is of'conicalshape, tapering towards the outlet. conventionally, it has a longitudinal or converging angle of about 30, although this angle may be varied somewhat in various valve designs. In the prior art structure of Figure 2, the reciprocable needle member 41 has a conical tip 43 of the same convergence angle as the valve seat. In aconventional valve, both angles are about 30", although they may vary somewhat as noted above.

With-the conventional structure of Fig. 1, when standard diesel fuel is fed, there are no substantial operating diflicultie's; However, when heavy residualtype fuel is supplied to the bore 29, and when the valve' closure mom ber 41 is moved to closed position byconve'ntional operating structure (not shown), it has been-found to bequite impossible to obtain'a clean cut-off of the fuel. As operation of the engine proceeds, there is gradually built up a deposit at portion 39 in the form of a hollow cone of carbon or coke-like material-which'ultimately clogs orseriously deflects or restricts'the fuelflow to the conduit 45 and oninto the engine. In actual'operation of a'marine vessel with this type of valve and with Bunker C oil, it was found necessary to remove valves and clean them about 40. times per month to maintain reasonably good engine performance. Such frequent valve overhauls obviously are uneconomic and are sufliciently serious and costly to prevent the use of this heavy fuel in commercial practice.

Hence, two preliminary steps were taken, as shown in Fig. 1, to improve the operation of the injection valve of Fig. 1. In the first place, the jacketing of the injector nozzle tip was improved by cutting out additional metal as may be seen by comparing the cooling space 51 of Fig. 1 and space 51A of Fig. 2. By this means, it was found possible to improve the operation somewhat by keeping the temperature of the fuel nozzle tip below a coking temperature of around 700 F. or so. However, this improvement per se did not prevent the dribbling of fuel after a valve was closed. The eventual build-up of deposits continued. It will be noted that cooling water is admitted into the cooling chambers through lines 55 and withdrawn through lines 56 in both Figs. 1 and 2, and also in Fig. 3, to be described below. It was found desirable to decrease the temperature of cooling water to such a degree that it emerged at a temperature not exceeding 150 F. and the emergent temperature was preferably held down to about F.

The needle valve tip in Fig. 2 (compare Fig. 1), was next machined to increase its angle by about 4 and thereby obtain theoretically a line cut-ofl at approximately the point indicated at 57 of Fig. 2. It was found, however, that the repeated reciprocation of the valve 41 gradually hammered down an annular surface at point 57. The leakage and dribbling of the heavy oil into the nozzle outlet portions continued with the objectionable results already described.

Referring now to Fig. 3, it was found after further study and experimentation that the combination of a short annular surface on the valve needle, of identical taper angle with the valve seat, solved the problem, provided that the tip portion of the needle was machined to a slightly convergent angle of about 2 to 6 from the angle of the conical valve seat. The optimum divergence between needle point and valve seat was found to be about 4 of arc. However, a slight tolerance above and below this angle was found permissible, the critical range being between about 2 and 6. Thus, as shown in Fig. 3, the valve seat is provided with a conical taper having a convergent angle of not less than 20, not more than 40; 30 being generally preferable. The needle is provided with a short seating surface from A; to /2 the needle diameter of identical angle. Thus, Where the valve seat has an angle of 30, the portion 60 of the needle also has an angle of 30. The tip portion of the needle is machined to a convergent angle 2 to 6 greater than the valve seat angle, or 32 to 36 when the basic angle is 30. Here, as noted above, the preferred angle for the needle tip was found to be about 34. This portion 61 apparently is critical. The scientific theory of its operation is not clearly understood, but the improvement immediately was found to be so effective that instead of having to dis mantle 40 valves per month during operation of the vessel, on a cylinder diesel engine, the valves remained relatively clean. It became necessary only to dismantle about one valve every two or three months, on the average.

The particular angle of the needle valve tip apparently has something to do with the optimum cut-off of the flow of fuel. Whatever may be the mechanism, this simple change in the angle of convergence of the valve parts, plus the improved jacketing and cooling of the nozzle tip, have made it possible to operate large diesel engines full time on heavy residual oil of Bunker C quality. These changes reduce the annual operating cost by sums amounting to many thousands of dollars per marine vessel per year. The same invention obviously is applicable to nonmarine diesel engines of suitable type.

It will be obvious that variations may be made in ap- 4 plication of the invention to particular valves and engines. The principles set forth above, however, constitute the basis of the present invention and it is intended by the claims appended below to cover variations such as would readily occur to those skilled in the art so far as the state of the prior art permits.

What is claimed is:

1. A diesel engine fuel injection valve for feeding heavy liquid residual fuel under high pressure, comprising a needle valve seat member having a large inlet opening converging in conical form towards a smaller outlet opening with a convergent angle along its longitudinal axis, of 20 to and a relatively movable needle having a relatively short tapered section of the same angle, adapted to fit in said seat in closed position near said large inlet end, and having a smaller projecting portion extending further into the seat member towards the smaller outlet opening, but converging more rapidly than the angle of the seat member by 2 to 6 of arc.

2. A valve according to claim 1 wherein the last mentioned angle is about 4 of arc.

3. A diesel engine fuel injection valve comprising a tapered conical 'heat member having an inlet opening of relatively large diameter, a smaller outlet opening, said openings being joined by a conical surface 'having a longi tudinal converging angle of about 30", a longitudinally reciprocable needle having an operating stem and mounted in axial alignment with said seat member, a short seating portion on said needle towards the stem adapted to cooperate with the seat near the inlet opening, said short portion being of identical taper angle with the seat and adapted to fit accurately therein to close said valve, and a smaller tapered portion projecting away from the stem and towards the outlet, said smaller tapered portion converging substantially to a point at an angle of about 34 so as to provide a narrow, diverging, self cleaning space between smaller portion of said valve seat and the point of the needle.

4. Valve according to claim 1 wherein the nozzle tip of the valve is provided with sufi'iciently close liquid cooling jacketing to keep its temperature constantly below fuel coking temperature.

5. Valve according to claim 3 wherein the nozzle tip of the valve is provided with sufficiently close liquid cooling jacketing to keep its temperature constantly below fuel coking temperature of around 700 F.

No references cited.

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