US2470747A - Dual fuel combustion system for internal-combustion engines - Google Patents

Description

May 17, 1949- H. F. SHEPHERD DUAL FUEL COIBUSTION SYSTEH- FOR INVENTO. E se/ewl F IG. 3 H l ATTORNEY Filed Sept. 12, 1945 INTERNAL COMBUST ION ENG I NES lll/ll lill Patented May 17, 1949 DUAL FUEL COMBUSTION SYSTEM FOR INTERN AL-COMBUSTION ENGINES Harold F. Shepherd, Springfield, Ohio, assignor to Tlie National Supply Company, Pittsburgh, Pa., a corporation oi' Pennsylvania Application September 12, 1945, Serial No. 615,782

(Cl. (S0- 16) 9 Claims. l

This invention relates to the four cycle Diesel engine operated on the dual fuel cycle wherein the quantity of oil or solid fuel injected in the usual manner is less than that required to carry the load imposed on the engine and is supplemented by a fuel gas of high spontaneous ignition temperature which is introduced on the suction stroke. The solid fuel may be used to initiate combustion only, or to supplant an insumcient gas supply.

When such engines are operated with natural induction of the air directly from the atmosphere the fuel gas may be introduced continuously into the -alr stream entering the cylinders. However, when such engines lare supercharged it is found advantageous to allow anunusually long period of overlap between the inlet opening and exhaust'closure during which time both valves are open and a large volume of air sweeps through, thoroughly scavenging the combustion chamber. lf the gas-air mixture were used for scavenging, a very considerable loss would take place. To provide against this loss the gas passage in the past has been provided with a timed valve for admission of gas to the cylinder only after thorough scavenging has ceased. This has been accomplished in two ways.

One method is to fit the inlet valve stem with a piston valve which has considerable lap, opening the gas passage only after the exhaust valve has been closed. This has the disadvantage that a special inlet cam, with an unfavorably slow opening contour, must be used since the usual cam design opens the valve fully in 100 to 120 of crankshaft travel, which angular intervals .are

about equal to the desired overlap and therefore the desired gas admission lag.

Another method is to place timed gas admission valves adjacent to each inlet valve. This design requires special cylinder heads and is undesirable since the simplicity of conversion from Diesel to dual fuel operation is one ofthe most attractive properties of the engine. It also requires that gas admission cease at an angular interval measurably before the inlet closes to make certain that the inlet passage is swept free of gaswhich would be carried to the exhaust unburned at the next scavenging interval.

The primary object of the present invention is to provide an apparatus which will successfully operate on a supercharged four cycle engine employing the dual fuel system wherein oil fuel and a fuel gas of high spontaneous -ignition temperature are simultaneously burned.

A further object of my invention is to provide an apparatus for a four cycle engine employing the dual fuel system wherein the ordinary check valve in the cylinder head, commonly used inl air starting engines, is used to admit the gas fuel.

A further object of my invention is to provide a means to continue the gas admission through the check valve during the entire aspiration period without danger of loss of -un-burned gas to the exhaust.

Another object of my invention contemplates the use of the cylinder head regularly used on Diesel engines being adaptable to be used with my dual fuel system without any alterations in its construction.

Another object of my invention is the provision of a simplied form of conversion from Diesel operation to dual fuel operation Iby the use of apparatus otherwise regularly required for normal Diesel operation. l

Another object of my invention is the provision of a simplified method employing the dual fuel principle in a conventional type of four cycle engine operating on the auto-ignition system'.

Another object of my invention is to provide an apparatus for a four cycle compression ignition engine employing the dual fuel system wherein gaseous fuel constitutes the major portion ofthe fuel used to produce a-higher thermal eiilciency than would be possible in an engine using gaseous fuel only.

Another object of my invention is to provide an apparatus for afour cycle compression ignition engine employing the dual fuel system wherein -a fuel gas of high spontaneous ignition temperature is introduced on the suction stroke followed by the injection of the solid fuel at firing time.

Further objects and advantages of my invention will be obvious and in part specifically referred to in the description and specification to follow, which taken in conjunction with the accompanying drawing, discloses a preferred form of apparatus in accordance with my invention. It should be understood, however, that the disclosure is only illustrative of the principles of my invention in its broader aspects.

Figure 1 is a schematic fragmentary cross sectiona1 view taken partly through one of the cylinders and partly diagrammatic to illustrate the operating features of my invention, the solid lines, showing the operating lever I8, push rod positions during the air starting period and l operation on oil fuel.

Figure 2 is a cross sectional view through the two-way, three position plug valve taken along the line 2-2 of Fig. 1. The connecting pipe lines are shown in full and the valve is shown connected to the high pressure starting air line.

Figure 3 is a view similar to Fig. 2 but showing the valve connected to the gas supply line.

Figure 4 is an end view of the operating hand wheel and indicator used in connection with the plug valve.

Figure 5 is a cross sectional view through the cam and valve operating lever used to operate the eccentric fulcrum that governs the manipulation of the check valve and is taken along the line 5 5 of Fig. 1, and shows the cam in position to operate the engine on gas or dual fuel.

Fig. 6 is a cross-sectional view through the cam and valve operating lever showing the cam in position to operate the starting air regulating valve or to operate the engine on oil fuel. The section is taken along the line 5--5 of Fig. l, the same as in Fig. 5.

Fig. '7 is a cross-sectional view through the two-way, three position plug valve taken along the line 2--2 of Fig. 1 (as in Figs. 2 and 3) but showing the plug in position to completely shut oil' both the high pressure starting air and the low pressure gas supply from'V the passage I5 and indicates the position of the plug when the hand wheel is in the Oil fuel position.

In carrying out my invention the normal valve and head design of a Diesel engine is used which is illustrated in Fig. 1. The only additional equipment required is that the valve be fitted with light gear for alternate mechanically timed operation as will be described later.

The preferred form of my invention disclosed in Fig. 1 shows only the operating mechanism for one cylinder and embodies the power cylinder I, piston 2, cylinder head 3, injection nozzle d, air inlet and exhaust valves 5 and 6 respectively. I also employ a check valve 'I positioned in each cylinder head 3. A starting air regulating valve 8 for each cylinder is located adjacent the continuously rotating cam shaft 9 driven through a conventional front end gear train .(not shown) from the crank shaft and in timed relation therewith and located outside the cylinder walls. The valves 8 are normally held in open position and out of contact with the seats 8a by the force exerted on them by the tension springs I3, surrounding the valve stems 8b and abutting against the spring seating surfaces I3a at all times except during the air starting period when the high pressure air overcomes the force of the springs I3 and urges the valves 8 against their seats 8a. at which time the stems 8b contact the cams I2 and the valves 8 are operated thereby. When starting air (of from 100 to 250 lbs. per sq. inch) is admitted to the passage I5 through the air main I'Il by opening the valve II to start the engine, the mechanically operated valves 8 are raised to their seats 8a by the unbalanced air pressure so that their stems come in range of the cams I2 on the camshaft 9. The roller I1 of the operating lever I8 is held out of contact with the cam I2 by the cam 21, forming a part of the extension 23 to the plug 22, which in the air starting position raises the push rod `30. The push rod 30 being pivotally connected to the lever 32 urges said lever to rotate about the eccentric fulcrum I9 and consequently rotates the lever I8 4 and roller II out of the operative range of the cam I2 as shown by the dotted lines in Fig. 1 while the position of the cam 2'I is shown in full lines in Fig. 6. The several valves 8, being actuated during the starting period in timed relation with the crankshaft by the cams I2, admit starting air to the cylinders in sequence through the check valves 1 in the cylinder heads until the explosion pressure holds the latter shut and prevents further admission of air, even when the starting air is not shut oil? immediately after the engine begins functioning as a result of fuel combustion. During the air starting and oil fuel operation of the engine the valves 'I are not actuated by the operating mechanism of lever Il'. When the air pressure is shut off, the starting air regulating valve B is retracted from the cam I2 by the light spring I3 and becomes inoperative.

These functions are operable only under the normal high pressure starting air (100 to 250 lbs. per sq. in.). If gas of the usual supply pressure of less than 10 lbs. per square inch were turned into the starting air system, the valve 8 would not be lifted into the air starting operating position with the ca m I2 since the closing pressure is effective on the valve stem area alone and is prevented from closing bythe force of spring I 3. The check valve I also would not open since it is spring loaded, as at I4, nominally for a full vacuum to prevent chattering when maneuvering. The timing would also be Wrong since the gas must be admitted on the suction stroke while compressed air for starting enters on what is regularly the power stroke.

My system operates by the automatic functioning of valve 8 only when starting on high pressure air and using oil as the starting fuel. During normal operation on gas the fuel gas under the usual supply pressure of less than 10 lbs. per sq. inch is admitted from the supply line 33 through the curved port 28 of the plug 22 in valve I6 to the passage I5 and on through the then non-functioning open valve 8, the passage 29, through the then cam operated gas inlet valve to the combustion chamber la. The lever I8 is normally held in contact with the stem o1.' valve 'I by means of the spring 2 I.

It is obvious that some device is necessary to prevent simultaneous manipulation of gas fueling and starting air functions. This is accomplished simply by using the two-Way, three position plug valve I3, and its operating mechanism in the manner to be described. The plug 22 of the valve I6 is provided with an extension 23 upon the end of which is secured a hand wheel 24 to operate the plug. This wheel is marked with Start, Oil fuel and Dual fuel positions and an indicator 25 is attached to a supporting frame 26 to register with these markings. A cam 2l is interposed between the valve I6 and the hand wheel 24 on the plug extension Afuel oil through the injection nozzle 4 on the power stroke of the engine. Air to support combustion is introduced throughthe air inlet valve 5, which functions at all times and for all fuels during the engine operation and in timed' relation with the engine crankshaft. The timing is regulated through a conventional front end gear train from the crankshaft (none of which are shown). The quantity of oil fuel to be admitted is regulated by a governor control mechanism (not shown).

In starting the engine the hand wheel 24 is turned to the Start position, moving the curved port 28 in the plug 22 into registry with the high pressure air supply main I to admit starting air through the air passage I (Figs. 1 and 2) through the starting air regulating valve l, passageway 29 and the check valve 1. This same movement of the hand wheel .24 moves the canili into the position shown in Fig. 6. The cam 2l in this position, bears against a push rod tt, which is guided in suitable bearings in the trame 26 and the upper Support 3i. The cam 2l urges the push rod 38 upwardly and, through lever 32 to which it is pivotally connected. ro-

, tates the eccentric fulcrum I9 about the shaft tt and holds the roller II of lever I8 out of contact with the cam l2. Under these conditions valve 'l becomes merely a spring loaded check valve and held in closed position by spring I4 except when the high pressure air passing through the starting air regulating valve 8 and passageway ttl forces said valve open.

With the hand wheel 2t in the "Start or the Oil fuel position there is no connection between the gas supply line 33 and the engine. However, through a set of timing gears (not shown) when the hand wheel 2t is in the Start posiwheel 24 is turned to the position marked Dual fue which connects the gas supply line 38 to the starting air passageway I5 through the curved port 28 in plug 22 (see Fig. 3), keeping the starting air in main I0 shut off and lowering the fulcrum I8 and the associated lever I8 to the position shown in full lines in Fig. 1 by rotating the cam 21 to the position shown in Fig. 5, thus setting the valve I into mechanical operation with tion as shown in Fig. 6 oil fuel is admitted on the power stroke to the combustion chamber Ia through the nozzle tl simultaneously with the high pressure air from the air main It as described above. liter the engine beings functioning as a result of oil fuel combustion there is no further need for the starting air, since the air to support combustion is introduced through the air inlet valve t which functions at all times on all fuels during the operation of the engine and in timed relation with the engine crank-shaft. The hand wheel it is 'then turned to the Oil iuel position, cutting off the starting air. Neither gas or starting air can be admitted to the passage l5 while the hand wheel 2t is in the Oil fuel position since the plug 22 of the valve I t is in the position as shown in Fig. 7, wherein both gas and high pressure starting air are cut off from the passage it. While the engine is functioning as a full Diesel, oil is delivered to the engine through the nozzle #i to maintain load and speed under the control of the governor described above but not shown. While the hand wheel 2t is in the Oil fuel position it does not influence the oil operation of the engine but the cam il, being in the same position as while the hand wheel td was in the Start" position as shown in Fig. 6, still holds the roller I'I out oi range of the cam l2 and consequently the lever I8 has no effect on the valve l, which is held in closed position by the spring I4 during the operation of the engine on oil fuel. Thus the handwheel operated plug valve IB functions as a device to prevent the simultaneous manipulation of the gas fueling and high pressure air starting means as well as to maintain these two functions in operative while the engine is operating as a full Diesel on oil fuel only.

When it is desired to operate on gas the hand correct timing for fuel admission, while the starting air regulating valve 8 remains open and out of action. The energizing effect of the tension spring 84 urges the free end of the push rod 30 into contact with the flat surface of the cam 21.

While my invention has been disclosed as carried out by apparatus of the above described specific construction, it should be understood that many changes maybe made therein without departing from the spirit of the invention in its broader aspects and I do not wish to be limited or restricted to the specific details set forth but wish to reserve to myself any further embodiments, modifications and variations that may appear to those skilled in the art or fall within the scope of the appended claims.

Having fully disclosed my invention, what I claim as new and desire to secure by United States Letters Patent is:

1. In a multi-cylinder compression. ignition engine adapted for the burning of dual fuels, including a high pressure starting air regulating valve adapted to control the introduction of high pressure starting air to start said engine, a checic valve in the cylinder head in communication with said starting air regulating valve through which high pressure starting air passes enroute to said cylinder, means to hold said starting air regulating valve open after the engine has been started and means to operate said check valve to control the admission of low pressure gaseous fuel passing through said open starting air regulating valve into said cylinder for engine operation.

2. In a lcompression ignition engine adapted for'the burning of dual fuels, including Va checlr valve in the cylinder head, a starting air regulating valve in communication with said check valve through a passageway and adapted to control the introduction of high pressure air through said check valvev to start said engine, means to maintain said starting air regulating valve open when starting air pressure is shut ofi", and selective means whereby said check valve may be used to control the introduction of low pressure gaseous fuel passing freely through said starting air regulating valve to the power cylinder for engine operation.

3. In a multi-cylinder four cycle engine adapted for the use of dual fuels, including a check valve in the cylinder head,v a starting air regulating valve in communication with said check valve through a connecting passageway, cam means to operate said starting air regulating valve at timed intervals to control the introduction of high pressure air through saidcheck valve to start said engine, means to hold said starting air regulating valve open and free from the action of said cam after the engine has started, and selective means whereby said check valve may be used to control the introduction of low pressure gaseous fuel passing freely through the open starting air regulating valve to the power cylinder for engine operation;

4. In a compression ignition engine adapted for the eflicient burning of dual fuels including a check valve in the cylinder head, a starting air regulating valve adjacent said check valve and positioned outside the cylinder walls, a passageway in direct communication with each of said above named valves, said starting air regulating valve being adapted to control the introduction of high pressure air through said check valve to start said engine, means to keep said starting air regulating valve open when starting air pressure is shut off and selective means whereby said check valve is utilizedA to control the introduction of low pressure gaseous fuel passing freely through said open starting air regulating valve and passageway to the power cylinder for engine operation.

5. In a device for the operation of a compression ignition engine adapted for the burning of dual fuels, having a starting air regulating valve, a power cylinder, a piston operable therein, a cylinder head provided with inlet and exhaust valves, solid fuel injection nozzle and a check valve therein in communication with said starting air regulating valve, the combination therewith of cam means to operate said starting air regulating valve at timed intervals to control the introduction of high pressure air through said check valve to start said engine, means to maintain said starting air regulating valve open when starting air pressure is shut on?, and selective means whereby said check valve is used to control the introduction of low pressure gaseous fuel admitted to the power'cylinder for engine operation.

6. An apparatus for multi-cylinder four'cycle engines adapted for the burning of dual fuels having a plurality of power cylinders, a. piston operable in each cylinder, a cylinder head for each cylinder and each head provided with inlet and exhaust valves, a solid fuel injection nozzle and a check valve, a starting air regulating valve adjacent each cylinder, the combination therewith of a passageway extending from said air regulating valve to said check valve, cam means for each cylinder to operate said starting air regulating valve at regulated timed intervals to control the introduction of a charge of high pressure air into said cylinders through said passageways and said check valves to start said engine,

means to maintain said starting air regulating valve open when starting air pressure is shut olf and selective means whereby said check valve is employed to control the introduction of low pressure gaseous fuel passing freely through said open starting air regulating valves to the power cylinder for engine operation.

7. Apparatus adapted to operate a compression ignition engine as a dual fuel engine including a cam on a camshaft, a starting air regulating valve operated' by said cam to admit high pressure starting air at timed intervals, a check valve in Number the cylinder head through which said starting air passes, means to maintain said starting air regulating valve open and out of range of said cam after said engine has been started, means to simultaneously shut off said high pressure air and admit low pressure gaseous fuel through said open starting air regulating valve and means secured to said last named means to control the operation of said check valve through said cam. to admit said gaseous fuel to said engine at timed intervals for gas fuel operation.

8. Apparatus adapted to operate a compression ignition engine as a dual fuel engine and provided with a cam on a. rotating camshaft to operate valves in the cylinder head to regulate the admission of the elements of combustion to the power cylinder at timed intervals for proper sequential operations including a starting air regulating valve to admit high pressure starting air, a check valve communicating with said air regulating valve, means to maintain said starting air regulating valve open and out of range of said cam after said engine has been started, means to simultaneously shut off said high pressure starting air and admit low pressure gaseous fuel through said open starting air regulating valve and cam means secured to and adapted to operate simultaneously with said last named means to position a set of operating levers to manipulate said check valve from said rotating cam to admit said gaseous fuel through said open starting air regulating valve to the said power cylinder at timed intervals for proper engine operation on gaseous fuel.

9. In a multi-cylinder compression ignition en gine adapted for the burning of dual fuels, including a check valve in the cylinder head, a starting air regulating valve in communication with said check valve and adapted to control the introduction of high pressure starting air through said check valve to start said engine, means to maintain said starting air regulating valve open when said high pressure starting air has been shut oi! and means to operate said check valve to control the admission of low pressure gaseous fuel passing freely through said open starting air regulating valve into said cylinder for engine operation.

HAROLD F. SHEPHERD.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Name Date 508,042 Niemczyk N v. 7, 1893 729,377 Meister et al May 26, 1903 2,010,469 Triebnigg Aug. 6, 1935 Schtte Apr. 23, 1940

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