US2555818A - Dual fuel engine - Google Patents

Description

June 5, 1951 p, s, 5|-||RLEY 2,555,818

DUAL FUEL ENGINE Filed July 24, 1946 2 Sheets-Sheet 1 IIEll i7 00 June 5, 1951 P. s. SHIRLEY 2,555,818

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Patented June 5, 1951 UNITED STATES PATENT OFFICE DUAL FUEL ENGINE Paul S. Shirley, Hamilton, jOhio, assignjor, by inesne assignments, to Baldwin-Lima-Hamib ton Corporation, a. corporation of Pennsylvania Application July 24, 1946, Serial No. 685,872 sola'ims. (01. 123-198) This invention relates to an internal combustion engine of the type that operates with gas and oil fuels and is particularly directed to the fuel controls of such an engine.

In the operation of engines on a combined fuel cycle it is customary to inject a pilot quantity of easily ignitable fuel oil which, in turn, ignites the main charge of gaseous fuel. The gas is injected under pressure at or shortly after the commencement of the engine compression stroke in such proportions that it will not ignite by the heat of compression alone. Thus the pilot injection of fuel oil is necessary for ignition and proper combustion timing. Under normal full load conditions the quantity of oil is 5% to of the total fuel taken on a thermal basis so that nearly the entire load is carried as a result of the burning of the gas.

Gas injection valves may be positively operated or may be operated by pressure differential, but in either case it sometimes occurs that the valve remains open beyond its intended period. If the valve is not closed when ignition takes place in the associated cylinder, flame passes back into the gas main and may create therein a serious explosion. Further, engines of this type operate ordinarily at substantially constant speed so that any radical departure from a predetermined normal speed is an indication of failure of one or more of the control elements so that the engine must be shut down before serious damage occurs.

The primary object of the present invention is to provide a control system for a dual fuel engine in which the supply of gas is quickly and positively cut off at the onset of any abnormal operating condition.

Another object of the invention is to provide a gas injection valve, functioning as part of a control system for a dual fuel engine in which the supply of gas is cut off whenever the injection valve fails to function normally.

Still another object of the invention is to provide a simple and efficient gas injection valve for a, dual fuel engine including hydraulic means to open the valve during a predetermined part or the engine cycle and pressure operated means to cut off the supply of gas to the valve should it fail to close at the end of its predetermined period of opening.

Other objects and advantages of the invention will become apparent from the following specification, reference being had to the accompanying drawings in which:

Figure 1 is a diagrammatic view, partly in 2 section, of an engine embodying the present invention; Fig. 2 is a central vertical section of a gas injection valve constructed in accordance with the invention; and Fig. 3 is a sectional view of a suitable quick closing valve.

Referring to the drawings, and particularly to Fig. 1, an engine is shown comprising a cylinder It in which a piston ll operates to move a cross head [2, connecting rod I 3 and crankshaft M. The piston controls exhaust ports l5 and scavenging air ports 15 in the usual manner. It will be apparent that the form of the engine is not important, that any suitable va'lving for the exhaust and charging air ports may be used, that the engine may be single or double acting and that any number and disposition of cylinders: may be used.

A pilot charge of fuel oil is injected into the cylinder at each stroke by a conventional injectionsystem including nozzle H and fuel pump I'8 driven from the engine crank shaft in the usual manner. A main governor 26, also driven by or in synchronism with the crank shaft and responsive to .changes in the load thereon controls the fuel pump IB through a link 2| and bell crank lever 22 the fulcrum of which is disposed to alter the quantity of fuel moved by the pump [8 at each stroke. The detailed construction of the pump is well known in the art and forms no part of the present invention. One arm of lever 22 is connected to the main governor and the other arm is made adjustable in length by any suitable means to provide any desired ratio of movement in a link 24 connected thereto. The .adjustment may be illustrated as taking the form of a screw connection .23 between link 24 and lever 22 whereby the end of the link is movedtoward and away from the fulcrum of the lever 22 to decrease or increase the movement imparted to the link by a given movement .of the lever. Such a device thus serves to adjust the ratio of movement in the respectiveelements.

Link 24 is connected to operate a gas valve actuating pump 25 which provides hydraulic actuation of a gas injection valve 26 through pipe 2.! in a manner hereinafter described. Actuating oil is supplied from a reservoir 28 by a pump 29 and is passed through a filter 30 prior to entering the system. Return to the reservoir may be through bypass 3|, valved shunt line .32 or through .a return 33 from the -injection valve 26.

Gas for the engine is supplied by a main containing gas under suitable pressure. A pres- .sure regulating valve 4! is interposed in theline connecting to the main, and a manual shut-off tothe engine cylinder.

valve 42 is also provided. In series with the manual shut-off 42 is a quick-closing or snap actuated valve 45 which may be of any suitable construction, one form being shown in Fig. 3. An air pump 43 is provided, connected to the gas line by a valved passage 44, and is used when the engine is operated on fuel oil alone as hereinafter described.

From the quick closing valve 45, gas passes directly to the injectionvalve 25 through a line it, or to all injection valves in a multi-cylinder engine. The quick closing valve 45 is adapted to be operated by any of three mechanisms each of which is responsive to a different abnormality. Thus the valve may be closed by an over-speed governor 56, by a low speed governor 52, or by sticking of the gas injection valve 26. Either direct or relay connections may be used between the operating instrumentality and the quick closing valve, a direct connection being shown in the case of the over-speed governor 50 and a by draulic relay in the case of 'the low speed governor 52. The relay may include a plunger 53 operating in a cylinder 54 to which oil under pressure is introduced from conduit 55 whenever a valve 56 is opened. The valve 55 is controlled by the governor collar and oil may be sup- 7 plied by pump 29 through a conduit 51.

whenever the pressure in the gas conduit exceeds the pressure in a front chamber 64 between partition 6| and the cylinder end of the valve.

The main valve between the gas conduit and the engine cylinder is designated 65. This valve is journalled in the partition i and cooperates with a properly formed seat to close the passage closed position by a spring 66 acting between partition 5i and a piston Bl fixed to the rear of "the valve and working in a cylindrical bore 58 of the valve body. Piston 5'! acts principally to prevent the escape of gas rearwardly past the valve.

A hydraulic actuator for the valve 65 includes a piston ll] operating in a cylinder 1 I. The rear of the piston works in a cushioning cylinder 12 to which actuating oil is introduced from conduit 2?. The piston is drilled axially as at 14 and the passage so formedterminates in an'annular relief passage 15, communicating therewith by a small side passage. When piston H1 has moved forwardly a predetermined distance, annular relief passage is registers with a side return orifice l6 permitting oil to pass through the piston to return conduit 33 by means of passage 18. Further forward movement of valve 65 by piston is thus prevented whenever oil is permitted to flow into the relief passage. The actuating system can be advantageously controlled at this point as well as at the actuating pump by inserting a piston type discharge valve 80 in passage '55 and loading the valve by a spring 82 acting on an enlarged valve head 84. The force of spring 82 is made adjustable by containing its outer end in a threaded cup 86. The force can thus be arranged so that discharge of actuating oil takes place only when the pressure in. passage 15 The valve 65 is urged to 4 reaches a definite value. The primary control of movement of the actuating piston II! is, however, derived from pump 25 which is preferably of the metering type commonly used with Diesel engine fuel injection systems. The delivery valve of the pump, however, is removed for this service. The characteristics and construction of these pumps are well known and can be so chosen that the same precisely measured quantity of actuating oil is introduced at each stroke'at a given adjustment, and the adjustment can be readily changed to introduce a greater or less quantity into the system to cause. a greater or less duration of opening of the gas injection valve 65.

An air bleeder screw is provided in the high point of the system and is interposed in the return passage 18. A small hole 9| is drilled in the screw 90 to form a continuous leak ofi passage from cushioning cylinder 12. The cushioning cylinder, together with the shaped end of piston 79, from which lands 92 project, serves to prevent fiuctuations of the piston and its associated valve '65 that might be caused by pressure waves in the pressure line 21. Since the injector will ordinarily be associated with others in a multicylinder engine, and long pressure lines are therefore necessary, such pressure waves are to be expected.

The rear end of injection valve 65 is provided with an enlarged stop head 93' to limit the movement of the valve toward the cylinder of the engine. Fouling of the valve by the engine piston is thus prevented should the valve stick in open position. A leak off passage 94 is formed on the wall surrounding the chamber in which the rear end of the valve reciprocates, and lubrication pas"- sages 95 and 96 likewise enter the injector body to maintain freedom of movement of the valve 65 therein at all points of support.

Considering now the front portion of the injector, as previously noted a check valve 63 is provided to cut oif this space from the gas passage 46 should valve 65 stick open. However, if a gas pressure of 20 pounds is used in the system,

the check valve will open for an undesirably long period in the cycle if the main valve becomes stuck so that more gas will enter the main cylinder than can safely be handled. In the event that the main valve 65 sticks, th pressure rise in the main cylinder at and after the compression stroke is so great that check valve 63 is held tightly closed, but this pressure exists only to a point in the cycle near the end of the expansion stroke so that gas could again flow into the cylinder at that time. The present invention effectively prevents this action by providing means to shut off the flow of gas whenever the pressure in cavity 64 rises to a predetermined level. This pressure is communicated through a conduit I00 to a cylinder I0! in which is dis- 7 posed a piston I02 normally biased to one position by a spring or other suitable device. Piston m2 is connected to quick closing valve 45 by a 5. toggle mechanism having centers at I I5, I I6, and I I1. The latter two centers are at spaced points on a bell crank lever H8, an end of which extends outwardly to connect to actuating rod I05. A spring I20, acting between lever I I3 and a cocking link l2l urges the lever H3 downwardly, in a direction tending to close valve H0. So long as the line of centers H5, H6, H1 is such that center H6 is urged against link I21, the valve will remain open, but as soon as the centers move out of line in the direction away from the link the valve I I will snap shut and must be manually reopened.

Operation The engine, in operation, is started on fuel oil alone, main gas valve 42 being closed. If a ratio adjustment device such as is indicated is used, the gas valve actuating pump 25 is thus set for zero delivery, but the gas is shut off at the manual control 42. Under these circumstances air supply pump 43 is put in operation by opening valve 44 so that air is introduced through cavity 64 and past injection valve 65 whenever the latter is open by periodic delivery from gas injection control pump 29. The temperature of valve 65 is thus kept within its normal operating range. At start, of course, the main governor 20 will be in wide open position, but it is free to move the adjusting means of the fuel oil pump IS without affecting gas injection control pump 29.

When the engine reaches and stabilizes at its running speed, adjustment of the gas-oil ratio may be made through adjustment 23 and link 24, and the main gas valve 42 gradually opened. At the same time air supply valve 44 is closed. The engine thus attains its normal running condition using approximately to fuel oil and 90% to 95% gas, on a thermal basis, and fluctuations in the load are reflected in main governor so that simultaneous adjustment of pump and pump [8 are made. The arrangement of the fuel oil gas ratio can be made automatic depending upon the governor motion and the gas density and heating value of gas.

During normal running, gas valve 65 is opened periodically by a discharge of actuating oil from pump 25 and the temperature of the valve is maintained within its proper range by the flow of gas through cavity 64 in the body of the valve. Check valve 63 remains open since, under proper running conditions, the pressure in the front chamber 64 of the gas injector will not exceed the pressure in the conduit 21.

Injection of gas continues so long as the discharge of pump 25 is sufficient to maintain the main valve 65 open by pressure on actuating piston 10. As previously noted, the main valve 65 is limited in it forward movement by the projecting head 93. Since no discharge valve is necessary to control properly the output of pump 25, oil is free to flow in both directions in the conduit connecting this pump with cylinder 'H. Fluctuations in the pressure in this line are smoothed out by cushioning cylinder 12 and by the spring loaded valve 80. As previously noted the duration of injection depends on the output characteristics and the adjusted position of pump 25 and actuating oil is returned to the system through conduit 33.

So long as the engine operates normally, quick closing valve remains open. However, when an abnormality occurs in the form of a speed fluctuation exceeding a predeterminedvalue or when pressure in the chamber 64 of the gas injection valve 2'5 reaches a predetermined level because of sticking or leakage of valve 65, bell crank lever I8 is moved downwardly and the quick closing valve 45 is snapped shut. The operator must then determine the cause of the failure and take steps to correct it before the engine can again be operated. In the event that the pressure in the front chamber 54 of the gas injection valve reaches a pressure in excess of the pressure in the gas conduit, check valve .63 will close so that the danger of flash-back to the gas manifold is eliminated.

While the invention has been described in conjunction with a particular form and disposition of the parts, it should be expressly understood that it is capable of numerous embodiments without departing from the scope of the appended claims.

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

1. In an internal combustion engine having a cylinder and operating at least partially on gaseous fuel, a gas conduit, an injector having a cavity connected to said conduit, a valve adapted to open communication between said cavity and said engine cylinder, a check valve operating to close the connection between said cavity and conduit whenever the pressure in the cavity exceeds the conduit pressure, and means to cut off the supply of gas to the conduit whenever the cavity pressure attains a predetermined value.

2. In an internal combustion engine having a cylinder and operating at least partially on gaseous fuel, a gas conduit, an injector having a cavity connected to said conduit, a valve adapted to open communication between said cavity and said engine cylinder, and means to cut off the supply of gas to said conduit whenever the cavity pressure attains a predetermined value, said means being so constructed that the engine is shut down and the means must be reset before the engine can again be started.

3. In an internal combustion engine having a cylinder and operating at least partially on gaseous fuel, a gas conduit, an injector having a cavity connected to said conduit, a valveadapted to open communication between said cavity and said engine cylinder, and means to cut oil the supply of gas to said conduit whenever the cavity pressure attains a predetermined value, said last means including a quick-closing valve that must be manually reset.

PAUL S. SHIRLEY.

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

UNITED STATES PATENTS Number Name Date 1,166,281 Ver Planck Dec. 28, 1915 1,138,628 Cook May 11., 1915 1,280,201 Frazier Oct. 1, 1918 1,568,588 Cushman Apr. 11, 1925 1,846,654 Prechtel Feb. 23 1932 2,036,989 Buchi Apr. '1, 1936 2,294,152 Yates et a1 Aug. 25, 1942 2,423,728 Ray July 8, 1947

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