US1094993A - Cooling internal-combustion engines. - Google Patents

Description

B. HOPKINSON.

COOLING INTERNAL COMBUSTION ENGINES.

APPLIGATION FILED JAN.3.1910.

1 094 993. Patented Apr. 28, 1914.

UNITED sTArEs PA'rENT OFFICE.

. BERTR AM HOPKINSON, OF CAMBRIDGE, ENGLAND.

COOLING INTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent.

Patented Apr. 28, 1914.

Application filed January 3, 1910. Serial No. 535,955.

methods of cooling these engines involve the circulation of water around the exterior of the cylinder; in the case of engines of large size it has been found necessary in addition to provide for the cooling of the piston and exhaust valves by the circulation of water through their substance. It has also been proposed to inject water into the interior of internal combustion engines for various purposes including that of cooling the metal. Such proposals have not hitherto been successful in practice. In many cases failure has arisen from the wrong manner of applying the water, which has been introduced in a fine spray. In some cases the water has been previously heated and in many instances it has been introduced with the air charge. It has not been clearly understood that if the water is to be eflicient as a cooling agent, it must reach the hot metal surfaces in a liquid condition, with -as little evaporation as possible on the way, and that it is the function of the water to abstract the heat direct from the metal and not from the gas. Another reason why water injection has not hitherto been a success is that it has been found to cause serious corrosion of the metal surfaces and greatly to increase the wear of the surfaces by washing away the lubricant.

- The chief object of my invention is to apply the cooling liquid in a more eflicient manner than heretofore so that as much of it' as possible shall be evaporated upon the surfaces to be cooled and as little of it as possible shall be evaporated before reaching those surfaces; I also prefer that the cooling liquid shall not remain in its liquid condition within the cylinder of the engine for I have found that the above mentioned diificulties of corrosion and lubrication are associated with the presence of liquid within the engine, and can be obviated or greatly reduced by avoiding as far as possible the presence of liquid.

According to my invention cold water is pro ected directly against the surfaces to be cooled in such a manner that it will reach such surfaces with as little evaporation as possible. In order to secure this result 1 project the water in the form of comparatively coarsedrops or jets against the surfaces to be cooled, which coarse drops or jets present a small surface to the gases in the-cylinder in comparison with their mass and consequently suffer but little loss by evaporation before they reach the surfaces to be cooled. This. effect is enhanced by the fact that they offer less resistance to projection through the gases in proportion to their mass than would finer drops or jets such as are produced by an atomizer and therefore reach the surfaces to be cooled in a shorter time. I prefer to project the water in such a manner and in such quantities that it will maintain the various internal surfaces at a temperature below the maximum temperature consistent with satisfactory working of the engine but above that required to vaporize it. In this manner all or nearly all the water is converted into steam and little or no water is permitted to remain in its liquid form within-the cylinder.

In order to reduce the deleterious effect of the water upon the life of the engine, it is advantageous to arrange for the water to be projected only on to the face of the piston and valves and the surface of the combustion chamber, leaving the piston to abstract by conduction the heat given up by the hot gases to those parts of the cylinder which the said piston uncovers during its stroke. In this manner the water falls only on places where it can do no harm, none of it falling upon the rubbing surface between the piston and the cylinder. The restriction of the water-cooling to the surface of the combustion chamber and the piston and valves, is preferably effected by timing the injection of the water to take place only during that portion of the revolutionmf the crank shaft when the piston is near the inner end of its stroke. D

My method. of cool ng will 1n most cases render it unnecessary to employ a waterjacket for the engine cylinder, but in some cases the usual. water jacket may if preferred still be employed, and my method of cooling be applied to the piston and exhaust valves only.

In one case of my invention I cool the cylinder end and combustion space by means of the circulation of Water and rely on the projection of water against the face of the piston for cooling not only the p1ston but also the cylinder walls by conduction through the piston.

In order that my said invention may be clearly understood and readily carried into effect, I will describe the same more fully with reference to the accompanying drawings, in which Figure 1 1s alongitudinal section and Fig.

' 2 a cross section of the combustion chamher end of an internal combustion engine, the piston being shown at the inner end of its strike. Fig. 3 is a sectional end elevation of the engine showing the external contrivances for causing the internal water-injection to take place. Fig. 4 is a detail view of one form of device for regulating the supply of the water.

A is the engine cylinder, B the combustion chamber. 6 is the inlet valve and b the exhaust valve therein, and C is the piston.

D is an injection pipe which terminates in a rose or perforated ring situated within the combustion chamber B. Through this pipe water is forced as hereinafter described, and is projected in the form of coarse drops or jets through the perforations against the wall of the combustion chamber B, the face of the piston C, and the valve 6, as shown in the drawings. These jets are distributed equally over the different parts of the combustion chamber and over the face of the piston. It may, however, be unnecessary to provide any jet of water for the exhaust valve 7) since if it is situated, as shown, beneath the pipe D, it will usually be sufficiently cooled by the drip of water from the pipe.

For the purpose of supplying water to the pipe D, the arrangement illustrated by way of example in Fig. 3 may be employed, wherein the pipe D extends beyond the interior of the combustion chamber B and,

after passing an automatic by-pass valve E, referred to later, communicates through a ball valve f with a force pump F. The plungenG of the force pump is actuated by one end of a lever H, which is pivoted at the point 72. and carries at its other end a roller h engaging with a cam J; this cam is carried on a shaft J, which I will assume to be the half-time shaft of an Otto cycle engine. The cam J is so related to the motion of the crank shaft of the engine that the instant when the roller h is on the point j of the cam J corresponds to a point in the revolution of the crank shaft when the piston has approached but has not quite reached the inner extremity of its stroke. Each time the cam performs a revolution, the roller It is lifted, the plunger G being thus depressed and water forced through the perforations in the pipe D. The depression of the plunger is complete when the point j on the cam J arrives under the roller h and this point corresponds to a position of the crank shaft which is some degrees past that corresponding to the inner extremity of the piston stroke. During the further revolution of the engine, the roller rests upon the circular portion of the cam J and no further injection of water takes place, the plunger G remaining at the bottom of its stroke. When the point j arrivesunder the roller h, the plunger is free to rise under the influence of a spring g, and in rising sucks water through the non-return valve f which communicates with a water supply. When the point j on the cam J has again arrived under the roller h, the barrel of the pump F is again full of water and the Whole operation is repeated, the complete revolution of the shaft that carries the cam corresponding, as .is usual in Otto cycle engines, to two complete revolutions of the crank shaft.

In order to adjust the quantity of water injected at each stroke of the pump so as to comply with the condition that the metal surfaces are to be maintained as far as possible at a temperature above that at which the water vaporizes, the force pum F may be provided with a hollow nut F w iich limits the upward travel of the plunger G by the engagement of a collar 9' on the plunger G with the nut F as shown in dotted lines.

into the pump at each suction stroke and consequently the quantity injected at each delivery stroke of the pump can be adjusted by hand to suit the requirements of the engine at any particular time. I find it convenient, however, to provide means for automatically regulating the quantity of water injected into the engine. For this purpose I have indicatedin the drawings a thermostat E which may be of any suitable form and be situated in a pocket B in the metal of the combustion chamber so as to assume the temperature thereof. The thermostat acts upon the supply of water in such a way as to cut off nearly the whole of it when the temperature of the engine falls below some predetermined point, say, 150 C. The superned on the hit-and-miss principle.

pose. A convenient form of the thermostat 1s shown in Fig. 4. The water fromthe pump F passes through thepipe D into a chamber'K (Fig. 4) whence it may pass through the continuation of the pipe D to the engine. The chamber K is fitted with a valve K through which, when opened, there is a communication to a by-pass pipe It. \Vhen the valve K is open, the water passes through the bypass in preference to enterin the engine by the pipe D. The valve K is actuated, through a spring is, by a piston 70 which at its other end is sub ect to the pressure of a thermostatic substance k When the tempearture of the engine reaches a certain point, the )ressure of the thermostatic substance is su 'cient to force up the valve K against its seating, thus closing the by-pass and causing the water to flow into the engine; when the temperature falls, the valve K is opened, by the falling of the piston k In some cases I prefer also automatically to control the supply of water in proportion to the supply of fuel. A convenient form of means for effecting this control is shown in Fig. 3 applied to an engine gov}; member L, which may be termed the pecker, is pivoted at l to the fuel-controlling lever Z. When the speed of the engine exceeds a certain value, the governor M, through the arm m and link Z-, operates to withdraw the pecker L from engagement with the fuel valve N, and thereby cut off the supply of fuel completely for one or more cycles of the engine in the usual manner. A link Z connected at one end to the aforesaid arm m, and a bell-crank Z operate a distance piece Z in such a manner as to push the latter nearer to the plunger G of the pump F (as shown by the dotted lines in Fig. 3) when the pecker L is withdrawn by the acti on of the governor as above described. In this position the distance piece Z engages with a collar fixed to theplunger G, thus preventing the plunger from rising, and thereby stopping the suction of water into the pump and its injection into the engine. In this manner water is only injected when the engine takes fuel and the quantity of water injected per minute is, apart from the action of the thermostat, proportional to the quantity of fuel supplied.

Although the means hereinbefore described have been found satisfactory in practice, it will be understood that I do not limit myself thereto, as any appropriate means Ina be employed for injecting the water an for controlling its amount so long as such means efiiciently fulfil the main conditions, namely that' the water shall be.

projected in coarse jets directly on to the face of the piston and valves and the surface of the combustion chamber, and that the parts on which the water impinges shall be maintained at a temperature above that at which the water vaporizes. For instance any convenient form of force ump may be employed and it may be drlven from the'main crank shaft of the engine instead of from the half-time shaft. Moreover I do not confine myself to the use of any particular form of thermostat and I'may arrange it to operate b directly altering the stroke of the pump, 1nstead of by means of a by-pass valve or in any other convenient manner.

The apparatus hereinbefore described with reference to the drawings may be applied with the necessary variations in construction, to any form of internal combustion engine, whether single-acting or doubleacting, involving any of the well-known cycles of operation. In the case of an engine working on the Otto cycle, the Water may be injected at "about the time when the exhaust stroke is completed and the suction stroke is about to commence, or at about the time when the compression stroke is completed and the working stroke is about to commence or at both of these times. I prefer, however, to inject during the latter period only and to commence the injection when the crank is from 30 to 45 short of its dead center position and to conclude the injection at about the corresponding period after such dead center position.

What I claim and desire to secure by Letters Patent of the United States is 1. In an internal combustion engine, the combination with the combustion chamber, the cylinder and the piston, of an injection pipe the end of which projects into the combustion chamber and has coarse perforations directed against the surfaces to be cooled, means operated from a shaft of the engine for forcing liquid in a cold condition through the perforations, a by-pass valve between the liquid-forcing means and the perforated end of the injection pipe, a thermostatic substance situated to respond to variations of temperature of the combustion chamber walls, and means whereby the thermostatic substance controls the by-pass valve.

2. In an internal combustion engine, the combination with the combustion chamber, the cylinder and the piston, of an injection pipe the end of which projects into the combustion chamber and has coarse perforations directed against the surfaces to be cooled, means operated from a shaft of the engine for forcing liquid in a cold condition through the perforations, means for automatically controlling the supply of fuel to the en ine, means actmg in conjunction with the uelcontrolling means to control the liquid-forcing means in accordance with the fuel supply and means acting independently of the fuel controlling means for so regulatin the amount of cooling liquid injected as to eep T. SELBY WARDLE.

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