Venturi exhaust cooler

Abstract

The kinetic energy of the exhaust gas from an internal combustion engine is utilized as a driving fluid to aspirate a large volume of quiescent ambient air as a driven fluid for cooling the exhaust gas quickly in a very short path of travel. This mode of operation is to be distinguished from conventional injector and ejector devices utilizing a current of air as the driving fluid. The present device utilizes the Coanda effect to introduce the exhaust gas around a lip on one end of a venturi tube, causing the gas to flow in a high velocity film adherent to the inner surface of the tube. This laminar flow draws in a large volume flow of air through the center of the venturi, cooling 1000.degree.F. exhaust gas down almost to ambient temperature in a distance of a few inches.

Description

BACKGROUND OF THE INVENTION

This invention relates to a venturi exhaust cooler for internal combustion engines.

In certain operations, as in mines and tunnels where workmen must work in a limited space around internal combustion engines, it is necessary to cool the engine exhaust before discharging it into the atmosphere in order to prevent injury and discomfort to the workmen. Ordinarily, this is accomplished by providing an exhaust pipe of sufficient length to reduce the temperature to a tolerable value. This is an undesirable expedient, however, because of the considerable length of pipe required and the physical space occupied by the pipe. Such engines are usually equipped with rather bulky accessory devices, making any additional space requirements objectionable, particularly in underground work where it is necessary to make the equipment and machinery as compact as possible.

Air injectors and ejectors have heretofore been proposed for airplane and automobile engine exhausts, utilizing a strong current of air developed by the movement of the vehicle. This means of cooling is not available to the present class of equipment which involves stationary engines and types of vehicles such as loaders which do all or most of their work while standing still. Other vehicles, such as rock and ore carriers, travel too slowly to generate an adequate air stream for cooling purposes.

Utilization of the air stream from the engine cooling fan is not satisfactory either, because of the space requirements of the ducting to convey the air stream from the fan back to the engine exhaust or, conversely, to convey the engine exhaust forward to the air stream from the fan. In order to simplify the construction and make the equipment as compact as possible, it is desirable to discharge the exhaust gases as close as possible to the exhaust manifold.

Another problem inherent in the operation of internal combustion engines in underground work is the usual requirement for a catalytic converter to remove certain noxious substances from the exhaust gas. Such converters require the exhaust gas to pass through at a temperature of at least 1000.degree.F. whereby there can be only a minimum of cooling between the engine and the converter. Thus, there is substantially no pre-cooling in the exhaust system and the exhaust gas must be introduced into the cooler at approximately its engine temperature.

Objects of the invention are, therefore, to provide an exhaust cooler for internal combustion engines which overcomes the problems pointed out above, to provide an exhaust cooler which does not require a long exhaust pipe and which does not require a moving air stream, to provide an improved venturi exhaust cooler, to provide a venturi exhaust cooler utilizing the kinetic energy of the exhaust gas as a driving fluid to aspirate a large volume of quiescent ambient air as a driven fluid for cooling the exhaust gas quickly in a very short path of travel, to provide a venturi exhaust cooler which may be disassembled for cleaning, and to provide a venturi exhaust cooler which is adjustable to minimize back pressure on the engine.

SUMMARY OF THE INVENTION

The present venturi cooler is to be distinguished from conventional injector and ejector devices using a current of air as the driving fluid. In the present device the kinetic energy of the exhaust gas from the internal combustion engine is utilized as a driving fluid to aspirate a large volume of quiescent ambient air as a driven fluid for cooling the exhaust gas quickly in a very short path of travel. The device utilizes the Coanda effect to introduce the exhaust gas around a lip on one end of a venturi tube, causing the gas to flow in a high velocity film adherent to the inner surface of the tube. This laminar flow draws in a large volume of air through the center of the venturi, cooling 1000.degree.F. exhaust gas down almost to ambient temperature in a distance of a few inches.

The device is adjustable to obtain maximum cooling effect and minimize back pressure on a particular engine and the device may be disassembled for cleaning.

The invention will be better understood and additional objects and advantages will become apparent from the following description of the preferred embodiment illustrated on the accompanying drawing. Various changes may be made, however, in the details of construction and arrangement of parts and certain features may be used without others. All such modifications within the scope of the appended claims are included in the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation view, with parts broken away and parts in section, showing a venturi exhaust cooler embodying the invention;

FIG. 2 is a view on the line 2--2 in FIG. 1;

FIG. 3 is a view on the line 3--3 in FIG. 2; and

FIG. 4 is a view similar to FIG. 3 showing a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 combustion engine 10 has an exhaust manifold 11 discharging into a short exhaust pipe 12. The exhaust gases are passed through a conventional cylindrical catalytic converter 13 which removes certain noxious substances. For effective operation, the gases must pass through catalytic converter 13 at a temperature not lower than 1000.degree.F. The hot exhaust gases leave converter 13 through a short pipe 14 to the present venturi exhaust cooler 20 whence they are discharged into the atmosphere.

Venturi cooler 20 is conveniently and economically made in two parts which may be disassembled for cleaning. The outer part is a shell or housing 21 having integral cooling fins 22 and a tubular inlet connection 23 which is adapted to be welded at 24 to the lower end of pipe 14. Housing 21 is cylindrical with an inturned radial flange or wall 25 on one end having an inner edge 26 defining an air inlet opening. The other end of housing 21 is internally threaded at 27 and provided with a setscrew 28.

Mounted within housing 21 is a venturi tube 30 having a curved outturned lip 31 on one end thereof spaced a short distance inside of flange 25 to provide an annular axial gap at 32 between said lip and flange. Lip 31 extends in a smooth curve from a reduced venturi throat 33. Flange 25 overlaps lip 31 a short distance in a radial direction, the inner edge 26 of the flange being of less diameter than lip 31 and of greater diameter than throat 33.

The other end of venturi tube 30 has threaded engagement with the screw thread 27 in housing 21 to support the venturi tube in the housing. This screw threaded connection permits axial adjustment of the gap 32, the adjustment being fixed by setscrew 28 which bears against a cylindrical surface 35 on the venturi tube. The threaded end of the venturi tube has a protruding end portion 36 of external hexagonal shape for convenient wrench adjustment and removal for cleaning.

The shape of venturi tube 30 provides an annular exhaust inlet chamber 40 surrounding the throat of the venturi tube within housing 21. Housing 21 and venturi tube 30 are preferably made as cast metal parts.

Exhaust gas entering chamber 40 can escape only through the orifice formed by annular gap 32. The adjacent position and overlapping relationship of flange 25 with respect to lip 31 produces a Coanda effect, causing the high velocity exhaust gas stream to follow the contour of lip 31 and throat 33 and adhere to these surfaces in laminar flow as indicated by arrows 41. By reason of the Coanda effect, no exhaust gas escapes through opening 26. The laminar flow of exhaust gas 41 through throat 33 creates a suction which pulls in a large volume of air through the center of the venturi as indicated by arrows 42 whereby exhaust gas leaving converter 13 at approximately 1000.degree.F. is cooled down almost to ambient temperature in approximately seven inches of travel through venturi tube 30. The Coanda effect is explained in Coanda U.S. Pat. No. 2,052,869.

The air flow 42 is induced entirely by the flow of exhaust gas 41 and does not require any external means for forcing the air through the venturi tube, such as the movement of a vehicle or an engine cooling fan. The ambient air available to opening 26 may be in a completely quiescent state. Thus, the exhaust gas 41 functions as a driving fluid and the air 42 functions as a driven fluid, which mode of operation is the reverse of conventional air injectors and ejectors for exhaust gases.

This unique mode of operation makes the present exhaust cooler effective on stationary engines and vehicle engines which operate under load while the vehicle is stationary or moving slowly. This mode of operation also allows the engine exhaust to be discharged in any direction and with a minimum of ducting so that lengthy exhaust pipes are not necessary in order to direct the exhaust away from working areas where workmen might be injured by exposure to a high temperature exhaust. Thus, the present exhaust may be discharged laterally in the most convenient position from the engine compartment of a vehicle or stationary machine without danger of burning workmen alongside the vehicle or machine.

The venturi tube adjustment at 27 permits use of one size of exhaust cooler on a variety of different engines. The venturi tube may be readily shifted axially toward or away from flange 25 to vary the opening of slot orifice 32 and produce the greatest cooling effect without objectionable back pressure for any given engine so that a different cooler does not have to be made for each different size and model of engine. This permits the casting in large volume of standard housing and venturi tube parts 21 and 31 which effects considerable economy of manufacture.

In the modification in FIG. 4 adjustment of orifice gap 32 is provided by shims 50 which may be added or removed as desired. Venturi tube 30a has an external flange 51 which is adjustably and detachably secured to an internal flange 52 in shell 21a by screws 53. Adding shims 50 increases the gap 32 and removing shims narrows the gap as described in connection with FIG. 3.

Claims

Having now described my invention and in what manner the same be used, what I claim as new and desire to protect by Letters Patent is:

1. A venturi exhaust cooler comprising a housing having an upstream end and a downstream end, cooling fins on the outside of said housing, an exhaust gas inlet connection in one side of said housing between said ends, an inturned flange on said upstream end forming an air inlet opening, a venturi tube having an upstream end and a downstream end, a curved outturned lip on said upstream end of said venturi tube spaced behind said housing flange, and means on the downstream ends of said housing and venturi tube for mounting said venturi tube in said housing, said housing and cooling fins extending substantially the full length of said venturi tube, the downstream end of said venturi tube being exposed to atmosphere and said venturi tube being removable through said downstream end of said housing for cleaning, said mounting means including longitudinal adjustment means to vary the spacing of said venturi tube lip behind said housing flange, and said housing forming an exhaust gas inlet chamber around said venturi tube causing exhaust gas from said chamber to follow the contour of said lip and tube in laminar flow under the Coanda effect and draw air through said inlet opening into the center of said tube to cool said exhaust gas.

2. An exhaust cooler as defined in claim 1, said mounting means comprising flanges on said downstream ends of said housing and venturi tube, and screws securing said flanges together, said adjustment means comprising shims between said flanges.

3. An exhaust cooler as defined in claim 1, said mounting and adjustment means comprising a screw threaded connection between said housing and venturi tube.