Patent Application
20110290207
This invention relates to diesel engines and particularly systems for enhancing the fuel economy of diesel engines.
Fuel additives have been developed which are mixed with fuel and delivered to the cylinders of engines together with the fuel. These fuel additives are useable in spark ignition engines, which run on fuels such as gasoline, oxygenated gasolines, and gasoline ethanol blends. Engines utilizing these fuels typically employ a pre-mixed homogenous combustion, where fuel is uniformly distributed in the combustion chamber thus allowing substantial quantities of the fuel additive to reach the cylinder wall, and thus ultimately engine components. The additive thus provides lubricity and friction modification to reduce the friction within the engine. In addition, these additives can also accumulate in the lubricant sump to continuously provide these performance benefits to the lubricant.
In diesel engines, however, a fueling strategy is typically employed where fuel is injected directly into the combustion chamber in such a way as to minimize the fuel contacting the cylinder walls, the additive is less likely to contact the cylinder wall and improve fuel economy. Therefore, fuel additives typically are more likely to improve the fuel economy of spark injection engines as opposed to diesel engines. It is therefore desirable to utilize a system to improve the fuel economy of diesel engines including diesel engines which employ additives, including fuel additives, intended to provide additional lubricity and friction modification to engine components.
In accordance with the principles of the present invention, a system for enhancing the fuel economy of a diesel engine via the introduction of additives is described herein. The system is particularly effective in a diesel engine of the type wherein each cylinder undertakes four strokes during a cycle. The method includes performing a first injection step by injecting fuel into a cylinder of a diesel engine to initiate combustion of the fuel within the cylinder, and performing a second injection step by injecting an additive into the cylinder during the cycle at a time different than the first injection step wherein the additive reaches and contacts the cylinder wall. The first and second injection steps may be repeated during different cycles to improve the fuel economy of the diesel engine.
The method and system of the present invention may be employed such that the second injection step includes injecting the additive when the additive is mixed within fuel, i.e., a fuel additive. The second injection step may occur at a time during a cycle after the piston reaches 40° after compression top dead center and at a time prior to when the piston in the cylinder reaches 10° before compression top dead center. The amount of fuel, cumulatively over time, included in the second injection steps may be less than the amount of fuel injected in the first injection step. The amount of fuel within the second injection step in aggregate, for example, may be less than about 10% of the amount of fuel injected during the first injection step. In some embodiments, the number of second injection steps will be substantially less than the first injection steps and it may be desirable to inject larger amounts in the individual second injection event, while maintaining lower cumulative second injection volume.
A concentration of additive within the fuel in the second injection step may be greater than the concentration of additive within the fuel during a first injection step. The additive may be injected into the fuel stream of the diesel engine at selective time intervals. The selective time intervals may be repeated periodically. The second injection step may be repeated during multiple consecutive cycles. For example, the second injection step may be repeated for up to 30 seconds after about at least 10 minutes of engine operation during which time no second injection step occurs. The method and system may be performed in multiple cylinders of the diesel engine.
In another aspect, the invention includes a system for enhancing the fuel economy of a diesel engine of the type wherein each cylinder undertakes four strokes during a cycle, and of the type having means for performing a first injection step by injecting fuel into a cylinder of a diesel engine to initiate combustion of said fuel within said cylinder. The system includes means for performing a second injection step by injecting an additive into the cylinder during said cycle at a time different than said first injection step wherein the additive reaches the cylinder wall; and means for repeating said first injection step and said second injection step during a different cycle to improve the fuel economy of said diesel engine. The system may incorporate a control means, such as a microprocessor controller, which allows the system to incorporate the above described methods. The additive may be a fuel additive, mixed with fuel.
The method and system of the present invention may be incorporated into a diesel engine of the type wherein each cylinder undertakes four strokes during a cycle. The system includes an engine block having a plurality of cylinders therein; means for performing a first injection step by injecting fuel into at least one of said cylinders to initiate combustion of said fuel within said cylinder near the end of a compression stroke of said cycle; means for performing a second injection step by injecting an additive into the cylinder during said cycle at a time different than said first injection step to allow said additive to reach the cylinder wall; and means for repeating said first injection step and said second injection step during a different cycle to improve the fuel economy of said diesel engine.
These and other aspects of the invention will become evident upon reference to the following detailed description of the invention and accompanying examples.
As shown in
Air may flow from an air inlet through a turbocharger and air filter and eventually to an electric throttle 22 and intake passage 21 into cylinder 10. Cylinder 10 is in fluid communication with intake passage 21 and exhaust passage 23. After combustion of an air and fuel mixture within the cylinder, exhaust gases generated within the cylinder 10 through exhaust passage 23 and through the turbocharger and eventually through the exhaust system of the diesel engine, which typically includes a diesel particulate filter.
A fuel line feeds fuel pump 14, which is in fluid communication with a fuel tank 8 containing fuel and an additive. Any additive, which provides increased fuel economy by virtue of, for example, its contact with engine components via the cylinder walls may be useable with the method and system of the present invention. One such fuel additive developed by Taconic Energy, Inc. is described in U.S. patent application Ser. No. 12/327,135 filed on Dec. 3, 2008, which is incorporated herewith in its entirety. This additive comprises alkanolamides which are free of esters, or has an amide to ester ratio of greater than 1.4 to 1. Such additives may be obtained from a reaction of a natural or synthetic oil, fatty acids and esters, with alkanolamine. Other additives that provide friction modification including friction modifying esters and amides derived from fatty acids and diacids may be used. However, commercially available acids or simple fatty esters that only act as diesel lubricity agents to reduce pump wear have not been shown to provide fuel economy benefits in spark initiated engines. For this reason they would not be expected to be effective in this application. The additive may be mixed with the fuel, as a fuel additive, within the fuel tank 8 and is transported to the cylinder 10 mixed with fuel via the fuel pump 14, common rail 13 and fuel injector 12.
Each cylinder 10 of the diesel engine is connected by a linkage to a crankshaft 11, which rotates and thereby causes reciprocating strokes of each piston within the cylinders including cylinder 10. The position of any piston within a cylinder may therefore be measured by the angle of rotation of the crankshaft 11 (i.e., crank angle). A crankshaft sensor 64 senses the crank angle of the crankshaft 11 and is connected electronically to a controller 70. The controller is typically a microprocessor, which also controls the fuel pump 14, electric throttle 22, one or more fuel injectors 12 and fuel pump 14.
An exhaust gas recirculation loop 31 is in fluid communication with exhaust passage 23 and intake passage 21. An exhaust gas recirculation (EGR) valve 33 is located within the exhaust gas recirculation loop 31 controls the amount of exhaust gas recirculated into the intake passage during operation of the diesel engine. The controller 70 also controls the operation of the EGR valve 33.
As shown in
The piston 10a within each cylinder typically undergoes four strokes during a cycle. Combustion occurs after air and fuel enter the cylinder and when the piston 10a is at or near, or slightly past, compression top dead center. Combustion causes the piston to translate toward the bottom of the cylinder 10 to a crank angle of bottom dead center (or 180° from compression top dead center). The crankshaft 11 then causes the piston 10a to enter the exhaust stroke, which translates the piston 10a towards the top of the cylinder causing the exhaust gases to pass through the exhaust valve and into the exhaust passage 23. At this point, the piston 10a is located at exhaust top dead center. As the crankshaft continues to rotate the piston will begin to translate towards the bottom of the cylinder during the intake stroke where air will enter the cylinder via the intake valve. As the crankshaft 11 continues to rotate the cylinder will reach intake bottom dead center (180° from top dead center) and then begin to translate towards the top of the cylinder 10 during the compression stroke where air within the cylinder will become compressed. Near, or slightly after, the end of the compression stroke, fuel again enters the cylinder 10 through the fuel injector 12 to caused combustion and the start of a new cycle. The four stroke cycle for each piston 10a is continuously repeated as the engine operates.
Near, or slightly after, the end of the compression stroke, described above, a first injection step occurs and fuel from the common rail 13 is injected by the fuel injector 12 into the cylinder 10 to initiate combustion. This combustion is caused by the compression of air with diesel fuel and powers the diesel engine. During the first injection step fuel is injected into the cylinder 10 via the fuel injector 12 at a point where the piston 10a is near compression top dead center. Fuel and additive, which may be mixed within the fuel in this first injection step, is unlikely to reach the cylinder wall 10c. Rather, combustion occurs preferably at a time prior to when any fuel reaches the cylinder wall 10c. Moreover, fuel contacting the cylinder wall 10c during this first injection step is not desirable since uncombusted fuel on the cylinder wall may make its way into the oil within the crankcase and thus dilute the oil's effectiveness.
Preferably, after the first injection step and after the piston stroke reaches 40° from compression top dead center, the second injection step may occur. This second injection step includes fuel additive injected from the fuel injector 12 into the cylinder 10. Because of the location of the piston 10a and flow characteristics within the cylinder due to the operating conditions therein, fuel additive injected into the cylinder contacts the cylinder wall 10c to provide friction modification. The fuel additive, which contacts the cylinder wall may, upon passage of the piston over the cylinder wall, mix with oil within the crankcase below the cylinder and thus provide additional friction modification to various engine components. This allows for increased fuel economy and reduced engine wear within diesel engines.
The second injection step may occur during a different time within the piston cycle. The controller 70 may control this second injection step, as well as the first injection step. The controller 70 controls injecting the additive, which may be mixed within the fuel via the fuel tank 8, into the cylinder through common rail 13 and fuel injector 12. The controller 70 may also control other various engine functions.
The controller 70 receives information regarding the position of the crank angle from the crank angle sensor 64. The controller 70 may then control the timing of the second injection step based upon the information received from the crank angle sensor 64. The controller may be programmed to perform the second injection step at a particular time during the piston cycle for each cylinder within a diesel engine by initiating the second injection step at the desired timing within a piston cycle.
Referring to
As shown in
In order to achieve the benefits of increased friction modification and fuel economy, the second injection step need not necessarily be performed during each piston cycle. For example, it is believed that the delivery of approximately 1 gram of fuel additive to the cylinder wall during each hour of engine operation will achieve the benefits of increased friction modification and fuel economy. In addition, it is believed that performing the second injection step during the early stages of the intake stroke will maximize the amount of fuel additive reaching the cylinder wall. The more fuel additive reaching the cylinder wall, the greater the increase in friction modification and fuel economy benefits for any fuel additive injected into the cylinder. Fuel additive injected into the cylinder, but not reaching the cylinder wall, will not achieve the benefits of the present invention.
The controller 70 may control the additive pump 36, and a sensor (not shown) may be included with the fuel additive reservoir 34 to sense the presence or absence of additive therein. Accordingly, the controller 70 may control the amount of fuel additive, if present in the fuel additive reservoir 34, from being pumped into the common rail 13 by fuel additive pump 36.
Using the system and embodiment of
In addition, in any of the embodiments shown herein, the controller 70 may control the frequency of the second injection step. For example, the second injection step need not be performed for every piston cycle. The second injection step may occur during multiple consecutive piston cycles for a defined period of time and then the second injection step may be eliminated for a defined period of time of engine operation. The second injection step may be used, for example, for up to approximately 30 seconds or more of engine operation and then stopped for approximately 10 minutes or more of engine operation. Such periodic implementation of the second injection step may be sufficient to provide the benefits of increased lubricity and fuel economy within diesel engines.
Such benefits may be achieved when, for example, a particular amount of fuel additive reaches the cylinder wall during a particular time of engine operation. Thus, the invention can be implemented by using multiple second injection steps for a particular time period, or a single injection step for the same time period, so that a particular aggregate amount of additive injected within such time period sufficient to provide enhanced fuel economy is used. For example, for each cylinder of a diesel engine, it is believed that one gram of fuel additive reaching a cylinder wall during one hour of engine operation will provide the benefits of increased friction modification in fuel economy. Therefore, the system of the present invention may be implemented to perform the second injection step in any selective pattern or frequency which will achieve the desired amount of fuel additive reaching the cylinder wall during each hour, or other time component, of engine operation.
It should be understood that the embodiments set forth herein are illustrative and that various modifications may be made to the disclosure herein without departing from the invention. For example, variations set forth herein may be modified without departing from the scope of the invention.
