Patent Application
20140345579
The present invention relates to internal combustion engines with reduced emissions. This applies to combustion engines that utilize exhaust gas recirculation (EGR) to effectively reduce engine emissions, and also to engine applications that benefit from faster warm-up behavior of the engine. Internal combustion engines that meet today's strict emissions regulations quite often employ EGR as a method to dilute the oxygen concentration of the combustion, and thereby reduce the formation of oxides of nitrogen. In order to effectively introduce enough EGR to the engine's intake manifold, the EGR is usually cooled by an EGR cooler to increase the density of EGR and prevent high combustion temperatures. These coolers are typically cooled by engine coolant, which increases the heat that must be removed by the vehicle's radiator and fan assembly.
In one aspect, the invention provides a method including operating an internal combustion engine producing, as a byproduct, exhaust gases. The flow of exhaust gases are segregated into a first, relatively hot flow and a second, relatively cold flow. The second flow is directed to an intake of the internal combustion engine for combustion with fresh intake air and fuel. Heat energy from the first flow is stored in a latent heat storage device. Heat energy is released from the latent heat storage device to reduce cold start emissions during a subsequent operation of the internal combustion engine after a period of shutoff.
In another aspect, the invention provides an internal combustion engine including a plurality of cylinders operable to combust a mixture of fuel and air. A vortex tube is coupled to the plurality of cylinders to receive a flow of exhaust gases from the plurality of cylinders. The vortex tube is operable to separate the flow of exhaust gases into a first, relatively hot flow discharged from a first outlet and a second, relatively cold flow discharged from a second outlet. An exhaust gas recirculation passage couples an intake of the engine and the second outlet of the vortex tube. A latent heat storage device is coupled to the first outlet of the vortex tube and is operable to store a quantity of heat energy supplied by the second flow. The latent heat storage device is coupled in heat exchange relationship with at least one of engine oil, engine coolant, and a catalyst.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
The relatively cold stream is routed to an intake manifold 48 of the engine 32 to provide cooled EGR to the cylinders 36 through the corresponding intake valves 52. As illustrated in
In some aspects of the invention, the hot exhaust stream from the vortex tube 20 is passed through a Latent Heat Storage (LHS) device 72 that is configured to capture heat from the exhaust gas for later use. One challenge for modern engine efficiency improvement and emissions reduction is the behavior of the engine and exhaust system when the system is started from an ambient temperature condition. In other words, when starting an engine after it has been completely cooled down to the ambient temperature after a period of shutoff (i.e., “cold start”). When an engine is cold, internal friction between moving parts, including the pistons within the cylinders, is significantly high. This is mostly due to the high viscosity of engine oil when cold, and results in relatively poor fuel efficiency. The engine must produce extra power to overcome the higher level of friction induced by cold oil. Additionally, a cold engine produces relatively cold temperature exhaust gas. Modern catalysts that reduce HC, CO and NOx emissions require a certain light-off temperature before they are effective in reducing emissions. This warm-up time can last several minutes after cold start before acceptable temperatures are reached, during which, high levels of emissions are experienced. Thus, cold starting can be a leading contributor in emissions in modern engines, especially where vehicles are used frequently for short trips and/or in cold weather in which a very large portion of the sum total of emissions may be generated during the warm-up period. The LHS device 72 is configured to capture or absorb heat from the relatively hot exhaust stream from the vortex tube 20 and is further configured to store this heat for use in warm-up assistance on a subsequent cold start. For example, using the LHS device 72 to rapidly heat the engine oil is an effective and inexpensive way to reduce engine friction, and improve the engine's warm-up characteristics, thereby reducing cold start emissions. Friction can be reduced by heating the engine oil directly, or by heating engine coolant, which in turn heats the engine block and engine oil to achieve faster warm-up to normal operating temperature. Alternatively, or in addition, the relatively hot exhaust from the first outlet 26 of the vortex tube 20 can be utilized to achieve faster catalyst warm-up, further improving engine emissions levels. For example, after storage within the LHS device 72, heat can be released to the catalyst through any desired mechanism establishing a heat exchange relationship therebetween. Regardless of how the heat is used during cold start, the relatively hot gases escaping the vortex tube 20 through the first outlet 26 can be used to charge the LHS device 72 to a higher energy state than with conventional exhaust directly from the exhaust manifold 40. This presents the advantage of using the LHS device 72 in combination with the vortex tube 20, which is that the benefit for warm-up is amplified due to the increased amount of heat that can be stored.
The LHS device 72 can contain a phase change material (PCM) that is capable of storing and delivering a high amount of thermal energy. This is primarily due to the high level of energy stored or delivered during the process of phase change (e.g., solid to liquid, and back). The characteristic of temperature vs. stored energy without phase change (sensible heat only) and with phase change are shown, respectively, in
During operation of the engine 32, the hottest fraction of the exhaust gas, from the vortex tube 20, is used to heat the PCM in the LHS device 72. Upon stopping, the engine 32 cools down from normal operating temperature, and if stopped long enough, reaches ambient temperature. When the engine 32 is re-started, engine oil is routed through the LHS device 72 via the oil pipe send 84 and return 88 and is heated by the PCM, which has stored the heat energy throughout the period between shutoff and re-start. This heating of the engine oil happens very fast, and can very quickly heat the oil (e.g., increasing oil temperature from TL to TH), and thus reduce friction so that fuel consumption is reduced to a level corresponding with normal operating temperature in much shorter duration from start-up. In some constructions, as shown in
A similar operation is carried out in the case where engine coolant, rather than oil, is the fluid heated by the PCM. It should also be noted that the LHS device 72 can be used to establish heat transfer to any combination of engine oil, engine coolant, and a catalyst.
This application claims priority to U.S. Provisional Patent Application No. 61/825,963, filed May 21, 2013, the entire contents of which are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61825963 | May 2013 | US |
