Patent Application
20130333673
1. Field of the Invention
The present invention relates generally to internal combustion engines, for example, internal combustion engines incorporating heated fuel temperature controls and exhaust gas recirculation components.
2. Description of the Related Art
Modern internal combustion engines are ubiquitous and utilized in many different applications, including most modern automobiles and in industrial manufacturing machinery. Internal combustion engines function by combusting a fuel (which can be several fuel types including a hydrocarbon based fuel or a biodiesel fuel and can be mixed with various additives such as ethanol) in a combustion chamber with an oxidative agent (typically ambient air) within a fluid-flow circuit (such as a fuel rail system). During the combustion process, the expansion of the high-temperature and high-pressure gases apply force to some component of the engine (typically pistons or turbine blades). The applied force moves the component over a distance, transforming chemical energy into mechanical energy.
In some engine systems, a source of heat is required for the proper or optimal function of one or more engine components or to heat the fuel itself. For example, many engine systems developed by the assignee of the present application, Transonic Combustion, Inc., utilize a heating source to elevate the temperature of the fuel to or toward supercritical conditions, which is beneficial for several reasons. These engine systems utilizing fuel in supercritical conditions often also utilize a cooled exhaust gas recirculation (“EGR”) system as a method of controlling combustion and subsequent emissions
Fuel heating and EGR cooling components in an engine system, such as described above, in various embodiments are interfaced with two separate and independent systems. The EGR is typically cooled by heat exchange with an engine coolant, which increases the heat of the coolant and necessitates greater radiator and coolant capacity in the engine system. The fuel heater is typically heated electrically, with electrical energy being provided by the alternator. This extracts energy that would otherwise be utilized to power the engine, reducing overall fuel efficiency. Additionally, the wire diameter and necessary electronics required to utilize and control such a fuel heating system add significant mass to the vehicle.
An efficient method and system for utilizing a fuel heating system together with an EGR cooling system is therefore needed.
Described herein are methods and systems for efficiently utilizing a fuel heating system together with an EGR cooling system. Embodiments incorporating features of the present invention utilize the available waste heat energy in the exhaust gas recirculation stream of an engine to heat the fuel. In certain embodiments, fuel is heated in this manner to supercritical or near supercritical levels, for example, by utilizing waste heat from the exhaust gas upstream of an EGR component, such as an EGR cooler, to heat the fuel to a desired temperature. In some embodiments this is accomplished by replacing a conventional EGR cooler with a fuel heat exchanger/EGR cooler. Many different arrangements are possible in designing fuel heat exchanger/EGR coolers such as shown by various alternative embodiments herein below.
The present disclosure describes various methods and systems which have several different advantages, some of which are as follows. One advantage of methods and systems according to the present disclosure is that fuel can be heated using heat from the exhaust gas upstream of the EGR cooler which would otherwise be wasted by heat transfer in the cooling stage of the EGR loop. Another advantage of the heat transfer from the exhaust gas to the fuel is that less heat remains in the exhaust gas that subsequently must be cooled by an EGR heat exchanger to reduce the heat remaining in the exhaust gas to acceptable levels for EGR. Yet another advantage is that by using exhaust gas to heat the fuel, the power requirement for various additional components, such as an electric fuel heater, is reduced and could potentially be negligible. This can result in a smaller electric heater being sufficient, thus providing power/performance savings, reduced overall vehicular weight and a longer service life.
Additional advantages of methods and systems disclosed herein include eliminating loss of enthalpy to the turbocharger, increasing packaging efficiency as the EGR loop is typically in an easier to access location, and allowing the fuel heat exchanger to not have to handle the volume of exhaust present at high-load conditions, thus reducing the chance for occurrence of overheating conditions.
In one embodiment disclosed herein, a method for heating fuel in an engine system comprises providing an engine system including a recirculating exhaust gas stream, placing a heat exchanger in the engine system such that the EGR stream passes through and provides waste heat to the heat exchanger, and flowing fuel through the heat exchanger so as to transfer the waste heat from the EGR stream to the fuel.
In another embodiment, a method for heating fuel in an engine system comprises providing an exhaust gas recirculating stream within an engine system, wherein the EGR stream flows through a heat exchanger, and the heat exchanger includes an EGR cooler, such that the exhaust gas recirculating stream provides waste heat to the heat exchanger followed by said EGR cooler, and then flowing fuel through said heat exchanger so as to transfer heat from the EGR stream to the fuel.
These and other further embodiments, features and advantages of the invention would be apparent to those skilled in the art based on the following detailed description, taken together with the accompanying drawings, in which:
The present disclosure is directed to methods and systems efficiently utilizing a fuel heating system together with an EGR cooling system. Embodiments incorporating features of the present invention utilize the available waste heat energy in the exhaust gas recirculation stream of an engine system to heat the fuel.
Adding a fuel heat exchanger/EGR cooler to a conventional EGR cooler can provide many benefits to the engine system, including, but not limited to, utilizing this structure allows fuel heating to be accomplished simultaneously with partial EGR gas cooling using waste EGR heat. An exhaust fuel heater/EGR cooler can be placed in many locations within an engine system as described below, including but not limited to a high pressure EGR loop directly upstream of the turbocharger or in a low pressure loop downstream of the turbocharger. This reduces the heat rejection requirement of the engine coolant and also reduces the electrical power requirements of the fuel heater. In addition, by moving the exhaust and fuel heat exchange components out of the main exhaust stream, there is no loss in enthalpy to the turbocharger, packing becomes easier (as the EGR loop can be in an easier access location) and the fuel heat exchanger does not have to handle the volume of exhaust present at higher load conditions (this can prevent or mitigate the effects of overheating).
In some embodiments of methods and systems incorporating features of the present invention a bypass mechanism, such as a bypass valve can be used. This allows fuel to be bypassed away from the EGR cooler portion of a fuel heat exchanger/EGR cooler during situations wherein exposure to the EGR cooler would be less than ideal, for example, during cold starts. In some embodiments, the bypass mechanism can comprise a variable bypass valve (such as a 3-way valve) that can be proportionally controlled, for example by an ECU with a sensor feedback loop. This proportional control enables the amount of fuel bypassed to a heater portion to be more precisely controlled. It is thus understood that the bypass mechanism can be adjusted such that it is “completely open” or “partially open” in order to vary the amount of fuel that is routed to a different in-line direction.
In some embodiments, when the bypass valve is open, for example, during an engine cold start, the fuel inside the heat exchange portion is exposed to exhaust temperatures without a fuel mass flow rate which improves fuel heating during cold starts. Once an acceptable fuel temperature has been reached (which can be detected by various means, for example, by a sensor feedback loop with the ECU), the fuel bypass mechanism can be closed (i.e. completely closed or proportionally closed) to begin fuel flow through the fuel heat exchanger and any downstream electric fuel heater power can be reduced.
During times when the fuel bypass valve is closed and the fuel is flowing through the heat exchanger and EGR gas temperature is high, the fuel can become overheated. The bypass mechanism can then be adjusted to bypass the fuel away from the fuel heat exchanger to more closely maintain a target fuel temperature. One additional benefit to utilizing a fuel bypass mechanism is that it enables a rapid response to fuel heat exchanger failure. If the fuel heat exchanger fails internally, then the fuel will enter into the EGR cooler and subsequently into the intake manifold, causing the engine to lose control or become damaged. However, a pressure sensor can be utilized, for example, in a feedback loop with an ECU, to determine the presence of a leak and the fuel bypass valve can be adjusted to prevent an excessive amounts of fuel from being released into the EGR cooler.
Throughout this disclosure, the preferred embodiments herein and examples illustrated are provided as exemplars, rather than as limitations on the scope of the present disclosure. As used herein, the terms “invention,” “method,” “system,” “present method,” “present system” or “present invention” refers to any one of the embodiments incorporating features of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “invention,” “method,” “system,” “present method,” “present system,” or “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s).
It is also understood that when an element or feature is referred to as being “on” or “adjacent” another element or feature, it can be directly on or adjacent the other element or feature or intervening elements or features that may also be present. Furthermore, relative terms such as “outer”, “above”, “lower”, “below”, and similar terms, may be used herein to describe a relationship of one feature to another. It is understood that these terms are intended to encompass different orientations in addition to the orientation depicted in the figures.
Although the terms first, second, etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated list items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. For example, when the present specification refers to “a” transducer, it is understood that this language encompasses a single transducer or a plurality or array of transducers. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
In reference to the present application the term, “in communication with” can refer to being in electrical communication with (e.g. a power supply and heater), able to transmit and/or receive information from (e.g. a sensor and an engine control unit (“ECU”)), or able to affect in a significant manner (e.g. a heater in communication with fuel in a given location is able to affect the temperature of that fuel).
In reference to the present application the term, “downstream” or “downstream from,” refers to the position of an object or a site for application of a method that receives the flow of fuel subsequent to another object. For example, if fuel passes through a rail system prior to entering an injector, the injector is said to be “downstream from” the rail system. Likewise, the term “upstream” or “upstream from” refers to the position of an object or a site for application of a method that receives the flow of fuel prior to another object.
Methods and systems disclosed herein can be utilized in any engine system that incorporates internal combustion features and are particularly suited for use in engines utilizing heated fuels. Examples of heated fuel injection systems, including their drawings, schematics, diagrams and related written description, are set forth in, for example, U.S. Pat. No. 8,176,900; U.S. Pat. No. 8,116,963; U.S. Pat. No. 8,079,348; U.S. Pat. No. 7,992,545; U.S. Pat. No. 7,966,990; U.S. Pat. No. 7,945,375; U.S. Pat. No. 7,762,236; U.S. Pat. No. 7,743,754; U.S. Pat. No. 7,657,363; U.S. Pat. No. 7,546,826; and U.S. Pat. No. 7,444,230, which are incorporated herein in their entirety by reference.
Embodiments of the invention are described herein with reference to different views and illustrations that are schematic illustrations of idealized embodiments of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are expected. Embodiments of the invention should not be construed as limited to the particular shapes of the regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing.
An engine system 100 can further comprise a first sensor 116 that can detect EGR pressure and EGR temperature and a second sensor 118 that can detect CAC pressure and CAC temperature. These sensors 116, 118 can be in communication with an ECU which can receive input from the sensors 116 (shown here placed in the location of an EGR valve), 118 (shown here placed near the throttle position), and can provide feedback control to individual engine components. Exhaust exits from the exhaust manifold 102, releasing exhaust in the form of smoke, Nox, CO and CO2. Ambient air can enter into the engine system 100 through an intake element 122, which can be a compressor. Although a particular engine system 100 has been disclosed, it is understood that this engine system is simply an example environment for embodiments incorporating features of the present invention and that many different engine systems can be utilized with methods, devices and systems according to the present disclosure.
The EGR cooler 112 in an engine system 100 can be replaced with a fuel heat exchanger/EGR cooler system 150 best shown in the enlarged view of
The fuel 156 having a first temperature can enter the fuel heat exchanger portion 152 where it can interact with heated exhaust gas from an exhaust manifold 102. The fuel can exit the fuel heat exchanger portion having a second temperature 158 and can further interact with additional elements such as a fuel heater 160, which can further heat the fuel, causing fuel having a third temperature to enter into a rail system 164 and subsequently into a fuel injector 166. The fuel injector 166 can further comprise a heater portion that allows fuel within the fuel injector to be further heated and injected into the combustion chamber through an injector 168 at a fourth temperature.
It is understood that while the heat exchanger and EGR cooler are referred to as separate structures, they can also be integrated structures, for example having the heat exchanger portion 152 and the coolant EGR portion 154 as combined structures located in a single housing.
Referring again to the fuel heat exchanger/EGR cooler 200 shown in
In embodiments of the present invention utilizing fuel under supercritical conditions, supercritical temperatures can still be primarily controlled by the electric heater 160 and the final heat of the fuel immediately prior to injection can still be controlled by a heater within or in communication with the fuel injector body 166 itself.
The fuel heat exchanger/EGR cooler 300 is arranged in a series flow with an EGR bypass mechanism. The EGR bypass mechanism comprises an EGR bypass valve 302 and a bypass tube 304. The arrangement of the fuel heat exchanger/EGR cooler 300 allows for the exhaust gas from the intake manifold 102 to directly bypass the fuel heat exchange portion 152 via bypass tube 304. This allows fuel to flow through the heat exchanger portion 152 directly but not be significantly heated during bypass. This embodiment is similar to the embodiment in
The above initial engine testing concluded that around 20-40% of the total exhaust gas stream is optimal for EGR to achieve NOx emission targets of 1.0 g/kWhr. These test results additionally demonstrated that EGR had the additional benefit of controlling in-cylinder pressure rise rates to less than 10 bar/deg across an engine load range. One advantage of this is that it helps reduce combustion noise associated with the combustion process. Testing was completed at 2000 rpm on a 390 cc single cylinder engine using gasoline fuel and a fuel injection system.
To obtain the results presented in
This application claims the benefit of U.S. Provisional Application Ser. No. 61/647,687 to Michael Frick et al., entitled Heating of Fuel with Exhaust Gas Recirculation, filed on May 16, 2012. This application also claims the benefit of U.S. Provisional Application Ser. No. 61/778,911, to Michael Frick et al., also entitled Heating of Fuel with Exhaust Gas Recirculation, filed on Mar. 13, 2013. Both of these provisional applications are hereby incorporated herein in their entirety by reference, including the drawings, charts, schematics, diagrams and related written description.
| Number | Date | Country | |
|---|---|---|---|
| 61647687 | May 2012 | US | |
| 61778911 | Mar 2013 | US |
