Patent Application
20140352656
The present invention relates generally to dual fuel internal combustion engines, and more particularly is concerned with systems and methods for control of intake flow through asymmetric intake passages connected to respective intake ports of a cylinder of a dual fuel internal combustion engine.
A dual fuel engine is an engine that includes a first fuel source that is utilized as the sole fuel source during certain operating conditions and a second fuel source that is integrated with the first fuel source at other operating conditions. In certain applications, the first fuel source is a diesel fuel and the second fuel source is natural gas. The diesel fuel provides the initial, low load levels of operation and is used for ignition for the natural gas at higher load operations. The substitution of natural gas for diesel fuel improves high load performance and emissions reduction, particularly when the engine is employed at locations where natural gas is abundant or available at low cost.
When the engine is operating in dual fuel mode, natural gas is introduced into the intake system. The air-to-natural gas mixture from the intake is drawn into the cylinder, just as it would be in a spark-ignited engine, but with a leaner air-to-fuel ratio. Near the end of the compression stroke, diesel fuel is injected, just as it would be in a traditional diesel engine. The diesel fuel ignites, and the diesel combustion causes the natural gas to burn. The dual fuel engine combusts a mixture of air and fuel in the cylinders to produce drive torque. A dual fuel engine can operate either entirely on diesel fuel or on the substitution mixture of diesel and natural gas, but cannot operate on natural gas alone. However, the dual fuel engine delivers the same power density, torque curve and transient response as the base diesel engine does.
While prior single fuel engine systems have employed devices that provide swirl and tumble characteristics to the intake flow, such devices are limited in the types of intake flow conditions that are created and have not been employed or controlled for operation of dual fuel engine systems. Thus, there remains a need for additional improvements in systems and methods for providing and controlling intake flow to the intake ports of dual fuel internal combustion engines that, for example, optimize operation, performance, and/or fuel economy.
Unique systems and methods are disclosed for dual fuel engines having a plurality of cylinders and at least two intake passages connected to respective intake ports of each cylinder. The intake passages are configured asymmetrically relative to one another, with one intake passage configured to produce swirl characteristics in the charge flow to the respective cylinder and the other intake passage configured to produce tumble characteristics in the charge flow to the respective cylinder.
In various embodiments, at least one of the intake passages also includes a throttle that is actuatable to control the characteristics of the charge flow through the intake passage to the cylinder in response to engine operating conditions. Accordingly, various charge flow characteristics to each cylinder can be created by controlling the throttle(s) in the intake passages. The throttles can be controlled so that the charge flow in the cylinders includes one or more of a high swirl and high tumble characteristic, a low swirl and a low tumble characteristic, a high swirl and low tumble characteristic, a low swirl and high tumble characteristic, a low restriction characteristic for maximum intake flow, a high restriction characteristic for minimum intake flow, and intermediate swirl or tumble characteristics with one of high, intermediate or low tumble or swirl characteristics. The engine operating conditions include any one or more of the operating mode of the internal combustion engine, the gas substitution rate, the quality of the fuel or fuels that provided to the cylinders, the lambda value of the exhaust output, knock conditions, mis-fire conditions, cylinder balance, exhaust output temperatures, load shedding conditions, and emergency shutdown conditions, among others
In other various embodiments, the throttles can be in the form of a plate that when closed covers all, a substantial portion, a majority, or less than half of the cross-sectional flow area defined by the intake passage. The plates may include flat sides, one or more contoured sides, perforated sides, square shape, oval shape, circular shape, or other shape. Each of the throttles can be electronically controlled with an actuator connected to an engine controller that is configured to provide throttle command signals to the actuator to position the throttles to provide the desired amount of charge flow with tumble and/or swirl characteristics to each cylinder in response to engine operating conditions.
These and other aspects, embodiments, forms, features and characteristics of the systems and methods disclosed herein as discussed further below.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein.
With reference to
Engine 30 includes an engine block 70 that at least partially defines the cylinders 31. A plurality of pistons (not shown) may be slidably disposed within respective cylinders 31 to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head 303 (
In one embodiment, engine 30 is a four stroke engine. That is, for each complete engine cycle (i.e., for every two full crankshaft rotations), each piston of each cylinder 31 moves through an intake stroke, a compression stroke, a combustion or power stroke, and an exhaust stroke. Thus, during each complete cycle for the depicted six cylinder engine, there are six strokes during which air is drawn into individual combustion chambers from intake supply conduit 26 and six strokes during which exhaust gas is supplied to exhaust manifold 32.
The engine 30 includes cylinders 31 connected to the intake system 22 to receive a charge flow and connected to exhaust system 24 to release exhaust gases produced by combustion of the primary and/or secondary fuels. Exhaust system 24 may provide exhaust gases to a turbocharger 46, although a turbocharger is not required. In still other embodiments, multiple turbochargers are included to provide high pressure and low pressure turbocharging stakes that compress the intake flow.
Furthermore, exhaust system 24 can be connected to intake system 22 with one or both of a high pressure exhaust gas recirculation (EGR) system 50 and a low pressure EGR system 60. EGR systems 50, 60 may include a cooler 52, 62 and bypass 54, 64, respectively. In other embodiments, one or both of EGR systems 50, 60 are not provided. When provided, EGR system(s) 50, 60 provide exhaust gas recirculation to engine 30 in certain operating conditions. In any EGR arrangement during at least certain operating conditions, at least a portion the exhaust output of cylinder(s) 31 is recirculated to the engine intake system 22. In the high pressure EGR system 50, the exhaust gas from the cylinder(s) 31 takes off from exhaust system 24 upstream of turbine 48 of turbocharger 46 and combines with intake flow at a position downstream of compressor 50 of turbocharger 46 and upstream of an intake manifold 28 of engine 30. In the low pressure EGR system 60, the exhaust gas from the cylinder(s) 31a-31f takes off from exhaust system 24 downstream of turbine 48 of turbocharger 46 and combines with intake flow at a position upstream of compressor 50 of turbocharger 46. The recirculated exhaust gas may combine with the intake gases in a mixer (not shown) of intake system 22 or by any other arrangement. In certain embodiments, the recirculated exhaust gas returns to the intake manifold 28 directly.
Intake system 22 includes one or more inlet supply conduits 26 connected to an engine intake manifold 28, which distributes the charge flow to cylinders 31 of engine 30. Exhaust system 24 is also coupled to engine 30 with an engine exhaust manifold 32. Exhaust system 24 includes an exhaust conduit 34 extending from exhaust manifold 32 to turbine 48 of turbocharger 46. An aftertreatment system (not shown) can be connected with an outlet conduit 68. The aftertreatment system may include, for example, oxidation devices (DOC), particulate removing devices (DPF, CDPF), constituent absorbers or reducers (SCR, AMOX, LNT), three-way catalysts for stoichiometric spark ignited engines, attenuation devices (mufflers), controllers, etc., if desired.
In one embodiment, exhaust conduit 34 is flowed coupled to exhaust manifold 32, and may also include one or more intermediate flow passages, conduits or other structures. Exhaust conduit 34 extends to turbine 48 of turbocharger 46. Turbocharger 46 may be any suitable turbocharger known in the art, including variable-geometry turbine turbochargers and waste-gated turbochargers. Turbocharger 46 may also include multiple turbochargers. Turbine 48 is connected via a shaft 49 to compressor 50 that is flow coupled to inlet supply conduit 26. Inlet supply conduit 26 may include a charge air cooler 36 downstream from compressor 50 and the EGR mixing location(s), if provided. In another embodiment, a charge air cooler 36 is located in the intake system 22 upstream of the EGR mixing locations.
In operation of internal combustion engine system 20, fresh air is supplied through inlet air supply conduit 23. The fresh air flow or combined flows can be filtered, unfiltered, and/or conditioned in any known manner, either before or after mixing with the EGR flow from EGR systems 50, 60 when provided. The intake system 22 may include components configured to facilitate or control introduction of the charge flow to engine 30, and may include an induction valve or throttle (not shown), one or more compressors 50, and charge air cooler 36. The induction valve may be connected upstream or downstream of compressor 50 via a fluid passage and configured to regulate a flow of atmospheric air and/or combined air/EGR flow to engine 30. Compressor 50 may be a fixed or variable geometry compressor configured to receive air or combined flow from the induction valve and compress the air or combined flow to a predetermined pressure level before engine 30. Charge air cooler 36 may be disposed within inlet air supply conduit 26 between engine 30 and compressor 50, and embody, for example, an air-to-air heat exchanger, an air-to-liquid heat exchanger, or a combination of both to facilitate the transfer of thermal energy to or from the flow directed to engine 30. The ambient air or combined air/EGR flow is pressurized with compressor 50 and sent through charge air cooler 36 and supplied to engine 30 through intake supply conduit 26 to engine intake manifold 28.
With reference to
The fueling from the first fuel source 102 is controlled to provide the sole fueling at certain operating conditions of engine 30, and fueling from the second fuel source 104 is provided to substitute for fueling from the first fuel source 102 at other operating conditions to provide a dual flow of fuel to engine 30. In embodiments where the first fuel source 102 is diesel fuel and the second fuel source 104 is natural gas, a control system including controller 200 is configured to control the flow of liquid diesel fuel from first source 102 and the flow of gaseous fuel from second source 104 in accordance with engine speed, engine loads, intake manifold pressures, and fuel pressures, for example. One example of a gas substitution control system and method for a dual fuel engine is disclosed in PCT Publication No. WO 2011/153069 published on Dec. 8, 2011, which is incorporated herein by reference.
A direct injector, as utilized herein, includes any fuel injection device that injects fuel directly into the cylinder volume, and is capable of delivering fuel into the cylinder volume when the intake valve(s) and exhaust valve(s) are closed. The direct injector may be structured to inject fuel at the top of the cylinder or laterally of the cylinder. In certain embodiments, the direct injector may be structured to inject fuel into a combustion pre-chamber. Each cylinder 31, such as the illustrated cylinders 31a-d in
A port injector, as utilized herein, includes any fuel injection device that injects fuel outside the engine cylinder in the intake manifold to form the air-fuel mixture. The port injector sprays the fuel towards the intake valve. During the intake stroke, the downwards moving piston draws in the air/fuel mixture past the open intake valve and into the combustion chamber. Each cylinder 31 may include one or more port injectors 118a-118d, respectively. Although not shown in
In certain embodiments, each cylinder 31 includes one of a port or direct injector that is capable of providing all of the designed primary fueling amount from first fuel source 102 for the cylinders 31 at any operating condition. Second fuel source 104 provides a flow of a second fuel to each cylinder 31 through a natural gas injector upstream of intake manifold 28 or by at least one additional port or direct injector at cylinders 31 to provide a second fuel flow to the cylinders 31 to achieve desired operational outcomes, such as improved efficiency, improved fuel economy, improved high load operation, and other outcomes.
One embodiment of system 20 includes fuel system 21 that includes at least one fuel source 102 to provide a primary fuel flow to all the cylinders 31 and a second fuel source 104 that provides a second fuel flow to all the cylinders 31 in addition to the primary fuel flow under certain operating conditions. First fuel source 102 includes a first fuel pump 105 that is connected to controller 200, and the second fuel source 104 includes a second fuel pump 106 that is connected to controller 200. Each of the cylinders 31 includes an injector, such as direct injectors 116a-116d associated with each of the illustrated cylinders 31a-31d of
Furthermore, cylinders 31a-31d may include a second injector, such as port injectors 118a-118d, electrically connected with controller 200. Second fuel pump 106 is connected to port injectors 118a-118d with a second fuel line 110. A control valve 112 can be provided in fuel line 110 and/or at one or more other locations in fuel system 21 that is connected to controller 200. Second fuel pump 106 is operable to provide a second fuel flow from second fuel source 104 in an amount determined by controller 200 that achieves a desired power and exhaust output from cylinders 31. In an alternative embodiment, in lieu of port injectors 118a-118d, an injector 114 is provided at the inlet to compressor 150 and is operable along with second fuel pump 106 to provide the second flow of fuel through fuel line 108 to the intake system 22 for transport to cylinders 31. In still another embodiment, second fuel pump 106 is omitted and fuel is supplied to injector 114 under pressure from a pressurized second fuel source 104. The fuel pumps 105, 106, control valve(s) 112, and/or injectors 114, 116, 118 can be operable to regulate the amount, timing and duration of the flows of the first and second fuels to cylinders 31 to provide the desired power and exhaust output.
Referring to
First intake port 302 is connected to a first intake passage 318 and second intake port 304 is connected to a second intake passage 320. Intake passages 318, 320 can be formed by separate tube members, by a dividing wall 322 in a single tube member or tube member portion 324, or a combination thereof such as shown in
Each of the intake passages 318, 320 includes a throttle arrangement to control the amount of intake charge flow therethrough. In the illustrated embodiment, first intake passage 318 includes a first throttle 326 and second intake passage 320 includes a second throttle 328. Each of throttles 326, 328 is connected to respective ones of first and second actuators 330, 332 that are electronically connected to and controlled by controller 200.
Furthermore, intake passage 318, 320 include one or more flow characteristic inducing elements 334, 336 that induce a characteristic to the charge flow passing therethrough. In the illustrated embodiment, first intake passage 318 includes a tumble flow inducing feature 334 that creates a tumble characteristic to the charge flow entering through first intake port 304. Second intake passage 320 includes a swirl flow inducing feature 336 that creates a swirl characteristic to the charge flow entering through second intake port 304. Flow characteristic inducing elements 334, 336 can be formed by, for example, one or more protuberances in the respective intake passage that direct the charge flow as shown. It is further contemplated that the flow characteristic inducing elements 334, 336 can be formed by valves, gates, the intake passage shape, or other suitable means.
As further shown in
Referring to
Referring to
In one embodiment, throttles 326, 328 are each formed by a plate-type structure mounted to a shaft 327, 329, respectively, that is connected to the respective actuator 330, 332. One or both of the plates can cover all or substantially all (more than 90%) of the respective charge flow area 319, 321 in the closed position. Alternatively, one or both of the plates can cover a major portion (50% or more) of the respective charge flow area 319, 321 in the closed position. The plate structures of throttles 326, 328 can be solid as shown, or include one or more perforations. The plate structures can also include one or more major surfaces (surfaces that face toward or away from the flow direction in the closed position) that are flat or contoured. The outer perimeter of the plates can define an oval, round, square, irregular, or other suitable shape.
In the throttle positions of
Furthermore, one or more of intake passages 318, 320 can be configured without a throttle 326, 328. For example, in
As discussed above, the positioning of each of throttles 326, 328 is provided by the respective actuator 330, 332 via control commands from controller 200. In certain embodiments of the systems disclosed herein, controller 200 is structured to perform certain operations to control engine operations and fueling of cylinders 31 with fueling system 21 to provide the desired speed and torque outputs. In certain embodiments, the controller 200 forms a portion of a processing subsystem including one or more computing devices having memory, processing, and communication hardware. The controller 200 may be a single device or a distributed device, and the functions of the controller 200 may be performed by hardware or software. The controller 200 may be included within, partially included within, or completely separated from an engine controller (not shown). The controller 200 is in communication with any sensor or actuator throughout the systems disclosed herein, including through direct communication, communication over a datalink, and/or through communication with other controllers or portions of the processing subsystem that provide sensor and/or actuator information to the controller 200.
Certain operations described herein include operations to determine one or more parameters. Determining, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g. a voltage, frequency, current, or PWM signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a non-transient computer readable storage medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.
The schematic flow description which follows provides an illustrative embodiment of a method for providing intake passage throttle control to the intake ports of cylinders 31 of a dual fuel internal combustion engine system 20. As used herein, a dual fuel system 21 is a fueling system in which a dual fueling mode is provided where each of the cylinders 31 of engine 30 receives a first fuel flow during all operating conditions and a second fuel flow in addition to the first fuel flow under certain other operating conditions. However, it is contemplated that the dual fueling system 21 can be operated in a single fuel mode from first fuel source 102 upon operator selection. Operations illustrated are understood to be exemplary only, and operations may be combined or divided, and added or removed, as well as re-ordered in whole or part, unless stated explicitly to the contrary herein. Certain operations illustrated may be implemented by a computer such as controller 200 executing a computer program product on a non-transient computer readable storage medium, where the computer program product comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.
In
Based on engine operating conditions determined at operation 404, procedure 400 continues at operation 406 in which charge flow characteristics are determined at operation 408 in response to the engine operating condition(s). For example, under certain operating conditions, charge flow in each cylinder 31 with a high swirl characteristic and a high tumble characteristic may be desired. Certain other operating conditions may dictate a high swirl characteristic and low tumble characteristic to the charge flow in each cylinder 31. Still other operating conditions may dictate a low swirl characteristic and high tumble characteristic to the charge flow in each cylinder 31. Other operating conditions may dictate a low swirl characteristic and low tumble characteristic to the charge flow in each cylinder 31. It is further possible to determine charge flow characteristics that are intermediate the high and low swirl characteristics and the high and low tumble characteristics.
In one specific embodiment with a dual fuel internal combustion engine system 20, there are operating conditions in which fueling to the plurality of cylinders 31 is provided entirely from first fuel source 102 such as at low load conditions. In one embodiment, low load conditions range from about 0% to 25% of the maximum load of engine 30. However, in other embodiments, fuel can be provided from first fuel source 102 and second fuel source 104 in low load conditions depending on engine characteristics, operating conditions, and application in which the engine is employed. Other engine operating conditions are dual fueling conditions in which fueling is provided to the plurality of cylinders 31 from the first fuel source 102 and the second fuel source 104. In one specific embodiment, an intermediate loading of engine 30 utilizes the first fuel at a first generally constant amount and the second fuel at a variable amount that increases as the loading on engine 30 increases. In one example, intermediate loading conditions of engine 30 ranges from about 25% to 90% of the maximum engine load. During this intermediate loading, the second fuel is substituted for the first fuel to meet the load requirements exceeding 25%, and the second fuel amount increases as the load increases to meet output demand, while the first fueling rate remains generally constant over the intermediate loading to provide desired combustion properties. A high loading condition of the dual fuel operating mode utilizes an increasing amount of both the first and second fuels to meet output requirements. In one specific example, the high loading condition ranges from about 90% to 100% of maximum engine loading.
In one implementation, the operator can select whether to operate in a single fuel mode so that fuel is provided entirely from first fuel source 102 or a dual fuel mode in which fuel from both sources 102, 104 can be employed at least during certain operating conditions. In a specific embodiment where first fuel 102 is diesel fuel and a single fuel mode is selected, at low load and/or cold start conditions, engine 30 operates only with diesel fuel from first fuel source 102. In these low load/cold start conditions, a high swirl characteristic and no or low tumble characteristic to the charge flow can be provided to ensure desired mixing of the first fuel with the charge flow for combustion in combustion chamber 31. As the engine load increases to the rated load, the other intake port inducing swirl flow can be opened to provide additional air flow to meet demand.
Once the charge flow characteristics are determined at operation 406, procedure 400 continues at operation 408 in which throttle commands are determined that position or orient throttles 326, 328 at the appropriate positions in intake passages 318, 320 to produce the desired charge flow characteristics in response to the engine operating conditions. The determined throttle commands are then communicated to actuators 330, 332 at operation 410 so that throttles 326, 328 are moved to the appropriate position or positions to produce the desired charge flow characteristics for the charge flow through each of the intake passages 318, 320 to the respective cylinder 31. Procedure 400 ends at operation 412 when operation of engine 30 is terminated.
Various aspects of the systems and methods disclosed herein are contemplated. For example, one aspect relates to a method that includes operating an internal combustion engine system. The internal combustion engine includes an engine with a plurality of cylinders and at least two fuel sources operably connected to the internal combustion engine system to provide a first fuel and a second fuel to each of the plurality of cylinders. The internal combustion engine system further includes an exhaust system and an intake system. The intake system is coupled to each of the plurality of cylinders with a first intake passage and a second intake passage connected to corresponding ones of first and second intake ports of the respective cylinder to provide a charge flow from the intake system to a combustion chamber of the respective cylinder. The method further includes inducing a tumble characteristic to the charge flow in the first intake passage; inducing a swirl characteristic to the charge flow in the second intake passage; determining an engine operating condition according to engine operating parameters; and for each of the plurality of cylinders, controlling a first throttle in the first intake passage and a second throttle in the second intake passage in response to the engine operating condition to regulate the charge flow from the first intake passage with the tumble characteristic to the combustion chamber and to regulate the charge flow from the second intake passage with the swirl characteristic to the combustion chamber.
According to another aspect, a system is disclosed that includes an engine having a plurality of cylinders, an intake system configured to direct a charge flow to all of the plurality of cylinders, an exhaust system configured to receive exhaust from a first portion of the plurality of cylinders and outlet the exhaust to atmosphere, a dedicated exhaust gas recirculation system configured to receive exhaust from a second portion of the plurality of cylinders and direct the exhaust from the second portion of the plurality of cylinders to the intake system, and a fuel system including at least one fuel source that is connected to each of the plurality of cylinders to provide a first fuel flow, the at least one fuel source further being connected to the second portion of the plurality of cylinders to provide a second fuel flow in addition to the first fuel flow.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.
In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.
