Patent Application
20110303197
The present disclosure generally relates to evaporative emission control systems for internal combustion engines, and more particularly relates to a microcondenser device for an evaporative emission control system associated with an internal combustion engine.
Conventional vehicle fuel systems associated with internal combustion engines typically employ a fuel canister for receiving fuel vapor from a vehicle's fuel tank. The fuel canister is adapted to temporarily retain the received vapor therein to prevent it from being released to the atmosphere. More particularly, fuel vapor can enter the fuel canister from the fuel tank wherein the fuel vapor is absorbed and retained in a carbon bed of the fuel canister. Typically, the retention of the displaced fuel vapor within the fuel canister is only temporary as the fuel vapor retained in the fuel canister is periodically purged to allow the canister to accommodate and absorb additional fuel vapor from the fuel tank. During such purging, the fuel vapor captured by the canister can be sent to the vehicle's engine, and particularly to an induction system of the engine, for combustion.
Various other systems have been proposed to more strictly control containment of fuel vapors and/or improve vehicle efficiency by controlling fuel vapor processing. For example, some systems include a bladder disposed in the vehicle's fuel tank that expands and contracts to control fuel vapor. A pump can be used in association with the bladder for applying pressure to the walls of the bladder. The pressure is applied for purposes of forcing the bladder walls against the fuel contained therein to prevent or limit vapor formation. A fuel canister, as described in the preceding paragraph, can optionally be used in the bladder fuel system for capturing fuel vapor that forms despite the use of the bladder.
Also known is a canisterless evaporative emission control system for an internal combustion engine. One particular known system includes a fuel tank wherein vaporized fuel is generated and a microcondenser device for processing the vaporized fuel received from the fuel tank. The microcondenser device has a heat sink portion formed of carbon foam in thermal communication with a thermoelectric element for removing heat from the heat sink portion. The fuel vapor is processed by passing the fuel vapor through the heat sink portion to remove heat therefrom and condense at least a portion of the fuel vapor to liquid fuel. Drawbacks of this known canisterless control system include significant power consumption requirements for the thermoelectric element and a significant volume of uncondensed fuel vapor passing through the microcondenser device.
According to one aspect, a microcondenser device is provided for an evaporative emission control system associated with an internal combustion engine. The device includes a housing having a lower wall and at least one side wall extending upward from the lower wall. The lower wall and the at least one side wall together define a chamber in the housing. A thermoelectric element is supported by the at least one side wall in spaced relation relative to the lower wall. An inlet is defined in the housing for admitting fuel vapor into the chamber. A condensation outlet is defined in the housing for discharging liquid fuel that is condensed from the fuel vapor in the chamber. A porous heat sink element is received in the chamber for absorbing the fuel vapor admitted through the inlet. The porous heat sink element is in conductive thermal contact with the thermoelectric element.
According to another aspect, a microcondenser device for an evaporative emission control system includes a housing having an inlet for receiving fuel vapor and a condensation outlet for discharging condensed fuel vapor. A porous heat sink element is disposed in the housing and fluidly interposed between the inlet and the condensation outlet for absorbing the fuel vapor received through the inlet. A thermoelectric element is in thermal contact with the thermal heat sink element for removing heat from the fuel vapor absorbed by the porous heat sink element to condense the fuel vapor. At least one support baffle supports the porous heat sink element within the housing.
According to a further aspect, a microcondenser device for an evaporative emission control system includes a housing having an inlet for receiving fuel vapor and a condensation outlet for discharging condensed fuel vapor. A porous heat sink element is disposed in the housing and is fluidly interposed between the inlet and the condensation outlet for absorbing the fuel vapor received through the inlet. A thermoelectric element is in thermal contact with the porous heat sink element for removing heat from the fuel vapor absorbed by the porous heat sink element to condense the fuel vapor. A heat removal assembly is in conductive thermal contact with a hot side of the microcondenser element for removing heat therefrom. The heat removal assembly comprises at least one of: a heat pipe or a liquid cooling circuit.
Referring now to the drawings wherein the showings are for purposes of illustrating one or more exemplary embodiments and not for purposes of limiting same,
One or more sensors can be provided on the intake pipe 14 for monitoring conditions at the intake pipe. For example, the intake pipe 14 can be provided with an intake pipe absolute pressure (PBA) sensor 34 for detecting an absolute pressure (PBA) in the intake pipe 14 and an intake air temperature (TA) sensor 36 for detecting an air temperature (TA) in the intake pipe 14 at positions downstream of the throttle valve 16. These sensors, including sensors 34, 36, can each output a signal corresponding to a sensed condition (e.g., PBA or TA) and supply the outputted signal to the ECU 20. In addition, the fuel tank 26 can be provided with one or more sensors for monitoring specific conditions associated therewith, including, for example, a tank pressure (PTANK) sensor 38 for detecting a pressure (PTANK) in the fuel tank, a fuel temperature (TGAS) sensor 40 for detecting a fuel temperature (TGAS) in the fuel tank 26, and a fuel level sensor 42 for detecting a fuel level (i.e., a remaining fuel amount) in the fuel tank 26. Like the other sensors described herein, the fuel tank sensors, including sensors 38, 40, 42, can each output a signal corresponding to a sensed condition at the fuel tank 26 and provide the signal to the ECU 20.
Additional sensors can be provided on or in association with the engine 12. More particularly, an engine rotational (NE) sensor 44 for detecting an engine rotational speed (NE) can be disposed near the outer periphery of a camshaft or crankshaft (both not shown) of the engine 12. There can also be provided an engine coolant temperature sensor 46 for detecting a coolant temperature (TW) of the engine 12 and an oxygen concentration sensor (also referred to as a “LAF sensor”) 48 for detecting an oxygen concentration in exhaust gases from the engine 12. Detection signals from these sensors 44, 46, 48 can be supplied to the ECU 20. The LAF sensor 48 can function as a wide-area air-fuel ratio sensor adapted to output a signal substantially proportional to an oxygen concentration and exhaust gases (i.e., proportional to an air-fuel ratio of air-fuel mixture supplied to the engine 12).
The evaporative emission control system 10 further includes a microcondenser device 50. With additional reference to
As will be described in more detail below, the microcondenser device 50 can also include a thermoelectric element 66 for condensing fuel vapors admitted through the inlet 54. The thermoelectric element 66 can be a Peltier microelement that employs or uses the Peltier effect to condense evaporative or vaporized fuel received from the fuel tank 26 via the vapor line 58. Advantageously, providing the thermoelectric element 66 as a Peltier microelement can be effective for condensing vaporized fuel from the fuel tank 26 while being of a small size and requiring minimum power consumption thereby not taxing the spatial layout of the vehicle or its electrical system. Operation of the microcondenser device 50 can occur as described in U.S. Pat. No. 7,527,045, which is expressly incorporated in its entirety herein.
With additional reference to
The thermoelectric element 66 is supported by the at least one side wall (i.e., side walls 72-78 in the embodiment illustrated in
A porous heat sink element 100 can be disposed in the housing 52, and particularly received in the chamber 80 of the housing 52. The porous heat sink element is fluidly interposed between the inlet 54 and the condensation outlet 56 for absorbing the fuel vapor received or admitted through the inlet 54. The thermoelectric element 66 can be in thermal contact with the porous heat sink element 100 for removing heat from the fuel vapor absorbed by the porous heat sink element 100 to condense the fuel vapor. In particular, the porous heat sink element 100 can be in conductive thermal contact with the thermoelectric element 66. In addition to be interposed between the inlet 54 and the condensation outlet 56, the porous heat sink element 100 is also fluidly interposed between the inlet 54 and the vapor outlet 62, which discharges fuel vapor that remains vaporized after passing through the porous heat sink 100.
In one embodiment, the porous heat sink element 100 is a carbon foam heat sink element. Being formed of carbon foam provides advantages such as higher thermal conductivity and greater surface area per unit volume than conventional heat sinks and/or heat sinks formed of aluminum fins. Moreover, the carbon foam heat sink element 100 has greater heat transfer efficiency than conventional arrangements which results in the overall electric load needed to power the microcondenser device 50 being considerably lower than would be necessary if the heat sink were formed with conventional fins.
In the illustrated embodiment, a copper plate 102 is interposed between the porous heat sink element 100 and the thermoelectric element 66. Accordingly, conductive heat transfer occurs from the porous heat sink element 100, then to the copper plate 102, and next to the thermoelectric element 66. Using the copper plate 102 allows for improved heat transfer from the porous heat sink element 100 to the thermoelectric element 66. In particular, the copper plate 102 can have an improved flatness, particularly on a side 104 that interfaces with the porous heat sink element 100 (i.e., improved flatness compared to other efficient heat transfer materials). In addition, a thermal paste 106 can be interposed between at least one of the copper plate 102 and the thermoelectric element 66 or the copper plate 102 and the porous heat sink element 100. In the illustrated embodiment, as shown, thermal paste 106 is interposed between both the copper plates 102 and the thermoelectric element 66 and the copper plate 102 and the porous heat sink element 100. The thermal paste 106 facilitates better heat transfer between conductive elements of the microcondenser device 50.
As shown in the illustrated embodiment, the copper plate 102 is supported by the shoulder 84 and the thermoelectric element 66 is supported on top of the copper plate 102. Together, the thermoelectric element 66 and the copper plate 102 are nestably received within the recess 82 defined in the housing 52. Particularly, in the illustrated embodiment, these elements 66, 102 form an upper side of the housing 52 and close the chamber 80 defined by the housing 52. A seal 108 can be interposed between the underside 104 of the copper plate 102 and the shoulder 84 defined in each of the side walls 72-78. The nesting relation of the copper plate 102 and the thermoelectric element 66 within the recess 82 and/or the provision of the seal 108 is believed to advantageously reduce or eliminate frost or fog formation on the microcondenser device 50, and particularly the housing 52 thereof, which improves efficiency of the device 50 (i.e., less power is needed to operate the device). [Question for inventors: what material is the seal 108 formed of?]
Also to improve efficiency of the microcondenser device 50, the housing 52 can be formed of a plastic material. This provides the housing 52 with a low heat mass body and a low thermal conductivity body material. The particular plastic material employed for the housing 52 can have sufficient rigidity while otherwise reducing the amount of energy needed for the thermoelectric element 66 to cool vaporized fuel passing through the porous heat sink element 100. Using plastic also provides an additional minimal weight benefit through the use of a lighter material.
Specifically, for example, the body material of the housing 52 can be polyamide, polyacetal, PEI, PPS, or any other fuel-resistant plastic material providing for low heat loss and/or low thermal mass. In addition, to further limit thermal loss to the environment, an insulation or an insulating layer can be disposed one of: around an exterior of the housing 52 or inside the housing around the porous heat sink element 100. In the illustrated embodiment, a foam insulating layer 110 is shown provided around an exterior of the housing 52. Alternatively, other insulating materials can be applied to the exterior of the housing 52. For example, aerogels or other foams can be applied to an exterior of the housing for insulating the housing from thermal losses to the surrounding environment.
The microcondenser device 50 can additionally include at least one support baffle supporting the porous heat sink element 100 within the housing 52. As will be described in more detail below, the at least one support baffle supports the porous heat sink element 100 in an elevated position (i.e., in spaced apart relation) from the lower wall 70 and in conductive thermal contact with the thermoelectric element 66. As will also be described in more detail below, the at least one support baffle can urge the porous heat sink element 100 toward the thermoelectric element 66 and/or into thermal contact with the thermoelectric element 66. The at least one support baffle can be one or more baffles shaped or configured to provide various sub-chambers within the chamber 80 of the housing 52. The baffles can be formed of a foam insulation material, such as a Teflon foam insulation, for example, which provides the baffles with some resiliency and enable the stacked baffles to urge the porous heat sink element 100 toward the copper plate 102, which assists in efficient heat transfer therebetween.
In the illustrated embodiment, the at least one support baffle includes a plurality of stacked baffles, which facilitates the baffles urging or supplying support pressure against the porous heat sink element 100. Whether stacked, shaped or otherwise configured, the one or more support baffles can be arranged to efficiently direct fuel vapor into the porous heat sink element 100 and/or to facilitate efficient liquid drainage (i.e., condensed fuel vapor). In the illustrated embodiment, the plurality of baffles includes a base baffle 112 having a cut out or recess 114 accommodating the condensation outlet 56. Intermediate baffles 116, 118, 120, 122 are stacked on the base baffle 112. In particular, intermediate baffles 116, 118 are together stacked and form a first pair of stacked baffles. Likewise, intermediate baffles 120, 122 are together stacked and form a second pair of stacked baffles. Thus, the baffles 116-122 are arranged in stacked pairs wherein the first pair of stacked baffles 116, 118 are together stacked adjacent the inlet 54 and the second pair of baffles 120, 122 are stacked adjacent the vapor outlet 62, and wherein the pairs of stacked baffles 116, 118 and 120, 122 flank the condensation outlet 56.
The baffles can be arranged so as to direct gas and/or liquid flow within the microcondenser device 50 and support the porous heat sink element 100. For example, upper baffles 124, 126 are disposed in stacked relation above the intermediate baffles 116-122 and can directly support the porous heat sink element 100. In particular, the illustrated embodiment, the upper baffle 124 is stacked on the first pair of intermediate baffles 116, 118 adjacent the vapor inlet 54 and the upper baffle 126 is stacked on the second pair of intermediate baffles 120, 122 adjacent the vapor outlet 62. Like the intermediate baffles 116-122, the upper baffles 124, 126 can be laterally spaced apart from one another to flank the condensation outlet 56.
In the illustrated embodiment of
The baffles also define a condensation chamber 130 vertically between the condensation outlet 56 and the porous heat sink element 100. As shown, the condensation chamber 130 is disposed below the porous heat sink element 100. This allows gravity to assist in removing condensed fuel from the porous heat sink element 100 and directing the same to the condensation outlet 56. The upper baffle 124 is smaller in the illustrated embodiment that the upper baffle 126, which defines an expanded area 132 of the condensation chamber 130. The expanded area 132 facilitates gravitational removal of condensed fuel from the porous heat sink element 100 on a side of the condensation chamber 130 adjacent the vapor inlet 54. [is this correct?]
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Advantageously, the microcondenser devices described herein can provide improved efficiencies which allow the devices to have smaller footprints when employed in a vehicle electrical system. It will be appreciated that various of the above-disclosed and other features and functions, or alternatives or varieties thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
