Patent Application
20150192046
The present disclosure relates generally to an after-treatment system for engines. More specifically, the present disclosure relates to the positioning of an injector unit in the after-treatment system.
After-treatment systems are generally employed in an internal combustion engine of a machine for treatment of exhaust gases. An after-treatment system commonly includes a number of injector units that inject a reductant fluid into a stream of exhaust gas. During operations, an injector tip of an injector unit is subjected to considerably high temperature conditions by the exhaust gas, which may damage the injector tip. Therefore, the after-treatment system generally employs a cooling circuit around the injector tip to inhibit the effects of such high temperatures. The cooling circuit commonly includes a coolant tank and a fluid pump and is adapted to circulate coolant within the injector unit. For this purpose, the injector unit includes a first port in fluid communication with the coolant tank and a second port in fluid communication with the fluid pump.
In conventional after-treatment systems, the injector unit is mounted on the after-treatment system, such that the first port and the second port are at a same height in reference to a horizontal axis of the engine. During hot engine shutdowns, the fluid pump may be inoperative (the fluid pump runs via the engine, therefore the fluid pump stops operation, when engine speed reaches 0 rpm) and the flow of coolant to the injector unit may temporarily cease, which may cause the coolant left in the injector units to evaporate. As a result, the vaporized coolant may flow through the first port to the coolant tank, exert vapor pressure on the condensed coolant of the coolant tank, and may cause the condensed coolant to replenish the fluid within the injector unit. However, in certain conditions, such as an operation of the machine on unleveled terrains, the second port may be tilted upwards relative to the first port. In such conditions, a considerable amount of vaporized coolant may unfavorably flow out or escape through the second port towards the fluid pump, while a relatively lesser quantity of vaporized coolant may flow to the coolant tank. As a result, a reverse flow of vaporized coolant is minimized, substantially reducing the capacity to cool the fuel injectors during a hot engine shutdown. This may result in heat up and damage to the injector tip of the injector unit.
Various aspects of the present disclosure illustrate an after-treatment system for an engine. The engine has a horizontal axis and a vertical axis. The after-treatment system includes a housing assembly, a coolant circuit with a coolant tank, and at least one injector unit. The injector unit includes a first port and a second port. The first port is in fluid communication with the coolant tank of the cooling circuit. The second port is in fluid communication with the first port. Moreover, the injector unit is mounted on the housing assembly, such that the first port is positioned substantially vertically above the second port, along the vertical axis. In addition, the injector unit includes a datum line that passes through the first port and the second port. An included angle defined by the datum line relative to the horizontal axis is generally about 60 degrees, when a width of the housing assembly is parallel to the horizontal axis.
Referring to
The engine 12 may be a multi-cylinder engine adapted to be employed in the machine (not shown), such as but not limited to, a construction machine, a marine machine, and/or a forest machine. For example, off-highway trucks, mining trucks, skid steer loaders, wheel loaders, track-type tractors, excavators, dozers, wheel loaders, and/or the like. Although the present disclosure proposes the deployment of a multi-cylinder diesel engine, an equivalent application to other engine types may also be contemplated.
As part of the after-treatment system 10, the DPF 16 may be selected from one of widely available DPF's in the market. The DPF 16 is connected to an exhaust port of the engine 12 and is configured to receive exhaust gas from the engine 12 in a raw, untreated state. Upon reception, the DPF 16 is adapted to filter or separate diesel particulate matter from the inflowing exhaust gas.
The exhaust conduit 20 is fluidly connected to the DPF 16 and is positioned downstream of the DPF 16 (along a gas flow direction, S). The exhaust conduit 20 may be shaped and structured as conventionally known and is adapted to receive a filtered exhaust gas from the DPF 16. The exhaust conduit 20 includes the mixing chamber 21, which typically facilitates a mixing of the filtered exhaust gases from the DPF 16 with a reductant fluid, such as the DEF. Although not limited, typical reductant fluids or DEFs may include anhydrous ammonia, aqueous ammonia, and/or urea.
The SCR 18 is fluidly connected downstream to the exhaust conduit 20 (along the gas flow direction, S). The SCR 18 includes a catalyst (not shown), such as titanium oxide, and other active catalytic components of oxides of base metals to convert nitrogen oxides in the exhaust gases into diatomic nitrogen and water. Base metals may include, but are not limited to, vanadium, molybdenum, and/or tungsten. As with the DPF 16, the SCR 18 may also be chosen from among the widely known SCR units available in the art.
The injector units 22 are arranged along a length of the exhaust conduit 20 and are adapted to periodically inject a predetermined quantity of DEF into the exhaust conduit 20. For this purpose, the injector units 22 are fluidly connected to the DEF tank 24. The injector units 22 include an injector tip 26 that injects the DEF to the exhaust conduit 20. Exhaust gas that flows through the exhaust conduit 20 may heat the injector tip 26 of each of the injector units 22. Therefore, the after-treatment system 10 employs the cooling circuit 14 to cool the injector tip 26 of each of the injector units 22.
The cooling circuit 14 is adapted to facilitate a flow of coolant (along a coolant flow direction, B) through the injector units 22, when actuated. The cooling circuit 14 includes a coolant reservoir 28, a fluid pump 30, and a coolant tank 32. The coolant reservoir 28 may be a storage tank that stores the coolant in liquid form. The fluid pump 30 is fluidly connected to the coolant reservoir 28 and is disposed downstream of the coolant reservoir 28 (along the coolant flow direction, B). The injector units 22 are further in fluid communication with the fluid pump 30 and are disposed downstream to the fluid pump 30 (along the coolant flow direction, B). The coolant tank 32 may be a phase separation tank connected to the injector units 22 and disposed downstream to the injector units 22 (along the coolant flow direction, B).
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During hot engine shutdowns, the fluid pump 30 is deactivated and a coolant flow (along the coolant flow direction, B) is halted (shown in
The mounting and arrangement of the injector unit 22 relative to a housing assembly 38 of the after-treatment system 10 will now be explained in detail. The engine 12 includes a horizontal axis X-X′ and a vertical axis Y-Y′, relative to which the mount and arrangement of the injector unit 22 is described. The after-treatment system 10 includes the housing assembly 38 that houses the DPF 16, the SCR 18, and the exhaust conduit 20 (as shown in
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Therefore, one can understand that, even when the machine (not shown) is operated in a tilted position of 45 degrees (in the clockwise direction and/or the counter-clockwise direction, relative to the horizontal axis X-X′) in side-to-side direction, the first port 34 is always maintained substantially vertically above the second port 36. This would ensure, that during the hot shutdowns of the machine (not shown), the hot coolant around the injector tip 26 is replaced by a cooler coolant and the vaporized hot coolant is expanded in the coolant tank 32.
Furthermore, the present disclosure contemplates mounting of the injector unit 22, such that the included angle, A (when the width, W, of the housing assembly 38 is parallel to the horizontal axis X-X′) is 60 degrees in the clockwise direction. However, a wide range of the included angle, A, may be contemplated. The injector unit 22 generally includes injector jets 40 that facilitates injection of the DEF into the exhaust conduit 20. The included angle, A (when the width, W, of the housing assembly 38 is parallel to the horizontal axis X-X′) is dependent on the number on injector jets 40 of the injector unit 22.
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In operation, the fluid pump 30 circulates the coolant through the injector unit 22, 22′, 22″ (in the coolant flow direction, B). More specifically, the fluid pump 30 supplies the coolant to the injector unit 22, 22′, 22″ via the second port 36, 36′, 36″. As the second port 36, 36′, 36″ is in fluid communication with the first port 34, 34′, 34″, through the coolant jackets (not shown), a flow of coolant through the injector unit 22, 22′, 22″ (in the coolant flow direction, B) is facilitated.
During hot engine shutdowns, the fluid pump 30 temporarily halts a coolant supply to the injector unit 22, 22′, 22″. Therefore, an amount of coolant left in the injector unit 22, 22′, 22″ heats up. In such situations, the resulting vaporized coolant is required to be drawn through the first port 34, 34′, 34″ to the coolant tank 32, to facilitate the reverse flow of the condensed coolant of the coolant tank 32 (along the flow direction, C). For this purpose, the first port 34, 34′, 34″ is required to be kept vertically above the second port 36, 36′, 36″. Although, the embodiment of the injector unit 22 with three injector jets 40 is described in the forthcoming disclosure, similar description for various other embodiments of the injector units 22′, 22″ may also be contemplated. In the current embodiment, the first port 34 of the injector unit 22 is required to be kept vertically above the second port 36, along the vertical axis Y-Y′.
In situations, when the machine (not shown) is on level terrain and the engine 12 is shutdown, the included angle, A (between the datum line D-D′ and the horizontal axis X-X′), is about 60 degrees in the clockwise direction. This facilitates the first port 34 to be maintained above the second port 36. Such an arrangement may cause the vaporized coolant to flow through the first port 34 to the coolant tank 32. Therefore, a resulting reverse flow of the coolant (in the flow direction, C) from the coolant tank 32 to the injector unit 22, is facilitated. This allows for cooling of the injector unit 22, when the engine 12 is shutdown and the machine (not shown) is on a levelled terrain.
In situations, such as when the machine (not shown) is on an unleveled terrain and the housing assembly 38 is at an inclination of 45 degrees in clockwise direction, and the engine 12 is shutdown, the included angle, A is about 105 degrees vertically above, in the clockwise direction. This facilitates the first port 34 to be vertically above the second port 36, along the vertical axis Y-Y′. Such an arrangement may cause the vaporized coolant to flow through the first port 34 to the coolant tank 32. This facilitates the reverse flow (in the flow direction, C) of coolant in liquid form in the coolant tank 32, to flow to the injector unit 22, which results in cooling of the injector unit 22.
In yet other situations, when the machine (not shown) is on unleveled terrain, the housing assembly 38 makes an inclination of 45 degrees in the counter-clockwise direction, and the engine 12 is shutdown, the included angle, A, is about 15 degrees vertically above, in the clockwise direction. This facilitates the first port 34 to be above the second port 36, along the vertical axis Y-Y′. Such an arrangement may cause vaporized coolant to flow through the first port 34 to the coolant tank 32. This facilitates the reverse flow of the condensed coolant (in the flow direction, C) from the coolant tank 32 to the injector unit 22. This results in the cooling of the injector unit 22. Therefore, the mount and arrangement of the injector unit 22, as disclosed in the present disclosure, maintains the reverse flow (in the flow direction, C) of coolant from the coolant tank 32 to the injector unit 22 during engine shutdowns. This facilitates cooling of the injector tip 26 of the injector unit 22 and prevention of damage to the injector tip 26.
It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claim.
