Patent Application
20210025314
The present disclosure generally relates to internal combustion engines configured to be operated with two types of fuel, in particular, to the protection of a NOx sensor provided in an exhaust system of such an internal combustion engine.
Internal combustion engines exhaust a complex mixture of air pollutants. These air pollutants are composed of gaseous compounds such as nitrogen oxides (NOx), and solid particulate matter also known as soot. Due to increased environmental awareness, exhaust emission standards have become more stringent, and the amount of NOx and soot emitted to the atmosphere by an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
In order to ensure compliance with the regulation of NOx, a strategy called selective catalytic reduction (SCR) for treating the exhaust gas can be implemented. SCR is a process where a gaseous or liquid reductant, e.g. ammonia, urea or an urea solution, is injected into the exhaust gas stream of an engine. The reductant reacts with nitrogen oxides in the exhaust gas to form water and nitrogen. Usually, urea is introduced into the exhaust gases in an amount sufficient to provide the degree of NOx reduction desired. The desired amount of the reductant can be controlled by, e.g., an urea injection system, for example, based on a detection by a NOx sensor.
In marine vessels, specifically large ships such as ferries, cruise ships or cargo ships, one or more internal combustion engines of the ship may be configured to operate with heavy fuel oil (HFO) and marine diesel oil (MDO). Due to environmental regulations, it may be necessary to change over between operating fuels. For example, while the ship may run on HFO at sea, it may be necessary to switch to running on MDO near harbors or the like, in order to meet emission standards such as IMO III.
Components in the emissions when operating with HFO, however, may interfere with the operation of a NOx sensor when the ship switches over to run on MDO. For example, a high sulfur content in HFO exhaust gas may damage or inhibit proper operation a NOx sensor. Arrangements such as the ones disclosed in European Patent Application EP 3 431 731 A1, which is assigned to Caterpillar Motoren GmbH & Co., discloses various arrangements with the goal of eliminating or minimizing damage to the operation of the NOx sensor as a result of HFO exhaust gas.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.
According to an aspect of the present disclosure, there is provided a NOx sensor protection system for an internal combustion engine configured to be selectively operated with a first fuel and a second fuel, and having an exhaust pipe configured to receive exhaust resulting from combustion of the first fuel or the second fuel in the internal combustion engine. The NOx sensor protection system includes a flow control device forming an internal chamber and a plurality of ports opening into the internal chamber. The plurality of ports includes an exhaust port configured to fluidly communicate with the exhaust pipe to receive exhaust flowing in the exhaust pipe, and a shield gas port configured to selectively receive a shield gas from an external source of shield gas. A NOx sensor is disposed within the internal chamber to measure a NOx concentration in the exhaust received within the internal chamber. The flow control device is configured to selectively allow a flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the first fuel, and a flow of the shield gas into the internal chamber to inhibit the flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the second fuel. The shield gas port and the NOx sensor are configured to direct the flow of shield gas from the shield gas port at an angle on the order of 135° to 180° to the NOx sensor.
According to another aspect of the present disclosure, there is provided a NOx sensor protection system for an internal combustion engine configured to be selectively operated with a first fuel and a second fuel, and an exhaust pipe configured to receive exhaust resulting from combustion of the first fuel or the second fuel in the internal combustion engine. The NOx sensor protection system includes a flow control device forming an internal chamber and a plurality of ports opening into the internal chamber. The plurality of ports includes an exhaust port configured fluidly communicate with the exhaust pipe to receive exhaust flowing in the exhaust pipe and direct the exhaust gas into the internal chamber, and a shield gas port configured to be selectively fluidly coupled to an external source of a shield gas and direct the shield gas into the internal chamber. A NOx sensor is disposed within the internal chamber to measure a NOx concentration in the exhaust received within the internal chamber. The flow control device is configured to selectively allow a flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the first fuel, and a flow of the shield gas into the internal chamber to inhibit the flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the second fuel. The shield gas port and the NOx sensor are configured to provide the flow of the shield gas from the shield gas port directly at the NOx sensor, the shield gas port being disposed within 2-5 mm of the NOx sensor.
According to yet another aspect of the present disclosure, there is provided a NOx sensor protection system for an internal combustion engine configured to be selectively operated with a first fuel and a second fuel, and an exhaust pipe configured to receive exhaust resulting from combustion of the first fuel or the second fuel in the internal combustion engine. The NOx sensor protection system includes a NOx sensor, a collection duct disposed within the flow of exhaust flowing in the exhaust pipe, a nozzle configured to selectively receive a shield gas from an external source of shield gas, and a flow control device including a manifold forming an internal chamber. The manifold has a plurality of bores opening into the internal chamber, the plurality of bores including a NOx sensor bore, an exhaust bore, a shield gas bore, and an exit opening. The collection duct is fluidly coupled to the exhaust bore to form an exhaust port, fluidly coupling exhaust flowing in the exhaust pipe to the exhaust port to provide a flow of exhaust into and through the internal chamber to the exit opening. The NOx sensor extends through the NOx sensor bore and disposed within the internal chamber to measure a NOx concentration in exhaust received within the internal chamber. The nozzle extends through the shield gas bore and forms a shield gas port. The flow control device is configured to selectively allow the flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the first fuel, and a flow of the shield gas through the shield gas port into the internal chamber to inhibit the flow of exhaust from the exhaust pipe to the NOx sensor when the internal combustion engine is operated with the second fuel.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.
The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.
This disclosure relates to internal combustion engines configured to be operated with two types of fuel, and more specifically to an exhaust treatment arrangement and an NOx sensor protection system. An exemplary internal combustion engine system 100 shown in
A turbocharger 108 may be provided to compress intake air supplied to internal combustion engine 102 via a compressor 109 associated with the air intake system 104. Further, a SCR aftertreatment module or system 110 is provided in an exhaust pipe 112 connected to internal combustion engine 102. The configuration of SCR system 110 may be of any appropriate configuration known, or developed in the future, and may include, for example, an SCR mixer 114 and an SCR reactor 116.
In accordance with an aspect of this disclosure, one or more NOx sensors are provided. In the illustrated embodiment of
Turning to
In this embodiment, the manifold 132 extends through a wall 136 of the exhaust pipe 112 into the interior of the exhaust pipe 112. It will be appreciated, however, that the manifold 132 may be contained entirely within or outside of the exhaust pipe 112. When extending through the wall 136 of the exhaust pipe 112, however, the entire manifold 132 may be accessed for replacement or other service by sliding the manifold 132 outward from the wall 136.
The supply of exhaust gas may be provided to the internal chamber 134 of the manifold 132 by any appropriate arrangement. In the illustrated exemplary embodiment, a collection duct 138 extends across the section of exhaust pipe 112 associated with the SCR system 110. As shown in
In order to sense the concentration of NOx within the exhaust gas provided to the internal chamber 134 of the manifold 132, the NOx sensor 118, 120 is disposed within the internal chamber 134 of the manifold 132. In at least one embodiment, the NOx sensor 118, 120 is mounted through a NOx sensor bore 144 in the manifold 132. As illustrated, for example, in
In order to allow the exhaust entering the internal chamber 134 of the manifold 132 to exit the internal chamber 134 and to ensure current sensor readings, the manifold 132 may include one or more exit openings 146, preferably disposed at a position(s) that causes the exhaust to flow along the NOx sensor 118 within the internal chamber 134 of the manifold 132. In at least one embodiment the manifold 132 includes exit openings 146 disposed along either side of the manifold 132. In order to promote the flow of exhaust through the internal chamber 134 to the exit openings 146, the exit openings 146 have a larger cross-section than a cross-section of the exhaust port 141 by which exhaust enters the internal chamber 134.
According to an aspect of this disclosure, when the engine 102 is operating on HFO fuel, a shield gas may be provided to the internal chamber 134 of the manifold 132 in order to provide air flow to purge the NOx sensor 118, 120 from high sulfur exhaust resulting from operation of the engine 102 on HFO fuel. While the shield gas may be any appropriate gas, in at least one embodiment, the shield gas is compressed air. To this end, the manifold 132 may be provided with a shield gas bore 148 through which shield gas maybe provided to the internal chamber 134 through a shield gas port 150. Shield gas may be provided to the shield gas port 150 by way of a gas supply line 152, which is fluidly coupled to an external source of shield gas 154, such as a compressor. The compressor may be compressor 109 associated with the air intake system 104 or a separate compressor unit associated, for example, with a dosing cabinet (not shown). The shield gas port 150 may be formed by the shield gas bore 148 itself or a nozzle 156 extending through the shield gas bore 148. Such a nozzle 156 may be fluidly coupled to the external source of shield gas 154.
In order to minimize or eliminate rapid temperature changes to the manifold 132 or the sensor 118, the shield gas provided through the shield gas port 150 may be adjusted to more closely conform to the temperature of the exhaust flowing through the exhaust port 141 to the internal chamber 134 of the manifold 132, and/or the environment in which the manifold 132 is disposed, that is, within the exhaust pipe 112. In at least one embodiment, the gas supply line 152 includes an elongated tube 158 disposed within the exhaust pipe 112 (see
According to an aspect of this disclosure, the shield gas port 150 is disposed to provide an effective flow of shield gas to inhibit the flow of exhaust to the NOx sensor 118, 120. In at least one embodiment the shield gas port 150 is disposed to provide a flow of shield gas to the NOx sensor 118, 120 at an angle on the order of 135° to 180°, that is an angle formed between a centerline 160 of the NOx sensor 118, 120 and a centerline 162 of the shield gas port 150, shown in
In at least one embodiment, the shield gas port 150 is disposed proximal to the NOx sensor 118, 120 to provide a direct flow of shield gas to the NOx sensor 118, 120. As used herein, the term “direct flow” means a flow directly toward, as opposed to a flow which is deflected from another surface. In at least one embodiment, the shield gas port 150 is disposed within 2-5 mm of the NOx sensor 118, 120. In at least one embodiment the shield gas port is disposed within 2 mm of the NOx sensor.
According to another aspect of the disclosure, the manifold 132 may be cast or machined. For example, the manifold 132 may be formed of a solid block of material, such as an aluminum alloy. The one or more exit openings 146 and the exhaust bore 140, NOx sensor bore 144, and shield gas bore 148 may be machined into the block. Alternatively, the manifold 132 may be cast as a unitary structure.
Herein, the term “internal combustion engine” may refer to internal combustion engines which may be used as main or auxiliary engines of stationary power providing systems such as power plants for production of heat and/or electricity as well as in ships/vessels such as cruise liners, cargo ships, container ships, and tankers. Fuels for internal combustion engines may include diesel oil, marine diesel oil, heavy fuel oil, alternative fuels or a mixture thereof, and natural gas.
Examples of internal combustion engines for the herein disclosed systems include medium speed internal combustion diesel engines, for example, engines of the series M20, M25, M32, M34DF, M43, M46DF manufactured by Caterpillar Motoren GmbH & Co. KG, Kiel, Germany, operated in a range of 500 to 1000 rpm.
Some embodiments of the NOx sensor protection system 130 may be utilized in the flow of exhaust gas, eliminating the need for an exhaust bypass pipe utilized in some prior art structures.
Some embodiments of the NOx sensor protection system 130 minimize the likelihood of thermal cracking of the NOx sensor 118, 120 by providing a heated flow of shield gas.
In some embodiments, the impact of manufacturing tolerances may be minimized by use of the manifold 132, which may allow for optimal placement of the NOx sensor 118, 120, shield gas port 150, and flow of exhaust from the exhaust port 141 to provide better flow past the NOx sensor 118, 120.
Some embodiments of the NOx sensor protection system 130 may provide an economical, efficient arrangement with a manifold 132 that may be machined in low volume applications.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
