US20160084135A1

US20160084135A1 - Catalyst Protection Against Hydrocarbon Exposure

Info

Publication number: US20160084135A1
Application number: US14/492,694
Authority: US
Inventors: Aaron Harmon; Joshua Ratts; Wilce Williams; Adwait Joshi; Brandon Abel
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2014-09-22
Filing date: 2014-09-22
Publication date: 2016-03-24

Abstract

A system to protect an after treatment system from the effects of hydrocarbon accumulation on a catalyst. An engine system microprocessor using software estimates the amount of hydrocarbon accumulation on the after treatment system based on engine system parameters and other parameters. The accumulated hydrocarbons can cause an exothermic event if the catalyst temperature is allowed to ramp up too quickly. Similarly, accumulated hydrocarbon can temporarily reduce after treatment system performance. In the case of SCR, the microprocessor can control a reductant injector to modulate the amount of reductant being injected into the after treatment system to control the amount of ammonia slip. Alternatively or in addition to, the microprocessor can communicate with proper electronic control modules to modulate the engine system parameters such as engine speed, fuel, and back pressure to control engine exhaust flow temperature during operation of the engine system.

Description

TECHNICAL FIELD

The disclosure relates generally to protecting after treatment systems in an engine system (Marine, Locomotive, Electric Power, Machine, etc.), and more particularly, to protecting the after treatment systems due to accumulation of hydrocarbon on catalysts.

BACKGROUND

Engines such as diesel or other lean burning engines generally provide more complete fuel combustion and better fuel efficiency but require higher operating pressures and temperatures compared to non-lean burning engines. With the higher pressures and temperatures, oxides of nitrogen (NO_x) emissions including nitric oxide (NO) and nitrogen dioxide (NO₂) are typically higher as oxygen and nitrogen tend to combine more easily at higher temperatures. NO_xemissions cause a number of environmental issues such as smog, acid rain, excess aqueous nutrients and so on. Thus, emissions control regulations limit the amount of NO_xemissions of engines and necessitate the use of reduction devices in the exhaust systems in order to reduce the NO_xemissions to an acceptable level.
An after treatment system, such as a selective catalytic reduction (SCR) device is typically used to control the NO_xemissions of engines. The catalyst converts NO_xgases into nitrogen gases and water with the aid of a reducing agent. The reducing agent typically contains hydrogen or the like, which is capable of removing oxygen from NO_xgases. Commonly used reducing agents are ammonia, Diesel Exhaust Fluid (DEF), urea, hydrocarbon-containing compounds and the like. The introduction of the reducing agent to the after treatment system allows for it to be adsorbed onto the catalyst to facilitate the reduction process. Typically, a solution of the reducing agent is internally or externally carried by an engine, and a supplying system injects the reducing agent into the exhaust gas stream entering the SCR system.
During engine operations, the unburned hydrocarbons in the exhaust stream enters the SCR system and can adsorb onto the catalyst. The hydrocarbons can be in liquid phase or can condense into the liquid phase upon contacting the catalyst surface. Once in the liquid phase, the hydrocarbons can adsorb and accumulate on the catalyst pores and void volumes. Rapid heating of the catalyst after prolonged idle or low temperature operations suitable for accumulation of hydrocarbons can ignite the hydrocarbons and cause an exothermic event that could potentially damage the catalyst. Alternatively, if the accumulated hydrocarbons don't ignite, they can inhibit the catalyst performance by blocking the active catalyst sites used for oxidation of hydrocarbons and carbon monoxide (diesel oxidation catalyst) and conversion of NO_xgases into nitrogen gases and water (selective catalytic reduction).
A system for coordinated engine and emissions control is described in U.S. Pat. App. No. 2013/0067894 (the '894 application) published on Mar. 21, 2013. The '894 application discloses a selective catalytic reduction control system that may incorporate a diesel engine or a model of the engine, a selective catalytic reduction exhaust after-treatment mechanism for connection to the engine, an engine controller, and a selective catalytic reduction controller connected to the selective catalytic reduction exhaust after treatment mechanism and to the engine controller. The engine controller and the selective catalytic reduction controller may provide coordinated control of the engine and selective catalytic reduction exhaust after-treatment mechanism to control an amount of pollutants in an exhaust emission from the engine. However, this system does not determine based on engine parameter inputs, the amount of hydrocarbons accumulation on the catalyst. The amount of hydrocarbon accumulation affects the efficiency of the catalyst in the SCR system and has the potential for an undesired exothermic event. Without determining the amount of hydrocarbon accumulation, the inlet temperature cannot be properly controlled to prevent the exothermic event and the reducing agent dosing cannot be properly modulated in order to not exceed ammonia slip targets.
Accordingly, there is a need for a system that efficiently utilizes an after treatment system that includes SCR to minimizes NH₃slip past the catalyst and/or prevents exothermic events due to accumulation of hydrocarbons on the catalyst.

SUMMARY

In one aspect, the disclosure is directed to a method for protecting an after treatment system from effects of hydrocarbon accumulation, the steps include receiving, at a microprocessor of an engine system, engine system parameters from a plurality of electronic control modules of the engine system, estimating, with the microprocessor of the engine system, an amount of engine out hydrocarbon based on the engine system parameters, receiving, from a memory, a correction factor that adjusts the estimated amount of engine out hydrocarbon, estimating, with the microprocessor of the engine system, a hydrocarbon mass on the after treatment system of the engine system with the adjusted estimated amount of engine out hydrocarbon, and modulating, with the microprocessor of the engine system, a reductant that is applied to the after treatment system of the engine system based on the estimated hydrocarbon mass.
In another aspect, a method of protecting an after treatment system from effects of hydrocarbon accumulation is disclosed and includes the steps of receiving, at a microprocessor of an engine system, engine system parameters from a plurality of electronic control modules of the engine system, estimating, with the microprocessor of the engine system, an amount of engine out hydrocarbon based on the engine system parameters, receiving, from a memory, a correction factor that adjusts the estimated amount of engine out hydrocarbon, estimating, with the microprocessor of the engine system, a hydrocarbon mass on the after treatment system of the engine system with the adjusted estimated amount of engine out hydrocarbon, and controlling gradual exhaust temperature ramp up, with the microprocessor of the engine system that is communicating with a first electronic control module of the plurality of electronic control modules, based on the estimated hydrocarbon mass.
In still another aspect, a system that protects an after treatment system of a vehicle from the effects of hydrocarbon accumulation that includes means for processing that communicates with a hydrocarbon estimation software stored on means for storing of an engine system computer, means for injecting configured to inject a reductant into the after treatment system, and means for interfacing that allows the means for processing to communicate with the means for injecting, wherein the means for processing executes the hydrocarbon estimation software to perform the steps of: receiving, at the means for processing, engine system parameters from a plurality of electronic control modules of the engine systems, estimating, with the means for processing, an amount of engine out hydrocarbon based on the engine system parameters, receiving, from the means for storing, a correction factor that adjusts the estimated amount of engine out hydrocarbon, estimating, with the means for processing, a hydrocarbon mass on the after treatment system of the engine system with the adjusted estimated amount of engine out hydrocarbon, and modulating, with the means for processing controlling the means for injecting, the reductant that is applied to the after treatment system of the engine system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary vehicle that utilizes an after treatment process according to the disclosure.

FIG. 2 is a perspective view of the after treatment system with the top removed to illustrate the components, and exhaust flow according to the disclosure.

FIG. 3 is a flow diagram of a method of protecting against hydrocarbon damage to the after treatment system according to the disclosure.

FIG. 4 illustrates components of an engine system computer according to the disclosure.

FIG. 5 is a diagram of steps to protect the after treatment from the effects of hydrocarbon accumulation according to the disclosure.

DETAILED DESCRIPTION

The disclosure sets forth a process and system to compensate for hydrocarbon accumulation in after treatment systems. The process and system set forth in the disclosure estimate or calculate the amount of hydrocarbon that is expected to accumulate on the after treatment system, such as the SCR and then proceeds to control the engine to gradually ramp-up the temperature in order to prevent the exothermic reaction that could damage the catalyst. In addition to or alternatively, the process and system can modulate the amount of reductant being added to the after treatment system in order to optimize the SCR catalyst performance based on the estimated or calculated hydrocarbon accumulation on the after treatment system. The process and system disclosed herein can be used not only on vehicles but all engine systems including marine, locomotive, electronic power, machines, etc.
FIG. 1 is an illustration of an engine system in an exemplary vehicle 100 that utilizes the after treatment process according to the disclosure. The vehicle 100 can be a wheeled dump truck or any off-highway vehicle being used in any manner or operation. The vehicle 100 is shown to include a chassis 112. The chassis 112 may be supported by wheels 113 (or tracks on other locomotion devices), and itself support an operator cabin 114 and an engine 115. A dump body 118 may be positioned above an actuator system 119, with both being supported by the chassis 112, as well. The actuator system 119 may include one or more hydraulic cylinders (not shown) to raise and lower the dump body 118 at a proximal end 120, and thereby inclining the dump body 118 in order to expel a payload 121 at a distal end 122.
In one aspect of the disclosure such as in a cold environment, the vehicle 100 will be left in idle for an extended period of time, such as overnight as it is difficult to start the diesel engine in cold temperatures. During extended low temperature operation, hydrocarbon can accumulate on the catalyst. Thus, when the operator operates the engine system within the vehicle 100 from the idle state to a working state, the after treatment system would heat up and can cause an exothermic reaction due to the accumulated hydrocarbons and thereby, potentially damaging the catalyst and other parts of the after treatment system. It should be noted that the processes and systems described herein can be applied in all types of temperature, weather and load conditions.
FIG. 2 is a perspective view of an after treatment system 220 with the top removed to illustrate the components, and exhaust flow. The after treatment system 220 can include a housing 222 that is supported on a base support 224 adapted to mount the after treatment system to a power system, such as a diesel engine 115 of the vehicle 100. The housing 222 can include a forward first wall 226, an opposing rearward second wall 228, and respective third and fourth sidewalls 230, 232. However, it should be appreciated that terms like forward, rearward and side are used only for illustrative purposes and should not be construed as a limitation on the claims. Additionally, extending between the forward first wall 226 and rearward second wall 228 and located midway between the third and fourth sidewalls 230, 232 can be an imaginary central system axis line 234.
To receive the untreated exhaust gasses into the after treatment system 220, one or more inlets 240 can be disposed through the forward first wall 226 of the housing 222 and can be coupled in fluid communication to the exhaust channel from an exhaust system. In the aspect illustrated, the after treatment system 220 includes two inlets 240 arranged generally in parallel and centrally located between the third and fourth sidewalls 230, 232 on either side of the system axis line 234 so that the entering exhaust gasses are directed toward the rearward second wall 228. However, other aspects of the after treatment system 220 may include different numbers and/or locations for the inlets 240. To enable the exhaust gasses to exit the after treatment system 220, two outlets 242 can also be disposed through the forward first wall 226 of the housing 222. Each outlet 242 can be parallel to the centrally oriented inlets 240.
To treat or condition the exhaust gasses, the housing 222 can contain various types or kinds of after treatment devices through which the gasses of the exhaust flow are directed. For example, and following the arrows indicating exhaust flow through the after treatment system 220, in order to slow the velocity of the incoming exhaust gasses for treatment, the inlets 240 can each be communicatively associated with an expanding, cone-shaped diffuser 244 mounted exteriorly of the forward first wall 226. Each cone-shaped diffuser 244 can direct the exhaust gasses to an associated diesel oxidation catalyst (DOC) 246 located proximate the forward first wall 226 inside the housing 222 that then directs the exhaust gasses to a common collector duct 248 centrally aligned along the system axis line 234. The DOC 246 can contain materials such as platinum group metals like platinum or palladium, which can catalyze carbon monoxide and hydrocarbons in the exhaust gasses to water and carbon dioxide via the following possible reactions:
CO+½O₂=CO₂ (1)
[HC]+O₂=CO₂+H₂O (2)
To further reduce emissions in the exhaust gasses and particularly to reduce nitrogen oxides such as NO and NO₂, sometimes referred to as NO_x, the after treatment system 220 may include an SCR system 250. In the SCR process, a liquid or gaseous reducing agent is introduced to the exhaust system and directed through an SCR catalyst along with the exhaust gasses. The SCR catalyst can include materials that cause the exhaust gasses to react with the reducing agent to convert the NO_xto nitrogen (N₂) and water (H₂O). A common reducing agent is urea ((NH₂)₂CO), though other suitable substances such as ammonia (NH₃), Diesel Exhaust Fluid (DEF) can be used in the SCR process. The reaction may occur according to the following general formula:
NH₃+NO_x=N₂+H₂O (3)
Referring again to FIG. 2, to introduce the reducing agent, the SCR system 250 includes a reductant injector 252 located downstream of the collector duct 248 and upstream of a centrally aligned mixing duct 254 that channels the exhaust gasses toward the rearward second wall 228 of the housing 222. The reductant injector 252 can be in fluid communication with a storage tank or reservoir storing the reducing agent and can periodically, or continuously, inject a quantity of the reducing agent into the exhaust gas flow in a process sometimes referred to as dosing. The amount of reducing agent introduced can be dependent upon the NO_xload of the exhaust gasses. The mixing duct 254 uniformly intermixes the reductant agent with the exhaust gasses before they enter the downstream SCR catalysts. Disposed at the end of the mixing duct 254 proximate the rearward second wall 228 can be a diffuser 256 that redirects the exhaust gas/reductant agent mixture toward the third and fourth sidewalls 230, 232 of the after treatment system 220. The third and fourth sidewalls 230, 232 can redirect the exhaust gas/reductant agent mixture generally back towards the forward first wall 226.
To perform the SCR reaction process, the after treatment system 220 can include a first SCR module 260 disposed proximate the third sidewall 230 and a second SCR module 262 disposed toward the fourth sidewall 232. The first and second SCR modules 260, 262 are oriented to receive the redirected exhaust gas/reducing agent mixture. The first and second SCR modules 260, 262 can accommodate one or more SCR catalysts 264, sometimes referred to as after treatment bricks. The term after treatment brick, however, may refer to a variety of exhaust after treatment devices, which SCR catalysts are a subset of Moreover, in different aspects, the SCR modules 260, 262 may be configured to accommodate any different number of after treatment bricks that may be in different shapes, sizes and/or configurations and that may operate by the same or different reaction processes.
To accommodate the plurality of SCR catalysts 264, the first and second SCR modules 260, 262 can include one or more sleeves 270 that can slidably receive the catalysts. The sleeves 270 can be generally elongated, tubular structures having a first end 274 and an opposing second end 276 aligned along a longitudinal sleeve axis 272. In some aspects, the first end 274 may be designated as an upstream end and the second end 276 may be designated as the downstream end thereby establishing the gas flow direction through the sleeves 270. In other aspects, the flow direction through the first and second SCR modules 260, 262 may be at least partially reversible so that either the first end or second end 274, 276 may function alternatively as the upstream or downstream ends. In those aspects that include more than one sleeve 270 in the first and second SCR modules 260, 262, the sleeves can be supported in a truss or frame 266 made, for example, from formed sheet metal or cast materials. The frame 266 can be oriented so that the first ends 274 are directed toward the respective third and fourth sidewalls 230, 232 and the second ends 276 communicate with a central region 280 of the after treatment system 220 generally surrounding but fluidly separated from the mixing duct 254. The central region 280 can direct the treated exhaust gases forward to the outlets 242 disposed through the forward first wall 226. In various aspects, one or more additional exhaust treatment devices can be disposed in the after treatment system 220 such as diesel particulate filters 282 for removing soot.
FIG. 3 is a flow diagram 300 of a method of protecting against hydrocarbon damage to an after treatment system according to the disclosure. An engine out hydrocarbon estimator 304 is used to estimate or calculate the amount of unburnt hydrocarbon that is present in the exhaust stream of the engine 115. One or more engine system parameters 302 can be provided to the engine out hydrocarbon estimator 304 so that it can estimate the unutilized hydrocarbon. The engine system parameters 302 may include the amount of fuel being injected into the engine, the engine speed (average speed or current speed), the engine timing, the total exhaust flow mass, the crank mode, inject enable, inlet manifold pressure or temperature, coolant temperature, ambient temperature and pressure, and other parameters that are stored in the various electronic control modules or sensors of the engine or vehicle.
These engine system parameters 302 will affect the amount of unburnt hydrocarbon that is present in the exhaust stream and enters the after treatment system 220. The exhaust stream can include engine slobber, blow by and the like. Once one or more engine system parameters, such as engine speed and the amount of fuel being injected are provided to the engine out hydrocarbon estimator 304, the estimator can include various known Maps or look up tables for a particular vehicle and or engine type (size) to estimate the unutilized hydrocarbon in grams/hour. These Maps and look up tables may be stored in the engine system computer 400 as discussed in FIG. 4.
Alternatively, models may be designed to provide such estimations and are well within the disclosure. One model equation can be:
$\frac{\partial C_{{HC}_{adsorbed}}}{\partial t} = r_{adsorption} - r_{desorption} - r_{oxidation}$

C_HC _absorbed=Concentration of adsorbed hydrocarbon [mol volume⁻¹]
r₁=rate of reaction i [mol volume⁻¹time⁻¹]
This model equation can be used to estimate the amount of hydrocarbon adsorbed (onto the SCR), which equal the rate of reaction for adsorption minus the rate of reaction for desorption minus the rate of reaction for oxidation.

The respective vehicle electronic control modules provide engine system parameters 302. As the engine out hydrocarbon estimator 304 includes various look up tables and Maps depending on the vehicle and/or engine type, the engine out hydrocarbon estimator 304 can provide an estimate or a calculation of engine hydrocarbon not utilized, such as engine hydrocarbon startup 308. At engine start up, the engine may produce a great amount of unburnt hydrocarbon because the engine has not warmed up to peak operating temperatures, where it is more efficient. Engine hydrocarbon start up 308 can also include warm and failed starts. The engine out hydrocarbon estimator 304 can also provide estimates of unburnt hydrocarbon in the exhaust stream for various engine hydrocarbon run mode 310, such as idle, fast, slow, coasting downhill, etc.
At this point, depending on the operating condition of the vehicle 100, either the estimate for the unburnt hydrocarbon in the exhaust stream at engine startup 308 or unburnt hydrocarbon in the exhaust stream for various engine hydrocarbon run mode 310 is provided to a catalyst hydrocarbon mass integrator 312, which determines the amount of hydrocarbon added or removed for each time step and subsequently calculates an overall hydrocarbon mass accumulated onto the catalyst 264. Additional after treatment system information 306 that can also be provided to the catalyst hydrocarbon mass integrator 312 includes the SCR temperature or any other catalyst being used in the after treatment system 220, the total mass exhaust flow, the catalyst volume, and the current hydrocarbon loading already accumulated on the after treatment system 220. Based on this information, the catalyst hydrocarbon mass integrator 312 calculates or estimates the catalyst hydrocarbon mass 314, which is the amount of hydrocarbon that has accumulate on the catalyst 264 at any given time.
If the accumulated hydrocarbon on the after treatment system 220 is not properly addressed, then an exothermic event may occur and damage the catalyst 264 and/or the catalyst active sites that may be covered by the accumulated hydrocarbon are not available to the reductant, thereby, increasing slip of exhaust gases and reductant derivatives, such as ammonia, into the environment. Various methods and systems are disclosed herein that can be implemented to mitigate the effects caused by accumulated hydrocarbon on the catalyst 264 including maximizing catalyst conversion capability 316 and catalyst inlet temperature protection 318.
Maximizing catalyst conversion capability 316 involves fluctuating the amount of reductant added to the after treatment system 220 by the reductant injector 252. As more hydrocarbon accumulates on the catalyst 264, the active sites available on the catalyst are decreased and thus, the reductant used to convert the NO_xto nitrogen (N₂) and water (H₂O) are not being utilized and are eventually exhausted into the environment and may exceed the allowable amount of ammonia slip in the case of ammonia producing reducing agents. Engine system computer 400 (discussed in FIG. 4 below) can control the reductant injector 252 so that the amount of reductant is fluctuated depending on the amount of calculated or estimated catalyst hydrocarbon mass 314 accumulation on the after treatment system 220. The more hydrocarbon accumulation on the catalyst 264 and thus, more blocked active sites on the catalyst 264 may require the engine system computer 400 to decrease the amount of reductant introduced into the exhaust stream in order to have more efficient conversion of the NOx. Alternatively, if the amount of calculated or estimated catalyst hydrocarbon mass 314 accumulation on the after treatment system 220 is less or more active sites on the catalyst 264 are available, then the engine system computer 400 can increase the amount of reductant introduced into the exhaust stream for more efficient conversion of the NOx.
In addition or alternatively to optimizing catalyst performance, the catalyst inlet temperature protection 318 can also be used. In this aspect, in order to prevent or reduce the possibility of an exothermic event occurring within the catalyst 264, the engine 115 exhaust flow and engine exhaust temperatures are controlled by controlling multiple aspects of the engine operation including, but not limited to, the engine speed, fueling, and backpressure of the engine system within the vehicle 100. In cold environments, the diesel engine 115 is often left in idle for an extended period of time, including overnight, as diesel engines are difficult to start up in cold temperatures. By only allowing the engine to slowly warm up to operating temperatures, the exothermic event may be avoided. The engine system computer 400 (discussed in FIG. 4) can be utilized to control various electronic control modules including modules that control engine speed and fuel injection. In one aspect, the electronic control modules can throttle or limit the amount of fuel that is injected into the engine in order to control the engine load and thus, can allow the exhaust temperatures to slowly increase regardless of the throttle position of the fuel pedal being operated by the operator. An estimated or measured temperature sensor located on or near the catalyst or in or near the after treatment system 220 can provided feedback to the engine system computer 400. In another aspect, the engine system computer 400 can control the electronic control modules to perform an automated engine warm up program based upon the calculated or estimated catalyst hydrocarbon mass 314. The engine warm up program can take into account the type of engine, the current engine temperature, the ambient temperature, the catalyst hydrocarbon mass 314 and the like in order to prevent a rapid increase in temperature of the engine 115 during operation.
FIG. 4 illustrates components of an engine system computer 400 according to the disclosure. The engine system computer 400 can include a microprocessor 402, a main memory 404, a network interface 406, a storage device 408, a display 414, a wireless interface 416, a user interface 418 and bus line 420. The microprocessor 402 may be a single microprocessor or multiple microprocessors, multiple core microprocessors, a field programmable gate array (FPGA), application-specific integrated circuit (ASIC), controllers and the like. It is contemplated that microprocessor 402 may communicate with other machine sensors (not shown), such as gas sensors, NO_xsensors, NH₃sensors, throttle position sensors, mass flow, rate sensors, pressure sensors, temperature sensors, intake manifold sensors, throttle position sensors, and/or any other system sensors that may provide information related to the operational characteristics of the engine.
Main memory 404 may contain certain software needed for the microprocessor 402, such as the bios and the like. In addition to or alternatively, there is a storage device 408 that includes an operating system 410 for the engine system computer 400 and programs 412, such as software programs (discussed herein) to protect the after treatment system 220 from the effects of hydrocarbon accumulation. The storage device 408 may be a hard drive, optical drive, a flash memory and the like. The operating system 410 can be any system such as Windows®, Mac O/S®, Linux, Android® and the like. Storage device 408 can also store one or more multi-dimensional Maps. Multi-dimensional Maps may be generated from steady-state simulations and/or empirical data and may include equations, graphs and/or tables related to the operational characteristics of after treatment system 220 and other information including hydrocarbon accumulation. For example, Maps may include equations, graphs and/or tables that relate a SCR device temperature (either measured or predicted) to an ability of SCR device to store reducing agent and to convert emissions gases. The equations may relate to calculating or estimating the engine out hydrocarbon estimator 304 and/or the catalyst hydrocarbon mass 314. The inputs fed into Maps may include engine air mass flow rate, manifold correction factor, inlet gas ratio, inlet NO₂over NO_xratio, inlet pressure, and inlet temperature of SCR device, ambient temperature, a total fuel quantity and/or engine speed. It is contemplated that Maps may further include other formulations and weighting and may include further inputs, such as, a space velocity and the like.
A display 414 can be provided and be placed at any convenient place in the vehicle 100 including a heads up display (HUD), a built-in display on the console of the vehicle, a remote and movable display and the like. The display 414 can be LED, VGA, OLED, plasma, touch screen and the like. Network interface 406 can connect the engine system computer 400 to other devices, such as a diagnostic tool, the after treatment system 220, reductant injector 252, sensors, electronic control modules, and the like. The network interface 406 can be USB, Fire wire, Thunderbolt, Ethernet, and the like. The wireless interface 416 can communicate with external devices, sensors, electronic control modules, networks, computers, diagnostic tools, tablets, and the like via various communication protocols, such as Wi-Fi, LAN, WAN, Bluetooth, wireless Ethernet, infrared, cellular, satellite and the like. A user interface 418 allows a user or an operator to interact with the engine system computer 400. The user interface 418 may be the touchscreen display 414. The components of the engine system computer may communicate with each other on the bus line 420.
FIG. 5 is a diagram 500 of steps to protect the after treatment system from the effects of hydrocarbon accumulation according to the disclosure. The protection starts at step 502. At step 504, engine system parameters 302 received from various electronic control modules of the vehicle 100 may be received at the microprocessor 402, which may be running the after treatment protection software. Engine system parameters 302 may include the amount of fuel being injected into the engine, the engine speed (average speed or current speed), the engine timing or idle rotation per minute, the total mass exhaust flow, the crank mode, inject enable, inlet manifold pressure or temperature, coolant temperature, ambient temperature and pressure, and other parameters. At step 506, microprocessor 402 estimates or calculates the engine out hydrocarbon in parts per million (PPM) using the engine out hydrocarbon estimator 304, which may also be a software module and includes various Maps, equations, or look up tables. Additionally, at step 508, a correction factor, such as a manifold correction factor, which may include intake manifold temperature may also be inputted into the engine out hydrocarbon estimator 304. At step 510, the microprocessor 402 converts to mass rate in grams/hour and then alternatively to grams/per second. Total mass exhaust flow from an electronic control module can also be used to convert to mass rate. The engine out hydrocarbon estimator 304 can provide mass rate for engine hydrocarbon at startup 308 and various engine hydrocarbon run mode 310. At step 512, the microprocessor 402 can use the catalyst hydrocarbon mass integrator 312, which can be a software module, to calculate the catalyst hydrocarbon mass 314 using the mass rate for engine hydrocarbon at startup 308 and/or various engine hydrocarbon run mode 310. Also inputted into the catalyst hydrocarbon mass integrator 312 are one or more of the following SCR in temperature, total mass exhaust flow, catalyst volume and current HC loading. Once the catalyst hydrocarbon mass is calculated various methods disclosed herein may be utilized to protect the after treatment system.
The methods may include one or both of steps 514 and 516. At step 514, the microprocessor 402 using the network interface 406 that is in communication with the reductant injector 252 controls the amount of reductant being injected into the after treatment system 220. If there is too much hydrocarbon accumulating on the after treatment system, such as the SCR, then the catalyst sites are covered and then excess reductant not being utilized will flow out of the exhaust stream into the environment causing excess ammonia slip beyond the acceptable range. Depending on the operating conditions of the engine 115, size of engine and other factors, the amount of reductant being injected can vary from about 0 to about 40 kg/hr. and normal operating conditions can be about 1-30 kg/hr. The amount of reductant being injected will be modulated by the microprocessor 402 depending on the amount of estimated or calculated hydrocarbon mass 314 on the after treatment system 220. Thus, the more hydrocarbon mass 314 on the after treatment system 220 that is beyond a predetermined level, the amount of reductant being injected will be modulated accordingly. Conversely, if the amount of hydrocarbon mass 314 is less than the predetermined level, then the amount of reductant being injected will be adjusted. The microprocessor 402 can continuously monitor and estimate or calculate the catalyst hydrocarbon mass 314 and adjust the reductant being injected accordingly.
At step 516, the microprocessor 402 through the network interface 406 communicates with the electronic control modules to modulate the engine operation due to the accumulation of the hydrocarbon on the after treatment system 220. At idle, the engine temperature may be around 50-150° C. depending on the ambient temperature. If the engine is allowed to increase to higher operating temperatures such as 300° C. or higher in a short amount of time, an exothermic event may occur due to the accumulated hydrocarbon on the after treatment system 220. Thus, the microprocessor 402 will control the engine temperature to gradually ramp up regardless of fuel throttle's position. In one aspect, the microprocessor 402 may modulate the amount of fuel that is being injected into the engine 115 regardless of the throttle position.
The steps outlined in FIG. 5 do not have to be performed in any particular order and any or all of the engine parameters need not be used to calculate the catalyst hydrocarbon mass. The steps may be performed automatically via software, processor, and electronic control modules without operator intervention or direction. Additionally, the processes and systems described herein are constantly and automatically estimating, calculating, adjusting, modulating, etc., due to different operating parameters of the engine system.
The present disclosure can be realized as computer-executable instructions on computer-readable media. The computer-readable media includes all possible kinds of media in which computer-readable data is stored or included or can include any type of data that can be read by a computer or a processing unit. The computer-readable media include for example and not limited to storing media, such as magnetic storing media (e.g., ROMs, floppy disks, hard disk, and the like), optical reading media (e.g., CD-ROMs (compact disc-read-only memory), DVDs (digital versatile discs), re-writable versions of the optical discs, and the like), hybrid magnetic optical disks, organic disks, system memory (read-only memory, random access memory), non-volatile memory such as flash memory or any other volatile or non-volatile memory, other semiconductor media, electronic media, electromagnetic media, infrared, and other communication media such as carrier waves (e.g., transmission via the Internet or another computer). Communication media generally embodies computer-readable instructions, data structures, program modules or other data in a modulated signal such as the carrier waves or other transportable mechanism including any information delivery media. Computer-readable media such as communication media may include wireless media such as radio frequency, infrared microwaves, and wired media such as a wired network. Also, the computer-readable media can store and execute computer-readable codes that are distributed in computers connected via a network. The computer readable medium also includes cooperating or interconnected computer readable media that are in the processing system or are distributed among multiple processing systems that may be local or remote to the processing system. The present disclosure can include the computer-readable medium having stored thereon a data structure including a plurality of fields containing data representing the techniques of the present disclosure.

INDUSTRIAL APPLICABILITY

The disclosure may be applicable to any after treatment systems including the catalyst therein that need protection from the effects of hydrocarbon accumulation. Accumulation of hydrocarbon on the catalyst can cause an exothermic event or blocking of the catalyst's active site leading to deteriorated catalyst performance. Specifically, the disclosure may include a controller with software modules that calculates or estimates the amount of hydrocarbon that accumulates on a catalyst of the after treatment system. Based on the amount of accumulation the controller can prevent the exothermic event by controlling the ramp-up temperature of the engine and/or fluctuate the amount of reductant being injected to decrease the amount of reductant slip.
The engine system computer 400 can include a microprocessor 402, a main memory 404, a network interface 406, a storage device 408, a display 414, a wireless interface 416, a user interface 418 and bus line 420. The microprocessor 402 may communicate with sensors, such as gas sensors, NOx sensors, NH3 sensors, throttle position sensors, mass flow rate sensors, pressure sensors, temperature sensors, intake manifold sensors, throttle position sensors, and/or any other system sensors that may provide information related to the operational characteristics of the engine. Storage device 408 can also store one or more multi-dimensional Maps, models or governing equations. Multi-dimensional Maps, models or equations may be generated from steady-state simulations and/or empirical data and may include equations, graphs and/or tables related to the operational characteristics of after treatment system and other information including hydrocarbon accumulation. The microprocessor 402 can estimate or calculate the engine out hydrocarbon in parts per million (PPM) using the engine out hydrocarbon estimator 304, which may also be a software module and includes various Maps, equations and/or look up tables. Engine parameters received from various electronic control modules of the vehicle 100 may be received at the microprocessor 402. The engine out hydrocarbon estimator 304 can provide mass rate for engine hydrocarbon at startup 308 and/or various engine hydrocarbon run mode 310. The microprocessor 402 can use the catalyst hydrocarbon mass integrator 312, which can be a software module, to calculate the catalyst hydrocarbon mass 314 using the mass rate for engine hydrocarbon at startup 308 and/or various engine hydrocarbon run mode 310. Also inputted into the catalyst hydrocarbon mass integrator 312 are one or more of the following SCR in temperature, total mass exhaust flow, catalyst volume and current HC loading. Once the catalyst hydrocarbon mass is calculated various methods disclosed herein may be utilized to protect the after treatment system.
Network interface 406 can connect the engine system computer 400 to other devices, such as a diagnostic tool, the after treatment system 220, reductant injector 252, sensors, electronic control modules, and the like. The microprocessor 402 using the network interface 406 that is in communication with the reductant injector 252 to control the amount of reductant being injected into the after treatment system. The amount of reductant being injected will be modulated by the microprocessor 402 depending on the amount of estimated or calculated hydrocarbon mass 314 on the after treatment system. The microprocessor 402 can control how the engine temperature ramps up regardless of how much throttle that the operator is giving the engine. In one aspect, the microprocessor 402 may control the amount of fuel that is being injected into the engine regardless of the throttle position.
Although specific exemplary aspects of the disclosure have been described, internal and external components and configurations may be implemented in reverse to provide the same benefits provided by the inventive aspects described. In addition, it will be appreciated by one skilled in the art that other related items can be incorporated and used along with aspects derived from the disclosure.
The many features and advantages of the disclosure are apparent from the detailed specification, and thus, it is intended by the appended claims to case all such features and advantages of the disclosure which fall within the true spirit and scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

Claims

We claim:

1. A method of protecting an after treatment system from effects of hydrocarbon accumulation, comprising the steps of:

receiving, at a microprocessor of an engine system, engine system parameters from a plurality of electronic control modules of the engine system;

estimating, with the microprocessor of the engine system, an amount of engine out hydrocarbon based on the engine system parameters;

receiving, from a memory, a correction factor that adjusts the estimated amount of engine out hydrocarbon;

estimating, with the microprocessor of the engine system, a hydrocarbon mass on the after treatment system of the engine system with the adjusted estimated amount of engine out hydrocarbon; and

modulating, with the microprocessor of the engine system, a reductant that is applied to the after treatment system of the engine system based on the estimated hydrocarbon mass.

2. The method of protecting of claim 1 further comprising the step of controlling a gradual engine ramp up, with the microprocessor of the engine system that is communicating with a first electronic control module of the plurality of electronic control modules, based on the estimated hydrocarbon mass.

3. The method of protecting of claim 2 further comprising preventing an exothermic event in the after treatment system by controlling the gradual engine ramp up.

4. The method of protecting of claim 1, wherein the correction factor is a manifold correction factor.

5. The method of protecting claim 1, wherein the engine system parameters are selected from an amount of fuel, an engine speed, an engine timing, a total mass exhaust flow, a crank mode, an injection amount, an inlet manifold pressure, an inlet manifold temperature, a coolant temperature, an ambient temperature and an ambient pressure.

6. The method of protecting of claim 1, wherein the estimated amount of engine out hydrocarbon includes a mass rate for engine hydrocarbon at startup or various engine hydrocarbon run mode.

7. The method of protecting of claim 1, wherein the microprocessor communicates with a reductant injector to modulate the applied reductant.

8. The method of protecting of claim 2 further comprising the step of receiving, with the microprocessor, sensor information from a sensor.

9. The method of protecting of claim 8, wherein the sensor is a throttle position sensor.

10. The method of protecting of claim 9, wherein the step of controlling the gradual engine ramp up allows the engine to gradually warm up regardless of a position of a throttle sensed by the throttle position sensor.

11. The method of protecting of claim 1, wherein the step of controlling engine ramp up includes controlling an amount of fuel being injected into the engine.

12. A method of protecting an after treatment system from effects of hydrocarbon accumulation, comprising the steps of:

controlling gradual exhaust temperature ramp up, with the microprocessor of the engine system that is communicating with a first electronic control module of the plurality of electronic control modules, based on the estimated hydrocarbon mass.

13. The method of protecting of claim 12 further comprising modulating, with the microprocessor of the engine system communicating with a reductant injector, a reductant that is applied to the after treatment system of the engine system.

14. The method of protecting of claim 12 further comprising preventing an exothermic event in the after treatment system by controlling step.

15. The method of protecting of claim 12, wherein the correction factor is a manifold correction factor.

16. The method of protecting of claim 12, wherein the estimated amount of engine out hydrocarbon includes a mass rate for engine hydrocarbon at startup or various engine hydrocarbon run mode.

17. The method of protecting of claim 12 further comprising the step of receiving, with the microprocessor of the engine system, sensor information from a throttle position sensor.

18. The method of protecting of claim 17, wherein the step of controlling the gradual engine ramp up allows the engine to gradually warm up regardless of a position of a throttle sensed by the throttle position sensor.

19. A system that protects an after treatment system of a vehicle from the effects of hydrocarbon accumulation, comprising:

means for processing that communicates with a hydrocarbon estimation software stored on means for storing of an engine system computer;

means for injecting configured to inject a reductant into the after treatment system; and

means for interfacing that allows the means for processing to communicate with the means for injecting, wherein the means for processing executes the hydrocarbon estimation software to perform the steps of:

receiving, at the means for processing, engine system parameters from a plurality of electronic control modules of the engine systems;

estimating, with the means for processing, an amount of engine out hydrocarbon based on the engine system parameters;

receiving, from the means for storing, a correction factor that adjusts the estimated amount of engine out hydrocarbon;

estimating, with the means for processing, a hydrocarbon mass on the after treatment system of the engine system with the adjusted estimated amount of engine out hydrocarbon; and

modulating, with the means for processing controlling the means for injecting, the reductant that is applied to the after treatment system of the engine system.

20. The system of claim 19, wherein the estimated amount of engine out hydrocarbon includes a mass rate for engine hydrocarbon at startup or various engine hydrocarbon run mode.