Abstract:
A method for calculating exhaust gas temperature indirectly at points in or around an engine exhaust after treatment system for use in determining an amount of unburned hydrocarbons resident therein at a given point in time.

Description:
TECHNICAL FIELD 
     The present disclosure relates to a method for calculating temperature, and more specifically a way to indirectly calculate an exhaust temperature at points in or around an engine after treatment system for use in determining an amount of unburned hydrocarbons resident therein at a given point in time. 
     BACKGROUND 
     Engines such as diesel or other lean burning engines generally provide more complete fuel combustion and better fuel efficiency than other types of engines. While these engines can be very efficient, they generally operate at higher temperatures and pressures than comparable non-lean burning engines. With the higher pressures and temperatures, oxides of nitrogen (NO x ) emissions including nitric oxide (NO) and nitrogen dioxide (NO 2 ) are typically higher as oxygen and nitrogen tend to combine more easily at higher temperatures. However, such NO x  emissions have been known to cause environmental issues and thus are subject to emissions control regulations. These emissions control regulations limit the amount of NO x  emissions engines are allowed to emit during normal operation and have resulted in the widespread use of NO x  reduction devices in engine exhaust systems in order to reduce the NO x  emissions to the required levels. 
     Specifically, one such after treatment system that has been widely used is known as a selective catalytic reduction (SCR) system. SCR systems generally utilize a catalyst that converts NO x  gases 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 x  gases. 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 enter 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. Unburned hydrocarbons are particularly known to be produced in the engine exhaust during pro-longed periods of engine idle usage and/or low temperature operations. If such a situation is followed by relatively rapid heating of the catalyst, the hydrocarbons can ignite and cause an exothermic event that could potentially damage the catalyst. Alternatively, if the accumulated hydrocarbons don&#39;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 x  gases into nitrogen gases and water (selective catalytic reduction). 
     For this reason, it is desirable to be able to determine the amount of accumulated hydrocarbons that may be trapped in an exhaust after treatment system on a real-time basis so that when levels reach a predetermined level, the issues may be dealt with so that the hyrdocarbons may be released from the after treatment safely and efficiently. Some examples of methods for releasing hydrocarbons include, but are not limited to, manipulating operating/idle conditions, modification of engine calibration/mapping, and limiting engine power output/temperature. 
     While it would be desired to directly measure the accumulated hydrocarbon level in the after treatment system itself, this can be a difficult characteristic to measure directly. However, it has been found that an accurate model can be utilized to calculate with some accuracy the amount of hydrocarbon build-up. One model that has been used to perform this estimation is Vanadia SCR HC Accumuation Model. One of the inputs needed to utilize this model is the temperature of the exhaust as it enters, or at various points in, the exhaust after treatment system. However, some engine systems do not incorporate a thermocouple or direct measuring sensor located at the points wherein this temperature is needed for the corresponding hydrocarbon accumulation model being used. Accordingly, in order to utilize the aforementioned model (or for any other purpose), it is desirable to have a method for calculating an exhaust temperature entering, or at various points within, the after treatment system utilizing available inputs other than directly measured temperatures. 
     It is known to calculate engine exhaust temperatures through indirect means, i.e. directly measured and/or calculated inputs other than the temperature itself. For example, U.S. Pat. No. 8,205,606 issued on Jun. 26, 2012 to Rodriguez et al. entitled “Model for inferring temperature of exhaust gas at an exhaust manifold using temperature measured at entrance of a diesel oxidation catalyst” (the &#39;606 patent) discloses one such method. As the title suggests, the &#39;606 patent discloses a method for calculating the temperature of an exhaust gas at an exhaust manifold based upon the temperature measured at the entrance of the exhaust after treatment system. More specifically, the &#39;606 patent discloses calculating this exhaust temperature based upon related parameters including engine operation conditions, ambient conditions, exhaust system characteristics, engine speed and load, etc. However, the &#39;606 patent does not disclose a method for calculating an exhaust temperature at an exhaust after treatment system inlet or at various points therein. 
     Accordingly, there is a need for a method for calculating an exhaust temperature at the exhaust after treatment inlet or at various points therein utilizing available inputs other than a directly measured temperature. 
     SUMMARY 
     In one aspect, the disclosure is directed to a method for calculating an engine exhaust temperature at the exhaust after treatment inlet. More specifically, one aspect of the disclosure provides a method for calculating an exhaust temperature at the exhaust after treatment inlet comprising the steps of: providing the exhaust temperature entering the turbine; calculating the amount of work extracted from the exhaust by a turbo; predicting the temperature for the exhaust flow exiting the turbine; and utilizing a heat transfer model to arrive at a predicted exhaust temperature at the exhaust after treatment system inlet. 
     In another aspect, the disclosure is directed to a method for calculating an engine exhaust temperature at a catalyst inlet point within an exhaust after treatment system. More specifically, in accordance with this aspect, a method for calculating an exhaust temperature at the catalyst inlet within the after treatment system may comprise the steps of: providing the exhaust temperature entering the turbine, calculating the amount of work extracted from the exhaust by a turbo; predicting the temperature for the exhaust flow exiting the turbine; and utilizing a heat transfer model to replicate heat transfer from the exhaust after treatment inlet to the inlet for the after treatment catalyst to arrive at a predicted exhaust temperature. 
     In another aspect of the disclosure, a heat transfer model may be used to replicate the engine thermal inertia and applied to the calculated turbine outlet temperature. In another aspect, a low pass filtering model may be applied to the predicted temperature to replicate thermocouple behavior. The temperature predicted according to the disclosure may be used in a strategy that determines an amount of unburned hydrocarbons resident in an after treatment system, and more specifically, in various catalysts utilized in an after treatment system, at a given point in time. Further in accordance with the disclosure, the predicted temperature may be used in a strategy that calculates accumulated urea deposits in an SCR and/or the quantity of ammonia slip from an SCR at any given time. In accordance with the disclosure, the calculated exhaust temperature may be used in an appropriate model to calculate hydrocarbon build-up within the exhaust after treatment system, and more particularly, hydrocarbon build-up within portions of the after treatment catalysts. In exhaust after treatment systems utilizing separate catalyst banks for each cylinder bank, the calculations may be performed separately for each cylinder bank. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of an exemplary vehicle that utilizes an after treatment system according to aspects of the present disclosure; 
         FIG. 2  is a perspective view of an exemplary after treatment system that may be used in accordance with aspects of the present disclosure; 
         FIG. 3  is a schematic diagram of components of an internal combustion engine in accordance with aspects of the present disclosure; 
         FIG. 4  is a schematic diagram of components of an engine system computer suitable for use in accordance with aspects of the present disclosure; 
         FIG. 5  is a flow diagram of a method for calculating an exhaust temperature at the inlet to an exhaust after treatment system in accordance with aspects of the present disclosure; and 
         FIG. 6  is a flow diagram of a method for calculating an exhaust temperature at the inlet to a catalyst bank of an exhaust after treatment system in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a method for calculating the exhaust temperature at the inlet of an exhaust after treatment system and/or at various points within an exhaust after treatment system including at the inlet to a catalyst bank therein. Further, the present disclosure is related to a method for calculating an amount of hydrocarbon build-up in an exhaust after treatment system utilizing an exhaust temperature calculated in accordance with the foregoing. 
     In accordance with the disclosure,  FIG. 1  is an illustration of an exemplary vehicle  100  incorporating an engine that may utilize an exhaust after treatment system in accordance with aspects of the disclosure. The vehicle  100  may 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 , for inclining the dump body  118  in order to expel a payload  121  at a distal end  122 . 
       FIG. 2  is a perspective view of an exhaust after treatment system  220  with the top removed to illustrate the components and the corresponding exhaust flow. The exhaust after treatment system  220  can include a housing  222  that is supported on a base support  224  adapted to mount the exhaust after treatment system  220  to an engine, 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 engine  115  exhaust gasses into the exhaust 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 embodiment illustrated, the after treatment system  220  may include two inlets  240 , corresponding to separate cylinder banks within the engine  115 , 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 . It is to be understood that while  FIG. 2  depicts an exhaust after treatment system  220  wherein the exhaust streams from both inlets  240  are mixed within the after treatment system  220 . However, it is within the scope of the disclosure to provide separate inlets  240  corresponding to separate engine  115  cylinder banks and wherein the exhaust flow therefrom may remain separated while being treated within the exhaust after treatment system  220 . 
     In accordance with the disclosure, two outlets  242  may be disposed through the forward first wall  226  of the housing  222  to enable the exhaust gasses to exit the after treatment system  220 . Each outlet  242  may be oriented in a parallel fashion to the centrally oriented inlets  240 . 
     To treat or condition the exhaust gasses, the housing  222  may 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+½O 2 ═CO 2   (1)
 
[HC]+O 2 =CO 2 +H 2 O  (2)
 
     To further reduce emissions in the exhaust gasses and particularly to reduce nitrogen oxides such as NO and NO 2 , 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 X  to nitrogen (N 2 ) and water (H 2 O). A common reducing agent is urea ((NH 2 ) 2 CO), though other suitable substances such as ammonia (NH 3 ), Diesel Exhaust Fluid (DEF) can be used in the SCR process. The reaction may occur according to the following general formula:
 
NH 3 +NO X =N 2 +H 2 O  (3)
 
     Referring again to  FIG. 2 , to introduce the reducing agent, the SCR system  250  may include 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 X  load 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 exhaust 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  may be 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. 
     In one aspect of the disclosure, such as in a cold environment, the vehicle  100  may be left in idle for an extended period of time, such as overnight. During such extended low temperature operation, hydrocarbons may accumulate on the catalysts (including in the DOCs  246  and the SCRs  250 ) in the exhaust after treatment system  220 . As discussed herein, the accumulation of hydrocarbons can be deleterious in that when the vehicle  100  is thereafter operated, an undesirable exothermic reaction may be induced in the after treatment system thereby, potentially, damaging the catalysts in the DOCs  246  and SCRs  250  and other parts of the after treatment system  220 . 
       FIG. 3  is a schematic drawing of a single cylinder bank  315  of an internal combustion engine  115  having a turbocharger system  312  and exhaust after treatment system  220  in accordance with aspects of the disclosure. It is to be understood that systems may be utilized having multiple cylinder banks  315  as is known in the art but for clarity sake, only a single cylinder bank  315  is shown herein. 
     In accordance with this disclosure, internal combustion engine  115  may have a cylinder bank  315  comprise of a plurality of combustion cylinders  314 . Each combustion cylinder  314  may be coupled with a corresponding intake manifold  316  and with a corresponding exhaust manifold  318 ,  320 . While a single intake manifold  316  is shown, it should be understood that more than one intake manifold may be used with or coupled to each combustion cylinder  314 , for providing an air mixture to each combustion cylinder  314 . A fuel, such as diesel fuel is injected into each combustion cylinder  314  and combusted therein, in a known manner. 
     Internal combustion engine  115  may include a first exhaust manifold  318  and a second exhaust manifold  320 . First exhaust manifold  318  may be fluidly coupled with three of the combustion cylinders  314 , and second exhaust manifold  320  may be fluidly coupled with the remaining three combustion cylinders  314 . Turbocharger system  312  may include a turbocharger  322  having a turbine  324  and a compressor  326 . Turbine  324  may have a turbine outlet  334  leading to an inlet  240  to the exhaust after treatment system  220 , a first inlet path  336  in fluid flow communication with first exhaust manifold  318  and a second inlet path  338  in fluid flow communication with second exhaust manifold  320 . A fluid conduit  340  connects first exhaust manifold  318  to first inlet path  336 , and a fluid conduit  342  fluidly connects second exhaust manifold  320  to second inlet path  338 . A turbine wheel (not shown) may be disposed on a shaft  350  drivingly coupled to a compressor wheel (not shown) in compressor  326 . A compressor inlet  352  and a compressor outlet  354  may be provided for compressor  326 . Compressor inlet  352  receives combustion gas from a source such as ambient air, and compressor outlet  354  supplies compressed combustion gas to intake manifold  316 . 
     In accordance with some aspects of the disclosure, the engine system may be equipped with an exhaust gas recirculation (EGR) system  360  as is known in the art. Such a system may include a duct  362  receiving exhaust gas from first exhaust manifold  318 , to direct the exhaust gas to intake manifold  316 . Duct  362  is connected to conduit  340  in fluid flow communication, and includes a valve  364  for controlling the flow of exhaust gas through duct  362 . A cooler  366  may be provided in duct  362  to lower the temperature of exhaust gas provided to intake manifold  316 . A fluid conduit  368  fluidly couples compressor outlet  354  to a mixer  370 . Mixer  370  also receives exhaust gas flow from duct  362 , and controls the mixture of compressed combustion gas from compressor  326  with exhaust gas recirculated from exhaust gas recirculation system  360 , and provides the mixture thereof to intake manifold  316  through a fluid conduit  372 . 
     An optional aftercooler  374  may be provided in fluid conduit  368 , and a valve  376  in conduit  368  may direct compressed gas flow to mixer  370  or through a fluid conduit  378  directly to fluid conduit  372 , thereby bypassing mixer  370 . Valve  376  may include an inlet  380  connected in fluid flow communication to conduit  368 , and receives compressed combustion gas from compressor  326 . Valve  376  may further include a first outlet  382  connected to conduit  368 , for directing compressed combustion gas flow towards mixer  370 , and a second outlet  384  connected in fluid flow communication to fluid conduit  378 . 
     During use of engine  115 , a fuel, such as diesel fuel, is injected into combustion cylinders  314  and combusted when a piston (not shown) disposed within each combustion cylinder  314  is at or near a top dead center position. Exhaust gas is transported from each combustion cylinder  314  to the exhaust manifold associated with it, either first exhaust manifold  318  or second exhaust manifold  320 . Exhaust gas within first exhaust manifold  318  is transported to first inlet path  336  and exhaust gas from second exhaust manifold  320  is transported to second inlet path  338 , for rotatably driving turbine wheel (not shown). Turbine  324  in turn rotatably drives compressor  326  via shaft  50 . The spent exhaust gas is discharged from turbine  324  to the after treatment system  220  through turbine outlet  334 . 
     Exhaust gas is recirculated from first exhaust manifold  318  to intake manifold  316  via EGR duct  362 , mixer  370  and fluid conduit  372 . Compressor  326  draws combustion air into compressor inlet  352 . The combustion air is compressed within compressor  326  and is discharged from compressor  326  through compressor outlet  354  and fluid conduit  368 . The compressed combustion air is cooled within aftercooler  374  and is transported to intake manifold  316  via mixer  370  and fluid conduit  372  for use in combustion occurring within combustion cylinders  314 . Mixer  370  combines fluid flow from EGR duct  362  and from fluid conduit  368 , and supplies the mixture thereof to intake manifold  316  through fluid conduit  372 . Valve  376  may be operated to bypass some or all of the compressed gas flow in conduit  368  to conduit  372  and intake manifold  316 , bypassing mixer  370 . EGR flow rate in duct  362  may be controlled by valve  364 . 
       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 x  sensors, NH 3  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. 
     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. 
     It is to be understood that multi-dimensional maps, models or equations disclosed herein and utilized in accordance with the disclosure 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 as is known in the art. For example, maps may include equations, graphs and/or tables that relate to a DOC and/or SCR device temperature (either measured or predicted) to an ability of SCR device to store reducing agent and to convert emissions gases. The inputs fed into the maps may include engine air mass flow rate, manifold correction factor, inlet gas ratio, inlet NO 2  over NO x  ratio, inlet pressure, and inlet temperature of SCR device, inlet temperature of DOC device, ambient temperature, a total fuel quantity, engine speed, etc. 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 flow diagram  500  of steps to calculate an inlet temperature for exhaust gases entering after treatment system  220  and utilizing the same in a hydrocarbon estimation strategy. The calculation starts at step  502 . At step  504 , the exhaust temperature T 1  entering the turbine  324  is either provided as an observed number from an associated sensor or calculated from various engine system parameters received from various electronic control modules of the vehicle  100 . The system parameters may be received at the microprocessor  402 , which may be running after treatment protection software. 
     At step  506 , the amount of work extracted from the exhaust by the turbine  324  may be calculated by a physics-based energy balance equation as is known in the art. For this calculation, engine system parameters 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. Using that calculation, a ΔT 1  may be calculated in a known manner. 
     At step  508  the predicted temperature for the exhaust flow exiting the turbine  324  may be calculated by subtracting the ΔT 1  temperature from the exhaust temperature T 1  prior to the turbine  324  to arrive at a T 2 . 
     At step  510  a low pass filtering model may be applied to the T 2  temperature. This low pass filtering model may be used to replicate the behavior of a thermocouple and/or provide a correction factor to correct for thermal inertia of the engine  115  “iron.” With respect to the thermal inertia correction, the calculated turbine  324  outlet exhaust temperature T 2  represents an instantaneous value which generally needs to be corrected for residual heat added to or removed from the exhaust gas as it flows through the engine  115 . In accordance with the disclosure, this correction for residual heat transfer in the engine  115  may be managed through filtering of the output signal. 
     At step  512  a heat transfer model may be applied to calculate a ΔT 2  from the turbine  324  outlet to the exhaust after treatment system  220  inlets  240 . In the present disclosure, given the location of the inlets  240  to the DOCs  270 , this temperature is essentially the temperature of the exhaust gas at the DOCs  270 . The ΔT 2  may be subtracted from the T 2  temperature to arrive at a T 3  temperature prior to the exhaust entering the DOCs  270  (see  FIG. 2 ). 
     At step  514  the calculated T 3  temperature may be passed to the hydrocarbon estimation model or strategy to determine the estimated amount of hydrocarbon build-up in the DOCs  270 . 
     In accordance with one aspect of the disclosure, separate inlet temperatures T 3  for each inlet  240  leading to the after treatment system  220  from each cylinder  314  bank may be calculated separately. Such a strategy is useful in engine  115  systems utilizing multiple cylinder  314  banks because each cylinder  314  bank utilizes separate DOC&#39;s  270 , respectively, and may accumulate hydrocarbons at different rates and thus the risk of exothermic events, damage are DOC  270  specific. 
       FIG. 6  is a flow diagram  600  of steps to calculate an inlet temperature for exhaust gases entering an SCR catalyst  250  bank of an after treatment system  220  and utilizing the same in a hydrocarbon estimation strategy. The calculation starts at step  602 . 
     At step  604 , the exhaust temperature T 1  entering the turbine  324  is either provided as an observed number from an associated sensor or calculated from various engine system parameters received from various electronic control modules of the vehicle  100 . The system parameters may be received at the microprocessor  402 , which may be running after treatment protection software. 
     At step  606 , the amount of work extracted from the exhaust by the turbine  324  may be calculated by a physics-based energy balance equation as is known in the art. For this calculation, engine system parameters 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. Using that calculation, a ΔT 1  may be calculated in a known manner. 
     At step  608  the predicted temperature for the exhaust flow exiting the turbine  324  may be calculated by subtracting the ΔT 1  temperature from the exhaust temperature T 1  prior to the turbine  324  to arrive at a T 2 . 
     At step  610  a low pass filtering model may be applied to the T 2  temperature. This low pass filtering model may be used to replicate the behavior of a thermocouple and/or provide a correction factor to correct for thermal inertia of the engine  115  “iron.” With respect to the thermal inertia correction, the calculated turbine  324  outlet exhaust temperature T 2  represents an instantaneous value which generally needs to be corrected for residual heat added to or removed from the exhaust gas as it flows through the engine  115 . In accordance with the disclosure, this correction for residual heat transfer in the engine  115  may be managed through filtering of the output signal. 
     At step  612  a heat transfer model may be applied to calculate a ΔT 2  from the turbine  324  outlet to the SCR  250  inlets. The ΔT 2  may be subtracted from the T 2  temperature to arrive at a T 4  temperature prior to the exhaust entering the SCRs  250  (see  FIG. 2 ). 
     At step  614  the calculated T 4  temperature may be passed to the hydrocarbon estimation model or strategy to determine the estimated amount of hydrocarbon build-up in the SCRs  250 . Further in accordance with another aspect of the disclosure, the calculated T 4  temperature may be used in a strategy that calculates accumulated urea deposits in the SCRs  250  and/or the quantity of ammonia slip from the SCRs  250  at any given time. 
     In accordance with one aspect of the disclosure, separate inlet temperatures T 4  for the inlet to each SCR  250  from each cylinder  314  bank may be calculated separately. Such a strategy is useful in engine  115  systems utilizing multiple cylinder  314  banks and wherein the exhaust gases remain segregated in the after treatment system  220  because each SCR  250  may accumulate hydrocarbons at different rates and thus the risk of exothermic events, damage are SCR  250  specific. 
     The steps outlined in  FIGS. 5 and 6  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. 
     The foregoing strategies assume valid turbocharger speed, turbine inlet temperature and mass flow measurements exist for each bank. Within the scope of the disclosure, it should be understood that these, and other, parameters may be directly measured or may be determined through calculations, modeling, etc. as is known in the art. In the event one of these required parameters is not available, the model is capable of being trained with empirical engine data, which can provide lesser but acceptable accuracy in a faulted condition. Also, because compressor maps are historically poor at low speeds and pressure ratios the model is capable of utilizing an empirical data mode as required for more accurate estimation as required to maintain accuracy of the predictions. 
     INDUSTRIAL APPLICABILITY 
     The disclosure is applicable to any engine systems having exhaust after treatment systems wherein it would be desirable to calculate a temperature of the exhaust either entering, or within, the exhaust after treatment system. Such engine systems particularly include after treatment systems having a catalyst therein that may need protection from the effects of hydrocarbon accumulation and wherein such a temperature may be necessary in the calculation of such hydrocarbon build-up. More specifically, the present disclosure is particularly useful in applications where it may be expensive and/or difficult to provide a thermocouple or other sensor to directly measure exhaust temperatures at the inlet to an exhaust after treatment system (or at various points therein). 
     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.