JP2018165490A - Method for estimating dispersion plate surface temperature - Google Patents
Method for estimating dispersion plate surface temperature Download PDFInfo
- Publication number
- JP2018165490A JP2018165490A JP2017063190A JP2017063190A JP2018165490A JP 2018165490 A JP2018165490 A JP 2018165490A JP 2017063190 A JP2017063190 A JP 2017063190A JP 2017063190 A JP2017063190 A JP 2017063190A JP 2018165490 A JP2018165490 A JP 2018165490A
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- urea water
- dispersion plate
- exhaust
- surface temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Exhaust Gas After Treatment (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Description
本発明は、排気通路における尿素水添加弁と触媒装置との間の部分に設置されて排気への尿素水の分散を促進する分散板の表面温度を推定する方法に関する。 The present invention relates to a method for estimating a surface temperature of a dispersion plate that is installed in a portion of an exhaust passage between a urea water addition valve and a catalyst device and promotes dispersion of urea water to exhaust gas.
排気に添加された尿素水を使って排気中の窒素酸化物（ＮＯｘ）を浄化する尿素ＳＣＲ（Selective Catalytic Reduction）システムを備える排気浄化装置が知られている。尿素ＳＣＲシステムは、排気通路における触媒装置よりも上流側の部分に設置されて、排気中に尿素水を噴射する添加弁を備えている。添加弁から噴射された尿素水は、排気の熱によって加水分解されてアンモニアに変化し、このアンモニアを還元剤として触媒装置でのＮＯｘの還元浄化が行われる。 2. Description of the Related Art There is known an exhaust purification device including a urea SCR (Selective Catalytic Reduction) system that purifies nitrogen oxide (NOx) in exhaust using urea water added to exhaust. The urea SCR system includes an addition valve that is installed in a portion upstream of the catalyst device in the exhaust passage and injects urea water into the exhaust. The urea water injected from the addition valve is hydrolyzed by the heat of the exhaust gas to change to ammonia, and NOx is reduced and purified in the catalyst device using this ammonia as a reducing agent.
さらに、こうした排気浄化装置において、排気通路における添加弁と触媒装置との間の部分に、フィンや網などにより構成された分散板が設けられたものがある。こうした分散板を備える排気浄化装置では、添加弁が噴射した尿素水が分散板に衝突することで、尿素水の気化や霧化を促し、加水分解によるアンモニアの生成を促進している。 Further, in such an exhaust purification device, there is one in which a dispersion plate made of fins, nets, or the like is provided in a portion between the addition valve and the catalyst device in the exhaust passage. In the exhaust emission control device provided with such a dispersion plate, urea water injected by the addition valve collides with the dispersion plate, thereby promoting vaporization and atomization of the urea water and promoting generation of ammonia by hydrolysis.
なお、分散板の表面温度が低い場合、同分散板の表面に尿素水が付着し易くなる。分散板の表面に付着した尿素水からは尿素由来の析出物が析出して、分散板の表面に堆積することがある。そこで従来、特許文献１に記載の車載用の排気浄化装置では、分散板の表面温度を推定し、その推定した表面温度が一定の値よりも低い場合には、添加弁による尿素水の噴射を禁止することで、分散板表面への析出物の堆積を抑えている。なお、同文献では、分散板を通過する排気の温度及び流量、車速、外気温に基づき、分散板と排気、及び外気との間の熱収支のモデルに従って、分散板の表面温度を推定している。 When the surface temperature of the dispersion plate is low, urea water tends to adhere to the surface of the dispersion plate. From urea water adhering to the surface of the dispersion plate, precipitates derived from urea may be deposited and deposited on the surface of the dispersion plate. Therefore, conventionally, in the on-vehicle exhaust purification device described in Patent Document 1, the surface temperature of the dispersion plate is estimated, and when the estimated surface temperature is lower than a certain value, urea water is injected by the addition valve. By prohibiting, deposition of deposits on the surface of the dispersion plate is suppressed. In this document, the surface temperature of the dispersion plate is estimated according to the heat balance model between the dispersion plate, the exhaust, and the outside air based on the temperature and flow rate of the exhaust gas passing through the dispersion plate, the vehicle speed, and the outside air temperature. Yes.
なお、分散板の表面温度には、その表面に付着した尿素水が少なからぬ影響を与える。また、そうした分散板表面の尿素水の付着量は時々刻々と変化するものとなっている。そのため、分散板の表面温度の正確な推定は、非常に難しいものとなっていた。 The surface temperature of the dispersion plate has a considerable influence of urea water adhering to the surface. In addition, the amount of urea water attached to the surface of such a dispersion plate changes from moment to moment. Therefore, accurate estimation of the surface temperature of the dispersion plate has been very difficult.
本発明は、こうした実情に鑑みてなされたものであり、その解決しようとする課題は、分散板の表面温度を正確に推定することのできる分散板表面温度の推定方法を提供することにある。 The present invention has been made in view of such circumstances, and a problem to be solved is to provide a method for estimating a dispersion plate surface temperature that can accurately estimate the surface temperature of the dispersion plate.
上記課題を解決する分散板表面温度の推定方法は、排気通路に設置された触媒装置と、同排気通路における触媒装置よりも上流側の部分に設置されて排気中に尿素水を噴射する添加弁と、同排気通路における触媒装置と添加弁との間の部分に設置されて添加弁が噴射した尿素水が衝突する分散板と、を備える排気浄化装置における分散板の表面温度を正確に推定する方法を提供するものとなっている。 A dispersion plate surface temperature estimation method that solves the above problems includes a catalyst device installed in an exhaust passage, and an addition valve that is installed in a portion upstream of the catalyst device in the exhaust passage and injects urea water into the exhaust gas And a dispersion plate installed in a portion between the catalyst device and the addition valve in the exhaust passage and collided with urea water injected by the addition valve, accurately estimates the surface temperature of the dispersion plate in the exhaust purification device It is meant to provide a method.
ここで、分散板に尿素水が恒常的に付着しているものと仮定する。添加弁の尿素水噴射は間欠的に行われており、分散板の尿素水の付着量は、添加弁が尿素水を噴射した直後には増加し、噴射していない期間には、蒸発により減少する。その結果、分散板に付着した尿素水（以下、付着尿素水と記載する）と周囲との熱収支は、非定常となり、同尿素水の温度（以下、付着尿素水温度Ｔadと記載する）は常に変動している。こうした変動する温度である付着尿素水温度Ｔadに対して、長期的な付着尿素水の熱収支が同等となる一定温度に換算したものを等価尿素水温度Ｔeqとする。等価尿素水温度Ｔeqは、単位時間当たりの添加弁の尿素水の噴射量（尿素水添加量Ｑ）が無限大の場合には、尿素水温度Ｔurと同じ温度となり、同尿素水添加量Ｑが０の場合には排気温度Ｔgasと同じ温度となる。そして、尿素水添加量が０と無限大の間の場合には、等価尿素水温度Ｔeqは、尿素水添加量Ｑに対して指数的に変化する値となる。すなわち、等価尿素水温度Ｔeqは、排気温度Ｔgas、尿素水温度Ｔur、尿素水添加量Ｑに対して下式の関係を満たす温度となる。なお、下式におけるｅはネイピア数を表し、τは定数となっている。 Here, it is assumed that urea water is permanently attached to the dispersion plate. The urea water injection of the addition valve is intermittently performed, and the adhesion amount of the urea water on the dispersion plate increases immediately after the addition valve injects the urea water, and decreases by evaporation during the non-injection period. To do. As a result, the heat balance between urea water adhering to the dispersion plate (hereinafter referred to as adhering urea water) and the surroundings becomes unsteady, and the temperature of the urea water (hereinafter referred to as adhering urea water temperature Tad) is It is constantly changing. An equivalent urea water temperature Teq is obtained by converting the adhering urea water temperature Tad, which is such a fluctuating temperature, to a constant temperature at which the long-term heat balance of the adhering urea water is equivalent. The equivalent urea water temperature Teq is the same as the urea water temperature Tur when the urea water injection amount (urea water addition amount Q) of the addition valve per unit time is infinite. In the case of 0, it becomes the same temperature as the exhaust temperature Tgas. When the urea water addition amount is between 0 and infinity, the equivalent urea water temperature Teq is a value that exponentially changes with respect to the urea water addition amount Q. That is, the equivalent urea water temperature Teq is a temperature that satisfies the relationship of the following equation with respect to the exhaust gas temperature Tgas, the urea water temperature Tur, and the urea water addition amount Q. Note that e in the following expression represents the number of Napier, and τ is a constant.
平衡温度Ｔtは、分散板を通過する排気の流量である排気流量Ｇａ、排気温度Ｔgas、等価尿素水温度Ｔeqに対して、下式の関係を満たす温度として求めることができる。なお、下式におけるＣgas、Ｃur、ｋは定数である。 The equilibrium temperature Tt can be obtained as a temperature that satisfies the relationship of the following expression with respect to the exhaust gas flow rate Ga, the exhaust gas temperature Tgas, and the equivalent urea water temperature Teq, which are the flow rates of the exhaust gas passing through the dispersion plate. Note that Cgas, Cur, and k in the following equation are constants.
一方、上述の等価尿素水温度Ｔeqに基づくことで、分散板に付着した尿素水が一時的に完全に蒸発した状態となるか否かを判定することが可能となる。すなわち、等価尿素水温度Ｔeqが既定の閾値（完全蒸発判定温度Ｔth）以上であるか否かで、付着尿素水が一時的に完全に蒸発した状態となるか否かを判定することができる。 On the other hand, based on the above-described equivalent urea water temperature Teq, it is possible to determine whether or not the urea water attached to the dispersion plate is temporarily completely evaporated. That is, whether or not the attached urea water is temporarily completely evaporated can be determined based on whether or not the equivalent urea water temperature Teq is equal to or higher than a predetermined threshold (complete evaporation determination temperature Tth).
上記推定方法では、こうした等価尿素水温度Ｔeqから、分散板に付着した尿素水が一時的に完全に蒸発した状態となるかどうかを判定している。そして、分散板の付着尿素水が一時的に完全に蒸発した状態となると判定した場合とそうでない場合とでは、上式における定数Ｃgas、Ｃurが異なった値となるものとして、平衡温度Ｔtを算出するようにしている。そのため、付着尿素水が一時的に完全に蒸発した状態となる場合、恒常的に存在する場合のいずれにおいても、それぞれの場合の熱収支の状態に応じた適切な値として平衡温度Ｔtを求めることが可能となる。したがって、上記分散板表面温度の推定方法によれば、分散板の表面温度を正確に推定することができる。 In the above estimation method, it is determined from such equivalent urea water temperature Teq whether or not the urea water attached to the dispersion plate is temporarily completely evaporated. Then, the equilibrium temperature Tt is calculated on the assumption that the constants Cgas and Cur in the above equation are different depending on whether or not the urea water adhering to the dispersion plate is temporarily completely evaporated. Like to do. Therefore, when the attached urea water is temporarily completely evaporated, the equilibrium temperature Tt is obtained as an appropriate value according to the state of the heat balance in each case where it always exists. Is possible. Therefore, according to the method for estimating the dispersion plate surface temperature, the surface temperature of the dispersion plate can be accurately estimated.
以下、分散板表面温度の推定方法の一実施形態を、図１〜図６を参照して詳細に説明する。ここではまず、本実施形態の推定方法による分散板表面温度の推定対象となる排気浄化装置の構成を説明する。 Hereinafter, an embodiment of a method for estimating the dispersion plate surface temperature will be described in detail with reference to FIGS. Here, first, the configuration of an exhaust emission control device that is an estimation target of the dispersion plate surface temperature by the estimation method of the present embodiment will be described.
図１に示すように、排気浄化装置１０は、車載用の内燃機関１１に設けられており、同内燃機関１１の排気通路１２に設置された尿素ＳＣＲシステムを備えている。
尿素ＳＣＲシステムは、排気中に尿素水を噴射する添加弁１３と、添加弁１３が噴射した尿素水が加水分解して生成されたアンモニアを還元剤として排気中のＮＯｘを還元浄化する触媒装置１４と、を備えている。添加弁１３は、排気通路１２における触媒装置１４よりも上流側の部分に設置されている。
As shown in FIG. 1, the exhaust purification device 10 is provided in a vehicle-mounted internal combustion engine 11 and includes a urea SCR system installed in an exhaust passage 12 of the internal combustion engine 11.
The urea SCR system includes an addition valve 13 for injecting urea water into exhaust gas, and a catalyst device 14 for reducing and purifying NOx in exhaust gas using ammonia generated by hydrolysis of urea water injected by the addition valve 13 as a reducing agent. And. The addition valve 13 is installed in a portion upstream of the catalyst device 14 in the exhaust passage 12.
さらに、尿素ＳＣＲシステムは、排気通路１２における添加弁１３と触媒装置１４との間の部分に設置された分散板１５を備えている。分散板１５は、網や複数のフィンにより構成されており、添加弁１３が噴射した尿素水が衝突することで、同尿素水を排気中に分散してその霧化や気化を促進する。なお、排気通路１２における添加弁１３よりも上流側の部分には、同部分を流れる排気の温度（以下、添加弁前排気温度Ｔｅと記載する）を検出する排気温度センサ１６が設置されている。 Further, the urea SCR system includes a dispersion plate 15 installed in a portion of the exhaust passage 12 between the addition valve 13 and the catalyst device 14. The dispersion plate 15 is composed of a net and a plurality of fins, and the urea water injected by the addition valve 13 collides to disperse the urea water in the exhaust gas and promote atomization and vaporization. An exhaust temperature sensor 16 for detecting the temperature of the exhaust gas flowing through the exhaust passage 12 upstream of the addition valve 13 (hereinafter referred to as pre-addition valve exhaust temperature Te) is installed in the exhaust passage 12. .
添加弁１３は、尿素水を貯留する尿素水タンク１７に、尿素水供給路１８を通じて接続されている。尿素水供給路１８の途中には、尿素水タンク１７内の尿素水を汲み出して添加弁１３に向けて送り出すポンプ１９が設けられている。また、尿素水供給路１８におけるポンプ１９と添加弁１３との間の部分には、添加弁１３に送られる尿素水の温度を、ひいては添加弁１３が噴射する尿素水の温度（以下、尿素水温度Ｔurと記載でする）を検出する尿素水温度センサ２０が設置されている。 The addition valve 13 is connected to a urea water tank 17 that stores urea water through a urea water supply path 18. In the middle of the urea water supply path 18, a pump 19 that pumps the urea water in the urea water tank 17 and sends it to the addition valve 13 is provided. Further, in the portion of the urea water supply path 18 between the pump 19 and the addition valve 13, the temperature of the urea water sent to the addition valve 13, and thus the temperature of the urea water injected by the addition valve 13 (hereinafter referred to as urea water). A urea water temperature sensor 20 for detecting a temperature Tur) is installed.
また、排気浄化装置１０は、電子制御ユニット２１を備えている。電子制御ユニット２１には、上記排気温度センサ１６、尿素水温度センサ２０の検出結果に加え、内燃機関１１の吸入空気量や燃料噴射量、外気温、車速などが入力されている。そして、電子制御ユニット２１は、内燃機関１１の運転状態から同内燃機関１１のＮＯｘの排出量を求めるとともに、その排出量分のＮＯｘを触媒装置１４で還元浄化するために必要な単位時間当たりの尿素水の添加量である要求添加量を算出している。そして、電子制御ユニット２１は、単位時間当たりの尿素水の総噴射量がその要求添加量と同じ量となるように添加弁１３の尿素水噴射の制御を行っている。 Further, the exhaust purification device 10 includes an electronic control unit 21. In addition to the detection results of the exhaust temperature sensor 16 and the urea water temperature sensor 20, the electronic control unit 21 receives the intake air amount, fuel injection amount, outside air temperature, vehicle speed, and the like of the internal combustion engine 11. Then, the electronic control unit 21 obtains the NOx emission amount of the internal combustion engine 11 from the operating state of the internal combustion engine 11, and per unit time necessary for reducing and purifying the NOx corresponding to the emission amount by the catalyst device 14. The required addition amount that is the addition amount of urea water is calculated. The electronic control unit 21 controls urea water injection of the addition valve 13 so that the total injection amount of urea water per unit time is the same as the required addition amount.
（分散板表面温度の推定）
続いて、電子制御ユニット２１が行う分散板１５の表面温度Ｔmの推定の詳細を説明する。
(Estimation of dispersion plate surface temperature)
Next, details of the estimation of the surface temperature Tm of the dispersion plate 15 performed by the electronic control unit 21 will be described.
図２に、表面温度Ｔmの推定にかかる分散板表面温度推定ルーチンのフローチャートを示す。電子制御ユニット２１は、内燃機関１１の運転中、既定の制御周期毎に、本ルーチンの処理を繰り返し実行する。 FIG. 2 shows a flowchart of a dispersion plate surface temperature estimation routine for estimating the surface temperature Tm. The electronic control unit 21 repeatedly executes the processing of this routine every predetermined control period during the operation of the internal combustion engine 11.
本ルーチンの処理が開始されると、まずステップＳ１００において、分散板１５を通過する排気の流量である排気流量Ｇａ、及び分散板１５を通過する時点の排気の温度である排気温度Ｔgasの算出が行われる。排気流量Ｇａは、内燃機関１１の吸入空気量や燃料噴射量等から求められている。また、排気温度Ｔgasは、添加弁前排気温度Ｔｅ、排気流量Ｇａ、車速、外気温等から算出されている。詳しくは、排気通路１２における排気温度センサ１６の設置位置から分散板１５の設置位置までの区間における外気への放熱による排気温度の低下量を、排気流量Ｇａ、車速、及び外気温から求め、その低下量を添加弁前排気温度Ｔｅから引いた差を排気温度Ｔgasの値として算出している。 When the processing of this routine is started, first, in step S100, the exhaust flow rate Ga that is the flow rate of the exhaust gas that passes through the dispersion plate 15 and the exhaust gas temperature Tgas that is the temperature of the exhaust gas that passes through the dispersion plate 15 are calculated. Done. The exhaust gas flow rate Ga is obtained from the intake air amount of the internal combustion engine 11, the fuel injection amount, and the like. The exhaust temperature Tgas is calculated from the pre-addition valve exhaust temperature Te, the exhaust flow rate Ga, the vehicle speed, the outside air temperature, and the like. Specifically, the amount of decrease in the exhaust temperature due to heat radiation to the outside air in the section from the installation position of the exhaust temperature sensor 16 to the installation position of the dispersion plate 15 in the exhaust passage 12 is obtained from the exhaust flow rate Ga, the vehicle speed, and the outside temperature. The difference obtained by subtracting the amount of decrease from the pre-addition valve exhaust temperature Te is calculated as the value of the exhaust temperature Tgas.
続いて、ステップＳ１１０において、添加弁１３が噴射した尿素水の温度である尿素水温度Ｔur、及び添加弁１３の単位時間当たりの尿素水の噴射量である尿素水添加量Ｑの読み込みが行われる。そして、続くステップＳ１２０において、排気温度Ｔgas、尿素水温度Ｔur、及び尿素水添加量Ｑに基づき、等価尿素水温度Ｔeqが算出される。 Subsequently, in step S110, the urea water temperature Tur that is the temperature of the urea water injected by the addition valve 13 and the urea water addition amount Q that is the injection amount of the urea water per unit time of the addition valve 13 are read. . In the subsequent step S120, the equivalent urea water temperature Teq is calculated based on the exhaust gas temperature Tgas, the urea water temperature Tur, and the urea water addition amount Q.
なお、ここで算出する等価尿素水温度Ｔeqは、次の温度となっている。分散板１５に尿素水が恒常的に付着しているものと仮定する。添加弁１３の間欠的な尿素水噴射のため、分散板１５の付着尿素水の温度（付着尿素水温度Ｔad）は、変動しているが、変動する温度である付着尿素水温度Ｔadを、長期的な付着尿素水の熱収支が同等となる一定温度に換算したものが等価尿素水温度Ｔeqである。 The equivalent urea water temperature Teq calculated here is the following temperature. It is assumed that urea water is permanently attached to the dispersion plate 15. Because of the intermittent urea water injection of the addition valve 13, the temperature of the attached urea water on the dispersion plate 15 (attached urea water temperature Tad) fluctuates. The equivalent urea water temperature Teq is converted to a constant temperature at which the heat balance of the typical attached urea water is equivalent.
図３に、尿素水添加量Ｑと等価尿素水温度Ｔeqとの関係を示す。尿素水添加量Ｑが無限大の場合には、添加弁１３から噴射された尿素水が無尽蔵に分散板１５に供給され続けることになるため、このときの等価尿素水温度Ｔeqは尿素水温度Ｔurと同じ温度となる。一方、尿素水添加量Ｑが０の場合には、等価尿素水温度Ｔeqは排気温度Ｔgasと同じ温度となる。そして、尿素水添加量Ｑが無限大と０との間の値である場合には、等価尿素水温度Ｔeqは、尿素水添加量Ｑに対して指数関数的に変化する値となる。したがって、等価尿素水温度Ｔeqは、排気温度Ｔgas、尿素水温度Ｔur、及び尿素水添加量Ｑに対して、式（１）の関係となる。同式におけるτは定数であり、その値は、実験やシミュレーション等の結果から求められている。なお、本明細書に記載の各数式において「ｅｘｐ（Ｘ）」は、ネイピア数ｅを底とし、変数Ｘを冪指数とする指数関数を表している。 FIG. 3 shows the relationship between the urea water addition amount Q and the equivalent urea water temperature Teq. When the urea water addition amount Q is infinite, the urea water injected from the addition valve 13 continues to be supplied infinitely to the dispersion plate 15, so that the equivalent urea water temperature Teq at this time is the urea water temperature Tur. The same temperature. On the other hand, when the urea water addition amount Q is 0, the equivalent urea water temperature Teq is the same temperature as the exhaust gas temperature Tgas. When the urea water addition amount Q is a value between infinity and 0, the equivalent urea water temperature Teq is a value that changes exponentially with respect to the urea water addition amount Q. Therefore, the equivalent urea water temperature Teq has the relationship of the expression (1) with respect to the exhaust gas temperature Tgas, the urea water temperature Tur, and the urea water addition amount Q. In the equation, τ is a constant, and the value is obtained from the results of experiments and simulations. In each equation described in this specification, “exp (X)” represents an exponential function with the Napier number e as the base and the variable X as the power exponent.
なお、分散板１５の付着尿素水が一時的に完全に蒸発した状態となる場合と、分散板１５の表面に恒常的に存在している場合とでは、分散板１５の熱収支の状態は異なったものとなる。 Note that the state of heat balance of the dispersion plate 15 differs between the case where the urea water adhering to the dispersion plate 15 is temporarily completely evaporated and the case where it is permanently present on the surface of the dispersion plate 15. It will be.
図４は、付着尿素水が分散板１５の表面に恒常的に存在する場合の、すなわち等価尿素水温度Ｔeqが完全蒸発判定温度Ｔth未満となる場合の分散板１５の表面温度Ｔm、及び付着尿素水温度Ｔadの推移を示している。同図の時刻ｔ１に添加弁１３が尿素水を噴射して、表面温度Ｔmよりも低温の尿素水が分散板１５に付着すると、付着した尿素水に熱を奪われて分散板１５の表面温度Ｔmは低下し始める。時刻ｔ１以降、付着尿素水温度Ｔadは、排気や分散板１５からの受熱により上昇するようになる。なお、分散板１５から付着尿素水への放熱量は、付着尿素水温度Ｔadが上昇して、分散板１５の表面温度Ｔmとの温度差が縮小するに従って、減少するようになる。そして、時刻ｔ２において、排気から分散板１５への受熱量と、分散板１５から付着尿素水への放熱量とが等しくなる熱的平衡点に到達するまで付着尿素水温度Ｔadが上昇すると、分散板１５の表面温度Ｔmは、低下から上昇に転じるようになる。そして、時刻ｔ３に、添加弁１３が再び尿素水を噴射するまでの期間、分散板１５の表面温度Ｔmは上昇するようになる。 FIG. 4 shows the surface temperature Tm of the dispersion plate 15 when the attached urea water is constantly present on the surface of the dispersion plate 15, that is, when the equivalent urea water temperature Teq is lower than the complete evaporation judgment temperature Tth, and the attached urea. The transition of water temperature Tad is shown. When the addition valve 13 injects urea water at time t1 in the figure and urea water having a temperature lower than the surface temperature Tm adheres to the dispersion plate 15, the surface temperature of the dispersion plate 15 is deprived of heat by the attached urea water. Tm begins to drop. After time t1, the attached urea water temperature Tad rises due to exhaust and heat received from the dispersion plate 15. The amount of heat released from the dispersion plate 15 to the attached urea water decreases as the attached urea water temperature Tad increases and the temperature difference from the surface temperature Tm of the dispersion plate 15 decreases. At time t2, when the attached urea water temperature Tad rises until reaching a thermal equilibrium point at which the amount of heat received from the exhaust to the dispersion plate 15 and the amount of heat released from the dispersion plate 15 to the attached urea water are equal, The surface temperature Tm of the plate 15 starts to increase from a decrease. At a time t3, the surface temperature Tm of the dispersion plate 15 rises until the addition valve 13 again injects urea water.
図５は、付着尿素水が一時的に完全に蒸発した状態となる場合の、すなわち等価尿素水温度Ｔeqが完全蒸発判定温度Ｔth以上となる場合の分散板１５の表面温度Ｔm、及び付着尿素水温度Ｔadの推移を示している。この場合にも、同図の時刻ｔ４に添加弁１３が尿素水を噴射して、表面温度Ｔmよりも低温の尿素水が分散板１５に付着すると、付着尿素水に熱を奪われて分散板１５の表面温度Ｔmは低下し始める。また、時刻ｔ４以降、付着尿素水温度Ｔadは、排気や分散板１５からの受熱により上昇するようになる。ただし、この場合には、上述の熱的平衡点に到達する前に、付着尿素水温度Ｔadが尿素水の沸点Ｔbに達する。そして、この場合には、同図の時刻ｔ５において付着尿素水が完全に蒸発した状態となった時点で、表面温度Ｔmが低下から上昇に転じ、時刻ｔ６に添加弁１３が再び尿素水を噴射するまで表面温度Ｔmは上昇し続ける。 FIG. 5 shows the surface temperature Tm of the dispersion plate 15 and the attached urea water when the attached urea water is temporarily completely evaporated, that is, when the equivalent urea water temperature Teq is equal to or higher than the complete evaporation judgment temperature Tth. The transition of temperature Tad is shown. Also in this case, when the addition valve 13 injects urea water at time t4 in the figure and urea water having a temperature lower than the surface temperature Tm adheres to the dispersion plate 15, heat is deprived by the attached urea water and the dispersion plate. The surface temperature Tm of 15 begins to decrease. Further, after time t4, the attached urea water temperature Tad rises due to exhaust or heat received from the dispersion plate 15. In this case, however, the attached urea water temperature Tad reaches the boiling point Tb of the urea water before reaching the above-described thermal equilibrium point. In this case, when the attached urea water is completely evaporated at time t5 in the same figure, the surface temperature Tm changes from lowering to rising, and the addition valve 13 injects urea water again at time t6. Until then, the surface temperature Tm continues to rise.
なお、いずれの場合にも、定常な状態が続けば、やがて、表面温度Ｔmは一定の温度に収束する。以下の説明では、このときの表面温度Ｔmの収束点を、平衡温度Ｔtと記載する。 In any case, if the steady state continues, the surface temperature Tm eventually converges to a constant temperature. In the following description, the convergence point of the surface temperature Tm at this time is described as an equilibrium temperature Tt.
平衡温度Ｔtは、分散板１５の熱収支を計算することで、下記のように求めることができる。以下に記載の各数式において、変数の上にドットが付されたものは、同変数を時間微分した値を表している。 The equilibrium temperature Tt can be obtained as follows by calculating the heat balance of the dispersion plate 15. In each mathematical expression described below, a dot on a variable represents a value obtained by differentiating the variable with respect to time.
ここで、排気から分散板１５への受熱量をｑgas、分散板１５から付着尿素水への放熱量をｑur、分散板１５の比熱をＣmとする。現在から時間ｔが経過した時点の分散板１５の表面温度Ｔmの変化速度（時間微分値）は、式（２）のように表せる。 Here, the amount of heat received from the exhaust to the dispersion plate 15 is qgas, the amount of heat released from the dispersion plate 15 to the attached urea water is qur, and the specific heat of the dispersion plate 15 is Cm. The rate of change (time differential value) of the surface temperature Tm of the dispersion plate 15 at the time when the time t has elapsed from the present can be expressed as in Expression (2).
そこで、図２の分散板表面温度推定ルーチンでは、上述のステップＳ１３０において、分散板１５の付着尿素水が一時的に完全に蒸発した状態となると判定された場合（Ｔeq≧Ｔth）と、同付着尿素水が恒常的に存在していると判定された場合（Ｔeq＜Ｔth）とで、定数Ｃgas、Ｃurに異なる値を設定している。すなわち、等価尿素水温度Ｔeqが完全蒸発判定温度Ｔth以上であって、付着尿素水が一時的に完全に蒸発した状態となると判定された場合（Ｓ１３０：ＹＥＳ）、ステップＳ１４０において、Ｃgas、Ｃurの値としてそれぞれＣgas1、Ｃur1が設定される。Ｃgas1、Ｃur1の値は、それぞれを式（６）におけるＣgas、Ｃurの値として設定したときに同式が、付着尿素水が一時的に完全に蒸発した状態となる場合の平衡温度Ｔｔを導く式となるように予め設定されている。これに対して、等価尿素水温度Ｔeqが完全蒸発判定温度Ｔth未満であり、付着尿素水が恒常的に存在していると判定された場合（Ｓ１３０：ＮＯ）、ステップＳ１５０において、Ｃgas、Ｃurの値としてそれぞれＣgas2、Ｃur2が設定される。Ｃgas1、Ｃur1の値は、それぞれを式（６）におけるＣgas、Ｃurの値として設定したときに同式が、付着尿素水が恒常的に存在する状態となっている場合の平衡温度Ｔｔを導く式となるように予め設定されている。 Therefore, in the dispersion plate surface temperature estimation routine of FIG. 2, when it is determined in step S130 described above that the attached urea water on the dispersion plate 15 is temporarily completely evaporated (Teq ≧ Tth), the same attachment is performed. Different values are set for the constants Cgas and Cur when it is determined that urea water is constantly present (Teq <Tth). That is, when it is determined that the equivalent urea water temperature Teq is equal to or higher than the complete evaporation determination temperature Tth and the attached urea water is temporarily completely evaporated (S130: YES), in step S140, Cgas and Cur are changed. Cgas1 and Cur1 are set as values, respectively. The values of Cgas1 and Cur1 are equations that lead to the equilibrium temperature Tt when the attached urea water is in a completely evaporated state when each is set as the value of Cgas and Cur in equation (6). Is set in advance so that On the other hand, when the equivalent urea water temperature Teq is lower than the complete evaporation determination temperature Tth and it is determined that the attached urea water is constantly present (S130: NO), in step S150, Cgas and Cur Cgas2 and Cur2 are set as values, respectively. The values of Cgas1 and Cur1 are equations for deriving the equilibrium temperature Tt when the attached urea water is constantly present when the values are set as the values of Cgas and Cur in equation (6), respectively. Is set in advance so that
なお、分散板１５の付着尿素水が一時的に完全に蒸発した状態となる場合には、恒常的に存在する場合よりも、分散板１５の表面温度Ｔmに与える排気からの受熱の影響がより大きくなる。そのため、Ｃgas1、Ｃur1、Ｃgas2、Ｃur2の各値は、「Ｃgas1／Ｃur1＞Ｃgas2／Ｃur2」を満たす関係となるように設定されている。 In addition, when the urea water adhering to the dispersion plate 15 is temporarily completely evaporated, the influence of the heat received from the exhaust on the surface temperature Tm of the dispersion plate 15 is more affected than when it is constantly present. growing. Therefore, the values of Cgas1, Cur1, Cgas2, and Cur2 are set so as to satisfy the relationship “Cgas1 / Cur1> Cgas2 / Cur2.”
こうして、ステップＳ１３０の判定結果に応じてＣgas、Ｃurの値が設定されると、ステップＳ１６０において式（６）に従って平衡温度Ｔtが算出される。また、続くステップＳ１７０では、排気流量Ｇａ、尿素水添加量Ｑ等から、なまし定数κの値が算出される。このとき、なまし定数κは、１以上の値を取るように算出されている。そして、ステップＳ１８０において、平衡温度Ｔｔ、なまし定数κ、及び表面温度Ｔｍの推定値に基づき、同表面温度Ｔｍの推定値である推定表面温度Ｔmpの値が更新された後、今回の本ルーチンの処理が終了される。なお、ステップＳ１７０での推定表面温度Ｔmpの値の更新は、式（７）の関係を満たすように行われる。なお、同式におけるＴmp［i-1］は推定表面温度Ｔmpの更新前の値を、Ｔmp［i］は推定表面温度Ｔmpの更新後の値を、それぞれ表している。 Thus, when the values of Cgas and Cur are set according to the determination result of step S130, the equilibrium temperature Tt is calculated in accordance with equation (6) in step S160. In the subsequent step S170, the value of the annealing constant κ is calculated from the exhaust gas flow rate Ga, the urea water addition amount Q, and the like. At this time, the annealing constant κ is calculated to take a value of 1 or more. In step S180, the estimated surface temperature Tmp, which is an estimated value of the surface temperature Tm, is updated based on the estimated values of the equilibrium temperature Tt, the annealing constant κ, and the surface temperature Tm. This process is terminated. Note that the update of the estimated surface temperature Tmp in step S170 is performed so as to satisfy the relationship of Expression (7). In the equation, Tmp [i-1] represents a value before updating the estimated surface temperature Tmp, and Tmp [i] represents a value after updating the estimated surface temperature Tmp.
図６に、尿素水添加量Ｑ以外は同一の条件で内燃機関１１を定常運転したときの尿素水添加量Ｑと等価尿素水温度Ｔeq及び推定表面温度Ｔmpとの関係を示す。等価尿素水温度Ｔeqは、尿素水添加量ＱがＱ１以下と場合に完全蒸発判定温度Ｔth以上となっている。よって、同図における尿素水添加量ＱがＱ１以下の領域（以下、完全蒸発領域と記載する）では、分散板１５の付着尿素水が一時的に完全に蒸発した状態となり、尿素水添加量ＱがＱ１を超える領域（以下、恒常付着領域と記載する）では、分散板１５に付着尿素水が恒常的に存在している状態となる。 FIG. 6 shows the relationship between the urea water addition amount Q, the equivalent urea water temperature Teq, and the estimated surface temperature Tmp when the internal combustion engine 11 is steadily operated under the same conditions except for the urea water addition amount Q. The equivalent urea water temperature Teq is equal to or higher than the complete evaporation determination temperature Tth when the urea water addition amount Q is Q1 or lower. Therefore, in the region where the urea water addition amount Q in FIG. 5 is equal to or less than Q1 (hereinafter referred to as a complete evaporation region), the attached urea water on the dispersion plate 15 is temporarily completely evaporated, and the urea water addition amount Q In a region where Q exceeds Q1 (hereinafter, referred to as a constant adhesion region), the attached urea water is constantly present on the dispersion plate 15.
なお、同図には、分散板１５の表面温度Ｔmの実測の結果が、白丸で示されている。また、同図に示す曲線Ｔmp2は、完全蒸発領域、恒常付着領域のいずれにおいても、式（６）における定数Ｃgas、Ｃurの値をＣgas2、Ｃur2に固定して平衡温度Ｔtの算出を行った場合の推定表面温度の算出結果を示している。こうした場合の推定表面温度の算出結果は、恒常付着領域では実測の結果に即した値となるが、完全蒸発領域では実測の結果から大きく乖離した値となる。これに対して、本実施形態の推定方法により算出した推定表面温度Ｔmpは、完全蒸発領域、恒常付着領域のいずれにおいても、実測の結果に即した値となっている。このように、本実施形態の推定方法では、逐次の分散板１５の表面温度Ｔmを正確に推定することができる。 In the figure, the results of actual measurement of the surface temperature Tm of the dispersion plate 15 are indicated by white circles. Further, the curve Tmp2 shown in the figure is obtained when the equilibrium temperature Tt is calculated with the constants Cgas and Cur in Equation (6) fixed to Cgas2 and Cur2 in both the complete evaporation region and the constant adhesion region. The calculation result of the estimated surface temperature of is shown. The calculation result of the estimated surface temperature in such a case is a value according to the actual measurement result in the permanent adhesion region, but is a value greatly deviating from the actual measurement result in the complete evaporation region. On the other hand, the estimated surface temperature Tmp calculated by the estimation method of the present embodiment is a value in accordance with the actual measurement result in both the complete evaporation region and the constant adhesion region. As described above, in the estimation method of the present embodiment, the surface temperature Tm of the successive dispersion plates 15 can be accurately estimated.
なお、このような逐次の分散板１５の表面温度Ｔmの正確な推定によっては、下記の制御が可能となる。
添加弁１３が噴射した尿素水の一部は分散板１５に付着するが、その付着した尿素水から尿素由来の析出物が析出して分散板１５の表面に堆積することがある。分散板１５には、その表面温度Ｔmが低いほど、尿素水が付着しやすくなる。また、付着した尿素水からの析出物の析出にかかる反応（変質や熱分解）の速度は、分散板１５の表面温度Ｔmに依存する。よって、分散板１５の表面温度Ｔmには、析出物の堆積が進行しやすい温度域が存在し、そうした温度域にあるときに、多量の尿素水添加を行えば、分散板１５への析出物の堆積が進行して、分散板１５に目詰まりを生じさせる虞がある。
In addition, the following control is attained by such an accurate estimation of the surface temperature Tm of the sequential dispersion plate 15.
Part of the urea water sprayed by the addition valve 13 adheres to the dispersion plate 15, but urea-derived precipitates may deposit from the attached urea water and deposit on the surface of the dispersion plate 15. The lower the surface temperature Tm, the easier the urea water adheres to the dispersion plate 15. Further, the speed of the reaction (degeneration or thermal decomposition) required for the precipitation of the precipitate from the attached urea water depends on the surface temperature Tm of the dispersion plate 15. Therefore, the surface temperature Tm of the dispersion plate 15 has a temperature range where the deposition of precipitates is likely to proceed, and if a large amount of urea water is added in such a temperature range, the precipitate on the dispersion plate 15 is deposited. As a result, the dispersion plate 15 may become clogged.
これに対しては、本実施形態の推定方法による分散板１５の表面温度Ｔmの推定結果（推定表面温度Ｔmp）から、分散板１５に尿素水が付着しやすい状態にあるかどうかを確認することができる。そこで、推定表面温度Ｔmpが、尿素水が付着しやすい温度域にある場合には、添加弁１３の尿素水噴射を禁止したり、尿素水添加量を減らしたりすることで、分散板１５への析出物の堆積を抑制することが可能となる。 For this, it is confirmed from the estimation result (estimated surface temperature Tmp) of the surface temperature Tm of the dispersion plate 15 by the estimation method of the present embodiment whether or not urea water is likely to adhere to the dispersion plate 15. Can do. Therefore, when the estimated surface temperature Tmp is in a temperature range in which urea water is likely to adhere, the urea water injection of the addition valve 13 is prohibited or the urea water addition amount is reduced, so that It becomes possible to suppress deposition of precipitates.
また、こうした析出物の堆積の進行速度は、分散板１５の表面温度Ｔmに依存する。そこで、推定表面温度Ｔmpに基づき、析出物の堆積の進行速度を求めるとともに、その値を積算することで、分散板１５の析出物の堆積量を推定することが可能となる。一方、分散板１５に堆積した析出物は、同析出物を燃焼可能な温度まで排気温度Ｔgasを高めることで除去できる。こうした析出物の除去制御は、燃料消費を伴うが、上記堆積量の推定結果に基づき同除去制御の実施判定を行えば、過不足なく効率的に除去制御を実施できるようになる。 Further, the speed of deposition of such precipitates depends on the surface temperature Tm of the dispersion plate 15. Therefore, it is possible to estimate the deposition amount of the precipitate on the dispersion plate 15 by determining the progress rate of the deposition of the precipitate based on the estimated surface temperature Tmp and integrating the value. On the other hand, the deposit deposited on the dispersion plate 15 can be removed by raising the exhaust gas temperature Tgas to a temperature at which the deposit can be combusted. Such deposit removal control involves fuel consumption. However, if the determination of the removal control is performed based on the estimation result of the accumulation amount, the removal control can be performed efficiently without excess or deficiency.
さらに、分散板１５に多量の尿素水が付着していると、添加弁１３が噴射した尿素水の分散板１５での分散が、ひいては尿素水の霧化や気化が抑えられて、アンモニアが生成され難くなる。そのため、そうした場合に尿素水添加を実施しても、尿素水の消費に相応するだけのＮＯｘ浄化率が得られない場合がある。一方、上述のように分散板１５の尿素水付着量は、同分散板１５の表面温度Ｔmに依存する。そこで、推定表面温度Ｔmpが、分散板１５の尿素水付着量があまり大きくならない温度域にあるときに、尿素水添加を行うようにすれば、ＮＯｘを効率的に浄化できるようになる。 Further, if a large amount of urea water is attached to the dispersion plate 15, the dispersion of the urea water injected by the addition valve 13 on the dispersion plate 15 and, in turn, the atomization and vaporization of the urea water are suppressed, and ammonia is generated. It becomes difficult to be done. For this reason, even if urea water is added in such a case, a NOx purification rate corresponding to the consumption of urea water may not be obtained. On the other hand, as described above, the urea water adhesion amount of the dispersion plate 15 depends on the surface temperature Tm of the dispersion plate 15. Therefore, if the estimated surface temperature Tmp is in a temperature range where the urea water adhesion amount of the dispersion plate 15 does not become so large, NOx can be efficiently purified by adding urea water.
１０…排気浄化装置、１１…内燃機関、１２…排気通路、１３…添加弁、１４…触媒装置、１５…分散板、１６…排気温度センサ、１７…尿素水タンク、１８…尿素水供給路、１９…ポンプ、２０…尿素水温度センサ、２１…電子制御ユニット。 DESCRIPTION OF SYMBOLS 10 ... Exhaust gas purification device, 11 ... Internal combustion engine, 12 ... Exhaust passage, 13 ... Addition valve, 14 ... Catalyst device, 15 ... Dispersion plate, 16 ... Exhaust temperature sensor, 17 ... Urea water tank, 18 ... Urea water supply path, DESCRIPTION OF SYMBOLS 19 ... Pump, 20 ... Urea water temperature sensor, 21 ... Electronic control unit.
Claims (1)
前記分散板を通過する排気の温度を排気温度Ｔgas、前記添加弁が噴射する尿素水の温度を尿素水温度Ｔur、同添加弁の単位時間当たりの尿素水の噴射量を尿素水添加量Ｑとし、ｅをネイピア数、τを定数としたとき、前記排気温度Ｔgas、前記尿素水温度Ｔur、及び前記尿素水添加量Ｑに対して、
前記分散板を通過する排気の流量を排気流量Ｇａ、既定の定数をｋとし、且つ、Ｃgas、Ｃurのそれぞれを、前記等価尿素水温度Ｔeqが既定の完全蒸発判定温度Ｔth以上である場合と前記等価尿素水温度Ｔeqが前記完全蒸発判定温度Ｔth未満の場合とで異なった値を取る定数としたとき、前記排気温度Ｔgas、前記排気流量Ｇａ、及び前記等価尿素水温度Ｔeqに対して、
分散板表面温度の推定方法。 A catalyst device installed in the exhaust passage; an addition valve installed in a portion upstream of the catalyst device in the exhaust passage to inject urea water into the exhaust; the catalyst device and the addition valve in the exhaust passage A dispersion plate surface temperature estimation method for estimating a surface temperature of the dispersion plate in an exhaust gas purification apparatus comprising:
The exhaust gas temperature passing through the dispersion plate is defined as the exhaust gas temperature Tgas, the urea water temperature injected by the addition valve is the urea water temperature Tur, and the urea water injection amount per unit time of the addition valve is the urea water addition amount Q. , E is a Napier number, and τ is a constant, the exhaust temperature Tgas, the urea water temperature Tur, and the urea water addition amount Q,
A flow rate of exhaust gas passing through the dispersion plate is defined as an exhaust gas flow rate Ga, a predetermined constant is k, and each of Cgas and Cur is determined when the equivalent urea water temperature Teq is equal to or higher than a predetermined complete evaporation determination temperature Tth and When the equivalent urea water temperature Teq is a constant that takes a value different from that when it is less than the complete evaporation determination temperature Tth, with respect to the exhaust temperature Tgas, the exhaust flow rate Ga, and the equivalent urea water temperature Teq,
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017063190A JP2018165490A (en) | 2017-03-28 | 2017-03-28 | Method for estimating dispersion plate surface temperature |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017063190A JP2018165490A (en) | 2017-03-28 | 2017-03-28 | Method for estimating dispersion plate surface temperature |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2018165490A true JP2018165490A (en) | 2018-10-25 |
Family
ID=63921709
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2017063190A Pending JP2018165490A (en) | 2017-03-28 | 2017-03-28 | Method for estimating dispersion plate surface temperature |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2018165490A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020208975A1 (en) * | 2019-04-12 | 2020-10-15 | 株式会社豊田自動織機 | Exhaust purifying device |
| CN112324547A (en) * | 2020-10-31 | 2021-02-05 | 同济大学 | Selective catalytic reduction control method and system suitable for mixed fuel |
-
2017
- 2017-03-28 JP JP2017063190A patent/JP2018165490A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020208975A1 (en) * | 2019-04-12 | 2020-10-15 | 株式会社豊田自動織機 | Exhaust purifying device |
| CN112324547A (en) * | 2020-10-31 | 2021-02-05 | 同济大学 | Selective catalytic reduction control method and system suitable for mixed fuel |
| CN112324547B (en) * | 2020-10-31 | 2021-12-31 | 同济大学 | Selective catalytic reduction control method and system suitable for mixed fuel |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112189083B (en) | Method and device for controlling a urea mixer for reducing NOx emissions from a combustion engine | |
| WO2019019046A1 (en) | Injection amount control method and device for scr urea injection system in engine | |
| JP2017025830A (en) | Exhaust emission control device for engine | |
| US9995197B2 (en) | Ammonia adsorption amount estimation apparatus, ammonia adsorption amount estimation method, and exhaust gas purification system for internal combustion engine | |
| JP2018165490A (en) | Method for estimating dispersion plate surface temperature | |
| US11846226B2 (en) | Exhaust gas mixer, system, and method of using | |
| EP2496802B1 (en) | Apparatus and method for estimating the temperature of a catalyst of an internal combustion engine | |
| JP2019007449A (en) | Exhaust emission control system of internal combustion engine | |
| JP6287539B2 (en) | Exhaust purification system | |
| JP2021148085A (en) | Urea scr system, control device of urea scr system and estimation method of accumulation amount of white product | |
| JP6120020B2 (en) | Exhaust gas purification device for internal combustion engine | |
| JP2017110596A (en) | Exhaust emission control device for internal combustion engine | |
| EP3070282B1 (en) | Exhaust emission control system of internal combustion engine | |
| JP6379057B2 (en) | Exhaust gas purification device for internal combustion engine | |
| KR20200022777A (en) | Method for controlling urea injection quantity of vehicle | |
| JP6179378B2 (en) | Exhaust purification device | |
| JP2005337040A (en) | Exhaust emission control device of internal combustion engine | |
| JP2022055025A (en) | Internal combustion engine system, white accumulation amount monitoring device for internal combustion engine system and white accumulation amount monitoring method for internal combustion engine system | |
| JP2015075069A (en) | Control device of internal combustion engine | |
| JP2018062901A (en) | Internal combustion engine control device | |
| JP2020041439A (en) | Controller of internal combustion engine | |
| JP2018150833A (en) | Exhaust emission control device for internal combustion engine | |
| JP2018205054A (en) | Temperature controller of air-fuel ratio sensor | |
| JP2015110922A (en) | Exhaust emission control system |