JP4026136B2

JP4026136B2 - Method and apparatus for evaluating pressure loss of honeycomb structure

Info

Publication number: JP4026136B2
Application number: JP2003051044A
Authority: JP
Inventors: 俊崇石澤; 直樹杉尾; 秀樹竹島; 謙一郎関口
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2003-02-27
Filing date: 2003-02-27
Publication date: 2007-12-26
Anticipated expiration: 2023-02-27
Also published as: JP2004257954A

Description

【０００１】
【発明の属する技術分野】
本発明は、排気ガスを浄化するのに使用されるハニカム構造体の圧力損失の評価方法に関する。
【０００２】
【従来の技術】
ディーゼルエンジンやガソリンエンジンなど内燃機関の排ガスを浄化するのに使用される排ガス浄化用ハニカム構造体は、一般にセラミックあるいは金属などの耐熱材料で構成されており，内燃機関の排気系に組みこまれ、排ガス中に含まれる有害物質を取り除く役割を果たす。前記排ガス浄化用ハニカム構造体には、触媒物質を担持することにより目的の有害物質を取り除く役割を果たすものや、主にディーゼルエンジンの排ガス中の粒子状物質（ＰａｒｔｉｃｕｌａｔｅＭａｔｔｅｒｓ、以下「ＰＭ」という）を前記ハニカム構造体がろ過捕捉し、排ガス浄化に寄与するディーゼルパティキュレートフィルタ（以下ＤＰＦという）用ハニカム構造体もある。
【０００３】
前記排ガス浄化用ハニカム構造体は、その圧力損失により排ガスの流れを妨げるためエンジン出力の低下の原因となる。また、前記ＤＰＦ用ハニカム構造体においては、排ガス中のＰＭが前記ＤＰＦ用ハニカム構造体内部に捕捉され蓄積されるのに伴い、圧力損失が高くなりエンジン出力の低下につながる。このためハニカム構造体の初期の圧力損失や、ＰＭの蓄積後の圧力損失を把握する必要がある。
【０００４】
さて、ハニカム構造体の「圧力損失」とは、ハニカム構造体を気体が通過したときのハニカム構造体の上流側の気体の圧力値から下流側の気体の圧力値を引いたものであり、排気ガスがハニカム構造体を通過する際に受ける抵抗が最大の要因となる。従って、ハニカム構造体の隔壁の材料、厚さ、気孔率、細孔径など、また排気ガスが流入するハニカム構造体の入口端部形状などを、適切にする必要がある。
【０００５】
ハニカム構造体の圧力損失を求めて、評価する手段としては、日本工業規格（ＪＩＳ）の自動車用エアクリーナの試験方法を用いることがある（例えば、非特許文献１参照）。この非特許文献１の試験装置は、供試体（ＪＩＳでは自動車用エアクリーナ）を収納する試験用チャンバと、試験用チャンバの出口側および入口側に接続した差圧計と、出口側から順に送気管を介して接続したアブソリュートフィルタ、空気流量計、空気流量制御装置、および排気送風機などからなる。そして、非特許文献１の試験装置で、供試体となるハニカム構造体の圧力損失を求める場合には、試験室の空気を１５分間以上流し、その後、差圧計により圧力損失を求めることになる。また、空気量、差圧などの値を、２０℃、相対湿度６５％、気圧１０１３ｈＰａの標準状態に補正して、圧力損失を求めることになる。また、例えば特許文献１に記載の発明のように前記ハニカム構造体を内燃機関の排気系に組み込み、求めた圧力損失をエンジンの排気流量で補正する方法や、特許文献２に記載の発明のように内燃機関を用いずに粒子含有気体発生器により前記ハニカム構造体に粒子を含有した気体を送り込み、前記ハニカム構造体の気体流入側と流出側との差圧より圧力損失を求める記載が見られる。これらはいずれも圧力損失の上昇後に測定を行うため、比較的容易に圧力損失が求められる。
【０００６】
ところで、前記ＤＰＦ用ハニカム構造体においては、一定量のＰＭが蓄積されるとこれを電気ヒータで燃焼させたり、逆洗エアーで除去しＤＰＦの再生を行う必要があるが、従来の電気ヒータで微粒子を燃焼再生する方法では、微粒子の自己発熱によりＤＰＦ用ハニカム構造体自体が溶損したり、また逆洗エアーを用いる場合は装置が複雑になる問題があり、最近では触媒物質の作用によりＤＰＦ用ハニカム構造体内で微粒子を連続的に燃焼させる技術（ＣＲＴシステム）が採用されるようになってきた。
【０００７】
【非特許文献１】
ＪＩＳＤ１６１２−１９８９自動車用エアクリーナの試験方法［第４頁第８．項（通気抵抗試験）、第２０頁第２．（１５）項（通気抵抗）、第２４頁（試験用ダスト）、第２７頁（図６パネル形フィルタエレメント用清浄効率及びダスト保持量試験装置）、第３２〜３４頁（標準状態に対する空気量及び通気抵抗の補正）］
【特許文献１】
特開平８−１０９８１８号公報
【特許文献２】
特許第２８０７３７０号公報
【０００８】
【発明が解決しようとする課題】
前記ＣＲＴシステムでは、定常状態においてＰＭは連続的に燃焼除去され蓄積されないので、ＰＭ蓄積による圧力損失の上昇はほとんどない。さらにＣＲＴシステムではＤＰＦ用ハニカム構造体の上流側に酸化触媒を担持したハニカム構造体の配置が不可欠である。場合によってはＤＰＦ用ハニカム構造体の下流側にＮＯｘ除去の触媒を担持したハニカム構造体の配置が必要になる事もあり、内燃機関の排気系全体の圧力損失が大きくなりエンジン出力の低下につながるので、ＤＰＦ用ハニカム構造体自体にも気孔率が５０％以上で平均細孔径１５μｍ以上の材料を用いたりセル構造を最適化する技術が適用される等、ＤＰＦ用ハニカム構造体そのものの圧力損失を低く抑えるための技術開発が進められており、その評価および検査を行うために低い圧力損失を精度良く求める必要がある。
【０００９】
ところがこのようなＤＰＦ用ハニカム構造体に前記自動車用エアクリーナの試験方法を用いて圧力損失を求めても、あるいは前記特許文献記載の圧力損失を求める方法を用いても、圧力損失自体が極めて小さい事から、ＤＰＦ用ハニカム構造体を流れる気体の流量および温度および湿度と測定環境の大気圧および温度および湿度のわずかな変化の影響が、圧力損失の値に大きくばらつきとして表れ、圧力損失を精度良く求めることは困難である。特に気体流量の変化については、流量制御弁のような流量を安定させる装置を用いてもなお存在する微小な流量の変化が、圧力損失の値に及ぼす影響は無視できない。したがって異なるハニカム構造体間の圧力損失のが異なると思われてもその差異が出ず、圧力損失を高精度に求めることができない。
【００１０】
したがって本発明の課題は、ハニカム構造体の圧力損失を高精度に求めることができる、ハニカム構造体の圧力損失の評価方法を得ることにある。特に、ハニカム構造体の隔壁の気孔率を５０％以上、平均細孔径を１５μｍ以上などとして圧力損失をさらに小さくした場合での、小さくした圧力損失の微妙な違いを高精度に求めることができる、ハニカム構造体の圧力損失の評価方法を得ることにある。
【００１１】
【課題を解決するための手段】
本発明者らは、上記課題について鋭意研究した。その結果、ハニカム構造体に供給する気体の流量の変化が少なく、安定した流れを保ったときの差圧を測定すれば、ハニカム構造体の圧力損失を高精度に求めることができるとの知見を得、本発明に想到した。
【００１２】
すなわち、本発明のハニカム構造体の圧力損失の評価方法は、ハニカム構造体に流量調整弁を用いて流量を略安定させた気体を供給して、前記ハニカム構造体の気体流入側と流出側の差圧から前記ハニカム構造体の圧力損失を求める方法であって、前記流量調整弁を用いてもなお存在する流量の変化の幅よりも小さい幅を有する気体の流量に対する許容範囲を決めて前記気体を連続して供給するとともに、前記気体の流量を微小時間間隔ごとに計測し、前記気体の流量の計測値が予め設定した所定時間中に連続して前記許容範囲にあるときに測定した前記差圧から、前記ハニカム構造体の圧力損失を求めることを特徴とする。
これにより、前記気体の流量変化が小さく安定した流れを保った状態でハニカム構造体の気体流入側と流出側との差圧を測定することにより、ハニカム構造体の圧力損失を高精度に評価することができ、特に、ハニカム構造体の隔壁の気孔率を５０％以上、平均細孔径を１５μｍ以上などとして圧力損失をさらに小さくした場合での、小さくした圧力損失の微妙な違いをさらに高精度に評価することができる。
【００１３】
ここで、気体の流量が許容範囲にあるとは、例えば、３０Ｎｍ^３／ｍｉｎを中心に、許容範囲が±０．９Ｎｍ^３／ｍｉｎにあることを言う。また差圧の測定は、前記気体の流量が所定時間内で許容範囲にあるときに測定するのみではなく、連続的に測定しておき、前記気体の流量が所定時間内で許容範囲にあるときの差圧のみを抽出して圧力損失を求めることもできることは言うまでもない。
【００１４】
また、本発明のハニカム構造体の圧力損失の評価方法は、前記気体の流量の計測値が予め設定した所定時間中に連続して前記許容範囲にあるときに前記ハニカム構造体の気体流入側と流出側との差圧を測定し、次いで前記所定時間の後に連続する予め設定した第２の所定時間中に連続して前記気体の流量の測定値が前記許容範囲にあるときに、前記差圧から圧力損失を求める方法を取ることもできる。これにより、前記気体の流量変化が小さく安定した流れを保った状態で、ハニカム構造体の気体流入側と流出側との差圧を測定し、かつ前記差圧の測定の後の前記気体の流量変化が小さいことを確認することにより、ハニカム構造体の圧力損失をより高精度に評価することができ、特に、ハニカム構造体の隔壁の気孔率を５０％以上、平均細孔径を１５μｍ以上などとして圧力損失をさらに小さくした場合での、小さくした圧力損失の微妙な違いを高精度に評価することができる。
ここで、ある経過した所定時間内とは例えば１０ｓ（秒）間、差圧の測定後に連続する第２の所定時間内とは前記１０ｓに続く例えば３ｓ間を言う。
【００１５】
また、本発明のハニカム構造体の圧力損失の評価方法は、前記流量調整弁を用いてもなお存在する流量の変化の幅よりも小さい幅を有する気体の流量に対する第１の許容範囲と、前記第１の許容範囲より狭く設定した第２の許容範囲とを決めて前記気体を連続して供給するとともに、前記気体の流量を微小時間間隔ごとに計測し、前記気体の流量の計測値が予め設定した所定時間中に連続して前記第１の許容範囲にあり、前記気体の流量の計測値の平均が前記所定時間内で前記第１の許容範囲と中心を同じくして前記第１の許容範囲の広くとも２／３の幅を持った範囲にあり、かつ前記所定時間内の予め設定した直近短時間（前記所定時間より長さが短く、その終了時が前記所定時間の終了時と同じ）の前記気体の流量の計測値が前記第２の許容範囲にあり、前記直近短時間での前記気体の流量の計測値の平均が前記第２の許容範囲と中心を同じくして前記第２の許容範囲の広くとも２／３の幅を持った範囲にあるときに前記ハニカム構造体の気体流入側と流出側との差圧を測定し、次いで前記所定時間の後に連続する予め設定した第２の所定時間中に連続して前記気体の流量の計測値が前記第２の許容範囲にあるときに、前記差圧から圧力損失を求める方法を取ることもできる。これにより前記気体の流量の変化、言いかえれば気体の流量のバラツキの平均値の変動が収束傾向にある、気体の流れがより安定した状況で測定することとなる。これにより、前記気体の流量変化が小さく、かつ小さく変化する気体の流量の平均値も収束傾向にある時点でハニカム構造体の気体流入側と流出側との差圧を測定し、前記差圧の測定の後の前記気体の流量変化が小さいことを確認することにより、ハニカム構造体の圧力損失をさらに高精度に評価することができ、特に、ハニカム構造体の隔壁の気孔率を５０％以上、平均細孔径を１５μｍ以上などとして圧力損失をさらに小さくした場合での、小さくした圧力損失の微妙な違いをさらに高精度に評価することができる。
ここで、気体の流量が第１の許容範囲とは、例えば１５Ｎｍ^３／ｍｉｎ±０．１Ｎｍ^３／ｍｉｎ以内に、第２の許容範囲とは、第１の許容範囲より狭い、例えば１５Ｎｍ^３／ｍｉｎ±０．０５Ｎｍ^３／ｍｉｎ以内を言う。
【００２６】
【発明の実施の形態】
以下、本発明を具体化した実施の形態の一例を詳細に説明する。なお、以下の説明においては、ＤＰＦおよび触媒コンバータをまとめて「ハニカム構造体」とする。
【００２７】
（実施の形態１）
図１は、実施の形態１において測定されるハニカム構造体１であり、（ａ）はその模式斜視図、（ｂ）は模式断面図である。このハニカム構造体１は、ディーゼルエンジンの排気系に配置されてＰＭを捕集する役割を果たし、強度と共に圧力損失が特に小さいことが要求されている。ハニカム構造体１は、外径２６７ｍｍ×長さ３０４ｍｍの円筒形状でコージェライト材の多孔質セラミック焼結体である。なお、コージェライト材以外にも、例えば炭化硅素、窒化硅素、アルミナなどを選択することができる。ハニカム構造体１には、外皮１ａ内に断面略正方形状の複数の貫通孔１ｂがその軸線方向に沿って規則的に配列されている。各貫通孔１ｂは隔壁１ｃによって互いに隔てられている。貫通孔１ｂの各端面１ｄ、１ｅは各封止材１ｆ、１ｇによって交互に封止されており、端面１ｄ、１ｅ全体としては市松模様になっている。隔壁１ｃは、厚さが０．３ｍｍ、ピッチが１．５ｍｍ、気孔率が６５％、平均細孔径が２０μｍとなっている。
【００２８】
ハニカム構造体１をディーゼルエンジンの排気系に配置したとき、排気ガスは、端面１ｄに開口した貫通孔１ｂから流入（矢印Ａ１）し、多孔質の隔壁１ｃを通過（矢印Ａ２）して隣接する貫通孔から流出（矢印Ａ３）する。このとき、排気ガス中に含まれるＰＭは隔壁１ｃで捕集される。そして、一定量のＰＭが蓄積されるとこれを電気ヒータで燃焼したりして、ハニカム構造体１の再生を行う。
【００２９】
次に、ハニカム構造体１の圧力損失の評価装置について説明する。図２は、ハニカム構造体１の圧力損失の評価装置の一例の模式図である。なお、試験用の気体としては、通常の空気を用いている。図２で、試験用チャンバ３には、緩衝材２を介してハニカム構造体１を収納している。緩衝材２はハニカム構造体１の周囲に巻き付けて試験用チャンバ３への出し入れを容易にすると共にハニカム構造体１を保護している。試験用チャンバ３は、入口側３ａを開いてハニカム構造体１の出し入れをできるようにし、また奥のストッパ（図示せず）でハニカム構造体１と緩衝材２の位置決めができるようにしている。試験用チャンバ３の入口側３ａおよび出口側３ｂには、ハニカム構造体１の差圧を検出してコンピュータ６に入力する差圧計５を接続している。試験用チャンバ３の出口側３ｂに続く送気管７ａには、流入したゴミなどを捕捉するアブソリュートフィルタ８を接続している。アブソリュートフィルタ８に続く送気管７ｂにはハニカム構造体１を通過した空気の流量を検出してコンピュータ６に入力する差圧式流量計１０を接続している。差圧式流量計１０に続く送気管７ｃには、コンピュータ６との入出力により空気の流量を制御する流量調整弁１１を接続している。流量調整弁１１に続く送気管７ｄには、コンピュータ６との入出力により一定出力で空気を吸引する排気送風機１２を接続している。また、試験用チャンバ３の入口側３ａには、測定環境中に浮遊する塵埃が試験用チャンバ３内に流入するを防止すると共に空気を整流してハニカム構造体１に供給するフィルタ４を備えている。
【００３０】
また、アブソリュートフィルタ８の前の送気管７ａには、送気管７ａを流れる空気の温度・湿度を検出して、コンピュータ６に入力するデジタル温度・湿度計９を備えている。フィルタ４の近くには、測定環境の温度・湿度・気圧を検出して、コンピュータ６に入力するデジタル温度・湿度・気圧計１３を備えている。
【００３１】
コンピュータ６には、ハニカム構造体１への空気の目標流量とこの目標流量に対する許容範囲を記憶させている。そして、コンピュータ６は、一定時間ごと同時に、空気の流量と、空気の温度・湿度、測定環境の温度・湿度・気圧のサンプリングを行い、空気の流量が許容範囲にあるときに検出した差圧計５の値に、空気の温度・湿度、測定環境の温度・湿度・気圧をもとに標準状態にする補正をかける演算を行い、圧力損失の値をディスプレイ６ａに表示している。なお、モニタ６ａの表示値が配線のノイズなどで各検出値と異なっている場合、ノイズを除去するように補正している。
【００３２】
次に、圧力損失の評価方法について説明する。
圧力損失には、ハニカム構造体１の圧力損失に加え、試験用チャンバ３の圧力損失も含まれている。このため事前に、ハニカム構造体１を試験用チャンバ３に収納しないで、試験用チャンバ３単独の圧力損失を測定している。通常、標準状態における試験用チャンバ３のみの圧力損失は一定であるので、いったん測定して得られた試験用チャンバ３の圧力損失をコンピュータ６に記憶させ、これを自動的に差し引いて、ハニカム構造体の圧力損失としている。なお、簡易的な圧力損失の評価方法としては、標準状態でない測定環境の場合に、試験用チャンバ３のみの差圧とハニカム構造体１の差圧の両方を測定し、標準状態における試験用チャンバ３の差圧との比からハニカム構造体１の差圧の測定値に補正を加えて標準状態して求めることもできる。
【００３３】
図３は、経過時間・空気の流量・差圧から、ハニカム構造体１の圧力損失を求めるための説明図である。図３では、ハニカム構造体１に、目標流量を１５Ｎｍ^３／ｍｉｎと決めて空気を連続して供給するように、コンピュータ６に入力している。なお、目標流量１５Ｎｍ^３／ｍｉｎは、ディーゼルエンジン実機での排気ガス温度が４００〜６００℃で流量が約３７〜４８Ｎｍ^３／ｍｉｎに相当させている。また、所定時間を１０ｓ（秒）とし、流量の許容範囲を１５±０．１Ｎｍ^３／ｍｉｎとした。そして圧力損失の評価装置を稼動し、ハニカム構造体１を通過する空気の流量を測定し、所定時間１０秒間で空気の流量の許容範囲を満足したときに、空気上流側と下流側との差圧を測定し、前記差圧からハニカム構造体１の圧力損失を求める。図３の例では経過時間６ｓ以降所定時間の１０秒間にて空気流量が許容範囲を満足しているため、経過時間１９ｓのハニカム構造体１の空気流入側と流出側との差圧の値より圧力損失を求めた。同様にハニカム構造体１の圧力損失を繰り返し求めたところ、圧力損失の値のバラツキは３％程度であった。
【００３４】
（実施の形態２）次に（実施の形態１）と同じ評価装置を用い、ハニカム構造体１の圧力損失を求めた別の方法を図４により説明する。ここでは所定時間を１０ｓとし、この間の流量の許容範囲を１５±０．１Ｎｍ^３／ｍｉｎとした。また、ハニカム構造体１の空気流入側と流出側との差圧の測定後の連続する第２の所定時間を３ｓとした。図４の例では経過時間４ｓ以降の１０秒間にて空気流量が許容範囲を満足しているため、経過時間１９ｓのハニカム構造体１の空気流入側と流出側との差圧を測定し、ついで１４ｓ以降１６ｓまでの３秒間の空気の流量が許容範囲を満足しているため、先に求めた差圧より圧力損失を求めた。同様にハニカム構造体１の圧力損失を繰り返し求めたところ、圧力損失の値のバラツキは３％以内に収めることが出来た。
【００３５】
（実施の形態３）次に（実施の形態１）および（実施の形態２）と同じ評価装置を用い、ハニカム構造体１の圧力損失を求めた別の方法を図５により説明する。ここでは所定時間を１０ｓ（秒）間とし、流量の許容範囲（第１の許容範囲）を１５±０．１Ｎｍ^３／ｍｉｎとし、かつ流量の平均を前記第１の許容範囲（１５±０．１Ｎｍ^３／ｍｉｎ）の２／３以下の１５±０．０５Ｎｍ^３／ｍｉｎとして、コンピュータ６に入力している。また、前記所定時間１０ｓ間内での直近短時間を５ｓ間とし、この間の流量の許容範囲（第２の許容範囲）を流量の第１の許容範囲より狭い許容範囲の１５±０．０５Ｎｍ^３／ｍｉｎとし、かつ平均の流量の許容範囲を前記第２の許容範囲の２／３以下の１５±０．０１Ｎｍ^３／ｍｉｎとして、コンピュータ６に入力している。また、差圧の測定後に連続する第２の所定時間を３ｓ間とし、この時間での流量の許容範囲を第２の許容範囲と同じ１５±０．０５Ｎｍ^３／ｍｉｎ以下として、コンピュータ６に入力している。また、差圧は、空気の温度２０℃、相対湿度６５％、気圧１０１３ｈＰａの標準状態に補正して求めている。図５の例では、経過時間１０ｓ以降の所定時間である１０秒間で空気の流量が前記第１の許容範囲である１５±０．１Ｎｍ^３／ｍｉｎを満足し、かつ流量の平均がその許容範囲である１５±０．０５Ｎｍ^３／ｍｉｎを満足している。そして、直近短時間の５ｓ間となる経過時間１５ｓ以降の５ｓ間にて、空気の流量が第２の許容範囲である１５±０．０５Ｎｍ^３／ｍｉｎを満足し、かつ流量の平均がその許容範囲である１５±０．０１Ｎｍ^３／ｍｉｎを満足している。そこで経過時間１９ｓでのハニカム構造体１の空気上流側と下流側との差圧を測定する。ついで、差圧測定後に連続する所定時間である経過時間２０ｓ以降の３ｓ間にて、空気の流量が許容範囲である１５±０．０５Ｎｍ^３／ｍｉｎを満足していることより、先に測定した前記差圧よりハニカム構造体１の圧力損失を求めた。
【００３６】
上記の測定方法により、異なるハニカム構造体１（Ａ，Ｂ）について、測定日を変えて各々８回、差圧を測定した。なお、ハニカム構造体１（Ａ，Ｂ）のみの差圧は、ハニカム構造体１（Ａ，Ｂ）を収納した状態の差圧から、ハニカム構造体１（Ａ，Ｂ）を収納しない試験用チャンバ３の差圧を引いて求めた。その結果を表１に示す。また、図６に、異なるハニカム構造体１（Ａ，Ｂ）についての測定回数ごとの差圧を示す。
【００３７】
（表１）

【００３８】
表１および図６に示すように、測定日を変えても、差圧のバラツキは±２％未満であり、ハニカム構造体１（Ａ，Ｂ）の圧力損失を高精度に評価できていることがわかる。また、ハニカム構造体１（Ａ，Ｂ）で差圧の平均が違っており、微妙な圧力損失の違いを高精度に評価できていることがわかる。
【００３９】
（実施の形態４）
前記実施の形態と同じ評価装置を用い、ハニカム構造体１の圧力損失を求めた別の方法として、空気の流量の許容範囲を１５±０．１Ｎｍ^３／ｍｉｎとし、許容範囲にある時の差圧を１０点抽出し、この１０点の差圧の平均値よりハニカム構造体１の圧力損失を求めた。また、ハニカム構造体１の圧力損失を求めた別の方法として、同様に空気の流量の許容範囲を１５±０．１Ｎｍ^３／ｍｉｎとし、許容範囲にある時の差圧を１１点抽出し、この１１点の差圧の中央値より圧力損失を求めた。これら２つの方法によりハニカム構造体１の圧力損失を繰り返し求めたところ、そのバラツキは何れも３％であった。
【００４０】
（実施の形態５）
図７は、実施の形態３に記した方法にて測定し、供給する空気や測定環境の条件、すなわち空気の温度・湿度、測定環境の温度・湿度・気圧が異なる時（Ｃ、Ｄ）の、同じハニカム構造体１で、経過時間ごとの差圧の変化を示す図である。ここで測定環境Ｃでは、測定室のエアコンが自動運転されておる状況で測定を行ったものであり、また測定環境Ｄは、測定室のエアコンが運転されていない状況で測定を行ったものである。なお、図７で、点線は、差圧を供給空気の温度・湿度および測定環境の温度・湿度・気圧から補正していない値であり、一方、実線はここでは標準状態に補正した値を示す。図７から、同じハニカム構造体１でも、補正していない場合には、差圧が異なり、しかも経過時間ごとにバラツキを持っているが、補正することで、殆ど一致した値となっている。したがって、差圧を測定するたびに気体の温度・湿度、測定環境の温度・湿度・気圧をもとに、これに補正を施す事が望ましいことが判る。
【００４１】
（実施の形態６）
図８は、実施の形態６での、ＣＲＴに用いられるハニカム構造体１の圧力損失の評価装置の模式図であり、ＰＭにあたるカーボン微粒子をハニカム構造体１に送り、ハニカム構造体１の圧力損失を測定できるようにしている。図８では、前述した実施の形態３と同じ構成のものは同符号で示している。図８の評価装置は、図２での試験用チャンバ３の入口側３ａのフィルタ４を外し、一方、カーボン微粒子１５ａの供給手段を設けている。すなわち、カーボン微粒子１５ａの供給手段は、入口３ａにダストインジェクタ１４の噴出口１４ａを対向させ、ダストインジェクタ１４には２本のチューブ１６を接続している。一方のチューブ１６はカーボン微粒子を貯留しているダストフィーダ１５に、他方のチューブ１６はドライヤ１７を介して空気圧縮機１８に接続している。空気圧縮機１８を作動させ、ダストフィーダ１５とダストインジェクタ１４間の攪拌機（図示せず）により、カーボン微粒子１５ａをダストインジェクタ１４に一定の投入量および速度で送り込んでいる。そして、空気圧縮機１８で圧縮し、またドライヤ１７で乾燥した圧縮空気をダストインジェクタ１４に送ることで、カーボン微粒子１５ａをダストインジェクタ１４に引き込み、カーボン混合気としてハニカム構造体１に向けて噴射している。
【００４２】
実施の形態３と同じように、ハニカム構造体１の圧力損失の評価装置を作動させ、空気が目標流量の１０Ｎｍ^３／ｍｉｎ近くとなり安定した時点で、ダストインジェクタ１４からハニカム構造体１に向けてカーボン微粒子１５ａの投入する。そして、カーボン微粒子１５ａの投入量が２ｇ／ｌ（リットル）になるまで１ｓ（秒）ごとに差圧計５で差圧を検出してコンピュータ６に入力する。コンピュータ６で、実施の形態３と同様に補正を行い圧力損失を求める。図９は、カーボン微粒子１５ａの投入量ごとの補正前と補正後の差圧を示す図である。図９から、補正前は、カーボン微粒子１５ａの投入量ごとの差圧が大きく脈動しているが、補正後は、差圧が安定している。したがって、補正後の差圧をもとに、カーボン微粒子１５ａを投入した際の圧力損失を高精度に評価できることがわかる。また、ＣＲＴに用いられるハニカム構造体１での、カーボン微粒子１５ａの投入量が２ｇ／ｌ（リットル）になるまでの圧力損失を高精度に評価できることがわかる。
【００４３】
（比較例）
図１０は、単一のハニカム構造体１の差圧を、本発明のハニカム構造体の圧力損失の評価方法および評価装置を用いて測定したものと、用いずに測定したものの比較を表す図である。この図の横軸は、日に１回測定したときの測定回数を示している。図１０に示すように、本発明のハニカム構造体の圧力損失の評価方法および評価装置を用いて測定したものは、用いずに測定したものに比較して、差圧のバラツキが小さく、本発明のハニカム構造体の評価方法および評価装置によるのが有効であることがわかる。
【００４４】
なお、実施の形態では、多孔質セラミック焼結体からなるハニカム構造体について説明したが、これに限らず、耐熱合金からなるハニカム構造体についても本発明のハニカム構造体の圧力損失の評価方法および評価装置を適用できることは言うまでもない。
【００４５】
【発明の効果】
以上、詳細に説明のとおり、本発明のハニカム構造体の評価方法によれば、ハニカム構造体の圧力損失を高精度に評価することができる。特に、ハニカム構造体の隔壁の気孔率を５０％以上、平均細孔径を１５μｍ以上などとして圧力損失をさらに小さくした場合での、小さくした圧力損失の微妙な違いを高精度に評価することができる。
【図面の簡単な説明】
【図１】実施の形態１において圧力損失を測定するハニカム構造体１であり、（ａ）はその模式斜視図、（ｂ）は模式断面図である。
【図２】実施の形態１での、ハニカム構造体１の圧力損失の評価装置の一例の模式図である。
【図３】実施の形態１での、経過時間・空気の流量・差圧から、ハニカム構造体１の圧力損失を求めるための説明図である。
【図４】実施の形態２での、経過時間・空気の流量・差圧から、ハニカム構造体１の圧力損失を求めるための説明図である。
【図５】実施の形態３での、経過時間・空気の流量・差圧から、ハニカム構造体１の圧力損失を求めるための説明図である。
【図６】実施の形態３での、異なるハニカム構造体１（Ａ，Ｂ）についての測定回数ごとの差圧を示す図である。
【図７】実施の形態５での、図２の圧力損失の評価装置を用い、供給する空気や測定環境の条件、すなわち空気の温度・湿度、測定環境の温度・湿度・気圧が異なる、同じハニカム構造体１（Ｃ，Ｄ）で、経過時間ごとの差圧の変化を示す図である。
【図８】実施の形態６での、ＣＲＴに用いられるハニカム構造体１の圧力損失の評価装置の模式図である。
【図９】実施の形態６での、カーボン微粒子１５ａの投入量ごとの補正前と補正後の差圧を示す図である。
【図１０】比較例での、本発明のハニカム構造体の圧力損失の評価方法および評価装置によらずに測定した、異なるハニカム構造体１（Ｅ，Ｆ）の流量および差圧を示す図である。
【符号の説明】
１ハニカム構造体（ＤＰＦ、触媒コンバータ）
１ａ外皮
１ｂ貫通孔
１ｃ隔壁
１ｄ、１ｅ端面
１ｆ、１ｇ封止材
２緩衝材
３試験用チャンバ
３ａ入口側
３ｂ出口側
４フィルタ
５差圧計
６コンピュータ
６ａモニタ
７ａ、７ｂ、７ｃ、７ｄ送気管
８アブソリュートフィルタ
９デジタル温度・湿度計
１０差圧式流量計
１１流量調整弁
１２排気送風機
１３デジタル温度・湿度・気圧計
１４ダストインジェクタ
１４ａ噴出口
１５ダストフィーダ
１５ａカーボン微粒子
１６チューブ
１７ドライヤ
１８空気圧縮機
Ａ１流入
Ａ２通過
Ａ３流出[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for evaluating pressure loss of a honeycomb structure used for purifying exhaust gas.
[0002]
[Prior art]
A honeycomb structure for exhaust gas purification used to purify exhaust gas from an internal combustion engine such as a diesel engine or a gasoline engine is generally composed of a heat-resistant material such as ceramic or metal, and is incorporated into the exhaust system of the internal combustion engine. It plays the role of removing harmful substances contained in the exhaust gas. The honeycomb structure for exhaust gas purification plays a role of removing a target harmful substance by supporting a catalyst substance, or particulate matter (hereinafter referred to as “PM”) mainly in exhaust gas of a diesel engine. There is also a honeycomb structure for a diesel particulate filter (hereinafter referred to as “DPF”) in which the honeycomb structure is filtered and captured to contribute to exhaust gas purification.
[0003]
Since the exhaust gas purification honeycomb structure obstructs the flow of exhaust gas due to its pressure loss, it causes a decrease in engine output. Further, in the DPF honeycomb structure, as PM in the exhaust gas is captured and accumulated in the DPF honeycomb structure, the pressure loss increases and the engine output decreases. For this reason, it is necessary to grasp the initial pressure loss of the honeycomb structure and the pressure loss after accumulation of PM.
[0004]
The “pressure loss” of the honeycomb structure is obtained by subtracting the pressure value of the gas on the downstream side from the pressure value of the gas on the upstream side of the honeycomb structure when the gas passes through the honeycomb structure. The resistance that the gas receives when passing through the honeycomb structure is the largest factor. Therefore, it is necessary to make appropriate the material, thickness, porosity, pore diameter, etc. of the partition walls of the honeycomb structure and the shape of the inlet end of the honeycomb structure into which the exhaust gas flows.
[0005]
As a means for obtaining and evaluating the pressure loss of the honeycomb structure, a Japanese Industrial Standard (JIS) automobile air cleaner test method may be used (for example, see Non-Patent Document 1). This test apparatus of Non-Patent Document 1 includes a test chamber for storing a specimen (automobile air cleaner in JIS), a differential pressure gauge connected to the outlet side and the inlet side of the test chamber, and an air supply tube in order from the outlet side. An absolute filter, an air flow meter, an air flow control device, an exhaust blower, and the like connected via each other. And when calculating | requiring the pressure loss of the honeycomb structure used as a test body with the test apparatus of a nonpatent literature 1, the air of a test chamber is flowed for 15 minutes or more, and a pressure loss is calculated | required with a differential pressure gauge after that. Further, the pressure loss is obtained by correcting values such as the air amount and the differential pressure to the standard state of 20 ° C., relative humidity 65%, and atmospheric pressure 1013 hPa. Further, for example, as in the invention described in Patent Document 1, the honeycomb structure is incorporated in an exhaust system of an internal combustion engine, and the obtained pressure loss is corrected by the exhaust flow rate of the engine, as in the invention described in Patent Document 2. There is a description in which a gas containing particles is fed into the honeycomb structure by a particle-containing gas generator without using an internal combustion engine, and pressure loss is obtained from a differential pressure between the gas inflow side and the outflow side of the honeycomb structure. . Since all of these are measured after the pressure loss rises, the pressure loss is required relatively easily.
[0006]
In the DPF honeycomb structure, when a certain amount of PM is accumulated, it is necessary to burn it with an electric heater or remove it with backwash air to regenerate the DPF. In the method of burning and regenerating fine particles, the DPF honeycomb structure itself is melted by self-heating of the fine particles, and there is a problem that the apparatus becomes complicated when backwash air is used. A technique (CRT system) for continuously burning fine particles in a honeycomb structure has been adopted.
[0007]
[Non-Patent Document 1]
JIS D 1612-1989 Automotive Air Cleaner Test Method [Page 4, Item 8. (Ventilation resistance test), page 20, second. Item (15) (ventilation resistance), page 24 (test dust), page 27 (FIG. 6 panel-type filter element cleaning efficiency and dust holding amount test device), pages 32-34 (air amount relative to standard conditions) And correction of ventilation resistance)]
[Patent Document 1]
JP-A-8-109818
[Patent Document 2]
Japanese Patent No. 2807370
[0008]
[Problems to be solved by the invention]
In the CRT system, in the steady state, PM is continuously burned and removed and is not accumulated, so there is almost no increase in pressure loss due to PM accumulation. Further, in the CRT system, it is indispensable to dispose a honeycomb structure carrying an oxidation catalyst on the upstream side of the DPF honeycomb structure. In some cases, it may be necessary to dispose a honeycomb structure carrying a NOx removal catalyst downstream of the DPF honeycomb structure, resulting in a large pressure loss in the exhaust system of the internal combustion engine, leading to a decrease in engine output. Therefore, the pressure loss of the DPF honeycomb structure itself, such as using a material having a porosity of 50% or more and an average pore diameter of 15 μm or more, or applying a technique for optimizing the cell structure is also applied to the DPF honeycomb structure itself. Technological development to keep it low is underway, and it is necessary to accurately obtain a low pressure loss in order to perform evaluation and inspection.
[0009]
However, even if such a DPF honeycomb structure is used to determine the pressure loss using the automotive air cleaner test method or the method for determining the pressure loss described in the patent document, the pressure loss itself is extremely small. Therefore, the effects of slight changes in the flow rate, temperature, and humidity of the gas flowing through the DPF honeycomb structure and the atmospheric pressure, temperature, and humidity in the measurement environment appear as large variations in the pressure loss values, and the pressure loss is obtained with high accuracy. It is difficult. In particular, regarding the change in the gas flow rate, the influence of the minute change in the flow rate still existing even when a device for stabilizing the flow rate such as a flow control valve is used on the value of the pressure loss cannot be ignored. Therefore, even if it seems that the pressure loss between different honeycomb structures is different, the difference does not occur, and the pressure loss cannot be obtained with high accuracy.
[0010]
Accordingly, an object of the present invention is to obtain a method for evaluating the pressure loss of a honeycomb structure, which can obtain the pressure loss of the honeycomb structure with high accuracy. In particular, when the pressure loss is further reduced by setting the porosity of the partition walls of the honeycomb structure to 50% or more, the average pore diameter to 15 μm or more, and the like, the subtle difference in the reduced pressure loss can be obtained with high accuracy. The object is to obtain a method for evaluating the pressure loss of a honeycomb structure.
[0011]
[Means for Solving the Problems]
The present inventors diligently studied on the above problems. As a result, it was found that the pressure loss of the honeycomb structure can be obtained with high accuracy by measuring the differential pressure when the flow rate of the gas supplied to the honeycomb structure is small and a stable flow is maintained. The present invention has been conceived.
[0012]
That is, the method for evaluating the pressure loss of the honeycomb structure of the present invention is applied to the honeycomb structure. A method of obtaining a pressure loss of the honeycomb structure from a differential pressure between a gas inflow side and an outflow side of the honeycomb structure by supplying a gas whose flow rate is substantially stabilized using a flow rate adjustment valve, the flow rate adjustment Even with the valve, it has a width that is smaller than the width of the flow change that still exists Continuous supply of the gas by determining the allowable range for the gas flow rate And measuring the flow rate of the gas every minute time interval, Flow rate of the gas Measured value of preset Predetermined time Continuously in the above The pressure loss of the honeycomb structure is obtained from the differential pressure measured when it is within an allowable range.
Thus, the pressure loss of the honeycomb structure is evaluated with high accuracy by measuring the differential pressure between the gas inflow side and the outflow side of the honeycomb structure while maintaining a small and stable flow rate of the gas. In particular, when the pressure loss is further reduced by setting the porosity of the partition walls of the honeycomb structure to 50% or more and the average pore diameter to 15 μm or more, etc., the subtle difference in the reduced pressure loss can be further improved. Can be evaluated.
[0013]
Here, the gas flow rate is within an allowable range, for example, 30 Nm ³ The tolerance is ± 0.9 Nm, centered on / min. ³ Say it is at / min. The differential pressure is measured not only when the gas flow rate is within an allowable range within a predetermined time, but also when continuously measured and the gas flow rate is within the allowable range within a predetermined time. It goes without saying that the pressure loss can be obtained by extracting only the differential pressure.
[0014]
Moreover, the evaluation method of the pressure loss of the honeycomb structure of the present invention is the flow rate of the gas. Measured value of preset Predetermined time Continuously in the above Measure the differential pressure between the gas inflow side and the outflow side of the honeycomb structure when it is within the allowable range, A preset second time after the predetermined time. Predetermined time Continuously in Flow rate of the gas Measured value of Can be obtained by calculating the pressure loss from the differential pressure. Thus, the pressure difference between the gas inflow side and the outflow side of the honeycomb structure is measured in a state where the change in the gas flow rate is small and a stable flow is maintained, and the gas flow rate after the measurement of the differential pressure is measured. By confirming that the change is small, the pressure loss of the honeycomb structure can be evaluated with higher accuracy. In particular, the partition wall porosity of the honeycomb structure is 50% or more, the average pore diameter is 15 μm or more, and the like. When the pressure loss is further reduced, a subtle difference in the reduced pressure loss can be evaluated with high accuracy.
Here, the predetermined elapsed time is, for example, 10 s (seconds) continuously after measuring the differential pressure. Second The term “within a predetermined time” refers to, for example, 3 s following 10 s.
[0015]
The method for evaluating the pressure loss of the honeycomb structure of the present invention is as follows. Even with the flow control valve, it has a width smaller than the width of the flow rate change that still exists For gas flow First Tolerance And a second tolerance range set narrower than the first tolerance range; And supply the gas continuously And measuring the flow rate of the gas every minute time interval, Flow rate of the gas Measured value of preset Predetermined time Continuously in the above In the first tolerance range, the gas flow rate Measured value of Within the predetermined time, the average of the first allowable range is the same as the center of the first allowable range and has a width of at most 2/3 of the first allowable range. Preset Latest short time (The length is shorter than the predetermined time, and the end time is the same as the end of the predetermined time) The gas flow rate of Measured value of The gas flow rate in the second allowable range and in the most recent short time Measured value of Between the gas inflow side and the outflow side of the honeycomb structure when the average is equal to the second permissible range and has a width of at most 2/3 of the second permissible range. Measure the differential pressure, then A preset second time after the predetermined time. Predetermined time Continuously in Flow rate of the gas Measured value of Said Second When the pressure is within the allowable range, a method of obtaining a pressure loss from the differential pressure can be used. As a result, the change in the gas flow rate, in other words, the variation in the average value of the gas flow rate variation tends to converge, and the measurement is performed in a more stable state of the gas flow. As a result, when the gas flow rate change is small and the average value of the gas flow rate that changes slightly tends to converge, the differential pressure between the gas inflow side and the outflow side of the honeycomb structure is measured. By confirming that the change in the flow rate of the gas after the measurement is small, the pressure loss of the honeycomb structure can be evaluated with higher accuracy. In particular, the porosity of the partition walls of the honeycomb structure is 50% or more, A subtle difference in the reduced pressure loss can be evaluated with higher accuracy when the average pore diameter is 15 μm or more and the pressure loss is further reduced.
Here, the first allowable range of the gas flow rate is, for example, 15 Nm ³ /Min±0.1Nm ³ Within 2 minutes, the second tolerance range is narrower than the first tolerance range, for example, 15 Nm ³ /Min±0.05Nm ³ / Min or less.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment embodying the present invention will be described in detail. In the following description, the DPF and the catalytic converter are collectively referred to as a “honeycomb structure”.
[0027]
(Embodiment 1)
FIG. 1 shows a honeycomb structure 1 measured in Embodiment 1, wherein (a) is a schematic perspective view and (b) is a schematic cross-sectional view. The honeycomb structure 1 is disposed in an exhaust system of a diesel engine and plays a role of collecting PM, and is required to have a particularly small pressure loss as well as strength. The honeycomb structure 1 is a porous ceramic sintered body of a cordierite material having a cylindrical shape with an outer diameter of 267 mm × length of 304 mm. In addition to the cordierite material, for example, silicon carbide, silicon nitride, alumina, or the like can be selected. In the honeycomb structure 1, a plurality of through holes 1b having a substantially square cross section are regularly arranged in the outer skin 1a along the axial direction thereof. Each through hole 1b is separated from each other by a partition wall 1c. The end faces 1d and 1e of the through hole 1b are alternately sealed by the sealing

materials

1f and 1g, and the end faces 1d and 1e as a whole have a checkered pattern. The partition wall 1c has a thickness of 0.3 mm, a pitch of 1.5 mm, a porosity of 65%, and an average pore diameter of 20 μm.
[0028]
When the honeycomb structure 1 is arranged in the exhaust system of a diesel engine, the exhaust gas flows in from the through hole 1b opened in the end face 1d (arrow A1), passes through the porous partition wall 1c (arrow A2), and is adjacent. It flows out of the through hole (arrow A3). At this time, PM contained in the exhaust gas is collected by the partition wall 1c. When a certain amount of PM is accumulated, it is burned by an electric heater, and the honeycomb structure 1 is regenerated.
[0029]
Next, an apparatus for evaluating the pressure loss of the honeycomb structure 1 will be described. FIG. 2 is a schematic diagram of an example of an apparatus for evaluating the pressure loss of the honeycomb structure 1. Note that normal air is used as the test gas. In FIG. 2, the honeycomb structure 1 is accommodated in the test chamber 3 via the buffer material 2. The cushioning material 2 is wrapped around the honeycomb structure 1 to facilitate loading and unloading into the test chamber 3 and protect the honeycomb structure 1. The test chamber 3 opens the inlet side 3a so that the honeycomb structure 1 can be taken in and out, and the honeycomb structure 1 and the buffer material 2 can be positioned by a stopper (not shown) at the back. A differential pressure gauge 5 that detects the differential pressure of the honeycomb structure 1 and inputs it to the computer 6 is connected to the inlet side 3 a and the outlet side 3 b of the test chamber 3. An absolute filter 8 that captures inflowing dust and the like is connected to the air supply pipe 7 a that follows the outlet side 3 b of the test chamber 3. A differential pressure type flow meter 10 that detects the flow rate of air that has passed through the honeycomb structure 1 and inputs it to the computer 6 is connected to the air supply pipe 7 b that follows the absolute filter 8. A flow rate adjusting valve 11 that controls the flow rate of air by input / output to / from the computer 6 is connected to the air supply pipe 7 c following the differential pressure type flow meter 10. An exhaust blower 12 that sucks air at a constant output by input / output with the computer 6 is connected to the air supply pipe 7 d following the flow rate adjusting valve 11. In addition, the inlet side 3a of the test chamber 3 is provided with a filter 4 that prevents dust floating in the measurement environment from flowing into the test chamber 3 and rectifies the air to supply the honeycomb structure 1. Yes.
[0030]
The air supply pipe 7 a in front of the absolute filter 8 is provided with a digital temperature / humidity meter 9 that detects the temperature and humidity of the air flowing through the air supply pipe 7 a and inputs the detected temperature and humidity to the computer 6. Near the filter 4, there is provided a digital temperature / humidity / barometer 13 for detecting the temperature / humidity / atmospheric pressure of the measurement environment and inputting it to the computer 6.
[0031]
The computer 6 stores a target flow rate of air to the honeycomb structure 1 and an allowable range for the target flow rate. The computer 6 samples the air flow rate, the air temperature / humidity, the temperature / humidity / atmospheric pressure of the measurement environment at the same time every certain time, and detects the differential pressure gauge 5 detected when the air flow rate is within the allowable range. The value of the pressure loss is calculated on the display 6a by performing a correction to the standard value based on the temperature / humidity of the air and the temperature / humidity / pressure of the measurement environment. When the display value on the monitor 6a is different from each detected value due to wiring noise or the like, correction is made so as to remove the noise.
[0032]
Next, a method for evaluating pressure loss will be described.
The pressure loss includes the pressure loss of the test chamber 3 in addition to the pressure loss of the honeycomb structure 1. For this reason, the pressure loss of the test chamber 3 alone is measured in advance without storing the honeycomb structure 1 in the test chamber 3. Usually, since the pressure loss of only the test chamber 3 in the standard state is constant, the pressure loss of the test chamber 3 obtained once measured is stored in the computer 6 and automatically subtracted to obtain the honeycomb structure. Body pressure loss. As a simple pressure loss evaluation method, in a measurement environment that is not in a standard state, both the differential pressure of only the test chamber 3 and the differential pressure of the honeycomb structure 1 are measured, and the test chamber in the standard state is measured. 3 can be obtained by correcting the measured value of the differential pressure of the honeycomb structure 1 from the ratio with the differential pressure of 3 in a standard state.
[0033]
FIG. 3 is an explanatory diagram for obtaining the pressure loss of the honeycomb structure 1 from the elapsed time, the air flow rate, and the differential pressure. In FIG. 3, the target flow rate is 15 Nm for the honeycomb structure 1. ³ / Min is input to the computer 6 so as to supply air continuously. The target flow rate is 15 Nm ³ / Min is an exhaust gas temperature of 400 to 600 ° C. and a flow rate of about 37 to 48 Nm in a diesel engine ³ / Min. The predetermined time is 10 s (seconds), and the allowable flow rate range is 15 ± 0.1 Nm. ³ / Min. Then, the pressure loss evaluation apparatus is operated, the flow rate of the air passing through the honeycomb structure 1 is measured, and when the allowable range of the air flow rate is satisfied within a predetermined time of 10 seconds, the difference between the upstream side and the downstream side of the air The pressure is measured, and the pressure loss of the honeycomb structure 1 is obtained from the differential pressure. In the example of FIG. 3, since the air flow rate satisfies the allowable range for 10 seconds after the elapsed time 6 s, the value of the differential pressure between the air inflow side and the outflow side of the honeycomb structure 1 at the elapsed time 19 s. The pressure loss was determined. Similarly, when the pressure loss of the honeycomb structure 1 was repeatedly obtained, the variation in the pressure loss value was about 3%.
[0034]
(Embodiment 2) Next, another method for determining the pressure loss of the honeycomb structure 1 using the same evaluation apparatus as that in Embodiment 1 will be described with reference to FIG. Here, the predetermined time is 10 s, and the allowable flow rate range is 15 ± 0.1 Nm. ³ / Min. In addition, after the measurement of the differential pressure between the air inflow side and the outflow side of the honeycomb structure 1, it continues Second The predetermined time was 3 s. In the example of FIG. 4, since the air flow rate satisfies the allowable range in 10 seconds after the elapsed time 4 s, the differential pressure between the air inflow side and the outflow side of the honeycomb structure 1 at the elapsed time 19 s is measured. Since the flow rate of air for 3 seconds from 14 s to 16 s satisfies the allowable range, the pressure loss was obtained from the differential pressure obtained previously. Similarly, when the pressure loss of the honeycomb structure 1 was repeatedly obtained, the variation in the value of the pressure loss could be kept within 3%.
[0035]
(Embodiment 3) Next, another method for determining the pressure loss of the honeycomb structure 1 using the same evaluation apparatus as in Embodiment 1 and Embodiment 2 will be described with reference to FIG. Here, the predetermined time is 10 s (seconds), and the allowable flow rate range (first allowable range) is 15 ± 0.1 Nm. ³ / Min and the average flow rate is the first allowable range (15 ± 0.1 Nm ³ 15 ± 0.05 Nm of 2/3 or less of / min) ³ / Min is input to the computer 6. Further, the shortest short time within the predetermined time 10 s is set to 5 s, and the allowable range of flow rate (second allowable range) during this period is 15 ± 0.05 Nm, which is narrower than the first allowable range of flow rate. ³ 15 ± 0.01 Nm that is 2/3 or less of the second allowable range and the allowable range of the average flow rate is ³ / Min is input to the computer 6. Also continued after measuring differential pressure Second The predetermined time is 3 s, and the allowable flow rate at this time is the same as the second allowable range 15 ± 0.05 Nm ³ / Min or less is input to the computer 6. The differential pressure is obtained by correcting to a standard state with an air temperature of 20 ° C., a relative humidity of 65%, and an atmospheric pressure of 1013 hPa. In the example of FIG. 5, the air flow rate is 15 ± 0.1 Nm that is the first allowable range in 10 seconds, which is a predetermined time after the elapsed time of 10 s. ³ / Min, and the average flow rate is within the allowable range of 15 ± 0.05 Nm ³ / Min is satisfied. Then, the air flow rate is 15 ± 0.05 Nm, which is the second allowable range, for 5 s after the elapsed time 15 s, which is between 5 s in the latest short time. ³ / Min, and the average flow rate is within the allowable range of 15 ± 0.01 Nm ³ / Min is satisfied. Therefore, the differential pressure between the upstream side and the downstream side of the honeycomb structure 1 at an elapsed time of 19 s is measured. Then, the air flow rate is within an allowable range of 15 ± 0.05 Nm during 3 seconds after the elapsed time 20 seconds, which is a predetermined time after the differential pressure measurement. ³ Since / min was satisfied, the pressure loss of the honeycomb structure 1 was determined from the differential pressure measured previously.
[0036]
With the measurement method described above, the differential pressure was measured for each of the different honeycomb structures 1 (A, B) eight times on different measurement days. Note that the differential pressure of only the honeycomb structure 1 (A, B) is a test chamber in which the honeycomb structure 1 (A, B) is not accommodated from the differential pressure in the state where the honeycomb structure 1 (A, B) is accommodated. It was obtained by subtracting the differential pressure of 3. The results are shown in Table 1. FIG. 6 shows the differential pressure for each number of measurements for different honeycomb structures 1 (A, B).
[0037]
(Table 1)

[0038]
As shown in Table 1 and FIG. 6, even if the measurement date is changed, the variation in the differential pressure is less than ± 2%, and the pressure loss of the honeycomb structure 1 (A, B) can be evaluated with high accuracy. I understand. Moreover, the average of the differential pressure is different between the honeycomb structures 1 (A, B), and it can be seen that a subtle difference in pressure loss can be evaluated with high accuracy.
[0039]
(Embodiment 4)
As another method for obtaining the pressure loss of the honeycomb structure 1 using the same evaluation apparatus as in the above embodiment, the allowable range of the air flow rate is 15 ± 0.1 Nm. ³ / Min, 10 points of differential pressure when the pressure is within the allowable range were extracted, and the pressure loss of the honeycomb structure 1 was determined from the average value of the differential pressures at the 10 points. Further, as another method for obtaining the pressure loss of the honeycomb structure 1, similarly, the allowable range of the air flow rate is set to 15 ± 0.1 Nm. ³ / Min., 11 points of differential pressure when it was within the allowable range were extracted, and the pressure loss was determined from the median value of the 11 points of differential pressure. When the pressure loss of the honeycomb structure 1 was repeatedly obtained by these two methods, the variation was 3%.
[0040]
(Embodiment 5)
FIG. 7 shows the measurement by the method described in the third embodiment, and the conditions of the supplied air and the measurement environment, that is, the temperature / humidity of the air and the temperature / humidity / pressure of the measurement environment are different (C, D) FIG. 3 is a diagram showing a change in differential pressure for each elapsed time in the same honeycomb structure 1. Here, the measurement environment C is measured in a state where the air conditioner in the measurement room is automatically operated, and the measurement environment D is measured in a state where the air conditioner in the measurement room is not operated. is there. In FIG. 7, the dotted line is a value in which the differential pressure is not corrected from the temperature / humidity of the supply air and the temperature / humidity / atmospheric pressure of the measurement environment, while the solid line is a value corrected to the standard state here. . From FIG. 7, even when the same honeycomb structure 1 is not corrected, the differential pressure is different and varies for each elapsed time, but the values are almost the same by correcting. Therefore, it is understood that it is desirable to make corrections based on the temperature / humidity of the gas and the temperature / humidity / pressure of the measurement environment every time the differential pressure is measured.
[0041]
(Embodiment 6)
FIG. 8 is a schematic diagram of an apparatus for evaluating the pressure loss of the honeycomb structure 1 used in the CRT according to the sixth embodiment. Carbon fine particles corresponding to PM are sent to the honeycomb structure 1 and the pressure loss of the honeycomb structure 1 is shown. Can be measured. In FIG. 8, the same components as those in the third embodiment are denoted by the same reference numerals. In the evaluation apparatus of FIG. 8, the filter 4 on the inlet side 3a of the test chamber 3 in FIG. 2 is removed, while a supply means for carbon fine particles 15a is provided. That is, the supply means of the carbon fine particles 15 a has the jet outlet 14 a of the dust injector 14 opposed to the inlet 3 a, and the two tubes 16 are connected to the dust injector 14. One tube 16 is connected to a dust feeder 15 storing carbon fine particles, and the other tube 16 is connected to an air compressor 18 via a dryer 17. The air compressor 18 is operated, and the carbon fine particles 15a are fed into the dust injector 14 at a constant input amount and speed by a stirrer (not shown) between the dust feeder 15 and the dust injector 14. Then, the compressed air that has been compressed by the air compressor 18 and dried by the dryer 17 is sent to the dust injector 14, whereby the carbon fine particles 15 a are drawn into the dust injector 14 and injected toward the honeycomb structure 1 as a carbon mixture. ing.
[0042]
In the same manner as in the third embodiment, the evaluation device for the pressure loss of the honeycomb structure 1 is operated so that the air has a target flow rate of 10 Nm. ³ The carbon fine particles 15a are charged from the dust injector 14 toward the honeycomb structure 1 when it becomes stable at around / min. Then, the differential pressure is detected by the differential pressure gauge 5 every 1 s (seconds) until the input amount of the carbon fine particles 15 a reaches 2 g / l (liter) and input to the computer 6. The computer 6 performs correction in the same manner as in the third embodiment to determine the pressure loss. FIG. 9 is a diagram showing the differential pressure before and after correction for each input amount of the carbon fine particles 15a. From FIG. 9, before the correction, the differential pressure for each input amount of the carbon fine particles 15a pulsates greatly, but after the correction, the differential pressure is stable. Therefore, it can be seen that the pressure loss when the carbon fine particles 15a are introduced can be evaluated with high accuracy based on the corrected differential pressure. It can also be seen that the pressure loss in the honeycomb structure 1 used for CRT can be evaluated with high accuracy until the input amount of the carbon fine particles 15a reaches 2 g / l (liter).
[0043]
(Comparative example)
FIG. 10 is a diagram showing a comparison of the differential pressure of a single honeycomb structure 1 measured using the pressure loss evaluation method and evaluation apparatus of the honeycomb structure of the present invention with those measured without using it. is there. The horizontal axis of this figure indicates the number of measurements when the measurement is performed once a day. As shown in FIG. 10, the pressure loss evaluation method and the evaluation apparatus for the honeycomb structure of the present invention measured with the evaluation apparatus and the evaluation apparatus showed less variation in the differential pressure compared to the measurement without using the honeycomb structure. It can be seen that it is effective to use the honeycomb structure evaluation method and evaluation apparatus.
[0044]
In the embodiment, the honeycomb structure made of a porous ceramic sintered body has been described. However, the present invention is not limited to this, and the honeycomb structure made of a heat-resistant alloy also has a method for evaluating the pressure loss of the honeycomb structure of the present invention. Needless to say, the evaluation device can be applied.
[0045]
【The invention's effect】
As described above in detail, according to the honeycomb structure evaluation method of the present invention, the pressure loss of the honeycomb structure can be evaluated with high accuracy. In particular, the subtle difference in the reduced pressure loss can be evaluated with high accuracy when the porosity of the partition walls of the honeycomb structure is 50% or more, the average pore diameter is 15 μm or more, and the pressure loss is further reduced. .
[Brief description of the drawings]
FIG. 1 is a honeycomb structure 1 for measuring pressure loss in Embodiment 1, wherein (a) is a schematic perspective view and (b) is a schematic cross-sectional view.
2 is a schematic diagram of an example of an apparatus for evaluating the pressure loss of the honeycomb structure 1 according to Embodiment 1. FIG.
FIG. 3 is an explanatory diagram for obtaining the pressure loss of the honeycomb structure 1 from the elapsed time, the air flow rate, and the differential pressure in the first embodiment.
Fig. 4 is an explanatory diagram for obtaining the pressure loss of the honeycomb structure 1 from the elapsed time, the air flow rate, and the differential pressure in the second embodiment.
FIG. 5 is an explanatory diagram for obtaining the pressure loss of the honeycomb structure 1 from the elapsed time, the air flow rate, and the differential pressure in the third embodiment.
[Fig. 6] Fig. 6 is a diagram showing a differential pressure for each number of measurements for different honeycomb structures 1 (A, B) in the third embodiment.
7 uses the pressure loss evaluation apparatus of FIG. 2 in Embodiment 5, and the conditions of the supplied air and the measurement environment, that is, the temperature / humidity of the air, and the temperature / humidity / pressure of the measurement environment are the same. It is a figure which shows the change of the differential pressure | voltage for every elapsed time in the honeycomb structure 1 (C, D).
Fig. 8 is a schematic diagram of an apparatus for evaluating pressure loss of a honeycomb structure 1 used for CRT in a sixth embodiment.
9 is a diagram showing a differential pressure before and after correction for each input amount of carbon fine particles 15a in Embodiment 6. FIG.
FIG. 10 is a diagram showing the flow rate and differential pressure of different honeycomb structures 1 (E, F) measured without using the evaluation method and evaluation apparatus for the pressure loss of the honeycomb structure of the present invention in a comparative example. is there.
[Explanation of symbols]
1 Honeycomb structure (DPF, catalytic converter)
1a outer skin
1b Through hole
1c Bulkhead
1d, 1e end face
1f, 1g Sealing material
2 cushioning material
3 Test chamber
3a Entrance side
3b Exit side
4 filters
5 Differential pressure gauge
6 Computer
6a monitor
7a, 7b, 7c, 7d
8 Absolute filter
9 Digital temperature / humidity meter
10 Differential pressure type flow meter
11 Flow control valve
12 Exhaust blower
13 Digital temperature / humidity / barometer
14 Dust injector
14a spout
15 Dust feeder
15a carbon fine particles
16 tubes
17 Dryer
18 Air compressor
A1 inflow
A2 passing
A3 outflow

Claims

A method of supplying a gas whose flow rate is substantially stabilized to a honeycomb structure using a flow rate adjusting valve, and obtaining a pressure loss of the honeycomb structure from a differential pressure between a gas inflow side and an outflow side of the honeycomb structure. The gas is continuously supplied by determining an allowable range for the flow rate of the gas having a width smaller than the width of the flow rate change that still exists even when the flow rate adjusting valve is used, and the flow rate of the gas is set at a minute time interval. from the differential pressure measured when measuring each, continuously during a predetermined measurement value of the flow rate of the gas preset time is in the allowable range, and wherein the determination of the pressure loss of the honeycomb structure To evaluate pressure loss of honeycomb structure.

When the measured value of the gas flow rate is continuously within the allowable range for a predetermined time set in advance , the differential pressure between the gas inflow side and the outflow side of the honeycomb structure is measured, and then after the predetermined time 2. The pressure loss is obtained from the differential pressure when the measured value of the flow rate of the gas is continuously within the allowable range during a second preset predetermined time. Evaluation method of pressure loss of honeycomb structure.

A first allowable range for the flow rate of a gas having a width smaller than the width of the flow rate change that still exists even when the flow rate adjusting valve is used, and a second allowable range set narrower than the first allowable range. The gas is continuously supplied and measured, and the flow rate of the gas is measured every minute time interval, and the measured value of the flow rate of the gas is continuously within the first allowable range for a predetermined time. And the average of the measured values of the gas flow rate is in a range having a width of at most 2/3 of the first allowable range in the same predetermined time as the first allowable range, And the measured value of the flow rate of the gas in the predetermined short time within the predetermined time (the length is shorter than the predetermined time and the end time is the same as the end time of the predetermined time) is the second allowable range. in Yes, the flow of meter of the last short time the gas A gas inlet side of the honeycomb structure when the average value is in the range with a wide with 2/3 of the width of the second tolerance range and around the same to the second tolerance range and outflow side When the measured value of the flow rate of the gas is within the second allowable range continuously during a second predetermined time that is continuous after the predetermined time. The pressure loss of the honeycomb structure according to claim 1 , wherein the pressure loss is obtained from