JP3930398B2

JP3930398B2 - Two-fluid injection internal combustion engine and method of operating the same

Info

Publication number: JP3930398B2
Application number: JP2002238718A
Authority: JP
Inventors: 純之介安藤; 高之山本; 晃広柚木
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2002-08-20
Filing date: 2002-08-20
Publication date: 2007-06-13
Anticipated expiration: 2022-08-20
Also published as: JP2004076655A

Description

【０００１】
【発明の属する技術分野】
本発明は、主燃料と高温水等の噴射流体とを燃焼室内に噴射して燃焼せしめる４サイクル二流体噴射内燃機関及びその運転方法に関する。
【０００２】
【従来の技術】
ディーゼル機関においては、機関のシリンダ内での燃焼過程で発生するＮＯｘ（窒素酸化物）の量を低減する手段として、燃焼室内へ水を直接噴射する技術が多く提供されている。
水を燃焼室内へ直接に噴射する形式の場合、水噴射は、通常、圧縮行程終期から燃焼行程の初期つまり燃焼過程前および／または燃焼行程中に行われる。かかる水の噴射タイミングを採ることにより、多量の水を燃焼室内へ噴射することができ、それによって、５０〜６０％程度のＮＯｘ削減が可能となっている。
【０００３】
４サイクルディーゼル機関において、前記のように燃焼室内への水噴射を、圧縮行程終期から燃焼行程の初期に行うようにした技術の１つとして、特開２００１−２００７６１号の発明がある。
かかる発明においては、圧力５ＭＰａ以上でかつ温度２５０℃以上の高圧水を機関の上死点の前後好ましくはクランク角で上死点前９０°〜上死点後６０°の範囲に行い、上死点前の燃焼室内に該燃焼室内温度よりも低温の前記高圧水を噴射することにより燃焼に伴い発生するＮＯｘ濃度を低減し、上死点後の燃焼室内に高圧水を噴射することにより排熱回収効果を向上させるようになっている。
【０００４】
【発明が解決しようとする課題】
４サイクルディーゼル機関においては、吸入行程においてピストンが下降する際の機関仕事は負の仕事となり、機関出力増大を制約する要因の１つとなっている。
前記特開２００１−２００７６１号の発明においても、吸入行程のピストン下降時には他の従来技術と同様に、フライホイールの慣性力によってピストンを下降させており、負の機関仕事となって機関出力増大の制約要因となっている。
【０００５】
また、前記特開２００１−２００７６１号の発明においては、高圧水を機関の上死点の前後（好ましくはクランク角で上死点前９０°〜上死点後６０°の範囲）に行うことにより燃焼室内におけるＮＯｘの生成量を低減しているが、吸入行程で燃焼室内に吸入した空気を圧縮し該圧縮空気中にて燃料及び水を噴射しているため、給気中の酸素がそのまま燃焼に供されることとなって、酸素濃度の高い状態での燃焼となりＮＯｘ濃度の低減を十分に成し得ない。
【０００６】
さらに、かかる発明を含む従来技術においては、排気弁と給気弁とがオーバーラップして開いている時期があることから、排気行程後半の前記オーバーラップ期間中に給気が行われて低温の給気が排気側に吹き抜けて排気系統の温度が低下し、高い排熱回収効率が得られない、
等の問題点を有している。
【０００７】
本発明は、かかる従来技術の課題に鑑み、吸入行程における負の機関仕事を無くして機関出力を増大するとともに、給気中の酸素濃度を低減することにより燃焼中におけるＮＯｘ生成を抑制し、さらには給気の排気側への吹き抜けを抑制して排熱回収効率を向上せしめ得る二流体噴射内燃機関及びその運転方法を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明はかかる従来技術の課題に鑑み、請求項１の発明として、主燃料と他の噴射流体とを燃焼室内に噴射して燃焼せしめる４サイクル二流体噴射内燃機関において、前記噴射流体を前記燃焼室内に噴射する噴射弁と、給排気上死点を含む該上死点近傍から所定期間に亘り前記噴射流体を噴射せしめるように前記噴射弁を開閉操作する流体噴射装置とを備え、前記内燃機関の給気弁の開弁時期と排気弁の閉弁時期とはオーバーラップしないように設定され、前記流体噴射装置は前記噴射弁による噴射流体の噴射始め時期を給気弁の開弁時期よりも早期とし、かつ前記給気弁の開弁前に該噴射流体の噴射期間が終了あるいは噴射期間終期になるように構成され、さらに、前記噴射流体の噴射始め時期を排気弁の閉弁時期よりも早期の排気行程後半になるように設定して排気弁が閉弁するまでの排気弁開期間と噴射弁開期間とがオーバーラップすることを特徴とする二流体噴射内燃機関を提供する。
【０００９】
請求項２記載の発明は請求項１に加えて、機関回転数を検出する回転数検出器と、機関の負荷（出力）を検出する負荷検出器とを備え、前記流体噴射装置は前記機関回転数及び負荷の検出値に基づき前記噴射弁の噴射タイミングを制御するように構成されたことを特徴とする。
【００１０】
【００１１】
【００１２】
次に、請求項３ないし５記載の発明は、請求項１ないし２の発明に係る二流体噴射内燃機関を運転する方法の発明に係り、請求項３の発明は、主燃料と他の噴射流体とを燃焼室内に噴射して燃焼せしめる４サイクル二流体噴射内燃機関の運転方法において、前記内燃機関の給気弁の開弁時期と排気弁の閉弁時期とはオーバーラップしないように設定され、前記噴射流体の噴射始め時期を給気弁の開弁時期よりも早期とし、かつ該噴射流体の噴射期間終了後あるいは噴射期間終期に前記給気弁を開弁し、さらに、前記噴射流体の噴射始め時期を排気弁の閉弁時期よりも早期の排気行程後半とし、排気弁が閉弁するまでの排気弁開期間と噴射弁開期間とをオーバーラップさせることを特徴とする。
請求項３において、請求項４のように前記噴射流体として高温水または水蒸気を用いるか、あるいは請求項５のように超臨界水を用いるのがよい。
【００１３】
【００１４】
かかる発明によれば、流体噴射装置は、機関のクランク角にて排気行程から吸入行程に移行する給排気上死点近傍で、給気弁の開弁時期よりも早期に（給排気上死点前３０°近傍で）噴射弁から燃焼室内への噴射流体つまり請求項４のような高温水または水蒸気あるいは請求項５のような超臨界水の噴射を開始せしめるとともに、前記給気弁の開弁前あるいは開弁初期に該噴射流体の噴射を終了せしめる。
【００１５】
従って、給排気上死点から給気弁が下降し始める直前に噴射弁から燃焼室内に噴射流体つまり高温水、水蒸気、超臨界水等の加圧された高温流体を噴射することによって、給気のポンピング仕事が付加されて機関出力が増大する。
また前記のように、給気弁の開弁時期よりも早期に燃焼室内に噴射流体を噴射し次いで給気弁を開いて給気を燃焼室内に供給するので、燃焼室内に投入される作動流体の総和は、噴射流体の噴射を行わない場合と同じであり、噴射流体の噴射による圧縮損失の増大はない。
【００１６】
また、吸入行程に入る段階で燃焼室内の作動流体に前記噴射流体が付加されることにより該作動流体の比熱が増大し、これにより燃焼温度が低下するため、燃焼室内におけるＮＯｘ（窒素酸化物）の生成量が低減される。
さらに、吸入行程に入る段階で燃焼室内に前記噴射流体が導入されることにより、圧縮行程に入る段階での燃焼室内における酸素濃度が前記噴射流体の混入相当分減少して燃焼が緩慢となり、燃焼室内におけるＮＯｘの生成量が低減される。
【００１７】
また前記噴射流体としては、請求項４のような高温水または水蒸気あるいは請求項５のような超臨界水が好適であるが、殊に請求項５のような超臨界水を用いれば、該超臨界水による拡散係数の増大によって水と燃料の均一相形成が容易となり局所的な高温燃焼部が少なくなり、燃焼室内における温度分布の均一化が促進され、ＮＯｘ発生の抑制効果がさらに増大する。
【００１８】
また本発明のように構成すれば、排気行程後半に噴射弁から燃焼室内に前記高温の噴射流体を噴射することにより、従来技術のように排気弁と給気弁とがオーバーラップして開き排気行程後半に給気が行われて低温の給気が排気側に吹き抜けて排気系統の温度が低下するのが回避され、従来技術における低温の給気に代えて高温の噴射流体が排気系統に供給されるため、排気ガスの熱回収が効率的になされるとともに、排気ガス温度よりも低温の前記噴射流体により排気ガスは適度に冷却されるので、過給機構成部材等の耐久性低下は回避できる。
【００１９】
また請求項２のように構成すれば、流体噴射装置において機関回転数及び機関負荷（出力）を含む機関運転状態の検出値に基づき、前記噴射流体の噴射タイミング及び噴射量を機関運転状態に適応して正確に設定することが可能となり、さらなる機関出力の増大効果、ＮＯｘ発生の抑制効果、及び排気ガスからの熱回収効率の増大効果が得られる。
【００２０】
【発明の実施の形態】
以下、本発明を図に示した実施例を用いて詳細に説明する。但し、この実施例に記載される構成部品の寸法、形状、その相対配置などは特に特定的な記載がない限り、この発明の範囲をそれのみに限定する趣旨ではなく単なる説明例に過ぎない。
【００２１】
図１は本発明の実施例に係る発電用４サイクルディーゼル機関の二流体噴射システムの系統図、図２は前記実施例における燃焼室周りの概略断面図である。図３は前記実施例における弁の開閉タイミングを示すグラフ図、図４は弁開閉タイミングの従来技術と本発明との比較グラフ図である。図５は吸入行程におけるシリンダ内圧力線図である。
【００２２】
全体システムを示す図１において、１はディーゼル機関（以下機関と略称する）、７は該機関１の給気マニホールド、８は排気マニホールド、３は該機関１に直結駆動される発電機である。４は過給機で、前記機関１の排気マニホールド８から排気管１０を経て導入される排ガスによりタービン４ａを駆動し該タービン４ａに直結駆動されるコンプレッサ４ｂにより空気を圧縮し該加圧空気即ち給気を、給気管９を通して前記機関１の給気マニホールド７に供給する。２は主燃料を高圧に加圧して前記機関１の燃料噴射弁１６（図２参照）に圧送する燃料噴射ポンプである。
【００２３】
５は排熱ボイラで、前記過給機４のタービン４ａを駆動し排気管１０を経て導入された排ガスと、給水ポンプ６により給水管２４を介して送給された水とを熱交換して該水を加熱し、高温水（あるいは後述するような超臨界水）を生成するものである。該排熱ボイラ５は公知の排熱ボイラを用いるので、その構造説明は省略する。
２６は高温水噴射ポンプで、前記排熱ボイラ５で生成された高温水を加圧して高圧の高温水として、高温水噴射管２５を通して前記機関１側の水噴射弁２２（図２参照）に圧送する。
【００２４】
２８は前記発電機３を駆動するための機関１の負荷（出力）を検出する負荷検出器、２９は機関回転数及び機関のクランク角を検出する回転数検出器である。該回転数検出器２９には必要に応じて機関のクランク角を検出するクランク角検出器を併設する。
２７は高温水噴射制御装置で、前記負荷検出器２８から入力される機関負荷（出力）の検出値及び回転数検出器２９から入力される機関回転数の検出値（必要に応じてクランク角の検出値）に基づき前記高温水噴射ポンプ２５に水噴射弁２２（図２参照）の噴射タイミングの制御操作信号を出力する。
【００２５】
前記機関１の燃焼室周りの概略を示す図２において、前記機関１は、シリンダライナ１９と、シリンダヘッド１２と、ピストンリング１３が介装され前記シリンダライナ１９内で往復運動するピストン１４と、前記ピストン１４の往復動力をクランク軸（図示省略）を介して前記発電機３に伝達する連接棒１５等とからなる。
また前記機関１において、２０は給気ポート、２１は排気ポート、１１は前記シリンダヘッド１２及びピストン１４にて区画形成される燃焼室である。
【００２６】
該燃焼室１１に対面する中央部には燃料噴射弁１６、その左右両側には前記給気ポートを開閉して燃焼室１１内に空気を給気する給気弁１７と、前記排気ポート２１を開閉して燃焼室１１からの排ガスの排出を行う排気弁１８とを具え、図３の弁の開閉タイミンググラフ図に示すように、機関１の基本動作である吸入、圧縮、燃焼、排気を４サイクルつまりクランク軸の２回転で完了する。
２２は本発明の対象となる水噴射弁で、前記給気弁１７及び排気弁１８の外側の燃焼室１１上部に１個あるいは複数個（この例では２個）設けられている。
【００２７】
かかる構成からなる二流体噴射システムを備えた４サイクルディーゼル機関の運転時において、図３の弁開閉タイミンググラフ図に示されるように、燃焼室１１内での燃焼が行われた後、ピストン１４の下死点前で排気弁１８が開かれると、排ガス（燃焼ガス）は排気ポート２１から排気管１０を通って過給機４のタービン４ａを駆動し、排気管１０を通って排熱ボイラ５に導かれる。
【００２８】
該排熱ボイラ５においては、前記排ガスと前記給水ポンプ６により給水管２４を通して送給された水とを熱交換することにより該水を加熱して水蒸気を含む高温水（あるいは後述する超臨界水）を生成する。この高温水は高温水噴射ポンプ２６により所定圧力に加圧され、機関１の水噴射弁２２に送給され、該水噴射弁２２から後述する噴射タイミングで以って燃焼室１１内に噴射される。
【００２９】
一方、前記過給機４のタービン４ａに直結駆動されるコンプレッサ４ｂで加圧された空気は給気管９を通って給気ポート２０に導かれ、後述するタイミングでの給気弁１７の開弁により燃焼室１１内に導入される。
そして、図３に示すように、吸入行程では前記給気弁１７の開弁とともにピストン１４が下死点まで下降し、該ピストン１４が下死点より一定角度（＋２０°〜８０°程度）上昇した時点で給気弁１７が閉じて圧縮行程に移行する。
【００３０】
圧縮行程においては、ピストン１４の上昇により燃焼室１１内の空気に圧縮作用が始まり、主燃料の自己着火温度以上の高温にする。そして圧縮行程の終期近くで（上死点より−１０°〜−２０°前後）燃料噴射弁１６により燃焼室１１内の空気中に主燃料を噴射すると、主燃料は自己着火により燃焼して温度及び圧力が急上昇し、ピストン１４は上死点を経て下死点に押し下げられ、膨張仕事をなす。
【００３１】
本発明においては、前記排気行程の終期から吸入行程の初期にかけての給排気上死点近傍において、前記水噴射弁２２から燃焼室１１内に高温水を噴射するように構成されている。
即ち、図３及び図４（Ｂ）に示されるように、給排気上死点近傍で、給気弁１７の開弁時期よりも早期に（好ましくは給排気上死点前３０°程度で）前記水噴射弁２２から燃焼室１１内への高温水（水蒸気を含む、以下同様）の噴射を開始せしめる。
そして前記給気弁１７の開弁前あるいは開弁時を含む開弁初期に該高温水の噴射を終了せしめる。図３においてＺ_２が前記水噴射弁２２の閉弁及び給気弁１７の開弁時期である。尚、図３においてＺ_１は従来技術における給気弁１７の開弁時期である。
【００３２】
前記高温水噴射制御装置２７は、前記のように機関のクランク角にて排気行程から吸入行程に移行する給排気上死点近傍で、給気弁１７の開弁時期よりも早期に高温水噴射ポンプ２６により圧送された加圧高温水を水噴射弁２２から燃焼室１１内へ噴射せしめるとともに、前記給気弁１７の開弁前あるいは開弁初期に該加圧高温水の噴射を終了せしめている。
【００３３】
前記高温水噴射制御装置２７による高温水の噴射時期及び噴射期間の制御は、該高温水噴射制御装置２７に負荷検出器２８から入力される機関負荷（出力）の検出値及び回転数検出器２９から入力される機関回転数の検出値（必要に応じてクランク角の検出値）に基づき、前記高温水噴射ポンプ２５に図３及び図４（Ｂ）のような水噴射弁２２の噴射タイミングの制御操作信号を出力して該高温水噴射ポンプ２５を駆動操作することにより行う。
このように構成すれば、前記高温水の噴射タイミング及び噴射量を機関運転状態に適応して正確に設定することが可能となり、機関出力の増大効果、ＮＯｘ発生の抑制効果、及び排気ガスからの熱回収効率の増大効果が得られる。
【００３４】
また、前記高温水噴射ポンプ２５及び水噴射弁２２の噴射タイミング及び噴射量制御は、前記給気弁１７及び排気弁１８の開閉タイミングとともに、図示しないクランク軸の回転に連動されるタイミングギアにより行ってもよい。
【００３５】
従ってかかる実施例によれば、給排気上死点から給気弁１７が下降し始める直前に水噴射弁２２から燃焼室１１内に加圧された高温水を噴射することによって、給気のポンピング仕事が付加されて機関出力が増大する。
即ち、従来技術においては図５のＡに示されるように吸入行程においてピストン１４が下降する際のシリンダ内圧力は小さく機関仕事は負の仕事となっているのに対し、本発明においては図５のＢに示されるように高温水の噴射による給気のポンピング仕事によって面積Ｓに相当する機関仕事が付加されることとなる。
【００３６】
尚、前記のように、給気弁１７の開弁時期よりも早期に燃焼室１１内に高温水を噴射し、次いで給気弁１７を開いて給気を燃焼室１１内に供給するので、該燃焼室１１内に投入される空気、主燃料、及び高温水からなる作動流体の総和は、高温水の噴射を行わない従来技術と同じであり、高温水の噴射による圧縮損失の増大はない。
【００３７】
また、吸入行程に入る段階で燃焼室１１内の作動流体に前記高温水が付加されることにより該作動流体の比熱が増大し、これにより燃焼温度が低下するため、燃焼室内におけるＮＯｘ（窒素酸化物）の生成量が低減される。
さらに、吸入行程に入る段階で燃焼室１１内に前記高温水が導入されることにより、圧縮行程に入る段階での燃焼室１１内における酸素濃度が前記高温水の混入相当分減少して燃焼が緩慢となり、該燃焼室１１内におけるＮＯｘの生成量が低減される。
【００３８】
また前記水噴射弁２２による高温水の噴射開始時期は、図３及び図４（Ｂ）に示されるように、排気行程後半に設定して水噴射弁２２の開弁初期に排気弁１８とオーバーラップして開弁せしめる。尚、図４（Ａ）は従来技術を示し、この場合は排気弁１８開弁終期と給気弁１７の開弁初期とがオーバーラップしている。
【００３９】
このように構成すれば、排気行程後半に水噴射弁２２から燃焼室１１内に前記高温水を噴射することにより、図４（Ａ）に示される従来技術のように排気弁１８と給気弁１７とがオーバーラップして開き、排気行程後半に給気が行われて低温の給気が排気側に吹き抜けて排気系統の温度が低下するのが回避され、従来技術における低温の給気に代えて高温水が排気系統に供給される。
これにより、排ガスの熱回収が効率的になされるとともに、排ガス温度よりも低温の前記高温水により排ガスは適度に冷却されるので、過給機４の構成部材等の耐久性低下は回避できる。
【００４０】
また前記水噴射弁２２から噴射される噴射流体として、前記高温水に代えて３７４℃以上でかつ２２ＭＰａ以上の超臨界水（あるいは２５０℃〜３００℃以上で１０ＭＰａ以上の亜臨界水を含む）を用いることができる。
前記超臨界水は、ディーゼルやガスタービンの場合、排ガスの温度が５５０℃若しくはそれ以上であることから、前記排熱ボイラ５において機関１からの排ガスにより給水ポンプ６から送給される給水を加熱することにより容易に製造できる。
【００４１】
前記超臨界水や２５０℃〜３００℃以上で１０ＭＰａ以上の亜臨界水は、その誘電率が有機溶媒程度なみに低くなり炭化水素系燃料との相互溶解性が向上するため、また拡散係数の増大によって水と燃料の均一相形成が容易となり、局所的な高温燃焼部が少なくなる。よって燃焼中におけるＮＯｘの生成を抑制できる。
また前記超臨界水や亜臨界水は、前記のように液状水に比べて拡散係数が大きく粘度が低くなって燃焼時に拡散し易くなり、燃焼効率の向上につながる。
また前記超臨界水や亜臨界水は、超臨界点近傍では温度・圧力により物性が大きく変化するために、温度・圧力を制御することによりこれらの物性をコントロールすることができる。これにより多種多様な炭化水素系燃料への対応、また負荷・回転数による燃料噴射の形態に応じた超臨界水の噴射が可能である。
【００４２】
また前記のように超臨界水は拡散係数が大きいため、燃料との混合が良好に行われ、さらに水や水蒸気のように燃料粒子と夫々独立して混合されるのではなく、超臨界水が有機溶媒のような特性を持つため、燃料に溶け込み、より均一な燃焼場を形成することができる。
ディーゼル機関は燃料と空気の比が、１：３０前後であることから、さらにこの燃料及び空気に超臨界水を燃料質量比２〜４程度（燃料：空気：臨界水＝１：３０：２〜４）噴射することにより、前記のような均一な燃焼場を得ることができる。
【００４３】
【発明の効果】
以上記載のごとく本発明によれば、給排気上死点から給気弁が下降し始める直前に噴射弁から燃焼室内に噴射流体つまり高温水、水蒸気、超臨界水等の加圧された高温流体を噴射することによって、前記噴射流体の噴射による圧縮損失の増大を回避しつつ、給気のポンピング仕事が付加されて機関出力が増大する。
【００４４】
また、作動流体に前記噴射流体が付加されることにより該作動流体の比熱が増大して燃焼温度が低下するため、燃焼室内におけるＮＯｘ（窒素酸化物）の生成量が低減される。
また、前記燃焼室内への噴射流体の導入により、圧縮行程に入る段階での燃焼室内における酸素濃度が減少して燃焼が緩慢となり、燃焼室内におけるＮＯｘの生成量が低減される。
【００４５】
また前記噴射流体として請求項５のような超臨界水を用いれば、該超臨界水による拡散係数の増大によって水と燃料の均一相形成が容易となり局所的な高温燃焼部が少なくなるとともに凝縮冷却が抑制されるため、燃焼室内における温度分布の均一化が促進され、ＮＯｘ発生の抑制効果がさらに増大する。
【００４６】
また本発明のように構成すれば、排気行程後半に噴射弁から燃焼室内に前記高温の噴射流体を噴射することにより、従来技術のような低温給気の排気側への吹き抜けが回避されて高温の噴射流体が排気系統に供給されるため、排気ガスの熱回収が効率的になされるとともに、排気ガス温度よりも低温の噴射流体により排気ガスは適度に冷却されるので、過給機構成部材等の耐久性低下を回避できる。
【図面の簡単な説明】
【図１】本発明の実施例に係る発電用４サイクルディーゼル機関の二流体噴射システムの系統図である。
【図２】前記実施例における燃焼室周りの概略断面図である。
【図３】前記実施例における弁の開閉タイミングを示すグラフ図である。
【図４】弁開閉タイミングの従来技術と本発明との比較グラフ図である。
【図５】吸入行程におけるシリンダ内圧力線図である。
【符号の説明】
１ディーゼル機関
２燃料噴射ポンプ
３発電機
４過給機
５排熱ボイラ
６給水ポンプ
９給気管
１０排気管
１１燃焼室
１２シリンダヘッド
１４ピストン
１６燃料噴射弁
１７給気弁
１８排気弁
２２水噴射弁
２６高温水噴射ポンプ
２７高温水噴射制御装置
２８負荷検出器
２９回転数検出器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a four-cycle two-fluid injection internal combustion engine in which main fuel and an injection fluid such as high-temperature water are injected into a combustion chamber for combustion, and an operating method thereof.
[0002]
[Prior art]
In a diesel engine, many techniques for directly injecting water into a combustion chamber are provided as means for reducing the amount of NOx (nitrogen oxide) generated in the combustion process in a cylinder of the engine.
In the case of the type in which water is directly injected into the combustion chamber, the water injection is usually performed from the end of the compression stroke to the beginning of the combustion stroke, that is, before the combustion process and / or during the combustion stroke. By adopting such water injection timing, a large amount of water can be injected into the combustion chamber, thereby reducing NOx by about 50 to 60%.
[0003]
In a four-cycle diesel engine, as one of techniques for performing water injection into the combustion chamber as described above from the end of the compression stroke to the beginning of the combustion stroke, there is an invention of Japanese Patent Application Laid-Open No. 2001-200761.
In this invention, high pressure water having a pressure of 5 MPa or more and a temperature of 250 ° C. or more is applied before and after the top dead center of the engine, preferably at a crank angle in a range of 90 ° before top dead center to 60 ° after top dead center. By injecting the high-pressure water having a temperature lower than the temperature in the combustion chamber into the combustion chamber before the point, the NOx concentration generated by combustion is reduced, and by exhausting the high-pressure water into the combustion chamber after the top dead center, exhaust heat is discharged. The collection effect is improved.
[0004]
[Problems to be solved by the invention]
In a four-cycle diesel engine, the engine work when the piston descends in the intake stroke is a negative work, which is one of the factors that limit the increase in engine output.
In the invention of Japanese Patent Laid-Open No. 2001-200761, the piston is lowered by the inertial force of the flywheel at the time of lowering of the piston during the intake stroke, and negative engine work increases engine output. It is a limiting factor.
[0005]
Further, in the invention of the aforementioned Japanese Patent Laid-Open No. 2001-200761, high-pressure water is supplied before and after the top dead center of the engine (preferably in the range of 90 ° before top dead center to 60 ° after top dead center at the crank angle). Although the amount of NOx generated in the combustion chamber is reduced, the air sucked into the combustion chamber during the intake stroke is compressed and fuel and water are injected into the compressed air. As a result, combustion occurs in a state where the oxygen concentration is high, and the NOx concentration cannot be sufficiently reduced.
[0006]
Further, in the prior art including such an invention, since there is a time when the exhaust valve and the air supply valve overlap and open, air is supplied during the overlap period in the latter half of the exhaust stroke, and the low temperature is reduced. The supply air blows to the exhaust side, the temperature of the exhaust system decreases, and high exhaust heat recovery efficiency cannot be obtained.
And so on.
[0007]
In view of the problems of the prior art, the present invention eliminates negative engine work in the intake stroke and increases engine output, and also reduces NOx generation during combustion by reducing the oxygen concentration in the supply air. An object of the present invention is to provide a two-fluid-injection internal combustion engine that can suppress the blow-through of the supply air to the exhaust side and improve the exhaust heat recovery efficiency, and an operating method thereof.
[0008]
[Means for Solving the Problems]
In view of the problems of the prior art, the present invention provides a four-cycle two-fluid injection internal combustion engine in which main fuel and another injection fluid are injected into a combustion chamber and combusted. An internal combustion engine comprising: an injection valve that injects into a room; and a fluid injection device that opens and closes the injection valve so as to inject the injection fluid over a predetermined period from the vicinity of the top dead center including a supply and exhaust top dead center The opening timing of the intake valve and the closing timing of the exhaust valve are set so as not to overlap, and the fluid injection device sets the injection start timing of the injection fluid by the injection valve to be higher than the opening timing of the supply valve. The injection period of the injection fluid is completed or the injection period ends before the opening of the air supply valve, and the injection start timing of the injection fluid is set to be higher than the closing timing of the exhaust valve. After an early exhaust stroke And set to be to the exhaust valve open period until the exhaust valve closing and the injection valve opening period is to provide a two-fluid injection internal combustion engine, characterized by overlapping.
[0009]
According to a second aspect of the present invention, in addition to the first aspect, the engine includes a rotational speed detector that detects the engine rotational speed and a load detector that detects a load (output) of the engine, and the fluid ejecting apparatus includes the engine rotational speed. The injection timing of the injection valve is controlled based on the number and the detected value of the load .
[0010]
[0011]
[0012]
Next, the invention described in claims 3 to 5 relates to an invention of a method for operating a two-fluid injection internal combustion engine according to the invention of claims 1 to 2 , and the invention of claim 3 relates to main fuel and other injection fluids. Is set so that the valve opening timing of the intake valve and the valve closing timing of the exhaust valve of the internal combustion engine do not overlap with each other. The injection fluid injection start timing is set earlier than the opening timing of the air supply valve, and the air supply valve is opened after the injection fluid injection period ends or at the end of the injection period, and the injection fluid injection The start timing is the latter half of the exhaust stroke earlier than the closing timing of the exhaust valve, and the exhaust valve opening period and the injection valve opening period until the exhaust valve closes are overlapped .
In claim 3 , high-temperature water or water vapor is preferably used as the jet fluid as in claim 4 , or supercritical water is preferably used as in claim 5 .
[0013]
[0014]
According to the invention, the fluid ejection device is a supply and exhaust near the top dead center to move to the suction stroke from the exhaust stroke at a crank angle of the engine, early (supply and exhaust top dead center than the opening timing of the supply valves The injection of the injection fluid from the injection valve into the combustion chamber, that is, high-temperature water or steam as in claim 4 or supercritical water as in claim 5 is started and the air supply valve is opened. The injection of the injection fluid is terminated before or at the beginning of the valve opening.
[0015]
Accordingly, by injecting an injection fluid, that is, a pressurized high-temperature fluid such as high-temperature water, water vapor, or supercritical water, from the injection valve into the combustion chamber immediately before the supply valve starts to descend from the top dead center of the supply / exhaust air, The pumping work is added and the engine output is increased.
Further, as described above, the injection fluid is injected into the combustion chamber earlier than the opening timing of the intake valve, and then the intake valve is opened to supply the supply air into the combustion chamber. Is the same as the case where the ejection fluid is not ejected, and there is no increase in compression loss due to the ejection of the ejection fluid.
[0016]
Further, when the injection fluid is added to the working fluid in the combustion chamber at the stage of entering the intake stroke, the specific heat of the working fluid is increased, thereby lowering the combustion temperature, so that NOx (nitrogen oxide) in the combustion chamber is reduced. The production amount of is reduced.
Further, when the injection fluid is introduced into the combustion chamber at the stage of entering the intake stroke, the oxygen concentration in the combustion chamber at the stage of entering the compression stroke is reduced by an amount corresponding to the mixing of the injection fluid, and the combustion becomes slow. The amount of NOx generated in the room is reduced.
[0017]
As the jet fluid, high-temperature water or water vapor as in claim 4 or supercritical water as in claim 5 is suitable, but in particular, if supercritical water as in claim 5 is used, The increase of the diffusion coefficient by the critical water facilitates the formation of a uniform phase of water and fuel, reduces the number of local high-temperature combustion parts, promotes the uniform temperature distribution in the combustion chamber, and further increases the NOx generation suppression effect.
[0018]
Further, according to the present invention, by injecting the high-temperature injection fluid from the injection valve into the combustion chamber in the latter half of the exhaust stroke, the exhaust valve and the intake valve are overlapped and opened as in the prior art. Air supply is performed in the second half of the stroke, and it is avoided that the low-temperature supply air blows to the exhaust side and the temperature of the exhaust system decreases, and hot injection fluid is supplied to the exhaust system instead of the low-temperature supply air in the prior art Therefore, heat recovery of the exhaust gas is efficiently performed, and the exhaust gas is appropriately cooled by the jet fluid having a temperature lower than the exhaust gas temperature, thereby avoiding a decrease in durability of the turbocharger components and the like. it can.
[0019]
According to the second aspect of the present invention, the injection timing and the injection amount of the injection fluid are adapted to the engine operation state based on the detected value of the engine operation state including the engine speed and the engine load (output) in the fluid injection device. Therefore, it is possible to set accurately, and an effect of further increasing the engine output, an effect of suppressing the generation of NOx, and an effect of increasing the efficiency of heat recovery from the exhaust gas can be obtained.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, unless otherwise specified, the dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention.
[0021]
FIG. 1 is a system diagram of a two-fluid injection system for a power generation four-cycle diesel engine according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view around a combustion chamber in the embodiment. FIG. 3 is a graph showing the opening / closing timing of the valve in the above embodiment, and FIG. 4 is a comparison graph of the prior art of the valve opening / closing timing and the present invention. FIG. 5 is a cylinder pressure diagram in the suction stroke.
[0022]
In FIG. 1 showing the entire system, 1 is a diesel engine (hereinafter abbreviated as an engine), 7 is an air supply manifold of the engine 1, 8 is an exhaust manifold, and 3 is a generator that is directly connected to the engine 1. A turbocharger 4 drives a turbine 4a with exhaust gas introduced from an exhaust manifold 8 of the engine 1 through an exhaust pipe 10 and compresses air by a compressor 4b that is directly connected to the turbine 4a. The supply air is supplied to the supply manifold 7 of the engine 1 through the supply pipe 9. A fuel injection pump 2 pressurizes the main fuel to a high pressure and feeds it to the fuel injection valve 16 (see FIG. 2) of the engine 1.
[0023]
An exhaust heat boiler 5 drives the turbine 4a of the supercharger 4 and exchanges heat between the exhaust gas introduced through the exhaust pipe 10 and the water fed by the feed water pump 6 through the feed water pipe 24. The water is heated to produce high-temperature water (or supercritical water as described later). Since the exhaust heat boiler 5 uses a known exhaust heat boiler, its structural description is omitted.
A high-temperature water injection pump 26 pressurizes the high-temperature water generated in the exhaust heat boiler 5 to form high-pressure high-temperature water and passes through the high-temperature water injection pipe 25 to the water injection valve 22 (see FIG. 2) on the engine 1 side. Pump.
[0024]
Reference numeral 28 denotes a load detector that detects the load (output) of the engine 1 for driving the generator 3, and reference numeral 29 denotes an engine speed detector that detects the engine speed and the crank angle of the engine. The rotation speed detector 29 is provided with a crank angle detector for detecting the crank angle of the engine as required.
Reference numeral 27 denotes a high-temperature water injection control device, which is a detection value of the engine load (output) input from the load detector 28 and a detection value of the engine speed input from the rotation speed detector 29 (if necessary, the crank angle Based on the detected value), a control operation signal for the injection timing of the water injection valve 22 (see FIG. 2) is output to the high-temperature water injection pump 25.
[0025]
In FIG. 2, which schematically shows the periphery of the combustion chamber of the engine 1, the engine 1 includes a cylinder liner 19, a cylinder head 12, and a piston 14 that reciprocates within the cylinder liner 19 with a piston ring 13 interposed therebetween. The connecting rod 15 and the like transmit the reciprocating power of the piston 14 to the generator 3 via a crankshaft (not shown).
In the engine 1, 20 is an air supply port, 21 is an exhaust port, and 11 is a combustion chamber defined by the cylinder head 12 and the piston 14.
[0026]
A fuel injection valve 16 is provided at the central portion facing the combustion chamber 11, and an air supply valve 17 that opens and closes the air supply port to supply air into the combustion chamber 11 on both the left and right sides thereof, and the exhaust port 21. And an exhaust valve 18 that opens and closes and exhausts the exhaust gas from the combustion chamber 11. As shown in the valve opening / closing timing graph of FIG. The cycle is completed in two revolutions of the crankshaft.
Reference numeral 22 denotes a water injection valve which is an object of the present invention, and one or a plurality (two in this example) are provided above the combustion chamber 11 outside the air supply valve 17 and the exhaust valve 18.
[0027]
When the four-cycle diesel engine having the two-fluid injection system having such a configuration is operated, as shown in the valve opening / closing timing graph of FIG. 3, after the combustion in the combustion chamber 11 is performed, the piston 14 When the exhaust valve 18 is opened before the bottom dead center, the exhaust gas (combustion gas) drives the turbine 4a of the supercharger 4 from the exhaust port 21 through the exhaust pipe 10 and passes through the exhaust pipe 10 to the exhaust heat boiler 5. Led to.
[0028]
In the exhaust heat boiler 5, high-temperature water (or supercritical water described later) containing water vapor is heated by exchanging heat between the exhaust gas and the water fed through the feed pipe 24 by the feed water pump 6. ) Is generated. The high-temperature water is pressurized to a predetermined pressure by a high-temperature water injection pump 26, supplied to the water injection valve 22 of the engine 1, and injected from the water injection valve 22 into the combustion chamber 11 at an injection timing described later. The
[0029]
On the other hand, the air pressurized by the compressor 4b directly connected to the turbine 4a of the supercharger 4 is guided to the air supply port 20 through the air supply pipe 9, and the air supply valve 17 is opened at the timing described later. Is introduced into the combustion chamber 11.
Then, as shown in FIG. 3, in the intake stroke, the piston 14 descends to the bottom dead center with the opening of the air supply valve 17, and the piston 14 rises by a certain angle (about + 20 ° to 80 °) from the bottom dead center. At that time, the air supply valve 17 is closed and the process proceeds to the compression stroke.
[0030]
In the compression stroke, the piston 14 ascends, and the compression action starts in the air in the combustion chamber 11 to a temperature higher than the self-ignition temperature of the main fuel. When the main fuel is injected into the air in the combustion chamber 11 by the fuel injection valve 16 near the end of the compression stroke (around −10 ° to −20 ° from the top dead center), the main fuel is burned by self-ignition and temperature Then, the pressure suddenly rises, and the piston 14 is pushed down to the bottom dead center through the top dead center to perform the expansion work.
[0031]
In the present invention, high temperature water is injected from the water injection valve 22 into the combustion chamber 11 in the vicinity of the top dead center of the supply / exhaust gas from the end of the exhaust stroke to the beginning of the intake stroke.
That is, as shown in FIGS. 3 and 4B, in the vicinity of the supply / exhaust top dead center, earlier than the opening timing of the intake valve 17 (preferably about 30 ° before the supply / exhaust top dead center). The injection of high-temperature water (including water vapor, the same applies hereinafter) from the water injection valve 22 into the combustion chamber 11 is started.
Then, the injection of the high-temperature water is terminated before the air supply valve 17 is opened or at the beginning of the valve opening, including when the valve is opened. In FIG. 3, Z ₂ is the closing timing of the water injection valve 22 and the opening timing of the air supply valve 17. Incidentally, Z ₁ in FIG. 3 is a valve opening timing of the intake valve 17 in the prior art.
[0032]
As described above, the high-temperature water injection control device 27 is in the vicinity of the top / dead center of supply / exhaust where the exhaust stroke is changed to the intake stroke at the crank angle of the engine, and the high-temperature water injection is earlier than the opening timing of the intake valve 17. The pressurized hot water pumped by the pump 26 is injected into the combustion chamber 11 from the water injection valve 22 and the injection of the pressurized hot water is terminated before or at the initial opening of the air supply valve 17. Yes.
[0033]
The high temperature water injection control device 27 controls the injection timing and the injection period of the high temperature water injection control device 27 by detecting the engine load (output) input from the load detector 28 to the high temperature water injection control device 27 and the rotational speed detector 29. 3 and FIG. 4 (B), the injection timing of the water injection valve 22 as shown in FIG. 3 and FIG. This is performed by outputting a control operation signal and driving the high-temperature water jet pump 25.
If comprised in this way, it will become possible to set correctly the injection timing and injection quantity of the said high temperature water according to an engine operating state, the increase effect of an engine output, the suppression effect of NOx generation, and exhaust gas from The effect of increasing the heat recovery efficiency is obtained.
[0034]
The injection timing and injection amount control of the high-temperature water injection pump 25 and the water injection valve 22 are performed by timing gears that are linked to the rotation of the crankshaft (not shown) together with the opening and closing timings of the air supply valve 17 and the exhaust valve 18. May be.
[0035]
Therefore, according to such an embodiment, the pumping of the supply air is performed by injecting the pressurized hot water into the combustion chamber 11 from the water injection valve 22 immediately before the supply valve 17 starts to descend from the top dead center of the supply and exhaust. Work is added and engine output increases.
That is, in the prior art, as shown in FIG. 5A, the pressure in the cylinder when the piston 14 descends in the intake stroke is small and the engine work is negative, whereas in the present invention, FIG. As shown in B, the engine work corresponding to the area S is added by the pumping work of the supply air by the injection of the high temperature water.
[0036]
As described above, high-temperature water is injected into the combustion chamber 11 earlier than the opening timing of the air supply valve 17, and then the air supply valve 17 is opened to supply the air into the combustion chamber 11. The sum of the working fluid made up of air, main fuel, and high-temperature water charged into the combustion chamber 11 is the same as in the prior art in which high-temperature water is not injected, and there is no increase in compression loss due to high-temperature water injection. .
[0037]
Further, when the high-temperature water is added to the working fluid in the combustion chamber 11 at the stage of entering the intake stroke, the specific heat of the working fluid increases, thereby lowering the combustion temperature. Therefore, NOx (nitrogen oxidation in the combustion chamber) Product) is reduced.
Further, when the high temperature water is introduced into the combustion chamber 11 at the stage of entering the intake stroke, the oxygen concentration in the combustion chamber 11 at the stage of entering the compression stroke is reduced by the amount corresponding to the mixing of the high temperature water, and combustion is performed. It becomes slow and the amount of NOx produced in the combustion chamber 11 is reduced.
[0038]
Moreover, the injection start timing of the high-temperature water by the water injection valve 22 is set in the latter half of the exhaust stroke as shown in FIGS. 3 and 4B, and is over the exhaust valve 18 at the initial stage of the water injection valve 22 opening. Wrap to open the valve. FIG. 4A shows the prior art. In this case, the exhaust valve 18 opening end and the air supply valve 17 initial opening overlap.
[0039]
If comprised in this way, the said high temperature water will be injected in the combustion chamber 11 from the water injection valve 22 in the latter half of an exhaust stroke, and the exhaust valve 18 and an air supply valve like the prior art shown to FIG. 4 (A). 17 is overlapped and opened in the latter half of the exhaust stroke, so that low temperature supply air is blown out to the exhaust side and the temperature of the exhaust system is not lowered. Hot water is then supplied to the exhaust system.
Thereby, the heat recovery of the exhaust gas is efficiently performed, and the exhaust gas is appropriately cooled by the high-temperature water lower than the exhaust gas temperature, so that it is possible to avoid a decrease in the durability of the constituent members of the supercharger 4.
[0040]
In addition, instead of the high-temperature water, supercritical water of 374 ° C. or higher and 22 MPa or higher (or subcritical water of 250 ° C. to 300 ° C. or higher and 10 MPa or higher) is used as the jet fluid injected from the water injection valve 22. Can be used.
In the case of diesel or gas turbine, the supercritical water has an exhaust gas temperature of 550 ° C. or higher, and thus heats the feed water supplied from the feed water pump 6 by the exhaust gas from the engine 1 in the exhaust heat boiler 5. Can be easily manufactured.
[0041]
Supercritical water and subcritical water of 10 MPa or more at 250 ° C. to 300 ° C. or higher have a dielectric constant as low as that of an organic solvent, improving mutual solubility with hydrocarbon fuel, and increasing the diffusion coefficient. This facilitates the formation of a uniform phase of water and fuel and reduces the number of local high-temperature combustion parts. Therefore, the generation of NOx during combustion can be suppressed.
Further, as described above, the supercritical water and subcritical water have a diffusion coefficient larger than that of liquid water and have a low viscosity so that they are easily diffused during combustion, leading to improvement in combustion efficiency.
In addition, the physical properties of the supercritical water and subcritical water largely change depending on the temperature and pressure near the supercritical point. Therefore, these physical properties can be controlled by controlling the temperature and pressure. As a result, it is possible to cope with a wide variety of hydrocarbon fuels and to inject supercritical water according to the form of fuel injection depending on the load / rotation speed.
[0042]
In addition, as described above, supercritical water has a large diffusion coefficient, so that mixing with fuel is performed well, and it is not mixed with fuel particles independently like water and water vapor, but supercritical water is not mixed. Since it has characteristics like an organic solvent, it can dissolve in fuel and form a more uniform combustion field.
Since the ratio of fuel to air is around 1:30 in a diesel engine, supercritical water is further added to the fuel and air at a fuel mass ratio of about 2 to 4 (fuel: air: critical water = 1: 30: 2 4) A uniform combustion field as described above can be obtained by injection.
[0043]
【The invention's effect】
As described above, according to the present invention, a pressurized high-temperature fluid such as an injection fluid, that is, high-temperature water, steam, supercritical water, or the like, is injected from the injection valve into the combustion chamber immediately before the supply valve starts to descend from the top dead center of supply / exhaust. By avoiding the increase in compression loss due to the injection of the injection fluid, the pumping work of the supply air is added to increase the engine output.
[0044]
In addition, the addition of the jet fluid to the working fluid increases the specific heat of the working fluid and lowers the combustion temperature, thereby reducing the amount of NOx (nitrogen oxide) generated in the combustion chamber.
In addition, the introduction of the injection fluid into the combustion chamber reduces the oxygen concentration in the combustion chamber at the stage of entering the compression stroke, slows the combustion, and reduces the amount of NOx generated in the combustion chamber.
[0045]
Further, if supercritical water as in claim 5 is used as the injection fluid, a uniform phase of water and fuel can be easily formed by increasing the diffusion coefficient due to the supercritical water, and the local high-temperature combustion part is reduced and condensation cooling is performed. Therefore, the uniformity of the temperature distribution in the combustion chamber is promoted, and the NOx generation suppressing effect is further increased.
[0046]
Further, according to the present invention, the high temperature injection fluid is injected into the combustion chamber from the injection valve in the latter half of the exhaust stroke, thereby avoiding the blowout of the low temperature air supply to the exhaust side as in the prior art. Since the exhaust fluid is supplied to the exhaust system, heat recovery of the exhaust gas is efficiently performed, and the exhaust gas is appropriately cooled by the injection fluid having a temperature lower than the exhaust gas temperature. It is possible to avoid a decrease in durability such as.
[Brief description of the drawings]
FIG. 1 is a system diagram of a two-fluid injection system for a power generation four-cycle diesel engine according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view around a combustion chamber in the embodiment.
FIG. 3 is a graph showing valve opening / closing timing in the embodiment.
FIG. 4 is a comparative graph between the prior art of valve opening / closing timing and the present invention.
FIG. 5 is a pressure diagram in a cylinder in a suction stroke.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Fuel injection pump 3 Generator 4 Supercharger 5 Exhaust heat boiler 6 Water supply pump 9 Supply pipe 10 Exhaust pipe 11 Combustion chamber 12 Cylinder head 14 Piston 16 Fuel injection valve 17 Supply valve 18 Exhaust valve 22 Water injection valve 26 High-temperature water injection pump 27 High-temperature water injection control device 28 Load detector 29 Rotation speed detector

Claims

In a four-cycle two-fluid injection internal combustion engine in which main fuel and another injection fluid are injected into a combustion chamber for combustion, an injection valve for injecting the injection fluid into the combustion chamber, and the top dead center including a top dead center for supply and exhaust A fluid injection device that opens and closes the injection valve so that the injection fluid is injected over a predetermined period from the vicinity of the point, and the opening timing of the intake valve and the closing timing of the exhaust valve of the internal combustion engine are over The fluid ejecting apparatus is set so as not to wrap, and the fluid injection device makes the injection fluid injection timing by the injection valve earlier than the valve opening timing of the air supply valve, and before the air supply valve is opened, The exhaust valve closes by setting the injection start timing of the injection fluid to be in the latter half of the exhaust stroke earlier than the closing timing of the exhaust valve. Exhaust valve opening period until Two-fluid injection internal combustion engine and the event opening period, characterized in that the overlap.

An engine speed detector for detecting the engine speed and a load detector for detecting a load (output) of the engine, wherein the fluid injection device is configured to inject injection timing of the injection valve based on the detected value of the engine speed and load. The two-fluid injection internal combustion engine according to claim 1, wherein the two-fluid injection internal combustion engine is configured to control the engine.

In the operation method of a four-cycle two-fluid injection internal combustion engine in which main fuel and another injection fluid are injected into the combustion chamber and combusted, the opening timing of the intake valve and the closing timing of the exhaust valve of the internal combustion engine are over Set so as not to wrap, the injection start timing of the injection fluid is earlier than the opening timing of the supply valve, and the supply valve is opened after the injection period of the injection fluid or at the end of the injection period, Further, the injection start timing of the injection fluid is set to the latter half of the exhaust stroke earlier than the closing timing of the exhaust valve, and the exhaust valve opening period and the injection valve opening period are overlapped until the exhaust valve is closed. A method of operating the two-fluid injection internal combustion engine.

4. A method for operating a two-fluid injection internal combustion engine according to claim 3, wherein high-temperature water or water vapor is used as the injection fluid.

The operation method of a two-fluid injection internal combustion engine according to claim 3, wherein supercritical water is used as the injection fluid .