METHOD FOR MEASURING NOX REMOVAL EFFICIENCY FOR ENGINE AND DEVICE FOR MEASURING THE SAME

• Main Authors: HIRAIWA SHUNSUKE, TANAKA HIRONAKA, SHIBATA JUMPEI, KOBAYASHI RYOHEI
• Format: Patent
• Language: English; Japanese
• Published: 02.11.2015
• Subjects: BLASTING; ENGINE PLANTS IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNALCOMBUSTION ENGINES; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES ORENGINES IN GENERAL; HEATING; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; STEAM ENGINES; TRANSPORTING; WEAPONS

PROBLEM TO BE SOLVED: To exactly obtain NOx removal efficiency of a NOx removal device in an engine system including a cylinder bypass line even if a NOx concentration in exhaust gas diluted more by air than that at an outlet side of the NOx removal device is measured.SOLUTION: A part of intake air from an exhaust gas turbocharger to an engine is bypassed to a merging part that is placed downstream from a catalyst type NOx removal device in an exhaust gas passage. Both Nox concentration and O2 concentration at a side downstream from the merging part in the exhaust gas passage are detected, a converted NOx concentration at an outlet of the NOx removal device when an oxygen concentration in the exhaust gas is set to a certain standard oxygen concentration, is obtained and then, the converted NOx concentration at the outlet side of the NOx removal device is represented as NOx*o and the converted NOx concentration at the inlet side of the NOx removal device is represented as NOx*i and NOx removal efficiency is obtained by the following equation(i) NOx removal efficiency (%)={(NOx*i-NOx*o)/NOx*i}×100(i) 【課題】シリンダバイパスラインを備えたエンジン系において、脱硝装置の出口側に比べて空気によって希釈された排ガスにおけるＮＯｘ濃度を測定する場合であっても、脱硝装置における脱硝率を正確に求める。【解決手段】排ガスターボチャージャからエンジンへの給気の一部が排ガス経路における触媒式脱硝装置よりも下流側の合流部にバイパスされる。排ガス経路における合流部よりも下流側でＮＯｘ濃度とＯ２濃度とを検出し、この検出したＮＯｘ濃度とＯ２濃度を用いて、排ガス中の酸素濃度を一定の標準酸素濃度にした場合の、脱硝装置出口側の換算ＮＯｘ濃度を求め、この脱硝装置出口側の換算ＮＯｘ濃度を「ＮＯｘ・ｏ」とし、脱硝装置入口側の換算ＮＯｘ濃度を「ＮＯｘ・ｉ」として、次式（ｉ）により脱硝率を求める。脱硝率（％）＝｛（ＮＯｘ・ｉ−ＮＯｘ・ｏ）／ＮＯｘ・ｉ｝?１００・・・（ｉ）【選択図】図１