고온고압 조건에서 Two-Photon LIF를 이용한 CO 측정에 관한 연구

오승묵(Seungmook Oh),김득상(Duksang Kim),Paul C. Miles,Will F. Colban 한국연소학회 2007 한국연소학회지 Vol.12 No.4

Carbon monoxide (CO) is not only an important intermediate species in chemical reaction mechanisms of hydrocarbon fuel combustion, but also a crucial pollutant species emitted from automotive engines. To better understand the physical processes impacting CO emissions, the development of laser-based measurement techniques that can visualize in-cylinder CO distributions is desirable. Among these techniques, Laser-Induced Fluorescence (LIF) is a sensitive and species-selective detection technique capable of good spatial resolution. However, some technical matters such as deep UV excitation, severe pressure dependency of the LIF signal, and potential interference from other species have been major challenges for CO LIF application. This study is focused on investigating the feasibility of CO two-photon LIF in a direct-injection diesel engine operating at typical pressure and temperature conditions with commercial grade diesel fuel. Spectroscopic analysis shows that the CO fluorescence signal can be separated from C₂ Swan band or broadband fluorescence from PAHs when the signal is collected near 483 nm. The signal-to-noise ratio of CO LIF deteriorate rapidly as pressure is increased, following P<SUP>-1.49</SUP> which matches the theoretical signal pressure dependency.

Crystal-field excitations and spin-phonon interactions inDyNi2B2C: Raman scattering study

Rho, Heesuk,Klein, Miles V.,Canfield, Paul C. American Physical Society 2010 Physical review. B, Condensed matter and materials Vol.82 No.6

저온 디젤 연소에서 스월비에 따른 CO 배출 및 연비 변화

국상훈(Sanghoon Kook),Paul C. Miles(Paul C. Miles),Michael Bergin(Michael Bergin),배충식(Choongsik Bae) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1

Engine-out CO emission was measured over a wide range of swirl ratios and injection timings on low-temperature diesel combustion regime in a small~bore single-cylinder diesel engine. Our previous work has shown that late-cycle mixing plays an important role even in so-called dilution-controlled low-temperature combustion systems. In this study. we employ multi-dimensional numerical simulation to characterize the flow structures and their impact on CO emissions. 65% exhaust gas recirculation is simulated with additional N₂ and CO₂, The CO emission shows optimal values at swirl ratio of 2.59 and limited ranges of injection timings. The numerical simulations show that the formed CO is trapped inside bowl at high swirl of 7.12. while CO is lifted out due to an enhanced reverse squish flow with a swirl ratio of 2.59. For a lower swirl ratio of 1.44, the existence of a single, large bulk flow structure limits the mixing process. The measured fuel conversion efficiency shows maximum value at low swirl ratio. The source of the maxima is clarified by the analysis of the work conversion efficiency, combustion efficiency, and heat transfer loss. Results show heat loss plays important role in determining the fuel conversion efficiency.

A novel method for correction of temporally- and spatially-variant optical distortion in planar particle image velocimetry

Zha, Kan,Busch, Stephen,Park, Cheolwoong,Miles, Paul C IOP Pub 2016 Measurement science & technology Vol.27 No.8

<P>In-cylinder flow measurements are necessary to gain a fundamental understanding of swirl-supported, light-duty Diesel engine processes for high thermal efficiency and low emissions. Planar particle image velocimetry (PIV) can be used for non-intrusive, <I>in situ</I> measurement of swirl-plane velocity fields through a transparent piston. In order to keep the flow unchanged from all-metal engine operation, the geometry of the transparent piston must adapt the production-intent metal piston geometry. As a result, a temporally- and spatially-variant optical distortion is introduced to the particle images. To ensure reliable measurement of particle displacements, this work documents a systematic exploration of optical distortion quantification and a hybrid back-projection procedure that combines ray-tracing-based geometric and <I>in situ</I> manual back-projection approaches.</P> <P>The proposed hybrid back-projection method for the first time provides a time-efficient and robust way to process planar PIV measurements conducted in an optical research engine with temporally- and spatially-varying optical distortion. This method is based upon geometric ray tracing and serves as a universal tool for the correction of optical distortion with an arbitrary but axisymmetric piston crown window geometry. Analytical analysis demonstrates that the ignorance of optical distortion change during the PIV laser temporal interval may induce a significant error in instantaneous velocity measurements. With the proposed digital dewarping method, this piston-motion-induced error can be eliminated. Uncertainty analysis with simulated particle images provides guidance on whether to back-project particle images or back-project velocity fields in order to minimize dewarping-induced uncertainties. The optimal implementation is piston-geometry-dependent. For regions with significant change in nominal magnification factor, it is recommended to apply the proposed back-projection approach to particle images prior to PIV interrogation. For regions with significant dewarping-induced particle elongation (<img ALIGN='MIDDLE' ALT='${{E}_{\text{p}}}>3$ ' SRC='http://ej.iop.org/images/0957-0233/27/8/085201/mstaa28ddieqn001.gif'/>), it is recommended to apply the proposed dewarping method to the vector fields resulting from PIV interrogation of raw particle image pairs.</P>

저온디젤연소엔진에서 미연탄화수소 생성에 관한 연구

오승묵(Seungmook Oh),Wiil F. Colban,Paul C. Miles 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The cycle-to-cycle variability and potential sources of unburned hydrocarbon (UHC) emissions are examined in a single-cylinder, light-duty diesel test engine operating in low-temperature combustion regimes. A fast flame ionization detector (FID) was employed to examine both cycle-to-cycle emissions behavior. A standard suite of emissions measurements, including CO, CO₂, NOx and soot, was also obtained. Measurements were made spanning a broad range of intake O₂ concentrations-to examine the UHC behavior of dilution-controlled combustion regimes-and spanning a broad range of injection timings-to clarify the behavior of increased UHC emissions in late-injection combustion regimes. Both low- and moderate-loads were investigated. The cycle-resolved UHC data showed that the coefficient of variation of single-cycle UHC did not increase with increases in UHC emissions as either O₂ concentration or injection timing was varied. Additionally, the crank-angle-resolved UHC measurements were coupled with a I-D engine model to examine the variation of exhaust mass flow rate of UHC within each cycle. The results showed that most of the UHC mass exited the cylinder during the latter part of the exhaust process, and that UHCs originating from cylinder wall and piston top quench layers are likely of greater importance than UHCs emitted from quench layers along the head.

고온고압 조건에서 Two-Photon LIF를 이용한 CO 측정에 관한 연구

Oh, Seung-Mook,Kim, Duk-Sang,Miles, Paul C.,Colban, Will F. 한국연소학회 2007 한국연소학회지 Vol.12 No.4

Carbon monoxide (CO) is not only an important intermediate species in chemical reaction mechanisms of hydrocarbon fuel combustion, but also a crucial pollutant species emitted from automotive engines. To better understand the physical processes impacting CO emissions, the development of laser-based measurement techniques that can visualize in-cylinder CO distributions is desirable. Among these techniques, Laser-Induced Fluorescence (LIF) is a sensitive and species-selective detection technique capable of good spatial resolution. However, some technical matters such as deep UV excitation, severe pressure dependency of the LIF signal, and potential interference from other species have been major challenges for CO LIF application. This study is focused on investigating the feasibility of CO two-photon LIF in a direct-injection diesel engine operating at typical pressure and temperature conditions with commercial grade diesel fuel. Spectroscopic analysis shows that the CO fluorescence signal can be separated from $C_2$ Swan band or broadband fluorescence from PAHs when the signal is collected near 483 nm. The signal-to-noise ratio of CO LIF deteriorate rapidly as pressure is increased, following $P^{-1.49}$ which matches the theoretical signal pressure dependency.