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Air-to-Fuel Ratio

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Yasuhiro Urata – One of the best experts on this subject based on the ideXlab platform.

  • flame chemiluminescence studies of cyclic combustion variations and air to fuel Ratio of the reacting mixture in a lean burn stratified charge spark ignition engine
    Combustion and Flame, 2004
    Co-Authors: P G Aleiferis, Y Hardalupas, A M K P Taylor, Kazuo Ishii, Yasuhiro Urata
    Abstract:

    The operating range of lean-burn spark-ignition engines is limited by the level of cyclic variability in the early flame development that typically corresponds to the 0-5% mass fraction burned duRation. An experimental investigation was undertaken to study the levels of flame chemiluminescence in an optical stratified-charge spark-ignition engine, using a Cassegrain optical system with high spatial resolution. Measurements of OH and CH-radical intensities were simultaneously acquired with double flame images per cycle for a range of Air-to-Fuel Ratios (A/F=12-22). These signals of chemiluminescence were used to evaluate the in-cylinder equivalence Ratio of the reacting mixture and to further examine its contribution to the flame growth speed and the cyclic variability in the crank angle by which 5% mass fraction was burned (θXb5%). Specifically, the Ratio of the OH/CH chemiluminescence signals was calibrated in the engine and tested extensively for different injection strategies and spark advances, to measure the “global” and “local” in-cylinder A/F Ratio around the spark plug. The complications encountered towards this goal are discussed in detail. The results showed that the equivalence Ratio exhibited large variations on a cycle-by-cycle basis and consistently produced negative correlation coefficients with θXb5%, especially for lean-set operating conditions (A/F=20-22). Particularly, for open-valve injection strategy that yielded a stratified mixture, the degree of this correlation lied in the range ≈-0.4 to -0.8, being lower for the locally measured A/F Ratio and higher for the globally evaluated one. Some issues related to the opposite gradients of the calibRation curves deduced for the measurement of the global and local in-cylinder A/F Ratios need to be examined outside the engine using a combustion facility with controlled conditions of pressure, temperature, turbulence intensity, and dilution by combustion residuals. © 2003 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  • flame chemiluminescence studies of cyclic combustion variations and air to fuel Ratio of the reacting mixture in a lean burn stratified charge spark ignition engine
    Combustion and Flame, 2004
    Co-Authors: P G Aleiferis, Y Hardalupas, Kazuo Ishii, A M K P Taylo, Yasuhiro Urata
    Abstract:

    The operating range of lean-burn spark-ignition engines is limited by the level of cyclic variability in the early flame development that typically corresponds to the 0-5% mass fraction burned duRation. An experimental investigation was undertaken to study the levels of flame chemiluminescence in an optical stratified-charge spark-ignition engine, using a Cassegrain optical system with high spatial resolution. Measurements of OH and CH-radical intensities were simultaneously acquired with double flame images per cycle for a range of Air-to-Fuel Ratios (A/F=12-22). These signals of chemiluminescence were used to evaluate the in-cylinder equivalence Ratio of the reacting mixture and to further examine its contribution to the flame growth speed and the cyclic variability in the crank angle by which 5% mass fraction was burned (θXb5%). Specifically, the Ratio of the OH/CH chemiluminescence signals was calibrated in the engine and tested extensively for different injection strategies and spark advances, to measure the “global” and “local” in-cylinder A/F Ratio around the spark plug. The complications encountered towards this goal are discussed in detail. The results showed that the equivalence Ratio exhibited large variations on a cycle-by-cycle basis and consistently produced negative correlation coefficients with θXb5%, especially for lean-set operating conditions (A/F=20-22). Particularly, for open-valve injection strategy that yielded a stratified mixture, the degree of this correlation lied in the range ≈-0.4 to -0.8, being lower for the locally measured A/F Ratio and higher for the globally evaluated one. Some issues related to the opposite gradients of the calibRation curves deduced for the measurement of the global and local in-cylinder A/F Ratios need to be examined outside the engine using a combustion facility with controlled conditions of pressure, temperature, turbulence intensity, and dilution by combustion residuals. © 2003 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

P G Aleiferis – One of the best experts on this subject based on the ideXlab platform.

  • flame chemiluminescence studies of cyclic combustion variations and air to fuel Ratio of the reacting mixture in a lean burn stratified charge spark ignition engine
    Combustion and Flame, 2004
    Co-Authors: P G Aleiferis, Y Hardalupas, A M K P Taylor, Kazuo Ishii, Yasuhiro Urata
    Abstract:

    The operating range of lean-burn spark-ignition engines is limited by the level of cyclic variability in the early flame development that typically corresponds to the 0-5% mass fraction burned duRation. An experimental investigation was undertaken to study the levels of flame chemiluminescence in an optical stratified-charge spark-ignition engine, using a Cassegrain optical system with high spatial resolution. Measurements of OH and CH-radical intensities were simultaneously acquired with double flame images per cycle for a range of Air-to-Fuel Ratios (A/F=12-22). These signals of chemiluminescence were used to evaluate the in-cylinder equivalence Ratio of the reacting mixture and to further examine its contribution to the flame growth speed and the cyclic variability in the crank angle by which 5% mass fraction was burned (θXb5%). Specifically, the Ratio of the OH/CH chemiluminescence signals was calibrated in the engine and tested extensively for different injection strategies and spark advances, to measure the “global” and “local” in-cylinder A/F Ratio around the spark plug. The complications encountered towards this goal are discussed in detail. The results showed that the equivalence Ratio exhibited large variations on a cycle-by-cycle basis and consistently produced negative correlation coefficients with θXb5%, especially for lean-set operating conditions (A/F=20-22). Particularly, for open-valve injection strategy that yielded a stratified mixture, the degree of this correlation lied in the range ≈-0.4 to -0.8, being lower for the locally measured A/F Ratio and higher for the globally evaluated one. Some issues related to the opposite gradients of the calibRation curves deduced for the measurement of the global and local in-cylinder A/F Ratios need to be examined outside the engine using a combustion facility with controlled conditions of pressure, temperature, turbulence intensity, and dilution by combustion residuals. © 2003 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  • flame chemiluminescence studies of cyclic combustion variations and air to fuel Ratio of the reacting mixture in a lean burn stratified charge spark ignition engine
    Combustion and Flame, 2004
    Co-Authors: P G Aleiferis, Y Hardalupas, Kazuo Ishii, A M K P Taylo, Yasuhiro Urata
    Abstract:

    The operating range of lean-burn spark-ignition engines is limited by the level of cyclic variability in the early flame development that typically corresponds to the 0-5% mass fraction burned duRation. An experimental investigation was undertaken to study the levels of flame chemiluminescence in an optical stratified-charge spark-ignition engine, using a Cassegrain optical system with high spatial resolution. Measurements of OH and CH-radical intensities were simultaneously acquired with double flame images per cycle for a range of Air-to-Fuel Ratios (A/F=12-22). These signals of chemiluminescence were used to evaluate the in-cylinder equivalence Ratio of the reacting mixture and to further examine its contribution to the flame growth speed and the cyclic variability in the crank angle by which 5% mass fraction was burned (θXb5%). Specifically, the Ratio of the OH/CH chemiluminescence signals was calibrated in the engine and tested extensively for different injection strategies and spark advances, to measure the “global” and “local” in-cylinder A/F Ratio around the spark plug. The complications encountered towards this goal are discussed in detail. The results showed that the equivalence Ratio exhibited large variations on a cycle-by-cycle basis and consistently produced negative correlation coefficients with θXb5%, especially for lean-set operating conditions (A/F=20-22). Particularly, for open-valve injection strategy that yielded a stratified mixture, the degree of this correlation lied in the range ≈-0.4 to -0.8, being lower for the locally measured A/F Ratio and higher for the globally evaluated one. Some issues related to the opposite gradients of the calibRation curves deduced for the measurement of the global and local in-cylinder A/F Ratios need to be examined outside the engine using a combustion facility with controlled conditions of pressure, temperature, turbulence intensity, and dilution by combustion residuals. © 2003 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Guoming G. Zhu – One of the best experts on this subject based on the ideXlab platform.

  • Transient Air-to-Fuel Ratio Control of an Spark Ignited Engine Using Linear Quadratic Tracking
    Journal of Dynamic Systems Measurement and Control, 2013
    Co-Authors: Pace Stephen D, Guoming G. Zhu
    Abstract:

    Modern spark ignited (SI) internal combustion engines maintain their Air-to-Fuel Ratio (AFR) at a desired level to maximize the three-way catalyst conversion efficiency and durability. However, maintaining the engine AFR during its transient opeRation is quite challenging due to rapid changes of driver demand or engine throttle. Conventional transient AFR control is based upon the inverse dynamics of the engine fueling dynamics and the measured mass air flow (MAF) rate to obtain the desired AFR of the gas mixture trapped in the cylinder. This paper develops a linear quadratic (LQ) tracking controller to regulate the transient AFR based upon a control-oriented model of the engine port fuel injection (PFI) wall wetting dynamics and the air intake dynamics from the measured airflow to the manifold pressure. The LQ tracking controller is designed to optimally track the desired AFR by minimizing the error between the trapped in-cylinder air mass and the product of the desired AFR and fuel mass over a given time interval. The performance of the optimal LQ tracking controller was compared with the conventional transient fueling control based on the inverse fueling dynamics through simulations and showed improvement over the baseline conventional inverse fueling dynamics controller. To validate the control strategy on an actual engine, a 0.4 l single cylinder direct-injection (DI) engine was used. The PFI wall wetting dynamics were simulated in the engine controller after the DI injector control signal. Engine load transition tests for the simulated PFI case were conducted on an engine dynamometer, and the results showed improvement over the baseline transient fueling controller based on the inverse fueling dynamics.

  • ACC – Air-to-Fuel Ratio regulation during SI to HCCI combustion mode transition using the LQ tracking control
    2012 American Control Conference (ACC), 2012
    Co-Authors: Xiaojian Yang, Guoming G. Zhu, Xuefei Chen
    Abstract:

    The combustion mode transition between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustions of an internal combustion (IC) engine is challenging due to the distinct engine operating parameters over the two combustion modes and the cycle-to-cycle residue gas dynamics during the mode transition. The control problem becomes even more complicated for a multi-cylinder engine without camless valve actuation. This paper studies the combustion mode transition problem of a multi-cylinder IC engine with dual-stage valve lift and electrical variable valve timing (VVT) systems. Hardware-in-the-loop (HIL) simulations were used to develop and validate the proposed control strategies. The HIL simulation results show that smooth combustion mode transition can be realized utilizing the hybrid combustion mode in a few engine cycles and in-cylinder Air-to-Fuel Ratio during the mode transition needs to be regulated to the desired level. This paper presents a model based linear quadratic tracking strategy to track the desired Air-to-Fuel Ratio by controlling the engine throttle. The HIL simulations demonstrated the effectiveness of the developed control strategies. As a result, it is feasible to have a smooth combustion mode transition with dual-stage valve lift and electrical VVT systems.

  • ACC – Air-to-Fuel Ratio control with adaptive estimation of biofuel content for diesel engine LNT regeneRation
    2012 American Control Conference (ACC), 2012
    Co-Authors: Xuefei Chen, Ibrahim Haskara, Yueyun Wang, Guoming G. Zhu
    Abstract:

    This paper presents a method of controlling the Air-to-Fuel Ratio (AFR) based upon an adaptively estimated biodiesel fuel content for a diesel engine equipped with the lean NOx trap (LNT) aftertreatment system. The fuel content (or percentage of biodiesel fuel) is estimated by an adaptive estimation scheme based upon the exhaust oxygen sensor signal during the normal engine opeRations and during the LNT regeneRation when the AFR is controlled in a closed loop. The engine system was modeled by a third order linear system in this study. A Linear Quadratic optimal tracking controller was used to regulate the engine AFR to the desired level during the LNT regeneRation period. The closed loop system robustness with respect to the air flow measurement error and the fuel content estimation error is also analyzed. Three adaptive control schemes were studied through simulations, and the best performance was obtained for the dual-gain scheme, where the low adaptive estimation gain is used during normal engine opeRations and high gain is used during the LNT regeneRation.