scholarly journals Evaluation of Non-condensable Gas Recirculation Flow in Steam Generator U-tubes during Reflux Condensation

10.5772/14796 ◽  
2011 ◽  
Author(s):  
Michio Murase ◽  
Takashi Nagae ◽  
Noritoshi Minami
Keyword(s):  
Steam Generator ◽  
Recirculation Flow ◽  
Gas Recirculation

Characterization of temporal variations and feedback timescales of exhaust gas recirculation gas properties using high-speed diode laser absorption spectroscopy for next-cycle control of cyclic variability

2018 ◽  
Vol 20 (8-9) ◽  
pp. 945-952
Author(s):  
Gurneesh S Jatana ◽  
Brian C Kaul
Keyword(s):  
High Speed ◽  
Control Strategies ◽  
Direct Injection ◽  
Exhaust Gas Recirculation ◽  
Gasoline Direct Injection ◽  
Exhaust Gas ◽  
Recirculation Flow ◽  
Cyclic Variability ◽  
Laser Absorption ◽  
Gas Recirculation

Dilute combustion offers efficiency gains in boosted gasoline direct injection engines both through knock-limit extension and thermodynamic advantages (i.e. the effect of γ on cycle efficiency), but is limited by cyclic variability at high dilution levels. Past studies have shown that the cycle-to-cycle dynamics are a combination of deterministic and stochastic effects. The deterministic causes of cyclic variations, which arise from feedback due to exhaust gas recirculation, imply the possibility of using active control strategies for dilution limit extension. While internal exhaust gas recirculation will largely provide a next-cycle effect (short-timescale feedback), the feedback of external exhaust gas recirculation will have an effect after a delay of several cycles (long timescale). Therefore, control strategies aiming to improve engine stability at dilution limit may have to account for both short- and long-timescale feedback pathways. This study shows the results of a study examining the extent to which variations in exhaust gas recirculation composition are preserved along the exhaust gas recirculation flow path and thus the relative importance and information content of the long-timescale feedback pathway. To characterize the filtering or retention of cycle-resolved feedback information, high-speed (1–5 kHz) CO2 concentration measurements were performed simultaneously at three different locations along the low-pressure external exhaust gas recirculation loop of a four-cylinder General Motors gasoline direct injection engine using a multiplexed two-color diode laser absorption spectroscopy sensor system during steady-state and transient engine operation at various exhaust gas recirculation levels. It was determined that cycle-resolved feedback propagates through internal residual gases but is filtered out by the low-pressure exhaust gas recirculation flow system and do not reach the intake manifold. Intermediate variations driven by flow rate and compositional changes are also distinguished and identified.

scholarly journals Short-term and long-term adaptation algorithm for low-pressure exhaust gas recirculation estimation in spark-ignition engines

2018 ◽  
Vol 20 (4) ◽  
pp. 424-440 ◽  
Author(s):  
Konstantinos Siokos ◽  
Rohit Koli ◽  
Robert Prucka
Keyword(s):  
Exhaust Gas Recirculation ◽  
Spark Ignition ◽  
Exhaust Gas ◽  
Spark Ignition Engines ◽  
Short Term ◽  
Adaptation Algorithm ◽  
Recirculation Flow ◽  
Gas Recirculation ◽  
Estimation Models

Low-pressure exhaust gas recirculation systems are capable of increasing fuel efficiency of spark-ignition engines; however, they introduce control challenges. The low available pressure differential that drives exhaust gas recirculation flow, along with the significant pressure pulsations in the exhaust environment of a turbocharged engine hamper the accuracy of feed-forward estimation models. For that reason, feedback measurements are required in an effort to increase prediction accuracy. Additionally, the accumulation of deposits in the exhaust gas recirculation system and the aging of the valve, change the flow characteristics over time. Under these considerations, an adaptation algorithm is developed which handles both short-term (operating-point-dependent errors) and long-term (system aging) corrections for exhaust gas recirculation flow estimation. The algorithm is based on an extended Kalman filter for joint state and parameter estimation and uses the output of an intake oxygen sensor to adjust the feed-forward prediction by creating an online adaptation map. Two different exhaust gas recirculation estimation models are developed and coupled with the adaptation algorithm. The performance of the algorithm for both estimation models is evaluated in real-time through transient experiments with a turbocharged spark-ignition engine. It is demonstrated that this methodology is capable of creating an adaptation map which captures system aging, while also reduces the estimation bias by more than four times resulting in a prediction error of less than 1%. Finally, this approach proves to be a valuable tool that can significantly reduce offline calibration efforts for such models.

An assessment of the impacts of low-pressure exhaust gas recirculation on the air path of a diesel engine equipped with electrically assisted turbochargers

2019 ◽  
Vol 22 (1) ◽  
pp. 3-21
Author(s):  
Kang Song ◽  
Devesh Upadhyay ◽  
Hui Xie
Keyword(s):  
Fuel Economy ◽  
Exhaust Gas Recirculation ◽  
Low Pressure ◽  
Exhaust Gas ◽  
Variable Geometry Turbocharger ◽  
Recirculation Flow ◽  
Electrically Assisted ◽  
Intake Pressure ◽  
Gas Recirculation ◽  
The Impact

The impact of assisted boosting technologies on the ability to maintain desired exhaust gas recirculation is investigated. Regenerative electrically assisted turbocharging is a promising technique for significantly reducing turbo lag. In addition to mitigating turbo lag, assisted boosting systems also allow fuel economy benefits through reduced pumping losses. Pumping loss reduction is achieved through optimally managing the exhaust pressure via vane position (for a variable geometry turbocharger) or waste gate position (for a waste-gated fixed geometry turbocharger). The consequent loss in exhaust turbine power, from reduced exhaust pressure, is supplemented by electrical assist power. Reduced exhaust pressure and a rapid increase in intake pressure results in a pressure differential across the high-pressure exhaust gas recirculation valve that may not support exhaust gas recirculation flow demands. Hence, a natural trade-off exists between the reduction of pumping loss and the ability to meet exhaust gas recirculation demand, as dictated by prescribed constraints on engine-out emissions. Low-pressure exhaust gas recirculation offers a potential solution that may allow the desired fuel economy improvements without sacrificing the desired exhaust gas recirculation fractions in the intake charge. In this article, we consider this problem and investigate the potential benefits of using low-pressure exhaust gas recirculation for assisted boosted systems.

scholarly journals Fundamental Study on Hydrogen Low-NOx Combustion Using Exhaust Gas Self-Recirculation

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 130
Author(s):  
Kenta Kikuchi ◽  
Tsukasa Hori ◽  
Fumiteru Akamatsu
Keyword(s):  
Flame Temperature ◽  
Reduction Rate ◽  
Exhaust Gas ◽  
Fundamental Study ◽  
Recirculation Flow ◽  
City Gas ◽  
Low Nox Combustion ◽  
Hydrocarbon Gas ◽  
Gas Recirculation ◽  
The Relationship

Hydrogen is expected to be a next-generation energy source that does not emit carbon dioxide, but when used as a fuel, the issue is the increase in the amount of NOx that is caused by the increase in flame temperature. In this study, we experimentally investigated NOx emissions rate when hydrogen was burned in a hydrocarbon gas burner, which is used in a wide temperature range. As a result of the experiments, the amount of NOx when burning hydrogen in a nozzle mixed burner was twice as high as when burning city gas. However, by increasing the flow velocity of the combustion air, the amount of NOx could be reduced. In addition, by reducing the number of combustion air nozzles rather than decreasing the diameter of the air nozzles, a larger recirculation flow could be formed into the furnace, and the amount of NOx could be reduced by up to 51%. Furthermore, the amount of exhaust gas recirculation was estimated from the reduction rate of NOx, and the validity was confirmed by the relationship between adiabatic flame temperature and NOx calculated from the equilibrium calculation by chemical kinetics simulator software.

NUMERICAL SIMULATION OF DRYOUT CHARACTERISTICS OF THE HELICAL ONCE-THROUGH STEAM GENERATOR

2018 ◽  
Author(s):  
Xiang Yu ◽  
Baozhi Sun ◽  
Jianxin Shi ◽  
Wanze Wu ◽  
Zhirui Zhao
Keyword(s):  
Numerical Simulation ◽  
Steam Generator
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