scholarly journals The effect of mixing rate and gas recirculation on biological CO2 methanation in two-stage CSTR systems

2021 ◽  
Vol 144 ◽  
pp. 105918
Author(s):  
Radziah Wahid ◽  
Svein Jarle Horn
Keyword(s):  
Mixing Rate ◽  
Two Stage ◽  
Co2 Methanation ◽  
Gas Recirculation

Model predictive air path control for a two-stage turbocharged spark-ignition engine with low pressure exhaust gas recirculation

2020 ◽  
Vol 21 (10) ◽  
pp. 1835-1845 ◽  
Author(s):  
Martin Keller ◽  
Severin Geiger ◽  
Marco Günther ◽  
Stefan Pischinger ◽  
Dirk Abel ◽  
...  
Keyword(s):  
Exhaust Gas Recirculation ◽  
Low Pressure ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Two Stage ◽  
Dynamic Controller ◽  
Recirculation Rate ◽  
Control Concept ◽  
Gas Recirculation

Innovative air path concepts for turbocharged spark-ignition engines with exhaust gas recirculation impose high demands on the control due to nonlinearities and cross-couplings. This contribution investigates the control of the air and exhaust gas recirculation paths of a two-stage turbocharged spark-ignition engine with low pressure exhaust gas recirculation. Using exhaust gas recirculation at high loads, the in-cylinder temperature can be lowered, reducing the knock tendency, while at the same time preventing the need for the enrichment of the air/fuel ratio. Air and exhaust gas recirculation paths are cross-coupled and show different delay times. To tackle these challenges, a data-based two-stage model predictive controller is proposed: The target selector accounts for the overactuated system structure, while the dynamic controller adjusts the charging pressure and exhaust gas recirculation rate. The prediction model setup is based on a small amount of dyno-run measurement data. To ensure real-time capability, the model is kept as simple as possible. This allows for fast turnaround times of the algorithm, while maintaining the necessary accuracy in steady-state and transient operation. This study focuses on a two-stage control concept based on a target selector for optimal stationary control inputs and the dynamic controller considering the dynamic behavior of the air and exhaust gas recirculation paths. Subsequently, the control concept for the two-stage turbocharged spark-ignition engine with low pressure exhaust gas recirculation is validated via experimental tests under real-driving conditions on an automotive test track, using a prototype test vehicle. Results show that boost pressure as well as exhaust gas recirculation rate setpoints are met without overshoot and control deviation with settling times being close to the boundaries set by the hardware.

scholarly journals The benefits of a mid-route exhaust gas recirculation system for two-stage boosted engines

2017 ◽  
Vol 19 (5) ◽  
pp. 553-569 ◽  
Author(s):  
Pavlos Dimitriou ◽  
James Turner ◽  
Richard Burke ◽  
Colin Copeland
Keyword(s):  
Response Time ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Transient Performance ◽  
Short Route ◽  
Two Stage ◽  
Recirculation System ◽  
Gas Recirculation

Exhaust gas recirculation is a widely known technique applied in internal combustion engines for controlling the combustion process and harmful emissions. The recirculation of gases can be achieved either by delivering burnt gases from upstream of the turbine to downstream of the compressor (short-route) or by taking the exhaust gas from downstream of the turbine and deliver to upstream of the compressor (long-route). Although long-route system is preferred for highly boosted engines due to the higher exhaust gas recirculation availability at low engine speeds, it lacks a fast response time during transient performance compared to the short-route system. This article examines the potentials of introducing an alternative exhaust gas recirculation route which can be applied in two-stage boosted engines. The proposed mid-route exhaust gas recirculation system, applied in a gasoline engine, combines the benefits of the long routes and short routes. The system provides high exhaust gas recirculation rates at all engine speeds while the transport delay in the case of transient operation is relatively short. The potential of a hybrid exhaust gas recirculation system combining mid-route and long-route exhaust gas recirculation is examined and various components’ (i.e. compressor, turbine and coolers) sizing and transient performance studies are performed to understand the trade-offs of the system. It was demonstrated that mid-route could provide high exhaust gas recirculation particularly at high- and low engine speeds. A combination of mid-route and long-route exhaust gas recirculation can provide maximum exhaust gas recirculation rates at all speeds with a maximum fuel consumption penalty of 1.4% at engine speeds below 2500 r/min. The reduction in exhaust gas recirculation response time was of the magnitude of 50%, while the faster exhaust gas recirculation purging time combined with the smaller turbine implemented dropped the load tip-in response time by 25%. The coolers’ sizing study revealed that a long-route exhaust gas recirculation cooler is unnecessary, whereas the mid-route exhaust gas recirculation cooler can also be omitted when the flow is delivered prior an intercooler with a 25% larger cooling capacity than of the baseline engine.

Turbocharging strategy among variable geometry turbine, two-stage turbine, and asymmetric two-scroll turbine for energy and emission in diesel engines

2019 ◽  
Vol 234 (7) ◽  
pp. 900-914
Author(s):  
Dengting Zhu ◽  
Zhenzhong Sun ◽  
Xinqian Zheng
Keyword(s):  
Internal Combustion Engines ◽  
Numerical Models ◽  
Exhaust Gas Recirculation ◽  
Internal Combustion ◽  
Exhaust Gas ◽  
Combustion Engines ◽  
Variable Geometry ◽  
Two Stage ◽  
Variable Geometry Turbine ◽  
Gas Recirculation

Energy saving and emission reduction are very urgent for internal combustion engines. Turbocharging and exhaust gas recirculation technologies are very significant for emissions and fuel economy of internal combustion engines. Various after-treatment technologies in internal combustion engines have different requirements for exhaust gas recirculation rates. However, it is not clear how to choose turbocharging technologies for different exhaust gas recirculation requirements. This work has indicated the direction to the turbocharging strategy among the variable geometry, two-stage, and asymmetric twin-scroll turbocharging for different exhaust gas recirculation rates. In the paper, a test bench engine experiment was presented to validate the numerical models of the three diesel engines employed with the asymmetric twin-scroll turbine, two-stage turbine, and variable geometry turbine. On the basis of the numerical models, the turbocharging routes among the three turbocharging approaches under different requirements for EGR rates are studied, and the other significant performances of the three turbines were also discussed. The results show that there is an inflection point in the relative advantages of asymmetric, variable geometry, and two-stage turbocharged engines. At the full engine load, when the EGR rate is lower than 29%, the two-stage turbocharging technology has the best performances. However, when the exhaust gas recirculation rate is higher than 29%, the asymmetric twin-scroll turbocharging is the best choice and more appropriate for driving high exhaust gas recirculation rates. The work may offer guidelines to choose the most suitable turbocharging technology for engine engineers and manufacturers to achieve further improvements in engine energy and emissions.

Two-stage self-seeding method for preparation of single crystals of poly(phenylene sulfide)

1989 ◽  
Vol 47 ◽  
pp. 368-369
Author(s):  
Sengshiu Chung ◽  
Peggy Cebe
Keyword(s):  
Single Crystals ◽  
High Performance ◽  
Dilute Solution ◽  
Two Stage ◽  
Annealing Behavior ◽  
High Performance Polymers ◽  
Seeding Method ◽  
Phenylene Sulfide

We are studying the crystallization and annealing behavior of high performance polymers, like poly(p-pheny1ene sulfide) PPS, and poly-(etheretherketone), PEEK. Our purpose is to determine whether PPS, which is similar in many ways to PEEK, undergoes reorganization during annealing. In an effort to address the issue of reorganization, we are studying solution grown single crystals of PPS as model materials.Observation of solution grown PPS crystals has been reported. Even from dilute solution, embrionic spherulites and aggregates were formed. We observe that these morphologies result when solutions containing uncrystallized polymer are cooled. To obtain samples of uniform single crystals, we have used two-stage self seeding and solution replacement techniques.

364: Two stage "Progressive Elongation of Spermatic Cord" Technique in Criptorchidism with very short Spermatic Vessels

2007 ◽  
Vol 177 (4S) ◽  
pp. 121-121
Author(s):  
Antonio Dessanti ◽  
Diego Falchetti ◽  
Marco Iannuccelli ◽  
Susanna Milianti ◽  
Gian P. Strusi ◽  
...  
Keyword(s):  
Spermatic Cord ◽  
Two Stage
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