Strategies for using valvetrain flexibility instead of exhaust manifold pressure modulation for diesel engine gas exchange and thermal management control

2019 ◽  
pp. 146808741988063 ◽  
Author(s):  
Kalen R Vos ◽  
Gregory M Shaver ◽  
Mrunal C Joshi ◽  
Aswin K Ramesh ◽  
James McCarthy
Keyword(s):  
Thermal Management ◽  
Pressure Control ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Valve Closure ◽  
Exhaust Manifold ◽  
Intake Valve ◽  
Cylinder Deactivation ◽  
Valve Opening ◽  
Gas Recirculation

At low-to-moderate loads, modern diesel engines manipulate exhaust manifold pressure to drive exhaust gas recirculation and thermally manage the aftertreatment. In these engines, exhaust manifold pressure control is typically achieved via either a valve after the turbine, a variable geometry turbine, or wastegating. The study described here demonstrates how valvetrain flexibility enables engine operation without requiring exhaust manifold pressure control. Specifically, intake valve closure modulation and cylinder deactivation at elevated engine speeds, along with exhaust valve opening modulation at low engine speeds, can match, or improve, efficiency and thermal management compared to a stock thermal calibration that requires exhaust manifold pressure control. During low-speed, low-load operation, the stock engine uses elevated exhaust manifold pressures to increase the required fueling (for thermal management) and to drive exhaust gas recirculation. Exhaust valve opening modulation can instead be implemented to enable similar aftertreatment warm-up, while cylinder deactivation allows aftertreatment temperature maintenance with a 40% reduction in fuel consumption. During high-speed, low-to-moderate loads, the stock engine implements thermal management operation by decreasing exhaust manifold pressure. Intake valve closure modulation together with cylinder deactivation can instead be implemented to enable fuel-efficient thermal management improvements via charge flow control.

Improving diesel engine efficiency at high speeds and loads through improved breathing via delayed intake valve closure timing

2017 ◽  
Vol 20 (2) ◽  
pp. 194-202 ◽  
Author(s):  
Kalen R Vos ◽  
Gregory M Shaver ◽  
Xueting Lu ◽  
Cody M Allen ◽  
James McCarthy ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Volumetric Efficiency ◽  
Exhaust Gas ◽  
Valve Closure ◽  
Effective Pressure ◽  
Intake Valve ◽  
Brake Mean Effective Pressure ◽  
Gas Recirculation

Valve train flexibility enables optimization of the cylinder-manifold gas exchange process across an engine’s torque/speed operating space. This study focuses on the diesel engine fuel economy improvements possible through delayed intake valve closure timing as a means to improve volumetric efficiency at elevated engine speeds via dynamic charging. It is experimentally and analytically demonstrated that intake valve modulation can be employed at high-speed (2200 r/min) and medium-to-high load conditions (12.7 and 7.6 bar brake mean effective pressure) to increase volumetric efficiency. The resulting increase in inducted charge enables higher exhaust gas recirculation fractions without penalizing the air-to-fuel ratio. Higher exhaust gas recirculation fractions allow efficiency improving injection advances without sacrificing NOx. Fuel savings of 1.2% and 1.9% are experimentally demonstrated at 2200 r/min for 12.7 and 7.6 bar brake mean effective pressure operating conditions via this combined strategy of delayed intake valve closure, higher exhaust gas recirculation fractions, and earlier injections.

scholarly journals Exploring alternative combustion control strategies for low-load exhaust gas temperature management of a heavy-duty diesel engine

2018 ◽  
Vol 20 (4) ◽  
pp. 381-392 ◽  
Author(s):  
Wei Guan ◽  
Hua Zhao ◽  
Zhibo Ban ◽  
Tiejian Lin
Keyword(s):  
Fuel Consumption ◽  
Control Strategies ◽  
Fuel Efficiency ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Valve Closure ◽  
Intake Valve ◽  
Gas Temperature ◽  
Exhaust Gas Temperature ◽  
Gas Recirculation

The employment of aftertreatment systems in modern diesel engines has become indispensable to meet the stringent emissions regulations. However, a minimum exhaust gas temperature of approximately 200 °C must be reached to initiate the emissions control operations. Low-load engine operations usually result in relatively low exhaust gas temperature, which lead to reduced or no exhaust emissions conversion. In this context, this study investigated the use of different combustion control strategies to explore the trade-off between exhaust gas temperature, fuel efficiency, and exhaust emissions. The experiments were performed on a single-cylinder heavy-duty diesel engine at a light load of 2.2 bar indicated mean effective pressure. Strategies including the late intake valve closing timing, intake throttling, late injection timing (Tinj), lower injection pressure (Pinj), and internal exhaust gas recirculation and external exhaust gas recirculation were investigated. The results showed that the use of external exhaust gas recirculation and lower Pinj was not effective in increasing exhaust gas temperature. Although the use of late Tinj could result in higher exhaust gas temperature, the delayed combustion phase led to the highest fuel efficiency penalty. Intake throttling and internal exhaust gas recirculation allowed for an increase in exhaust gas temperature at the expense of higher fuel consumption. In comparison, late intake valve closure strategy achieved the best trade-off between exhaust gas temperature and net indicated specific fuel consumption, increasing the exhaust gas temperature by 52 °C and the fuel consumption penalty by 5.3% while reducing nitrogen oxide and soot emissions simultaneously. When the intake valve closing timing was delayed to after −107 crank angle degree after top dead centre, however, the combustion efficiency deteriorated and the HC and CO emissions were significantly increased. This could be overcome by combining internal exhaust gas recirculation with late intake valve closure to increase the in-cylinder combustion temperature for a more complete combustion. The results demonstrated that the ‘late intake valve closure + internal exhaust gas recirculation’ strategy can be the most effective means, increasing the exhaust gas temperature by 62 °C with 4.6% fuel consumption penalty. Meanwhile, maintaining high combustion efficiency as well as low HC and CO emissions of diesel engines.

Emission reduction through internal and low-pressure loop exhaust gas recirculation configuration with negative valve overlap and late intake valve closing strategy in a compression ignition engine

2017 ◽  
Vol 18 (10) ◽  
pp. 973-990 ◽  
Author(s):  
Jaeheun Kim ◽  
Choongsik Bae
Keyword(s):  
High Pressure ◽  
Nitrogen Oxides ◽  
Exhaust Gas Recirculation ◽  
Low Pressure ◽  
Exhaust Gas ◽  
Effective Pressure ◽  
Intake Valve ◽  
Trade Off ◽  
Indicated Mean Effective Pressure ◽  
Gas Recirculation

An investigation was carried out to examine the feasibility of replacing the conventional high-pressure loop/low-pressure loop exhaust gas recirculation with a combination of internal and low-pressure loop exhaust gas recirculation. The main objective of this alternative exhaust gas recirculation path configuration is to extend the limits of the late intake valve closing strategy, without the concern of backpressure caused by the high-pressure loop exhaust gas recirculation. The late intake valve closing strategy improved the conventional trade-off relation between nitrogen oxides and smoke emissions. The gross indicated mean effective pressure was maintained at a similar level, as long as the intake boosting pressure kept changing with respect to the intake valve closing timing. Applying the high-pressure loop exhaust gas recirculation in the boosted conditions yielded concern of the exhaust backpressure increase. The presence of high-pressure loop exhaust gas recirculation limited further intake valve closing retardation when the negative effect of increased pumping work cancelled out the positive effect of improving the emissions’ trade-off. Replacing high-pressure loop exhaust gas recirculation with internal exhaust gas recirculation reduced the burden of such exhaust backpressure and the pumping loss. However, a simple feasibility analysis indicated that a high-efficiency turbocharger was required to make the pumping work close to zero. The internal exhaust gas recirculation strategy was able to control the nitrogen oxides emissions at a low level with much lower O2 concentration, even though the initial in-cylinder temperature was high due to hot residual gas. Retardation of intake valve closing timing and intake boosting contributed to increasing the charge density; therefore, the smoke emission reduced due to the higher air–fuel ratio value exceeding 25. The combination of internal and low pressure loop loop exhaust gas recirculation with late intake valve closing strategy exhibited an improvement on the trade-off relation between nitrogen oxides and smoke emissions, while maintaining the gross indicated mean effective pressure at a comparable level with that of the high-pressure loop exhaust gas recirculation configuration.

Utilizing low airflow strategies, including cylinder deactivation, to improve fuel efficiency and aftertreatment thermal management

2017 ◽  
Vol 18 (10) ◽  
pp. 1005-1016 ◽  
Author(s):  
Aswin K Ramesh ◽  
Gregory M Shaver ◽  
Cody M Allen ◽  
Soumya Nayyar ◽  
Dheeraj B Gosala ◽  
...  
Keyword(s):  
Thermal Management ◽  
Fuel Efficiency ◽  
Diesel Oxidation Catalyst ◽  
Oxidation Catalyst ◽  
Particulate Filter ◽  
Valve Closure ◽  
Intake Valve ◽  
Warm Up ◽  
Cylinder Deactivation ◽  
Brake Mean Effective Pressure

Approximately 30% of the fuel consumed during typical heavy-duty vehicle operation occurs at elevated speeds with low-to-moderate loads below 6.5 bar brake mean effective pressure. The fuel economy and aftertreatment thermal management of the engine at these conditions can be improved using conventional means as well as cylinder deactivation and intake valve closure modulation. Airflow reductions result in higher exhaust gas temperatures, which are beneficial for aftertreatment thermal management, and reduced pumping work, which improves fuel efficiency. Airflow reductions can be achieved through a reduction of displaced cylinder volume by using cylinder deactivation and through reduction of volumetric efficiency by using intake valve closure modulation. This paper shows that, depending on load, cylinder deactivation and intake valve closure modulation can be used to reduce the fuel consumption between 5% and 25%, increase the rate of warm-up of aftertreatment, maintain higher temperatures, or achieve active diesel particulate filter regeneration without requiring dosing of the diesel oxidation catalyst.

Modeling and control of fuel distribution in a dual-fuel internal combustion engine leveraging late intake valve closings

2016 ◽  
Vol 18 (8) ◽  
pp. 797-809 ◽  
Author(s):  
Mateos Kassa ◽  
Carrie Hall ◽  
Andrew Ickes ◽  
Thomas Wallner
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Combustion Process ◽  
Exhaust Gas Recirculation ◽  
Internal Combustion ◽  
Dual Fuel ◽  
Exhaust Gas ◽  
Intake Valve ◽  
Fuel Distribution ◽  
Gas Recirculation

In internal combustion engines, cycle-to-cycle and cylinder-to-cylinder variations of the combustion process have been shown to negatively impact the fuel efficiency of the engine and lead to higher exhaust emissions. The combustion variations are generally tied to differences in the composition and condition of the trapped mass throughout each cycle and across individual cylinders. Thus, advanced engines featuring exhaust gas recirculation, flexible valve actuation systems, advanced fueling strategies, and turbocharging systems are prone to exhibit higher variations in the combustion process. In this study, the cylinder-to-cylinder variations of the combustion process in a dual-fuel internal combustion engine leveraging late intake valve closing are investigated and a model to predict and address one of the root causes for these variations across cylinders is developed. The study is conducted on an inline six-cylinder heavy-duty dual-fuel engine equipped with exhaust gas recirculation, a variable geometry turbocharger, and a fully flexible variable intake valve actuation system. The engine is operated with late intake valve closure timings in a dual-fuel combustion mode in which a high reactivity fuel is directly injected into the cylinders and a low reactivity fuel is port injected into the cylinders. The cylinder-to-cylinder variations observed in the study have been associated with the maldistribution of the port-injected fuel, which is exacerbated at late intake valve timings. The resulting difference in indicated mean effective pressure between the cylinders ranges from 9% at an intake valve closing of 570° after top dead center to 38% at an intake valve closing of 620° after top dead center and indicates an increasingly uneven fuel distribution. The study leverages both experimental and simulation studies to investigate the distribution of the port-injected fuel and its impact on cylinder-to-cylinder variation. The effects of intake valve closing as well as the impact of intake runner length on fuel distribution were quantitatively analyzed, and a model was developed that can be used to accurately predict the fuel distribution of the port-injected fuel at different operating conditions with an average estimation error of 1.5% in cylinder-specific fuel flow. A model-based control strategy is implemented to adjust the fueling at each port and shown to significantly reduce the cylinder-to-cylinder variations in fuel distribution.

Lyapunov-Based Nonlinear Feedback Control Design for Exhaust Gas Recirculation Loop of Gasoline Engines

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Weihai Jiang ◽  
Tielong Shen
Keyword(s):  
Dynamical Behavior ◽  
Control Design ◽  
Exhaust Gas Recirculation ◽  
Feedback Stabilization ◽  
Design Stage ◽  
Exhaust Gas ◽  
Exhaust Manifold ◽  
Challenging Issue ◽  
Gas Recirculation ◽  
Recirculation Loop

For gasoline engine with an exhaust gas recirculation loop, a challenging issue is how to achieve maximum brake efficiency while providing the desired torque. This paper presents a solution to this challenging issue via dynamical control approach which consists of two phases: optimal equilibrium point generation and feedback regulation of the optimized operating mode. First, a mean-value model is developed to represent the dynamical behavior of the intake manifold and exhaust manifold focused on gas mass flows. Then, the control scheme is constructed based on the control-oriented model. Mainly, the optimal set-points are designed by solving the optimal programming problem of maximizing the brake efficiency under demand torque constraint which is the first control design stage, and the dynamical model to the feedback stabilization regulation control for improving transient performance is at the second stage. Lyapunov-based design is used for the derivation of the state feedback law. Furthermore, the proposed exhaust manifold pressure estimator is also coupled into the controller to replace the cost prohibitive exhaust pressure sensor. Finally, experimental validations on the test bench are provided to evaluate the proposed controller.

Diesel engine aftertreatment warm-up through early exhaust valve opening and internal exhaust gas recirculation during idle operation

2017 ◽  
Vol 19 (7) ◽  
pp. 758-773 ◽  
Author(s):  
Dheeraj B Gosala ◽  
Aswin K Ramesh ◽  
Cody M Allen ◽  
Mrunal C Joshi ◽  
Alexander H Taylor ◽  
...  
Keyword(s):  
Steady State ◽  
Diesel Engine ◽  
Large Fraction ◽  
Test Procedure ◽  
Exhaust Gas Recirculation ◽  
Exhaust Valve ◽  
Exhaust Gas ◽  
Warm Up ◽  
Valve Opening ◽  
Gas Recirculation

A large fraction of diesel engine tailpipe NOx emissions are emitted before the aftertreatment components reach effective operating temperatures. As a result, it is essential to develop technologies to accelerate initial aftertreatment system warm-up. This study investigates the use of early exhaust valve opening (EEVO) and its combination with negative valve overlap to achieve internal exhaust gas recirculation (iEGR), for aftertreatment thermal management, both at steady state loaded idle operation and over a heavy-duty federal test procedure (HD-FTP) drive cycle. The results demonstrate that implementing EEVO with iEGR during steady state loaded idle conditions enables engine outlet temperatures above 400 °C, and when implemented over the HD-FTP, is expected to result in a 7.9% reduction in tailpipe-out NOx.

The effect of axial charge stratification and exhaust gases on combustion ‘development’ in a homogeneous charge compression ignition engine

2008 ◽  
Vol 222 (11) ◽  
pp. 2171-2183 ◽  
Author(s):  
P G Aleiferis ◽  
A G Charalambides ◽  
Y Hardalupas ◽  
A M K P Taylor ◽  
Y Urata
Keyword(s):  
Exhaust Gas Recirculation ◽  
Injection Timing ◽  
Cylinder Wall ◽  
Exhaust Gas ◽  
Compression Ignition ◽  
Intake Valve ◽  
Stratified Charge ◽  
Hcci Combustion ◽  
Gas Recirculation ◽  
Homogeneous Charge

A high-swirl low-compression-ratio, optically accessed engine that was able to produce a stratified charge was used to investigate the differences in homogeneous charge compression ignition (HCCI) combustion and in the propagation of the autoignition front between a non-stratified and a stratified charge. Natural-light images were acquired using a fast camera to visualize HCCI combustion and to quantify the location of autoignition, the apparent ‘propagation speed’ of the autoignition front, and its variations between closed-valve injection timing (leading to a nearly homogeneous charge) and open-valve injection timing (leading to a strongly axially stratified charge), owing to temperature inhomogeneities that were introduced by utilizing a camshaft which allowed 40 per cent internal exhaust gas recirculation (iEGR). Experimental results show that, in the case without exhaust gas recirculation (EGR) and with closed-valve injection timing, autoignition started under the primary intake valve near the cylinder wall, while, in the case without EGR and with open-valve injection timing, autoignition started between the exhaust valve and the secondary intake valve, closer to the centre of the piston. With 40 per cent iEGR and closed-valve injection timing, autoignition started between the exhaust valve and the primary intake valve near the cylinder wall. These differences can be explained by the difference in the location of hot gases due to the injection timing or due to iEGR. Finally, without EGR, a ‘uniform’ autoignition front of HCCI combustion from the original sites of autoignition was observed compared with a more ‘random development’ of the autoignition front with 40 per cent iEGR. Strong local inhomogeneities (possibly a very rich mixture at a low temperature) could be present with 40 per cent iEGR.

scholarly journals Systems optimisation of an active thermal management system during engine warm-up

2012 ◽  
Vol 226 (10) ◽  
pp. 1365-1379 ◽  
Author(s):  
Richard D Burke ◽  
Andy J Lewis ◽  
Sam Akehurst ◽  
Chris J Brace ◽  
Ian Pegg ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Thermal Management ◽  
Management System ◽  
Thermal State ◽  
Exhaust Gas Recirculation ◽  
Exhaust Gas ◽  
Warm Up ◽  
Thermal Management System ◽  
Recirculation System ◽  
Gas Recirculation

Active thermal management systems offer a potential for small improvements in fuel consumption that will contribute to upcoming legislation on carbon dioxide emissions. These systems offer new degrees of freedom for engine calibration; however, their full potential will only be exploited if a systems approach to their calibration is adopted, in conjunction with other engine controls. In this work, a design-of-experiments approach is extended to allow its application to transient drive cycles performed on a dynamic test stand. Experimental precision is of crucial importance in this technique since even small errors would obscure the effects of interest. The dynamic behaviour of the engine was represented mathematically in a manner that enabled conventional steady state modelling approaches to be employed in order to predict the thermal state of critical parts of the engine as a function of the actuator settings. A 17-point test matrix was undertaken, and subsequent modelling and optimisation procedures indicated potential 2–3% fuel consumption benefits under iso-nitrogen oxide conditions. Reductions in the thermal inertia appeared to be the most effective approach for reducing the engine warm-up time, which translated approximately to a 1.3% reduction in the fuel consumption per kilogram of coolant. A novel oil-cooled exhaust gas recirculation system showed the significant benefits of cooling the exhaust gases, thereby reducing the inlet gas temperature by 5 °C and subsequently the nitrogen oxide emissions by 6%, in addition to increasing the warm-up rate of the oil. This suggested that optimising the thermal management system for cooling the gases in the exhaust gas recirculation system can offer significant improvements. For the first time this paper presents a technique that allows simple predictive models of the thermal state of the engine to be integrated into the calibration process in order to deliver the optimum benefit. In particular, it is shown how the effect of the thermal management system on the nitrogen oxides can be traded off, by advancing the injection timing, to give significant improvements in the fuel consumption.

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