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 Cyclic NO2:NOx ratio from a diesel engine undergoing transient load steps

2019 ◽  
Vol 22 (1) ◽  
pp. 284-294 ◽  
Author(s):  
FCP Leach ◽  
MH Davy ◽  
MS Peckham
Keyword(s):  
Diesel Engine ◽  
High Speed ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Formation Mechanisms ◽  
Exhaust Gas ◽  
Work Cycle ◽  
Wide Range ◽  
Gas Recirculation ◽  
Aftertreatment Systems

As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO2/NOx ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NOx aftertreatment systems. In this work, cycle-to-cycle NO and NOx emissions have been measured using a Cambustion CLD500, and the cyclic NO2/NOx ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NOx, and hence NO2/NOx ratio, are instantaneous upon a step change in engine load. NO2/NOx ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO2 than have been previously reported in the literature are observed.

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.

Effects of Exhaust Gas Recirculation on Particulate Morphology from a Diesel Engine

2013 ◽  
Vol 664 ◽  
pp. 926-930
Author(s):  
Wei Zhang ◽  
Xiao Dong Wang ◽  
Rui Sun ◽  
Jian Wei Sun ◽  
Wei Han
Keyword(s):  
Particle Size ◽  
Diesel Engine ◽  
Primary Particle ◽  
Morphological Characteristics ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Injection System ◽  
Exhaust Gas ◽  
Aggregate Particle ◽  
Gas Recirculation

The effects of EGR operating mode on particulate morphology were investigated for a 5.79-liter diesel engine which was equipped with a turbocharged and inter-cooled air induction system, a common-rail direct fuel injection system, and an EGR system. Morphological characteristics, such as primary particle size, number concentration and aggregate particle size were investigated by a transmission electron microscope (TEM) analysis and a electrical low pressure impactor (ELPI) under engine operating conditions of 0.41 in fuel/air ratio at different exhaust gas recirculation (EGR) rate from 0～35%. The experimental results indicated that primary particle were in the range of 17.05nm～18.34nm, which increased with increased EGR rate. As EGR rate increased, aggregate particle size were measured in a narrow range from 120nm to 170nm.

Experimental Study on Effects of Nozzle Hole Geometry on Achieving Low Diesel Engine Emissions

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Prashanth K. Karra ◽  
Song-Charng Kong
Keyword(s):  
Diesel Engine ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Injection System ◽  
Exhaust Gas ◽  
Convergent Nozzle ◽  
Wide Range ◽  
Soot Emissions ◽  
Gas Recirculation ◽  
Injection Pressures

Three injectors with different nozzle geometries were tested in a multicylinder diesel engine with a high-pressure common-rail injection system. Various injection pressures were tested along with exhaust gas recirculation to achieve low NOx and soot emissions. The injectors used in the study included a six-hole nozzle, a ten-hole nozzle, and a six-hole convergent nozzle with a K-factor of 3. All three injectors had the same flow numbers. All three injectors tested were effective in reducing NOx and soot emissions at appropriate conditions. It was found that low temperature combustion can be achieved by using high levels of exhaust gas recirculation with late injection timings. High injection pressures significantly reduced soot emissions at conventional injection timings. The effect of injection pressure was not significant at retarded injection timings, i.e., 5 ATDC. The convergent nozzle was found to produce higher soot emissions compared with the straight-hole nozzle under the same injection conditions. Effects of the convergent nozzle on NOx emissions and fuel consumption were not significant. The small nozzle size in the ten-hole injector can generate smaller fuel drops and lead to better atomization. The ten-hole injector appeared to have better air utilization and resulted in significant reductions in NOx and soot emissions over a wide range of operating conditions.

Nonlinear Compensators of Exhaust Gas Recirculation and Variable Geometry Turbocharger Systems using Air Path Models for a CRDI Diesel Engine

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
Yeongseop Park ◽  
Inseok Park ◽  
Joowon Lee ◽  
Kyunghan Min ◽  
Myoungho Sunwoo
Keyword(s):  
Diesel Engine ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Variable Geometry ◽  
Variable Geometry Turbocharger ◽  
Model Based ◽  
Path Models ◽  
Gas Recirculation ◽  
Feedforward Compensators

This paper investigates the design of model-based feedforward compensators for exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems using air path models for a common-rail direct injection (CRDI) diesel engine to cope with the nonlinear control problem. The model-based feedforward compensators generate set-positions of the EGR valve and the VGT vane to track the desired mass air flow (MAF) and manifold absolute pressure (MAP) with consideration of the current engine operating conditions. In the best case, the rising time to reach 90% of the MAF set-point was reduced by 69.8% compared with the look-up table based feedforward compensators.

scholarly journals Characterisation and optimisation of a real-time diesel engine model

2017 ◽  
Vol 231 (14) ◽  
pp. 1913-1934 ◽  
Author(s):  
Peter G Dowell ◽  
Sam Akehurst ◽  
Richard D Burke
Keyword(s):  
Diesel Engine ◽  
Real Time ◽  
Exhaust Gas Recirculation ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
Step Size ◽  
Time Model ◽  
Crank Angle ◽  
Run Time ◽  
Gas Recirculation

Accurate real-time engine models are an essential step to allow the development of control algorithms in parallel to the development of engine hardware using hardware-in-the-loop applications. A physics-based model of the engine high-pressure air path and combustion chamber is presented. The model was parameterised using data from a small set of carefully selected operating conditions for a 2.0 l diesel engine. The model was subsequently validated over the complete engine operating map with exhaust gas recirculation and without exhaust gas recirculation. A high level of fit was achieved with R2 values above 0.94 for the mean effective pressure and above 0.99 for the air flow rate. The model run time was then reduced for real-time application by using forward differencing and single-precision floating-point numbers and by calculating the in-cylinder prediction for only a single cylinder. A further improvement of 25% in the run time was achieved by improving the submodels, including the strategic use of one-dimensional and two-dimensional look-up tables with optimised resolution. The model exceeds the performance of similar models in the literature, achieving a crank angle resolution of 0.5° at 4000 r/min. This simulation step size still yields good accuracy in comparison with a crank angle resolution of 0.1° and was validated against the experimental results from a New European Driving Cycle. The real-time model allows the development of control strategies before the engine hardware is available, meaning that more time can be spent to ensure that the engine can meet the performance and the emissions requirements over its full operating range.

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.

scholarly journals Effects of Hot Exhaust Gas Recirculation (EGR) on the Emission and Performance of a Single-Cylinder Diesel Engine

2019 ◽  
Vol 16 (2) ◽  
pp. 6660-6674
Author(s):  
M. A. A. Mossa ◽  
A. A. Hairuddin ◽  
A. A. Nuraini ◽  
J. Zulkiple ◽  
H. M. Tobib
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Direct Injection ◽  
Exhaust Gas Recirculation ◽  
Exhaust Emission ◽  
Exhaust Gas ◽  
Single Cylinder ◽  
Emission Level ◽  
Brake Mean Effective Pressure ◽  
Gas Recirculation

With the increment in global demand for energy, there is a need to reduce vehicle emission, which is among the major causes of air pollution around the world. In order to reduce the emissions levels, this study focuses on the effects of hot exhaust gas recirculation (EGR) system on the performance and emissions of a direct injection (DI) diesel engine. The performance studied includes engine power, torque, brake mean effective pressure, fuel consumption and the exhaust emission. The engine used in this study was a single-cylinder, four-stroke engine with an air-cooled system at a rated speed of 3600 rpm with displacement of 0.219 litres. The engine was operated at varying speeds of 1600 to 3600 rpm with different percentages of EGR (5%, 7%, 10% and 15%). Based on the results, it was shown that EGR had decreased the engine brake power and torque while increasing fuel consumption at the same time. The engine with EGR has reduced the emission level of NOx from 800 to 240 ppm and CO2, from 9% to 4%, while increasing the CO from 2% to 4% and UHC from 10 to 100 ppm. Hence, it was concluded that low emission level of NOx and CO2 could be obtained using EGR as it can be used to improve the emission level of a homogeneous charge compression ignition (HCCI) even further in the extension of this study.

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