Optimal Exhaust Valve Opening Control for Fast Aftertreatment Warm Up in Diesel Engines

2018 ◽  
Author(s):  
Rasoul Salehi ◽  
Anna G. Stefanopoulou
Keyword(s):  
Fuel Consumption ◽  
Catalytic Reduction ◽  
Test Procedure ◽  
Careful Consideration ◽  
Exhaust Valve ◽  
Power Stroke ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Warm Up ◽  
Valve Opening

This paper proposes to optimally adjust the exhaust valve opening (EVO) timing for faster selective catalytic reduction (SCR) aftertreatment system warm-up during the cold start phase of the federal test procedure (FTP). Early termination of the power stroke by EVO timing advance increases the engine exhaust gas temperature. It, on the other hand, causes exhaust flow rate reduction that decreases the coefficient of the heat transfer from the exhaust gas to the catalyst. The competing effects along with the fuel consumption increase associated with early EVO need careful consideration and the optimal EVO timing is a load-dependent balance of all these effects. This careful balance is achieved in this paper by dynamic programing (DP). Specifically, the minimum time to light-off (TTL) is formulated and applied to the cold phase of the FTP. A high fidelity detailed and verified engine and aftertreatment model is effectively simplified to enable utilizing computationally expensive DP optimization algorithm. Optimization results indicate that advancing the EVO reduces the TTL for the SCR catalyst from 659 s to 500 s, a 24% reduction. This fastest possible increase in the SCR temperature is shown to be with an expense of 4.1% increase in the fuel consumption. The results are dependent to the target light-off temperature and the load profile. Assuming a specific light-off temperature and the FTP, possible rule-based scenarios for online optimization are discussed.

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.

Implementing variable valve actuation on a diesel engine at high-speed idle operation for improved aftertreatment warm-up

2019 ◽  
Vol 21 (7) ◽  
pp. 1134-1146
Author(s):  
Kalen R Vos ◽  
Gregory M Shaver ◽  
Mrunal C Joshi ◽  
James McCarthy
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
Exhaust Valve ◽  
Exhaust Gas ◽  
Warm Up ◽  
Aftertreatment System ◽  
Idle Speed ◽  
Variable Valve Actuation ◽  
Brake Mean Effective Pressure ◽  
Valve Opening

Aftertreatment thermal management is critical for regulating emissions in modern diesel engines. Elevated engine-out temperatures and mass flows are effective at increasing the temperature of an aftertreatment system to enable efficient emission reduction. In this effort, experiments and analysis demonstrated that increasing the idle speed, while maintaining the same idle load, enables improved aftertreatment “warm-up” performance with engine-out NOx and particulate matter levels no higher than a state-of-the-art thermal calibration at conventional idle operation (800 rpm and 1.3 bar brake mean effective pressure). Elevated idle speeds of 1000 and 1200 rpm, compared to conventional idle at 800 rpm, realized 31%–51% increase in exhaust flow and 25 °C–40 °C increase in engine-out temperature, respectively. This study also demonstrated additional engine-out temperature benefits at all three idle speeds considered (800, 1000, and 1200 rpm, without compromising the exhaust flow rates or emissions, by modulating the exhaust valve opening timing. Early exhaust valve opening realizes up to ~51% increase in exhaust flow and 50 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder via an early blowdown of the exhaust gas. This early blowdown of exhaust gas also reduces the time available for particulate matter oxidization, effectively limiting the ability to elevate engine-out temperatures for the early exhaust valve opening strategy. Alternatively, late exhaust valve opening realizes up to ~51% increase in exhaust flow and 91 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder to pump in-cylinder gases across a smaller exhaust valve opening. In short, this study demonstrates how increased idle speeds, and exhaust valve opening modulation, individually or combined, can be used to significantly increase the “warm-up” rate of an aftertreatment system.

Use of Early Exhaust Valve Opening to Improve Combustion Efficiency and Catalyst Effectiveness in a Multi-Cylinder RCCI Engine System: A Simulation Study

2014 ◽  
Author(s):  
Anand Nageswaran Bharath ◽  
Nitya Kalva ◽  
Rolf D. Reitz ◽  
Christopher J. Rutland
Keyword(s):  
System Simulation ◽  
Combustion Efficiency ◽  
Exhaust Valve ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Flow Rates ◽  
Low Load ◽  
Valve Opening ◽  
Engine System ◽  
Exhaust Gas Temperature

Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) can result in significant improvements of fuel economy and emissions reduction. However, they can produce significant carbon monoxide and unburnt hydrocarbon emissions at low load operating conditions due to poor combustion efficiencies at these operating points, which is a consequence of the low combustion temperatures that cause the oxidation rates of these species to slow down. The exhaust gas temperature is also not high enough at low loads for effective performance of turbocharger systems and diesel oxidation catalysts (DOC). The DOC is extremely sensitive to exhaust gas temperature changes and lights off only when a certain temperature is reached, depending on the catalyst specifications. Uncooled EGR can increase combustion temperatures, thereby improving combustion efficiency, but high EGR concentrations of 50% or more are required, thereby increasing pumping work and reducing volumetric efficiency. However, with early exhaust valve opening, the exhaust gas temperature can be much higher, allowing lower EGR flow rates, and enabling activation of the DOC for more effective oxidization of unburnt hydrocarbons and CO in the exhaust. In this paper, a multi-cylinder engine system simulation of RCCI at low load operation with early exhaust valve opening is presented, along with consideration of the exhaust aftertreatment system. The combustion process is modeled using the 3D CFD code, KIVA, and the heat release rates obtained from this combustion are used in a GT-Power model of a turbocharged, multi-cylinder light-duty RCCI engine for a full system simulation. The post-turbine exhaust gas is fed into GT-Power’s aftertreatment model of the engine’s DOC to determine the catalyst response. It is confirmed that opening the exhaust valve earlier increases the exhaust gas temperature, and hence lower EGR flow rates are needed to improve combustion efficiency. It was also found that exhaust temperatures of around 457 K are required to light off the catalyst and oxidize the unburnt hydrocarbons and CO effectively. Performance of the DOC was drastically improved and higher amounts of unburnt hydrocarbons were oxidized by increasing the exhaust gas temperature.

Exhaust valve profile modulation for improved diesel engine curb idle aftertreatment thermal management

2021 ◽  
pp. 146808742096910
Author(s):  
Mrunal C Joshi ◽  
Dheeraj Gosala ◽  
Gregory M Shaver ◽  
James McCarthy ◽  
Lisa Farrell
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Thermal Management ◽  
Exhaust Valve ◽  
Outlet Temperature ◽  
Exhaust Manifold ◽  
Warm Up ◽  
Valve Opening ◽  
Active Regeneration ◽  
Negative Valve Overlap

Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulation as a technique to increase engine-outlet temperature for ATS thermal management, without requiring modulation of exhaust manifold pressure. Experimental steady state results at 800 RPM/1.3 bar BMEP (curb idle) demonstrate that early exhaust valve opening with negative valve overlap (EEVO+NVO) can achieve engine-outlet temperature in excess of 255°C with 5.7% lower fuel consumption, 12% lower engine out NOx and 20% lower engine-out soot than the conventional thermal management strategy. Late exhaust valve opening with internal EGR via reinduction (LEVO+Reinduction) resulted in engine-outlet temperature in excess of 280°C, while meeting emission constraints at no fuel consumption penalty. This work also demonstrates that LEVO in conjunction with modulation of exhaust manifold pressure results in engine-outlet temperature in excess of 340°C while satisfying desired emission constraints. Aggressive use of LEVO can result in engine-outlet temperatures of 460°C, capable of active regeneration of DPF at curb idle, without the significant increase in engine-out soot emissions seen in previously studied strategies.

scholarly journals Late Fuel Post-Injection Influence on the Dynamics and Efficiency of Wall-Flow Particulate Filters Regeneration

2019 ◽  
Vol 9 (24) ◽  
pp. 5384 ◽  
Author(s):  
José Ramón Serrano ◽  
Pedro Piqueras ◽  
Joaquín de la Morena ◽  
Enrique José Sanchis
Keyword(s):  
Fuel Consumption ◽  
Particulate Filter ◽  
Exhaust Gas ◽  
Post Injection ◽  
Gas Temperature ◽  
Diesel Particulate ◽  
Particulate Filters ◽  
Exhaust Temperature ◽  
Injection Parameters ◽  
Wall Flow

Late fuel post-injections are the most usual strategy to reach high exhaust temperature for the active regeneration of diesel particulate filters. However, it is important to optimise these strategies in order to mitigate their negative effect on the engine fuel consumption. This work aims at understanding the influence of the post-injection parameters, such as its start of injection and its fuel quantity, on the duration of the regeneration event and the fuel consumption along it. For this purpose, a set of computational models are employed to figure out in a holistic way the involved phenomena in the interaction between the engine and the exhaust gas aftertreatment system. Firstly, an engine model is implemented to evaluate the effect of the late fuel post-injection pattern on the gas properties at the exhaust aftertreatment system inlet in different steady-state operating conditions. These are selected to provide representative boundary conditions of the exhaust gas flow concerning dwell time, exhaust temperature and O 2 concentration. In this way, the results are later applied to the analysis of the diesel oxidation catalyst and wall-flow particulate filter responses. The dependence of the diesel particulate filter (DPF) inlet temperature is discussed based on the efficiency of each post-injection strategy to increase the exhaust gas temperature. Next, the influence on the dynamics of the regeneration of the post-injection parameters through the change in gas temperature and O 2 concentration is finally studied distinguishing the pre-heating, maximum reactivity and late soot oxidation stages as well as the required fuel consumption to complete the regeneration process.

scholarly journals A model-based and experimental approach for the determination of suitable variable valve timings for cold start in partial load operation of a passenger car single-cylinder diesel engine

2018 ◽  
Vol 20 (1) ◽  
pp. 141-154 ◽  
Author(s):  
P Maniatis ◽  
U Wagner ◽  
T Koch
Keyword(s):  
Diesel Engine ◽  
Experimental Investigations ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Warm Up ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Residual Gas ◽  
Dimensional Simulation ◽  
Exhaust Gas Temperature

A manipulation of the charge exchange allows controlling the amount of residual gas during engine warm-up. The residual gas during the warm-up phase leads to an increase of the exhaust gas temperature and supports to reach the exhaust after-treatment system operating temperature faster. In addition, the warm residual gas increases the combustion chamber temperature, which reduces the HC and CO emissions. However, fuel consumption increases. For that reason, such heating measures should be the best compromise of both, exhaust gas temperature increase and engine efficiency, in order to provide efficient heating strategies for passenger car diesel engines. Therefore, simulative and experimental investigations are carried out at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology to establish a reliable cam design methodology. For the experimental investigations, a modern research single-cylinder diesel engine was set up on a test bench. In addition, a one-dimensional simulation model of the experimental setup was created in order to simulate characteristics of valve lift curves and to investigate their effects on the exhaust gas temperature and the exhaust gas enthalpy flow. These simulations were based on design of experiments (DoE), so that all characteristics can be used sustainably for modeling and explaining their influences on the engine operation. This methodology allows numerically investigating promising configurations and deriving cam contours which are manufactured for testing. To assess the potential of these individual configurations, the results obtained were compared with each other as well as with the series configuration. Results show that the combination of DoE and one-dimensional simulation for the design of camshaft contours is well suited which was also validated with experimental results. Furthermore, the potential of residual gas retention by favorable configurations with a second event already revealed in various publications could be confirmed with respect to exhaust gas temperature increase and engine efficiency.

scholarly journals The Experimental and Simulation Study of Selective Catalytic Reduction System in a Single Cylinder Diesel Engine Using NH3as a Reducing Agent

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Manoj Kumar Athrashalil Phaily ◽  
Sreekumar Jayachandra Sreekala ◽  
Padmanabha Mohanan
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Mass Flow ◽  
Catalytic Reduction ◽  
Pt Catalyst ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Single Cylinder ◽  
Induction Rate ◽  
Exhaust Gas Temperature

Selective catalytic reduction (SCR) technology has been widely used in automotive applications in order to meet the stringent limits on emission standards. The maximum NOxconversion efficiency of an SCR depends on temperature and mass flow rate of an exhaust gas. In order to assess the suitability of Cordierite/Pt catalyst for low temperature application, an experimental work is carried out using single cylinder diesel engine for different load conditions by varying ammonia induction rate from 0.2 kg/hr to 0.8 kg/hr. The simulation is carried out using AVL FIRE for the validation of experimental results. From the study, it has been found that for 0.6 kg/hr ammonia induction rate the maximum conversion is achieved, whereas, for 0.8 kg/hr, conversion is reduced due to desorption of ammonia. Also it has been found that, at 75% of load, for all mass flow rates of ammonia the conversion was drastically reduced due to higher exhaust gas temperature and higher emission of unburnt hydrocarbons. More than 55% of NOxconversion was achieved using Cordierite/Pt catalyst at a temperature of 320°C.

scholarly journals An Experimental Study on the Performance Characteristics of a Diesel Engine Fueled with ULSD-Biodiesel Blends

2020 ◽  
Vol 10 (2) ◽  
pp. 183-190
Author(s):  
Viet Dung Tran ◽  
Anh Tuan Le ◽  
Anh Tuan Hoang
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Thermal Efficiency ◽  
Cooling System ◽  
Specific Fuel Consumption ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Brake Thermal Efficiency ◽  
Exhaust Gas Temperature ◽  
Low Sulfur

As a rule, the highest permissible sulfur content in the marine fuel must drop below 0.5% from 1 January 2020 for global fleets. As such, ships operating in emission control areas must use low sulfur or non-sulfur fuel to limit sulfur emissions as a source of acid rain. However, that fact has revealed two challenges for the operating fleet: the very high cost of ultra-low sulfur diesel (ULSD) and the installation of the fuel conversion system and the ULSD cooling system. Therefore, a solution that blends ULSD and biodiesel (BO) into a homogeneous fuel with properties equivalent to that of mineral fuels is considered to be significantly effective. In the current work, an advanced ultrasonic energy blending technology has been applied to assist in the production of homogeneous ULSD-BO blends (ULSD, B10, B20, B30, and B50 with blends of coconut oil methyl ester with ULSD of 10%, 20%, 30% and 50% by volume) which is supplied to a small marine diesel engine on a dynamo test bench to evaluate the power and torque characteristics, also to consider the effect of BO fuel on specific fuel consumption exhaust gas temperature and brake thermal efficiency. The use of the ultrasonic mixing system has yielded impressive results for the homogeneous blend of ULSD and BO, which has contributed to improved combustion quality and thermal efficiency. The results have shown that the power, torque, and the exhaust gas temperature, decrease by approximately 9%, 2%, and 4% respectively with regarding the increase of the blended biodiesel rate while the specific fuel consumption and brake thermal efficiency tends to increase of around 6% and 11% with those blending ratios.

Modeling the Effect of Temperature on Propylene Conversion during Warm-Up in a Monolithic Converter

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Sanchita Chauhan ◽  
V. K Srivastava
Keyword(s):  
Catalyst Surface ◽  
Effect Of Temperature ◽  
Exhaust Gas ◽  
Catalytic Converters ◽  
Gas Temperature ◽  
Warm Up ◽  
One Dimensional ◽  
Runge Kutta Method ◽  
Propylene Conversion ◽  
Account Heat

In order to improve air quality, catalytic converters have been extensively employed throughout the world. These monolithic catalytic converters are very effective in reducing pollution only after they have heated up. The catalyst warming-up process takes some time and during this period a considerable amount of pollutants, especially hydrocarbons, is released into the atmosphere. In this paper, a one-dimensional model for the hydrocarbon propylene was developed, taking into account heat and mass transfer between the exhaust gas and the catalyst surface and the catalytic reaction. The equations so formed are a set of ordinary differential equations (ODEs) and a partial differential equation (PDE). The ODEs are solved using the Runge-Kutta method of fourth order and the PDE by backward implicit scheme. The effect of varying the inlet gas temperature and initial catalyst solid temperatures on conversion of propylene was analysed.

Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Jinbiao Ning ◽  
Fengjun Yan
Keyword(s):  
Control Strategy ◽  
Disturbance Rejection ◽  
Catalytic Reduction ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Model Uncertainties ◽  
Compound Control ◽  
Active Disturbance Rejection ◽  
Exhaust Gas Temperature ◽  
Scr System

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.

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