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

Self Cite

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.

Section: Motivation For Aftertreatment Tm High-speed Idle Strategiesmentioning

confidence: 99%

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

Vos

Shaver

Joshi

et al. 2019

Self Cite

“…As presented in multiple studies, elevated idle speed results in higher exhaust gas enthalpy due to the higher mass flow rates while the temperature remains at the same levels 8 and CDA leads to increased exhaust gas temperatures and lower flows, a fact which allows an already warm aftertreatment system to maintain its thermal status while the engine operates with higher fuel efficiency. [14][15][16] Finally, fuel injection in the downpipe upstream of the diesel oxidation catalyst (DOC) with the use of a fifth injector is a potential non engine-based thermal management strategy. Hydrocarbons (HC) injection upstream of the DOC for an exothermic reaction is an efficient method for a fast heat-up of the SCR, provided that the DOC has reached its operating temperature whereas a non-optimum injection control strategy can result in potential HC slip.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of thermal management technologies for fuel efficient cold-start emissions reduction in diesel engines

Tziolas,

Koltsakis,

Zingopis

et al. 2023

The ultra-low NOx emission limits for heavy and mid-duty vehicles, which are expected to be imposed in both Europe and the USA by 2027, together with the enforcement of continuous decrease in CO2 emission levels, make the need for adoption of newer technologies in the automotive industry imperative. To achieve low tailpipe NOx emissions, the accelerated warm-up of the exhaust aftertreatment system is of great importance. On the other hand, the thermal management strategies applied for this purpose result in fuel consumption penalty and consequently higher CO2 as it can be widely found in the literature. Thus, the use and optimization of advanced thermal management technologies is critical to decrease the NOx– fuel penalty trade-off on the basis of complete driving cycles. In the present work an integrated modeled-based approach is implemented by coupling advanced, predictive 1D engine, and aftertreatment simulation models which are extensively validated via dedicated experimental data. The main goal of this approach is to define and investigate multiple engine or aftertreatment-based thermal management technologies, as well as a combination of them, creating a more efficient warm-up mode for the engine. Thermal measures such as cylinder deactivation, retarded start of the main injection, late intake valve closing (Miller cycle), intake throttling, elevated idle speed, and secondary fuel injection upstream the DOC are evaluated for their effect on the exhaust system heat-up time, the fuel consumption penalty and more importantly, for their impact on the tailpipe NOx emissions calculated by this holistic simulation approach.

“…[10][11][12] In the recent years, different strategies have been developed to improve the thermal efficiency of the ICE and accelerate its thermal transient. Some of these strategies are the cylinder cutout 13 or the variable valve timing (VVT), 14,15 which can be combined with novel strategies as the cylinder ventilation. 16 Another strategy that offers good results is the cylinder deactivation (CDA).…”

Section: Introductionmentioning

confidence: 99%

EGR cylinder deactivation strategy to accelerate the warm-up and restart processes in a Diesel engine operating at cold conditions

Galindo

Dolz

Monsalve‐Serrano

et al. 2021

The aftertreatment systems used in internal combustion engines need high temperatures for reaching its maximum efficiency. By this reason, during the engine cold start period or engine restart operation, excessive pollutant emissions levels are emitted to the atmosphere. This paper evaluates the impact of using a new cylinder deactivation strategy on a Euro 6 turbocharged diesel engine running under cold conditions (−7°C) with the aim of improving the engine warm-up process. This strategy is evaluated in two parts. First, an experimental study is performed at 20°C to analyze the effect of the cylinder deactivation strategy at steady-state and during an engine cold start at 1500 rpm and constant load. In particular, the pumping losses, pollutant emissions levels and engine thermal efficiency are analyzed. In the second part, the engine behavior is analyzed at steady-state and transient conditions under very low ambient temperatures (−7°C). In these conditions, the results show an increase of the exhaust temperatures of around 100°C, which allows to reduce the diesel oxidation catalyst light-off by 250 s besides of reducing the engine warm-up process in approximately 120 s. This allows to reduce the CO and HC emissions by 70% and 50%, respectively, at the end of the test.