Multi-objective optimizations of the boot injection strategy for reactivity controlled compression ignition engines

As legislations set very stringent environmental and fuel economy standards, researchers have pushed into a continuous development in all areas of the diesel engine. The recent evolution of the injection technologies has permitted to modify the fuel-delivery strategies. From what was a single pulse per injection event, modern systems allow to inject up to eight different times precisely per combustion cycle. In such sense, experimental results of the rate of injection and momentum flux could be useful for validation and improvement of computational models. Moreover, accurately quantifying the injected mass per pulse in a fuel–gas interface can provide data with more realistic engine-like conditions. To this end, this research presents measurements of the rate of injection and momentum flux for two simple multiple injection strategies: a pilot-main and a main-post. Boundary conditions included two rail and discharge pressures, two different pilot/post quantities and four dwell times. A new approach was employed to estimate the mass allocation with the momentum flux data, and results were compared to the rate of injection traces to verify the distribution calculated. On the results, signals for each pulse were successfully decoupled using its rising and falling edge. The shot-to-shot variability of the pilot/post injection was highly dependent on its transitory characteristics, and on the dwell time for post injections due to internal pressure waves. The injected mass per pulse was successfully measured as well in the momentum flux test rig, and the energizing time changed slightly to account for the different operation interfaces. Signals from both measurement campaigns showed a remarkable agreement when compared, ascertain the possibility of measuring the injected mass, and its allocation for multiple injection strategies, in the momentum flux test rig.

Section: Introductionmentioning

confidence: 99%

Measurements of the mass allocation for multiple injection strategies using the rate of injection and momentum flux signals

Payri

Gimeno

Martí-Aldaraví

et al. 2020

“…Different metrics exist to quantify combustion noise, from the HCCI-suited ringing intensity (RI; MW/m 2 ) indicating the power flux delivered by the pressure waves, 29 to the Noise (dB) indicating the perceived noise outside of the engine (more indicated for conventional engine modes). 30 Given that the RI metric has been specifically developed for HCCI engines and is still being used today (see for example), 31,32 this metric uncertainty will be developed here-under. However, the uncertainty related to any other metric can be obtained following the general methodology developed in this article.…”

Section: Results: Uncertainties On the Physical Quantities Requiring mentioning

confidence: 99%

Uncertainty quantification from raw measurements to post-processed data: A general methodology and its application to a homogeneous-charge compression–ignition engine

Pochet

Jeanmart

Contino

2019

Internal combustion engines have been improved for many decades. Yet, complex phenomena are now resorted to, for which any optimum might be unstable: noise, low-temperature heat release timing, stratification, pollutant sweet spots, and so on. In order to make reliable statements on an improvement, one must specify the uncertainty related to it. Still, uncertainty quantification is generally missing in the piston engine experimental literature. Therefore, we detailed a mathematical methodology to obtain any engine parameter uncertainty and then used it to derive the uncertainty expressions of the physical quantities of the most generic homogeneous-charge compression–ignition research engine (mass-flow-induced mixture with [Formula: see text] fuel). We then applied those expressions on an existing hydrogen homogeneous-charge compression–ignition test bench. This includes the uncertainty propagation chain from sensor specifications, user calibrations, intake control, in-cylinder processes, and post-processing techniques. Directly measured physical quantities have uncertainties of around 1%, depending on the sensor quality (e.g. pressure, volume), but indirectly measured quantities relying on modelled parameters have uncertainties higher than 5% (e.g. wall heat losses, in-cylinder temperature, gross heat release, pressure rise rate). Other findings that such an analysis can bring relate, for example, to the physical quantities driving the uncertainty and to the ones that can be neglected. In the case of the homogeneous-charge compression–ignition engine considered, the effects of blow-by, bottle purity and air moisture content were found negligible; the post-processing for effective compression ratio, effective in-cylinder temperature, and top dead centre offset were found essential; and the pressure and volume uncertainties were found to be the main drivers to a large extent. The obtained numeric values serve the general purpose of alerting the experimenter on uncertainty order of magnitudes. The developed methodology shall be used and adapted by the experimenter willing to study the uncertainty propagation in their setup or willing to assess the adequacy of a sensor performance.

“…89 This could possibly be due to the fact that among the various diesel LTC strategies, RCCI offers the best control over the combustion process by tailoring the mixture reactivity inside the combustion chamber according to the engine demand by using two fuels of different reactivity. 38, 93–95 However, depending on the engine type and air handling limitation, full load may not be achieved in RCCI similar to other LTC modes. 87,90 Despite the benefits, complexity due to the requirement of a dual fuel injection system and associated controls remains in RCCI.…”

Section: Types Of Diesel Ltc Strategymentioning

confidence: 99%

Prospective fuels for diesel low temperature combustion engine applications: A critical review

Krishnasamy

Gupta

Reitz

2020

Low Temperature Combustion (LTC) strategies are most promising to simultaneously reduce oxides of nitrogen (NOx) and soot emissions from diesel engines along with offering higher thermal efficiency. Commercial wide spread implementation of diesel LTC strategies requires several challenges to be addressed, including lack of precise ignition timing control, widening the narrow operating load ranges and reducing high unburned fuel emissions. These challenges can be addressed through modifications in the engine or fuel design or both. The timing and rate of combustion in several LTC strategies are controlled primarily by the chemical kinetics of the fuel. Since, diesel fuel reactivity and volatility are tailor-made to perform well under conventional diesel combustion conditions, its application in LTC poses several problems, as highlighted in this paper. Hence, it is important to identify suitable alternative fuels for the different diesel LTC strategies. The published literature on LTC over the past 25 years is critically analyzed to discuss the evolution of the different diesel LTC strategies, their operability limits, the challenges and the controlling parameters for each strategy. This is followed by in-depth analysis of the role of the fuel and the fuel requirements for each strategy. Further, the importance of adopting a hybrid surrogate modeling approach to enable numerical simulation of diesel LTC is highlighted. A novel attempt of relating various diesel low temperature combustion (LTC) strategies based on the approach followed to achieve positive ignition dwell through different injection strategies, utilizing high exhaust gas recirculation (EGR), and dual fuels is presented. The need for replacing diesel with alternative liquid fuels in LTC strategies is presented by highlighting the fundamental problems associated with diesel fuel characteristics. The review concludes by suggesting potential alternative fuels for various diesel LTC strategies and provides directions for future work to address the challenges facing compression ignition LTC operation.