An experimental analysis of performance and exhaust emissions of a CRDI diesel engine operating on mixtures containing mineral and renewable components

The manuscript presents a comparative analysis of the performance and emission characteristics of a compression ignition engine equipped with a Common Rail injection system. The engine is fueled with diesel-biodiesel mixtures containing 25% and 50% share (by volume) of renewable components. Conventional diesel is used as a reference. Turkey lard and rapeseed oil are used as raw materials and subjected to the single-stage transesterification process to obtain methyl esters. The experiments are performed on a medium-duty, turbocharged, inter-cooled, Common Rail Direct Injection (CRDI) diesel engine. This study concentrates on one engine speed of 1500 rpm, typical for gen-set applications, and mid-load range from 100 Nm to 200 Nm. The scope of measurements covers the analysis of exhaust gasses concentration and engine efficiency parameters. In addition, the in-cylinder pressure measurements are performed in order to provide insight into the differences in combustion characteristics between examined fuel mixtures. The study reveals that the addition of the renewable component to fuel mixture positively affects a number of examined performance parameters as well as decreases the concentration of the examined toxic exhaust components, in the majority of cases.fi=vertaisarvioitu|en=peerReviewed

Renewable Fuels for Internal Combustion Engines

The continuous need for systematization and open dissemination of knowledge on Renewable Fuels intended for use in Internal Combustion Engines forms the premise of the presented Special Issue titled “Renewable Fuels for Internal Combustion”. Experts in the field were encouraged to share their latest findings in the form of original research papers, case studies, or short reviews. Works targeting all aspects of the value chain were considered necessary, including the following: (liquid and gaseous) fuel production process, upgrading (catalytic and fractional blending), up to end, valorization in combustion engines (conventional and advanced concepts). Finally, techno-economic analyses aiming to valorize the value chain holistically were warmly encouraged to submit papers in this Special Issue of the Energies Journal. In this book, the reader will find successful submissions that present the latest findings from the discussed research field, encapsulated into nine chapters.© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioimaton|en=nonPeerReviewed

Integrated 1D Simulation of Aftertreatment System and Chemistry-Based Multizone RCCI Combustion for Optimal Performance with Methane Oxidation Catalyst

This paper presents a comprehensive investigation into the design of a methane oxidation catalyst aftertreatment system specifically tailored for the Wärtsilä W31DF natural gas engine which has been converted to a reactivity-controlled compression ignition NG/Diesel engine. A GT-Power model was coupled with a predictive physical base chemical kinetic multizone model (MZM) as a combustion object. In this MZM simulation, a set of 54 species and 269 reactions as chemical kinetic mechanism were used for modelling combustion and emissions. Aftertreatment simulations were conducted using a 1D air-path model in the same GT-Power model, integrated with a chemical kinetic model featuring 15 catalytic reactions, based on activation energy and species concentrations from combustion outputs. The latter offered detailed exhaust composition and exhaust thermodynamic data under specific operating conditions, effectively capturing the intricate interactions between the investigated aftertreatment system, combustion, and exhaust composition. Special emphasis was placed on the formation of intermediate hydrocarbons such as C2H4 and C2H6, despite their concentrations being lower than that of CH4. The analysis of catalytic conversion focused on key species, including H2O, CO2, CO, CH4, C2H4, and C2H6, examining their interactions. After consideration of thermal management and pressure drop, a practical choice of a 400 mm long catalyst with a density of 10 cells per cm2 was selected. Investigations of this catalyst’s specification revealed complete CO conversion and a minimum of 89% hydrocarbon conversion efficiency. Integrating the exhaust aftertreatment system into the air path resulted in a reduction in engine-indicated efficiency by up to 2.65% but did not affect in-cylinder combustion.© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Variable valve actuation for efficient exhaust thermal management in an off-road diesel engine

Exhaust thermal management (ETM) is crucial for effective emission mitigation in integrated exhaust aftertreatment systems of modern off-road diesel powertrains. However, conventional ETM strategies incur a significant fuel efficiency penalty. This study addresses the issue by investigating the application of variable valve actuation (VVA) for efficient ETM. For the first time, this investigation is conducted on a representative state-of-the-art off-road powertrain platform. It explores four VVA strategies with unprecedent level of rigour, employing a model-based approach that enables extended insights beyond stand-alone testing. Experiments with an EU Stage-V off-road diesel engine provide the baseline for validating a one-dimensional model in GT-Suite. A meticulously calibrated, predictive combustion model enables precise cross-evaluation of how VVA strategies affect exhaust gas temperature (EGT), efficiency, engine-out emissions and combustion characteristics, considering all trade-offs. VVA simulations are performed at three low-load operating points, where engine operation borders catalyst light-off temperature (LOT). The findings impartially confirm that cylinder deactivation (CDA) and intake modulation are the most promising VVA strategies for off-road engines, with EGT increments surpassing +250 °C and +150 °C respectively, accompanied by minor fuel penalties (up to +3.5 %). CDA demonstrated fuel savings of up to −2.5 % at certain points, due to reduced pumping and friction losses. Intake modulation displayed large reduction in engine-out NOx (>90 %) and minimal penalties in carbon emissions (HC, CO, and soot). The results underscore VVÁs potential as an efficient ETM option to help the next generation of off-road diesels to comply with upcoming EPA Tier 5 emission legislation.© 2024 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

An applicable approach to mitigate pressure rise rate in an HCCI engine with negative valve overlap

Low-temperature combustion in a homogeneous-charge compression-ignition (HCCI) engine offers high thermalefficiency while cutting offemissions. However, HCCI’s feasibility is hampered by excessive peak pressure riserates under high load, causing combustion noise and possible engine damage. This study considers extending thehigh-load limit in a boosted HCCI engine accommodating variable valve timing and fuel reforming during ne-gative valve overlap. Three techniques are evaluated on a research engine: (i) exhaust valve timing retardation(ii) boost pressure adjustment and (iii) reduction of fuel subjected to reforming. Two load regimes are explored:a mid-load point with indicated mean effective pressure of 0.61 MPa; and high-load conditions achieved by 25%more fuelling. The former is often reported as boundary condition for HCCI’s, the latter is usually far beyond theacceptable pressure rise rate limit. Results indicate that strategies (i) and (iii) offer a trade-off-free solution forhigh-load extension. This can be realized as a supervisory, in-cylinder pressure based, control function.Independently of the pressure rise rate mitigation method considered, two key variables are crucial for closed-loop control: the in-cylinder volume at 50% fuel burnt and the combustion duration. They are closely coupledand can be real-time calculated using well-established control framework based on sensing the combustiontiming. The expansion rate and differences in fuel mass subjected to reforming are secondary for pressure riserate estimation and should be considered if greater accuracy is required.fi=vertaisarvioitu|en=peerReviewed

Development of a digital twin for real-time simulation of a combustion engine-based power plant with battery storage and grid coupling

Coordinated control of combustion engine-based power plants with battery storage is the next big thing for optimising renewable energy. Digital twins can enable such sophisticated control but currently are too simplistic for the required insight. This study explores the feasibility of a fully physics-based combustion engine model in real-time co-simulation with an electrical power plant model, including battery storage. A detailed, crank-angle resolved, one-dimensional model of a large-bore stationary engine is reduced to a fast-running model (FRM). This engine digital twin is coupled with a complete power plant control model, developed in Simulink. Real-time functions are tested on a dedicated rapid-prototyping system using a target computer. Measurement data from the corresponding power plant infrastructure provide validation for the digital twin. The model-in-the-loop simulations show real-time results from both the standalone combustion and electric submodels mostly within 5% of measured values. The model coupling for fully predictive simulation was tested on a desktop computer, showing expected functionality and validity within 4% and 8% of the respective measured generator and converter outputs. However, execution time of the FRM needs reducing when moving to final hardware-in-the-loop implementation of a complete power plant model.© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Comparative study of combustion and emissions of diesel engine fuelled with FAME and HVO

This study investigates combustion and emission characteristics of a contemporary single-cylinder compression ignition engine fuelled with diesel, fatty acid methyl esters (FAME) and hydrotreated vegetable oil (HVO). These two drop-in fuels have an increasing share in automotive supply chains, yet have substantially different physical and auto-ignition properties. HVO has a lower viscosity and higher cetane number, and FAME has contrary characteristics. These parameters heavily affect mixture formation and the following combustion process, causing that the engine pre-optimized to one fuel option can provide deteriorated performance and excess emissions if another sustainable option is applied. To investigate the scale of this problem, injection pressure sweeps were performed around the stock, low NOX and low PM engine calibration utilizing split fuel injection. The results showed that FAME and HVO prefer lower injection pressures than diesel fuel, with the benefits of simultaneous reduction of all emission indicators compared to DF. Additionally, reduction of injection pressure from 80 MPa to 60 MPa for biodiesels at low engine load resulted in improved brake thermal efficiency by 1 percentage point, due to reduced parasitic losses in the common rail system.This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/)fi=vertaisarvioitu|en=peerReviewed

Partially premixed combustion of hydrotreated vegetable oil in a diesel engine : Sensitivity to boost and exhaust gas recirculation

Hydrotreated vegetable oil (HVO) has potential to emerge as an alternative fuel to mineral diesel due to its favourable properties. The present study investigated HVO under partially premixed compression ignition combustion mode with boost-exhaust gas recirculation (EGR) and also in conventional combustion mode. Single-cylinder engine tests focused on optimising a single representative operating point in the middle of the engine operating envelope. The optimisation focused on the trade-off between NOX and particulate matter, as the adopted multi-pulse strategy provides stable combustion onset independently of the cylinder mixture conditions. Sensitivity in emissions comes from large differences in the early, premixed combustion phase. Air-path optimized HVO combustion favours higher EGR rates (25 % vs. 20 %) and lower boost pressures than diesel (130 kPa vs 165 kPa). At such conditions HVO has 1.5 percentage points higher indicated thermal efficiency (43.5 %) than diesel. At the same time, HVO yields an ultra-low particulate level (0.055 g/kWh) and engine-out NOX emissions are 46 % better than optimised diesel combustion. Together with a 37 % reduction in total hydrocarbon emissions, the elimination of aromatics also provides an additional incentive for HVO.© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Research of Parameters of a Compression Ignition Engine Using Various Fuel Mixtures of Hydrotreated Vegetable Oil (HVO) and Fatty Acid Esters (FAE)

The present study is aimed at studying the energy and environmental performance at various engine loads (BMEP) with identical start of injection (SOI) for all fuel types. The combustion parameters for the fuel mixtures were analyzed using the AVL BOOST software (BURN subroutine). Five different blends were tested, consisting completely of renewable raw materials based on hydrotreated vegetable oil (HVO) and fatty acid methyl ester (FE100), and the properties of diesel fuel (D) were compared with respect to these blends. The mixtures were mixed in the following proportions: FE25 (FE25HVO75), FE50 (FE50HVO50), FE75 (FE75HVO25). In this study, diesel exhaust was found to produce higher NOx values compared to FE blends, with HVO being the lowest. Hydrocarbon and smoke emissions were also significantly lower for blends than for diesel. Possible explanations are the physical properties and fatty acid composition of fuel mixtures, affecting injection and further combustion. The results showed that blends containing more unsaturated fatty acids release more nitrogen oxides, thus having a lower thermal efficiency compared to HVO. No essential differences in CO emissions between D and HVO were observed. An increase in this indicator was observed at low loads for mixtures with ester. CO2 was reduced in emissions for HVO compared to the aforementioned blends and diesel. The results of the combustion analysis show that with a high content of unsaturated fatty acids, mixtures have a longer combustion time than diesel fuel.© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed