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Open research questions in Advanced Combustion Engine Technologies

128 gap statements mined from Advanced Combustion Engine Technologies papers in our 4.5M-paper local library, which holds 2,302 papers on the topic — drawn mostly from each paper's own stated research gap, future-work, challenge and limitation notes, and its abstract. The ones listed below are a selection still marked open; each names the study that raised it, with a DOI link where the paper has one.

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What the literature leaves open

  • The need to keep the system within a narrow operating window bounded by misfire, knock, NOx, N2O, and NH3 slip. The uncertainty in the feasible operating region of an ammonia-hydrogen engine.

    Control Strategies and Intelligent Optimization for Ammonia–Hydrogen Dual-Fuel Engines: A Control-Oriented Review · 2026 · DOI

  • The lack of a deep learning model for predicting NOx emissions from diesel engines using steady-state data. The need for data augmentation to improve prediction performance. The uncertainty about the effect of the amount of synthetic data on prediction performance.

    Deep Learning Model for Transient NOx Emission Prediction of Diesel Engines Based on Steady-State Data with Data Augmentation · 2026 · DOI

  • The algorithm can not handle transient behaviour. The computation time of the algorithm needs to be reduced. The method is demonstrated in simulation, not in experimental setup. The study neglects the correlation between output variables.

    Automated and risk-aware engine control calibration using constrained Bayesian optimization · 2026 · DOI

  • The need for improved efficiency and environmental performance of diesel generators in Arctic microgrids. The challenge of optimizing diesel engine operation under Arctic conditions. The lack of a unified, surrogate-assisted optimization framework for calibrating engine operation.

    Surrogate-Assisted Multi-Objective Optimization of Engine-Level Pneumatic Assistance for Arctic Diesel Generators · 2026 · DOI

  • The need for a modular decision-making framework for impeller optimization that considers design objectives, simulation constraints, and the physical characteristics of turbomachinery. The lack of a comprehensive analysis of recent studies on advanced computational and hybrid optimization techniques.

    Hybrid Optimization Approaches for Impeller Design in Turbomachinery: Methods, Metrics, and Design Strategies · 2025 · DOI

  • The use of natural gas with diesel can increase CO and HC emissions while decreasing NOx and CO2. The use of hydrogen with diesel can reduce CO, CO2, and HC emissions but increase NOx. The paper identifies the need to mitigate the disadvantages of using these fuels separately, such as poor lean combustion ability and slow burning.

    A Comprehensive Review on the Hydrogen–Natural Gas–Diesel Tri-Fuel Engine Exhaust Emissions · 2024 · DOI

  • There is a lack of literature studies on HNG–diesel engine emissions that are considered helpful to researchers. The paper aims to address this gap by providing a comprehensive review of recent research on the topic.

    A Comprehensive Review on the Hydrogen–Natural Gas–Diesel Tri-Fuel Engine Exhaust Emissions · 2024 · DOI

  • However, the influence of engine geometry on HDDF combustion behaviour remains insufficiently understood.

    Investigating the effects of stroke-to-bore ratio on the performance of hydrogen-fuelled diesel engines · 2026 · DOI

  • Nonalternant polycyclic aromatic hydrocarbons (PAHs) incorporating five-membered rings are fundamental intermediates linking planar aromatics to curved carbon nanostructures including fullerenes and nanotubes, yet their formation mechanisms are not fully understood.

    Indenyl-Benzyl Radical Recombination Leads to the Formation of Fluoranthene, a Non-Alternant Polycyclic Aromatic Hydrocarbon · 2026 · DOI

  • However, the impact of injection timing (IT) on the combustion, performance, and emissions of diesel engines fueled with BTL diesel-Spirulina microalgae biodiesel blends remains underexplored.

    Effect of injection timing on combustion, performance, and emissions of a diesel engine fueled with novel biomass-to-liquid diesel and Spirulina microalgae biodiesel blends · 2025 · DOI

  • Experimental insights into high-MEF operation are scarce, particularly for large-bore engines, leaving critical knowledge gaps in understanding combustion and performance characteristics of methanol PRDF engines.

    Combustion mode analysis of a large-bore methanol premixed dual-fuel engine with high methanol energy fractions · 2025 · DOI

  • The uncertainty of predictions via the Bayesian approach is crucial since the aviation fuel data is often limited, making the predictive models prone to overfitting.

    A Bayesian ensemble approach for improved sustainable aviation fuel modeling · 2025 · DOI

  • This study tackles the gap in research regarding the optimization of engine conditions for n-pentanol-gasoline blends in SI engines, with a particular focus on n-pentanol as a renewable fuel.

    Reducing environmental pollution by optimizing oxidative fuel and gasoline mixtures in modern heat engines · 2024 · DOI

  • Nevertheless, the chemical interaction between ozone and the species in the residual gas has not yet been investigated in the literature.

    The influence of residual gas on ozone-assisted combustion in an HCCI reciprocating engine · 2024 · DOI

  • The study aims to address this gap by investigating the environmental effects of using HDPE pyrolysis oil-gasoline blends in SI engines.

    Environmental Effects of Exhaust Emission from Spark Ignition Engine Fuelled with 4 percent HDPE Pyrolysis Oil-Gasoline Blend: Artificial Neural Network Modelling · 2026 · DOI

  • The study is limited to a review of existing literature, without new experimental data. The analysis is focused on the combustion process and emissions, without considering other factors such as stove design and user practices.

    PRESSURE DEPENDENT EMISSION CHARACTERISTICS OF ADULTERATED KEROSENE IN DOMESTIC PRESSURE STOVES: A REVIEW · 2026 · DOI

  • The study only used a limited steady-state experimental dataset. The model did not explicitly include temperature conditions as input variables. The study did not evaluate the model's performance on a large-scale dataset.

    Deep Learning Model for Transient NOx Emission Prediction of Diesel Engines Based on Steady-State Data with Data Augmentation · 2026 · DOI

  • Experimental investigations are relatively limited, particularly for large-bore engines.

    Status and Prospects of Glow Plug-Assisted Ignition Technology for Methanol Engines: A Review · 2026 · DOI

  • A constant-speed stationary engine was selected for this study because it has rarely been studied.

    Effect of compression ratio and hydrogen addition on performance and different phases of hydrogen/diesel combustion in reactivity controlled compression ignition engine · 2025 · DOI

  • The increasing complexity of Internal Combustion Engines - The need to balance thermal efficiency and greenhouse gas emissions - The challenge of dealing with risks and uncertainties associated with operational safety and combustion…

    Automated and risk-aware engine control calibration using constrained Bayesian optimization · 2026 · DOI

  • The study only investigates two feedforward ANN configurations, - the experiment is limited to a specific internal combustion engine simulation, - the results may not be generalizable to other nonlinear dynamic…

    Impact of Neural Network Initialisation Seed and Architecture on Accuracy, Generalisation and Generative Consistency in Data-Driven Internal Combustion Engine Modelling · 2026 · DOI

  • Investigating the application of high-capacity ANN configurations to other nonlinear dynamic systems, - exploring the use of different ANN architectures and initialisation seeds, - analyzing the effect of ANN capacity on predictive accuracy in various engineering…

    Impact of Neural Network Initialisation Seed and Architecture on Accuracy, Generalisation and Generative Consistency in Data-Driven Internal Combustion Engine Modelling · 2026 · DOI

  • Directions for future research are outlined, - The study advances surrogate-assisted optimization for hybrid energy systems operating under demanding Arctic…

    Surrogate-Assisted Multi-Objective Optimization of Engine-Level Pneumatic Assistance for Arctic Diesel Generators · 2026 · DOI

  • Limited to a few design parameters, - Simplifications in computational fluid dynamic modeling, - Experimental data collection…

    A Combined 1D/3D Method to Accurately Model Fuel Stratification in an Advanced Combustion Engine · 2025 · DOI

  • Investigating other design parameters, - Exploring alternative fuels, - Improving computational…

    A Combined 1D/3D Method to Accurately Model Fuel Stratification in an Advanced Combustion Engine · 2025 · DOI

Most-cited papers in Advanced Combustion Engine Technologies

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Open questions raised by papers listed on this page include: (1) The lack of a deep learning model for predicting NOx emissions from diesel engines using steady-state data (“Deep Learning Model for Transient NOx Emission Prediction of Diesel Engines…”, 2026); (2) The lack of a unified, surrogate-assisted optimization framework for calibrating engine operation (“Surrogate-Assisted Multi-Objective Optimization of Engine-Level Pneumatic…”, 2026); (3) The influence of engine geometry on HDDF combustion behaviour remains insufficiently understood (“Investigating the effects of stroke-to-bore ratio on the performance of…”, 2026); (4) The lack of a comprehensive analysis of recent studies on advanced computational and hybrid optimization techniques (“Hybrid Optimization Approaches for Impeller Design in Turbomachinery: Methods,…”, 2025); (5) The impact of injection timing (IT) on the combustion, performance, and emissions of diesel engines fueled with BTL diesel-Spirulina microalgae biodiesel blends remains underexplored (“Effect of injection timing on combustion, performance, and emissions of a…”, 2025). 128 gap statements have been mined from Advanced Combustion Engine Technologies papers in our 4.5M-paper local library, which holds 2,302 papers on the topic; the gaps come from whichever of those papers state one. They are mostly the research gaps the authors state and the papers' abstracts, plus future-work, limitations and challenges passages. The ones listed below are a selection still marked open; each names the study that raised it, with a DOI link where the paper has one, so you can read the original claim in context.

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