Combustion Institute

Sustainable aviation fuels (SAFs) are receiving increasinglyhighattention by science, industry, and politics as they are consideredan effective tool to reduce the impact of aviation on the climatesystem and air quality. While numerous experimental studies on theeffects of SAFs were performed, these are often limited to specifictest scenarios or engine measurements. This work combines predictionsbased on the DLR SimFuel platform with field data from the first campaignto investigate a 34% hydrotreated esters and fatty acids (HEFA) SAFblend under real-world operating conditions during regular passengerflights. For this purpose, an Airbus A320-251N flying between Copenhagenand Arlanda was fueled with conventional Jet A-1 for 30 flights during1 week and with a 34% HEFA SAF blend for 85 flights in 2 weeks. Thecorresponding exhaust gas plumes during taxiing were analyzed by theDLR mobile lab. Equipped with state-of-the-art instruments, this analysiscontains total and non-volatile particle number concentrations andsize distribution, gas analytics (CO2 and NOx), and weather parameters. The results confirm thebeneficial effects of SAF usage toward the air quality by reducingtotal particle emissions by about 10% and non-volatile particle emissionsby about 40%. Also, this data set obtained under real-world conditionsprovides a valuable basis for model development and validation.

This work presents a thermodynamic analysis of a six-stroke cycle implemented in Spark-Ignition (SI) engines. The cycle configuration comprises two distinct combustion phases: (1) initial combustion of a methane-hydrogen mixture under fuel-lean conditions (λ > 1), yielding exhaust gases containing residual oxygen, followed by (2) secondary hydrogen injection during the expansion phase to facilitate complete utilization of the remaining oxidizer. The investigation evaluates the system's thermodynamic performance through parametric variation of both the fuel composition (CH₄/H₂ ratio) and the equivalence ratio during primary combustion. The results obtained indicate that the changes in the peak temperature of the second part of the cycle are small, up to 60K relative to the mean value. The fuel mix with =3.0 showed the highest cycle efficiency at 50.73%, indicating the best performance among all cases. According to the data, better performance can be achieved by optimizing cycle parameters such as regeneration, intercooling, pressure ratios, and component efficiency in addition to raising the maximum temperature. In conclusion, better outcomes are not always guaranteed by higher temperatures. Increasing thermal input alone is not as important as designing and optimizing cycles efficiently.

The paper presents a review study comparative life cycle assessment (LCA) of selected 12-meter urban buses powered by hybrid, battery-electric, and hydrogen fuel cell systems. The review is based on Environmental Product Declarations (EPDs) and follows ISO 14040/44 standards, using a cradle-to-grave approach and a functional unit of 1 passenger-kilometer. Environmental impacts are assessed across raw material extraction, production, operation, maintenance, and end-of-life stages. Results of review show that the operation phase has the highest share of total greenhouse gas emissions, particularly when fossil-based energy is used. For electric and hydrogen buses, upstream processes also contribute significantly due to material and component complexity. The findings highlight the role of energy mix and vehicle structure in determining the total impact, stressing the importance of full life cycle assessment in evaluating sustainable transport solutions. EPD can be the first step for developing a Digital Product Passport (DPP) for the buses.

The advancement of combustion engines is driven by stricter emission regulations (e.g., Euro/EPA standards), requiring innovations in lubrication. Modern oils must ensure wear protection, emission system compatibility (e.g., DPFs, SCRs) and fuel efficiency. This paper analyzes updates to ACEA, API, and OEM specifications, focusing on oxidation resistance, low-SAPS formulations, and fuel economy. The trend toward low-viscosity oils (0W-20, 0W-16) reduces friction but challenges lubrication under high loads. The study evaluates these changes’ impact on engine durability and future oil development amid tightening sustainability and emission norms. This article will analize lubricant requirments for passenger cars and light commercial vehicles.

Future low-carbon energy systems will show reduced generation from synchronous generators. The resulting loss of inertia can lead to a high rate of change of frequency after a disturbance and, thus, to potentially unrecoverable system states. Yet, inertial response constraints are rarely considered in large-scale capacity expansion planning models investigating decarbonization pathways. We thus present a convex formulation of a coordinated capacity expansion problem for generator, transmission, and storage expansion. Next to a unit commitment relaxation, the formulation includes linearized rate of change of frequency constraints that model the inertial response to a priori defined disturbances such as a large power injection deficit or a system split. In a numerical experiment, we solve model instances that cover the European power system at high spatial and temporal resolution and, moreover, consider the inertial responses from synchronous generators and inverter-based resources. Our results show that inertia provision from battery energy storage systems with grid-forming inverters is already valuable today due to enabling decreased conventional generation. Moreover, we find that future low-carbon energy systems can ensure sufficient capacities for inertial response by equipping a share of battery energy storage systems with grid-forming inverters at a negligible system cost increase.

The improvement of unleaded fuels in general aviation represents a significant milestone in the pursuit of establishing a greener and more sustainable air transportation system. Conventional aviation fuels, such as AVGAS 100LL, have TEL (Tetraethyl Lead) in their composition, which is used to increase the octane rating of fuel and improve the efficiency of piston engines used in aviation. However, these substances are considered toxic, and their emissions into the atmosphere have negative effects on the environment and human health. Therefore, very strict air quality standards have been established by the European Union and member states. Years of research and cooperation throughout the aviation sector have contributed to the elimination of lead-containing fuels from most aircraft used in general aviation operations. Most engines have already been certified for the usage of unleaded gasoline, and so are all new engines. Nevertheless, one-third of the engines currently in use in the EU are not certified to burn unleaded fuel. Besides the lead, other toxic compounds are also being emitted with exhaust gases like CO2, NOx, and UHC. In this article, the discussion is about the profits of pursuing a zero-lead policy within General Aviation and the risks associated with introducing a leaded avgas prohibition without a valid alternative.

The article provides a detailed description of the design and key parameters of the GTM-120 turbine engine, along with flow calculations for this power unit at a selected operating point. These calculations were performed using GasTurb software, which is also capable of assessing nitrogen oxide emissions. Additionally, the article outlines the test stand and the methodology used to determine toxic compounds emitted by the engine. It analyzes the measured results of various exhaust components produced during the engine's operation, specifically focusing on the levels of nitrogen oxides and carbon oxides as influenced by rotational speed and temperature. Conducted studies have established a testing methodology for aviation turbine engines, based on the type of analyzer used. This methodology will facilitate the evaluation of other aviation turbine engines on stationary test stands.

This study evaluates the performance of aftermarket and OEM diesel particulate filters (DPFs) using a particle number counter (PNC) during stationary Periodic Technical Inspection (PN-PTI) tests. Several European countries have already implemented regulations requiring this test to ensure that vehicles equipped with DPFs meet the stringent particle number (PN) emission limits. In this work, measurements were conducted on various vehicles with new and conditioned DPFs. The results revealed significant variability in PN emissions, with some filters failing to meet the required limits. Key contributors to elevated PN levels were identified, including filter aging and inadequate conditioning procedures. Based on the findings, the paper proposes practical recommendations and diagnostic approaches to support compliance with PN-PTI test requirements.

The study contains an analysis of the acceleration process of a passenger vehicle equipped with an IC powertrain, aimed at determining a throttle control strategy that minimizes fuel consumption during acceleration while maintaining adequate dynamic performance. The first stage involved measuring traction parameters for a constant assumed engine power. The second stage focused on determining a control trajectory that would ensure minimal fuel consumption during acceleration. To achieve this the acceleration process was examined during a flexibility test in the speed range from 12.5 to 35 m/s, following an acceleration pedal control line related to the crankshaft rotation speed. Implementing the acceleration process along this control line resulted in a reduction in acceleration dynamics, accompanied by a decrease in fuel consumption per distance traveled by nearly 51%. An analysis of the average acceleration values for a given drivetrain gear ratio revealed that exceeding a throttle position of 70% yields no significant improvement in vehicle dynamics. The optimal throttle positions during acceleration were found to be within the range of 25% to 70%.

The purpose of this article is to determine if, in the case of inability to carry out diagnostic tests at engine operating loads in the range of 70÷90%, engine functional systems can generate diagnostic signals in the form of changes in heat balance components. The motivation for working on the selected topic was the need to evaluate the effectiveness of graphical forms of heat balance representation, especially Sankey diagrams, in heat engine diagnostics, using a four-stroke diesel engine as an example. Interpretation of the results was carried out based on simulations performed using Blitz-PRO software and experimental tests carried out on a test bench. For the numerical simulations, the object under analysis was modeled, which was a single-cylinder, four-stroke diesel engine Andoria S320. Both numerical simulations and experimental tests were carried out for three engine operating states: the reference state and two malfunction states: in the air intake system and the fuel supply system. The analyses made it possible to draw conclusions. It was assessed that carrying out the analysis of the Sankey diagram for partial load doesn’t bring significant diagnostic information.