• Energy Research

Vehicles with hybrid drive systems, are increasingly more often being equipped with solutions that increase the drive systems efficiency. One of such solutions is to use an increased supply voltage for electric motors of such vehicles. The battery voltage is increased several times in the inverter system in order to increase the electrical power supplied to the electric motor. This article presents possible uses of such voltage amplification (called boost) in urban traffic conditions. The tests used the latest models of vehicles with hybrid drive systems equipped with the same drive units: Lexus NX 300h and Toyota RAV4 Hybrid. The study analyses the conditions of starting such a system and the characteristics of its operation. It has been shown that the amplification of the voltage powering the electrical machinery in both vehicles occurs at high torque values. The maximum voltage amplification–almost threefold (up to 650 V) allows a two-fold increase in the torque of the drive system.

Drop-in fuels for aviation gas-turbine engines have been introduced recently to mitigate global warming. Despite their similarity to the fossil fuel Jet A-1, their combustion in traditional combustors should be thoroughly analyzed to maintain engine health and low emissions. The paper introduces criteria for assessing the impact of the chemical composition of fuels on combustion in the DEGN 380 turbofan. Based on previous emission-test results, the power functions of carbon monoxide and its emission index were adopted as the model of combustion. Based on the general notation of chemical reactions leading to the production of CO in combustion, the regression coefficients were given a physical meaning by linking them with the parameters of the kinetic equations, i.e., the reaction rate constant of CO and CO2 formation expressed as exponential functions of combustor outlet temperature and the concentration of O2 in the exhaust gas, as well as stoichiometric combustion reactions. The obtained empirical functions show that, in the entire range of engine operating parameters, synthetic components affect the values of the rate constants of CO and CO2 formation. It can be explained by the change in activation energy determined for all chain-of-combustion reactions. The activation energy for the CO formation chain changes in the range between 8.5 kJ/mol for A0 and 24.7 kJ/mol for A30, while for the CO2 formation chain between 29.8 kJ/mol for A0 and 30.8 kJ/mol for A30. The reactivity coefficient lnαiCOACODCO changes between 2.29 for A0 and 6.44 for A30, while lnαiCO2ACO2DCO2 changes between 7.90 for A0 and 8.08 for A30.

The operation of conventional (hydrocarbon) fuels causes certain effects in the internal combustion engine. Despite the satisfactory efficiency of internal combustion engines, their fuel systems, particularly the injectors, are subject to constant fouling. The article analyzes the possibility of reducing the deposit of high-pressure gasoline injectors using the alcohol addition of ethanol and butanol. The study was conducted under the engine and non-engine conditions. Fuel injection timing was analyzed when fueling with different mixtures, and non-engine analyses were conducted to determine changes affecting the injectors. The results indicate the possibility of reducing injector hole coking using ethanol and butanol as a 20% additive to the base fuel.

Fuel cells are one of the zero-emission elements of modern automotive drive systems. This article presents theoretical identification of the component parameters of indicators for the fuel cell operating conditions. Activation, ohmic, and mass transport losses were identified. Current–voltage characteristics were provided along with an analysis of typical cell losses. The actual performance characteristics of fuel cells were analyzed for Toyota Mirai I and II generation vehicles. The fuel cells operating conditions were derived and analyzed in the context of real driving conditions. Therefore, urban, rural, and motorway conditions were used. The vehicles were equipped with PEM fuel cells supplying power equal to 114 kW (1st gen.) or 128 kW (2nd gen.). The average fuel cell stack power values depend on the driving conditions: urban (about 10 kW), rural (20 kW) and motorway (about 30–40 kW) driving modes. The different power ratings of fuel cells combined with different battery generations resulted in a variation in the cells operating conditions. Analyses conducted in various traffic conditions indicated the possibility of determining losses related to the fuel cells. The analysis of fuel cell losses shows the greatest values for activation losses when the cells are under high load (for both generations)—i.e., in motorway driving conditions. The voltage of resistive losses reached its maximum in urban driving conditions when the load on the fuel cells was small.

Aviation in Europe is required to use fuels containing up to 2 wt. % of sustainable aviation fuels (SAFs). A better understanding of the impact of SAFs on the combustion process will be helpful in solving problems that may arise from the widespread use of these kinds of fuels. It was assumed that the reactivity coefficient αi and the activation energy could be a criteria for assessing the impact of SAFs on the combustion process. Based on DGEN engine tests, the following activation energy values of CO2 and CO formation reactions were obtained—Jet A-1: EaCO2/R=3480 and EaCO/R=982; A30: EaCO2/R=3705 and EaCO/R=2903; and H30: EaCO2/R=3637 and EaCO/R=2843. These results indicate differences in the structure of combustion reaction chains involved by the SAF addition to Jet A-1 fuel. The same conclusion has been formulated on the basis of the reactivity coefficient αi. The values of maximum cylinder pressure (Pmax) obtained during indicator RCCM (rapid compression combustion machine) tests correlated with both the activation energy and coefficients of reactivity. This suggests that the influence of SAF addition to Jet A-1 fuel on the structure of chemical reactions chain during RCCM tests is similar to the influence during DGEN 380 tests. The assumption stated above was confirmed. This indicates the possibility of the preliminary forecasting of CO2 and CO emissions from the DGEN 380 engine based on the test at the RCCM stand.

This article investigates the impact of loading on the hybrid powertrain of the FCAT-30 model, equipped with a proton-exchange-membrane fuel cell (PEMFC) and a nickel–metal hydride (NiMH) battery. This study involves analyzing structural component performance based on voltage and current measurements of the fuel cell, battery, and powertrain. Tests conducted under different load conditions reveal significant differences in battery current and fuel-cell voltage, highlighting the crucial role of the battery in the powertrain. External loading induces cyclic operation of the fuel cell, generating peak power. The energy balance analysis demonstrates that, under no-load conditions, the vehicle consumes 37.3% of its energy from the fuel cell, with a total energy consumption of 3597 J. Under load, the energy from the battery is significantly utilized, resulting in a constant fuel-cell share of approximately 19%, regardless of the vehicle’s load. This study concludes that the battery predominantly drives the powertrain, with the fuel cell acting as a secondary energy source. These findings provide valuable insights into the power distribution and energy balance in the hybrid powertrain. Using a load driving profile reduced the fuel-cell-stack energy contribution by 6.85% relative to driving without an external load.

Correct fuel atomization is an important parameter in the process of preparing a combustible mixture. Distortions of the atomization can lead to unfavorable effects in the combustion process. This paper presents an analysis of the fuel atomization characteristics of high-pressure fuel injector tests. Optically tested injectors were previously tested in a 48 h engine test carried out in accordance with the CEC F-113-KC procedure, using alternative fuels with ethanol blends. As a result of engine tests on fuels containing various amounts of ethanol admixture, the injectors became contaminated. The effect of the deposits on the geometric atomization indicators was determined. This paper focuses on analyzing the area of the atomized spray in a constant volume chamber at different parameters, reflecting real operating conditions. We found that the addition of ethanol (20%) increases the observed spray area for all test points. Complementing the quantitative results is a qualitative analysis of fuel atomization for injector tests previously run on varying fuels.

Modern internal combustion powertrains are the main source of propulsion for on-road and non-road vehicles. However, they are increasingly being replaced by electric or fuel cell-equipped alternative propulsion systems. The article presents a study of fuel cell characteristics operating under both static and dynamic conditions, with a 1.2 kW fuel cell set with a voltage converter and lead-acid batteries. In the conducted tests, the fuel cell stack's maximum efficiency reached 65%. Load tests (static and dynamic) have indicated higher fuel cell efficiencies when using hybrid operation with a DC/DC converter and battery.

Hydrogen-fueled engines require large values of the excess air ratio in order to achieve high thermal efficiency. A low value of this coefficient promotes knocking combustion. This paper analyzes the conditions for the occurrence of knocking combustion in an engine with a turbulent jet ignition (TJI) system with a passive pre-chamber. A single-cylinder engine equipped with a TJI system was running with an air-to-fuel equivalence ratio λ in the range of 1.25–2.00, and the center of combustion (CoC) was regulated in the range of 2–14 deg aTDC (top dead center). Such process conditions made it possible to fully analyze the ascension of knock combustion until its disappearance with the increase in lambda and CoC. Measures of knock in the form of maximum amplitude pressure oscillation (MAPO) and integral modulus of pressure oscillation (IMPO) were used. The absolute values of these indices were pointed out, which can provide the basis for the definition of knock combustion. Based on our own work, the MAPO index > 1 bar was defined, determining the occurrence of knocking (without indicating its quality). In addition, taking into account MAPO, it was concluded that IMPO > 0.13 bar·deg is the quantity responsible for knocking combustion.

Abstract The process of fuel combustion in a diesel engine is determined by factors existing during liquid fuel injection and atomisation. The physicochemical properties of the fuel to a large extent decide upon the quality of this phase of cylinder fuelling. So it is important to ensure appropriate properties of a fuel affecting its atomisation and, as a result, combustion. The paper deals with the topic of diesel oil improvers and the analysis of their influence on atomisation and combustion indices. In the studies base diesel oil and a diesel fuel improved by a package of additives, were used. The process of conventional and improved fuel injection was analysed by using optical examinations. The amount of released heat was evaluated during the studies carried out on combustion. Significant aspects of the applied improvers in relation to fuel injection and its combustion have been indicated.