Search Results (378)

Turbocharger compressor geometry affects the pressure ratio, flow range, and efficiency distribution of the compressor map, but the influence pathway from compressor geometry to engine fuel economy and emissions trade-off has not been sufficiently quantified. This study develops a surrogate-assisted multi-objective optimization framework that couples compressor and engine models. A calibrated one-dimensional compressor model generated a geometry-specific map for each design, which was imported into a validated one-dimensional engine model to calculate brake-specific fuel consumption and brake-specific NOx emissions at four loads. The results for the four loads were aggregated into weighted brake-specific fuel consumption (BSFC_w) and weighted brake-specific NOx emissions (BSNOx_w). Extreme gradient boosting (XGBoost) surrogate models are trained to predict these weighted responses. The non-dominated sorting genetic algorithm II (NSGA-II) identified Pareto-optimal compressor geometries. Representative solutions were re-evaluated using the original coupled models. The Pareto front reveals a clear trade-off between BSFC_w and BSNOx_w, with the minimum-BSFC_w and minimum-BSNOx_w solutions defining the respective lower bounds within the investigated design space. For the selected trade-off solution, BSNOx_w was 1.18 g/(kW·h) lower than the baseline value, while BSFC_w was 0.82 g/(kW·h) higher. Compressor geometry alters the distribution of engine operating points on the compressor map under different loads, thereby affecting the trade-off between fuel economy and NOx emissions. Full article

Currently, high-speed gasoline engines are increasingly focusing on miniaturization and efficiency. Compared with turbocharging, mechanical supercharging is undoubtedly the more suitable technical approach for small, high-speed gasoline engines. To clarify the influence of the proposed supercharging approach on power, thermal efficiency and emissions within a broad range of engine speeds, this study designed two supercharging schemes (with different supercharger/crankshaft transmission ratios), and conducted bench tests comparing with the original engine. The results showed that the boost effect was more pronounced under medium load conditions. At full load, the high-speed supercharging scheme (94.5/86 ratio) on average improved torque by 10.8%, while the low-speed boost mode (86/61 ratio) only took effect after 5500 rpm. But at 60% load, 94.5/86 and 86/61, respectively, improved torque by 24.4% and 11.7%; thermal efficiencies of both supercharging schemes were almost the same and higher than that of the original operation by 0.8%; thus, the specific fuel consumption was reduced, on average, by ~9.5%. After boosting, the ignition phase was delayed due to the knock limit, but the high cylinder temperature promoted the recovery of the combustion rate in the later stage. In terms of emissions, NO_x increased by 28% with the 94.5/86 scheme, while it decreased very slightly with the 86/61 scheme. CO rose by 3.7% under the 94.5/86 scheme, while it almost did not change under the 86/61 scheme operation, and HC increased by 13% and decreased by 21%, respectively, under the high and low boosting schemes. In conclusion, our proposed supercharging approach improved power and thermal efficiency and afforded a compromise emission effect. This study has revealed the performance trade-off rules of different boosting modes, which can provide important theoretical and technical support for the mechanical supercharging modification of high-speed gasoline engines. Full article

The transport sector plays a significant role in air pollution, and real-world emissions measurements are becoming increasingly important. In this study, emissions from a turbocharged, direct-injection gasoline internal combustion engine (ICE) vehicle and a port fuel injection (PFI) hybrid electric vehicle (HEV) were compared using a portable emissions measurement system (PEMS) under real-world driving conditions. The CO₂, CO, NO_x, and PN emissions of the two vehicles were measured in urban, rural, and motorway sections. HEV CO₂ emissions were ~20% lower than ICE emissions in the entire Real Driving Emissions (RDE) cycle, while in urban operation, they were almost 50% lower. PN emissions were lower for HEV in rural and motorway sections than for ICE, but significant PN peaks occurred during the early urban phase, attributable to the slower engine warm-up of the HEV. Machine learning analysis (Random Forest and Extra Trees Regressor) indicated that coolant temperature was the dominant driver of HEV PN emissions. The results indicate that powertrain characteristics and thermal management strongly influence real-world driving emissions, highlighting their importance for the further development of hybrid vehicles. Full article

This paper proposes a data-driven framework for simulating turbocharger (TC) failure scenarios and modelling specific fuel oil consumption (SFOC) degradation in two-stroke low-speed marine diesel engines. A GaussianCopula model was fitted to the joint distribution of fifteen variables, using approximately eleven months of operational sensor data (n = 480 clean records, 4 h interval, January–December 2014) taken from a container ship. Three physically motivated failure scenarios were produced: turbine blade fouling, bearing wear and compressor surge. Predictive models trained on the real dataset achieved R² = 0.9998 for TC RPM and R² = 0.984 for fuel flow when using Gradient Boosting with 5-fold cross-validation. Feature importance analysis showed that the dominant determinants of TC speed were scavenging air intake pressure (35.3%) and engine power (MCR, 31.3%). Shaft power (45.5%) and TC RPM (19.3%) together explained most of the fuel consumption variance. Simulated failure scenarios produced SFOC increases of +6.6% (fouling), +9.6% (surge), and +13.3% (bearing wear) when compared to a normal operating baseline of 202 g/kWh, which is in line with published empirical data from MAN B&W engine performance curves. An IsolationForest anomaly detector trained only on normal operating samples flagged failure scenario records at a rate of 17.5–23.7%, which demonstrates that moderate-sensitivity early warning detection is feasible from routine sensor streams. The results show that TC condition monitoring could serve as a leading indicator of fuel-efficiency degradation. This has significant implications for condition-based maintenance planning and CII (Carbon Intensity Indicator) compliance. Full article

With the development of shipping to harsh marine environment, it is very important to understand the transient behavior of a marine diesel engine in high sea conditions. Wave-induced hull motion will lead to severe load fluctuations and air-fuel ratio imbalance. In this study, an integrated simulation platform coupled with environmental loads, hull dynamics, propeller characteristics and a high-fidelity thermodynamic engine model was constructed to explore the response characteristics of the propulsion system. The model integrates a zero-dimensional multi-zone combustion method, turbocharger dynamic characteristics and an incremental PID governor, and has been verified based on the bench test data of TBD234V12 diesel engine and the 20 m Wigley standard ship. The simulation results under the sea conditions from level 7 to 9 show that the transient load has a nonlinear amplification effect. Specifically, from sea state 7 to sea state 9, the engine load fluctuation range expands by 2.0 times, while the main peak amplitude of speed fluctuation increases by 3.7 times. Furthermore, the peak exhaust pressure rises by 1.8 times, and the exhaust temperature fluctuation amplitude broadens by 35%. Frequency domain analysis further identified the low-frequency energy concentration phenomenon in the exhaust pressure spectrum and the precursor characteristics of compressor surge. The research results quantify the deterioration law of thermodynamic stability and mechanical stress under wave disturbance, and provide an important reference for the formulation of an engine robust control strategy and fatigue life assessment under high sea conditions. Full article

Health monitoring of marine turbochargers under real-ship operation is complicated by operating-condition variability, recurrent online cleaning, and limited fault labels. This study presents a maintenance-aware temporal contrastive autoencoder (TCCL-AE) for health index (HI) learning from multivariate real-ship monitoring data. The framework aims to learn an HI that tracks degradation while reducing sensitivity to short-term operating-condition fluctuations by incorporating maintenance information into latent-state evolution and introducing temporal contrastive learning. The model includes a temporal encoder for window-level feature extraction, a latent decomposition module for separating degradation-related and condition-related information, and a Health Coupling Module for representing maintenance-induced recovery. The training objective combines temporal contrastive learning, observation reconstruction, and maintenance consistency. Experiments on multi-voyage real-ship data indicate that the learned HI reflects long-term degradation evolution and maintenance-related recovery, while remaining comparatively smooth under variable operating conditions. The resulting HI provides a continuous representation for condition tracking and maintenance-related interpretation during long-horizon monitoring. Full article

In the current environmental and political scenario, hybrid vehicles play crucial roles in the transition to sustainable mobility. The role of internal combustion engines (ICEs) is also of utmost importance to comply with the even more stringent emissions regulations. To that end, also considering the need for increased power density in ICEs, turbocharging allows for improved performance and reduced emissions. Within this context, the present paper introduces the novelties of a patented turbo compound layout with supercharging capabilities, i.e., the Turbo Generator Electric Multistage Supercharger (TGEMS) system. The analysis also allowed for providing evidence of a “backpressure supercompensation effect” associated with rising exhaust backpressure in the ICE. TGEMS introduces a novel compressor group decoupled from the turbine. The analyses were carried out on a 2.0 L turbocharged gasoline direct injection engine. The “supercompensation” phenomenon was isolated using a stepwise procedure in which TGEMS was initially applied to the baseline engine to be exploited on a modified configuration featuring a downscaled turbine. The results were analyzed from the perspectives of specific fuel consumption reduction and total power output as well as operating flexibility increase. The results indicate that, in a context like TGEMS, the assumption that rising exhaust backpressure is always penalizing is no longer valid. Under higher backpressure conditions, TGEMS alone achieved −4.92% in specific fuel consumption at 5000 rpm, with +8.75% in maximum power output. Moreover, with the configuration with a downscaled turbine and the possibility to control the engine operating line, specific fuel consumption reductions of −7.93% at 5000 rpm and −6.83% at 3000 rpm were achieved. The maximum power output increment was +11.04%. These outcomes could open up to new downsizing perspectives and a new generation of “super-backpressured engines”. Full article

Hybridization in vehicle powertrains extends beyond the aggregate system level and can target individual components to enhance engine performance. While prior studies have highlighted the performance benefits of electrified turbochargers, this work focuses on mitigating engine-out emissions for a medium- to heavy-duty diesel engine with an electrified airpath. Unlike conventional engines and actuators, the alternative engine architecture with an electrified airpath provided superior airpath control. This is critical for fuel-led diesel engines, where the initial combustion cycles during the tip-in phase of a transient operate at a rich equivalence ratio. In this work, a 3.2 L two-cylinder opposed piston two-stroke (OP2S) engine equipped with an Electrically Assisted Turbocharger (EAT) and an electrically operated EGR pump was experimentally tested in a Hardware in the Loop (HIL) setup under transient conditions. Actuator positions were varied to identify strategies that mitigate soot and NO_x without compromising transient response. The experiments are discussed case-wise, where the effects of each airpath actuator, including fuel rate shaping, are analyzed, showing to what extent each strategy mitigates emissions. At the end, an optimized case is presented to the readers for their perusal. The electrified airpath, along with fuel rate shaping, demonstrated cumulative soot reduction up to 92% and NO_x emissions by 77% for a transient load step between 3 and 13 bar BMEP at a mid-engine speed of 1250 rpm. Full article

In recent years, numerous studies have focused on reducing emissions from modern reciprocating engines without compromising their performance characteristics. One promising approach is to use Mild-Hybrid engines as an alternative proposal to the conventional reciprocating ones. This study aims to investigate how the hybridization will impact the main performance variables and the pollutant emissions of a turbocharged, modern aircraft spark-ignition (SI) engine—specifically, the ROTAX 914. The engine is analyzed under three distinct operating conditions at three different altitudes, defined by different combinations of engine speed and throttle position, using conventional aviation fuel (AVGAS 100LL). The analysis is conducted using GT-POWER, an advanced engine simulation software that allows for complete engine modeling and parameterization across a wide range of operating conditions. The accuracy of the simulated engine model is validated by comparing its output to experimental data obtained from the engine’s technical manuals. Key performance indicators examined in this study include brake power (We), brake torque (Mσ), brake specific fuel consumption (BSFC), and emissions of nitrogen monoxide (NO) and carbon monoxide (CO). Therefore, the proposed model can be employed to investigate the operational behavior of the ROTAX 914 UL aircraft engine when integrated into a hybrid aircraft propulsion system, in which the engine is connected in series with an electric battery. In particular, the model enables parametric studies on the effects of varying engine–battery hybridization levels—defined as the respective contributions of the engine and the battery to the total propulsive power available at the aircraft propeller—on the main performance variables and emissions of the ROTAX 914 UL engine in different altitudes. The primary objective is to assess the effects of series hybridization on engine operation and its most significant emissions. This is accomplished by operating the ICE at a lower operating condition, because it is connected with a battery, which helps the engine deliver the required output power sooner. The results suggest that increasing the power output delivered by the battery, so the ICE is operating in lower loads, can significantly enhance the performance and environmental efficiency of a turbocharged aircraft SI engine at different flight altitudes. In conclusion, series hybridization presents a promising solution for improving present-day reciprocating SI engines. Full article

This paper presents an analysis of the dynamic parameters of vehicles powered by an electric drive unit based on a permanent magnet synchronous motor (PMSM) and a conventional drive system based on a spark-ignition combustion engine. The research subjects were a Mercedes-Benz EQA 250+ and an Audi A3 8V 35 TFSI with a turbocharged 1.5 dm³ engine. The paper presents an analysis of changes in power and torque as a function of engine speed (ICE) and driving speed of the electric vehicle (BEV). The study demonstrated fundamental differences, primarily the progression of the external characteristic curves of the engines and changes in vehicle dynamics. The research shows differences in the elasticity depending on the type of the drive motor. The research was conducted using a chassis dynamometer that allowed for a deeper understanding of the operation of the electric vehicle drive system and the identification of significant differences and dependencies in the external characteristics. Full article

Centrifugal compressors (CCs) are key components of marine power plants (MPPs), supporting engine boosting, boil-off gas (BOG) handling on liquefied natural gas (LNG) carriers, and auxiliary services such as heating, ventilation, and air conditioning (HVAC). However, recent publications are often fragmented by domain (aerodynamics, mechanical design, standards, and digitalization), complicating cross-domain engineering decisions for marine duty cycles. This structured review follows an explicit protocol to synthesize peer-reviewed studies (2015–2025) retrieved from Scopus and Web of Science and organizes the evidence by application class: turbocharger-integrated stages for marine diesel and gas-turbine engines, LNG/BOG compression trains, and auxiliary onboard services. The synthesis consolidates (i) aerodynamic KPIs (pressure ratio, efficiency, surge and stall margins, and operating range), (ii) mechanical and lifecycle enablers (seals, bearings, and rotordynamics), and (iii) quantified impacts of digital methods (control, diagnostics, and digital twins). Reported trends include single-stage pressure ratios of ~5.4–5.7, multistage overall pressure ratios exceeding 10, and surge-margin improvements of ~40–44% associated with advanced diffusers as well as casing and endwall treatments. Industrial case studies (non-marine) report downtime reductions of ~25–35% and maintenance-cost reductions of ~25%, while evaluated diagnostic datasets show high accuracy. Key gaps remain in marine-specific validation datasets and harmonized testing and data standards. Full article

This research presents the design, numerical analysis, and experimental validation of a compact radial turbine intended for mini-turbocharger applications in UAV power systems. To meet the stringent requirements of UAV propulsion—such as lightweight construction, high efficiency at small scales, and stable performance across varying operating altitudes—a test rig was constructed to experimentally estimate turbine torque and shaft power across selected operating conditions. Complementary CFD simulations were performed to evaluate aerodynamic behavior, including flow distribution, torque generation, and power output at multiple rotational speeds matched to experimental mass-flow rates. Additional high-speed CFD simulations were conducted to predict turbine performance in operational regimes typical of UAV engines, where experimental testing is challenging. The combined CFD–experimental methodology provides accurate performance prediction for micro-scale radial turbines across different volute geometries and operating conditions. The results contribute essential insights for the development of next-generation miniaturized turbochargers aimed at enhancing UAV engine efficiency, high-altitude capability, and overall flight endurance. Full article

Aviation hydrogen internal combustion engines represent a critical pathway for rapid decarbonization due to their reliability and compatibility with existing aircraft platforms. However, the significant reduction in air density at high altitudes causes severe power degradation in naturally aspirated port-fuel-injected hydrogen internal combustion engines, making turbocharging essential for maintaining propulsion capability. This study utilizes a combined experimental and simulation framework to investigate turbocharger matching for power recovery in a 1.4 L hydrogen engine. A simulation model was constructed and validated against experimental data within a 5% error margin to ensure technical accuracy. Theoretical compressor and turbine operating parameters were derived for altitudes ranging from 4 to 8 km, comparing two boost-pressure control strategies: variable geometry turbine and waste-gate turbine. The results demonstrate that both boosting strategies successfully restore sea-level power at altitudes up to 8 km, increasing high-altitude power output by approximately four-fold to five-fold compared to naturally aspirated conditions. Specifically, the variable of geometry turbine demonstrates superior overall performance, maintaining normalized turbine efficiencies between 78.4% and 96.3% while achieving lower pumping losses and improved brake thermal efficiency. These advantages arise from the variable geometry turbine’s ability to optimize exhaust-energy utilization across varying altitudes. This study establishes a quantitative methodology for turbocharger matching, providing essential guidance for developing efficient, high-altitude hydrogen propulsion systems. Full article

This paper presents an experimental investigation of hydrogen enrichment effects on combustion behavior and exhaust emissions in a self-developed micro gas turbine fueled with a propane–butane mixture. Hydrogen was blended with the base fuel in volume fractions of 0–30%, and combustion was examined under unloaded operating conditions at three global equivalence ratios (ϕ = 0.7, 1.1, and 1.3). The global equivalence ratio (ϕ) is defined as the ratio of the actual fuel–air ratio to the corresponding stoichiometric fuel–air ratio, with ϕ < 1 representing lean, ϕ = 1 stoichiometric, and ϕ > 1 fuel-rich operating conditions. The micro gas turbine is based on an automotive turbocharger coupled with a custom-designed counterflow combustion chamber developed specifically for alternative gaseous fuel research. Exhaust gas emissions of CO, CO₂, and NO_x were measured using a laboratory-grade FTIR analyzer (Horiba Mexa FTIR Horiba Ltd., Kyoto, Japan), while combustion chamber temperature was monitored with thermocouples. The results show that hydrogen addition significantly influences flame stability, combustion temperature, and emission characteristics. Increasing the hydrogen fraction led to a pronounced reduction in CO emissions across all equivalence ratios, indicating enhanced oxidation kinetics and improved combustion completeness. CO₂ concentrations decreased monotonically with hydrogen enrichment due to the reduced carbon content of the blended fuel and the shift of combustion products toward higher H₂O fractions. In contrast, NO_x emissions increased with increasing hydrogen content for all tested equivalence ratios, which is attributed to elevated local flame temperatures, enhanced reaction rates, and the formation of locally near-stoichiometric zones in the compact combustor. A slight reduction in NO_x at low hydrogen fractions was observed under near-stoichiometric conditions, suggesting a temporary shift toward a more distributed combustion regime. Overall, the findings demonstrate that hydrogen–propane–butane blends can be stably combusted in a micro gas turbine without major operational issues under unloaded conditions. While hydrogen addition offers clear benefits in terms of CO reduction and carbon-related emissions, effective NO_x mitigation strategies will be essential for future high-hydrogen microturbine applications. Full article

Direct injection in hydrogen engines enables flexible combustion control, improves engine efficiency, and reduces the risk of abnormal combustion. However, implementing this injection strategy is challenging due to the need to provide a relatively high volumetric fuel flow rate, achieve a specified degree of mixture stratification, and account for the functional and technological limitations of the injection system. These challenges highlight the relevance and objectives of the present study. The mathematical model of a turbocharged engine cycle has been refined to account for the influence of injection parameters on combustion kinetics. On the basis of mathematical modeling, the injection pressure and injector area were determined to ensure the specified injection conditions. For the late injection strategy, a method was proposed to select the start of injection based on a specified value of the “relative ignition timing” criterion. Engine operation was simulated across the full range of operating modes for both early and late injection strategies. The results show that the late injection strategy increases the maximum indicated thermal efficiency by approximately 2%, reduces peak in-cylinder pressure by about 1 MPa, lowers maximum nitrogen oxide emissions by a factor of 1.4, and ensures knock-free operation across all modes compared to early injection. Full article