Search Results

Abstract The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage.

Abstract The two-branch exhaust of an asymmetric twin-scroll turbocharged engine are asymmetrically and periodically complicated, which has great impact on turbine matching. In this article, a matching effect of turbine speed parameter on asymmetric twin-scroll turbines based on the exhaust pulse energy weight distribution of a heavy-duty diesel engine was introduced. First, it was built as an asymmetric twin-scroll turbine matching based on exhaust pulse energy distribution. Then, by comparing the average matching point and energy matching points on the corresponding turbine performance map, it is revealed that the turbine speed parameter of energy matching points was a significant deviation from the turbine speed parameter under peak efficiency, which leads to the actual turbine operating efficiency lower than the optimal state.

Abstract In this study, we have investigated the microstructural characteristics, the mechanical properties, and the dry sliding wear behavior of a ceramic coating consisting of zirconia (ZrO2) and alumina (Al2O3) deposited by flame spraying. A series of wear tests were carried out under a variety of loads and at two different sliding speeds. The evaluation included an examination of the coating microstructure, microhardness, coefficient of friction (COF), and wear resistance of the flame-sprayed coating. The results showed that the coatings had a perfectly structured micro-architecture and were metallurgically bonded to the substrate. The Al2O3 coating exhibited a fine granular structure with pores and oxides. The microstructure of Al2O3-10 wt.% ZrO2, on the other hand, showed a blocky structure with a uniform distribution of ZrO2 inclusions in the composite coating.

Abstract The notable increase in combustion noise in the 7–10 kHz band has become an issue in the development of pre-chamber jet ignition combustion gasoline engines that aim for enhanced thermal efficiency. Combustion noise in such a high-frequency band is often an issue in diesel engine development and is known to be due to resonance in the combustion chamber. However, there are few cases of it becoming a serious issue in gasoline engines, and effective countermeasures have not been established. The authors therefore decided to elucidate the mechanism of high-frequency combustion noise generation specific to this engine, and to investigate effective countermeasures. As the first step, in order to analyze the combustion chamber resonance modes of this engine in detail, calculation analysis using a finite element model and experimental modal analysis using an acoustic excitation speaker were conducted.

Abstract Improving thermal efficiency of an internal combustion engine is one of the most cost-effective ways to reduce life cycle-based CO2 emissions for transportation. Lean burn technology has the potential to reach high thermal efficiency if simultaneous low NOx, HC, and CO emissions can be achieved. Low NOx can be realized by ultra-lean (λ ≥ 2) spark-ignited combustion; however, the HC and CO emissions can increase due to slow flame propagation and high combustion variability. In this work, we introduce a new combustion concept called turbulent jet-controlled compression ignition, which utilizes multiple turbulent jets to ignite the mixture and subsequently triggers end gas autoignition. As a result, the ultra-lean combustion is further improved with reduced late-cycle combustion duration and enhanced HC and CO oxidation. A low-cost passive prechamber is innovatively fueled using a DI injector in the main combustion chamber through spray-guided stratification.

Abstract Composite ceramic brake discs are made of ceramic material reinforced with carbon fibers and offer exceptional advantages that translate directly into higher vehicle performance. In the case of an electric vehicle, it could increase the range of the vehicle, and in the case of conventional internal combustion engine vehicles, it means lower fuel consumption (and consequently lower CO2 emissions). These discs are typically characterized by complex internal geometries, further complicated by the presence of drilling holes on both friction surfaces. To estimate the aerothermal performance of these discs, and for the thermal management of the vehicle, a reliable model for predicting the air flowing across the disc channels is needed. In this study, a real carbon-ceramic brake disc with drilling holes was investigated in a dedicated test rig simulating the wheel corner flow conditions experimentally using the particle image velocimetry technique and numerically.

Abstract Neutron diffraction is a powerful tool for noninvasive and nondestructive characterization of materials and can be applied even in large devices such as internal combustion engines thanks to neutrons’ exceptional ability to penetrate many materials. While proof-of-concept experiments have shown the ability to measure spatially and temporally resolved lattice strains in a small aluminum engine on a timescale of minutes over a limited spatial region, extending this capability to timescales on the order of a crank angle degree over the full volume of the combustion chamber requires careful design and optimization of the engine structure to minimize attenuation of the incident and diffracted neutrons to maximize count rates.

Abstract Methanol is emerging as an alternate internal combustion engine fuel. It is getting attention in countries such as China and India as an emerging transport fuel. Using methanol in spark ignition engines is easier and more economical than in compression ignition engines via the blending approach. M85 (85% v/v methanol and 15% v/v gasoline) is one of the preferred blends with the highest methanol concentration. However, its physicochemical properties significantly differ from gasoline, leading to challenges in operating existing vehicles. This experimental study addresses the challenges such as cold-start operation and poor throttle response of M85-fueled motorcycle using a port fuel injection engine. In this study, M85-fueled motorcycle prototype is developed with superior performance, similar/better drivability, and lower emissions than a gasoline-fueled port-fuel-injected motorcycle.

Abstract Research into efficient internal combustion (IC) engines need to continue as the majority of vehicles will still be powered by IC or hybrid powertrains in the foreseeable future. Recently, lean-burn gasoline compression ignition (GCI) with high-pressure direct injection has been receiving considerable attention among the research community due to its ability to improve thermal efficiency and reduce emissions. To maximize GCI benefits in engine efficiency and emissions tradeoff, co-optimization of the combustion system and fuel formation is required. Thus, it is essential to study the spray characteristics of different fuels under engine-like operating conditions. In this work, high-pressure spray characteristics are experimentally studied for three blends of gasoline, namely, Naphtha, E30, and research octane number (RON) 98. A single-hole custom-built injector was used to inject fuel into a constant volume chamber with injection pressure varying from 40 MPa to 100 MPa.

Abstract Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance.

Abstract The use of data-driven algorithms for the integration or substitution of current production sensors is becoming a consolidated trend in research and development in the automotive field. Due to the large number of variables and scenarios to consider; however, it is of paramount importance to define a consistent methodology accounting for uncertainty evaluations and preprocessing steps, that are often overlooked in naïve implementations. Among the potential applications, the use of virtual sensors for the analysis of solid emissions in transient cycles is particularly appealing for industrial applications, considering the new legislations scenario and the fact that, to our best knowledge, no robust models have been previously developed.

Abstract Pre-chamber turbulent jet ignition (TJI) is a method of generating distributed ignition sites through multiple high-speed turbulent jets in order to achieve an enhanced burn rate in the engine cylinder when compared to conventional spark plug ignition. To study the gas-dynamic interactions between the two chambers in a gasoline engine, a three-dimensional numerical model was developed using the commercial CFD code CONVERGE. The geometry and parameters of the engine used were based on a modified turbocharged GM four-cylinder 2.0 L GDI gasoline engine. Pre-chambers with nozzle diameters of 0.75 mm and 1.5 mm were used to investigate the effect of pre-chamber geometry on pre-chamber charging, combustion, and jet formation. The local developments of gas temperature and velocity were captured by adaptive mesh refinement, while the turbulence was resolved with the k-epsilon model of the Reynolds averaged Navier–Stokes (RANS) equations.

Abstract Quantifying exhaust gas composition and temperature in vehicles with internal combustion engines (ICEs) is crucial to understanding and reducing emissions during transient engine operation. This is particularly important before the catalytic converter system lights off (i.e., during cold start). Most commercially available gas analyzers and temperature sensors are far too slow to measure these quantities on the timescale of individual cylinder-firing events, thus faster sensors are needed. A two-color mid-infrared (MIR) laser absorption spectroscopy (LAS) sensor for gas temperature and carbon monoxide (CO) mole fraction was developed and applied to address this technology gap. Two quantum cascade lasers (QCLs) were fiber coupled into one single-mode fiber to facilitate optical access in the test vehicle exhaust. The QCLs were time-multiplexed in order to scan across two CO absorption transitions near 2013 and 2060 cm–1 at 15 kHz.

Abstract Exhaust emission standards for road vehicles require on-board diagnostics (OBD) of all comprehensive powertrain components (CCMs) impacting pollutant emissions. The legislation defines the generic malfunction criteria and pollutant threshold limits to trigger the component functional degradation. The electric drivetrain in xEV (more than one propulsion energy converter) applications substitutes or supports the internal combustion engine (ICE) operation with electric machine (EM) power. Malfunctions in the electric drivetrain will lead to an increase in ICE power demand. Hence, the electric drive system is classified as a comprehensive component in the OBD legislation. The regulation defines monitoring of the EM performance. The malfunctions that could prevent the EM(s) from properly operating emission control strategies, including any ICE control activation or electric drivetrain performance degradation, should be monitored by the OBD system.

Abstract Lean combustion has the potential to achieve high thermal efficiency for internal combustion engines. However, natural gas (NG) engines often suffer from slow burning rates and large cyclic variations when adopting lean combustion. In this study, the effects of spark plug gaps (SPGs) on methane lean combustion are optically investigated under high ignition energy conditions. Synchronization measurements of in-cylinder pressure and high-speed photography are performed for combustion analysis. The results show that large SPGs with high ignition energy exhibit great improvement in engine combustion stability and power capability. Under ultra-lean conditions, a large SPG with a high ignition energy of 150–200 mJ can extend the lean limit to 1.55. Combustion images indicate that this is contributed by the enlarged initial flame kernel, which promotes early flame propagation.

Abstract The development of efficient and reliable ignition systems for lean fuel-air mixtures is of great interest for applications associated with the use of combustion in transportation, electricity production, and other heavy industries. In this study, we report the use of repetitive nanosecond pulsed surface discharges for the ignition of lean methane (CH4)-air mixtures at pressures above 1 bar. Powered by ten 10-ns voltage pulses at 10 kHz, a commercially available non-resistive spark plug was used to generate surface discharges, which were able to ignite CH4-air mixtures at 1.5 bar and with equivalence ratios (ϕ) ranging from 1.0 to 0.5. At the leanest conditions, e.g., ϕ ≤ 0.6, nitric oxide (NO) and nitrogen dioxide (NO2) emission were reduced to <10% of their values at ϕ = 1.0, demonstrating the advantage of lean burn in emission reduction.

Abstract This work describes an investigation of measurement techniques for the indicated mean effective pressure (IMEP) on a 55 cc single-cylinder, 4.4 kW, two-stroke, spark ignition (SI) engine intended for use on Group 1 and Group 2 remotely piloted aircraft (RPAs). Three different sensors were used: two piezoelectric pressure transducers (one flush mount and one measuring spark plug) for measuring in-cylinder pressure and one capacitive sensor for determining the top dead center (TDC) position of the piston. The effort consisted of three objectives: to investigate the merits of a flush mount pressure transducer compared to a pressure transducer integrated into the spark plug, to perform a parametric analysis to characterize the effect of the variability in the engine test bench controls on the IMEP, and to determine the thermodynamic loss angle for the engine.

Abstract The pre-chamber ignition system accelerates combustion efficiently by supplying multiple ignition points, high ignition energy, and strong turbulent disturbance. This system expands the lean combustion limit and improves combustion stability on natural gas engines. This work studied the effects of pre-chamber volume variations on combustion, performance, and emission behaviors of a natural gas lean-burn engine under experimental and numerical methods. Results show an increase in the pre-chamber volume from 0.3% to 4.4% of compression volume can increase the in-cylinder pressure in single-stage combustion. The energy and exergy efficiency of the engine Model-1.3% increased up to 43.7% and 41.9%, respectively, which are the highest values among the prepared models. Simultaneously, the model heat loss with the maximum pre-chamber volume was two times higher than the minimum pre-chamber volume.

Abstract As a carbon-free power with excellent performance, the direct injection (DI) hydrogen-fueled internal combustion engine (H2-ICE) has the potential to contribute to carbon dioxide (CO2)-neutral on-road transport solutions. Aiming at high thermal efficiency, the influences of key factors on thermal efficiency over wide operating conditions of a turbocharging DI H2-ICE were investigated under the lean-burn strategy. And the nitrogen oxides (NOx) emission characteristics region was clarified in the high efficiency. The results confirm the optimal ignition strategy with the CA50 of 8–9 crank angle degrees after top dead center (°CA ATDC). The late-injection strategy manifests a significant advantage in brake thermal efficiency (BTE) compared with the early-injection strategy, and this advantage can be amplified by the increased load or injection pressure. The effects of injection (EOIs) pressure on BTE exhibit different laws at different EOIs.

Abstract Natural gas (NG) can be compressed to a high pressure of around 200 bar for use in engines and other applications. Compressed natural gas (CNG) contains 87–92% methane (CH4) and has a low carbon-to-hydrogen ratio compared to other hydrocarbon (HC) fuels. Due to this, it can potentially reduce carbon dioxide (CO2) emissions by more than 20% compared to conventional fuels like diesel or gasoline. This makes CNG one of the most environmentally friendly fuels for internal combustion engines (ICEs). To improve the thermal efficiency of ICEs, higher compression ratios (CRs) and leaner combustion are essential. Since CNG is a gaseous fuel, it has several advantages over liquid fuels due to its favorable physical and chemical properties. A few of these advantages are minimal fuel evaporation issues, a low-carbon content in the fuel composition and a high-octane number. The CNG high-octane number allows for a high CR, resulting in higher thermal efficiency and lower emissions.