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Abstract Gasoline particulate filters (GPFs) are important aftertreatment components that enable gasoline direct injection (GDI) engines to meet European Union (EU) 6 and China 6 particulate number emissions regulations for nonvolatile particles greater than 23 nm in diameter. GPFs are rapidly becoming an integral part of the modern GDI aftertreatment system. The Active Exhaust Tuning (EXTUN) Valve is a butterfly valve placed in the tailpipe of an exhaust system that can be electronically positioned to control exhaust noise levels (decibels) under various vehicle operating conditions. This device is positioned downstream of the GPF, and variations in the tuning valve position can impact exhaust backpressures, making it difficult to monitor soot/ash accumulation or detect damage/removal of the GPF substrate. The purpose of this work is to present a unique example of subsystem control and diagnostic architecture for an exhaust system combining GPF and EXTUN.

Abstract More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.

Abstract This article serves as a proof-of-concept and feasibility analysis regarding a variable compression ratio (VCR) engine design utilizing an exhaust valve opening during the compression stroke to vary the compression ratio instead of the traditional method of changing the cylinder or piston geometry patented by Ford, Mercedes-Benz, Nissan, Peugeot, Gomecsys, et al. [1]. In this concept, an additional exhaust valve opening was used to reduce the virtual compression ratio of the engine, without geometric changes. A computational fluid dynamic model in ANSYS Forte was used to simulate a single-cylinder, cold flow, four-stroke, direct injection engine cycle. In this model, the engine was simulated at a compression ratio of 10:1. Then, the model was modified to a compression ratio of 17:1. Then, an additional valve opening at the end of the compression stroke was added to the 17:1 high compression model.

Abstract The free piston linear generator (FPLG) is a novel machine that functions as an Auxiliary Power Unit (APU) for hybrid electric vehicles, which contains two opposed free piston engines and one linear generator between them. FPLG has attracted extensive interest for its potential advantages in terms of high power density and multi-fuel flexibility. The guarantee of FPLG generating electricity steadily and efficiently is the high controllability of compression ratio. In this article, a control-oriented discrete-time model was established based on Otto cycle. Since the fluctuation of in-cylinder pressure caused by instable fuel injection mass and combustion process is the main disturbance, a composite controller is designed to precisely control the compression ratio of FPLG. The composite controller is made up of a feedforward controller and a feedback tracking controller.

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Abstract The article describes the results achieved in developing a new diesel combustion system for passenger car application that, while capable of high power density, delivers excellent fuel economy through a combination of mechanical and thermodynamic efficiencies improvement. The project stemmed from the idea that, by leveraging the high fuel injection pressure of last generation common rail systems, it is possible to reduce the engine peak firing pressure (pfp) with great benefits on reciprocating and rotating components’ light-weighting and friction for high-speed light-duty engines, while keeping the power density at competitive levels. To this aim, an advanced injection system concept capable of injection pressure greater than 2500 bar was coupled to a prototype engine featuring newly developed combustion system. Then, the matching among these features has been thoroughly experimentally examined.

Abstract Higher water evaporation and proper water vapor distribution in the cylinder are very vital for improving emission and performance characteristics of water-injected engines. The concentration of water vapor should be higher and uniform near the walls of the combustion chamber and nil at the spark plug location. In direct water-injected engines, water evaporation, vapor distribution, and spray impingement are highly dependent on injector parameters, viz., water injector orientation (WIO), location, and spray angle. Therefore, in this article, a computational fluid dynamics (CFD) investigation is conducted to study the effects of water injector spray angle (WISA), and WIO on the water evaporation, emission, and performance characteristics of a four-stroke, wall-guided gasoline direct injection (GDI) engine. The WISA is varied from 10° to 35°, whereas the WIO is varied from 15° to 35° in steps of 5°.

Abstract Interactions between fuel sprays and stepped-lip diesel piston bowls can produce turbulent flow structures that improve efficiency and emissions, but the underlying mechanisms are not well understood. Recent experimental and simulation efforts provide evidence that increased efficiency and reduced smoke emissions coincide with the formation of long-lived, energetic vortices during the mixing-controlled portion of the combustion event. These vortices are believed to promote fuel-air mixing, increase heat-release rates, and improve air utilization, but they become weaker as main injection timing is advanced nearer to the top dead center (TDC). Further efficiency and emissions benefits may be realized if vortex formation can be strengthened for near-TDC injections. This work presents a simulation-based analysis of turbulent flow evolution within a stepped-lip combustion chamber.

Abstract Cycle-by-cycle combustion prediction in real time during engine operation can serve as a vital input for operating at optimal performance conditions and for emission control. In this work, a real-time capable physics-based combustion model has been proposed for the prediction of the heat release rate in a direct injection diesel engine. The model extends the approaches proposed earlier in the literature by considering spray dynamics such as spray penetration and Sauter mean diameter in order to calculate the mass of evaporated fuel from the spray. Wall impingement of the liquid spray is predicted by considering the liquid length based on the prevailing in-cylinder conditions. These effects are considered even after the hydraulic end of injection till the last droplet of fuel impinges on the combustion chamber wall. The fuel evaporated from the wall film and its contribution to the kinetic energy of the charge are also considered.

Abstract Diesel engines are an important technology for transportation of both people and goods. However, historically they have suffered a significant downside of high soot and nitrogen oxides (NOx) emissions. Recently, ducted fuel injection (DFI) has been demonstrated to attenuate soot formation in compression-ignition engines and combustion vessels by 50% to 100%. This allows for diesel engines to be run at low-NOx emissions that would have otherwise produced significantly more soot due to the soot/NOx tradeoff. Currently the root causes of this soot attenuation are not well understood. To be able to better optimize DFI for use across a variety of engines and conditions, it is important to understand clearly how it works. This study expands on the current understanding of DFI by using numerical modeling under nonreacting conditions to provide insights about the roles of entrainment and mixing that would have been much more challenging to obtain experimentally.

Abstract The article discusses the possibilities of detecting defects in the marine diesel engine injection system on a selected example. Basing on statistical data, it was pointed out that these engines had a significant failure rate in relation to the failure rate of other machinery and equipment used on ships. First, it concerns damage of the elements of the injection systems. Therefore, basing on the results of the authors’ own research, the possibility of improving diagnostic methods of the injection system that can be used in the ship operation process was pointed out. First, high diagnostic effectiveness of the analysis of pressure changes measured in the injection system was pointed out here. At the same time, taking into account the difficulties of such measurement in the conditions of the ship’s power plant, it has been shown that very good diagnostic effects can be obtained by using indicator diagrams to calculate heat release characteristics.

Abstract Diesel engines include systems for cooling, lubrication, and fuel injection and contain a variety of components. A malfunction in any of the engine systems or the presence of any faulty element influences engine performance and deteriorates its components. This research is concerned with the untimely appearance of vital cracks in the liners of a turbocharged heavy-duty Diesel engine. To find the root causes for premature failure, rigorous examinations through visual observations, material characterization, and metallographic investigations are performed. These include Scanning Electron Microscope (SEM) and Energy-Dispersive Spectroscopy (EDS), fracture mechanics analysis, and performance examination, which are also followed by Finite Element Moldings. To find the proper remedy to resolve the problem, drawing a precise and reliable picture of the engine’s operating conditions is required.

Abstract Recent research has demonstrated that gasoline compression ignition (GCI) can improve the soot-oxides of nitrogen (NOx) trade-off of conventional diesel engines due to the beneficial properties of light distillate fuels. In addition to air handling and aftertreatment, fuel systems also require further development to realize the potential efficiency and emissions benefits of GCI. Injector one-dimensional (1-D) hydraulic modeling is an important design tool used for this purpose. The current study is a continuation of prior work that used computed physical fuel properties and hydraulic models to accurately simulate high-pressure injection behavior relevant to GCI. With respect to fuel characteristics for the model, physical properties were validated by direct comparison to measurements at temperatures and pressures reaching 150°C and 2500 bar, respectively.

Abstract Electrostatic discharge during aircraft refueling operations has long been recognized as a safety hazard. To reduce the chances of this happening, different practices were developed, the most common being the addition of a static dissipator additive (SDA). Nowadays, the SDA is a well-established requirement in all the leading jet-fuel specifications and is in widespread use in commercial and military aviation industries. To deepen the understanding of the electrostatic behavior of nonconductive jet fuel and SDA, the Israeli Air Force (IAF) has conducted small-scale refueling tests in a simulated aircraft fuel tank. In these tests, the effect of flow rate, residence time, SDA concentration, bounding, grounding, and the method of filling were evaluated by measuring the electrostatic field strength generated. The simulation of the aircraft fuel tank was obtained using a nonconductive plastic tank jointed with a small faucet at the bottom.

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Abstract CNG is at present retaining a growing interest as a factual alternative to traditional fuels for SI engines, thanks to its high potentials in reducing the engine-out emissions. Increasing thrust into the exploitation of NG in the transport field is in fact produced by the even more stringent emission regulations that are being introduced into the worldwide scenario. Moreover, the transport sector accounts for the 27% of the overall energy consumptions and up to the 13% in terms of global emissions. The present paper aims at deeply investigating into the potentials of a heavy-duty engine running on CNG and equipped with two different injection systems, an advanced single point (SP) one and a prototype multi-point (MP) one. The considered 7.8-liter engine was designed and produced to implement a SP strategy and hence modified to run with a dedicated MP system.

Abstract Turbulent jet ignition (TJI) is a pre-chamber initiated combustion technology that has been demonstrated to provide low temperature, faster burn rate combustion of lean and intake charge diluted air-fuel mixtures. Dual mode turbulent jet ignition (DM-TJI) is a novel concept wherein a separate air supply is provided for the pre-chamber apart from the conventional auxiliary fuel as supplied for TJI systems. The current study aims to extend the lean flammability limit of a gasoline-fueled engine using DM-TJI. Ignition delay time and combustion behavior of ultra-lean iso-octane/air mixture (Lambda ≅ 3.0) was studied using a TJI-based optically accessible rapid compression machine. High-speed fuel spray recordings in the pre-chamber were obtained using borescope imaging setup. Images of the reacting turbulent jet and subsequent combustion in the main chamber were captured using a visible color camera.

Abstract The influence of the intake valve lift of two Miller cycles on the in-cylinder flow field inside a DISI engine is studied experimentally since changes of the engine flow field directly affect the turbulent mixing and the combustion process. For the analysis of the impact of the valve timing on the general flow field topology and on the large-scale flow structures, high-speed stereo-scopic particle-image velocimetry measurements are conducted in the tumble plane and the cross-tumble plane. The direct comparison to a standard Otto intake valve lift curve reveals evidently different impacts on the flow field for both Miller cam shafts. A Miller cycle that features late intake valve closing shows a flow field comparable to the standard Otto valve timing and a tumble vortex of strong intensity can be identified.

Abstract A fully predictive one-dimensional model of a Common Rail injection apparatus for diesel passenger cars is presented and discussed. The apparatus includes high-pressure pump, high-pressure pipes, injectors, rail and a fuel-metering valve that is used to control the rail pressure level. A methodology for separately assessing the accuracy of the single submodels of the components is developed and proposed. The complete model of the injection system is finally validated by means of a comparison with experimental high-pressure and injected flow-rate time histories. The predictive model is applied to examine the fluid dynamics of the injection system during either steady-state or transient operations. The influence of the pump delivered flow-rate on the rail-pressure time history and on the injection performance is analysed for different energizing times and nominal rail pressure values.

Abstract In order to improve performance and minimize pollutant emissions in gasoline turbocharged direct-injection (GTDi) engines, different injection strategies and technologies are being investigated. The inclusion of exhaust gas recirculation (EGR) and the variation of the start of injection (SOI) are some of these strategies that can influence the air-to-fuel (AF) mixture formation and consequently in the combustion process and pollutant emissions. This paper presents a complete study of the engine performance, pollutant emissions and aftertreatment efficiency that produces the SOI variation with a fixed EGR rate in a 4-cylinder, turbocharged, gasoline direct-injection engine with 2.0 L displacement. The equipment used in this study are TSI-EEPS for particle measurement and HORIBA MEXA 1230-PM for soot measurement being HORIBA MEXA 7100-DEGR with a heated line selector the system employed for regulated gaseous emission measurement and aftertreatment evaluation.