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Abstract One of the key factors for accurate mass burn fraction and energy conversion point calculations is the accuracy of the compression ratio. The method presented in this article suggests a workflow that can be applied to determine or correct the compression ratio estimated geometrically or measured using liquid displacement. It is derived using the observation that, in a motored engine, the heat losses are symmetrical about a certain crank angle, which allows for the derivation of an expression for the clearance volume [1]. In this article, a workflow is implemented in real time, in a current production engine indicating system. The goal is to improve measurement data quality and stability for the energy conversion points calculated during measurement procedures. Experimental and simulation data is presented to highlight the benefits and improvement that can be achieved, especially at the start of combustion.

Abstract An in-cylinder combustion analysis and a computational fluid dynamics (CFD) coolant flow analysis were performed using AVL FIRE software, which provided the heat transfer boundary conditions (HTBCs) to the temperature field calculation of the cylinder head. Based on the measured material performance parameters such as stress-strain curve under different temperatures and E-N curve, creep, and oxidation data material performance, the cylinder head-gasket-cylinder block finite element analysis (FEA) was performed. According to the temperature field calculation results, the maximum temperature of the cylinder head is 200°C that is within the limit of ALU material. The temperature of the water is more than 21.1°C below the critical burnout point temperature. The high-cycle fatigue (HCF) and thermal-mechanical fatigue (TMF) analysis of the cylinder head were performed by FEMFAT software.

Abstract In recent years, lean-burn gasoline Spark-Ignition (SI) engines have been a major subject of investigations. With this solution, in fact, it is possible to simultaneously reduce NOx raw emissions and fuel consumption due to decreased heat losses, higher thermodynamic efficiency, and enhanced knock resistance. However, the real applicability of this technique is strongly limited by the increase in cyclic variation and the occurrence of misfire, which are typical for the combustion of homogeneous lean air/fuel mixtures. The employment of a Pre-Chamber (PC), in which the combustion begins before proceeding in the main combustion chamber, has already shown the capability of significantly extending the lean-burn limit. In this work, the potential of an ultralean PC SI engine for a decisive improvement of the thermal efficiency is presented by means of numerical and experimental analyses.

Abstract Direct dual fuel stratification (DDFS) strategy benefits the advantages of the RCCI and PPC strategies simultaneously. DDFS has improved control over the heat release rate, by injecting a considerable amount of fuel near TDC, compared to RCCI. In addition, the third injection (near TDC) is diffusion-limited. Consequently, piston bowl geometry directly affects the formation of emissions. The modified piston geometry was developed and optimized for RCCI by previous scholars. Since all DDFS experimental tests were performed with the modified piston profile, the other piston profiles need to be investigated for this strategy. In this article, first, a comparative study between the three conventional piston profiles, including the modified, stock, and scaled pistons, was performed. Afterward, the gasoline injector position was shifted to the head cylinder center for the stock piston. NOX emissions were improved; however, soot was increased slightly.

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 In recent years, several innovative diesel combustion systems were developed and optimized in order to enhance the air and injected fuel mixing for engine efficiency improvements and to mitigate the formation of fuel-rich regions for soot emissions reduction. With these aims, a three-dimensional computational fluid dynamics (3D-CFD) numerical study was carried out in order to evaluate the impact of three different piston bowl geometries on a passenger car four-cylinder diesel engine, 1.6 liters. Once the numerical model was validated considering the baseline re-entrant bowl, two innovative bowl geometries were defined: one based on the stepped-lip bowl; the other including a number of radial bumps equal to the nozzle holes number. Firstly, the rated power engine operating condition was investigated under nonreacting conditions to evaluate the piston bowl effects on the in-cylinder mixing.

Abstract With highway vehicles using over 20% of the total energy consumption in the United States, making strides in improving their fuel economy will positively influence the nation’s environmental impact. One methodology to accomplish this outcome is by reducing vehicle weight. In this regard, since the internal combustion (IC) engine is a major contributor to the mass of an automobile, it is an ideal area to target. Prior efforts in this area include using alternative materials (e.g., aluminum or magnesium) to decrease weight. Here, additive manufacturing (AM) is an appealing option due to its freedom from typical manufacturing constraints and the ability to produce highly optimized designs using nonconventional powertrain materials (e.g., titanium). The use of AM has the potential to increase reliability, improve performance, decrease production cost, and possibly minimize the number of parts.

Abstract Cavitation erosion caused by high-frequency vibrating walls can appear in the cooling circuit of internal combustion engines along the liners. The vibrations caused by the mechanical forces acting on the crank drive can lead to temporary regions of low pressure in the coolant with local vapor formation, and vapor collapse close to the liner walls leads to erosion damage, which can strongly reduce the lifetime of the entire engine. The experimental investigation of this phenomenon is so time consuming and expensive, which it is usually not feasible during the design phase. Therefore, numerical tools for erosion damage prediction should be preferred. This study presents a numerical workflow for the prediction of cavitation erosion damages by coupling a three-dimensional (3D) Multi-Body-Dynamic (MBD) simulation tool with a 3D Computational Fluid Dynamics (CFD) solver.

Abstract Currently, the governments are encouraging automotive vehicle manufacturers to produce electric vehicles (EVs) as these vehicles have a zero-emission footprint. Generally, the EVs are expected to be quieter compared to internal combustion engine (ICE) vehicles. But the absence of engine noise in EVs brings more challenges for noise, vibration, and harshness (NVH) as the other noise sources become more audible. Most of these noise sources are tonal in nature and, hence, cause discomfort to the passengers. The present work is related to the noise refinement in a pure EV. The dominant noise sources observed in this vehicle are the electric powertrain, cooling fan, and air compressor. The powertrain consists of a traction motor and a gearbox (GB) with a planetary gear system. The root cause identification of electric powertrain noise has been investigated with masking trials and with the acoustic camera.

Abstract In stationary natural gas engines, lean-burn combustion offers higher engine efficiencies with simultaneous compliance with emission regulations. A prominent problem that one encounters with lean operation is cyclic variations. Advanced ignition systems offer a potential solution as they suppress cyclic variations in addition to extending the lean ignition limit. In this article, the performance of three ignition systems-conventional spark ignition (SI), single-point laser ignition (LI), and prechamber equipped laser ignition (PCLI)-in a single-cylinder natural gas engine is presented. First, a thorough discussion regarding the efficacy of several metrics, in addition to coefficient of variation of indicated mean effective pressure (COV_IMEP), in representing combustion instability is presented. This is followed by a discussion about the performance of the three ignition systems at a single operational condition, that is, same excess air ratio (λ) and ignition timing (IT).

Abstract This article presents a misfire detection index for motorcycles with a single-cylinder engine. Compared with automobiles with multicylinder engines, attempts to diagnose single-cylinder motorcycle engine misfires have been rare. Therefore, a new index, detrended engine rpm amplitude (DERA), is proposed to detect misfires using tooth time measured by the crankshaft position sensor; thus, there is no additional cost for the DERA index. This index is defined as the difference between the squares of the maximum and minimum values of engine speed (rpm) detrended by the engine speed trend line, instead of the linear regression method. Thus calculating the DERA index becomes simple and fast, and it is advantageous to reduce the computation time. Here the engine speed trend line is a line connecting the engine speeds at the first teeth of the current and subsequent cycles.

Abstract The article presents the development of a lean approach for virtual electronic control unit (ECU) calibration. In this calibration method, virtual models are used to improve the calibration quality or reduce the calibration effort. Unlike state-of-the-art approaches, no dedicated engine simulation models for hardware-in-the-loop (HiL) operation are utilized. The developed engine simulation consists of physical ECU real-time capable 0D models. Major benefit of this approach is the multiple use of the developed models for virtual calibration of customer ECUs and vehicle operation using rapid-control-prototyping-ECUs (RCP-ECUs). The engine model consists of a physical air path, an air charge model, a gas exchange and a torque model as well as a novel mathematical combustion and exhaust gas temperature model. The configuration of the engine model was done for a turbocharged four-cylinder gasoline reference engine.

Abstract Gasoline compression ignition (GCI) is a family of combustion strategies that can be used to achieve low emissions and fuel consumption in medium- and heavy-duty applications while taking advantage of projected cost advantages of gasoline over diesel fuel in the future. In particular, high fuel stratification GCI (HFS-GCI) has been shown to have CDC-like thermal efficiency and combustion control by utilizing near-TDC injection timings to achieve a principally mixing-controlled combustion event. The stability of HFS-GCI combustion at low loads has been shown to be the principal challenge to its implementation in production applications and in this study, a novel class of cylinder deactivation strategies to achieve stable HFS-GCI combustion down to no-load (0 kW brake power) is proposed and studied. 1D simulations were carried out in GT-POWER and coupled experiments were carried out in a single-cylinder medium-duty test cell with an on-road 87AKI gasoline fuel.

Abstract The main technical barrier to commercial use of microturbines is its low efficiency, not exceeding 15%. Efficiency and specific power are as high as the Turbine Inlet Temperature (TIT), generally limited to 950°C in microturbines, as its tiny rotors make internal blade cooling impossible. This work uses Computational Fluid Dynamics (CFD) to develop an external cooling system of the blades of a microturbine by incorporating a compressor into the disk to blow air over the blades’ walls. The engine used as the basis of the work is the FD-3/64. The work was divided into two steps. In the first, Step 1, the reactive flow in the combustor was simulated to obtain the boundary conditions for Step 2. In Step 2, the flow through the turbine wheel during rotation is simulated. Four rotor models were simulated.

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