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An analysis method for characterizing fuel behavior during spark-ignition engine starting has been developed and applied to several sets of start-up data. The data sets were acquired from modern production vehicles during room temperature engine start-up. Two different engines, two control schemes, and two engine temperatures (cold and hot) were investigated. A cycle-by-cycle mass balance for the fuel was used to compare the amount of fuel injected with the amount burned or exhausted as unburned hydrocarbons. The difference was measured as “fuel unaccounted for”. The calculation for the amount of fuel burned used an energy release analysis of the cylinder pressure data. The results include an overview of starting behavior and a fuel accounting for each data set Overall, starting occurred quickly with combustion quality, manifold pressure, and engine speed beginning to stabilize by the seventh cycle, on average.

THE thermodynamic analysis of an internal-combustion engine, even in the idealized case, is in general more complex than a similar analysis of an engine cycle in which the fluid undergoes no chemical change. It is the purpose of this paper to show that, despite the inherent complexity of the problem, an exact solution by graphical methods is possible, and the method is very similar in nature to those used in connection with the Mollier diagram for steam. Two types of charts are presented, one descriptive of the thermodynamic properties of the airfuel mixture (and residual products of combustion) before combustion, the other descriptive of the properties of the equilibrium mixture after combustion. Full allowance is made for the variation of specific heats with temperature and for the complex dissociation at the high temperatures attained after combustion. All calculations are based on the most recent basic thermodynamic data available in the literature.

A new ring pack model has been developed based on the curved beam finite element method. This paper describes the second part of this model: simulating oil transport around the ring pack system (two compression rings and one twin-land oil control ring (TLOCR)) through the ring-liner interfaces by solving the oil film thickness on the liner. The ring dynamics model in Part 1 calculates the inter-ring gas pressure and the ring dynamic twist which are used in the ring-liner lubrication model as boundary conditions. Therefore, only in-plane conformability is calculated to obtain the oil film thickness on the liner. Both global process, namely, the structural response of the rings to bore distortion and piston tilt, and local processes, namely, bridging and oil-lube interaction, are considered. The model was applied to a passenger car engine.

The NOx emissions during the crank-start and cold fast-idle phases of a GDI engine are analyzed in detail. The NOx emissions of the first 3 firing cycles are studied under a wide set of parameters including the mass of fuel injected, start of injection, and ignition timing. The results show a strong dependence of the NOx emissions with injection timing; they are significantly reduced as the mixture is stratified. The impact of different valve timings on crank-start NOx emissions was analyzed. Late intake and early exhaust timings show similar potential for NOx reduction; 26-30% lower than the baseline. The combined strategy, resulting in a large symmetric negative valve overlap, shows the greatest reduction; 59% lower than the baseline. The cold fast-idle NOx emissions were studied under different equivalence ratios, injection strategies, combustion phasing, and valve timings. Slightly lean air-fuel mixtures result in a significant reduction of NOx.

In a previous study, a wide range of gasolines with RON∼90 were tested in a single cylinder engine operated in HCCI mode using negative valve overlap, and all were found to have very similar behavior near the low-load limit. Here we broaden the range of gasolines to include PRF90 and PRF60. At high engine speed, both PRF60 and PRF90 behave similarly to all the other gasolines tested. However, at 1000 RPM, PRF90 is very different from all the other gasolines: it ignites very late, and the engine cannot be operated at low load. Simulations using a popular fuel chemistry model cannot distinguish PRF60 and PRF90 under these conditions. However, a new fuel chemistry model correctly shows the onset of fuel sensitivity at low engine speed. Sensitivity analyses indicate the low-load limit at low engine speed strongly depend on both the chemistry parameters and on the heat-transfer parameters.

The oil control ring (OCR) controls the supply of lubricating oil to the top two rings of the piston ring pack and has a significant contribution to friction of the system. This study investigates the two most prevalent types of OCR in the automotive market: the twin land oil control ring (TLOCR) and three piece oil control ring (TPOCR). First, the basis for TLOCR friction on varying liner roughness is established. Then the effect of changing the land width and spring tension on different liner surfaces for the TLOCR is investigated, and distinct trends are identified. A comparison is then done between the TLOCR and TPOCR on different liner surfaces. Results showed the TPOCR displayed different patterns of friction compared the TLOCR in certain cases.

The NOx emission and knock characteristics of a PFI engine operating on ethanol/gasoline mixtures were assessed at 1500 and 2000 rpm with λ =1 under Wide-Open-Throttle condition. There was no significant charge cooling due to fuel evaporation. The decrease in NOx emission and exhaust temperature could be explained by the change in adiabatic flame temperature of the mixture. The fuel knock resistance improved significantly with the gasohol so that ignition could be timed at a value much closer or at MBT timing. Changing from 0% to 100% ethanol in the fuel, this combustion phasing improvement led to a 20% increase in NIMEP and 8 percentage points in fuel conversion efficiency at 1500 rpm. At 2000 rpm, where knocking was less severe, the improvement was about half (10% increase in NIMEP and 4 percentage points in fuel conversion efficiency).

A model for calculating the residual gas fraction in spark ignition engines has been formulated. The model accounts explicitly for the contribution due to the back flow of exhaust gas to the cylinder during the valve overlap period. The model has been calibrated with in-cylinder hydrocarbon measurements at different values of intake pressure, engine speed, and valve overlap timings.

PARAMOUNT among the problems relating to the efficiency of the internal-combustion engine is that of breathing capacity, or air consumption. Considering volumetric efficiency to be the most valuable parameter in an analytical or experimental approach to this problem, the authors of this paper have devoted several years of study to this factor in relation to 4-stroke engines. The studies have resulted in extensive findings, some of which have already been published. This paper attempts to bring together in readable form the results of the work to date, including both published and unpublished data. The authors discuss in detail the effect of volumetric efficiency on operating variables, piston speed, inlet-valve flow capacity, cylinder design, and size. They introduce a gulp factor, the inlet-valve Mach index, and explain how this factor can be used to guide engineers.

The distribution of lubricating oil plays a critical role in determining the friction between piston skirt and cylinder liner, which is one of the major contributors to the total friction loss in internal combustion engines. In this work, based upon the experimental observation an existing model for the piston secondary motion and skirt lubrication was improved with a physics-based model describing the oil film separation from full film to partial film. Then the model was applied to a modern turbo-charged SI engine. The piston-skirt FMEP predicted by the model decreased with larger installation clearance, which was also observed from the measurements using IMEP method at the rated. It was found that the main period of the cycle exhibiting friction reduction is in the expansion stroke when the skirt only contacts the thrust side for all tested installation clearances.

Lubricating oil consumption (LOC) is a direct source of hydrocarbon and particulate emissions from internal combustion engines. LOC also inhibits the lifetime of exhaust aftertreatment system components, preventing their ability to effectively filter out other harmful emissions. Due to its influence on piston ring- bore conformability, bore distortion is arguably the most critical parameter for engine designers to consider in prevention of LOC. Bore distortion also has a significant influence on the contact forces between the piston ring and cylinder wall, which determine the wear rate of the ring and cylinder wall and can cause durability issues. Two drivers of bore distortion: thermal expansion and head bolt stresses, are routinely considered in conformability and contact analyses. Separately, bore distortion/vibration due to piston impact and combustion/cylinder pressures has been previously analyzed in wet liner engines for coolant cavitation and noise considerations.

In an engine system, the piston pin is subjected to high loading and severe lubrication conditions, and pin seizures still occur during new engine development. A better understanding of the lubricating oil behavior and the dynamics of the piston pin could lead to cost- effective solutions to mitigate these problems. However, research in this area is still limited due to the complexity of the lubrication and the pin dynamics. In this work, a numerical model that considers structure deformation and oil cavitation was developed to investigate the lubrication and dynamics of the piston pin. The model combines multi-body dynamics and elasto-hydrodynamic lubrication. A routine was established for generating and processing compliance matrices and further optimized to reduce computation time and improve the convergence of the equations. A simple built-in wear model was used to modify the pin bore and small end profiles based on the asperity contact pressures.

Protecting the piston ring and liner interface is critical to the proper operation of internal combustion engines. Specifically, the dry region, which is the portion of the liner above the Top Dead Center (TDC) of the Oil Control Ring (OCR), needs proper lubrication to reduce wear and to maintain sustainability. However, the mechanisms by which oil is distributed to such region have not been investigated. This paper presents the first attempt to understand dry region lubrication by means of the oil-gas interaction below the top ring gap through a combination of experimental and modeling approaches. An optical engine with 2D Laser Induced Fluorescence (2D-LIF) technique was applied to visualize the oil flow below the top ring gap. It was observed that the two vortices downstream the top ring gap can cause oil bridging towards the liner, providing lubrication to the ring-liner interface.

Ground impact caused by road debris can result in very severe fire accident of Electric Vehicles (EV). In order to study the ground impact accidents, a Finite Element model of the battery pack structure is carefully set up according to the practical designs of EVs. Based on this model, the sequence of the deformation process is studied, and the contribution of each component is clarified. Subsequently, four designs, including three enhanced shield plates and one enhanced housing box, are investigated. Results show that the BRAS (Blast Resistant Adaptive Sandwich) shield plate is the most effective structure to decrease the deformation of the battery cells. Compared with the baseline case, which adopts a 6.35-mm-thick aluminum sheet as the shield plate, the BRAS can reduce the shortening of cells by more than 50%. Another type of sandwich structure, the NavTruss, can also improve the safety of battery pack, but not as effectively as the BRAS.

Accurately predicting real-world vehicle energy consumption is essential for optimizing vehicle designs, enhancing energy efficiency, and developing effective energy management strategies. This paper presents a data-driven approach that utilizes machine learning techniques and a comprehensive dataset of vehicle parameters and environmental factors to create precise energy consumption prediction models. The methodology involves recording real-world vehicle data using data loggers to extract information from the CAN bus systems for ICE and hybrid electric, as well as hydrogen and battery fuel cell vehicles. Data cleaning and cycle-based analysis are employed to process the dataset for accurate energy consumption prediction. This includes cycle detection and analysis using methods from statistics and signal processing, and then pattern recognition based on these metrics.

Internal combustion (IC) engines still power most of the vehicles on road and will likely to remain so in the near future, especially for heavy duty applications in which electrification is typically more challenging. Therefore, continued improvements on IC engines in terms of efficiency and longevity are necessary for a more sustainable transportation sector. Two important design objectives for heavy duty engines with wet liners are to reduce friction loss and to lower the risks of cavitation damages, both of which can be greatly influenced by the piston-liner clearance and the design of the piston skirt. However, engine design optimization is difficult due to the nonlinear interactions between the key design variables and the design objectives, as well as the multi-physics and multi-scale nature of the mechanisms that are relevant to the design objectives.

Recent studies have shown that for a given RON, fuels with a higher sensitivity (RON-MON) tend to have better antiknock performance at most knock-limited conditions in modern engines. The underlying chemistry behind fuel sensitivity was therefore investigated to understand why this trend occurs. Chemical kinetic models were used to study fuels of varying sensitivities; in particular their autoignition delay times and chemical intermediates were compared. As is well known, non-sensitive fuels tend to be paraffins, while the higher sensitivity fuels tend to be olefins, aromatics, diolefins, napthenes, and alcohols. A more exact relationship between sensitivity and the fuel's chemical structure was not found to be apparent. High sensitivity fuels can have vastly different chemical structures. The results showed that the autoignition delay time (τ) behaved differently at different temperatures. At temperatures below 775 K and above 900 K, τ has a strong temperature dependence.