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Technical Paper

Ensemble Empirical Mode Decomposition for Characterising Exhaust Nano-Scale Particle Emissions of a Turbocharged Gasoline Power Unit

2023-10-31
2023-01-1665
This paper presents a method for analysing the characteristics of nano-scale particles emitted from a 1.6 Litre, 4-stroke, gasoline direct injection (GDI) and turbocharged spark ignition engine fitted with a three-way catalytic converter. Ensemble Empirical Mode Decomposition (EEMD) is employed in this work to decompose the nano-scale particle size spectrums obtained using a differential mobility spectrometer (DMS) into Intrinsic Mode Functions (IMF). Fast Fourier Transform (FFT) is then applied to each IMF to compute its frequency content. The results show a strong correlation between the IMFs of specific particle ranges and the IMFs of the total particle count at various speed and load operating conditions. Hence, it is possible to characterise the influence of specific nano-scale particle ranges on the total particulate matter signal by analysing the frequency components of its IMFs using the EEMD-FFT method.
Technical Paper

Hybrid Experimental-CFD Mapping Approach for Twin-Entry Turbo Turbine

2023-10-31
2023-01-1604
The steady flow hot-gas stand test is a widely used method for experimentally characterising turbocharger turbines to produce maps for use in 1D engine simulations. However, for twin entry turbine stages with two volutes, measuring multiple maps at different ratios of mass flow in each volute is time-consuming. This study investigated how computational fluid dynamics (CFD) simulation could reduce the experimental effort for mapping twin-entry turbines, especially for unequal admission conditions. The study is based on a case study of a medium-duty twin-entry turbine, characterising its performance both experimentally and using 3D simulations with ANSYS CFX®. In total, nine maps were produced: one at equal admission, two single admissions, and six unequal admissions conditions. The unequal admission maps were recorded at constant pressure ratios between the two scrolls; the scroll pressure ratio varied from 0.58 to 1.75.
Technical Paper

Simulation Study on EGR Condensate Flow and Uniformity of Each Cylinder in the Intake Manifold

2023-10-30
2023-01-7034
As engine technology developed continuously, engine with both turbocharging and EGR has been researched due to its benefit on improving the engine efficiency. Nevertheless, a technical issue has raised up while utilizing both turbocharging and EGR at the same time: excess condensed water existed in intake manifold which potentially trigger misfire conditions. In order to investigate the root-cause, a CFD model (conducted by CONVERGE CFD software) was presented and studied in this paper which virtually regenerated intake manifold flow-field with EGR condensed water inside. Based on the simulated results, it concluded that different initial conditions of EGR condensed water could significantly change the amount of water which deposited in each cylinder. Thus, a coefficient of variation of deposited condensed water amount among these cylinders, was marked as the evaluation reference of cylinder misfire.
Journal Article

Divided Exhaust Period Assessment for Fuel-Enrichment Reduction in Turbocharged Spark-Ignition Engines

2023-10-26
Abstract Turbocharged spark-ignition (SI) engines, owing to frequent engine knocking events, utilize retarded spark timing that causes combustion inefficiency, and high turbine inlet temperature (Trb-In T) levels. Fuel enrichment is implemented at high power levels to prevent excessive Trb-In T levels, resulting in an additional fueling penalty and higher CO emissions. In current times, fuel-enrichment reductions are of high strategic importance for engine manufacturers to meet the imminent emissions regulations. To that end, the authors investigated the divided exhaust period (DEP) concept in a 2.2 L turbocharged SI engine with a geometric compression ratio of 14 by decoupling blowdown (BD) and scavenge (SC) events during the exhaust process. Using a validated 1D engine model, the authors first analyzed the DEP concept in terms of pumping mean effective pressure (PMEP) and engine knocking (KI) reduction.
Technical Paper

Developing a numerical method for simulating physical and chemical processes that lead to LSPI

2023-09-29
2023-32-0082
Low speed pre-ignition (LSPI) is a limiting phenomenon for several of the technologies being pursued as part of the low carbon agenda. To achieve maximum power density and efficiency engines are being downsized and turbocharged, while Direct- injection technologies are becoming ever more prominent. All changes that increase the propensity of LSPI. The low speed-high load operation envelope is limited due to LSPI. Hydrogen engines are also being explored, however, with such a low minimum enthalpy of ignition, LSPI is a major limitation to thermal efficiency. Several techniques are utilized in this study to investigate physical and physio-chemical aspects of lubricant initiated LSPI. Where possible attempts have been to validate methodologies or directional alignment with published data. The basis of the methodologies used is a validated 1D predictive combustion model of a single cylinder GTDI engine, that was used to provide simulation boundary conditions.
Technical Paper

A Study on Developing MPI Hydrogen ICE over 2MPa BMEP for Medium Duty Vehicles

2023-09-29
2023-32-0037
Hydrogen ICE can achieve carbon neutrality and is adaptable to medium and heavy-duty vehicles, for which electricity is not always a viable option. It can also be developed using high-quality conventional diesel/gasoline engine technology. Furthermore, it allows for the conversion of existing engines to hydrogen ICE, making it highly marketable. The reliability and durability of MPI hydrogen ICE is better than that of DI, and MPI has an advantage over DI in terms of cruising range because the low-pressure injection of hydrogen reduces the remaining hydrogen in the tank. Improving MPI output is, however, an important subject, and achieving this requires suppressing abnormal combustion such as pre-ignition. In this study, an inline four-cylinder 5L turbo-charged diesel engine was converted to a hydrogen engine. Hydrogen injectors were installed in the intake ports and spark plugs were installed instead of diesel fuel injectors.
Technical Paper

Understanding degradation of engine oil additives and its effect on abnormal combustion in a gasoline engine

2023-09-29
2023-32-0035
Engine oils and their additives are formulated to meet required performance areas such as lubrication, detergency, dispersancy, anti-wear, and so on. Understanding degradation of engine oil additives is important to formulate oils with long time durability. Engine oil additives have been found to affect abnormal combustion in turbocharged gasoline direct injection (TGDI) engines, called low speed pre-ignition (LSPI). Some of metal containing additives such as zinc dithiophosphates (ZnDTP) and molybdenum dithiocarbamates (MoDTC) have been found to reduce LSPI events. In this study, we investigated degradation of ZnDTP and MoDTC in gasoline engine operation and effects of the degradation on LSPI performance.
Technical Paper

Improvement of Post-Oxidation Phenomena with Lambda-split, Post-Injection and Mixing Improvement of Exhaust Gas in Turbocharged GDI Engine

2023-09-29
2023-32-0094
Post-oxidation has been used to enhance the chemical reactions in the exhaust gas pipes, leading to the activations of the turbocharger and catalyst at cold state. In this research, a detailed study of the various mechanisms for post-oxidation is performed. For the post-oxidation activation, the unburned gas species (CO, THC, H2) in the exhaust manifold must be produced by some methodologies, such as scavenging, lambda-split, and post-injection. The required amount of O2 concentration can be either supplied by the scavenging (valve overlap tuning) or the secondary air injection (SAI) system. Mixing the species is also an important key to promoting post- oxidation, and an internal bypass adapter with a modified exhaust adapter shape was developed and evaluated.
Award

Cliff Garrett Turbomachinery Engineering Award - Participate - SAE International

2023-08-31
Established in 1984, this award promotes engineering developments and the presentation of SAE papers on turbomachinery and/or developments that enable or advance the use of turbomachinery. The award honors Cliff Garrett and the inspiration he provided to engineers by his example, support, encouragement, and many contributions as an aerospace pioneer. To perpetuate recognition of Garrett's achievements and dedication as an aerospace pioneer, SAE administers an annual lecture by a distinguished authority in the engineering of turbomachinery and/or engineering related to creating, enabling, or advancing applications of turbomachinery in power systems, on-highway, off-highway, aircraft, and/or spacecraft uses. The award is made possible by a contribution from the Garrett Corp.
Journal Article

Gas-Dynamic Interactions between Pre-Chamber and Main Chamber in Passive Pre-Chamber Ignition Gasoline Engines

2023-08-30
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.
Technical Paper

Indirect Assessment of Isentropic Efficiency in Turbocharger Turbines via Mechanical Efficiency Evaluation under Quasi-Adiabatic Test

2023-08-28
2023-24-0121
The isentropic efficiency estimation of small radial turbines is an important aspect of turbocharger performance evaluation. Because of inaccuracies in measuring the outlet temperature due to the non-homogeneous flow field distribution, it is common practice to refer to the thermomechanical efficiency, defined as the product of mechanical and turbine isentropic efficiencies. This paper proposes a method for the indirect evaluation of turbine isentropic efficiency through specific experimental tests. In particular, the evaluation of friction losses in the bearings can be assessed thanks to experimental investigations in quasi-adiabatic condition. By maintaining the turbine inlet temperature and the average temperature of lubricating oil and water-cooling circuit equal to the compressor outlet temperature, a negligible heat transfer between turbine and compressor can be achieved.
Technical Paper

Exploring the Potential of Hydrogen Opposed Piston Engines for Single-Cylinder Electric Generators: A Computational Study

2023-08-28
2023-24-0128
One of the main challenges related to the use of Hydrogen in Internal Combustion Engines is the trade-off between NOx emissions and brake power output: on the one hand, a lean premixed charge (Lambda ≈2.5) is generally able to provide a regular and efficient combustion, yielding near-zero NOx emissions; on the other hand, the power density tends to be very poor, due to the huge amount of air required by the thermodynamic process. As a further penalization, the injection of a gaseous fuel during the intake process has a negative impact on volumetric efficiency. Supercharging can be a solution for addressing the problem, but at the cost of an increase of complexity, cost and overall dimensions. An alternative path is represented by the 2-stroke cycle, and, in particular, by the opposed piston (OP) design. Most of the existing OP engines are compression ignited, but Spark ignition and direct fuel injection can be implemented without relevant modifications to the layout of cylinders.
Technical Paper

Experimental Analysis of a Single-Cylinder Large Bore Engine with External Supercharging in Diesel/CNG Dual-Fuel Mode

2023-08-28
2023-24-0058
The need for a quick reduction in greenhouse gasses and noxious emissions is pushing maritime transportation to increase the use of alternative fuels. Natural Gas (NG) is well recognized as an effective solution to limit the use of marine diesel oil in the short/mid-term. In this scenario, dual-fuel technology is used to enable a conventional diesel engine to operate with a share of gaseous fuel while retaining the capability to run in full diesel mode. Dual-fuel (DF) engines allow the use of natural gas, or biomethane from renewable sources, as the main fuel, with advantages over CO2, SOx and PM emissions with the same levels of NOx. This paper presents an experimental study investigating the effects of the diesel injection strategy on performance and emissions of a dual-fuel, single-cylinder, large bore, 4-stroke engine for marine applications.
Technical Paper

Potentials of Air Path Variabilities and Water Injection in HD Gas Engines

2023-08-28
2023-24-0120
The transportation sector, and commercial vehicles in particular, play an important role in global CO2 emissions. For this reason, the EU recently decided to reduce CO2 emissions from commercial vehicles by 30% until 2030. One alternative to conventional diesel propulsion is the usage of stoichiometric natural gas combustion. Due to the lowered C/H ratio and the cost effective exhaust after treatment (EAT) in form of a three way catalyst (TWC), less CO2 is emitted and it is possible to comply even with most stringent NOX legislations. However, the stoichiometric combustion of natural gas has also disadvantages. In particular, the throttling and retarded 50 % mass fuel burned (MFB50) positions due to knocking lead to efficiency losses. One way to minimize these is the usage of exhaust gas re-circulation (EGR), Miller cycle and water injection. The reduced knocking tendency allows the geometric compression ratio to be increased further, which leads to an additional efficiency advantage.
Technical Paper

High Performance and Near Zero Emissions 2-Stroke H2 Engine

2023-08-28
2023-24-0068
The paper presents a preliminary study on a virtual 2-stroke 3-cylinder 0.9 L DI SI supercharged engine running on Hydrogen (H2), able to meet both high performance targets and ultra-low emissions limits (NOx<20 ppm). Combustion is similar to a conventional 4-stroke H2 DI engine, while the design of the cylinder and the actuation law of both intake and exhaust valves are specifically optimized for the 2-stroke cycle. In comparison to a more conventional 2-stroke loop scavenged engine, with piston-controlled ports, the use of poppet valves enables a more flexible control of the gas exchange process and to maintain the same design of a 4-stroke engine for pistons, cylinders block, crankcase and lubrication system. On the other hand, it is more difficult to avoid the short-circuit of the fresh charge, while permeability of the valves becomes quite critical at high engine speed.
Technical Paper

Turbocharging Automotive Engines: A Decision-Making Approach for Optimal Turbocharger Selection

2023-08-28
2023-24-0003
An approach for turbocharging automotive engines to reach targeted performance was developed in which the environmental and economic aspects during the turbocharger-engine matching process were considered. Three numerical assessment levels based on output performance, exhaust emissions and techno-economic metrics are established to support users during the decision-making of adequate turbochargers that meets targeted data in terms of boosting and emissions. Satisfactory improvements are measured from a 1.5L, three-cylinders, turbocharged Diesel engine, in terms of brake specific fuel consumption, thermal efficiency and NOx concentrations of about 1.73% (decrease in fuel consumption of around 2.22ml/s), 1.76%, and 4.53% (correspond to a diminution of around 217.54ppm), respectively, at the engine’s extreme conditions (full load and rated power).
Technical Paper

Numerical Study on the Effect of Injector Nozzle Hole Number on Diesel Engine Performance under Plateau Conditions

2023-08-28
2023-24-0033
Diesel engines operated at high altitudes would experience performance degradation due to the fuel-air amount mismatch, resulting in combustion deterioration. Technologies that supplement oxygen concentration, such as intake oxygen enrichment, turbocharging and the addition of oxygenated fuel additives, can help restore performance at high altitudes, but each has its own limitations Operating diesel engines at high altitudes still generates extremely lean fuel-air mixtures, making the improved utilization of excess air the most economically efficient approach to optimize engine performance under such conditions.
Journal Article

Transient Response of Turbocharged Compression Ignition Engine under Different Load Conditions

2023-07-26
Abstract In urban roads the engine speed and the load vary suddenly and frequently, resulting in increased exhaust emissions. In such operations, the effect of air injection technique to access the transient response of the engine is of great interest. The effectiveness of air injection technique in improving the transient response under speed transient is investigated in detail [1]; however, it is not evaluated for the load transients. Load step demand of the engine is another important event that limits the transient response of the turbocharger. In the present study, response of a heavy-duty turbocharged diesel engine is investigated for different load conditions. Three cases of load transients are considered: constant load, load magnitude variation, and load scheduling. Air injection technique is simulated and after optimization of injection pressure based on orifice diameter, its effect on the transient response is presented.
Technical Paper

Real Time Simulation of Various Loads and Validation of Radiator CAC Assembly Used in Commercial Vehicle Engines

2023-05-25
2023-28-1337
Due to the emerging technologies and globalization, expectations of the customers on commercial vehicles are getting increased over the period. It is an important duty of an OEM to deliver a perfectly configured product to suit the customer requirements. When it comes to configuration of a vehicle, engine power is one of the key factors which indicate the performance of that vehicle. There is a tough competition between every OEM to increase the engine power for enhancing the overall operational performance. One method to increase power is to improve its volumetric efficiency. This is achieved with help of turbocharger and Charge Air Cooler (CAC). CAC improves volumetric efficiency by increasing intake air-charge density. Any failure on CAC leads to lower the volumetric efficiency and increase in turbocharger loading. This paper deals with the validation of CAC assembly using different test conditions by analyzing potential failure modes against the field issues.
Technical Paper

Virtual Acoustic Prototyping of Automotive Boosting Systems in Vehicle Environment, a Hybrid Approach

2023-05-08
2023-01-1147
In the context of automotive air boosting systems, such as turbochargers and full-cell compressors, earlier and more realistic noise evaluations are crucial in evaluating the impact a design has on the final acoustic performance perceived by the end user in the vehicle cabin environment. This requires a combined assessment of the acoustic sources from boosting systems, other vehicle interior noise sources, and the acoustic transfer path from the boosting system to the vehicle cabin. Performing such an assessment experimentally cannot be done early in development with representative hardware and can be expensive. Also, managing such an assessment entirely through simulations is very complex and error prone. The present study proposes a hybrid approach to tackle this noise challenge.
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