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Technical Paper

A Solution to Fuel Vaporization Problem in a Power Nozzle

2009-04-20
2009-01-1051
A power nozzle is a fuel injection actuator in which fuel is instantly compressed and then discharged by a solenoid piston pump with nozzle. Fuel vaporization inside the power nozzles is a challenging issue. This paper presents an effective solution to the fuel vaporization problem in the power nozzle. An applied physical process, fluid boundary layer pumping (FBLP), is found in this study. FBLP can result in fuel circulation within the fuel line of the power nozzle, which on one hand brings heat out of the power nozzle, and on the other hand blocks vapor from entering the piston pump.
Technical Paper

Using Multiple Injection Strategies in Diesel PCCI Combustion: Potential to Extend Engine Load, Improve Trade-off of Emissions and Efficiency

2011-04-12
2011-01-1396
The Premixed Charge Compression Ignition (PCCI) engine has the potential to reduce soot and NOx emissions while maintaining high thermal efficiency at part load conditions. However, several technical barriers must be overcome. Notably ways must be found to control ignition timing, expand its limited operation range and limit the rate of heat release. In this paper, comparing with single fuel injection, the superiority of multiple-pulse fuel injection in extending engine load, improve emissions and thermal efficiency trade-off using high exhaust gas recirculation (EGR) and boost in diesel PCCI combustion is studied by engine experiments and simulation study. It was found that EGR can delay the start of hot temperature reactions, reduce the reaction speed to avoid knock combustion in high load, is a very useful method to expand high load limit of PCCI. EGR can reduce the NOx emission to a very small value in PCCI.
Technical Paper

A Hybrid Combustion Control Strategy for Heavy Duty Diesel Engines Based on the Technologies of Multi-Pulse Injections, Variable Boost Pressure and Retarded Intake Valve Closing Timing

2011-04-12
2011-01-1382
Combustion control strategy for high efficiency and low emissions in a heavy duty (H D) diesel engine was investigated experimentally in a single cylinder test engine with a common rail fuel system, EGR (Exhaust Gas Recirculation) system, boost system and retarded intake valve closing timing actuator. For the operation loads of IMEPg (Gross Indicated Mean Effective Pressure) less than 1.1 MPa the low temperature combustion (LTC) with high rate of EGR was applied. The fuel injection modes of either single injection or multi-pulse injections, boost pressure and retarded intake valve closing timing (RIVCT) were also coupled with the engine operation condition loads for high efficiency and low emissions. A higher boost pressure played an important role in improving fuel efficiency and obtaining ultra-low soot and NOx emissions.
Journal Article

Experimental Investigation of Droplet Dynamics and Spray Atomization inside Thermostatic Expansion Valves

2011-04-12
2011-01-0129
In this paper, experimental investigation on spray atomization and droplet dynamics inside a thermostatic expansion valve (TXV), a component commonly used in vehicle refrigeration system, was conducted. A needle and an orifice were copied from a commercial TXV and machined to be mounted inside a chamber with optical access so that the flow inside the TXV is simulated and visualized at the same time. The break-up and atomization of the refrigerant were documented near the downstream of the orifice under different feed conditions for two TXV with different geometry. A Phase Doppler Anemometry (PDA) system was used later to measure the size and velocity of atomized refrigerant droplets. The results showed that the droplet size variation along the radial direction is slightly decreased at near downstream and increased at farther downstream due to the coalescence.
Journal Article

Disturbance Estimation Based Modeling Technique for Control and Prediction in Controllable Mechanical Turbo-Compounding System

2016-04-05
2016-01-0023
Modeling techniques matter a lot in many fields of engine engineering. Models are requested not only for control design but also for dynamic prediction. However, problems might be encountered during modeling process either because of the system complexity or the unaffordable modeling cost. As a result, a new modeling technique based on disturbance estimation is proposed in this paper. By employing the proposed modeling technique, models are set up in real time with the online information from input and output. The uncertainties of system dynamics are handled as internal disturbance of the system, while the perturbation from outside are taken as the external disturbance, and the combination of the two can be estimated online by a kind of active observer called extended state observer (ESO).
Technical Paper

Research in the Effects of Intake Manifold Length and Chamber Shape on Performance for an Atkinson Cycle Engine

2016-04-05
2016-01-1086
In order to improve the fuel consumption and expand the range of low fuel consumption area of a 1.5L Atkinson cycle PFI engine, the effect of the intake manifold length and chamber shape on the engine performance is investigated by setting up a GT-power (1-D) and an AVL-Fire (3-D) computational model which are calibrated with experimental data. After this the new engine was transformed to the test bench to do the calibration experiment. The results demonstrate that the intake manifold case_1 (the length is 300mm, side intake form) matched with a new designed chamber improves combustion in cylinder with a range 1.6∼7.4g/(kW•h) reduced in fuel consumption of speed that has been studied; the case_3 (the length is 100mm, intermediate intake form) matched with the new designed chamber with a range 3.86∼7g/(kW•h) reduced in fuel consumption of speed that has been studied. Both case_1 and case_3 expand the range of low fuel consumption area significantly.
Technical Paper

Characteristics of Sub/Supercritical Gasoline and Iso-Octane Jets in High Temperature Environment

2019-04-02
2019-01-0289
Based on the temperature and pressure in the cylinder of GDI (Gasoline Direct Injection) engines under the common operating conditions, jets´ characteristics of gasoline and iso-octane at different fuel temperatures under the high ambient temperature were studied by means of high-speed photography and striation method. It is found that the supercritical gasoline jet shows the morphological collapse of jet center and the protrusion of the front surface, but the iso-octane jet doesn´t. Meanwhile, as the fuel temperature rises, the flash boiling and the interference between adjacent plumes affect the gasoline jet, and cause the center of the jet to form a high-speed and low-pressure zone, hence the air entrainment in this region contributes to the collapse of jets. The collapse and convergence of jets´ morphology are the main reasons for the change of penetration and cone angle.
Technical Paper

Experimental Study on Impingement of Fuel Droplet on Substrates

2019-04-02
2019-01-0300
Within a gasoline direct injection (GDI) engine, the impingement of fuel droplet on substrates induces various problems such as particular matter emission, oil dilution and abnormal combustion. Therefore, in order to solve these problems, it is urgent to have a clear understanding of the impingement behavior of fuel droplet impacting on substrates. Most previous studies have focused on the impingement of either water droplet on dry solid surface or the impinging droplet on the liquid film of the same type of liquid, while little research has been conducted on the impingement of fuel droplet on relevant substrates existing in GDI engines. The impingement of fuel droplet with higher Weber number on dry surface, fuel film and oil film with different thickness and viscosity were investigated experimentally. Results show that fuel droplet impacting on dry wall is easy to be deposited to form a fuel film. The fuel film attached to the wall is the main reason for the splash.
Technical Paper

Characteristics of Single Fuel Droplet Impact on Oil Film

2019-04-02
2019-01-0304
In order to better understand the spray impingement behavior of the gasoline direct injection (GDI) engine, this paper used the laser induced fluorescence (LIF) test method to conduct basic research on the fuel droplet impact onto the oil film. The effects of different incident droplet Weber number, dimensionless oil film thickness and oil film viscosity on the morphology of oil film after impact were investigated. And the composition of splashing droplets after impingement was analyzed. The morphology of oil film after impact was divided into three categories: stable crown, delayed splash crown, and prompt splash crown. The stable crown has only splashing fuel droplets, the splashing droplets of delayed splash crown are consist of fuel and oil film. The splashing droplets of prompt splash crown mainly include the oil film. It is shown that the larger the Weber number of incident droplets, the larger the dimensionless crown height and diameter, the easier the oil film will splash.
Technical Paper

An Assessment of the Impact of Exhaust Turbine Redesign, for Narrow VGT Operating Range, on the Performance of Diesel Engines with Assisted Turbocharger

2019-04-02
2019-01-0326
Electrically assisted turbochargers are a promising technology for improving boost response of turbocharged engines. These systems include a turbocharger shaft mounted electric motor/generator. In the assist mode, electrical energy is applied to the turbocharger shaft via the motor function, while in the regenerative mode energy can be extracted from the shaft via the generator function, hence these systems are also referred to as regenerative electrically assisted turbochargers (REAT). REAT allows simultaneous improvement of boost response and fuel economy of boosted engines. This is achieved by optimally scheduling the electrical assist and regeneration actions. REAT also allows the exhaust turbine to operate within a narrow range of optimal vane positions relative to the unassisted variable geometry turbocharger (VGT). The ability to operate within a narrow range of VGT vane positions allows an opportunity for a more optimal turbine design for a REAT system.
Technical Paper

Three-Dimensional Multi-Scale Simulation for Large-Scale Proton Exchange Membrane Fuel Cell

2019-04-02
2019-01-0381
PEMFC (proton exchange membrane or polymer electrolyte membrane fuel cell) is a potential candidate as a future power source for automobile applications. Water and thermal management is important to PEMFC operation. Numerical models, which describe the transport and electrochemical phenomena occurring in PEMFCs, are important to the water and thermal management of fuel cells. 3D (three-dimensional) multi-scale CFD (computational fluid dynamics) models take into account the real geometry structure and thus are capable of predicting real operation/performance. In this study, a 3D multi-phase CFD model is employed to simulate a large-scale PEMFC (109.93 cm2) under various operating conditions. More specifically, the effects of operating pressure (1.0-4.0 atm) on fuel cell performance and internal water and thermal characteristics are studied in detail under two inlet humidities, 100% and 40%.
Technical Paper

A Quasi-2D Transient Multiphase Modeling of Cold Start Processes in Proton Exchange Membrane Fuel Cell

2019-04-02
2019-01-0390
It’s well known that startup process of proton exchange membrane fuel cells (PEMFCs) under subzero temperature is extremely significant because of its influence on fuel cell performance and durability. In the study, a quasi-2D numerical model is developed and dynamic equations of mass conservation, energy conservation, membrane water conservation, ice conservation, species conservation are all considered. Three different hydrogen supply modes are studied in detail: flow-through anode (FTA) mode, dead-ended anode (DEA) mode and off-gas recirculation (OR) mode. It is found that the local current density (LCD) and temperature distribution vary remarkably along flow channel in OR mode as t > 500s due to nitrogen crossover and accumulation. During the cold start operation, the DEA mode and OR mode hold more water in anode catalyst layer (ACL) which reduces the effects of hydraulic permeation, resulting in more ice formation in cathode catalyst layer (CCL) and slower temperature rising.
Technical Paper

Dynamic Characteristics Analysis and Fatigue Damage Estimation of a Compressor Blade under Fluid-Structure Interaction

2018-04-03
2018-01-1206
During the aero-engine operation, the compressor blades are subjected to periodic inertial force and aerodynamic excitation caused by blade rotation and airflow disturbance, respectively. Under the coupling alternating loads, the blade is prone to high cycle fatigue failure. In this paper, a time domain calculation model of fluid-structure interaction (FSI) is established to study the vibration characteristics of the blade and its failure modes are analyzed. Then, the fatigue damage of the blade under multi-level loading is evaluated by the nonlinear damage accumulation model. Considering the coupling effect of the airflow and the blade, computational fluid dynamics (CFD) is applied to calculate the aerodynamic parameters on the blade surface under different working conditions, which is imported to the finite element (FE) model to analyze the dynamic characteristics.
Technical Paper

Effect of Turbulence-Chemistry Interaction on Spray Combustion: A Large Eddy Simulation Study

2019-04-02
2019-01-0203
Although turbulence plays a critical role in engines operated within low temperature combustion (LTC) regime, its interaction with chemistry on auto-ignition at low-ambient-temperature and lean-oxygen conditions remains inadequately understood. Therefore, it is worthwhile taking turbulence-chemistry interaction (TCI) into consideration in LTC engine simulation by employing advanced combustion models. In the present study, large eddy simulation (LES) coupled with linear eddy model (LEM) is performed to simulate the ignition process in n-heptane spray under engine-relevant conditions, known as Spray H. With LES, more details about unsteady spray flame could be captured compared to Reynolds-averaged Navier-Stokes equations (RANS). With LEM approach, both scalar fluctuation and turbulent mixing on sub-grid level are captured, accounting for the TCI. A skeletal mechanism is adopted in this numerical simulation, including 41 species and 124 reactions.
Technical Paper

Experimental Comparison between Stratified Flame Ignition and Micro Flame Ignition in a Gasoline SI-CAI Hybrid Combustion Engine

2017-03-28
2017-01-0737
Controlled Auto-Ignition (CAI), also known as Homogeneous charge compression ignition (HCCI), has been the subject of extensive research because of their ability to providing simultaneous reduction in fuel consumption and NOx emissions in a gasoline engine. However, due to its limited operation range, combustion mode switching between CAI and spark ignition (SI) combustion is essential to cover the overall operational range of a gasoline engine for passenger car applications. Previous research has shown that the SI-CAI hybrid combustion has the potential to control the ignition timing and heat release process during both steady state and transient operations. However, it was found that the SI-CAI hybrid combustion process is often characterized with large cycle-to-cycle variations, due to the flame instability at high dilution conditions.
Technical Paper

Experimental and Modelling Investigations of the Gasoline Compression Ignition Combustion in Diesel Engine

2017-03-28
2017-01-0741
In this work the gasoline compression ignition (GCI) combustion characterized by both premixed gasoline port injection and gasoline direct injection in a single-cylinder diesel engine was investigated experimentally and computationally. In the experiment, the premixed ratio (PR), injection timing and exhaust gas recirculation (EGR) rate were varied with the pressure rise rate below 10 bar/crank angle. The experimental results showed that higher PR and earlier injection timing resulted in advanced combustion phasing and improved thermal efficiency, while the pressure rise rates and NOx emissions increased. Besides, a lowest ISFC of 176 g/kWh (corresponding to IMEP =7.24 bar) was obtained, and the soot emissions could be controlled below 0.6 FSN. Despite that NOx emission was effectively reduced with the increase of EGR, HC and CO emissions were high. However, it showed that GCI combustion of this work was sensitive to EGR, which may restrict its future practical application.
Technical Paper

Co-Simulation and Analysis on Aerodynamic Noise at the Engine Inlet

2018-04-03
2018-01-0686
As the intake noise is a major contributing factor to automotive passenger compartment noise levels, it has received much more attention than before. Because the plastic manifolds could induce and transmit more noise owing to their lighter weight, aerodynamic noise has become a more serious problem in plastic manifolds than in conventional aluminum-made manifolds. Due to the complexity of aerodynamic noise of the intake system, it is difficult to predict the noise precisely, especially for the part whose frequency is higher than 1000 Hz. This paper introduces a new co-simulation method to simulate the aerodynamic noise at the engine inlet. With the coupled simulation between two programs, GT-Power and Fluent, it could simulate the gas flow inside the engine intake system, under the actual running condition of engine.
Technical Paper

Effect of Ashless Dispersant on the Morphology, Size, Nanostructure and Graphitization Degree of Diesel Exhaust Particles

2018-04-03
2018-01-0636
The aim of this research is to investigate the effects of ashless dispersant of lube oils on diesel exhaust particles. Emphasis is placed on particle size, morphology, nanostructure and graphitization degree. Three kinds of lube oils with different percentages of ashless dispersant were used in a two-cylinder diesel engine. Ashless dispersant (T154), which is widely used in petrochemical industry, were added into baseline oil at different blend percentages (4.0% and 8.0% by weight) to improve lubrication and cleaning performance. A high resolution Transmission Electron Microscope (HRTEM) and a Raman spectroscopy were employed to analyze and compare particle characteristics. According to the experiment results, primary particles diameter ranges from 3 nm to 65 nm, and the diameter distribution conformed to Gaussian distribution. When the ashless dispersant was used, the primary particles diameter decrease obviously at both 1600 rpm and 2200 rpm.
Technical Paper

Experimental Investigation of Combustion and Emission Characteristics of Stoichiometric Stratified Flame Ignited (SFI) Hybrid Combustion in a 4-Stroke PFI/DI Gasoline Engine

2019-04-02
2019-01-0960
Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), can improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, the difficulty in combustion phasing control and violent combustion at high loads limit the commercial application of CAI combustion. To overcome these problems, stratified mixture, which is rich around the central spark plug and lean around the cylinder wall, is formed through port fuel injection and direct injection of gasoline. In this condition, rich mixture is consumed by flame propagation after spark ignition, while the unburned lean mixture auto-ignites due to the increased in-cylinder temperature during flame propagation, i.e., stratified flame ignited (SFI) hybrid combustion.
Technical Paper

Dilution Boundary Expansion Mechanism of SI-CAI Hybrid Combustion Based on Micro Flame Ignition Strategy

2019-04-02
2019-01-0954
In decade years, Spark Ignition-Controlled Auto Ignition (SI-CAI) hybrid combustion, also called Spark Assisted Compression Ignition (SACI) has shown its high-efficiency and low emissions advantages. However, high dilution causes the problem of unstable initial ignition and flame propagation, which leads to high cyclic variation of heat release and IMEP. The instability of SI-CAI hybrid combustion limits its dilution degree and its ability to improve the thermal efficiency. In order to solve instability problems and expand the dilution boundary of hybrid combustion, micro flame ignition (MFI) strategy is applied in gasoline hybrid combustion engines. Small amount of Dimethyl Ether (DME) chosen as the ignition fuel is injected into cylinder to form micro flame kernel, which can stabilize the ignition combustion process.
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