Multi-Cycle Simulation of the Mixture Formation Process of an High Performance Engine at Part Load Condition

2012 ◽  
Author(s):  
Claudio Forte ◽  
Gian Marco Bianchi ◽  
Enrico Corti ◽  
Stefano Fantoni
Keyword(s):  
High Performance ◽  
Load Condition ◽  
Experimental Tests ◽  
Fuel Mixture ◽  
Critical Issue ◽  
Transient Condition ◽  
Mixture Formation ◽  
Part Load ◽  
Cycle Simulation ◽  
Load Conditions

Transient operation of engines leads to air fuel (A/F) ratio excursions, which can increase engine emissions. These excursions have been attributed to the formation of fuel films in the intake port, which are caused by a portion of the intake fuel impinging and adhering on the relatively cool port surface. These films act as a source or sink which cause the AF variations depending upon the transient condition. Gaining a fundamental understanding of the nature and quantity of such films may assist in future fuel mixture preparation designs that could aid in emission reductions, yet would not require overly expensive nor complicated systems. The control of air to fuel ratio is a critical issue for high performance engines: due to the low stroke-to-bore ratio the maximum power is reached at very high regimes, letting little time to the fuel to evaporate and mix with air. The injector located upstream the throttle causes a lot of fuel to impinge the throttle and intake duct walls, slowing the dynamics of mixture formation in part load conditions. The aim of this work is to present a CFD methodology for the evaluation of mixture formation dynamics applied to a Ducati high performance engine under part load conditions. The phenomena involved in the process are highly heterogeneous, and particular care must be taken to the choice of CFD models and their validation. In the present work all the main models involved in the simulations are validated against experimental tests available in the literature, selected based on the similarity of physical conditions of those of the engine configuration under analysis. The multi-cycle simulation methodology here presented reveals to be a useful tool for the evaluation of the mixture dynamics and for the evaluation of injection wall film compensator models.

CFD Methodology for the Simulation of Mixture Formation of High Performance PFI Engines

2011 ◽  
Author(s):  
Claudio Forte ◽  
Gian Marco Bianchi ◽  
Enrico Corti ◽  
Gaspare Argento ◽  
Stefano Fantoni
Keyword(s):  
High Performance ◽  
Experimental Tests ◽  
Critical Issue ◽  
Spark Ignition Engines ◽  
Mixture Formation ◽  
Injection Process ◽  
Cfd Models ◽  
Cycle Simulation ◽  
Spark Plug ◽  
The Stability

Mixture composition strongly influences the stability of combustion of spark ignition engines. The control of air to fuel ratio at ignition is a critical issue for high performance engines: due to the low stroke-to-bore ratio the maximum power is reached at very high regimes, letting little time to the fuel to evaporate and mix with air. The aim of this work is to present a CFD methodology for the evaluation of mixture formation applied to a Ducati high performance engine. The phenomena involved in the process are highly heterogeneous, and particular care must be taken to the choice of CFD models and their validation. In the present work all the main models involved in the simulations are validated against experimental tests available in the literature, selected based on the similarity of physical conditions with those of the engine configuration under analysis. The multi-cycle simulation methodology here presented reveals to be a useful tool for the evaluation of the mixture quality around the spark plug at ignition, allowing a parametric analysis of the effects of the injection process on engine output.

Numerical Investigation on Mixture Formation in a Turbocharged Port-Injection Natural Gas Engine Using Multiple Cycle Simulation

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Zhenkuo Wu ◽  
Zhiyu Han
Keyword(s):  
Fuel Injection ◽  
Load Condition ◽  
Operating Conditions ◽  
Injection Timing ◽  
Mixture Formation ◽  
Natural Gas Engine ◽  
Cycle Simulation ◽  
Mixture Preparation ◽  
Spark Timing ◽  
Multiple Cycle

In the present study, multidimensional computational fluid dynamics (CFD) simulations were carried out to study mixture formation in a turbocharged port-injection natural gas engine. In order to achieve robust simulation results, multiple cycle simulation was employed to remove the inaccuracies of initial conditions setting. First, the minimal number of simulation cycles required to obtain convergent cycle-to-cycle results was determined. Based on this, the in-cylinder mixture preparation for three typical operating conditions was studied. The effects of fuel injection timing and intake valve open scheme on the mixture formation were evaluated. The results demonstrated that three simulation cycles are needed to achieve convergence of the results for the present study. The analysis of the mixture preparation revealed that only in the initial phase of the intake stroke, there is an obvious difference between the three operating conditions. At the spark timing, for 5500 rpm, full load condition mixture composition throughout the cylinder is flammable, and for 2000 rpm, 2 bar operating condition part of the mixture is lean and nonflammable. The fuel injection timing has an insignificant impact on the mixture flammability at the spark timing. It was observed that the designed nonsynchronous intake valve open scheme has stronger swirl and x-direction tumble motion than the baseline case, leading to better mixture homogeneity and spatial distribution. With an increase in volumetric efficiency, particularly at 2000 rpm, full load condition, by 4.85% compared to the baseline, which is in line with experimental observation.

scholarly journals Analysis of Unsteady Flow Characteristics of Centrifugal Pump under Part Load Based on DDES Turbulence Model

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tang Xin ◽  
Liu Zhili ◽  
Zhao Meng ◽  
Yang Haotian ◽  
Jiang Wei ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Radial Velocity ◽  
Centrifugal Pump ◽  
Turbulence Model ◽  
Vortex Structure ◽  
Guide Vane ◽  
Load Condition ◽  
Wake Flow ◽  
Part Load ◽  
Load Conditions

To better reveal the mechanism of the rotor-stator interference between the impeller and the guide vane and the evolution process of the stall vortex under the part-load conditions, numerical simulation is carried out based on the DDES turbulence model, which can better capture vortex structure. And the pressure pulsation and the radial velocity distribution of the centrifugal pump are studied. The vortex structure and pressure fluctuation of pump internal flow field under part-load condition of Q = 0.4 Qdes are mainly analyzed. The analysis results show that the stall vortex is formed at the inlet of the impeller and evolves to the outlet of the impeller, the front cover to the rear cover according to the fluid flow direction, and then disappears. Besides, under the part-load condition, the vorticity of the impeller outlet is always obviously less than that of the impeller inlet as the flow rate increases. Due to the asymmetric action of the volute, the radial velocity distribution law of flow channel C1 is different from other flow channels at different blade heights. By analyzing the radial velocity, the phenomenon that the jet-wake flow impacts the guide vane with the rotation of the impeller is the main reason for the rotor-stator interference. And large radial velocity gradients appear at the front and rear cover plates, which will cause high energy loss and reduce pump efficiency. Besides, the conclusion can be drawn that the region with the strongest rotor-stator interference is the inlet region of the guide vane suction surface. It also occurs near the volute tongue but is lower due to the effect of the guide vane. This research may serve as a reference for the safe operation of centrifugal pumps under part-load conditions.

A Multiple-Zone Cycle Simulation for Spark-Ignition Engines: Thermodynamic Details

2001 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Combustion Process ◽  
Load Condition ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Engine Operation ◽  
Part Load ◽  
Cycle Simulation ◽  
The Individual

Abstract A thermodynamic cycle simulation was developed for a spark-ignition engine which included the use of multiple zones for the combustion process. This simulation was used to complete analyses for a commercial, spark-ignition V-8 engine operating at a part load condition. Specifically, the engine possessed a compression ratio of 8.1:1, and had a bore and stroke of 101.6 and 88.4 mm, respectively. A part load operating condition at 1400 rpm with an equivalence ratio of 1.0 was examined. Results were obtained for overall engine performance, for detailed in-cylinder events, and for the thermodynamics of the individual processes. In particular, the characteristics of the engine operation with respect to the combustion process were examined. Implications of the multiple zones formulation for the combustion process are described.

A Computer Program for Simulating Transient Behavior in Steam Turbine Stage Pressure of AHWR

2006 ◽  
Author(s):  
Anu Dutta ◽  
I. Thangamani ◽  
G. Chakraborty ◽  
A. K. Ghosh ◽  
H. S. Kushwaha
Keyword(s):  
System Analysis ◽  
Mathematical Formulation ◽  
Load Condition ◽  
Low Pressure ◽  
Research Centre ◽  
Turbine Stage ◽  
Feed System ◽  
Part Load ◽  
Desalination Plant ◽  
Load Conditions

It is proposed to couple the Advanced Heavy water reactor (AHWR), which is being developed by Bhabha Atomic Research Centre, India, with a desalination plant. The objective of this coupling is to produce system make-up and domestic water. The proposed desalination plant needs about 1.9 kg/sec of steam and the minimum pressure requirement is 3 bars. The desalination plant can be fed with bled steam extracted from a suitable stage in low pressure turbine. As the turbine stage pressure changes with the load, it is essential to know the availability of bled steam at aforesaid pressure for various load condition. The objective of the present study is to identify a suitable extraction point so as to ensure availability of steam at desired condition for desalination plant, even at part load conditions. In order to fulfill the above objective a steam and feed system analysis code was developed which incorporates the mathematical formulation of different components of the steam and feed system such as, high pressure (HP) and low pressure (LP) turbines, re-heater, feed heaters etc. The dynamic equations are solved simultaneously to obtain the stage pressure at various load conditions. Based on the results obtained, the suitable extraction stage in LP turbine was selected. This enables to determine the lowest possible part load operation up to which availability of desalination plant could be ensured.

Influence of Blade Pitch and Number of Blades of a Pump Inducer on Single and Two-Phase Flow Performance

2020 ◽  
Author(s):  
Michael Mansour ◽  
Trupen Parikh ◽  
Dominque Thévenin
Keyword(s):  
High Performance ◽  
Two Phase Flow ◽  
Low Flow ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Phase Mixing ◽  
Part Load ◽  
Two Phases ◽  
Load Conditions

Abstract This study investigates the influence of various inducer configurations upstream of a pump impeller on the single and two-phase flow performance. Three pitch values (P = 0.151, 0.251, and 0.351 m), as well as three different numbers of blades (N = 2, 3, and 4 blades), were studied, leading to a total of 9 different inducer geometries. The main objective of the present study is to analyze and compare the corresponding performances and the two-phase mixing behavior, which is necessary for improving the two-phase pumping ability. 3D steady-state simulations using the Moving Reference Frame (MRF) approach were applied for single-phase flow, while a transient setup using a moving-mesh approach was employed for two-phase simulations. Turbulence was modeled by the Reynolds Stress Model (RSM), whereas the Volume of Fluid (VOF) method was applied to model air-water interactions. The results show that the increase in the number of blades leads to a high performance drop at overload (high-flow) conditions, but only to a slight performance enhancement at part-load (low-flow) conditions. Additionally, the effective flow range of the inducer corresponding to high efficiency becomes narrower for a higher number of blades. Concerning the inducer pitch, at part-load conditions, a lower pitch is slightly beneficial to smoothly suck the flow and damp the low-flow vortices; employing a high pitch at these conditions results in intensified flow vortices, reducing slightly the performance. On the other hand, the blade pitch is very influential for the performance at optimal and overload conditions, where a lower pitch causes flow blockage, leading to significant performance deterioration and a very limited range of applications. Generally, it was found that a modification of the inducer configuration affects the performance much more at overload compared to part-load conditions. Concerning two-phase mixing performance, the highest pitch provides the best mixing since the inducer is able to effectively churn the two phases. Similarly, an increase in the number of blades amplifies the turbulence between the two phases, thus improving mixing. Overall, a higher inducer pitch and a low to moderate number of inducer blades best ensure high performance, wide working range, and efficient two-phase mixing.

Results From an Engine Cycle Simulation of Compression Ratio and Expansion Ratio Effects on Engine Performance

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Compression Ratio ◽  
Load Condition ◽  
Engine Performance ◽  
Constant Load ◽  
Expansion Ratio ◽  
Heat Losses ◽  
Spark Ignition Engine ◽  
Maximum Efficiency ◽  
Part Load ◽  
Cycle Simulation

This investigation quantified the effects of compression ratio (CR) and expansion ratio (ER) on performance, efficiency, and second law parameters for an automotive, spark-ignition engine. The well known increase in engine performance for increasing CR and ER is demonstrated. These increases for brake engine performance are modest for CRs greater than about 10 for the conditions studied. The results demonstrated that the increasing friction and heat losses for the higher CRs are of the same order as the thermodynamic gains. Also, the results included the destruction of availability during combustion. For a part load condition, the availability destroyed decreased from about 23% to 21% for CRs of 4 and 10, respectively. In addition, this study examined cases with greater ERs than CRs. The overall cycle for these cases is often called an “Atkinson” cycle. For most cases, the thermal efficiency first increased as ER increased, attained a maximum efficiency, and then decreased. The decrease in efficiency after the maximum value was due to the increased heat losses, increased friction, and ineffective exhaust processes (due to the reduced cylinder pressure at the time of exhaust valve opening). For part load cases, the higher ER provided only modest gains due to the increased pumping losses associated with the constant load requirement. For the wide open throttle cases, however, the higher ERs provided significant gains. For example, for a compression ratio of 10, expansion ratios of 10 and 30 provided brake thermal efficiencies of about 34% and 43%, respectively. Although the net thermodynamic gains are significant, large ERs such as 30 may not be practical in most applications.

Efficient Instruction and Data Caching for High Performance Embedded Processors

1970 ◽  
pp. 9
Author(s):  
A. Ferrerón Labari ◽  
D. Suárez Gracia ◽  
V. Viñals Yúfera
Keyword(s):  
Embedded Systems ◽  
Power Consumption ◽  
Low Power ◽  
Interconnection Networks ◽  
High Performance ◽  
Critical Issue ◽  
Content Management ◽  
Structure Design ◽  
Portable Devices ◽  
On Chip

In the last years, embedded systems have evolved so that they offer capabilities we could only find before in high performance systems. Portable devices already have multiprocessors on-chip (such as PowerPC 476FP or ARM Cortex A9 MP), usually multi-threaded, and a powerful multi-level cache memory hierarchy on-chip. As most of these systems are battery-powered, the power consumption becomes a critical issue. Achieving high performance and low power consumption is a high complexity challenge where some proposals have been already made. Suarez et al. proposed a new cache hierarchy on-chip, the LP-NUCA (Low Power NUCA), which is able to reduce the access latency taking advantage of NUCA (Non-Uniform Cache Architectures) properties. The key points are decoupling the functionality, and utilizing three specialized networks on-chip. This structure has been proved to be efficient for data hierarchies, achieving a good performance and reducing the energy consumption. On the other hand, instruction caches have different requirements and characteristics than data caches, contradicting the low-power embedded systems requirements, especially in SMT (simultaneous multi-threading) environments. We want to study the benefits of utilizing small tiled caches for the instruction hierarchy, so we propose a new design, ID-LP-NUCAs. Thus, we need to re-evaluate completely our previous design in terms of structure design, interconnection networks (including topologies, flow control and routing), content management (with special interest in hardware/software content allocation policies), and structure sharing. In CMP environments (chip multiprocessors) with parallel workloads, coherence plays an important role, and must be taken into consideration.

scholarly journals Intrinsic Self-Healing Epoxies in Polymer Matrix Composites (PMCs) for Aerospace Applications

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 201
Author(s):  
Stefano Paolillo ◽  
Ranjita K. Bose ◽  
Marianella Hernández Santana ◽  
Antonio M. Grande
Keyword(s):  
High Performance ◽  
Polymer Matrix Composites ◽  
Critical Issue ◽  
General Description ◽  
Self Healing ◽  
Matrix Composites ◽  
Testing Procedures ◽  
Aerospace Applications ◽  
Polymer Properties ◽  
Healing Efficiency

This article reviews some of the intrinsic self-healing epoxy materials that have been investigated throughout the course of the last twenty years. Emphasis is placed on those formulations suitable for the design of high-performance composites to be employed in the aerospace field. A brief introduction is given on the advantages of intrinsic self-healing polymers over extrinsic counterparts and of epoxies over other thermosetting systems. After a general description of the testing procedures adopted for the evaluation of the healing efficiency and the required features for a smooth implementation of such materials in the industry, different self-healing mechanisms, arising from either physical or chemical interactions, are detailed. The presented formulations are critically reviewed, comparing major strengths and weaknesses of their healing mechanisms, underlining the inherent structural polymer properties that may affect the healing phenomena. As many self-healing chemistries already provide the fundamental aspects for recyclability and reprocessability of thermosets, which have been historically thought as a critical issue, perspective trends of a circular economy for self-healing polymers are discussed along with their possible advances and challenges. This may open up the opportunity for a totally reconfigured landscape in composite manufacturing, with the net benefits of overall cost reduction and less waste. Some general drawbacks are also laid out along with some potential countermeasures to overcome or limit their impact. Finally, present and future applications in the aviation and space fields are portrayed.

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