Quantitative analysis on cold start process of a PEMFC stack with intake manifold

2021 ◽  
Author(s):  
Huipeng Niu ◽  
Changwei Ji ◽  
Shuofeng Wang ◽  
Chen Liang
Keyword(s):  
Quantitative Analysis ◽  
Cold Start ◽  
Intake Manifold ◽  
Start Process

Cold-Start Computational Fluid Dynamics Simulation of Spark-Ignition Direct-Injection Engine

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Xiaofeng Yang ◽  
Tang-Wei Kuo ◽  
Kulwinder Singh ◽  
Rafat Hattar ◽  
Yangbing Zeng
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Engine Speed ◽  
Direct Injection ◽  
Cold Start ◽  
Spark Ignition ◽  
Dynamics Simulation ◽  
Residual Fraction ◽  
Direct Injection Engine ◽  
Start Process

Reliably starting the engine during extremely cold ambient temperatures is one of the largest calibration and emissions challenges in engine development. Although cold-start conditions comprise only a small portion of an engine's typical drive cycle, large amounts of hydrocarbon and particulate emissions are generated during this time, and the calibration of cold-start operation takes several months to complete. During the cold start period, results of previous cycle combustion event strongly influences the subsequent cycle due to variations in engine speed, residual fraction, residual wall film mass, in-cylinder charge and wall temperatures, and air flow distribution between cylinders. Including all these parameters in computational fluid dynamics (CFD) simulation is critical in understanding the cold start process in transient and cumulative manner. Measured cold start data of a production of four-cylinder spark-ignition (SI) direct-injection engine were collected for this study with an ambient temperature of −30 °C. Three-dimensional (3D) transient engine flow, spray, and combustion simulation over first three consecutive engine cycles is carried out to provide a better understanding of the cold-start process. Measured engine speed and one-dimensional (1D) conjugate heat transfer (CHT) model is used to capture realistic in-cylinder flow dynamics and transient wall temperatures for more accurate fuel–air mixing predictions. The CFD predicted cumulative heat release trend for the first three cycles matches the data from measured pressure analysis. The same observation can be made for the vaporized fuel mass as well. These observations are explained in the report.

A Novel Method to Estimate Parameters of the Wall-Wetting Fuel Model in MPFI Engines for Cold Start and Warm Up Conditions

2004 ◽  
Author(s):  
M. Shahbakhti ◽  
M. Ghafuri ◽  
A. R. Aslani ◽  
A. Sahraeian ◽  
S. A. Jazayeri ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Cold Start ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Exhaust Emission ◽  
Model Parameters ◽  
Transfer Model ◽  
Fuel Film ◽  
Warm Up ◽  
Fuel Ratio

In order to fulfill the LEV/ULEV exhaust emission standards, it is necessary to have a precise control of air fuel ratio under transient conditions especially during cold start and warm up periods. The objective in this study was to estimate parameters of a fuel delivery model and use them to provide a correct fuel injection compensation strategy. In this study, fuel transfer characteristics of intake port of a typical fuel-injected spark ignition engine have been determined for engine warm-up conditions following cold starts at temperature down to −15°C and extending to fully-warmed-up conditions, using a method based upon perturbing fuel injection rate and recording AFR (Air Fuel Ratio) response. Since there was no cold chamber available to perform tests in cold start conditions, a new method was utilized to simulate cold start conditions. This method can be used on any PFI engine with closed valve injection strategy. Following the estimation of fuel transfer model parameters, the variation of fuel film deposit factor (X), fuel film evaporation time constant (τf) and transport delay to oxygen sensor (ΔT) parameters over a range of temperatures, engine speeds and intake manifold pressures have been evaluated, providing a good insight to define transient fuel compensation requirements for cold start and warm up conditions.

scholarly journals Modelling of the air pollutants’ cold-start emissions depending on average vehicles’ speed

2021 ◽  
Author(s):  
Piotr Laskowski ◽  
Magdalena Zimakowska-Laskowska ◽  
Damian Zasina
Keyword(s):  
Air Pollutants ◽  
Cold Start ◽  
Air Pollutant ◽  
Passenger Cars ◽  
Average Speed ◽  
Speed Fluctuations ◽  
Start Process

The aim of the study is to present the results of mathematically modeled influence of the average speed on the pollutant released in the air during the cold-start process. There were taken into consideration the emission from the passenger cars (PCs) for the different fuel types, vehicles’ segments (including hybrid), and the Euro standard. In the article the simulations was performed using the COPERT software, as well as WLTP-based research. The modelling results there are presented show that the change in average speed has a significant effect on air pollutant (CO2, NOx, NMVOC, CO) emissions released in cold-start process. Furthermore, the results show that pollutants’ emissions are sensitive to average speed fluctuations.

Development and Optimization of a Two-Valve Spark-Ignition Direct-Injection (SIDI) Small Block Engine

2013 ◽  
Author(s):  
David J. Cleary ◽  
Ronald O. Grover ◽  
David P. Sczomak
Keyword(s):  
Fuel Economy ◽  
Fuel Injection ◽  
Systems Approach ◽  
Direct Injection ◽  
Cold Start ◽  
Intake Manifold ◽  
Fuel Injector ◽  
Power Performance ◽  
Charge Motion ◽  
Small Block

A systems approach is implemented to fully optimize the overall performance of a gasoline SIDI two-valve “small block” engine. The objective is to maximize fuel economy while achieving significant improvements in idle stability, cold-start emissions, and torque and power performance relative a baseline port-fuel-injected (PFI) engine. The scope includes the optimization of the fuel injector, piston, cylinder head, cams, in-cylinder charge motion, and the intake-manifold. The results show that the SIDI engine provides the potential to achieve 6.5% better fuel economy; a result of higher efficiency when implementing a higher geometric compression ratio and significantly better combustion performance. A multiple fuel-injection strategy is examined to provide lower HC emissions at a representative cold-start operating condition. The engine’s idle stability is improved by a factor of three; the individual contributions from a better combustion system design and from multiple fuel injections are identified. The new SIDI engine concept demonstrated significantly better wide-open-throttle (WOT) performance, including up to 10% higher torque and 6% more power when using premium fuel. This document further demonstrates the performance sensitivity to engine design variables while emphasizing the importance of using a systems approach to achieve optimized performance for the direct-injection engine technology.

scholarly journals Analysis of the Failure Modes in the Polymer Electrolyte Fuel Cell Cold-Start Process—Anode Dehydration or Cathode Pore Blockage

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 256 ◽  
Author(s):  
Lei Yao ◽  
Fangfang Ma ◽  
Jie Peng ◽  
Jianbo Zhang ◽  
Yangjun Zhang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Water Content ◽  
Polymer Electrolyte ◽  
Failure Modes ◽  
Cold Start ◽  
Polymer Electrolyte Fuel Cell ◽  
Freezing Process ◽  
Initial Membrane ◽  
Pore Blockage ◽  
Start Process

In this study, the cold-start failure processes of a polymer electrolyte fuel cell have been investigated numerically for different initial membrane water content λ 0 and the startup current densities I 0 . The result shows that the failure of the cell cold-start process is mostly attributed to the anode dehydration when the cell operates with relatively large current density. However, the failure is dominated by the cathode pore blockage when the cell starts with relatively high initial membrane water content. Corresponding maps for the classification of startup failure modes are plotted on the λ 0 − I 0 plane with different startup temperatures. Three zones, including the anode dehydration, the cathode pore blockage, and the ambiguous region, can be observed. They can be distinguished with different startup failure mechanisms. The anode dehydration zone is expanded as the cell startup temperature drops due to the weakening of the membrane water back-diffusion ability. In the ambiguous region, the startup failure phenomena may be either anode dehydration or cathode pore blockage, which depends on the stochastic freezing process of the supercooled water.

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