An Approach for Investigating Adaptive Control Strategies to Improve Combustion Stability Under Dilute Operating Conditions

2005 ◽  
Author(s):  
K. Dean Edwards ◽  
Robert M. Wagner ◽  
Timothy J. Theiss ◽  
C. Stuart Daw
Keyword(s):  
Adaptive Control ◽  
Emission Reduction ◽  
Internal Combustion Engines ◽  
Control Strategies ◽  
Fuel Efficiency ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Combustion Model ◽  
Combustion Instabilities ◽  
The Impact

Dilute operation of internal combustion engines through lean fueling and/or high levels of exhaust gas recirculation (EGR) is frequently employed to increase fuel efficiency, reduce NOx emissions, and promote enhanced combustion modes such as HCCI. The maximum level of dilution is limited by the development of combustion instabilities that produce unacceptable levels of cycle-to-cycle combustion variability. These combustion instabilities are frequently stimulated by the nonlinear feedback associated with the residual and recirculated exhaust gases exchanged between successive cycles. However, with the application of adaptive control, it is possible to limit the severity of the combustion variability and regain efficiency and emission reduction benefits that would otherwise be lost. In order to better characterize the benefits of adaptive control, we have employed a two-zone phenomenological combustion model to simulate the onset of combustion instabilities under dilute operating conditions and illustrate the impact of these instabilities on emissions and fuel efficiency. The two-zone in-cylinder combustion model is coupled to a WAVE engine-simulation code, allowing rapid simulation of several hundred successive engine cycles with many external engine parametric effects included. By applying adaptive feedback control to the WAVE model, we demonstrate how mitigation of the extreme combustion events can result in improved efficiency and reduced emissions levels. We expect that this approach can be used to estimate the potential benefits of implementing adaptive control strategies on specific engine platforms to achieve further efficiency and emission-reduction gains.

scholarly journals Effect of Cylinder-by-Cylinder Variation on Performance and Gaseous Emissions of a PFI Spark Ignition Engine: Experimental and 1D Numerical Study

2021 ◽  
Vol 11 (13) ◽  
pp. 6035
Author(s):  
Luigi Teodosio ◽  
Luca Marchitto ◽  
Cinzia Tornatore ◽  
Fabio Bozza ◽  
Gerardo Valentino
Keyword(s):  
Internal Combustion Engines ◽  
Numerical Study ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Gaseous Emissions ◽  
Performance And Emissions ◽  
The Impact

Combustion stability, engine efficiency and emissions in a multi-cylinder spark-ignition internal combustion engines can be improved through the advanced control and optimization of individual cylinder operation. In this work, experimental and numerical analyses were carried out on a twin-cylinder turbocharged port fuel injection (PFI) spark-ignition engine to evaluate the influence of cylinder-by-cylinder variation on performance and pollutant emissions. In a first stage, experimental tests are performed on the engine at different speed/load points and exhaust gas recirculation (EGR) rates, covering operating conditions typical of Worldwide harmonized Light-duty vehicles Test Cycle (WLTC). Measurements highlighted relevant differences in combustion evolution between cylinders, mainly due to non-uniform effective in-cylinder air/fuel ratio. Experimental data are utilized to validate a one-dimensional (1D) engine model, enhanced with user-defined sub-models of turbulence, combustion, heat transfer and noxious emissions. The model shows a satisfactory accuracy in reproducing the combustion evolution in each cylinder and the temperature of exhaust gases at turbine inlet. The pollutant species (HC, CO and NOx) predicted by the model show a good agreement with the ones measured at engine exhaust. Furthermore, the impact of cylinder-by-cylinder variation on gaseous emissions is also satisfactorily reproduced. The novel contribution of present work mainly consists in the extended numerical/experimental analysis on the effects of cylinder-by-cylinder variation on performance and emissions of spark-ignition engines. The proposed numerical methodology represents a valuable tool to support the engine design and calibration, with the aim to improve both performance and emissions.

scholarly journals Comparative study on combustion characteristics of lean premixed CH4/air mixtures in RCM using spark ignition and turbulent jet ignition in terms of orifices angular position change

2019 ◽  
Vol 176 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Wojciech BUESCHKE ◽  
Maciej SKOWRON ◽  
Krzysztof WISŁOCKI ◽  
Filip SZWAJCA
Keyword(s):  
Internal Combustion Engines ◽  
Positive Impact ◽  
Angular Position ◽  
Turbulent Jet ◽  
Combustion Stability ◽  
Optical Observations ◽  
Charge Movement ◽  
Position Change ◽  
Lean Burn ◽  
The Impact

The increase in ignitability consist a main aim of implementation of the turbulent jet ignition (TJI) in relation to the combustion of diluted charges. Such an ignition system has been introduced to the lean-burn CNG engine in the scope of GasOn-Project (Gas Only Internal Combustion Engines). In this study the impact of TJI application on the main combustion indexes has been investigated using RCM and analyzed on the bases of the indicating and optical observations data. The images have been recorded using LaVision HSS5 camera and post-processed with Davis software. Second part of the study based on indicating measurements consist the analysis of combustion regarding the variation in the geometry of pre-chamber nozzles. It has been noted, that combustion with TJI indicates signi- ficantly bigger flame luminescence and simultaneously – faster flame front development, than the combustion initiated with conventional SI. The positive impact of nozzles angular position on engine operational data has been found in the static charge movement conditions, regarding the combustion stability.

scholarly journals Knock Intensity Distribution and a Stochastic Control Framework for Knock Control

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Mateos Kassa ◽  
Carrie Hall ◽  
Michael Pamminger ◽  
Thomas Wallner
Keyword(s):  
Lognormal Distribution ◽  
Control Strategies ◽  
Fuel Efficiency ◽  
Probabilistic Approach ◽  
Engine Performance ◽  
Operating Conditions ◽  
Control Approach ◽  
Spark Timing ◽  
Almost All ◽  
Knock Control

Abstract One of the main factors limiting the efficiency of spark-ignited (SI) engines is the occurrence of engine knock. In high temperature and high pressure in-cylinder conditions, the fuel–air mixture auto-ignites creating pressure shock waves in the cylinder. Knock can significantly damage the engine and hinder its performance; as such, conservative knock control strategies are generally implemented which avoid such operating conditions at the cost of lower thermal efficiencies. Significant improvements in the performance of conventional knock controllers are possible if the properties of the knock process are better characterized and exploited in knock controller designs. One of the methods undertaken to better characterize knocking instances is to employ a probabilistic approach, in which the likelihood of knock is derived from the statistical distribution of knock intensity (KI). In this paper, it is shown that KI values at a fixed operating point for single fuel and dual fuel engines are accurately described using a mixed lognormal distribution. The fitting accuracy is compared against those for a randomly generated mixed-lognormally distributed dataset, and shown to exceed a 95% accuracy threshold for almost all of the operating points tested. Additionally, this paper discusses a stochastic knock control approach that leverages the mixed lognormal distribution to adjust spark timing based on KI measurements. This more informed knock control strategy would allow for improvements in engine performance and fuel efficiency by minimizing knock occurrences.

A Control Oriented SI and HCCI Hybrid Combustion Model for Internal Combustion Engines

2010 ◽  
Author(s):  
Xiaojian Yang ◽  
Guoming G. Zhu ◽  
Zongxuan Sun
Keyword(s):  
Steady State ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Fuel Efficiency ◽  
Combustion Process ◽  
Internal Combustion ◽  
Mean Value ◽  
Combustion Model ◽  
Zone Model ◽  
Transient Control

The combustion mode transition between SI (spark ignited) and HCCI (Homogeneously Charged Compression Ignition) of an IC (Internal Combustion) engine is challenge due to the thermo inertia of residue gas; and model-based control becomes a necessity. This paper presents a control oriented two-zone model to describe the hybrid combustion that starts with SI combustion and ends with HCCI combustion. The gas respiration dynamics were modeled using mean-value approach and the combustion process was modeled using crank resolved method. The developed model was validated in an HIL (Hardware-In-the-Loop) simulation environment for both steady-state and transient operations in SI, HCCI, and SI-HCCI hybrid combustion modes through the exhaust valve timing control (recompression). Furthermore, cooled external EGR (exhaust gas re-circulation) was used to suppress engine knock and enhance the fuel efficiency. The simulation results also illustrates that the transient control parameters of hybrid combustion is quite different from these in steady state operation, indicating the need of a control oriented SI-HCCI hybrid combustion model for transient combustion control.

Impact of Fuel Composition on Blow Off and Flashback in Swirl Stabilized Lean Premixed Combustion

2013 ◽  
Author(s):  
Amin Akbari ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Fuel Composition ◽  
Pure Hydrogen ◽  
Combustion Properties ◽  
Lean Premixed ◽  
The Impact

Co firing of natural gas with renewable fuels such as hydrogen can reduce greenhouse gas emissions, and meet other sustainability considerations. At the same time, adding hydrogen to natural gas alters combustion properties, such as burning speeds, heating values, flammability limits, and chemical characteristics. It is important to identify how combustion stability relates to fuel mixture composition in industrial gas turbines and burners and correlate such behavior to fuel properties or operating conditions. Ultimately, it is desired to predict and prevent operability issues when designing a fuel flexible gas turbine combustor. Fuel interchangeability is used to describe the ability of a substitute fuel composition to replace a baseline fuel without significantly altering performance and operation. Any substitute fuel, while maintaining the same heating load as the baseline fuel, must also provide stable combustion with low pollutant emissions. Interchangeability indices try to predict the impact of fuel composition on lean blowoff and flashback. Correlations for operability limits have been reported, though results are more consistent for blowoff compared to flashback. Yet, even for blowoff, some disagreement regarding fuel composition effects are evident. In the present work, promising correlations and parameters for lean blow off and flashback in a swirl stabilized lean premixed combustor are evaluated. Measurements are conducted for fuel compositions ranging from pure natural gas to pure hydrogen under different levels of preheat and air flow rates. The results are used to evaluate the ability of existing approaches to predict blowoff and flashback. The results show that, while a Damköhler number approach for blowoff is promising, important considerations are required in applying the method. For flashback, the quench constant parameter suggested for combustion induced vortex breakdown was applied and found to have limited success for predicting flashback in the present configuration.

Adaptive Wiebe Function Parameters for a Port-Fuel Injected Hydrogen-Fueled Engine

2019 ◽  
Author(s):  
Shah Saud Alam ◽  
Christopher Depcik
Keyword(s):  
Experimental Data ◽  
Mass Fraction ◽  
Internal Combustion Engines ◽  
Operating Conditions ◽  
High Mass ◽  
Parameter Determination ◽  
Complete Combustion ◽  
Burn Rate ◽  
The Impact ◽  
Wiebe Function

Abstract Current unmanned aerial vehicle (UAV) propulsion technologies includes hydrogen fuel cells, battery systems, and internal combustion engines (ICE). However, relying on a single propulsion technology might result in a limited operational range. This can be mitigated by utilizing a hybrid configuration involving a battery pack and an ICE or a fuel cell for charging. Due to its significant weight advantage and high mass-specific energy content, hydrogen (H2) is an ideal fuel for both power plant options. However, use of H2 with an ICE requires precise operational control through combustion process simulation with the predictive approximation of the mass fraction burned profile. In this area, the relatively simple single-Wiebe function is widely deployed for a variety of different fuels, as well as combustion regimes. In general, the description of the single-Wiebe function includes the extent of complete combustion (a), magnitude of the maximum burn rate (m), and combustion duration (θd). However, the literature often provides values for these parameters without necessarily relating them to operational characteristics that can influence ICE power. As a result, it is critical to correlate the burn rate of the fuel to ICE operating parameters, such as the engine compression ratio, inlet pressure, mean piston speed, exhaust gas recirculation level, equivalence ratio, and spark timing. Therefore, in an attempt to physically define these parameters, this effort performs a sensitivity analysis using linear regression (least squares method) to assess the impact of engine operating conditions on the Wiebe function in comparison to experimental data for port-fuel injected hydrogen ICEs. The result is a model that can estimate the values of a, m, and θd in combination with a relatively high coefficient of determination (R2) when compared to the experimental mass fraction burned profiles. Finally, others can expand this methodology to any experimental data for engine and fuel-specific Wiebe parameter determination.

scholarly journals Simulation of the performance of alternative refrigerants in liquid chillers

2001 ◽  
Vol 215 (4) ◽  
pp. 429-441 ◽  
Author(s):  
I. N. Grace ◽  
S. A. Tassou
Keyword(s):  
Dynamic Models ◽  
Control Strategies ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
System Component ◽  
Alternative Refrigerants ◽  
Expansion Valve ◽  
Shell And Tube Evaporator ◽  
The Impact

The impact of refrigeration systems on the environment can be reduced by (a) the use of alternative refrigerants which are less harmful to the environment and (b) the optimization of systems and control strategies to deliver increased levels of energy efficiency. Mathematical modelling offers the opportunity to test the performance of systems under different operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady state behaviour and this is of particular importance for liquid chillers since these systems can operate under transient conditions for long periods. This paper covers the development of a general dynamic model for the simulation of liquid chillers. Brief descriptions of the system component models are given, including a semihermetic reciprocating compressor and thermostatic expansion valve as well as a shell-and-tube evaporator and condenser. The paper demonstrates the application of the model to simulate the performance of a liquid chiller retrofitted with a range of alternative refrigerants. The performance of the system is determined in terms of cooling capacity, power consumption and coefficient of performance for a range of different operating conditions. The relative performance of each refrigerant is discussed and the preferred alternative identified for typical applications.

scholarly journals The Influence of Charge Motion on Pre-Chamber and Main Chamber Combustion in a Highly Dilute Jet Ignition Engine

2021 ◽  
Vol 6 ◽  
Author(s):  
Michael Bunce ◽  
Alasdair Cairns ◽  
Sai Krishna Pothuraju Subramanyam ◽  
Nathan Peters ◽  
Hugh Blaxill
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
System Optimization ◽  
Combustion Stability ◽  
Main Chamber ◽  
Charge Motion ◽  
Ignition System ◽  
Lean Combustion ◽  
Si Engines ◽  
The Impact

Though there are multiple viable powertrain options available for the automotive sector, those that contain internal combustion engines will continue to account for the majority of global sales for the next several decades. It is therefore imperative to continue the pursuit of novel combustion concepts that produce efficiency levels significantly higher than those of current engines. Introducing high levels of dilution in spark ignited (SI) engines has consistently proven to produce an efficiency benefit compared to conventional stoichiometric engine operation. However, this combustion mode can present challenges for the ignition system. Pre-chamber jet ignition enables stable, highly dilute combustion by both increasing the ignition energy present in the system and distributing it throughout the combustion chamber. Previous work by the authors have shown that jet ignition produces 15–25% increases in thermal efficiency over baseline SI engines with only relatively minor changes to engine architecture. Lean combustion in general and jet ignition in particular represent fundamentally different engine operating modes compared to those of conventional stoichiometric SI engines. Therefore, there are some system sensitivities not present in stoichiometric engines that must be investigated in order to fully optimize the jet ignition system. Differing types and magnitudes of charge motion are incorporated in SI engines to aid with mixture preparation but the influence of charge motion over lean combustion performance, particularly in jet ignition engines, is less well understood. This study analyzes the impact that charge motion has on both pre-chamber and main chamber combustion. A 1.5 L 3-cylinder gasoline engine is outfitted with multiple intake port configurations producing varying magnitudes and types of charge motion. Pre-chamber and main chamber combustion stability and other burn parameter responses are analyzed across multiple speeds and loads, including at critical operating points such as a catalyst heating condition. The results show that there is combustion sensitivity to charge motion, resulting in >1 percentage point spread in peak thermal efficiency for the configurations tested, and that this sensitivity manifests most significantly under low ignitability conditions such as heavy dilution. These results provide guidance for future system optimization of jet ignition engines.

Combustion Tuning Guidelines: Understanding and Mitigating Dynamic Instabilities in Modern Gas Turbine Combustors

2004 ◽  
Author(s):  
Leonard C. Angello ◽  
Carlo Castaldini
Keyword(s):  
Operating Conditions ◽  
Combustion Noise ◽  
Combustion Stability ◽  
Combustion Instabilities ◽  
Monitoring And Control ◽  
Single Digit ◽  
Active Monitoring ◽  
Critical System ◽  
Premature Failure ◽  
And Control

DLN combustors used in modern utility Combustion Turbines (CTs) must operate within tight tolerances of equivalence ratio, fuel/air mixing and turbulence in order to deliver single digit NOx emission performance, while maintaining combustion stability and design power output. As lean NOx emissions from large CTs are driven to increasingly lower levels, even small changes in combustion conditions or manufacturing tolerances can lead to the onset of combustion instabilities and acoustic combustion noise. If left unattended, dynamic oscillations in ultra-low NOx premix combustors can produce resonant acoustics that can in turn cause adverse impacts on performance, including the ability to deliver capacity, or the premature failure of critical system components and emergency shut-downs. For example, it is widely accepted that extreme changes in ambient temperature, or minor changes in fuel composition and temperature, or the use of power augmentation techniques under certain conditions, can lead to combustion instabilities. EPRI is leading a multi-task program to map the operating regime for stable combustion in modern DLN combustors; identify key operating conditions that most influence the onset of combustion instabilities; and develop DLN tuning guidelines based on users’ experience and vendors’ monitoring and control systems. The overall objective of these projects is to maximize the operational flexibility of modern CTs based on implementation of active monitoring and control guidelines aimed at anticipating, preventing, and effectively responding to the onset of combustion-induced dynamic instabilities and CT noise. This paper briefly discusses the dynamics of combustion instabilities in premix DLN combustors; presents the preliminary results from detailed parametric analysis of a large database; and our findings on DLN tuning approaches such as modulating fuel flows and changing inlet guide vanes, that can be used effectively to control combustion instabilities.

Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Emissions

2018 ◽  
Author(s):  
L. Mazzei ◽  
S. Puggelli ◽  
D. Bertini ◽  
A. Andreini ◽  
B. Facchini ◽  
...  
Keyword(s):  
Combustion Process ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Combustion Model ◽  
Flame Spray ◽  
Lean Burn ◽  
Flamelet Generated Manifold ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
The Impact

Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation however involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. Also the conditions at the combustor exit are a concern, as high turbulence, residual swirl and the impossibility to adjust the temperature profile with dilution holes determine a harsher environment for nozzle guide vanes. This work describes the final stages of the design of an aeronautical effusion-cooled lean burn combustor. Full annular tests were carried out to measure temperature profiles and emissions (CO and NOx) at the combustor exit. Different operating conditions of the ICAO cycle were tested, considering Idle, Cruise, Approach and Take-Off. Scale-adaptive simulations with the Flamelet Generated Manifold combustion model were performed to extend the validation of the employed CFD methodology and to reproduce the experimental data in terms of RTDF/OTDF profiles as well as emission indexes. The satisfactory agreement paved the way to an exploitation of the methodology to provide a deeper understanding of the flow physics within the combustion chamber, highlighting the impact of the different operating conditions on flame, spray evolution and pollutant formation.

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