Knock Prediction in Industrial Dual Fuel Engines Using a Two-Zone Combustion Model With Consideration of Chemical Kinetics

2008 ◽  
Author(s):  
Ahmed Al-Sened ◽  
Hesameddin Safari ◽  
Mojtaba Keshavarz ◽  
Ghasem Javadirad
Keyword(s):  
Diesel Fuel ◽  
Fuel Injection ◽  
Chemical Reactivity ◽  
Gaseous Fuel ◽  
Combustion Model ◽  
Dual Fuel ◽  
Injection Timing ◽  
Boost Pressure ◽  
Fuel Mass ◽  
Dual Fuel Engines

Knock is well recognized as a destructive phenomenon to be avoided when running dual fuel engines. Typically, it occurs at high loads and high ambient temperatures and its onset has always been difficult to predict, particularly where multiple fuels are present. In a dual fuel engine, knock can occur from either the diesel or the gaseous fuel and it is recognised that the ratio of diesel fuel mass to gaseous fuel mass is an important index in determining which type of knock is predominant. This paper describes the development of a two-zone predictive model for the onset of knock in a dual fuel engine. Prediction of spark knock onset is the main objective of present work. A 9-step short mechanism with 11 chemical species, developed specifically for modelling dual fuel operation, is used to determine the chemical reactivity of the end-gas zone. The contribution of pilot diesel fuel combustion is taken into account by a heat release model. Chemical equilibrium is assumed for the burned gas zone. Simulation results predict the point of knock-limited BMEP and its dependency on operating parameters such as air intake temperature, boost pressure, start of pilot fuel injection timing and compression ratio. The results were first validated against some published engine analysis data and also some in-house performance prediction data. Secondly, a known dual-fuel development engine was simulated. Finally, the performance of an engine which had been converted from diesel to dual fuel during its service life was modeled but commercial constraints prevent the identification of this engine within this paper. However, good agreement with existing performance data was demonstrated in all these cases.

A phenomenological combustion analysis of a dual-fuel natural-gas diesel engine

2016 ◽  
Vol 231 (1) ◽  
pp. 66-83 ◽  
Author(s):  
Shuonan Xu ◽  
David Anderson ◽  
Mark Hoffman ◽  
Robert Prucka ◽  
Zoran Filipi
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Heat Release ◽  
Diesel Fuel ◽  
Fuel Injection ◽  
Dual Fuel ◽  
Injection Timing ◽  
Heavy Duty ◽  
Engine System ◽  
Wiebe Function

Energy security concerns and an abundant supply of natural gas in the USA provide the impetus for engine designers to consider alternative gaseous fuels in the existing engines. The dual-fuel natural-gas diesel engine concept is attractive because of the minimal design changes, the ability to preserve a high compression ratio of the baseline diesel, and the lack of range anxiety. However, the increased complexity of a dual-fuel engine poses challenges, including the knock limit at a high load, the combustion instability at a low load, and the transient response of an engine with directly injected diesel fuel and port fuel injection of compressed natural gas upstream of the intake manifold. Predictive simulations of the complete engine system are an invaluable tool for investigations of these conditions and development of dual-fuel control strategies. This paper presents the development of a phenomenological combustion model of a heavy-duty dual-fuel engine, aided by insights from experimental data. Heat release analysis is carried out first, using the cylinder pressure data acquired with both diesel-only and dual-fuel (diesel and natural gas) combustion over a wide operating range. A diesel injection timing correlation based on the injector solenoid valve pulse widths is developed, enabling the diesel fuel start of injection to be detected without extra sensors on the fuel injection cam. The experimental heat release trends are obtained with a hybrid triple-Wiebe function for both diesel-only operation and dual-fuel operation. The ignition delay period of dual-fuel operation is examined and estimated with a predictive correlation using the concept of a pseudo-diesel equivalence ratio. A four-stage combustion mechanism is discussed, and it is shown that a triple-Wiebe function has the ability to represent all stages of dual-fuel combustion. This creates a critical building block for modeling a heavy-duty dual-fuel turbocharged engine system.

Combustion Quasi-Two Zone Predictive Model for Dual Fuel Engines

1999 ◽  
Author(s):  
G. H. Abd Alla ◽  
H. A. Soliman ◽  
O. A. Badr ◽  
M. F. Abd Rabbo
Keyword(s):  
Predictive Model ◽  
Combustion Process ◽  
Chemical Species ◽  
Kinetic Scheme ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Gaseous Fuel ◽  
Combustion Model ◽  
Dual Fuel ◽  
Dual Fuel Engines

Abstract A quasi-two zone predictive model developed in the present work for the prediction of the combustion processes in dual fuel engines and some of their performance features. Methane is used as the main fuel while employing a small quantity of liquid fuel (pilot) injected through the conventional diesel fuel system. This model emphasizes the effects of chemical kinetics activity of the premixed gaseous fuel on the combustion performance, while the role of the pilot fuel in the ignition and heat release processes is considered. A detailed chemical kinetic scheme consists of 178 elementary reaction steps and 41 chemical species is employed to describe the oxidation of the gaseous fuel from the start of compression to the end of expansion process. The associated formation and concentrations of exhaust emissions are correspondingly established. This combustion model is able to establish the development of the combustion process with time and the associated important operating parameters such as pressure, temperature, rates of energy release and composition. Predicted values for methane operation show good agreement with corresponding previous experimental values over a range of operating conditions mainly associated with high load operation.

3D-CFD Simulation of Diesel and Dual Fuel Engine Combustion

2007 ◽  
Author(s):  
Chengke Liu ◽  
G. A. Karim
Keyword(s):  
Cfd Simulation ◽  
Fuel Injection ◽  
Combustion Process ◽  
Dual Fuel ◽  
Injection Timing ◽  
Combustion Chambers ◽  
Detailed Chemical Kinetics ◽  
Swirl Chamber ◽  
Dual Fuel Engines ◽  
Combustion Processes

A 3D-CFD model with a reduced detailed chemical kinetics of the combustion of diesel and methane fuels is developed while considering turbulence during combustion to simulate the mixture flow, formation and combustion processes within diesel and diesel/methane dual fuel engines having swirl chambers. The combustion characteristics of the pilot injection into a small pre-chamber are also investigated and compared with those within a swirl chamber. Modeling results were validated by a group of corresponding experimental data. The spatial and temporal distributions of the mixture temperature, pressure and velocity under conditions with and without liquid fuel injection and combustion are compared in the swirl and main combustion chambers. The effects of engine speed, injection timing, and the addition of carbon dioxide on the combustion process of dual fuel engines are investigated. It is found that in the absence of any fuel injection and combustion, the swirl center is initially formed at the bottom left of the swirl chamber, and then moved up with continued compression in the top-right direction toward the highest point. The swirling motion within the swirl and main combustion chambers promotes the evaporation of the liquid pilot and the combustion processes of diesel and dual fuel engines. It was observed that an earlier autoignition can be obtained through injecting the pilot fuel into the small prechamber compared to the corresponding swirl chamber operation. It is to be shown that reduced engine emissions and improved thermal efficiency can be achieved by two-stage HCCI combustion.

Ignition Delay in Dual Fuel Engines: An Extended Correlation for Gaseous Fuels

2001 ◽  
Author(s):  
A. Bilcan ◽  
M. Tazerout ◽  
O. Le Corre ◽  
A. Ramesh
Keyword(s):  
Ignition Delay ◽  
Energy Content ◽  
Gaseous Fuel ◽  
Dual Fuel ◽  
Polytropic Index ◽  
Injection Timing ◽  
Producer Gas ◽  
Gaseous Fuels ◽  
Specific Heats ◽  
Dual Fuel Engines

Abstract Agricultural & municipal waste and wood residues can be easily converted to biogas or producer gas and used for producing heat and power. The main problem with these fuels is their low energy content. This is due to the presence of certain non-combustible gases like CO2 and N2 in these fuels. The use of these gases in SI engines is associated with problems like unstable operation and high levels of HC and CO emissions. Gaseous fuel can be easily used with good efficiencies and low emissions in diesel engines running in the dual-fuel mode. In dual-fuel engines, these gaseous fuels are inducted along with air and ignited after compression by a small spray of diesel called the pilot. The presence of these gases alters the thermodynamic properties of the intake charge and significantly influence the ignition delay of the pilot diesel fuel and hence the performance of the engine. The aim of this paper is to modify an existing correlation for ignition delay in a dual-fuel engine to incorporate the effects of the gaseous fuel concentration and composition on the polytropic index. An ignition delay correlation of a biogas dual-fuel engine was modified so that it can be used with any primary fuel. The polytropic index was assumed to be a function of the ratio of specific heats. Further, the effect of injection timing on ignition delay was included. The adapted model was introduced in a simulation program and the results of ignition delay were compared with those given in the literature for a dual-fuel engine. In addition, the correlation was used to predict the ignition delay of the pilot fuel when biogas, LPG, natural gas and producer gas were treated as primary fuels. The results obtained with the new correlation have been compared with experimental values from a LPG-diesel dual fuel engine. The comparison was also made for a biogas dual fuel engine. Errors less than 10% were obtained for both of the fuels between the experimental measurements and simulation results.

Three-Dimensional Computational Fluid Simulation of Diesel and Dual Fuel Engine Combustion

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Chengke Liu ◽  
G. A. Karim
Keyword(s):  
Fuel Injection ◽  
Combustion Process ◽  
Fluid Simulation ◽  
Dual Fuel ◽  
Injection Timing ◽  
Detailed Chemical Kinetics ◽  
Mixture Flow ◽  
Swirl Chamber ◽  
Dual Fuel Engines ◽  
Combustion Processes

A 3D computational fluid dynamics model with a reduced detailed chemical kinetics of the combustion of diesel and methane fuels is developed while considering turbulence during combustion to simulate the mixture flow, formation, and combustion processes within diesel and diesel/methane dual fuel engines having swirl chambers. The combustion characteristics of the pilot injection into a small prechamber are also investigated. Modeled results were validated by a group of corresponding experimental data. The spatial and temporal distributions of the mixture temperature, pressure, and velocity under conditions with and without liquid fuel injection and combustion are compared. The effects of engine speed, injection timing, and the addition of carbon dioxide on the combustion process of dual fuel engines are investigated. It is found that in the absence of any fuel injection and combustion, the swirl center is initially formed at the bottom-left of the swirl chamber, and then moved up with continued compression in the top-right direction toward the highest point. The swirling motion within the swirl and main combustion chambers promotes the evaporation of the liquid pilot and the combustion processes of diesel and dual fuel engines. It was observed that an earlier autoignition can be obtained through injecting the pilot fuel into the small prechamber compared with the corresponding swirl chamber operation. It is to be shown that reduced engine emissions and improved thermal efficiency can be achieved by a two-stage homogenous charge compression ignition combustion.

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