Numerical Analysis of the Combustion Process in Dual-Fuel Engines With Direct Injection of Natural Gas

2018 ◽  
Author(s):  
Michael Jud ◽  
Christoph Wieland ◽  
Georg Fink ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Direct Injection ◽  
Computing Time ◽  
Combustion Process ◽  
Gas Jet ◽  
Combustion Model ◽  
Dual Fuel ◽  
Detailed Chemistry ◽  
Geometric Configurations ◽  
Temperature Levels

An efficient computational fluid dynamics model for predicting high pressure dual-fuel combustion is one of the most essential steps in order to improve the concept, to reduce the number of experiments and to make the development process more coste-efficient. For Diesel and natural gas such a model developed by the authors is first used to analyze the combustion process with respect to turbulence chemistry interaction and to clarify the question whether the combustion process is limited by chemistry or the mixing process. On the basis of these findings a reduced reaction mechanism is developed in order to save up to 35% of computing time. The prediction capability of the modified combustion model is tested for different gas injection timings representing different degrees of premixing before ignition. Compared to experimental results from a rapid compression expansion machine, the shape of heat release rate, the ignition timing of the gas jet and the burnout are well predicted. Finally, misfiring observed at different geometric configurations in the experiment are analyzed with the model. It is identified that in these geometric configurations at low temperature levels the gas jet covers the preferred ignition region of the diesel jet. Since the model is based on the detailed chemistry approach, it can in future also be used for other fuel combinations or for predicting emissions.

Predicting Ignition and Combustion of a Pilot Ignited Natural Gas Jet Using Numerical Simulation Based on Detailed Chemistry

2017 ◽  
Author(s):  
Michael Jud ◽  
Georg Fink ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Direct Injection ◽  
Dual Fuel ◽  
Pressure Curve ◽  
Detailed Chemistry ◽  
Dual Fuel Combustion ◽  
Good Agreement

In this paper, a multidimensional computational fluid dynamics (CFD) model coupled with detailed chemistry calculations was used to analyze dual-fuel combustion based on high pressure direct injection of natural gas. The main focus was to analyze the capability of predicting pressure curve and heat release rate (HRR) for different injection strategies. Zero-dimensional homogeneous constant volume reactor calculations were used to select a reaction mechanism for the temperature range below 800 K. As the best-performing mechanism, the Chalmers mechanism was chosen. To validate the numerical model, the setup was first split into a single gas injection and a single Diesel injection. They were validated individually using shadowgraphs obtained from a Rapid Compression Expansion Machine (RCEM). Diesel ignition timing and position in the combustion chamber were close to experimental results. Gas direct injection showed good agreement with regard to penetration and mixing. In the dual-fuel setup, the injection timing of natural gas was varied to create a first case with mainly diffusive combustion and a second case with mainly premixed combustion of natural gas. For both setups good agreement with pressure curve and heat release rate were achieved. A qualitative comparison of shadowgraphs with the density field highlights the important points to predict dual-fuel combustion.

scholarly journals Use of Adaptive Injection Strategies to Increase the Full Load Limit of RCCI Operation

2015 ◽  
Author(s):  
Reed Hanson ◽  
Andrew Ickes ◽  
Thomas Wallner
Keyword(s):  
Natural Gas ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Direct Injection ◽  
Peak Load ◽  
Combustion Process ◽  
Pressure Rise ◽  
Dual Fuel ◽  
The Impact ◽  
Injection Strategies

Dual-fuel combustion using port-injection of low reactivity fuel combined with direct injection of a higher reactivity fuel, otherwise known as Reactivity Controlled Compression Ignition (RCCI), has been shown as a method to achieve low-temperature combustion with moderate peak pressure rise rates, low engine-out soot and NOx emissions, and high indicated thermal efficiency. A key requirement for extending to high-load operation is moderating the reactivity of the premixed charge prior to the diesel injection. One way to accomplish this is to use a very low reactivity fuel such as natural gas. In this work, experimental testing was conducted on a 13L multi-cylinder heavy-duty diesel engine modified to operate using RCCI combustion with port injection of natural gas and direct injection of diesel fuel. Engine testing was conducted at an engine speed of 1200 RPM over a wide variety of loads and injection conditions. The impact on dual-fuel engine performance and emissions with respect to varying the fuel injection parameters is quantified within this study. The injection strategies used in the work were found to affect the combustion process in similar ways to both conventional diesel combustion and RCCI combustion for phasing control and emissions performance. As the load is increased, the port fuel injection quantity was reduced to keep peak cylinder pressure and maximum pressure rise rate under the imposed limits. Overall, the peak load using the new injection strategy was shown to reach 22 bar BMEP with a peak brake thermal efficiency of 47.6%.

Fundamental Study of Diesel-Piloted Natural Gas Direct Injection Under Different Operating Conditions

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Direct Injection ◽  
Combustion Process ◽  
Operating Conditions ◽  
Gas Jet ◽  
Ignition And Combustion

Natural gas as an alternative fuel in engine applications substantially reduces both pollutant and greenhouse gas emissions. High pressure dual fuel (HPDF) direct injection of natural gas and diesel pilot has the potential to minimize methane slip from gas engines and increase the fuel flexibility, while retaining the high efficiency of a diesel engine. Speed and load variations as well as various strategies for emission reduction entail a wide range of different operating conditions. The influence of these operating conditions on the ignition and combustion process is investigated on a rapid compression expansion machine (RCEM). By combining simultaneous shadowgraphy (SG) and OH* imaging with heat release rate analysis, an improved understanding of the ignition and combustion process is established. At high temperatures and pressures, the reduced pilot ignition delay and lift-off length minimize the effect of natural gas jet entrainment on pilot mixture formation. A simple geometrical constraint was found to reflect the susceptibility for misfiring. At the same time, natural gas ignition is delayed by the early pilot ignition close to the injector tip. The shape of heat release is only marginally affected by the operating conditions and mainly determined by the degree of premixing at the time of gas jet ignition. Luminescence from the sooting natural gas flame is generally only detected after the flame extends across the whole gas jet at peak heat release rate. Termination of gas injection at this time was confirmed to effectively suppress soot formation, while a strongly sooting pilot seems to intensify soot formation within the natural gas jet.

Fundamental Study of Diesel-Piloted Natural Gas Direct Injection Under Different Operating Conditions

2018 ◽  
Author(s):  
Georg Fink ◽  
Michael Jud ◽  
Thomas Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Direct Injection ◽  
Combustion Process ◽  
Operating Conditions ◽  
Gas Jet ◽  
Ignition And Combustion

Natural gas as an alternative fuel in engine applications substantially reduces both pollutant and greenhouse gas emissions. High pressure dual fuel direct injection of natural gas and Diesel pilot has the potential to minimize methane slip from gas engines and increase the fuel flexibility, while retaining the high efficiency of a Diesel engine. Speed and load variations as well as various strategies for emission reduction entail a wide range of different operating conditions. The influence of these operating conditions on the ignition and combustion process is investigated on a rapid compression expansion machine. By combining simultaneous Shadowgraphy and OH* imaging with heat release rate analysis, an improved understanding of the ignition and combustion process is established. At high temperatures and pressures the reduced pilot ignition delay and lift-off length minimize the effect of natural gas jet entrainment on pilot mixture formation. A simple geometrical constraint was found to reflect the susceptibility for misfiring. At the same time natural gas ignition is delayed by the early pilot ignition close to the injector tip. The shape of heat release is only marginally affected by the operating conditions and mainly determined by the degree of premixing at the time of gas jet ignition. Luminescence from the sooting natural gas flame is generally only detected after the flame extends across the whole gas jet at peak heat release rate. Termination of gas injection at this time was confirmed to effectively suppress soot formation, while a strongly sooting pilot seems to intensify soot formation within the natural gas jet.

scholarly journals Simulation of the combustion in a dual fuel engine with a divided pilot dose

2012 ◽  
Vol 151 (4) ◽  
pp. 43-54
Author(s):  
Zdzisław STELMASIAK ◽  
Marcin MATYJASIK
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Diesel Oil ◽  
Combustion Model ◽  
Dual Fuel ◽  
Variable Load ◽  
Simulation Studies ◽  
Combustion Dynamics ◽  
Injection Angle ◽  
Ecological Features

The paper presents a simulation of the combustion process in a dual fuel engine fueled with natural gas and diesel oil with a divided fuel dose. Diesel fuel doses – the pilot and the extra dose were injected at different times and the combustion process was different in terms of dynamics and duration. The task of the additional fuel dose was to maintain combustion, which should lead to improved engine efficiency and better ecological features. Dynamometer tests have confirmed the initial assumptions. Simulation studies have been conducted based on the original combustion model assuming different combustion of two different doses of diesel oil and natural gas. The parameters of the medium in the combustion chamber and the energy-related effect are a superposition of three separate fuel combustion processes of different combustion dynamics. The validation of the model was based on an SB3.1 engine test (engine operating under variable load and speed). Simulation studies have shown a significant effect of the initiating dose and the injection angle of the additional dose on the engine combustion parameters. The conclusions from the simulation studies can be used for the adjustment of dual fuel engines fueled with natural gas and diesel oil.

scholarly journals A Numerical Study on the Combustion Process and Emission Characteristics of a Natural Gas-Diesel Dual-Fuel Marine Engine at Full Load

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1342
Author(s):  
Van Chien Pham ◽  
Jae-Hyuk Choi ◽  
Beom-Seok Rho ◽  
Jun-Soo Kim ◽  
Kyunam Park ◽  
...  
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Simulation Software ◽  
Dual Fuel ◽  
Injection Timing ◽  
Emission Characteristics ◽  
Cylinder Pressure ◽  
Marine Engine ◽  
Full Load ◽  
Simulation Results

This paper presents research on the combustion and emission characteristics of a four-stroke Natural gas–Diesel dual-fuel marine engine at full load. The AVL FIRE R2018a (AVL List GmbH, Graz, Austria) simulation software was used to conduct three-dimensional simulations of the combustion process and emission formations inside the engine cylinder in both diesel and dual-fuel mode to analyze the in-cylinder pressure, temperature, and emission characteristics. The simulation results were then compared and showed a good agreement with the measured values reported in the engine’s shop test technical data. The simulation results showed reductions in the in-cylinder pressure and temperature peaks by 1.7% and 6.75%, while NO, soot, CO, and CO2 emissions were reduced up to 96%, 96%, 86%, and 15.9%, respectively, in the dual-fuel mode in comparison with the diesel mode. The results also show better and more uniform combustion at the late stage of the combustions inside the cylinder when operating the engine in the dual-fuel mode. Analyzing the emission characteristics and the engine performance when the injection timing varies shows that, operating the engine in the dual-fuel mode with an injection timing of 12 crank angle degrees before the top dead center is the best solution to reduce emissions while keeping the optimal engine power.

Simulation Research on Combustion Process in a Natural Gas-Diesel Dual-Fuel Marine Engine

2014 ◽  
Vol 525 ◽  
pp. 227-231 ◽  
Author(s):  
Min Xiao ◽  
Chun Long Feng
Keyword(s):  
Natural Gas ◽  
Total Energy ◽  
Combustion Process ◽  
Power Reduction ◽  
Dual Fuel ◽  
Injection Timing ◽  
Simulation Research ◽  
Injection Duration ◽  
Medium Speed ◽  
The Right

In order to solve the problem of Diesel natural gas dual fuel engine, such as power reduction, low charging efficiency, the conception of diesel engine fueled with pilot-ignited directly-injected liquefied natural gas is put forward. On the basis of this theory, a medium speed diesel of the marine is refitted into dual fuel engine, in order to keep original power, decrease the temperature of combustion and reduce emission. The LNG injection timing, duration of LNG injection and the different ratios the pilot diesel to total energy are studied the method of AVL FIRE software. Conclusions are as follows: When the different ratios pilot diesel to total energy is 0.5%, the engine can not work; Delaying the LNG injection timing, shortening the LNG injection duration and choose the right ratios pilot diesel to total energy can reach the indicated power of original machine, and the NOx emissions level will be greatly reduced.

scholarly journals Numerical Study of Engine Performance and Emissions for Port Injection of Ammonia into a Gasoline\Ethanol Dual-Fuel Spark Ignition Engine

2021 ◽  
Vol 11 (4) ◽  
pp. 1441
Author(s):  
Farhad Salek ◽  
Meisam Babaie ◽  
Amin Shakeri ◽  
Seyed Vahid Hosseini ◽  
Timothy Bodisco ◽  
...  
Keyword(s):  
Numerical Study ◽  
Combustion Process ◽  
Engine Performance ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Combustion Model ◽  
Dual Fuel ◽  
Spark Ignition Engines ◽  
Performance And Emissions ◽  
Hc Emissions

This study aims to investigate the effect of the port injection of ammonia on performance, knock and NOx emission across a range of engine speeds in a gasoline/ethanol dual-fuel engine. An experimentally validated numerical model of a naturally aspirated spark-ignition (SI) engine was developed in AVL BOOST for the purpose of this investigation. The vibe two zone combustion model, which is widely used for the mathematical modeling of spark-ignition engines is employed for the numerical analysis of the combustion process. A significant reduction of ~50% in NOx emissions was observed across the engine speed range. However, the port injection of ammonia imposed some negative impacts on engine equivalent BSFC, CO and HC emissions, increasing these parameters by 3%, 30% and 21%, respectively, at the 10% ammonia injection ratio. Additionally, the minimum octane number of primary fuel required to prevent knock was reduced by up to 3.6% by adding ammonia between 5 and 10%. All in all, the injection of ammonia inside a bio-fueled engine could make it robust and produce less NOx, while having some undesirable effects on BSFC, CO and HC emissions.

Prediction of Pressure Rise in a Gas Turbine Exhaust Duct Under Flameout Scenarios While Operating On Hydrogen and Natural Gas Blends

2021 ◽  
Author(s):  
Orlando Ugarte ◽  
Suresh Menon ◽  
Wayne Rattigan ◽  
Paul Winstanley ◽  
Priyank Saxena ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Combustion Model ◽  
Computational Domain ◽  
Cfd Model ◽  
Exhaust Duct ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Abstract In recent years, there is a growing interest in blending hydrogen with natural gas fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity CFD model provide a cost-effective way of assessing the safety risk. In this study, a computational model is implemented to perform three dimensional, compressible and unsteady simulations of reacting flows in a gas turbine exhaust duct. Computational results were validated against data obtained at the simulated conditions in a representative geometry. Due to the enormous size of the geometry, special attention was given to the discretization of the computational domain and the combustion model. Results show that CFD model predicts main features of the pressure rise driven by the combustion process. The peak pressures obtained computationally and experimentally differed in 20%. This difference increased up to 45% by reducing the preheated inflow conditions. The effects of rig geometry and flow conditions on the accuracy of the CFD model are discussed.

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