Influence of Prechamber-Geometry and Operating-Parameters on Cycle-to-Cycle Variations in Lean Large-Bore Natural Gas Engines

2012 ◽  
Author(s):  
S. Kammerstätter ◽  
T. Sattelmayer
Keyword(s):  
Natural Gas ◽  
Light Emission ◽  
Combustion Process ◽  
Pressure Rise ◽  
Operating Parameters ◽  
Main Chamber ◽  
Ignition Probability ◽  
Natural Gas Engines ◽  
University Of Munich ◽  
Large Cylinder

Lean large-bore natural gas engines are usually equipped with gas-scavenged prechambers. After ignition and during combustion in the prechamber hot reacting jets penetrate the main chamber and provide much higher ignition energies than electric spark plugs. Although prechambers stabilize combustion, limitations of the concept are observed at very lean main chamber mixtures and large cylinder diameters, which appear as cycle-to-cycle variations of heat release and pressure. At the Thermodynamics Institute of the Technical University of Munich cycle-to-cycle variations are investigated in an unique periodically chargeable high pressure combustion cell with full optical access to the entire main chamber. Recently, the influence of the ignition timing, the amount of scavenge-gas of the prechamber and the cross section of the prechamber exit orifices on cycle-to-cycle variations have been studied. From the pressure traces characteristic parameters of the combustion process like the ignition probability, the ignition delay and the rate of the pressure rise have been derived. By analysing the emission of OH*-chemiluminescence in terms of reacting area and light emission and on the basis of numerical simulations information on the source of cycle-to-cycle variations is obtained. Finally it is shown that cycle-to-cycle variations can be reduced remarkably by appropriate selection and combination of prechamber geometry and operating parameters.

Jet-Penetration in Prechamber-Ignited Lean Large-Bore Natural Gas Engines

2012 ◽  
Author(s):  
S. Kammerstätter ◽  
S. Bauer ◽  
T. Sattelmayer
Keyword(s):  
Natural Gas ◽  
Heat Release ◽  
Reaction Zone ◽  
Pressure Rise ◽  
Chamber Pressure ◽  
Main Chamber ◽  
Penetration Length ◽  
Ignition Probability ◽  
Natural Gas Engines ◽  
Jet Penetration

Combustion in lean large-bore natural gas engines is usually initiated by gas-scavenged prechambers. The hot reacting products of the combustion in the prechamber penetrate the main chamber as reacting jets, providing high ignition energy for the lean main chamber charge. The shape and intensity of the reaction zone in these jets are the key elements for efficient ignition and heat release in the main chamber. The influence of geometrical and operational parameters on the reaction during jet penetration was investigated in detail. As the periodically chargeable high pressure combustion cell used in the study provides full optical access to the entire main chamber the evolution of the spatial distribution of the reaction zones was investigated in terms of OH*-chemiluminescence. As jet penetration is a very fast and highly transient process the emission of OH* was recorded at a frequency of f = 30000 Hz. The macroscopic reaction zone parameters in the jet region (penetration length and angle, reacting area and light emission) reveal the influence of orifice size and prechamber gas injection on the heat release in the shear layer between the jet and the lean charge in the main chamber. In addition, the influence of the development of the reaction in these zones on the ignition probability and the main chamber pressure rise is shown. With an appropriate selection of the combination of the prechamber orifice geometry and the operating parameters significant improvements of ignition probability and heat release in the main chamber were obtained.

The scavenging timing of pre-chamber on the performance of a natural gas engine

2020 ◽  
pp. 146808742096087
Author(s):  
Xue Yang ◽  
Yong Cheng ◽  
Pengcheng Wang
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Injection System ◽  
Maximum Pressure ◽  
Ignition Process ◽  
Main Chamber ◽  
Ignition Timing ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine

The pre-chamber ignition system scavenged with natural gas can effectively improve the in-cylinder combustion process and extend the lean-burn limit of natural gas engines. The scavenging process affects the flow field and fuel-air mixture concentration distribution in the pre-chamber and affects the combustion process in the pre-chamber as well as the ignition process in the main chamber. This has a significant influence on the performance of natural gas engines. It is supposed that the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing affects the combustion process in the pre-chamber. To verify this suppose, an independent injection system for injecting natural gas into the pre-chamber is designed and experiments are carried out on a single-cylinder natural gas engine. The ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing is adjusted by changing the injection start angle of the scavenging process. The combustion process in the pre-chamber and the main chamber are analyzed using the in-cylinder pressures. The results indicate that, with the delay of the injection start angle, the ratio of natural gas remaining in the mixture inside the pre-chamber at the ignition timing increases, the combustion process in the pre-chamber is enhanced, the maximum pressure difference between two chambers increases and appears earlier. The energy of the hot jets and the penetration of the jets increase, which enhances the combustion process in the main chamber.

CFD Modeling of the Performance of a Prechamber for Use in a Large Bore Natural Gas Engine

2005 ◽  
Author(s):  
Allan Kirkpatrick ◽  
Gi-Heon Kim ◽  
Daniel Olsen
Keyword(s):  
Natural Gas ◽  
Fuel Injection ◽  
Combustion Process ◽  
Three Dimensional ◽  
Cfd Modeling ◽  
Main Chamber ◽  
Gas Engine ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Cfd Models

The topic of this paper is the performance of a prechamber for use in a large bore two stroke natural gas engine. With increased regulation of emissions from stationary natural gas engines, there has been interest in modification of the combustion process, such as extending the lean limit, to reduce NOx emissions. One promising combustion technique uses an ignition prechamber. CFD models of a prechamber and the cylinder were developed in order to simulate the performance of a prechamber ignition system. The modeling included a full three dimensional transient analysis with scavenging, moving piston, and main chamber fuel injection. The CFD analysis included the fuel injection into the prechamber, pressurization by the inflowing main chamber gases, spark ignition, combustion, and flame propagation into the main combustion chamber. The computations indicated that the prechamber is more well mixed than the main engine chamber, with the prechamber mixture close to stoichiometric for better ignition. There is a strong, well-organized vortex in the prechamber induced by the incoming jet from the main chamber. The combustion flame in the prechamber travels in the direction of the gas vortex along lines of increasing equivalence ratio. The flame then propagates across the main cylinder in a very uniform fashion, indicating that there is sufficient energy to ignite the lean, partially mixed mixture in the main chamber. The orientation of the prechamber nozzle was also investigated, and an orientation of twenty degrees relative to the main chamber was found to produce a flame that did not impinge on the piston.

Effects of Natural Gas Compositions on Engine In-Cylinder Process

2015 ◽  
Vol 1092-1093 ◽  
pp. 498-503
Author(s):  
La Xiang ◽  
Yu Ding
Keyword(s):  
Natural Gas ◽  
Alternative Fuels ◽  
Combustion Process ◽  
Engine Performance ◽  
Maximum Temperature ◽  
Maximum Pressure ◽  
Test Bed ◽  
Promising Alternative ◽  
Natural Gas Engines ◽  
Lower Maximum

Natural gas (NG) is one of the most promising alternative fuels of diesel and petrol because of its economics and environmental protection. Generally the NG engine share the similar structure profile with diesel or petrol engine but the combustion characteristics of NG is varied from the fuels, so the investigation of NG engine combustion process receive more attentions from the researchers. In this paper, a zero-dimensional model on the basis of Vibe function is built in the MATLAB/SIMULINK environment. The model provides the prediction of combustion process in natural gas engines, which has been verified by the experimental data in the NG test bed. Furthermore, the influence of NG composition on engine performance is investigated, in which the in-cylinder maximum pressure and temperature and mean indicated pressure are compared using different type NG. It is shown in the results that NG with higher composition of methane results in lower maximum temperature and mean indicated pressure as well as higher maximum pressure.

Effect of Engine Operating Parameters on Combustion and Emission Characteristics

1992 ◽  
Author(s):  
Jiang Lu ◽  
Ashwani K. Gupta ◽  
Eugene L. Keating
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Chamber ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Internal Combustion ◽  
Operating Parameters ◽  
Emission Characteristics ◽  
Pollutants Emission

Abstract Numerical simulation of flow, combustion, heat release rate and pollutants emission characteristics have been obtained using a single cylinder internal combustion engine operating with propane as the fuel. The data are compared with experimental results and show excellent agreement for peak pressure and the rate of pressure rise as a function of crank angle. The results obtained for NO and CO are also found to be in good agreement and are similar to those reported in the literature for the chosen combustion chamber geometry. The results have shown that both the combustion chamber geometry and engine operating parameters affects the flame growth within the combustion chamber which subsequently affects the pollutants emission levels. The code employed the time marching procedure and solves the governing partial differential equations of multi-component chemically reacting fluid flow by finite difference method. The numerical results provide a cost effective means of developing advanced internal combustion engine chamber geometry design that provides high efficiency and low pollution levels. It is expected that increased computational tools will be used in the future for enhancing our understanding of the detailed combustion process in internal combustion engines and all other energy conversion systems. Such detailed information is critical for the development of advanced methods for energy conservation and environmental pollution control.

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.

Phenomenological Modeling of Combustion in Pre-Chamber and the Pilot Flame for Natural Gas Engines

2019 ◽  
Author(s):  
Long Liu ◽  
Xia Wen ◽  
Qian Xiong ◽  
Xiuzhen Ma
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Alternative Fuels ◽  
Gas Flow ◽  
Combustion Process ◽  
Clean Energy ◽  
Combustion Model ◽  
Flame Surface ◽  
Flow Process ◽  
Natural Gas Engines

Abstract With energy shortages and increasing environmental problems, natural gas, as a clean energy, has the advantages of cheap price and large reserves and has become one of the main alternative fuels for marine diesel engines. For large bore natural gas engines, pre-chamber spark plug ignition can be used to increase engine efficiency. The engine mainly relies on the flame ejected from the pre-chamber to ignite the mixture of natural gas and air in the main combustion chamber. The ignition flame in the main combustion chamber is the main factor affecting the combustion process. Although the pre-chamber natural gas engines have been extensively studied, the characteristics of combustion in the pre-chamber and the development of ignition flame in the main combustion chamber have not been fully understood. In this study, a two-zone phenomenological combustion model of pre-chamber spark-ignition natural gas engines is established based on the exchange of mass and energy of the gas flow process in the pre-chamber and the main combustion chamber. The basic characteristics of the developed model are: a spherical flame surface is used to describe the combustion state in the pre-chamber, and according to the turbulent jet theory, the influence of turbulence on the state of the pilot flame is considered based on the Reynolds number. According to the phenomenological model, the time when the flame starts to be injected from the pre-chamber to the main combustion chamber, and the parameters such as the length of the pilot flame are analyzed. The model was verified by experimental data, and the results showed that the calculated values were in good agreement with the experimental values. It provides an effective tool for mastering the law of flame development and supporting the optimization of combustion efficiency.

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

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Reed Hanson ◽  
Andrew Ickes ◽  
Thomas Wallner
Keyword(s):  
Natural Gas ◽  
Thermal Efficiency ◽  
Fuel Injection ◽  
Experimental Testing ◽  
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 (DI) 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 13 l multicylinder heavy-duty diesel engine modified to operate using RCCI combustion with port injection of natural gas and DI 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 (CDC) and RCCI combustion for phasing control and emissions performance. As the load is increased, the port fuel injection (PFI) quantity was reduced to keep peak cylinder pressure (PCP) and maximum pressure rise rate (MPRR) under the imposed limits. Overall, the peak load using the new injection strategy was shown to reach 22 bar brake mean effective pressure (BMEP) with a peak brake thermal efficiency (BTE) of 47.6%.

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.

System Model for Selective NOx Recirculation (SNR) to be Used in Stationary Lean-Burn Natural Gas Engines

2006 ◽  
Author(s):  
A. Zimmerman ◽  
C. Tissera ◽  
E. Tatli ◽  
N. Clark ◽  
R. Atkinson ◽  
...  
Keyword(s):  
Natural Gas ◽  
Combustion Process ◽  
Force Model ◽  
Treatment Technology ◽  
Lean Burn ◽  
Mass Percent ◽  
Natural Gas Engines ◽  
Sorbent Material ◽  
Nox Adsorption ◽  
Adsorption Desorption

A model for a possible system to implement Selective NOx Recirculation (SNR) technology for stationary lean-burn natural gas engines was developed. SNR is a NOx (NOx includes the various oxides of nitrogen found in an exhaust stream) removal after-treatment technology with four phases; cooling the hot exhaust gas, NOx adsorption onto a sorbent material, periodic NOx desorption using heat, and NOx decomposition within the combustion process. This paper presents the model, summarizes the research used to develop the model, and presents model output. NOx decomposition in the combustion process was investigated by injecting nitric oxide (NO) into the intake of a Cummins L10G natural gas fueled spark-ignited engine (210 kW at 2100 rpm). Experimental campaigns were conducted during lean-burn and rich-burn operation to quantify in-cylinder NOx decomposition. Data previously published suggest that rich burn is essential for adequate NOx decomposition and that lean burn was ineffective. The NOx adsorption/desorption characteristics of the sorbent material were quantified using a bench top adsorption system equipped with four thermocouples, an in-line heater, a mass flow controller and a Rosemont Analytical NOx analyzer. The sorbent chamber was filled with activated carbon sorbent material. Extensive testing of the adsorption characteristics using 500 ppm NO (balance nitrogen) from a pressure tank yielded a mass percent of .0005 NO to carbon. These results suggested that unacceptably large adsorbers would be needed in industrial applications. However, further measurement using real exhaust showed a loading of 0.65 mass percent of NO to carbon. The presence of oxygen and water are implicated in this improved adsorption. This scaled system considered the heating rates (for desorption) and cooling rates (for adsorption) for the bed at the time when desorption and adsorption processes were initiated. An adsorption/desorption model that considered gas temperature and heat and mass transfer was formulated based on these data. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passed over fresh sorbent material.

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