Natural Gas Injection Research Articles

An optical investigation of combustion process of a direct high-pressure injection of natural gas

More than 90% of worldwide cargo transportation is carried out by ships. Nowadays, a contradictory circumstance like tough exhaust emission regulations for ocean-going ships by International Maritime Organization (IMO) and deterioration in the quality of marine fuel forces some challenges. A change to another fuel, such as liquefied natural gas (LNG), is conceivable. To create ideas for such the new combustion system, it is essential to visualize the combustion process and find the actual problems. For that target, a world largest class Rapid Compression and Expansion Machine (RCEM with 200-mm-wide or 240-mm-diameter window) that holds under 20 MPa cylinder pressure has been designed and built by the authors. This RCEM is equipped with several electronically controlled fuel injection systems for both liquid fuel and gas fuel. Characteristics of diesel spray combustion and gas injection (GI) combustion can be analyzed using direct photography and some kinds of laser optical techniques. After one-shot burning of the fuel, the burnt gas is sent from RCEM to a gas analyzer and NOx, CO, CO2 and THC can be measured. In this paper, a fundamental difference of combustion process between diesel and GI is made clear. However, as GI combustion emits much higher NOx than the lean-burn, some measures like EGR is necessary for the IMO Tier 3 NOx regulation. The GI combustion under EGR atmosphere (lower oxygen %) is also visualized. Some data of GI combustion are obtained by above-mentioned experiments. However, the phenomena are too complicated. As the next task, to create and validate a calculation model is important to optimize the GI system. In this study, the three-dimensional CFD code, KIVA3V, combined with the software tool for solving complex chemical kinetics, SENKIN, was modified for GI combustion.

The influence of injection strategy on mixture formation and combustion process in a direct injection natural gas rotary engine

The application of direct injection (DI) technology is considered as an effective way to improve the performance of the rotary engine. This work seeks to numerically dissect the influence of injection strategy on mixture formation and combustion process in a DI natural gas rotary engine. A 3D dynamic simulation model established in our previous work was used to acquire some critical information which was difficult to obtain through experimental investigations. These were the flow field, the fuel distribution, the temperature field and some intermediate concentration fields in the combustion chamber. Simulation results showed that for mixture formation, the motion mechanism of the fuel varies with the injection position. The mass of fuel located at the back of the combustion chamber for injection nozzles A, B and C, was determined by the intensity of vortex I, the coupling function between the value of the impact angle and the intensity of vortex I, and the value of the impact angle respectively. In addition, with retarded injection timing, the accumulation area of fuel for all injection nozzle positions moved from the back to the front of the combustion chamber at ignition timing. For combustion process, the overall combustion rate for the injection strategy (case A4) whose nozzle was 50mm apart along the engine major axis and whose injection timing was 360°CA (BTDC), was the fastest. Compared with the out-cylinder premixed gas-filling method (case premix method), the improved combustion rate of case A4 had a 29.7% increase in peak pressure, but also a certain increase in NO emissions.

Numerical investigation of the effect of injection strategy on mixture formation and combustion process in a port injection natural gas rotary engine

This work aimed to numerically study the influence of injection strategy on mixture formation and combustion process in a port injection natural gas rotary engine. On the base of a 3D dynamic simulation model which was established in our previous work, some critical information was obtained, which was difficult to obtain through experiment, in terms of the flow field, the fuel distribution, the temperature field and the concentration fields of some intermediates. Simulation results showed that for mixture formation, the movements of fuel in injection stage were mainly controlled by the intensity of the vortex I for injection timing, and the value of jet flux for injection duration respectively. With retarded injection timing, the decreasing intensity of the vortex I resulted in less fuel moving toward the back of the combustion chamber. With the extension in injection duration, the decreasing value of jet flux resulted in more fuel staying at the back of the combustion chamber. For combustion process, the overall combustion rate for injection strategy which had an injection timing of 390°CA (BTDC) and injection duration of 51.5°CA (case ID4) was the fastest. This was mainly due to the fact that the accumulation area of fuel was at the middle and front of the combustion chamber. Meanwhile, fuel concentration near the leading and trailing spark plugs was conducive for the flame kernel formation. Compared with the injection strategy which had an injection timing of 450°CA (BTDC) and an injection duration of 55°CA (case IT1), the improved combustion rate of case ID4 had a 23% increase in the peak pressure, but also a certain increase in NO emissions.

Influence of conveyance methods for pulverised coal injection in a blast furnace

Pulverised coal injection (PCI) is a widely adopted industry practice for reducing blast furnace coke rates. The conditions under which pulverised coal (PC) is injected and combusted, including the co-injection of natural gas (NG), can lead to complex combustion phenomena inside the blast furnace, which must be understood to provide improved furnace performance. This research examines computational simulations of the co-injection phenomena, as well as the industrial drivers behind the project. A wide-ranging parametric study was conducted utilising numerous variations in furnace operating conditions, as well as a new technique for the conveyance of PC. It was found that utilising NG as the carrier gas for PCI could increase coal burnout across the raceway region from about 71% to approximately 87% without altering the design of the tuyere/blowpipe region, with an increase to 96% possible if a shift to a dual lance design for NG injection is considered.

Pore-scale numerical modeling of relative permeability curves for CO2\u2013oil fluid system with an application in immiscible CO2 flooding

CO2 injection is considered as one of the proven EOR methods and is being widely used nowadays in many EOR projects all over the globe. The process of in situ displacement of oil with CO2 gas is implemented in both miscible and immiscible modes of operation. In some oil reservoirs, CO2 miscibility will not be attained due to fluid composition characteristics as well as in situ pressure and temperature conditions. Laboratory determination of gas–oil relative permeability curves is usually performed with air, nitrogen, or helium gases, and the results are then implemented for both natural depletion processes (especially in reservoirs with “solution gas” or “gas cap” drive mechanisms) and gas injection processes. For the gas injection processes, it is therefore necessary to find out how selection of the gas phase would affect the relative permeability curves when the intention of developing the curves is to use them for immiscible CO2 displacement. In this study, a reservoir simulator was first used to quantitatively analyze the effect of variation in relative permeability data (due to the use of different gas phases) on production performance of a reservoir. Then, computational analysis was performed on changes in relative permeability curves upon using different gas phases with the aid of pore-scale modeling using statistical methods. To predict gas–oil relative permeability curves, a Shan–Chen-type multi-component multiphase Lattice Boltzmann pore-scale model for two-phase flow in a 2D porous medium was developed. Fully periodic and “full-way” bounce-back boundary conditions were applied in the model to get infinite domain of fluid with nonslip solid nodes. Incorporation of an external body force was performed by Guo scheme, and the influence of pore structure and capillary number on relative permeability curves was also studied for CO2–oil as well as N2–oil fluid pairs. The modeled relative permeability curves were then compared with experimental results for both these fluid pairs.

On the simulation of industrial gas dynamic applications with the discontinuous Galerkin spectral element method

In the present investigation, we demonstrate the capabilities of the discontinuous Galerkin spectral element method for high order accuracy computation of gas dynamics. The internal flow field of a natural gas injector for bivalent combustion engines is investigated under its operating conditions. The simulations of the flow field and the aeroacoustic noise emissions were in a good agreement with the experimental data. We tested several shock-capturing techniques for the discontinuous Galerkin scheme. Based on the validated framework, we analyzed the development of the supersonic jets during different opening procedures of a compressed natural gas injector. The results suggest that a more gradual injector opening decreases the noise emission.

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

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%.

Variation of Crude Oil Physical Properties and Oil Recovery of Natural Gas Flood Under Different Pressures

ABSTRACTFor the gas flood process, crude oil physical properties including oil volume and viscosity would be greatly changed resulting from gas solution and extraction. First, solubility of natural gas in oil and brine was measured and compared. Meanwhile, the resulting oil expansion and viscosity reduction were experimentally tested. Second, oil viscosity increase due to extraction was studied by extraction experiments. Finally, oil recovery of natural gas and propane-enriched natural gas flood was studied under different pressures. Results show that solubility of natural gas in oil is dozens of times of that in brine. Variation of crude oil physical properties during natural gas injection mainly includes the remarkable volume expansion and viscosity reduction caused by gas dissolution into oil, and the oil volume shrinkage and viscosity increase caused by extraction are not so significant. The oil recovery of natural gas flood grows linearly with increased injection pressure and gas solubility in oil, but is still less than 90% even at 55 MPa, which indicates immiscible flood at 55 MPa. Addition of propane to natural gas is proved to be helpful for enhancing oil recovery and achieving miscibility.

Solar generated steam injection in heavy oil reservoirs: A case study

Combination of solar generated steam technology and enhanced oil recovery (EOR) techniques have attracted a great deal of attention due to its positive impact on economics and on the environment. Solar steam project has already proven itself as it can reduce both gas consumption and CO2 emissions by up to 80%. However, operational issues as well as geographical factors (i.e. terrain suitability, drill sites and future field development plans) may affect solar EOR operations. In this study, a heavy oil field in Southeast Turkey was evaluated to find whether solar EOR is technically and economically feasible. Operational data such as injection rate, steam temperature and steam quality were determined by using a numerical model. A solar collector system was designed and combined with the steam injection method. Results indicated that direct normal insolation (DNI) of the oil field location was not high enough to maintain continuous steam injection. In order to sustain continuous steam injection natural gas burner back-up system must be used when DNI is intermittent to maintain required steam especially during winter nights. Economic analysis of combined system showed that fuel saving cannot compensate the initial cost of solar project with current oil price.

Study of Natural Gas Engine using Non-Premixed Combustion Model

Direct injection natural gas engines are used in many heavy duty vehicles. Similar to diesel engines, high thermal efficiency and power density is maintained in such direct injection natural gas engines. In such engines, natural gas is injected directly into the combustion chamber. Then the gas mixes with the high pressure air in the combustion chamber and combustion occurs. The main objective is to simulate a cycle, from the end of the compression stroke to 50° after TDC. Simulation would be done keeping methane as fuel. A 30 degree sector of a 4-stroke engine which corresponds to one fuel injector hole is modeled. Since combustion simulation is to be studied, the simulation starts at 20 degree crank angle (CA) before the start of injection (SOI) and ends at 50 degree CA after top dead center (TDC). A simplified model of the engine with no valves is modeled since during the entire combustion process, both the valves remain closed.

CORRECTION OF INJECTORS REDUCED CHARACTERISTICS BASED ON THE MACHINES PARAMETRIC DIAGNOSTICS RESULTS

A procedure is offered for recalculation of values of the centrifugal natural gas injectors’ basic parameters characterizing the technological capabilities of these machines and their performance efficiency. The recalculation is based on the data on the machines current technical state. This procedure use allows for operating the injectors more rationally with the account of their actual state and thus improving the cost/performance ratios of gas-transporting systems.

Estimation of asphaltene precipitation in light, medium and heavy oils: experimental study and neural network modeling

Asphaltene can precipitate in oil reservoirs as a result of natural depletion and/or gas injection crippling the oil production performance. Most of the conventional models for asphaltene precipitation cannot precisely capture the asphaltene precipitation at a wide pressure range and for different oil types. To have a precise model that can be used for various oil types at a wide range of pressure conditions, a comprehensive artificial neural network (ANN) model was proposed to estimate the weight percent of precipitated asphaltene in different oil types (three oil types, namely light, medium and heavy). The dilution ratio, pressure, molecular weight of solvent, API gravity and resin-to-asphaltene ratio were considered as the model input parameters. The oil samples were thus categorized based on the differences in their API gravity and resin-to-asphaltene ratio. Five hundred and fifty experimental precipitation datapoints were obtained from our experimental apparatus in a wide range of pressure, dilution ratio and injected fluid molecular weight, and used to make a comprehensive databank for model calibration and verification. At the test stage, the coefficient of correlation (R2) was higher than 0.98 and mean square error was less than 0.04 indicating the good performance of the proposed model. Furthermore, a comparison between the prediction of ANN model and two types of alternative approaches, namely the thermodynamic and the fractal/aggregation approaches, was performed. For this purpose, the prediction of two of the widely used solubility models, Flory---Huggins and Modified Flory---Huggins and also a polydisperse thermodynamic model was compared to the prediction of the proposed ANN model. In addition to those, as a fractal/aggregation model, a scaling model was also selected and employed to compare its performance against that of the proposed ANN model. The ANN model showed a better performance as compared to the other conventional models. The results demonstrated that the proposed model provides acceptable prediction for different oil types over a wide range of pressure which is a difficult task for most of the conventional techniques.

Combustion process and emissions of a heavy-duty engine fueled with directly injected natural gas and pilot diesel

In this paper, the combustion process and emissions of a heavy-duty engine fueled with directly injected natural gas and pilot diesel were experimentally explored. The experiments were carried out under two operating points (A:1275rpm BMEP 1.05MPa, B:1550rpm BMEP 1.05MPa) with diesel rail pressure (DRP) varied from 18MPa to 30MPa and start of natural gas injection (NSOI) in the range of 1°BTDC to 19°BTDC. Based on the experimental results, as the injection timing advances, the maximum in-cylinder pressure and NOx emissions increase, the flame development duration and brake specific fuel consumption (BSFC) decrease, the maximum heat release rate shows a trend of first decrease and then increase while the changing trend for carbon monoxide (CO) emissions is first increase and then decrease; as the injection pressure raises, the combustion process takes place earlier, causing negative effects on nitrogen oxides (NOx) emissions; with higher engine speed, however, the combustion events are delayed, leading to lower peak value of heat release rate, improved CO and NOx emissions, impaired total hydrocarbon (THC) emissions and higher BSFC.

Mixture formation analysis in a direct-injection NG SI engine under different injection timings

This paper investigates into the mixture formation in a direct injection, turbocharged, spark-ignition, CNG engine. The engine features a pent-roof combustion chamber, a bowl in piston and an outward-opening poppet valve injector, which is located centrally in the chamber dome. In the last few years, many studies have been conducted focusing on direct injection natural gas engines, and the end-of-injection timing has been identified as the main parameter affecting the quality and completeness of the mixture formation process. This paper aims at contributing to the progress of this research field, by means of the presentation and discussion of a large number of experimental and numerical data. The results obtained from the authors’ CFD model, which has been developed and validated within the InGAS Collaborative Project of the EC, are in fact introduced and correlated to the outcomes of the experimental activity done by AVL GmbH, Graz, as part of the same research project. This synergy allowed a deep understanding of the mixture formation process, over a wide range of operating conditions.As a matter of fact, the mixture formation process in a direct injection gaseous-fuel engine differs significantly from direct-injection engines fuelled by gasoline. In fact, the gas jet momentum is lower, reducing the penetration, and the mixture formation strongly relies on the charge motion generated during the intake stroke. More precisely, the work presented in this paper showed that several factors exert an influence on the fuel–air mixing process: jet shape, interaction with piston and/or with the charge motion, and time available for mixing between the end-of-injection and the spark timing, and these may combine differently depending on the specific working point. On an average, at low load and low-medium speeds, the injection should better take place during the second part of the induction stroke. On the other hand, at high speed or high load the injection timing needs to be advanced till around 250–300° CA degrees before firing TDC, in order to increase the time available for mixing as much as possible.

Experimental investigation on performance and heat release analysis of a pilot ignited direct injection natural gas engine

Pilot ignited direct injection natural gas engines undertake significant advantages over conventional diesel engine with specific combustion mode. In this paper, extensive experiments have been carried out to provide further understanding of performance and heat release rate under different operating conditions. Through the experimental investigations and detailed analysis, it is demonstrated that shortened injection interval and diesel injection pulse width as well as increased injection pressure lead to an increase in maximum in-cylinder pressure and deteriorated combustion noise. The maximum heat release rate is raised by retarding injection timing, reducing injection interval, shortening diesel injection pulse width and increasing injection pressure. The stability of combustion shows uncertain trends with the variation of injection timing and pilot diesel injection quantity, while can be generally improved by the adoption of shorter injection interval and lower injection pressure. It is also revealed that fuel economy can benefit from the application of advanced injection timing, smaller diesel injection pulse width, shorter injection interval and higher injection pressure.

Influence of methane emissions and vehicle efficiency on the climate implications of heavy-duty natural gas trucks.

While natural gas produces lower carbon dioxide emissions than diesel during combustion, if enough methane is emitted across the fuel cycle, then switching a heavy-duty truck fleet from diesel to natural gas can produce net climate damages (more radiative forcing) for decades. Using the Technology Warming Potential methodology, we assess the climate implications of a diesel to natural gas switch in heavy-duty trucks. We consider spark ignition (SI) and high-pressure direct injection (HPDI) natural gas engines and compressed and liquefied natural gas. Given uncertainty surrounding several key assumptions and the potential for technology to evolve, results are evaluated for a range of inputs for well-to-pump natural gas loss rates, vehicle efficiency, and pump-to-wheels (in-use) methane emissions. Using reference case assumptions reflecting currently available data, we find that converting heavy-duty truck fleets leads to damages to the climate for several decades: around 70-90 years for the SI cases, and 50 years for the more efficient HPDI. Our range of results indicates that these fuel switches have the potential to produce climate benefits on all time frames, but combinations of significant well-to-wheels methane emissions reductions and natural gas vehicle efficiency improvements would be required.

발전용 대형 디젤 엔진의 천연가스-디젤혼소 운전 특성에 대한 수치해석 연구

Abstract - This study is an 1-D numerical study prior to modification of diesel engine for power plants to natural gas/diesel dual fuel engine using GT-Power with 1.5MW diesel engine for power generation. Natural gas injector was installed to intake manifold for dual fuel engine model. Effects on engine performance and characteristics were investigated when dual fuel is used in unmodified diesel engine. The analysis was done un-der 5 conditions from 0% to 40% of mixing rate on 720RPM engine speed. As a result of research, the engine performance was decreased as increasing ratio of natural gas. Engine brake power was decreased by 18.4% un-der 40% mixing rate condition. To clarify the reason, effects of injection timing and period were evaluated with DOE method. Considering this result, optimization was done for these parameters. Also, comparison between performances of dual fueled engine and diesel engine was made after optimizing the timing of injection by DOE method. As a result, engine brake power was decreased by 8.55% under mixing rate 40% condition show-ing 12.5% improvement.Key words : dual fuel, engine, natural gas, numerical analysisKIGAS Vol. 19, No. 2, pp 29~36, 2015 http://dx.doi.org/10.7842/kigas. 2015.19.2.29(Journal of the Korean Institute of Gas)

Combustion Simulation of Dual Fuel CNG Engine Using Direct Injection of Natural Gas and Diesel

Combustion Simulation of Dual Fuel CNG Engine Using Direct Injection of Natural Gas and Diesel

Direct Injection of Natural Gas at up to 600 Bar in a Pilot-Ignited Heavy-Duty Engine

Direct Injection of Natural Gas at up to 600 Bar in a Pilot-Ignited Heavy-Duty Engine

Influence of added hydrogen on underground gas storage: a review of key issues

The existing infrastructure of the natural gas transportation pipeline network and underground gas storage (UGS) facilities in Germany provides an opportunity and huge capacity to feed, transport and store hydrogen and synthetic fuel gases containing hydrogen, produced from renewable sources. At low hydrogen concentrations, only minor changes to gas transportation equipment will be required. In contrast, the UGS designed in converted gas fields and aquifers are particularly susceptible to the effect of hydrogen. Due to a lack of adequate knowledge about the hydrogen concentration in natural gas, which can be tolerated by the downhole equipment, reservoir and caprocks, the injection of natural gas containing hydrogen in the existing porous UGS is strongly limited. Key issues addressed in this paper are the change in capacity and efficiency of UGS associated with the blending of hydrogen in the stored natural gas, the geological integrity of the reservoir and caprocks, the technical integrity of gas storage wells, durability of the materials used for well completions, corrosion and environmental risks associated with the products of microbial metabolism.