Natural Gas Injection Research Articles

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.

Parametric investigation of natural gas port injection and diesel pilot injection on the combustion and emissions of a turbocharged common rail dual-fuel engine at low load

In this paper, a common rail diesel research engine was converted to operate in dual-fuel mode and extensive experiments were conducted to investigate the effects of natural gas injection timing on the combustion and emissions performance under different pilot injection pressure and timing at low load conditions. The presented results include the cylinder pressure, heat release rate (HRR), ignition delay, combustion duration and brake thermal efficiency, as well as CO, HC and NOx emissions at different natural gas injection timing under pilot injection pressure (46 and 72MPa) and pilot injection timing (−8° and −17° ATDC) operation conditions at low load (BMEP=0.24MPa). The results indicated that retarded natural gas injection timing can achieve a stratified-like air–fuel mixture in cylinder under the different pilot injection conditions, which provided a method to improve the combustion performance and exhaust emissions at low load. Moreover, under higher pilot injection pressure (72MPa) conditions, better combustion performance, such as shorter ignition delay and combustion duration, higher brake thermal efficiency, were achieved; however, the exhaust emissions significantly increased compared with those under lower pilot injection pressure (46MPa). On the other hand, under the advanced pilot injection timing (−17° ATDC), the combustion performance was radically better, THC and CO emissions were lower but the NOx emissions were significantly higher compared with those under the regular pilot injection timing (−8° ATDC). This is attributed to faster flame propagation speed, better combustion phasing and higher volumetric efficiency. Consequently, employing appropriate natural gas injection timing accompanied with reasonable pilot injection parameters is critical to further improve combustion performance and exhaust emissions of a dual-fuel engine at low loads.

微粉炭燃焼性に及ぼす高炉への都市ガス吹き込みの影響

Reducing CO2 emission in ironmaking process is pressing issue. Low RAR (reducing agent rate) operation of the blast furnace and the utilization of hydrogenous reducing agent are effective to reduce CO2 emission. In this study, the influence of the hydrogenous reducing agent on the combustibility of the pulverized coal was examined by using a small scale combustion furnace. As a result, the combustibility of the pulverized coal was improved by simultaneous injection of the pulverized coal and the hydrogenous reducing agent. Furthermore, the fundamental study about the effect of natural gas (CH4) injection point on the combustibility of the pulverized coal was conducted by experiment using above mentioned small scale combustion furnace and by three-dimensional numerical analysis for further high efficiency. In the case of the relative position of CH4 injection point and the pulverized coal injection point being near, the ignition point of the pulverized coal came closer to lance tip. Especially, in the case of CH4 injection point being upstream in blow pipe about 0 to 20 mm from the pulverized coal injection point, the fastest ignition of the pulverized coal was confirmed by experimental and calculation results.

Asphaltene laboratory assessment of a heavy onshore reservoir during pressure, temperature and composition variations to predict asphaltene onset pressure

An Iranian heavy oil reservoir recently encountered challenges in oil production rate, and further investigation has proven that asphaltene precipitation was the root cause of this problem. In addition, CO2 gas injection could be an appropriate remedy to enhance the production of heavy crudes. In this study, high pressure-high temperature asphaltene precipitation experiments were performed at different temperatures and pressures to investigate the asphaltene phase behavior during the natural depletion process and CO2 gas injection. Compositional modeling of experimental data predicted onset points at different temperatures which determine the zone of maximum probability of asphaltene precipitation for the studied heavy oil reservoir. Also, the effect of CO2 gas injection was investigated as a function of CO2 concentration and pressure. It was found that a CO2-oil ratio of 40% is the optimum for limiting precipitation to have the least formation damage and surface instrument contamination.

Spray Characteristics of Diesel-CNG Dual Fuel Jet Using Schlieren Imaging Technique

Natural gas is a low cost fuel with high availability in nature. However, it cannot be used by itself in conventional diesel engines due to its low flame speed and high ignition temperature. The addition of a secondary fuel to enhance the mixture formation and combustion process facilitate its wider use as an alternative fuel. An experimental study was performed to investigate the diesel-CNG dual fuel jet characteristics such as: jet tip penetration, jet cone angle and jet tip velocity. A constant-volume optical chamber was designed to facilitate maximum optical access for the study of the jet macroscopic characteristics at different injection pressures and temperatures. The bottom plate of the test rig was made of aluminum (piston material) and it was heated up to 500 K at ambient pressure. An injector driver was used to control the single-hole nozzle diesel injector combined with a natural gas injector. The injection timing of both injectors were synchronized with a camera trigger. Macroscopic properties of diesel and diesel-CNG dual fuel jets were recorded with a high speed camera using the Schlieren imaging technique and associated image processing. Measurements of the jet characteristics of diesel and diesel-CNG dual fuel are compared together under evaporative and non-evaporative conditions as well as different injection pressures are presented in this paper.

Effects of Injection Parameters on the Combustion and Emission Characteristics of Diesel-Piloted Direct-Injection Natural Gas Engine during Idle Conditions

AbstractThe purpose of this paper is to investigate the effects of injection parameters on combustion and emission characteristics of a six-cylinder diesel-piloted direct-injection natural gas engine at idle conditions. The tests were conducted at three injection pressures (15, 18, and 24 MPa), two different injection intervals (0.7 and 1.0 ms), and start of natural gas injection in the range of 4–13° before top dead center (BTDC). The experimental results revealed that in terms of cylinder pressure and heat release rate, the maximum cylinder pressure and the maximum heat release rate were substantially higher at the injection pressure of 24 MPa and increased gradually with advanced injection timing, while only slightly influenced by injection interval. In terms of combustion parameters, the ignition delay was reduced by adoption of higher injection pressure and the rapid combustion duration was extended more evidently with the advance of injection timing. In terms of emissions, application of relatively ...

A Comparison of Natural Depletion and Different Scenarios of Injection in the Reservoir From the Beginning of Oil Production

This research comprises natural depletion, associate, and CO2 gas injection with regard to asphaltene precipitation and permeability reduction. For the sake of achievement these goals experiments were undertaken by core flood and asphaltene static apparatus. Natural depletion was performed at 4500, 3050, 2250, 1450, and 900 Psig and it has been seen maximum amount of asphaltene precipitation located at saturation pressure. The results demonstrate that asphaltene precipitation during natural depletion was higher than CO2 and associate gas injection. Also it was seen asphaltene precipitation rate during CO2 and associate gas injection was lower than natural depletion. Based on results, amount of asphaltene precipitation was differing according to type of gas. The results of the study indicate asphaltene precipitation during CO2 injection was more than associate gas injection. Finally it was seen the permeability reduction during associate was less than CO2 and natural depletion for this kind of Iranian carbonate sample.