Improving the Efficiency of the Advanced Injection Low Pilot Ignited Natural Gas Engine Using Organic Rankine Cycles

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. K. Srinivasan ◽  
P. J. Mago ◽  
G. J. Zdaniuk ◽  
L. M. Chamra ◽  
K. C Midkiff
Keyword(s):  
Natural Gas ◽  
Conversion Efficiency ◽  
Waste Heat ◽  
Injection Timing ◽  
Base Line ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Fuel Conversion ◽  
Lean Combustion ◽  
Organic Rankine Cycles

Intense energy security debates amidst the ever increasing demand for energy in the US have provided sufficient impetus to investigate alternative and sustainable energy sources to the current fossil fuel economy. This paper presents the advanced (injection) low pilot ignition natural gas (ALPING) engine as a viable, efficient, and low emission alternative to conventional diesel engines, and discusses further efficiency improvements to the base ALPING engine using organic rankine cycles (ORC) as bottoming cycles. The ALPING engine uses advance injection (50–60deg BTDC) of very small diesel pilots in the compression stroke to compression ignite a premixed natural gas-air mixture. It is believed that the advanced injection of the higher cetane diesel fuel leads to longer in-cylinder residence times for the diesel droplets, thereby resulting in distributed ignition at multiple spatial locations, followed by lean combustion of the higher octane natural gas fuel via localized flame propagation. The multiple ignition centers result in faster combustion rates and higher fuel conversion efficiencies. The lean combustion of natural gas leads to reduction in local temperatures that result in reduced oxides of nitrogen (NOx) emissions, since NOx emissions scale with local temperatures. In addition, the lean premixed combustion of natural gas is expected to produce very little particulate matter emissions (not measured). Representative base line ALPING (60deg BTDC pilot injection timing) (without the ORC) half load (1700rpm, 21kW) operation efficiencies reported in this study are about 35% while the corresponding NOx emission is about 0.02g∕kWh, which is much lower than EPA 2007 Tier 4 Bin 5 heavy-duty diesel engine statutes of 0.2g∕kWh. Furthermore, the possibility of improving fuel conversion efficiency at half load operation with ORCs using “dry fluids” is discussed. Dry organic fluids, due to their lower critical points, make excellent choices for waste heat recovery Rankine cycles. Moreover, previous studies indicate that dry fluids are more preferable compared to wet fluids because the need to superheat the fluid to extract work from the turbine is eliminated. The calculations show that ORC—turbocompounding results in fuel conversion efficiency improvements of the order of 10% while maintaining the essential low NOx characteristics of ALPING combustion.

Improving the Efficiency of the Advanced Injection Low Pilot Ignited Natural Gas Engine Using Organic Rankine Cycles

2007 ◽  
Author(s):  
K. K. Srinivasan ◽  
P. J. Mago ◽  
G. J. Zdaniuk ◽  
L. M. Chamra ◽  
K. C. Midkiff
Keyword(s):  
Natural Gas ◽  
Conversion Efficiency ◽  
Injection Timing ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Fuel Conversion ◽  
Lean Combustion ◽  
Organic Rankine Cycles ◽  
Heavy Duty Diesel ◽  
Increasing Demand

Intense energy security debates amidst the ever increasing demand for energy in the country have provided sufficient impetus to investigate alternative and sustainable energy sources to the current fossil fuel driven economy. This paper presents the Advanced injection Low Pilot Ignition Natural Gas (ALPING) engine as a viable, efficient and low emissions alternative to conventional diesel engines, and discusses further efficiency improvements to the base ALPING engine using Organic Rankine Cycles (ORC) as bottoming cycles. The ALPING engine uses very small diesel pilots, injected early in the compression stroke to compression-ignite a premixed natural gas–air mixture. It is believed that the advanced injection of the higher cetane diesel fuel leads to longer incylinder residence times for the diesel droplets, thereby resulting in distributed ignition at multiple spatial locations, followed by lean combustion of the higher octane natural gas fuel via localized flame propagation. The multiple ignition centers result in faster combustion rates and higher fuel conversion efficiencies. The lean combustion of natural gas leads to reduction in local temperatures and oxides of nitrogen (NOx) emissions, since NOx emissions scale with local temperatures. In addition, the lean combustion of natural gas is expected to produce very little particulate matter (PM) emissions (not measured). Representative baseline ALPING (60° BTDC pilot injection timing) (without the ORC) half load (1700 rev/min, 21 kW) operation efficiencies reported in this study are about 35 percent while the corresponding NOx emissions is about 0.02 g/kWh, which is much lower than EPA 2007 tier 4 heavy duty diesel engine statutes of 0.2 g/kWh. Furthermore, the possibility of improving fuel conversion efficiency at half load operation with Organic Rankine Cycles using “dry fluids” are discussed. Dry organic fluids, due to their lower critical points, make excellent choices for bottoming Rankine cycles. Moreover, previous studies indicate that “dry fluids” are more preferable compared to wet fluids because the need to superheat the fluid to extract work from the turbine is eliminated. It is estimated that ORC–turbocompounding results in fuel conversion efficiency improvements of the order of 10 percent while maintaining the essential low NOx characteristics of ALPING combustion.

scholarly journals Effect of hydrogen addition in diesel/natural gas dual-fuel combustion with late injection

2021 ◽  
Vol 312 ◽  
pp. 08005
Author(s):  
Antonio Caricato ◽  
Antonio Paolo Carlucci ◽  
Antonio Ficarella ◽  
Luciano Strafella
Keyword(s):  
Natural Gas ◽  
Conversion Efficiency ◽  
Early Stage ◽  
Combustion Process ◽  
Pollutant Emission ◽  
Dual Fuel ◽  
Injection Timing ◽  
Pilot Injection ◽  
Fuel Conversion ◽  
Hydrogen Addition

In a previous work, the effectiveness of late pilot injection on improving combustion behaviour – in terms of fuel conversion efficiency and pollutant emission levels – in a diesel/natural gas dual-fuel engine was assessed. Then, an additional set of experiments was performed, aiming at speeding up the combustion process possibly without penalizing NOx levels. Therefore, hydrogen was added to natural gas in a percentage equal to 10%. Results show that hydrogen addition has a significant effect on the combustion development specially during the early stage of combustion: ignition delay is shortened and combustion centre is advanced, while the combustion duration increases when pilot injection timing is set to conventional values, while remains basically unchanged for late timings. Fuel conversion efficiency is only slightly penalized when hydrogen is added. Moreover, it was confirmed that, in general, combustion strategy with late pilot injection timing does not penalize fuel conversion efficiency; indeed, in some cases, it actually increases. Concerning regulated emission levels, it is again proven that late pilot injection does not penalize pollutant production: the hydrocarbons and carbon monoxide reduce as pilot injection is delayed, probably due to the higher temperatures reached into the cylinder during most part of the expansion stroke. Moreover, adding hydrogen always reduces their levels. Concerning NOx, they are drastically reduced delaying pilot injection; as expected, hydrogen addition promotes NOx formation, but the increase, evident with conventional pilot injection timings, becomes marginal with late injection strategy. Therefore, combustion strategy performance with late pilot injection in dual-fuel diesel/natural gas combustion conditions can be further improved with 10% hydrogen addition to natural gas.

scholarly journals Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 261 ◽  
Author(s):  
Alberto Boretti
Keyword(s):  
High Pressure ◽  
Steady State ◽  
Liquid Phase ◽  
Natural Gas ◽  
Power Density ◽  
Conversion Efficiency ◽  
Liquefied Natural Gas ◽  
Dual Fuel ◽  
Fuel Conversion ◽  
Better Than

Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better than diesel engine-out emissions for CO2, as well as particulate matter, unburned hydrocarbons, and nitrous oxides. The adoption of injection in the liquid phase permits to further improve the power density as well as the fuel conversion efficiency. Here, a model is developed to study a high-pressure, 1600 bar, liquid phase injector for liquefied natural gas (LNG) in a high compression ratio, high boost engine. The engine features two direct injectors per cylinder, one for the diesel and one for the LNG. The engine also uses mechanically assisted turbocharging (super-turbocharging) to improve the steady-state and transient performances of the engine, decoupling the power supply at the turbine from the power demand at the compressor. Results of steady-state simulations show the ability of the engine to deliver top fuel conversion efficiency, above 48%, and high efficiencies, above 40% over the most part of the engine load and speed range. The novelty of this work is the opportunity to use very high pressure (1600 bar) LNG injection in a dual fuel diesel-LNG engine. It is shown that this high pressure permits to increase the flow rate per unit area; thus, permitting smaller and lighter injectors, of faster actuation, for enhanced injector-shaping capabilities. Without fully exploring the many opportunities to shape the heat release rate curve, simulations suggest two-point improvements in fuel conversion efficiency by increasing the injection pressure.

scholarly journals Energy and Exergy Analysis of Different Exhaust Waste Heat Recovery Systems for Natural Gas Engine Based on ORC

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2378 ◽  
Author(s):  
Guillermo Valencia ◽  
Armando Fontalvo ◽  
Yulineth Cárdenas ◽  
Jorge Duarte ◽  
Cesar Isaza
Keyword(s):  
Natural Gas ◽  
Conversion Efficiency ◽  
Power Output ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Energy And Exergy ◽  
Net Power Output

Waste heat recovery (WHR) from exhaust gases in natural gas engines improves the overall conversion efficiency. The organic Rankine cycle (ORC) has emerged as a promising technology to convert medium and low-grade waste heat into mechanical power and electricity. This paper presents the energy and exergy analyses of three ORC–WHR configurations that use a coupling thermal oil circuit. A simple ORC (SORC), an ORC with a recuperator (RORC), and an ORC with double-pressure (DORC) configuration are considered; cyclohexane, toluene, and acetone are simulated as ORC working fluids. Energy and exergy thermodynamic balances are employed to evaluate each configuration performance, while the available exhaust thermal energy variation under different engine loads is determined through an experimentally validated mathematical model. In addition, the effect of evaporating pressure on the net power output, thermal efficiency increase, specific fuel consumption, overall energy conversion efficiency, and exergy destruction is also investigated. The comparative analysis of natural gas engine performance indicators integrated with ORC configurations present evidence that RORC with toluene improves the operational performance by achieving a net power output of 146.25 kW, an overall conversion efficiency of 11.58%, an ORC thermal efficiency of 28.4%, and a specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas flow, 1.784 lambda, and 1758.77 kW of mechanical engine power.

Visualization study of natural gas direct injection combustion

2003 ◽  
Vol 217 (8) ◽  
pp. 667-676 ◽  
Author(s):  
Z Huang ◽  
S Shiga ◽  
T Ueda ◽  
H Nakamura ◽  
T Ishima ◽  
...  
Keyword(s):  
Natural Gas ◽  
High Speed ◽  
Fuel Injection ◽  
Single Injection ◽  
Direct Injection ◽  
Video Camera ◽  
Injection Timing ◽  
Lean Combustion ◽  
High Speed Video Camera ◽  
Wrinkled Flame

A visualization study of natural gas direct injection combustion was carried out by using a high speed video camera. The results show that the distribution of the stratified mixture di ers with the injection mode, with parallel and single injection tending to form a higher degree of mixture stratification than opposed injection. Flame propagates toward the downstream direction in the cases of parallel and single-injection combustion, and flame propagates outward from the centre of the combustion chamber in the case of opposed injection combustion. A characteristic of turbulent combustion with a wrinkled flame front is presented in natural gas direct injection combustion. Super-lean combustion can be realized owing to the formation of an ignitable stratified mixture with the optimum setting of the fuel injection timing.

The Advanced Low Pilot Ignited Natural Gas Engine: A Low NOx Alternative to the Diesel Engine

2003 ◽  
Author(s):  
Kalyan K. Srinivasan ◽  
Sundar R. Krishnan ◽  
Satbir Singh ◽  
K. Clark Midkiff ◽  
Stuart R. Bell ◽  
...  
Keyword(s):  
Natural Gas ◽  
Low Cost ◽  
Injection Timing ◽  
Nox Emissions ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Engine Stability ◽  
Unburned Hydrocarbons ◽  
Cylinder Compression ◽  
Diesel Operation

High nitrogen oxides (NOx) and particulate matter (PM) emissions restrict future use of conventional diesel engines for efficient, low-cost power generation. The advanced low pilot ignited natural gas (ALPING) engine described here has potential to meet stringent NOx and PM emissions regulations. It uses natural gas as the primary fuel (95 to 98 percent of the fuel energy input here) and a diesel fuel pilot to achieve compression ignition. Experimental measurements are reported from a single cylinder, compression-ignition engine employing highly advanced injection timing (45°–60°BTDC). The ALPING engine is a promising strategy to reduce NOx emissions, with measured full-load NOx emissions of less than 0.25 g/kWh and identical fuel economy to baseline straight diesel operation. However, unburned hydrocarbons were significantly higher for ALPING operation. Engine stability, as measured by COV, was 4–6 percent for ALPING operation compared to 0.6–0.9 percent for straight diesel.

NOx Emissions From a Diesel Engine Fueled With Natural Gas

1995 ◽  
Vol 117 (4) ◽  
pp. 290-296 ◽  
Author(s):  
Y. Tao ◽  
K. B. Hodgins ◽  
P. G. Hill
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Ignition Delay ◽  
Substantial Reduction ◽  
Equilibrium Concentration ◽  
Nox Emission ◽  
Combustion Model ◽  
Injection Timing ◽  
Exhaust Pipe ◽  
Nox Emissions

The performance and emission characteristics of a single-cylinder two-stroke diesel engine fueled with direct injection of natural gas entrained with pilot diesel ignition enhancer have been measured. The thermal efficiency of the optimum gas-diesel operation was shown to exceed that of the conventional diesel at full load, but to be less at part load where the ignition delay was excessive. At high load, where the NOx emission problem is most serious, substantial reduction in NOx emission rate was obtained with delay of injection timing and also with use of exhaust gas recirculation. Measured cylinder pressures were used with a three-zone combustion model to determine ignition delay and the temperatures of the burned gas. The predicted NOx emissions based on equilibrium concentration of NO at the maximum burned gas temperature were found to correlate closely with exhaust pipe measurements of NOx.

Ignition in Pilot-Ignited Natural Gas Low Temperature Combustion: Multi-Zone Modeling and Experimental Results

2009 ◽  
Author(s):  
Sundar Rajan Krishnan ◽  
Kalyan Kumar Srinivasan ◽  
Kenneth Clark Midkiff
Keyword(s):  
Natural Gas ◽  
Shell Model ◽  
Ignition Delay ◽  
Combustion Engine ◽  
Engine Performance ◽  
Intake Manifold ◽  
Model Parameters ◽  
Injection Timing ◽  
Oxides Of Nitrogen ◽  
Gas Combustion

In previous research conducted by the authors, the Advanced Low Pilot-Ignited Natural Gas (ALPING) combustion employing early injection of small (pilot) diesel sprays to ignite premixed natural gas-air mixtures was demonstrated to yield very low oxides of nitrogen (NOx) emissions and fuel conversion efficiencies comparable to conventional diesel and dual fuel engines. In addition, it was observed that ignition of the diesel-air mixture in ALPING combustion had a profound influence on the ensuing natural gas combustion, engine performance and emissions. This paper discusses experimental and predicted ignition behavior for ALPING combustion in a single-cylinder engine at a medium load (BMEP = 6 bar), engine speed of 1700 rpm, and intake manifold temperature (Tin) of 75°C. Two ignition models were used to simulate diesel ignition under ALPING conditions: (a) Arrhenius-type ignition models, and (b) the Shell autoignition model. To the authors’ knowledge, the Shell model has previously not been implemented in a multi-zone phenomenological combustion simulation to simulate diesel ignition. The effects of pilot injection timing and Tin on ignition processes were analyzed from measured and predicted ignition delay trends. Experimental ignition delays showed a nonlinear trend (increasing from 11 to 51.5 degrees) in the 20°–60° BTDC injection timing range. Arrhenius-type ignition models were found to be inadequate and only yielded linear trends over the injection timing range. Even the inclusion of an equivalence ratio term in Arrhenius-type models did not render them satisfactory for the purpose of modeling ALPING ignition. The Shell model, on the other hand, predicted ignition better over the entire range of injection timings compared to the Arrhenius-type ignition delay models and also captured ignition delay trends at Tin = 95°C and Tin = 105°C. Parametric studies of the Shell model showed that the parameter Ap3, which affects chain propagation reactions, was important under medium load ALPING conditions. With all other model parameters remaining at their original values and only Ap3 modified to 8 × 1011 (from its original value of 1 × 1013), the Shell model predictions closely matched experimental ignition delay trends at different injection timings and Tin.

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