Extending the Lean Limit of Natural Gas Engines

2008 ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Lean Burn ◽  
Stratified Charge ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Charge Mixture ◽  
Cyclic Variations ◽  
Lean Limit ◽  
The Stability

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural gas fuelled engines have been developed, and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce Bsfc by up to 4.8% in a Ricardo Hydra engine, while the NOx – efficiency tradeoff was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.

Extending the Lean Limit of Natural-Gas Engines

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Lean Burn ◽  
Stratified Charge ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Charge Mixture ◽  
Cyclic Variations ◽  
Lean Limit ◽  
The Stability

Two different methods to improve the thermal efficiency and reduce the emissions from lean-burn natural-gas fueled engines have been developed and are described in this paper. One method used a “squish-jet” combustion chamber designed specifically to enhance turbulence generation, while the second method provided a partially stratified-charge mixture near the spark plug in order to enhance the ignition of lean mixtures of natural gas and air. The squish-jet combustion chamber was found to reduce brake specific fuel consumption by up to 4.8% in a Ricardo Hydra engine, while the NOx efficiency trade-off was greatly improved in a Cummins L-10 engine. The partially stratified-charge combustion system extended the lean limit of operation in the Ricardo Hydra by some 10%, resulting in a 64% reduction in NOx emissions at the lean limit of operation. Both techniques were also shown to be effective in increasing the stability of combustion, thereby reducing cyclic variations in cylinder pressure.

Experimental study of combustion strategy for jet ignition on a natural gas engine

2020 ◽  
pp. 146808742097775
Author(s):  
Ziqing Zhao ◽  
Zhi Wang ◽  
Yunliang Qi ◽  
Kaiyuan Cai ◽  
Fubai Li
Keyword(s):  
Experimental Study ◽  
Natural Gas ◽  
Efficient Points ◽  
Lean Burn ◽  
Gas Engine ◽  
Absolute Value ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Excess Air ◽  
Lean Limit

To explore a suitable combustion strategy for natural gas engines using jet ignition, lean burn with air dilution, stoichiometric burn with EGR dilution and lean burn with EGR dilution were investigated in a single-cylinder natural gas engine, and the performances of two kinds of jet ignition technology, passive jet ignition (PJI) and active jet ignition (AJI), were compared. In the study of lean burn with air dilution strategy, the results showed that AJI could extend the lean limit of excess air ratio (λ) to 2.1, which was significantly higher than PJI’s 1.6. In addition, the highest indicated thermal efficiency (ITE) of AJI was shown 2% (in absolute value) more than that of PJI. Although a decrease of NOx emission was observed with increasing λ in the air dilution strategy, THC and CO emissions increased. Stoichiometric burn with EGR was proved to be less effective, which can only be applied in a limited operation range and had less flexibility. However, in contrast to the strategy of stoichiometric burn with EGR, the strategy of lean burn with EGR showed a much better applicability, and the highest ITE could achieve 45%, which was even higher than that of lean burn with air dilution. Compared with the most efficient points of lean burn with pure air dilution, the lean burn with EGR dilution could reduce 78% THC under IMEP = 1.2 MPa and 12% CO under IMEP = 0.4 MPa. From an overall view of the combustion and emission performances under both low and high loads, the optimum λ would be from 1.4 to 1.6 for the strategy of lean burn with EGR dilution.

Use of Railplugs to Extend the Lean Limit of Natural Gas Engines

2004 ◽  
Author(s):  
Hongxun Gao ◽  
Ron Matthews ◽  
Sreepati Hari ◽  
Matt Hall
Keyword(s):  
Natural Gas ◽  
Stability Limit ◽  
High Energy ◽  
Lean Burn ◽  
Ignition System ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Spark Plug ◽  
Lean Mixtures ◽  
Ignition Characteristics

Ignition of extremely lean mixtures is a very challenging problem, especially for the low speed, high load conditions of large-bore natural gas engines. This paper presents initial results from testing a high energy ignition system, the railplug, which can assure ignition of very lean mixtures by means of its high energy deposition and high velocity jet of the plasma. Comparisons of natural gas engine tests using both a spark plug and a railplug are presented and discussed in this paper. The preliminary engine test show that the lean stability limit (LSL) can be extended from an equivalence ratio, φ, of ∼0.63 using a spark plug down to 0.56 using a railplug. The tests show that the railplug is very promising ignition system for lean burn natural gas engines and potentially for other engines that operate with very dilute mixtures. The ignition characteristics of different railplug geometric and circuit designs are also discussed.

scholarly journals Lean-Burn Stationary Natural Gas Reciprocating Engine Operation With a Prototype Miniature Diode Side Pumped Passively Q-Switched Laser Spark Plug

2008 ◽  
Author(s):  
Dustin L. McIntyre ◽  
Steven D. Woodruff ◽  
Michael H. McMillian ◽  
Steven W. Richardson ◽  
Mridul Gautam
Keyword(s):  
Natural Gas ◽  
Laser System ◽  
Lean Burn ◽  
Engine Operation ◽  
Natural Gas Engines ◽  
Spark Plug ◽  
Laser Spark ◽  
Laser Systems ◽  
Laser Design ◽  
Engine Testing

To meet the ignition system needs of large bore lean burn stationary natural gas engines a laser diode side pumped passively Q-switched laser igniter was developed and used to ignite lean mixtures in a single cylinder research engine. The laser design was produced from previous work. The in-cylinder conditions and exhaust emissions produced by the miniaturized laser were compared to that produced by a laboratory scale commercial laser system used in prior engine testing. The miniaturized laser design as well as the combustion and emissions data for both laser systems was compared and discussed. It was determined that the two laser systems produced virtually identical combustion and emissions data.

Precombustion Chamber Design and Performance Studies for a Large Bore Natural Gas Engine

2005 ◽  
Author(s):  
Daniel B. Olsen ◽  
Jessica L. Adair ◽  
Bryan D. Willson
Keyword(s):  
Natural Gas ◽  
Performance Studies ◽  
Engine Performance ◽  
Precombustion Chamber ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Fuel Flow ◽  
Spark Plug ◽  
Lean Limit ◽  
And Performance

Precombustion chamber (PCC) ignition is a common method for extending the lean limit and reducing combustion variability in large bore (36–56 cm) natural gas engines. An important component that commonly fails and requires regular replacement, besides the spark plug, is the checkvalve. The checkvalve meters fuel flow into the PCC. In this program the use of an electronic valve for monitoring fuel to the PCC instead of the checkvalve is investigated. Metering the fuel into the PCC with an electronic valve provides a number of different options for improving performance in addition to the benefit of extended valve life. PCC nozzle design is also evaluated as a means for improving PCC and engine performance. Additionally, emissions formation in the PCC is evaluated through the use of a separate pressure transducer in the PCC and a fast sample valve that extracts gas from the PCC.

Ignition System Designed to Extend the Plug Life, and the Lean Limit in a Natural Gas Engine

2003 ◽  
Author(s):  
A. K. Chan ◽  
S. H. Waters
Keyword(s):  
Natural Gas ◽  
Engine Performance ◽  
Ignition System ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Dc System ◽  
Spark Plug ◽  
Long Duration ◽  
Discharge Duration ◽  
Lean Limit

An ignition system that is based on the alternating (AC) rather than the traditional direct (DC) current in the spark plug discharge has been developed at the Caterpillar Technical Center. This system can generate a long duration discharge with controllable power. It is believed that such an ignition system can provide both a leaner operating limit and a longer spark plug life than a traditional DC system due to the long discharge duration and the low discharge power. The AC ignition system has successfully been tested on a Caterpillar single cylinder G3500 natural gas engine to determine the effects on the engine performance, combustion characteristics and emissions. The test results indicate that while the AC ignition system has only a small impact on engine performance (with respect to a traditional DC system), it does extend the lean limit with lower NOx emissions. Evidences also show the potential of reduce spark plug electrode erosions from the low breakdown and sustaining discharge powers from the AC ignition system. This paper summarizes the prototype design and engine demonstration results of the AC ignition system.

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