Effects of Burn Rate Parameters on Nitric Oxide Emissions for a Spark Ignition Engine: Results from a Three-Zone, Thermodynamic Simulation

2003 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Nitric Oxide ◽  
Thermodynamic Simulation ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Nitric Oxide Emissions ◽  
Burn Rate

First and Second Law Analyses of a Spark-Ignition Engine Using Either Isooctane or Hydrogen: An Initial Assessment

2006 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Nitric Oxide ◽  
Thermal Efficiency ◽  
Equivalence Ratio ◽  
Performance Metrics ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Cycle Simulation ◽  
Nitric Oxide Emissions

The use of either hydrogen or isooctane for a spark-ignition engine was examined using a thermodynamic cycle simulation including the second law of thermodynamics. The engine studied was a 5.7 liter, automotive engine operating from idle to wide open throttle. The hydrogen or isooctane was assumed premixed with the air. Two features of hydrogen combustion that were included in the study were the higher flame speeds (shorter burn durations) and the wider lean flammability limits (lean equivalence ratios). Three cases were considered for the use of hydrogen: (1) standard burn duration and an equivalence ratio of 1.0, (2) a shorter burn duration and an equivalence ratio of 1.0, and (3) a shorter burn duration and variable, lean equivalence ratios. The results included thermal efficiencies, other performance metrics, second law parameters, and nitric oxide emissions. In general, for the cases with an equivalence of 1.0, the brake thermal efficiency was slightly lower for the hydrogen cases due to the higher temperatures and higher heat losses. For the variable, lean equivalence ratio cases, the thermal efficiency was higher for the hydrogen case relative to the isooctane case. Due to the higher temperatures, the hydrogen cases had over 50% higher nitric oxide emissions compared to the isooctane case at the base conditions. In addition, the second law analyses indicated that the destruction of availability during the combustion process was lower for the base hydrogen case (11.2%) relative to the isooctane case (21.1%).

Detailed Results for Nitric Oxide Emissions as Determined From a Multiple-Zone Cycle Simulation for a Spark-Ignition Engine

2002 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Nitric Oxide ◽  
Compression Ratio ◽  
Equivalence Ratio ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Base Case ◽  
Gas Temperature ◽  
Cycle Simulation ◽  
Nitric Oxide Emissions

A thermodynamic cycle simulation was developed for spark-ignition engines which included a formulation using multiple zones for the combustion process and the capability to compute the net nitric oxide (NO) change due to the “thermal” formation mechanism. This simulation was used to complete analyses for a commercial, 5.7 l spark-ignition V-8 engine operating at a part load operating condition at 1400 rpm with an equivalence ratio of 1.0. The engine possessed a compression ratio of 8.1:1, and had a bore and stroke of 101.6 and 88.4 mm, respectively. At the base case conditions, the nitric oxide emissions were 15.7 g/bhp-hr (2903 ppm). The effects of equivalence ratio, combustion duration, spark timing, exhaust gas recirculation, compression ratio, speed and load on nitric oxide changes were examined. Results for instantaneous nitric oxide as a function of crank angle are presented. The use of an adiabatic zone was shown to dramatically increase the nitric oxide levels relative to using the burned gas temperature. For the base case, almost 50% more nitric oxide was computed using the adiabatic temperature relative to the burned gas temperature. The importance of gas temperature, cylinder gas pressure, and composition is illustrated.

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