Measurement and Monitoring of Formaldehyde from Reciprocating Internal Combustion Engines

摘要

This paper describes the status of an ongoing research program conducted by. URS Corporation for GTI (formerly GRI) to evaluate and characterize formaldehyde emissions from internal combustion (IC) engines in the natural gas industry. One objective of this research is to provide the gas industry with a predictive tool based on engine design and operating parameters to estimate formaldehyde emissions from IC engines to determine major source applicability. Extensive parametric test data have been collected using Fourier Transform Infrared (FTIR) spectroscopy on a number of 2-stroke engines representing different engine design characteristics. A statistical formaldehyde emissions prediction model based on engine operating and design parameters was developed from the parametric data collected on several Cooper engines tested under this program. Computational fluid dynamics (CFD) modeling techniques are also being used to model differences in scavenging, fuel/air mixing, and NO_x emissions between two engine models: one for a Clark TLA and the other for a Cooper GMVH engine. Each model simulates the in-cylinder three dimensional transient flow, temperature, and species concentration fields for a complete cycle of engine operation, including the scavenging, compression, fuel injection, combustion, and expansion processes. Preliminary model results of peak pressure, bulk air flow, and exhaust emissions quantities for the base case compared well with field measurements. Preliminary results of the exhaust gas scavenging process are presented for both engines. For the Cooper engine model the fuel/air mixing process is discussed based on initial base case results. A NO_x emissions model has been included in the CFD model for the Clark engine. The model is based on the extended Zeldovich mechanism modified for spark-ignited internal combustion . engines. The CFD tool will be used to identify and correlate key engine design parameters with NO_x and formaldehyde emissions and to characterize the differences in these key parameters among engine designs. While NO_x emissions will be explicitly predicted in the CFD model, formaldehyde emissions will be correlated in the statistical model with fuel/air mixing and scavenging efficiency. The CFD models can also be used to identify and evaluate the effects of various equipment retrofit alternatives on performance and emissions.