Summer 2003 NASA Faculty Fellowship Program

NASA Glenn Research Center (GRC), Cleveland, Ohio

August 21, 2003

Activities and Accomplishments Summary Report

by
Milivoje Kostic
Associate Professor of Mechanical Engineering
Northern Illinois University
Web: www.kostic.niu.edu ; email: kostic@niu.edu

NASA GRC Combustion Branch
NASA Colleague: Dr. Chi-Ming Lee, Branch Chief

Particulate and Gaseous Emissions Measurement System (PAGEMS) Project
Dr. Paul Penko, Project Leader

During my participation in the Summer 2003 NASA Faculty Fellowship Program at Glenn Research Center (GRC) in Cleveland, Ohio, I have been working on the Particulate and Gaseous Emissions Measurement System (PAGEMS) Project, leaded by Dr. Paul Penko of NASA. PAGEMS is a state-of-the-art NASA facility used to measure particulate and gaseous emissions from combustors and full scale aircraft gas turbine engines. All PAGEMS equipment and instrumentation are located in a mobile van, which facilitates easy transition to different testing locations. PAGEMS has been used to measure particulate emissions from flame tubes and sector rigs at NASA GRC, full scale gas turbine engines at Pratt & Whitney, and different jet exhaust emissions at NASA Langley Research Center. A dedicated computer controls the data acquisition and operation of PAGEMS. The operating software is written using LabVIEW application software. Extractive sampling of combustion gases from aircraft gas turbine combustors and engines is employed. Differential Mobility Analyzers (DMA) and Condensation Nuclei Counters (CNC) are used to characterize the emissions in terms of particulate total concentration, size distribution, hydration property, and volatility. A gas analysis suite measures HC, O₂, CO₂, CO, NO_x, and SO₂ levels in the sample gases. Data can be collected over a wide range of operating conditions, pressures from sub atmospheric up to 60 atm, particulates in the size range 10 - 450 nm (nanometer), and gas species down to the ppm level.

The research objective of the PAGEMS project is to provide a comprehensive database of particulate and gaseous emissions from combustors and jet engine exhausts that are correlated to engine/combustor parameters. Clean burning aircrafts that do not harm human and the global environment is a major NASA research objective of this project.

I have been working on three different assignments related to the PAGEMS project:

I. Particle-Size Distribution Data Presentation (Manuscript in PDF format):
Critical issues related to proper evaluation and presentation of aerosols’ particle property distribution, as a function of a characteristic particle property itself is studied, relevant conclusions drawn and documented in a written report. Aerosol particle distributions often span over several orders of magnitudes, necessitating the particle distribution data presentation in a semi-logarithmic plot. Some researchers present their particle distribution data, not only in the semi-logarithmic coordinate system, but also define new, the so called logarithmic density distribution. This ‘artificial scaling’ with value of independent coordinate of actual density distribution, will not only skew the distribution, but also shift the modal vales and thus further misrepresents the actual particle distribution, since the maximums of the two density distributions are not at the same modal values. It is concluded that it is often necessary and useful to graphically represent the particle true density distribution in semi-logarithmic coordinate system, but it is meaningless and unnecessary (does not serve any purpose) to evaluate the logarithmic density distribution, since it may introduce dimensional and scaling problems, and misrepresentation of actual or true density distribution, including shifting of the modal values, as demonstrated in the written report.

II. Error or Uncertainty Analysis of Measurement Results (Manuscript in PDF format):
Uncertainty or error analysis of measurement results is not a deterministic (exact), but rather holistic and probabilistic in nature. Its complexity and ambiguity (not only what is measured, but what contributes to measurement errors and uncertainty, the latter being open ended), contributes that the uncertainty analysis is often misunderstood, misrepresented or even avoided. Objectives of this assignment were to resolve existing confusion, to embrace the very concept of measurement uncertainty, and to provide effective guidelines to account for the most contributing sources of errors (which is important and possible!), since accounting for all sources of measurement errors is not necessary (and also impossible). A written report includes initial uncertainty analysis of PAGEMS measurements using MS Excel functions, and related presentation was given on August 1, 2003 at Ohio Aerospace Institute (OAI) as part of the NASA Faculty Fellowship Lecture Series, and also during a Combustion Branch meeting at NASA GRC.

III. Enhancement of LabVIEW Data Acquisition Program for GRC PAGEMS Project:
    See: LabVIEW & Data Acquisition-DAQ
            Modern Experimental Methods with DAQ and LabVIEW - Professional Development Workshop Series
Existing LabVIEW application software program for PAGEMS is modified and enhanced with the following Data Acquisition (DAQ) functions. In addition to one Analog Input (AI) signal measurements, the program is modified to include five (5) analog input measurements, for flow rate, humidity and temperature sensors, with an easy interface for adjustments of sensors’ calibration parameters. More analog inputs channels, up to the capacity of the DAQ card (8 differential or 16 single-reference-ended) may be added when needed. One Analog Output (AO) is added to control actuator of the flow rate valve. Another AO has been used to control Differential Mobility Analyzer’s (DMA) voltages. Since the existing DAQ card has only two AO channels, for more AO channels a new DAQ card will be needed. The LabVIEW program interface is enhanced with user-friendlier features, and all measured data are written to a file for future post-processing, including the date and time of measurements. It is recommended to further enhance the LabVIEW application program to include all necessary monitoring and recording of all measured parameters, as well as interactive processing and presentation of results in numerical and graphical form.