Simultaneous Velocity, Temperature, and Formaldehyde Imaging to Study Ignition in High-Pressure Turbulent Jets - Topic b.i.4
Abstract
The mechanism of ignition in high-pressure turbulent fuel jets is not fully understood, in part, due to the complex coupling of turbulence and chemistry at challenging experimental conditions. It remains an important area for research due to its relevance to practical devices. Recent numerical simulations have led to a complex conceptual model for high-pressure jet ignition at diesel-engine-relevant conditions. Unfortunately, experimental measurements that can validate the proposed model are lacking. Validation and development of deeper understanding of the ignition mechanism requires simultaneous measurements of velocity, temperature, and chemical species fields. Recent work funded by ARO through a short-term innovative research (STIR) grant has shown the promise of aerosol phosphor thermometry (APT) to make high-precision temperature measurements at temperatures relevant for high-pressure jet ignition. Measurements of temperature using APT are readily coupled with particle image velocimetry (PIV) using the seeded particles to simultaneously measure the velocity and temperature fields. The proposed work will combine simultaneous velocity and temperature measurements using APT-PIV with simultaneous formaldehyde planar laser-induced fluorescence (PLIF) mole fraction measurements, through careful diagnostic design, providing a powerful tool to study the ignition of high-pressure turbulent fuel jets. This is an increasingly important area of research for the Army due to the desire to operate diesel engines on fuels with a wide range of ignition properties. The proposed work will build on recent results to implement APT-PIV with simultaneous formaldehyde PLIF for the study of turbulent jet ignition processes. The work will develop and apply a temporal filtering technique for APT to reject short-lived fluorescence interferences. The APT-PIV diagnostic will be designed specifically to address the needs of measurements in diesel engines and will be integrated with the formaldehyde PLIF mole fraction diagnostic. This will include selection of a phosphor composition that will enable measurements over the temperature range of interest from 700 K to 1150 K for pressures ranging from 10 bar to 100 bar and design of the technique to minimize sources of uncertainty. Formaldehyde mole fraction distributions will be quantified by correcting formaldehyde PLIF measurements for temperature and pressure dependence. The work will quantify uncertainty resulting from composition variation impacts on formaldehyde PLIF signal. A novel method to correct for broadband fluorescence from interfering species will be developed and applied. This will enable quantitative single-shot measurements of formaldehyde mole fraction distributions in challenging engine environments. The developed laser-based diagnostics will be validated and applied in an optical engine. Measurements in an igniting turbulent fuel jet will be performed in a small-bore diesel optical engine at thermodynamic conditions relevant to Army engine applications. The goal of these measurements will be twofold, first to demonstrate and validate application of the technique in the environment the technique was designed for and, second, to generate the first data of its kind focused on the ignition process of high-pressure turbulent fuel jets of interest to the Army.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 01, 2019
- Source ID
- W911NF1910238
Entities
People
- David A Rothamer
Organizations
- Army Contracting Command
- United States Army
- University of Wisconsin–Madison