National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
CBET Research Highlights 
Notable Accomplishments from CBET Awards
1407 - Part A - Unraveling Fire Suppression Sprays
Andre Marshall  -  University of Maryland College Park

Outcome or Accomplishment:  Researchers at the University of Maryland have identified the essential flow structures responsible for the complex sprays generated by fire sprinklers.  The discovery of these structures has been leveraged to provide, for the first time, full descriptions of fire sprinkler sprays.

Impact:  The ability to fully describe fire sprinkler sprays will provide industry with new insight to support innovation in fire suppression products and engineering practices.

Andre Marshall Image 1
Figure 1.  Sprinkler sprays are generated as the initial jet flow is deflected radially outward along the tines and as the jet flow is forced downward through the slots.  Fast exposure photography reveals for the first time these canonical structures that produce the sprinkler spray.
Andre Marshall Image 2
  Figure 2.  Fire suppression spray characteristics; (a) illustration showing stages of the water transport process from injection to delivery; (b) innovative laser based measurements of drop size and number density near the injector exit quantifying complex spatial distribution of spray in the context of the tine / slot structure.
Andre Marshall Image 3
  Figure 3.  Dispersion and surface wetting prediction from a commercial sprinkler.  The predictions were performed using the initial spray basis functions.
Andre Marshall Image Image 4a
  Figure 4a.  Near-field measurements in a commercial sprinkler showing the three-dimensional tine slot structure and its interaction with frame arms; a) photograph of thin streams generated along the deflector.
Andre Marshall Image 4b
  Figure 4b.  Near-field measurements in a commercial sprinkler showing the three-dimensional tine slot structure and its interaction with frame arms; b) preliminary Spatially-resolved Spray Scanning System (SSSS) measurements of flux distribution.  The SSSS was invented at University of Maryland and provides unprecedented characterization of the sprinkler discharge.
Andre Marshall Image 5a
  Figure 5a.  Preliminary measurements from a prototype Spatially-resolved Spray Scanning System; a) Bottom view sprinkler flux iso-contour (~ 0.02 m from sprinkler centerline).
Andre Marshall Image 5b
  Figure 5b.  Preliminary measurements from a prototype Spatially-resolved Spray Scanning System; b) flux iso-contour displayed with spray initiation measurements.
Credit for All Images:  Andre W. Marshall, University of Maryland, College Park, MD

Explanation/background:  The enormous complexity of the fire suppression problem is daunting.  It is understandable that progress to establish analytical capabilities for evaluating suppression performance has been slow.  However, the absence of this analytical capability has locked the fire safety industry into a costly empirical spiral inhibiting innovation.
The uncertainty in defining the initial spray and related discharge characteristics makes analysis of spray dispersion and the associated fire suppression performance difficult.  Researchers at the University of Maryland are addressing this uncertainty by sorting through the details of the spray generation process in fire sprinklers.  This research has led to a number of advancements in the measurement and analysis of fire suppression sprays.  These experimental and analytical advancements have provided clarity in characterizing these complex sprays while creating critical pathways for the development of computational based approaches to support the design and evaluation of water-based fire suppression systems.

CBET Research Highlight - Part B - Engineering Technical Information

1407 - Unraveling Fire Suppression Sprays

Andre Marshall  -  University of Maryland College Park

Background:  Water based fire suppression systems are deployed almost everywhere for property protection and more importantly life safety.  These systems have largely been designed based on codes, standards, and empirical guidance.  However, following other fields of engineering, performance base design is becoming increasingly popular in Fire Protection Engineering especially for applications that deviate significantly from previous design experience.  Computational Fluid Dynamics (CFD) has become a leading tool for performance-based design in fire (e.g. design of smoke management systems).  It should be noted that the CFD based performance based design concept has not yet been realized for fire suppression applications.
Despite continuous improvements to CFD models used in fire analysis, the complexity of the physical processes governing fire suppression still make it difficult to apply these tools for fire suppression analysis.  In fact, the uncertainty in defining the initial spray and related discharge characteristics makes analysis of spray dispersion and the associated fire suppression performance difficult from the very beginning.  The fire suppression spray research at the University of Maryland has addressed this uncertainty and to a large extent removed it through novel measurement and analytical methods.

Results:  This research program largely focuses on near-field measurements to better understand atomization phenomena of fire suppression sprays.  Shadowgraphy measurements are performed very close to nozzles (e.g. sprinklers) to understand the topology of the readily atomized thin streams created by these devices and the resulting spray characteristics.  The research has produced 3 M.S., 1 Ph.D., a number of international internships, and several undergraduate student experiences.
An award winning study from this research revealed the unique tine/slot sheet structure of sprinklers associate with their geometry.  The sprinkler spray forms distinct sheets based on its tine and slot geometry.  Detailed drop size measurements have been conducted aligned with the tines and slots to reveal and understand the complex three dimensional spray generated by the sprinkler.  A basis function framework was also developed to express the vast quantity of drop data (from the tine and slot locations alone) in a practical physically meaningful format.  The basis functions describe the stochastic location (and thus number density), size, and velocity of the drops using a compact set of coefficients with physical significance.  The basis function approach was reported in another award winning paper and combined with an elegant means of predicting drop locations yielding a provisional software patent (PP: 61/548530) to facilitate the design and analysis of sprinkler systems.
A Spatially-resolved Spray Scanning System (SSSS) inspired by research challenges associated with resolving the spatial variation in these sprinkler sprays has been developed.  The SSSS has been documented as a University of Maryland invention and a provisional patent will be pursued.  Further development of the SSSS has been proposed to an NSF through the Major Research Instrumentation (MRI) program.  The complexity and three-dimensionality of the spray and its relationship with the deflector geometry can be clearly observed using this scanning technique.  The SSSS provides a complete scan of the spray moving beyond the discrete tine and slot method currently used.  This complete scan is particularly important because of geometric details of the sprinkler such as the frame arms, which produce complex deviations from the strict tine/slot symmetry of the nozzle.  The SSSS would provide a more comprehensive dataset for determining the basis functions, which would account for details of the sprinkler geometry (i.e. frame arms), which are currently neglected due to insufficient data.

Scientific Uniqueness:  The NSF funded research is unique because it provides extremely high-fidelity measurements of the sprinkler spray revealing a rational structure and detailed characteristics which previously had been dismissed as being too complex for evaluation.  The research further quantified these characteristics in a comprehensive framework suitable for engineering evaluation and product comparisons as well as sophisticated integration into computational tools for spray dispersion performance evaluation.

CBET Strategic Outcome Goals include:
- 1Discovery:  This NSF funded research revealed that the complex sprays generated by fire suppression sprays actually results from simple structures that are readily evaluated.  Novel laser-based measurements were determined to be well-suited for detailed characterization of these sprays in all of their complexity.  At the same time, an analytical framework was developed to make sense' out of the overwhelming data obtained in the detailed characterization in terms of physically meaningful parameters useful for engineering analysis and integration into computational fluid dynamics (CFD) codes.
- 2Research Infrastructure:  The laser-based diagnostics techniques developed in this research program have inspired new inventions for the analysis of fire suppression sprays.  The detailed measurements combined with the analytical framework for compressing and representing the data establishes a new paradigm for treatment of fire suppression sprays.

Transformative Research:  The spray characterization methods developed in this research reveal characteristics of the fire suppression sprays in unprecedented detail.  The ability to see and understand fire suppression sprays with this fidelity creates opportunities for development of new nozzle technology and enables computational based evaluation of fire suppression performance not before possible.

Intellectual Merit:  Dispersed spray interactions (with hot gases, flames, and thermal radiation) and delivered spray interactions (with burning and heated target surfaces) are important in determining fire suppression performance.  This research would for the first time offer a comprehensive foundation for validating suppression performance including detailed canonical experiments, well-instrumented full-scale tests relevant to industry, and harmonized analysis.

Broader Impacts Overview:  Water-based fire suppression systems (e.g. sprinklers, water mists, hose streams) represent truly ubiquitous forms of engineering used for life safety and infrastructure protection.  The underlying suppression technology is anchored largely in phenomenological observations, empiricism, and qualification tests.  The University of Maryland Fire Protection Engineering Department has embarked on an ambitious effort to perform the focused experiments and model development required to equip computational based modeling tools used in fire safety analysis with validated spray measurements and models enabling a major step forward in CFD based evaluation of fire suppression performance.  This capability would equip engineers with tools required for performance based fire suppression analysis and design perhaps leading to new technologies and engineering practices for life safety and infrastructure protection.
Broader Impacts of this research include:
- 1Benefits to society:  The research findings related to fire suppression sprays enables the development of new fire suppression nozzle technology and modern computationally based engineering practices for fire suppression system development.
- 2Broadening participation of underrepresented groups:  The Principal Investigator is from an underrepresented group and actively works with the University of Maryland Center for Minorities in Science and Engineering (CMSE) on programs to broaden the participation of underrepresented groups in engineering.
- 3Advancing discovery and understanding while promoting teaching, training, and learning:   The research has produced 3 M.S., 1 Ph.D., a number of international internships, and several undergraduate student experiences.  The current research team consists of 1 post-doctoral fellow, 1 Ph.D. student, and an international intern.
- 4Enhancing the infrastructure for research and education:  This NSF funded research has inspired the development of new measurement techniques, which have been adopted by industrial leaders (e.g. FM Global).  New measurement techniques have been conceived and follow-up funds have been requested to develop these ideas further (e.g. Proposal No. 1229506, MRI: Development of Spatially-resolved spray scanning system (SSSS)).
- 5Disseminating broadly to enhance scientific and technological understanding:  The research has produced 7 publications (two of which were award winning listed below).  The Principal Investigator has also shared results with practitioners at professional conferences and workshops who may implement and leverage some of the findings in addition to researchers.
           Ren, N., Blum, A., Zheng, Y. H., Do, C., and Marshall, A. W., "Quantifying the Initial Spray from Fire Sprinklers," Fire Safety Science - Proceedings of the Ninth International Symposium, IAFSS, Karlsruhe, Deutschland, 2008.  (Best Paper - Symposium)
           Ren, N., Baum, H. R., and Marshall, A. W., "A Comprehensive Methodology for Characterizing Sprinkler Sprays," Proceedings of the Combustion Institute, Vol. 33, p 2547-2554, 2011.  (Best Paper - Fire Colloquium)

Program Director:
Arvind Atreya
CBET Program Director - Combustion, Fire, and Plasma systems
NSF Award Number:   0645063
Award Title:   CAREER: Exploring Jet Fragmentation and Atomization for Combustion and Fire Suppression Systems
Principal Investigator:   Andre Marshall
Institution Name:   University of Maryland College Park
Program Element Code:   1407
CBET Research Highlight:   Fiscal Year 2012
Approved by CBET on:   21 May 2012

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This CBET Research Highlight was Updated on 8 June 2012.