Advisor(s)

M. (Mohamad) Metghalchi

Date of Award

8-2011

Date Accepted

8-2011

Degree Grantor

Northeastern University

Degree Level

M.S.

Degree Name

Master of Science

Department or Academic Unit

College of Engineering. Department of Mechanical and Industrial Engineering

Keywords

burning, flame, HFC-152a, refrigerant, speed, velcocity

Disciplines

Heat Transfer, Combustion | Mechanical Engineering

Abstract

Of recent importance is the laminar burning speed of hydrofluorocarbons (HFCs) used in the refrigerant industry. Since the adoption of the Montreal Protocol in 1989 and the Kyoto Protocol in 1997 there has been an ongoing phase-out of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) which deplete the ozone layer. Refrigerant companies are working to develop alternatives to CFC and HCFC based chemicals that have long been used in air conditioning and refrigeration systems. Alternatives that are currently in use include HFCs such as (HFC-134a); however HFC-134a has recently been deemed an environmental danger as well and will be phased out accordingly. Other HFCs with desirable thermodynamic properties are potential replacements but they are flammable and so the potential for ignition must be evaluated very carefully. The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) and the International Organization for Standardization (ISO) are finalizing a new international standard that specifies that laminar burning speed will be the parameter that classifies a chemical as being mildly flammable.

Laminar burning speed and flame structure of 1,1-difluroethane (HFC-152a)/air difluoromethane (HFC-32)/air mixtures has been studied. Experiments have been carried out in constant volume vessel coupled with a Schlieren/shadowgraph system and CMOS high speed camera capable of taking flame snapshots up to 40,000 frames per second. Laminar burning speed was determined using a thermodynamic model that employs the pressure rise history of the combustion process. Experiments were conducted for ambient initial conditions over a wide range of equivalence ratios. Laminar burning speed of HFC-152a/air mixtures has been measured for temperature range of 298 to 400 K and pressure range of 1.0 to 4.0 atm. Preliminary burning speeds of HFC32/air mixtures are discussed as is the impact of buoyant rise on measureing the burning speeds of slower burning mixtures. The effect of equivalence ratio on flame structure was also studied. The presence of hydrofluoric acid in the products of combustion was observed along with its effects on the experimental apparatus. The results of laminar burning speed have been compared with others in the literature. Recommendations are made for future measurements on fuel mixtures containing HFC samples.

Document Type

Master's Thesis

Rights Holder

Casey Bennett


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