A. M. Birk

Fire Testing of Total Containment Pressure Vessels

In North America certain hazardous materials are transported in rail tank cars that must be able to survive an engulfing liquid hydrocarbon pool fire for 100 minutes without rupture. To meet this requirement these tanks are normally equipped with pressure relief valves (PRV) and some form of thermal insulation or thermal protection (TP). These tanks sometimes have non-accident releases (NAR) due to unwanted activation of, or leakage from the pressure relief valves (PRV). These NARs are a nuisance for Industry and for this reason, the industry now wants to remove the PRVs from certain tanks. This is known as total containment and is common practice in Europe. However, Europe does not have a 100 minute fire survival requirement. This paper is about a series of fire tests of 1/3 rd linear scale US DOT 111 Tanks cars. The 2.4 m3 vessels were subjected to fully engulfing fires generated by liquid propane fueled burners.

NEAR FIELD EFFECTS OF SMALL SCALE WATER BLEVE

This paper presents preliminary results collected with a new experimental apparatus developed to collect close-in overpressure data from small scale water BLEVE. The apparatus consists of a sealed aluminium tube pressurized and heated up until rupture, representing a realistic pressure vessel failure. Various types of failure were obtained, from partial opening to catastrophic failure, giving detailed data on the blast overpressure, the load generated by the failure on the ground, and the transient pressure in the vessel. High speed imaging of the failure gives new insight to the close-in conditions of the explosive release. A CFD modelling work aimed to investigate the ability of CFD to model the blast pressure peaks from a pressurized vapour space. A shock tube configuration was selected, and a series of experiments were performed to provide experimental data. A very good agreement was observed which validates a first step in BLEVE simulation by CFD.

Rail Tank Car Total Containment Fire Testing: Results and Observations

The frequent incidences of Non-Accident Releases (NARs) of lading from tank cars have resulted in an increasing interest in transporting hazardous materials in total containment conditions (i.e., no pressure relief devices). However, the ability of tank cars to meet thermal protection requirements provided in the Code of Federal Regulations under conditions of total containment has not been established. The intent of this effort was to evaluate through a series of third-scale fire tests, the ability of tank cars to meet the thermal protection requirements under total containment conditions, with a particular focus on caustic ladings. A previous paper on this effort described the test design and planning effort associated with this research effort.A series of seven fire tests were conducted using third scale tanks. The test fires simulated fully engulfing, hydrocarbon fueled, pool fire conditions. The initial tests were conducted with water as a lading under jacketed and non-jacketed conditions and also with different fill levels (98% full or 50% full). Additionally, two tests were conducted with the caustic, Sodium Hydroxide as the lading, each test with a different fill level. In general, the tanks with water were allowed to fail or reach near-failure conditions, whereas, the tests with the caustic lading were not allowed to proceed near failure for safety reasons. This paper describes the results and observations from the fire tests, and discusses the various factors that affected the fire test performance of the test tanks.Review of results from the one-third scale tests, and subsequent scaling to full-scale suggest that a full-scale tank car filled with 50% NaOH solution is unlikely to meet the 100-minute survival requirement under conditions of total containment.Copyright

Experimental and Computational Study of Flow and Heat Transfer Inside a Heated Exhaust Strut

The flow and heat transfer inside a short airfoil shaped turbine exhaust strut was studied experimentally and computationally. A combination of transient and steady IR thermographic techniques were used to measure the heat transfer, and showed that the streamwise evolution of the heat transfer could be reliably described using a power law type relationship. Steady RANS CFD using the realizable k-epsilon was unable to accurately predict the observed heat transfer, with the main limitations of the model being a) a fundamental inability to calculate secondary flows and b) an underestimation of the restriction on boundary layer growth rates imposed by the opposing walls. The experiments showed that heat transfer rates were much higher in thinner regions of the strut, and lower in thicker regions. The CFD predicted an essentially uniform heat transfer rate, independent of the local strut thickness.Copyright

Influence of Inlet Boundary Conditions on Simulations of an Asymmetric Diffuser With the V2F Turbulence Model

A set of numerical simulations were performed on an asymmetric, two dimensional diffuser using ANSYS Fluent 14.0, a commercially available RANS based CFD code. The Display Formulaν′2¯-f turbulence model, which has previously been shown to be a good model for this geometry, was implemented through a user defined function, and the influence of inlet boundary conditions was evaluated. It was shown that the inlet velocity and turbulence profiles had a significant effect on the calculated performance of the diffuser, especially in terms of the onset of diffuser stall. It was shown that when the boundary conditions were set appropriately, excellent agreement with LES and experimental data was obtained.Copyright

Rail Tank Car Total Containment Fire Testing: Planning and Test Development

Given the frequent incidences of Non-Accident Releases (NARs) of hazardous materials from tank cars, there in an increasing interest in transporting hazardous materials in total containment conditions (i.e., no pressure relief devices). However, the ability of tank cars to meet thermal protection requirements provided in the Code of Federal Regulations under conditions of total containment has not been established. Also, the modeling tool commonly used by industry to evaluate thermal protection, AFFTAC, has not been validated under these conditions. The intent of this effort was to evaluate through a series of third-scale fire tests, the ability of tank cars to meet the thermal protection requirements under total containment conditions, and also, to validate AFFTAC for such conditions.This paper describes the test design and planning effort associated with this research, including the design and evaluation of a fire test setup to simulate a credible, fully engulfing, pool fire that is consistent and repeatable, and the design and hydro-static testing of a third-scale tank specimen. The fire design includes controls on the spatial distribution and temperature variation of the flame temperature, the heat flux, and the radiative balance, to best reflect large liquid hydrocarbon pool fire conditions that may be experienced during derailment scenarios.Copyright

Experimental Observations of Flow Over an Airfoil in a Confined Duct

The flow around a NACA 0020 airfoil strut placed in the centre of a rectangular duct has been studied. The performance of the strut was characterized in terms of its effect on the mean flow, as well as in terms of overall losses. It was shown that the main influences of increasing the confined mixing length downstream of the airfoil wake were to reduce the total system dump loss (kinetic energy loss) through the use of a Carnot diffuser, and to slightly increase the wake spreading rate. In addition to creating a reference dataset for CFD comparison and validation, some phenomenon were particularly identified for future CFD investigation. It was shown that there may be some benefit to adjusting the turbulent Prandtl number for Turbulent Kinetic Energy during CFD simulations of this same problem. It was also shown that studying the particular effects of the Carnot diffuser on the development and migration of the wall-airfoil interface vortices would give useful insight into the physical mechanisms driving this change in performance.© 2014 ASME

Influence of Tip Shape on Reynolds Number Sensitivity for a Seven Hole Pressure Probe

The effects of tip shape on the Reynolds number sensitivity of a seven hole pressure probe are studied over a range of flows associated with practical use of turbomachinery. It is shown that at low flow angles, the response of a conical or hemispherical tipped probe is independent of Reynolds number above Re = 3000, and at high flow angles, Re = 6000. Despite there not being a discernable difference in the average error in flow properties at different Reynolds numbers between the two tip shapes, it is shown that the hemispherical tip is preferred because the pressure distributions around the tip are more consistent.Copyright

Improvements to Common Data Reduction and Calibration Methods for Seven Hole Probes

The influence of calibration data sorting procedures and the order of polynomial curve fit used to calibrate seven hole pressure probes in subsonic, incompressible flow are discussed. It is shown that the inclusion of fourth order polynomial terms is necessary to properly model the physical response of the probe. It is also shown that the uniformity of probe response error is be significantly affected by polynomial extrapolation near sector boundaries, and that the uniformity can be improved by using some calibration points in multiple sectors.Copyright