Flame attachment effect on the distributions of flow, temperature and heat flux of inclined fire plume

2021 ◽  
Vol 174 ◽  
pp. 121313
Author(s):  
Ying Zhang ◽  
Wei Zhang ◽  
Yifan Lin ◽  
Yue Chen ◽  
Kaiyuan Li
Keyword(s):  
Heat Flux ◽  
Fire Plume ◽  
Flow Temperature

Analysis of the Unsteady Overtip Casing Heat Transfer in a High Speed Turbine

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
S. Lavagnoli ◽  
G. Paniagua ◽  
C. De Maesschalck ◽  
T. Yasa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Convective Heat Transfer Coefficient ◽  
Tip Clearance ◽  
Heat Flux Sensor ◽  
Flow Temperature ◽  
Local Flow ◽  
Essential Information ◽  
Transfer Pressure

In modern gas turbine engines, the rotor casing is vulnerable to thermal failures due to large unsteady heat fluxes. The rotor tip flow unsteadiness is induced by the periodic passage of the rotor blades, with an intensity dependent on the tip gap geometry. Hence, the understanding of the physics is of paramount importance to develop appropriate predictive tools and improve the cooling schemes. The present research aims at providing essential information on the flow conditions, which should serve to assess the relative impact of the overtip flow, tip gap magnitude, and work extraction processes on the casing thermal load. This paper presents simultaneous measurements of steady and unsteady heat transfer, pressure and rotor tip clearance in the casing of a transonic turbine stage. The research article was tested in a compression tube facility operating at engine representative conditions (vane Mach number 1.07, vane outlet Reynolds number 1.3 × 106, pressure ratio is 2.92, at 6790 rpm). The rotor blade geometry has a flat tip with a nominal tip clearance of about 0.4% of blade height. The heat transfer, pressure, and tip clearance data were obtained at three circumferential positions around the turbine casing. The heat flux was monitored using a single-layered thin film gauge able to resolve with high fidelity the wall temperature fluctuations. The heat flux sensor was mounted on a probe equipped with a heating device that allows varying the wall temperature. A series of experiments was performed at different heating rates to derive the local adiabatic wall temperature and the adiabatic convective heat transfer coefficient. A high bandwidth capacitive sensor provided the instantaneous value of the single blade tip clearance. A simple zero-dimensional model has been proved effective to predict the local flow temperature while the rotor spins up prior to the test, and estimate the overtip flow temperature during a test.

scholarly journals Experimental study on the radiant heat flux of wall-attached fire plume generated by rectangular sources

2021 ◽  
Vol 159 ◽  
pp. 106605 ◽  
Author(s):  
Xianjia Huang ◽  
Yuhong Wang ◽  
He Zhu ◽  
Le He ◽  
Fei Tang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Radiant Heat ◽  
Radiant Heat Flux ◽  
Fire Plume

Analysis of the Unsteady Overtip Casing Heat Transfer in a High Speed Turbine

2012 ◽  
Author(s):  
S. Lavagnoli ◽  
G. Paniagua ◽  
C. De Maesschalck ◽  
T. Yasa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Convective Heat Transfer Coefficient ◽  
Tip Clearance ◽  
Heat Flux Sensor ◽  
Flow Temperature ◽  
Local Flow ◽  
Essential Information ◽  
Transfer Pressure

In modern gas turbine engines, the rotor casing is vulnerable to thermal failures due to large unsteady heat fluxes. The rotor tip flow unsteadiness is induced by the periodic passage of the rotor blades, with an intensity dependent on the tip gap geometry. Hence, the understanding of the physics is of paramount importance to develop appropriate predictive tools and improve the cooling schemes. The present research aims at providing essential information on the flow conditions, which should serve to assess the relative impact of the overtip flow, tip gap magnitude and work extraction processes on the casing thermal load. This paper presents simultaneous measurements of steady and unsteady heat transfer, pressure and rotor tip clearance in the casing of a transonic turbine stage. The research article was tested in a compression tube facility operating at engine representative conditions (vane Mach number 1.07, vane outlet Reynolds number 1.3×106, pressure ratio is 2.92, at 6790 RPM). The rotor blade geometry has a flat tip with a nominal tip clearance of about 0.4% of blade height. The heat transfer, pressure, and tip clearance data were obtained at three circumferential positions around the turbine casing. The heat flux was monitored using a single-layered thin film gauge able to resolve with high-fidelity the wall temperature fluctuations. The heat flux sensor was mounted on a probe equipped with a heating device that allows varying the wall temperature. A series of experiments was performed at different heating rates to derive the local adiabatic wall temperature and the adiabatic convective heat transfer coefficient. A high bandwidth capacitive sensor provided the instantaneous value of the single blade tip clearance. A simple zero-dimensional model has been proved effective to predict the local flow temperature while the rotor spins up prior to the test, and estimate the overtip flow temperature during a test.

scholarly journals Experimental investigation of the physical mechanisms governing the spread of wildfires

2010 ◽  
Vol 19 (5) ◽  
pp. 570 ◽  
Author(s):  
Frédéric Morandini ◽  
Xavier Silvani
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flame Front ◽  
Fire Regime ◽  
Radiant Heat ◽  
Fire Spread ◽  
Fire Plume ◽  
Physical Mechanisms ◽  
Fire Front ◽  
Observed Behaviour

One of the objectives of the present study is to gain a deeper understanding of the heat transfer mechanisms that control the spread of wildfires. Five experimental fires were conducted in the field across plots of living vegetation. This study focussed on characterising heat transfer ahead of the flame front. The temperature and heat flux were measured at the top of the vegetation as the fire spread. The results showed the existence of two different fire spread regimes that were either dominated by radiation or governed by mixed radiant–convective heat transfer. For plume‐dominated fires, the flow strongly responds to the great buoyancy forces generated by the fire; this guides the fire plume upward. For wind‐driven fires, the flow is governed by inertial forces due to the wind, and the fire plume is greatly tilted towards unburned vegetation. The correlations of the temperature (ahead of the flame front) and wind velocity fluctuations change according to the fire regime. The longitudinal distributions of the radiant heat flux ahead of the fire front are also discussed. The data showed that neither the convective Froude number nor the Nelson convection number – used in the literature to predict fire spread regimes – reflect the observed behaviour of wind‐driven fires.

Investigation of the Exposure From a Realistic Undercar Fire on a Railcar Floor

2018 ◽  
Author(s):  
M. J. DiDomizio ◽  
C. Luo ◽  
S. Yazdani ◽  
B. Lattimer
Keyword(s):  
Heat Flux ◽  
Fire Resistance ◽  
Large Scale ◽  
Resistance Test ◽  
Fire Plume ◽  
Fire Dynamics ◽  
Geometric Configurations ◽  
Fire Resistance Test ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The objective of this research is to use testing and modeling to quantify realistic exposure fires under a railcar and compare these exposures to those in a fire resistance test. A series of tests were conducted on a railcar floor mockup, scaled to 40% of a full railcar width, exposed to fire from below. Two fires were considered, one representing a 1.9 MW diesel fire (e.g. resulting from a ruptured fuel tank) and another representing a 0.3 MW trash fire (e.g. resulting from a collection of trash and debris under the railcar). Two geometric configurations were tested including a floor with equipment box obstructions and a flat floor without undercar obstructions. For the diesel fire, the heat flux directly above the fire reached 75 kW/m2 for the flat configuration and 95 kW/m2 for the obstructed configuration, while gas temperatures directly above the fire reached 750°C and 950°C, respectively. Temperatures and heat flux varied greatly over the floor geometry for the realistic fires, resulting in thermal gradients that are not characteristic of a fire resistance test. Computational fluid dynamics simulations were used to model these different fire exposures under the railcar floor mockup as tested. The fire dynamics predicted were consistent with those measured. In the region of the mockup where the fire plume impinges, heat flux was predicted to within 11–22% of that measured. In the surrounding regions of the mockup, heat flux was predicted to within 22–40% of measured values. This level of agreement is appropriate for large-scale fire experiments, and the results demonstrate that the model is validated for use in the configurations considered in this study.

scholarly journals Analysis for Fire Plume Temperature in Developing Area and Radiation Heat Flux Distribution in Small-scale Pool Fire

2018 ◽  
Vol 211 ◽  
pp. 606-613 ◽  
Author(s):  
Gan-su Shen ◽  
Jun-cheng Jiang ◽  
Kui-bin Zhou ◽  
Shao-jie Zhang ◽  
Fan Wu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Pool Fire ◽  
Small Scale ◽  
Heat Flux Distribution ◽  
Radiation Heat ◽  
Radiation Heat Flux ◽  
Fire Plume ◽  
Plume Temperature ◽  
Developing Area

Siphon Flows in Stratified Coronal Loops

1994 ◽  
Vol 144 ◽  
pp. 185-187
Author(s):  
S. Orlando ◽  
G. Peres ◽  
S. Serio
Keyword(s):  
Heat Flux ◽  
Scaling Laws ◽  
Flow Model ◽  
Supersonic Flows ◽  
Coronal Loops ◽  
Characteristic Parameters

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.

Sign in / Sign up

Export Citation Format

Share Document