Calculated Heat Release Research Articles

Investigation of thermal response of glass bulb sprinklers using plunge and ramp tests

The thermal behaviour of glass bulb sprinklers was investigated in a heated wind tunnel under various test conditions. The response parameters considered were the response time index (RTI), the conduction parameter (C) and the change of phase parameter (CHP). Combinations of one, two and three response parameters were used to predict the response times of various wind-tunnel test conditions, and for slow, medium and fast growth rate fires. These calculations indicate that the wind-tunnel results cannot be fully explained in the framework of the thermal response models applied. Tests with a high precondition temperature of the sprinkler resulted in higher RTI values compared with cases with normal precondition temperatures. A plausible explanation for the higher RTI values could be a time delay caused by temperature gradients within the glass bulb. This indicates that the CHP parameter previously explained in terms of work needed to shatter the glass bulb, more likely reflects an affect of thermal time delay. Calculated heat release rates at sprinkler response under a growing fire condition were used to evaluate the thermal response models. For the fast, medium and slow fire growth rates, the heat release rates at sprinkler response were found to be similar, whether based on calculations with two parameters (RTI and C) or with all three parameters (RTI, C, CHP). When using the RTI value only, however, the predicted rate of heat release at sprinkler response decreased significantly.

Calculations of subsonic and supersonic turbulent reacting mixing layers using probability density function methods

A particle method applying the probability density function (PDF) approach to turbulent compressible reacting flows is presented. The method is applied to low and high Mach number reacting plane mixing layers. Good agreement is obtained between the model calculations and the available experimental data. The PDF equation is solved using a Lagrangian Monte Carlo method. To represent the effects of compressibility on the flow, the velocity PDF formulation is extended to include thermodynamic variables such as the pressure and the internal energy. Full closure of the joint PDF transport equation is made possible in this way without coupling to a finite-difference-type solver. The stochastic differential equations (SDE) that model the evolution of Lagrangian particle properties are based on existing models for the effects of compressibility on turbulence. The chemistry studied is the fast hydrogen–fluorine reaction. For the low Mach number runs, low heat release calculations are performed with equivalence ratios different from one. Heat release is then increased to study the effect of chemical reaction on the mixing layer growth rate. The subsonic results are compared with experimental data, and good overall agreement is obtained. The calculations are then performed at a higher Mach number, and the results are compared with the subsonic results. Our purpose in this paper is not to assess the performances of existing models for compressible or reacting flows. It is rather to present a new approach extending the domain of applicability of PDF methods to high-speed combustion.

ENGINE HEAT RELEASE VIA SPREAD SHEET

Calculation of rates of heat release from engine fuels provides a useful diagnostic tool. As one example, thetechnique was useful in discovering that retarding injection timing will reduce the proportion of premixed combustion andthereby reduce NOx emissions from a diesel engine. The technique for calculating heat release rates was proposed morethan 30 years ago. Initially a cumbersome technique, it has been simplified over the years. In the present work, the authorpresents equations which allow calculation of heat release rates within a spread sheet.

Study of Heat Rejection Mechanism of a Direct-injection Diesel Engine. 2nd Report. Effects of Combustion Control Item on Heat Flux.

Experimental investigations are being conducted on a single-cylinder direct-injection diesel engine to examine the effects of combustion chamber specifications and swirl ratios on the heat release and transient heat transfer characteristics. Heat rejection was examined on the basis of heat release calculations using cylinder pressure time histories. Transient surface temperature data obtained from stationary locations in the piston and cylinder head were used as the basis for determining the transient heat flux rates. The results showed good agreement with the heat rejection calculated from cylinder pressure data and that transient heat flux in a piston cavity was reduced with the larger cavity diameter and a higher swirl ratio. On the other hand, a transient heat flux in a piston head was not changed by the cavity diameter and swirl ratio.

Modelling the heat release rate of aircraft cabin panels in the cone and OSU calorimeters

AbstractA computer model was developed to calculate the heat release rate of aircraft cabin panels in the OSU calorimeter based on their thermophysical, thermochemical and geometrical properties. It calculates the temperature profile through the panel as a function of time and uses the measured kinetic constants of the individual materials to deduce the mass loss rate. The mass loss rate is multiplied by the heat of combustion of the volatiles to obtain the heat release rate which would be measured in the Cone calorimeter. This heat release rate is used in an energy balance at the surface of the specimen to calculate the rise in enthalpy of the flue gases in the OSU calorimeter and thus the specimen's heat release rate in that apparatus. The calculated heat release rates are in reasonable agreement with measurements in the Cone and OSU calorimeters.

Flame Heights And Heat Release Rates Of 1991 Kuwait Oil Field Fires

A series of measurements were made in the Al MawqB/Al Ahmadi oil field region of Kuwait to explore the feasibility of assessing the heat release rate of individual well fires through flame height and thermal radiation measurements. The heat release rate (Q in kW) of the crude oil well fires was correlated with the flame height (Z, in meters) using Q = ( ~ / 0 . 2 1 ) ~ ~ . The 12 Kuwait oil field fires measured ranged in calculated heat release rate from 90 MW to 2 GW which correspond to flow rates of 0.003 m3/s (1500 bblslday) to 0.059 m3/s (30000 bblslday). Based on these twelve burning well measurements, the estimated total flow from the 651 damaged wells, both burning and leaking in March, 1991, was 14 m3/s (7,400,000 bblslday) which is only 20 percent greater than published National Oceanic and Atmospheric Administration (NOAA) estimates based on information from the Kuwait Oil Company.

The Measurement Of Heat Release Rates By Oxygen Consumption Calorimetry In Fires Under Suppression

A series of open-space fire experiments was conducted at the National Fire Laboratory (NFL) to validate the capabilities of the NFL room-size oxygen-consumption calorimeter, and to assess the importance of accounting for actual water vapour content in the exhaust gases in calculating heat release rates (HRR). Water spray was used to partially suppress some of the fires, and to add significantly to the humidity of the exhaust gases. The equations normally used in the fire research community for oxygen calorimeter assume unsuppressed fires, and that water vapour in the exhaust gases is due solely to the humidity of the incoming air and to combustion reactions. This paper derives the basic equations for computing heat release rates based on the principle of nitrogen balance. The general equations take into account all sources of water vapour, including incoming air, combustion reactions, and evaporation due to suppression. The equations are then simplified to i) neglect all humidity, and, ii) consider only the humidity of the incoming air. The predictions of the HRR from the three sets of equations are compared with the HRR calculated for unsuppressed fires and with the HRR obtained by measuring fuel consumption rates. As long as the water vapour content in the exhaust gases is less than 7 %, both simplified equations can be used to measure the HRR of partially suppressed fires, without significant error. For larger concentrations of water vapour, water vapour should be measured and the full equations used.

A mathematical model for calculating heat release rate in the room corner test

A mathematical model is presented for calculating the heat release rate in the room corner test, where lining materials are mounted on both walls and ceiling. The model is based on a thermal theory for concurrent flow flame spread. By using a simple mathematical representation of the heat release rate from the cone calorimeter, analytical solutions are arrived at for the velocity and position of the pyrolysis front in the room corner test as well for as the heat release rate from the burning material. Results from calculations are compared with those from experiments, showing good agreement for 11 materials out of 12.

火炎のゆらぎの周波数による発熱量の推定

火炎のゆらぎの周波数による発熱量の推定

中速ディーゼル機関における熱発生率のシミュレーション手法

This paper discusses the tentative calculation method for simulating the heat release rate which is indispensable for predicting the medium speed diesel engine performance. The combustion tests were conducted in the medium speed diesel engines with 220mm and 240mm bore using the marine diesel fuel oil and the degraded heavy fuel oils, and the relationship between the cumulated quantity of fuel injection rate and the cumulated quantity of heat release rate obtained from those tests is examined. The results indicate that the shape in the unburnt quantity mode of fuel injected into the combustion chamber is divided into three stages, and the first and the second stages can be approximately shown as the linear function, the third stage can be approximately shown as the exponential function. Further, the heat release rate can be simulated by means of this calculation method using the coefficients and the exponents which are evaluated from the relations between the cumulated quantities, and using the input data for the fuel injection mode. And the agreement between the measured and the calculated heat release rate is found to be good in trend and in magnitude.

Experiments With Coal Fuels in a High-Temperature Diesel Engine

The combustion of 50 wt percent coal slurries, using water, diesel fuel, and methanol as carrier liquids, was investigated in a single-cylinder research engine. High temperatures were achieved in the engine cylinder using low-heat-rejection engine technology, electrically heated glow plugs, and heated inlet air. Comparisons of the fuels and different methods of providing high cylinder temperature were made using cylinder pressure data and heat release calculations. Autoignition of the coal/water slurries was attained using auxiliary heat input. The burning rates of all the autoignited slurries were significantly enhanced by using a pilot injection of diesel fuel. Under some operating conditions the engine thermal efficiency was equal to diesel fuel performance. It was apparent that engines designed for coal slurry should maximize the prechamber volume.