Fuel Consumption Calculation

The two possible solutions are to increase the size of the piping and install cross-connected regulators on each burner, or raise the discharge pressure of the combustion air blower and add a cross-connected regulator to each burner, accepting different firing rates from the individual burners. 

If the combustion air is preheated, repiping with mass flow air/fiiel ratio for the zone is a must. To reduce burner-to-bumer differences in air/fiiel ratio, design the air velocities in the piping to a maximum of 40 ft/sec (12.2 m/s) actual velocity, and add air and gas flow meters and a limiting orifice valve in each burner s gas line for setting the air/fuel ratio at each burner. 

Use the graphs and diagrams from section 5.1, repeating the three steps from section 5.5, with equation 2.1 = equation 5.3 = equation 5.4. 

Step 2. Predict the %available heat (which is 100% - %flue losses) by reading it from an available heat chart (figs. 5.1 or 5.2). Section 5.1 explains how to determine flue gas exit temperature. 

Step 3. Divide the total heat need for load and furnace (from Step 1) by the %avail-able heat divided by 100% (from step 2, as a decimal). 

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Figure 6.30 shows the grand composite curve plotted from the problem table cascade in Fig. 6.186. The starting point for the flue gas is an actual temperature of 1800 C, which corresponds to a shifl ed temperature of (1800 — 25) = mS C on the grand composite curve. The flue gas profile is not restricted above the pinch and can be cooled to pinch temperature corresponding to a shifted temperature of 145 C before venting to the atmosphere. The actual stack temperature is thus 145 + 25= 170°C. This is just above the acid dew point of 160 C. Now calculate the fuel consumption ...

The fuel consumption is now calculated by taking the flue gas from theoretical flame temperature to ambient temperature ... 

Natural gas containing 98% methane and 2% nitrogen by volume is burned in a furnace with 15% excess air. The fuel consumption is 20 cubic meters per second, measured at 290°K and 101.3 kPa (or 14.7 psia). The problem is to determine how much air is required under these conditions. In addition, we want to determine the baseline environmental performance of the furnace by calculating the quantity and composition of the flue gas. 

NOTE All boiler plant operators are urged to meter the MU water consumption as an aid to calculating a material balance. Steam generation rates can be reasonably accurately determined from the fuel consumption because records of fuel costs are always maintained. Daily and weekly BD rates usually can be estimated from the use of a measuring bucket or pipe velocity table. The difference between steam production and MU represents a combination ofBD and loss of CR. 

For the calculation of WTW energy requirements and GHG emissions we have made the simplification that the fuel consumption of a vehicle fuelled with ethanol (e.g., E85) is the same as that of a vehicle fuelled with pure gasoline. Methanol is used in fuel cell vehicles with on-board fuel processors. Table 7.2 shows the properties of different transportation fuels. 

Oxidation of Benzene Because of the complexity of the aromatics chemistry, large uncertainties remain in the oxidation mechanisms for even the simplest aromatic species, benzene and toluene [12,113]. The overall oxidation behavior (i.e., the fuel consumption rate) can be calculated with some confidence, but predictions of the concentration of intermediate species may be off by orders of magnitude. 

Fig. 1 shows the results of such a calculation. (The model gives a rate of fuel consumption which can be as much as an order of magnitude too small. This occurs because the model neglects additional reactions which increase the ratio of [OH] to [CH3] during fuel consumption.) Initially [r] is zero and A is the dominant term in eq. 1, but B[r] rapidly becomes larger and [r] increases exponentially as seen at the left of Fig. 1. Eventually as [r] increases, C[r]2 becomes comparable to b[r] and the time derivative becomes very small, as in the middle of Fig. 1.

The combustion reaction rate is controlled both by the availability of fuel and oxygen kinetic effects (temperature). In full-scale fire modeling, the resolvable length and time scales are usually much larger than those associated with the scales of the chemical combustion reaction, and it is common to assume that the reactions are infinitely fast. The local reaction rate depends on the rate at which oxygen and fuel are transported toward the surface of stoichiometric mixture fraction, shown in Figure 20.2 as a point where both oxygen and fuel mass fractions go to zero. For almost 20 years, the EBU or eddy dissipation models were the standard models used by the combustion CFD community. With the EBU, in its simplest form, the local rate of fuel consumption is calculated as [3] ... 

Heepke s calculations showed that the per-cremation coke consumption of a medium-sized oven at thermal equilibrium amounts to 30 kg (66 lbs) of coke (plus the wooden coffin weighing 40 kg, or 88 lbs). However, Heepke s findings are marred by errors both in approach and in arithmetic, and his conclusions are thus questionable. If one takes his errors into account, one arrives at a coke requirement of 20.5 kg (45.1 lbs). This result is consistent with those of experimental origin. The experiment conducted by R. Kessler with coke fuel on January 5,1927, indicated the following fuel consumption ... 

The fuel consumption relating to the eight cremations exclusive of the preheating of the oven still includes the consumption producing the heat that is absorbed by the oven s firebrick up to the point where thermal equilibrium is reached. A calculation to take into account the heat loss caused by radiation and conduction shows that the coke consumption for a cremation in an oven at thermal equilibrium is about 20 kg (44 lbs). 

Eerformance in terms of pounds of fuel consumed per horsepower-our. For electric power plants, fuel consumption is reported in terms of kilowatts. Auxiliaries included with engine-efficiency calculations vary with industry practice. 

After Xc is obtained, the local average rates of fuel consumption and of heat release may be calculated, in the flame-sheet approximation, from the formulas... 

The water content in the microemulsion fuels was compensated for at injection, and the water was disregarded in the calculations of the fuel consumption. The fuel consumption expressed as g fuel per horse-power-hr increased by approximately 9% for the microemulsion fuels containing 10 and 30% (w/w) of water and by 4% for the fuel with 20% compared with the reference fuel. These increases were approximately independent of injection timing (°BTDC), used speed, and load. 

Optimization of internal engine combustion in respect of fuel efficiency and pollutant minimization requires detailed insight in the microscopic processes in which complex chemical kinetics is coupled with transport phenomena. Due to the development of various pulsed high power laser sources, experimental possibilities have expanded quite dramatically in recent years. Laser spectroscopic techniques allow nonintrusive measurements with high temporal, spectral and spatial resolution. New in situ detection techniques with high sensitivity allow the measurement of multidimensional temperature and species distributions required for the validation of reactive flow modeling calculations. The validated models are then used to And optimal conditions for the various combustion parameters in order to reduce pollutant formation and fuel consumption. 

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