Heat Release Intensity Research Articles

Impact of pressure on high intensity colorless distributed combustion

In recent years, colorless distributed combustion (CDC) has been shown to provide ultra-low pollutants emission, enhanced stability, fuel flexibility and thermal field uniformity. To achieve CDC conditions, fuel–air mixture must be properly prepared prior to the mixture ignition. In this paper, the impact of moderate pressure increase on a test combustor is examined with emphasis on pollutants emission under near CDC conditions. Increase in pressure at constant mass flow rate resulted in a significant increase in NO emission and departure from CDC conditions. This is a result of reduction of the volume flow rate and injection velocity with pressure increase, as well as an increase in the apparent residence time of gases within the combustor. These conditions led to less than adequate mixing and more residence time of gases in the post flame zone to form NOx. CO emissions were reduced as longer residence time allowed for complete conversion of CO to CO2. Also, the increase in pressure enhanced chemical kinetics and suppressed dissociation. Increasing the combustor pressure with constant heat release intensity, where mass flow rates are increased to keep the apparent residence time constant, showed a slight increase (1PPM) of NO under premixed conditions and significant reduction of CO. OH∗ chemiluminescence showed that the reaction zone did not change with increase in pressure under premixed combustion. For non-premixed combustion, the reaction zone intensity increased and was more concentrated with increase in pressure to result in higher emissions as compared to the premixed case. In both cases, CO emission was significantly reduced due to the increased heat load and temperatures within the combustor. Relations describing change of NO and CO emissions with pressure were used to predict the combustor emissions at higher pressures. Difference between premixed and non-premixed modes revealed the need for more adequate mixing, necessary for CDC condition. Increase in pressure without considering flow velocities and flowfield can lead to departure from CDC conditions with simultaneous increase in emissions.

Thermal crisis of a vortex source in a real gas flowing into vacuum with heat supply under constant pressure

Thermal crisis of a vortex source at energy input under constant pressure is investigated. The energy release intensities per unit mass and per unit volume are analyzed for the case of the vortex source flow into vacuum (regime I). Analytical solutions for gasdynamic parameters and an algorithm for constructing the heat release intensity function for different variants of vortex sources are studied. Limitations on the extension of a constant-pressure interval are determined, and the dependences of the energy input area critical coordinates, critical temperature, and energy input parameters on the mass flow, gas circulation, and initial coordinate of the energy input area are obtained. A small correction to the gas specific heat with rising temperature and a significant correction to the specific heat at a stagnation temperature of 1000 K are considered.

Velocity and turbulence effects on high intensity distributed combustion

High intensity distributed combustion assists to provide substantial performance improvement for gas turbine applications for our quest to simultaneously seek improved pattern factor, ultra-low emission of NOx and CO, low noise, enhanced stability, fuel flexibility and higher efficiency. In such combustion method, controlled mixing between the injected air, fuel and hot reactive gases from within the combustor prior to mixture ignition must occur to achieve distributed reactions in the entire combustion chamber. Near zero emission of NO and CO has been achieved using methane as the fuel under distributed combustion conditions at high heat (energy) release intensity of 22–36MW/m3atm. The conditions to form distributed reaction in the combustor are further investigated through variation of air injection velocity with the output parameters focused on pollutants emission and combustor performance. The isothermal flowfield is examined using particle image velocimetry (PIV) to determine key features associated with the flowfield and its effects on pollutants emission and stability. The results showed higher entrainment and turbulence at increased injection velocity. Increase in injection velocity decreased NO emissions by some 20–48% with minimal impact on CO emission under premixed fuel–air condition. Less than 4ppm of NO was achieved at an injection velocity of 46m/s at an equivalence ratio of 0.7 and heat (energy) release intensity of 31.5MW/m3atm using normal temperature air. High injection velocity at the same operating condition decreased NO emission by some 20% to 3.2ppm. Higher injection velocity under preheated inlet air condition further decreased NO to 2ppm (48% reduction) at an equivalence ratio of 0.5. The results under non-premixed combustion conditions showed similar behavior. The reduction of NO with single injection parameter is attributed to improved distributed reaction condition from direct entrainment and rapid mixing of reactive species present in the combustion zone under high intensity combustion conditions.

Prediction of the Thermoacoustic Combustion Instabilities in Practical Annular Combustors

A three-dimensional finite element code is used for the eigenvalue analysis of the thermoacoustic combustion instabilities modeled through the Helmholtz equation. A full annular combustion chamber, equipped with several burners, is examined. Spatial distributions for the heat release intensity and for the time delay are used for the linear flame model. Burners, connecting the plenum and the chamber, are modeled by means of the transfer matrix method. The influence of the parameters characterizing the burners and the flame on the stability levels of each mode of the system is investigated. The obtained results show the influence of the 3D distribution of the flame on the modes. Additionally, the results show what types of modes are most likely to yield humming in an annular combustion chamber. The proposed methodology is intended to be a practical tool for the interpretation of the thermoacoustic phenomenon (in terms of modes, frequencies, and stability maps) both in the design stage and in the check stage of gas turbine combustion chambers.

Thermogravitational mechanism of alignment of the front of chemoconvection patterns with an exothermic chemical reaction

This paper studies the stability of the front of chemoconvective finger patterns spontaneously formed in a two-layer system of reacting liquids placed in a narrow gap between two solid plates. The mathematical model of this process includes a system of equations that take into account chemical reaction, diffusion, and convection, written in the Hele-Shaw approximation. Numerical analysis of the model shows that with increasing intensity of heat release, the envelope of the salt fingers is smoothed and chemoconvection occurs in a narrow region adjacent to the interface.

The shortest period of coal spontaneous combustion on the basis of oxidative heat release intensity

It’s necessary to forecast the shortest spontaneous combustion period for preventing and controlling the coal spontaneous combustion. During the experimental process, a calculating model of the SSCP is established on the basis of the oxidative heat release intensity and thermal capacity at different temperatures. According to the basic parameters of spontaneous combustion, heat of water evaporation and gas desorption, the SSCPs of different coals are further predicted. Finally, this study analyzed the relationships of the SSCP and the judging indexes of the self-ignite tendency. The result shows that the SSCP non-linearly increases with the decrease of dynamic oxygen adsorption and increase of activation energy. Compared with the practical fire situation of mine, this reliable method can meet the actual requirement of mine production.

Convection of a heat-generating fluid in a rotating horizontal cylinder

Thermal convection of a fluid in a horizontal cylinder rotating about its own axis with uniformly volume-distributed internal heat sources is experimentally investigated. The enclosure boundary temperature was kept constant. The threshold of the excitation of convective flows and their structure are studied as functions of the heat-release intensity and the rotation velocity. The experiments are performed with water and water-glycerin solutions. It is shown that rapidly rotating fluid is in a stable quasiequilibrium state, namely, the temperature distribution is axisymmetric and has a maximum at the center of the enclosure. It is found that with decrease in the rotation velocity a convective flow arises thresholdwise, in the form of vortex cells periodically arranged along the axis. The thermal convection in the rotating enclosure is shown to be determined by the effects of two different mechanisms. One of these is due to the centrifugal force of inertia and plays the stabilizing role, while the other, thermovibrational mechanism is connected with nonisothermal fluid oscillations under the action of gravity in the enclosure-fitted reference frame and is responsible for the occurrence of mean thermal convection. The boundaries of the convection generation are plotted in the plane of the governing dimensionless parameters and the heat transfer in the supercritical region is studied.

Combined effects of cooled EGR and a higher geometric compression ratio on thermal efficiency improvement of a downsized boosted spark-ignition direct-injection engine

The downsized boosted spark-ignition direct-injection (SIDI) engine has proven to be one of the most promising concepts to improve vehicle fuel economy. However, the boosted engine is typically designed at a lower geometric compression ratio (CR) due to the increased knock tendency in comparison to naturally aspirated engines, limiting the potential of improving fuel economy. On the other hand, cooled exhaust gas recirculation (EGR) has drawn attention due to the potential to suppress knock and improve fuel economy. Combing the effects of boosting, increased CR and cooled EGR to further improve fuel economy within acceptable knock tolerance has been investigated using a 2.0L downsized boosted SIDI engine over a wide range of engine operating conditions from 1000rpm to 3000rpm at low to high loads. To clarify the mechanism of this complicated effects, the first law of thermodynamics analysis was conducted with the inputs from GT-Power® engine simulation.Experiment results indicate that cooled EGR provides more brake thermal efficiency improvement than increasing geometric CR from 9.3 to 10.9. The benefit of brake thermal efficiency from the higher CR is limited to low load conditions. The attributes for improving brake thermal efficiency by cooled EGR include reduced heat transfer loss, reduced pumping work and increased ratio of specific heats for all the engine operating conditions, as well as higher degree of constant volume heat release only for the knock-limited high load conditions. The combined effects of 18–25% cooled EGR and 10.9 CR lead to 2.1–3.5% improvements in the brake thermal efficiency (6–9% improvements in the fuel economy) compared to the baseline (9.3 CR without EGR). Among several effects contributing to the fuel economy improvement, the theoretical thermal efficiency improvement is primary which is caused by increased ratio of specific heats and increased geometric CR. The reduction in heat transfer loss due to lower combustion temperature with EGR is the secondary effect.

Preparation and properties of epoxy resin composites containing hexaphenoxycyclotriphosphazene

Hexaphenoxycyclotriphosphazene (HPCTP) was synthesized by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and phenol. The chemical structure of HPCTP was then characterized by Fourier transform infrared spectroscopy as well as 1H and 31P nuclear magnetic resonance spectroscopy. The synthesized HPCTP was incorporated into the diglycidyl ether of bisphenol A to prepare epoxy resin (EP) composites using 4,4′-diamino diphenylmethane as curing agent. The thermal and flame-retardant properties of cured samples were investigated by differential scanning calorimetry, thermogravimetric analysis, UL-94 vertical burning test, and cone calorimetry. Evaluation of thermal properties demonstrated that the resulting composites achieved high thermal stability with high char yields. The UL-94 V-0 rating was easily achieved with the addition of HPCTP, and the heat release intensity simultaneously decreased. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed that HPCTP can enhance the thermal stability and flame retardancy of epoxy resin.

Fuel flexible distributed combustion for efficient and clean gas turbine engines

The need for fuel flexible ultra-low emission gas turbine combustors is imminent to secure future power needs. Distributed combustion technology is demonstrated to provide significant performance improvement of gas turbine combustors including uniform thermal field in the entire combustion chamber (improved pattern factor) at very high combustion intensity, ultra-low emission of NOx and CO, low noise, enhanced stability, higher efficiency and alleviation of combustion instability. Distributed reaction conditions were achieved using swirl for desirable controlled mixing between the injected air, fuel and hot reactive gases from within the combustor prior to mixture ignition. In this paper, distributed combustion is further investigated using a variety of fuels. Gaseous (methane, diluted methane, hydrogen enriched methane and propane) and liquid fuels, including both traditional (kerosene) and alternate fuels (ethanol) that cover a wide range of calorific values are investigated with emphasis on pollutants emission and combustor performance with each fuel. For liquid fuels, no atomization or spray device was used. Performance evaluation with the different fuels was established to outline the flexibility of the combustor using a wide range of fuels of different composition, phase and calorific value with specific focus on ultra-low pollutants emission. Results obtained on pollutants emission and OH* chemiluminescence for the specific fuels at various equivalence ratios are presented. Near distributed combustion conditions with less than 8PPM of NO emission were demonstrated under novel premixed conditions for the various fuels tested at heat (energy) release intensity (HRI) of 27MW/m3-atm. and a rather high equivalence ratio of 0.6. Higher equivalence ratios lacked favorable distributed combustion conditions. For the same conditions, CO emission varied for each fuel; less than 10ppm were demonstrated for methane based fuels, while heavier liquid fuels provided less than 40ppm CO emissions. Lower emissions of NO (<4.5PPM) were also demonstrated at lower equivalence ratios. This demonstration outlines the combustor ability for fuel flexibility without any modifications to the combustor injectors, while maintaining high performance. Further reduction of NOx can be possible by establishing true distributed combustion condition, in particular at higher equivalence ratios.

Thermodynamic analysis of EGR effects on the first and second law efficiencies of a boosted spark-ignited direct-injection gasoline engine

Exhaust gas recirculation (EGR) is effective to improve fuel economy of spark-ignition gasoline engines, but the detailed mechanism needs to be further investigated. In this paper, an in-depth analysis of the effects of cooled EGR on the fuel conversion efficiency of a boosted, spark-ignited, direct-injection, gasoline engines operated at the full, medium and low loads is conducted with the engine experiment and 1-D cycle simulation based on the first and second laws of thermodynamics. For all the operating loads, EGR increases the ratio of specific heat of working gas, reduces the fraction of heat transfer through the combustion chamber walls, and improves the pumping work during the gas exchanging stroke. Besides, EGR may replace the fuel enrichment at high load, advance the combustion phasing and increase the degree of constant volume heat release at the medium and high loads. As a result, about 1.1–4.1% improvements in the brake thermal efficiency are obtained by the 12–17% EGR at different loads. Despite the increased fraction of combustion-generated irreversibility (destruction in availability or exergy), the fraction of indicated work in the total availability increases with EGR for all the operating loads. Among the influencing factors, the effect of reduction in the heat transfer loss owing to EGR is dominant in improvement of the fuel conversion efficiency at constant air–fuel ratio, while replacement of the fuel enrichment with EGR is most effective at full load.

Novel mixing for ultra-high thermal intensity distributed combustion

Ultra-high thermal intensity colorless distributed combustion has been examined for our quest to achieve near zero pollutants emission and enhanced performance. Reverse-cross flow configuration has been investigated at thermal intensities in the range of 270–420MW/m3-atm with specific focus on the exhaust emissions, distribution of intermediate radical species and flow field within the combustor. Novel simplified geometry is used for easy transition to practical ultra-high thermal intensity gas turbine engine applications. The combustion intensities demonstrated here are significantly higher than that used in current gas turbine engines. Numerical simulations under non-reacting conditions are used to understand the effects of fuel injection in reverse-cross flow configuration. Ultra-low NO emissions were achieved for both the premixed (2ppm) and non-premixed (5ppm) mode at thermal intensity of 317MW/m3-atm. The CO emission of about 100ppm and UHC emission of less than 10ppm, revealed very high combustion efficiency at high heat release intensities. Novel mixing technique is also investigated to further decrease the emissions and enhance reaction distribution. In this case the fuel jet is diluted with a portion of the required air while a portion of the fuel is introduced with the air jet. The equivalence ratio of each of the air jet and fuel jet were kept well outside of the methane air flammability limits, for mitigating the possibility of flame flashback. This approach has demonstrated near zero NO emission, equivalent to that encountered in premixed combustion mode. Numerical simulation and OH* chemiluminescence showed that the mixing and combustion behavior is dictated by the high momentum of the diluted fuel jet suggesting favorably mixed oxidizer prior to ignition that results in lower NO emissions. Results obtained with different air jet and fuel jet equivalence ratios on the emissions of NO and CO, and OH* chemiluminescence are presented with view to further develop ultra-high thermal intensity zero emission combustors.

A Numerical Study on Premixed Bluff Body Flame of Different Bluff Apex Angle

In order to investigate effects of apex angle (α) on chemically reacting turbulent flow and thermal fields in a channel with a bluff body V-gutter flame holder, a numerical study has been carried out in this paper. With a basic geometry used in a previous experimental study, the apex angle was varied from 45° to 150°. Eddy dissipation concept (EDC) combustion model was used for air and propane premixed flame. LES-Smagorinsky model was selected for turbulence. The gird-dependent learning and numerical model verification were done. Both nonreactive and reactive conditions were analyzed and compared. The results show that asαincreases, recirculation zone becomes bigger, and Strouhal number increases a little in nonreactive cases while decreases a little in reactive cases, and the increase ofαmakes the flame shape wider, which will increase the chamber volume heat release ratio and enhance the flame stability.

Convective instability of a water-vapor-saturated atmospheric layer. The formation of localized and periodic cloud structures

The classical Rayleigh problem of convective instability is generalized to the case of water vapor condensation in the atmosphere. We present an analytical solution demonstrating a fundamental difference between moist convection and Rayleigh convection: the curve of the critical Rayleigh number versus the number characterizing the intensity of condensation heat release consists of two parts, with spatially localized neutral solutions corresponding to one of them. Spatially periodic neutral solutions correspond to the second part of the curve; these are characterized by a significant localization of the regions of ascending motions. The theory describes the nucleation and development of individual convective clouds and ordered cloud structures.

Acoustic characteristics of a barrier-discharge XeCl excilamp

The generation of an acoustic signal by means of voltage pulses (f = 15 kHz) applied to the electrodes of a barrier-discharge excilamp based on a Xe/Cl2 = (50–500)/1 mixture kept at a pressure of 5–500 Torr is studied. It is shown that, from the time variation of the acoustic signal intensity, one can judge the time instant the excilamp starts operating in a steady mode. Optimal (in power and efficiency) operating conditions of the excilamp are found (Xe/Cl2 = 240/1, p = 98 Torr, η ≈ 9.5%). It is experimentally demonstrated that the discharge energy at a low pressure is spent largely on heating the gas. This is indicative of the volume heat release and volume glow discharge (as the pressure grows, the efficiency of this source of energy consumption drops and more and more energy is spent on acoustic vibration excitation). Under higher pressures, the Fourier spectrum of the acoustic signal becomes richer, the intensity of the spectrum rises, and the dispersion of the signal grows. At very high pressures, the intensity of the acoustic signal drops to a level corresponding to the natural vibrations of the excilamp envelope without the discharge (when the discharge is quenched, the Fourier spectrum of the signal becomes depleted and contains only harmonics corresponding to the carrier frequency of voltage pulses from the power source).

Mixture Preparation Effects on Distributed Combustion for Gas Turbine Applications

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (∼10 ppm) and CO (∼21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3-atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.

Partial crack closure in a perforated body with heat release

On the basis of the methods of the theory of thermoelasticity, we give a mathematical description of the effect of partial crack closure in an isotropic body with heat release weakened by a doubly periodic sys- tem of cooling cylindrical channels with circular cross sections. It is customary to believe that, as the in- tensity of heat release in the body increases, its elastic properties become temperature-dependent and the material is destroyed. It is assumed that the phenomenon of partial crack closure occurs under the action of thermal loading. At present, much attention is given to the investigation of doubly periodic problems of fracture mechanics, connected with the numerical analysis of fuel elements operating in nuclear reactors. These elements operate under extremely severe conditions caused by the presence of high temperatures and great powers of heat release. To guarantee the reliability of nuclear reactors, it is necessary to study the stress-strain state and fracture of fuel elements. The problems of strength of solid nuclear fuel remain urgent at present and, clearly, the interest to these problems will permanently grow in the future due to the existing trend of increase in the amount of energy released by this type of fuel. The problem of thermoelastic equilibrium of a plane weakened by a doubly periodic system of holes was studied in (1-3) under the assumption that the elastic characteristics of the body E (modulus of elasticity) and ν (Poisson's ratio) are independent of temperature. As the intensity of heat release q in the body increases, the zones of high stresses with doubly periodic location are formed around the holes. These stresses promote the formation and growth of cracks on the surfaces of the holes. The analysis of the stressed state of the body with hollows in the process of heat release shows (4) that the zones of compressive stresses are formed in the body in the course of its operation. We assume that the body with heat release contain zones in which the crack lips are in contact. We also assume that these zones adjoin the crack tips and their unknown sizes are comparable with the crack length. Further, it is assumed that the intensity of heat release is uniform over the entire volume of the body, that the heat is removed only through the surfaces of cylindrical channels, that the characteristics of the body E and ν depend on the drop of temperature, that the body is subjected to the action solely of internal thermal stresses but not to the action of external forces, that the stresses formed in the body do not go beyond the limits of elastic strains, that the properties of the material are isotropic in all directions, and that the body is in the stationary state.

Development and assessment of a new methodology for end of combustion detection and its application to cycle resolved heat release analysis in IC engines

The heat release analysis has proved to be a powerful diagnostic tool for the analysis of the combustion process in spark ignition engines. Still, a fine tuning of the heat transfer correlations embedded in the heat release models is necessary for a correct diagnostic analysis of the pressure signal. To that end, a new methodology has been developed and assessed to properly locate the end of combustion on the basis of the heat release intensity. The results produced by the proposed method have been compared to those obtained by applying different methodologies available in the literature. The newly developed method has proved to be accurate and consistent and has allowed a reliable estimation of the end of combustion on a cycle-by-cycle basis. An extensive burn rate analysis has also been accomplished by means of a heat release model previously developed and purposely modified to embed the new end of combustion detection procedure. The main combustion related quantities have been considered for the experimental investigation to appropriately quantify the engine cyclic variability as a function of the relative air-to-fuel ratio. The experimental tests have been performed on a naturally aspirated 2L engine featuring a fast-burn combustion chamber and running on gasoline and natural gas as well as on a 1.2L turbocharged natural gas engine displaying a disk shaped combustion chamber. The diagnostic tool has proved to properly match the nonlinear behavior of the quantities related to the combustion duration in the cycle-resolved analysis and a general good agreement with previous works has emerged as far as the coefficient of variations of the main combustion parameters are concerned. Moreover, thanks to the automatic facet the proposed methodology retains, it is strongly recommended when an extensive cycle-by-cycle and cylinder-to-cylinder analysis needs to be performed. Finally, regardless of the considered fuel, the heat release model embedding the EOC detection procedure proved to be capable of properly detecting the combustion features induced by a fast-burn combustion chamber with respect to a traditional one. As a matter of fact, smaller Δθ10–90% values and an overall reduced cyclic dispersion were highlighted for the 2L engine.

Low calorific value fuelled distributed combustion with swirl for gas turbine applications

Distributed combustion offers significant performance improvement with near zero emissions for industrial gas turbine applications. Our efforts to further develop zero emission distributed combustion are explored here by utilizing swirl to the flow. The beneficial aspects of distributed swirl combustion using a cylindrical geometry combustor has shown low emissions of NO and CO, and significantly improved pattern factor using methane as the fuel at high thermal intensity. Biofuels, syngas and landfill gases offer superior use in gas turbine combustion. However, they are characterized by their low calorific value. Results are presented here from the distributed swirl combustor with simulated low calorific value fuels with defined mixture of methane diluted with nitrogen. The calorific value of the fuel obtained provided comparable adiabatic flame temperature and flame speed to those characteristic of low to medium calorific value syngas fuels. The results are compared with the methane fueled combustor. Experimental results from the distributed swirl combustor using methane fuel at an equivalence ratio of 0.6 and a heat release intensity of 27MW/m3-atm showed low levels of NO (∼9PPM) and low CO (∼21PPM) under non-premixed conditions. Novel Premixed Combustion design demonstrated 4PPM of NO and 11PPM of CO. In contrast methane diluted with nitrogen resulted in a dramatic decrease of NO emissions (30–50%), to provide NO emission of 7PPM (for non-premixed case) and 2.8PPM (premixed case), at the same conditions, with minimal impact on CO for all the conditions examined here. The combustor provided no instability or flame flashback at higher fuel flow rates (to maintain the same thermal load as with methane fuel). Results obtained with different calorific value fuels on the emissions of NO and CO, lean stability limit and OH* chemiluminescence are presented. The results showed favorable operation of the distributed swirl combustor for applications with both high and low calorific value fuels, such as, methane, synfuel and landfill gases to power the gas turbines without any combustor modifications.

Improvement in Diesel Combustion with Emulsified Blends of Aqueous Ethanol and Diesel Fuel

This paper discusses the operational characteristics of two emulsified blends of aqueous ethanol and diesel fuel in a DI diesel engine with supercharging and cooled EGR. Two emulsified blends: one with 25 vol% aqueous ethanol (E20W5, Ethanol: 20 vol%, Water: 5 vol%) and the other with 50 vol% aqueous ethanol (E40W10, Ethanol: 40 vol%, Water: 10 vol%) were examined. Silent, low NOx, and smokeless combustion was realized over a wide load range with the emulsified fuel, E40W10 when the quantity of pilot injection and the intake oxygen content were optimized. The results show that smokeless operation can be established with low pressure injection and low intake oxygen content. The degree of constant volume heat release and the indicated thermal efficiency with the emulsified fuels improved over a wide load range as the pilot injection quantity was increased and the heat release with the pilot injection was retarded to near TDC. The degree of constant volume heat release with the emulsified fuel also improved, mainly due to the reduction in afterburning with smaller quantities of the main injection.