Reduction of nitric oxide emissions from a combustor

A turbojet combustor and method for controlling nitric oxide emissions by employing successive combustion zones is described. After combustion of an initial portion of the fuel in a primary combustion zone, the combustion products of the primary zone are combined with the remaining portion of fuel and additional plenum air and burned in a secondary combustion zone under conditions that result in low nitric oxide emissions. Low nitric oxide emissions are achieved by a novel turbojet combustor arrangement which provides flame stability by allowing stable combustion to be accompanied by low nitric oxide emissions resulting from controlled fuel-lean combustion (ignited by the emission products from the primary zone) in a secondary combustion zone at a lower combustion temperature resulting in low emission of nitric oxide

CAI combustion with methanol and ethanol in an air-assisted direct injection SI engine

Copyright © 2009 SAE International. This paper is posted on this site with permission from SAE International. Further use of this paper is not permitted without permission from SAECAI combustion has the potential to be the most clean combustion technology in internal combustion engines and is being intensively researched. Following the previous research on CAI combustion of gasoline fuel, systematic investigation is being carried out on the application of bio-fuels in CAI combustion. As part of an on-going research project, CAI combustion of methanol and ethanol was studied on a single-cylinder direct gasoline engine with an air-assisted injector. The CAI combustion was achieved by trapping part of burnt gas within the cylinder through using short-duration camshafts and early closure of the exhaust valves. During the experiment the engine speed was varied from 1200rpm to 2100rpm and the air/fuel ratio was altered from the stoichiometry to the misfire limit. Their combustion characteristics were obtained by analysing cylinder pressure trace. The experimental results show that both oxygenate fuels, methanol and ethanol, can lead to CAI combustion as well as gasoline fuel. The load of CAI combustion was increased and emissions were lower with the two oxygenate fuels. Methanol was found to have highest output and lowest energy consumption among the three fuels tested. CAI combustion characteristics of the oxygenate fuels were more affected by the amount of burnt residuals trapped than that of gasoline fuel

Numerical Analysis of Solid Rocket Motor Instabilities With AP Composite Propellants

A non-steady model for the combustion of ammonium perchlorate composite propellants has been developed in order to be incorporated into a comprehensive gasdynamics model of solid rocket motor flow fields. The model including the heterogeneous combustion and turbulence mechanisms is applied to nonlinear combustion instability analyses. This paper describes the essential mechanisms and features of the model and discusses the methodology of non-steady calculations of the combustion instabilities of solid rocket motors

Combustion

Match, wood, flame. Pyrocultures, settler colonial pyrophobia. Internal combustion. Wildfire. Petrocapitalist immolation. This short photo essay reflects on fire as simultaneously a sensuous phenomenon of everyday life and an entity that, because of both its presence and its absence in particular formations, makes worlds. To be aware, both corporeally and politically, of our involvement in pyric practices and regimes allows us to begin to imagine what it might mean to understand and change our relations to fire as part of a larger project of energetic transformation: bodily, socially, politically

Effect of tangential swirl air inlet angle on the combustion efficiency of a hybrid powder-solid ramjet

A new ramjet configuration using powder and solid fuel as propellant is investigated, namely, hybrid powder-solid ramjet (HPSR). Boron particles were used as the powder in this study. In order to improve combustion efficiency of boron and simplify the engine structure, a tangential swirl air inlet is adopted on the HPSR. Ignition model based on the multi-layer oxide structure and Global reaction combustion model of boron particles, the Lagrangian particle trajectory model and the realizable k-ε turbulence model were implemented to calculate three-dimensional two-phase flow and combustion in the HPSR with the different tangential air inlet angles (0°,5°, 10°, 15°, 20°, 25°). The effects of tangential air inlet angles on the ignition and combustion of boron were analyzed. The results show that when the tangential swirl air inlet angle is 10°, the combustion efficiency of boron particles and the total combustion efficiency of engine are the highest; the temperature distribution in the second combustion chamber is uniform, and the ignition distance of particles is small, for the HPSR configuration tested

Investigation of transition between spark ignition and controlled auto-ignition combustion in a V6 direct-injection engine with cam profile switching

Controlled auto-ignition (CAI) combustion, also known as Homogeneous Charge Compression Ignition (HCCI) can be achieved by trapping residuals with early exhaust valve closure in a direct fuel injection in-cylinder four-stroke gasoline engines (through the employment of low-lift cam profiles). Due to the operating region being limited to low and mid-load operation for CAI combustion with a low-lift cam profile, it is important to be able to operate SI combustion at high-load with a normal cam profile. A 3.0L prototype engine was modified to achieve CAI combustion, using a Cam Profile Switching mechanism which has the capability to switch between high and low-lift cam-profiles. A strategy was used where a high-profile could be used for SI combustion and a low-lift profile was used for CAI combustion. Initial analysis showed that for transitioning from SI to CAI combustion, misfire occurred on the first CAI transitional cycle. Subsequent experiments showed that the throttle opening position and switching time could be controlled avoiding misfire. Further work investigated transitioning at different loads and from CAI to SI combustion

Numerical Modelling for Process Investigation of a Single Coal Particle Combustion and Gasification

Combustion and Gasification are commercial processes of coal utilization, and therefore continuous improvement is needed for these applications. The difference between these processes is the reaction mechanism, in the case of combustion the reaction products are CO2 and H2O, whereas in the case of gasification the products are CO, H2 and CH4. In order to investigate these processes further, a single coal particle model has been developed. The definition of the chemical reactions for each process is key for model development. The developed numerical model simulation uses CFD (Computational Fluid Dynamic) techniques with an Eddy Break Up (EBU) model and a kinetics parameter for controlling the process reaction. The combustion model has been validated and extended to model the gasification process by inclusion of an additional chemical reaction. Finally, it is shown that the single coal particle model could describe single coal particle combustion and gasification. From the result, the difference between single coal particle combustion and gasification can clearly be seen. This simulation model can be considered for further investigation of coal combustion and gasification application processes

Optical study of flow and combustion in an HCCI engine with negative valve overlap

One of the most widely used methods to enable Homogeneous Charge Compression Ignition (HCCI) combustion is using negative valve overlapping to trap a sufficient quantity of hot residual gas. The characteristics of air motion with specially designed valve events having reduced valve lift and durations associated with HCCI engines and their effect on subsequent combustion are not yet fully understood. In addition, the ignition process and combustion development in such engines are very different from those in conventional spark-ignition or diesel compression ignition engines. Very little data has been reported concerning optical diagnostics of the flow and combustion in the engine using negative valve overlapping. This paper presents an experimental investigation into the in-cylinder flow characteristics and combustion development in an optical engine operating in HCCI combustion mode. PIV measurements have been taken under motored engine conditions to provide a quantitative flow characterisation of negative valve overlap in-cylinder flows. The ignition and combustion process was imaged using a high resolution charge coupled device (CCD) camera and the combustion imaging data was supplemented by simultaneously recorded in-cylinder pressure data which assisted the analysis of the images. It is found that the flow characteristics with negative valve overlapping are less stable and more valve event driven than typical spark ignition in-cylinder flows, while the combustion initiation locations are not uniformly distributed. © 2006 IOP Publishing Ltd

Autothermal Reforming of Methane with Integrated CO2 Capture in a Novel Fluidized Bed Membrane Reactor. Part 2 Comparison of Reactor Configurations

The reactor performance of two novel fluidized bed membrane reactor configurations for hydrogen production with integrated CO2 capture by autothermal reforming of methane (experimentally investigated in Part 1) have been compared using a phenomenological reactor model over a wide range of operating conditions (temperature, pressure, H2O/CH4 ratio and membrane area). It was found that the methane combustion configuration (where part of the CH4 is combusted in situ with pure O2) largely outperforms the hydrogen combustion concept (oxidative sweeping combusting part of the permeated H2) at low H2O/CH4 ratios (<2) due to in situ steam production, but gives a slightly lower hydrogen production rate at higher H2O/CH4 ratios due to dilution with combustion products. The CO selectivity was always much lower with the methane combustion configuration. Whether the methane combustion or hydrogen combustion configuration is preferred depends strongly on the economics associated with the H2O/CH4 ratio

The study of air fuel ratio for open furnace MILD combustion of biogas on bluff-body burner

Economical fuel cost is very critical in the heating industry. Lean combustion with high air fuel ratio (AFR) is normally practiced by the industry. Low air fuel ratio or rich combustion will result in unburned hydrocarbons (UHC). UHC is a waste and pollution to the environment. This paper discussed on the modelling of air fuel ratio for the moderate and intense low oxygen dilution (MILD) combustion of biogas on bluff-body burner. Biogas is a low calorific value (LCV) gas which was formulated by using 50% methane, 20% hydrogen and 30% carbon dioxide. AFR is the ratio of air and fuel injected to the combustion chamber. Nozzle outlet size for air and fuel plays important role to determine AFR. In this study, the air and fuel nozzle size ratio used is 23:1. The AFR will be evaluated based on the UHC produced by the combustion. Stoichiometric AFR occurred when zero UHC and zero excess oxygen flow through the EGR pipe. The result shows that when AFR is 4.0, zero UHC was detected in the EGR. UHC in EGR will be waste and create unwanted combustion at the wrong location