Etude du comportement d’échangeurs présentant en entrée un gaz chargé en humidité : Etude de la condensation dans un RAS air/eau glycolée

Report (2008)

Propulsion vehicle integration for reusable launcher using in-flight oxygen collection

in Aerospace Science and Technology (2008), 12(6), 429-435

The use of in-flight oxygen collection has shown to significantly improve space launcher performance. The conceptual approach followed by Belgian teams working on oxygen collection has been to try to ... [more ▼]

The use of in-flight oxygen collection has shown to significantly improve space launcher performance. The conceptual approach followed by Belgian teams working on oxygen collection has been to try to widening the available design margins in order to reduce the required technological leap and limit the economical risk associated with such a development. The aim of the ESA-funded theoretical and experimental study on an air separation device is to demonstrate the possibility of performing efficient air distillation in a compact rotating column. An integration of the vehicle, propulsion system and separation unit designs is presented. The objective is to optimise the overall vehicle performance while keeping technological difficulty and system complexity at a reasonable level. Reference vehicles are presented within their specific mission profiles with an emphasis on TSTO's. Different layouts of the internal energy and mass flowsheets have been studied and were compared in order to make best use of the refrigeration capacity of the hydrogen fuel running through the propulsion system during the first phase of the flight. In those flowsheets, the separator is considered as a classical distillation tray column. That analysis provides the requirements in terms of heat exchange capacity, compression ratios and number of so-called transfer units needed in the separator. The system is intentionally kept simple to limit complexity, but the analysis is thorough and accurate, including, for example, the effect of the presence of argon. Results for a supersonic carrier are presented. A compact separation unit has been designed in order to reach those requirements. That includes internals, practical building with estimates of pressure drops, separation performance and flow limitation. Main results are given, sizing of the separator bed is provided for a carrier plane showing that such on-board separator is indeed practical. (C) 2007 Elsevier Masson SAS. All rights reserved. [less ▲]

Etude du comportement d’échangeurs présentant en entrée un gaz chargé en humidité : Etude de la condensation dans le RAS air/air

Report (2008)

Adaptation des brûleurs SOCOMEF pour l'utilisation de biocombustibles : Cas des biodiesels

Report (2008)

Compact Air Separation Technology For In-Flight Oxygen Collection

in 15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference (2008, April)

In the context of an ESA-funded study on an air separation device intended to provide in-flight Oxygen Collection capability to future launchers, experimental and system level investigations are performed ... [more ▼]

In the context of an ESA-funded study on an air separation device intended to provide in-flight Oxygen Collection capability to future launchers, experimental and system level investigations are performed. The project consortium is run by the Université Libre de Bruxelles and includes the Belgian Defence, Techspace Aero (Safran Group) and Liège university among others. In-flight Oxygen Collection has already been described in previous publications, mainly as a conceptual approach. The improvement potentials have been studied and possible uses of the technology go beyond the concept presented here. That is in the aerospace field and also outside, in a much wider range of applications. Hardware work on compact separation are seldom described. As the setup was nearing completion, design know how improved. The last problems were solved and the setup was made fully operational and subject to testing. The following review summarizes the work with latest information on the technological and experimental aspects. In the vehicles using air separation and collection, the cooling capacity of the fuel, liquid hydrogen, is used during a first air breathing phase of the flight to enrich in oxygen and liquefy a fraction of the incoming air. Compact and light weight heat exchanger, coupled to the separator, perform that task. The main advantages of the concept, applied in our preferred concept to TSTO’s, are a much reduced take off mass, a reduced mass for the liquid rocket engines and a much increased operational flexibility in terms of reachable orbit and launch window. Moreover, unlike scramjet propulsion, separation does not rely on high technology material but on readily available material and hardware used with proper design know how and appropriate expertise. The experimental setup development follows a somewhat different route. Liquid and saturated gaseous air are prepared in special heat exchangers before the separator can be fed, the cold source used being liquid nitrogen. The experimental separator itself is, in reality, a 'section' of a real separator. Disposing of the fluids in this machine deserves special care, since pressure has to be controlled while a liquid seal has to be kept stable in most of the operating conditions. Some workarounds had to be developed for that last problem and different solutions were kept available during the testing. Separating is an aspect, interactively measuring -required to tune to proper performance- is another. The operating fluids, that are supposed to be liquid or gaseous in the simple modeling, are in practice often two phase, which is difficult to asses during test and which can strongly impact flow and concentration measurements. High temperature gradients, low temperatures had to be considered for mechanical, sealing and bearing design, nevertheless, strong uncertainty remained before separation results are presented and demonstrate the concept. Most result went above expectations and much further compactification potentials are present. The know how gathered from testing experience allows to foresee improvement directions, both in the global concept and the detail design of a real unit. Those results will allow to extrapolate the real potentials of the separator design developed by our laboratory to the bigger units required for a real concept. [less ▲]

Feasibility study of the diluted combustion in a semi-industrial boiler at low temperatures

in 8th European Conference on Industrial Furnaces and Boilers (2008, March)

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess ... [more ▼]

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess the technical feasibility and highlight the specific problems of application of diluted combustion in a medium scale boiler. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which could prevent from getting the minimum level of reactants dilution and temperature needed to reach diluted combustion regime. The idea is to perform direct injection of the air and the gas in the combustion chamber in order to get a high dilution of the reactants and a mixture temperature above the auto-ignition threshold. Our test bench consists in a Viessmann hot water boiler whose nominal output power is 370 kW. The combustion chamber of this boiler is cylindrical (length = 1.41 m, diameter = 0.56 m) and is watercooled. A preliminary CFD study (Fluent ®) has first been performed to select on the market a jet burner (to be used for the preheating of the combustion chamber) and to determine the position of the air and gas injectors able to generate the requirements of diluted combustion. The selected burner has been purchased and fitted on the boiler. Then, the boiler-burner set has been characterized experimentally in normal combustion regime in order to adapt the boundary conditions to the heat balance. The temperature and the CO concentration will be measured in several locations in the combustion chamber at different firing rate and air excess. In short, the selected burner provides as expected the required preheating and the generated flame doesn’t impact the bottom of the combustion chamber. The results obtained experimentally confirm the simulation results in normal combustion regime. The last part of this work will consist in the determination of the feasibility of the diluted combustion in this boiler. [less ▲]

Simulation model of an industrial boiler equipped with a natural gas burner – part I: Model presentation

Report (2007)

CO emissions of fuel oil boilers in transient and cyclic regimes: performance of burners without and with “antidrip” systems

Conference (2007, September)

CO emission peaks from fuel oil boilers in transient and cyclic regimes have been measured in previous studies. In order to evaluate these emissions, tests have been performed without and with an anti ... [more ▼]

CO emission peaks from fuel oil boilers in transient and cyclic regimes have been measured in previous studies. In order to evaluate these emissions, tests have been performed without and with an anti-drip system installed on the burner nozzle. Flue gas composition was measured using classical analysers (CO2, O2, CO and NOx) and CO emissions results were analysed and discussed. It was found that the anti-drip system reduced cold start CO emissions and did not affect steady-state CO emissions. At first, no reduction was noticed when the burner was cycling. Further investigation indicated that there was an experimental artefact caused by an air volume trapped in the pressure measurement system. When the air was purged and with the anti-drip system, CO peaks when the burner was cycling were strongly reduced and CO emissions remained under European standards limits. [less ▲]

Feasibility study of the diluted combustion in a semi-industrial boiler at low temperatures

Conference (2007, September)

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main ... [more ▼]

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which prevents from getting the minimum level of reactants dilution and temperature needed to reach mild combustion regime. Last year, a preliminary CFD study was performed to select a jet burner and secondary gas injector able to generate sufficient dilution and temperature of the air and gas jets before they meet in the combustion chamber of the boiler. In this work, the optimization of the position and the diameter of the gas injector has been performed. Finally, the boundary conditions and the parameters of the combustion model have been investigated. [less ▲]

Simulation model of an industrial fuel oil boiler

Report (2007)