Practical uses of liquid methane in rocket engine applications

<div class="section abstract"><div class="htmlview paragraph">The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap.</div><div class="htmlview paragraph">This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR. The main objectives are to identify the complex mechanisms involved in the combustion process and to define the optimal hydrogen ratio for each combustion mode.</div><div class="htmlview paragraph">The study combines engine tests and 0D modeling. Tests were carried out on a spark-ignited single-cylinder engine adapted to CNG operation with 2 different compression ratios 9,5:1 and 11,5:1. Computations allow studying separately the different phenomena linked to the progressive addition of hydrogen in the fuel. Hence, using 0D modeling, the effects due only to the combustion speed evolution, as a function of hydrogen ratio in the fuel, were then quantified using experimental results as comparison basis.</div><div class="htmlview paragraph">The engine test results reveal that the impact of hydrogen is limited in stoichiometric conditions except for CO₂ savings. A ratio of 10 to 20 vol. % of hydrogen seems to be optimal to reach interesting HC emissions reduction without an excessive lowering of the operation range. The results are more encouraging for lean-burn operation as the lean limit of equivalence ratio is extended for more than 0,125 with 40 vol. % of hydrogen. NOx emissions and consumption were significantly reduced (-92% for NOx) while maintaining constant HC and CO emissions compared to methane operation. Hydrogen stabilizes and speeds up combustion especially in very diluted mixtures. Furthermore, hydrogen increases EGR tolerance for the same reasons as in lean-burn mode: in comparison, identical very-low NOx levels were reached with smaller consumption gains. Finally, the engine test results show that the highest tested ratio of hydrogen (up to 40%) in methane for very diluted mixtures with air or EGR drastically reduce NOx emissions without penalty on engine performances.</div><div class="htmlview paragraph">Computations prove that the evolution in terms of thermodynamic properties of the fuel is not the most important contribution to the evolution of combustion. The effect of hydrogen addition contributes mainly to increase the combustion speed. Moreover, lean burn operation results demonstrate that the increase of combustion speed due to hydrogen addition is enhanced. This can only be explained by the increase of thermo-diffusivity which has an opposite and larger effect than the slowdown of laminar flame velocity conventionally described in the literature.</div></div>

Significant differences exist between the behaviour of cooled turbine blades under engine conditions and their behaviour as predicted in design calculations. This paper presents a comparison between engine test data, static cascade rig data, and design predictions. Wherever possible, the reasons for the differences are identified and cross referenced to recently reported research work. In some cases hard supportive evidence for phenomena observed on research rigs has been obtained from engine tests. The data is presented for two subsonic aerofoil designs with several different cooling configurations.

disparity in time and length scales exist in close proximity to one another. Although advances in the field have been made, the largest and most reliable source of information to date applicable to the design of improved combustion devices is the store of experimental data from full-scale engine tests. Consequently, the motivation behind the present work was to gain further insight into the mechanisms associated with combustion instability by providing a detailed, concise account and analyses of the design attributes which led to dynamic stability in F-l developmental injectors. Objectives were 1) to preserve the experience gained through development of the F-l engine; 2) to merge full-scale test results with corresponding theories and experiments; and 3) to analyze the effect of proposed solutions. To facilitate analysis, all available full-scale component and engine test data have been combined into a single data base. This compilation provides a complete genealogy of F-l developmental injector design configurations, and contains all available measured and observed test results. Table 1 lists the injector design parameters and test results acquired. The complete data base is available as an appendix to a separate technical report prepared by the authors.1 These data have been assembled from a variety of sources.2^ Reference 2 is a chronological tabulation of full-scale injector component test results recorded at the test site. This document lists the injectors tested along with the date, chamber pressure, thrust, run time, mixture ratio, bomb size, and damp times, as well as observations made during various tests. Reference 3 contains a set of 16 reports (four volumes of four reports each) which present a somewhat chronological account of the methodology leading to a dynamically stable injector design. Full-scale engine and component test results are discussed throughout this set of reports. Reference 4 provides a broad overview of the problems and solutions encountered with combustion instability in the F-l engine. Finally, Refs. 5 and 6 are weekly

Further development of rocket-and-space, aviation and other special equipment can be based on the use of liquefied natural gas (LNG), including pure liquefied methane (LM). This cryogenic fuel is characterized by relative safety; on its basis it is possible to provide such technical and tactical indicators of aircraft that are unattainable when using traditional fuels. Cryogenic systems for liquefying natural gas developed by PJSC Cryogenmash with extraction of liquid methane by condensation and stage separation methods, as well as rectification, are considered in the paper. The calculations show that the choice of the technology for extracting liquid methane from LNG is implemented depending on the requirements for LM as a fuel component of liquid rocket engines. The method of low-temperature condensation with stage separation provides a reduction in the concentration of low-boiling impurities (nitrogen, oxygen, hydrogen, helium). The method based on rectification allows reducing the content in LM not only of low-boiling impurities, but also of high-boiling impurities.

Organomolybdenum compounds are versatile lubricant additives of interest in the design of engine oils to meet the new ILSAC (International Lubricant Standardization and Approval Committee) GF‐3 performance standard, especially for fuel efficiency. In this work, organomolybdenum and 13 other components were studied by experimental design and statistical analysis to determine their effects on friction, wear, and oxidation properties. The resulting linear model was used to construct a trial engine oil formulation. Engine test results, including some new tests required for ILSAC GF‐3, confirmed some of the strengths of organomolybdenum compounds, as well as their sensitivity to other additives in the formulation.

The first airplane working on cryogenic fuel was developed in the USSR in early 1980s on the basis of the passenger aircraft Tu-154. It was then modified using a hydrogen engine installed instead of one of the three kerosene engines. That bypass turbo-jet engine was developed in Russia (Samara) under the guidance of General Designer academician N.D. Kuznetsov. The engine working on liquid hydrogen was designated NK-88 and the one working on liquid methane NK-89. A unique hydrogen turbopump unit was created for the supply of cryogenic fuel. The unit can also be used for liquid methane due to the possibility of readjusting the rotor frequency. To minimize the financial expenditures it is proposed to use the turbo-pump in low-thrust rocket engines that use liquid methane as fuel.

Hydrogen and Methane are two fluids that are either used or in discussion as propellants for upper and lower stage rocket engines. The conception of a regenerative cooling system is a crucial part in the design of a rocket engine and so is the detailed knowledge of the coolants behavior and the heat transfer capabilities. Hydrogen is a very efficient and well known cooling fluid whereas the properties of methane as a cooling fluid are intensively investigated nowadays. Experiments were performed with a subscale combustion chamber that is divided into four sectors around the circumference each containing rectangular cooling channels with different aspect ratios. Cryogenic hydrogen and liquid methane were used as cooling fluids. These experiments provide a broad data basis that is used for the validation of CFD simulations. The simulations are capable of predicting wall temperatures for high pressure conditions. Thermal stratification effects that are known to limit cooling properties in high aspect ratio cooling channels arise for both fluids, but the effects are much stronger for hydrogen compared to methane. However in the vicinity to the critical point, when it comes to heat transfer deterioration, the simulations show large deviations to the experimental values.

The world energy reserves are depleting day-by-day and the demand is increasing. This leads to search for suitable renewable alternative fuels. Among the available alternative fuels, biodiesel can be used as an immediate substitute for the diesel engine. However, the biodiesel fuelled diesel engine gives lower brake thermal efficiency due to higher viscosity and lower volatility of the biodiesel. Hence, in this work, an attempt was made to increase the performance of the biodiesel fuelled engine using ceramic coating on the engine combustion chamber components. In this experimental study, engine components such as cylinder head, piston, exhaust and inlet valves were coated with Nickel Chromium (NiCr) alloy and Yttria Stabilized zirconia (Y 2 O 3 –ZrO 2 ) of thickness 250 μm using plasma spray coating. Since mahua oil has significant potential for the biodiesel production, it was used for the biodiesel production. In this work, the engine tests were conducted on a single cylinder four stroke direct injection diesel engineand different blends were used as the fuels. The engine performance and emission characteristics were analysed by varying the load under both coated and uncoated conditions of the engine and results were compared with neat diesel. From the engine test results, it was observed that the engine performance with biodiesel blends such as B10 and B20, was increased from 3 to 7% depends upon the load on the engine with thermal barrier coating as compared to the normal engine without coating.

Development of Transient Pulse Detonation Engine Cycle Analysis and Performance Prediction (PDE-CAPP) Code

<div class="htmlview paragraph">Design studies supported by laboratory test data have shown that graphite fiber composite fan blades in subsonic turbofan engines offer significant potential reductions in weight for both the fan rotor and containment structure as well as reduced sensitivity to fatigue failure from foreign object damage. However, substantial progress in the application of composite material technology including mechanical properties, design, development, processing and inspection methods must be accomplished in order to realize these potential improvements over conventional titanium fan blade materials. Turbofan aircraft engines are subjected to foreign object impact by birds, ice balls, ice slabs, rocks, sand, rain, and miscellaneous objects like blown tire treads in addition to operation with inlet distortion. Graphite composite blades must be designed to tolerate these types of damage and still produce power comparable to current engines before they can seriously be considered for flight applications.</div> <div class="htmlview paragraph">In 1969, the General Electric Company selected a high bypass engine as the test vehicle for initial application of graphite fiber composite fan blades. A two phase design, manufacturing and development program was initiated to produce a graphite composite first stage fan rotor suitable for flight application. The first phase of this program, completed in 1970, was directed toward identifying the problems and producing graphite composite fan blades for engine test evaluation with unshrouded titanium blades in the same rotor.</div> <div class="htmlview paragraph">This report presents a status summary of the composite fan blade design, manufacturing and development effort including the results of the crosswind engine testing of these blades at General Electric's engine test facility at Peebles, Ohio.</div>

Analytical formulations for nitrogen oxides emissions estimation of a hydrogen fueled Synergetic Air-Breathing Rocket Engine (SABRE) in air-breathing mode

Comparison of unshrouded impeller analysis and experiment

The paper describes an analysis of the condensation of moist air in very long intake ducts of jet engines during stationary operation. Problems arising from such condensation include fan overspeed and increased stagnation pressure loss in the intake duct. The analysis demonstrates that, for moderate values of relative humidity, homogeneous condensation will occur in an outer annulus adjacent to the intake cowling if the local flow Mach number attains values of about 1.0. In the central region of the intake duct, where design Mach numbers of 0.8 may be attained, homogeneous condensation is unlikely to occur except, possibly, when the relative humidity is close to 100% and the ambient temperature very high. However, if the intake duct is very long, significant heterogeneous condensation on foreign particles present in the atmosphere is possible. The concentration of foreign nuclei required for this type of condensation is comparable to the likely levels of contamination at many industrial test sites. The effects of condensation on engine test results are twofold. Firstly, condensation is a thermodynamically irreversible process and results in an increase of entropy and hence loss of total pressure in the intake duct. Uncorrected measurements using Pitot probes may not record this loss correctly. Secondly, the mass and energy transfer between the phases during the condensation process has a tendency to accelerate the flow approaching the engine, an effect which may be counteracted by a reduction in mass flowrate in order to maintain the static pressure constant. These conclusions are in agreement with experimental results obtained on-site during the testing of a jet engine fitted with a very long intake duct.

A rising demand for efficient and reusable rocket engines leads to the development of a new generation of methane fueled rocket engines. The most crucial part is the optimal design of the cooling system, with minimal hydrodynamic losses. Therefore a precise knowledge of the heat transfer processes in the combustion chamber and primarily in the cooling channels is necessary. Cooling channels with a high aspect ratio (height-to-width-ratio) in a wall material with high thermal conductivity are known to improve cooling efficiency with only moderate increase in hydrodynamic losses. In this paper tests will be presented, that were performed with a cylindrical combustion chamber. This chamber is divided into 4 sections around the circumference, each containing cooling channels with different aspect ratios (1.7, 3.5, 9.2 and 30). Cryogenic hydrogen and liquid methane at temperatures as low as 60 K for hydrogen and 130 K for methane respectively were used as cooling fluids. Results show a distinct thermal stratification for both coolants and a very high influence of changing fluid properties close to the critical point for methane.

This paper deals with the development and the applications of a computational transient model of the VINCI cryogenic expander cycle upper stage rocket engine, tested in the frame of the FLPP Expander Demonstration Program managed by the European Space Agency (ESA). Snecma has been developing a transient system model of the VINCI engine since the beginning of the engine development, and the constant use of transient simulation was one of the major factors contributing to the success of the first two VINCI engines test campaigns. Simulation results have been found to be in good agreement with the measurements from the very first tests. The model accurately predicts the engine global behavior during start-up and shutdown, as well as the engine steady-state performance, and it also describes correctly the transient behavior of complex subsystems such as the combustion chamber or the turbopumps. This paper provides an overview of the physical content of the VINCI engine transient model. Simulation results from the model are compared with engine test data, and the model representativeness is discussed in detail. A focus is made on highly unsteady phenomena, such as valve maneuverings, and their effects on the whole engine behavior. I. Introduction HIS paper deals with the development and the applications of a computational transient model of the VINCI rocket engine. The VINCI is a cryogenic expander cycle engine, basis of a demonstration program preparing an application on the European launchers, in the frame of the European Space Agency (ESA) Future Launcher Preparatory Program (FLPP). The VINCI development in 200 5 and 2006 was conducted in the frame of the predevelopment of a cryogenic upper stage, under contract from the Centre National d’Etudes Spatiales (CNES), the French Space Agency, on behalf of ESA. The Space Engines Division of Snec ma in Vernon, France, acting as a prime contractor, is in charge in particular of the engine overall system design and integration. Snecma has been developing a transient system model of the VINCI engine since the beginning of the engine development, in order to predict its behavior during start-up and shutdown transients, as well as during potential failure scenarios. This model can also be used to identify possible undesirable unsteady effects that may occur during the engine transient operation phases, and to assess the consequences of any design changes. The constant use of tran sient system simulation has been one of the major success factors of the first two VINCI engines test campaigns that took place from May to July 2005 (M1 engine) and from November 2005 to February 2006 (M2 engine). During a test campaign, the model was used on a systematic basis in order to perform risk analysis for the subsequent tests, and to gain a physical knowledge of the engine behavior complementary to the one coming from raw measurements. Thanks to the intensive modeling work done at Snec ma, and to the experience gained from subsystem and component tests, simulation results were found to be in good agreement with measurements. A fairly good agreement was obtained from the very first tests, despite the fact that the VINCI engine is the first cryogenic expander cycle engine ever built and tested in Western Europe. The model accurately predicts the engine global behavior during start-up and shutdown, as well as the engine steady-state performance, and it also describes correctly the transient behavior of complex subsystems such as the combustion chamber or the turbopumps. This publication provides an overview of the physical content of the VINCI engine transient model, including the modeling process of the different subsystems. Simulation results from the model are compared with engine test data, and the model representativeness is discussed in detail. A focus is made on highly unsteady phenomena, such as valve maneuverings, and their effects on the whole engine behavior.