Engine Cycle Analysis Research Articles

3D fluid–structure interaction analysis of a typical liquid rocket engine cycle based on a novel viscoplastic damage model

SUMMARYIn many space missions, expandable or reusable launch systems are used. In this context, the reliable design of liquid rocket engines (LREs) is a key issue. In the present paper, we present a novel combination of numerical schemes. It is applied to model the extreme physical phenomena a typical LRE undergoes during its loading cycles. The numerical scheme includes a partitioned fluid–structure interaction (FSI) algorithm in combination with a unified viscoplastic damage model. This allows the complex description of the material response under cyclic thermomechanical loading taking place in LREs. In this regard, we focus on the response of the cooling channel wall that is made from copper alloys. For the coupled FSI analysis, the individual domains of the rocket thrust chamber are modeled by a 3D parametrized approach. The well‐established single field solver codes, DLR TAU for the hot gas and ABAQUS FE software for the structural domain, are coupled via the inhouse developed simulation environment ifls. Ifls provides the necessary algorithms for a partitioned coupling approach such as individual code steering, data interpolation, time integration and iteration control. Finally, the results of an FSI analysis of a complete engine cycle are presented. They show the potential of the new numerical scheme for the lifetime prediction of LREs.Copyright © 2013 John Wiley & Sons, Ltd.

Airbreathing rotating detonation wave engine cycle analysis

A cycle analysis model for an airbreathing, rotating detonation wave engine (RDE) is presented. The engine consists of a steady inlet system with an isolator which delivers air into an annular combustor. A detonation wave continuously rotates around the combustor with side relief as the flow expands towards the nozzle. A model for the side relief is used to find the pressure distribution around the combustor. Air and fuel enter the combustor when the rarefaction wave pressure behind the detonation front drops to the inlet supply pressure. To create a stable RDE, the inlet pressure is matched in a convergence process with the average combustor pressure by increasing the annulus channel radial width with respect to the isolator channel. Performance of this engine is considered using several parametric studies and compared with rocket-mode computational results. A hydrogen–air RDE reaches a specific impulse of 3800 s and can reach a flight speed of Mach 5.

Exergy Analysis of Porous Medium Combustion Engine Cycle

The need of the fossil fuels is ever increasing in the areas of manufacturing, transportation, heating, and electricity. Nearly 90% of the energy requirement in transport sector is met by combustion of fossil fuels only. Porous media (PM) combustion is an effective method, which can increase the combustion efficiency as well as minimize environmental pollution. The present paper is aimed at thermodynamic analysis of ideal IC engine cycles with porous media combustion. Two practically possible cycles, namely, periodic and permanent contact of gas with porous medium are considered, and the ideal cycle analyses are made. It is found that PM engine with periodic contact is more efficient than permanent contact type. The exergy analysis also reveals that the energy loss due to irreversibilities in the periodic contact type is less than that of the permanent contact type. With the help of model calculations and graphs, the performance of these two cycles is compared and optimal operating conditions are also evaluated and presented along with the suggestions for enhancing the performance of homogeneous PM combustion in IC engines.

CFD Analyses on 2-Stroke High Speed Diesel Engines

In recent years, interest has been growing in the 2-Stroke Diesel cycle, coupled to high speed engines. One of the most promising applications is on light aircraft piston engines, typically designed to provide a top brake power of 100-200 HP with a relatively low weight. The main advantage yielded by the 2-Stroke cycle is the possibility to achieve high power density at low crankshaft speed, allowing the propeller to be directly coupled to the engine, without a reduction drive. Furthermore, Diesel combustion is a good match for supercharging and it is expected to provide a superior fuel efficiency, in comparison to S.I. engines. However, the coupling of 2-Stroke cycle and Diesel combustion on small bore, high speed engines is quite complex, requiring a suitable support from CFD simulation. In this paper, a customized version of the KIVA-3v code (a CFD program for multidimensional analyses) has been used to address ports and combustion chamber design of a new project (a 3-cylinder 1.8L engine, with a power rating up to 150 HP). Multidimensional calculations have been supported by 1D engine cycle analyses, using GT-Power. Two types of combustion-scavenging system have been considered, both of them featuring direct injection: a configuration with exhaust poppet valves and another one with piston controlled ports. A development of both projects has been performed through a coupled 1d-3d computational approach. A first set of KIVA calculations has been performed, in order to characterize the scavenging and the port flow patterns of both configurations, considering three different operating conditions, representative an aircraft engine. Then, several combustion simulations have been run, for defining two chambers able to match the project goals (high fuel efficiency, limited in-cylinder peak-pressure). For the two best configurations, the most interesting calculation results are presented in the paper.

Towards a full two dimensional gas turbine performance simulator

AbstractIn commercially available gas turbine performance simulation tools, individual engine components are typically represented with non-dimensional maps of experimental or default data. In those cases where actual component characteristics are not available and default characteristics are used instead, conventional tools can deviate substantially at off-design and transient conditions. Similarly, when real component characteristics are available, conventional engine cycle simulation tools can not predict the performance of the engine at other than nominal conditions satisfactorily, or account for the impact of changes in component geometry.This study looked into the full integration of two-dimensional streamline curvature component models with a low fidelity cycle program. Firstly, the obtained engine performance was compared against the one calculated based on default component characteristics. As a second case study, a range of flight Mach numbers and angles of attack were examined together with the effect of three different intake lip geometries on the performance of a notional, two-spool, low-bypass ratio, military engine. Two-dimensional models were used in the engine cycle analysis to provide a more accurate, physics- and geometry-based estimate of intake and fan performances.The analysis carried out by this study demonstrated relative changes in the predicted engine performance larger than 1%. For briefness, representative results are presented and discussed in this paper for one flight Mach number and angle of attack setting. More importantly, this research effort established the necessary methodology and technology required towards a full, two-dimensional engine cycle analysis at an affordable computational resource in the very short term.

Performance analysis of a spin quantum heat engine cycle with internal friction

An irreversible cycle model of a quantum heat engine with internal friction is established, which is composed of two adiabatic and two isomagnetic field processes. The working substance of the cycle consists of an ensemble of many non-interacting spin-1/2 systems. Based on a quantum master equation and semi-group approach, the general performance characteristics of the heat engine are investigated. The general expressions for several important parameters, such as the efficiency, power output, and rate of the entropy production, are derived. The performance of the cycle is optimized with respect to the temperatures of the working substance. By numerical solutions, the maximum power output and the corresponding parameters are calculated. The optimal regions of efficiency, temperatures of the working substance, and cycle period are determined. Moreover, the performance of the heat engine in the frictionless case is obtained, which is different from that in the friction case. Finally, the results obtained are generalized to the performance optimization of the heat engine working with spin-J systems.

A comparison of component zooming simulation strategies using streamline curvature

Typically gas turbine engine component characteristics are represented via non-dimensional maps of experimental or default data. In those cases where actual component characteristics are not available and default characteristics are used instead, conventional engine cycle simulation tools can deviate substantially at off-design and transient conditions. Similarly, when real component characteristics are available, conventional tools cannot predict the performance of the engine at other than nominal conditions satisfactorily, or account for the impact of changes in component geometry. Component zooming simulation strategies allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This study looked into the direct comparison of three, well-established zooming strategies utilizing a two-dimensional streamline curvature component model and a low fidelity cycle program. The validated performance of a two-dimensional, low-pressure, compressor model was integrated with a notional, two-spool, low-bypass ratio, military engine model, according to the ‘de-coupled’, ‘iterative’, and ‘fully integrated’ approaches to high-fidelity analysis. The two-dimensional model was used in the engine cycle analysis to provide a more accurate, physics- and geometry-based estimate of fan performance. Although large differences in the simulated engine performance were not observed as expected, this analysis provided a very valuable insight as to the actual speed of execution, practicality, applicability, and potential of the zooming strategies mentioned above. More importantly, this research effort established the necessary methodology and technology required towards a full, two-dimensional engine cycle analysis at an affordable computational resource in the very short term.

Design and Test of a Modular Waverider Hypersonic Intake

*† A study of some modular stream-traced hypersonic intakes is presented. These intakes capture a part of a known flowfield by replacing the streamlines that pass through the perimeter of a sector capture shape with solid boundary layer-corrected surfaces. Modules are combined to form an engine with circular external profile and with each intake module feeding a separate combustor. The intakes studied are derived from internally compressive, axisymmetric flowfields with either constant slope or constant pressure boundary conditions. The number of modules varies between three and six. Stream thrust averaging is used to determine equivalent one-dimensional flow for input to a scramjet engine cycle analysis. For a given contraction ratio, the full mass capture engine performance of the modular waverider intakes is comparable with the performance of isentropic spike intake designs when combustor skin friction is neglected. However the low wetted area of the modular combustor design has a significant advantage when combustor skin friction is considered. A four-module waverider intake model was built using stereo lithography and tested at Mach 7 in the University of Oxford gun tunnel, and was shown to be self-starting in QinetiQ’s High Density Tunnel at Mach 7. The stream thrust averaged properties were determined experimentally by measurement of axial force and mass capture. Schlieren photographs and surface pressure measurements are presented. Skin friction in the model isolator section was found to affect intake performance by increasing the amount of compression and reducing efficiency.

Design and Test of a Hypersonic Isentropic-Spike Intake with Aligned Cowl

A study of reexpansion scramjet intakes is presented. Reexpansion intakes employ mixed external-internal compression with the internal contraction fixed by starting requirements and a cowl aligned with the external flow to minimize intake contribution to vehicle drag. As a result of the starting limitation, the captured flow is partially reexpanded, resulting in nonuniform flow at the intake exit. Stream thrust averaging was used to determine equivalent one-dimensional flow for input to a scramjet engine cycle analysis. Engine performance increases with compression, and thus optimum turning-angle appears to be at the limit for detachment of the internal cowl shock. An axisymmetric reexpansion intake was built using stereo lithography and tested at Mach 7.1 in the University of Oxford gun tunnel. The stream-thrust-averaged properties were determined experimentally from measurements of axial force and mass capture. Schlieren and surface-pressure measurements were taken. Skin friction in the model isolator section was found to significantly affect intake performance, increasing the amount of compression and reducing efficiency. Starting characteristics were determined experimentally in QinetiQ’s High Density Tunnel.

Numerical and Engine Cycle Analyses of a Pulse Laser Ramjet Vehicle

A preliminary feasibility study of a laser ramjet SSTO has been conducted using engine cycle analysis. Although a large amount of laser energy is lost due to chemically frozen flow at high altitudes, the laser ramjet SSTO was found to be feasible with 100 MW laser power for 100 kg vehicle mass and 1 m2 vehicle cross-section area. Obtained momentum coupling coefficient, Cm, was validated by means of CFD. As a result, the engine cycle analysis was under-estimating Cm. This would be because of the strong unsteady energy input in the actual heating process and the spatially localized pressure on the afterbody.

99/02364 Coal gasification apparatus

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles. The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps. The fuel pump(s) are driven in a conventional manner, for example, using a fuel-rich gas-generator cycle. Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4% lower while providing much lower oxygen temperature, more efficient tank pressurizing system and built-in roll control. This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle. Another semi-expander cycle can be considered as an improvement of gas-generator cycle. All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen. Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse, via optimization of mixture ratio. It is especially the case for upper stage engines. The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization. It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines. Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses. It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions. A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles. The newly-developed software RECS was used for the comparative analysis of engine cycles.

99/02402 Biological fluidized bed treatment of wastewater from by-product coking operations: full scale case history

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles. The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps. The fuel pump(s) are driven in a conventional manner, for example, using a fuel-rich gas-generator cycle. Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4% lower while providing much lower oxygen temperature, more efficient tank pressurizing system and built-in roll control. This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle. Another semi-expander cycle can be considered as an improvement of gas-generator cycle. All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen. Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse, via optimization of mixture ratio. It is especially the case for upper stage engines. The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization. It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines. Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses. It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions. A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles. The newly-developed software RECS was used for the comparative analysis of engine cycles.

99/02336 Changes in the structure of coals of different rank due to oxidation—effects on pyrolysis behavior

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles. The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps. The fuel pump(s) are driven in a conventional manner, for example, using a fuel-rich gas-generator cycle. Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4% lower while providing much lower oxygen temperature, more efficient tank pressurizing system and built-in roll control. This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle. Another semi-expander cycle can be considered as an improvement of gas-generator cycle. All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen. Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse, via optimization of mixture ratio. It is especially the case for upper stage engines. The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization. It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines. Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses. It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions. A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles. The newly-developed software RECS was used for the comparative analysis of engine cycles.

99/02348 Late Permian coal-bearing carbonate successions in southern China: coal accumulation on carbonate platforms

Improved liquid rocket engine cycles were proposed and analyzed via comparison with existing staged combustion and gas-generator cycles. The key features of the proposed cycles are regenerative cooling of thrust chamber by oxygen and subsequent use of this oxygen for driving one or two oxygen pumps. The fuel pump(s) are driven in a conventional manner, for example, using a fuel-rich gas-generator cycle. Comparison with staged combustion cycle based on oxygen-rich pre-burner showed that one of the proposed semi-expander cycles has a specific impulse only on 0.4% lower while providing much lower oxygen temperature, more efficient tank pressurizing system and built-in roll control. This semi-expander cycle can be considered as a more reliable and cost-effective alternative of staged combustion cycle. Another semi-expander cycle can be considered as an improvement of gas-generator cycle. All proposed semi-expander cycles were developed as a derivative of thrust chamber regenerative cooling performed by oxygen. Analysis of existing oxygen/kerosene engines showed that replacing of kerosene regenerative cooling with oxygen allows a significant increase of achievable specific impulse, via optimization of mixture ratio. It is especially the case for upper stage engines. The increasing of propellants average density can be considered as an additional benefit of mixture ratio optimization. It was demonstrated that oxygen regenerative cooling of thrust chamber is a feasible and the most promising option for oxygen/kerosene engines. Combination of oxygen regenerative cooling and semi-expander cycles potentially allows creating the oxygen/kerosene propulsion systems with minimum specific impulse losses. It is important that such propulsion systems can be fully based on inherited and well-proven technical solutions. A hypothetic upper stage engine with thrust 19.6 kN was chosen as a prospective candidate for theoretical analysis of the proposed semi-expander cycles. The newly-developed software RECS was used for the comparative analysis of engine cycles.

Finite-time view of the stirling engine

We present a finite-time thermodynamic analysis of the Stirling engine cycle based on mass and energy balances with associated heat-transfer-rate equations. These governing equations are formulated as normalized ordinary differential equations which are solved numerically. The effects of heat-transfer contact time and regeneration on power output and efficiency are studied. The results show that there exists an optimum power output for a given engine design, based on engine speed and heat-transfer contact time.

Turbine combustor preliminary design approach

Semiempirical correlations calibrated with data from a wide variety of existing gas turbine combustors are rearranged and organized into a burner design methodology, yielding position and size of primary and secondary air penetration holes and swirler angle, as well as required atomization from both pilot and main fuel injectors at engine start and low power operating conditions. The methodology assumes the design fuel has been chosen and that combustor inlet conditions, overall length, and diameter (or annulus height) are known from mission and engine cycle analyses. Output parameters are based on quantitative specifications of maximum NO.X and CO emissions indices, maximum blowout fuel/air ratio at start and idle power, minimum combustion efficiency, and coldest fuel temperature at start (ground or at altitude). Insofar as possible, the methodology is verified with measurements for the three configurations of a can combustor developed for vehicular applications.

An Analysis of the Otto Cycle Taking Into Consideration the Effect of Varying Operating Parameters

An analysis of internal combustion engine cycles using thermodynamic charts usually involves a lengthy trial-and-error process. A graphical analysis of the results of many cycles, however, enables equations to be developed for theoretical mean effective pressure and efficiency of the Otto cycle in terms of intake and exhaust pressures, fuel-air ratio, compression ratio, and fresh charge temperature. These equations enable quick solution of a particular cycle and the effects of operating parameters on engine performance to be studied. Experimental results show similar relationships between engine performance and operating parameters to those obtained theoretically.

LXXIII. Variable specific-heat corrections for the efficiency of the basic internal-combustion thermodynamic cycle and their application to the Constant-volume, Constant-pressure, Diesel and Humphrey Pump cycles

Summary The following paper is offered as a contribution to the problem of facilitating variable specific-heat analysis as applied to internal-combustion motor problems in general. The approach made to these problems is new, in so far as it involves the inclusion of a fifth ratio into the analysis of the basic internal-combustion engine cycle. This ratio, besides introducing a symmetry into the resulting expressions, also enables fairly convenient expressions to be obtained for the various thermodynamic quantities such as thermal efficiency, etc.