Engine Performance Simulation Research Articles

Multiple-Point Adaptive Performance Simulation Tuned to Aeroengine Test-Bed Data

Adaptive simulation technology enables the calibration of a performance simulation code to a given in-service gas turbine and provides correct prediction of its performance. This is a fundamental prerequisite for reliable gas-path diagnostics and performance health monitoring. In this paper, a new offdesign performance adaption algorithm is introduced. Cranfield University's consolidated engine performance simulation code PYTHIA is enhanced with the capability of offdesign performance adaptation to model available field data. The software minimizes, via a genetic algorithm, an objective function that measures the error between an initial engine model output and the real engine data by varying some characteristics' scaling factors. In this study, a multiple-point adaptation procedure was applied to a two-shaft aeroengine. This generated an optimized engine model that minimized its deviations from a set of test-bed data. The adapted model was then tested against different real data, resulting in an average error, over 8 measured parameters, of less than 0.35%.

Optimal Mission Analysis Accounting for Engine Aging and Emissions

An aircraft mission analysis procedure, accounting for engine aging deterioration and incorporating emission estimation capability, is presented. It consists of three main modules: a flight simulation module, an engine performance simulation module, and an optimizer. A key feature of the approach is the incorporation of engine deterioration modeling. This extends the procedure’s ability to estimate onboard performance of an engine as it ages through time and usage. Additionally, the possibility to investigate environmental impact is offered through pollutant emission semi-empirical correlations, which are coupled to the engine performance calculations. The adaptive character of the models employed allows for accurate performance and emission estimations once an initial set of data is available for the engine. The proposed procedure allows the optimization of a flight scenario for a variety of aircrafts, missions, and engine condition combinations in order to meet predefined criteria. Mission profile characteristics (e.g., cruise, altitude, and speed) providing optimum overall performance in terms of fuel conservation, time related costs, or pollutant production are studied.

Simulation and experimental research on a mixed pulse converter turbocharging system

A newly developed turbocharging system, called a mixed pulse converter (MIXPC), is proposed and the performance of the proposed system applied to diesel engines is evaluated. The aim of this proposed system is to reduce the scavenging interference between cylinders, and to lower the pumping loss in cylinders and the brake specific fuel consumption (BSFC). In addition, exhaust manifolds of simplified design can be constructed with small dimensions, low weight, and a single turbine entry. An engine performance simulation code, in which a second-order finite volume method + total variation diminishing method is used to simulate the one-dimensional unsteady gas dynamic phenomenon in intake and exhaust pipe systems, has been developed. By simulating a locomotive diesel engine using the module pulse converter (MPC) turbocharging system and the MIXPC, it is found that not only is the average scavenging coefficient of the MIXPC larger than that of the MPC, but also cylinders of the MIXPC have more homogeneous scavenging coefficients than those of the MPC, and the pumping loss and BSFC of the MIXPC are lower than those of the MPC. To validate the prediction results, experiments on a locomotive diesel engine equipped with a MIXPC have been successfully completed. Experimental results show that the MIXPC turbocharging system reduces the exhaust gas temperature before turbine by 80°C and BSFC at part load by 4.3 g/kW h, and the exhaust gas temperatures at each cylinder outlet at high load are more uniform. The diesel engine equipped with the MIXPC has the potential to increase its power to 115 per cent load.

A de-coupled approach to component high-fidelity analysis using computational fluid dynamics

This study focuses on a simulation strategy that will 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. The technique described in this paper is called ‘de-coupled’ high-fidelity analysis and utilizes an object-oriented, zero-dimensional gas turbine modelling and performance simulation system and a three-dimensional computational fluid dynamics (CFD) component model. The technique involves the generation of a component characteristic map without the parallel or iterative execution of the non-dimensional cycle and the three-dimensional CFD model. Therefore, a faster high-fidelity engine performance simulation can be achieved at run time. This paper demonstrates the ‘de-coupled’ approach to component high-fidelity analysis by using a three-dimensional CFD intake model of a high by-pass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The CFD-generated performance map can fully define the characteristics of the intake at several operating conditions and power settings, and is subsequently used to provide a more accurate, physics-based estimate of intake performance (i.e. pressure recovery) and hence, engine performance, replacing the default, empirical values within the non-dimensional cycle model. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the CFD-generated map is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance > 1 per cent.

Improvement of Engine Performance and NOx Simulation Technology

Thanks to the progress in both computer system hardware and software, the engine performance and exhaust emission precisely can be simulated by using virtual engine model of one dimension with codes. Therefore, it came to be able to shift from a relative evaluation by the single cylinder model with the overall turbocharger efficiency to an absolute evaluation by the multi cylinder model (full model) with the turbocharger map. As a result, the simulation accuracy for the engine performance and exhaust emission estimation has been improved.This paper presents the improvement of engine performance simulation technology by using the examples of engine simulation calculations and engine experimental results. In these analyses, the multi cylinder model is introduced for simulating the engine performance and exhaust emission and the results are compared with the experimental results.

Grid-based distributed simulation of an aero engine

In the design phase of an aircraft engine, integrated design and accurate performance simulations have become essential. Predictive integrated system modeling is now a pressing issue in the design of aircraft engines. For computationally-intensive analysis, components may be distributed across heterogeneous computing architectures and operating systems. However, the traditional distributed systems are not sufficiently robust or flexible to support the integration and distributed simulation. Designers and engineers may face these difficulties when designing aero engine systems that need to evolve and change rapidly. Grid computing may be introduced to mitigate these problems. This paper develops a system, which serves as a scientific co-laboratory. It provides a flexible environment for defining, modifying, and simulating component-based aero gas turbine models, and enables users to customize and extend the framework to add new functionality or adapt simulation behavior as required. A distributed gas turbine engine model is developed and simulated to illustrate the use of the framework.

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

Background . This study focuses on a simulation strategy that will 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 work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.

Measuring wave dynamics in IC engine intake systems

Wave dynamics in the intake system are known to strongly influence the performance of naturally aspirated internal combustion (IC) engines. Detailed measurements of the wave dynamics are required to optimize the performance of an engine, to validate the results of an engine performance simulation or to better understand the physics of the intake system. Five different methods for making such measurements are discussed in this paper. Four are based on different forms of pressure measurement and one uses hot-wire anemometry. The different methods are investigated by using results obtained on a single cylinder research engine. The different methods are used to produce measurements of fluctuating pressure and velocity as well as the specific acoustic impedance ratio of the intake pipe. Both time and frequency domain results are considered. The conclusion is that no single method is perfect or indeed universally applicable to all situations and in a typical investigation of wave action more than one method is likely to be used. The combined use of two methods, wave decomposition and an unusual bi-directional pitot-static tube, seems to offer a robust reliable and useful strategy for measuring wave dynamics in the intake pipe that should prove successful on most IC engines.

Extensible object model for gas turbine engine simulation

This paper presents an extensible object model for gas turbine engine performance simulation. The extension method for gas path balancing is analyzed and a new design rationale is developed to overcome deficiencies of the traditional component-based object modeling method. A class framework implementing this rationale is described and the dynamic performance of a three-shaft gas turbine engine is simulated to evaluate the model’s effectiveness.

Development of a shear layer ignition model for application to direct-injection diesel engines

A transient, one-dimensional spray shear layer ignition model has been formulated to provide a methodology for predicting the autoignition period in direct-injection, quiescent chamber diesel engines. This approach focuses on including the influence of key injection and thermodynamic parameters that affect this key diesel combustion phenomenon. In particular, these important parameters include injection rate, mean spray angle, bulk in-cylinder instantaneous temperature and pressure, and residual gas fraction from a thermodynamic point-of-view. The proposed shear layer model agreed fairly well with experimental autoignition data derived from indirectly measured engine bulk fuel burning rate profiles even though ignition is modeled only according to a one-step Arrhenius-type reaction that accounts for both local shear layer equivalence ratio and temperature. In particular, the proposed model exhibited improved predictive capability in comparison to published zero-dimensional diesel engine autoignition correlations that are typically employed in bulk parameter, diesel engine performance simulation models.

中型4ストローク低速機関のNOx低減

The study of reducing NOx emission without increasing specific fuel oil consumption was conducted using medium bore size 4-stroke low speed diesel engine. Engine performance simulation was done before engine test. Designed parts owing to the calculation result were evaluated by means of a test on a 6 cylinder engine (bore: 340mm, stroke: 680mm, rated engine speed: 280min-1) . From these studies, practical technique of reducing NOx emission and specific fuel oil consumption was found, and this improved NOx emission level is within IMO NOx regulation. This paper reports these engineering findings.

1201 船舶ディーゼル機関のNOx低減(OS.7 環境・省エネ・リサイクル)

The study of reducing NOx emission in marine diesel engine without increasing specific fuel oil consumption is a matter of no little interest to the engine manufacturer. Engine performance simulation was done before engine test. Optimized design components owing to the calculation predict of reducing NOx were evaluated by means of a test on a 6 cylinder medium bore size 4-stroke low speed diesel engine (bore: 340mm, stroke: 680mm, rated engine speed: 280min-1). From these studies, practical technique of reducing NOx emission and specific fuel oil consumption was found, and this improved NOx emission level is within IMO NOx regulation. This paper reports these engineering findings.

Performance Simulation of Marine Diesel Engines with SELENDIA

This paper describes a diesel engine simulation code, named SELENDIA, jointly developed by EcoleCentrale de Nantes, France, and the University of New Orleans. The adopted models for steady-state and transient response simulation are briefly introduced in addition to various validation results. The capabilities of the code are illustrated by a study regarding the transient response of a sequentially turbocharged marine diesel engine as well as the simulation of engine performance under extreme conditions and the investigation of engine pollutant emissions.

Analysis of stratified EGR and air on combustion and NO formation in a spark-ignition engine

Using a phenomenological model (Brunel Engine Emissions, Performance and Autoignition Simulation, BEEPAS) developed at Brunel University, the influence of stratified exhaust gas recycled (EGR) and stratified air (lean burn) on spark-ignition (SI) engine performance and NO emission were analysed. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air—fuel charge, a dilution region without any combustible charge and a mixing region lying between the core and the dilution region. Three mixture stratification parameters were investigated: the amount of mixing in the cylinder, the extent of dilution in the mixing region and the gradient of stratification in the mixing region. In addition, the difference in the effects on combustion and NO formation of stratified EGR and air was analysed. The results indicate that stratified air operation is better for improving engine efficiency than stratified EGR operation. It was found that the longer combustion duration, as well as the increased heat capacity of EGR, contributes to the superiority of stratified EGR over stratified air in the suppression of in-cylinder NO formation. For the same initial charge temperature, stratified EGR has a much lower dilution limit than stratified air owing to retardation of flame propagation. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation.

Hydrogen as an additive to methane for spark ignition engine applications

The performance of a gas fuelled spark ignition engine is enhanced when relatively small amounts of hydrogen are present with methane. This improvement in performance, which is especially pronounced at operational equivalence ratios that are much leaner than the stoichiometric value, can be attributed largely to the faster and cleaner burning characteristics of hydrogen in comparison to methane. Through analytical simulation of engine performance, the addition of hydrogen is considered through its production in situ on board the engine by electrolysis of water with the necessary energy supplied from engine power. It is shown that when the work energy required for the production of hydrogen by electrolysis is taken into account, the range of viable operation of such an engine is very narrow. This would render the whole concept of in situ hydrogen production through water electrolysis uneconomical in conjunction with engine operation, even though the presence of additional oxygen produced with the hydrogen tends, in principle, to improve engine performance beyond that observed with hydrogen addition. © 1999 International Association for Hydrogen Energy.

Development of a muffler for control of noise pollution in a diesel engine

The present work aims at controlling the noise level of a diesel engine by developing an exhaust muffler for the same, since exhaust noise is the single largest contributor to the overall noise from the engine. The TATA 1210 six-cylinder diesel engine was considered for test purposes. A simulated design, developed by Ricardo with the application of the engine performance simulation program WAVE, was taken up, and this was modified in certain aspects to suit the engine under consideration. The muffler was fabricated and data were recorded for evaluation of the acoustic performance as well as the engine performance and for purposes of comparison with the existing muffler as well as with the open-ended exhaust system. The new muffler was found to be superior to the existing one in terms of both acoustic performance and engine performance. With the new muffler, the maximum noise reduction obtained was 19.3 dB(A) and the maximum brake thermal efficiency obtained was 39 per cent, while with the existing muffler the corresponding values were 14.5 dB(A)and 37.4 per cent. The present work has thus experimentally shown that results from WAVE can be modified and applied to an alternative design.

98/03241 Reduction of emission from spark-ignition engines in USA and Europe

Nowadays, EGR systems are being incorporated in the research focused on spark-ignition direct-injection engines as a solution to the problems presented by them; i.e. knock risk and high combustion temperature which produces high NOx emission. Since the major part of the investigations are centered on engine performance or engine simulation aside pollutants emission and aftertreatment evaluation, this paper focuses on these topics: gaseous and particle emission analysis and aftertreatment efficiency evaluation when cooled LP-EGR system is applied to a GTDi engine.This work has been performed in a 4-cylinder, turbocharged, direct-injection gasoline engine with 2.0 L displacement. The equipment used in this study are TSI-EEPS for particle measurement and HORIBA MEXA 1230-PM for soot measurement being HORIBA MEXA 7100-DEGR with a heated line selector the system employed for regulated gaseous emission measurement and aftertreatment evaluation. A reduction around 50% of NOx with an increase of HC and CO emissions was found in medium-load operating points. At full-load conditions, the suppression of fuel enrichment including EGR leads in a drastically reduction in CO maintaining similar HC and NOx emissions. Furthermore, PN and soot emissions also decrease as EGR is included and spark timing advanced in all the tested conditions.

MODELING AND SIMULATION OF COMPRESSION IGNITION ENGINES

ABSTRACT Modeling of a compression ignition engine was carried out covering losses emanent from imperfect construction of real engines such as progressive combustion, valve timing, and heat transfer. Furthermore, friction was included to obtain brake performance. Simulation of engine performance was tackled by varying engine speed, compression ratio and injection timing over wide range. The results were compared with those obtained from the experiemntal facility. Predictions by the model compare favourably with experiment within 9·3% and 9·7% for power and sfc respectively. The losses considered in this work amount to about 30% of the fuel energy input at the design point.

MODELING AND SIMULATION OF SPARK IGNITION ENGINES

ABSTRACT Modeling is important because it saves time, effort and cost needed for engine development and prediction of performance. In this work, losses due to imperfect construction of the real engine, including progressive combustion, valve timing and heat transfer have been modeled besides engine friction. Hence, it becomes possible to convert the output of the fuel-air cycle into net brake performance. Simulation of engine performance was carried out by varying engine speed, compression ratio and spark advance over wide range. Hence, it was possible to compare the results with those from experiments on a single cylinder engine. The model predictions were found to compare favourably with experiment within 4·6% in power and 2·9% in SFC. The losses considered in this work amount to about 14% of the fuel energy input.

A Review of Internal Combustion Engine Losses Part 2: Studies for Global Evaluations

The global evaluation of losses is important in providing information about the behaviour of an engine. This may be used, for instance, in design and development of new models, where one with inherently the lowest friction may be chosen with a consequent potential gain in fuel economy. This paper reviews studies on the determination of total engine losses. Experimental works are reported from which, sometimes with theoretical support, empirical formulae are obtained that allow an extension of the results to engines similar to those investigated. Besides formulae in which losses are expressed as an equivalent pressure averaged in the complete cycle, more detailed formulae for the determination of instantaneous loss torques are reported, which are also useful in obtaining a better evaluation of the engine speed trend in fault diagnosis. All formulae can be used in computer programs for the numerical simulation of engine performance, a use that can reduce the time needed for experimental work.