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Simulation Research of the Influence of Compression Ratio on the Performance of an Aircraft Piston Diesel Engine

Grabowski Łukasz, Karpiński Paweł, Magryta Paweł

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 3

175--181

EN

In recent years, the opposed-piston engines have become increasingly popular in the automotive and aerospace industries. Therefore, it is necessary to conduct the research on this type of drive. The paper presents the simulation research of a two-stroke opposed-piston diesel engine designed for propulsion of light aircrafts. The influence of the change of the compression ratio on the selected engine performance was investigated (indicated mean effective pressure, peak firing temperature and pressure, specific fuel consumption, power consumed by the compressor). The AVL BOOST software was used to perform the simulation tests. A zero-dimensional engine model equipped with a mechanical compressor was developed. On the basis of the created model, a series of calculations was performed for the assumed values of the compression ratio for four engine operating points: take-off power, maximum continuous power and cruising power at two different altitudes. The obtained results were subjected to a comparative analysis and the most important conclusions connected with the influence of the change in the compression ratio on the achieved performance were presented.

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Experimental research of two stroke aircraft diesel engine

Grabowski Łukasz, Karpiński Paweł, Barański Grzegorz

Combustion Engines

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2019

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R. 58, nr 4

75--79

EN

This paper presents the results of experimental studies of the opposed-piston diesel engine. This engine was designed during one of the stages of the research on a new-type drive unit for gyrocopter applications. In order to conduct research, a special test stand as well as control and measurement systems were developed. As part of the work on the engine, the fuel injection system, engine temperature control system and measurement systems were designed. In addition, a computer program has been developed for the fuel injection system control (injectors, valves fuel pressure regulators). The paper presents the results of the preliminary tests for a single value of engine speed (1500 rpm) and three values of load defined by torque. The measured value of the indicated pressure made it possible to calculate the maximum pressure. The results obtained from the bench tests were analyzed.

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Numerical investigation on low calorific syngas combustion in the opposed-piston engine

Pyszczek R., Mazuro P., Jach A., Teodorczyk A.

Combustion Engines

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2017

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R. 56, nr 2

53--63

EN

The aim of this study was to investigate a possibility of using gaseous fuels of a low calorific value as a fuel for internal combustion engines. Such fuels can come from organic matter decomposition (biogas), oil production (flare gas) or gasification of materials containing carbon (syngas). The utilization of syngas in the barrel type Opposed-Piston (OP) engine arrangement is of particular interest for the authors. A robust design, high mechanical efficiency and relatively easy incorporation of Variable Compression Ratio (VCR) makes the OP engine an ideal candidate for running on a low calorific fuel of various composition. Furthermore, the possibility of online compression ratio adjustment allows for engine the operation in Controlled Auto-Ignition (CAI) mode for high efficiency and low emission. In order to investigate engine operation on low calorific gaseous fuel authors performed 3D CFD numerical simulations of scavenging and combustion processes in the 2-stroke barrel type Opposed-Piston engine with use of the AVL Fire solver. Firstly, engine operation on natural gas with ignition from diesel pilot was analysed as a reference. Then, combustion of syngas in two different modes was investigated – with ignition from diesel pilot and with Controlled Auto-Ignition. Final engine operating points were specified and corresponding emissions were calculated and compared. Results suggest that engine operation on syngas might be limited due to misfire of diesel pilot or excessive heat releas which might lead to knock. A solution proposed by authors for syngas is CAI combustion which can be controlled with application of VCR and with adjustment of air excess ratio. Based on preformed simulations it was shown that low calorific syngas can be used as a fuel for power generation in the Opposed-Piston engine which is currently under development at Warsaw University of Technology.

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Experimental test stand for development of an opposed-piston engine and initial results

Kalke J., Opaliński M., Mazuro P.

Combustion Engines

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2017

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R. 56, nr 2

76--82

EN

The article presents the reason for developing a 0D predictive and diagnostic model for opposed-piston (OP) engines. Firstly, a description of OP engines, together with their most important advantages and challenges are given together with current research work. Secondly, a PAMAR-4 engine characteristic is presented. After that the proposed 0D predictive model is described and compared with the commercially availible software. Test stand with most important sensors and solutions are presented. After that the custom Engine Control Unit software is characterized together with a 0D diagnostic model. Next part discusses specific challenges that still have to be solved. After that the preliminary test bed results are presented and compared to the 0D simulations. Finally, the summary together with possible future improvement of both 0D predictive model and test bed capabilities are given.

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Evaluation of the effect of variable compression ratios performance on opposed piston 2-stroke engine

Alqahtani A., Wyszynski M. L., Mazuro P., Xu H.

Combustion Engines

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2017

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R. 56, nr 4

97--106

EN

Numerous skills involving the introduction of (OP) opposed piston engine have been developed in the recent past. Indeed, novel techniques can help to improve the performance of the engine. The aim of this paper is to model and simulate a simple single-cylinder two-stroke opposed-piston engine and minimise fuel consumption and heat loss, using the software programme AVL BOOST™. AVL BOOST is an engine modelling software, which analyses the performance of a modelled single cylinder two-stroke opposed-piston engine by changing desired parameters. In order to meet this aim, experimental results from a unique engine are used to make a comparison with the results obtained from AVL BOOST model. Six combinations of compression ratios (12, 13.5, 15, 16.5, 18 and 19.5) are analysed in this study with the engine speed running at 420 rpm and 1500 rpm. In addition to the compression ratios, the effect of stroke-to-bore (S/B) ratios on OP2S performance is investigated. Various values of S/B ratios, whilst maintaining a constant swept volume, port geometry and combustion timing, and their effect on fuel consumption and heat loss are analysed in this study. A comparison between the two engine speeds with increasing combinations of compression ratios, and the S/B ratios revealed minimal differences in peak pressure, peak temperature, IMEP, ISFC, indicated efficiency and total heat loss. Detailed analyses of these parameters are highlighted in discrete sections of this paper.

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Compression Auto-Ignition Control in a 2-stroke Barrel-type Opposed-Piston Engine

Pyszczek R., Mazuro P., Teodorczyk A.

Archivum Combustionis

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2017

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Vol. 37 nr 1

25--42

EN

The aim of this study is to investigate a possibility of Compression Auto-Ignition (CAI) control in a turbocharged 2-stroke barrel type Opposed-Piston (OP) engine fueled with a gasoline. The barrel type OP engine arrangement is of particular interest for the authors because of its robust design, high mechanical efficiency and relatively easy incorporation of a Variable Compression Ratio (VCR). A 3D CFD numerical simulations of the scavenging and combustion processes were performed with use of the AVL Fire solver that is based on a Finite Volume Method (FVM) discretization and offers a number of tools dedicated to numerical simulations of working processes in internal combustion engines. The VCR and water injection were considered for the ignition timing control. A number of cases was calculated with different engine compression ratios, different equivalence ratios and different amount of injected water. Results show that proposed measures should be appropriate for controlling the CAI combustion process. Furthermore, application of these solutions in the real engine can significantly contribute to increase in efficiency and decrease in emissions.

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Investigation into the effect of bore/stroke ratio on a single cylinder two stroke opposed piston engin

Alqahtani A. M., Wyszynski M. L., Mazuro P.

Journal of KONES

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2016

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Vol. 23, No. 2

9--16

EN

Opposed-piston (OP) engine’s promising fuel efficiency has attracted the interest of automotive industry in the recent years. The opposed-piston two-stroke (OP2S) engine technology heightens this fuel efficiency benefit and offers advances in structure, power density and thermal efficiency whilst sustaining its lower cost and weight. Today thermodynamic modelling remains an indispensable and cost effective route in the development and optimisation of internal combustion engines (ICEs). To achieve this goal, the OP2S engine is simulated and validated against experimental results in AVL Boost™, which is hailed as one of the most reliable and advanced engine simulation tools. Detailed analyses of the piston dynamics, heat release, scavenging and heat transfers are highlighted in discrete sections of this paper. Having compared distinct heat release models, the Wiebe 2-Zone model emerged efficacious in replicating the heat release characteristics of the PAMAR™ engine. In comparing the numerical and experimental results, the simulation revealed minimal differences in peak pressure, peak temperature and maximum pressure raise rate, under ±2.5% differences for indicated power, IMEP, indicated thermal efficiency (ITE) and ISFC. Subsequently, confidence taken from the validated numerical model is then deployed to investigate the effect of stroke-to-bore (S/B) ratio on OP2S performance. Three combinations of S/B ratios (0.5, 1.25, and 1.69) with identical swept volume are analysed in this study. Utilisation of the validated model ensured the standardisation of intake, exhaust and the combustion systems in order to isolate the effects of S/B ratio. Results indicate that heat losses decrease with increasing S/B ratio because of the reduced surface area-to-volume in the cylinder. Consequently, an improvement in ITE and mechanical efficiency is observed with reduced ISFC for higher S/B ratios. A tendency of upsurge in combustion efficiency is also evident for higher S/B ratio due to reduced heat transfer near minimum volume of the combustion chamber.

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Numerical investigation of the swirl combustion chamber for the Opposed-Piston Compression-Ignition engine

Pyszczek R., Kalke J., Mazuro P.

Archivum Combustionis

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2016

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Vol. 36 nr 2

83--104

EN

The possibility of achieving high thermodynamic efficiency brings opposed-piston (OP) engines back into interest of research centers. If made as 2-stroke, the possibility of unidirectional scavenging arises together with lower engine cost due to removal of unnecessary parts like camshafts or poppet valves. Unfortunately, in the OP design the injection is perpendicular to cylinder axis, which is ineffective with conventional diesel injectors. Following article will present the proposed solution to this particular problem using an externally-attached swirl combustion chamber. The qualitative assessment of ability to meet the design expectations was performed in AVL Fire. The authors describe the CFD model and injector used for simulation. Contour plots and charts are given to compare the results. A variety of geometrical cases were analyzed. The recapitulation gives a critical evaluation of the proposed solution.