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1

Investigations of the city bus powertrain efficiency

Wendeker Mirosław, Grabowski Łukasz

Combustion Engines

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2024

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R. 63, nr 1

134--139

EN

Research work on the energy efficiency of vehicles is driven, among other things, by limits related to fuel consumption and carbon dioxide emissions. This also applies to city buses, where fuel consumption averages between 25 and 30 dm3 per 100 km, which can be converted into approximately 87 kg CO2 per dm3. This article, therefore, presents the results of a study of the total efficiency of the power train of a city bus, taking into account the internal combustion engine, transmission, torque converter, and tire friction on the rollers. The test object was a 12-metre city bus equipped with diesel engines and an automatic gearbox. The tests were carried out on a chassis dynamometer by implementing the World Harmonized Vehicle Cycle (WHVC). The WHVC driving test is a synthesis of the vehicle's on-road speeds and consists of three stages: Urban, Rural, and Motorway. During the tests, the fuel consumption, vehicle speed, and power generated at the wheels of the bus were recorded. From this, efficiency was calculated as the ratio of the power measured at the wheels of the bus to the power contained in the fuel supplied to the engine. Efficiency was shown to range from 5 to 22%.

2

Hydration heat generation and dissipation in diaphragm walls

Grabowski Łukasz, Mitew-Czajewska Monika

Archives of Civil Engineering

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2024

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Vol. 70, nr 2

661--675

EN

This study focuses on the complex dynamics of heat dissipation within diaphragm walls during concrete hydration, crucial in construction engineering. Experimental measurements from three sites in Poland, featuring diaphragm walls of varying thicknesses, ranging from 1 to 1.5 meters, were compared to a numerical model. The model, using a Finite Difference Method, incorporated stages of execution of adjacent panels and their thermal influence. The results closely mirrored the measured temperatures, validating the accuracy of its predictions. Despite minor discrepancies, mostly within ±3ºC, the method effectively approximated real-life scenarios. Suggestions for model enhancements include incorporating the effect of concrete admixtures and refining the modeling of sequential panel execution. The thermal soil parameters, their possible range, and their impact on hydration heat dissipation in deep foundations emerged as crucial insights. This research serves as a foundation for deeper investigations into early-age behavior in deep foundations, aiming to extend the analysis to stress and strain domains to unravel characteristic cracking patterns observed in diaphragm walls.

PL

Artykuł koncentruje się na badaniu złożonych procesów dyssypacji ciepła w ścianach szczelinowych podczas hydratacji betonu, co jest istotne w inżynierii budowlanej. Przeprowadzono eksperymenty na trzech różnych placach budowy w Polsce, gdzie ściany szczelinowe miały różne grubości od 1 do 1,5 metra. Zebrane pomiary porównano z modelem numerycznym, który wykorzystuje metodę różnic skończonych obejmował również zmienność parametrów w czasie na skutek wykonania sąsiedniej sekcji ściany szczelinowej. Model wykazał znaczną zgodność z rzeczywistymi temperaturami, co potwierdza jego trafność predykcyjną. Chociaż zaobserwowano pewne różnice, głównie w granicach ±3°C, metoda skutecznie oddaje realne warunki. Zalecenia dotyczące ulepszeń modelu obejmują uwzględnienie domieszek do betonu oraz optymalizację modelowania sekwencji wykonania paneli sąsiednich. Istotnym wnioskiem są również informacje o parametrach termicznych gruntu i ich wpływie na dyssypację ciepła w betonie. Badania te stanowią podstawę dla dalszych badań nad zachowaniem konstrukcji w początkowych fazach wiązania betonu fundamentów głębokich. Celem jest rozszerzenie analizy na pole naprężeń i odkształceń, co pozwoli zrozumieć charakterystyczne zarysowania obserwowane w ścianach szczelinowych.

3

Toxic Emission During Road Tests of Urban Bus

Magryta Paweł, Grabowski Łukasz, Barański Grzegorz, Wendeker Mirosław

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 6

16--26

EN

The article presents the results of toxic emissions in road tests of an urban bus. The object of the study was the Mercedes Connecto city bus. The results of toxic emissions were recorded in real time while bus drives with the use of the Semtech Ecostar exhaust gas analysis system. The study involved a planned bus SORT 2 test cycle. During the tests, the fuel consumption and exhaust gases such as CO2, CO, NOx, HC, NMHC, and O2 were recorded. The driving conditions in the study were constant (test cycles took place at the airport), exhaust gas temperature (hot engine) was also constant, etc. The results were based on average values from 5 test cycles for each test. The influence of electric load in the bus grid on the level of toxic emissions was measured. It has been proven that fuel consumption and CO2 emissions increased, which means a change in the value of components of toxic emissions. This fact evident from the increased CO emissions and decreased O2 emissions. Logically, the air-fuel mixture may have been enriched due to the increased demand for effective power generated by the engine crankshaft.

4

Early-age thermal-shrinkage cracking in deep foundations

Grabowski Łukasz, Mitew-Czajewska Monika

Studia Geotechnica et Mechanica

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2021

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Vol. 43, nr s1

510--520

EN

With the growing rate of urbanisation, deep foundations are playing an ever-larger role in the development of cities, reaching deeper than before to fulfil the requirements of new constructions. While current European standards include design procedures for structural and geotechnical design, they lack provisions for massive deep foundations with regard to early-age thermal effects. This paper presents aspects of the phenomenon especially important for deep foundations and discusses normative requirements that influence their thermal behaviour. Further, the paper describes the methods and results of the research carried out in the United Kingdom on 1.50-m-thick diaphragm walls of a deep circular shaft. Shaft features are described, as well as the materials used. The measurements were carried out using vibrating wire strain gauges coupled with temperature readings. The results presented refer to one of the test panels concreted in January 2020. The temperature results are analysed together with the influence of work scheduling on the readings. Strain results that indicate contractive behaviour of the test panel are investigated together with the possible causes leading to such readings. Plans and directions for future research are discussed.

5

Analyzing mechanical vibrations of an aircraft opposed piston engine

Biały Michał, Grabowski Łukasz, Skórzyński Bartłomiej, Barański Grzegorz, Majczak Adam

Combustion Engines

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2021

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R. 60, nr 4

3--7

EN

The paper presents the results of the bench tests to measure mechanical vibrations of a new aircraft opposed piston engine with reciprocating pistons. The PLZ-100 engine is a three-cylinder, six-piston, two-shaft drive unit with a two-stroke diesel cycle. This type of engine is dedicated for powering light aircraft, e.g. autogyros. The tests were carried out on a test bench at the Lublin University of Technology. The engine was loaded with constant torque, for several fixed values of rotational speed of a crankshaft. The angle of the start of diesel injection was changed for each of the rotational speeds. The mechanical vibrations that accompanied the operation of this drive unit were recorded with three measurement transducers and a National Instruments conditioning system. Each of the transducers was mounted on a different axis of the engine. The signals were analyzed from their diagrams with the DIAdem software. The results were the diagrams of effective speed and vibration acceleration to conduct a vibration-acoustic evaluation of the PLZ-100, detect and prevent various types of defects or failures.

6

Measuring Regenerative Braking Electricity Generated by the City Bus with Internal Combustion Engine

Wendeker Mirosław, Gęca Michał Jan, Grabowski Łukasz, Barański Grzegorz

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 3

215--223

EN

Engine braking, just when the vehicle consumes no fuel, is an important component of the energy balance. In such states, the bus loses its cumulated kinetic and potential energies but alternators recover a portion of these energies into electricity. Simultaneously, electricity consumption in the diesel-engine city bus is a key component of the overall energy balance. A total energy output of receivers can be more than 4 kW. This paper presents the research results on performance of a serial bus driving varied urban routes. The recorded and investigated parameters include a total amount fuel and electricity consumed and an amount of electricity generated. Engine braking states were calculated with a created algorithm. On average, 17% of electricity was generated by bus engine braking. The research results and investigation refer to the entire year.

7

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.

8

Turbocharging the aircraft two-stroke diesel engine

Karpiński Paweł, Pietrykowski Konrad, Grabowski Łukasz

Combustion Engines

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2019

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R. 58, nr 3

112--116

EN

The power and efficiency of a two-stroke engine strongly depends on the efficiency of the scavenging process which consists in removing the rest of the exhaust gases from the cylinder and filling it with a fresh charge. The quality of the charge exchange process is significantly influenced by the construction of the intake system. The paper presents a zero-dimensional model of the aircraft two-stroke opposed-piston diesel engine with two variants of the intake system: with a mechanical compressor and a turbocharger connected in series with a mechanical compressor. Simulation studies of the developed cases were carried out in the AVL BOOST software. For the defined engine operating points, its performance was compared for different designs of the intake system. It was confirmed that the use of a turbocharger with a mechanical compressor extends the range of operating at high altitudes.

9

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.

10

An investigation of the fuel injector dedicated to the aircraft opposed-piston two-stroke diesel engine

Siadkowska Ksenia, Wendeker Mirosław, Grabowski Łukasz

Combustion Engines

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2019

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R. 58, nr 2

151--155

EN

The paper presents the research results of the injector construction with the modified injection nozzle. The injector is designed for a prototype opposed-piston aircraft diesel engine. The measurements were based on the Mie scattering technique. The conditions of the experiment corresponded to maximum loads similar to those occurring at the start. The measuring point was selected in line with the analysis of engine operating conditions: combustion chamber pressure at the moment of fuel delivery (6 MPa) and fuel pressure in the injection rail (140 MPa). The analysis focused on the average spray range and distribution, taking into account the differences between holes in the nozzle. As a result of the conducted research, the fuel spray range was defined with the determined parameters of injection. The fuel spray ranges inside the constant volume chamber at specific injection pressures and in the chamber were examined, and the obtained results were used to verify and optimize the combustion process in the designed opposed-piston two-stroke engine.