Wyniki wyszukiwania - BazTech

1

Investigation of waste heat recovery for automobile application based on a thermoelectric module

Buchalik R., Buczkowski D., Przybyła G., Nowak G.

Journal of KONES

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2016

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Vol. 23, No. 4

25--32

EN

The article presents a brief discussion about issues of energy harvesting of waste heat generated during the operation of the SI (spark ignition) internal combustion engine (ICE). The available methods of implementation and the problems associated with them were presented. In recent years, there has been an increase in the significance of successful researches on new types of thermoelectric modules. Despite relatively low efficiency of the thermoelectric modules, a systematic growth in their interest is observed. Their application seems to be reasonable because of many advantages - mainly the simplicity. The paper contains the literature review in the subject of interest. For the purpose of this work, a test rig was designed and manufactured. The test rig consists of a single thermoelectric module and makes it possible to work in variety of operating conditions for different values of the exhaust gas flow rate and temperature. It is equipped with an automatic, servo controlled, movable element, which control direction of the exhaust gas flow and as a result changes the heat flux transferred via the thermoelectric module. This solution allows achieving the maximum power of the thermoelectric module in a wide range of ICE operating conditions and also allows adjusting operating parameters to actual working conditions of the whole system. The problems encountered during the construction of the test rig and the proposed solutions of practical implementation were described. Experimental research was conducted on a small size automobile petrol engine. The influence of electrical parameters at the output on the whole system was analysed. The results suggest that the actual thermoelectric module parameters, especially the thermal conductivity, vary from declared by the producer. Maximum achieved electric power output reached about 10 W from a single thermoelectric module (57 mm x 54 mm), which is nearly half of the declared value.

2

Energy aspects of the SI engine load adjustment by early closing of inlet or exhaust valve

Żmudka Z., Postrzednik S., Przybyła G.

Journal of KONES

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2016

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Vol. 23, No. 4

583--590

EN

The theoretical analysis of the SI engine load adjustment has been presented. The load especially in SI engine is highly dependent on the process of charge exchange. This process has significant impact on the effectiveness of an engine work because it is connected with the necessity of overcoming the flow resistance, then with the necessity of doing a work, so-called the charge exchange work. The flow resistance caused by throttling valve is especially high during part load operation. The open theoretical cycle has been assumed as a model of processes proceeding in the engine. Using fully variable inlet and exhaust valves timing the cycle can be realized e.g. according to two systems: system with early inlet valve closing (EIVC) and system with early exhaust valve closing (EEVC). Both systems have been analysed individually and comparatively with the open Seiliger-Sabathe cycle, which is theoretical cycle for the classical throttle governing of an engine load. Benefits resulting from application of the systems with independent inlet and exhaust valves control have been assessed on the basis of the selected parameters: a fuel dose, a cycle work, a charge exchange work and a cycle efficiency. The use of the analysed systems to governing of the SI engine load will enable to eliminate a throttling valve from inlet system and reduce the charge exchange work, especially within the range of part load operation. Decrease of the charge exchange work leads to increase of the internal and effective works, which results in increase of the effective efficiency of the spark ignition engine. Additionally, the EEVC enables realization of the internal EGR.

3

Correlations of wiebe function parameters for combustion simulation in SI engine fuelled with gaseous fuels

Przybyła G., Postrzednik S., Żmudka Z.

Journal of KONES

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2016

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Vol. 23, No. 2

293--300

EN

Combustion simulation in SI engine fuelled with unconventional gaseous fuels becomes more necessary in last years. The reason is because the use of e.g. biogases from anaerobic digester process or gasification of biomass to produce "green energy". From the view of energy balance of small CHP units, the SI engine seems to be most efficient appliance as a part of this unit. Through 1D, simulation of in-cylinder pressure a fast prediction of engine performance is possible. In this case, the Mass Fraction Burn (MFB) function can be used. The MFB reflect the amount of fuel burned throughout the combustion process in an internal combustion engine. SI engine combustion simulation by using a Wiebe function to represent the MFB is very often used in a 1D-engine code that allow for fast calculations and a good accuracy of results. This paper deals with calculations of Wiebe function coefficients based on experimental data of four stroke naturally aspirated SI engine fuelled with natural gas and simulated producer gas. The Wiebe function parameters are determined over a range of fuel compositions and air excess ratio by fitting the Wiebe function curve to the experimentally obtained MFB data from a single-zone Heat Release Rate (HRR) analysis.

4

Throttleless control of SI engine load by fully flexible inlet valve actuation system

Żmudka Z., Postrzednik S., Przybyła G.

Combustion Engines

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2016

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R. 55, nr 1

44--48

EN

A system with independent, early inlet valve closure (EIVC) has been analysed. The open, theoretical cycle has been assumed as a model of processes proceeding in the engine with variable inlet valve actuation. The system has been analysed individually and comparatively with open Seiliger-Sabathe cycle which is theoretical cycle for the classic throttle governing of engine load. The influence of EIVC on fuel economy, cycle work, relative charge exchange work and cycle efficiency has been theoretically investigated. The use of the analysed system to governing of an engine load will enable to eliminate a throttling valve from inlet system and reduce the charge exchange work, especially within the range of partial load. The decrease of the charge exchange work leads to an increase of the internal and effective works, which results in an increase of the effective efficiency of the spark ignition engine.

5

The heat transfer coefficient calculations of internal combustion engine fuelled with natural gas

Przybyła G., Postrzednik S., Żmudka Z.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2015

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z. 87 [291], nr 1

71--80

EN

In this paper the calculations of heat transfer coefficient in the combustion chamber of the internal combustion engine fuelled with natural gas is presented. The mean value of heat transfer coefficient has been calculated using Woschni and Nusselt equation and compared with results obtained using algorithm based on experimental data. The proposed algorithm can be helpful to determine the average values of heat transfer coefficient from working medium to the combustion chamber walls (crown of a cylinder head, cylinder walls and piston head) during combustion process. The calculation method includes modified one zone heat release model in combustion chamber of SI engine. Proposed method is based on the energy balance equation closed by the coefficient which expresses the heat losses to the walls of the combustion chamber.

PL

W pracy przedstawiono obliczenia współczynnika przenikania ciepła w komorze spalania silnika wewnętrznego spalania zasilanego gazem ziemnym. Średnią wartość współczynnika przenikania ciepła obliczono za pomocą równania Woschni oraz Nusselta i porównano z wynikami uzyskanymi za pomocą algorytmu opartego na danych eksperymentalnych. Zaproponowany algorytm może być pomocny do określenia średnich wartości współczynnika przenikania ciepła z czynnika roboczego do ścian komory spalania (głowicy cylindra, ściany cylindrów i głowicy tłoka) podczas procesu spalania. Metoda obliczeniowa obejmuje zmodyfikowany model wydzielania ciepła w komorze spalania silnika ZI. Proponowany sposób opiera się na równaniu bilansu energetycznego zamkniętym przez współczynnik, który wyraża straty ciepła do ścianek komory spalania.

6

Main conditions and effectiveness of gas fuel use for powering of dual fuel IC self-ignition engine

Postrzednik S., Przybyła G., Żmudka Z.

Transport Problems

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2015

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T. 10, z. 3

99--111

EN

Internal combustion engines are fuelled mostly with liquid fuels (gasoline, diesel). Nowadays the gaseous fuels are applied as driving fuel of combustion engines. In case of spark ignition engines the liquid fuel (petrol) can be totally replaced by the gas fuels. This possibility in case of compression engines is essentially restricted through the higher self-ignition temperatures of the combustible gases in comparison to classical diesel oil. Solution if this problem can be achieved by using of the dual fuel system, where for ignition of the prepared fuel gas - air mixture a specified amount of the liquid fuel (diesel oil) should be additionally injected into the combustion chamber. For assurance that the combustion process proceeds without mistakes and completely, some basic conditions should be satisfied. In the frame of this work, three main aspects of this problem are taken into account: a. filling efficiency of the engine, b. stoichiometry of the combustion, c. performance of mechanical parameters (torque, power). A complex analysis of these conditions has been done and some achieved important results are presented in the paper.

PL

Silniki spalinowe są zwykle zasilane paliwami ciekłymi (benzyna, ON). Aktualnie do napędu tych silników często wykorzystywane są paliwa gazowe, przy czym zazwyczaj stosowany jest zapłon iskrowy. W przypadku silników z zapłonem samoczynnym wymagane jest użycie podwójnego systemu paliwowego (tzw. systemu dualnego), w ramach którego łącznie z paliwem gazowym podawana jest nieduża dawka paliwa ciekłego, inicjująca zapłon przygotowanej gazowo-powietrznej mieszanki palnej. W celu zapewnienia, że proces spalania będzie przebiegać prawidłowo, a pracujący silnik osiągnie wymagany moment obrotowy (moc efektywną), wiele uwarunkowań powinno być ściśle dotrzymanych. W artykule przeprowadzono teoretyczno-obliczeniową analizę uwarunkowań związanych z prawidłowym funkcjonowaniem silnika spalinowego, wyposażonego w dwupaliwowy układ zasilania w aspekcie uwarunkowań stechiometrycznych oraz pozyskiwanego momentu obrotowego.

7

Laboratory tests of small power generator driven by SI engine

Buchalik R., Buczkowski D., Przybyła G.

Combustion Engines

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2015

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R. 54, nr 3

752--759

EN

This work presents the results of the laboratory tests of low-power generator with an SI engine. Laboratory studies were conducted to determine the energy performance of the system (electric power, energy efficiency) and its harmful effects on the environment (emission of CO, HC and NOx). The investigated object is a model with a power rating of 900 W. The generator is a single-cylinder, four-stroke internal combustion engine with spark ignition and cylinder capacity of 49cm3. Energy efficiency of the specified variable values of the load generator was determined. The maximum efficiency value reaches 13%. High levels of carbon monoxide in the exhaust gas was observed. Furthermore the potential applicability of the generator as a motor drive for micro-vehicle for the Shell Eco-marathon competition was considered.

PL

Niniejsza praca zawiera wyniki badań agregatu prądotwórczego małej mocy z silnikiem ZI. Przeprowadzono badania laboratoryjne mające na celu wyznaczenie parametrów energetycznych układu (moc elektryczna, sprawność energetyczna) jego szkodliwego oddziaływania na środowisko naturalne (wskaźniki emisji CO, HC oraz NOx). Badany agregat to model o mocy znamionowej 900 W. Napęd generatora stanowi jednocylindrowy, czterosuwowy silnik spalinowy z zapłonem iskrowym o pojemności skokowej 49cm3. Określono sprawność energetyczną układu dla zmiennych wartości obciążenia generatora. Maksymalna wartość sprawności kształtuje się na poziomie 13%. Zaobserwowano bardzo wysoki poziom zawartości tlenku węgla w spalinach. Ponadto określono potencjał możliwości zastosowania silnika agregatu jako jednostki napędowej mikropojazdu.

8

Experimental study on performance and emission characteristics of lean burn SI engine fuelled with hydrogen methane blends

Przybyła G., Nagaraja S.

Combustion Engines

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2015

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R. 54, nr 3

556--562

EN

An experimental study on the performance and exhaust emissions of a spark ignition engine fueled with methane(CH4)-hydrogen (H2) blends was carried out at a constant speed of 1500 rpm and fixed excess air ratio (λ) of 1.5. The tests were carried out for pure methane and 2 blends (93% (by vol.) CH4 + 7% (by vol.) of H2, 77% (by vol.) CH4 + 23% (by vol.) of H2) at part load conditions in a naturally aspirated, three cylinder engine with a compression ratio of 9.3:1. The effects of hydrogen addition was studied at various spark timing and it is observed that the Maximum Brake Torque timing (MBT) retarded with increase in concentration of hydrogen. The coefficient of variation in indicated mean effective pressure (COVimep) decreases in blends, indicating stable combustion with hydrogen enrichment. A decrease in burn duration is observed and the crank angle at which peak pressure occurred, is tending towards top dead center (TDC) with increase in concentration of hydrogen due to higher laminar flame speed of the mixture enriched with hydrogen. In case of blends, specific emissions of carbon monoxide (CO) and unburned hydrocarbons (HC) decreases. However, there is considerable increase in specific emissions of oxides of nitrogen (NOx).

PL

Przeprowadzono badania eksperymentalne energetycznych parametrów pracy silnika spalinowego ZI oraz jego oddziaływania na środowisko naturalne podczas zasilania mieszaniną metanu z wodorem. Analizowano pracę silnika podczas spalania mieszanki ubogiej (λ = 1,5) przy stałej prędkości obrotowej wynoszącej 1500 obr/min. Badania wykonano dla zasilania czystym metanem oraz dwiema mieszankami o różnym udziale objętościowym wodoru tj. 7% H2, 93% CH4 oraz 23% H2, 77% CH4. Badano wpływ kąta wyprzedzenia zapłonu na przebieg procesu spalania. Zaobserwowano, że optymalna wartość kąta wyprzedzenia zapłonu zmniejsza się dla wyższej zawartości wodoru w mieszance palnej. Ponadto wskaźnik sygnalizujący poziom niepowtarzalności pracy indykowanej w kolejnych cyklach roboczych osiąga niższe wartości dla mieszanek wzbogaconych wodorem, co oznacza stabilniejszy przebieg procesu spalania. Spalanie mieszanek metanu z wodorem prowadzi do nieznacznego ograniczenia emisji CO oraz HC, natomiast wielkość emisji NOx rośnie za sprawą wyższej temperatury spalania dla mieszanki CH4 , H2.

9

Uwarunkowania efektywnego wykorzystania paliwa gazowego do napędu silnika spalinowego z zapłonem samoczynnym

Postrzednik S., Przybyła G., Żmudka Z.

Instal

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2014

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nr 7/8

36--41

PL

Tłokowe silniki spalinowe zasilane są zazwyczaj paliwami ciekłymi (benzyna, olej napędowy). Obecnie do napędu silników spalinowych często wykorzystywane są także paliwa gazowe. W tym zakresie zwykle stosowane są systemy z zapłonem iskrowym, chociaż spotkać można inne rozwiązania. W przypadku silników z zapłonem samoczynnym (diesle) wymagane jest zastosowanie podwójnego systemu paliwowego (tzw. systemu dualnego), w ramach którego łącznie z paliwem gazowym podawana jest nieduża dawka paliwa ciekłego, która inicjuje zapłon przygotowanej gazowo – powietrznej mieszanki palnej. Dla zapewnienia, że proces spalania przebiegać będzie prawidłowo, a pracujący silnik osiągnie wymagany moment obrotowy (moc efektywną), szereg uwarunkowań powinno być ściśle dotrzymane. W pracy dokonano teoretyczno – obliczeniowej analizy uwarunkowań związanych z prawidłowym funkcjonowaniem silnika spalinowego, wyposażonego w podwójny system paliwowy. Uzyskane wyniki pozwalają ocenić celowość stosowania dostępnego paliwa gazowego, a także na odpowiednie zaprogramowanie badań eksperymentalnych w zakresie racjonalnego wykorzystania różnych gazów do napędu silników spalinowych.

EN

Internal combustion engines are fuelled mostly with liquid fuels (gasoline, diesel). Nowadays more and more the gaseous fuels are applied as driving fuel of combustion engines. In case of spark ignition engines the liquid fuel (petrol) can be replaced totally without additional troubles by the gas fuels. This possibility in case of compression engines is essentially restricted. Self-ignition of the fuel gas appears at higher temperatures in comparison to selfignition of classical diesel oil. Solution if this problem can be achieved by using of the dual fuel system. The diesel engine can be fulfilled with the fuel gas basically, but for ignition of the prepared fuel gas – air mixture a specified amount of the liquid fuel (diesel oil) should be additionally injected into the combustion chamber. Diesel engine working with the dual fuel system has to perform simultaneously the needed effective mechanical torque and power output. For assurance that the combustion process in the cylinder proceeds without mistakes and completely, some basic conditions should be satisfied. In the frame of this work, three main aspects of this problem are taken into account: a. filling of the engine, b. stoichiometry of the combustion, c.performance of mechanical parameters (torque, power). A complex analysis of these conditions connected with the dual fuel combustion process has been done and some results of the carried out investigations are presented in the paper.

10

Badania silnika spalinowego ZI zasilanego gazem ziemnym do zastosowań w mikrokogeneracji

Przybyła G., Postrzednik S.

Instal

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2014

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nr 5

14--19

PL

W artykule przedstawiono wyniki badań eksperymentalnych silnika spalinowego o zapłonie iskrowym, zasilanego stechiometryczną oraz ubogą mieszanką gazu ziemnego z powietrzem. Przeprowadzono obliczenia wartości opałowej mieszanki gazowo-powietrznej w szerokim zakresie zmienności stosunku nadmiaru powietrza. Badaniom podlegał silnik spalinowy małej mocy. Standardowo ten typ silnika stosowany jest w przemyśle motoryzacyjnym, a ze względu na niską cenę zakupu oraz koszty eksploatacji może znaleźć zastosowanie w układach kogeneracyjnych małej mocy. Głównym celem niniejszej pracy jest określenie parametrów energetycznych silnika oraz jego oddziaływania na środowisko podczas spalania mieszanek ubogich gazu ziemnego. Zaobserwowano wyraźny wpływ stosunku nadmiaru powietrza na parametry energetyczne oraz ekologiczne silnika spalinowego zasilanego gazem ziemnym GZ50. Wartość sprawności energetycznej wzrasta niespełna o ok. 2 punkty procentowe przy zmianie wartości stosunku nadmiaru powietrza od mieszanki stechiometrycznej do wartości λ=1,5.

EN

In this paper the experimental results of SI engine fuelled with lean mixture of natural gas are presented. the calculations of the calorific value of air-gas mixtures in a wide range of the excess air ratio variation has been done.The experiments were carried out on the petrol engine with a low engine displacement. Typical SI engine was selected in order to evaluate the potential application of gaseous fuel (i.e. natura gas). These types of engines are available on a wide scale and commonly used in automotive sector because of the low purchase price and operating costs. It is expected that after minor modifications, the engine can easily operate in micro CHP system. The main goal of this work is to determine the performance of the engine and its impact on the environment during the combustion of the lean natural gas mixtures. There was a clear effect of excess air ratio on the performance and environmental impact of internal combustion engine powered by natural gas GZ50. The engine efficiency increase about 2 percentage points when changing the value of the excess air ratio of the mixture to the stoichiometric λ=1.5.

11

Realization of the Atkinson-Miller cycle in spark-ignition engine by means of the fully variable inlet valve control system

Żmudka Z., Postrzednik S., Przybyła G.

Archives of Thermodynamics

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2014

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Vol. 35, no. 3

191--205

EN

The theoretical analysis of the charge exchange process in a spark ignition engine has been presented. This process has significant impact on the effectiveness of engine operation because it is related to the necessity of overcoming the flow resistance, followed by the necessity of doing a work, so-called the charge exchange work. The flow resistance caused by the throttling valve is especially high during the part load operation. The open Atkinson-Miller cycle has been assumed as a model of processes taking place in the engine. Using fully variable inlet valve timing the A-M cycle can be realized according to two systems: system with late inlet valve closing and system with early inlet valve closing. The systems have been analysed individually and comparatively with the open Seiliger-Sabathe cycle which is a theoretical cycle for the classical throttle governing of the engine load. Benefits resulting from application of the systems with independent inlet valve control have been assessed on the basis of the selected parameters: fuel dose, cycle work, charge exchange work and a cycle efficiency. The use of the analysed systems to governing of the SI engine load will enable to eliminate a throttling valve from the system inlet and reduce the charge exchange work, especially within the range of part load operation.

12

The lean mixture combustion of simulated producer gas in SI engine

Przybyła G., Szlęk A., Ziółkowski Ł.

Journal of KONES

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2013

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Vol. 20, No. 3

331--338

EN

In this paper the experimental results of spark ignited (SI) engine fuelled with lean mixture of simulated producer gas compared with chosen gaseous fuels are presented. The SI engine test fuelled with simulated producer gas, natural gas and simulated biogas with variable value of excess air ratio has been done. The experiments were carried out on the petrol engine with a low engine displacement. Typical SI engine was selected in order to evaluate the potential application of gaseous fuel (i.e. producer gas, natural gas or biogas). These types of engines are available on a wide scale and commonly used in automotive sector because of the low purchase price and operating costs. It is expected that after minor modifications, the engine can easily operate in micro CHP system. The main goal of this work is to determine the performance of the engine and its impact on the environment during the combustion of the lean producer gas mixtures. The study shows the impact of both the excess air ratio and the type of fuel used for engine performance and emission index. Combustion of lean mixtures of producer gas leads to an increase of carbon monoxide in the exhaust. Increasing the value of excess air ratio affects the growth of indicated efficiency of the engine

13

The heat transfer coefficient calculation in the ice cylinder based on in-cylinder pressure data

Przybyła G., Postrzednik S., Żmudka Z.

Journal of KONES

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2013

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Vol. 20, No. 4

382--388

EN

In this paper the calculations algorithm of heat-transfer coefficient in the combustion chamber of the internal combustion engine is presented. Developed algorithm is based on the in cylinder pressure data. The proposed algorithm can be helpful to determine the average values of heat-transfer coefficient from working medium to the combustion chamber walls (crown of a cylinder head, cylinder walls and piston head) during combustion process. The calculation method includes modified one zone heat release model in combustion chamber of SI engine. Proposed method consists in closing the energy balance equation by the coefficient which expresses the heat losses to the walls of the combustion chamber. The average value of the heat losses during combustion process is calculated by two steps. Firstly, the integration of the energy balance equation (without specifying the heat losses) leads to designation of the so-called net value of heat released in cylinder. In the next step the amount of the total energy supplied to the cylinder is determined taking into account the chemical energy of the supplied fuel. The difference between the supplied value of chemical energy and heat released net value allows to determine the heat losses average value. In last stage, the heat flow equation leads to calculate the mean value of heat transfer coefficient during combustion process.

14

Influence of the exhaust gas recirculation on the oxygen contents and its excess ratio in the engine combustion chamber

Postrzednik S., Żmudka Z., Przybyła G.

Journal of KONES

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2013

|

Vol. 20, No. 3

315--321

EN

Exhaust gas recirculation (EGR) can be realized on the external or internal way. The main goal of EGR is to decrease the combustion temperature of the combustible mixture by increasing the relative heat capacity of the working medium. An additional effect is to reduce the oxygen content in the gas mixture flowing into the combustion chamber. To quantify the exhaust gas recirculation some descriptive parameters are defined, including: – exhaust gas recirculation rate R, – multiple of exhaust gas recirculation K, – relative exhaust gas recirculation W. The analysis concerns the effective oxygen excess ratio Oef in the combustible mixture and the so-called internal oxygen excess ratio Ow,, which additionally takes into account the supplied oxygen with the recirculation stream. It was found that with increasing of the exhaust gas recirculation degree systematically decreases the content of the oxygen [O2]d in the combustible mixture, while increases the oxygen excess ratio Oef observed in the exhaust gases. Changes of this all parameters influence the combustion coditions in the engine cylinder, and next the achieved specifaic work, energy efficiency and emission of the combustion engine. An advanced system with independent, early exhaust valve closing enables realization of an internal EGR. Effectiveness of internal recirculation is lower than the external recirculation.

15

Charge exchange control in a SI engine by early exhaust valve closing

Żmudka Z., Postrzednik S., Przybyła G.

Journal of KONES

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2013

|

Vol. 20, No. 1

387--394

EN

The paper tackles the problems connected with the charge exchange in internal combustion engines. The theoretical analysis of the charge exchange process in the SI engine has been presented. A system with independent, early exhaust valve closing has been analysed. The analysed system enables realization of an internal EGR and elimination of a throttling valve from an inlet system and reduce the charge exchange work, especially within the range of partial load. The decrease of the charge exchange work leads to an increase of the internal and effective works, which results in an increase of the effective efficiency of the spark ignition engine. The open, theoretical cycle has been assumed as a model of processes proceeding in an engine. The system has been analysed individually and comparatively with open Seiliger-Sabathe cycle. Benefits resulting from application of the system with early exhaust valve closing have been assessed on the basis of the selected parameters: a fuel dose, a cycle work, a relative charge exchange work and a cycle efficiency. The best results within decrease of fuel consumption and increase of cycle efficiency are obtained for low engine load. The main parameters characterizing the process of the internal exhaust gas recirculation were also determined. These are the ratio and the multiplicity of the exhaust gas recirculation.

16

Stechiometryczne uwarunkowania oraz skutki realizacji recyrkulacji spalin

Postrzednik S., Żmudka Z., Przybyła G.

Combustion Engines

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2013

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R. 52, nr 3

379--382

PL

Zasadniczym celem stosowania recyrkulacji spalin jest obniżenie temperatury spalania mieszanki palnej, poprzez wzrost względnej pojemności cieplnej czynnika roboczego. Do ilościowego ujęcia recyrkulacji wykorzystano pojęcia: stopień R, krotność K recyrkulacji spalin oraz jej wartość względna W. Analiza dotyczy stechiometrycznych skutków recyrkulacji: udziału tlenu [O2]d w mieszaninie gazów dopływających do komory spalania, efektywnego λ ef stosunku nadmiaru tlenu oraz tzw. wewnętrznego stosunku nadmiaru tlenu λw, w którym uwzględnia się tlen dostarczany ze strumieniem recyrkulujących spalin. Dzięki przeprowadzonej analizie uwarunkowań i skutków recyrkulacji okazało się, ze wzrostem stopnia recyrkulacji systematycznie zmniejsza się udział [O2]d tlenu w mieszance palnej, a jednocześnie obserwuje się wzrost wewnętrznego stosunku nadmiaru tlenu λ w. Ustalone współzależności wpływają istotnie na parametry (ciśnienie p, temperaturę T) obiegu silnika, pozyskiwaną pracę mechaniczną oraz sprawność energetyczną, a także na emisję substancji szkodliwych.

EN

The main goal of EGR is to decrease the combustion temperature of the combustible mixture by increasing the relative heat capacity of the working medium. An additional effect is to reduce the oxygen content in the gas mixture flowing into the combustion chamber. The analysis concerns the effective oxygen excess ratio λ ef in the combustible mixture and the so-called internal oxygen excess ratio λw, which additionally takes into account the supplied oxygen with the recirculation stream. It was found that with increasing of the exhaust gas recirculation degree systematically decreases the content of the oxygen [O2]d in the combustible mixture, while increases the oxygen excess ratio λ ef observed in the exhaust gases. Changes of this all parameters influence the achieved specifaic work, energy efficiency and emission of the combustion engine.

17

Podstawowe uwarunkowania oraz efektywność wykorzystania paliwa gazowego do napędu silnika spalinowego z zapłonem samoczynnym

Postrzednik S., Żmudka Z., Przybyła G.

Combustion Engines

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2013

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R. 52, nr 3

866--871

PL

Tłokowe silniki spalinowe zasilane są zazwyczaj paliwami ciekłymi (benzyna, olej napędowy). Aktualnie do napędu silników spalinowych wykorzystywane są często także paliwa gazowe. W tym zakresie zwykle stosowane są systemy z zapłonem iskrowym, chociaż spotkać można inne rozwiązania. W przypadku silników z zapłonem samoczynnym wymagane jest zastosowanie podwójnego systemu paliwowego (tzw. systemu dualnego), w ramach którego łącznie z paliwem gazowym podawana jest nieduża dawka paliwa ciekłego, która inicjuje zapłonu przygotowanej gazowo - powietrznej mieszanki palnej. Dla zapewnienia, że proces spalania przebiegać będzie prawidłowo, a pracujący silnik osiągnie wymagany moment obrotowy (moc efektywną), sze-reg uwarunkowań powinno być ściśle dotrzymane. W pracy dokonano teoretyczno - obliczeniowej analizy uwarunkowań związanych z prawidłowym funkcjonowaniem silnika spalinowego, wyposażonego w dwupaliwowy system zasilania; w aspekcie uwarunkowań stechiometrycznych oraz pozyskiwanego momentu obrotowego.

EN

Internal combustion engines are fuelled mostly with liquid fuels. Nowadays more and more the gaseous fuels are applied as driving fuel of combustion engines. In case of spark ignition engines the liquid fuel (petrol) can be replaced totally without additional troubles by the gas fuels. This possibility in case of compression engines is essentially restricted. Self-ignition of the fuel gas appears at higher temperatures in comparison to self-ignition of classical diesel oil. Solution if this problem can be achieved by using of the dual fuel system. The diesel engine can be fulfilled with the fuel gas basically, but for ignition of the prepared fuel gas - air mixture a specified amount of the liquid fuel (diesel oil) should be additionally injected into the combustion chamber. Diesel engine working with the dual fuel system has to perform simultaneously the needed effective mechanical torque and power output. For assurance that the combustion process in the cylinder proceeds without mistakes and completely, some basic conditions should be satisfied. In the frame of this work, three main aspects of this problem are taken into account: a. filling of the engine, b. stoichiometry of the combustion, c. performance of mechanical parameters (torque, power). A complex analysis of these conditions connected with the dual fuel combustion process has been done and some results of the carried out investigations are presented in the paper.

18

Analiza procesu spalania ubogich mieszanek paliw gazowych w silniku ZI

Przybyła G., Postrzednik S., Żmudka Z.

Combustion Engines

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2013

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R. 52, nr 3

371--378

PL

W artykule przedstawiono wyniki badań teoretycznych i eksperymentalnych silnika spalinowego o zapłonie iskrowym, zasilanego ubogimi mieszankami gazu z powietrzem. Przeprowadzono obliczenia wartości opałowej mieszanki gazowo-powietrznej (ed,v) dla wybranych paliw gazowych (gaz ziemny, biogaz, gaz z procesów zgazowania paliw stałych). Na podstawie własności tych paliw, określona została sprawność teoretycznego obiegu Otto, stosując zmienne wartości nadmiaru powietrza. Badania przeprowadzono na silniku o niskiej objętości skokowej. Tego typu silniki są stosowane w przemyśle motoryzacyjnym, a ze względu na niską cenę zakupu oraz koszty eksploatacji mogą być stosowane w układach kogeneracyjnych małej mocy. Głównym celem niniejszej pracy jest określenie parametrów silnika spalinowego ZI podczas spalania mieszanek ubogich. Jak wykazała analiza, największa różnica w wartościach (ed,v) energii chemicznej mieszanki palnej dla analizowanych paliw występuje w zakresie mieszanek stechiometrycznych. W tym miejscu różnica Δ ed,v pomiędzy gazem ziemnym, a przykładowym gazem ze zgazowania biomasy wynosi ok. 35%, podczas gdy w zakresie mieszanek ubogich różnica ta jest znacznie niższa. Dla bardzo wysokich wartości stosunku nadmiaru powietrza λ wspomniana różnica osiąga wartość „0”. Zaobserwowano wyraźny wpływ stosunku nadmiaru powietrza na nierównomierność pracy silnika bazującego na średnim ciśnieniu indykownym (COVIMEP). Wartości tego wskaźnika rosną ze wzrostem stosunku nadmiaru powietrza. Uzyskane wyniki kształtują się na dopuszczalnym poziomie ze względu na zastosowanie silnika w układzie CHP i osiągają wartość poniżej 5%.

EN

In this paper the results of the theoretical and experimental study of an internal combustion engine, fuelled with lean air – gas mixtures, are presented. Calorific value of air-fuel mixture were calculated for several chosen gaseous fuels such as: natural gas, landfill gas, and producer gas. Based on these fuels, the performance of a theoretical Otto cycle was investigated using variable air excess values. The experiments were carried out on a petroleum engine with a low engine displacement. A typical SI engine was selected in order to evaluate the potential application of a gaseous fuel (i.e. natural gas). These types of engines are widely available and commonly used in the automotive sector because of low purchase prices and operating costs. It is expected that after minor modifications, the engine can easily operate in a low power co-generation mode. The main objective is to evaluate the performance of the engine under lean air/fuel mixture conditions. The analysis shows that the most significant difference in the calorific value of air fuel mixture (ed,v) for chosen fuels is occured for stoichiometric mixtures. At this point the difference Δ ed,v between natural gas and the producer gas is about 35%, while for the lean mixtures the difference is much less. The slight impact of air excess ratio on COVIMEP was noticed. The value decreases insensibly with air excess ratio decreasing. Obtained results are located at acceptable levels for power generation sources and are less than 5 %.

19

Analiza efektywności niezależnego sterowania zaworami wylotowymi jako sposobu realizacji wewnętrznej recyrkulacji spalin

Żmudka Z., Postrzednik S., Przybyła G.

Combustion Engines

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2013

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R. 52, nr 3

338--345

PL

Przeprowadzono analizę systemu z niezależnym, wcześniejszym zamknięciem zaworu wylotowego, który umożliwia realizację wewnętrznej recyrkulacji spalin oraz wyeliminowanie przepustnicy w silniku ZI. Odniesieniem dla oceny korzyści oraz badania efektywności pozyskiwania pracy, w wyniku zastosowania tego systemu sterowania, jest otwarty obieg teoretyczny Seiligera-Sabathe’a z powszechnie stosowaną klasyczną regulacją dławieniową obciążenia. Analizę porównawczą efektywności zastosowania zaproponowanego systemu przeprowadzono opierając się na wybranych wielkościach: dawce paliwa, pracy obiegu, względnej pracy wymiany ładunku oraz sprawności obiegu. Najlepsze efekty w zakresie zmniejszenia dawki paliwa i zwiększenia sprawności obiegu dla analizowanego systemu, w porównaniu do systemu z regulacją dławieniową, uzyskuje się w obszarze średniego obciążenia silnika.

EN

A system with independent, early exhaust valve closing has been analysed. The analysed system enables realization of an internal EGR and elimination of a throttling valve from inlet system of a spark ignition engine. The open, theoretical cycle has been assumed as a model of processes proceeding in an engine. The system has been analysed individually and comparatively with open Seiliger-Sabathe cycle. Benefits resulting from application of the system with early exhaust valve closing have been assessed on the basis of the selected parameters: a fuel dose, a cycle work, a relative charge exchange work and a cycle efficiency. The best results within decrease of fuel consumption and increase of cycle efficiency are obtained for mean engine load.

20

Late intake valve closing as a way of the throttleless control of SI engine load

Żmudka Z., Postrzednik S., Przybyła G.

Journal of KONES

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2012

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Vol. 19, No. 1

491-499

EN

The paper tackles the problems connected with the charge exchange in internal combustion engines. The theoretical analysis of the charge exchange process in the SI engine has been presented. The realization of the charge exchange process is connected with the necessity of overcoming the flow resistances, then with the necessity of doing a work, so-called the charge exchange work. The flow resistance caused by throttling valve is especially high at the partial load running of an engine. A system with independent, late intake valve closing has been analysed. The use of the analysed system to governing of an engine load will enable to eliminate a throttling valve from inlet system and reduce the charge exchange work, especially within the range of partial load. The decrease of the charge exchange work leads to an increase of the internal and effective works, which results in an increase of the effective efficiency of the spark ignition engine. The open, theoretical Atkinson-Miller cycle has been assumed as a model of processes proceeding in the engine with variable intake valve actuation. The system has been analysed individually and comparatively with open Seiliger-Sabathe cycle, which is theoretical cycle for the classic throttle governing of engine load. Benefits resulting from application of the system with late intake valve closing have been assessed on the basis of the selected parameters: a fuel dose, a cycle work, relative charge exchange work and cycle efficiency.