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ISSN 1392-1134

Aleksandro Stulginskio Universiteto mokslo darbai, 2012, 44 (1-3), 211-22

Research papers of Aleksandras Stulginskis University, 2012, vol 44, no 1-3, 211-222

DUAL-FUELLING COMPRESSION IGNITION ENGINE WITH

METHANE AND DIESEL OIL

METANU IR DYZELINU VEIKIANČIO DYZELINIO VARIKLIO DARBO

RODIKLIŲ TYRIMAS

Sławomir Wierzbicki*, Andrzej Piętak*, Maciej Imiołek*, Anna Imiołek**

*University of Warmia and Mazury in Olsztyn Faculty of Technical Sciences ,

** University of Warmia and Mazury in Olsztyn Faculty of Environmental Management &

Agriculture

e-mail: slawekw@uwm.edu.pl

Gauta 2012-04-30 , pateikta spaudai 2012-09-07

The paper presents the effect of the main parameters of pilot dose ignition:

injection advance angle and injector opening time on the combustion process in a dual fuel

compression ignition engine.

The results presented in the paper show the recorded changes of pressure in the

combustion chamber with a constant fuel pilot dose and different ignition advance angles.

In addition, example changes of combustion pressure are presented, recorded at a constant

pilot dose injected at variable pressures and variable injector opening times.

Compression ignition engine, methane, dual fuel system, combustion process.

Introduction

The need to reduce the emission of greenhouse gases, as well as the limited

resources of petroleum, has been a driving force for searching for new, alternative

sources of energy which can be used for powering combustion engines.

The current regulations concerning the use of renewable fuels, e.g.

Directive No. 2001/77/EC of the European Parliament and of the Council of 27

September 2001 on the promotion of electricity produced from renewable energy

sources in the internal electricity market has required the generation of at least

7.5% of electricity obtained from renewable sources since 2010 and the share of

this energy must amount at least to 20% by 2020. Another document imposing an

obligation to reduce the emission of greenhouse gases is the Kyoto Protocol, the

signatories of which, including Poland, agreed to reduce their own emissions to

negotiated values by 2012, presented in the annex to the protocol (at least 5% of

the emission level of 1990), e.g. carbon dioxide, methane, nitric oxides – gases

emitted by engines and causing the greenhouse effect [1, 3, 7, 12].

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One of the possible methods for lowering the discharge of toxic

components into the atmosphere is the wider use of methane as a fuel for

combustion engines. Methane can originate from fossil fuels – natural gas (CNG),

as well as biogas obtained from various sources, first of all such as: waste dumps,

municipal waste, post-production waste of the fruit and vegetable processing plants

and farm waste [2, 6, 7, 10, 11].

Currently, powering combustion engines with methane is becoming

increasingly more popular, which can be seen by the constant increase in the

number of stations where filling up with this fuel is possible. In many European

towns, municipal buses are powered only by CNG. The application of CNG as a

fuel for engines makes it possible to significantly reduce the concentration of toxic

compounds and exhaust gas smokiness. The interest in methane results not only

from the existence of large resources of this fuel, but it is also dictated by

ecological and economic factors. CNG is currently the cheapest fuel widely applied

in the economy [4, 6, 7, 10, 11].

Methane as fuel for combustion engines is increasingly often used for

powering spark ignition combustion engines, which is confirmed by the

continuously expanding networks of methane filling stations. A serious

impediment in applying methane as an engine fuel is its low condensation point –

162°C. Nowadays, technologies have been developed to be used for constructing

special tanks to store methane in a liquid form (LNG), but the time of this storage

is limited. Therefore, in practice, it is most often used in a compressed form

(CNG). The application of methane in a compressed form requires the use of

relatively large fuel tanks, which increases the weight of the entire vehicle, makes

it difficult to install them on a vehicle and significantly reduces the range of the

vehicle [3, 6, 7, 10, 11].

Unfortunately, the application of methane as a fuel for diesel engines is

impeded by a relatively high self-ignition temperature of about 540°C. Therefore,

in order to use methane as a fuel for diesel engines, it is necessary to adapt the

engine to work in a dual fuel system.

Internal combustion engines supplied with gas

Currently, gas-powered engines are being in several ways [9, 10, 5]. The

research conducted on using gaseous fuels to power combustion engines includes:

Spark ignition engines:

- studies on feeding engines with CNG, LNG and LPG,

- studies on feeding engines with biogas.

Compresion-ignition engines:

- feeding engines with CNG, LNG, LPG (dual-fuel feeding),

- feeding engines with biogas (via modification of an engine;

change in the compression ratio, additional ignition unit),

- feeding engines with modified LPG and NG (using fuel additives

enabling self-ignition).

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Methane will not start to burn in a self-ignition engine unless a certain dose

of diesel oil initiating ignition is injected into the combustion chamber filled with a

methane-oxygen mixture or else an electric spark is used to ignite the fuel. Some

modifications are introduced so as to substitute the DO injection unit with a CNG

feeding system equipped with spark ignition (change in a spark ignition engine).

The diesel oil metering is altered, being now reduced to an ignition dose, and the

feeding unit is adapted to supply gaseous fuel. There are also solutions in which a

compersion-ignition engine is converted into a dual-fuel engine fed with CNG or

petrol during the start-up phase. In a dual-fuel diesel engine, the fuel could be

CNG, LPG or biogas used as the main dose and biogas as a dose initiating the

ignition, the so-called pilot dose.

The test stand and research methods

The research carried out in the Department of Mechatronics of the

University of Warmia and Mazury in Olsztyn aimed at determining the minimum

dose of diesel oil injected into the combustion chamber to ensure proper ignition of

the methane-air mixture compressed in the combustion chamber.

The research was conducted on the basis of a HATZ 1B40 single-cylinder,

low-power engine driving a three-phase generator (tab. 1). The examined engine

was fitted with a prototypical system of methane-air fuelling and a system for

controlling and adjusting the supplied dose of methane. The examined engine was

subject to modernization, consisting of supplying gas (CNG) to the mixer in the

inlet system. After mixing with air, the gas was sucked into the cylinder. The

original system of fuelling the engine with diesel oil was replaced with a laboratory

Common Rail system. With this aim in view, a standard mechanical injector was

replaced with an electromagnetic injector with similar nozzle parameters. The basic

parameters of injector operation were controlled by a specially-developed system

ensuring continuous choice of parameters of injector operation, such as (fig. 1):

– duration of the impulse for injector opening – with 10 s adjustment;

– fuel injection advance angle – with crank angle adjustment of 0.5°;

– possibility of dividing an injected fuel dose into four parts, with possible

individual adjustment of duration and beginning of injection for each of the

doses.

Table 1. Technical characteristics of the Hatz 1B40 engine

1 lentelė. Variklio Hatz 1B40 techninės charakteristikos Engine type HATZ, 1B 40, 4-stroke, air-cooled

Rated power 6.8 kW at 3000 rpm

Number of cylinders 1

Engine displacement 462 cm3

Cylinder diameter 88 mm

Piston stroke 76 mm

Compression ratio 21

Mixture making system direct injection

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Fig. 1. A view of a HATZ 1B40 engine with a system for controlling,

monitoring and fuelling with CNG and diesel oil

1 pav. Variklio HATZ 1B40 maitinamo gamtinėmis dujomis ir dyzelinu

matavimo ir valdymo įrangos bendras vaizdas

Fig. 2. Oscillogram of selected signals in the elaborated steering system for a

HATZ 1B40 engine, presetting: 1 – signal from the crankshaft, 2 – signal of the

location of a piston in TDC between the compression and work strokes, 3 – signal

from the valve timing phase sensor, 4 – signal of the electromagnetic injector

steering.

2 pav. Variklio HATZ 1B40 pasirinktų darbinių parametrų signalų oscilogramos:

1 – alkūninio veleno; 2 – stūmoklio padėties; 3 – skirstymo veleno padėties

jutiklis; 4 – elektromagnetinio purkštuko valdymo signalas.

For this aim, the engine was instrumented with such devices as a

crankshaft’s location and speed sensor, valve timing phase sensor, and temperature

sensors, which provided signals (fig. 2) necessary for the engine to work properly.

The elaborated systems ensured external steering and selection of diesel oil and

CNG injection parameters during dual-fuel or single-fuel feeding. The CR fuelling

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system was fitted with a controlled fuel pressure regulator in the tank, with the

possibility of its continuous adjustment.

During the tests, the following parameters were measured:

– a dose of diesel oil injected into the combustion chamber;

– instant consumption of CNG;

– engine speed;

– power received from the system;

– course of pressure changes in the combustion chamber as a

function of the crank angle.

Additionally, the following parameters of engine operation were controlled

during the tests:

– temperature of the engine head;

– temperature of engine lubrication oil;

– temperature of exhaust gases in the exhaust manifold;

– signal from the knock sensor installed on the engine head.

The system of engine indicating was used, AVL Indimodul 621 (Fig. 3),

was used for recording pressure in the combustion chamber. This set consists of a

charge amplifier – FlexIFEM Piezo 2P2E AVL, a crank angle encoder – 365C

AVL, a piezoelectric sensor for measuring dynamic pressure in the cylinder – GM

12D AVL. During operation, the IndiModul system was controlled by the IndiCom

computer software suite. The pressure values in the combustion chambers were

recorded at every crank angle of 0.5°.

Fig. 3. The view of the engine indicating system: a) charge amplifier – FlexIFEM

Piezo 2P2E AVL and IndiCom software, b) piezoelectric sensor GM 12D AVL,

c) crank angle encoder – 365C AVL

3 pav. Variklio parametrų indikavimo sistemos bendras vaizdas: a) signalų

stiprintuvas – FlexIFEMPjezo 2P2E AVL ir Indicom programinė įranga b)

pjezoelektrinis jutiklis – GM 12D AVL, c) alkūninio veleno padėties jutiklis

Encoder–365C AVL

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Results

The results of the research described in the further part of the study were

obtained after carrying out a series of experiments on the test stand, maintaining

the same power received from the generator during each series. The research was

carried at

– constant pressure of diesel oil injection of 40 MPa;

– constant advance angle of pilot dose injection of 14.5 °CA;

– constant engine speed of 3000 rpm.

The measurements were taken for the following values of power received

from the generator: 0.6 kW, 1 kW, 2 kW, 3 kW, 4 kW, which corresponds to:

12.5%, 21%, 42%, 63% and 85% of the rated load of the examined system.

For each value of the initial power of the tested system, the measurements

began with engine operating on diesel oil only. For subsequent measurements, the

share of diesel oil was reduced in a fuelling dose, compensating it with an

increased share of CNG. Records was made until the moment of obtaining the

lowest possible dose of diesel oil at which the engine operated evenly and no

unfavourable phenomena, such as “engine knocking” or an excessive increase in

engine or exhaust gas temperatures occurred.

Figures 4 and 5 present the average sample courses of pressure recorded in

the combustion chamber. As can be clearly seen from these diagrams, an increase

of the share of methane in the dose fuelling the engine results in delaying the

moment at which the maximum pressure occurs in the combustion chamber. As a

result of load expansion in the combustion chamber, the value of the maximal

pressure is also lowered. During the research presented in this paper, a constant

advance angle of the pilot dose injection was maintained, amounting to 14.5° CA.

Fig. 6 and 7 presents the effect of the injection lead angle for the dose

initiating self-ignition for a diesel oil dose equivalent to 50% and 22% of the dose

for diesel oil supply alone. The next Fig. 8 shows the effect of the injection lead

angle for the initiating dose for different proportions between individual fuels on

changes of maximum pressure in the combustion chamber.

While analysing the recorded pressure changes in the combustion chamber,

it can be claimed that the share of methane in the dose powering the engine, at

diesel oil doses up to 20%, results in increasing the maximum pressure in the

chamber, with the growing rate of its increase. At lower doses of diesel oil

initiating self-ignition, the maximum pressure in the combustion chamber

decreases in comparison to fuelling the engine only with diesel oil. However, it

should be emphasized that, in this case, combustion is extended over time, which

results in a high increase of methane consumption.

The diagrams clearly demonstrate a strong effect of the advanced angle of

diesel oil injection on the course of the pressure increase in the combustion

chamber. At an injection angle of the piloting dose lower than 22°CA before TDC,

the pressure graph has two maxima: the first related to the compression of the

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mixture and the second resulting from the delayed self-ignition of the diesel oil -

methane - air mixture.

Fig. 4. Selected sample courses of pressure in the combustion chamber recorded

for the generator load of 2 kW

4 pav. Slėgis variklio degimo kameroje, esant skirtingoms degalų rūšims ir

pastoviai 2 kW generatoriaus apkrovai

Fig. 5. Selected sample courses of pressure in the combustion chamber recorded

for the generator load of 3 kW

5 pav. Slėgis variklio degimo kameroje, esant skirtingoms degalų rūšims ir

pastoviai 3 kW generatoriaus apkrovai

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Fig. 6. Average changes of pressure in the combustion chamber at dual fuel engine

supply with diesel oil at varied pilot dose injection angle, at Pe=2kW, a dose of

diesel oil of 50%: 1 – 14°CA, 2 – 16°CA, 3 – 18°CA, 4 – 20°CA, 5 – 22°CA, 6 –

24°CA, 7 – 26°CA

6 pav. Vidutinis slėgio kitimas degimo kameroje, variklyje su dvejopa degalų

tiekimo sistema, esant įvairiems kintamiems dyzelinių degalų porcijų įpurškimo

kampams, Pe = 2kW, dyzelinių degalų kiekis 50%: 1 - 14 ° CA, 2-16 ° CA, 3- 18 °

CA, 4 - 20 ° CA, 5 - 22 ° CA, 6 - 24 ° CA, 7 - 26 ° CA

Fig. 7. Average changes of pressure in the combustion chamber at dual fuel engine

supply with diesel oil at varied pilot dose injection angle, at Ne=2kW, n=3000

rpm, a dose of diesel oil of 22%: 1 – 14°CA, 2 – 16°CA, 3 – 18°CA, 4 – 20°CA,

5 – 22°CA, 6 – 24°CA

7 pav. Vidutinis slėgio kitimas degimo kameroje, variklyje su dvejopa degalų

tiekimo sistema, esant įvairiems kintamiems dyzelinių degalų porcijų įpurškimo

kampams, Pe = 2kW, n = 3000min-1

dyzelinių degalų kiekis 22%: 1 - 14 ° CA,

2-16 ° CA, 3- 18 ° CA, 4 - 20 ° CA, 5 - 22 ° CA, 6 - 24 ° CA

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Fig. 8. The effects of advance angle of the pilot dose injection on the

maximum pressure of combustion, at various proportions of diesel oil and

CNG

8 pav. Uždegimo dozės įpurškimo paskubos kampo įtaka, maksimaliam slėgiui

variklio degimo kameroje, esant skirtingoms dyzelino ir CNG proporcijoms

The effect of the share of methane in the dose powering engine the course

of pressure changes at constant advance angle diesel oil injection is presented in the Fig. 9.

Fig. 9. Average changes of pressure in the combustion chamber at double-fuel

engine fuelled with diesel oil (DO) at a varied constant angle of pilot dose

injection of 20°CA, at Ne=2kW, n=3000 rpm, and various shares of methane in

the dose powering the engine: 1 – 100% DO, 2 – 50% DO+CNG, 3 – 33%

DO+CNG, 4 – 22% DO+CNG, 5 – 12% DO + CNG

9 pav. Vidutinis slėgio kitimas degimo kameroje, variklyje su dvejopa degalų

tiekimo sistema, dyzeliniais degalais (DO), esant įpurškimo paskubos kampui

20 °, Pe = 2kW, n = 3000min-1

dyzelinių degalų kiekis 22%: 1 - 100% DO, 2 -

50% DO + CNG, 3 - 33% DO + CNG, 4 - 22% do + CNG, 5 - 12% do + CNG

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Conclusions

The results presented above demonstrate the effects of basic parameters of

injection of the pilot dose of diesel oil, i.e. the amount of the dose, its injection

advance angle and the course of pressure changes in the combustion chamber of

the dual fuel diesel engine. The results obtained demonstrate the effect of those

parameters on the course of combustion in those engines. On the basis of these

results, it can be concluded that in the case of small, unloaded diesel engines of

relatively high rotational speed, the best course of combustion is ensured by the

percentage of the methane dose not exceeding 80% of the total dose. At higher

shares of methane in the supplied dose, fuel combustion is extended over time,

which results in high energy losses.

The obtained preliminary results comply with press reports concerning

prototypical solutions for engines applied in farm tractors manufactured by

STAYER and VALTRA, powered by the dual fuel system with diesel oil and

methane supplied in the form of biogas.

Acknowledgment

This paper was partially financed by research grant No N N509 573039,

given by Polish Ministry of Science and Higher Education.

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8. Rożycki A.: Analysis of performances of a dual-fuel turbocharged

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12. Wierzbicki S.: Effect of the parameters of pilot dose injection in a dual

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Powertrain and Transport. Vol. 18, No. 3, 2011, str. 499-506.

Sławomir Wierzbicki, Andrzej Piętak, Maciej Imiołek,

Anna Imiołek

METANU IR DYZELINU VEIKIANČIO DYZELINIO VARIKLIO DARBO

RODIKLIŲ TYRIMAS

Reziumė

Straipsnyje pateikiama pagalbinės uždegimo dozės pagrindinių parametrų -

įpurškimo paskubos kampo ir įpurškimo trukmės – įtaka dviejų rūšių degalais

veikiančio dyzelinio variklio degimo procesui.

Straipsnyje pateikiami rezultatai rodo degimo kameroje užfiksuotus slėgio

pokyčius esant pastoviai pagalbinei degalų porcijai ir skirtingiems įpurškimo

paskubos kampams. Papildomai pateiktos indikatorinės diagramos, užrašytos esant

pastoviai pagalbinei įpurškiamų degalų porcijai ir kintamiems įpurškimo slėgiams

bei purkštuvo atsidarymo momentams.

Dyzelinis variklis, metanas, dviejų degalų rūšių variklio maitinimo sistema,

degimo procesas.

222

Славомир Вержбицкий, Андржей Петак, Мацей Имиолек, Анна Имиолек

ИССЛЕДОВАНИЕ РАБОЧИХ ПАРАМЕТРОБ ДИЗЕЛЬНОГО ДВИГАТЕЛЯ,

РАБОТАЮЩЕГО НА МЕТАНЕ И ДИЗЕЛЬНОМ ТОПЛИВЕ

Резюме

В статье представлено влияние основных параметров пилотной дозы

дизельного топлива – угла опережения впрыска и продолжительности

впрыска - на рабочуй процесс двухтопливного дизельного двигателя.

В статье представлены зависимости изменения давления в камере

сгорания при постоянной пилотной дозе дизельного топлива и различных

углав опережения впрыска. Также представлены индикаторные диаграмы,

полученные при постоянной пилотной дозе и различных давлениях и начале

впрыска.

Дизельный двигатель, метан, двухтопливная система, процесс

сгорания.