Green Fuels and their impact on the performance and the exhaust gases in Diesel Engines

22/04/23 TEI OF THESSALONIKI 1

Green Fuels and their impact on the performance and the

exhaust gases in Diesel Engines

J. TRIANDAFYLLISProfessor in the Department of Vehicle

[email protected]


Contents1. Introduction.2. Effects on engine performance (these

notes are based on bibliography source 3).

3. Measurements of two cars with diesel engines at the Karel de Grote- Hogeschool.

4. Bibliography.


1. IntroductionTHE SIGNIFICANCE OF PLANT OILS AS

BIO-FUELS. Bio-fuels are oils derived from plants, such as

sunflower oil, cottonseed oil, and safflower oil. Bio-fuels can be utilized in mixtures with diesel

oil to improve the quality of the vehicle exhaust gases, and thus, to improve the air quality.

The air quality can be improved because the bio-fuels when are burnt, do not produce PAH (polyaromatic hydrocarbons), unburnt hydrocarbons, and products of sulphur.


2. Effects on Engine Performance

2.1 Heating Value Since a bio-fuel is mixed

with diesel, from now on, let us refer to it as biodiesel.

The most important property of a fuel is its lower heating value (LHV), because it affects the quality of combustion, and thus, the production of power.

The lower heating value of all biodiesels is lower than that of diesel.

FUEL Lower Heating ValuekJ/kg

Number 2 diesel

43357

Sunflower oil methylester

38565

Cottonseed oil

methylester

38926

Frying oil ethylester

37225


Production of Biodiesel


2. Effects on Engine Performance2.2 Fuel economy Fuel consumption can be calculated from

the carbon dioxide emissions and an analysis of the fuel carbon content.

It is more accurate to combine CO2 emission measurements with a gravimetric measurement of fuel consumption.

From tests it was found that biodiesel and mixtures of biodiesel with diesel exhibit a fuel economy proportional to their lower heating value.


2. Effects on Engine PerformanceCycle Biodiesel

% 1988 DDC 6V-92TA (mpg)

1981 DDC 8V-71 (mpg)

CBD Stock 0 3,69 3,59 CBD Stock 20 3,68 3,63 CBD 1,5̊Timing change 20 3,54 3,59 CBD Catalyst 20 3,35 3,18 CBD Timing + Catalyst 20 3,26 3,30

Arterial Stock 0 4,67 3,92 Arterial Stock 20 4,72 3,1 Arterial 1,5T̊iming change 20 4,89 3,93 Arterial Catalyst 20 4,64 3,40 Arterial Timing + Catalyst 20 4,56 3,84

Composite Stock 0 3,70 3,66 Composite Stock 20 3,63 3,52 Composite 1,5T̊iming change 20 3,50 3,63 Composite Catalyst 20 3,34 3,21 Composite Timing + Catalyst 20 3,33 3,43



2.3 Torque and Acceleration The torque is related to the energy level of

the fuel. Studies have shown torque reductions for

biodiesel and biodiesel mixtures. Acceleration is also reduced for biodiesel

and biodiesel mixtures. Therefore, horsepower is also reduced.


2. Effects on Engine Performance Peak torque is not significantly

affected up to 35% biodiesel.% Biodiesel Peak torque, ft-lb

(1200 RPM) 0 1283 0 1279 0 1278 0 1286 20 1275 35 1270 65 1256 100 1210


2. Effects on Engine Performance2.4.1 Durability studies Engines run with biodiesel mixtures

experience problems caused by 1. The appearance of coke deposits on the

valves caused by low volatility fuel at light loads.

2. Plugged filters and injectors by unreacted mono-, di-, and triglycerides, free fatty acids, methanol and glycerol found in raw plant oils.

3. Pump failure caused by deteriorating seals.


2. Effects on Engine Performance2.4.2 Elastomer compatibility Many of the problems encountered in the

durability studies are traced to the incompatibility of biodiesels with certain elastomers.

Methylesters cause the swelling of trilobutyldilene and nitrile rubber, a material that is commonly used in automotive seals and gaskets.

Fluorine containing elastomers do not swell at the presence of biodiesels.


2. Effects on Engine Performance2.4.3 Biodiesel lubricity Fuel lubricity is important because in

many fuel pumps the moving parts are actually lubricated by the diesel fuel itself.

From tests it was shown that soybean and rapeseed oil methylesters have superior lubricity when compared to low sulfur diesels.


2. Effects on Engine Performance2.5 Emissions Diesel engines are regulated for smoke opacity, total

nitrogen oxides (NOx), total particulate matter less than 10 μm (PM-10 or PM), carbon monoxide (CO), and total hydrocarbon (THC).

The useful diesel engine life is 290.000 miles. The diesel engines must meet the emissions criteria throughout their useful life.

Aldehydes and poly-aromatic hydrocarbons (PAH) are not currently regulated. They may be regulated in the future in order to minimize the amount of toxins in the air.

The quantity of CO and THC derived from diesel engines is generally small. For this reason biodiesel fuels are considered for their impact upon PM and NOx .


2. Effects on Engine Performance2.5.1 Emissions in two-stroke engines For two-stroke engines without timing

changes or exhaust catalyst, the use of biodiesels cause the following changes in the emissions

1. NOx increases 2. PM, CO and THC decrease3. The soot (solid carbon fraction of PM)

decreases.



2.5.1Emissions in two-stroke engines(cont.)As the Oxygen content in the Biodiesel mixture increases, the NOx increases and the PM decreases.


2. Effects on Engine Performance2.5.1 Emissions in two-stroke

engines (cont.)From dynamometer and chassis tests on two-stroke engines, it was found that

The PM emissions depend on engine wear because worn engines slip oil past the rings to the air intake ports.

The NOx emissions are independent of engine type, injector technology, and wear.


2. Effects on Engine Performance2.5.1 Emissions in two-stroke engines

(cont.) Retarding the injection timing from 1-4o of older engines

run with soy biodiesel, the emissions of NOx were decreased to the level of the engine run with only diesel. At the same time, the PM emissions increased since the NOx were decreased.

This can be theoretically corrected by the presence of an oxidation catalyst. In practice the catalyst does not “capture” the liquid oil droplets and soot and cannot oxidize them.

The general conclusion is that biodiesel increases NOx and decreases hydrocarbons and CO. PM emissions decrease or stay constant for worn engines.


2. Effects on Engine Performance2.5.2 Emissions in four stroke-engines

Tests showed a similar behavior on emissions between four- and two-stroke engines.


2. Effects on Engine Performance2.5.2 Emissions in four stroke-engines (cont.)

However, the NOx emissions rise much slower with increasing oxygen content than in the two-stroke engines. This can be explained from the fact that modern four-stroke engines have sophisticated electronic controls that vary the fuel injection timing and other engine parameters to minimize emissions.

The PM emissions decrease more rapidly in four-stroke than in two-stroke engines. This can be attributed to the fact that four-stroke engines are more efficiently lubricated and thus, have lower liquid oil emissions, typically 30% lower than in the two-stroke.


2. Effects on Engine Performance2.5.2 Emissions in four stroke-engines

(cont.) The use of an oxidation catalyst yields enhanced

PM emissions reduction. The presence of such catalyst and the use of a biodiesel mixture can reduce the PM emissions by 50%.

One can reduce the NOx emissions by increasing the cetane number or decreasing the aromatics.

Retarding the injection timing produced similar results, except that the NOx emissions were smaller. At the same time the PM emissions increased.


2. Effects on Engine Performance2.6 Smoke opacity Tests showed that in two-stroke engines

the use of biodiesels did not reduce smoke opacity.

However, the combination of an oxidation catalyst and biodiesel produced a significant reduction in smoke opacity, especially in the lugging mode (lugging: engine at low speed under high load).


2. Effects on Engine Performance2.7Air toxins The use of biodiesels increases the

emission of liquid oil droplets from the lube oil or from the fuel.

There is a decrease of PAH emissions and in the mutagenic activity of the diesel exhaust with the use of biodiesels.


3. Measurements at the Karel de Grote-Hogeschool and at TEI of Thessaloniki3.1 Introduction

Measurements were made by the staff of Professor M. Pecqueur on two cars in the Combustion Laboratory in the Department of Industrial Sciences and Technology of the Karel de Grote-Hogeschool, Hoboken, Belgium. Similar measurements were done by the staff of Professor John Triandafyllis in the Department of Vehicles at TEI of Thessaloniki on one car. The cars were run under full load at 30, 50, 90 and 120 km/h speeds.


Bio-fuels used

Two bio-fuels were chosen to be converted chemically to bio-diesels:

Cottonseed oil, which was produced in Macedonia, Greece.

Used cooking oils which were collected in the city of Antwerp, Belgium.

The conversion to bio-diesels was accomplished by Professor Serge Tavernier in the Department of Industrial Sciences and Technology of the Karel de Grote-Hogeschool, Hoboken, Belgium.


3. Investigation goals

Performance of the diesel engines run with the bio-diesel mixtures as compared to their performance run only with diesel.

Two fuel temperatures were used, at 20oC and at 40oC in order to investigate the effect of the fuel temperature.

The engines were run at two different values of injection timing, -5o and +5o in order to investigate the effect of the injection timing upon NOx and soot in the exhaust gases.


Investigation goals

TO COMPARE THE EMISSIONS OF PM, NOx AND CO2 BETWEEN DIRECT AND INDIRECT IGNITION ENGINES FUELED BY THE SAME METHYLESTER MIXTURES.


TEST VEHICLESCharacteristics VOLVO V70 FORD

TRANSIT FORD

ESCORT Injection diesel direct direct indirect

Engine size, liters 2.5 2.5 1.6 Max Power (kw)

at RPM 103

at 4000 74

at 4000 40

at 4800 Compression

ratio 20.5:1 18.3:1 21.5:1

Turbocharged Yes No No EGR Yes Yes No

Engine management

system

ECU No No


TEST CONDITIONS IN THE DYNAMOMETER

VOLVO FORD TRANSIENT

FORD ESCORT

Second gear

27 kw at 1780 RPM

26 kw at 1930 RPM

15 kw at 1867 RPM

Third gear

28 kw at 1900 RPM

27 kw at 2050 RPM

15.6 kw at 2091 RPM

Fourth gear

41 kw at 3430 RPM

28 kw at 2730 RPM

20.2 kw at 2749 RPM


TEST EQUIPMENTEquipment Greek lab. Belgian lab.

Chassis dynamometer

Cartec AHS Prueftechnik

Prefilter Signal 351X Own design Gas Analyzer Andros 6800 Hermann HGA 500 Smoke Meter Bosch Opacimeter

RTM 430 SPX Dieseltune DX 230 Digital Smoke

meter


PerformanceVOLVO diesel engine

FUEL TEMP. 20C 40C

ENGINE POWER, kW

TORQUE, Nm RPM

ENGINE POWER, kW

MAX.TORQUE, Nm RPM

DIESEL 47 130 3486 46 125 3484 B10COTTON 47 131 3445 48 133 3475 B50COTTON 49 130 3567 48 136 3378 B100COTTON 49 132 3499 49 132 3500 DIESEL 46 125 3484 46 125 3484 B10FR.OIL 49 138 3364 49 138 3364 B50FR.OIL 48 131 3502 48 131 3502 B100FR.OIL 48 134 3444 48 134 3444


PerformanceFORD diesel engine

FUEL TEMP. 40C

IGNITION TIMING -5o +5o

ENGINE POWER, kW

TORQUE, Nm RPM

ENGINE POWER, kW

MAX.TORQUE, Nm RPM

DIESEL 36 136 2563 38 129 2829 B10FR.OIL 40 149 2515 36 125 2786 B50FR.OIL 40 150 2498 35 118 2862 B100FR.OIL 38 146 2519 37 128 2793


Effect of fuel temperature

EFFECT OF FUEL TEMP.

050

100150200250300350400450500

0 50 100 150

SPEED, km/h

SOO

T, m

g/m

3

40C-B100COTTON

20C-B100COTTON

40C-B10COTTON

20C-B10COTTON

EFFECT OF FUEL TEMP.

0 100 200 300 400 500 600 700 800 900

1000

0 20 40 60 80 100 120 140 SPEED, km/h

NOx, ppm

20C- B100COTTON 40C- B100COTTON 20C-B10COTTON

40C-B10COTTON


Effect of injection timing

EFFECT OF INJECTION TIMING at 30 km/h

0200400600800

1000

NOx,

ppm

-55FactoryValue

EFFECT OF INJECTION TIMING at 30 km/h

050

100150

SOO

T, m

g/m

3

-55FactoryValue


Effect of bio-diesel content

NOx vs. SPEEDFUEL TEMP. 40C

0100200300400500600700800900

1000

0 50 100 150

SPEED, km/h

NO

x, pp

m

DIESELB10COTTONB20COTTONB30COTTONB40COTTONB50COTTONB100COTTON

SOOT vs. SPEEDFUEL TEMP. 40C

0100200300400500600700

0 50 100 150

SPEED, km/h

SOO

T, m

g/m

3 DIESEL

B10COTTON

B20COTTON

B30COTTON

B40COTTON

B50COTTON

B100COTTON


Conclusions The conversion of the pure cottonseed oil and of the

used cooking oil into bio-diesel produced fuel that at 40oc exhibited excellent properties, especially in the value of their viscosity that approached that of diesel. With the mixtures of these two bio-diesels with diesel as fuel, both cars ran smoothly, even at 100% bio-diesel.

The chassis measurements at full load showed a 10% increase in engine power when run with the mixtures of bio-diesel.

The fuel temperature change did not affect the power measurements. There was a small increase in the soot and NOx values when the fuel temperature increased.


Conclusions With increasing bio-diesel content the soot values

dramatically decrease as compared to pure diesel as a fuel; the soot value was measured at 601 mg/m3 with diesel as a fuel as compared to 174,45 mg/m3 with B100 cottonseed bio-diesel.

The injection timing was changed from its factory value by 5o , delaying it and advancing it. There was an increase in soot and a decrease in the NOx values with advanced timing as compared to delayed timing.


TEST RESULTSPM comparison

0

100

200

300

400

500

600

Volvo 27Kw at 1780 RPM Escort 15Kw at 1867RPM

Volvo 28Kw at 1900 RPM Escort 15,6Kw at 2091RPM

Volvo 41 Kw at 3430 RPM Escort 20,2Kw at2749 RPM

mg/m³

Escort Diesel Volvo Diesel Escort B10 cotton Volvo B10 Cotton Escort B20 cottonVolvo B20 cotton Escort B30 Cotton Volvo B30 cotton Escort B40 cotton Volvo B40 CottonEscort B50 Cotton Volvo B50 cotton Escort B100 Cotton Volvo B100 Cotton

PM comparison

0

50

100

150

200

250

Transit 26Kw at 1930 RPM Escort 15Kw at 1867RPM

Transit 27Kw at 2050 RPM Escort 15,6Kw at2091 RPM

Transit 28 Kw at 2730 RPM Escort 20,2Kw at2749 RPM

mg/m³

Escort Diesel Transit Diesel Escort B10 cotton Transit B10 Cotton Escort B30 Cotton Transit B30 cotton Escort B50 Cotton Transit B50 cottonEscort B100 Cotton Transit B100 Cotton


TEST RESULTSNOX comparison

0

100

200

300

400

500

600

700

800

900

1000


Volvo 28Kw at 1900 RPM Escort 15,6Kw at 2091RPM


PPM


NOX comparison

0

100

200

300

400

500

600

700

800




PPM

Escort Diesel Transit Diesel Escort B10 Cotton Transit B10 CottonEscort B30 Cotton Transit B30 Cotton Escort B50 Cotton Transit B50 CottonEscort B100 Cotton Transit B100 Cotton


TEST RESULTSCO2 comparison

9,500

10,000

10,500

11,000

11,500

12,000

12,500


Volvo 28Kw at 1900 RPM Escort 15,6Kw at2091 RPM


Vol%


CO2 comparison

0,000

2,000

4,000

6,000

8,000

10,000

12,000

14,000




Vol%

Escort Diesel Transit Diesel Escort B10 Cotton Transit B10 CottonEscort B30 Cotton Transit B30 Cotton Escort B50 Cotton Transit B50 CottonEscort B100 Cotton Transit B100 Cotton


CONCLUSIONS PM emissions are consistently lower for all biodiesel

blends as compared to neat diesel. This decrease is more pronounced at lower power levels.

NOX emissions are consistently higher for all biodiesel blends as compared to neat diesel. This increase is more pronounced at higher power levels. NOX emissions increase in the Volvo and Ford Transit, but they do not vary appreciably in the Ford Escort.

CO2 emissions with all blends are consistently lower in the VOLVO engine, increase in the FORD ESCORT and do not vary appreciably in the FORD TRANSIT engine when compared to neat diesel, except at the fourth gear.


DIRECT vs. INDIRECT With regards to lower NOX emissions in the Ford Escort

it should be noted that the combustion temperature in an IDI engine is lower than in a DI engine due to higher heat losses in the area of the prechamber, and therefore NOX emissions are reduced.

Other reasons for explaining the data differences are the presence of an ECU management system in the VOLVO, the EGR system for the recirculation of the exhaust gases in the VOLVO and FORD TRANSIT engines and the absence of an ECU or EGR system in the Greek FORD ESCORT.


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Documents

Green Fuels and their impact on the performance and the exhaust gases in Diesel Engines