Performance and Emission Study of a PCCI-DI Engine Fuelled by Diethyl Ether-Biodiesel-Diesel Blends

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An Experimental Study on the Performance and Emission Characteristics of PCCI- DI Engine Fuelled with Diethyl ether-Biodiesel-Diesel Blends

S. Srihari, S. Thirumalini, K. Prashanth

PII: S0960-1481(17)30015-0

DOI: 10.1016/j.renene.2017.01.015

Reference: RENE 8453

To appear in: Renewable Energy

Received Date: 02 July 2016 Revised Date: 04 January 2017 Accepted Date: 06 January 2017

Please cite this article as: S. Srihari, S. Thirumalini, K. Prashanth, An Experimental Study on the Performance and Emission Characteristics of PCCI-DI Engine Fuelled with Diethyl ether-Biodiesel- Diesel Blends, Renewable Energy (2017), doi: 10.1016/j.renene.2017.01.015

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HIGHLIGHTS

 Performance of PCCI-DI engine with DEE, CSO biodiesel and diesel blends was studied.

 NO

_x

, smoke and HC emissions are lower for 65% Diesel-20% Biodiesel- 15% Diethyl ether blend.

 Increase of Brake thermal efficiency of 13% was observed for the blend

in PCCI-DI mode.

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1

An Experimental Study on the Performance and

2

Emission Characteristics of PCCI-DI Engine Fuelled

3

with Diethyl ether-Biodiesel-Diesel Blends

4 S.Srihari^1*, S.Thirumalini², K.Prashanth³

5 ^1*Assistant Professor, Dept. of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita 6 Vishwa Vidyapeetham, Amrita University, India, and [email protected]

7 ²Professor, Dept. of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita Vishwa 8 Vidyapeetham, Amrita University, India, and [email protected]

9 ³PG Scholar , Dept. of Mechanical Engineering, Amrita School of Engineering, Coimbatore, Amrita 10 VishwaVidyapeetham, Amrita University, India and [email protected]

11

12 Abstract

13 The possible depletion of fossil fuels has created the need for alternate fuels 14 worldwide and engine developers are prompted to investigate the viability of such fuels.

15 Further, stringent emission norms have created the need for low emission engines. The 16 objective of this work is to evaluate the effect of diethyl ether in biodiesel-diesel blends on 17 the performance and emission characteristics in a Premixed Charge Compression Ignition- 18 Direct Injection (PCCI-DI) engine. Biodiesel obtained from cotton seed oil is used for this 19 study. PCCI-DI engine is operated with main injection and pilot injections with varying 20 percentages of DEE along with 20% biodiesel blended with neat diesel. The emission 21 characteristics show a discernible reduction in emissions (NOx, CO and HC) vis-a-vis 22 biodiesel-diesel blends. Benefits like reduction in the quantum of smoke produced and 23 improvement in Brake thermal efficiency are also noticed in specific cases.

24 Keywords: Emission; Cottonseed biodiesel; Diethyl ether; Premixed charge; Oxygenated 25 additive

26 1. Introduction

27 Newer methods of combustion have been found to reduce emissions in diesel engines 28 considerably. One among them is the Premixed Charge Compression Ignition (PCCI) which 29 is a type of Homogenous Charge Compression Ignition (HCCI) [1-3]. In this, part of the fuel 30 is injected into a vaporiser unit utilising a pilot injector. The vaporized fuel is inducted into 31 the inlet manifold and the rest of the fuel is injected using the main injector (direct injection) 32 [4,5].The PCCI combustion can be controlled and the engines operating regime can be 33 extended. This also has the capability for the simultaneous reduction of NOx and soot [6,7].

34 External mixture formation techniques do not require any modification in the 35 injection system of the engine [8]. One significant advantage is the availability of time for 36 mixing the fuel and air leading to a more homogenous mixture. The method adopted to 37 achieve this is by injecting fuel directly into the intake manifold. However, it has the 38 disadvantage of increased chances of wall wetting [9]. The other method is to induct 39 vaporized fuel produced using a vaporizer and pilot injector. This facilitates better mixing of 40 fuel and air with minimal wall wetting [10].

41 The limitations of HCCI engines are its limited operating range and the difficulty to 42 control combustion parameters. The limited operating range is due to the high rates of 43 pressure rise at high loads and misfiring at low loads, specifically when the charge is too lean.

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1 Controlling combustion is a challenge since the start of combustion depends on various 2 factors including fuel properties, auto ignition characteristics, homogeneity of the fuel air 3 mixture, and temperature and pressure conditions within the combustion chamber [11].

4 A Premixed Charge Compression Ignition Engine with Direct Injection (PCCI-DI) 5 will help overcome these limitations to some extent [12]. A pilot injector injects a small 6 quantity of fuel directly into the fuel vaporizer which is connected to intake manifold. A 7 premixed charge of this fuel and air is inducted into the cylinder and rest of the fuel is 8 injected through the main injector of the engine. The advantage is that it can be used as a dual 9 fuel engine capable of controlling the combustion characteristics by using different fuels for 10 the pilot and main injections [13]. Among various fuels that can be used, diethyl ether (DEE), 11 ethanol, methanol in diesel blends show promise as an alternative fuel, mainly due to its 12 renewable nature. These blends indicate the possibility of simultaneous reduction of NOx and 13 soot. Due to its lower heat content, the peak combustion temperatures tend to reduce leading 14 to a reduction in NOx. In addition, due to its higher oxygen content, soot is also likely to 15 reduce [14-16]. It is reported that the lower energy release rates of these blends help extend 16 the operating range of the engine [17]. The fuel lubricity for these blends has to be taken into 17 account since it decreases with increasing percentage of ethanol, which may affect the 18 engine’s fuel injection system in the long run [18].

19 Biodiesel fuel is a renewable source of energy and can be obtained from plants, 20 animal feedstock, biomass etc. [19-21]. It is seen that inedible cottonseed oil converted to 21 biodiesel is a good alternative [22-24]. Cottonseed(CSO) biodiesel is obtained using trans- 22 esterification process by adding sodium hydroxide (NaOH) as catalyst and methanol as 23 reagent [25-27].The diesel fuel blended with 20% biodiesel in PCCI engine is considered 24 [28,29]. The possible disadvantages due to the addition of biodiesel could be increased fuel 25 consumption and HC emissions [30,31]. S. Ki Yoon et al [32] highlight the effects of canola 26 oil biodiesel-diesel blends from 10%, 20% and 30% in diesel engine with exhaust gas 27 recirculation (EGR). It is seen that considerable reduction in CO and PM emissions is 28 achieved, whereas BSFC and NOx show an increase. It is reported that the CO and PM 29 emissions decrease with increase in biodiesel content in the biodiesel-diesel blend.

30 Nevertheless, an increase in biodiesel content increases the NOx emissions [33]. It is seen that 31 an increase in brake thermal efficiency of 3% to 8% can also be achieved with biodiesel 32 blends [33,34]. D.H. Qi et al [35] highlight the effect of DEE and ethanol additives in a 33 soybean biodiesel-diesel blended diesel engine. Here, it is seen that an addition of 5% diethyl 34 ether to a 25% biodiesel-diesel blend improves the stability without any modifications to the 35 engine. In addition to it, BSFC is also seen decreased. The higher oxygen content and the 36 property of high volatility of DEE and ethanol make them potential contenders for use as an 37 additive in biodiesel-diesel blends. It is also observed that addition of DEE in the biodiesel 38 diesel blend reduces smoke and NO_x at higher loads.

39 The aforesaid limitations of biodiesel in PCCI engines, can be overcome by the 40 addition of additives such as DEE which has the potential qualities of high cetane number, 41 low auto ignition temperature and low viscosity [36-38]. The reduction in exhaust emissions 42 with addition of DEE in biodiesel is also reported by many authors [39-46]. Here, it is seen 43 that the performance and emission characteristics of DEE-CSO biodiesel-diesel blends in 44 PCCI-DI engine are not investigated and have the potential to be explored.

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1 In the present work diesel blended with 20% CSO biodiesel are tested with varying 2 percentages of DEE additive. Three cases are specifically chosen viz. 5%, 10% and 15%. The 3 blends are represented as DBD-1for 75%D-20%BD-5%DEE; DBD-2 for 70%D-20%BD- 4 10%DEE; and DBD-3 for 65%D-20%BD-15% DEE. The experiments are conducted in a 5 PCCI-DI engine for different loading conditions. The performance and emissions are 6 compared with 20% CSO biodiesel-80% diesel blend (80D-20BD) and neat diesel (D-D).

7 The performance and emissions parameters looked into are: The brake specific fuel 8 consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature, cylinder 9 pressure, NOx, CO, HC and smoke concentration.

10 2. Materials and methods

11 The experiment is performed on a single cylinder, four stroke direct injection diesel engine 12 coupled with an eddy current dynamometer, the schematic of which is shown in Figure 1. A 13 vaporizer unit is attached to the engine inlet manifold. A pilot injector (solenoid injector) 14 injects the secondary fuel into the vaporizer. The injection pressures for the main and pilot 15 injections are 180 bar and 3.5 bar respectively.

16

17 Figure 1. Schematic layout of experimental setup

18 The actual experimental setup is shown in Figure 2. A load cell attached to the eddy current 19 dynamometer is used to measure the load. A Kistler piezoelectric pressure transducer coupled 20 with a charge amplifier mounted on the cylinder head is used to acquire in-cylinder pressure 21 data. The pressure data is measured for 100 working cycles and the average is taken for 22 analysis. The crank angle encoder is mounted on the crankshaft as shown in Figure 1. The 23 pressure transducer has the capability to measure upto 250 bar and the crank angle encoder is 24 having a resolution of 0.1°. The secondary fuel is injected at a constant rate of 0.06 gm/s into 25 the fuel vaporizer, irrespective of the speed and load conditions. The pilot injector which 26 injects the secondary fuel is controlled by an electronic control unit (ECU). An ATmega328P 27 processor duly programmed is used in the ECU to control the fuel injection. The main fuel 28 injection is controlled by fuel injection pump and the flow rate is measured using column- 29 tube manometer. The crank angle data is acquired using a data acquisition system.

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1

2 Figure 2. Engine test bed

3 Specifications of the engine chosen for the study are given in Table 1. Resolution and range 4 of the exhaust gas analyser for the emission species are given in Table 2. Uncertainties of 5 various measured and calculated parameters are given in Table 3. The fuel properties are 6 shown in Table 4.

7 Table 1

8 Specifications of engine

Model Greaves GL-400

Bore 63mm

Stroke 86mm

Displacement 395cm³

Maximum engine output (kW @rpm) 5.5kW @3600rpm

Compression ratio 18:1

9

10 Table 2

11 Specification details of the gas analyzer and smoke meter

Model of the gas analyser Pollutant Range Resolution

MEXA 584L CO 0-10 % vol. 0.01 % vol.

,, HC 0-20000 ppm vol. 1 ppm vol.

,, NOx 0-5000 ppm vol. 1 ppm vol.

Smoke Meter AVL 415S Smoke 0-10 FSN 0.001FSN

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1 Table 3

2 Uncertainties of measured and calculated parameters

S.No Parameter Percentage uncertainty

1. CO ±0.01

2. HC ±0.1

3. NOx ±0.1

4. BTE ±1%

5. BSFC ±1.5%

3

4 Table 4

5 Properties of fuels.

Properties/ Fuels Diesel Cottonseed

bio-diesel Diethyl ether

Density (kg/m³) 820 922 713

Calorific

value(kJ/kg) 44800 39500 33893

Cetane Number 49 89 125

Auto ignition

temperature(˚C) 210 380 160

Flash point (˚C) 46 205 45

Fire point (˚C) 52 228 44

Oxidation stability(hours) (ASTM D2274)

16 10 -

Acid Number(mg

KOH/g) - 0.04 -

Water and Residue

content(%Vol) - 0.05 0.5

Latent heat of vaporization (kJ/kg)

250 235 460

6

7 The experiment is conducted from no load to the maximum load of 14 Nm at 2000rpm.

8 Emissions such as CO, HC and NOx are measured using MEXA-584L emission gas analyser 9 and smoke with AVL 415S smoke meter. Cotton seed biodiesel is prepared by heating 1000 10 ml of oil up to 60^°C and adding 180 ml of methanol along with 4 grams of sodium hydroxide 11 (NaOH). The oil is stirred at a constant speed of 850 rpm for 2 hours after which the mixture 12 is allowed to settle for 10 hours for the reaction to complete. This enables the biodiesel and 13 the glycerol to get separated. Glycerol is removed and the remaining biodiesel is water 14 washed to remove soap and other water soluble substances. A maximum of 820 ml of cotton

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1 seed biodiesel can be obtained from 1 litre of raw cotton seed oil. The biodiesel is filtered 2 twice to remove the impurities and it is then heated to about 60°C to remove the water 3 particles. The experiment is conducted using this biodiesel for DBD-1, DBD-2, DBD-3 and 4 80D-20BD blends, and D-D in the PCCI-DI engine. Root-sum-square method [44] is used for 5 uncertainty calculations of observed data and is presented in Appendix A.

6 3. Results and Discussions 7 3.1 Emission characteristics

8 The emissions for different blends of DEE-CSO-diesel are observed and are compared with 9 that of 80D-20BD and D-D.

10 Figure 3 shows the comparison of NOx values for each blend from no load to maximum load 11 of 14 Nm at 2000 rpm. It is seen from the plot that the NOx levels for D-D and 80D-20BD are 12 considerably higher than the NO_x levels for DBD-2 and DBD-3 irrespective of the load 13 conditions. However, the DBD-1 blend doesn’t show any discernible reduction in NOx

14 emissions. The low NOx level of DBD-2 and DBD-3 could be mainly due to reduction in 15 combustion temperature with the addition of DEE. It is also seen that the increase in 16 percentage of DEE significantly decreases the NOx emissions. The main reason for this 17 phenomenon is mainly due to the increase in latent heat of vaporization of the blends with the 18 increasing percentage of DEE [40, 46]. Another reason could be the higher cetane number 19 achieved with the addition of DEE which in-turn improves the combustion quality. It is seen 20 that an average reduction of 29.6% and 22.3% are achieved for DBD-2 blend when compared 21 to 80D-20BD and D-D respectively. The corresponding reductions in NO_x level for the DBD- 22 3 blend are seen to be 42% and 46%.

23

24

0 0 . 5 1 1 . 5 2 2 . 5 3

0 50 100 150 200 250 300 350 400 450 500 550

D-D DBD-1 DBD-2 DBD-3 80D-20BD

BRAKE POWER (kW)

NOx (ppm)

25 Figure 3. Comparison of nitrogen oxides with brake power

26 The variation of CO emissions with brake power (BP) is shown in Figure 4. It is observed 27 that for the simple biodiesel-diesel blend, the CO emission is far higher than that of D-D for 28 all loads. Further DBD-1, DBD-2 and DBD-3 do not, in any way, produce any reduction in 29 CO emissions when compared to that of D-D and it almost remain at-par with D-D. However,

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1 it is seen that using DEE with the biodiesel-diesel blend is far better than using a simple 2 biodiesel-diesel blend.

3

4

0 0 . 5 1 1 . 5 2 2 . 5 3

0 0.02 0.04 0.06 0.08 0.1 0.12

BRAKE POWER (kW)

CO (%Vol)

5 Figure 4. Comparison of carbon monoxide with brake power

6 Figure 5 shows the variation of HC at various load conditions. The HC emissions are much 7 higher for biodiesel-diesel blend than that of a simple D-D for all loads. DBD-1 doesn’t give 8 a discernible improvement in HC emissions with that of simple D-D. However, DBD-2 and 9 DBD-3 are worth considering as the HC emissions are fairly low in the two cases when 10 compared to that of simple D-D. This could be due to the addition of DEE which tends to 11 support the combustion process. Here the fuel bound oxygen oxidizes the HC molecules 12 converting them into H2O and CO2 and thus facilitating complete combustion [40,32].As for 13 HC emissions, it is seen that a reduction of 15% and 40% can be achieved on an average with 14 DBD-3 blend when compared to that of D-D and 80D-20BD respectively.

15

16

0 0 . 5 1 1 . 5 2 2 . 5 3

0 5 10 15 20 25 30 35 40 45 50 55

BRAKE POWER (kW)

HC (ppm)

17 Figure 5. Comparison of hydrocarbon with brake power

18 Figure 6 shows variation of smoke concentration from the engine at various brake load 19 conditions. At very high loads the smoke level for all the blends are fairly lower than that of 20 simple D-D. But, at low and medium loads the smoke level seems to be almost the same for

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1 all the blends. Nevertheless, for DBD-2 and DBD-3 the smoke level is low for all the loads 2 when compared to that of other blends. Thus DBD-2 and DBD-3 can be considered as better 3 options as far as smoke concentration is concerned. Here, in the case of DBD-3 a reduction in 4 smoke concentration of 50% and 32% is observed when compared to that of D-D and 80D- 5 20BD at full load. The corresponding values for DBD-2 are 30% and 38.5%. The reason for 6 this reduction in smoke concentration can be attributed to the reduction in density due to the 7 addition of DEE and the corresponding altered spray pattern leading to better fuel-air mixing 8 process [46]. Another reason could be the absence of fuel rich zone in the cylinder that leads 9 to reduced smoke as is seen in the results obtained by D.H. Qi et al [35].

10

11

0 0 . 5 1 1 . 5 2 2 . 5 3

0 1 2 3 4 5 6

BRAKE POWER (kW)

SMOKE CONCENTRATION (FSN)

12 Figure 6. Comparison of smoke with brake power

13 3.2 Performance Characteristics

14 Figure 7 shows the brake specific fuel consumption for various load conditions and blends.

15 At full load DBD-3 is seen to have the minimum BSFC (0.2593 kg/kWh) and D-D the 16 maximum (0.3187 kg/kWh). The corresponding values for DBD-2, DBD-1 and 80D-20BD 17 are respectively 0.3124 kg/kWh, 0.3005 kg/kWh and 0.2593 kg/kWh. At half load the BSFCs 18 for DBD-3, DBD-2, DBD-1, 80D-20BD and D-D are respectively 0.3570 kg/kWh, 0.3784 19 kg/kWh, 0.3779 kg/kWh ,0.3377 kg/kWh and 0.3830 kg/kWh. Here, it is seen that BSFC for 20 DBD-3 is higher than that of 80D-20BD. A close perusal of the results shows that the BSFC 21 for all the blends are more or less close to each other for all the loads. However, excepting for 22 the full load condition the BSFC is more for DBD-3 than for D-D. This can be attributed to 23 lower calorific value of DBD-3 blend. This is one negative aspect of the DBD-3 blend. The 24 result obtained is also seen to follow the trends obtained by D.H. Qi et al [35].

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1

0 0 . 5 1 1 . 5 2 2 . 5 3

0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.750.8 0.85

BRAKE POWER (kW)

BSFC (kg/kWh)

2 Figure 7. Comparison of brake specific fuel consumption with brake power

3 Figure 8 shows the variation of exhaust gas temperature (EGT) with brake power. A 4 reduction in EGT is seen for 80D-20BD blend for all loads when compared to D-D. This is 5 because of the increase in ignition delay which is caused due to increase in the blend density.

6 Further, it takes a longer duration to vaporize the fuel in the pre-mixed combustion phase 7 which reduces the combustion temperature. Besides, the delayed heat release during the later 8 stage of combustion is another reason for the reduction in EGT. Early start of the combustion 9 due to shorter premixed combustion phase and lower calorific value can also lead to 10 reduction in exhaust gas temperature as is seen for the DEE blends [34].The decrease in EGT 11 is advantageous as it can increase the expansion work and life of the engine.

12

13

0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5

100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500

BRAKE POWER (kW)

EGT (°C)

14

15 Figure 8. Comparison of exhaust gas temperature with brake power

16 Figure 9 represents the variation in brake thermal efficiency with brake power for different 17 blends. It is seen that BTE of DBD-3 and 80D-20BD is greater than other biodiesel blends 18 irrespective of the load. Adding DEE to biodiesel-diesel blends decreases viscosity of the 19 blend and causes improvement in the spray pattern and atomization. The fine fuel particles

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1 mix thoroughly with partially premixed charge and thereby improve combustion [35,43]. It is 2 observed that for medium loads (1.5-2.5kW) BTE is slightly lower for DBD-3 than that of 3 80D-20BD. This reduction in BTE at medium loads for DBD-3 is in-line with the result 4 obtained by S. Sivalakshmi et al [40] and A.S. Ramadhas et al [46]. But, BTE for DBD-3 5 shows a higher value for low loads and high loads. The BTE for DBD-1 and DBD-2 remains 6 at par with that of D-D for all loads.

7

0 0 . 5 1 1 . 5 2 2 . 5 3

0 5 10 15 20 25 30 35

BRAKE POWER (kW)

BRAKE THERMAL EFFICIENCY (%)

8 Figure 9. Comparison of brake thermal efficiency with brake power 9

10

11 Figure 10. Comparison of in-cylinder pressure with brake power

12 Figure 10 shows the variation of in-cylinder pressure with crank angle for 2000 rpm at 7 Nm 13 load condition. Advancement in the start of combustion for different blends of DEE is 14 observed. This is due to the low auto ignition temperature and high vaporization rate of 15 diethyl ether. An increase in peak pressure is observed for all the DEE blends when compared 16 to that of D-D and 80D-20BD. A reduction in ignition delay is also observed for all the

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1 slight knocking tendency in the cylinder is also seen and this could be due to the higher heat 2 release rate.

3

4

64.092 63.936

62.084

64.199

60.126

5 Figure 11. Comparison of peak cylinder pressure at 7 Nm for the blends

6 Figure 11 indicates the peak in-cylinder pressure for the different fuel blends at a load of 7 7 Nm at 2000rpm. The highest peak pressure of 64.199 bar is observed for DBD-3 blend. This 8 could be due to increase in peak temperature, higher vaporization rate and higher premixed 9 combustion heat release rate when compared to that of other blends. The peak pressure 10 obtained for the DBD-3 blend at this load is found to be 6% more than that of 80D-20BD 11 blend and 0.16% more than that of D-D.

12 4. Conclusion

13 The following conclusions are made from the tests conducted on the PCCI-DI engine with 14 different blends of diesel, biodiesel and DEE.

15  The peak cylinder pressure achieved for DBD-3 blend is higher than that obtained for

16 other blends.

17  The fuel properties, viz. density, cetane number and auto ignition temperature are 18 seen improved with the addition of DEE.

19  Significant reduction in NOx, HC and CO emission is seen for DBD-3 blend.

20  The smoke emission is found to be less for DBD-3 when compared to other blends.

21  BSFC is seen higher for DEE blend when compared to that of D-D and 80D-20BD.

22  BTE for DBD-3 blend is found to be higher than that of D-D, DBD-1 and DBD-2 for 23 all the loads.

24  Excepting for medium loads DBD-3 gives a better efficiency than that of 80D-20BD.

25 Appendix A

26 a) Sample calculation

27 i) Brake power (BP) =2 NWr/60 = 2 x x 2000 x 37.5 x 0.2/ 60000𝜋 𝜋

28 =1.532 kW

29

30 ii) Calculation of fuel consumption (FC)

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1 = V x Specific gravity of fuel x 3600/ (t x density of water)

2 =40 x 0.820x3600/ (227.76 x 1000) = 0.51844 kg/h

3

4 iii) Calculation of fuel power (FP) = FC x CV/3600 = 0.51844 x 43500/ 3600

5 = 6.264 kW

6

7 iv) Calculation of brake thermal efficiency = (BP/FP) x 100

8 = (1.532/6.264) x 100 = 24.457 %

9 b) Uncertainty analysis 10

11 i) Calculation of uncertainty in brake power

12 ∆BP/BP = {[∆W/W]²+ [∆N/N]²+ [∆r/r]²}^1/2 Eq. (A.1) 13 ii) Calculation of uncertainty in fuel consumption

14 ∆FC/FC = {[∆V/V]²+ [∆t/t]²}^1/2 Eq. (A.2) 15 iii) Calculation of uncertainty in fuel power

16 ∆FP/FP = {[∆V/V]²+ [∆t/t]²}^1/2 Eq. (A.3) 17 iv) Calculation of uncertainty in fuel consumption

18 ∆BTE/BTE = {[∆BP/BP]²+ [∆FC/FC]²}^1/2 Eq. (A.4) 19

20 c) Sample calculation for uncertainty

21 The measuring devices were chosen in order to keep the experimental uncertainties as 22 minimum as possible. The probable errors in the stop watch (∆t), speed indicator (∆N), 23 graduated burette (∆V), measuring scale (∆r) and strain gauge type load cell (∆W) are 24 0.01sec, 5 rpm, 0.1 cc, 0.001 m and 0.1 kg respectively. The equation from (A.1) to (A.4) 25 was used for the uncertainty calculations.

26

27 i) Uncertainty in BP = {[0.1/10]²+[5/2000]²+[0.001/0.2]²}^1/2= 0.011456 kW

28 =1.14%

29 ii) Uncertainty in FC = {[0.1/40]²+[0.01/227.76]²}^1/2= 0.00253 kg/h = 1.5 % 30

31 iii) Uncertainty in FP = {[0.1/40]²+[0.01/227.76]²}^1/2= 0.00253 kg/h = 1.5 % 32

33 iv) Uncertainty in BTE = {[0.011456]²+[0.01/0.00253]²}^1/2 = 0.01174 = ± 1 % 34

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