Renewable Energy Technology 3(2+1)

Lesson 31. Engine testing for biodiesel blends

31.2. Performance evaluation of biodiesel blends in Power tiller engine under laboratory condition

An engine test rig was developed specifically for the purpose of testing Power tiller engine. The test rig used an electrical dynamometer consisting of an AC generator and load created by a panel of incandescent bulbs. The torque input into the dynamometer was measured by a transmission torque sensor.  The rated speed of the engine is 2200 rpm and that for the dynamometer is 1500 rpm.  A ‘V” belt speed reduction device was provided between engine output shaft and the dynamometer input shaft. The engine was modified by mounting three grove V belt pulley of 110 mm pitch circle diameter at the center of the fly wheel in place of the original pulley. The engine, V belt drive, torque transducer and alternator were mounted on a frame structure.

The drive from the engine pulley was transmitted to a speed reduction pulley on the dynamometer shaft. The larger pulley had a pitch circle diameter of 160 mm, so as to provide a speed reduction of 1:1.45. The driven pulley was mounted on a 40 mm diameter shaft which was supported on a two pedestal bearings. The bearings in turn were mounted to support brackets welded on the main frame. The torque transducer used for measuring the line torque was mounted on separate pedestal in line with the dynamometer shaft. The pulley shaft torque transducer and alternator were coupled through suitable flange couplings. The overall view of the experimental setup is shown in Fig. 7.

The Power tiller engine performance was evaluated using IS test code 9935-1981, the test was carried out at two different conditions of the engines.

1. Torque – Speed test at varying throttle setting

2. Varying load test

31.2.1 Torque–Speed test at varying throttle setting

During this test, the power, torque and fuel consumption were measured as a function of speed by gradually loading after stabilized working condition of the engine. Stable operation conditions were maintained for a minimum period of 5 minute at each load setting before beginning the test measurement. The no-load engine speed before and after every test was recorded to verify that there is no change in throttle setting.
The Torque - Speed curve of power tiller engine was recorded with three high idle speeds of   2200, 2000 and 1800 rpm under different load levels for all the selected biodiesel blends.

After the test, the following characteristics curves of the engine were drawn

1. Power as a function of engine speed

2. Torque as a function of engine speed

3. SFC as a function of engine speed

4. Fuel consumption as function of engine speed

(i) Torque Vs Speed

The maximum torque at 2200 rpm is 34.15 for D100 but it gradually reduced with increased proportion of biodiesel in the blend and decreases to around 32 Nm.
The different blend shows the reduction of 2-5 per cent torque as compare to diesel. Similarly reduction in maximum torque values was observed at 2000 and 1800 rpm. The maximum torque at rated Power tiller engine speed of 2200 rpm decreased.

(ii)  Power Vs Torque

The maximum power obtained at any throttle setting is gradually reduced as the blend become richer in biodiesel. The power at 2200 rpm is differenced by 8.1 per cent for D100 and B100 while the corresponding changes at 2000 and 1800 rpm where
3.8 and 8.1 per cent respectively.

(iii)  SFC Vs Speed

The important observation from the engine testing is the increase in SFC with increase in blend ratio. The minimum SFC for D100 is 0.232 kg/ kWh while it increased to 0.248, 0.25, 0.24, 0.266 and 0.277 as the blend ratio was increased from D100 to B100. The primary reason for the increased in SFC may be the lower calorific value of the fuel as the blend ratio is increased.

The behavior of the engine when operating with different blends was presented in Table 5 and Fig 8 to 13.

Table 5 Torque, Power, SFC and FC Vs Speed of power tiller engine for variable throttle tests

Throttle speed, rpm	Torque Vs Speed			Power Vs Speed		SFC Vs Speed		FC Vs Speed
	Max. T, Nm (1)	Max T-S, rpm (2)	T/100 rpm (3)	Max P, kW (4)	Max P-S, rpm (5)	Min. SFC, kg/kWh (6)	Min. SFC-S, kg/kWh (7)	Max. FC, l/h (8)	Max. FC-S, rpm (9)
D100 fuel
2200	34.15	1933	25.60	6.91	1933	0.232	2042	2.11	1864
2000	33.25	1735	17.71	6.04	1735	0.227	1814	1.82	1753
1800	30.10	1604	21.05	5.06	1604	0.230	1604	1.44	1604
B20 blend
2200	33.31	1853	21.44	6.65	1979	0.248	2040	2.04	2041
2000	33.78	1667	17.12	6.1	1763	0.23	1829	1.78	1667
1800	31.11	1533	23.11	5.24	1638	0.227	1661	1.50	1638
B40 blend
2200	32.46	1764	25.77	6.39	1824	0.250	1824	2.0	1978
2000	32.19	1621	23.13	5.89	1752	0.251	1859	1.78	1752
1800	28.45	1558	17.62	4.76	1652	0.249	1647	1.14	1532
B60 blend
2200	32.28	1758	18.15	6.79	2017	0.240	1758	2.04	2017
2000	31.04	1742	12.52	5.66	1742	0.259	1899	1.74	1742
1800	29.35	1608	16.89	4.95	1608	0.177	1614	1.56	1608
B80 blend
2200	33.30	1835	16.30	6.51	1961	0.266	1998	2.04	1961
2000	32.72	1728	22.23	6.01	1804	0.254	1804	1.78	1805
1800	30.36	1519	1704	4.96	1625	0.266	1550	1.48	1625
B100 blend
2200	32.48	1868	23.67	6.35	1868	0.277	1789	2.04	1969
2000	32.19	1722	17.12	5.81	1722	0.272	1815	1.83	1722
1800	29.21	1518	18.60	4.65	1518	0.273	1630	1.59	1513

1- Maximum Torque, Nm

2- Speed Corresponding value of Maximum Torque, rpm

3- Torque/100 rpm

4- Maximum power, kWh

5- Speed Corresponding value of Maximum Power, rpm

6- Minimum value of Specific fuel consumption, kg/kWh

7- Speed Corresponding value of Minimum Specific fuel consumption, rpm

8- Maximum Fuel consumption, l/h

9- Speed Corresponding value of Maximum Fuel consumption, rpm

31.2.2 Varying load test

The variable load test was conducted as per IS test cod 9935-1981. During this test, speed torque and hourly fuel consumption were measured as a function of power. The test was conducted in following sequence of loading and each load state was maintained for 20 minute duration.

1. 85 per cent of the load corresponding to the load at maximum power

2. Minimum load

3. 50 per cent of the load defined at (a)

4. Load corresponding to the load at maximum power

5. 25 per cent of the load at maximum power (a), and

6. 75 per cent of the load defined at (a)

The variable load test was conducted at engine rated speed of 2200 rpm for all blend levels throughout the experiment as per SAE J708c- “Agriculture tractor test code” of Society of Automotive engineers and IS 9935-1981-Test code for Power tiller. The power, torque and fuel consumption were measured as a function of power by gradually loading after stabilized working condition of the engine are reached. The performances of the engine under varying load test with different blends are tabulated from Table 6 to Table 11 and shown in Fig.14.

Table 6 Engine performance during variable load test for D100 at 2200 rpm idle speed

 

Table 7 Engine performance during variable load test for B20 biodiesel blend at  2200 rpm idle speed

 

Table 8 Engine performance during variable load test for B40 biodiesel blend at 200 rpm idle speed

 

Table 9 Engine performance during variable load test for B60 biodiesel blend at 2200 rpm idle speed

 

 Table 10 Engine performance during variable load test for B80 biodiesel blend at 2200 rpm idle speed

 

Table 11 Engine performance during variable load test of B100 at 2200rpm idle speed

 

31.2.3. Performance of biodiesel run power tiller under field condition

To measure the average fuel consumption rate of the power tiller engine during field operation, the field test of the power tiller was conducted. Fuel consumption for rotavator operation under dry soil condition was measured. The field trials were conducted at Eastern block of Tamil Nadu Agricultural University campus.

The power tiller engine was run in the field by marking a known distance and operated at three different Low speed gears viz., L- I, II & III.  In each gear, the power tiller was operated for 45 minutes. The area covered, forward travel speed and time taken for tillage in each forward speed was recorded.  The field test was run with B40 biodiesel blend and diesel fuel.  The performance of the power tiller is tabulated in Table 11.13. The field view of the power tiller under test is given in Fig.15.

It was observed that the fuel consumption rate slightly decreased when the forward speed was increased from 1.5 to 2.13 km/h. However when forward speed was increased to 4.04 km/h (gear III) the fuel consumption was rapidly increased. The comparison of fuel consumption between D100 and B40 shows that the  consumption of B40 fuel l/h was 17.2 per cent more than D100 at 1.5 km/h (I gear), While this value decreased to 15.74 per cent at  2.13 km/h (II gear) and 6.02 per cent at 4.40 km/h (III gear).

It is seen that as the speed is increased the fuel consumption per hectare is reduced from 7.68 at I gear to 4.1 l/ha at III gear for diesel fuel. The fuel consumption per hectare for B40 is 8.55 l/ha at I gear but reduced to 4.94 l/ha at III gear. This clearly shows that the fuel consumption per ha is 20 per cent more for B40 than diesel. The fuel consumption per hectare reduces rapidly when the forward speed is increased and confirming the “Gear-up throttle-down” strategy for enhancing fuel performance for power tillers.

 

Table 12 Fuel performance of power tiller engine in rotary tillage operation with D100 and B40 biodiesel blend

Gear selection	D100				B40
	Forward speed, km/h	Area covered, ha/h	Fuel consumption		Forward speed, km/h	Area covered,  ha/h	Fuel consumption
			l/h	l/ha			l/h	l/ha
L-I	1.5	0.151	1.16	7.68	1.58	0.159	1.36	8.55
L- II	2.13	0.213	1.08	5.07	2.1	0.207	1.25	6.03
L- III	4.04	0.405	1.66	4.1	3.56	0.356	1.76	4.94

 

31.2.4. Engine emission while operation with biodiesel blend

The Multi gas analyzer and Diesel Smoke tester were procured from M/s. Nevco Engineers, Chennai, Tamil Nadu. The specifications of the equipments are given below.

i) Flue Gas Analyser Model: KM 9106 (Quintox) – O₂ (0-25%), CO 0-10%, CO₂ (0-20%), CO/CO₂ (Calculated) Make: M/s. Kane International Ltd., U.K.               Optional:  NO (0 - 5000 ppm), NO₂ (0 - 1000 ppm), SO₂ (0 - 5000ppm).

ii) Smoke meter – Diesel smoke tester Model: DS-2000; Make: Koen Co., Ltd, Korea. Range: 0.0 to 100%

In the present investigation the power tiller engine emissions were measured during the variable load test. The data recorded during each set of trail for different blends is given in Table 13 and is shown in Fig 16 to 19.  The recording flue gas analyzer model KM 9106 of Quintox was used to measure the exhaust emissions. The particulate emission was measured using Koen DC-2000 model of Diesel smoke tester (smoke density meter).

(i) Carbon dioxide (CO₂) emission

It is observed that D100 and B20 exhibit gradual increase of CO₂ concentration in the 3 - 7 kW range. However B80 and B100 show a steep increase in the 3-4.5 kW range then drops by around 1%.  It is interesting to note that the CO₂% of all blends almost converges to a value of 7-8% at a load of 7 kW. From these patterns it can be concluded that up to about 50% of the rated load there is no significant difference between the blends in terms of CO₂ concentration. Fuels with lesser biodiesel per cent show lesser CO₂ emission at loads of 6-7 kW. The CO₂ emission converges towards 7-8%.

(ii) Carbon monoxide (CO) emission

It is observed that there is no significant difference between D100 and B20 in terms of CO emission over the entire operating range. The B40, B60, B80 and B100 showed higher values of CO emission than D100 above 4 kW load. Higher concentration of CO in jatropha oil blended with diesel as compared to D100.

(iii) Oxygen emission

The residual O₂ in the exhaust gas is linearly decreased from around 16% at 1kW to around 8% at 7 kW. The highest concentration of O₂ is observed in blends with lesser biodiesel at a given power output. The air requirement for diesel fuel is lesser than biodiesel blends. The differences tend to reduce as the load reaches the peak value.
At part load operation, better performance can be obtained by ensuring higher air flow in biodiesel run engines.

(iv) Oxides of Nitrogen emission

The NO_x emission of D100 and B20 are almost identical and that of B40 and B60 are identical. The NO_x values gradually increase from around 100 ppm at 1 kW to 300 ppm at around 7 kW.  Except for B100 all other blends show all most linear increase in NO_x in the 1 to 7 kW range.

Table 13 Exhaust gas emission of variable load test for diesel and biodiesel blends

Blends	Loads	O2, %	CO2, %	CO, %	NO2, ppm	NO, ppm	NOx, ppm	SO2 ppm
D100	a	10.5	8.2	0.141	5	334	339	64
	b	16.7	3.1	0.019	7	85	92	0
	c	15.0	5.7	0.017	6	197	203	5
	d	8.8	8.0	0.197	4	319	323	70
	e	15.7	5.4	0.015	7	132	139	1
	f	12.6	7.0	0.020	6	261	267	16
B20	a	10.2	8.8	0.143	5	353	358	47
	b	16.2	3.5	0.024	7	90	97	0
	c	14.0	5.9	0.022	6	215	221	5
	d	8.9	8.5	0.200	4	336	348	52
	e	15.7	5.5	0.023	7	126	133	1
	f	12.0	7.2	0.024	5	269	274	16
B40	a	10.3	8.6	0.137	1	390	391	28
	b	16.5	3.3	0.023	5	93	98	0
	c	13.8	5.9	0.024	1	186	187	1
	d	8.7	7.8	0.188	1	378	379	30
	e	15.1	5.6	0.022	3	134	137	0
	f	12.3	7.9	0.027	2	217	219	7
B60	a	9.8	7.7	0.139	1	392	393	23
	b	16.3	3.5	0.022	3	76	79	0
	c	12.5	6.1	0.023	2	189	191	1
	d	8.7	7.5	0.185	1	384	385	23
	e	14.3	5.7	0.022	4	136	140	1
	f	11.8	8.3	0.25	2	220	222	4
B80	a	9.7	7.5	0.145	2	379	381	19
	b	16.5	3.3	0.025	4	67	71	0
	c	11.7	5.8	0.024	2	245	247	2
	d	8.5	7.6	0.217	2	351	353	19
	e	13.7	5.9	0.023	3	179	182	1
	f	10.1	8.6	0.033	2	316	318	2
B100	a	10.1	7.8	0.147	3	360	363	9
	b	16.2	3.4	0.027	4	45	49	0
	c	12.0	6.2	0.025	3	295	298	0
	d	8.8	7.8	0.223	3	348	351	13
	e	14.0	5.7	0.024	4	109	113	0
	f	10.6	8.5	0.037	3	352	355	1

 

a, 85 percent of the load corresponding to the  load at maximum

b, Minimum load

c, 50 percent of the load defined at (a)

d, Load corresponding to the load at    maximum power

e, 25 percent of the load at maximum power(a), and

f, 75 percent of the load defined at (a)

(v) Smoke density emission of exhaust gas

The smoke density of exhaust gas for diesel and selected biodiesel for the blends are plotted as a function of engine power in Fig.20.

Table 14 Smoke density of diesel and biodiesel blends at various loads

Load / Blends	D100	B20	B40	B60	B80	B100
85 per cent of the load corresponding to the load at maximum	67.8 (Bad)	51.3 (Bad)	50.3 (Bad)	42.3 (Good)	30.7 (Good)	31.4 (Good)
Minimum load	12.0 (Good)	7.5 (Good)	7.5 (Good)	6.1 (Good)	5.3 (Good)	4.7 (Good)
50 per cent of the load defined at (a)	27.3 (Good)	22.8 (Good)	21.1 (Good)	24.5 (Good)	19.5 (Good)	21.9 (Good)
Load corresponding to the load at     maximum power	72.1 (Bad)	56.9 (Bad)	53.4 (Bad)	50.1 (Bad)	43.0 (Good)	38.6 (Good)
25 per cent of the load at maximum power (a)	7.9 (Good)	8.0 (Good)	6.51 (Good)	6.2 (Good)	5.7 (Good)	4.8 (Good)
75 per cent of the load defined at (a)	28.1 (Good)	24.0 (Good)	36.3 (Good)	34.0 (Good)	28.2 (Good)	21.9 (Good)

 

The smoke density was found to increase with increase in load in almost linear pattern from 1 to 4.5 kW.  In 4.5 to 7 kW, D100 showed rapid increase in smoke density while B100 showed minimum increase in smoke density.  The correlation between low black smoke emission and high NO_x concentration was also observed.

31.3. Performance evaluation of biodiesel blends in a variable compression test rig

31.3.1 Methodologies adopted

Variable Compression Ratio Multifuel Engine Test Rig procured from Legion Brothers, Bangalore (Fig. 6) was used for testing the engine performance and emission studies.  The Engine specifications are given below in table 6.

Table 6. Specification of variable compression multifuel engine

BHP	3 HP
Speed	1500 to 2000 RPM variable speed for SI operation, Governed speed for 1500 RPM for CI operation.
Compression Ratio	5:1 to 20:1
Bore; Stroke	80 mm; 110 mm
Type of Ignition	Spark ignition (time adjustable 0 to 70 deg ATDC, 0 to 70 deg BTDC) or Compression ignition
Method of Loading	Eddy Current Dynamometer
Method of Cooling	Water

To study engine performance, the compression ratios for diesel, biodiesel and their blends were selected as 14:1, 16:1, 18:1 and 20:1 and the load ranges were selected as no load, 2 k g, 4 kg, 6 kg and 8 kg as the engine used for this study having load range from no load to 8 kg load. 

31.3.2 Performance evaluation results

The effect of different compression ratios, loads and blends on the engine performance and emission characteristics were studied in the form of Brake Power (BP), Specific Fuel Consumption (SFC), Brake Thermal Efficiency (BTE) and Heat Balance Chart (HBC).  It was found out that BSFC was higher for Jatropha biodiesel (0.425 kg kWh^-1) compare to diesel (0.350 kg kWh^-1) but for B20 it was lower (0.340 kg kWh^-1) than both biodiesel and diesel. The optimum compression ratio for Jatriopha biodiesel, B20 and diesel was found at 20:1, 18:1 and 16:1, respectively.  The higher BTE was obtained for B20 and B40 (27.07 and 26.45 %) than other blends at compression ratio 18:1.  The temperature of exhaust gas and heat input was increased with increase in percentage of Jatropha biodiesel and the maximum values were 559ºC and 43987.5 kJ h^-1, respectively which were higher than diesel (519ºC and 29222.4 kJ h^-1, respectively). 

The CO₂ emission was found to be higher for Jatropha biodiesel (9.2 %) than diesel (8.1 %).  The reduced percentage of CO and SO₂ was observed for all blends as compared to diesel at different loads.  The SO₂ emission of Jatropha biodiesel was found to be nil due to zero sulphur content and was higher for diesel (61 ppm).  Due to the presence of higher oxygen molecule in Jatropha biodiesel, NOx emission was increased with increase in blend proportion of Jatropha biodiesel and was maximum for B100 (428 ppm) compared to diesel (413 ppm).