Applied Thermal Engineering 114 (2017) 118–129

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Applied Thermal Engineering

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Research Paper

Experimental investigations on DI (direct injection) diesel engineoperated on dual fuel mode with hydrogen and mahua oil methyl ester(MOME) as injected fuels and effects of injection opening pressure

http://dx.doi.org/10.1016/j.applthermaleng.2016.11.1521359-4311/� 2016 Elsevier Ltd. All rights reserved.

⇑ Corresponding author.E-mail address: sapquadri@gmail.com (S.A.P. Quadri).

Ahmed Syed a, Syed Azam Pasha Quadri a,⇑, G. Amba Prasad Rao b, Mohd Wajid a

aDepartment of Mechanical Engineering, Lords Institute of Engineering and Technology, Hyderabad, Telangana, IndiabDepartment of Mechanical Engineering, National Institute of Technology, Warangal, Telangana, India

h i g h l i g h t s

� Experiment was conducted by varying IOP from 200 to 275 bar in steps of 25 bar.� Maximum BTE and minimum BSFC were found at 250 bar of befit IOP & deviate at 275 bar.� Reduction in HC & CO emissions & slight increase in NOx emissions were observed.� By adding hydrogen, peak cylinder pressure and peak heat release rate increased.

a r t i c l e i n f o

Article history:Received 6 June 2016Revised 19 November 2016Accepted 21 November 2016Available online 23 November 2016

Keywords:Injection opening pressureMahuaPerformanceCombustionEmissionsHydrogen-B20

a b s t r a c t

The influence of injection opening pressure (IOP) for 20% blend (B20) of mahua oil methyl ester (MOME)and 22.5 liters per minute (lpm) of hydrogen dual fuel mode was investigated based on the performance,combustion and emission characteristics of a single cylinder, four stroke, direct injection (DI) dieselengine with a rated power of 3.5 kW at a rated speed of 1500 rpm. Experiments performed at four differ-ent IOP of 200, 225, 250 and 275 bar that were compared using the diesel operation at 200 bar as thebaseline. Maximum brake thermal efficiency, minimum brake specific fuel consumption, and lowestHC, CO and smoke emissions with increased concentration of NOx were obtained at IOP of 250 bar forB20-hydrogen dual fuel mode. Further increase in IOP to 275 bar results in decreased brake thermal effi-ciency, increase in HC, CO and smoke emissions whereas the concentration of NOx slightly diminished.Present investigations revealed that the IOP of 250 bars for 22.5 lpm hydrogen with B20 dual fuel modeis optimum.

� 2016 Elsevier Ltd. All rights reserved.

1. Introduction

Petroleum based fuels are likely to be unavailable in the futureif no attention is paid to its proliferous consumption in internalcombustion (IC) engines. Environmental warnings and limitedextent of petroleum fuels have prompted the search for alternativefuels (mostly bio-fuels) for internal combustion (IC) engines. Bio-diesels that meet the criteria have been used by a number of aca-demic researchers [3,12,15,47] who have stated that, biodieselexhibits very similar engine performance characteristics attributedto diesel fuel [9,42,50,62] and diminishes the exhaust emissionsfrom diesel engines [4,5,41]. The performance in terms of brakethermal efficiency (BTE) of the engine running on bio-diesel

blends is equivalent to that of diesel fuel. This is in agreementwith the findings reported by numerous investigators[23,53,60,63,72,74,79,81,86] while fueling diesel engines bybio-diesels attained from rapeseed, palm, sunflower, soybean,sunflower, canola, olive, karanja, jatropha, mahua and rubber seedoils. Among all these mahua seeds are abundantly available andare great potential source of energy.

Based on the climatic conditions and the nature of soil differentnations are in hunt of different alternative to the diesel fuel. Indiais a country of tropical climatic condition with wide verity of soil atdifferent regions. India is rich in forest having wide range of treesyielding significant quantity of oilseeds. Madhuca longifolia is anIndian tree favorable to climatic conditions of the nation producing1,80,000 tons of oil.

The seeds of tree contain about 40% pale yellow oil, afterprocessing the commercial oils are generally greenish yellow with

Nomenclature

B20 20% blend of biodieselBSFC brake specific fuel consumptionBTDC before top dead centreBTE brake thermal efficiencyCO carbon monoxideH2 hydrogenHC hydrocarbons

HSU Hartridge Smoke UnitIOP injection opening pressurelpm liters per minuteNHRR net heat release rateNOx oxides of nitrogenppm parts per millionFIP fuel injection pressure

A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129 119

disagreeable odor and taste. Mahua oil has a calorific value 5%lower than the diesel fuel [88,89]. Kinematic viscosity and catenenumber is slightly higher than the diesel which is appreciativefor the combustion process. Flash point and fire point is high,which is advantage for the fuel transportation. The various proper-ties of mahua oil methyl ester [MOME] are tabulated in the Table 1.

Although bio-diesel is environmentally friendly, non-toxic,renewable, and readily available compared to conventional diesel[42,61], it does have numerous problems which need to beaddressed. some of them are lower calorific value, higher flashpoint, poor cold flow properties, poor oxidative stability, higher vis-cosity [2], that leads to problems in atomization and poor combus-tion inside the combustion chamber of a diesel engine [54,64,80].High viscosity of vegetable oils and bio-diesel result in pooratomization of fuel spray by injecting large droplets. Fuel sprayjet has a solid stream rather than small droplets. This results inimproper mixing of fuel with air in the combustion chamber [77].The solution to the difficulties has been obtained in a number ofways, such as blending of edible/non-edible oils with diesel, pre-heating the oils, thermal cracking and trans-esterification. Most ofthe findings revealed [51,57], that trans-esterification is the bestway to use vegetable oil as a fuel in existing diesel engine. BTE isreduced and BSFC is increased using higher percentage of bio-diesel in the fuel blend [26,35,49]. B20 gives higher BTE at higherengine load condition than any other blend. Literature shows that,a diesel engine can be operated successfully with a blend of 20%vegetable oil and 80% diesel fuel with no modification withoutdamage to engine parts [73]. Nagaraju et al. [55] conducted exper-iments on high speed diesel injection (HSDI) diesel engine to deter-mine the effect of B20 on the combustion, performance and exhaustemissions characteristics. Their results showed lower emissions ofNOx, HC, CO and soot for B20 when compared to diesel fuel.

Hydrogen is an exceptional fuel having excellent combustioncharacteristics, such as its high calorific value, good physical andchemical properties, environmental benefits and renewability.The feature of extremely clean burning makes hydrogen an excel-lent fuel for IC engines to potentially eradicate harmful engineexhaust emissions like hydrocarbons (HC), carbon monoxides(CO), particulate matters (PM) [67]. The wide flammability limitof hydrogen in air offers lean operation that will result in low con-centration of NOx besides higher thermal efficiencies [21]. sincehydrogen has a self-ignition temperature of 576 �C, ignition ofhydrogen may not be attained by compression alone [20]. Certainsources of ignition should be located inside the combustion cham-

Table 1Properties of raw mahua, mahua oil bio-diesel and diesel.

Fuel property Raw Mahua

Density at 15 �C (kg/m3) 960Viscosity at 40 �C (mm2/s) 24.58Calorific value (MJ/kg) 36.10Flash point (�C) 232Cetane number –Carbon residue (%) 3.70

ber to ensure the ignition of hydrogen. Lee et al. [43] investigatedthe hydrogen fueled engine performance by using solenoid in-cylinder injection and external fuel injection in dual fuel mode. Arise of 22% in BTE was observed at low loads and 5% at high loadsin dual fuel mode compared to direct injection. Lee et al. [44] pro-posed that, the direct injection of hydrogen in dual mode deliversgreater stability and maximum power. Yet the maximum efficiencymay possibly be achieved by external mixture formation in hydro-gen engine. Subramanian and Chintala [76] investigated the per-formance and emissions on biodiesel fuelled diesel enginesupplemented with hydrogen. Results indicated 46% drop in CO2

emission using lesser quantity of 20% hydrogen energy share at fullload condition with dual fuel operation. Yadav et al. [84] tested onKirlosker

TAF1 diesel engine; they observed a very significant improve-ment in the performance and emissions with a small quantity ofhydrogen enrichment.

The injection opening pressure (IOP) plays a significant part inmetering the anticipated quantity of fuel at correct time contingenton engine operating conditions that affects performance and for-mation of pollutants inside the DI (direct injection) diesel enginecombustion chamber [6,28,29,56,83]. In diesel engines, the directinjection fuel system is used to attain a high degree of atomizationin order to enable increased evaporation rates in short time andsufficient spray penetration in order to reach improved air-fuelmixing possibilities and subsequently enhance the combustionprocess [7,32,52].

Bakar et al. [66] Shehata et al. [48] conducted test on dieselengine with injection pressure ranging from 180 to 220 bar with10 bar intervals running at a speed range of 600–1600 rpm with200 rpm. In the subsequent trial, the diesel engine loads were triedwere in the range of 55–80% at 5% intervals, engine speed was fixedat 1600 rpm and the IOP from 180 to 220 bar with 10 bar intervals.The results showed that, engine operated at IOP of 220 bar exhibitsbest performance. BTE and BSFC are improved at increased IOP of200 bar. During these conditions they concluded that, the increasedBTE and decreased BSFC approach 15% from the original IOP of180 bar; however the values of Pmax for diesel fuel are slightlyhigher than those for blended fuels irrespective of the engine oper-ating conditions. Kato et al. [37] experimented DI diesel engineusing high fuel injection pressures as a means to reduce PM emis-sions without increasing NOx emissions. High FIPs appear to inducea very different spray structure than low FIP sprays due to cavita-tions created in the nozzles at high FIPs, which results in significant

Diesel B20 Hydrogen

850 856 0.08382.60 2.78 –42.20 41.70 119.9368 96 –50.6 51.2 –0.17 0.17 0.0

Table 2Engine specifications.

Type of ignition Compression ignition

Rated power (kW) 3.5Max. speed (rpm) 2000Min. idle speed (rpm) 750Bore (mm) 87.5Stroke (mm) 110Connecting rod length (mm) 234Compression ratio 17.5Cylinder capacity (cc) 661Fuel injection Direct injectioninjection timing (deg BTDC) 23Injection opening pressure (bar) 200Dynamometer Eddy current typeStarting Auto start

120 A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129

faster atomization. On the other hand, higher FIPs improve fuel–airmixing, followed by faster combustion, that directly influence pol-lutant formation. Kannan and Udayakumar [33] used a dieselengine to study the effect of IP on performance and emissions. Theyconcluded that, significant improvement in performance and lowemissions occur at high IP of 200 bars. Canakci et al. [16] witnesseda reduction of engine efficiency, Peak pressure, ROHR and increasein engine emissions of smoke opacity, UHC and CO except NOx andCO when the injection pressure becomes lower than the engineoriginal injection pressure. Reddy et al. [68,69] conducted tests ondiesel engine using cotton seed oil methyl ester and jatropha oilseparately blended with diesel fuel to evaluate the combustionand emissions characteristics by varying IOP. They concluded that,the values of BTE increases and BSFC decreases as the IP is increasedfrom 170 to 200 bar. They found good improvement in performanceand emission when the injection timing is retarded with greaterinjection rate. At full output, NOx level and smoke with jatrophaoil are 1162.5 ppm and 2 BSU, while they are 1760 ppm and 2.7BSU with diesel fuel. They concluded that the BTE increases whenthe injection rate is dropped with jatropha oil. They also concludedthat a noticeable improvement in performance, emissions and com-bustion parameters can be acquired by properly optimizing the IOP,IT, injection rate and enhancing the swirl level of neat jatropha oiloperated diesel engine. Sayin et al. [14] evaluated the performanceand emission characteristics of a DI diesel engine running on etha-nol (B5, B10 and B15) blended-diesel fuel and effects of injectionpressure and injection timing on it. They conducted tests on threedifferent IOPs of 180, 200 and 220 bar and ITs of 15�, 20� and 25�BTDC at 20 Nm engine load and 2200 rpm. Engine shows best per-formance of BSEC at the original IOP and IT. For all test fuels, there isa lower HC, CO emissions and increased NOx emission at theadvanced IT. Jindal et al. [71] experimented the effect of injectionpressure and compression ratio on performance and emission char-acteristics of CI engine fuelled with JO bio-diesel. Escalation in CRaccompanying with rise in IOP develops the performance of theengine. As the CR is increased, HC and EGT increases, howeversmoke and CO emission decreases. Concentrations of NOx are unaf-fected at higher IOP. It is concluded that JO bio-diesel fuelled engineshould be operated at higher CR and IOP. Dhananjaya et al. [22] con-ducted experiments to study the impact of injection parameters onsemi adiabatic CI engine fueled with blends of Jatropha oil methylesters. Satisfactory values of BTE, BSEC and emission characteristicswere attained up to B25 of JOME and diesel fuel. With increased IOPand advanced injection timing, semi-adiabatic engine fuelled withB20 JOME exhibited enhanced combustion performance and lowerexhaust emissions related to other blends. Kapilan et al. [36] stud-ied the effect of injection pressure of 160–220 bar in steps of 20 baron the performance and emission of diesel engine running on 20%blend of karanja oil methyl ester. They found that the IOP of200 bar gives higher brake thermal efficiency, due to enhancedcombustion of fuel that may be due to better atomization and mix-ing of fuel with air. Kapilan et al. [34] conducted tests on a singlecylinder CI engine fuelled with MO biodiesel at different injectionopening pressures and loads. They witnessed that the higher IOPof 200 bar give rise to improved BTE of both MO and diesel fueloperation. They also observed lower HC, CO, and smoke emissionsand slightly higher NOx emissions with MO operation. Puhanet al. [65] examined the influence of variable IOP of 200, 220 and240 bar on the performance and emissions characteristics of a die-sel engine fuelled with linolenic linseed methyl ester. The resultsrevealed that, at the optimum fuel IOP of 240 bar with linseedmethyl ester, the BTE and BSFC were similar to diesel fuel, while areduction in HC, CO and smoke emissions with increased NOx emis-sions were observed compared to diesel fuel.

In the current study, the effects of pilot fuel injection openingpressure on performance, combustion and emission characteristics

were examined by B20–hydrogen dual fuel mode of operation in asingle cylinder DI diesel engine. Hydrogen, which was inducted inair, acts as primary fuel that needs to be ignited with the help ofB20 as pilot fuel.

2. Experimental setup and procedure

The experiment was conducted on fully computer interface, sin-gle cylinder, four stroke, multi fuel, water cooled engine with eddycurrent loading as described in Table 2, while a schematic diagramof the test rig setup is shown in Fig. 1 all the experiments were car-ried out at full load with a constant speed of 1500 rpm. The engineinstrumentation is given in Table 3. The in-cylinder pressure wasrecorded using a piezoelectric sensor. A digital shaft encoder wasused to measure the crankshaft position. The signals from Piezosensors and the crank encoder were acquired using national instru-ments logical card. Data acquisition and combustion data analysiswere measured using National Instrument Lab VIEW acquisition-system developed in-house. The test rig include other standardengine instrumentation, such as a thermocouple to measure oil,air, inlet manifold and exhaust temperature and pressure gaugemounted at relevant points. The combustion analysis was basedon the averaged value of 100 cycles after the engine reached steadystate operation. During the first phase of operation the engine wasstarted on diesel fuel to generate baseline data. In the second phaseof operation, the engine was made to run on B20 fuel after reachingstable conditions the results are compared to baseline data. In thethird phase of operation engine running on B20 fuel and inductedair is enriched with a low concentration of hydrogen (20, 22.5 and25 lpm), the results were obtained at all loading conditions for fourdifferent injection opening pressures of 200, 225, 250 and 275 bar.Prevention of explosive atmosphere in the test bench room wastaken care by means of monitoring leakages of hydrogen supplyline, air and a powerful ventilation system. Hydrogen cylinder isplaced at a safe distance from the engine to avoid heat transferto the cylinder. The performance characteristics, combustiondetails, and exhaust emissions are noted for analysis. Engineexhaust emissions are measured using advanced MN-05 multi-gas analyzer (5 gas version).

3. Results and discussion

The experimental investigations focus on engine performanceand combustion analysis of optimized injection opening pressure.For this, initially the hydrogen flow rate is optimized. Hence threedifferent hydrogen flow rates tested during this operation were20, 22.5 and 25 lpm. The maximum brake thermal efficiencywas obtained at 22.5 lpm flow rate of hydrogen, beyond this flowrate the engine performance was drastically decreased as well as

Fig. 1. Schematic view of experimental test setup.

Table 3Instrumentation data.

Particulars Specifications Uncertainty

Dynamometer Eddy current dynamometer of Model AG10, Make Saj Test Plant Pvt. Ltd. Speed ± 1% and torque ± 0.4%Load sensor Make Sensortronics, Model 60001. ±0.2%Air flow transmitter Make Wika, Model SL1. ±0.5%Fuel flow transmitter Differential pressure type-Make Yokogawa – Model EJA110E-S1-JMS5J-912NN Made in Japan. ±0.065Piezo Sensors Make PCB Piezotronics, Model SM111A22. ±0.1%Crank angle sensor Make Kubler-Germany, Model 8.3700.1321.0360. ±0.2%Temperature sensor Make Radix, Type RTD, PT100 measures engine water inlet temperature,

engine water outlet temperature, calorimeter water inlet temperatureand calorimeter water outlet temperature.

±1%

Temperature sensor Make Radix, Thermocouple type K (Chromel/Alumel) measures Exhaustgas temperature at calorimeter inlet and outlet.

±0.8%

Rotameter Eureka model PG-1 to 21. ±2%Exhaust gas analyzer MN-05multi gas analyzer, Infrared spectroscopy technology CO % volume ± 1.18%

O2 % volume ± 0.7%CO2 % volume ± 0.9%NOx (PPM) ± 0.2%

A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129 121

knocking tendency was observed which makes it difficult to runat higher loads as shown in Fig. 2. Therefore in the present exper-imental investigation 22.5 lpm of hydrogen is inducted in con-junction with air in hydrogen–B20 dual fuel mode and theresults were obtained at all loading conditions for four differentinjection opening pressures of 200, 225, 250 and 275 bar. Theoptimized parameters for the engine running on dual mode ofhydrogen-B20 on the performance, emission and combustioncharacteristics are:

� Hydrogen flow rate of 22.5 liters per minute� Pilot fuel injection timing of 27� BTDC.

3.1. Energy share

The energy share of the inducted fuel in hydrogen operatedengine is an important parameter for analyzing the premixed lean

combustion. Hydrogen and B20 together contributes energy inorder to develop required amount of power [18]. During combus-tion, hydrogen consumption remains unchanged with the changein the load and injection opening pressure, while B20 consumptionvaried with the load and injection opening pressure. The energyshare of a fuel strongly depends on rate of fuel consumption,calorific value of fuel, rate of combustion [19].

The energy share of hydrogen is lower at higher load in thedual fuel operation with the increased injection opening pres-sure. This is associated to higher energy release from B20 at arelatively high load, since in the dual fuel operation the quantityof hydrogen inducted in the intake manifold was kept constantat 22.5 lpm throughout the load spectrum, whereas the B20 con-sumption was varied with respect to load to maintain the loadand speed of the engine. The energy share of hydrogen increaseswith the increase in injection opening pressures from 200 to250 bar respectively, this is due to the near complete combus-

0 25 50 75 10016

18

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24

26

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32

BTE

(%) a

t Inj

ectio

n op

enin

g pr

essu

re o

f 250

bar

Load (%)

B20 + 20 lpm Hydrogen B20 + 22.5 lpm Hydrogen B20 + 25 lpm Hydrogen

Fig. 2. Variation of BTE with load for B20 with different Hydrogen flow rates atInjection opening pressure of 250 bar.

122 A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129

tion of hydrogen-B20 mixture. On the other hand, with furtherincreasing the injection opening pressure to 275 bar tends todiminish the in-cylinder temperatures of B20-hydrogen mixturethat was not enough to propagate the flame in the whole chargemixture and results in more incomplete combustion of the mix-ture [10].

The energy share in the dual fuel mode is manipulated as theratio of energy supplied by the primary fuel (hydrogen) to thesum of the energy supplied by the primary fuel and the pilot fuel(hydrogen + B20).

Energy Equivalent to B20 ¼ _mB20 x LHVB20

Energy Equivalent to H2 ¼ _mH2 x LHVH2

Energy share by B20

¼ Energy Equivalent to B20Energy Equivalent to B20þ Energy Equivalent to H2

Energy share by H2

¼ Energy Equivalent to H2

Energy Equivalent to B20þ Energy Equivalent to H2

Table 4Energy shares of B20 and Hydrogen at different injection opening pressure.

Mode ofoperation

Load(%)

Brake power(kW)

Volume of B20(lpm)

Volume of H2

(lpm)EnergB20 (

B20 25 0.55 0.0063 – 3.74850 1.22 0.0102 6.06875 2.80 0.0186 11.06100 3.69 0.0253 15.05

B20 + H2 at200 bar

25 0.55 0.0052 22.5 3.09350 1.22 0.0090 22.5 5.35475 2.80 0.0164 22.5 9.756100 3.69 0.0228 22.5 13.56

B20 + H2 at225 bar

25 0.55 0.0046 22.5 2.73650 1.22 0.0079 22.5 4.69975 2.80 0.0157 22.5 9.340100 3.69 0.0215 22.5 12.79

B20 + H2 at250 bar

25 0.55 0.0036 22.5 2.14150 1.22 0.0066 22.5 3.92675 2.80a 0.0139a 22.5a 8.269100 3.69 0.0186 22.5 11.06

B20 + H2 at275 bar

25 0.55 0.0047 22.5 2.79650 1.22 0.0078 22.5 4.64075 2.80 0.0152 22.5 9.042100 3.69 0.0208 22.5 12.37

a Optimum values of energy share for B20 + H2 at 250 bar IOP. And the experimental

where _mB20, _mH2 are the mass flow rates of B20 and hydrogen,and LHV is the lower heating value of the fuel used. The energyshares of B20 and hydrogen at the hydrogen induction rate of22.5 lpm or 0.112 kg/h with different injection opening pressuresare given in Table 4.

The variation in the energy share with load at different injectionopening pressures for B20 is depicted in Fig. 3 and for hydrogen isshown in Fig. 4.

3.2. Combustion analysis

3.2.1. Cylinder pressureFig. 5 depicts the variation of cylinder pressure as a function of

load for different injection opening pressures with engine runningon pure diesel, B20 and as well as B20 with hydrogen at 22.5 lpmflow rate of hydrogen. At rated injection opening pressure of200 bar, the peak pressure values for pure diesel, B20 and B20 with22.5 lpm hydrogen flow rate are obtained as 43.8, 46.3 and 59.7 barat 25% load, 51.7, 54 and 65.1 bar at 50% load, 61.9, 64.8 and 71 barat 75% load, 56, 58.7 and 68.5 bar at 100% load. Peak pressure val-ues increases with the increase of engine load from 25 to 75% dueto the increase of pilot fuel mass and this results in elevated heatrelease. Peak pressure is dependent on the portion of energy liber-ated through premixed combustion, that in turn governed by thedelay period [27]. At full load condition there is substantialdecrease of peak pressures with pure diesel, B20 and B20 withhydrogen for a given injection opening pressure because of the lessburning of fuel and late combustion caused respectively by thedecreased combustion duration and delay period. Peak pressurevalues increases with the increase of injection opening pressurefrom 200 to 250 bar and the highest pressure values for pure diesel,B20 and B20 with 22.5 lpm hydrogen flow rate are obtained at250 bar as 48.1, 50.7 and 64.2 bar at 25% load, 55.3, 57.9 and69.5 bar at 50% load, 65.5, 67 and 77.3 bar at 75% load, 61.8, 64.6and 75.4 bar at 100% load. The increase in Peak pressure from200 to 250 bar injection opening pressure may be attributed tothe shorter delay period due to increase in cylinder temperaturepreceded by proper atomization [7,32] and premixed combustion[45,70]. Further increase in injection opening pressure of 275 baris subjected to lower peak pressure values due to longer delay per-iod due to improper mixing of high velocity droplets of B20 enter-

y equivalent ofkW)

Energy equivalent ofH2 (kW)

B20 energyshare (%)

H2 energyshare (%)

0 – 100 –2 10055 10015 100

6 3.7688 45.08 54.913 3.7688 58.68 41.327 3.7688 72.14 27.8642 3.7688 78.26 21.74

6 3.7688 42.07 57.939 3.7688 55.50 44.502 3.7688 71.25 28.7508 3.7688 77.24 22.76

7 3.7688 36.24 63.765 3.7688 51.02 48.984a 3.7688a 68.69a 31.31a

55 3.7688 74.59 25.41

1 3.7688 42.59 57.414 3.7688 55.18 44.828 3.7688 70.58 29.4243 3.7688 76.65 23.35

results obtained at these optimum values are shown in Table 5.

Table 5Experimental results at optimized injection opening pressure of 250 bar.

Parameter Load (%) Neat diesel B20 B20 + 22.5 lpm H2 Parameter value at 75% load

gBTH (%) 25 18.29 20.64 20.63 Max50 23.98 25.59 26.1975 26.72 29.31 32.06100 25.51 28.24 29.06

BSFC (kg/kW-hr) 25 0.398 0.364 0.338 Min50 0.330 0.318 0.28075 0.284 0.269 0.255100 0.319 0.286 0.260

HC (ppm) 25 108 85 35 Min50 103 79 2875 71 47 15100 85 59 20

CO (% vol.) 25 0.458 0.327 0.129 Min50 0.165 0.112 0.06275 0.048 0.032 0.009100 0.068 0.048 0.012

NOx (ppm) 25 115 134 166 Max50 200 222 25475 333 366 391100 324 349 374

Cylinder pressure (bar) 25 48.1 50.7 64.2 Max50 55.3 57.9 69.575 65.5 67 77.3100 61.8 64.6 75.4

Max HRR (J/�CA) 25 26.8 30.4 41.9 Max50 33.7 35.1 47.275 37.8 40.5 56.6100 36 38.7 53.9

A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129 123

ing the combustion chamber [8], and results in improper combus-tion because of lesser heat release rate [29], less momentum of thespray [31,40].

3.2.2. Net heat release rateFig. 6 portrays the variation of Net Heat Release Rate as a func-

tion of load for different injection opening pressures with enginerunning on pure diesel, B20 and as well as B20 with hydrogen at22.5 lpm flow rate of hydrogen. At rated injection opening pressureof 200 bar, the NHRR values for pure diesel, B20 and B20with 22.5 lpm hydrogen flow rate are obtained as 20, 23 and36.1 J/�CA at 25% load, 28.1, 31.7 and 44.5 J/�CA at 50% load, 33.3,36 and 50 J/�CA at 75% load, 31.9, 33.4 and 47.6 J/�CA at 100% load.

0 25 50 75 100

35

40

45

50

55

60

65

70

75

80

Ene

rgy

Sha

re (%

)

Load (%)

B20 at 200 bar B20 at 225 bar B20 at 250 bar B20 at 275 bar

Fig. 3. Variation in energy share of B20 with load at different injection openingpressure.

The increase of engine load from 25 to 75% promotes pilot fuelmass and this result in elevated heat release. At full load conditionwith pure diesel, B20 and B20 with hydrogen for a given injectionopening pressure NHRR values decreases because of impropercombustion. NHRR values increases with the increase of injectionopening pressure from 200 to 250 bar and the maximum pressurevalues for pure diesel, B20 and B20 with 22.5 lpm hydrogen flowrate are obtained at 250 bar as 26.8, 30.4 and 41.9 J/�CA at 25%load, 33.7, 35.1 and 47.2 J/�CA at 50% load, 37.8, 40.5 and 56.6 J/�CA at 75% load, 36, 38.7 and 53.9 J/�CA at 100% load. NHRRincreases from 200 to 250 bar injection opening pressure, becauseof more accumulation of pilot fuel in the combustion chamber [58],the combustion duration is shortened [45], the in-cylinder peak

0 25 50 75 100

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55

60

65

Ene

rgy

Sha

re (%

)

Load (%)

Hydrogen at 200 bar Hydrogen at 225 bar Hydrogen at 250 bar Hydrogen at 275 bar

Fig. 4. Variation in energy share of hydrogen with load at different injectionopening pressure.

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80 IOP @ 200 bar

Cyl

inde

r Pre

ssur

e (b

ar)

Load (%)

IOP @ 225 bar

Load (%)

IOP @ 250 bar

Load (%)

IOP @ 275 bar

Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

Fig. 5. Variation of Cylinder Pressure with load for Pure Diesel, B20 and B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

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60IOP @ 200 bar

NH

RR

(J/d

eg C

A)

Load (%)

IOP @ 225 bar

Load (%)

IOP @ 250 bar

Load (%)

IOP @ 275 bar

Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

Fig. 6. Variation of Net Heat Release Rate with load for Pure Diesel, B20 and B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

124 A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129

pressure increases subsequently the peak value of heat release ratealso increases [30]. Beyond 275 bar injection opening pressure,NHRR decreased due to poor atomization [8], also some of the pilotfuel quenched on the walls of cylinder does not take part incombustion [25].

3.3. Engine performance

3.3.1. Brake thermal efficiencyFig. 7 illustrates the change in BTE by varying injection opening

pressures of 200, 225, 250 and 275 bar with pure diesel, B20 andB20 with 22.5 lpm hydrogen respectively. The BTE at 75% load

for rated IOP of 200 bar is 28.89% for B20 with hydrogen whencompared to 25.50, 22.96% with B20, pure diesel. BTE increaseswith the increase in load due to proper combustion that wasassisted by increased in-cylinder temperatures, accordinglyimproved vaporization of fuel resulting in improved BTE [38].The BTE at 75% load for IOP of 225, 250 and 275 bar is 29.11,32.05 and 30.06% for B20 with hydrogen when compared to26.23, 29.31 and 27.49% with B20 and 24.52, 26.72 and 25.72%with pure diesel respectively.

BTE increases from IOP of 200–250 bar, since during high injec-tion pressure, pilot fuel droplets gets atomized and instanta-neously vaporizes because of improved air-fuel mixing resulting

0 25 50 75 100

14

16

18

20

22

24

26

28

30

32

0 25 50 75 100

14

16

18

20

22

24

26

28

30

32

0 25 50 75 100

14

16

18

20

22

24

26

28

30

32

0 25 50 75 100

14

16

18

20

22

24

26

28

30

32

BTE

(%)

Load (%)

IOP @ 275 bar

)%(daoL)%(daoL

IOP @ 250 barIOP @ 225 bar

Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

IOP @ 200 bar

Fig. 7. Variation of Brake Thermal Efficiency with load for Pure Diesel, B20 and B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129 125

in near complete combustion [7,32] compared to the bigger sizedroplets formed at low injection pressure that slowly vaporize[11,17]. Further increase of IOP to 275 bar tends to decrease BTE,this is due to reduction in the size of fuel droplets that will havelesser momentum and affect the fuel distribution in the air tendtowards incomplete combustion [8,30,78].

3.3.2. Brake specific fuel consumptionFig. 8 shows the variation in BSFC by varying injection opening

pressures of 200, 225, 250 and 275 bar with pure diesel, B20 andB20 with 22.5 lpm hydrogen respectively. The BSFC at 75% load

0 25 50 75 100

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0 25 50 75 100

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.

0.

0.

0.

0.

0.

0.

0.

0.

IOP @ 225 bar

BS

FC (k

g/kW

h)

Load (%)

IOP @ 200 bar

Load (%)

Fig. 8. Variation of Brake Specific Fuel Consumption with load for Pure Diesel, B2

for rated IOP of 200 bar is 0.3012 kg/kW-h for B20 with hydrogenwhen compared to 0.3416, 0.3796 kg/kW-h with B20, pure diesel.BSFC decreases with the increase in load due to proper combustion[38]. The BSFC at 75% load for IOP of 225, 250 and 275 bar is0.2885, 0.2553 and 0.2784 kg/kW-h for B20 with hydrogen whencompared to 0.3343, 0.2694 and 0.3182 kg/kW-h with B20 and0.3560, 0.2842 and 0.3389 kg/kW-h with pure diesel respectively.BSFC reduces from IOP of 200–250 bar, because of finer atomiza-tion of pilot fuel droplets and better mixing of air–fuel [7,32,71]compared to the bigger size droplets formed at low injection pres-sure that slowly vaporize [11,17]. Further increase of IOP to

0 25 50 75 100

25

30

35

40

45

50

55

60

65

0 25 50 75 100

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

IOP @ 275 barIOP @ 250 bar

Load (%) Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

0 and B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

126 A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129

275 bar results in increased BSFC, this may be due to poor combus-tion and lower penetration, poor dispersion of the fuel and weakair entrainment [39,85].

3.4. Engine emissions

3.4.1. HydrocarbonFig. 9 depicts the variation in HC emissions by varying injection

opening pressures of 200, 225, 250 and 275 bar with pure diesel,B20 and B20 with 22.5 lpm hydrogen respectively. HC emissionsat 75% load for rated IOP of 200 bar is 61 ppm for B20 with hydro-gen when compared to 95, 120 ppm with B20, pure diesel. HCemissions reduced with the increase in load. The HC emissions at

0 25 50 75 100

15

30

45

60

75

90

105

120

135

150

165

0 25 50 75 100

15

30

45

60

75

90

105

120

135

150

165

1

3

4

6

7

9

10

12

13

15

16

IOP @ 225 bar

HC

(ppm

)

Load (%)

IOP @ 200 bar

Load (%)

Fig. 9. Variation of Hydrocarbon emissions with load for Pure Diesel, B20 an

0 25 50 75 100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

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0.6

0.8

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1.2

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0.2

0.4

0.6

0.8

1.0

1.2

IOP @ 225 bar

CO

(% v

ol.)

Load (%)

IOP @ 200 bar

Load (%)

Fig. 10. Variation of Carbon monoxide emissions with load for Pure Diesel, B20

75% load for IOP of 225, 250 and 275 bar is 28, 15 and 21 ppmfor B20 with hydrogen when compared to 55, 47 and 51 ppm withB20 and 81, 71 and 74 ppm with pure diesel respectively. At lowIOP due to improper atomization HC increases [16]. HC diminishedfrom IOP of 200–250 bar, because of proper combustion [6,56] andelevated cylinder wall temperatures reduces in quench layer [82].Further increase of IOP to 275 bar results in increased formation ofHC because of shorter delay period and rapid combustion [78].

3.4.2. Carbon monoxideFig. 10 portrays the variation in CO emissions by varying injec-

tion opening pressures of 200, 225, 250 and 275 bar with pure die-sel, B20 and B20 with 22.5 lpm hydrogen respectively. CO

0 25 50 75 100

5

0

5

0

5

0

5

0

5

0

5

0 25 50 75 100

15

30

45

60

75

90

105

120

135

150

165

IOP @ 275 barIOP @ 250 bar

Load (%) Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

d B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

0 25 50 75 100 0 25 50 75 100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

IOP @ 275 barIOP @ 250 bar

Load (%) Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

and B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129 127

emissions at 75% load for rated IOP of 200 bar is 0.01% vol. for B20with hydrogen when compared to 0.04, 0.069% vol. with B20, purediesel. CO emissions reduce with the increase in load due to ele-vated cylinder temperatures at high loads [31]. The CO emissionsat 75% load for IOP of 225, 250 and 275 bar is 0.01, 0.009 and0.01% vol. for B20 with hydrogen when compared to 0.038, 0.031and 0.039% vol. with B20 and 0.059, 0.048 and 0.065% vol. withpure diesel respectively. CO emissions reduce from IOP of 200–250 bar, because of complete combustion of the smaller droplets[13,59]. Further increase of IOP to 275 bar results in more CO emis-sions because of lack of mixing of fuel with air and insufficient timefor combustion [78].

3.4.3. Nitrogen oxidesFig. 11 illustrates the changes in NOx concentrations by varying

injection opening pressures of 200, 225, 250 and 275 bar with purediesel, B20 and B20 with 22.5 lpm hydrogen respectively. Concen-tration of NOx at 75% load for rated IOP of 200 bar is 354 ppm forB20 with hydrogen when compared to 310, 308 ppm with B20,pure diesel. NOx emissions escalate by increasing engine load, asthe load increases the in-cylinder temperatures increases [24,75].NOx emissions at 75% load for IOP of 225, 250 and 275 bar is

0 25 50 75 1000

50

100

150

200

250

300

350

400

0 25 50 75 1000

50

100

150

200

250

300

350

400

5

10

15

20

25

30

35

40

NO

x (p

pm)

Load (%) Load (%)

IOP @ 225 barIOP @ 200 bar

Fig. 11. Variation of Nitrogen oxide emissions with load for Pure Diesel, B20 a

Fig. 12. Variation of Hartridge Smoke Unit (HSU) with Injection openin

371, 391 and 383 ppm for B20 with hydrogen when compared to351, 366 and 359 ppm with B20 and 319, 333 and 325 ppm withpure diesel respectively. Concentration of NOx increases from IOPof 200–250 bar, because of rapid combustion [87] and high in-cylinder gas temperature, peak pressure attained [46] with ele-vated pilot injection pressure [1,29]. Further increase of IOP to275 bar lowers the NOx emissions because of improper combus-tion that results in lower in-cylinder temperatures when comparedto IOP of 250 bar [78].

3.4.4. SmokeSmoke is an unwanted by product of combustion generally a

collection of solid and liquid particulates and gases. Quantity ofsmoke formation depends upon the fuel air ratio, type of fuel andinjection opening pressure. Fig. 12 illustrates the changes in smokeconcentration by varying injection opening pressures of 200, 225,250 and 275 bar with B20, pure diesel and B20 with 22.5 lpmhydrogen respectively. Concentration of smoke for IOP 200 bar is36.3 HSU for B20 with hydrogen, when compared with 49.52 and41.83 HSU with B20 and pure diesel. Smoke emissions decreaseswith increasing IOP. Smoke emissions at IOP 225,250 and 275 baris 31.11, 24.88 and 29.86 HSU for B20 with hydrogen and 42.09,

0 25 50 75 1000

0

0

0

0

0

0

0

0

0 25 50 75 1000

50

100

150

200

250

300

350

400

Load (%)

IOP @ 275 barIOP @ 250 bar

Load (%)

Pure Diesel B20 B20 + 22.5 lpm Hydrogen

nd B20 with 22.5 lpm Hydrogen at different Injection Opening Pressure.

g pressure for Pure diesel, B20 and B20 with 22.5 lpm hydrogen.

128 A. Syed et al. / Applied Thermal Engineering 114 (2017) 118–129

33.67 and 40.40 HSU and 35.55, 28.44 and 34.13 HSU for B20 andpure diesel respectively. Smoke level diminishes with the increasein IOP because of the improved mixture formation and with theaddition of H2 the smoke emission is further decreased due tohigher diffusivity of H2. After an IOP of 275 bar there is an increasein smoke emission because too high IOP leads to delay injection.

4. Conclusion

A single cylinder compression ignition engine was operatedsuccessfully using B20 as pilot fuel and hydrogen as inducted fuelat different injection opening pressures. Tests carried out at 200,225, 250 and 275 bar IOP indicated that 250 bar IOP is optimumpressure for better performance and least emissions. The followingconclusions are summarized based on the experimental resultsobtained for hydrogen operated engine with B20 as pilot fuelinjected with 250 bar injection opening pressure and comparedto pure diesel operation at rated injection opening pressure of200 bar at 75% load.

� BTE improved by 28%.and the maximum BTE was observed atIOP of about 250 bars and at 75% engine load. BTE was foundminimum at 200 bars.

� B20 with 22.5 lpm of hydrogen reduces BSFC by 33%. Brakespecific fuel consumption was continuously decreasing withthe increase in IOP. Minimum brake specific fuel consumptionwas noticed at 250 bars and BSFC was found maximum at lowervalue of injection opening pressure.

� Insertion of hydrogen effects the emission by decreasing HCemissions by about 87% with the increasing load.

� Minimum CO emissions were accounted and were reduced by86% than the pure diesel mode.

� The NOx emissions were increased with the increasing IOP anengine load. NOx emissions were measured minimum at lowerIOP and engine load values. It escalates about 21% at 250 bars ofIOP and 75% engine load.

� Peak cylinder pressure and peak heat release rate was detectedat higher values of IOP.

Experimental investigations revealed that the supply of22.5 lpm hydrogen in direct injection diesel engine running onB20 and operated with increased injection opening pressure of250 bar gives maximum brake thermal efficiency than at 275 bar.Also, HC and CO emissions are reduced at the penalty of increasedNOx emissions than that of diesel fuel operation.

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