Biogas Fuel For Internal Combustion Engines

N. Mustafi, R. R. Raine and P. K. BansalDepartment of Mechanical Engineering

The University of Auckland

Outline: Literature Review

1. Spark ignition (SI) engines2. Compression ignition (CI) engines3. Conclusions4. Future research scope …

What is biogas and why ?

The extensive use of fossil fuels in internal combustion (IC) engines – a major concern of the global environment pollution

Their reserves are depleting rapidly

To look for and to use the alternative fuels especially in IC engines

Biogas produced by anaerobic fermentation of organic wastes,

Biogas = CH4 + CO2 + H2S + N2 + H2 etc.

What is biogas and why ?

Biogas can be regarded as an alternative fuel for IC engines because-

-- Renewable fuel produced from waste biomass

-- It has a typical calorific value of 21.48 MJ/m3

-- It’s combustion does not increase the net amount of CO2 in the atmosphere and free from SOx emissions

Studies on SI engines (1)

Alder et al. (1989); Karim et al. (1992)

Effect of fuel quality on engine performances

Studies on SI engines (2)

Huang et al.(1998)

2500 r/min, RAFR = 0.97 and CO2 fraction = 37.5%

speed = 2000 r/min, CR = 13 and RAFR = 0.98

• Cylinder peak pressure decreases

Studies on SI engines (3)

At full throttle and MBT

Fuel-1: 60% NG/40% CO2Fuel-2: 75% NG/25% CO2Fuel-3: 55% NG/35% CO2/ 10%N2

Wong J.K.S. (1977) and Midkiff et al. (2001) respectively

At full throttle, 2350 rpm andMBT timing

• BP decreases and BSEC increases

Studies on SI engines (4)

Fuel-1: 60% NG/40% CO2Fuel-2: 75% NG/25% CO2Fuel-3: 55% NG/35% CO2/ 10%N2

Huang et al. (1998); Midkiff et al. (2001)

• BTE decreases

• NOx decreases substantially

bte

Relative A/F ratio

NGBiogas ABiogas B

Biogas C

Gasoline

NG+15%CO2 -Biogas ANG+25%CO2 - Biogas BNG+38%CO2 - Biogas C

Studies on SI engines (5)

Midkiff et al. (2001)

• Both HC and CO increase a little compared to NG

Studies on SI engines (6)

Modelling and computer simulation works:

– SIMGAS for thermodynamic cycle analysis

– Mass fraction burnt, burn duration

– Turbulent burning velocity

– Effects of ST and A/F ratio, and emissions

– Piston ring blowby flowrate

– Engine overhaul life

Studies on SI engines (7)

Whiston et al. (1991); Stone et al. (1993)

• Veltur peaks decrease • Causes longer burn duration

Studies on SI engines (8)

Stone et al. (1993); Tanoue et al. (2000)

• Fast burn improves efficiency Effect of H2 addition

Indi

cate

d ef

ficie

ncy

(%)

Brak

e ef

ficie

ncy

(%)

Studies on SI engines (9)

Two major problems encountered at co-generation systems– Failure of wrist pins and corrosion of the main and rod

bearings– Carbon diposits around the piston and valves

Solutions: Use of high TBN engine oil and

frequent oil monitoring

Pellerin et al. (1988); Fulton A.C. (1991)

Studies on CI engines (1)

Operate on dual-fuel mode for gaseous fuelling

Bilcan et al. (2003); Bari S. (1996); Mathur et al. (1986)

Biogas with upto 30% CO2 could improve engine performance --- as compared with NG

They offer higher efficiencies than SI, due to a higher CR

Smoke and SO2 emissions can be reduced

Studies on CI engines (2)

Henam et al. (1998); Bari S. (1996)

• ηoverall decreases but improves compared to SI engines

• upto ≈ 30% CO2 in biogas improves bsfc

Studies on CI engines (3)

– No predictions either for combustion analysis or exhaust emissions

• Modelling and computer simulation works:

pilotfm& primaryfm&– the engine load for a given and

– NOx using exhaust gas temperature – Ignition delay– Thermodynamic cycle analysis for engine performances

Conclusions

promising alternative renewable fuel for IC engines

Dual-fuel CI engine applications have greater potentials

Limited Research is available in the literature on both SI and CI engines.

Higher CR, advanced ST and possibly small amount of H2addition could make biogas comparable to NG

Future Research Scope

Study and analysis of cyclic variability of SI engine operated with biogas

Modelling and computer simulation of biogas operated SI engines to predict the optimum ST, CO2%, CR, ignition source, emissions etc. to provide improved engine performances

Experimental investigation of a dual-fuel CI engine operated with biogas-diesel along with PM emissions

Modelling and computer simulation of biogas-diesel dual-fuel CI engines to predict the optimum operating parameters/conditions to provide improved engine performances

Development of a lean mixture, fast burning SI engine for biogascombustion

Thank you