1

Conversion of Diesel/S.I. Engines to Operate on Biogas

Dr. Ram Chandra

Assistant Professor

Centre for Rural Development and Technology

Indian Institute of Technology Delhi

Hauz Khas, New Delhi – 110 016

I.C. Engines

Requirement of Conversion

– Petrol Engine conversion

– Gas carburetor

– Governing Mechanism

• Diesel Engine Conversion

– Ignition Mechanism/ignition advance

– Gas carburetor

– Governing Mechanism

Conversion of Diesel Engine to Gaseous Engine

• Gas –Air Mixing

• Compression Ratio

– LPG, Natural Gas CR=11

– Alcohol (jet enlarged) CR=12

– Petrol CR=7.7 – 9.5

– Biogas CR =10-12

• Ignition Advance

• More Wear & Tear because of less lubrication

Fig.1 : Schematic Diagram for Conversion of Diesel engine to 100% Biogas Engine

Spark Plug

Air Filter

MANUAL GAS CONTROL VALVE

BIO – GASDIGESTER

Electronic ignition Mechanism on cam shaft

ENGINE

Governor Control Unit

VenturiButterfly

Diaphragm operated Biogas Valve

Biogas

Speed Pick up sensor

Flywheel

Exhaust

Air Gas Mixture

Distributor

Modifications of the Engine

• Removal of fuel injection pump, fuel lines and injector,

• Reduction of compression ratio,

• Modification in cylinder head for installation of spark plug in the injector hole,

• Mounting of an ignition system with contact breaker assembly, ignition coil, spark plug,

• Installation of Gas carburetor

• Installation of Governing Mechanism

Flow Diagram

Existing Diesel Engine

Disassemble engine, Remove piston, Remove fuel Pump, Remove Injector

Change compression Ratio

Enlarge injector hole dia to adapt spark plug

Install the ignition mechanism on cam shaft/

Crank shaft .

Install gas carburetor.

Advance the ignition mechanism

Diesel engine converted to 100% Biogas

Engine/Producer gas

Actuator ECU UNIT Speed Sensor on Flywheel Speed Sensor

Electronic Governing Mechanism

ACTUATOR

GOVERNING

BUTTERFLY OF

CARBURETTOR

Spark Plug Distributor

H.T. Coil

Spark Ignition Mechanism

Spark plug in head

of the engine

Electronic Distributor

mounted on camshaft

H.T COIL

Vacuum operated Biogas Diaphragm Valve

Gas Carburetor/Air-gas Mixing

Diaphragm control

Gas Valve

Manual control

Gas Valve

Gas Carburettor

Diesel Engine Converted to 100% Biogas Generator-12 KW at IIT Delhi

Diesel Engine Converted to 100% Biogas Engine 3KVA (Single cylinder),7.5 KVA (Double cylinder)

Schematic Diagram for Conversion to Bio fuel Engine in Dual Fuel Mode using

Diesel and Biogas

VENTURIDIESEL

INJECTOR

DIESEL

FUEL FILTER

AIR

FILTER

MANUAL GAS CONTROL VALVE

BIO – GAS

DIGESTER

GOVERNOR

FUEL PUMP

ENGINE

GAS

CONTROL

VALVE

Dual Fuel Biogas Generator

Petrol Engine Converted to 100% Bio-Gas Engine

16

5.9 kW Diesel Engine Converted to Gas Engine

Brake Power

Engine Speed

Specific gas consumption rate

Brake thermal efficiency

Relative air/fuel ratio of combustion

22

Engine parameter at 12.65 CR Ignition advance (0TDC)

30 35 40

Brake power output (kW) 3.548 (CNG)

3.500 (enriched biogas)

2.581 (biogas)

3.914 (CNG)

3.800 (enriched biogas)

2.661 (biogas)

3.763 (CNG)

3.650 (enriched biogas)

2.661 (biogas)

Engine speed (rpm) 1409–1544 (CNG); 1402–1537 (enriched biogas), 1228–1437 (biogas)

Specific gas consumption (g/kWh) 465–1550 (CNG)

471-1667 (enriched biogas)

651–3524 (biogas)

409–1240 (CNG)

421-1304 (enriched biogas)

625–3550 (biogas)

535–1240 (CNG)

548-1391 (enriched biogas)

626–3674 (biogas)

Maximum brake thermal efficiency, % 18.8 (CNG)

21.8 (enriched biogas)

22.5 (biogas)

22.2 (CNG)

26.2 (enriched biogas)

23.3 (biogas)

19.4 (CNG)

20.9 (enriched biogas)

23.3 (biogas)

Range of relative air/fuel ratio of combustion 1.1–1.5 (CNG)

1.0-1.9 (enriched biogas)

0.5–0.7 (biogas)

0.6–1.1 (CNG)

0.4-1.1 (enriched biogas)

0.5–0.8 (biogas)

0.6–1.8 (CNG)

0.8-1.5 (enriched biogas)

0.5–0.9 (biogas)

Maximum load development, % 59.7 (CNG)

59.2 (enriched biogas)

53.4 (biogas)

68.2 (CNG)

66.6 (enriched biogas)

53.5 (biogas)

67.9 (CNG)

66.2 (enriched biogas)

51.9 (biogas)

Performance results: stationary engine

Chandra et al., 2011. Applied Energy, 88;3969–3977.

Thank You