Thermodynamic analysis of a tractor engine using GT POWER

Aim:

Thermodynamic analysis of a tractor engine.

Objective:

Do thermodynamic analysis of an engine for tractor application for use in India with following targets,

• Power 75 HP
• bsfc targets- min 210 g/kh and max 225 g/kWh
• cooled EGR configuration

Hint

1)Naturally aspirated engine BMEP can not be more than 8 bar, no limit to Turbocharged engines

2)Tractor engines are designed for Max Torque conditions

3)Max Torque is 20% more than rated Torque

4)Consider rated speed as 2200 rpm and intermediate speed as 1300 rpm

5)Consider rated A/F ratio as 25 and intermediate A/F ratio as 22

Tractor engine configuration:

Tractors are generally classified by the no of wheels

2-wheel tractor or single axis tractor

4-wheel tractor or two axle tractors

Tractor specification:

1. HP- 75
2. No of cylinders-4
3. Capacity- 3500cc, turbocharged
4. Rated speed-2100rpm
5. Intermediate speed-1300rpm

Computing bore and diameter from the engine capacity

`Capacity=pi/4*d^2*l*N`

Generally, tractor engine is described as square engine giving bore to diameter ratio 1:1.

The bore is finalized to 100mm and stroke length 110mm. tractors engine are under square engine which provide torque at less engine speed. Under square engine are tuned to exhibit peak torque at low rpm than over square engine.

Simulation model:

6-cylinder DI engine model

EGR model

Combining DI engine and EGR model configuration

Boundary conditions:

Engine geometric conditions

Bore=100 mm

Stroke=110 mm

CR=16.5

Inlet valve cam dynamic condition

The inlet valve diameter 45.5mm

Exhaust valve cam dynamic condition

The exhaust valve diameter 37.5mm

Case set up as function of rpm, air fuel ratio

GT Post:

Pressure variation in the tractor system model at 2200 rpm

Temperature variation in the tractor system model 2200 rpm

Pressure variation in the tractor system model at 1300 rpm

Temperature variation in the tractor system model 1300 rpm

Inline cylinder pressure variation

Temperature variation

Engine performance data

BP at 2200rpm=82.2kw

BP at 1300rpm=53.7kw

Brake torque at 2200rpm=356.8Nm

Brake torque at 1300rpm=394.8Nm

Air flow rate at 2200rpm=463.7kg/hr

Air flow rate at 1300rpm=259.7kg/hr

A/F ratio at 2200rpm= 24.97

A/F ratio at 1300rpm= 21.92

BSFC target at 2200rpm= 225.9 g/kw-hr

BSFC target at 1300rpm= 220.4 g/kw-hr

From the simulation output data, we find correlation with the target values. The thermodynamic analysis of tractor engine with the following parameter are approximately equal to final values. With EGR configuration, the nox and CO ppm values are also reduced.

Conclusions:

• The tractor engine model is designed by combining a 6-cylinder DI with an EGR model configuration.
• The simulation is tested for rated rpm and intermediate rpm speed.
• The values correlates with the target values satisfactorily, with having less nox emission characteristics.