Case study on heavy duty CI engine for tractor application using GT-SUITE

Objective:

1. To model a heavy duty CI engine to suit target specifications

2. To perform case study on naturally aspirated, turbocharged and EGR engine.

Engine specifications:

Type: CI engine

Number of cylinders: 4

Bore(mm): 100

Stroke(mm): 110

Capacity: 3.455 L

Connecting rod length(mm): 220

Compression ratio: 16.5

Target performance specifications:

Case 1: Naturally aspirated 4-cylinder CI engine

Case 1 results:

Case 1 Discussions:

1. Practically, brake mean effective pressure(BMEP) for naturally aspirated engines is usually less than 8 bar. The same can be observed in case 1 model, BMEP is 6.04 and 4.86 bar in Max torque and Max power condition.

2. From above results,we can observe that since engine is naturally aspirated, air flow rate is much less than target air flow rate.Therefore to achieve the desired air flow rate, engine needs to be turbocharged.

3. Due to less air flow rate achieved in naturally aspirated engine, we can observe power and torque is also much less than target values.However, target bsfc and air fuel ratio is maintained in order to maintain emission levels.

4. In order to maintain air fuel ratio, fuel injected to the cylinder is set low according to achieved air flow rate.

5. Max in cylinder pressure is 43.36 and 42.05 bar in max power and max torque conditions. Max in cylinder temperature is 1777 and 1917 k in max power and max torque conditions.

Case 2: Turbocharged, intercooled 4 cylinder CI engine

In this case we have considered turbocharged engine with compressor outlet and turbine inlet pressure to be 2 bar. From compressor outlet, intercooler is connected in order to send denser air charge into the cylinder by decreasing the temperature.

Case 2 results:

Case 2 discussions:

1. The BMEP attained in max power and max torque condition is suitable for turbocharged engine.

2. The target max power 75 kW is obtained at 2200 rpm and 50.5 kW is obtained at max torque condition.

3. 370.8 Nm torque(close to target max torque) is obtained at max torque condition at 1300 rpm and 326 Nm is obtained at max power condition.

4. The target bsfc(i.e. 210 to 225) is attained at both Max torque and Max power condition.

5. Target Air flow rate is obtained at both max torque and max power condition.Since denser air is sent to cylinder by turbocharged engine, air flow rate is higher than that of naturally aspirated engine.

6. Since air flow rate is increased, in order to maintain the target air fue ratio, fuel injected is increased.Hence more power obtained than naturally aspirated.

7. Maximum pressure is 93.5 and 85.84 bar in max power and max torque condition, higher than that of naturally aspirated.

8. Maximum temperature is 1802 and 1945 k in max power and max torque condition, higher than that of naturally aspirated.

9. Due to increase in cylinder temperature, Nox emission in turbocharged engine is higher than naturally aspirated engine. Exhaust gas re-circulation technique can be adopted in turbocharged engine in order to reduce the NOx emissions.

Case 3: Turbocharged 4 cylinder engine with EGR

Case 3 results:

Case 3 Discussions:

1. Slight reduction in power ad torque can be observed due to exhaust gas re-circulation.

2. We can also observe reduction in maximum pressure as compared to case 2 model.

3. Exhaust gas re-circulation percentage is around 7 which is in permissible limit.

4. Reduction in Nox emission can be observed in EGR model compared to turbocharged model.

Conclusion:

Target performance specifications are obtained in Case 2 and case 3. Expected change in engine performance can be observed in all modelled cases.i.e increase in air flow rate due to turbocharged engine compared to naturally aspirated. Also decrease in Nox emission in EGR model.