Understand different types of Turbocharger & explore Diesel VGT EGR

Title: Understand different types of Turbocharger & explore Diesel VGT EGR

Objective: 1. Understand diffrent type of Turbocharger

                2. plot operating point on compressor & turbine maps

                3. Explore Diesel VGT EGR

1. Diffrent types of Turbocharger & locate in to GT Power

Types of Turbocharger

1. Single Turbocharger (Fixed geometry)

Single turbochargers are what most people think of as turbos. By differing the size of the elements within the turbo, completely different torque characteristics can be achieved. Large turbos provide higher levels of top end power, whilst smaller turbos can spool faster and provide better low-end power. They are a cost-effective way of increasing engine power and efficiency, and as such have become increasingly popular, allowing smaller engines to increase efficiency by producing the same power as larger naturally-aspirated engines, but with a lower weight. They do however tend to work best within a narrow RPM range, and drivers will often experience ‘turbo-lag’ until the turbo starts to operate within its peak rev band.

2. Waste-gate Turbocharger

Nowadays, vehicles with turbocharged engines feature the wastegate turbocharger. This technology helps to deliver optimum engine performance during peak operating conditions. In addition, the wastegate valve prevents the turbocharger from over-running. Particularly, it also avoids the engine from over-boost and prevents any mechanical failure.
This feature in the turbocharger consists of a bypass valve. It circumvents some part of the exhaust gas going to the turbine and releases them into the outlet. Furthermore, the waste-gate turbocharger has a bypass valve built into the turbine housing. It diverts some of the exhaust gases away from the turbine wheel through this valve

3. Variable geometry Turbine Variable-geometry turbochargers (VGTs)

are a type of turbochargers, usually designed to allow the effective aspect ratio of the turbocharger to be altered as conditions change. This is done because the optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, VGTs have a minimal amount of lag, a low boost threshold, and high efficiency at higher engine speeds.

4. Twin-Turbo

                                    
As the name implies twin-turbos mean adding a second turbocharger to an engine. In the case of V6 or V8 engines, this can be done by assigning a single turbo to work with each cylinder bank. Alternatively, one smaller turbo could be used at low RPMs with a larger turbo for higher RPMs. This second configuration (known as twin sequential turbocharging) allows for a wider operating RPM range, and provides better torque at low revs (reducing turbo lag), but also gives power at high RPMs. Unsurprisingly, having two turbos, significantly increases the complexity and associated costs.

5. Electric Turbocharger

An electric turbocharger is used to eliminate turbo lag and assist a normal turbocharger at lower engine speeds where a conventional turbo is not most efficient. This is achieved by adding an electric motor that spins up the turbo’s compressor from start and through the lower revs, until the power from the exhaust volume is high enough to work the turbocharger. This approach makes turbo lag a thing of the past, and significantly increases the RPM band within which the turbo will efficiently operate. So far, so good. It appears that electronic turbos are the answer to all the negative characteristics of conventional turbochargers, however there are some disadvantages. Most are around cost and complexity, as the electric motor must be accommodated and powered, plus also cooled to prevent reliability issues.

locate example of GT-POWER

1.Fixed geometry Turbocharger

2. Twin Turbocharger

3.Wastegate Turbocharger

4. Variable geometry Turbocharger(VGT)

Explore Tutorial No.6 & 7

above model for fixed geometery. so, we can see that turbine & compressor is connected with shaft. for operate the compressor & turbine there is need to provide the input, so we can map with current running model. it's very important to test the turbocharger at diffrent altitude. so, consider the three diffrent altitude 0, 2000, 4000

Case setup

Turbine input map data

Case 1 operating point for compressor while solving equation 

above picture for compressor efficiency & speed . when model is running it will show the operating point is within range or not.

Case 3 operating point for compressor while solving equation 

above picture for altitude of 4000 . so, its shows that compressor is operate within range 

Engine performance for diffrent three cases

as altitude increase power get reduce , its due to rpm is reduce & also air flow rate is reduces 

Compressor at diffrent three cases

from above picture we can see that at higher altitude 4000, there compressor preesure output ratio is reduces

Turbine at diffrent three cases

from above picture we can see that at higher altitude 4000, there turbine preesure output ratio is reduces

Compressor & turbine efficiency & pressure ratio

from above picture its seen that turbine give higher efficiecy than the compressor

Operating point on compressor

from above picture we can see that as point procced from 1 to 3, there is mass flow rate is reduces & pressure ratio is reduces 

Operating point on Turbine

Variable geometery Turbocharger

By use of variable geometery turbo we can vary the aspect ratio so, we can create any pressure ratio, so, it' s advantange that we can get sudden acceleration by use of respective pressure ratio. by variable geometery we can set the BMEP whatever we want. specially in hilly roads its helpful because we can get easily pressure ratio.

Explore Variable geometery Turbocharger

Case setup

above case setup made for target BMEP & engine speed

operting point for case 3

Engine performance

at lower 1500rpm produces power is 32.5 kw due to air flow rate , fuel flow rate  &air fuel ratio reduces

Compressor performance at diffrent cases

as Engine rpm reuces there is reduction of overall pressure ratio & output pressure

Turbocharger performance at diffrent cases

as Engine rpm reuces there is reduction of overall pressure ratio & output pressure

Compressor & Turbocharger efficiency 

Compresor gives higher efficiency  because of its operating favourable zone

Final operating point on compressor 

from above picture we can see that as point procced from 1 to 5, there is mass flow rate is reduces & pressure ratio is reduces.

Overall conclusion

1. Turbocahrger is manly use for increase the ouput power of vehicle

2. Turbocharger have diffrent type & its uses as per operating condition & type of vehicle

3. Altitude is affected on engine performance. so, by providing correct mass of fuel we can obtain better output power.

4. By use of Wastgate turbocharger we can set the pressure ratio of turbocharger & also we can avoid the mechancal damage.

5. Variable geometery turbocharger is useful for operate diffrent altitude as well as its useful for to get quick acceleration there is use.