gt-suite european user conference - gamma … european user conference e-charging on a high...

GT-Suite European User Conference

E-Charging on a High Performance Diesel engine

D. Peci, C. Venezia

EMEA Region - Powertrain Engineering

Powertrain Research&Technology

Frankfurt, Germany

October 26th, 2015

Introduction

2

Aim:

using the current e-charging technology, is it possible to use the e-booster together with a traditional

VGT turbocharger, in a "two-stage-like" configuration for High Performances?

Case study:

High Performance Diesel engine, starting from an existing baseline to a high-output version, with a

new specific turbocharger.

The Challenge:

increased targets both for rated power and low-end torque.

Is the e-booster capable of steady-state operation to ensure the required boost pressure for target

low-end torque, working together with a high-end power-oriented VGT?

October 26th, 2015

Increased low-end torque target: high boosting demand for the e-booster

in steady-state conditions

Higher top power: fully demanded to the new

turbo-matching, larger than the baseline TC

E-Charging on a High Performance Diesel engine - GT-Suite European User Conference

Key-points - AGENDA

3

Turbo-matching: the new VGT turbocompressor has to reach target rated power, but the matching has

to be oriented to reduce TC size as much as possible. How to avoid critical torque gaps in the medium

rpm range?

e-booster layout: on the considered engine, the e-compressor can be placed upstream the compressor

or downstream the CAC. What are the concerns, advantages and drawbacks of these two possible

solutions?

Full load performance: is the low-end target torque reached within e-booster limits? If no, what kind of

assumptions can be made to ensure vehicle target performances?

Transient response: typical time-to-boost reduction expected with e-booster is achievable also with a

larger turbo-matching?

Conclusions: can the e-booster ensure the performance improvement requested for a two-stage like

solution, matched with a standard VGT turbocharger?

E-Charging on a High Performance Diesel engine - GT-Suite European User Conference October 26th, 2015

Key-points - AGENDA

4



rpm range?



solutions?








Important step: to optimize volumetric efficiency and intake/exhaust systems permeability, leading to

higher performances with a limited increase of the boost pressure. This means also a small increase in

TC size, and then a limited impact on engine transient response.

Turbo-matching

5

The baseline TC has to be replaced with a new one for

higher rated power: this change leads to a lack of torque in

the low-end region, that has to be filled with the e-booster.

New VGT turbo: higher top power, but worse low-end performances. eBooster is called to a steady-state operation to satisfy low-end torque target.

Brake Torque

610% volumetric efficiency improvement

Volumetric Efficiency

Different matching and different placement on the high-end side: same PR as a lower performance version

Points on compressor map


Key-points - AGENDA

6



rpm range?



solutions?








e-booster layout: "UPSTREAM"

7

The e-booster is located upstream the compressor.

BENEFITS

Easy installation for the eC;

the e-booster can be used to reduce compressor PR in

full load conditions (to keep operating points within the

compressor map);

both HP and LP EGR circuits allowed;

charge air from e-booster and compressor is cooled

(mandatory for gasoline applications).

DRAWBACKS

Transient response is not the fastest possible (big

volume to pressurize);

possible layout complication due to LP EGR circuit

integration at compressor inlet.


The e-booster is located downstream the CAC, without

additional charge air cooler (due to layout constraints).

BENEFITS

Fast transient response;

the e-booster can be used to reduce compressor outlet

temperature in full load conditions;

e-booster cooling circuit can be easily integrated with

CAC or WCAC water circuit.

DRAWBACKS

Charge air from e-booster is not cooled: temperatures

may be OK for Diesel engines (close to intake temp. with

HP EGR, but in full load conditions…);

only LP EGR circuit allowed;

eC map not fully exploitable, if working under high boost

from TC (eC required power depends on air density).

e-booster layout: "DOWNSTREAM"

8 E-Charging on a High Performance Diesel engine - GT-Suite European User Conference October 26th, 2015

The e-booster is located downstream the CAC, without

additional charge air cooler (due to layout constraints).

BENEFITS

Fast transient response;

the e-booster can be used to reduce compressor outlet

temperature in full load conditions

e-booster cooling circuit can be easily integrated with

CAC or WCAC water circuit.

DRAWBACKS

Charge air from e-booster is not cooled: temperatures

may be OK for Diesel engines (close to intake temp. with

HP EGR, but in full load conditions…);

only LP EGR circuit allowed;

eC map not fully exploitable, if working under high boost

from TC (eC required power depends on air density).

e-booster layout: "DOWNSTREAM"


The considered e-booster is a 48V device.

Peak power is allowed during the launch phase, that brings the

e-booster speed from min to max rpm in 0.3 sec.

Activation time at maximum power for transient operation depends on

coolant temperature.

Max power considered for pure steady-state operation is about 1 kW.

e-booster use is foreseen up to 1750 rpm in a "two-stage-like"

configuration, but improvements in traditional compressor operation

are expected up to 3000 rpm (reduction of compressor outlet

temperature, in a "downstream" layout).

e-booster: info


e-booster: control strategy in GT-Power

11

The e-booster instantaneous torque is sensed, filtered and used to calculate the instantaneous speed

that would be needed to reach maximum e-booster power. This speed value is constantly compared to

e-booster maximum speed, then the minimum between these two values is actuated.

In the very first phase of e-booster activation, the maximum speed profile is imposed, to prevent speed

oscillations due to possible instability (there is no risk to exceed maximum power in this phase, since

the instantaneous mass flow rate is quite low).

time signal (switch enabler)

Air to intake manifold

Air from CAC

e-booster bypass is controlled to ensure fast transient response


Key-points - AGENDA

12



rpm range?



solutions?








Full load steady-state performance (1/3)

13

Intake manifold pressure Brake Torque

The target torque curve is achieved by using the e-booster at its maximum speed/power.

The e-booster effect is added to engine performance without eC. Three curves are compared:

- no e-booster (performance with new VGT TC only);

- e-booster optimized (e-booster optimized for maximum performance);

- e-booster limited @ 1 kW.

All the configurations have the same combustion laws and the same A/F ratio limits.



14


Curves without e-booster and with partialized e-booster have the operating points placed on the surge line. By using the e-booster it is possible to move the points inwards.

The "downstream" layout may be critical in terms of

intake manifold temperature, when the e-booster is

running at maximum speed/power.

On the other hand, this layout is positive in terms of

compressor outlet temperature, since the e-booster

can be used to reduce the boost demand for the

turbocharger.

An additional charge air cooler downstream the

e-booster would be a great improvement, but with an

increase in cost and layout complication.

Temp. @ compressor outlet

Intake manifold temperature



15

Looking at the required e-booster power, the use of

the e-compressor in a "two-stage-like" configuration

is very challenging, especially in the low-end zone:

this is due to possible thermal issues.

The comparison in terms of Brake Torque (slide 13)

shows that in "e-booster limited" conditions the low-

end torque is quite below the target. However, the

actual engine response to a full-performance request

should be evaluated taking into account the vehicle

characteristics (transmission…).

Points on e-booster map

12501750 rpm: e-booster used for low-end torque target accomplishment

20003000 rpm: e-booster used for compressor outlet

temperature reduction

e-booster power (el.)

e-booster active: 12503000 rpm


e-booster speed




Key-points - AGENDA

16



rpm range?



solutions?








Transient response - Load steps @ 2250 rpm

17

e-booster speed

e-booster speed is limited by maximum electric power

MAX speed

Brake Torque

Part load stabilization (with EGR)

Intake manifold pressure


e-booster electric power is limited to its maximum value

(after a small overshoot)

MAX el. power


Transient response - Load steps @ 1250 rpm

18

e-booster speed

MAX speed

e-booster runs at its maximum speed

Intake manifold pressure


e-booster speed is not limited by maximum electric power

MAX el. power

Brake Torque

Part load stabilization (with EGR)

Torque gap without e-booster!!!


Transient response - vehicle acceleration (1/3)

19

The entire boosting system on this engine configuration is made of two different parts with their

peculiar features:

- the VGT TC has high boosting capability, but also great inertia;

- the e-booster is very fast in its response, but it can provide a limited PR for a limited time

(depending on many factors, for example coolant temperature, air temperature, etc.).

How does this system react to a hard vehicle maneuver?

To define a very challenging test, a 80-140 km/h acceleration has been performed with a simplified

vehicle model, by locking the transmission in its highest gear, to understand the effect of the e-booster

and possible issues related to its operation.

Vehicle speed Part load stabilization

(with EGR)

Engine torque



20


The e-booster response is very fast: it helps

reducing the huge impact of VGT TC inertia on

vehicle acceleration.

The stand-alone turbocharger can provide the

required boost pressure above 1800 rpm only.

Looking at the compressor map, the acceleration

with e-booster is less critical in terms of surge.

Boost pressure

e-booster response: very fast

Upstream e-booster

Downstream e-booster

Engine rpm



21

Points on e-booster map

In the first part of the acceleration, the e-booster is

driven at its maximum speed, then, once the

maximum electric power is reached, the speed is

controlled in order not to exceed this value.

e-booster speed



Key-points - AGENDA

22



rpm range?



solutions?








Conclusions

23

A "two-stage-like" charging system made by a large turbocharger + e-booster is capable of good

performance improvement. This solution can be very simple to implement on a vehicle, especially in a

scenario ruled by electrification of the vehicle architecture.

To ensure good performances, the synergy between the TC and the e-booster has to be optimized:

- the turbocharger inertia must be the lowest possible (each improvement on engine side would

help the boosting system to work better);

- e-booster and turbocharger have to be properly coupled (smooth transition between low and

medium engine speeds in full load): for this reason a VGT turbocharger is required;

- the e-booster layout must be carefully evaluated; a HP EGR circuit does not work with the

"downstream" e-booster layout, so a LP EGR circuit is needed;

- an additional CAC downstream the e-booster could improve low-end performances.

For the considered system, some vehicle maneuvres involving frequent and close accelerations may

be critical in terms of e-booster activations, resulting in poor engine response to vehicle dynamics

requests.

However, this boosting architecture has been found interesting and its potential will be exploitable with

further development of the electrical components.


24

THANK YOU FOR YOUR ATTENTION

QUESTIONS?


gt-suite european user conference - gamma … european user conference e-charging on a high...

Documents