Pathways to the ultra- efficient powertrain – towards 60% … · 2017. 3. 15. · Future...

Future Powertrain 2017

Dr Robert Morgan

Deputy Head, AEC

University of Brighton

Pathways to the ultra-efficient powertrain –towards 60% efficiency

Copyright University of Brighton 2016Confidential

Advanced Engineering CentreUniversity of Brighton

2

Improving thermal efficiency

through fundamental

understanding of the in

cylinder processes


Are we at to the end of the road?3

Mechanical losses 3%

Finite combustion 3%

Blowby 1%

Cycle to Cycle variations 2%

Gas exchange 2%

Heat transfer 7%

TOTAL 18%

Stone 2012

Mercedes F1

Wartsila

RT-flex58T


Changing the rules – the split cycle engine, a new thermodynamic cycle

4

Less work of compression

Pre combustion waste

heat recovery

1. Isothermal compression

2. Isobaric heating

3. Mixed cycle heat addition

4. Expansion

Independent

optimisation of the

compression &

expansion cylinders


Why hasn't it been done before?5

�Several engines with split compressor and

combustion cylinders have been proposed

�Only the Isoengine recovered heat between the

chambers

1909 Ricardo “Dolphin” engine1

2004 “ISOENGINE”2

1 Engines and Enterprise: The Life and Work of Sir Harry Ricardo 2nd Ed 2Isoengine data analysis and future design options. Coney et al. CIMAC Congress 2004, Paper 83, Koyoto3http://www.scuderigroup.com/engine-development/

Scuderi Engine3


There are multiple challenges in practically implementing the recuperated split cycle engine

6

�Effective isothermal compression

�High pressure recuperation, practical for

mass manufacture

�Practical valve system with a very short

induction period at high T & P

�Achieving complete and rapid combustion in

the expansion stroke

Cryopower ULTRA

Isoengine, Cool R√


Ideal pressure trace – minimal compression work, inlet / chamber pressure equalised, rapid burn

7

Inlet pressure

Cylin

der

pre

ssure

Exhaust valve liftInlet valve lift

~30° period

TDC

Crank angle

Rapid burn,

12-20°ATDC

Pressure rise caused by air

induction, not compression!


Engine system installation at Brighton 8

Gas burner tube at c. 900° C

Gas storage bottles

Engine installation

�High pressure air system, delivers air up to 70 bar

�Gas burner delivers heated air at 800°C

�Prototype recuperator from Hiflux

�Split lubrication and cooling system


800rpm, 47.9Nm, 900bar rail, 23:1 AFR, 25bar inletStart of Combustion phased to IVC

9

Inlet air works against pistonChamber filled

prior to ignition


14 degrees of retard achieved, increasing torque to 91Nm

10

8.5bar/deg

30% increase

In volume

Inlet valve restricting flow

and so the chamber is

not fully filled

Less works

against piston,

Some work

recovery ATDC


1200 rpm, 800bar rail, 23.9:1 AFR, 30bar, 688degC inletCombustion still stable with 6 degrees retard

11


Impact on cycle efficiency12

-20

-15

-10

-5

0

5

10

15

-30 -20 -10 0 10 20 30

Ch

an

ge

in

th

erm

al e

ffic

ien

cy

, %

Change in combustion period, degrees crank


How does the split cycle engine compare?(update from FPT2016)

13

45% BTE

Isothermal

compression

Recuperation

Optimisation of

CR/ER & insulation

Baseline

Reduce H2 slip

43% BTE Current

best in class heavy

duty diesel

50% BTE

55% BTE

60% BTE

Fast burning fuel

58% BTE

Advanced

combustion

48% BTE

Advanced

combustion

47% BTE

WHR

50% BTE

WHR

Advanced

combustion

(two fuels) +WHR

Waste

heat

recovery

Chemical

looping

Split cycle

Closed hybrid cycles?

Improved

optimisation

Normal

fuels


Concluding remarks14

�Are we approaching the limits of what can be achieved with a conventional

Otto or Diesel cycle?

�But the reciprocating engine still offers many advantages over other solutions

in particular in high power – long range applications

�New approaches are needed to achieve a clean propulsion system that breaks

the 50% efficiency barrier

�The split cycle engine offers a solution, with the potential to approach 60% BTE

�Testing has proved the viability of the combustion system – the main

outstanding challenge!

Pathways to the ultra- efficient powertrain – towards 60% … · 2017. 3. 15. · Future...

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