This document discusses active charge air cooling (ACC) technology from Air Cycle Technology Ltd. ACC aims to control intake manifold temperature through a turbo-expander to improve engine performance, fuel economy and emissions. It presents ACC as a solution to constraints on spark ignition engines like knock, fuel enrichment and particulate emissions. Testing showed a prototype ACC system increased power by 10% and allowed increased ignition timing and air-fuel ratios on a dyno test, resulting in an 11% max power increase. The conclusion is that ACC is a feasible technical approach that has been demonstrated through development of a functioning prototype system.

1. Air Cycle Technology Ltd
Active Charge Air Cooling
for Combustion Improvement
Chris Whelan & Steve Hinton
October 2017

2. Air Cycle Technology Ltd
Contents
Technology drivers & constraints
Solutions & challenges
Tman: a key variable
Why ACC?
ACC system & modelling
Turbo-expander
Results
Conclusion
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3. Air Cycle Technology Ltd
Drivers & constraints
Technology drivers:
- Increased specific output
- Cycle efficiency
- Real-world fuel economy
- Legislated emissions
Constraints:
- Detonation (SI)
- Fuel enrichment/fuel economy (SI)
- Pm emissions (SI, CI)
- NOx emissions (CI)
- Transient response (SI, CI)
- Thermal & mechanical loads (SI, CI)
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4. Air Cycle Technology Ltd
Solutions & challenges (SI)
Status/current products:
CR, fuel enrichment, high load Pm, thermal/mechanical loading
High load EGR:
Boost system, charge cooling, thermal/mechanical loads
Water injection:
‘Range’
Miller cycle:
Boost system, charge cooling, transient response, mechanical loads
VCR:
Real-world fuel economy, base engine design
REDUCED CHARGE AIR TEMP BENEFITS ALL THESE SOLUTIONS
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5. Air Cycle Technology Ltd
Solutions & challenges
Active charge air temperature control makes a positive contribution to the
ACU/APC Thermal Power Roadmap
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6. Air Cycle Technology Ltd
Combustion Efficiency (gasoline)
• INSERT University of Berlin work
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Knock limited spark
timing increases linearly
with reducing Tman

7. Air Cycle Technology Ltd
Tman: a key variable
Intake manifold temperature (Tman) is a key variable:
• Engine power & torque
• Vehicle performance consistency & repeatability
• Fuel economy & emissions
Today, management of Tman is predominantly ‘reactive’
• Tman varies widely with ambient temp and boost pressure/temp
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R: Comp pressure ratio
Pamb: 100 Kpa
Tamb: 20 degC
Comp Eff: 75%
CAC Eff: 85%

8. Air Cycle Technology Ltd
Why ACC?
ACC = Active Charge (Air Temperature) Control
Pro:
Tman control over wide speed/load range
Sub-ambient Tman
Consistent & repeatable vehicle performance
CR increase ~ real-world fuel economy
Reduced thermal/mechanical loads
‘Additive’ powertrain system
Con:
Air-cycle cooling: COP <1
Increased primary boost pressure & cooling
Increased pre-turbine pressure & exhaust residuals
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9. Air Cycle Technology Ltd
Bypass for charge air temperature
control in intake manifold
Primary intercooler
ACC concept
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CAC 1
CAC 2
ENGINE
TURBOCHARGER
TURBO-EXPANDER
ACC intercooler

10. Air Cycle Technology Ltd
Turbo-expander
• Key component in ACC system
• Current unit in low-volume production:
High efficiency turbine: 80~85% over wide pressure ratio range
Aluminium housings & wheels
Sealed bearings
• Further weight/size/cost reductions for high volume production
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11. Air Cycle Technology Ltd
Vehicle installation
C/D class passenger car:
• 1.8 litre turbocharged gasoline, 180 PS
• Prototype turbo-expander
• Air-cooled intercooler
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Turbo-expander
Air-cooled intercooler

12. Air Cycle Technology Ltd
On-road test (1)
• Demo vehicle
• Prototype turbo-expander, Tman control OFF
• ACC effective over wide speed & load range
• Excellent transient response
• 10% power increase
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Intake manifold
temperature
Turbo-expander
speed
Primary CAC
temp OUT

13. Air Cycle Technology Ltd
On-road test (2)
• Zenos E10R
• Dry road, 10 degC ambient
• Prototype turbo-expander
• Logging & control system operational
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Control valve
modulation
Intake manifold
temperature
controlled close to
target

14. Air Cycle Technology Ltd
Vehicle Dyno Test
Skoda vRS:
• Rolling road dyno test
• Std. (=BL) and ACC configurations
• ACC build has re-mapped ignition timing
and AFR
• Max. power increased from 168 > 186 bhp
• AFR increased from 10:1 > 12:1 above
4500 rpm, (pro-rata above 3350 rpm)
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Summary
• 11% max. power increase at same engine speed
• 20% AFR increase above 3350 rpm (= 20% BSFC
improvement)

15. Air Cycle Technology Ltd
Conclusion
• ACC is a feasible technical response to current engine
technology drivers and constraints
• A functioning system is now in development
• Consistent and close charge air temperature control has been
demonstrated
• Modelling of engine, turbo-expander & ACC system has been
validated
• ACC diesel engine opportunities for engine-out NOx reduction
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