An innovative and Cost-effective Pneumatic Mild Hybrid Technology for Buses and Commercial Vehicles

Transcription

1 Islands of Excellence (IOE): An innovative and Cost-effective Pneumatic Mild Hybrid Technology for Buses and Commercial Vehicles Yan Zhang, Hua Zhao, and Tom Ma Centre for Advanced Powertrain and Fuels School of Engineering and Design Brunel University London, UK. Jing Feng, Zhiqiang Lin, and Jie Shen Guanxi Yuchai Machinery Company, China FISITA 2012 Beijing 27 th ~29 th, Nov. 2012

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3 BRUNEL UNIVERSITY London Location: West London, close to London Heathrow Airport ) Named after most famous British Engineer in Victorian Period

4 Centre for Advanced Powertrain and Fuels (CAPF) Prof. Hua Zhao Director, Head of Mech. Eng. Dept. Dr L. Ganippa Prof. A. Megaritis Prof. T. Ma Dr A. Cairns Dr J. Chen Dr Jun Xia Senior Lecturer Professor Associate Senior Lecturer Lecturer Lecturer Regenerative Engine Braking & Air Hybrid Powertrain Gasoline Engines Diesel Engines Laser Diagnostics CFD & Simulation Control Techniques 2/4 stroke Multi. injection Temperature Boosted DI Spray formation PIV flow KIVA3v Star-CD Control DI CAI HCCI LIF fuel & species LES Fault Diagnostics PFI CAI Fuel reforming H-S Imaging DNS Fault Tolerance CAI/SI Piston bowl PLIEF 2-phase Gas Dynamic Bio- Fuels Alter. Fuels SRS species Thermodynamic After-treatment LII, 2-color

5 World Class Facilities and Equipment Internationally Leading Research Optical SI/CI engines Camless engine Centre for for Advanced Powertrain and Fuels (CAPF) Steady and Transient engine test-beds

6 Brunel RegenEBD A novel engine technology of regenerative compressed air for trucks and buses

7 Conventional EBD Engine Braking Devices are well established in HD vehicles as an aid to slow down vehicles Add-on valve actuation/timing devices applied to the exhaust valve Air bleeder type Exhaust Intake Bleed type EBD Compression release type Exhaust Intake Compression release EBD Braking energy is released into exhaust system (wasted) and creates much noise

8 Brunel RegenEBD Regenerative Engine Braking Device on Intake valves Exhaust Intake RegenEBD Bleeder Type Exhaust Intake RegenEBD Compression Release EBD technology re-located to intake valve Add-on air capture device to inlet manifold Compressed air produced regeneratively using braking energy, stored and later re-used for engine stop/starts and boost assist Minimised noise from EBD

9 Brunel RegenEBD Activated only during engine braking No compromise to design of existing engine No change to engine full load performance, fuel efficiency and exhaust emissions during normal firing conditions Ideal for idle-off stop/starts in urban buses Potential for air-assisted boost in trucks and commercial vehicles Brunel world-wide patents

10 Brunel RegenEBD (single intake port) Exhaust Intake RegenEBD Bleeder Type Intake system EBD Boost

11 Engine Braking Performance and Compressed Air Capture (1500rpm, 150 litre air tank) Braking Torque State of Charge in Air Tank Engine Torque (N.m) Expansion 180 Exhaust 360 Intake 540 Compression720 Engine Crankangle (deg) Pressure (Pa) 8.E+05 7.E+05 6.E+05 5.E+05 4.E+05 3.E+05 2.E+05 1.E+05 Air tank pressure against 120 th, 240 th, 360 th engine revolutions for charging the air tank pressure from 1 bar to 7.1 bar 0.E+00 0 Expansion 180 Exhaust 360 Intake 540 Compression 720 Engine Crankangle (deg) It takes 240 engine revolutions to top-up the air tank from 4 bar to 7 bar in Compressor Mode during engine braking (9.6 sec at 1500 rpm)

12 Driving Cycle Analysis Millbrook London Transport Bus Driving Cycle 3000 Yuchai Base vehicle YC6A Air hybrid vehicle 2500 Idle on Engine speed (rpm) Idle off Matlab Simulink model of air hybrid vehicle Time (s)

13 Predicted results of London Bus Route drive cycle litres airtank 7.25L engine 16 tonne urban bus Airtank Pressure (bar) Fuel consumption (g) Time (s) 4000 Yuchai bus 3500 Air hybrid bus Time (s) In the drive cycle, there are 52 bus stops en-route of which 44 are idle off stop/starts sustainable with regenerative braking energy 27% of braking energy absorbed 6.2% reduction in fuel consumption Average >500 stop/starts per day for the bus poses no cycle life problem with compressed air energy storage

14 Implementation at YuChai: 1 st Generation RegenEBD sandwich plate with full-time Reed Valves Simple Reed valve (cracked Reed pedal) (proof-of-concept) Improved Reed Valve

15 Implementation at YuChai: RegenEBD sandwich plate with on/off Poppet Valves and Part-time Reed Valves Reed Valve Intake manifold Sandwich Plate Assembly with On/Off Poppet Valves and part-time Reed Valve RegenEBD operation Normal engine operation Engine intake port

16 Yuchai Engine Testbench Results Power output Power (kw) Base engine 1 st Reed valves 2 nd Reed valves Poppet valves Fuel consumption Speed BSFC(g/kWh) Base engine 1 st Reed valves 2 nd Reed valves Poppet valves Speed

17 Vehicle Trials over the Kunming bus cycle (1 st Gen. RegenEBD with part-time reed valves and on/off poppet valves) Stop/starts at some but not all bus stops More stop/starts if more compressed air is available

18 Yuchai Bus Test Results Stop/start controller and data logger rpm MPa Engine idle at bus stop Signal for idle shut off Air starter triggered by AccPedal Rapid start up to idle speed

19 Air Bleeder (Jake Brake) Improvements with 2 nd Generation RegenEBD Air Connectors Air connector fully retractable no flow restriction to engine volumetric efficiency Minimum auxiliary volume higher compression pressure and more compressed air produced during the same engine braking cycle hence more air available for stop/starts and boost-assist Disc valve replaces reed valve for single intake port better reliability for single intake port applications Intake manifold

20 Comparison of Engine Braking Performance (1500rpm, Bleeder type RegenEBD) 1 st gen. single intake port with Reed valve 2 nd gen. twin intake ports with air connector th 200th 300th -50 Engine Torque (N.m) Expansion 180 Exhaust 360 Intake 540 Compression 720 Engine Crankangle (deg) 2 nd gen. RegenEBD with air connectors produces higher braking torque

21 Comparison of Air Charging Process (1500rpm, Bleeder type RegenEBD) 1 st gen. single intake port with Reed valve 2 nd gen. twin intake ports with air connector th engine revolution 7 Pressure (bar) th engine revolution 100th engine revolution Expansion 180 Exhaust 360 Intake 540 Compression 720 Engine Crankangle (deg) 2 nd gen. RegenEBD with air connectors leads to faster charging, higher compressed air pressure and more compressed air captured (smaller tank at higher pressure to support more stop/starts and boost-assist)

22 Air charging improvement with 2 nd Generation RegenEBD 1 st generation RegenEBD takes 200 engine revolutions or approx 8 seconds braking to charge a 150L air tank from 5 bar to 8 bar 2 nd generation RegenEBD takes 120 engine revolutions or approx 5 seconds braking to charge a 150L air tank from 5 bar to 10 bar

23 2 nd Generation RegenEBD with Air Connectors For a 7.25L turbocharged diesel engine with two intake ports and 40L compressed air tank: 1. Irrespective of the EBD types, RegenEBD can produce more than120 litres of free air compressed from 4 to 10 bar in 4 seconds. 2. Compression release type RegenEBD generates higher braking torque, faster and greater compressed air pressure.

24 Benchmark RegenEBD system is a very simple embodiment of regenerative braking energy recovery at very low cost compared to complex electric hybrid systems Minimal modification required to existing powertrain/transmission systems Potential for retrofit in existing vehicles Expected payback period for operators should be months not years

25 Summary A cost-effective pneumatic regenerative stop-start hybrid system (RegenEBD) for buses and parcel delivery vehicles has been proposed and investigated on a bus diesel engine on an engine test bed. A city bus equipped with the RegenEBD engine was commissioned to demonstrate the potential of the RegenEBD. The results show that the fuel economy can be improved by 5%- 10% for inner city buses. In order to further improve the air charging efficiency and hence fuel economy, alternative intake designs without permanent Reed valves are proposed and being developed and their performance and effect on RegenEBD system will be reported in near future.

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