Low pressure gas engines The industry standard. CIMAC discussion Athens 22. January 2015 Marcel Ott, General Manager, DF Technology

Transcription

1 Low pressure gas engines The industry standard CIMAC discussion Athens 22. January 2015 Marcel Ott, General Manager, DF Technology

2 Development path for gas powered marine engines 29 km3 LNGC MV Venator 7RNMD90 Moss S/Y NOR stroke low pressure Dual-Fuel engine stroke low pressure spark ignited engine stroke low pressure Dual-Fuel engine stroke high pressure Dual Fuel engine 6RTA84 at IHI, Japan 1987 high pressure Gas diesel engine 1995 Break through 4-stroke low pressure DF engine 2-stroke 4-stroke 2 Wärtsilä 26 January 2015 RS

3 Dual fuel test engine 6RTFlex50DF in Italy 6RT-flex50 Diesel engine installed in engine lab in Trieste, Italy in 2011 One cylinder converted for gas operation for concept development: - Concept and design alternatives evaluated Engine converted to full scale in summer 2013: - Engine performance mapped - Control system development - Component reliability tests - >1000 running hours logged RT-flex50DF test engine 3 Wärtsilä 26 January 2015 RS

4 Dual fuel test engine W-X72DF in Japan Strong support/interest from Japanese customers in Low Pressure DF engines - Cooperation with Japanese licensee Diesel United Ltd. W6X72DF test engine will be installed at Diesel United s facilities Engine started on diesel, gas start in the coming month Main objectives: - Additional test engine/facility - Further combustion and performance optimization, on larger bore engine sizes - Component reliability confirmations W-X72DF test engine 4 Wärtsilä 26 January 2015 RS

5 2-stroke low pressure dual fuel concept The Principle Engine operating according to Otto process Pre-mixed Lean burn technology Low pressure gas admission at mid stroke Ignition by pilot fuel in pre-chamber 5 Wärtsilä 26 January 2015 RS

6 2-stroke low pressure dual fuel concept The main merits Low gas pressure < 16bar - Simple and reliable gas supply system - Simple gas sealing - Wide selection of proven compressors/ pumps (piston or centrifugal) Lean Burn Otto combustion means IMO Tier III compliance: - Without additional equipment (EGR/SCR) - Without additional fuel consumption Scavenging Compression/ gas admission Ignition expansion - Without compromised component reliability Pre-mixed lean-burn combustion 6 Wärtsilä 26 January 2015 RS

7 2-stroke low pressure lean burn principle Lower peak temperatures Lower NO x formation! Diesel, max flame temp. Engine operating according to the Otto process Air and gas premixed before combustion: - lean mixture: more air available than needed for stoichiometric combustion - Cold flame temperature Low NOx Lower wall heat losses - No local rich combustion low particulate matter (PM) External ignition by pre-chamber - Provides energy needed to ignite gas - Good ignition stability with very low pilot fuel amount (<1% of full load energy input) Otto, max flame temp. 7 Wärtsilä 26 January 2015 RS

8 Total emission picture of low pressure principle Total hydro carbon contribution to CO2 equivalent emissions -15% PM further reduced by the DF technology with lean-burn Otto combustion with prechamber ignition Unlike CO 2, methane disappears over time. Its short term effect is 28 times stronger as a green house gas *) Methane slip = THC emissions (Total Unburned Hydrocarbons). Included in total CO 2 equivalent -85% Tier3! -99% -98% LP Potential to further reduce methane slip on the 2-s DF 2-s DF Otto process contributes positively to reduce the total emission scope compared to any engine operating in the Diesel process *) : IPCC report Climate Change Wärtsilä 26 January 2015 RS

9 Engine power Low pressure dual fuel engine output Methane number: 105% 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% Power output vs Methane number R2 R4 Typical max. service load Preliminary, to be confirmed 50% Methane Number MN Methane Number, MN rating on R1 to R3 line rating on R2 to R4 line Maximum output may be limited by methane number (MN), if rating point close to R1-R3 No output limitation from MN if rating point close to R2-R4 Considerations: MN of LNG is typically Gases with lower MN can be burned by reducing engine power output Operating area for low speed engines is typically < 85% CMCR 9 Wärtsilä 26 January 2015 RS

10 Firing pressure [bar] Firing pressure [bar] Knocking: What is that? Cylinder pressure Knock sensor signal Fig.: 1 Crank angle Fig.: 2 Normal combustion (Fig 1) Ignition Flame front propagation Knocking combustion (Fig. 2) Spontaneous ignition of end gas towards end of combustion Knock detected by Cylinder pressure trace - One pressure sensor per cylinder Knock detector signal (structure borne noise) - One knock sensor per cylinder For each individual cylinder and cycle 10 Wärtsilä 26 January 2015 RS

11 BMEP Operating window Thermal efficiency NOx emissions Misfiring Knocking: Safe detection and prevention! BMEP / engine load / torque - Reduction in power output allows a wider operating window Increased air/fuel ratio: - reduces knock tendency - Increases thermal efficiency - lowers NOx emissions Knocking Engine control system: - Adjusts air / fuel ratio and balances cylinders to avoid knocking or misfiring - releases safety measures in case knocking or misfiring is occurring Air / Fuel ratio 11 Wärtsilä 26 January 2015 RS

12 Low pressure dual fuel combustion stability Combustion stability criteria: cycle-to-cycle variation of IMEP Example: IMEP history over 300 cycles at full load (test engine 6RT-flex50DF) - In diesel operation - In gas operation Stable combustion comparable in both operating modes 12 Wärtsilä 26 January 2015 RS

13 Load response of Wärtsilä 2-stroke DF engines 6RT-flex50DF engine test results Water brake load variation with wave load profile Engine running in gas mode Engine control system covers any load and operation mode and enables even manoeuvring on gas! 13 Wärtsilä 26 January 2015 RS

14 Low pressure system fuel requirements Pilot fuel types: DMA, DMZ and DMB distillate fuels (as 4-s DF standard) Gas fuel requirements (as 4-s DF standard): HFO requirements as on std. diesel engines 14 Wärtsilä 26 January 2015 RS

15 Conclusion Low-pressure DF is the technology of choice and the industry standard! Operational experience from over s DF engines Incorporated running experience in 2-s DF engine design Reliability, safety, performance and emissions results confirmed on 6RT-flex50DF test engine Questioned areas from the market: Methane slip Methane Number / power limitations Load acceptance Safety principles Combustion stability 15 Wärtsilä 26 January 2015 RS