Power comes with many things, not least responsibility. Caterpillar’s new high-speed genset has not only smashed through the output ceiling of its competitors, but it was also built from the blocks of a newly developed emissions control technology. PEi reports from the launch of the 2-4 MW range.
Robin Rowshangohar, Assistant Editor
Speed is something celebrated as much as it is strived for. Olympic runners are cheered on to win gold, thoroughbred horses are roared on to be first past the post and race car enthusiasts do their best to be heard above the most powerful of engines, urging their favourite to see the chequered flag first.
Every year people flock to Indianapolis to watch pinnacles of high-speed engine technology flying round its famous track, so it is perhaps fitting that Caterpillar chose to unveil what it hopes will prove to be a landmark in high speed diesel engine technology at its factory just outside the race car capital.
The new C175 engine began its life in 2003 when the first technical drawings were penned by a specialist team, many of whom were responsible for Cat’s existing high-speed offering, the 3500 series. At present the largest output of a high-speed genset is 2.2 MW, while medium-speed genset packages typically do not come into their own until the 5 MW output range. The C175 genset range will offer a variety of packages that range in output from 2.5 MW to 4 MW.
“The 3500 didn’t have any stretch left,” according to Joel Haeflin, global marketing manager for Caterpillar’s Electric Power Division, explaining how the new product is more than just an extension of a high-speed engine that is now 25 years old. “We took a clean sheet of paper to create a product for a reasonably untapped market.”
A clean start
The challenge to create a new force in high-speed engine technology has seen Caterpillar design and implement a raft of new technologies and invest well in excess of $100 million in new facilities at its 111 500 m2 manufacturing plant in Lafayette, specifically for C175 production. Caterpillar is confident its new centreline engine will fill a gap in the market and convert those who have previously shunned genset technology.
Figure 1. The finished product
Those responsible for developing the C175 highlight five areas that were key to creating a high-speed engine capable of generating almost double the power of its nearest rival. Piston and bearing surface speeds, combustion optimization, thermal loading/decreased heat rejection, performance/power capability and core component materials. In order to further tempt customers, the project was designed to have as compact design as possible. Building an engine with 40 per cent greater power density than a medium-speed equivalent placed more pressure on developing innovative solutions to meet these challenges.
To counter the problem of piston and bearing surface wear a lube system was developed that features a pressure regulation valve, allowing the engine to maintain optimum oil pressure at all speeds and loads. It also improves cold start capability by providing full gallery oil pressure in less than four seconds. Two cooling jets per piston were also incorporated into the design.
A building block of the engine design is the Common Rail Fuel System that utilizes a high pressure fuel pump and control valve to maintain the desired fuel rail pressure. The system has the capability to deliver multiple injections within a single combustion event with what Caterpillar calls “unprecedented precision and repeatability”. Each injection event is controlled in timing and volume to maximize combustion efficiency and reduce emissions.
This fuel system is part of Caterpillar’s Acert emission control technology, which is now used in around 330 000 engines worldwide. Also part of Acert, which was three years in development at a cost of $0.5 billion, is the C175 engine platform’s electronics and controls. As part of an integrated system, the ADEM A4 controller works to provide low fuel consumption and reduce emissions. It also precisely maintains coolant temperature and oil viscosity to add reliability and durability to all engine parts.
The Acert air system was also incorporated to enhance engine breathing. It uses a tall cross-flow cylinder head that has been designed with larger ports to allow more cool, clean air into the combustion chamber. This helps provide the engine with higher power density and reduced cooling needs by minimizing heat transfer between both the intake and exhaust ports, as well as the manifolds. The air system also contains a turbocharger with a cast titanium compressor impeller that helps extend turbocharger life to at least one major overhaul – translating into 24 000 hours for 60 Hz, 1800 r/min, and 28 000 hours for 50 Hz, 1500 r/min models. The C175’s cooling system was also redesigned in order to maximize heat rejection and obtain higher overall engine efficiency by only targeting areas of the engine that require cooling. In addition, the length of the exhaust port is reduced to minimize unnecessary heat rejection into the jacket water. Test results have shown this to provide an improvement in heat rejection per kW produced of between 20 and 30 per cent.
The C175 was designed with a core engine system to enable greater cylinder pressure capability. Creating something with so much power packed in so tightly, should at first approach throw up all manner of maintenance headaches. Not so, says Doug Long, the engineering manager with responsibility for C175 testing: “We tried to purposefully package the key maintenance equipment outside of the central V.”
Figure 2. The C175-12 being manufactured at Caterpillar’s manufacturing plant in Indiana, USA
The engine design includes technological enhancements and advances in major components such as the crankshaft, bearings, piston, rod, block, liner, head, valves and valve mechanism and camshaft. With larger main and pin diameters, the C175 crankshaft, built on a robust steel forging, is designed for the currently announced ratings and will provide room for future rating growth, should the market have the desire for it.
A bigger, robust steel-forged crankshaft handles bigger loads, while the cast iron engine block provides increased strength and lighter weight; so more power is generated from a smaller package. Comparing the C175 with a Caterpillar medium-speed genset of the same power output range (the 3608), the high-speed offering has a footprint of approximately half the size (11.8 m2) and is around half the weight. Its power density is 20 per cent greater than typical high-speed alternatives and 40 per cent better than medium-speed alternatives.
As the cloak surrounding the C175 genset is pulled away to great fanfare and it is unveiled as a product for the first time, it seems quite remarkable that all of this has been achieved in just three years, begging the question of what problems the team encountered along its way.
“It’s been surprisingly smooth, the way it’s come together,” says Bill Barber, product manager for Caterpillar’s electric power division. “If we were developing it for just one application it would be a lot easier,” he quips, but where this may have been a problem for some, Caterpillar has switched this around to draw from experience in its other divisions. Decibel levels for instance, in some of Caterpillar’s other areas, have to be lower, so the company has incorporated this knowledge into the C175 resulting in preliminary noise testing showing that the engine, when measured alone, reaches between 105-108 decibels. This figure pleases Barber, who expects this figure to fall as the finesse touches are added. Also, in vibration tests the C175 has performed superbly, according to Barber, who says: “It shows that the guys who put the engine together got it right”.
All this is very well, but having created a high-speed engine that is capable of generating more power than any other before it while operating to meet the strictest emissions standards, it would be a shame if it was ruled out of the race before it had begun due to prohibitive costs. “We expect it to be significantly lower than a medium-speed equivalent,” says Barber, who points to a comparison between four C175 2.5 MW machines and 10 MW worth of its medium speed 3616 genset. In continuous duty, over ten years, a 50 Hz offering shows the C175 provides 3 per cent better fuel consumption, installation costs will be lower and the initial genset cost will also be less. It again proves cheaper when comparing two separate 20 MW standby plants, one made up of seven C175 2.5 MW engines and one made up of ten of Caterpillar’s high-speed 3516 2 MW gensets. In this scenario, over ten years, the C175 has a 14 per cent lower balance of plant cost.
“Customers have a lot of headaches with medium-speed engines, including our own, and the cost per kW is higher,” says Haeflin, “Customers who were put off by medium-speed, will now hopefully reconsider.”
Around 30 different applications are planned for the C175 engine, as it becomes one of Caterpillar’s centreline engines. It is being launched as a genset for electric power first of all and will be followed by roles in the petroleum, marine and rail industries over the next few years. The engine has just entered the field test phase and 15 genset units are currently part of a fleet of 30 being put through their paces in North America, Madagascar, Peru and Brazil.
Aiming to meet power growth first and then the market created by tougher emission controls, Caterpillar plans to begin production of the C175-16 (3 MW) in 2007, followed by the C175-20 (4 MW) in 2008 and the C175-12 (2.5 MW) in 2009. This final package will be ready to meet the Tier 4 emissions regulations when they are introduced in the US.
The order board for C175 genset packages will be fully opened by the fourth quarter of this year and as the company revs up on the starting grid, one thing is for certain, when the lights hit green, this genset range has the credentials to leave the rest vying for its slipstream.