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Cummins Targeting 50% Efficiency and 2010 Emissions via Waste Heat Recovery Scheme

Cummins is working with a scheme for waste heat recovery to boost performance of its heavy-duty diesel engines to 50% Brake Thermal Efficiency while meeting the upcoming 2010 EPA emissions specifications.

Cummins has already demonstrated heavy-duty diesel engine performance of 45% Brake Thermal Efficiency with 2007 EPA emissions (earlier post). On the emissions front, meeting 2010 requirements entails a significant decrease of NOx emissions from 1.2 g/bhp-hr to 0.2 g/bhp-hr.

Brake Thermal Efficiency represents in percentage terms the amount of energy converted from fuel into useful mechanical work by the engine. A engine with a higher BTE level is more efficient, offering the potential for increased fuel efficiency and associated reductions in CO2 emissions. Percentage point improvements in this are hard-earned.

The majority of the heat energy of the fuel is unused

With average heavy-duty diesel BTE of around 42%, most of the heat energy released through combustion is lost. Cummins—and many others—reason that minimizing heat rejection while improving BTE would be ideal. Low Heat Rejection Engines (LHRE) using a variety of mechanisms have been a subject of study for years.

Cummins is dividing its work on this project into two components: continued optimization of the base engine, and development of the waste heat recovery system.

Work on the base engine platform involves further optimization of combustion, improvements to the high pressure common rail injection system, more low-temperature cooled EGR, and reduction of mechanical parasitic losses.

For the energy recovery system, Cummins has opted to go with a Rankine Bottoming Cycle system for the generation of electricity from the waste heat.

The basic Rankine cycle has four stages:

  1. A working fluid is pumped from low to high pressure by a pump. Cummins is using a mix of Flourinal and water.

  2. The pressurized liquid is heated at constant pressure by an external heat source (in this case, the exhaust gas) to become a superheated vapor.

  3. The superheated vapor expands through a turbine to generate power output.

  4. The vapor then enters a condenser where it is cooled to become a saturated liquid. This liquid then re-enters the pump and the cycle repeats.

Rankinelayout_2 Rankineschematic
Concept Layout for Max BTE Demo Using Rankine Bottoming Cycle system.Demonstration schematic.

Cummins considered and rejected other approaches, including variants and combinations of Rankine Bottoming, turbocompounding and thermoelectrics, because of complexity or constraints on power delivery.

Current thermoelectric waste heat recovery schemes still do not provide enough power recovery for Cummins’ needs. The Rankine Bottoming Cycle, according to Cummins’ analysis, is proven in other industries, capable of recovering and delivering adequate power, could work for the out-of-vehicle high-BTE demonstration and is suitable for future on-board integration.

The fixed-nozzle, axial inflow turbine generator projected for the demonstration has a 50,000 rpm design point speed, with 400–450 VAC output. Target power is approximately 45kWe, with 77% turbine efficiency at the design point. Flourinol cools the bearings and the generator. This unit is not designed for future in-vehicle applications.



Harvey D

It seems that Cummings is doing exactly what the Administration said was not possible, i.e. increasing efficency and reducing pollution at the same time. This proves there's no need to relax the pollution standards to get better engine efficiency. The same logic should apply to refineries and tar sands extraction.


Rankine-cycle engines react slowly to changes in heat input and have one preferred power setting, but a hybrid could stash away the power in batteries when the throttle was lifted.  This would also work well with the TIGERS scheme to recover energy from the pressure of the exhaust gas.

You might want to pre-clear links to GCC itself with your anti-spam system... just a hint.

Jesse Jenkins

I agree, they could easily use the TIGERS device to recover energy from the exhaust. In fact, I don't see any reason why TIGERS shouldnt be installed in every new IC engine.

Props to Cummings though for boosting efficiency AND cutting emissions. If only we could get GM and Ford to commit to do this in all their models too...

Jesse Jenkins

Oh, that's right, it's because Ford and GM are too busy losing money to do something smart like change their business strategy. That might help them actually make money ... a novel concept for Detroit but I think they might like it...


No brainiac Gm is providing health care for 1 million former uaw workers and 200k current ones at an enormous cost. Even a small agreement recently just saved gm 1 billion a year and its been said the grand total for the 1 million former workers and 200k current ones is 70 BILLION.

Thier costs plus americans tendancy to equate small cars with cheap cars means they cant compete.

Ford is only managing it by using non unionized workers in mexico and other places to make thier smaller cars. Ford also has a massive health care burden.

Both likely will go bankrupt to get out from under the health care costs.


Maybe GM have their priorities wrong then. Maybe they should look after the current and former employees first, then take care of the stock holders.


Excuse me did you just have a brain fart? Gm and ford can no more keep running while making cars for more then everyone else then the corner grocer can try to sell me cheetos for 5 bucks a bag!

It was different when it was a hummer or a suv. Selling a 7 buck coffee and making a buck 20 when everyone around you makes 2 bucks is very different from selling a 2 buck coffee and losing 50 cents when everyone else makes 10.

One is called being nice the other is called YOUR FIRED!


GM, like all publicly-held corporations, has a fiduciary duty to the stockholders to maximize their profits (or minimize losses).  Doing what you desire could conceivably land the board and management in jail; it would certainly see them sued for many billions in personal damages, and thrown out at the next board elections if not sooner.


It looks like "Flourinal" is a mispelling, and the correct spelling is either "Fluorinel" or "Fluorinal".

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