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Record efficiency for a gas engine
At the end of May, the final meeting of the "Horizon 2020" project "GasOn" with the EU Commission took place in Brussels. The aim of this EU project was the further development of gas engines for cars and vans. Around 20 partners participated, including ETH Zurich and Empa as well as four European automobile manufacturers and well-known suppliers. Gas-powered vehicles generally emit less pollutants than petrol or diesel cars. They are likely to gain importance in the future due to their possibility of being powered by renewable energy.
[...] A highly efficient combustion process was implemented for a gas engine with two liters displacement: A lean gas mixture is ignited by means of a thimble-sized, flow-calmed prechamber. In the ETH laboratory for aerothermochemistry and combustion systems, basic experiments were carried out in optically accessible engines. These were used to investigate the behavior of the ignition in the prechamber and the overflow of the hot rays into the main combustion chamber. Based on these data, numerical tools were developed in order to calculate the processes in detail using computer simulations. These results allowed Volkswagen Group Research to optimize the design of the prechamber and the main combustion chamber. Empa scientists set up an engine accordingly and investigated the combustion process. An engine control system developed by the Institute for Dynamic Systems and Control Technology at ETH Zurich was used, which coordinates the complex overall system and enables adaptation to new findings at the same time.
Compared to the state of the art, the consumption of the new gas engine with prechamber combustion process was reduced by 20 percent (converted into WLTP standard consumption for a mid-size passenger car). The peak efficiency in the best engine configuration was over 45 percent, with efficiencies of over 40 percent achieved over a wide operating range. Such values are currently only achieved by significantly larger engines, such as those used in commercial vehicles, stationary or marine applications. 45 percent is a new record for passenger car engines. By way of comparison, petrol engines typically have efficiencies of 35 to 40 percent. The GasOn project has not yet dealt with the exhaust gas treatment of such an engine; there is still need for further research, due to the lean combustion process.
(Score: 3, Interesting) by hwertz on Friday June 21 2019, @06:05AM (2 children)
Devil's in the details -- I would not be surprised to find out existing engine designs could hit that 45% efficiency already, IF you don't have to worry about emissions. MANY engine projects since the 1980s have shown amazing efficiency gains, which then dwindle to being no gains once you have to control your NoX emissions and run a catalytic converter behind it. On the other hand, electronic engine control has SERIOUSLY advanced in the last 10 or 20 years... see below.
The last two cars I've had, the 2000 Regal has a Series II 3800 V6, and the current 2013 Chevy Cruze has a 1.4L turbo engine. These are like polar opposites technology-wise.
The 3800 -- very nice running engine but engine control technology wise... multiport fuel injection, electronic ignition, 4-speed automatic. Computer-controlled EGR, catalytic converter, electronically controlled smog pump. That's about it. The big limits on these setups are the necessity of EGR -- this cuts efficiency some (although besides emissions it helps you not burn your valves!), and since at least the mid-1980s, cars with a cat that due lean burn cruising etc. HAVE to periodically dump in extra fuel to keep the catalytic converter lit. (GM got a HUGE fine for this in the mid-1980s; the EPA decided that even though the vehicles in question were meeting emissions, the extended use of lean burn was causing the cat to shut down, and choose to fine the hell out of them for "disabling" the emissions system.) Based on these kind of engines, I could see these guys hitting 45%, then finding they are down to 35% once they throw on everything needed to meet emissions.
My current vehicle, a Cruze with 1.4L turbo -- I don't know how they made the Cruze so heavy but it has almost the same curb weight as the Regal. 1.5x the gas mileage, and about the same acceleration (3/4ths the power, but 4/3rds the gears -- 6 speed auto instead of 4.) Electronic throttle control, variable valve timing, and it plays some odd tricks with the turbo (like spinning it up while coasting to reduce pumping losses of the engine; and using it to generate gobs of low end torque so it can cruise along in top gear, not just to make power when you have it floored. It seriously feels like it has about 90% the low end torque of the 3800 V6, and with closer gears on the 6-speed it can often pull up hills at lower RPM than the 3800 did). No EGR valve, it can avoid the NoX production with the valve timing and such. Based on this, I could see this 45% efficiency engine being able to use variable valve timing, electronic throttle control, etc. to simply avoid the "dirty" operating regions with little efficiency loss.
(Score: 1) by hwertz on Friday June 21 2019, @06:08AM
Responding to myself... oh, "gas" as in methane. Well, I think a lot of what I wrote still applies -- I suspect even with a methane engine, many problems of the past regarding emissions can be solved with newer engine management techniques.
(Score: 2) by wisnoskij on Sunday June 23 2019, @09:29PM
I never understood the whole dwindling efficiency with respect to emissions. In any combustion the general rule is the more efficient the burn the cleaner the emissions. If you don't burn it, it just gets spewed out the tail pipe, and it is better to spew out plant food instead of oils.