We Have Ignition: Hyundai's Experimental Gas Engine Runs Without Spark Plugs
02-27-2014, 06:33 AM
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We Have Ignition: Hyundai's Experimental Gas Engine Runs Without Spark Plugs
http://www.caranddriver.com/features...-plugs-feature
We Have Ignition: Hyundai's Experimental Gas Engine Runs Without Spark Plugs
A gasoline engine with diesel-like thermal efficiency.
Things look familiar outside, assuming you’re accustomed to engines that are both turbo- and supercharged.
Combustion engineers mounting a last stand against electric propulsion harbor bizarre fantasies. The gasoline guys dream of the diesel’s potent torque curves and exemplary thermal efficiency. Diesel devotees yearn for cheaper fuel and relief from expensive injection systems and complex emissions controls.
But what if both camps collaborated on one super engine combining the best of both technologies? You’d get what Hyundai and Delphi call Gasoline Direct-Injection Compression Ignition (GDCI): a gas engine needing no spark plugs.
Engineers have been studying this alternative for more than a decade. GM and Honda both demonstrated cars powered by homogeneous-charge compression-ignition engines running on gasoline. More recently, Hyundai and Delphi advanced the cause by switching to stratified charge (a rich mixture in part of the cylinder) in a 180-hp 1.8-liter four-cylinder using auto ignition from idle to a 4500-rpm redline. When the study moves out of the lab into two test cars later this year, it should be clear whether the combination of diesel efficiency and gasoline con*ven*i*ence is within reach.
Hyundai’s experimental engine—equipped with direct injection, variable valve timing, a turbo, a supercharger, and exhaust-gas recirculation—looks fairly normal on the outside. What’s weird are pistons with soup bowls cast into their crowns. With no spark plugs in the way, the injectors can squirt fuel into the exact center of each bowl. GDCI achieves auto ignition by heating intake air with carefully controlled amounts of exhaust gas followed by squeezing the dickens out of the mix with a 14.8:1 compression ratio. Injecting a small dose of gas just before top dead center, and the main fuel squirt just after that point, yields cylinder pressures that rise far more gently than those found in any diesel. This improves efficiency, since combustion pressure is working against a descending piston. Lean fuel-air mixtures, minimal heat lost through the cylinder walls, no throttling, and the large expansion ratio (the flip side of compression ratio) deliver fuel efficiency comparable to a diesel, according to Hyundai’s GDCI expert, the suitably named Nayan Engineer. (Mark Sellnau served as Delphi’s engineering manager on this project.) Best results derive from minimal swirl in the piston bowl. Fuel-injection pressures are in the gasoline-engine range, or only a fifth of what’s required in a diesel, yielding major savings in cost, lower parasitic losses, and quieter operation versus diesels. The supercharger delivers intake air at low speeds and loads when there’s insufficient exhaust energy to spin the turbo.
Cleaning up what exits the combustion chambers poses no major hassles. The typical diesel bugaboos—particulates and high NOx emissions—are not an issue because of GDCI’s low combustion temperatures. The lean mixtures reduce the standard three-way catalyst’s effectiveness, a concern addressed by fitting a second oxidation catalyst to diminish carbon-monoxide and hydrocarbon emissions.
It all adds up to a 10-to-15-percent efficiency improvement without switching to a troublesome fuel. Strides like this will keep the internal-combustion engine eligible for stand-alone or hybrid-propulsion duties for decades to come.
We Have Ignition: Hyundai's Experimental Gas Engine Runs Without Spark Plugs
A gasoline engine with diesel-like thermal efficiency.
Things look familiar outside, assuming you’re accustomed to engines that are both turbo- and supercharged.
Combustion engineers mounting a last stand against electric propulsion harbor bizarre fantasies. The gasoline guys dream of the diesel’s potent torque curves and exemplary thermal efficiency. Diesel devotees yearn for cheaper fuel and relief from expensive injection systems and complex emissions controls.
But what if both camps collaborated on one super engine combining the best of both technologies? You’d get what Hyundai and Delphi call Gasoline Direct-Injection Compression Ignition (GDCI): a gas engine needing no spark plugs.
Engineers have been studying this alternative for more than a decade. GM and Honda both demonstrated cars powered by homogeneous-charge compression-ignition engines running on gasoline. More recently, Hyundai and Delphi advanced the cause by switching to stratified charge (a rich mixture in part of the cylinder) in a 180-hp 1.8-liter four-cylinder using auto ignition from idle to a 4500-rpm redline. When the study moves out of the lab into two test cars later this year, it should be clear whether the combination of diesel efficiency and gasoline con*ven*i*ence is within reach.
Hyundai’s experimental engine—equipped with direct injection, variable valve timing, a turbo, a supercharger, and exhaust-gas recirculation—looks fairly normal on the outside. What’s weird are pistons with soup bowls cast into their crowns. With no spark plugs in the way, the injectors can squirt fuel into the exact center of each bowl. GDCI achieves auto ignition by heating intake air with carefully controlled amounts of exhaust gas followed by squeezing the dickens out of the mix with a 14.8:1 compression ratio. Injecting a small dose of gas just before top dead center, and the main fuel squirt just after that point, yields cylinder pressures that rise far more gently than those found in any diesel. This improves efficiency, since combustion pressure is working against a descending piston. Lean fuel-air mixtures, minimal heat lost through the cylinder walls, no throttling, and the large expansion ratio (the flip side of compression ratio) deliver fuel efficiency comparable to a diesel, according to Hyundai’s GDCI expert, the suitably named Nayan Engineer. (Mark Sellnau served as Delphi’s engineering manager on this project.) Best results derive from minimal swirl in the piston bowl. Fuel-injection pressures are in the gasoline-engine range, or only a fifth of what’s required in a diesel, yielding major savings in cost, lower parasitic losses, and quieter operation versus diesels. The supercharger delivers intake air at low speeds and loads when there’s insufficient exhaust energy to spin the turbo.
Cleaning up what exits the combustion chambers poses no major hassles. The typical diesel bugaboos—particulates and high NOx emissions—are not an issue because of GDCI’s low combustion temperatures. The lean mixtures reduce the standard three-way catalyst’s effectiveness, a concern addressed by fitting a second oxidation catalyst to diminish carbon-monoxide and hydrocarbon emissions.
It all adds up to a 10-to-15-percent efficiency improvement without switching to a troublesome fuel. Strides like this will keep the internal-combustion engine eligible for stand-alone or hybrid-propulsion duties for decades to come.
02-27-2014, 07:10 AM
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VERY interesting indeed. Interesting to see the hybrid of a gasoline SIDI engine and a diesel CIDI engine... I think it will feel more like a diesel because there will still need to be long strokes and heavy blocks to deal with the big pressures in there. However... I am curious about the injection system. Mainly:
First of all, direct injection has always had very high injection pressures. The name of the game on any DI engine is to ramp up the injection pressure until something conks out within warranty period. I'm talking like 30,000 psi plus... it has numerous benefits.
The other part about the dual injection phases too... that has been run-of-the-mill diesel tech since the early 2000s. It stops things grenading due to huge pressure spikes and it has the added benefit of cutting down on diesel clatter.
Anyhoo. Diesel is generally harder to ignite, and once you do light it, its equivalent octane rating (diesels use cetane ratings among other things) is quite low. So regular petrol should be an interesting fuel to use in this kind of engine. No DOUBT it has had plenty of its own teething issues. And no DOUBT this has been thought of decades ago, probably by mercedes. I'm just waiting for someone better at me than chemistry to come on and remind me why this was a sh*t idea to begin with.
Excited child out
low injection pressures
and
Injecting a small dose of gas just before top dead center, and the main fuel squirt just after that point, yields cylinder pressures that rise far more gently than those found in any diesel.
and
Injecting a small dose of gas just before top dead center, and the main fuel squirt just after that point, yields cylinder pressures that rise far more gently than those found in any diesel.
First of all, direct injection has always had very high injection pressures. The name of the game on any DI engine is to ramp up the injection pressure until something conks out within warranty period. I'm talking like 30,000 psi plus... it has numerous benefits.
The other part about the dual injection phases too... that has been run-of-the-mill diesel tech since the early 2000s. It stops things grenading due to huge pressure spikes and it has the added benefit of cutting down on diesel clatter.
Anyhoo. Diesel is generally harder to ignite, and once you do light it, its equivalent octane rating (diesels use cetane ratings among other things) is quite low. So regular petrol should be an interesting fuel to use in this kind of engine. No DOUBT it has had plenty of its own teething issues. And no DOUBT this has been thought of decades ago, probably by mercedes. I'm just waiting for someone better at me than chemistry to come on and remind me why this was a sh*t idea to begin with.
Excited child out
02-27-2014, 02:14 PM
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Nobody else has done this because gasoline is less forgiving than diesel. The design will have to be very precise, and everything will have to work right forever.