I'm old enough to remember a lot of interest in turbine engines for autos in the 19060's. Chrysler in particular tried to get them working well. But interest died out, with a lot of discouragement from materials requirements, engine performance, and many issues. I have heard virtually no reports of any recent interest and I wonder why?
From what I remember there were some issues around the materials needed, especially about metal alloys to withstand high temperatures and high centrifugal forces in a rotating blade system. However, those issues are even more important for jet engines, and development in that field has been substantial. Beyond just developing materials that can do the job, I expect the costs of those materials also have been reduced.
On the performance side, I do recall several areas where turbine engines simply did not match how conventional reciprocating piston engines are used in automobiles. They are very poor for supplying braking power when you throttle back. The do not change operating speed quickly, and have a more limited range of operating speeds than a piston engine. I believe fuel efficiency also is impacted significantly at upper and lower ends of the speed range. The common operating rotational rate is much higher than a piston engine so gearing that down to driveline components is an issue, but not a terribly complex one.
Then I started thinking about current development trends for Hybrid and Plug-In Hybrid vehicles. For many reasons those "problems" with turbine engines are NOT problems in hybrid systems. The engine does NOT provide drive force or braking force directly to the wheel motors. The engine is designed primarily to drive a generator system to keep the battery fully charged, and almost all of the high variability in load demands of driving is borne by the electrical system drawing power from the battery. That battery is a HUGE buffer between engine load and wheel motor load. That means the engine speed can be kept within a narrow range for optimal fuel efficiency and does not need to change quickly. The torque load required from the engine does vary, certainly more than its speed needs to change, but again no rapid or large changes required. I suspect that is managed by fuel / air mixture and not speed, but I don't know. Even the size and max horsepower requirements are easier to deal with. In a classic auto design the engine must be built to provide very high work output for high-acceleration needs, but those last only for relatively short periods before workload settles back. In a Hybrid system the engine needs only to be able to exceed by a reasonable margin the longer-term AVERAGE power needs, since it can play "catch-up" after the battery has satisfied short-term needs.
So there's an amateur looking at this with questions. I consider myself a reasonably good home handyperson and backyard mechanic. But I do realize I do NOT have enough knowledge of these details, particularly about real turbine engines. Any one out there with a much better understanding that might explain why there is NOT much interest currently in turbine engines for Hybrid vehicles?
From what I remember there were some issues around the materials needed, especially about metal alloys to withstand high temperatures and high centrifugal forces in a rotating blade system. However, those issues are even more important for jet engines, and development in that field has been substantial. Beyond just developing materials that can do the job, I expect the costs of those materials also have been reduced.
On the performance side, I do recall several areas where turbine engines simply did not match how conventional reciprocating piston engines are used in automobiles. They are very poor for supplying braking power when you throttle back. The do not change operating speed quickly, and have a more limited range of operating speeds than a piston engine. I believe fuel efficiency also is impacted significantly at upper and lower ends of the speed range. The common operating rotational rate is much higher than a piston engine so gearing that down to driveline components is an issue, but not a terribly complex one.
Then I started thinking about current development trends for Hybrid and Plug-In Hybrid vehicles. For many reasons those "problems" with turbine engines are NOT problems in hybrid systems. The engine does NOT provide drive force or braking force directly to the wheel motors. The engine is designed primarily to drive a generator system to keep the battery fully charged, and almost all of the high variability in load demands of driving is borne by the electrical system drawing power from the battery. That battery is a HUGE buffer between engine load and wheel motor load. That means the engine speed can be kept within a narrow range for optimal fuel efficiency and does not need to change quickly. The torque load required from the engine does vary, certainly more than its speed needs to change, but again no rapid or large changes required. I suspect that is managed by fuel / air mixture and not speed, but I don't know. Even the size and max horsepower requirements are easier to deal with. In a classic auto design the engine must be built to provide very high work output for high-acceleration needs, but those last only for relatively short periods before workload settles back. In a Hybrid system the engine needs only to be able to exceed by a reasonable margin the longer-term AVERAGE power needs, since it can play "catch-up" after the battery has satisfied short-term needs.
So there's an amateur looking at this with questions. I consider myself a reasonably good home handyperson and backyard mechanic. But I do realize I do NOT have enough knowledge of these details, particularly about real turbine engines. Any one out there with a much better understanding that might explain why there is NOT much interest currently in turbine engines for Hybrid vehicles?