Shortround6
Major General
There are so many more ways to improve recip efficiency and fuel economy, it is just not attainable for jets or turbines. And why all the gear box talk about the props I showed? I was not suggesting to hook them to a turbine that turns in the 10,000 plus rpm range.
Overhaul? Some industrial diesel type engines are in the 16000 to 20000 hour range, so again with proper engineering desired effects can be obtained.
A modern reciprocating engine using jet fuel (a diesel) would be great engine for a modern airship, otherwise not so much.
You have a real problem with any reciprocating engine trying to make power. They are basically air pumps and the more air you can put through them in a given amount of time the more power you can make. There are three basic ways to do this, more displacement of the engine (size and number of cylinders) for air per revolution of the crankshaft. More revolutions of the crankshaft per unit of time. using a supercharger to force more air into the engine. Many engines use all three.
Each as some drawbacks or associated penalties/trade-offs.
large displacement means a large (bulky) and quite possible heavy engine. Higher rpm means a lot stress on the components, engine may be small but not as light as it might appear. Will need a reduction gear adding weight and cost. Superchargers have few problems of their own but generally allow for smaller physical engines.
Every engine is a collection of trade-offs and you wave a "proper engineering" magic wand and get the results you desire.
Many diesel engines have 3 or 4 different power levels listed on the specification sheets.
1. is for station powerplant use, electric generator, water pump or other near 24 hour a day 7 day a week use where reliability is paramount
2. is for general use like over the road trucks, for engines that are of that size range. a bit higher power can be used for increased performance being traded for a bit shorter life.
3. is for fire trucks or emergency equipment, more power for fewer hours per year in operation.
4. may be for military use. often the most power and least life, large engines in an armoured vehicle require larger armoured hull to accommodate them which can bring on large weight gains for the complete vehicle. Military also has the budget and facilities to do more frequent engine swaps for repairs than most civil operators.
even boat/marine diesels are given different rating depending on the type of boat/ship they are going in. Commercial fishing boat or work boat vs yacht or sport fishing boat.
Ratings are modified by fitting different size/capacity injectors and limiting RPM.
for aircraft use you want the highest power to weight ratio you can get which means you can throw station power plant engine life right out the window. Stationary power plants have the least constraints on weight or physical size for a given level of power.
You don't get the reliability/long life of a stationary power plant by waving a magic wand and claiming "proper engineering". Part of the proper engineering of that stationary power plant was using an engine of sufficient size/weight to get the power desired for the number of hours of operation desired.
Over the road trucks, boats and other mobile users get properly engineered engines to suit the weight and space limits of the vehicle/boat in question, the intended loads and speeds and the expected hours per month or year of operation.
Aircraft are the same. A properly engineered engine will suit the intended use of the aircraft. A 2-4 seat private plane that flies only a few hundred hours a year (or less) can make do with an engine that requires overhaul at 1000 hours or so (modern version of old engines can double that) and go years between overhauls. while even a small commuter plane hauling 12 passengers and flying 8 hours a day, 6 days a week would rack up 2496 hours a year. Having to change engines (or overhaul in place?) twice a year might be unacceptable if there is an alternative.