The 004 engine was not really ahead of its time. Though it used an axial compressor opposed to the first operational allied jets, it was a very conservative design meant to work with little developmental issues. This was done to expedite time to production. Overall this decision was a good one as it enabled the 004 to enter production ahead of other designs, but it was bulky, especially for an axial design, and actually wider than the radial HeS-8 (001) engine (though it was significantly more powerful) and had a low thrust/weight (around 1.2). The fully developed version of the original design was the 004D which was a decent engine in all and competitive to other production designs of the time, but still was a bit behind its potential.
Quote: ("Franz opted for a design that was at once conservative and revolutionary. His design differed from von Ohain's in that he utilised a new type of compressor which allowed a continuous, straight flow of air through the engine (an axial compressor), recently developed by the Aerodynamische Versuchsanstalt (AVA - Aerodynamic Research Institute) at Göttingen. The axial-flow compressor not only had excellent performance, about 78% efficient in "real world" conditions, but it also had a smaller cross-section, important for a high-speed aircraft design.
On the other hand, he aimed to produce an engine that was far below its theoretical potential, in the interests of expediting development and simplifying production. One major decision was to opt for a simple combustion area using six "flame cans", instead of the more efficient single annular can. For the same reasons, he collaborated heavily on the development of the engine's turbine with Allgemeine Elektricitäts-Gesellschaft (AEG - General Electric Company) in Berlin, and instead of building development engines, opted to begin work immediately on the prototype of an engine that could be put straight into production. Franz's conservative approach came under question from the RLM, but was vindicated when even given the developmental problems that it was to face, the 004 entered production and service well ahead of its more technologically advanced competitor, the BMW 003.)"
The only German engine that could have been produced in war-time to be usefull (at least by early 1944 and possibly before the 004 reached full production) would have been the HeS-30 (006) design, it was far ahead in effeciency, had thrust equivelent to the 004, but weighed under 900lbs and with a diameter of only 24in it was also the smallest. (about the same weight and thrust as the J31 or Derwent but with the thinness of an axial design) It was also quite short at around 104in in length. It also used the simpler flame cans like the 004 which posed fewer problems than the annular one of the 003. Of course this engine was originally a Junkers design, but Muller left when Jumo was baught an their engine (004) took priority. I wouldn't consider the HeS-011 that great because, despite it being advanced and powerful, it was unrealistic for the short-term and was soon outclassed by allied engines like the J33 and J35. It was also not as ready as the 004H which was more powerfull and copperable to the nonafterburning production J35 from 1947. (the J35 beig designed in the early 40's as a turboprop and redesigned and tested to symilar results to the 011, in 1944)
It should be noted that the HeS-30 (006) was originaly a Jumo designed engine but in a 1939 merger the head designer and half the team decided to leave and was quickly taken up bu Heinkel. Had Jumo taken more interest in this design it might have been ahead of the 004 as it took over a year to transfer the whole projest to Heinkel and as it was the 006 was only a few months behind the 004 the prototype running on the bench shortly after the 004A. The 006's overall performance wan't matched until late 1947.
Many american designs, and a few british ones were also ahead of the times and quite advanced. The Metrovick F.2, Britain's first working axial engine, was an awsome design, its performance being symilar tho the D.H. Goblin and smaller but was too unreliable for war use. It was tested in the Meteor I a few months after the Halford H-1 and welland powered ones were in late 1943, both the welland, and F.2 powered prototypes crashed in April of 1944. The F.2 was developed further into the successful A.S. Saphire engine.
The Lockheed L-1000 (later J37) was also very advanced, but ultimately was never produced. The J35 was already mentioned above and was also very advanced. The J35 was developed from the turboprop TG-100 / TG-31 project, the TG-180 had an out put of 2,545lb of thrust, being run for the first time on the 21/4/1944. The first all-American design produced in the US was the Westinghouse J30 first run in early 1943 the final version was in the same class as the BMW-003 (at 1600 lbf thrust, later 1650 lbf) and entering production by early 1945. The only production aircraft to use it was the FH Phantom. But it was developed into the 3000 lbf J34 which powered several planes, most notably, the Phantom's successor, the F2H Banshee.
The jet engine that was most ahead of its time would have to be the first operating one: Conada's "air reactive" engine, a motorjet, built in 1910!
see:
Coanda
and
Coandă-1910 - Wikipedia, the free encyclopedia
Of course the motor-jet wasn't a long-term jet design but could have paved the way for turbojets much earlier, particularly in terms of combustion-chamber and exhaust design.
