Prof. Dr.-Ing. Kollmann is one of the most important aeronautical engineers in the story of piston aeroengine development in Germany in WWII. In 12 years, Dr.-Ing. Kollmann progressed from the role of senior engineer to chief engineer of the aeroengine design department in Daimler-Benz. This book is an historical record of his own engineering work in developing high performance piston aeroengines. The original document that Dr.-Ing. Kollmann wrote in 1947 is presented here in English with extensive additional material by the authors.

The idea of precompression of the cylinder charge air is as old as the internal combustion itself. It is generally accepted that the first supercharger design in the modern sense was actually a turbocharger , patented in 1905 by the Swiss engineer Alfred Büchi (1879-1959). It comprised an axial compressor, an aftercooler and an exhaust gas turbine applied to a radial piston-cylinder engine as shown in the German patent drawings in Figure 8-1. Not surprisingly, it took him more than two decades to make the system work due to low component efficiencies, i.e., the problem that bedeviled all early gas turbine inventors due to the insufficient knowledge of aerodynamics.

There were a number of aircraft and engine manufacturers active in Germany in 1930s and 1940s. Some were quite well known, e.g., Messerschmitt (former Bayerische Flugzeugwerke), Focke-Wulf, Junkers, Dornier, etc. Some others were rather obscure, e.g., Hamburger Flugzeugbau, Klemmflugzeugbau , etc. The Reichsluftfahrtministerium (RLM) had a rather convoluted designation system (they thought that it was an improvement over the older one, of course) to provide a (supposedly) simple and unambiguous identification of every German civilian and military aircraft and its corresponding airframe design. Manufacturers were represented by two letters: the first letter in upper case, the second usually in lower case. A selection of the most famous ones is listed in Table 12-1. It should be noted that a mass-production model by a certain manufacturer, say, Messerschmitt Bf 109, were manufactured in the factories of other manufacturers (e.g., Fieseler or Gotha) under license. This system was under the control of the RLM (later in the war, starting in early 1944, under the supervision of the Armament Ministry – see below).

For the last 200 years or so, humans have been living in the epoch of power inwhich the heat engine has been the dominant device for converting heat to work and power. The development of the heat engine was for most of that time slow and chaotic and carried out mainly by poorly qualified practitioners who had no knowledge of basic theories of energy and energy conversion to mechanical work. In the field of engineering mechanics, drawings of early steam engines depict various, at times strange, inefficient mechanisms to convert steam power to mechanical power, such as the walking beam and sun and planet gear systems. The piston-crankmechanismwas first used in a steam engine in 1802 by Oliver Evans (Sandfort 1964) despite a design being proposed as early as 1589 for converting the rotary motion of an animal-driven machine to reciprocating motion in a pump. The first internal combustion engine (ICE) to bemade available commercially was Lenoir’s gas engine in 1860. This engine was also the first to employ a piston-crankmechanism to convert reciprocating motion of the piston to rotary motion, which has become, despite its shortcomings, a fixed feature and highly efficient mechanism in modern reciprocating engines. However, engine designers were never fully satisfied with this mechanism due to the need to balance numerous parasitic forces generated during operation and were constantly looking for alternative ways of obtaining direct rotary motion. This is said to have been one of the stimuli to develop steam and gas turbines in which a fluid, flowing through blades, causes the shaft to rotate, thus eliminating the need for a crankshaft. The results are smoother operation, lower levels of vibration, and low-cost support structures. All of these developments occurred over a very long period of time with advances in the science of engineering mechanics (more specifically, engineering dynamics), together with other engineering science branches such as fluid mechanics and thermodynamics.

In Figure 2.1 a pump installation with a single acting piston pump is represented. The piston pump works according to the classic crank-connecting rod mechanism (Figure 2.2)

In Figure 7.1 a horizontal piston compressor is shown, together with its indicator diagram. Vertically the pressure in the cylinder is set out; horizontally, the volume in the cylinder, that is taken by the gas that has to be compressed.

In this study, detailed load analysis under service loading conditions was performed for connecting rod of MF-285 tractor engine (by using the Mathematica software), followed by finite element analysis (FEA) to capture stresses and fatigue cycle (by using ANSYS software). The results of the study shows that maximum tensile stress occurs on the small end of connecting rod caused by inertia loads and friction between piston pin and connecting rod bush and equals 280 MPa, maximum compressive stress occurs on the big end of connecting rod caused by preload of screws and equals 165 MPa. In new connecting rods whit structure like structure of this connecting rod stresses are between 160 to 250 MPa. Fatigue cycle was calculated equal 108 cycles. Proper fatigue cycle for connecting rods equals 108 to 109. According to that maximum stresses was more than common rang, seems it caused to happen least fatigue cycle. According to results of this study, it could be proposed to lessen friction between piston pin and connecting rod bush, changing in manufacture process, changing in connecting rod material, optimization of reciprocating mass and increasing the diameter of small end of connecting rod to redesign and optimize the model for better resistance under hard loads.

It is evident that a closed hot-air engine with a power cylinder separate from the displacer cylinder works with a lower compression ratio than one with a single-cylinder design, due to the presence of a disproportionately large clearance volume. This considerably reduces the specific power, so that engines of the type described in the last section could hardly be suitable for applications other than mechanical toys or small models where efficiency did not matter. Although a patent registered in 1845 by Franchot described an engine with piston and displacer working in the same cylinder, Stirling's original design seemed to have been entirely forgotten for the next 50 years until the first engines by Lehmann were produced on the European continent. These engines were practically identical to Stirling's first design, except that they had a horizontal cylinder, direct contact between cylinder bottom and flames, and a more compact link mechanism to reduce overall size (Eckerth 1869a, Röntgen 1888). An early model of the Lehmann engine is shown in Fig. 3.1. A very long cylinder ABCD was used, closed at the hot end and with the power piston UU reciprocating in the open end, which was kept cool by a water-jacket LMNP . About a third of the cylinder was enclosed by the furnace. The hot gases surrounded the lower end of the cylinder and kept it hot, after which they escaped through the smoke stack RR . The airtight hollow displacer was strengthened by a riveted plate KK to an extension of which the piston rod was attached. EF was a wooden plate closing the front of the displacer, and HG a domed metal cap closing the hot end. The weight of the displacer was taken on a support roller O . Between the displacer and the cylinder there was a narrow annular space through which the working fluid passed when transferred from one end of the cylinder to the other, but apparently no regenerator was fitted. The working piston UU was constructed similarly to a bicycle pump with a dished leather washer, which allowed additional air to enter whenever the internal pressure fell below atmospheric. The driving mechanism, by which the motion of the displacer was advanced by about 65° with reference to the working piston, was very similar to that employed on the Ericsson engine. According to Eckerth such an engine with piston diameter 0.349 m and stroke 0.244 m, gave 0.984 h.p. at 97 r/min, with a thermal efficiency of 4 per cent, which corresponds to a specific power of 1.2 h.p. per cubic foot swept volume. The mechanical efficiency was quoted as 65 per cent (Delabar 1864, Eckerth 1869b, Knoke 1899).

For the understanding of cycle thermodynamics and of the technology of construction, the period from the mid-1960s to the mid-1980s was essentially one of consolidation. Rapid advances in computing capacity encouraged the development of ambitious simulations of the gas process cycle. With the notable exception of a contribution by Miyabe et al. (1982), however, study of the regenerator continued in isolation and without impact on Stirling engine design. The era saw a number of new embodiments. The free-piston variant was invented (Finkelstein 1963a, b, 1964). West (1970) proposed the liquid-piston or Fluidyne engine. Bradley (1974) demonstrated an engine operating from a low-temperature source, possibly the first of a type to become known as the ‘Low Δ T ’ genre.