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Ring wear may not be a problem in most current automotive engines. However, a small alteration in the ring face geometry can significantly affect the hydrodynamic lubrication characteristics of the ring. This in turn can cause excessive frictional losses and blowby in an engine. As engines become more compact and highly loaded, ring wear is likely to be more severe than in current engines. In order to assess the effect of ring loading, a piston ring wear model has been developed through the use of ring dynamics analysis with the assumption of a linear relationship between ring wear and the friction work applied on the surface of the ring. This ring wear analysis clearly shows that the higher the engine speed, the lower the wear rates at the same power output. This finding is consistent with the limited experimental data available.

A numerical study was conducted to examine how leakages across apex seals affect the flow field in one combustion chamber of a motored, two-dimensional, Wankel rotary engine. Results are presented which show the effects of engine speed, leakage area, and compression ratio on velocity field, distribution of turbulent kinetic energy, and volume-averaged pressure when there are apex seal leakages. These results indicate that apex seal leakages can have a significant effect on the flow field. This numerical study is based on the density-weighted-ensemble-averaged continuity, “full compressible” Navier-Stokes, and total energy equations, closed by a k-ε model of turbulence with wall functions. The numerical method used to obtain solutions was the approximate factorization algorithm of the ADI type. All convection terms were treated by second-order accurate upwind differencing through flux-vector splitting. All diffusion terms were treated by second-order accurate central differencing.

The effects of mixture stratification at the intake port and gaseous fuel injection on the flow field and fuel-air mixing in a two-dimensional rotary engine model have been investigated by means of a two-equation model of turbulence, an algebraic grid generation method and an approximate factorization time-linearized numerical technique. It is shown that the fuel distribution in the combustion chamber is a function of the air-fuel mixture fluctuations at the intake port The fuel is advected by the flow field induced by the rotor and is concentrated near the leading apex during the intake stroke. During compression, the fuel concentration is highest near the trailing apex and lowest near the rotor. The penetration of gaseous fuel injected into the combustion chamber during the compression stroke increases with the injection velocity and results in recirculation zones between the injector and the leading apex and between the injector and the trailing apex.

A two-dimensional, implicit finite-difference method of the control-volume variety, a two-equation model of turbulence, and a discrete droplet model have been used to study the flow field, turbulence levels, fuel penetration, vaporization and mixing in Diesel engine-type environments. Good agreement with the droplet penetration data of Hiroyasu and Kadota has been obtained for a range of ambient pressures neglecting the effects of void fraction, droplet coalescence and droplet collisions in the simulation. The model has also been used to study the effects of the intake swirl angle on the flow field, turbulence levels, fuel penetration, vaporization and mixing in a two-stroke Diesel engine operating under motored conditions. Numerical simulations indicate that as the intake swirl angle is increased, the fuel penetration, vaporization and mixing increase.

Real time work cell pressures are incorporated into a dynamic analysis of the gas sealing grid in Rotary Combustion Engines. The analysis which utilizes only first principal concepts accounts for apex seal separation from the trochoidal bore, apex seal shifting between the sides of its restraining channel, and apex seal rotation within the restraining channel. The results predict that apex seals do separate from the trochoidal bore and shift between the sides of their channels. The results also show that these two motions are regularly initiated by a seal rotation. The predicted motion of the apex seals compares favorably with experimental results. Frictional losses associated with the sealing grid are also calculated and compare well with measurements obtained in a similar engine. A comparison of frictional losses when using steel and carbon apex seals has also been made as well as friction losses for single and dual side sealing.

The purpose of these experiments was to determine the performance of a turbocharged rotary engine at power levels above 75 kw (100 hp). A twin rotor turbocharged Mazda engine was tested at speeds of 3000 to 6000 rpm and boost pressures to 7 psi. The NASA-developed combustion diagnostic instrumentation was used to quantify IMEP, PMEP, peak pressure and face-to-face variability on a cycle-by-cycle basis. Results of this testing showed that at 5900 RPM a 36 percent increase in power was obtained by operating the engine in the turbocharged configuration. When operating with lean carburetor jets at 105 hp (78.3 kw) and 4000 RPM, a brake specific fuel consumption of 0.45 lbm/lb-hr was measured.

This experimental work demonstrates the use of a NASA designed, real time Indicated Mean Effective Pressure (IMEP) measurement system which will be used to judge proposed improvements in cycle efficiency of a rotary combustion engine. This is the first self-contained instrument that is capable of making real time measurements of IMEP in a rotary engine. Previous methods used require data recording and later processing using a digital computer. The unique features of this instrumentation include its ability to measure IMEP on a cycle by cycle, real time basis and the elimination of the need to differentiate the volume function in real time. Measurements at two engine speeds (2000 and 3000 RPM) and a full range of loads are presented, although the instrument was designed to operate to speeds of 9000 RPM.