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A new generation of Wankel rotary engines that can offer multifuel capability, increased fuel economy, and improved performance and reliability could have a profound influence on the design of future power plants for aircraft, automotive and other applications. The recent advances in adiabatic diesel engine technology have potential to improve the Wankel rotary engine. In this paper, the potential benefits of adiabatic Wankel engine and advanced concepts like- advanced turbochargers, high compression ratio, faster combustion, and reduced leakage have been assessed. A Wankel simulation model was used to predict performance of the adiabatic Wankel engine with these advanced concepts- predicting an overall improvement of 25.5% in ISFC and 34.5% in power output. Also, excellent multifuel capability of adiabatic Wankel engine is expected.

Use of continuous fiber reinforced ceramic matrix composites (FRCMC) for turbopump hot section components offers a number of benefits. The performance benefits of increased turbine inlet temperature are apparent and readily quantifiable. Perhaps less obvious are the potential benefits of increased component life. At nominal turbopump operating conditions, FRCMC offer increased operating temperature margin relative to conventional materials. This results in potential for significant life enhancement. Other attributes (e.g., thermal shock resistance and high cycle fatigue endurance) of FRCMC provide even greater potential to improve life and reduce maintenance requirements. Silicon carbide (Sic) matrix composites with carbon fibers (C/SiC) do not degrade when exposed to hydrogenrich steam for 10 hours at 1200°C. This FRCMC is resistant to thermal shock transients far in excess of those anticipated for advanced, high temperature turbomachinery.

Current activities in seals for space propulsion turbomachinery that the NASA Lewis Research Center sponsors are surveyed. The overall objective is to provide the designer and the researcher with the concepts and the data to control seal dynamics and leakage. Included in the program are low-leakage seals, such as the brush seal, the “ceramic rope” seal, low-leakage seals for liquid oxygen turbopumps, face seals for two-phase flow, and swirl brakes for stability. Two major efforts are summarized: a study of seal dynamics in rotating machinery and an effort in seals code development.

This report discusses application of a new lightweight carbon-carbon (C-C) space radiator technology developed under the NASA Civil Space Technology Initiative (CSTI) High Capacity Power Program to a 20 kWe lunar based power system. This system comprises a nuclear (SP-100 derivative) heat source, a Closed Brayton Cycle (CBC) power conversion unit with heat rejection by means of a plane radiator. The new radiator concept is based on a C-C composite heat pipe with integrally woven fins and a thin walled metallic liner for containment of the working fluid. Using measured areal specific mass values (1.5 kg/m2) for flat plate radiators, comparative CBC power system mass and performance calculations show significant advantages if conventional heat pipes for space radiators are replaced by the new C-C heat pipe technology.

To support the Space Exploration Initiative, studies were performed to investigate and characterize Dynamic Isotope Power System (DIPS) alternatives for the surface mission elements associated with a lunar base and subsequent manned Mars expedition. A key part of this characterization was to determine how the mission environment affects system design. The impact of shielding to provide astronaut protection from power system radiation was also examined. Impacts of mission environment and shielding were examined for two representative DIPS types (closed Brayton cycle and Stirling cycle converters). Mission environmental factors included: (1) thermal background; (2) dust and atmospheric corrosion; (3) meteoroid damage; and (4) presence of an atmosphere on Mars. Physical effects of these factors on thermal power systems were identified and their parametric range associated with the mission and mission environment were determined.

Results of steady-state reverse and forward-to-reverse thrust transient performance tests are presented. The original QCSEE 4-segment variable fan nozzle was retested in reverse and compared with a continuous, 30° half-angle conical exlet. Data indicated that the significantly more stable, higher pressure recovery flow with the fixed 30° exlet resulted in lower engine vibrations, lower fan blade stress and approximately a 20% improvement in reverse thrust. Objective reverse thrust of 35% of takeoff thrust was reached. Thrust response of less than 1.5 sec was achieved for the approach and the takeoff-to-reverse thrust transients.

The short takeoff and landing capabilities that characterize the performance of powered-lift aircraft are dependent on engine thrust and are, therefore, severely affected by loss of an engine. This paper shows that the effects of engine loss on the short takeoff and landing performance of powered-lift aircraft can be effectively mitigated by cross-shafting the engine fans in a twin-engine configuration. Engine-out takeoff and landing performances are compared for three powered-lift aircraft configurations: one with four engines, one with two engines, and one with two engines in which the fans are cross-shafted. The results show that the engine-out takeoff and landing performance of the cross-shafted two-engine configuration is significantly better than that of the two-engine configuration without cross-shafting.