Rolls-Royce Motor Cars

About: Rolls-Royce Motor Cars is a based out in . It is known for research contribution in the topics: Turbine & Gas compressor. The organization has 3845 authors who have published 4934 publications receiving 58973 citations. The organization is also known as: Rolls-Royce Motor Cars Limited.

Isothermal fatigue of an aluminide-coated single-crystal superalloy:Part I

Abstract: The isothermal fatigue behavior of a high-activity aluminide-coated single-crystal superalloy was studied in air at test temperatures of 600 °C, 800 °C, and 1000 °C. Tests were performed using cylindrical specimens under strain control at ∼0.25 Hz; total strain ranges from 0.5 to 1.6 pet were investigated. At 600 °C, crack initiation occurred at brittle coating cracks, which led to a significant reduction in fatigue life compared to the uncoated alloy. Fatigue cracks grew from the brittle coating cracks initially in a stage II manner with a subsequent transition to crystallographic stage I fatigue. At 800 °C and 1000 °C, the coating failed quickly by a fatigue process due to the drastic reduction in strength above 750 °C, the ductile-brittle transition temperature. These cracks were arrested or slowed by oxidation at the coating-substrate interface and only led to a detriment in life relative to the uncoated material for total strain ranges of 1.2 pet and above 800 °C. The presence of the coating was beneficial at 800 °C for total strain rangesless than 1.2 pet. No effect of the coating was observed at 1000 °C. Crack growth in the substrate at 800 °C was similar to 600 °C; at 1000 °C, greater plasticity and oxidationrwere observed and cracks grew exclusively in a stage II manner.

Single vs. Two Stage High Pressure Turbine Design of Modern Aero Engines

Abstract: In this paper, the two-stage shrouded HPT engine configuration rated at 22000 lbs thrust is used as the baseline from which a single stage HPT unshrouded design is systematically derived to evaluate the potential weight and cost advantage. The baseline thermodynamic cycle at the rated thrust level was modified in order to optimize the turbine inlet temperature, overall pressure ratio, and core flow with a single stage HPT and deliver competitive performance. The comparative study, although preliminary in depth, has led to the advantages and disadvantages associated with an unshrouded single versus a two-stage shrouded HPT design. The results compare design configuration, secondary air system, weight, safety, life, specific fuel consumption (SFC), and future thrust growth capability. The main advantages of the single stage application are reductions in cost and complexity of design, lower turbine gas temperature, and ease of maintenance. The main disadvantages are in reduced turbine polytropic/isentropic efficiency for HPC pressure ratio greater than 9, increased SFC, higher rim speed, higher HPT exit Mach number, higher bypass ratio to achieve the desired thrust level, and possibly higher weight. A quantitative statement on the reduction of engine cost/weight is premature until a detailed design and the associated cost-benefit is performed. The paper concludes by recommending that the design philosophy of the modern unmixed turbofan engine (single or two-stage HPT) leads to a balance between the selected turbine gas temperature versus the by-pass ratio in order to minimize cost and maximize the thrust-to-weight ratio and the cycle efficiency. In either ease, the expected high reliability and reduced engine cost/weight in the context of future thrust-growth capability need to be demonstrated by proven technology which seem to favor the two-stage HPT configuration.Copyright © 1999 by ASME

Statistical analysis of recast formation in laser drilled acute blind holes in CMSX-4 nickel superalloy

Abstract: The present study investigates the effects of four controllable variables on the metallurgy and drilling velocity of laser percussion drilled acute (30° to surface) blind holes in 2 mm thick flat pieces of nickel superalloy—CMSX-4 material. Design of experiment and statistical modelling were used in the experimental study to understand parameter interactions. Pulse energy, pulse width, pulse frequency and gas pressure were chosen as the independent process variables. The response surface method was used to develop the models for each of the responses: physical characteristics of wall and bottom recast layer and drilling velocity (function of material removal rate). A central composite design was chosen as it offered the most economical number of experiments for the required information. The significant process factors in each model were identified based on the analysis of variance and the models were checked by complete residual analysis. It was found that high pulse energy and short pulse width gave the maximum drilling velocity and lowest recast layer thickness at the hole bottom, whereas low pulse energy and short pulse width minimised the wall recast layer thickness.