Investigations of the synergy of Composite Cycle and intercooled recuperation

ABSTRACTThe synergistic combination of two promising engine architectures for future aero engines is presented. The first is the Composite Cycle Engine, which introduces a piston system in the high pressure part of the core engine, to utilise closed volume combustion and high temperature capability due to instationary operation. The second is the Intercooled Recuperated engine that employs recuperators to utilise waste heat from the core engine exhaust and intercooler to improve temperature levels for recuperation and to reduce compression work. Combinations of both architectures are presented and investigated for improvement potential with respect to specific fuel consumption, engine weight and fuel burn against a turbofan. The Composite Cycle alone provides a 15.6% fuel burn reduction against a turbofan. Options for adding intercooler were screened, and a benefit of up to 1.9% fuel burn could be shown for installation in front of a piston system through a significant, efficiency-neutral weight decrease. Waste heat can be utilised by means of classic recuperation to the entire core mass flow before the combustor, or alternatively on the turbine cooling bleed or a piston engine bypass flow that is mixed again with the main flow before the combustor. As further permutation, waste heat can be recovered either after the low pressure turbine – with or without sequential combustion – or between the high pressure and low pressure turbine. Waste heat recovery after the low pressure turbine was found to be not easily feasible or tied to high fuel burn penalties due to unfavourable temperature levels, even when using sequential combustion or intercooling. Feasible temperature levels could be obtained with inter-turbine waste heat recovery but always resulted in at least 0.3% higher fuel burn compared to the non-recuperated baseline under the given assumptions. Consequently, only the application of an intercooler appears to provide a considerable benefit for the examined thermodynamic conditions in the low fidelity analyses of various engine architecture combinations with the specific heat exchanger design. Since the obtained drawbacks of some waste heat utilisation concepts are small, innovative waste heat management concepts coupled with the further extension of the design space and the inclusion of higher fidelity models may achieve a benefit and motivate future investigations.

Selected Tribological Properties of A390.0 Alloy

Emergence of new designs for internal combustion engines resulted in a necessity to search for new materials which will rise to excessive technological requirements under operating conditions of modern internal combustion engines of up to 150 kW. Focusing only on material properties, theoretically existing alloys should meet presents requirements. More importantly, existing materials are well fitted to the entire crank-piston system. Thus, there is a need for a more thorough examination of these materials. The paper presents studies on determination of coefficient of friction μ and wear for the A390.0 alloy modified with AlTi5B master alloy combined with EN GJL-350 cast iron. The characteristics of a T-11 tribological tester (pin on disc) used for the tests, as well as the methodology of the tribological tests, were described. Also, the analysis of the surface distribution of elements for the pin and the disc was presented. The studies were realized in order to find whether the analyzed alloy meets the excessive requirements for the materials intended for pistons of modern internal combustion engines. The results show that the A390.0 alloy can only be applied to a load of 1.4 MPa. Above this value was observed destructive wear, which results in the inability to use it in modern internal combustion engines.

Analysis and Optimization of the Piston System Using CAD/CAE Engineering Environment

This article presents the approach to the problem considered with optimizing the stress distribution and functioning of a crankshaft system of a piston engine. One of possible methods of investigating such a problem is simulation of work of the analyzed mechanical system. This approach allows observing the work of a modeled system and improving the designed system. In this work was applied the PLM Siemens NX software. This advanced CAD/CAE/CAM environment let to model any complex system of a technical mean. Using this environment it is possible to model and analyze new solution, which allow significantly optimizing the functioning conditions of a piston engine. One of such a solution is the MDI system presented in the work.

Analysis, Fabrication, and Testing of a Liquid Piston Compressor Prototype for an Ocean Compressed Air Energy Storage (OCAES) System

Previous work concerning ocean compressed air energy storage (OCAES) systems has revealed the need for an efficient means for compressing air that minimizes the energy lost to heat during the compression process. In this paper, we present analysis, simulation, and testing of a tabletop proof-of-concept experiment of a liquid piston compression system coupled with a simulated OCAES system, with special attention given to heat transfer issues. An experimental model of a liquid piston system was built and tested with two different materials, polycarbonate and aluminum alloy, used for the compression chamber. This tabletop liquid piston system was tested in conjunction with a simulated OCAES system, which consisted of a hydrostatic tank connected to a compressed-air source from the wall to mimic the constant hydrostatic pressure at ocean depth experienced by the air stored in an actual OCAES system. Good agreement was found between the experimental and numerical studies and demonstrated that the heat transfer characteristics of a liquid piston compression process are effective in reducing the increase in air temperature that occurs during the compression process. The results also suggest that it may be possible to achieve a near-isothermal process with a fully optimized liquid piston compression system.

Research of Numberical Solution on Kinetic and Tribological Coupled Model of Piston Systems

This paper establishs a coupled model on kinetic and tribological of cylinder liner-piston-piston ring system and takes the cylinder liner-piston system as an automatic control system based on the finite difference method and overrelaxation iteration method; the numerical solutions of the model is put forward and designed the overall the calculation process of coupling model, providing theoretical basis for further analyzing the piston system dynamic performance.